JP2010061810A - Optical element for optical pickup device, and optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element for an optical pickup device, an aberration compensating element for an optical pickup device, a condensing element for an optical pickup device, an objective lens system, the optical pickup device, and an optical information recording/reproducing device to include a high-density optical disk employing a bluish-purple laser light source and a DVD, and to properly record and/or reproduce information on plural optical information recording media using different wavelengths. <P>SOLUTION: The optical element for optical pickup devices reproduces information from and/or records information to first and second optical information recording media using luminous flux of first and second wavelengths λ1 and λ2. The optical element includes: an optical function surface having a superposition type diffractive structure where a plurality of ring-shaped zones having a plurality of steps formed in the inside are arranged around a light axis; and an optical function surface having a diffractive structure composed of a plurality of ring-shape zones divided by steps in the direction of a light axis. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical element, an aberration correction element, a condensing element, an objective optical system, an optical pickup apparatus and an optical information recording / reproducing apparatus using these optical elements.

In recent years, in an optical pickup device, a laser light source used as a light source for reproducing information recorded on an optical disc and recording information on the optical disc has been shortened. For example, a blue-violet semiconductor laser, A laser light source having a wavelength of 405 nm such as a blue-violet SHG laser that performs wavelength conversion of an infrared semiconductor laser using harmonic generation is being put into practical use.
When these blue-violet laser light sources are used, 15 to 20 GB of information can be recorded on an optical disk having a diameter of 12 cm when an objective lens having the same numerical aperture (NA) as that of a DVD (digital versatile disk) is used. When the NA of the objective lens is increased to 0.85, 23 to 25 GB of information can be recorded on an optical disk having a diameter of 12 cm. Hereinafter, in this specification, an optical disk and a magneto-optical disk using a blue-violet laser light source are collectively referred to as a “high density optical disk”.

Incidentally, in a high density optical disk using an objective lens with NA of 0.85, coma aberration generated due to the inclination (skew) of the optical disk increases, so the protective layer is designed thinner than in the case of DVD (0 of DVD). The amount of coma with respect to the skew is reduced.
By the way, simply saying that information can be appropriately recorded / reproduced with respect to such a high-density optical disc cannot be said to have sufficient value as a product of an optical disc player. In light of the reality that DVDs and CDs (compact discs) on which a variety of information is recorded are currently being sold, it is not possible to record / reproduce information on high-density optical discs. Similarly, making it possible to appropriately record / reproduce information on DVDs and CDs leads to an increase in commercial value as an optical disc player for high-density optical discs. From such a background, an optical pickup device mounted on an optical disc player for high density optical discs appropriately records information while maintaining compatibility with both high density optical discs, DVDs, and even CDs. It is desirable to have reproducible performance.

As a method for appropriately recording / reproducing information while maintaining compatibility with both high-density optical discs and DVDs, and even CDs, optical components for high-density optical discs and optical components for DVDs and CDs are used. A method of selectively switching the system to and from the recording density of the optical disk for recording / reproducing information is conceivable. However, since a plurality of optical systems are required, it is disadvantageous for miniaturization and the cost increases.
Therefore, in order to simplify the configuration of the optical pickup device and reduce the cost, the optical system for high-density optical discs and the optical system for DVDs and CDs must be shared in compatible optical pickup devices. It is preferable to reduce the number of optical components constituting the optical pickup device as much as possible.
As an objective optical system for an optical system that can be used in common for a plurality of types of optical discs having different recording densities, the lens surface as described in Patent Documents 1 and 2 is centered on the optical axis. There is known a technique for providing an annular structure that forms a plurality of uneven structures in each annular zone.

JP-A-9-306018 JP 2002-277732 A

In the techniques described in the above two patent documents, the depth of the step of the concavo-convex structure formed in the annular zone is set to either the DVD recording / reproducing wavelength λ1 or the CD recording / reproducing wavelength λ2. By setting the depth so that a phase difference is not substantially added between adjacent concavo-convex structures (for example, λ1), the concavo-convex structure gives a phase difference only to the other wavelength (for example, λ2). I have to.
Furthermore, since the number of concave and convex structures formed in each annular zone is such that a phase difference of an integral multiple of the wavelength is given between adjacent annular zones when a light beam having a wavelength λ2 passes through the annular zone structure, Only the light beam having the wavelength λ2 is diffracted by the structure. The uneven structure formed in each annular zone at this time is further set so that both the transmittance (diffraction efficiency) with respect to the wavelength λ1 and the wavelength λ2 is large.
In the objective optical system described in Patent Document 1, when a light beam having a wavelength λ2 is diffracted by an annular structure, spherical aberration generated due to a difference in thickness of the protective layer between DVD and CD is canceled out. In the objective optical system of Patent Document 2, when the light beam having the wavelength λ2 is diffracted by the annular structure, it is caused by the difference in the protective layer thickness between the DVD and the CD. Since spherical aberration that cancels the generated spherical aberration is added to the light flux having the wavelength λ2, information can be recorded / reproduced with respect to the DVD and the CD by the common objective optical system.

Both of the techniques disclosed in Patent Documents 1 and 2 realize compatibility between two types of optical disks, DVD and CD, and record / reproduce wavelengths of high-density optical disks (near 400 nm) and DVD recording. / Spherical aberration that occurs due to the difference in the protective layer thickness between the high-density optical disc and the DVD is corrected for the reproduction wavelength (near 650 nm), and high transmittance (diffraction for both wavelengths) In order to realize compatibility between the high-density optical disc and the DVD, there is no disclosure regarding the optimal annular zone structure (for example, the number of concavo-convex structures formed in each annular zone). It is difficult to apply the technology disclosed in the literature as it is.
Further, in order to appropriately record / reproduce information using a common objective optical system for the high-density optical disc and the DVD, the thickness of the protective layer between the high-density optical disc and the DVD as described above is required. In addition to the spherical aberration that occurs due to the difference, it is necessary to solve problems inherent to high-density optical disks.

Problems inherent to high-density optical discs are (1) chromatic aberration associated with the shorter wavelength of the laser light source, and (2) spherical aberration variation associated with higher numerical aperture.
Among these, (1) is a problem that manifests in the blue-violet wavelength region because the wavelength dispersion of the optical material (change in refractive index with respect to a minute wavelength change) is large. When switching from information reproduction to recording or information recording to reproduction on an optical disc, the oscillation wavelength changes because the output of the semiconductor laser light source changes (so-called mode hopping). This wavelength change is about several nanometers. However, since the wavelength dispersion is large in the blue-violet wavelength region, it becomes a defocused state until the objective optical system refocuses, and appropriate recording / reproducing characteristics cannot be obtained.
Further, (2) is a problem that is manifested because spherical aberration generated in the objective optical system increases in proportion to the fourth power of the numerical aperture. In an objective optical system having a high numerical aperture, the spherical aberration when the wavelength of the incident light beam changes increases, so that the tolerance for the wavelength of the laser light source becomes severe. In particular, this problem becomes more apparent because of the influence of wavelength dispersion in the blue-violet wavelength region. In order to reduce the manufacturing cost, it is effective to use a plastic lens as the objective optical system. However, since spherical aberration generated due to a change in refractive index due to a temperature change increases, When the temperature of the recording medium changes, the information recording / reproducing characteristics with respect to the high-density optical disk are hindered.

An object of the present invention is to take the above-mentioned problems into consideration, and to record information on a plurality of types of optical information recording media having different wavelengths to be used, including high-density optical disks and DVDs that use a blue-violet laser light source. Optical element for optical pickup device, aberration correction element for optical pickup device, condensing element for optical pickup device, objective optical system, optical pickup device, and optical information recording / reproducing device capable of appropriately performing reproduction Is to provide.

In this specification, an optical disk using a blue-violet semiconductor laser or a blue-violet SHG laser as a light source for recording / reproducing information is generally referred to as a “high-density optical disk”, and information is obtained by an objective optical system with NA of 0.85. In addition to a standard optical disc having a protective layer thickness of about 0.1 mm, information is recorded / reproduced by an objective optical system with NA of 0.65, and the protective layer thickness is 0. It also includes an optical disc with a standard of about 6 mm. In addition to an optical disc having such a protective layer on its information recording surface, an optical disc having a protective film with a thickness of several to several tens of nanometers on the information recording surface, the thickness of the protective layer or protective film It also includes an optical disc with 0. In this specification, the high-density optical disk includes a magneto-optical disk that uses a blue-violet semiconductor laser or a blue-violet SHG laser as a light source for recording / reproducing information.
In this specification, DVD is a general term for DVD-series optical disks such as DVD-ROM, DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, and DVD + RW. Is a generic term for CD-series optical disks such as CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW and the like.

In the present specification, the “superposition type diffractive structure” means that, as schematically shown in FIG. 26, each annular zone R _3i is a plurality of annular zones R _3i arranged continuously around the optical axis. Furthermore, it refers to a structure that is divided into steps by a plurality of steps d _{3i in} the optical axis direction. Such superposition type diffraction structure, the depth of the step d _3i delta, by appropriately setting the step number N, as described above, selectively diffracts only one of a plurality of different light beams having wavelengths, and The light beam of other wavelengths is transmitted without being diffracted, the diffraction orders of the light beams of a plurality of wavelengths are made different from each other, or the diffraction efficiency is extremely reduced for a light beam of a specific wavelength, It is possible to give to a plurality of incident light beams having different wavelengths. Note that such an action of extremely reducing the diffraction action and the diffraction efficiency is given to the diffracted light having the maximum diffraction efficiency among the diffracted lights of various orders generated from the light flux of each wavelength. In the present specification, a light beam that is transmitted without being diffracted by this “superimposition type diffractive structure” (that is, without giving a substantial optical path difference) is referred to as “0th-order diffracted light” for convenience.
In the present specification, the “diffractive structure” means, as schematically shown in FIG. 27, a sawtooth shape (FIG. 27A) continuously arranged around the optical axis or a step shape (FIG. 27 ( b)) is composed of a plurality of annular zones R _1i , and each annular zone R _1i is divided by a step d _{1i in the} optical axis direction. This “diffractive structure” generates diffracted light having a diffraction order with an absolute value of 1 or more according to the wavelength of the incident light beam. In the present specification, the “superimposed diffractive structure” in which each annular zone is further divided in a step shape is distinguished from this “diffractive structure”. FIG. 27 shows the case where the direction of the step d _1i is the same within the effective diameter, but the case where the direction of the step d _1i is reversed within the effective diameter is also included in the “diffractive structure” in this specification.

In this specification, the “optical path difference providing structure” means a plurality of rings that are continuously arranged around the optical axis and divided by a step d _2i in the optical axis direction, as schematically shown in FIG. A structure composed of the band R _{2i is} indicated. Among these ring zones R _2i , the ring zones inside the ring zones located at a predetermined height within the maximum effective diameter are shifted in the optical axis direction so that the optical path length becomes shorter as the distance from the optical axis increases. Further, the annular zone outside the annular zone located at a predetermined height within the maximum effective diameter is shifted in the optical axis direction so that the optical path length becomes longer as the distance from the optical axis increases. Here, the annular zone located at a predetermined height is preferably such that the height from the optical axis at the center is within the range of 60% to 85% of the maximum effective diameter.
Further, in this specification, the “optical path difference providing structure” is composed of a central region C including the optical axis and a plurality of annular zones R _2i divided by fine steps d _2i outside the central region C. The annular zone R _2iA adjacent to the outside of the central region C is formed by _shifting in the optical axis direction so that the optical path length becomes shorter with respect to the central region C, and the annular zone at the maximum effective diameter position. R _2iB is formed by _shifting in the optical axis direction so that the optical path length becomes longer with respect to the annular zone R _2iC adjacent to the inner side thereof, and the height is within a range of 60% to 85% of the maximum effective diameter. one annular R _2id the central portion is located, by shifting in the optical axis direction so that the optical path length is reduced with respect to the annular R _2if adjacent zones R _2Ie adjoining its inside and its outside It can also be expressed as a formed structure. Here, the “central region C” is an optical functional region that includes the optical axis and is surrounded by a step d 2 _iA that is closest to the optical axis.

Spherical aberration can be corrected by the optical path difference providing structure having such a configuration. For example, in an objective optical system composed of an aberration correction element and a condensing element, both of which are plastic lenses, a change in spherical aberration (see wavefront aberration a in FIG. 29) accompanying an increase in temperature of the condensing element is applied to an optical path difference providing structure. When the correction is performed by the aberration correction element in which is formed, the depth of the step d _2i is set so as to satisfy d _2i = p · λ ₀ / (N ₀ −1). However, p is an integer greater than or equal to 1, λ ₀ (μm) is the design wavelength, and N ₀ is the refractive index at the design reference temperature of the plastic lens.
At the reference temperature, the optical path difference due to the step d _2i is an integral multiple of the design wavelength λ ₀ , so that the optical path difference is not substantially given. On the other hand, when the temperature rises, the refractive index of the plastic lens decreases, so the optical path difference due to the step d _2i deviates slightly from an integer multiple of the design wavelength λ ₀ , as shown in FIG. 29b. In this way, wavefront aberration of the opposite sign to the wavefront aberration (FIG. 29a) of the light converging element when the temperature rises occurs, and the wavefront aberrations act in a direction to cancel each other (c in FIG. 29).
FIG. 26 to FIG. 28 are schematic views when each structure is formed on a plane parallel plate. In this specification, each structure is in the form of FIG. 26 to FIG. 28 unless departing from the above definition. It is not limited only.

  In this specification, the term “aberration correction element” refers to the difference in protective layer thickness between optical discs of the above-described superposition type diffractive structure formed on the optical functional surface and having different protective layer thicknesses. The optical element which has a function which suppresses the spherical aberration which arises due to. In the present specification, the aberration correction element may be composed of a plurality of optical elements instead of only one optical element. In addition, the “light condensing element” is an optical element disposed at a position facing the optical disk in the optical pickup device, and condenses the light beam emitted from the aberration correction element, and a plurality of types of optical disks having different standards. These optical elements have a function of forming an image on each information recording surface. The “light condensing element” may be composed of not only one optical element but also a plurality of optical elements.

In this specification, the “objective optical system” refers to an optical system including at least the above-described condensing element. The objective optical system may be composed only of a light condensing element.
Furthermore, in the present specification, when there is an optical element that is integrated with such a condensing element and performs tracking and focusing by an actuator, an optical system composed of these optical element and condensing element is referred to as an objective optical system. It is defined as Therefore, the above-described aberration correction element is included in the optical element that is integrated with the condensing element and performs tracking and focusing by the actuator.
In this specification, “to form a good wavefront” on the information recording surface of the optical disc means that the incident light beam is condensed on the information recording surface of the optical disc so that the wavefront aberration is 0.07λ RMS or less. It is synonymous with doing.

In order to solve the above problems, the invention described in claim 1 is directed to a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. A second optical information recording medium that reproduces and / or records information and has a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source An optical element for an optical pickup device that reproduces and / or records information with respect to
The optical element includes an optical functional surface on which a superposition type diffractive structure, which is a structure in which a plurality of annular zones having a plurality of steps formed therein are arranged around the optical axis, and a step in the optical axis direction. And an optical functional surface on which a diffractive structure composed of a plurality of divided annular zones is formed.
According to a second aspect of the present invention, in the optical element for the optical pickup device according to the first aspect,
Of the diffracted light generated when the light beam having the first wavelength λ1 is incident on the diffractive structure, the diffraction order of the diffracted light having the maximum diffraction efficiency is n1, and the light beam having the second wavelength λ2 is incident on the diffractive structure. When the diffraction order of the diffracted light having the maximum diffraction efficiency among the diffracted light generated in this case is n2, the depth of the step of the diffractive structure is set so as to satisfy the following expression (1) It is characterized by.
n1> n2 (1)

According to a third aspect of the present invention, in the optical element for an optical pickup device according to the first or second aspect, the first wavelength λ1 (μm) and the second wavelength λ2 (μm) are respectively the following (2): And the diffraction order n1 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the first wavelength λ1 is incident on the diffractive structure, and the second wavelength λ2 Of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam of the incident light enters the diffractive structure, the combinations of the diffraction orders n2 having the maximum diffraction efficiency are (n1, n2) = (2, 1), (3, 2). , (5, 3), (8, 5), or (10, 6).
0.39 <λ1 <0.42 (2)
0.63 <λ2 <0.68 (3)
According to a fourth aspect of the present invention, in the optical element for an optical pickup device according to any one of the first to third aspects, an element having an optical functional surface on which the diffractive structure is formed is the optical element. The refractive index at the first wavelength λ1 is in the range of 1.5 to 1.6, and the Abbe number at the d-line is in the range of 50 to 60, The depth d1 in the optical axis direction of the step closest to the optical axis satisfies any of the following formulas (4) to (8).
1.2 μm <d1 <1.7 μm (4)
2.0 μm <d1 <2.6 μm (5)
3.4 μm <d1 <4.1 μm (6)
5.6 μm <d1 <6.5 μm (7)
6.9 μm <d1 <8.1 μm (8)

According to a fifth aspect of the present invention, in the optical element for an optical pickup device according to any one of the first to fourth aspects, the cross-sectional shape including the optical axis of the diffractive structure is a step shape. To do.
A sixth aspect of the present invention is the optical element for an optical pickup device according to any one of the first to fourth aspects, wherein the cross-sectional shape including the optical axis of the diffractive structure is a sawtooth shape. To do.
According to a seventh aspect of the present invention, in the optical element for an optical pickup device according to any one of the first to sixth aspects, the optical element is composed of one element, and the superimposed diffractive structure is It is formed on one optical functional surface of the optical element, and the diffractive structure is formed on the other optical functional surface of the optical element.

According to an eighth aspect of the present invention, in the optical element for an optical pickup device according to any one of the first to seventh aspects, the superimposed diffractive structure is adjacent to the light flux having the first wavelength λ1. An optical path difference is given to the light flux having the second wavelength λ2 without substantially giving an optical path difference between the annular zones.
The invention according to claim 9 is the optical element for the optical pickup device according to any one of claims 1 to 8, wherein the first wavelength λ1 (μm) and the second wavelength λ2 (μm) are respectively It satisfies the following formulas (2) and (3).
0.39 <λ1 <0.42 (2)
0.63 <λ2 <0.68 (3)

According to a tenth aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source An optical element for an optical pickup device that performs recording,
The optical element includes an optical functional surface on which a superposition type diffractive structure, which is a structure in which a plurality of annular zones having a plurality of steps formed therein are arranged around the optical axis, and a step in the optical axis direction. And an optical function surface on which an optical path difference providing structure composed of a plurality of divided annular zones is formed.
The invention according to claim 11 is the optical element for the optical pickup device according to claim 10, wherein the annular zone of the optical path difference providing structure is more than the annular zone located at a predetermined height within the maximum effective diameter. The inner ring zone is shifted in the optical axis direction so that the optical path length becomes shorter as the distance from the optical axis increases, and the outer ring zone located at a predetermined height within the maximum effective diameter is The optical path length is changed so that the optical path length becomes longer as the distance from the optical axis increases.

According to a twelfth aspect of the present invention, in the optical element for an optical pickup device according to the eleventh aspect, the height from the optical axis in the central portion of the annular zone located at the predetermined height is a maximum effective diameter of 60. % To 85% in height.
According to a thirteenth aspect of the present invention, in the optical element for an optical pickup device according to any one of the tenth to twelfth aspects, the first wavelength λ1 (μm), the second wavelength λ2 (μm), and the optical path. Of the steps of the difference providing structure, the depth d2 (μm) of the step closest to the optical axis in the optical axis direction, and among the optical elements, the first of the elements having the optical function surface on which the optical path difference providing structure is formed. Depending on the refractive index N _λ1 with respect to the wavelength λ1 and the refractive index N _λ2 with respect to the second wavelength λ1 of the optical element, Φ1 and Φ2 represented by the following expressions (9) and (10) are respectively (11) to (11) 13) It is characterized by satisfy | filling Formula.
Φ1 = d2 (N _λ1 −1) / λ1 (9) Φ2 = d2 (N _λ2 −1) / λ2 (10)
INT (Φ1) ≦ 20 (1
1)
0 ≦ | INT (Φ1) −Φ1 | ≦ 0.4 (12)
0 ≦ | INT (Φ2) −Φ2 | ≦ 0.4 (13)
However, INT (Φi) (i = 1, 2) is an integer obtained by rounding Φi.

According to a fourteenth aspect of the present invention, in the optical element for an optical pickup device according to the thirteenth aspect, the element having the optical function surface on which the optical path difference providing structure is formed is the first wavelength. The refractive index at λ1 is in the range of 1.5 to 1.6 and the Abbe number at the d-line is in the range of 50 to 60, and the following equations (14) and (15) It is characterized by satisfying.
INT (Φ1) = 5p (14)
INT (Φ2) = 3p (15)
However, p is an integer of 1 or more.
The invention according to claim 15 is the optical element for an optical pickup device according to any one of claims 10 to 14, wherein the optical element is composed of one element, and the superimposed diffractive structure is It is formed on one optical functional surface of the optical element, and the optical path difference providing structure is formed on the other optical functional surface of the optical element.

According to a sixteenth aspect of the present invention, in the optical element for an optical pickup device according to any one of the tenth to fifteenth aspects, the superimposed diffractive structure is adjacent to the light flux having the first wavelength λ1. An optical path difference is given to the light flux having the second wavelength λ2 without substantially giving an optical path difference between the annular zones.
The invention according to claim 17 is the optical element for an optical pickup device according to any one of claims 10 to 16, wherein the first wavelength λ1 (μm) and the second wavelength λ2 (μm) are respectively It satisfies the following formulas (2) and (3).
0.39 <λ1 <0.42 (2)
0.63 <λ2 <0.68 (3)

The invention according to claim 18 is the optical element for an optical pickup device according to any one of claims 1 to 17, wherein the first wavelength λ1 (μm) and the second wavelength λ2 (μm) are as follows. While satisfying the expressions (2) and (3), in the superposition type diffractive structure, the depth Δ (μm) in the optical axis direction of the step formed in each annular zone, and among the optical elements, the superposition type diffraction A refractive index N _λ1 with respect to the first wavelength λ1 of the element having an optical functional surface formed with a structure substantially satisfies the following expression (16).
0.39 <λ1 <0.42 (2)
0.63 <λ2 <0.68 (3)
Δ = 2m · λ1 / (N _λ1 −1) (16)
However, N is either 3 or 4 or 5, and m is an integer of 1 or more.
According to a nineteenth aspect of the present invention, in the optical element for an optical pickup device according to the eighteenth aspect, an element having an optical functional surface on which the superposition type diffractive structure is formed is the first wavelength. The refractive index at λ1 is in the range of 1.5 to 1.6, and the Abbe number at the d-line is in the range of 50 to 60. The combination of the number N of the formed steps and the depth D (μm) in the optical axis direction of the annular zone closest to the optical axis among the annular zones is any of the following formulas (17) to (19): It is characterized by.
When N = 3, 4.1 ≦ D ≦ 4.8 (17)
When N = 4, 5.4 ≦ D ≦ 6.4 (18)
When N = 5, 7.0 ≦ D ≦ 7.9 (19)

According to a twentieth aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Used in an optical pickup device for recording, the light beam having the first wavelength λ1 is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 is collected in the second optical information recording. An objective optical system used for focusing on an information recording surface of a medium,
An optical element for an optical pickup device according to any one of claims 1 to 9, wherein the diffractive structure has the objective optical system when the first wavelength λ1 changes within a range of ± 10 nm. It has a function of suppressing chromatic aberration that occurs due to the chromatic dispersion.

According to a twenty-first aspect of the present invention, in the objective optical system according to the twentieth aspect, the diffractive structure exhibits axial chromatic aberration of the objective optical system when the first wavelength λ1 changes within a range of ± 10 nm. It has the function to suppress.
The invention according to claim 22 is the objective optical system according to claim 20 or 21, wherein the diffractive structure has a wavelength dispersion of the objective optical system when the first wavelength λ1 changes within a range of ± 10 nm. It has a function of suppressing a change in spherical aberration caused by the above.
According to a twenty-third aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Used in an optical pickup device for recording, the light beam having the first wavelength λ1 is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 is collected in the second optical information recording. An objective optical system used for focusing on an information recording surface of a medium, including an optical element for an optical pickup device according to any one of claims 1 to 9,
The objective optical system includes a plastic lens having a positive paraxial power, and the diffractive structure suppresses a change in spherical aberration caused by a change in refractive index of the plastic lens due to a change in environmental temperature. It has a function.

According to a twenty-fourth aspect of the present invention, in the objective optical system according to the twenty-third aspect, when the first wavelength λ1 changes to the long wavelength side, the objective optical system changes the spherical aberration in a direction of insufficient correction. When the first wavelength λ1 is changed to the short wavelength side, the spherical aberration has a wavelength dependency such that the spherical aberration changes in the overcorrection direction.
The invention according to claim 25 is the objective optical system according to any one of claims 20 to 24, wherein the objective optical system includes an aberration correction element and the first wavelength λ1 emitted from the aberration correction element. Is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 emitted from the aberration correction element is condensed on the information recording surface of the second optical information recording medium. The superposition type diffractive structure and the diffractive structure are formed on the optical function surface of the aberration correction element.

According to a twenty-sixth aspect of the present invention, in the objective optical system according to any one of the twentieth to twenty-fifth aspects, the cross-sectional shape including the optical axis of the diffractive structure is a stepped shape.
According to a twenty-seventh aspect of the present invention, in the objective optical system according to any one of the twentieth to twenty-fifth aspects, the cross-sectional shape including the optical axis of the diffractive structure is a sawtooth shape.
The invention according to claim 28 is the objective optical system according to any one of claims 20 to 27, wherein the superposition type diffractive structure includes a protective layer of the first optical information recording medium and the second optical information. It has a function of correcting spherical aberration caused by the difference in the thickness of the protective layer of the recording medium.

According to a twenty-ninth aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Used in an optical pickup device for recording, the light beam having the first wavelength λ1 is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 is collected in the second optical information recording. An objective optical system used for focusing on an information recording surface of a medium,
An optical element for an optical pickup device according to any one of claims 10 to 17, wherein the optical path difference providing structure is configured such that the objective wavelength when the first wavelength λ1 changes within a range of ± 10 nm. It has a function of suppressing a change in spherical aberration caused by chromatic dispersion of the optical system.

According to a thirty-third aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Used in an optical pickup device for recording, the light beam having the first wavelength λ1 is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 is collected in the second optical information recording. An objective optical system used for focusing on an information recording surface of a medium,
An optical element for an optical pickup device according to any one of claims 10 to 17, wherein the objective optical system has a plastic lens having a positive power in a paraxial axis, and the optical path difference providing structure is It has a function of suppressing a spherical aberration change caused by a change in the refractive index of the plastic lens due to a change in environmental temperature.

According to a thirty-first aspect of the invention, in the objective optical system according to the thirty-third aspect, the optical path difference providing structure has a spherical aberration added to the light flux having the first wavelength λ1 when the environmental temperature rises. The spherical aberration has a temperature dependency such that the spherical aberration to be added to the light beam having the first wavelength λ1 changes in the undercorrection direction when the environmental temperature is lowered due to the change in the undercorrection direction. And
The invention according to claim 32 is the objective optical system according to claim 30 or 31, wherein the annular zone of the optical path difference providing structure is located inside a zone located at a predetermined height within the maximum effective diameter. The annular zone is shifted in the optical axis direction so that the optical path length becomes shorter as the distance from the optical axis increases, and the annular zone outside the annular zone located at a predetermined height within the maximum effective diameter is the optical axis. The optical path length is changed so that the optical path length becomes longer as the distance from the optical axis increases.

According to a thirty-third aspect of the present invention, in the objective optical system according to the thirty-second aspect, the height from the optical axis at the center of the annular zone located at the predetermined height is 60% to 85% of the maximum effective diameter. The height is within the range of
The invention according to claim 34 is the objective optical system according to any one of claims 29 to 33, wherein the objective optical system includes an aberration correction element and the first wavelength λ1 emitted from the aberration correction element. Is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 emitted from the aberration correction element is condensed on the information recording surface of the second optical information recording medium. The superposition type diffractive structure and the optical path difference providing structure are formed on the optical function surface of the aberration correction element.

Ｂ_２とＢ_４の符号が互いに異なることを特徴とする。
但し、λは入射光束の波長、λＢは製造波長、ｈは光軸に垂直な方向の高さ（ｍｍ）、Ｂ_２ｊは光路差関数係数、ｎは回折次数である。 A thirty-fifth aspect of the present invention is the objective optical system according to any one of the twenty-ninth to thirty-fourth aspects, wherein the superposition type diffractive structure includes a protective layer of the first optical information recording medium and the second optical information. It has a function of correcting spherical aberration caused by the difference in the thickness of the protective layer of the recording medium.
The invention according to claim 36 is the objective optical system according to any one of claims 20 to 35, wherein the optical path difference added to the transmitted wavefront by the superposition type diffractive structure is defined by the following equation:

B ₂ and B ₄ have different signs.
Where λ is the wavelength of the incident light beam, λB is the manufacturing wavelength, h is the height (mm) in the direction perpendicular to the optical axis, B _2j is the optical path difference function coefficient, and n is the diffraction order.

A 37th aspect of the present invention is the objective optical system according to any one of the 20th to 36th aspects, wherein the objective optical system includes an aberration correction element having an optical functional surface on which the superposition type diffractive structure is formed. The light beam having the first wavelength λ1 emitted from the aberration correction element is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 emitted from the aberration correction element. And a condensing element which is a plastic lens of one group and one piece used for condensing the light on the information recording surface of the second optical information recording medium,
The paraxial power P1 (mm ⁻¹ ) of the aberration correction element with respect to the first wavelength λ1 satisfies the following expression (20).
P1> 0 (20)
The invention according to Claim 38 is the objective optical system according to any one of Claims 20 to 37, wherein the objective optical system includes an aberration correction element having an optical function surface on which the superimposed diffractive structure is formed. The light beam having the first wavelength λ1 emitted from the aberration correction element is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 emitted from the aberration correction element. And a condensing element having a one-group structure used for condensing light on the information recording surface of the second optical information recording medium,
The ratio of the paraxial power P1 (mm ⁻¹ ) of the aberration correction element to the first wavelength λ1 and the paraxial power P2 (mm ⁻¹ ) of the light collecting element to the first wavelength λ1 is as follows. The expression (21) is satisfied.
| P1 / P2 | ≦ 0.2 (21)

The invention according to claim 39 is the objective optical system according to claim 38, wherein the condensing element is a cyclic polyolefin-based plastic lens, and the plastic lens is refracted with respect to a wavelength of 405 nm at a temperature of 25 ° C. Abbe number _[nu d in rate _{N 405,} and the d-line, -5 ° C. refractive index for the wavelength 405nm with temperature change within the temperature range of to 70 ° C. the rate of change _dN 405 / dT is less than (22) to (24 ) Is satisfied.
1.54 <N ₄₀₅ <1.58 (22)
50 <ν _d <60 (23)
−10 × 10 ⁻⁵ (° C. ⁻¹ ) <dN ₄₀₅ / dT <−8 × 10 ⁻⁵ (° C. ⁻¹ ) (24)

The invention according to claim 40 is the objective optical system according to claim 38, wherein the condensing element is formed using a material in which particles having a diameter of 30 μm or less are dispersed in a plastic material. And
The invention according to claim 41 is the objective optical system according to claim 38, characterized in that the condensing element is a glass lens.

According to a forty-second aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source An optical pickup device for recording, comprising the optical element for an optical pickup device according to any one of claims 1 to 19.
According to a forty-third aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source An optical pickup device for recording, comprising the objective optical system according to any one of claims 20 to 41.

The invention according to claim 44 is characterized in that the optical pickup device according to claim 42 or 43 is mounted and at least one of the following (I) to (IV) can be executed. Information recording / reproducing apparatus.
(I) Recording information on the first optical information recording medium and recording information on the second optical information recording medium (II) Recording information on the first optical information recording medium and the second optical information Reproduction of information recorded on a recording medium (III) Reproduction of information recorded on the first optical information recording medium, and recording of information on the second optical information recording medium (IV) First optical information recording medium Of information recorded on the recording medium and reproduction of information recorded on the second optical information recording medium

According to the first aspect of the present invention, the number of steps formed in each annular zone of the superposition type diffractive structure, the depth of the steps formed in each annular zone, and the arrangement of each annular zone are appropriately set. By setting, the light beam having the first wavelength λ1 can be transmitted without being diffracted substantially without being diffracted, and the light beam having the second wavelength λ2 can be diffracted by being given the light path difference. Therefore, it becomes possible to correct the spherical aberration caused by the difference in the protective layer thickness between the high-density optical disc and the DVD, and high transmittance (diffraction efficiency) with respect to the light flux of any wavelength. It can be secured. In addition, the superposition type diffractive structure plays a role of a dichroic filter that transmits the light beam having the first wavelength λ1 without diffracting it, and makes the light beam having the second wavelength λ2 flare by making the diffraction efficiency extremely small. It is also possible.
For example, in a common objective optical system for a high-density optical disc and a DVD, a spherical aberration generated due to a difference in the protective layer thickness between the high-density optical disc and the DVD is corrected within the numerical aperture NA2 of the DVD. 1 is formed, and the light beam having the first wavelength λ1 is transmitted as it is without being diffracted into the region from the numerical aperture NA2 to the numerical aperture NA1 of the high-density optical disk, and converted into a light beam having the second wavelength λ2. On the other hand, by forming the second superposition type diffractive structure that makes the diffraction efficiency extremely small and flare, information can be recorded / reproduced appropriately for any optical disc, and the aperture switching function for DVD An objective optical system having the following can be provided.

  In addition, in order to appropriately record / reproduce information with respect to a high-density optical disk, a means for correcting axial chromatic aberration is provided so that collection due to instantaneous wavelength change of a laser light source called mode hopping is provided. It is necessary to prevent deterioration of optical performance. This is because the wavelength dispersion of the optical material in the blue-violet region becomes very large, and a large focus position shift occurs even with a slight wavelength change.

  As one standard for high-density optical discs, an optical disc has been proposed in which the numerical aperture of the objective optical system is increased to about 0.85. However, as the numerical aperture of the objective optical system increases, the optical disc is generated due to a change in wavelength of the incident light beam. Since the spherical aberration change becomes large, a problem that a laser light source having a wavelength error cannot be used due to a manufacturing error becomes obvious. Therefore, since it is necessary to select a laser light source, the manufacturing cost of the optical pickup device increases.

  In addition, since the specific gravity of the plastic lens is smaller than that of the glass lens, the burden on the actuator that drives the objective optical system can be reduced, and the objective optical system can be tracked at high speed. In addition, a plastic lens manufactured by injection molding can be mass-produced with stable quality and high accuracy by producing a desired mold with good manufacturing. However, when the numerical aperture of the objective optical system is increased, if the objective optical system is a plastic lens, the influence of the refractive index change accompanying the temperature change is increased. This is because the spherical aberration caused by the refractive index change increases in proportion to the fourth power of the numerical aperture.

  Therefore, in the present invention, by providing a diffractive structure on the optical functional surface of the optical element, the focus position shift with respect to the wavelength change of the incident light beam, the spherical aberration change with the wavelength change of the incident light beam, or the spherical aberration change with the refractive index change. Therefore, even when the wavelength change or temperature change of the incident light beam occurs, the recording / reproducing characteristics with respect to the high density optical disk can be favorably maintained.

However, since the wavelength difference between the light source for the high-density optical disk and the light source for the DVD is large, if the diffracted light of the same diffraction order generated in the above-described diffraction structure is used as a light flux for recording / reproducing with respect to each optical disk, 2 Sufficient diffraction efficiency cannot be obtained with respect to light beams having wavelengths of two light sources. To solve this problem, as in the invention of claim 2, the diffraction order n2 of the diffracted light used for the DVD is lower than the diffraction order n1 of the diffracted light used for the high-density optical disk. If the diffractive structure is designed so as to satisfy the above, it is possible to sufficiently secure the diffraction efficiency with respect to the light beams having the wavelengths of the two light sources.
Specifically, the diffraction orders n1 and n2 are preferably a combination as in the invention of claim 3 because high diffraction efficiency can be secured for the wavelengths λ1 and λ2. There are other combinations of diffraction orders n1 and n2 that can ensure high diffraction efficiency for a light beam of any wavelength. However, if the diffraction order becomes too large, the wavelength of the incident light beam will change. The accompanying decrease in diffraction efficiency is undesirably large.

  The element in which the diffractive structure is formed is formed of a material having a refractive index with respect to the first wavelength λ1 in the range of 1.5 to 1.6 and an Abbe number at the d-line in the range of 50 to 60. In this case, the depth d1 of the step located closest to the optical axis among the steps of the diffractive structure is set to any one of the expressions (4) to (8). Therefore, high diffraction efficiency can be secured for the light fluxes having the first wavelength λ1 and the second wavelength λ2. Note that the combination of the diffraction orders n1 and n2 and the step d1 are such that (n1, n2) = (2,1) corresponds to the equation (4), and (n1, n2) = (3, 2) is the equation (5). (N1, n2) = (5, 3) corresponds to equation (6), (n1, n2) = (8, 5) corresponds to equation (7), and (n1, n2) = (10, 6) corresponds to equation (8).

As a specific shape of such a diffractive structure, the cross-sectional shape including the optical axis is a step shape as in the invention described in claim 5.
The specific shape of the diffractive structure may be a sawtooth shape in cross section including the optical axis, as in the sixth aspect of the invention.
In order to provide a high added value to the optical element and at the same time achieve a reduction in cost, as in the invention of claim 7, the optical element is composed of one element, and a superposition type diffractive structure and a diffractive structure are provided. Is preferably formed on each optical functional surface of the element.

  As described above, since the wavelength dispersion of the optical material is increased by shortening the wavelength of the light source, the problem of chromatic aberration becomes obvious in the objective optical system. Here, “chromatic aberration” refers to at least one of “axial chromatic aberration” in which the paraxial focal position moves due to wavelength change and “chromatic spherical aberration” in which spherical aberration changes due to wavelength change. In particular, since the spherical aberration increases in proportion to the fourth power of the numerical aperture, when the objective optical system has a high numerical aperture, the above-mentioned problem of “chromatic spherical aberration” becomes more obvious. Therefore, as described in claims 20 to 22, in order to appropriately record / reproduce information with respect to a high-density optical disk, the diffraction structure is generated due to wavelength dispersion of the objective optical system. It is preferable to have a function of suppressing chromatic aberration.

In addition, it is advantageous to reduce the cost and weight by constructing the objective optical system with a plastic lens. However, when the temperature in the optical pickup device changes because the influence of the refractive index change due to the temperature change increases. In addition, the recording / reproducing characteristics of information on a high-density optical disk are hindered. In order to maintain good recording / reproducing characteristics even when the temperature in the optical pickup device changes, the diffraction structure is generated due to a change in the refractive index of the plastic lens. It is preferable to have a function of suppressing spherical aberration.
Specifically, as in the invention of claim 24, when the first wavelength λ1 becomes longer, the spherical aberration changes in the direction of insufficient correction, and when the first wavelength λ1 becomes shorter, the spherical aberration becomes smaller. It is preferable to give the objective optical system the wavelength dependency of spherical aberration that changes in the overcorrected direction by the action of the diffractive structure.
In addition, when a structure having a step in the optical axis direction such as a superposition type diffractive structure or a diffractive structure is formed in an optical element having a large curvature, the transmittance is lowered due to the influence of the flux of the stepped portion. In order to prevent such a decrease in transmittance, as in the invention described in claim 25, the objective optical system is composed of an aberration correcting element and a condensing element, and the superposition type diffractive structure and diffractive structure are provided on the aberration correcting element. Preferably formed.

According to the invention described in claim 10, as in the invention described in claim 1, spherical aberration generated due to the difference in the protective layer thickness between the high-density optical disk and the DVD is caused by the superimposed diffraction structure. In addition to being able to correct, it is possible to ensure high transmittance (diffraction efficiency) for a light flux of any wavelength. In addition, the superposition type diffractive structure plays a role of a dichroic filter that transmits the light beam having the first wavelength λ1 without diffracting it, and makes the light beam having the second wavelength λ2 flare by making the diffraction efficiency extremely small. It is also possible.
In the present invention, since the optical path difference providing structure is provided on the optical function surface of the optical element, the function of suppressing the spherical aberration change with respect to the wavelength change of the incident light beam and the spherical aberration change with the refractive index change is provided. Even when the wavelength change or temperature change of the incident light beam occurs, the recording / reproducing characteristics for the high-density optical disk can be maintained well.

In order to correct the spherical aberration by the optical path difference providing structure, as in the invention of claim 11, among the annular zones of the optical path difference providing structure, than the annular zone located at a predetermined height within the maximum effective diameter. The inner ring zone is shifted in the optical axis direction so that the optical path length becomes shorter as it moves away from the optical axis, and the outer ring zone located at a predetermined height within the maximum effective diameter is It is preferable that the optical path length is shifted so that the optical path length increases as the distance from the axis increases. This suppresses changes in spherical aberration due to changes in the wavelength of the incident light beam and changes in spherical aberration due to changes in the refractive index. It becomes possible to do.
The height from the optical axis in the central portion of the annular zone located at the predetermined height is a height within the range of 60% to 85% of the maximum effective diameter, as in the invention of claim 12. Is preferred.

  In order to increase the transmittance of the optical path difference providing structure with respect to the light beams having the first wavelength λ1 and the second wavelength λ2, the position closest to the optical axis among the steps of the optical path difference providing structure is provided. The depth d2 of the step and the optical path differences Φ1 and Φ2 added to the light beams having the first wavelength λ1 and the second wavelength λ2 by the step are set so as to satisfy the expressions (11) to (13). Is preferred. When the above equation is not satisfied, high-order spherical aberration occurs for a light beam of any wavelength when the wavelength of the incident light beam changes or when the refractive index changes due to a temperature change. Although higher-order spherical aberration does not affect the recording / reproducing performance, it is substantially equivalent to a decrease in transmittance. If these expressions are satisfied, the generation of higher-order spherical aberration can be suppressed for the light flux of any wavelength, and the transmittance can be increased.

  The element in which the optical path difference providing structure is formed is made of a material whose refractive index with respect to the first wavelength λ1 is in the range of 1.5 to 1.6 and whose Abbe number at the d-line is in the range of 50 to 60. If it is formed, it is preferable that the optical path differences Φ1 and Φ2 satisfy the expressions (14) and (15), as in the invention of claim 14. The expression (14) means that the optical path difference Φ1 added to the light beam having the first wavelength λ1 by the step closest to the optical axis is approximately five times the first wavelength λ1. As described above, when the depth d2 of the step closest to the optical axis is set, the optical path difference Φ2 added to the light flux having the second wavelength λ2 by this step is substantially equal to the second wavelength λ2. Since it becomes three times, generation of high-order spherical aberration can be suppressed for light beams of any wavelength, and the transmittance can be increased.

A specific example will be described below. “ZEONEX 330R” (product name), which is an optical plastic material of Nippon Zeon Co., Ltd., with respect to the first wavelength λ1 when the first wavelength λ1 and the second wavelength λ2 are 0.405 μm and 0.655 μm, respectively. The refractive index N _λ1 is 1.5252, and the refractive index N _λ2 for the second wavelength _λ2 is 1.5070. The depth d2 of the step located closest to the optical axis is
d2 = 5 · λ1 / (N _λ1 −1)
= 5.0.405 / (1.52522-1)
= 3.856 μm
In this case, the optical path difference Φ1 added to the light beam having the first wavelength λ1 by this step is five times the first wavelength λ1 (that is, p = 1 in the equation (14)). . The optical path difference Φ2 added to the light flux having the second wavelength λ2 due to the step of this depth is obtained from the equation (10):
Φ2 = d2 · (N _λ2 −1) / λ2
= 3.856. (1.5070-1) /0.655
= 2.98
Thus, the optical path difference Φ2 is substantially three times the second wavelength λ2, so that the generation of higher-order spherical aberration can be suppressed even for the light flux having the second wavelength λ2, and the transmittance can be increased. .
Further, in order to provide a high added value to the optical element and at the same time achieve a reduction in cost, as in the invention of claim 15, the optical element is composed of one element, and a superposition type diffractive structure and an optical path are provided. It is preferable to form a difference providing structure on each optical functional surface of the element.

As described above, the problem of “chromatic spherical aberration” in which the spherical aberration changes due to the wavelength change becomes obvious as the light source wavelength becomes shorter and the objective optical system has a higher numerical aperture. Therefore, as described in claim 29, in order to appropriately record / reproduce information with respect to a high-density optical disk, the diffractive structure has chromatic aberration caused by wavelength dispersion of the objective optical system. It is preferable to have a suppressing function.
In addition, it is advantageous to reduce the cost and weight by constructing the objective optical system with a plastic lens. However, when the temperature in the optical pickup device changes because the influence of the refractive index change due to the temperature change increases. In addition, the recording / reproducing characteristics of information on a high-density optical disk are hindered. In order to maintain good recording / reproducing characteristics even when the temperature in the optical pickup device changes, the optical path difference providing structure is caused by the refractive index change of the plastic lens, as in the invention of claim 30. It is preferable to have a function of suppressing the generated spherical aberration.

Specifically, as in the invention of claim 31, the spherical aberration added to the light flux having the first wavelength λ1 changes in the direction of insufficient correction when the refractive index decreases with an increase in environmental temperature, A spherical surface generated in a plastic lens as the temperature changes by forming an optical path difference providing structure with temperature dependence of spherical aberration that changes in the overcorrection direction when the refractive index increases as the environmental temperature decreases. It becomes possible to suppress a change in aberration.
As described above, the method of suppressing the spherical aberration change accompanying the temperature change of the plastic lens by using the optical path difference providing structure uses the spherical aberration change accompanying the refractive index change of the optical path difference providing structure, and therefore, diffraction using wavelength dependence. Unlike the case of the structure, even if the wavelength of the laser light source does not change due to the temperature change, the effect of suppressing the spherical aberration change works.

A specific configuration of the optical path difference providing structure is, as in the invention of claim 32, of the annular zones of the optical path difference providing structure, the inner ring of the annular zone located at a predetermined height within the maximum effective diameter. The band is shifted in the direction of the optical axis so that the optical path length becomes shorter with increasing distance from the optical axis, and the ring zone outside the ring zone located at a predetermined height within the maximum effective diameter is separated from the optical axis. It is preferable that the optical path length be changed in the direction of the optical axis so that the change in the spherical aberration due to the change in the wavelength of the incident light beam and the change in the spherical aberration due to the change in the refractive index can be suppressed. .
The height from the optical axis in the central portion of the annular zone located at the predetermined height is a height within the range of 60% to 85% of the maximum effective diameter as in the invention of claim 33. Is preferred.
Further, when a structure having a step in the optical axis direction, such as a superposition type diffractive structure or an optical path difference providing structure, is formed in an optical element having a large curvature, the transmittance is lowered due to the influence of the light flux being displaced by the step portion. In order to prevent such a decrease in transmittance, as in the invention described in claim 34, the objective optical system is composed of an aberration correcting element and a condensing element, and the aberration correcting element is provided with a superposition type diffractive structure and an optical path difference. It is preferable to form a structure.

  As a specific configuration of the superposition type diffractive structure, as in the invention of claim 18, the number N of steps formed in each annular zone is set to either 3 or 4 or 5 (that is, each annular zone is The optical path difference added to the light beam having the first wavelength λ1 by the depth Δ in the optical axis direction of the step is substantially 2 m times the first wavelength λ1 (however, divided into four, five, or six). , M is an integer of 1 or more), so that the superposition type diffractive structure does not substantially give an optical path difference to the light beam having the first wavelength λ1, but to the light beam having the second wavelength λ2. By providing the optical path difference, it is possible to selectively diffract the light beam having the second wavelength λ2, and to ensure high transmittance (diffraction efficiency) for the light beam of any wavelength.

As in the nineteenth aspect of the invention, the element in which the superposition type diffractive structure is formed has a refractive index with respect to the wavelength λ1 in the range of 1.5 to 1.6 and an Abbe number at the d-line of 50. In the case of being formed from a material in the range of ˜60, the number N of steps formed in each ring zone and the depth D = Δ for one ring zone constituted by N steps. It is preferable to set (N + 1) to satisfy any one of the expressions (17) to (19).
As a result, the 0th-order diffracted light that does not substantially give an optical path difference to the light beam having the first wavelength λ1 is given to the light beam having the first wavelength λ1, and the optical path difference is given to the light beam having the second wavelength λ2. Since + 1st order diffracted light can be generated by applying the spherical aberration, the spherical aberration caused by the difference in the thickness of the protective layer between the high-density optical disc and the DVD can be effectively corrected, and the light flux of any wavelength can be corrected. High transmittance (diffraction efficiency) can be secured

Also, as in the invention of claim 36, by occupying different codes of B ₂ and B ₄ each other, it is possible to increase the change amount of h per unit change amount of the optical path difference function phi _b. This corresponds to an increase in the minimum width of the annular zone of the superposition type diffractive structure, and it is possible to improve the transmittance and facilitate the die processing. In order to further achieve these functions and effects, it is preferable to set the sizes of B ₂ and B ₄ so that the optical path difference function φ _b has an inflection point within the effective diameter. Here will be described the case where the optical path difference function phi _b has the inflection point within the effective diameter, the difference between the actual shape of the case having no inflection point. The shape of the case where the optical path difference function phi _b has the inflection point within the effective diameter, the boundary as shown in FIG. 17, the ring-shaped zone located inflection point (8 th zones from the inside 17) As a result, the inclination direction of the annular zone is changed. The shape of the case where the optical path difference function phi _b does not have the inflection point within the effective diameter, as shown in FIG. 16, the inclination direction of all zones are identical.

When the objective optical system is composed of an aberration correction element and a condensing element that is a plastic lens of one group per group as in the invention described in claim 37, the paraxial axis of the aberration correction element for the first wavelength λ1 It is preferable that the light P1 at λ1 be positive so that the light beam having the first wavelength λ1 enters the light collecting element as a convergent light beam. In general, NA _∞ (hereinafter referred to as converted NA) obtained by converting the numerical aperture NA of a finite conjugate type (magnification m ≠ 0) condensing element into an infinite conjugate type is NA _∞ = NA (1-m). Can be expressed. Therefore, since the converted NA can be reduced in a condensing element on which a convergent light beam is incident (that is, m> 0), it is possible to suppress a change in spherical aberration generated in the condensing element with a temperature change.

Further, as in the invention of claim 38, the paraxial power P1 of the aberration correcting element for the first wavelength λ1 and the paraxial power P2 of the light converging element for the first wavelength λ1 satisfy Expression (21). It is preferable to set as follows. In this way, it is possible to ensure a sufficient working distance with respect to the DVD by providing the light collecting element arranged on the optical disc side exclusively with the refractive power for the incident light beam. Further, since a structure having a step in the optical axis direction such as a superposition type diffractive structure is formed on the optical function surface of the aberration correction element, the path is blocked by the step portion and does not contribute to the formation of a focused spot. The ratio of the luminous flux can be suppressed, and the decrease in transmittance can be prevented.
The operational effect of claim 39 is the same as the operational effect of claim 112 described later.
The operation and effect of claim 40 are the same as the operation and effect of claim 114 described later.
The operational effect of claim 41 is the same as the operational effect of claim 113 described later.

According to a 45th aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And reproducing information from the second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source and / or Alternatively, information is recorded on a third optical information recording medium having a protective layer with a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. An optical element for an optical pickup device that performs reproduction and / or recording,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposition type diffractive structure is formed.
According to the invention of claim 45, the optical functional surface of the aberration correction element is divided into a plurality of optical functional regions centered on the optical axis, and the superposition type diffractive structure is formed in the specific optical functional region. Since only one of the three wavelengths can be selectively diffracted and the other wavelengths can be transmitted without being diffracted, the arrangement of each annular zone of the superposition type diffractive structure can be set appropriately. For example, high transmittance (diffraction) for all three wavelengths while correcting spherical aberration caused by the difference in the thickness of the protective layer between the three types of optical disks, such as high density optical disk, DVD, and CD. Efficiency) can be ensured. In addition, by making the diffraction orders of the three wavelengths different, the degree of freedom in optical design is expanded, or for a specific wavelength, the diffraction efficiency is extremely reduced to block specific wavelengths and transmit other wavelengths. It can play the role of a dichroic filter.
In addition, by providing the condensing element arranged on the optical disc side exclusively with the refractive power with respect to the incident light beam, the protective layer thickness of the three types of optical discs with different standards is sufficient to ensure a working distance with respect to the CD. It becomes possible.
Further, since a structure having a fine step such as a superposition type diffractive structure is formed on the optical function surface of the aberration correction element, the path is blocked by the step portion, and the light flux that does not contribute to the formation of the condensing spot is formed. The ratio can be suppressed and a decrease in transmittance can be prevented.

The invention according to claim 46 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness of t1, using a light beam having a first wavelength λ1 emitted from a first light source. And reproducing information from the second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source and / or Alternatively, information is recorded on a third optical information recording medium having a protective layer with a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. An optical element for an optical pickup device that performs reproduction and / or recording,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
A first magnification m1 when information is reproduced and / or recorded on the first optical information recording medium, and a second magnification when information is reproduced and / or recorded on the second optical information recording medium. The magnification m2 is substantially the same.

According to the invention of claim 46, the optical functional surface of the aberration correction element is divided into a plurality of optical functional regions centered on the optical axis, and the superposition type diffractive structure is formed in the optical functional region including the optical axis. Since only one of the three wavelengths can be selectively diffracted and the other wavelengths can be transmitted without being diffracted, the arrangement of each annular zone of the superposition type diffractive structure can be set appropriately. For example, when the protective layer of the high-density optical disc is 0.6 mm, which is the same as that of the DVD, the protective layer thickness of the high-density optical disc and the DVD is kept substantially the same as the magnification m1 for the high-density optical disc and the magnification m2 for the DVD. Spherical aberration caused by the difference can be corrected.
As a result, a collimating lens for a high-density optical disk and a collimating lens for a DVD can be shared, and a light source module in which a light source for a high-density optical disk and a light source for a DVD are packaged can be used. The number of optical components of the pickup device can be reduced.
The step amount Δ and the step number N of the superposition type diffractive structure are preferably combinations as shown in Tables 1 to 8 described later.
In addition, by providing the condensing element arranged on the optical disc side exclusively with the refractive power with respect to the incident light beam, the protective layer thickness of the three types of optical discs with different standards is sufficient to ensure a working distance with respect to the CD. It becomes possible.
Further, since a structure having a fine step such as a superposition type diffractive structure is formed on the optical function surface of the aberration correction element, the path is blocked by the step portion, and the light flux that does not contribute to the formation of the condensing spot is formed. The ratio can be suppressed and a decrease in transmittance can be prevented.

  A 47th aspect of the present invention is the optical element for an optical pickup apparatus according to the 46th aspect, wherein a diffractive power in a paraxial axis of the superposition type diffractive structure with respect to the second wavelength λ2 is negative. .

According to the invention of claim 47, when the high-density optical disc is thinner than the DVD, such as an optical disc having a protective layer thickness of 0.1 mm, the magnification m1 with respect to the high-density optical disc is If the magnification m2 for the DVD is the same, the spherical aberration for the DVD changes in the overcorrection direction because the protective layer of the DVD is thick.
In such a case, as in the invention of claim 47, the paraxial power with respect to the second wavelength λ2 of the superposition type diffractive structure is made negative, and the light flux having the second wavelength λ2 is incident on the light collecting element as divergent light. By doing so, the change in spherical aberration in the overcorrection direction can be canceled by the change in magnification of the light converging element.
With such a configuration, since the occurrence of coma aberration due to the optical axis shift between the aberration correction element and the condenser lens with respect to the second wavelength λ2 is reduced, the process of integrating the aberration correction element and the condenser lens is easy. become.

  According to a 48th aspect of the present invention, in the optical element for an optical pickup device according to the 46th or 47th aspect, the superposition type diffractive structure adds an uncorrected spherical aberration to the second wavelength λ2. It is characterized by.

Alternatively, as described in the invention of claim 48, when the spherical aberration in the undercorrection direction is added to the second wavelength λ2 by the superposition type diffractive structure, the change in the spherical aberration in the overcorrection direction is canceled out. be able to.
With such a configuration, coma aberration generated when an oblique light beam having the second wavelength λ2 is incident is reduced, so that a tolerance for an optical axis deviation between the light source for DVD and the optical element is increased. As a result, the optical pickup device The manufacturing cost is reduced.
The paraxial power with respect to the second wavelength λ2 of the superposition type diffractive structure may be negative, and spherical aberration in the direction of insufficient correction may be added to the second wavelength λ2 by the superposition type diffractive structure.

The invention according to a 49th aspect is the optical element for an optical pickup device according to any one of the 46th to 48th aspects, wherein the first magnification m1 and the second magnification m2 satisfy the following expression (25): It is characterized by satisfying.
m1 = m2 = 0 (25)

  If the magnification m1 for the high-density optical disk and the magnification m2 for the DVD are 0 as in the invention according to claim 49, there is no change in the object point position even if the optical element is shifted in the track direction of the optical disk. Good tracking characteristics can be obtained.

According to a fifty-fifth aspect of the present invention, in the optical element for an optical pickup device according to any one of the eleventh to 46th aspects, information is reproduced and / or recorded on the third optical information recording medium. In this case, the third magnification m3 satisfies the following expression (26).
−0.25 <m3 <−0.10 (26)

As will be described later in Tables 1 to 8 as an example, the step of the superposition type diffractive structure so that only the second wavelength λ2 of the three wavelengths is selectively diffracted and the other wavelengths are transmitted without being diffracted. When the amount Δ and the number of steps N are set appropriately, the superposed diffractive structure cannot correct the spherical aberration change in the overcorrection direction that occurs for the CD having the thickest protective layer. Thus, as in the invention of claim 50, it is possible to correct such a change in spherical aberration by setting the magnification m3 for CD within the range of the expression (26).
Furthermore, if the divergent light beam is made incident on the CD, a working distance with respect to the CD can be sufficiently secured even with an optical element having a small focal length, which is advantageous for downsizing the optical pickup device. is there.

  The invention according to claim 51 is an optical element for an optical pickup device according to any one of claims 46 to 50, wherein the first light source and the second light source are packaged light source modules, The optical element condenses the light beam having the first wavelength λ1 emitted from the light source module on the information recording surface of the first optical information recording medium, and has the second wavelength λ2 emitted from the light source module. The light beam is condensed on the information recording surface of the second optical information recording medium.

  According to the invention of claim 51, since the magnification m1 for the high density optical disk and the magnification m2 for the DVD are substantially the same, the use of the light source module in which the light source for the high density optical disk and the light source for the DVD are packaged is used. Is possible. Thereby, the number of optical components of the optical pickup device can be reduced.

The invention according to claim 52 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness of t1, using a light beam having a first wavelength λ1 emitted from a first light source. And reproducing information from the second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source and / or Alternatively, information is recorded on a third optical information recording medium having a protective layer with a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. An optical element for an optical pickup device that performs reproduction and / or recording,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
A second magnification m2 when information is reproduced and / or recorded on the second optical information recording medium, and a third magnification when information is reproduced and / or recorded on the third optical information recording medium. The magnification m3 is substantially the same.

According to the invention of claim 52, the optical functional surface of the aberration correction element is divided into a plurality of optical functional regions centered on the optical axis, and the superposition type diffractive structure is formed in the optical functional region including the optical axis. As a result, only one of the three wavelengths can be selectively diffracted and the other wavelengths can be transmitted without being diffracted. With this setting, the spherical aberration caused by the difference in the protective layer thickness between the DVD and CD can be corrected while the magnification m2 for DVD and the magnification m3 for CD are substantially the same.
This makes it possible to use a light source module in which a light source for DVD and a light source for CD are packaged, so that the number of optical components of the optical pickup device can be reduced.
The step amount Δ and the step number N of the superposition type diffractive structure are preferably combinations as shown in Tables 1 to 8 described above.
In addition, by providing the condensing element arranged on the optical disc side exclusively with the refractive power with respect to the incident light beam, the protective layer thickness of the three types of optical discs with different standards is sufficient to ensure a working distance with respect to the CD. It becomes possible.
Further, since a structure having a fine step such as a superposition type diffractive structure is formed on the optical function surface of the aberration correction element, the path is blocked by the step portion, and the light flux that does not contribute to the formation of the condensing spot is formed. The ratio can be suppressed and a decrease in transmittance can be prevented.

  The invention according to claim 53 is the optical element for an optical pickup device according to claim 52, wherein the diffractive power in the paraxial axis of the superposition type diffractive structure with respect to the second wavelength λ2 is positive. .

If the magnification m2 for DVD and the magnification m3 for CD are the same, the spherical aberration for DVD changes in the direction of insufficient correction because the protective layer of DVD is thinner than CD.
In such a case, as in the invention of claim 53, the paraxial power with respect to the second wavelength λ2 of the superposition type diffractive structure is assumed to be positive, and the light flux having the second wavelength λ2 enters the condensing element as convergent light. By doing so, it is possible to cancel the above-described change in spherical aberration in the direction of insufficient correction due to the change in magnification of the condensing element.
With such a configuration, since the occurrence of coma aberration due to the optical axis shift between the aberration correction element and the condenser lens with respect to the second wavelength λ2 is reduced, the process of integrating the aberration correction element and the condenser lens is easy. become.

  The invention according to claim 54 is the optical element for an optical pickup device according to claim 52 or 53, wherein the superposition type diffractive structure adds an overcorrected spherical aberration to the second wavelength λ2. It is characterized by.

Alternatively, as in the invention of claim 54, when the spherical aberration in the overcorrection direction is added to the second wavelength λ2 by the superposition type diffractive structure, the change in the spherical aberration in the direction of the undercorrection is canceled out. be able to.
With such a configuration, coma aberration generated when an oblique light beam having the second wavelength λ2 is incident is reduced, so that a tolerance for an optical axis deviation between the light source for DVD and the optical element is increased. As a result, the optical pickup device The manufacturing cost is reduced.
In addition, the paraxial power with respect to the second wavelength λ2 of the superposition type diffractive structure may be positive, and spherical aberration in the overcorrection direction may be added to the second wavelength λ2 by the superposition type diffractive structure.

According to a 55th aspect of the present invention, in the optical element for an optical pickup device according to any one of the 52nd to 54th aspects, information is reproduced and / or recorded on the first optical information recording medium. In this case, the first magnification m1 satisfies the following expression (27).
m1 = 0 (27)

  According to the invention of claim 55, for example, if the magnification m1 for a high-density optical disk is 0, even if the optical element is shifted in the track direction of the optical disk, there is no change in the object point position. can get.

The invention according to claim 56 is the optical element for an optical pickup device according to any one of claims 52 to 55, wherein the second magnification m2 and the third magnification m3 are the following (28) and ( 29) It is characterized by satisfy | filling Formula.
m2 = m3 (28)
−0.25 <m2 <−0.10 (29)

  As will be described later in Tables 1 to 8 as an example, the step of the superposition type diffractive structure so that only the second wavelength λ2 of the three wavelengths is selectively diffracted and the other wavelengths are transmitted without being diffracted. When the amount Δ and the number of steps N are set appropriately, the superposed diffractive structure cannot correct the spherical aberration change in the overcorrection direction that occurs for the CD having the thickest protective layer. Therefore, as in the invention of claim 56, by making the magnification m3 with respect to the CD within the range of the expression (28), it becomes possible to correct such a spherical aberration change.

  The invention according to claim 57 is the optical element for the optical pickup device according to any one of claims 52 to 56, wherein the second light source and the third light source are packaged light source modules, The optical element condenses the light beam having the second wavelength λ2 emitted from the light source module on the information recording surface of the second optical information recording medium, and has the third wavelength λ3 emitted from the light source module. The light beam is condensed on the information recording surface of the second optical information recording medium.

  According to the invention of claim 57, since the magnification m2 for DVD and the magnification m3 for CD are substantially the same, a light source module in which a light source for DVD and a light source for CD are packaged can be used. Thereby, the number of optical components of the optical pickup device can be reduced.

The invention according to claim 58 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And reproducing information from the second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source and / or Alternatively, information is recorded on a third optical information recording medium having a protective layer with a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. An optical element for an optical pickup device that performs reproduction and / or recording,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
The first light flux λ1 and the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps among the discontinuous steps formed in each annular zone in the superposition type diffractive structure are as follows: (30) and (31) are satisfied.
0.39 μm <λ1 <0.42 μm (30)
P> 3 μm (31)

According to the invention of claim 58, the optical functional surface of the aberration correction element is divided into a plurality of optical functional regions centered on the optical axis, and the superposition type diffractive structure is formed in the specific optical functional region. Therefore, only one of the three wavelengths can be selectively diffracted, and the other wavelengths can be transmitted without being diffracted. In this case, high transmittance (for all three wavelengths) can be achieved while correcting the spherical aberration caused by the difference in the thickness of the protective layer between the three types of optical disks such as high density optical disk, DVD, and CD. (Diffraction efficiency) can be ensured. In addition, by making the diffraction orders of the three wavelengths different, the degree of freedom in optical design is expanded, or for a specific wavelength, the diffraction efficiency is extremely reduced to block specific wavelengths and transmit other wavelengths. It can play the role of a dichroic filter.
Furthermore, the superposition type diffractive structure of the present invention has a structure in which each annular zone is divided in steps by a plurality of discontinuous steps in the optical axis direction, but the interval in the direction perpendicular to the optical axis between adjacent steps. If (the width of each staircase structure) becomes too small, the problem that die processing by SPDT becomes difficult becomes obvious. In addition, the reduction in diffraction efficiency due to the shape error of the mold increases as the wavelength becomes shorter.
Therefore, in the present invention, the minimum value P of the width of the staircase structure is not made larger than 3 μm to facilitate the die processing by SPDT, and the diffraction due to the shape error of the die with respect to the wavelength λ1 in the blue-violet region. The reduction in efficiency is prevented from becoming too large.
In addition, by providing the condensing element arranged on the optical disc side exclusively with the refractive power with respect to the incident light beam, the protective layer thickness of the three types of optical discs with different standards is sufficient to ensure a working distance with respect to the CD. It becomes possible.
Further, since a structure having a fine step such as a superposition type diffractive structure is formed on the optical function surface of the aberration correction element, the path is blocked by the step portion, and the light flux that does not contribute to the formation of the condensing spot is formed. The ratio can be suppressed and a decrease in transmittance can be prevented.

The invention according to claim 59 is the optical element for an optical pickup device according to claim 58, wherein, in the superimposed diffractive structure, among the discontinuous steps formed in each annular zone, adjacent steps are provided. The minimum value P of the gap in the direction perpendicular to the optical axis satisfies the following expression (32).
P> 5 μm (32)

  As in the 59th aspect of the invention, in order to make the above effect more effective, it is preferable to set the minimum value P of the width of the staircase structure to be larger than 5 μm.

The invention according to claim 60 is the optical element for the optical pickup device according to claim 58, wherein in the superposition type diffractive structure, among the discontinuous steps formed in each annular zone, adjacent steps are provided. The minimum value P of the interval in the direction perpendicular to the optical axis between the two satisfies the following expression (33).
P> 10 μm (33)

  As in the sixty-sixth aspect of the invention, in order to make the above-described effects more effective, it is preferable that the minimum value P of the width of the staircase structure be larger than 10 μm.

The invention according to claim 61 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And reproducing information from the second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source and / or Alternatively, information is recorded on a third optical information recording medium having a protective layer with a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. An optical element for an optical pickup device that performs reproduction and / or recording,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
When the optical path difference added to the transmitted wavefront by the superposition type diffractive structure is defined by Equation 1, the signs of B ₂ and B ₄ are different from each other.
According to the invention of claim 61, that the signs of B ₂ and B ₄ are made different from each other, it is possible to increase the change amount of h per unit change amount of the optical path difference function phi _b. This corresponds to an increase in the minimum width of the annular zone of the superposition type diffractive structure, and it is possible to improve the transmittance and facilitate the die processing. In order to further achieve these functions and effects, it is preferable to set the sizes of B ₂ and B ₄ so that the optical path difference function φ _b has an inflection point.

  The invention according to claim 62 is the optical element for an optical pickup device according to any one of claims 58 to 61, wherein information is reproduced and / or recorded on the first optical information recording medium. The first magnification m1 in the case, the second magnification m2 in the case where information is reproduced and / or recorded on the second optical information recording medium, and the information reproduction and / or information on the third optical information recording medium. Alternatively, the third magnification m3 when recording is different from each other.

  If an attempt is made to ensure a large minimum value P of the width of the staircase structure, the aberration correction effect due to the superposition type diffractive structure cannot be obtained sufficiently, and the protective layer thickness between three types of optical disks such as high-density optical disk, DVD, and CD The problem that the spherical aberration caused by the difference cannot be corrected becomes obvious. Therefore, as in the invention of claim 62, the magnification m1 for the high-density optical disc, the magnification m2 for the DVD, and the magnification m3 for the CD are made different from each other to correct the spherical aberration remaining without being corrected by the superposition type diffractive structure. Is preferred.

According to a 63rd aspect of the present invention, in the optical element for an optical pickup device according to the 62nd aspect, the first magnification m1, the second magnification m2, and the third magnification m3 are the following (34): Thru | or (36) Formula is satisfy | filled.
m1 = 0 (34)
-0.08 <m2 <-0.01 (35)
−0.25 <m3 <−0.10 (36)

  Specifically, the magnification m1 for the high-density optical disc, the magnification m2 for the DVD, and the magnification m3 for the CD are preferably within the range of the equations (34) to (36) as in the invention of claim 63. .

According to the invention of claim 64, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1, using a light beam having a first wavelength λ1 emitted from the first light source. And reproducing information from the second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source and / or Alternatively, information is recorded on a third optical information recording medium having a protective layer with a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. An optical element for an optical pickup device that performs reproduction and / or recording,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function areas, at least two optical function areas are provided with a plurality of ring zones each having a predetermined number of discontinuous steps formed continuously around the optical axis. A superposed diffractive structure is formed,
In the superposition type diffractive structure, one of the number N of the discontinuous steps formed in each annular zone and the depth Δ (μm) of the discontinuous steps in the optical axis direction is determined for each optical function region. It is characterized by being different.

According to the invention of claim 64, the optical function surface of the aberration correction element is divided into a plurality of optical function regions centered on the optical axis, and the superposition type diffractive structure is formed in the plurality of optical function regions, By varying either the number N of discontinuous steps formed in each annular zone or the depth Δ (μm) of the discontinuous steps in the optical axis direction for each optical functional region, diffraction of three wavelengths is performed. It has the role of a dichroic filter that increases the degree of freedom in optical design by varying the order, or makes the diffraction efficiency extremely small for a specific wavelength, blocks the specific wavelength, and transmits other wavelengths. Can be made.
In addition, by providing the condensing element arranged on the optical disc side exclusively with the refractive power with respect to the incident light beam, the protective layer thickness of the three types of optical discs with different standards is sufficient to ensure a working distance with respect to the CD. It becomes possible.
Further, since a structure having a fine step such as a superposition type diffractive structure is formed on the optical function surface of the aberration correction element, the path is blocked by the step portion, and the light flux that does not contribute to the formation of the condensing spot is formed. The ratio can be suppressed and a decrease in transmittance can be prevented.

According to a 65th aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And reproducing information from the second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source and / or Alternatively, information is recorded on a third optical information recording medium having a protective layer with a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. An optical element for an optical pickup device that performs reproduction and / or recording,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is formed with a diffractive structure composed of a plurality of annular zones divided by a step around the optical axis.

According to a 66th aspect of the present invention, in the optical element for an optical pickup device according to the 65th aspect, the depth of the step of the diffractive structure is a diffracted light generated when a light beam having the first wavelength λ1 is incident. The diffraction order n2 of the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light beam having the second wavelength λ2 is incident on the diffraction order n1 of the diffracted light having the maximum diffraction efficiency, The diffraction order n3 of the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light beam having the third wavelength λ3 is incident is designed to be lower. .

According to a 67th aspect of the present invention, in the optical element for an optical pickup device according to the 66th aspect, the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm). Satisfy the following equations (37) to (39), and the combination of the diffraction order n1, the diffraction order n2, and the diffraction order n3 is (n1, n2, n3) = (2, 1, 1) , (4, 2, 2), (6, 4, 3), (8, 5, 4), or (10, 6, 5).
0.39 <λ1 <0.42 (37)
0.63 <λ2 <0.68 (38)
0.75 <λ3 <0.85 (39)

The invention according to claim 68 is the optical element for an optical pickup device according to claim 66 or 67, wherein the aberration correction element has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1. And the depth d1 in the optical axis direction of the step closest to the optical axis among the steps of the diffractive structure is expressed by the following equation (40). ) To (44).
1.2 μm <d1 <1.7 μm (40)
2.6 μm <d1 <3.0 μm (41)
4.4 μm <d1 <5.0 μm (42)
5.6 μm <d1 <6.5 μm (43)
6.9 μm <d1 <8.1 μm (44)

  The invention according to claim 69 is the optical element for an optical pickup device according to any one of claims 65 to 68, wherein the diffraction structure has the first wavelength λ1 changed within a range of ± 10 nm. In this case, it has a function of suppressing a focus position shift caused by chromatic aberration of the light collecting element.

  The invention according to claim 70 is the optical element for an optical pickup device according to claim 69, wherein the diffractive structure is arranged such that when the first wavelength λ1 changes within a range of ± 10 nm, the light collecting element. It has a function of suppressing axial chromatic aberration caused by chromatic aberration.

  The invention according to claim 71 is the optical element for an optical pickup device according to claim 69 or 70, wherein the diffraction structure is arranged such that the first wavelength λ1 changes when the first wavelength λ1 changes within a range of ± 10 nm. It has a function of suppressing a change in spherical aberration caused by chromatic aberration of an optical element.

  The invention according to claim 72 is the optical element for an optical pickup device according to any one of claims 65 to 71, wherein the condensing element is a plastic lens, and the diffractive structure is the first element. When one wavelength λ1 changes to the long wavelength side, the spherical aberration changes in the direction of insufficient correction, and when the first wavelength λ1 changes to the short wavelength side, the spherical aberration changes in the overcorrection direction. It has a function of suppressing a spherical aberration change caused by a change in the refractive index of the condensing element due to a change in environmental temperature by having a wavelength dependency of the spherical aberration.

The invention according to claim 73 is the optical element for the optical pickup device according to claim 72, wherein at least one of the optical function surfaces of the aberration correction element includes a central optical function including an optical axis. It is divided into a region and a peripheral optical functional region surrounding the periphery of the central optical functional region, and the diffractive structure is formed only in the peripheral optical functional region.

  The invention according to claim 74 is the optical element for an optical pickup device according to any one of claims 65 to 73, wherein the cross-sectional shape including the optical axis of the diffractive structure is a step shape. And

  The invention according to claim 75 is the optical element for an optical pickup device according to any one of claims 65 to 73, wherein the cross-sectional shape including the optical axis of the diffractive structure is a sawtooth shape. And

  The invention according to claim 76 is the optical element for an optical pickup device according to any one of claims 65 to 75, wherein the superposition type diffractive structure is formed on one optical functional surface of the aberration correction element. The diffractive structure is formed on the other optical functional surface of the aberration correction element.

According to the invention of claim 65, the optical functional surface of the aberration correction element is divided into a plurality of optical functional regions centered on the optical axis, and the superposition type diffractive structure is formed in the specific optical functional region. Therefore, only one of the three wavelengths can be selectively diffracted, and the other wavelengths can be transmitted without being diffracted. In this case, high transmittance (for all three wavelengths) can be achieved while correcting the spherical aberration caused by the difference in the thickness of the protective layer between the three types of optical disks such as high density optical disk, DVD, and CD. (Diffraction efficiency) can be ensured. In addition, by making the diffraction orders of the three wavelengths different, the degree of freedom in optical design is expanded, or for a specific wavelength, the diffraction efficiency is extremely reduced to block specific wavelengths and transmit other wavelengths. It can play the role of a dichroic filter.
In addition, in order to appropriately record / reproduce information on / from a high-density optical disk, a means for correcting chromatic aberration is provided so that light collecting performance by instantaneous wavelength change of a laser light source called mode hopping is provided. It is necessary to prevent deterioration. This is because the wavelength dispersion of the lens material in the blue-violet region becomes very large, and a large focus position shift occurs even with a slight change in wavelength.

As one standard for high-density optical discs, optical discs have been proposed in which the NA of the objective lens is increased to about 0.85. However, as the NA of the optical element increases, the change in spherical aberration caused by the change in the wavelength of the incident light beam increases. Therefore, the problem that a laser light source having a wavelength error cannot be used due to a manufacturing error becomes obvious. Therefore, since it is necessary to select a laser light source, the manufacturing cost of the optical pickup device increases.
By the way, since the specific gravity of the plastic lens is smaller than that of the glass lens, the burden on the actuator that drives the objective optical system can be reduced, and the objective optical system can be tracked at high speed. In addition, a plastic lens manufactured by injection molding can be mass-produced with stable quality and high accuracy by producing a desired mold with good manufacture. However, when the NA of the objective optical system is increased, if the objective optical system is a plastic lens, the influence of the refractive index change accompanying the temperature change is increased. This is because the spherical aberration caused by the refractive index change increases in proportion to the fourth power of NA.

Therefore, in the present invention, by providing a diffractive structure on the optical function surface of the aberration correction element, a focus position shift with respect to a change in wavelength of the incident light beam, a change in spherical aberration with respect to a change in wavelength of the incident light beam, Since the change in spherical aberration accompanying the change in refractive index is suppressed, the recording / reproduction characteristics for the high-density optical disk can be maintained well even when the wavelength or temperature of the incident light beam changes.
In addition, by providing the condensing element arranged on the optical disc side exclusively with the refractive power with respect to the incident light beam, the protective layer thickness of the three types of optical discs with different standards is sufficient to ensure a working distance with respect to the CD. It becomes possible.
Furthermore, since a structure having a fine step such as a superposition type diffractive structure or a diffractive structure is formed on the optical function surface of the aberration correction element, the path is blocked by the step portion, contributing to the formation of a focused spot. It is possible to suppress the ratio of the luminous flux not to be transmitted, and to prevent a decrease in transmittance.

However, since there is a large wavelength difference between the light source for high-density optical discs and the light source for DVDs and CDs, the same-order diffracted light generated by the above-described diffraction structure is used as a light flux for recording / reproduction with respect to each optical disc. If used, sufficient diffraction efficiency cannot be obtained for three wavelengths. With respect to such a problem, as in the invention of claim 66, the diffraction order n2 of the diffracted light used for the DVD and the CD are different from the diffraction order n1 of the diffracted light used for the high-density optical disc. If the diffractive structure is designed so that the diffraction order n3 of the diffracted light used in this way has a lower order, it is possible to sufficiently secure the diffraction efficiency for the three wavelengths.
Specifically, the diffraction orders n1, n2, and n3 are preferably a combination as in the invention of claim 67, because high diffraction efficiency can be secured for all wavelengths λ1 to λ3.

When the aberration correction element is made of a material having a refractive index with respect to the wavelength λ1 in the range of 1.5 to 1.6 and an Abbe number in the d-line in the range of 50 to 60, As in the invention of claim 68, among the steps of the diffractive structure, the depth d1 of the step closest to the optical axis is set so as to satisfy any one of the expressions (40) to (44). Then, high diffraction efficiency can be secured for all wavelengths λ1 to λ3. The combination of the diffraction orders n1, n2, and n3 and the step d1 are such that (n1, n2, n3) = (2, 1, 1) corresponds to the equation (40), and (n1, n2, n3) = (4 , 2, 2) corresponds to the equation (41), (n1, n2, n3) = (6, 4, 3) corresponds to the equation (42), and (n1, n2, n3) = (8, 5 , 4) corresponds to the equation (43), and (n1, n2, n3) = (10, 6, 5) corresponds to the equation (44).
In general, an optical pickup device requires a larger laser power when recording information on an optical disc than when reproducing information. For this reason, when switching from reproduction to recording, a wavelength change may occur with a change in laser power (mode hopping). Such a mode hopping causes a focus position shift in the objective optical system, so that the defocus state continues until the focus servo responds. In the invention of claim 69, since the focus position shift in the blue-violet region of the condensing element is suppressed by the diffraction structure of the aberration correcting element, even when the blue-violet laser light source causes mode hopping, it is satisfactory. Condensing performance can be maintained.
In order to suppress the focus position shift in the blue-violet region of the condensing element, specifically, as in the invention of claim 70, the axial chromatic aberration is reduced by making the power in the paraxial axis of the diffractive structure positive. It is preferable to suppress it.

Further, in order to suppress the change in spherical aberration that occurs in the light converging element due to the change in the wavelength of the incident light beam, which becomes apparent when the NA of the optical element increases, the invention of claim 72 is specifically provided. Thus, when the wavelength of the incident light beam becomes longer, the spherical aberration changes in the direction of under-correction, and when the wavelength of the incident light beam becomes shorter, the wavelength of the spherical aberration changes in the direction of over-correction. It is preferable to suppress the spherical aberration change generated in the light converging element by providing the diffractive structure with the dependency.
In addition, in order to suppress the change in spherical aberration that occurs in the condensing element, which is a plastic lens, due to the change in refractive index, which becomes apparent when the NA of the optical element becomes large, when the wavelength of the incident light beam becomes long, It is preferable to give the diffraction structure wavelength dependency of the spherical aberration so that the spherical aberration changes in the overcorrection direction when the spherical aberration changes in the direction of insufficient correction and the wavelength of the incident light beam becomes short. In a condensing element that is a plastic lens, the refractive index decreases as the temperature rises, so the spherical aberration changes in the overcorrected direction, and the refractive index increases as the temperature decreases, so the spherical aberration changes in the undercorrected direction. On the other hand, the laser light source has a characteristic that the wavelength becomes longer as the temperature rises, and the wavelength becomes shorter as the temperature falls. If this characteristic is used, it becomes possible to cancel the spherical aberration change generated in the light converging element by giving the diffraction structure wavelength dependency of the spherical aberration as described above. In order to effectively suppress the change in spherical aberration that occurs in the condensing element, it is preferable to form the diffractive structure on an aspherical surface.

A diffractive structure for suppressing a change in spherical aberration that occurs in a condensing element with a temperature change is used to form a spot on the information recording surface of three optical discs. In the case of forming in the optical function region, it is necessary to have a diffractive structure as in the invention of claims 66 to 68. In such a case, it is impossible in principle to set the diffraction efficiency to 100% for all three wavelengths. Accordingly, as in the invention of claim 73, the optical functional surface of the aberration correction element is divided into a central optical functional region including the optical axis and a peripheral optical functional region surrounding the central optical functional region, It is preferable to form a diffractive structure only in the optical function region. For example, when the peripheral optical functional area is an optical functional area (for example, NA 0.60 to NA 0.85) corresponding to the NA of the DVD to the NA of the high-density optical disc, the optimized wavelength of the diffraction structure is set to the wavelength λ1. The diffraction efficiency with respect to the wavelength λ1 can be made 100%, and the transmittance with respect to the wavelengths λ2 and λ3 in the central optical function region that is a continuous aspheric surface where no diffraction structure is formed is high. It becomes possible. Since the spherical aberration increases in proportion to the fourth power of NA, the spherical aberration can be effectively corrected by the diffractive structure in the peripheral optical functional region without forming a diffractive structure in the central optical functional region having a small NA. .
As a specific shape of such a diffractive structure, a cross-sectional shape including an optical axis is a stepped shape as in the invention described in Item 74.
The specific shape of the diffractive structure may be a sawtooth shape in cross section including the optical axis, as in the invention described in Item 75.
In order to facilitate the processing of the mold of the aberration correction element, it is preferable to form the superposition type diffractive structure and the diffractive structure on different optical function surfaces as in the invention of claim 76.

According to a 77th aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And reproducing information from the second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source and / or Alternatively, information is recorded on a third optical information recording medium having a protective layer with a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. An optical element for an optical pickup device that performs reproduction and / or recording,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
At least one of the optical functional surfaces of the aberration correction element has an optical path difference providing structure comprising a central region including the optical axis and a plurality of annular zones divided by steps on the outside of the central region. Is formed.

According to the invention of claim 77, the optical functional surface of the aberration correction element is divided into a plurality of optical functional regions centered on the optical axis, and the superposition type diffractive structure is formed in the specific optical functional region. Since only one of the three wavelengths can be selectively diffracted and the other wavelengths can be transmitted without being diffracted, the arrangement of each annular zone of the superposition type diffractive structure can be set appropriately. Then, while correcting the spherical aberration caused by the difference in the thickness of the protective layer between the three types of optical disks, such as the high density optical disk, DVD, and CD, high transmittance for all three wavelengths ( (Diffraction efficiency) can be ensured. In addition, by making the diffraction orders of the three wavelengths different, the degree of freedom in optical design is expanded, or for a specific wavelength, the diffraction efficiency is extremely reduced to block specific wavelengths and transmit other wavelengths. It can play the role of a dichroic filter.
Further, in the present invention, by providing an optical path difference providing structure on the optical function surface of the aberration correcting element, a focus position shift with respect to the wavelength change of the incident light beam and a spherical aberration with respect to the wavelength change of the incident light beam generated in the light collecting element. Since the change of the spherical aberration due to the change and the change of the refractive index is suppressed, the recording / reproduction characteristics with respect to the high-density optical disk can be satisfactorily maintained even when the wavelength change or temperature change of the incident light beam occurs.
Further, by appropriately setting the amount of step between adjacent annular zones of the optical path difference providing structure, the protective layer thickness between a plurality of types of optical discs having different protective layer thicknesses as in the superposition type diffractive structure. By providing the function of suppressing the spherical aberration caused by the difference, it is possible to increase the degree of freedom in designing the optical element of the present invention.
In addition, by providing the condensing element arranged on the optical disc side exclusively with the refractive power with respect to the incident light beam, the protective layer thickness of the three types of optical discs with different standards is sufficient to ensure a working distance with respect to the CD. It becomes possible.
Furthermore, since a structure having a fine step, such as a superposition type diffractive structure or an optical path difference providing structure, is formed on the optical function surface of the aberration correction element, the path is blocked by the step portion to form a condensed spot. The ratio of the luminous flux that does not contribute to light can be suppressed, and the decrease in transmittance can be prevented.

  The invention described in Item 78 is the optical element for the optical pickup device described in Item 77, wherein both the light condensing element and the aberration correcting element are plastic lenses, and the optical path difference providing structure has an environmental temperature. Increases, the spherical aberration added to the first wavelength λ1 changes in the direction of insufficient correction, and when the environmental temperature decreases, the spherical aberration added to the first wavelength λ1 is corrected. It has a function of suppressing a spherical aberration change caused by a change in the refractive index of the light converging element due to a change in environmental temperature by having the temperature dependence of the spherical aberration that changes in an excessive direction.

  The invention according to claim 79 is the optical element for an optical pickup device according to claim 78, wherein, in the optical path difference providing structure, the annular zone adjacent to the outside of the center region is in relation to the center region. It is formed by shifting in the optical axis direction so as to shorten the optical path length, and the annular zone at the maximum effective diameter position is shifted in the optical axis direction so that the optical path length becomes longer with respect to the annular zone adjacent to the inner side. The annular zone at a position of 75% of the maximum effective diameter is shifted in the optical axis direction so that the optical path length becomes shorter with respect to the annular zone adjacent to the inside and the annular zone adjacent to the outside. It is characterized by being formed.

The invention described in Item 80 is the optical element for an optical pickup device described in any one of Items 77-79, wherein the first wavelength λ1 (μm), the second wavelength λ3 (μm), the Third wavelength λ3 (μm), depth d2 (μm) in the optical axis direction of the step closest to the optical axis among the steps of the optical path difference providing structure, refractive index N _{λ1 of the} aberration correction element with respect to the first wavelength _λ1 The refractive index N _{λ2 of} the aberration correction element with respect to the second wavelength λ1 and the refractive index N λ3 of the aberration correction element with respect to the third wavelength λ3 _{are represented} by the following expressions (45) to (47), respectively. , Φ2, and Φ3 satisfy the following expressions (48) to (51).
Φ1 = d2 (N _λ1 −1) / λ1 (45)
Φ2 = d2 (N _λ2 −1) / λ2 (46)
Φ3 = d2 (N _λ3 −1) / λ3 (47)
INT (Φ1) ≦ 10 (48)
0 ≦ | INT (Φ1) −Φ1 | ≦ 0.4 (49)
0 ≦ | INT (Φ2) −Φ2 | ≦ 0.4 (50)
0 ≦ | INT (Φ3) −Φ3 | ≦ 0.4 (51)
However, INT (Φi) (i = 1, 2, 3) is an integer obtained by rounding Φi.

  The invention according to Item 81 is the optical element for an optical pickup device according to any one of Items 77 to 80, wherein the superposition type diffractive structure is formed on one optical function surface of the aberration correction element. The optical path difference providing structure is formed on the other optical functional surface of the aberration correction element.

According to the 78th aspect of the invention, in order to suppress the change in spherical aberration caused by the change in the refractive index of the condensing element, which is a plastic lens, the aberration correction element is a plastic lens, and the refractive index is lowered. By forming an optical path difference providing structure that has a refractive index dependency of spherical aberration so that the spherical aberration changes in the overcorrection direction when the spherical aberration changes in the undercorrection direction and the refractive index increases. It becomes possible to cancel the spherical aberration change that occurs in the condensing element with the change. Thereby, even when the NA of the optical element becomes large, it is possible to provide an optical element having a small change in recording / reproducing characteristics with respect to a high-density optical disk accompanying a temperature change.
In addition, as in the present invention, when the spherical aberration change accompanying the temperature change of the condensing element is suppressed by the optical path difference providing structure, the change in the refractive index of the aberration correcting element is used, so the wavelength dependence of the diffractive structure is used. Unlike the case of suppressing the spherical aberration change of the condensing element, the effect of suppressing the spherical aberration works even if the wavelength of the laser light source does not change due to the temperature change.
A specific structure of such an optical path difference providing structure is that, as in the invention according to claim 79, the annular zone adjacent to the outside of the central region is arranged in the optical axis direction so that the optical path length is shorter than the central region. The annular zone at the maximum effective diameter position formed by shifting is formed by shifting in the optical axis direction so that the optical path length is longer with respect to the annular zone adjacent to the inside thereof, and the position of 75% of the maximum effective diameter. The ring zone in is a structure formed by shifting in the optical axis direction so that the optical path length is shorter with respect to the ring zone adjacent to the inside and the ring zone adjacent to the outside. With this structure, the spherical aberration changes in the direction of undercorrection when the refractive index is low, and the spherical aberration changes in the overcorrection direction when the refractive index is high. It is possible to provide the optical path difference giving structure.

The invention of claim 80, wherein the optical path difference providing structure is formed in a common optical functional region of light beams of three wavelengths used for forming spots on the information recording surfaces of the three optical disks. As shown in (4) to (51), the depth d2 of the level difference closest to the optical axis and the optical path differences Φ1 to Φ3 added to the wavelengths λ1 to λ3 by the level difference are expressed by equations (45) to (51). It is preferable to set so as to satisfy.
If these equations are not satisfied, the wavelength difference between the light source for the high-density optical disk and the light source for the DVD or CD is large, so high-order spherical aberration occurs for any wavelength. Although higher-order spherical aberration does not affect the recording / reproducing performance, it is substantially equivalent to a decrease in transmittance. If these equations are satisfied, the generation of higher-order spherical aberration can be suppressed for any wavelength, and the transmittance can be increased.
In order to facilitate the processing of the mold of the aberration correction element, it is preferable to form the superposition type diffractive structure and the optical path difference providing structure on separate optical function surfaces as in the invention of claim 81.

In the invention according to item 82, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And reproducing information from the second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source and / or Alternatively, information is recorded on a third optical information recording medium having a protective layer with a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. An optical element for an optical pickup device that performs reproduction and / or recording,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
The condensing element is a plastic lens having one lens element per group,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposition type diffractive structure is formed,
The paraxial power P1 (mm ⁻¹ ) of the aberration correction element with respect to the first wavelength λ1 satisfies the following expression (52).
P1> 0 (52)

The invention according to claim 83 is the optical element for the optical pickup device according to claim 82, wherein the aberration correction element is a plastic lens, and refraction in the paraxial direction of the aberration correction element with respect to the first wavelength λ1. The power PR (mm ⁻¹ ) satisfies the following expression (53).
PR> 0 (53)

  The invention according to an 84th aspect is the optical element for an optical pickup device according to any one of the 45th to 83rd aspects, wherein the optical functional region in which the superimposed diffractive structure is formed includes an optical axis. It is a functional area.

The invention according to claim 85 is the optical element for an optical pickup device according to claim 84, wherein the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm). In the superposition type diffractive structure formed in the optical functional region including the optical axis, the number N of the discontinuous steps formed in each annular zone, and the depth Δ of the discontinuous steps in the optical axis direction (Μm), the refractive index N _{λ1 of} the aberration correction element with respect to the first wavelength λ1, the refractive index N _{λ2 of} the aberration correction element with respect to the second wavelength λ1, and the refractive index N of the aberration correction element with respect to the third wavelength λ3. _{According to λ3} , φ1, φ2, and φ3 represented by the following equations (54) to (56) respectively satisfy the following equations (57) to (59).
φ1 = Δ (N _λ1 −1) (N + 1) / λ1 (54)
φ2 = Δ (N _λ2 −1) (N + 1) / λ2 (55)
φ3 = Δ ( _Nλ3−1 ) (N + 1) / λ3 (56)
0 ≦ | INT (φ1) −φ1 | ≦ 0.4 (57)
0 ≦ | INT (φ2) −φ2 | ≦ 0.4 (58)
0 ≦ | INT (φ3) −φ3 | ≦ 0.4 (59)
However, INT (φi) (i = 1, 2, 3) is an integer obtained by rounding off φi.

The invention described in Item 86 is the optical element for optical pickup device described in Item 85, wherein the φ1 and the number N of the discontinuous steps formed in each annular zone are the following (60) And (61) is satisfied.
φ1 ≦ 24 (60)
3 ≦ N ≦ 11 (61)

The invention according to an 87th aspect is the optical element for an optical pickup device for an optical pickup apparatus according to any one of the 84th to 86th aspects, wherein the superposition formed in an optical function region including the optical axis. The type diffractive structure provides an equivalent first optical action to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3, and the first optical effect is applied to the light flux having the second wavelength λ2. It is characterized in that a second optical action different from the mechanical action is given.

  According to an 88th aspect of the present invention, in the optical element for an optical pickup device according to the 87th aspect, the first optical action is performed on the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. The second optical action is first-order diffraction that diffracts the light beam having the second wavelength λ2 in the first-order direction. It is characterized by.

The invention according to Item 89 is the optical element for the optical pickup device according to Item 88, wherein the aberration correction element has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1. And the Abbe number at the d-line is formed from a material in the range of 50 to 60, and the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm), In the superposition type diffractive structure formed in the optical function region including the optical axis, the number N of the discontinuous steps formed in each annular zone while satisfying the following expressions (62) to (64), respectively. And the depth D (μm) in the optical axis direction of the annular zone is any one of the following formulas (65) to (68).
0.39 <λ1 <0.42 (62)
0.63 <λ2 <0.68 (63)
0.75 <λ3 <0.85 (64)
When N = 3, 4.1 ≦ D ≦ 4.8 (65)
When N = 4, 5.4 ≦ D ≦ 6.4 (66)
When N = 5, 7.0 ≦ D ≦ 7.9 (67)
When N = 6, 8.4 ≦ D ≦ 9.0 (68)

  According to a 90th aspect of the present invention, in the optical element for an optical pickup device according to the 87th aspect, the first optical action is performed on the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. The second optical action is second-order diffraction that diffracts the light beam having the second wavelength λ2 in the second-order direction. It is characterized by.

The invention according to item 91 is the optical element for optical pickup device according to item 90, wherein the aberration correction element has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1. And the Abbe number at the d-line is formed from a material in the range of 50 to 60, and the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm), In the superposition type diffractive structure formed in the optical function region including the optical axis, the number N of the discontinuous steps formed in each annular zone while satisfying the following equations (69) to (71). The depth D (μm) in the optical axis direction of the annular zone is any one of the following formulas (72) to (75).
0.39 <λ1 <0.42 (69)
0.63 <λ2 <0.68 (70)
0.75 <λ3 <0.85 (71)
When N = 8, 11.3 ≦ D ≦ 12.7 (72)
When N = 9, 12.8 ≦ D ≦ 14.1 (73)
When N = 10, 14.2 ≦ D ≦ 15.6 (74)
When N = 11, 15.7 ≦ D ≦ 17.2 (75)

  The invention according to Item 92 is the optical element for the optical pickup device according to any one of Items 84 to 91, wherein the superposition type diffractive structure is formed in all of the plurality of optical function regions. It is characterized by being.

The invention according to claim 93 is the optical element for an optical pickup device according to any one of claims 45 to 91, wherein at least one of the plurality of optical function areas includes the optical function area. The superposition type diffractive structure is not formed.

  The invention according to claim 94 is the optical element for an optical pickup device according to any one of claims 45 to 93, wherein the superposition type diffractive structure is formed on a plurality of optical functional surfaces of the aberration correction element. It is characterized by being.

The invention according to claim 95 is the optical element for an optical pickup device according to any one of claims 45 to 94, wherein the thickness t1 of the protective layer of the first optical information recording medium, and the second The thickness t2 of the protective layer of the optical information recording medium satisfies the following expression (76).
0.8 ≦ t1 / t2 ≦ 1.2 (76)

  According to a 96th aspect of the present invention, in the optical element for an optical pickup device according to the 95th aspect, the plurality of optical function areas are two optical function areas, and the optical function area is a light beam. The light flux of the first wavelength λ1 to the light flux of the third wavelength λ3 incident on the optical function area including the axis are respectively on the information recording surfaces of the first optical information recording medium to the third optical information recording medium. The light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 that form a good wavefront and enter the optical function region that does not include the optical axis of the two optical function regions, respectively, A good wavefront is formed on the information recording surface of the optical information recording medium and the second optical information recording medium.

  The invention according to claim 97 is the optical element for an optical pickup device according to claim 96, wherein the superposition type diffractive structure is provided in an optical function region that does not include the optical axis, of the two optical function regions. The diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light beam having the third wavelength λ3 is incident on the superimposed diffractive structure is 40% or less. Features.

  A 98th aspect of the present invention is the optical element for an optical pickup device according to the 96th or 97th aspect, wherein the superposition type diffraction is not included in the optical function area that does not include the optical axis, of the two optical function areas. The superposition type diffractive structure gives an equivalent optical action to the light beam having the first wavelength λ1 and the light beam having the second wavelength λ2, and the light beam having the third wavelength λ3. Thus, by giving an optical action different from the optical action, the light beam having the third wavelength λ3 transmitted through the superposition type diffractive structure is spotted on the information recording surface of the third optical information recording medium. The flare component does not contribute to formation.

  According to a 99th aspect of the present invention, in the optical element for an optical pickup device according to the 95th aspect, the plurality of optical functional areas are three optical functional areas, and among the three optical functional areas, a light The light flux of the first wavelength λ1 to the light flux of the third wavelength λ3 incident on the optical function area including the axis are respectively on the information recording surfaces of the first optical information recording medium to the third optical information recording medium. A favorable wavefront is formed, and among the three optical function regions, the light flux having the first wavelength λ1 and the second wavelength λ2 incident on the optical function region adjacent to the outside of the optical function region including the optical axis in the previous period. Each light beam forms a good wavefront on the information recording surfaces of the first optical information recording medium and the second optical information recording medium, and is incident on the outermost optical functional area among the three optical functional areas. The first wavelength λ1 The light beam forms a good wavefront on the information recording surface of the first optical information recording medium.

According to a 100th aspect of the present invention, in the optical element for an optical pickup device according to the 99th aspect, an optical functional region adjacent to the outside of the optical functional region including the optical axis among the three optical functional regions. Has a diffractive efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the third wavelength λ3 is incident on the superposed diffractive structure. It is characterized by being 40% or less.

  The invention according to claim 101 is the optical element for an optical pickup device according to claim 99 or 100, wherein an optical function adjacent to the outside of the optical function area including the optical axis among the three optical function areas. The superposition type diffractive structure is formed in the region, and the superposition type diffractive structure gives an equivalent optical action to the light flux of the first wavelength λ1 and the light flux of the second wavelength λ2, and By applying an optical action different from the optical action to the light beam having the three wavelengths λ3, the light beam having the third wavelength λ3 that has passed through the superposition type diffractive structure is transmitted to the third optical information recording medium. The flare component does not contribute to spot formation on the information recording surface.

  The invention according to claim 102 is the optical element for an optical pickup device according to any one of claims 99 to 101, wherein the outermost optical function region is the outermost optical function region of the three optical function regions. A superposition type diffractive structure is formed, and the diffraction efficiency η2 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the second wavelength λ2 is incident on the superposition type diffractive structure is 40%. The diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the third wavelength λ3 is incident is 40% or less.

  The invention according to Claim 103 is the optical element for an optical pickup device according to any one of Claims 99 to 102, wherein, of the three optical function areas, the outermost optical function area includes the optical element area. A superposition type diffractive structure is formed, and the superposition type diffractive structure has an optical action different from the optical action given to the light flux of the first wavelength λ1, and the light flux of the second wavelength λ2 By giving to the wavelength λ3, the light beams having the second wavelength λ2 and the third wavelength λ3 transmitted through the superposition type diffractive structure are respectively stored in the information on the second optical information recording medium and the third optical information recording medium. The flare component does not contribute to spot formation on the recording surface.

  According to a 104th aspect of the present invention, in the optical element for an optical pickup device according to any one of the 45th to 94th aspects, the thickness t1 of the protective layer of the first optical information recording medium, and the second The thickness t2 of the protective layer of the optical information recording medium satisfies the following expression (77). t1 / t2 ≦ 0.4 (77)

  The invention according to claim 105 is the optical element for the optical pickup device according to claim 104, wherein the plurality of optical function areas are three optical function areas, and among the three optical function areas, light The light flux of the first wavelength λ1 to the light flux of the third wavelength λ3 incident on the optical function area including the axis are respectively on the information recording surfaces of the first optical information recording medium to the third optical information recording medium. A favorable wavefront is formed, and among the three optical function regions, the light flux having the first wavelength λ1 and the second wavelength λ2 incident on the optical function region adjacent to the outside of the optical function region including the optical axis in the previous period. Each light beam forms a good wavefront on the information recording surfaces of the first optical information recording medium and the second optical information recording medium, and is incident on the outermost optical functional area among the three optical functional areas. The first wave The light flux of λ1 is characterized by forming a good wave front on the information recording surface of the first optical information recording medium.

  The optical element for an optical pickup device according to claim 105 is an optical functional area adjacent to the outside of the optical functional area including the optical axis, out of the three optical functional areas. Is formed with the diffractive efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the third wavelength λ3 is incident on the superposed diffractive structure. It is characterized by being 40% or less.

According to a 107th aspect of the present invention, in the optical element for an optical pickup device according to the 105th or 106th aspect, an optical function adjacent to the outside of the optical functional area including the optical axis among the three optical functional areas. The superposition type diffractive structure is formed in the region, and the superposition type diffractive structure gives an equivalent optical action to the light flux of the first wavelength λ1 and the light flux of the second wavelength λ2, and By applying an optical action different from the optical action to the light beam having the three wavelengths λ3, the light beam having the third wavelength λ3 that has passed through the superposition type diffractive structure is transmitted to the third optical information recording medium. The flare component does not contribute to spot formation on the information recording surface.

  108. The optical element for an optical pickup device according to any one of claims 105 to 107, wherein the outermost optical function region is the outermost optical function region of the three optical function regions. A superposition type diffractive structure is formed, and the diffraction efficiency η2 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the second wavelength λ2 is incident on the superposition type diffractive structure is 40%. The diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the third wavelength λ3 is incident is 40% or less.

  The invention according to claim 109 is the optical element for an optical pickup device according to any one of claims 105 to 108, wherein the outermost optical function area of the three optical function areas is not in the outermost optical function area. A superposition type diffractive structure is formed, and the superposition type diffractive structure has an optical action different from the optical action given to the light flux of the first wavelength λ1, and the light flux of the second wavelength λ2 By giving to the wavelength λ3, the light beams having the second wavelength λ2 and the third wavelength λ3 transmitted through the superposition type diffractive structure are respectively stored in the information on the second optical information recording medium and the third optical information recording medium. The flare component does not contribute to spot formation on the recording surface.

The invention according to claim 110 is the optical element for an optical pickup device according to any one of claims 45 to 109, wherein the paraxial power P1 (mm ⁻ of the aberration correcting element with respect to the first wavelength λ1 ^1), and satisfies the power P2 (mm ^-1) and has the following (78) below the paraxial of the light focusing element for said first wavelength .lambda.1.
| P1 / P2 | ≦ 0.2 (78)

  The invention described in Item 111 is the optical element for an optical pickup device described in any one of Items 45-110, wherein the aberration correction element is a plastic lens.

  The invention described in Item 112 is characterized in that in the optical element for an optical pickup device described in any one of Items 45-111, the condensing element is a plastic lens.

  The invention according to claim 113 is the optical element for an optical pickup device according to any one of claims 45 to 111, wherein the light condensing element is a glass lens.

  The invention according to claim 114 is the optical element for an optical pickup device according to any one of claims 45 to 111, wherein the condensing element disperses particles having a diameter of 30 nm or less in a plastic material. It is characterized by being molded using the material made.

  The invention according to claim 115 is the optical element for an optical pickup device according to any one of claims 45 to 114, wherein the condensing element includes the first wavelength λ1 and the first optical information recording medium. Aberration correction is performed so that the thickness is less than the Marshall limit with respect to the thickness t1 of the protective layer.

According to the invention of claim 82, the optical functional surface of the aberration correction element is divided into a plurality of optical functional regions centered on the optical axis, and the superposition type diffractive structure is formed in the specific optical functional region. Therefore, only one of the three wavelengths can be selectively diffracted, and the other wavelengths can be transmitted without being diffracted. In this case, high transmittance (for all three wavelengths) can be achieved while correcting the spherical aberration caused by the difference in the thickness of the protective layer between the three types of optical disks such as high density optical disk, DVD, and CD. (Diffraction efficiency) can be ensured. In addition, by making the diffraction orders of the three wavelengths different, the degree of freedom in optical design is expanded, or for a specific wavelength, the diffraction efficiency is extremely reduced to block specific wavelengths and transmit other wavelengths. It can play the role of a dichroic filter. Since the specific gravity of the plastic lens is smaller than that of the glass lens, the burden on the actuator that drives the objective optical system can be reduced, and the objective optical system can be tracked at high speed. In addition, a plastic lens manufactured by injection molding can be mass-produced with stable quality and high accuracy by producing a desired mold with good manufacture. However, when the NA of the objective optical system is increased, if the objective optical system is a plastic lens, the influence of the refractive index change accompanying the temperature change is increased. This is because the spherical aberration caused by the refractive index change increases in proportion to the fourth power of NA.

Therefore, in the present invention, the power P1 at the paraxial axis of the aberration correction element with respect to the wavelength λ1 is set to be positive so that the light beam with the wavelength λ1 is incident as the convergent light beam on the condensing element. In general, NA∞ (hereinafter referred to as converted NA) converted to infinite luminous flux incidence for a finite conjugate (magnification m ≠ 0) condensing element with a numerical aperture NA is NA∞ = NA (1-m). Can be expressed. Therefore, since the converted NA can be reduced in the condensing element where the magnification m> 0 where the convergent light beam is incident, it is possible to suppress a change in spherical aberration generated in the condensing element with a temperature change.
In addition, by providing the condensing element arranged on the optical disc side exclusively with the refractive power with respect to the incident light beam, the protective layer thickness of the three types of optical discs with different standards is sufficient to ensure a working distance with respect to the CD. It becomes possible.
Furthermore, since a structure having a fine step such as a superposition type diffractive structure or a diffractive structure is formed on the optical function surface of the aberration correction element, the path is blocked by the step portion, contributing to the formation of a focused spot. It is possible to suppress the ratio of the luminous flux not to be transmitted, and to prevent a decrease in transmittance.

In order to more effectively suppress a change in spherical aberration that occurs in the light converging element due to a temperature change, as in the invention according to claim 83, the aberration correction element is a plastic lens, and the aberration correction element for wavelength λ1 It is preferable to make the refractive power PR in the paraxial axis of the positive. Since the refractive index of the plastic lens decreases as the temperature rises, when the aberration correction element is a positive lens, the convergence of the incident light beam with respect to the condensing element becomes small. This is equivalent to a reduction in the magnification m of the condensing element, so that the spherical aberration changes in the direction of insufficient correction due to this change in magnification. On the other hand, in the light condensing element, when the temperature rises, the spherical aberration changes in the overcorrection direction, so that it is possible to cancel the spherical aberration change due to the change in magnification.
According to the invention of claim 84, by forming the superposition type diffractive structure in the optical functional region including the optical axis, only one of the three wavelengths is selectively diffracted and the other wavelengths are not diffracted. Therefore, if the arrangement of the annular zones of the superposition type diffractive structure is appropriately set, spherical aberration caused by the difference in the protective layer thickness between the high-density optical disc and the DVD, Spherical aberration that occurs due to the difference in the protective layer thickness between DVD and CD can be corrected.
It should be noted that the step amount Δ and the step number N of the superposition type diffractive structure are preferably combinations as shown in Tables 1 to 8 described later.

In the case of forming the superposition type diffractive structure in a common optical function region of light beams of three wavelengths used for forming spots on the information recording surfaces of the three optical discs, the invention of claim 85 exists. As described above, the optical path difference addition amounts φ1 to φ3 corresponding to the wavelengths λ1 to λ3 for one pitch constituted by the step depth Δ and N steps are satisfied to satisfy the equations (54) to (59). It is preferable to set to. This makes it possible to ensure high transmittance (diffraction efficiency) for all three wavelengths.
If φ1 becomes too large, the depth of one step becomes large. As a result, the depth Δ (N + 1) for one pitch becomes large, and if the number N of steps becomes too large, The width of the staircase structure becomes smaller. As a result, it becomes difficult to process the mold, and the problem that the fluctuation of the transmittance (diffraction efficiency) with respect to the minute wavelength change of the incident light flux becomes large becomes apparent. In order to avoid the manifestation of these problems, as in the invention of claim 86, the optical path difference added amount φ1 of one pitch with respect to the wavelength λ1 of the superposition type diffractive structure and each annular zone are formed. It is preferable that the step number N satisfies the expressions (60) and (61).

The superposition type diffractive structure effectively prevents spherical aberration caused by the difference in the protective layer thickness between the high-density optical disc and the DVD, or spherical aberration caused by the difference in the protective layer thickness between the DVD and CD. In order to correct this, as in the invention of claim 87, an equivalent optical action is given to the wavelength λ1 and the wavelength λ3 by the superposition type diffractive structure, and a different optical is applied to the wavelength λ2. In order to provide a specific effect, the depth Δ of the step of the superposition type diffractive structure and the optical path difference addition amounts φ1 to φ3 for each wavelength of wavelengths λ1 to λ3 for one pitch composed of N steps are determined. Is preferred.
Thus, while maintaining the magnification m1 for the high density optical disc and the magnification m2 for the DVD substantially the same, the spherical aberration caused by the difference in the protective layer thickness between the high density optical disc and the DVD is corrected, or the magnification m2 for the DVD. It is possible to correct the spherical aberration caused by the difference in the protective layer thickness between the DVD and the CD while the magnification m3 with respect to the CD is substantially the same.

Specifically, as in the invention described in Item 88, the superposition type diffractive structure does not substantially give an optical path difference between the adjacent annular zones with respect to the wavelengths λ1 and λ3 (0 For the second order diffraction) and the wavelength λ2, it is preferable that the first order diffracted light is generated by providing an optical path difference between adjacent annular zones.
More specifically, as in the invention according to Item 89, the aberration correcting element has a refractive index with respect to the wavelength λ1 in the range of 1.5 to 1.6 and an Abbe number at the d-line of 50. When formed from a material in the range of ˜60, the number N of steps formed in each annular zone and the depth D = Δ (N + 1) for one pitch constituted by N steps. ) Is preferably set to satisfy any one of formulas (65) to (68).

It should be noted that equations (65) to (68), which are preferable combinations of the number N of steps formed in each annular zone and the depth D of one pitch formed by N steps, are shown in Table 1 described later. Corresponds to the expression (65), Table 2 corresponds to the expression (66), Table 3 corresponds to the expression (67), and Table 4 corresponds to the expression (68).
As a result, for the wavelengths λ1 and λ3, zero-order diffracted light that does not substantially give an optical path difference between adjacent annular zones is given, and for the wavelength λ2, an optical path difference is given between adjacent annular zones. Can generate first-order diffracted light and can ensure high transmittance (diffraction efficiency) for all wavelengths λ1 to λ3.

Further, as in the invention of claim 90, the superposition type diffractive structure does not substantially give an optical path difference between adjacent annular zones with respect to the wavelengths λ1 and λ3 (0th order diffraction), For the wavelength λ2, a structure may be adopted in which second-order diffracted light is generated by providing an optical path difference between adjacent annular zones.
In this case, as in the invention described in claim 91, the number N of steps formed in each annular zone and the depth D = Δ (N + 1) for one pitch constituted by N steps. (72) to (75)
It is preferable to set so as to satisfy any one of the formulas.
As a result, for the wavelengths λ1 and λ3, zero-order diffracted light that does not substantially give an optical path difference between adjacent annular zones is given, and for the wavelength λ2, an optical path difference is given between adjacent annular zones. Can generate second-order diffracted light and can ensure high transmittance (diffraction efficiency) for all wavelengths λ1 to λ3.
Note that Table 5 described later corresponds to Expression (72), Table 6 corresponds to Expression (73), Table 7 corresponds to Expression (74), and Table 8 corresponds to Expression (75).

Further, as in the invention of claim 92, the superposition type diffractive structure may be formed not only in the optical function region including the optical axis but also in all the optical function regions.
Alternatively, as in the invention of claim 93, there is an optical functional region in which the superimposed diffractive structure is formed only in the necessary optical functional region, and the superimposed diffractive structure is not formed, according to the function to be given to the superimposed diffractive structure. There may be.
Furthermore, as in the invention of claim 94, the superposition type diffractive structure may be formed on a plurality of optical functional surfaces of the aberration correction element. In this case, each step structure formed in each annular zone Therefore, there is an advantage that the die processing by SPDT is facilitated, and that the diffraction efficiency reduction due to the shape error of the die does not become too large with respect to the wavelength λ1 in the blue-violet region.
According to the invention of claim 95, information is recorded / reproduced by an objective optical system with NA of 0.65, and a standard high-density optical disc having a protective layer thickness of about 0.6 mm, a DVD and a CD are used. The optical element having the superposition type diffractive structure of the present invention can also be applied to a compatible pickup device.
In such a case, as in the invention of claim 96, when the effective diameter for the wavelength λ1 of the aberration correction element is the same as the effective diameter for the wavelength λ2, the optical function surface of the aberration correction element is effective for the wavelength λ3. It is preferable to divide into two optical function areas, an optical function area including an optical axis corresponding to the diameter and an optical function area surrounding the periphery.

Then, as in the invention of claim 97, a superposition type diffractive structure is formed in an optical function region corresponding to the effective diameters for the wavelengths λ1 and λ2 from the effective diameter for the wavelength λ3, and each annular zone of the superposition type diffractive structure. The number N of steps formed inside and the depth D corresponding to one pitch composed of N steps are set appropriately, so that the light beams having wavelengths λ1 and λ2 are transmitted with high transmittance (diffraction efficiency). Thus, it is preferable that the diffraction efficiency with respect to the light beam having the wavelength λ3 is made extremely small so as to have the role of a dichroic filter.
As a result, since the aperture is automatically limited to the CD, an optical element having a simple configuration that does not require an aperture limiting element as a separate member can be provided.
Examples of such a superposition type diffractive structure include structures shown in Tables 11 to 13 described later.
As described above, when the superposition type diffractive structure formed in the optical function region corresponding to the effective diameters for the wavelengths λ1 and λ2 from the effective diameter for the wavelength λ3 is provided with the aperture limiting function, the invention according to the 98th aspect is provided. In addition, an optical effect equivalent to that of the light beams having the wavelengths λ1 and λ2 is given to the light beam having the wavelength λ3, and a different optical action is given to the light flux having the wavelength λ3, and the superposition type diffractive structure is transmitted. It is preferable that the light flux having the wavelength λ3 is a flare component that does not contribute to spot formation on the information recording surface of the CD.
A specific example of such a superposition type diffractive structure is as shown in Table 11 for diffracting only the light beam having the wavelength λ3 in the ± second order direction without substantially giving an optical path difference to the light beams having the wavelengths λ1 and λ2. Structure.

On the other hand, when the effective diameter for the wavelength λ1 of the aberration correction element is different from the effective diameter for the wavelength λ2, the optical function surface of the aberration correction element is within the effective diameter for the wavelength λ3 as in the invention of claim 99. An optical functional area including the corresponding optical axis, an optical functional area corresponding to the effective diameter for the wavelength λ2 from the effective diameter for the wavelength λ3 surrounding the periphery, and an effective for the wavelength λ1 from the effective diameter for the wavelength λ2 surrounding the periphery It is preferable to divide the optical function region into three optical function regions corresponding to the diameter. As in the invention of claim 100, the optical function region corresponding to the effective diameter with respect to the wavelength λ2 from the effective diameter with respect to the wavelength λ3, A superposition type diffractive structure is formed, and the number N of steps formed in each annular zone of the superposition type diffractive structure and a depth D corresponding to one pitch composed of N steps are appropriately set. Thus, it is preferable that the light beams having the wavelengths λ1 and λ2 are transmitted with high transmittance (diffraction efficiency), and that the diffraction efficiency for the light beam having the wavelength λ3 is made extremely small so as to serve as a dichroic filter.
As a result, since the aperture is automatically limited to the CD, an optical element having a simple configuration that does not require an aperture limiting element as a separate member can be provided.
Examples of such a superposition type diffractive structure include structures shown in Tables 11 to 13 described later.

As described above, when the superposition type diffractive structure formed in the optical function region corresponding to the effective diameter for the wavelength λ2 from the effective diameter for the wavelength λ3 has an aperture limiting function, The wavelength transmitted through the superposition type diffractive structure as a structure that gives an equivalent optical action to the light flux of wavelength λ1 and wavelength λ2 and gives an optical action different from that of the light flux of wavelength λ3. It is preferable that the light flux of λ3 is a flare component that does not contribute to spot formation on the information recording surface of the CD.
A specific example of such a superposition type diffractive structure is as shown in Table 11 for diffracting only the light beam having the wavelength λ3 in the ± second order direction without substantially giving an optical path difference to the light beams having the wavelengths λ1 and λ2. Structure.
Furthermore, as in the invention of claim 102, a superposition type diffractive structure is formed in an optical function region corresponding to an effective diameter for wavelength λ1 from an effective diameter for wavelength λ2, and in each annular zone of this superposition type diffractive structure. The number N of the formed steps and the depth D corresponding to one pitch formed by the N steps are appropriately set so that the light beam having the wavelength λ1 is transmitted with high transmittance (diffraction efficiency), and the wavelength λ2 It is preferable to have the role of a dichroic filter by extremely reducing the diffraction efficiency with respect to the light beam of λ3.
Thereby, since the aperture limitation for the CD and the DVD is automatically performed, an optical element having a simple configuration that does not require the aperture limiting element as a separate member can be provided.

As described above, when the superposition type diffractive structure formed in the optical function region corresponding to the effective diameter for the wavelength λ1 from the effective diameter for the wavelength λ2 has an aperture limiting function, As a structure that gives an optical action different from that of the light beam of wavelength λ1 to the light beams of wavelength λ2 and wavelength λ3, the light beams of wavelengths λ2 and λ3 that have passed through the superposition type diffractive structure are onto the information recording surfaces of DVD and CD. It is preferable that the flare component does not contribute to spot formation.
A specific example of such a superposition type diffractive structure diffracts the light beam having the wavelength λ2 in the −2 order direction without substantially giving an optical path difference to the light beam having the wavelength λ1, and the light beam having the wavelength λ3 is ± It is the structure of Table 14 diffracted in the third-order direction.
In the inventions of claims 99 to 103 described above, the function and effect have been described by taking as an example the case where the effective diameter for the wavelength λ1 is larger than the effective diameter for the wavelength λ2. However, the effective diameter for the wavelength λ2 is Even when the diameter is larger than the effective diameter, the same effect can be provided.

According to the invention of claim 104, a standard high-density optical disc (for example, a Blu-ray disc) in which information is recorded / reproduced by an objective optical system of NA 0.85, and the thickness of the protective layer is about 0.1 mm; The optical element having the superposition type diffractive structure of the present invention can also be applied to a pickup device compatible with DVD and CD.
In such a case, as in the invention of claim 105, the optical function surface of the aberration correcting element is made effective for the optical function region including the optical axis corresponding to the effective diameter with respect to the wavelength λ3 and the wavelength λ3 surrounding the optical function region. It is preferable to divide the optical function region into an optical function region corresponding to the effective diameter corresponding to the wavelength λ2 from the diameter and further to an optical function region corresponding to the effective diameter corresponding to the wavelength λ1 from the effective diameter corresponding to the wavelength λ2 surrounding the periphery.

Then, as in the invention of claim 106, a superposition type diffractive structure is formed in an optical function region corresponding to an effective diameter for wavelength λ2 from an effective diameter for wavelength λ3, and in each annular zone of this superposition type diffractive structure. The number N of the formed steps and the depth D corresponding to one pitch formed by the N steps are appropriately set so that the light beams having the wavelengths λ1 and λ2 are transmitted with high transmittance (diffraction efficiency), It is preferable to provide a role of a dichroic filter by extremely reducing the diffraction efficiency with respect to the light beam having the wavelength λ3.
As a result, since the aperture is automatically limited to the CD, an optical element having a simple configuration that does not require an aperture limiting element as a separate member can be provided.
Examples of such a superposition type diffractive structure include structures shown in Tables 11 to 13 described later.
As described above, when the superposition type diffractive structure formed in the optical function region corresponding to the effective diameter with respect to the wavelength λ2 from the effective diameter with respect to the wavelength λ3 has an aperture limiting function, as in the invention of claim 107, The wavelength transmitted through the superposition type diffractive structure as a structure that gives an equivalent optical action to the light flux of wavelength λ1 and wavelength λ2 and gives an optical action different from that of the light flux of wavelength λ3. It is preferable that the light flux of λ3 is a flare component that does not contribute to spot formation on the information recording surface of the CD.
A specific example of such a superposition type diffractive structure is as shown in Table 11 for diffracting only the light beam having the wavelength λ3 in the ± second order direction without substantially giving an optical path difference to the light beams having the wavelengths λ1 and λ2. Structure.

Furthermore, as in the invention of claim 108, a superposition type diffractive structure is formed in an optical functional region corresponding to an effective diameter for wavelength λ1 from an effective diameter for wavelength λ2, and in each annular zone of this superposition type diffractive structure By appropriately setting the number N of the formed steps and the depth D corresponding to one pitch formed by the N steps, the light beam having the wavelength λ1 is transmitted with high transmittance (diffraction efficiency), and the wavelength λ2 It is preferable to have the role of a dichroic filter by extremely reducing the diffraction efficiency with respect to the light beam of λ3.
Thereby, since the aperture limitation for the CD and the DVD is automatically performed, an optical element having a simple configuration that does not require the aperture limiting element as a separate member can be provided.
As described above, when the superposition type diffractive structure formed in the optical function region corresponding to the effective diameter for the wavelength λ1 from the effective diameter for the wavelength λ2 has an aperture limiting function, as in the invention of claim 109, As a structure that gives an optical action different from that of the light beam of wavelength λ1 to the light beams of wavelength λ2 and wavelength λ3, the light beams of wavelengths λ2 and λ3 that have passed through the superposition type diffractive structure are onto the information recording surfaces of DVD and CD. It is preferable that the flare component does not contribute to spot formation.
A specific example of such a superposition type diffractive structure diffracts the light beam having the wavelength λ2 in the −2 order direction without substantially giving an optical path difference to the light beam having the wavelength λ1, and the light beam having the wavelength λ3 is ± It is the structure of Table 14 diffracted in the third-order direction.

Further, as in the invention of claim 110, it is preferable to set the paraxial power P1 of the aberration correcting element and the paraxial power P2 of the light converging element for the wavelength λ1 so as to satisfy the expression (78). .
As a result, the light condensing element arranged on the optical disk side can have a refractive power with respect to the incident light beam, so that among the three types of optical disks of different standards, the protective layer has the largest working distance with respect to the CD. Can be secured.
Furthermore, the ratio of the light flux that does not contribute to the formation of the focused spot can be suppressed because the path is blocked by the step portion of the superposition type diffractive structure, the diffractive structure, or the optical path difference providing structure, and the decrease in transmittance can be prevented.
As in the invention of claim 111, when the aberration correction element is a plastic lens, it is preferable because transferability at the time of molding a fine structure such as a superposition type diffractive structure, a diffractive structure or an optical path difference providing structure can be improved. .

According to the invention of claim 112, when the light condensing element is a plastic lens, mass production with stable quality and high accuracy can be achieved. If the light condensing element having a large light condensing power is a plastic lens, the influence of the refractive index change due to the temperature change becomes large, but the aberration correcting element used in combination with this is as described in claims 64, 76, 81. With this configuration, it is possible to effectively suppress spherical aberration due to a change in refractive index.
On the other hand, as in the invention of claim 113, when the light condensing element is a glass lens, it is possible to obtain a light condensing element having high reliability with respect to light resistance, temperature resistance, transmittance, etc. for light in the blue-violet region. it can.
If a glass glass material having a glass transition point Tg of 400 ° C. or lower is used as the glass lens, it is possible to mold at a relatively low temperature, thereby extending the life of the mold. Thereby, the manufacturing cost of a condensing element can be reduced.
Examples of such a glass material having a low glass transition point Tg include K-PG325 and K-PG375 (both product names) manufactured by Sumita Optical Glass Co., Ltd.

但し、ｎはレーザ光源の波長に対する前記集光レンズの屈折率であり、αは集光素子の線膨張係数であり、[R]は集光素子の分子屈折力である。
一般的なプラスチック材料の場合は、第１項に比べて第２項の寄与が小さいので第２項はほぼ無視出来る。たとえば、アクリル樹脂（ＰＭＭＡ）の場合、線膨張係数αは７×１０^-5である、上式に代入すると、Ａ＝−１２×１０^-5となり、実測値と概ね一致する。
ここで、本発明での集光素子では、直径が３０ｎｍ以下の微粒子プラスチック材料中に分散させることにより、実質的に上式の第２項の寄与を大きくし、第１項の線膨張による変化と打ち消しあうようにさせている。 Further, as a material for the light collecting element, a material in which particles having a diameter of 30 nm or less are dispersed in a plastic material as in the invention of claim 114 may be used.
By uniformly mixing an inorganic material whose refractive index increases as the temperature rises with a plastic material whose refractive index increases as the temperature rises, it becomes possible to cancel the temperature dependence of both refractive indices. Thereby, an optical material having a small refractive index change accompanying a temperature change while maintaining the moldability of the plastic material (hereinafter, such an optical material is referred to as “athermal resin”).
Here, the temperature change of the refractive index of the condensing element will be described. The rate of change of the refractive index with respect to the temperature change is obtained by differentiating the refractive index n with respect to the temperature t based on the Lorentz-Lorenz formula.
It is represented by A shown in Equation 2 below.

However, n is the refractive index of the said condensing lens with respect to the wavelength of a laser light source, (alpha) is a linear expansion coefficient of a condensing element, [R] is the molecular refractive power of a condensing element.
In the case of a general plastic material, since the contribution of the second term is smaller than that of the first term, the second term can be almost ignored. For example, in the case of acrylic resin (PMMA), the linear expansion coefficient α is 7 × 10 ^{−5, and if} it is substituted into the above equation, A = −12 × 10 ⁻⁵ , which substantially matches the actual measurement value.
Here, in the condensing element of the present invention, the dispersion of the fine particle plastic material having a diameter of 30 nm or less substantially increases the contribution of the second term of the above formula, and the change due to the linear expansion of the first term. To cancel each other.

Specifically, it is preferable to suppress the refractive index change rate with respect to the temperature change, which was conventionally about −12 × 10 ⁻⁵ , to an absolute value of less than 10 × 10 ⁻⁵ . More preferably, it is preferably less than 8 × 10 ⁻⁵ , and more preferably less than 6 × 10 ⁻⁵ , in order to reduce the change in spherical aberration accompanying the temperature change of the condensing element.
For example, by dispersing fine particles of niobium oxide (Nb 2 O 5) in acrylic resin (PMMA), the dependency of the refractive index change on the temperature change can be eliminated.
The plastic material used as a base material has a volume ratio of 80 and niobium oxide in a ratio of about 20, and these are uniformly mixed. There is a problem that the fine particles are likely to aggregate, but a technique of applying a charge to the particle surface to disperse the particles is also known, and a necessary dispersion state can be generated.
This volume ratio can be appropriately increased or decreased in order to control the rate of change in refractive index with respect to temperature change, and a plurality of types of nano-sized inorganic particles can be blended and dispersed.

The volume ratio is 80:20 in the above example, but can be appropriately adjusted between 90:10 and 60:40. If the volume ratio is smaller than 90:10, the effect of suppressing the change in refractive index is reduced. Conversely, if the volume ratio exceeds 60:40, a problem arises in the moldability of the athermal resin, which is not preferable.
The fine particles are preferably inorganic and more preferably oxides. And it is preferable that it is an oxide which the oxidation state is saturated and does not oxidize any more.
It is preferable to be an inorganic substance in order to keep the reaction with a plastic material, which is a high molecular organic compound, low. Can be prevented. In particular, oxidation is likely to be accelerated under the severe condition of being irradiated with a blue-violet laser at a high temperature. However, with such an inorganic oxide, it is possible to prevent transmittance deterioration and wavefront aberration deterioration due to oxidation.

When the diameter of the fine particles dispersed in the plastic material is large, the incident light beam is easily scattered and the transmittance of the light collecting element is lowered. In a blue-violet laser used for recording / reproducing information in a high-density optical disk, the laser power for obtaining stable laser oscillation for a long time is about 30 mW. This is disadvantageous from the standpoint of speeding up information recording and handling multi-layer discs. Therefore, the diameter of the fine particles dispersed in the plastic material is preferably 20 nm or less, and more preferably 10 to 15 nm or less in order to prevent a decrease in transmittance of the light collecting element.
In general, the shorter the wavelength and the larger the NA, the more difficult the optical element is to manufacture. Therefore, as in the invention of claim 115, the light converging element is combined with the aberration correcting element so that the aberration correction is optimized with respect to the wavelength λ1 of the high-density optical disk and the thickness t1 of the protective layer. In such a case, it is preferable to facilitate the performance as an optical element for a high-density optical disk.

In the invention described in Item 116, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 by using a light beam having a first wavelength λ1 emitted from the first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an optical pickup for recording,
The optical pickup device has an objective for condensing the light beams of the first wavelength λ1 to the third wavelength λ3 on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, respectively. Having an optical system,
The optical element according to any one of claims 45 to 115 is used as the objective optical system.

The invention described in claim 117 is equipped with the optical pickup device described in claim 116, records information on the first optical information recording medium to the third optical information recording medium, and the first optical information recording. It is possible to execute at least one of reproduction of information on the medium to the third optical information recording medium.
In the invention described in Item 118, information is reproduced and / or recorded on the first optical information recording medium having the protective layer having the thickness t1, using the light beam having the first wavelength λ1 emitted from the first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an aberration correction element for an optical pickup device that performs recording,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposition type diffractive structure is formed.

The invention according to claim 119 is the aberration correction element for an optical pickup device according to claim 118, wherein the optical function region in which the superposition type diffractive structure is formed is an optical function region including an optical axis, The diffractive power at the paraxial axis of the superposition type diffractive structure with respect to the second wavelength λ2 is negative.
According to a 120th aspect of the present invention, in the aberration correction element for an optical pickup device according to the 118th or 119th aspect, the optical functional region in which the superposition type diffractive structure is formed is an optical functional region including an optical axis. The superposition type diffractive structure adds an uncorrected spherical aberration to the second wavelength λ2.
The invention according to claim 121 is the aberration correction element for an optical pickup device according to claim 118, wherein the optical functional region in which the superposition type diffractive structure is formed is an optical functional region including an optical axis, The diffractive power in the paraxial axis of the superposition type diffractive structure with respect to the second wavelength λ2 is positive.

The invention according to claim 122 is the aberration correction element for an optical pickup device according to claim 118 or 121, wherein the optical function region in which the superposition type diffractive structure is formed is an optical function region including an optical axis. The superposition type diffractive structure adds overcorrected spherical aberration to the second wavelength λ2.
The invention described in claim 123 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1, using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an aberration correction element for an optical pickup device that performs recording,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
The first light flux λ1 and the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps among the discontinuous steps formed in each annular zone in the superposition type diffractive structure are as follows: (79) and (80) are satisfied.
0.39 μm <λ1 <0.42 μm (79)
P> 3 μm (80)

The invention according to claim 124 is the aberration correction element for an optical pickup device according to claim 123, wherein in the superposition type diffractive structure, among the discontinuous steps formed in each annular zone, adjacent steps are provided. The minimum value P of the interval in the direction perpendicular to the optical axis between them satisfies the following expression (81).
P> 5 μm (81)
The invention according to claim 125 is the aberration correction element for an optical pickup device according to claim 124, wherein in the superposition type diffractive structure, among the discontinuous steps formed in each annular zone, adjacent steps are provided. The minimum value P of the interval in the direction perpendicular to the optical axis between the two satisfies the following expression (82).
P> 10 μm (82)
According to a 126th aspect of the present invention, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an aberration correction element for an optical pickup device that performs recording,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
When the optical path difference added to the transmitted wavefront by the superposition type diffractive structure is defined by the above equation 1, B ₂
And B ₄ have different signs.

The invention according to claim 127 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an aberration correction element for an optical pickup device that performs recording,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function areas, at least two optical function areas are provided with a plurality of ring zones each having a predetermined number of discontinuous steps formed continuously around the optical axis. A superposed diffractive structure is formed,
In the superposition type diffractive structure, one of the number N of the discontinuous steps formed in each annular zone and the depth Δ (μm) of the discontinuous steps in the optical axis direction is determined for each optical function region. It is characterized by being different.

According to the invention of claim 128, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an aberration correction element for an optical pickup device that performs recording,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of ring-shaped optical function regions around the optical axis, and at least of the plurality of ring-shaped optical function regions. In one optical functional region, a superposition type diffractive structure is formed, which is a structure in which a plurality of annular zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is formed with a diffractive structure composed of a plurality of annular zones divided by a step around the optical axis.

The invention according to claim 129 is the aberration correction element for an optical pickup device according to claim 128, wherein the depth of the step of the diffractive structure is diffracted light generated when a light beam having the first wavelength λ1 is incident. The diffraction order n2 of the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light beam having the second wavelength λ2 is incident on the diffraction order n1 of the diffracted light having the maximum diffraction efficiency, The diffraction order n3 of the diffracted light having the maximum diffraction efficiency out of the diffracted light generated when the light beam having the third wavelength λ3 is incident is designed to be lower. .
The invention according to claim 130 is the aberration correcting element for an optical pickup device according to claim 129, wherein the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm). Satisfy the following equations (83) to (85), and the combination of the diffraction order n1, the diffraction order n2, and the diffraction order n3 is (n1, n2, n3) = (2, 1, 1) , (4, 2, 2,), (6, 4, 3), (8, 5, 4), or (10, 6, 5).
0.39 <λ1 <0.42 (83)
0.63 <λ2 <0.68 (84)
0.75 <λ3 <0.85 (85)

The invention according to claim 131 is the aberration correction element for an optical pickup device according to claim 129 or 130, wherein the aberration correction element has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1. And the depth d1 of the step closest to the optical axis among the steps of the diffractive structure is expressed by the following equation (86). ) To (90).
1.2 μm <d1 <1.7 μm (86)
2.6 μm <d1 <3.0 μm (87)
4.4 μm <d1 <5.0 μm (88)
5.6 μm <d1 <6.5 μm (89)
6.9 μm <d1 <8.1 μm (90)
The invention according to claim 132 is the aberration correcting element for an optical pickup device according to any one of claims 128 to 131, wherein the diffraction power PD0 (mm) in the paraxial direction of the diffractive structure with respect to the first wavelength λ1. ^-1 ), diffractive power PD1 (mm ^-1 ) in the paraxial direction for a wavelength 10 nm longer than the first wavelength λ1 of the diffractive structure, paraxial for the wavelength of the diffractive structure 10 nm shorter than the first wavelength λ1 Is characterized in that the diffraction power PD2 (mm ⁻¹ ) satisfies the following expression (91).
PD2 <PD0 <PD1 (91)

The invention according to claim 133 is the aberration correction element for an optical pickup device according to any one of claims 128 to 132, wherein the diffractive structure is formed when the first wavelength λ1 is changed to a longer wavelength side. Is characterized in that the spherical aberration has a wavelength dependency such that the spherical aberration changes in the overcorrection direction when the spherical aberration changes in the undercorrection direction and the first wavelength λ1 changes to the short wavelength side. And
The invention according to claim 134 is the aberration correction element for an optical pickup device according to claim 133, wherein at least one of the optical function surfaces of the aberration correction element includes a central optical function including an optical axis. It is divided into a region and a peripheral optical functional region surrounding the periphery of the central optical functional region, and the diffractive structure is formed only in the peripheral optical functional region. The invention according to claim 135 is the aberration correction element for an optical pickup device according to any one of claims 128 to 134, wherein the cross-sectional shape including the optical axis of the diffractive structure is a step shape. And

The invention according to claim 136 is the aberration correction element for an optical pickup device according to any one of claims 128 to 134, wherein a cross-sectional shape including the optical axis of the diffractive structure is a sawtooth shape. And
The invention according to claim 137 is the aberration correction element for an optical pickup device according to any one of claims 128 to 136, wherein the superposition type diffractive structure is formed on one optical functional surface of the aberration correction element. The diffractive structure is formed on the other optical functional surface of the aberration correction element.

In the invention according to claim 138, information is reproduced and / or recorded on the first optical information recording medium having the protective layer having the thickness t1 by using the light beam having the first wavelength λ1 emitted from the first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an aberration correction element for an optical pickup device that performs recording,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
At least one of the optical functional surfaces of the aberration correction element has an optical path difference providing structure comprising a central region including the optical axis and a plurality of annular zones divided by steps on the outside of the central region. Is formed.

The invention according to claim 139 is the aberration correction element for an optical pickup device according to claim 138, wherein the optical path difference providing structure adds to the first wavelength λ1 when the environmental temperature rises. The spherical aberration has a temperature dependency such that the spherical aberration added to the first wavelength λ1 changes in the overcorrection direction when the spherical aberration changes in the undercorrection direction and the environmental temperature decreases. Features.
The invention according to claim 140 is the aberration correction element for an optical pickup device according to claim 139, wherein, in the optical path difference providing structure, the annular zone adjacent to the outside of the central region is in relation to the central region. It is formed by shifting in the optical axis direction so as to shorten the optical path length, and the annular zone at the maximum effective diameter position is shifted in the optical axis direction so that the optical path length becomes longer with respect to the annular zone adjacent to the inner side. The annular zone at a position of 75% of the maximum effective diameter is shifted in the optical axis direction so that the optical path length becomes shorter with respect to the annular zone adjacent to the inside and the annular zone adjacent to the outside. It is characterized by being formed.

The invention according to claim 141 is the aberration correction element for an optical pickup device according to any one of claims 138 to 140, wherein the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the The third wavelength λ3 (μm), the depth d2 (μm) of the step closest to the optical axis among the steps of the optical path difference providing structure, the refractive index N _{λ1 with} respect to the first wavelength λ1 of the aberration correcting element. , the aberration correcting refractive index N _.lambda.2 for said second wavelength λ1 of the _element, the refractive index N _{[lambda] 3} for the third wavelength [lambda] 3 of the aberration correcting element, are expressed by the following (92) to (94) below Φ1 , Φ2, and Φ3 satisfy the following expressions (95) to (98).
Φ1 = d2 · (N _λ1 −1) / λ1 (92)
Φ2 = d2 · (N _λ2 −1) / λ2 (93)
Φ3 = d2 · (N _λ3 −1) / λ3 (94)
INT (Φ1) ≦ 10 (95)
0 ≦ | INT (Φ1) −Φ1 | ≦ 0.4 (96)
0 ≦ | INT (Φ2) −Φ2 | ≦ 0.4 (97)
0 ≦ | INT (Φ3) −Φ3 | ≦ 0.4 (98)
However, INT (Φi) (i = 1, 2, 3) is an integer obtained by rounding Φi.

The invention according to claim 142 is the aberration correction element for an optical pickup device according to any one of claims 138 to 141, wherein the superposition type diffractive structure is formed on one optical functional surface of the aberration correction element. The optical path difference providing structure is formed on the other optical functional surface of the aberration correction element.
The invention according to claim 143 provides the aberration correction element for an optical pickup device according to any one of claims 118 to 142, wherein the optical functional region in which the superposition type diffractive structure is formed includes an optical axis. It is a functional area.

The invention according to claim 144 is the aberration correction element for an optical pickup device according to claim 143, wherein the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm). In the superposition type diffractive structure formed in the optical function region including the optical axis, the number N of the discontinuous steps formed in each annular zone, and the depth Δ of the discontinuous steps in the optical axis direction (Μm), the refractive index N _{λ1 of} the aberration correction element with respect to the first wavelength λ1, the refractive index N _{λ2 of} the aberration correction element with respect to the second wavelength λ1, and the refractive index N of the aberration correction element with respect to the third wavelength λ3. _{According to λ3} , φ1, φ2, and φ3 represented by the following equations (99) to (101) respectively satisfy the following equations (102) to (104).
φ1 = Δ · (N _λ1 −1) · (N + 1) / λ1 (99)
φ2 = Δ · (N _λ2 −1) · (N + 1) / λ2 (100)
φ3 = Δ · (N _λ3 −1) · (N + 1) / λ3 (101)
0 ≦ | INT (φ1) −φ1 | ≦ 0.4 (102)
0 ≦ | INT (φ2) −φ2 | ≦ 0.4 (103)
0 ≦ | INT (φ3) −φ3 | ≦ 0.4 (104)
However, INT (φi) (i = 1, 2, 3) is an integer obtained by rounding off φi.

The invention according to claim 145 provides the aberration correction element for an optical pickup device according to claim 144, wherein the φ1 and the number N of the discontinuous steps formed in each annular zone are the following (105): And (106) is satisfied.
φ1 ≦ 24 (105)
3 ≦ N ≦ 11 (106)
The invention according to claim 146 is the aberration correction element for an optical pickup device for an optical pickup device according to any one of claims 143 to 145, wherein the superposition is formed in an optical function region including the optical axis. The type diffractive structure provides an equivalent first optical action to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3, and the first optical effect is applied to the light flux having the second wavelength λ2. It is characterized in that a second optical action different from the mechanical action is given.
According to a 147th aspect of the present invention, in the aberration correction element for an optical pickup device according to the 146th aspect, the first optical action is performed on the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. The second optical action is first-order diffraction that diffracts the light beam having the second wavelength λ2 in the first-order direction. It is characterized by.

The invention according to claim 148 is the aberration correction element for an optical pickup device according to claim 147, wherein the aberration correction element has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1. And the Abbe number at the d-line is formed from a material in the range of 50 to 60, and the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm), The number N of the discontinuous steps formed in each annular zone in the superposition type diffractive structure formed in the optical function region including the optical axis, while satisfying the following expressions (107) to (109) respectively. And the depth D (μm) in the optical axis direction of the annular zone is one of the following formulas (110) to (113), respectively.
0.39 <λ1 <0.42 (107)
0.63 <λ2 <0.68 (108)
0.75 <λ3 <0.85 (109)
When N = 3, 4.1 ≦ D ≦ 4.8 (110)
When N = 4, 5.4 ≦ D ≦ 6.4 (111)
When N = 5, 7.0 ≦ D ≦ 7.9 (112)
When N = 6, 8.4 ≦ D ≦ 9.0 (113)

According to a 149th aspect of the present invention, in the aberration correction element for an optical pickup device according to the 146th aspect, the first optical action is performed on the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. The second optical action is second-order diffraction that diffracts the light beam having the second wavelength λ2 in the second-order direction. It is characterized by.
The invention according to claim 150 is the aberration correction element for an optical pickup device according to claim 149, wherein the aberration correction element has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1. And the Abbe number at the d-line is formed from a material in the range of 50 to 60, and the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm), In the superposition type diffractive structure formed in the optical function region including the optical axis, the number N of the discontinuous steps formed in each annular zone while satisfying the following expressions (114) to (116) respectively. The depth D (μm) in the optical axis direction of the annular zone is any one of the following formulas (117) to (120).
0.39 <λ1 <0.42 (114)
0.63 <λ2 <0.68 (115)
0.75 <λ3 <0.85 (116)
When N = 8, 11.3 ≦ D ≦ 12.7 (117)
When N = 9, 12.8 ≦ D ≦ 14.1 (118)
When N = 10, 14.2 ≦ D ≦ 15.6 (119)
When N = 11, 15.7 ≦ D ≦ 17.2 (120)

The invention according to claim 151 is the aberration correction element for an optical pickup device according to any one of claims 143 to 150, wherein the superposition type diffractive structure is formed in all of the plurality of optical function regions. It is characterized by being.
The invention according to claim 152 is the aberration correction element for an optical pickup device according to any one of claims 118 to 150, wherein at least one of the plurality of optical function areas includes the optical function area. The superposition type diffractive structure is not formed.
The invention according to claim 153 is the aberration correction element for an optical pickup device according to any one of claims 118 to 152, wherein the superimposed diffractive structure is formed on a plurality of optical functional surfaces of the aberration correction element. It is characterized by being.

The invention according to claim 154 is the aberration correction element for an optical pickup device according to any one of claims 118 to 153, wherein the plurality of optical function regions are two optical function regions, and the two Of the optical function areas, the superposition type diffractive structure is formed in an optical function area that does not include the optical axis, and diffraction that occurs when a light beam having the third wavelength λ3 is incident on the superposition type diffractive structure. Of the light, the diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency is 40% or less.
The invention according to claim 155 is the aberration correction element for an optical pickup device according to any one of claims 118 to 154, wherein the plurality of optical function areas are two optical function areas, and the two The superposition type diffractive structure is formed in the optical function region that does not include the optical axis in the optical function region, and the superposition type diffractive structure has the light flux of the first wavelength λ1 and the light flux of the second wavelength λ2. And an optical action different from the optical action for the light beam having the third wavelength λ3, so that the third diffractive structure transmitted through the superposition type diffractive structure is given. The light beam having the wavelength λ3 is a flare component that does not contribute to spot formation on the information recording surface of the third optical information recording medium.

The invention according to claim 156 is the aberration correction element for an optical pickup device according to any one of claims 118 to 153, wherein the plurality of optical function areas are three optical function areas, and the three The superposition type diffractive structure is formed in the optical function region adjacent to the outside of the optical function region including the optical axis, and the light beam having the third wavelength λ3 is formed in the superposition type diffractive structure. The diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when incident is 40% or less.
The invention according to claim 157 is the aberration correction element for an optical pickup device according to any one of claims 118 to 153, 156, wherein the plurality of optical function areas are three optical function areas, The superposition type diffractive structure is formed in an optical function region adjacent to the outside of the optical function region including the optical axis among the three optical function regions, and the superposition type diffractive structure has the first wavelength λ1. By applying an equivalent optical action to the light flux and the light flux of the second wavelength λ2, and applying an optical action different from the optical action to the light flux of the third wavelength λ3, the superposition is performed. The light beam having the third wavelength λ3 that has passed through the diffractive structure is a flare component that does not contribute to spot formation on the information recording surface of the third optical information recording medium.

The invention according to claim 158 is the aberration correcting element for an optical pickup device according to any one of claims 118 to 153, 156, 157, wherein the plurality of optical function areas are three optical function areas. The superposition type diffractive structure is formed in the outermost optical function region among the three optical function regions, and is generated when the light beam having the second wavelength λ2 is incident on the superposition type diffractive structure. The diffraction efficiency η2 of the diffracted light having the maximum diffraction efficiency among the diffracted light to be transmitted is 40% or less, and the diffraction having the maximum diffraction efficiency among the diffracted lights generated when the light flux having the third wavelength λ3 is incident. The light diffraction efficiency η3 is 40% or less.
The invention according to claim 159 is the aberration correction element for an optical pickup device according to any one of claims 118 to 153 and 156 to 158, wherein the plurality of optical function areas are three optical function areas. The superposition type diffractive structure is formed in the outermost optical function region among the three optical function regions, and the superposition type diffractive structure is an optical component that is applied to the light flux having the first wavelength λ1. By applying an optical action different from the action to the light flux of the second wavelength λ2 and the third wavelength λ3, the light flux of the second wavelength λ2 and the third wavelength λ3 transmitted through the superposition type diffractive structure. The flare components do not contribute to spot formation on the information recording surfaces of the second optical information recording medium and the third optical information recording medium, respectively.

The invention according to claim 160 is the aberration correction element for an optical pickup device according to any one of claims 118 to 159, wherein the aberration correction element is a plastic lens.
The invention according to claim 161 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1, using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an optical pickup for recording,
The optical pickup device converts the first wavelength λ1 to the third wavelength λ3 emitted from the first light source to the first optical information recording medium to the third optical information, respectively. Having a condensing element for condensing on the information recording surface of the recording medium;
The aberration correction element according to any one of claims 118 to 160 is disposed in an optical path between the first light source to the third light source and the light condensing element.
The invention described in Item 162 includes the optical pickup device described in Item 161, records information on the first optical information recording medium to the third optical information recording medium, and the first optical information recording. It is possible to execute at least one of reproduction of information on the medium to the third optical information recording medium.

The invention according to claim 163 reproduces and / or records information on the first optical information recording medium having the protective layer having the thickness t1 by using the light beam having the first wavelength λ1 emitted from the first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or a condensing element for an optical pickup device for recording,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposition type diffractive structure is formed.

The invention according to claim 164 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or a condensing element for an optical pickup device for recording,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
A first magnification m1 when information is reproduced and / or recorded on the first optical information recording medium, and a second magnification when information is reproduced and / or recorded on the second optical information recording medium. The magnification m2 is substantially the same.

The invention according to claim 165 is the condensing element for an optical pickup device according to claim 164, wherein the superposition type diffractive structure adds an uncorrected spherical aberration to the second wavelength λ2. And
The invention according to claim 166 is characterized in that, in the light condensing element for the optical pickup device according to claim 164 or 165, the first magnification m1 and the second magnification m2 satisfy the following expression (121): To do.
m1 = m2 = 0 (121)
The invention described in Item 167 is the condensing element for an optical pickup device described in any one of Items 164 to 166, wherein information is reproduced and / or recorded on the third optical information recording medium. In this case, the third magnification m3 satisfies the following expression (122).
−0.25 <m3 <−0.10 (122)

  The invention according to claim 168 is the light condensing element for the optical pickup device according to any one of claims 164 to 167, wherein the first light source and the second light source are packaged light source modules, The condensing element condenses the light beam having the first wavelength λ1 emitted from the light source module on the information recording surface of the first optical information recording medium, and the second wavelength λ2 emitted from the light source module. Is condensed on the information recording surface of the second optical information recording medium.

The invention according to claim 169 reproduces and / or records information on the first optical information recording medium having the protective layer having the thickness t1 by using the light beam having the first wavelength λ1 emitted from the first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or a condensing element for an optical pickup device for recording,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
A second magnification m2 when information is reproduced and / or recorded on the second optical information recording medium, and a third magnification when information is reproduced and / or recorded on the third optical information recording medium. The magnification m3 is substantially the same.
According to a 170th aspect of the present invention, in the condensing element for an optical pickup device according to the 169th aspect, the superposition type diffractive structure adds an overcorrected spherical aberration to the second wavelength λ2. And

The invention according to claim 171 provides the first magnification in the case where information is reproduced from and / or recorded on the first optical information recording medium in the condensing element for the optical pickup device according to claim 169 or 170. m1 satisfies the following expression (123).
m1 = 0 (123)
The invention described in Item 172 is the light collecting element for an optical pickup device described in any one of Items 169 to 171, wherein the second magnification m2 and the third magnification m3 are the following (124) and ( 125) is satisfied.
m2 = m3 (124)
−0.25 <m2 <−0.10 (125)
The invention according to claim 173 is the light condensing element for the optical pickup device according to any one of claims 169 to 172, wherein the second light source and the third light source are packaged light source modules, The condensing element condenses the light beam having the second wavelength λ2 emitted from the light source module on the information recording surface of the second optical information recording medium, and the third wavelength λ3 emitted from the light source module. Is condensed on the information recording surface of the second optical information recording medium.

The invention described in claim 174 reproduces and / or records information on the first optical information recording medium having the protective layer having the thickness t1 by using the light beam having the first wavelength λ1 emitted from the first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or a condensing element for an optical pickup device for recording,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
The first light flux λ1 and the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps among the discontinuous steps formed in each annular zone in the superposition type diffractive structure are as follows: (126) and (127) are satisfied.
0.39 μm <λ1 <0.42 μm (126)
P> 3 μm (127)

The invention according to claim 175 is the condensing element for an optical pickup device according to claim 174, wherein, in the superposition type diffractive structure, among the discontinuous steps formed in each annular zone, adjacent steps are provided. The minimum value P of the interval in the direction perpendicular to the optical axis between the above satisfies the following expression (128).
P> 5 μm (128)
The invention according to claim 176 is the light condensing element for the optical pickup device according to claim 175, wherein in the superposition type diffractive structure, among the discontinuous steps formed in each annular zone, adjacent steps are provided. The minimum value P of the interval in the direction perpendicular to the optical axis between the two satisfies the following expression (129).
P> 10 μm (129)
The invention according to claim 177 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or a condensing element for an optical pickup device for recording,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
When the optical path difference added to the transmitted wavefront by the superposition type diffractive structure is defined by the above equation 1, the signs of B ₂ and B ₄ are different from each other.
The invention according to claim 178 is the condensing element for an optical pickup device according to any one of claims 174 to 177, wherein information is reproduced and / or recorded on the first optical information recording medium. A first magnification m1 in the case, a second magnification m2 in the case of reproducing and / or recording information on the second optical information recording medium, and an information reproduction and / or information on the third optical information recording medium. Alternatively, the third magnification m3 when recording is different from each other.

The invention according to claim 179 is the light condensing element for an optical pickup device according to claim 178, wherein the first magnification m1, the second magnification m2, and the third magnification m3 are the following (130): Thru | or (132) Formula is satisfy | filled, It is characterized by the above-mentioned.
m1 = 0 (130)
−0.08 <m2 <−0.01 (131)
−0.25 <m3 <−0.10 (132)
In the invention according to claim 180, information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness of t1, using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or a condensing element for an optical pickup device for recording,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function areas, at least two optical function areas are provided with a plurality of ring zones each having a predetermined number of discontinuous steps formed continuously around the optical axis. A superposed diffractive structure is formed,
In the superposition type diffractive structure, one of the number N of the discontinuous steps formed in each annular zone and the depth Δ (μm) of the discontinuous steps in the optical axis direction is determined for each optical function region. It is characterized by being different.

The invention according to claim 181 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or a condensing element for an optical pickup device for recording,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is formed with a diffractive structure composed of a plurality of annular zones divided by a step around the optical axis.
The invention according to claim 182 is the light condensing element for the optical pickup device according to claim 181, wherein the depth of the step of the diffractive structure is diffracted light generated when a light beam having the first wavelength λ1 is incident. The diffraction order n2 of the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light beam having the second wavelength λ2 is incident on the diffraction order n1 of the diffracted light having the maximum diffraction efficiency, The diffraction order n3 of the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light beam having the third wavelength λ3 is incident is designed to be lower. .

The invention according to claim 183 is the light collecting element for an optical pickup device according to claim 182, wherein the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm). Satisfy the following equations (133) to (135), and the combination of the diffraction order n1, the diffraction order n2, and the diffraction order n3 is (n1, n2, n3) = (2, 1, 1) , (4, 2, 2,), (6, 4, 3), (8, 5, 4), or (10, 6, 5).
0.39 <λ1 <0.42 (133)
0.63 <λ2 <0.68 (134)
0.75 <λ3 <0.85 (135)
The invention according to claim 184 is the light condensing element for the optical pickup device according to claim 182 or 183, wherein the light condensing element has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1. And the depth d1 in the optical axis direction of the step closest to the optical axis among the steps of the diffractive structure is expressed by the following equation (136). ) To (140).
1.2 μm <d1 <1.7 μm (136)
2.6 μm <d1 <3.0 μm (137)
4.4 μm <d1 <5.0 μm (138)
5.6 μm <d1 <6.5 μm (139)
6.9 μm <d1 <8.1 μm (140)

The invention according to claim 185 is the condensing element for an optical pickup device according to any one of claims 181 to 184, wherein the diffractive structure has the first wavelength λ1 changed within a range of ± 10 nm. In this case, it has a function of suppressing a focus position shift caused by chromatic aberration of the light collecting element.
The invention according to claim 186 is the light condensing element for an optical pickup device according to claim 185, wherein the diffraction structure has a paraxial diffraction power PD0 (mm ⁻¹ ) with respect to the front first wavelength λ1, and the diffraction structure. of, before the diffraction power PD1 paraxial for 10nm wavelength longer than the first wavelength λ1 (mm ^-1), the diffractive structure, before diffracting power PD2 paraxial for 10nm shorter wavelengths than the first wavelength .lambda.1 (mm ^{- 1} ) satisfies the following expression (141).
PD2 <PD0 <PD1 (141)
The invention according to claim 187 is the light condensing element for an optical pickup device according to claim 185 or 186, wherein the diffractive structure has spherical aberration when the first wavelength λ1 is changed to the long wavelength side. When the first wavelength λ1 changes to the short wavelength side when the first wavelength λ1 changes to the short wavelength side, the spherical aberration has a wavelength dependency such that the spherical aberration changes to the overcorrection direction.

The invention according to claim 188 is the light collecting element for an optical pickup device according to any one of claims 181 to 187, wherein the light collecting element is a plastic lens, and the diffractive structure is the first element. When one wavelength λ1 changes to the long wavelength side, the spherical aberration changes in the direction of insufficient correction, and when the first wavelength λ1 changes to the short wavelength side, the spherical aberration changes in the overcorrection direction. It has a function of suppressing a spherical aberration change caused by a change in the refractive index of the light condensing element due to a change in environmental temperature by having a wavelength dependency of the spherical aberration.
The invention according to claim 189 is the condensing element for the optical pickup device according to claim 188, wherein at least one of the optical functional surfaces of the condensing element includes a central optical function including an optical axis. It is divided into a region and a peripheral optical functional region surrounding the periphery of the central optical functional region, and the diffractive structure is formed only in the peripheral optical functional region.

The invention according to claim 190 is the condensing element for an optical pickup device according to any one of claims 181 to 189, wherein the cross-sectional shape including the optical axis of the diffractive structure is a sawtooth shape. Features.
The invention according to claim 191 is the light condensing element for the optical pickup device according to any one of claims 181 to 190, wherein the superposition type diffractive structure is formed on one optical functional surface of the light condensing element. The diffractive structure is formed on the other optical functional surface of the light collecting element.

The invention according to claim 192 reproduces and / or records information on the first optical information recording medium having the protective layer having the thickness t1 by using the light beam having the first wavelength λ1 emitted from the first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or a condensing element for an optical pickup device for recording,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface has an optical path difference providing structure including a central region including the optical axis and a plurality of annular zones divided by steps on the outer side of the central region. Is formed.

The invention according to claim 193 is the light condensing element for the optical pickup device according to claim 192, wherein the light condensing element is a plastic lens, and the optical path difference providing structure is provided when the environmental temperature rises. When the spherical aberration added to the first wavelength λ1 changes in the undercorrected direction and the environmental temperature decreases, the spherical aberration added to the first wavelength λ1 changes in the overcorrected direction. It has a function of suppressing the spherical aberration change caused by the refractive index change of the light condensing element due to the environmental temperature change by having the temperature dependence of the spherical aberration.
The invention according to claim 194 is the light condensing element for the optical pickup device according to claim 193, wherein, in the optical path difference providing structure, the annular zone adjacent to the outside of the central region is in relation to the central region. It is formed by shifting in the optical axis direction so as to shorten the optical path length, and the annular zone at the maximum effective diameter position is shifted in the optical axis direction so that the optical path length becomes longer with respect to the annular zone adjacent to the inner side. The annular zone at a position of 75% of the maximum effective diameter is shifted in the optical axis direction so that the optical path length becomes shorter with respect to the annular zone adjacent to the inside and the annular zone adjacent to the outside. It is characterized by being formed.

The invention according to claim 195 is the light collecting element for an optical pickup device according to any one of claims 192 to 194, wherein the first wavelength λ1 (μm), the second wavelength λ3 (μm), the The third wavelength λ3 (μm), the depth d2 (μm) of the step closest to the optical axis among the steps of the optical path difference providing structure, the refractive index N _{λ1 with} respect to the first wavelength λ1 of the condensing element , the refractive index N with respect to the second wavelength λ1 of the light converging element _.lambda.2, the refractive index N _{[lambda] 3} for the third wavelength [lambda] 3 of the light focusing element, are expressed by the following (142) to (144) below Φ1 , Φ2, and Φ3 satisfy the following expressions (145) to (148).
Φ1 = d2 · (N _λ1 −1) / λ1 (142)
Φ2 = d2 · (N _λ2 −1) / λ2 (143)
Φ3 = d2 · (N _λ3 −1) / λ3 (144)
INT (Φ1) ≦ 10 (145)
0 ≦ | INT (Φ1) −Φ1 | ≦ 0.4 (146)
0 ≦ | INT (Φ2) −Φ2 | ≦ 0.4 (147)
0 ≦ | INT (Φ3) −Φ3 | ≦ 0.4 (148)
However, INT (Φi) (i = 1, 2, 3) is an integer obtained by rounding Φi. The invention according to claim 196 is the light condensing element for the optical pickup device according to any one of claims 192 to 195, wherein the superposition type diffractive structure is formed on one optical functional surface of the light condensing element. The optical path difference providing structure is formed on the other optical functional surface of the light collecting element.

The invention according to claim 197 is the light condensing element for an optical pickup device according to any one of claims 163 to 196, wherein the optical function region in which the superposition type diffractive structure is formed includes an optical axis. It is a functional area.
The invention according to claim 198 is the light condensing element for the optical pickup device according to claim 197, wherein the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm). In the superposition type diffractive structure formed in the optical functional region including the optical axis, the number N of the discontinuous steps formed in each annular zone, and the depth Δ of the discontinuous steps in the optical axis direction ([mu] m), the refractive index N _.lambda.1 with respect to the first wavelength .lambda.1 of the light focusing _element, the refractive index N _.lambda.2 for said second wavelength .lambda.2 of the light focusing _element, the refractive index N with respect to the third wavelength λ3 of the light converging element _{According to λ3} , φ1, φ2, and φ3 represented by the following equations (149) to (151) respectively satisfy the following equations (152) to (154).
φ1 = Δ · (N _λ1 −1) · (N−1) / λ1 (149)
φ2 = Δ · (N _λ2 −1) · (N−1) / λ2 (150)
φ3 = Δ · (N _λ3 −1) · (N−1) / λ3 (151)
0 ≦ | INT (φ1) −φ1 | ≦ 0.4 (152)
0 ≦ | INT (φ2) −φ2 | ≦ 0.4 (153)
0 ≦ | INT (φ3) −φ3 | ≦ 0.4 (154)
However, INT (φi) (i = 1, 2, 3) is an integer obtained by rounding off φi.

The invention according to claim 199 is the light condensing element for an optical pickup device according to claim 198, wherein the φ1 and the number N of the discontinuous steps formed in each annular zone are the following (155): And (156) is satisfied.
φ1 ≦ 24 (155)
3 ≦ N ≦ 11 (156)
According to a 200th aspect of the present invention, in the condensing element for an optical pickup device for an optical pickup device according to any one of the 197 to 199, the superposition formed in an optical function region including the optical axis. The type diffractive structure provides an equivalent first optical action to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3, and the first optical effect is applied to the light flux having the second wavelength λ2. It is characterized in that a second optical action different from the mechanical action is given.

The invention according to claim 201 is the light condensing element for the optical pickup device according to claim 200, wherein the first optical action is applied to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. The second optical action is first-order diffraction that diffracts the light beam having the second wavelength λ2 in the first-order direction. It is characterized by. The invention according to claim 202 is the light condensing element for the optical pickup device according to claim 201, wherein the light condensing element has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1s. And the Abbe number at the d-line is made of a material in the range of 50-60, and the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm) In the superposition type diffractive structure formed in the optical function region including the optical axis, the number N of the discontinuous steps formed in each annular zone while satisfying the following expressions (157) to (159). And a combination of the depth D (μm) in the optical axis direction of the annular zone is any one of the following formulas (160) to (163).
0.39 <λ1 <0.42 (157)
0.63 <λ2 <0.68 (158)
0.75 <λ3 <0.85 (159)
When N = 3, 4.1 ≦ D ≦ 4.8 (160)
When N = 4, 5.4 ≦ D ≦ 6.4 (161)
When N = 5, 7.0 ≦ D ≦ 7.9 (162)
When N = 6, 8.4 ≦ D ≦ 9.0 (163)

According to a 203th aspect of the present invention, in the condensing element for an optical pickup device according to the 200th aspect, the first optical action is performed on the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. The second optical action is second-order diffraction that diffracts the light beam having the second wavelength λ2 in the second-order direction. It is characterized by. According to a 204th aspect of the present invention, in the condensing element for an optical pickup device according to the 203rd aspect, the condensing element has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1. And the Abbe number at the d-line is formed from a material in the range of 50 to 60, and the first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm), In the superposition type diffractive structure formed in the optical function region including the optical axis, the number N of the discontinuous steps formed in each annular zone while satisfying the following equations (164) to (166). And the depth D (μm) in the optical axis direction of the annular zone is any one of the following formulas (167) to (170), respectively.
0.39 <λ1 <0.42 (164)
0.63 <λ2 <0.68 (165)
0.75 <λ3 <0.85 (166)
When N = 8, 11.3 ≦ D ≦ 12.7 (167)
When N = 9, 12.8 ≦ D ≦ 14.1 (168)
When N = 10, 14.2 ≦ D ≦ 15.6 (169)
When N = 11, 15.7 ≦ D ≦ 17.2 (170)

According to a 205th aspect of the present invention, in the condensing element for an optical pickup device according to any one of the 197 to 204, the superposition type diffractive structure is formed in all of the plurality of optical function regions. It is characterized by being.
According to a 206th aspect of the present invention, in the condensing element for an optical pickup device according to any one of the 163th to 204th aspects, at least one of the plurality of optical functional areas includes the optical functional area. The superposition type diffractive structure is not formed.
The invention according to claim 207 is the light condensing element for the optical pickup device according to any one of claims 163 to 206, wherein the superposition type diffractive structure is formed on a plurality of optical functional surfaces of the aberration correction element. It is characterized by being.

The invention described in Item 208 is the light condensing element for the optical pickup device described in any one of Items 163 to 207, wherein the thickness t1 of the protective layer of the first optical information recording medium, and the second The thickness t2 of the protective layer of the optical information recording medium satisfies the following expression (171).
0.8 ≦ t1 / t2 ≦ 1.2 (171)
According to a 209th aspect of the present invention, in the condensing element for the optical pickup device according to the 208th aspect, the plurality of optical functional areas are two optical functional areas. The light flux of the first wavelength λ1 to the light flux of the third wavelength λ3 incident on the optical function area including the axis are respectively on the information recording surfaces of the first optical information recording medium to the third optical information recording medium. The light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 that form a good wavefront and enter the optical function region that does not include the optical axis of the two optical function regions, respectively, A good wavefront is formed on the information recording surface of the optical information recording medium and the second optical information recording medium.
The invention according to claim 210 is the light condensing element for the optical pickup device according to claim 209, wherein the superposition type diffractive structure is provided in an optical function region that does not include the optical axis, of the two optical function regions. The diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency out of the diffracted light generated when the light beam having the third wavelength λ3 is incident on the superimposed diffractive structure is 40% or less. Features.

The invention according to claim 211 is the light condensing element for the optical pickup device according to claim 209 or 210, wherein the superposition type diffraction is not included in the optical function area that does not include the optical axis, of the two optical function areas. The superposition type diffractive structure gives an equivalent optical action to the light beam having the first wavelength λ1 and the light beam having the second wavelength λ2, and the light beam having the third wavelength λ3. Thus, by giving an optical action different from the optical action, the light beam having the third wavelength λ3 transmitted through the superposition type diffractive structure is spotted on the information recording surface of the third optical information recording medium. A flare component that does not contribute to formation is characterized.
According to a 212th aspect of the present invention, in the light concentrating element for an optical pickup device according to the 208th aspect, the plurality of optical function areas are three optical function areas, and the optical function area includes a light beam. The light flux of the first wavelength λ1 to the light flux of the third wavelength λ3 incident on the optical function area including the axis are respectively on the information recording surfaces of the first optical information recording medium to the third optical information recording medium. A favorable wavefront is formed, and among the three optical function regions, the light flux having the first wavelength λ1 and the second wavelength λ2 incident on the optical function region adjacent to the outside of the optical function region including the optical axis in the previous period. Each light beam forms a good wavefront on the information recording surfaces of the first optical information recording medium and the second optical information recording medium, and is incident on the outermost optical functional area among the three optical functional areas. The first wavelength λ One light beam forms a good wavefront on the information recording surface of the first optical information recording medium.

The invention according to claim 213 is the condensing element for an optical pickup device according to claim 212, wherein, among the three optical function areas, an optical function area adjacent to the outside of the optical function area including the optical axis is provided. Has a diffractive efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the third wavelength λ3 is incident on the superposed diffractive structure. It is characterized by being 40% or less.
The invention according to claim 214 is the condensing element for the optical pickup device according to claim 212 or 213, wherein the optical function adjacent to the outside of the optical function area including the optical axis among the three optical function areas. The superposition type diffractive structure is formed in the region, and the superposition type diffractive structure gives an equivalent optical action to the light flux of the first wavelength λ1 and the light flux of the second wavelength λ2, and By applying an optical action different from the optical action to the light beam having the three wavelengths λ3, the light beam having the third wavelength λ3 that has passed through the superposition type diffractive structure is allowed to pass through the third optical information recording medium. The flare component does not contribute to spot formation on the information recording surface.

The invention according to claim 215 is the light concentrating element for an optical pickup device according to any one of claims 212 to 214, wherein the outermost optical function area of the three optical function areas is A superposition type diffractive structure is formed, and the diffraction efficiency η2 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the second wavelength λ2 is incident on the superposition type diffractive structure is 40%. The diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the third wavelength λ3 is incident is 40% or less.
The invention described in Item 216 is the light condensing element for the optical pickup device according to any one of Items 212 to 215, wherein the outermost optical function region of the three optical function regions is included in the outermost optical function region. A superposition type diffractive structure is formed, and the superposition type diffractive structure has an optical action different from the optical action given to the light flux of the first wavelength λ1, and the light flux of the second wavelength λ2 By giving to the wavelength λ3, the light beams having the second wavelength λ2 and the third wavelength λ3 transmitted through the superposition type diffractive structure are respectively stored in the information on the second optical information recording medium and the third optical information recording medium. The flare component does not contribute to spot formation on the recording surface.

The invention described in Item 217 is the light condensing element for the optical pickup device described in any one of Items 163 to 207, wherein the thickness t1 of the protective layer of the first optical information recording medium, and the second The thickness t2 of the protective layer of the optical information recording medium satisfies the following expression (172).
t1 / t2 ≦ 0.4 (172)
The invention described in Item 218 is the light condensing element for the optical pickup device described in Item 217, wherein the plurality of optical function regions are three optical function regions. The light flux of the first wavelength λ1 to the light flux of the third wavelength λ3 incident on the optical function area including the axis are respectively on the information recording surfaces of the first optical information recording medium to the third optical information recording medium. A favorable wavefront is formed, and among the three optical function areas, the light flux having the first wavelength λ1 and the second wavelength λ2 incident on the optical function area adjacent to the outside of the optical function area including the optical axis in the previous period. Each light beam forms a good wavefront on the information recording surfaces of the first optical information recording medium and the second optical information recording medium, and is incident on the outermost optical functional area among the three optical functional areas. The first wavelength λ One light beam forms a good wavefront on the information recording surface of the first optical information recording medium.

The invention according to claim 219 is the light condensing element for the optical pickup device according to claim 218, wherein the optical function area adjacent to the outside of the optical function area including the optical axis among the three optical function areas. Is formed with the diffractive efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the third wavelength λ3 is incident on the superposed diffractive structure. It is characterized by being 40% or less.
The invention according to claim 220 is the light condensing element for the optical pickup device according to claim 218 or 219, wherein the optical function adjacent to the outside of the optical function area including the optical axis among the three optical function areas. The superposition type diffractive structure is formed in the region, and the superposition type diffractive structure gives an equivalent optical action to the light flux of the first wavelength λ1 and the light flux of the second wavelength λ2, and By applying an optical action different from the optical action to the light beam having the three wavelengths λ3, the light beam having the third wavelength λ3 that has passed through the superposition type diffractive structure is transmitted to the third optical information recording medium. The flare component does not contribute to spot formation on the information recording surface.

The invention according to claim 221 is the light concentrating element for an optical pickup device according to any one of claims 218 to 220, wherein the outermost optical function area of the three optical function areas is not in the outermost optical function area. A superposition type diffractive structure is formed, and the diffraction efficiency η2 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the second wavelength λ2 is incident on the superposition type diffractive structure is 40%. The diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the third wavelength λ3 is incident is 40% or less.
The invention according to claim 222 is the light-collecting element for an optical pickup device according to any one of claims 218 to 221, wherein the outermost optical function region is the outermost optical function region of the three optical function regions. A superposition type diffractive structure is formed, and the superposition type diffractive structure has an optical action different from the optical action given to the light flux of the first wavelength λ1, and the light flux of the second wavelength λ2 By giving to the wavelength λ3, the light beams having the second wavelength λ2 and the third wavelength λ3 transmitted through the superposition type diffractive structure are respectively stored in the information on the second optical information recording medium and the third optical information recording medium. The flare component does not contribute to spot formation on the recording surface. The invention described in Item 223 is the light collecting element for an optical pickup device according to any one of Items 163 to 222, wherein the light collecting element is a plastic lens.

The invention described in Item 224 is the light condensing element for the optical pickup device according to any one of Items 163 to 222, wherein the light condensing element is a glass lens having a glass transition point Tg of 400 ° C. or lower. It is characterized by being.
The invention according to claim 225 is the light concentrating element for an optical pickup device according to any one of claims 163 to 223, wherein the light condensing element disperses particles having a diameter of 30 nm or less in a plastic material. It is characterized by being molded using the material made.
The invention described in claim 226 reproduces and / or records information on the first optical information recording medium having the protective layer having the thickness t1 by using the light beam having the first wavelength λ1 emitted from the first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an optical pickup for recording,
The optical pickup device has an objective for condensing the light beams of the first wavelength λ1 to the third wavelength λ3 on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, respectively. Having an optical system,
The light collecting element according to any one of claims 163 to 225 is used as the objective optical system.

The invention according to claim 227 includes the optical pickup device according to claim 226, records information on the first optical information recording medium to the third optical information recording medium, and the first optical information recording. It is possible to execute at least one of reproduction of information on the medium to the third optical information recording medium.
The invention according to claim 228 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an optical pickup device for recording,
The optical pickup device includes an objective for condensing the light beams having the first wavelength λ1 to the third wavelength λ3 on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, respectively. An optical system, a diaphragm, and a driving device that integrally drives the objective optical system and the diaphragm in a direction perpendicular to the optical axis;
In the objective optical system, at least one of the optical functional surfaces is divided into a plurality of ring-shaped optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
Furthermore, it has a configuration in which at least one light beam among the light beam having the first wavelength λ1 to the light beam having the third wavelength λ3 is incident on the objective optical system in a non-parallel state,
Among the first light source to the third light source, in the optical path between the objective optical system and at least one light source that emits the light beam incident in a non-parallel state to the objective optical system In addition, a coma aberration correcting element having a function of reducing coma generated when the objective optical system is driven in a direction perpendicular to the optical axis by the driving device is arranged.

The invention according to claim 229 is the optical pickup device according to claim 228, wherein the coma aberration correcting element is configured such that the objective optical system is driven when the objective optical system is not driven in a direction perpendicular to the optical axis by the driving device. Within the effective diameter through which the light beam incident in a non-parallel state passes, the spherical aberration is corrected to be below the diffraction limit, and outside the effective diameter, it has spherical aberration in the overcorrected direction. It is characterized by.
According to a 230th aspect of the present invention, in the optical pickup device of the 229th aspect, the light beam incident in a non-parallel state with respect to the objective optical system is a divergent light beam.

The invention described in Item 231 is that in the optical pickup device described in Item 229 or 230, the light beam incident in a non-parallel state to the objective optical system is a light beam of the third wavelength λ3. Features.
The invention described in Item 232 is the optical pickup device according to any one of Items 229 to 231, wherein the light beam incident in a non-parallel state with respect to the objective optical system has the second wavelength λ <b> 2. It is a light beam.
The invention according to claim 233 is the optical pickup device according to any one of claims 229 to 232, wherein the light beam incident in a non-parallel state with respect to the objective optical system has the second wavelength λ2. A light beam and a light beam having the third wavelength λ3.

The invention according to claim 234 is the optical pickup device according to claim 233, wherein the coma aberration correcting element is disposed in a common optical path of the light flux of the second wavelength λ2 and the light flux of the third wavelength λ3,
When the objective optical system is not driven in the direction perpendicular to the optical axis by the driving device, the wavelength is within an effective diameter through which the second wavelength λ2 incident in a non-parallel state to the objective optical system passes. The spherical aberration of λ2 is corrected so as to be equal to or less than the diffraction limit, the spherical aberration of the wavelength λ2 is set in an overcorrected direction outside the effective diameter, and the objective optical system is perpendicular to the optical axis by the driving device. When the lens is not driven in any direction, the spherical aberration of the wavelength λ3 is corrected to be equal to or less than the diffraction limit within the effective diameter through which the third wavelength λ3 incident in a non-parallel state with respect to the objective optical system passes. In addition, outside the effective diameter, the spherical aberration of the wavelength λ3 is in an overcorrected direction.
The invention according to claim 235 is the optical pickup device according to claim 233 or 234, wherein at least one optical function surface of the coma aberration correcting element has a plurality of rings divided by a step around the optical axis. A diffractive structure composed of a band is formed.

The invention described in Item 236 is the optical pickup device described in any one of Items 233 to 235, wherein the second light source and the third light source are packaged light source modules.
The invention according to claim 237 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an optical pickup device for recording,
The optical pickup device has an objective for condensing the light beams of the first wavelength λ1 to the third wavelength λ3 on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, respectively. Having an optical system,
In the objective optical system, at least one of the optical functional surfaces is divided into a plurality of ring-shaped optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
Further, among the light beams having the first wavelength λ1 to the light beams having the third wavelength λ3, at least two light beams are incident on the objective optical system at different magnifications.
Among the first light source to the third light source, the light source that emits the at least two light beams that are incident on the objective optical system at different magnifications is a packaged light source module,
A superposition type diffractive structure, which is a structure in which a plurality of annular zones each having a predetermined number of discontinuous steps formed therein are continuously arranged around the optical axis, is formed on at least one optical functional surface. A divergence angle conversion element for converting a divergence angle of at least one light beam out of the light beams emitted from the light source module and guiding it to the objective optical system, an optical path between the light source module and the objective optical system It is arranged inside.

The invention according to claim 238 is the optical pickup apparatus according to claim 237, wherein the superposition type diffractive structure formed in the divergence angle conversion element is one light beam out of the light beams emitted from the light source module. A first optical action is given to the light beam, and a second optical action different from the first optical action is given to light beams of other wavelengths.
The invention according to claim 239 is the optical pickup device according to claim 238, wherein the light flux emitted from the light source module is two light fluxes, and the two light fluxes are a light flux having the first wavelength λ1. It is a light beam having the second wavelength λ2.
According to a 240th aspect of the present invention, in the optical pickup device according to the 238th aspect, the light beams emitted from the light source module are two light beams, and the two light beams are a light beam having the second wavelength λ2. It is a light beam having the second wavelength λ3.
The invention described in Item 241 is the optical element for an optical pickup device described in any one of Items 45-115, wherein the wavelength is not present on at least one of the optical function surfaces of the optical element. A selective filter is formed, and the optical functional surface on which the wavelength selective filter is formed is divided into an optical functional region including an optical axis and a peripheral optical functional region surrounding the periphery of the optical functional surface. In the optical function area including the axis, the light flux of the first wavelength λ1 to the light flux of the third wavelength λ3 is transmitted, and in the peripheral optical function area, the light flux of the third wavelength λ3 is blocked or reflected. It is characterized by having a wavelength selectivity of transmittance that transmits a light beam of one wavelength λ1 and a light beam of the second wavelength λ2.

  The optical element for an optical pickup device according to any one of claims 45 to 115, wherein the wavelength of the optical element on at least one of the optical functional surfaces of the optical element is A selection filter is formed, and the optical functional surface on which the wavelength selection filter is formed includes an optical functional region including an optical axis, a first peripheral optical functional region surrounding the periphery, and a second peripheral surrounding the periphery. The wavelength selective filter is divided into a peripheral optical function region, and the wavelength selection filter transmits the light beam having the first wavelength λ1 to the light beam having the third wavelength λ3 in the optical function region including the optical axis. In the peripheral optical function region, the light beam having the third wavelength λ3 is blocked or reflected, and the light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 are transmitted. In the second peripheral optical function region, Said It has a wavelength selectivity of transmittance that blocks or reflects the light beam having the second wavelength λ2 and the light beam having the third wavelength λ3, and transmits the light beam having the first wavelength λ1.

The invention described in Item 243 is the optical element for the optical pickup device described in Item 241 or 242, wherein the wavelength selection filter is formed on at least one optical function surface of the aberration correction element. And
The invention described in Item 244 is the optical element for the optical pickup device described in Item 241 or 242, wherein the wavelength selection filter is formed on at least one optical function surface of the light collecting element. And
The invention according to claim 245 is the optical pickup device according to claim 116, wherein the optical pickup device has an aperture limiting element disposed on a light incident surface side of the objective optical system, and A wavelength selective filter is formed on at least one optical functional surface, and the optical functional surface on which the wavelength selective filter is formed is divided into an optical functional region including an optical axis and a peripheral optical functional region surrounding the periphery. The wavelength selection filter transmits the light beam having the first wavelength λ1 to the light beam having the third wavelength λ3 in the optical function region including the optical axis, and the third wavelength λ3 in the peripheral optical function region. The light beam has a transmittance wavelength selectivity so that the light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 are transmitted.
The invention according to claim 246 is the optical pickup apparatus according to claim 116, wherein the optical pickup apparatus has an aperture limiting element disposed on a light beam incident surface side of the objective optical system, and A wavelength selective filter is formed on at least one optical functional surface, and the optical functional surface on which the wavelength selective filter is formed includes an optical functional region including an optical axis and a first peripheral optical functional region surrounding the periphery. And the second peripheral optical functional region surrounding the periphery, and the wavelength selective filter includes the light flux of the first wavelength λ1 to the third wavelength λ3 in the optical functional region including the optical axis. In the first peripheral optical function region, the light beam having the third wavelength λ3 is blocked or reflected, and the light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 are transmitted. In the second peripheral optical function region, the wavelength selectivity of the transmittance is such that the light beam having the second wavelength λ2 and the light beam having the third wavelength λ3 are blocked or reflected, and the light beam having the first wavelength λ1 is transmitted. It is characterized by having.
The invention according to claim 247 is the optical pickup device according to claim 245 or 246, wherein the optical pickup device has a drive device for driving the objective optical system at least in a direction perpendicular to the optical axis, The aperture limiting element is driven in the direction perpendicular to the optical axis integrally with the objective optical system by the driving device.

The invention according to claim 248 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And / or reproducing and / or reproducing information with respect to a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source Recording is performed and information is reproduced from a third optical information recording medium having a protective layer having a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. And / or an optical pickup for recording,
The optical pickup device has a structure in which a plurality of annular zones having a predetermined number of discontinuous steps formed therein are continuously arranged around the optical axis, and the first light flux and the third light flux Includes a diffractive lens having at least one optical surface on which a superposition type diffractive structure that gives a phase difference only to the second light flux is provided, and the first wavelength that has passed through the diffractive lens. a condensing element for condensing the light beams of λ1 to the third wavelength λ3 on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, respectively.
The magnification of the optical system composed of the diffractive lens and the condensing element with respect to the light beam having the first wavelength λ1 is m1, and the second of the optical system composed of the diffractive lens and the condensing element.
When the magnification with respect to the light beam with wavelength λ2 is m2, and the magnification with respect to the light beam with the third wavelength λ3 of the optical system composed of the diffractive lens and the condenser element is m3, the following equation (173) is satisfied. It is characterized by.
m1 ≧ m2> m3 (173)

The invention described in Item 249 is the optical pickup device described in Item 248, characterized in that the following expression (174) is satisfied.
m1 = m2 (174)
According to a 250th aspect of the present invention, in the optical pickup device according to the 248th aspect, the following expressions (175) and (176) are satisfied.
m1 = m2 = 0 (175)
−0.25 <m3 <−0.10 (176)

According to the invention of claim 248, by setting the magnification m3 for the third light beam of the optical system composed of the diffractive lens and the condensing element so as to satisfy the expression (173), the high-density optical disc and the CD It becomes possible to correct spherical aberration caused by the difference in the thickness of the protective layer.
Note that the second light beam used for recording / reproducing information with respect to the DVD is subjected to a diffractive action by adding a phase difference due to the superposition type diffractive structure, so that the diffractive action protects the high-density optical disc and the DVD. Spherical aberration that occurs due to the difference in layer thickness can be corrected.
In order to improve the characteristics of the optical pickup device and to facilitate the design and manufacture of the optical pickup device, the optical pickup device includes a diffractive lens and a condensing element. It is preferable that the magnifications m1 and m2 for the first light beam and the second light beam of the optical system are the same as in the equation (174).

  More preferably, as in the invention of claim 250, the magnifications m1 and m2 for the first light beam and the second light beam of the optical system composed of the diffractive lens and the condensing element are as in the equation (175). In this case, it is preferable to set the magnification m3 for the third light flux so as to satisfy the expression (176).

The invention according to claim 251 reproduces and / or records information on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from a first light source. And reproducing information from the second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) emitted from the second light source and / or Alternatively, information is recorded on a third optical information recording medium having a protective layer with a thickness t3 (t3> t2) using a light beam having a third wavelength λ3 (λ3> λ2) emitted from the third light source. An optical pickup device for reproducing and / or recording,
The optical pickup device collects the light beams of the first wavelength λ1 to the third wavelength λ3 on the information recording surfaces of the first information recording medium to the third information recording medium, respectively. And an aberration correction element having a phase structure, and spherical aberration correction means,
The aberration correction element corrects spherical aberration caused by the condensing element and / or spherical aberration caused by the difference between t1 and t2 due to the difference between the first wavelength λ1 and the second wavelength λ2. Has function,
The spherical aberration correcting means has a function of correcting spherical aberration generated due to a difference between the thickness t1 and the thickness t3.

The invention described in Item 252 is the optical pickup device described in Item 251, wherein the phase structure is any one of a superposition type diffraction structure, a diffraction structure, and an optical path difference providing structure.
The invention according to claim 253 is the optical pickup device according to claim 252, wherein the optical path difference added to the first light flux by the phase structure is an integral multiple of the first wavelength λ1. To do.
The invention described in Item 254 is the optical pickup device described in Item 253, wherein the optical path difference added to the first light flux by the phase structure is an even multiple of the first wavelength λ1. To do.

The invention according to claim 255 is the optical pickup device according to claim 254, wherein the optical pickup device has a second phase structure which is either a diffraction structure or an optical path difference providing structure. And an optical path difference added to the first light flux by the second phase structure is an odd multiple of the first wavelength λ1.
According to a 256th aspect of the present invention, in the optical pickup device according to any one of the 251th to 255th aspects, an optical system comprising the condensing element and the aberration correcting element with respect to the first wavelength λ1. The magnification m1 is substantially equal to the magnification m2 with respect to the second wavelength λ2.

The invention according to Claim 257 is the optical pickup device according to any one of Claims 251 to 256, wherein the condensing element is provided for the first wavelength λ1 and the protective layer having the thickness t1. Spherical aberration correction is optimized.
The invention described in Item 258 is the optical pickup device described in any one of Items 251 to 257, in which the condensing element and the aberration correcting element do not change their relative positional relationship. It is retained.

The invention described in Item 259 is the optical pickup device described in any one of Items 251 to 258, wherein the spherical aberration correcting means is a liquid crystal that causes a phase change with respect to a transmitted light beam by application of a voltage. A liquid crystal phase control element comprising a layer and electrode layers facing each other for applying a voltage to the liquid crystal element, wherein the liquid crystal phase control element performs phase control of the third light flux to Spherical aberration that occurs due to the difference between the thickness t1 and the thickness t3 is corrected.
The invention according to claim 260 is the optical pickup apparatus according to claim 259, wherein the liquid crystal phase control element selectively performs only phase control of the third light flux.

The invention according to Item 261 is the optical pickup device according to any one of Items 251 to 258, wherein the spherical aberration correcting means is an actuator and a movable lens that can be displaced at least in the optical axis direction by the actuator. A movable lens unit composed of a group, wherein the movable lens unit changes the magnification of the condensing element, thereby causing spherical aberration caused by the difference between the thickness t1 and the thickness t3. It is characterized by correcting.
The invention described in Item 262 is the optical pickup apparatus described in Item 261, wherein the magnification m3 of the light collecting element with respect to the third wavelength λ3 satisfies the following expression (177).
−0.15 <m3 <−0.02 (177)
The invention described in Item 263 is the optical pickup device described in any one of Items 251 to 261, wherein at least two of the first light source to the third light source are integrated. It is characterized by.
The invention described in Item 264 is the optical pickup device described in Item 263, wherein all of the first light source to the third light source are integrated.

According to the invention of claim 251, the first optical information recording medium (for example, high-density optical disk) and the second optical information recording medium (for example, DVD) can be compatible by the function of the phase structure. Thus, the function of the spherical aberration correction means enables compatibility between the first optical information recording medium (for example, a high-density optical disk) and the third optical information recording medium (for example, CD). Here, the phase structure has a function of correcting spherical aberration caused by the condensing element and / or spherical aberration caused by the difference between t1 and t2 due to the difference between the first wavelength λ1 and the second wavelength λ2. The former case corresponds to the case where t1 and t2 are the same (for example, t1 = 0.6 mm HD DVD and t2 = 0.6 mm DVD), and in the latter case, t1 and t2 are mutually This corresponds to different cases (for example, t1 = 0.1 mm Blu-ray disc and t2 = 0.6 mm DVD).
As the phase structure, as in the invention of claim 252, the superposition type diffractive structure schematically shown in FIG. 26, the diffractive structure schematically shown in FIG. 27, and the optical path schematically shown in FIG. Any of the difference providing structures may be used.

Further, as in the invention of claim 253, the phase structure may be designed so that the optical path difference added to the first light flux when passing through the phase structure is an integral multiple of the first wavelength λ1. preferable. As a result, it is possible to prevent a decrease in the transmittance of the phase structure of the first light flux.
According to the invention of claim 254, if the phase structure is designed so that the optical path difference added to the first light flux when passing through the phase structure is an even multiple of the first wavelength λ1, It is also possible to prevent a decrease in the transmittance of the phase structure of the light beam and the third light beam.
However, when the phase structure is designed so that the optical path difference added to the first light flux is an even multiple of the first wavelength λ1, the actions added to the first light flux and the third light flux that pass through the phase structure are mutually different. Will be equal. For this reason, the phase structure cannot reduce the spherical aberration due to the difference between t1 and t3, increasing the burden on the spherical aberration correcting means.

  Therefore, as in the invention of claim 255, a second aberration correction element having a second phase structure that is either a diffraction structure or an optical path difference providing structure is provided, and passes through the second phase structure. At this time, it is preferable to design the second phase structure so that the optical path difference added to the first light flux is an odd multiple of the first wavelength λ1. In this case, when the third light flux passes through the second phase structure, an optical path difference that is a half integer multiple of λ3 is added. As a result, the transmittance of the second phase structure of the third light flux is lowered, but an action different from that of the first light flux can be added to the third light flux that passes through the second phase structure. Therefore, it is possible to reduce the spherical aberration due to the difference between t1 and t3, and the burden on the spherical aberration correcting means can be reduced. As described above, since the spherical aberration due to the difference between t1 and t3 can be reduced by the phase structure, the optical axis is obtained by the actuator as described in the invention of claim 260 described later as spherical aberration correcting means. In the case of using a movable lens unit having a lens group that can be shifted in the direction, the absolute value of the magnification m3 with respect to the third light beam λ3 of the condensing element does not become too large. As a result, good tracking characteristics of the light collecting element can be obtained.

  When the phase structure is a superposition type diffractive structure, the number of divisions in each annular zone is set to 4, 5, or 6 (that is, the number of steps in each annular zone is any of 3, 4, or 5). The depth Δ in the optical axis direction of the step in each annular zone is preferably set so as to substantially satisfy Δ = 2m · λ1 / (Nλ1-1). Most preferably, the number is 5 and m = 1. Thereby, when passing through the superposition type diffractive structure, only the second light flux is given a phase difference and diffracted, so that compatibility between the first optical information recording medium and the second optical information recording medium can be achieved. It is possible to suppress a decrease in transmittance of the phase structure of the light beam. Note that m is a positive integer of 5 or less, and Nλ1 is the refractive index of the aberration correction element with respect to the first wavelength λ1.

When the phase structure is a diffractive structure, the diffraction order n1 of the diffracted light generated when the first light beam is incident, the diffraction order n2 of the diffracted light generated when the second light beam is incident, the third light beam It is preferable to set the depth of the step of each annular zone so that the diffraction order n3 of the diffracted light generated when is incident satisfies the following relationship.
n1 ≧ n2 ≧ n3
Here, the diffraction order refers to the diffraction order of the diffracted light having the maximum diffraction efficiency among the diffracted lights of various diffraction orders generated in the diffractive structure. Of these combinations of diffraction orders, (n1, n2, n3) = (1,1,1), (2,1,1), (3,2,1), (3,2,1) are preferred. 2), (8, 5, 4). The combination of (n1, n2, n3) = (2, 1, 1), (8, 5, 4) is particularly preferable in order to ensure high diffraction efficiency of all the first to third light beams. .

  When the phase structure is an optical path difference providing structure, the optical path difference between adjacent annular zones (expressed in units of wavelengths of the respective light beams) is expressed as Φ1 and second light flux with respect to the first light flux. On the other hand, when Φ2 and Φ3 for the third light flux, (Φ1, Φ2, Φ3) = (1λ1, 1λ2, 1λ3), (2λ1, 1λ2, 1λ3), (3λ1, 2λ2, 1λ3), (3λ1, 2λ2, 2λ3) or (8λ1, 5λ2, 4λ3) is preferable. A combination of (Φ1, Φ2, Φ3) = (2λ1, 1λ2, 1λ3), (8λ1, 5λ2, 4λ3) is particularly preferable in order to ensure a high transmittance of all the first to third light beams.

According to the invention of claim 256, the conjugate length of the optical system composed of the condensing element and the aberration correcting element can be made the same for the first light flux and the second light flux. The optical component for one light beam and the optical component for the second light beam can be shared, and the configuration of the optical pickup device can be simplified.
In general, the required accuracy of an optical element becomes stricter as the wavelength becomes shorter. According to the invention of claim 257, by optimizing the light condensing element with respect to the first wavelength λ1 and the protective layer having the thickness t1, the first light condensing element requiring particularly high accuracy. It becomes easier to obtain characteristics with respect to wavelength.

When the first optical information recording medium and the second optical information recording medium are interchanged by the action of the phase structure, coma is easily generated due to the eccentricity of the light converging element and the aberration correcting element in the direction perpendicular to the optical axis. Resulting in. According to the invention of claim 258, when the condensing element and the aberration correcting element are integrated and tracking driving is performed, the occurrence of the coma aberration can be suppressed, and good tracking characteristics can be obtained.
As a method of integrating the condensing element and the aberration correcting element, the flange portions of the respective elements may be joined together, or may be integrated via a joining member that is a separate member, You may integrate by incorporating an element.

As spherical aberration correcting means for performing compatibility between the first optical information recording medium and the third optical information recording medium, a third transmission that is transmitted by applying a voltage to the liquid crystal layer as described in the invention of claim 259. Liquid crystal phase control means for controlling the phase of the light beam can be used. Such a liquid crystal phase control means is advantageous in reducing the size of the optical pickup device because it does not require a mechanically movable portion.
In addition, since the spherical aberration increases in proportion to the fourth power of the effective diameter (that is, the numerical aperture NA of the light converging element), the liquid crystal phase control element is made to have a first light beam having a large effective diameter and a third light beam having a small effective diameter. If this is shared, the problem of insufficient correction of spherical aberration with the third light beam becomes obvious. “Shared” as used herein refers to performing phase control on light fluxes of respective wavelengths. For example, the third wavelength λ3 is 785 nm, the numerical aperture NA of the CD is 0.45, the first wavelength λ1 is 405 nm, the numerical aperture NA of the high-density optical disk is 0.85, and ± 0.2λRMS (λ = λ1) When spherical aberration is added to the first light beam, the amount of spherical aberration that can be added to the third light beam is about ± 0.01λRMS (λ = λ3) (= ± 0.2 × {(0. 45 ⁴ /785)/(0.85 ^4/405)}). Since the spherical aberration that can be corrected by the liquid crystal phase control element is about ± 0.2λ RMS, when the liquid crystal control phase element is shared by the first light flux and the third light flux, the spherical aberration addition amount in the third light flux is Insufficient, the compatibility between the first optical information recording medium and the third optical information recording medium cannot be performed. Therefore, as in the invention of claim 260, it is preferable that only the phase control of the third light beam is selectively performed so that sufficient spherical aberration can be added to the third light beam.

As a spherical aberration correction means for performing compatibility between the first optical information recording medium and the third optical information recording medium, a movable lens unit having a lens group that can be shifted in the optical axis direction by an actuator as described in claim 261. A lens unit may be used. Since the movable lens unit corrects the spherical aberration due to the difference between t1 and t3 by changing the magnification of the condensing element, there is no occurrence of coma due to the optical axis deviation from the condensing element, and the condensing element It is advantageous in that there is no need to drive tracking together.
As a specific form of such a movable lens unit, a coupling lens for converting the divergence angle of the divergent light beam emitted from the third light source and guiding it to the light collecting element may be used. A collimating lens for converting the divergent light beam into a parallel light beam and guiding it to the light collecting element, or for converting the divergent angle of the divergent light beam emitted from the third light source and guiding it to the light collecting element. It may be a beam expander lens disposed in an optical path between the coupling lens and the condensing element.

  In particular, by arranging the above-mentioned movable lens unit in a common optical path through which the first to third light beams pass, the wavelength variation due to the manufacturing error of the first light source, and the concentration of the condensing element due to the temperature change Thickness variation and thickness distribution due to interlayer focus jump at the time of recording / reproducing with respect to multilayer type optical information recording medium such as two-layer, four-layer, etc., and manufacturing error of the protective layer of the first optical information recording medium It is also possible to correct spherical aberration caused by the above, etc., so that the recording / reproducing characteristics for the first optical information recording medium can be improved.

As the actuator for shifting the movable lens group in the optical axis direction, a stepping motor, a solenoid, a voice coil actuator, an actuator using a piezoelectric element, or the like can be used. Since a technique for moving an optical element in the optical axis direction by a stepping motor or a voice coil actuator is known, a detailed description thereof is omitted here. As an actuator using a piezoelectric element, a small linear actuator using a piezoelectric element as described in the following document can be used.
OPTICS DESIGN, No. 26, 16-21 (2002)

Further, in the movable lens unit, only one lens group may be shifted, or a plurality of actuators may be mounted to shift the plurality of lens groups. Moreover, it is good also as a structure which shifts one lens group with several actuators from which a response frequency band mutually differs.
When a movable lens unit having a lens group that can be shifted in the optical axis direction by an actuator is used as the spherical aberration correction means, the magnification m3 of the light converging element with respect to the third light beam λ3 as in the invention of claim 261. By shifting the movable lens group so as to satisfy the expression (177), it is possible to satisfactorily correct spherical aberration caused by the difference between t1 and t3.

  The optical pickup device according to the present invention can also be applied to a configuration in which three light sources having different wavelengths are separately provided, but at least of the three light sources as in the invention of claim 263. Use of a light source in which two light sources are integrated is advantageous in reducing the size and cost of the optical pickup device. In particular, as in the invention of claim 264, it is preferable to use a light source in which all three light sources are integrated. As a light source in which these light sources are integrated, a light source (a so-called one-chip laser) in which the light emitting points of the respective light sources are formed on one semiconductor chip may be used. You may use the light source (what is called 1 can laser) stored in the housing | casing. Moreover, you may use the light source module which further integrated these light sources with which these several light sources were integrated, and the photodetector.

  According to the present invention, information can be appropriately recorded and / or reproduced on a plurality of types of optical information recording media having different wavelengths to be used, including high-density optical discs and DVDs that use blue-violet laser light sources. An optical element for the optical pickup device, an aberration correction element for the optical pickup device, a condensing element for the optical pickup device, an objective optical system, an optical pickup device, and an optical information recording / reproducing device can be obtained.

It is a principal part top view which shows the structure of an optical pick-up apparatus. It is drawing which shows the structure of a superposition type | mold diffractive optical element. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is drawing which shows the structure of a superposition type | mold diffractive optical element. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is drawing which shows the structure of a superposition type | mold diffractive optical element. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is drawing which shows the structure of a superposition type | mold diffractive optical element. It is drawing for demonstrating the principle of an effect | action of a superposition type | mold diffraction structure. It is drawing for demonstrating the principle of an effect | action of a superposition type | mold diffraction structure. It is drawing for demonstrating the principle of an effect | action of a superposition type | mold diffraction structure. It is a graph which shows the relationship between the transmittance | permeability of a wavelength selection filter, and a numerical aperture. It is a graph which shows the relationship between the transmittance | permeability of a wavelength selection filter, and a numerical aperture. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is drawing which shows the structure of a superposition type | mold diffractive optical element. It is sectional drawing which shows the structure of a superposition type | mold diffractive optical element. It is sectional drawing which shows the structure of a superposition type | mold diffractive optical element. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is an optical path figure of an optical pick-up apparatus. It is an optical path figure of an optical pick-up apparatus. It is an optical path figure of an optical pick-up apparatus. It is a figure for demonstrating a superposition type | mold diffraction structure. It is figure (a), (b) for demonstrating a diffraction structure. It is a figure for demonstrating an optical path difference providing structure. It is a figure for demonstrating the function of an optical path difference providing structure. It is a principal part top view which shows the structure of an optical pick-up apparatus. It is a principal part top view which shows the structure of an optical pick-up apparatus.

First, the operation of the superposition type diffractive structure in the present invention will be described with an example.
One example of the superposition type diffractive structure included in the optical element of the present invention is shown in FIGS. 9 to 11, the superposition type diffractive structure has a structure in which a sawtooth-shaped annular zone structure (diffraction relief surface) is divided into a plurality of staircases. In this example, each adjacent staircase is the shortest. With respect to the longest wavelength and the longest wavelength, an optical path difference is generated by an integral multiple of each wavelength, and a phase difference is not substantially generated.
If the step amount per step is Δ, the wavelength of interest is λ, and the refractive index of the medium constituting the step at this wavelength is n, the optical path difference caused by this step is expressed as Δ (n−1). Therefore, if the step amount Δ is determined so as to satisfy Δ (n−1) = jλ1, an optical path difference is generated at this wavelength by j (integer) times the wavelength λ1. In addition, λ3 is set as the other wavelength, and integers j and k that satisfy jλ1≈kλ3 are selected,
Δ (n−1) = jλ1 = kλ3
If the step amount Δ is provided so as to satisfy the above, the step difference causes an optical path difference of j times the wavelength for the wavelength λ1 and k times the wavelength for the wavelength λ3, so that the two wavelengths λ1 and λ3 are substantially As a result, the wave fronts are uniform and no phase difference occurs.

For example, when λ1 = 405 nm and λ3 = 785 nm, j = 2 and k = 1 are selected (that is, the step amount Δ = 2 × 405 / (n−1)), and 2 × 405≈1 × 785. Therefore, at this wavelength, an optical path difference of two wavelengths occurs as shown in FIG. 9 at a wavelength of λ1 = 405 nm, and an optical path difference of approximately one wavelength occurs as shown in FIG. 10 at λ3 = 785 nm. Such a structure in which a plurality of steps are gathered has the same phase for the wavelengths λ1 and λ3, and thus has no effect on the transmitted light.
However, for light with a wavelength λ2 = 655 nm different from λ1 and λ3, there is an optical path difference of δ = 2 × 405 × (1.5066-1) / (1.52477-1) −655 = 127 nm per step. (Where 1.5247 is the refractive index of the optical element material with respect to wavelength λ1 and 1.5066 is the refractive index of the optical element material with respect to wavelength λ2, as will be described later). When the substantially serrated relief structure having a pitch is divided (that is, one pitch is divided into five), an optical path difference corresponding to one wavelength of the wavelength λ2 is generated (127 × 5 = 635≈1 × 655). As shown in FIG. 3, the wavefronts having adjacent pitches are overlapped with each other with a shift of one wavelength. That is, + 1st order diffracted light is generated.
As shown in FIG. 11, the wavefronts of adjacent pitches overlap each other with a shift of one wavelength. That is, + 1st order diffracted light is generated.
The diffraction efficiency ηm of the m-th order by this superposition type diffractive structure is such that the number of discontinuous steps included in one pitch is N, the step height per step is Δ, the wavelength is λ, and the wavelength of the optical element material is λ. When the refractive index is n, it is expressed by the following equations (Equation 3 and Equation 4).

When calculating the above example, λ1 and λ3 are not diffracted, that is, 0th-order diffracted light is generated, but their diffraction efficiencies are 100% and 99.6%, respectively. %.
In the above calculation, it is assumed that the optical element material is a plastic material having a refractive index nd of d-line of 1.5091 and an Abbe number νd of 56.5, and the refractive index of the optical element material with respect to λ1. Is 1.5247, the refractive index of the optical element material for λ2 is 1.5066, and the refractive index of the optical element material for λ3 is 1.5050.
As you can see from this equation, if you increase the number of steps N, only the left fractional expression in [] remains,
The right side asymptotically approaches 1, and an expression giving the diffraction efficiency of a normal sawtooth diffractive element is obtained. When N takes a finite value, various actions are performed. As this action, in the case of λ1 = 405 nm, λ2 = 650 nm, and λ3 = 785 nm, the combinations shown in the following table (Tables 1 to 8) can be considered including the above example.

In the table, φ represents the optical path difference of the superposition type diffractive structure for one pitch composed of N steps as given by (Equation 4) in units of wavelength, and conversely, the step for one pitch. The quantity Δ (N + 1) uses this φ,
Δ (N + 1) = φλ / (n−1)
Given in. Since φ at each wavelength has the same step amount Δ (N + 1), it varies depending on the wavelength. M is the diffraction order at which the diffraction efficiency is maximized, and the diffraction efficiency at that time is ηm. In this calculation, the above plastic material is assumed as the optical element material.

Thus, the superposition type diffractive structure of the present invention selectively diffracts only one of the three wavelengths and diffracts the other wavelengths by appropriately setting the step amount Δ and the step number N. Therefore, the thickness of the protective layer between three types of optical disks such as a high-density optical disk, a DVD, and a CD can be determined by appropriately setting the arrangement of the annular zones of the superposition type diffractive structure. It is possible to secure high transmittance (diffraction efficiency) for all three wavelengths while correcting spherical aberration caused by the difference.
Further, as described above, the superposition type diffractive structure of the present invention selectively diffracts only one of the three wavelengths and transmits the other wavelengths without diffracting them. The diffraction orders of the wavelengths can be made different, or the diffraction efficiency can be made extremely small for a specific wavelength so as not to flare and contribute to light collection.
For example, as shown in Tables 9 to 10 below, if the step amount Δ and the step number N are set, the diffraction orders of the three wavelengths can be made different, so that the degree of freedom in optical design can be expanded.

In addition, when the step amount Δ and the number N of steps are set as shown in Tables 11 to 14 below, the diffraction efficiency is extremely reduced for a specific wavelength so that it does not contribute to condensing by flaring. It becomes possible.

In Tables 11 to 13, a high transmittance (diffraction efficiency) of 85% or more is secured for the wavelength λ1 and the wavelength λ2, and the diffraction efficiency is remarkably lowered for the wavelength λ3, being 50% or less. It has become. In Table 14, a high transmittance (diffraction efficiency) of 100% is ensured for the wavelength λ1, and the diffraction efficiency is remarkably reduced to 50% or less for the wavelengths λ2 and λ3. Yes. When such a superposition type diffractive structure is applied to an objective optical system that can be used in common with high-density optical discs, DVDs, and CDs, the role of a dichroic filter that blocks specific wavelengths and transmits other wavelengths Can be carried.
For example, when the numerical apertures of the high-density optical disc, the DVD, and the CD are different from each other, the first optical functional area corresponding to the NA of the CD is set to one optical functional surface of the objective optical system (for example, within NA 0.45). And a second optical function area corresponding to the NA of the DVD from the NA of the CD (for example, NA 0.45 to NA 0.60), and a third optical function area corresponding to the NA of the high density optical disk from the NA of the DVD ( For example, by dividing into three optical function areas of NA 0.60 to NA 0.85) and forming the superposition type diffractive structures of Tables 11 to 13 in the second optical function area, it is possible to block only the wavelength of λ3. It becomes possible.

Furthermore, by forming the superposition type diffractive structure shown in Table 14 in the third optical function region, it becomes possible to block the wavelength of λ2 and the wavelength of λ3.
As described above, by forming the superposition type diffractive structures shown in Tables 11 to 14 in a specific optical function region, an objective optical system having a simple configuration that does not require a separate aperture limiting element can be realized.
In the structures of Tables 1 to 14, the operating wavelengths λ1, λ2, and λ3 are 405 nm, 655 nm, and 785 nm, respectively, and the refractive indexes with respect to λ1, λ2, and λ3 are 1.5247 and 1.5066, respectively. This is an example of a part of the superimposition type diffractive structure that is optimal for the optical element material of 1.5050, and the structure is not necessarily optimal when using a wavelength or optical element material different from these. Do not mean. That is, the superposition type diffractive structure in the present invention is not limited to the structures shown in Tables 1 to 14, and various changes can be made according to the wavelength used and the characteristics of the optical element material.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
[First embodiment]
FIG. 1 is a diagram schematically showing a configuration of a first optical pickup device PU1 capable of appropriately recording / reproducing information for any of the high density optical disc HD, DVD, and CD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, the numerical aperture NA1 = 0.85, and the optical specification of the DVD is the wavelength λ2 = 658 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.60. The optical specification of the CD is a wavelength λ3 = 785 nm, the protective layer PL3 has a thickness t3 = 1.2 mm, and a numerical aperture NA3 = 0. .45. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

The optical pickup device PU1 is a high-density optical disc in which a blue-violet semiconductor laser LD1 that emits light and emits a laser beam of 408 nm and a photodetector PD1 are integrated when information is recorded / reproduced on the high-density optical disc HD. The first light emitting point EP1 that is emitted when recording / reproducing information with respect to the HD module MD1 and DVD, and is emitted when performing recording / reproducing information with respect to the CD. A second light emitting point EP2 that emits a laser beam of 785 nm, a first light receiving unit DS1 that receives a reflected beam from the information recording surface RL2 of the DVD, and a first beam that receives the reflected beam from the information recording surface RL3 of the CD. A DVD / CD laser module LM1, an aberration correction element L1, and the aberration correction element L. Objective optical system OBJ having a function of condensing the laser beam transmitted through RL1, RL2 and RL3 on both surfaces, and a condensing element L2 having an aspherical surface, biaxial actuator AC, high density The optical disk HD includes a stop STO corresponding to a numerical aperture NA of 0.85, a polarization beam splitter BS, and a collimating lens COL.
In addition to the blue-violet semiconductor laser LD1 described above, a blue-violet SHG laser can also be used as a light source for the high-density optical disk HD.

  When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU1, as shown by a solid line in FIG. The violet semiconductor laser LD1 is caused to emit light. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is converted into a substantially parallel light beam through the collimating lens COL, and after passing through the polarization beam splitter BS, the light beam diameter is regulated by the stop STO, and the high-density optical disk by the objective optical system OBJ. It becomes a spot formed on the information recording surface RL1 via the HD protective layer PL1. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ, the stop STO, the polarization beam splitter BS, and the collimating lens COL, and then becomes a convergent light beam. Converges on the light receiving surface of the photodetector PD1. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD1.

  Further, in the optical pickup device PU1, when information is recorded / reproduced with respect to the DVD, the first light emission point EP1 is caused to emit light. The divergent light beam emitted from the first light emitting point EP1 is reflected by the prism PS and reflected by the polarization beam splitter BS as depicted in the ray path by the wavy line in FIG. 1, and then is reflected by the objective optical system OBJ. The spot is formed on the information recording surface RL2 via the protective layer PL2. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the objective optical system OBJ, reflected by the polarization beam splitter BS, then reflected twice inside the prism PS and condensed on the light receiving part DS1. And the information recorded on DVD can be read using the output signal of light-receiving part DS1.

  In addition, when recording / reproducing information with respect to the CD in the optical pickup device PU1, the second light emitting point EP2 is caused to emit light. The divergent light beam emitted from the second light emitting point EP2 is reflected by the prism PS and reflected by the polarization beam splitter BS as depicted by the two-dot chain line in FIG. 1, and then the objective optical system OBJ. As a result, the spot is formed on the information recording surface RL1 via the protective layer PL1 of the CD. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ, reflected by the polarization beam splitter BS, then reflected twice inside the prism PS and condensed on the light receiving part DS2. And the information recorded on CD can be read using the output signal of light-receiving part DS2.

Next, the configuration of the objective optical system OBJ will be described. The aberration correction element L1 is a plastic lens having a refractive index nd at the d-line of 1.5091 and an Abbe number νd of 56.5, a refractive index with respect to λ1 of 1.5242, and a refractive index with respect to λ2 of 1.5064. , Λ3 has a refractive index of 1.5050. The condensing element L2 is a plastic lens having a refractive index nd of 1.5435 at the d-line and an Abbe number νd of 56.3. Further, a flange portion FL1 formed integrally with the optical function portion is provided around each optical function portion (region of the aberration correction element L1 and the condensing element L2 through which the laser beam from the blue-violet semiconductor laser LD1 passes). , FL2 and a part of the flange portions FL1, FL2 are joined together.
In addition, when integrating the aberration correction element L1 and the condensing element L2, they may be integrated via a separate joining member.
As shown in FIG. 2, the optical functional surface S1 of the aberration correction element L1 on the semiconductor laser light source side includes a first optical functional area AREA1 including an optical axis corresponding to an area within the numerical aperture 0.45 of CD, and CD The second optical function area AREA2 corresponding to the area from the numerical aperture 0.45 to the numerical aperture 0.66 of the DVD, and the area from the numerical aperture 0.60 of the DVD to the numerical aperture 0.85 of the high-density optical disk HD Is divided into a third optical functional area AREA3 corresponding to the superposed diffraction structures HOE1, HOE2, HOE1, HOE2, HOE3 is formed in the first optical functional area AREA1, the second optical functional area AREA2, and the third optical functional area AREA3, respectively.

In the superposition type diffractive structure HOE1 formed in the first optical functional area AREA1, the depth d31 of the staircase structure formed in each annular zone is:
d31 = 2λ1 / (n−1) (μm)
The number of steps N in each annular zone is set to 4. However, λ1 represents the wavelength of the laser beam emitted from the blue-violet semiconductor laser LD1 in units of microns (here, λ1 = 0.408 μm), and n is a refractive index with respect to the wavelength λ1 of the aberration correction element L1. is there.
When a laser beam having a wavelength λ1 is incident on the staircase structure whose depth in the optical axis direction is set in this way, an optical path difference of 2 × λ1 (μm) occurs between adjacent staircase structures, and the wavelength λ1 Since the laser beam is substantially not given a phase difference, it is transmitted without being diffracted. In the following description, a light beam that is transmitted without being substantially given a phase difference by the superposition type diffractive structure is referred to as zero-order diffracted light.

When a laser beam having a wavelength λ3 (here, λ3 = 0.785 μm) from the second light emitting point EP2 is incident on this staircase structure, (2 × λ1 / λ3) between adjacent staircase structures. An optical path difference of × λ3 (μm) occurs. Since λ3 is approximately twice as large as λ1, an optical path difference of approximately 1 × λ3 (μm) occurs between adjacent staircase structures, and the laser beam with the wavelength λ3 is substantially in the same manner as the laser beam with the wavelength λ1. Since no phase difference is given, the light is transmitted without being diffracted (0th order diffracted light).
On the other hand, when a laser beam having a wavelength λ2 (here, λ2 = 0.658 μm) from the first emission point EP1 is incident on this staircase structure, the number of steps N in each annular zone is set to 4. Therefore, the laser beam having the wavelength λ2 is diffracted in the + 1st order direction (+ 1st order diffracted light) with a phase difference according to the incident part of the superposition type diffractive structure HOE1. At this time, the diffraction efficiency of the + 1st order diffracted light of the laser beam with the wavelength λ2 is 87.5%, but the amount of light is sufficient for recording / reproducing information with respect to the DVD.

  The width Λ1 of each annular zone of the superposition type diffractive structure HOE1 and the inclination direction of each annular zone (in FIG. 1, the inclination direction of the envelope l1 of each staircase structure) are diffracted when a laser beam having a wavelength λ2 is incident. It is set so that spherical aberration in the overcorrected direction is added to the + 1st order diffracted light by the action. The magnification m3 of the objective optical system OBJ with respect to the wavelength λ3 is determined so that the spherical aberration due to the difference in thickness between the protective layer PL1 of the high-density optical disc HD and the protective layer PL3 of the CD is corrected. As described above, when the magnification m2 for the wavelength λ2 and the magnification m3 for the wavelength λ3 are substantially the same, the spherical aberration due to the difference in thickness between the protective layer PL1 of the high-density optical disk HD and the protective layer PL2 of the DVD is excessive. As a result, the spherical aberration of the laser light beam having the wavelength λ2 that has passed through the objective optical system OBJ and the protective layer PL2 of the DVD is in the direction of insufficient correction.

Here, the width Λ1 of each annular zone of the superimposing type diffractive structure HOE1 and the inclination direction of each annular zone are + 1st order diffracted light due to diffracting action when a laser beam having a wavelength λ2 is incident on the superposing type diffractive structure HOE1. The amount of spherical aberration in the overcorrection direction added to the above, the spherical aberration in the direction of undercorrection generated due to the fact that the magnification m2 with respect to the wavelength λ2 and the magnification m3 with respect to λ3 are substantially the same cancel each other. It is set to be. As a result, the laser beam having the wavelength λ2 transmitted through the superposition type diffractive structure HOE1 and the protective layer PL2 of the DVD forms a good spot on the information recording surface RL2 of the DVD.
Further, in the superposition type diffractive structure HOE2 formed in the second optical functional area AREA2, the depth d32 of the staircase structure formed in each annular zone is:
d32 = 3λ1 / (n−1) (μm)
The number of steps N in each annular zone is set to 4.

When a laser beam having a wavelength λ1 is incident on the staircase structure whose depth in the optical axis direction is set in this way, an optical path difference of 3 × λ1 (μm) occurs between adjacent staircase structures, and the wavelength λ1 Since the laser beam is substantially given no phase difference, it is transmitted without being diffracted (0th order diffracted light).
In addition, when a laser beam having a wavelength λ2 from the first light emission point EP1 is incident on this staircase structure, the number of steps N in each annular zone is set to 4, so the laser beam having a wavelength λ2 is The phase difference is given according to the incident part of the superposition type diffractive structure HOE2, and diffracts in the −1st order direction (−1st order diffracted light). At this time, the diffraction efficiency of the −1st order diffracted light of the laser beam having the wavelength λ2 is 87.5%, but the amount of light is sufficient for recording / reproducing information with respect to the DVD.

Here, the width Λ2 of each annular zone of the superimposing type diffractive structure HOE2 and the inclination direction of each annular zone are −1 next time due to the diffraction action when the laser beam having the wavelength λ2 is incident on the superposing type diffractive structure HOE2. The amount of spherical aberration in the overcorrection direction added to the folded light, the above-mentioned spherical aberration in the undercorrection direction, which is caused by making the magnification m2 for the wavelength λ2 and the magnification m3 for the wavelength λ3 substantially the same. They are set to cancel each other. As a result, the laser beam having the wavelength λ2 transmitted through the superposition type diffractive structure HOE2 and the protective layer PL2 of the DVD forms a good spot on the information recording surface RL2 of the DVD.
On the other hand, when a laser beam having a wavelength λ3 from the second light emission point EP2 is incident on this staircase structure, the laser beam having a wavelength λ3 is given a phase difference according to the portion where the superposition type diffractive structure HOE2 is incident. Diffracted in the -2nd order direction (-2nd order diffracted light). At this time, the diffraction efficiency of the −2nd order diffracted light of the laser beam having the wavelength λ3 is extremely low, 24.9%. When the laser beam having the wavelength λ3 is incident on the superposition type diffractive structure HOE2, in addition to the above-described −2nd order diffracted light, + 2nd order diffracted light and + 3rd order diffracted light are also generated, but their diffraction efficiencies are 23.1%, 11.1%, which is even lower than the diffraction efficiency of -2nd order diffracted light.

In the above description, the superposition type diffractive structure HOE1 is used in order to correct the spherical aberration in the undercorrection direction, which is caused by making the magnification m2 for the wavelength λ2 and the magnification m3 for the wavelength λ3 substantially the same. The HOE 2 has a structure that generates spherical aberration in an overcorrected direction when a laser beam with a wavelength λ 2 is incident. When the laser beam is incident, the divergence of the λ2 laser beam may be reduced and emitted.
In this case, the laser beam having the wavelength λ2 incident on the superposition type diffractive structures HOE1 and HOE2 is emitted with a reduced divergence. Since this corresponds to an increase in magnification for the condensing element L2, spherical aberration in the overcorrected direction is added to the laser light beam having the wavelength λ2 incident on the condensing element L2 due to this change in magnification. The spherical aberration in the overcorrection direction and the spherical aberration in the undercorrection direction, which are caused by making the magnification m2 for the wavelength λ2 and the imaging magnification m3 for the wavelength λ3 substantially the same, are canceled out. The widths Λ1, Λ2 between the annular zones of the superposition type diffractive structures HOE1, HOE2 and the inclination direction of each annular zone are determined.

Furthermore, in the superposition type diffractive structure HOE23 formed in the third optical function area AREA3, the depth d33 of the staircase structure formed in each annular zone is:
d33 = 1λ1 / (n−1) (μm)
The number N of steps in each annular zone is set to 5.
When a laser beam having a wavelength λ1 is incident on the staircase structure whose depth in the optical axis direction is set in this way, an optical path difference of 1 × λ1 (μm) is generated between adjacent staircase structures, and the wavelength λ1 Since the laser beam is substantially given no phase difference, it is transmitted without being diffracted (0th order diffracted light).

On the other hand, when a laser beam having a wavelength λ2 from the first light emission point EP1 is incident on this staircase structure, the laser beam having a wavelength λ2 is given a phase difference according to the incident site of the superposition type diffractive structure HOE3. Diffracted in the second order direction (second order diffracted light) At this time, the diffraction efficiency of the −2nd-order diffracted light of the laser beam having the wavelength λ2 is extremely low at 39.1%. When the laser beam having the wavelength λ2 is incident on the superposition type diffractive structure HOE3, ± 3rd order diffracted light is generated in addition to the above-mentioned −2nd order diffracted light, but this diffraction efficiency is 11.0%. It is even lower than the diffraction efficiency of the next diffracted light. That is, since the superposition type diffractive structure HOE3 functions in the same manner as a dichroic filter that selectively blocks the laser beam having the wavelength λ2, the first optical pickup device PU1 needs to additionally include an aperture limiting element for the DVD. There is no simple structure.
Further, when a laser beam having a wavelength λ3 from the second light emission point EP2 is incident on this staircase structure, the laser beam having a wavelength λ3 has a phase difference according to the portion where the superposition type diffractive structure HOE3 is incident. Diffracted in the given ± 3rd direction (± 3rd order diffracted light). At this time, the diffraction efficiency of the ± 3rd order diffracted light of the laser beam having the wavelength λ3 is extremely low at 40.5%. That is, since the superposition type diffractive structure HOE2 and the superposition type diffractive structure HOE3 described above function in the same manner as a dichroic filter that selectively blocks the laser beam having the wavelength λ3, in the first optical pickup device PU1, There is no need to separately install an aperture limiting element for the CD, and the structure can be simplified.

Further, as shown in FIG. 2, the optical function surface S2 on the optical disc side of the aberration correction element L1 includes a fourth optical function area AREA4 including an optical axis corresponding to an area within the numerical aperture 0.60 of the DVD, and the DVD. Are divided into a fifth optical functional area AREA5 corresponding to the area from the numerical aperture 0.60 to the numerical aperture 0.85 of the high-density optical disc HD, and a plurality of rings having a sawtooth cross section including the optical axis. Diffraction structures DOE1 and DOE2 composed of bands are formed in the optical function area AREA4 and the optical function area AREA5, respectively.
The diffractive structures DOE1 and DOE2 are structures for suppressing the chromatic aberration of the objective optical system OBJ in the blue-violet region and the spherical aberration change accompanying the incident wavelength change.
In the diffractive structure DOE1, the height d01 of the step closest to the optical axis has a diffraction efficiency of 100% for a light flux with a wavelength of 390 nm (the refractive index of the aberration correction element L1 with respect to the wavelength of 390 nm is 1.5273). And satisfies the above-described expression (16). When the laser beam having the wavelength λ1 is incident on the diffractive structure DOE1 in which the step depth is set as described above, the + 2nd order diffracted light is generated with the diffraction efficiency of 96.8%, and the laser beam having the wavelength λ2 is incident. + 1st order diffracted light is generated with a diffraction efficiency of 93.9%, and when a laser beam having a wavelength of λ3 is incident, + 1st order diffracted light is generated with a diffraction efficiency of 99.2%. Therefore, sufficient diffraction efficiency is obtained in any wavelength region. Even when the chromatic aberration is corrected in the blue-violet region, the chromatic aberration correction in the wavelength region of the wavelength λ2 and the wavelength λ3 is not excessive.

On the other hand, since the diffractive structure DOE2 is optimized for the wavelength λ1, when a laser beam having the wavelength λ1 is incident on the diffractive structure DOE2, + 2nd order diffracted light is generated with a diffraction efficiency of 100%.
Further, in the diffractive structures DOE1 and DOE2, in the blue-violet region, when the wavelength of the incident light beam becomes longer, the spherical aberration changes in the direction of insufficient correction, and when the wavelength of the incident light beam becomes shorter, the spherical aberration is corrected. It has the wavelength dependence of spherical aberration that changes in the excess direction. As a result, the change in spherical aberration that occurs in the condensing element with the change in incident wavelength is canceled out, so it is possible to relax the standard for the oscillation wavelength of the blue-violet semiconductor laser LD1.

  In the aberration correction element L1 of the present embodiment, the superposition type diffractive structure is formed on the optical function surface S1 on the semiconductor laser light source side, and the type diffractive structure is formed on the optical function surface S2 on the optical disc side. Conversely, a configuration may be adopted in which a mold diffractive structure is formed on the optical functional surface S1 on the semiconductor laser light source side and a superimposed diffractive structure is formed on the optical functional surface S2 on the optical disk side.

[Second Embodiment]
FIG. 3 is a diagram schematically showing a configuration of the second optical pickup device PU2 capable of appropriately recording / reproducing information on any of the high density optical disc HD, the DVD, and the CD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, and the numerical aperture NA1 = 0.85. The optical specification of the DVD is the wavelength λ2 = 658 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.67. The optical specification of the CD is a wavelength λ3 = 785 nm, the protective layer PL3 has a thickness t3 = 1.2 mm, and the numerical aperture NA3 = 0. .45. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

  The optical pickup device PU2 records / reproduces information to / from the first light emitting point EP1 that emits a 408 nm laser beam when recording / reproducing information on the high-density optical disc HD and DVD. From a second light emitting point EP2 that emits a laser beam of 658 nm, a first light receiving unit DS1 that receives a reflected light beam from the information recording surface RL1 of the high-density optical disk HD, and an information recording surface RL2 of the DVD. 785 nm laser emitted when information is recorded / reproduced to / from the high-density optical disk HD / DVD laser module LM2 and CD composed of the second light receiving unit DS2 that receives the reflected light beam and the prism PS. A CD module MD2 in which an infrared semiconductor laser LD3 that emits a light beam and a photodetector PD3 are integrated, an aberration correction element L1, and this Objective optical system OBJ, biaxial actuator comprising a condensing element L2 whose both surfaces are aspherical and has a function of condensing the laser beam transmitted through the difference correction element L1 on the information recording surfaces RL1, RL2, RL3 The aperture stop STO, the polarization beam splitter BS, the collimating lens COL, and the coupling lens CUL corresponding to the numerical aperture NA 0.85 of AC and the high-density optical disk HD are configured.

  In the optical pickup device PU2, when information is recorded / reproduced with respect to the high-density optical disc HD, the first light emitting point EP1 is caused to emit light. The divergent light beam emitted from the first light emitting point EP1 is reflected by the prism PS as shown by the solid line in FIG. 3 and is converted into a substantially parallel light beam through the collimator lens COL, and then the polarization beam splitter. The light beam diameter is controlled by the stop STO through the BS, and becomes a spot formed on the information recording surface RL1 via the protective layer PL1 of the high-density optical disk HD by the objective optical system OBJ. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ, the stop STO, and the polarization beam splitter BS, and is then converged by the collimator lens COL and reflected twice inside the prism PS. The light is condensed on the light receiving part DS1. Then, information recorded on the high density optical disk HD can be read using the output signal of the light receiving unit DS1.

  In addition, when recording / reproducing information with respect to the DVD in the optical pickup device PU2, the second light emitting point EP2 is caused to emit light. The divergent light beam emitted from the second light emission point EP2 is reflected by the prism PS as shown by the dotted line in FIG. 3 and is converted into a substantially parallel light beam through the collimator lens COL. The spot passes through the BS and becomes a spot formed on the information recording surface RL2 by the objective optical system OBJ via the protective layer PL2 of the DVD. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface R2 is transmitted again through the objective optical system OBJ and the polarization beam splitter BS, and then is converged by the collimator lens COL, reflected twice inside the prism PS, and received by the light receiving unit DS2. Condensed to And the information recorded on DVD can be read using the output signal of light-receiving part DS2.

  When information is recorded / reproduced with respect to a CD, the CD module MD2 is operated to cause the infrared semiconductor laser LD3 to emit light, as indicated by the two-dot chain line in FIG. The divergent light beam emitted from the infrared semiconductor laser LD3 is reflected by the polarization beam splitter BS after the divergence angle is converted by the coupling lens CUL, and is reflected by the objective optical system OBJ via the CD protective layer PL3. It becomes a spot formed on RL3. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL3 is transmitted again through the objective optical system OBJ, then reflected by the polarization beam splitter BS, the divergence angle is converted by the coupling lens CUL, and the CD HD module MD2 Converge on the light receiving surface of the photodetector PD3. And the information recorded on CD can be read using the output signal of photodetector PD3.

Next, the configuration of the objective optical system OBJ will be described. The aberration correction element L1 is a plastic lens having a refractive index nd at the d-line of 1.5091 and an Abbe number νd of 56.5, a refractive index with respect to λ1 of 1.5242, and a refractive index with respect to λ2 of 1.5064. , Λ3 has a refractive index of 1.5050. The condensing element L2 is a plastic lens having a refractive index nd of 1.5435 at the d-line and an Abbe number νd of 56.3. Further, a flange portion FL1 formed integrally with the optical function portion is provided around each optical function portion (region of the aberration correction element L1 and the condensing element L2 through which the laser beam from the blue-violet semiconductor laser LD1 passes). , FL2 and a part of the flange portions FL1, FL2 are joined together.
In addition, when integrating the aberration correction element L1 and the condensing element L2, they may be integrated via a separate joining member.

As shown in FIG. 4, the optical function surface S1 on the semiconductor laser light source side of the aberration correction element L1 includes a sixth optical function area AREA6 including an optical axis corresponding to an area within the numerical aperture 0.67 of the DVD, and the DVD. Is divided into a seventh optical function area AREA7 corresponding to the area from the numerical aperture 0.67 to the numerical aperture 0.85 of the high-density optical disk HD. The sixth optical function area AREA6 A superposition type diffractive structure HOE4, which is a structure in which a plurality of annular zones formed with a staircase structure are arranged around the optical axis, is formed.
In the superposition type diffractive structure HOE4 formed in the sixth optical function area AREA6, the depth d34 of the staircase structure formed in each annular zone is
d34 = 2λ1 / (n−1) (μm)
The number of steps N in each annular zone is set to 4. However, λ1 represents the wavelength of the laser beam emitted from the blue-violet semiconductor laser LD1 in units of microns (here, λ1 = 0.408 μm), and n is a refractive index with respect to the wavelength λ1 of the aberration correction element L1. is there.

When a laser beam having a wavelength λ1 from the first light emission point EP1 is incident on the staircase structure whose depth in the optical axis direction is set in this way, 2 × λ1 (μm) between adjacent staircase structures. An optical path difference is generated, and the laser beam having the wavelength λ1 is transmitted without being diffracted because it does not substantially give a phase difference (0th order diffracted light).
Further, when a laser beam having a wavelength λ3 (here, λ3 = 0.785 μm) is incident on the staircase structure, the wavelength λ3 is approximately twice as long as λ1, and therefore, between adjacent staircase structures, approximately 1 × An optical path difference of λ3 (μm) is generated, and the laser beam having the wavelength λ3 is transmitted without being diffracted (0th-order diffracted light) because a phase difference is not substantially given like the laser beam of λ1.
On the other hand, when a laser beam having a wavelength λ2 (here, λ2 = 0.658 μm) from the second emission point EP2 is incident on this staircase structure, the number N of steps in each annular zone is set to 5. Therefore, the laser beam of λ2 is diffracted in the + 1st order direction (+ 1st order diffracted light) with a phase difference according to the incident part of the superposition type diffractive structure HOE1. At this time, the diffraction efficiency of the + 1st order diffracted light of the laser beam with the wavelength λ2 is 87.5%, but the amount of light is sufficient for recording / reproducing information with respect to the DVD.

The width Λ4 of each annular zone of the superposition type diffractive structure HOE4 and the inclination direction of each annular zone (inclination direction of the envelope l4 of each staircase structure in FIG. 3) are diffracted when a laser beam of wavelength λ2 is incident. It is set such that spherical aberration in the direction of insufficient correction is added to the + 1st order diffracted light by the action.
The objective optical system OBJ is designed so that the spherical aberration is minimized with respect to the combination of the wavelength λ1, the magnification m1 = 0, and the protective layer PL1 of the high-density optical disc HD. Therefore, as in the present embodiment, when the magnification m1 for the laser beam of wavelength λ1 and the magnification m2 for the laser beam of wavelength λ2 are substantially the same, the protective layer PL1 of the high-density optical disk HD and the protective layer of the DVD Due to the difference in the thickness of PL2, the spherical aberration of the laser light beam having the wavelength λ2 transmitted through the objective optical system OBJ and the protective layer PL2 of the DVD is in the overcorrection direction.

Here, the width Λ4 of each annular zone of the superimposing type diffractive structure HOE4 and the inclination direction of each annular zone are + 1st order diffracted light due to the diffraction action when a laser beam having a wavelength λ2 is incident on the superposing type diffractive structure HOE4. The amount of spherical aberration in the direction of undercorrection added to the above and the spherical aberration in the direction of overcorrection generated due to the fact that the magnification m1 for the wavelength λ1 and the magnification m2 for the wavelength λ2 are substantially the same cancel each other. It is set to be. As a result, the laser beam having the wavelength λ2 transmitted through the superposition type diffractive structure HOE4 and the protective layer PL2 of the DVD forms a good spot on the information recording surface RL2 of the DVD.
In the above description, in order to correct the spherical aberration in the overcorrection direction caused by making the magnification m1 with respect to the wavelength λ1 and the magnification m2 with respect to λ2 substantially the same, the superposition type diffractive structure HOE4 is The structure is such that spherical aberration in the direction of insufficient correction occurs when a laser beam with wavelength λ2 is incident. However, the diffraction power of the superposition type diffractive structure HOE4 is set to be negative, and the laser beam with wavelength λ2 is incident. In this case, the laser beam having the wavelength λ2 may be emitted with an increased divergence.

In this case, the laser beam having the wavelength λ2 incident on the superposition type diffractive structure HOE4 is emitted with a high divergence. Since this corresponds to a reduction in magnification for the condensing element L2, spherical aberration in the direction of insufficient correction is added to the laser light beam having the wavelength λ2 incident on the condensing element L2 due to this change in magnification. The superposition type so that the spherical aberration in the undercorrection direction and the spherical aberration in the overcorrection direction generated due to the fact that the magnification m1 with respect to the wavelength λ1 and the magnification m2 with respect to λ2 are substantially the same are canceled out. The width Λ4 between the annular zones of the diffractive structure HOE4 and the inclination direction of each annular zone are determined.
Further, as shown in FIG. 4, the optical function surface S2 on the optical disc side of the aberration correction element L1 includes an eighth optical function area AREA8 including an optical axis corresponding to an area within the numerical aperture 0.67 of the DVD, and the DVD. Are divided into a ninth optical function area AREA9 corresponding to the area from the numerical aperture 0.67 to the numerical aperture 0.85 of the high-density optical disc HD, and a plurality of rings having a sawtooth cross-section including the optical axis. Diffraction structures DOE3 and DOE4 composed of bands are formed in the optical function area AREA8 and the optical function area AREA9, respectively.
The diffractive structures DOE3 and DOE4 are structures for suppressing the chromatic aberration of the objective optical system OBJ in the blue-violet region and the spherical aberration change accompanying the temperature change.

In the diffractive structure DOE3, the height d03 of the step closest to the optical axis has a diffraction efficiency of 100% with respect to a light flux with a wavelength of 390 nm (the refractive index of the aberration correction element L1 with respect to the wavelength of 390 nm is 1.5273). And satisfies the above-described expression (16). When the laser beam having the wavelength λ1 is incident on the diffractive structure DOE1 in which the step depth is set as described above, the + 2nd order diffracted light is generated with the diffraction efficiency of 96.8%, and the laser beam having the wavelength λ2 is incident. + 1st order diffracted light is generated with a diffraction efficiency of 93.9%, and when a laser beam having a wavelength of λ3 is incident, + 1st order diffracted light is generated with a diffraction efficiency of 99.2%. Therefore, sufficient diffraction efficiency is obtained in any wavelength region. Even when the chromatic aberration is corrected in the blue-violet region, the chromatic aberration correction in the wavelength region of the wavelength λ2 and the wavelength λ3 is not excessive.
On the other hand, since the diffractive structure DOE4 is optimized for the wavelength λ1, the diffractive structure DOE4 is used.
On the other hand, when a laser beam having a wavelength λ1 is incident, + 2nd order diffracted light is generated with a diffraction efficiency of 100%.

Furthermore, in the diffractive structures DOE3 and DOE4, in the blue-violet region, when the wavelength of the incident light beam becomes longer, the spherical aberration changes in the direction of insufficient correction, and when the wavelength of the incident light beam becomes shorter, the spherical aberration is corrected. It has the wavelength dependence of spherical aberration that changes in the excess direction. Accordingly, the usable temperature range of the objective optical system OBJ, which is a high NA plastic lens, is expanded by canceling out the spherical aberration change generated in the light condensing element in accordance with the environmental temperature change.
The aberration correction element L1 of the present embodiment has a configuration in which the superposition type diffractive structure is formed on the optical function surface S1 on the semiconductor laser light source side and the type diffractive structure is formed on the optical function surface S2 on the optical disc side. Conversely, a configuration may be adopted in which a mold diffractive structure is formed on the optical functional surface S1 on the semiconductor laser light source side, and a superimposed diffractive structure is formed on the optical functional surface S2 on the optical disk side.

Further, since the objective optical system OBJ of the present embodiment is an optical system in which the sine condition is corrected for an object point at infinity, the sine condition for a finite object point is not satisfied. Therefore, when a divergent light beam is incident on the objective optical system OBJ as in the case of recording / reproducing information with respect to a CD, the objective optical system OBJ is in a direction perpendicular to the optical axis (CD track direction). When shifted, the light emitting point of the infrared semiconductor laser LD3 becomes an off-axis object point, and thus coma aberration occurs.
The coupling lens CUL is a coma correction element having a function of reducing such coma aberration. When the objective optical system OBJ is not driven in the direction perpendicular to the optical axis by the biaxial actuator AC, the laser beam having the wavelength λ3 is used. Is designed so that the spherical aberration is corrected to be equal to or less than the diffraction limit within the effective diameter through which the lens passes, and the spherical aberration is generated outside the effective diameter in the overcorrected direction.
As a result, when the objective optical system OBJ is shifted in the direction perpendicular to the optical axis, the laser beam having the wavelength λ3 passes through the region designed to have a large spherical aberration, so that the coupling lens CUL and the objective Coma aberration is added to the laser beam having the wavelength λ3 that has passed through the optical system OBJ. The direction and magnitude of the spherical aberration outside the effective diameter of the coupling lens CUL cancels out this coma aberration and the coma aberration caused by the fact that the emission point of the infrared semiconductor laser LD3 becomes an off-axis object point. Has been determined to be.

By using it in combination with the coupling lens CUL designed in this way, it becomes possible to improve the tracking characteristic for the CD of the objective optical system OBJ that does not satisfy the sine condition for the finite object point. .
Here, the opening switching when information is recorded / reproduced with respect to the DVD and the CD in the second optical pickup device PU2 of the present embodiment will be described.
In the second optical pickup device PU2, since NA1, NA2, and NA3 are different from each other, when recording / reproducing information on a DVD or CD, it is necessary to switch the aperture according to the numerical aperture of each optical disc. is there.
Since the superposition type diffractive structure HOE4 is formed in the sixth optical function area AREA6 including the optical axis, the spherical aberration with respect to the wavelength λ2 is corrected only for the light beam passing through the sixth optical function area AREA6. The light beam that passes through the seventh optical function area AREA 7 surrounding the periphery is not corrected. Accordingly, of the light beam having the wavelength λ2 incident on the objective optical system OBJ, the light beam that passes through the seventh optical function area AREA7 becomes a flare component that does not contribute to spot formation on the information recording surface RL2 of the DVD.
Since this is equivalent to automatically switching the aperture corresponding to NA2, in the second optical pickup device PU2, it is not necessary to separately provide an aperture limiting element corresponding to the numerical aperture NA2 of the DVD.
On the other hand, since the objective optical system OBJ does not have an aperture switching function for the wavelength λ3, it is necessary to separately provide an aperture limiting element corresponding to the numerical aperture NA3 of the CD. The objective optical system OBJ has an aberration as the aperture limiting element. Optical functional surface S1 on the semiconductor laser light source side of the correction element L1
A wavelength selection filter WF is formed on the substrate.

As shown in FIG. 12, the wavelength selection filter WF transmits all wavelengths from λ1 to λ3 in the region within NA3, and has a wavelength selectivity with a transmittance that blocks only wavelength λ3 in the region outside NA3. The aperture switching corresponding to NA3 is performed by such wavelength selectivity.
The wavelength selection filter WF may have a wavelength selectivity of transmittance as shown in FIG. This wavelength selection filter WF transmits all wavelengths from λ1 to λ3 in the region within NA3, blocks only wavelength λ3 in the region from NA3 to NA2, and blocks wavelengths λ2 and λ3 in the region from NA2 to NA1. Since the wavelength selectivity of the transmittance is high, aperture switching corresponding to NA2 and NA3 can be performed by such wavelength selectivity.
In this embodiment, the wavelength selection filter WF is formed on the optical function surface of the aberration correction element L1. However, the wavelength selection filter WF may be formed on the optical function surface of the condensing element L2, or the wavelength selection filter WF. An aperture limiting element AP formed on the optical functional surface may be separately mounted. In this case, it is preferable that the aperture limiting element AP and the objective optical system OBJ are integrally driven for tracking by the biaxial actuator AC.

[Third embodiment]
FIG. 5 is a diagram schematically showing a configuration of a third optical pickup device PU3 capable of appropriately recording / reproducing information for any of the high-density optical disc HD, DVD, and CD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, the numerical aperture NA1 = 0.85, and the optical specification of the DVD is the wavelength λ2 = 658 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.67. The optical specification of the CD is a wavelength λ3 = 785 nm, the protective layer PL3 has a thickness t3 = 1.2 mm, and the numerical aperture NA3 = 0. .51. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

The optical pickup device PU3 is a high-density optical disc in which a blue-violet semiconductor laser LD1 that emits light and emits a laser beam of 408 nm and a photodetector PD1 are integrated when information is recorded / reproduced on the high-density optical disc HD. The first light emitting point EP1 that emits light when emitting / recording information to / from the HD module MD1 and DVD and the light emitted when recording / reproducing information to / from the CD. A second light emitting point EP2 that emits a laser beam of 785 nm, a first light receiving unit DS1 that receives a reflected beam from the information recording surface RL2 of the DVD, and a first beam that receives the reflected beam from the information recording surface RL3 of the CD. A DVD / CD laser module LM1, an aberration correction element L1, and the aberration correction element L. Objective optical system OBJ having a function of condensing the laser beam transmitted through the information recording surfaces RL1, RL2, and RL3 and a condensing element L2 having both surfaces aspherical, a biaxial actuator AC, a high density The optical disk HD includes a stop STO corresponding to a numerical aperture NA of 0.85, a polarization beam splitter BS, a collimating lens COL, and a coupling lens CUL.
In addition to the blue-violet semiconductor laser LD1 described above, a blue-violet SHG laser can also be used as a light source for the high-density optical disk HD.

  When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU3, the high-density optical disk HD module MD1 is actuated as shown by the solid line in FIG. The violet semiconductor laser LD1 is caused to emit light. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is converted into a substantially parallel light beam through the collimating lens COL, and after passing through the polarization beam splitter BS, the light beam diameter is regulated by the stop STO, and the high-density optical disk by the objective optical system OBJ. It becomes a spot formed on the information recording surface RL1 via the HD protective layer PL1. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ, the stop STO, the polarization beam splitter BS, and the collimating lens COL, and then becomes a convergent light beam. Converges on the light receiving surface of the photodetector PD1. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD1.

  Further, when recording / reproducing information with respect to the DVD in the optical pickup device PU3, the first light emission point EP1 is caused to emit light. The divergent light beam emitted from the first light emitting point EP1 is reflected by the prism PS as shown by the ray path in FIG. 5, and the divergent angle is converted by the coupling lens CUL, and then the polarized beam. It is reflected by the splitter BS and becomes a spot formed on the information recording surface RL2 by the objective optical system OBJ via the DVD protective layer PL2. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the objective optical system OBJ and reflected by the polarization beam splitter BS, and then the divergence angle is converted by the coupling lens CUL, and the inside of the prism PS. It is reflected twice and collected on the light receiving part DS1. And the information recorded on DVD can be read using the output signal of light-receiving part DS1.

  Further, in the optical pickup device PU3, when information is recorded / reproduced with respect to the CD, the second light emission point EP2 is caused to emit light. The divergent light beam emitted from the second light emitting point EP2 is reflected by the prism PS and its divergence angle is converted by the coupling lens CUL, as depicted by the two-dot chain line in FIG. The spot is reflected by the polarization beam splitter BS and becomes a spot formed on the information recording surface RL1 by the objective optical system OBJ via the CD protective layer PL1. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ and reflected by the polarization beam splitter BS, and then the divergence angle is converted by the coupling lens CUL, and the inside of the prism PS. Reflected twice and collected on the light receiving part DS2. And the information recorded on CD can be read using the output signal of light-receiving part DS2.

Next, the configuration of the objective optical system OBJ will be described. The aberration correction element L1 is a plastic lens having a refractive index nd at the d-line of 1.5091 and an Abbe number νd of 56.5, a refractive index with respect to λ1 of 1.5242, and a refractive index with respect to λ2 of 1.5064. , Λ3 has a refractive index of 1.5050. The condensing element L2 is a plastic lens having a refractive index nd of 1.5435 at the d-line and an Abbe number νd of 56.3. Further, a flange portion FL1 formed integrally with the optical function portion is provided around each optical function portion (region of the aberration correction element L1 and the condensing element L2 through which the laser beam from the blue-violet semiconductor laser LD1 passes). , FL2 and a part of the flange portions FL1, FL2 are joined together.
In addition, when integrating the aberration correction element L1 and the condensing element L2, they may be integrated via a separate joining member.
As shown in FIG. 6, the optical function surface S1 of the aberration correction element L1 on the semiconductor laser light source side includes the tenth optical function area AREA10 including the optical axis corresponding to the area within the numerical aperture 0.67 of the DVD, and the DVD. Are divided into an eleventh optical function area AREA11 corresponding to an area from the numerical aperture 0.67 to the numerical aperture 0.85 of the high-density optical disc HD, and a plurality of annular zones in which a staircase structure is formed. Are formed in the tenth optical function area AREA10.

In the superposition type diffractive structure HOE5 formed in the tenth optical function area AREA10, the depth d35 of the staircase structure formed in each annular zone is
d35 = 2λ1 / (n−1) (μm)
The number of steps N in each annular zone is set to 4. However, λ1 represents the wavelength of the laser beam emitted from the blue-violet semiconductor laser LD1 in units of microns (here, λ1 = 0.408 μm), and n is a refractive index with respect to the wavelength λ1 of the aberration correction element L1. is there.
When a laser beam having a wavelength λ1 is incident on the staircase structure whose depth in the optical axis direction is set in this way, an optical path difference of 2 × λ1 (μm) occurs between adjacent staircase structures, and the wavelength λ1 Since the laser beam is substantially given no phase difference, it is transmitted without being diffracted (0th order diffracted light).
Further, when a laser beam having a wavelength λ3 (here, λ3 = 0.785 μm) is incident on the staircase structure, the wavelength λ3 is approximately twice as long as λ1, and therefore, between adjacent staircase structures, approximately 1 × An optical path difference of λ3 (μm) is generated, and the laser beam having the wavelength λ3 is transmitted without being diffracted (0th-order diffracted light) because a phase difference is not substantially given like the laser beam of λ1.

On the other hand, when a laser beam having a wavelength λ2 (here, λ2 = 0.658 μm) from the second emission point EP2 is incident on this staircase structure, the number N of steps in each annular zone is set to 5. Therefore, the laser beam of λ2 is diffracted in the first order direction (+ 1st order diffracted light) with a phase difference according to the incident part of the superposition type diffractive structure HOE5. At this time, the diffraction efficiency of the + 1st order diffracted light of the laser beam with the wavelength λ2 is 87.5%, but the amount of light is sufficient for recording / reproducing information with respect to the DVD.
The width Λ5 of each annular zone of the superposition type diffractive structure HOE5 and the inclination direction of each annular zone (in FIG. 5, the inclination direction of the envelope 15 of each staircase structure) It is set such that spherical aberration in the direction of insufficient correction is added to the + 1st order diffracted light by the action.

Furthermore, the minimum value P of the width of the staircase structure of the superposition type diffractive structure HOE5 facilitates die processing by SPDT, and the diffraction efficiency drop due to the shape error of the die becomes too large for the wavelength λ1 in the blue-violet region. In order to avoid this, it is set so as to satisfy the above formula (9).
For this reason, the spherical aberration in the overcorrection direction generated due to the thicknesses of the protective layer PL1 of the high-density optical disk HD and the protective layer PL2 of the DVD cannot be corrected only by the action of the superposition type diffractive structure HOE5.
Therefore, the magnification m2 of the objective optical system OBJ with respect to the wavelength λ2 is set so that the spherical aberration in the overcorrection direction remaining without being corrected by the superposition type diffractive structure HOE5 is corrected. As a result, the laser beam having the wavelength λ2 transmitted through the superposition type diffractive structure HOE5 and the protective layer PL2 of the DVD forms a good spot on the information recording surface RL2 of the DVD.

In the above description, the superposition type diffractive structure HOE5 is configured to generate a spherical aberration in the direction of insufficient correction when a laser beam having a wavelength λ2 is incident. However, the superposition type diffractive structure HOE5 has a negative diffractive power. In this case, the laser beam having the wavelength λ2 may be emitted when the divergence of the laser beam having the wavelength λ2 is increased.
In this case, the laser beam having the wavelength λ2 incident on the superposition type diffractive structure HOE5 is emitted with a high divergence. Since this corresponds to a reduction in magnification for the condensing element L2, spherical aberration in the direction of insufficient correction is added to the laser light beam having the wavelength λ2 incident on the condensing element L2 due to this change in magnification. Also in this case, the width Λ5 between the annular zones of the superposition type diffractive structure HOE5 and the inclination direction of each annular zone are determined so as to satisfy the above-described equation (9), and the magnification with respect to the wavelength λ2 of the objective optical system OBJ m2 is determined so that the spherical aberration in the overcorrected direction remaining without being corrected by the superposition type diffractive structure HOE5 is corrected.

Furthermore, the optical function surface S2 on the optical disc side of the aberration correction element L1 includes a twelfth optical function area AREA12 including an optical axis corresponding to an area within the numerical aperture 0.67 of the DVD, as shown in FIG.
It is divided into a thirteenth optical function area AREA13 corresponding to an area from the numerical aperture 0.67 of DVD to the numerical aperture 0.85 of the high-density optical disk HD, and the cross-sectional shape including the optical axis is a plurality of sawtooth shapes Diffraction structures DOE5 and DOE6 each composed of an annular zone are formed in the optical function area AREA12 and the optical function area AREA13, respectively.
The diffractive structures DOE5 and DOE6 are structures for suppressing the chromatic aberration of the objective optical system OBJ in the blue-violet region and the spherical aberration change accompanying the temperature change. The specific structure is the diffractive structure DOE3 of the optical pickup device PU2. Since it is the same as DOE4, detailed description is omitted here.

In the aberration correction element L1 of the present embodiment, the superposition type diffractive structure is formed on the optical functional surface S1 on the semiconductor laser light source side, and the diffractive structure is formed on the optical functional surface S2 on the optical disc side. On the contrary, a configuration may be adopted in which a diffractive structure is formed on the optical function surface S1 on the semiconductor laser light source side and a superposition type diffractive structure is formed on the optical function surface S2 on the optical disk side.
In addition, the coupling lens CUL sets the divergence angle between the laser beam having the wavelength λ2 emitted from the first emission point EP1 and the laser beam having the wavelength λ3 emitted from the second emission point EP2, respectively. This is an optical element for converting and emitting the divergence angle corresponding to the magnification m2 for the wavelength λ2 of the system OBJ and the magnification m3 for the wavelength λ3.

The coupling lens CUL is a plastic lens having a refractive index nd at the d-line of 1.5091, an Abbe number νd of 56.5, a refractive index with respect to λ2 of 1.5064, and a refractive index with respect to λ3 of 1.5050. It is.
Here, the paraxial refraction power of the coupling lens CUL with respect to the wavelength λ2 is such that the divergence angle of the laser beam having the wavelength λ2 emitted from the first emission point EP1 is set to the magnification m2 with respect to the wavelength λ2 of the objective optical system OBJ. It is determined so that it can be emitted after being converted into a corresponding divergence angle.
The optical functional surface S2 on the optical disc side of the coupling lens CUL includes a fourteenth optical functional area AREA14 (not shown) including an optical axis corresponding to an area within the numerical aperture 0.51 of the CD, and a numerical aperture 0. 51 to 15th optical function area AREA15 (not shown) corresponding to the area from the numerical aperture of DVD to 0.67, and a plurality of annular zones formed with a staircase structure inside the optical axis A superposition type diffractive structure HOE6 which is a structure arranged as a center is formed in the optical function area AREA14.

In the superposition type diffractive structure HOE6 formed in the fourteenth optical function area AREA14, the depth d36 of the staircase structure formed in each annular zone is:
d36 = 1λ2 / (n−1) (μm)
The number N of steps in each annular zone is set to 5. Here, λ2 represents the wavelength of the laser beam emitted from the first light emission point EP1 in units of microns, and n is the refractive index with respect to the wavelength λ2 of the coupling lens CUL.
When a laser beam having a wavelength λ2 is incident on the staircase structure whose depth in the optical axis direction is set in this way, an optical path difference of 1 × λ1 (μm) is generated between adjacent staircase structures, and the wavelength λ2 Since the laser beam is substantially given no phase difference, it is transmitted without being diffracted (0th order diffracted light).

On the other hand, when a laser beam having a wavelength λ3 from the second emission point EP2 is incident on this staircase structure, the number N of steps in each annular zone is set to 5, so that the laser beam of λ3 is A phase difference is given according to the incident part of the superposition type diffractive structure HOE6, and diffracted in the −1st order direction (−1st order diffracted light). At this time, the diffraction efficiency of the minus first-order diffracted light of the laser beam having the wavelength λ3 is 91.1%, but the amount of light is sufficient for recording / reproducing information with respect to the CD.
The paraxial diffraction power for the wavelength λ3 of the superposition type diffractive structure HOE6 is set to be negative, and the width Λ6 of each annular zone of the superposition type diffraction structure HOE6 and the inclination direction of each annular zone (in FIG. 5). The inclination direction of the envelope 16 of each step structure) is such that the divergence angle of the laser beam having the wavelength λ3 emitted from the second emission point EP2 corresponds to the divergence angle corresponding to the magnification m3 with respect to the wavelength λ3 of the objective optical system OBJ. It has been decided to be converted.

Thus, by utilizing the wavelength selectivity of the diffractive action of the superposition type diffractive structure HOE6, even when the magnification m2 with respect to the wavelength λ2 and the magnification m3 with respect to the wavelength λ3 of the objective optical system OBJ are different from each other, a DVD laser The DVD / CD laser module LM1 in which the light source and the CD laser light source are integrated can be used.
Here, the aperture switching when information is recorded / reproduced on the DVD and CD in the third optical pickup device PU3 of the present embodiment will be described.
In the third optical pickup device PU3, NA1, NA2, and NA3 are different from each other. Therefore, when recording / reproducing information on a DVD or CD, it is necessary to switch the aperture according to the numerical aperture of each optical disc. is there.
Since the superposition type diffractive structure HOE5 is formed in the tenth optical function area AREA10 including the optical axis, the spherical aberration with respect to the wavelength λ2 is corrected only for the light beam passing through the tenth optical function area AREA10, The light beam passing through the eleventh optical function area AREA11 surrounding the periphery is not corrected. Accordingly, of the light beam having the wavelength λ2 incident on the objective optical system OBJ, the light beam that passes through the eleventh optical function area AREA11 becomes a flare component that does not contribute to spot formation on the information recording surface RL2 of the DVD.
Since this is equivalent to automatically switching the aperture corresponding to NA2, in the third optical pickup device PU3, it is not necessary to separately provide an aperture limiting element corresponding to the numerical aperture NA2 of the DVD.

On the other hand, since the objective optical system OBJ does not have an aperture switching function for the wavelength λ3, it is necessary to separately provide an aperture limiting element corresponding to the numerical aperture NA3 of the CD. The objective optical system OBJ has an aberration as the aperture limiting element. A wavelength selection filter WF is formed on the optical function surface S1 on the semiconductor laser light source side of the correction element L1.
As shown in FIG. 12, the wavelength selection filter WF transmits all wavelengths from λ1 to λ3 in the region within NA3, and has a wavelength selectivity with a transmittance that blocks only wavelength λ3 in the region outside NA3. The aperture switching corresponding to NA3 is performed by such wavelength selectivity.
The wavelength selection filter WF may have a wavelength selectivity of transmittance as shown in FIG. This wavelength selection filter WF transmits all wavelengths from λ1 to λ3 in the region within NA3, blocks only wavelength λ3 in the region from NA3 to NA2, and blocks wavelengths λ2 and λ3 in the region from NA2 to NA1. Since the wavelength selectivity of the transmittance is high, aperture switching corresponding to NA2 and NA3 can be performed by such wavelength selectivity.
In this embodiment, the wavelength selection filter WF is formed on the optical function surface of the aberration correction element L1. However, the wavelength selection filter WF may be formed on the optical function surface of the condensing element L2, or the wavelength selection filter WF. An aperture limiting element AP formed on the optical functional surface may be separately mounted. In this case, it is preferable that the aperture limiting element AP and the objective optical system OBJ are integrally driven for tracking by the biaxial actuator AC.

[Fourth embodiment]
FIG. 7 is a diagram schematically showing a configuration of a fourth optical pickup device PU4 capable of appropriately recording / reproducing information for any of the high-density optical disc HD, DVD, and CD. The optical specification of the high-density optical disc HD is the wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.6 mm, and the numerical aperture NA1 = 0.65. The optical specification of the DVD is the wavelength λ2 = 658 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.65. The optical specifications of the CD are a wavelength λ3 = 785 nm, a protective layer PL3 has a thickness t3 = 1.2 mm, and a numerical aperture NA3 = 0. .50. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

The optical pickup device PU4 is a high-density optical disc in which a blue-violet semiconductor laser LD1 that emits a 408 nm laser beam and a photodetector PD1 are integrated when information is recorded / reproduced on the high-density optical disc HD. The first light emitting point EP1 that emits light when emitting / recording information to / from the HD module MD1 and DVD and the light emitted when recording / reproducing information to / from the CD. A second light emitting point EP2 that emits a laser beam of 785 nm, a first light receiving unit DS1 that receives a reflected beam from the information recording surface RL2 of the DVD, and a first beam that receives the reflected beam from the information recording surface RL3 of the CD. DVD / CD laser module LM1, objective optical system OBJ, biaxial actuator composed of two light receiving sections DS2 and prism PS C, diaphragm STO corresponding to numerical aperture NA0.65 of the high density optical disk HD, the polarizing beam splitter BS, and a collimator lens COL.
In addition to the blue-violet semiconductor laser LD1 described above, a blue-violet SHG laser can also be used as a light source for the high-density optical disk HD.

  When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU4, the high-density optical disk module MD1 is operated as shown in FIG. The violet semiconductor laser LD1 is caused to emit light. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is converted into a substantially parallel light beam through the collimating lens COL, and after passing through the polarization beam splitter BS, the light beam diameter is regulated by the stop STO, and the high-density optical disk by the objective optical system OBJ. It becomes a spot formed on the information recording surface RL1 via the HD protective layer PL1. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ, the stop STO, the polarization beam splitter BS, and the collimating lens COL, and then becomes a convergent light beam. Converges on the light receiving surface of the photodetector PD1. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD1.

  In addition, when recording / reproducing information with respect to the DVD in the optical pickup device PU4, the first light emission point EP1 is caused to emit light. The divergent light beam emitted from the first light emitting point EP1 is reflected by the prism PS and reflected by the polarization beam splitter BS as depicted in the ray path by the wavy line in FIG. 7, and then is reflected by the objective optical system OBJ. The spot is formed on the information recording surface RL2 via the protective layer PL2. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the objective optical system OBJ, reflected by the polarization beam splitter BS, then reflected twice inside the prism PS and condensed on the light receiving part DS1. And the information recorded on DVD can be read using the output signal of light-receiving part DS1.

  In addition, when recording / reproducing information with respect to the CD in the optical pickup device PU4, the second light emitting point EP2 is caused to emit light. The divergent light beam emitted from the second light emitting point EP2 is reflected by the prism PS and reflected by the polarization beam splitter BS, as shown by the two-dot chain line in FIG. 7, and then the objective optical system OBJ. As a result, the spot is formed on the information recording surface RL1 via the protective layer PL1 of the CD. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ, reflected by the polarization beam splitter BS, then reflected twice inside the prism PS and condensed on the light receiving part DS2. And the information recorded on CD can be read using the output signal of light-receiving part DS2.

Next, the configuration of the objective optical system OBJ will be described. The objective optical system OBJ is a plastic lens having a refractive index nd of d09 of 1.5091, an Abbe number νd of 56.5, a refractive index with respect to λ1 of 1.5242, and a refractive index with respect to λ2 of 1.5064. , Λ3 has a refractive index of 1.5050.
As shown in FIG. 8, the optical function surface S1 on the side of the semiconductor laser light source of the objective optical system OBJ includes a sixteenth optical function area AREA16 including an optical axis corresponding to an area within the numerical aperture 0.50 of CD, and CD Are divided into a seventeenth optical function area AREA17 corresponding to an area from a numerical aperture 0.50 to a numerical aperture 0.65 of a high-density optical disk HD (DVD), and a plurality of staircase structures are formed therein. Is formed in the sixteenth optical function area AREA16. The superposition type diffractive structure HOE7 has a structure in which the annular zones are arranged around the optical axis.

  The width Λ7 of each annular zone of the superimposing type diffractive structure HOE7 and the inclination direction of each annular zone are determined with respect to the + 1st order diffracted light by the diffraction action when the laser beam having the wavelength λ2 is incident on the superposing type diffractive structure HOE7 The amount of spherical aberration in the overcorrection direction to be added, and the spherical aberration in the direction of undercorrection generated due to the fact that the magnification m2 with respect to the wavelength λ2 and the magnification m3 with respect to λ3 are substantially the same cancel each other. Is set. As a result, the laser beam having the wavelength λ2 transmitted through the superposition type diffractive structure HOE1 and the protective layer PL2 of the DVD forms a good spot on the information recording surface RL2 of the DVD.

Since the specific structure of the superposition type diffractive structure HOE7 is the same as that of the superposition type diffractive structure HOE1 of the optical pickup device PU1, detailed description thereof is omitted here.
In the superposition type diffractive structure HOE7, similarly to the superposition type diffractive structure HOE1 of the optical pickup device PU1, the diffractive power at the paraxial axis is set to be positive, and when the laser beam having the wavelength λ2 is incident, The laser beam may be emitted with a small divergence.
Further, an optical path difference providing structure NPS that is a structure for suppressing a change in spherical aberration accompanying a temperature change of the objective optical system OBJ in the blue-violet region is formed on the entire surface of the optical functional surface S1 on the semiconductor laser light source side of the objective optical system OBJ. Is formed.

In the optical path difference providing structure NPS, the height d11 of the step closest to the optical axis is designed such that an optical path difference of 10 × λ1 (μm) is added to the wavelength λ1 between adjacent step structures. When the optical path differences Φ2 and Φ3 added to the wavelengths λ2 and λ3 by the adjacent annular zones divided by the steps are calculated by the above-described equations (22) and (23), Φ2 = 5. 99, and Φ3 = 5.01. Since Φ2 and Φ3 are substantially integers, high-order spherical aberration due to the optical path difference providing structure NPS is small, and high transmittance can be realized.
Furthermore, as shown in FIG. 8, in the optical path difference providing structure NPS, the annular zone adjacent to the outside of the central region is formed by being shifted in the optical axis direction so that the optical path length is shorter than the central region. The annular zone at the effective diameter position is formed by shifting in the optical axis direction so that the optical path length is longer with respect to the annular zone adjacent to the inside, and the annular zone at a position of 75% of the maximum effective diameter is the inner side thereof. Is formed by shifting in the optical axis direction so that the optical path length is shorter with respect to the annular zone adjacent to the outer zone and the annular zone adjacent to the outer zone.

The optical path difference providing structure NPS having such a configuration is a spherical surface in which the spherical aberration changes in the undercorrection direction when the refractive index is low, and the spherical aberration changes in the overcorrection direction when the refractive index is high. Since the aberration has a refractive index dependency, it is possible to suppress a change in spherical aberration accompanying a temperature change of the objective optical system OBJ in the blue-violet region.
A diffractive structure DOE7 composed of a plurality of annular zones whose sawtooth shape is included in the cross section including the optical axis is formed on the entire optical functional surface of the collimator lens COL on the optical disk side. This is a structure for suppressing the chromatic aberration of the objective optical system OBJ in the region.
Here, the aperture switching when information is recorded / reproduced with respect to the CD in the fourth optical pickup device PU4 of the present embodiment will be described.
In the fourth optical pickup device PU4, since NA1 (= NA2) and NA3 are different, it is necessary to switch the aperture according to the numerical aperture NA3 when recording / reproducing information on / from the CD.

Since the objective optical system OBJ does not have an aperture switching function for the wavelength λ3, it is necessary to separately provide an aperture limiting element corresponding to the numerical aperture NA3 of the CD. The objective optical system OBJ is provided on the side of the semiconductor laser light source as the aperture limiting element. A wavelength selection filter WF is formed on the optical function surface S1.
As shown in FIG. 12, the wavelength selection filter WF transmits all wavelengths from λ1 to λ3 in the region within NA3, and has a wavelength selectivity with a transmittance that blocks only wavelength λ3 in the region outside NA3. The aperture switching corresponding to NA3 is performed by such wavelength selectivity.
When NA1, NA2 and NA3 are different from each other, it is preferable that the wavelength selective filter WF has wavelength selectivity of transmittance as shown in FIG. Through all wavelengths from λ3 to λ3, the wavelength selectivity of the transmittance is such that only the wavelength λ3 is blocked in the region of NA3 to NA2, and the wavelengths λ2 and λ3 are blocked in the region of NA2 to NA1. With such wavelength selectivity, aperture switching corresponding to NA2 and NA3 can be performed.
In the present embodiment, the wavelength selection filter WF is formed on the optical function surface of the objective optical system OBJ. However, the aperture selection element AP having the wavelength selection filter WF formed on the optical function surface is separately mounted. Also good. In this case, it is preferable that the aperture limiting element AP and the objective optical system OBJ are integrally driven for tracking by the biaxial actuator AC.

[Fifth embodiment]
FIG. 14 is a diagram schematically showing a configuration of a fifth optical pickup device PU5 capable of appropriately recording / reproducing information for any of the high density optical disc HD, DVD, and CD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, the numerical aperture NA1 = 0.85, and the optical specification of the DVD is the wavelength λ2 = 658 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.60. The optical specification of the CD is a wavelength λ3 = 785 nm, the protective layer PL3 has a thickness t3 = 1.2 mm, and a numerical aperture NA3 = 0. .45. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.
The optical pickup device PU5 is a high density in which a blue-violet semiconductor laser LD1 that emits light and emits a laser beam of 408 nm and a photodetector PD1 are integrated when recording / reproducing information on a high density optical disk HD. Optical disk HD module MD1, DVD module MD2, CD in which red semiconductor laser LD2 that emits a 658 nm laser beam and light detector PD2 is integrated when recording / reproducing information on DVD is integrated On the other hand, a CD module MD3 in which an infrared semiconductor laser LD3 that emits a 785 nm laser beam and emits a laser beam of 785 nm and an optical detector PD3 are integrated when recording / reproducing information, an aberration correction element L1, and the aberration correction element. Both surfaces having a function of condensing the laser beam transmitted through L1 on the information recording surfaces RL1, RL2, and RL3 Objective optical system OBJ composed of condensing element L2 made spherical, aperture limiting element AP, biaxial actuator AC, stop STO corresponding to numerical aperture NA 0.85 of high density optical disk HD, first polarizing beam splitter It is composed of BS1, a second polarizing beam splitter BS2, a collimating lens COL, a one-axis actuator UAC, and a beam shaping element SH.

When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU5, as shown in FIG. The semiconductor laser LD1 is caused to emit light. The divergent light beam emitted from the blue-violet semiconductor laser LD1 passes through the beam shaping element SH, so that its cross-sectional shape is shaped from an ellipse to a circle, passes through the first polarization beam splitter BS1, and is collimated by the collimating lens COL. After being converted into a parallel beam, the beam passes through the second polarizing beam splitter BS2, the beam diameter is regulated by the stop STO, the aperture limiting element AP, and the protective layer PL1 of the high-density optical disc HD is passed through the objective optical system OBJ. And a spot formed on the information recording surface RL1. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ, the aperture limiting element AP, the second polarization beam splitter BS2, and the collimator lens COL, and then becomes a convergent light beam. The light passes through the beam splitter BS1 and the beam shaping element SH, and converges on the light receiving surface of the photodetector PD1 of the HD module MD1 for high density optical disc. Then, information recorded on the high-density optical disk HD can be read using the output signal of the photodetector PD1.

Further, when information is recorded / reproduced with respect to the DVD by the optical pickup device PU5, the DVD module MD2 is operated to emit the red semiconductor laser LD2 as shown by the dotted line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 to be reflected is reflected by the first polarizing beam splitter BS1, converted into a parallel light beam by the collimating lens COL, and then transmitted through the second polarizing beam splitter BS2 to be used as an aperture limiting element. The beam diameter is regulated by the AP, and the spot is formed on the information recording surface RL2 via the protective layer PL2 of the DVD by the objective optical system OBJ. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the objective optical system OBJ, the aperture limiting element AP, the second polarization beam splitter BS2, and the collimator lens COL, and then becomes a convergent light beam. It is reflected by the beam splitter BS2 and converges on the light receiving surface of the photodetector PD2 of the DVD module MD2. And the information recorded on DVD can be read using the output signal of photodetector PD2.
When recording / reproducing information on / from a CD, the CD module MD3 is operated to cause the infrared semiconductor laser LD3 to emit light, as shown by the two-dot chain line in FIG. The divergent light beam emitted from the infrared semiconductor laser LD3 is reflected by the second polarization beam splitter BS2, and then the diameter of the light beam is regulated by the aperture limiting element AP. The objective optical system OBJ passes through the CD protective layer PL3. The spot is formed on the information recording surface RL3. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL3 is transmitted again through the objective optical system OBJ, then reflected by the second polarization beam splitter BS2, and is reflected on the light receiving surface of the photodetector PD3 of the CD module MD3. Converge. And the information recorded on CD can be read using the output signal of photodetector PD3.

Next, the configuration of the objective optical system OBJ will be described. The aberration correction element L1 is a plastic lens having a refractive index nd at the d-line of 1.5091 and an Abbe number νd of 56.5, a refractive index with respect to λ1 of 1.5242, and a refractive index with respect to λ2 of 1.5064. , Λ3 has a refractive index of 1.5050. The condensing element L2 is a plastic lens having a refractive index nd of 1.5435 at the d-line and an Abbe number νd of 56.3. Further, a flange portion FL1 formed integrally with the optical function portion is provided around each optical function portion (region of the aberration correction element L1 and the condensing element L2 through which the laser beam from the blue-violet semiconductor laser LD1 passes). , FL2 and a part of the flange portions FL1, FL2 are joined together.
As shown in FIG. 15A, the optical function surface S1 on the semiconductor laser light source side of the aberration correction element L1 is an eighteenth optical function area AREA18 including the optical axis corresponding to the area within the numerical aperture 0.60 of the DVD. And the nineteenth optical function area AREA19 corresponding to the area from the numerical aperture 0.60 of the DVD to the numerical aperture 0.85 of the high-density optical disk HD. A superposition type diffractive structure HOE8 having a structure in which a plurality of annular zones having a staircase structure are arranged around the optical axis is formed.
Since the structure of the superposition type diffractive structure HOE8 formed in the eighteenth optical function area AREA18 is the same as the superposition type diffractive structure HOE4 in the second optical pickup device PU2, detailed description thereof is omitted here.

Further, the optical function surface S2 on the optical disc side of the aberration correction element L1 is, as shown in FIG. 15C, a twentieth optical function area AREA20 including the optical axis corresponding to the area within the numerical aperture 0.60 of DVD. And a 21st optical function area AREA21 corresponding to an area from the numerical aperture 0.60 of the DVD to the numerical aperture 0.85 of the high-density optical disk HD, and the cross-sectional shape including the optical axis is a sawtooth shape. Diffraction structures DOE8 and DOE9 each including a plurality of annular zones are formed in the optical function area AREA20 and the optical function area AREA21, respectively.
The diffractive structures DOE8 and DOE9 are structures for suppressing the chromatic aberration of the objective optical system OBJ in the blue-violet region and the spherical aberration change accompanying the temperature change, and the structure is the diffractive structure DOE3 in the second optical pickup device PU2. Since it is the same as DOE4, detailed description is omitted here.
The aberration correction element L1 of the present embodiment has a configuration in which the superposition type diffractive structure is formed on the optical function surface S1 on the semiconductor laser light source side and the type diffractive structure is formed on the optical function surface S2 on the optical disc side. Conversely, a configuration may be adopted in which a mold diffractive structure is formed on the optical functional surface S1 on the semiconductor laser light source side, and a superimposed diffractive structure is formed on the optical functional surface S2 on the optical disk side.
In addition, the collimating lens COL of the present embodiment is configured such that its position can be shifted in the optical axis direction by the uniaxial actuator UAC. This makes it possible to correct the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disc HD, so that good recording / reproducing characteristics can always be maintained for the high-density optical disc HD. it can.

The cause of spherical aberration to be corrected by adjusting the position of the collimating lens COL is, for example, wavelength variation due to manufacturing error of the blue-violet semiconductor laser LD1, change in refractive index or refractive index distribution of the objective optical system OBJ due to temperature change, two-layer disc These include focus jumps between layers at the time of recording / reproduction with respect to a multi-layer disc such as a four-layer disc, and thickness variations and thickness distributions due to manufacturing errors of the protective layer PL1.
In the above description, the case where the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disk HD is corrected has been described. You may make it correct | amend by position adjustment of COL.
In the present embodiment, when information is recorded / reproduced on a DVD or CD, a bonding member is used as an element for switching the aperture of the objective optical system OBJ in accordance with the numerical aperture NA of each optical disc. An aperture limiting element AP integrated with the objective optical system OBJ via B is provided.
On the optical function surface of the aperture limiting element AP, a wavelength selection filter WF having wavelength selectivity of transmittance as shown in FIG. 13 is formed. This wavelength selection filter WF transmits all wavelengths from λ1 to λ3 in the region within NA3, blocks only wavelength λ3 in the region from NA3 to NA2, and blocks wavelengths λ2 and λ3 in the region from NA2 to NA1. Since the wavelength selectivity of the transmittance is high, aperture switching corresponding to NA2 and NA3 can be performed by such wavelength selectivity.
Note that the objective optical system OBJ in the present embodiment has an aperture switching function corresponding to the numerical aperture NA2 of the DVD, similarly to the second optical pickup device PU2 and the third optical pickup device PU3. The filter WF may have wavelength selectivity of transmittance as shown in FIG.

<Sixth embodiment>
FIG. 18 is a diagram schematically showing a configuration of a sixth optical pickup device PU6 capable of appropriately recording / reproducing information for any of the high density optical disc HD, DVD, and CD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, the numerical aperture NA1 = 0.85, and the optical specification of the DVD is the wavelength λ2 = 658 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.60. The optical specification of the CD is a wavelength λ3 = 785 nm, the protective layer PL3 has a thickness t3 = 1.2 mm, and a numerical aperture NA3 = 0. .45. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

The optical pickup device PU6 is a high-density optical disc in which a blue-violet semiconductor laser LD1 that emits a laser beam of 408 nm and emits a laser beam of 408 nm and a photodetector PD1 are integrated when information is recorded / reproduced on the high-density optical disc HD. The first light emitting point EP1 that emits light when emitting / recording information to / from the HD module MD1 and DVD and the light emitted when recording / reproducing information to / from the CD. A second light emitting point EP2 that emits a laser beam of 785 nm, a first light receiving unit DS1 that receives a reflected beam from the information recording surface RL2 of the DVD, and a first beam that receives the reflected beam from the information recording surface RL3 of the CD. A DVD / CD laser module LM1, an aberration correction element L1, and the aberration correction element L. Objective optical system OBJ, aperture limiting element AP, biaxial, composed of a condensing element L2 having aspherical surfaces on both sides, which has a function of condensing the laser beam transmitted through the information recording surfaces RL1, RL2, RL3 The actuator AC, a diaphragm STO corresponding to the numerical aperture NA 0.85 of the high-density optical disk HD, a one-axis actuator UAC, an expander lens EXP, a polarizing beam splitter BS, a collimating lens COL, a coupling CUL, and a beam shaping element SH Yes.
In addition to the blue-violet semiconductor laser LD1 described above, a blue-violet SHG laser can also be used as a light source for the high-density optical disk HD.

The expander lens EXP is composed of a first lens EXP1 having a negative refractive power in the paraxial axis and a second lens EXP2 having a positive refractive power in the paraxial axis.
When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU6, as shown by the solid line in FIG. The semiconductor laser LD1 is caused to emit light. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is transmitted through the beam shaping element SH so that its cross-sectional shape is shaped from an ellipse to a circle, and then converted into a parallel light beam by the collimator lens COL. The diameter of the high-density optical disk HD is increased by transmitting through the second lens EXP2, and after passing through the polarization beam splitter BS, the beam diameter is regulated by the stop STO, and transmitted through the aperture limiting element AP, and by the objective optical system OBJ. It becomes a spot formed on the information recording surface RL1 through the protective layer PL1. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ.

The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ, the aperture limiting element AP, the polarization beam splitter BS, the second lens EXP2, the first lens EXP1, the expander lens EXP, and the collimating lens COL. After that, it becomes a convergent light beam, passes through the beam shaping element SH, and converges on the light receiving surface of the photodetector PD1 of the HD module MD1 for high density optical disc. Then, information recorded on the high-density optical disk HD can be read using the output signal of the photodetector PD1.
When the optical pickup device PU6 records / reproduces information with respect to the DVD, the light emitting point EP1 is caused to emit light. The divergent light beam emitted from the light emitting point EP1 is reflected by the prism PS, converted into a parallel light beam by the coupling lens CUL, and then reflected by the polarization beam splitter BS, as depicted in the ray path in FIG. Then, it becomes a spot formed on the information recording surface RL2 via the protective layer PL2 of the DVD by the objective optical system OBJ. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ.

The reflected light beam modulated by the information pits on the information recording surface RL2 is again transmitted through the objective optical system OBJ, reflected by the polarization beam splitter BS, then converged by the coupling lens CUL, and reflected twice inside the prism PS. Then, the light is condensed on the light receiving part DS1. And the information recorded on DVD can be read using the output signal of light-receiving part DS1.
When the optical pickup device PU6 records / reproduces information with respect to a CD, the light emitting point EP2 is caused to emit light. The divergent light beam emitted from the light emitting point EP2 is reflected by the prism PS as depicted in the two-dot chain line in FIG. 18, and then the divergence angle is converted by the coupling lens CUL, and the polarization beam splitter BS. Is reflected by the aperture limiting element AP, and becomes a spot formed on the information recording surface RL1 via the protective layer PL1 of the CD by the objective optical system OBJ. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ and the aperture limiting element AP, reflected by the polarization beam splitter BS, and then reflected twice inside the prism PS to receive the light receiving part DS2. Condensed to And the information recorded on CD can be read using the output signal of light-receiving part DS2.

Next, the configuration of the objective optical system OBJ will be described. The aberration correction element L1 is a plastic lens having a refractive index nd at the d-line of 1.5091 and an Abbe number νd of 56.5, a refractive index with respect to λ1 of 1.5242, and a refractive index with respect to λ2 of 1.5064. , Λ3 has a refractive index of 1.5050. The condensing element L2 is a glass lens having a refractive index nd of 1.662 at the d-line and an Abbe number νd of 61.2. In addition, the aberration correction element L1, the condensing element L2, and the aperture limiting element AP are integrated through the bonding member B.
The optical functional surface S1 on the semiconductor laser light source side of the aberration correction element L1 is not shown, but the 22nd optical functional area AREA22 including the optical axis corresponding to the area within the numerical aperture 0.60 of the DVD and the DVD It is divided into a 23rd optical function area AREA23 corresponding to an area from the numerical aperture 0.60 to the numerical aperture 0.85 of the high-density optical disc HD, and the 22nd optical function area AREA22 has a staircase inside. A superposition type diffractive structure HOE9, which is a structure in which a plurality of annular zones in which the structure is formed, is arranged around the optical axis is formed.

Since the structure of the superposition type diffractive structure HOE9 formed in the twenty-second optical function area AREA22 is the same as that of the superposition type diffractive structure HOE4 in the second optical pickup device PU2, detailed description thereof is omitted here.
In the aberration correction element L1 of the present embodiment, the superposition type diffractive structure is formed on the optical function surface S1 on the semiconductor laser light source side. On the contrary, the superposition type is formed on the optical function surface S2 on the optical disc side. It is good also as a structure which formed the diffraction structure.
Further, the first lens EXP1 of the expander lens EXP of the present embodiment is configured such that its position can be shifted in the optical axis direction by a uniaxial actuator UAC. This makes it possible to correct the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disc HD, so that good recording / reproducing characteristics can always be maintained for the high-density optical disc HD. it can.
The cause of the occurrence of spherical aberration to be corrected by adjusting the position of the first lens EXP1 is, for example, wavelength variation due to manufacturing error of the blue-violet semiconductor laser LD1, refractive index change or refractive index distribution of the objective optical system OBJ due to temperature change, two layers These include a focus jump between layers at the time of recording / reproducing with respect to a multi-layer disk such as a disk, a four-layer disk, a thickness variation due to a manufacturing error of the protective layer PL1, a thickness distribution, and the like.

Furthermore, a diffractive structure DOE10 is formed on the optical function surface of the second lens EXP2 on the optical disc side, which is composed of a plurality of annular zones having a sawtooth shape. Diffractive structure DOE10 is a structure for correcting the chromatic aberration of the objective optical system OBJ in the blue violet area, the power P _.lambda.1 paraxial of the second lens EXP2 with respect to the wavelength .lambda.1, the second lens EXP2 with respect to the wavelength λ1 + 10 (nm) The paraxial power P _{λ1 + 10} and the paraxial power P _λ1-10 of the second lens EXP2 with respect to the wavelength λ1-10 (nm) are:
P _{λ1 + 10} <P _λ1 <P _λ1-10
The diffractive power at the paraxial axis of the diffractive structure DOE 10 is determined so as to satisfy the following relationship.
In addition, the coupling lens CUL sets the divergence angle between the laser beam having the wavelength λ2 emitted from the first emission point EP1 and the laser beam having the wavelength λ3 emitted from the second emission point EP2, respectively. This is an optical element for converting and emitting the divergence angle corresponding to the magnification m2 for the wavelength λ2 of the system OBJ and the magnification m3 for the wavelength λ3. In this embodiment, since m2 = 0, the laser beam having the wavelength λ2 emitted from the first light emission point EP1 is converted into a parallel beam by passing through the coupling lens CUL.

The coupling lens CUL is a plastic lens having a refractive index nd at the d-line of 1.5091, an Abbe number νd of 56.5, a refractive index with respect to λ2 of 1.5064, and a refractive index with respect to λ3 of 1.5050. It is.
The optical functional surface on the optical disc side of the coupling lens CUL is not shown, but the twenty-fourth optical functional area AREA24 including the optical axis corresponding to the area within the numerical aperture 0.45 of CD and the numerical aperture 0 of CD. Divided into a 25th optical function area AREA25 corresponding to an area from .45 to a numerical aperture of DVD 0.60, and a plurality of annular zones in which a staircase structure is formed are arranged around the optical axis The superposed diffractive structure HOE10, which is the above structure, is formed in the 24th optical function area AREA24.
Since the structure of the superposition type diffractive structure HOE10 formed in the twenty-fourth optical function area AREA24 is the same as the superposition type diffractive structure HOE6 in the third optical pickup device PU3, a detailed description is omitted here.
Further, in the present embodiment, when information is recorded / reproduced with respect to the CD, an element for switching the aperture of the objective optical system OBJ according to the numerical aperture NA3 of the CD is provided via the joining member B. An aperture limiting element AP integrated with the objective optical system OBJ is provided.

On the optical function surface of the aperture limiting element AP, a wavelength selection filter WF having a wavelength selectivity of transmittance as shown in FIG. 12 is formed. This wavelength selection filter WF has a wavelength selectivity of a transmittance that transmits all wavelengths λ1 to λ3 in the region inside NA3 and blocks only wavelength λ3 in the region outside NA3. With such wavelength selectivity, aperture switching corresponding to NA3 is performed.
Note that the objective optical system OBJ in the present embodiment has an aperture switching corresponding to the numerical aperture NA2 of the DVD, like the second optical pickup device PU2, the third optical pickup device PU3, and the fifth optical pickup device PU5. The aperture switching function corresponding to NA2 is performed by this aperture switching function.

<Seventh embodiment>
FIG. 19 is a diagram schematically showing a configuration of a seventh optical pickup device PU7 capable of appropriately recording / reproducing information on any of the high density optical disc HD, the DVD, and the CD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, the numerical aperture NA1 = 0.85, and the optical specification of the DVD is the wavelength λ2 = 658 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.60. The optical specification of the CD is a wavelength λ3 = 785 nm, the protective layer PL3 has a thickness t3 = 1.2 mm, and a numerical aperture NA3 = 0. .45. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

The optical pickup device PU7 is used for recording / reproducing information to / from the blue-violet semiconductor laser LD1, DVD that emits light and emits a laser beam of 408 nm when recording / reproducing information on the high-density optical disk HD. Red semiconductor laser LD2 that emits light and emits a laser beam of 658 nm, photodetector PD1 that is used in common with high-density optical disk HD and DVD, and emits a laser beam of 785 nm that is emitted when information is recorded / reproduced. The CD module MD3 in which the infrared semiconductor laser LD3 and the photodetector PD3 are integrated, the aberration correction element L1, and the laser beam transmitted through the aberration correction element L1 are condensed on the information recording surfaces RL1, RL2 and RL3. Objective optical system OBJ composed of a condensing element L2 having aspheric surfaces on both sides, and a wavelength selective filter WF, liquid crystal phase control element LCD, biaxial actuator AC, stop STO corresponding to numerical aperture NA 0.85 of high density optical disk HD, first polarizing beam splitter BS1, second polarizing beam splitter BS2, third polarizing beam It is composed of a splitter BS3, a first collimating lens COL1, a second collimating lens COL2, a sensor lens SEN, and a beam shaping element BS.
In addition to the blue-violet semiconductor laser LD1 described above, a blue-violet SHG laser can also be used as a light source for the high-density optical disk HD.

When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU7, the blue-violet semiconductor laser LD1 is caused to emit light as indicated by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is transmitted through the beam shaping element SH so that its cross-sectional shape is shaped from an ellipse to a circle, and then converted into a parallel light beam by the first collimator lens COL1. After passing through the first to third polarizing beam splitters BS1, BS2, and BS3, the diameter of the light beam is regulated by the stop STO, the light is transmitted through the wavelength selection filter WF and the liquid crystal phase control element LCD, and the high-density optical disc HD by the objective optical system OBJ. The spot is formed on the information recording surface RL1 through the protective layer PL1. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ.
The reflected light beam modulated by the information pits on the information recording surface RL1 is again transmitted through the objective optical system OBJ, the liquid crystal phase control element LCD, the wavelength selection filter WF, and the third polarization beam splitter BS3, and then the second polarization beam splitter. Reflected by BS2, astigmatism is given by the sensor lens SEN, converted into a convergent light beam, and converged on the light receiving surface of the photodetector PD1. Then, information recorded on the high-density optical disk HD can be read using the output signal of the photodetector PD1.

  Further, when information is recorded / reproduced with respect to the DVD in the optical pickup device PU7, the red semiconductor laser LD2 is caused to emit light as shown by the broken line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is converted into a parallel light beam by the second collimating lens COL2, reflected by the first polarizing beam splitter BS1, and then the second and third polarizing beam splitters BS2 and BS3. Is transmitted through the wavelength selection filter WF and the liquid crystal phase control element LCD, and becomes a spot formed on the information recording surface RL2 by the objective optical system OBJ through the protective layer PL2 of the DVD. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ.

The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the objective optical system OBJ, the liquid crystal phase control element LCD, the wavelength selection filter WF, and the third polarization beam splitter BS3, and then the second polarization beam splitter. Reflected by BS2, astigmatism is given by the sensor lens SEN, converted into a convergent light beam, and converged on the light receiving surface of the photodetector PD1. And the information recorded on DVD can be read using the output signal of photodetector PD1.
Further, when recording / reproducing information on / from a CD, the CD module MD3 is operated to cause the infrared semiconductor laser LD3 to emit light, as shown by the two-dot chain line in FIG. The divergent light beam emitted from the infrared semiconductor laser LD3 is reflected by the third polarizing beam splitter BS3, and then the light beam diameter is regulated by the wavelength selection filter WF, passes through the liquid crystal phase control element LCD, and the objective optical system OBJ. As a result, the spot is formed on the information recording surface RL3 via the CD protective layer PL3. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ.
The reflected light beam modulated by the information pits on the information recording surface RL3 is again transmitted through the objective optical system OBJ, the liquid crystal phase control element LCD, and the wavelength selection filter WF, and is then reflected by the third polarization beam splitter BS3 to be a CD module. It converges on the light receiving surface of the photodetector PD3 of MD3. And the information recorded on CD can be read using the output signal of photodetector PD3.

Next, the configuration of the objective optical system OBJ will be described. The aberration correction element L1 is a plastic lens having a refractive index nd at the d-line of 1.5091 and an Abbe number νd of 56.5, a refractive index with respect to λ1 of 1.5242, and a refractive index with respect to λ2 of 1.5064. , Λ3 has a refractive index of 1.5050. The condensing element L2 is a plastic lens having a refractive index nd of 1.5435 at the d-line and an Abbe number νd of 56.3. Further, a flange portion FL1 formed integrally with the optical function portion is provided around each optical function portion (region of the aberration correction element L1 and the condensing element L2 through which the laser beam from the blue-violet semiconductor laser LD1 passes). , FL2 and a part of the flange portions FL1, FL2 are joined together.
The optical function surface S1 on the semiconductor laser light source side of the aberration correction element L1 is not shown, but the twenty-sixth optical function area AREA26 including the optical axis corresponding to the area within the numerical aperture 0.60 of the DVD and the DVD The area is divided into a twenty-seventh optical function area AREA27 corresponding to an area from the numerical aperture 0.60 to the numerical aperture 0.85 of the high-density optical disk HD. A superposition type diffractive structure HOE11 is formed, which is a structure in which a plurality of annular zones in which the structure is formed are arranged around the optical axis.
Since the structure of the superposition type diffractive structure HOE11 formed in the twenty-sixth optical function area AREA26 is the same as the superposition type diffractive structure HOE4 in the second optical pickup device PU2, detailed description thereof is omitted here.

Further, the optical function surface S2 on the optical disc side of the aberration correction element L1 is not illustrated, but the 28th optical function area AREA28 including the optical axis corresponding to the area within the numerical aperture 0.60 of the DVD and the DVD. A plurality of annular zones that are divided into a 29th optical function area AREA 29 corresponding to an area from a numerical aperture of 0.60 to a numerical aperture of 0.85 of the high-density optical disc HD, and whose cross-sectional shape including the optical axis is a sawtooth shape Are formed in the optical functional area AREA 28 and the optical functional area AREA 29, respectively.
The diffractive structures DOE11 and DOE12 are structures for suppressing the chromatic aberration of the objective optical system OBJ in the blue-violet region and the spherical aberration change accompanying the temperature change, and the structure is the diffractive structure DOE3 in the second optical pickup device PU2. Since it is the same as DOE4, detailed description is omitted here.
The aberration correction element L1 of the present embodiment has a configuration in which the superposition type diffractive structure is formed on the optical function surface S1 on the semiconductor laser light source side and the type diffractive structure is formed on the optical function surface S2 on the optical disc side. Conversely, a configuration may be adopted in which a mold diffractive structure is formed on the optical functional surface S1 on the semiconductor laser light source side, and a superimposed diffractive structure is formed on the optical functional surface S2 on the optical disk side.

In addition, the liquid crystal phase control element LCD of the present embodiment includes a liquid crystal layer that causes a phase change with respect to a light beam that is transmitted by application of a voltage, electrode layers that face each other for applying a voltage to the liquid crystal element, and electrodes And a power supply for supplying voltage to the layers. At least one of the electrode layers facing each other is divided into a predetermined pattern. By applying a voltage to this electrode layer, the alignment state of the liquid crystal element changes, and a predetermined phase is added to the transmitted light beam. It is possible. This makes it possible to correct the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disc HD, so that good recording / reproducing characteristics can always be maintained for the high-density optical disc HD. it can.
The cause of the spherical aberration corrected by the liquid crystal phase control element LCD is, for example, wavelength variation due to manufacturing error of the blue-violet semiconductor laser LD1, refractive index change or refractive index distribution of the objective optical system OBJ due to temperature change, two-layer disk, These include focus jumps between layers at the time of recording / reproducing with respect to a multi-layer disc such as a four-layer disc, thickness variation and thickness distribution due to manufacturing errors of the protective layer PL1, and the like.

In the above description, the case of correcting the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disc HD has been described. However, the spherical aberration of the spot formed on the information recording surface RL2 of the DVD or the CD The spherical aberration of the spot formed on the information recording surface RL3 may be corrected by the liquid crystal phase control element LCD. In particular, when recording / reproducing information with respect to a CD, the liquid crystal phase control element LCD corrects spherical aberration caused by the difference in thickness between the protective layer PL1 and the protective layer PL3. Thus, since the magnification m3 of the objective optical system OBJ with respect to the third light beam can be set larger, it is possible to suppress the occurrence of coma aberration during tracking driving.
Further, the objective optical system OBJ and the liquid crystal phase control element LCD are integrated with each other through the bonding member B.
Further, in the present embodiment, the wavelength selection filter WF for switching the aperture of the objective optical system OBJ according to the numerical aperture NA3 of the CD when recording / reproducing information on the CD is used for the liquid crystal phase control. It is formed on the semiconductor laser light source side of the element LCD.

The wavelength selective filter WF has a wavelength selectivity of transmittance as shown in FIG. 12, and this wavelength selective filter WF transmits all wavelengths from λ1 to λ3 in the region inside NA3 and in the region outside NA3. The wavelength selectivity of the transmittance is such that only the wavelength λ3 is blocked, and the aperture switching corresponding to NA3 is performed by the wavelength selectivity.
Note that the objective optical system OBJ in the present embodiment has an aperture switching corresponding to the numerical aperture NA2 of the DVD, like the second optical pickup device PU2, the third optical pickup device PU3, and the fifth optical pickup device PU5. The aperture switching function corresponding to NA2 is performed by this aperture switching function.

<Eighth embodiment>
FIG. 20 is a diagram schematically showing a configuration of an eighth optical pickup device PU8 capable of appropriately recording / reproducing information for both the high-density optical disc HD and the DVD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 407 nm, the thickness t1 of the protective layer PL1 is 0.1 mm, and the numerical aperture NA1 = 0.85. The optical specification of the DVD is the wavelength λ2 = 660 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.65. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

The optical pickup device PU8 is used for recording / reproducing information to / from the blue-violet semiconductor laser LD1, DVD that emits light and emits a laser beam of 407 nm when recording / reproducing information on the high-density optical disk HD. A red semiconductor laser LD2 that emits a 660 nm laser beam, a photodetector PD that is used in common with a high-density optical disk HD and a DVD, an aberration correction element L1, and a laser beam that has passed through the aberration correction element L1 is converted into an information recording surface RL1, Objective optical system O composed of a condensing element L2 having both surfaces aspherical and having a function of condensing on RL2
BJ, liquid crystal phase control element LCD, biaxial actuator AC, stop STO corresponding to numerical aperture NA 0.85 of high-density optical disc HD, first polarizing beam splitter BS1, second polarizing beam splitter BS2, and first collimating lens It is composed of COL1, a second collimating lens COL2, a sensor lens SEN, and a beam shaping element BS.
In addition to the blue-violet semiconductor laser LD1 described above, a blue-violet SHG laser can also be used as a light source for the high-density optical disk HD.

When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU8, the blue-violet semiconductor laser LD1 is caused to emit light, as shown by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is transmitted through the beam shaping element SH so that its cross-sectional shape is shaped from an ellipse to a circle, and then converted into a parallel light beam by the first collimator lens COL1. After passing through the first and second polarizing beam splitters BS1 and BS2, the beam diameter is regulated by the stop STO, the liquid crystal phase control element LCD is transmitted, and the objective optical system OBJ passes through the protective layer PL1 of the high-density optical disc HD. The spot is formed on the information recording surface RL1. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ.
The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ and the liquid crystal phase control element LCD, then reflected by the second polarization beam splitter BS2, and astigmatism by the sensor lens SEN. Is converted into a convergent light beam and converges on the light receiving surface of the photodetector PD1. Then, information recorded on the high-density optical disk HD can be read using the output signal of the photodetector PD1.

  Further, when information is recorded / reproduced with respect to the DVD in the optical pickup device PU8, the red semiconductor laser LD2 is caused to emit light as indicated by the broken line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is converted into a parallel light beam by the second collimating lens COL2, reflected by the first polarizing beam splitter BS1, and then the second polarizing beam splitter BS2, the liquid crystal phase control element. The spot is transmitted through the LCD and is formed on the information recording surface RL2 by the objective optical system OBJ via the protective layer PL2 of the DVD. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ.

  The reflected light beam modulated by the information pits on the information recording surface RL2 is again transmitted through the objective optical system OBJ and the liquid crystal phase control element LCD, then reflected by the second polarization beam splitter BS2, and astigmatism by the sensor lens SEN. Is converted into a convergent light beam and converges on the light receiving surface of the photodetector PD1. And the information recorded on DVD can be read using the output signal of photodetector PD1.

  Next, the configuration of the objective optical system OBJ will be described. The aberration correction element L1 and the condensing element L2 are both plastic lenses. Further, a flange portion FL1 formed integrally with the optical function portion around each optical function portion (region of the aberration correction element L1 and the condensing element L2 through which the laser beam from the blue-violet semiconductor laser LD1 passes). , FL2 and a part of the flange portions FL1, FL2 are joined together.

The optical function surface S1 on the semiconductor laser light source side of the aberration correction element L1 is not shown, but the 30th optical function area AREA30 including the optical axis corresponding to the area within the numerical aperture 0.65 of the DVD, and the DVD It is divided into a thirty-first optical function area AREA31 corresponding to an area from the numerical aperture 0.65 to the numerical aperture 0.85 of the high-density optical disc HD. A superposition type diffractive structure HOE12 is formed, which is a structure in which a plurality of annular zones in which the structure is formed are arranged around the optical axis.
The structure of the superposition type diffractive structure HOE12 formed in the 30th optical function area AREA30 is:
Since it is the same as the superposition type diffractive structure HOE4 in the second optical pickup device PU2, a detailed description is omitted here.

Further, on the optical functional surface S2 on the optical disc side of the aberration correction element L1, a diffractive structure DOE13 including a plurality of annular zones having a sawtooth shape in cross section including the optical axis is formed.
The diffractive structure DOE13 is a structure for suppressing the longitudinal chromatic aberration of the objective optical system OBJ in the blue-violet region and the spherical aberration change accompanying the temperature change, and the step in the optical axis direction is incident with a light beam having a wavelength of λ1 = 407 nm. In some cases, the + 5th order diffracted light is designed to be generated with a diffraction efficiency of 100%. When a light beam with a wavelength λ2 = 660 nm is incident on the diffractive structure DOE 13, + 3rd order diffracted light is generated with a diffraction efficiency of 99.8%, and high diffraction efficiency is ensured for any wavelength.

  In the aberration correction element L1 of the present embodiment, the superposition type diffractive structure is formed on the optical function surface S1 on the semiconductor laser light source side, and the type diffractive structure is formed on the optical function surface S2 on the optical disc side. Conversely, a configuration may be adopted in which a mold diffractive structure is formed on the optical functional surface S1 on the semiconductor laser light source side and a superimposed diffractive structure is formed on the optical functional surface S2 on the optical disk side.

  In addition, the liquid crystal phase control element LCD of the present embodiment includes a liquid crystal layer that causes a phase change with respect to a light beam transmitted through application of a voltage, electrode layers that face each other for applying a voltage to the liquid crystal element, and electrodes And a power supply for supplying voltage to the layers. At least one of the electrode layers facing each other is divided into a predetermined pattern. By applying a voltage to this electrode layer, the alignment state of the liquid crystal element changes, and a predetermined phase is added to the transmitted light beam. It is possible. This makes it possible to correct the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disk HD, so that good recording / reproducing characteristics can always be maintained for the high-density optical disk HD. it can.

  The cause of the occurrence of spherical aberration corrected by the liquid crystal phase control element LCD is, for example, wavelength variation due to manufacturing error of the blue-violet semiconductor laser LD1, refractive index change or refractive index distribution of the objective optical system OBJ due to temperature change, two-layer disk, These include focus jumps between layers at the time of recording / reproduction with respect to a multi-layer disc such as a four-layer disc, and thickness variations and thickness distributions due to manufacturing errors of the protective layer PL1.

In the above description, the case of correcting the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disc HD has been described. However, the spherical aberration of the spot formed on the information recording surface RL2 of the DVD is changed to the liquid crystal phase. You may make it correct | amend by control element LCD.
Further, the objective optical system OBJ and the liquid crystal phase control element LCD are integrated with each other through the bonding member B.
The objective optical system OBJ in the present embodiment is similar to the second optical pickup device PU2, the third optical pickup device PU3, the fifth optical pickup device PU5, and the seventh optical pickup device PU7. An aperture switching function corresponding to the numerical aperture NA2 is provided, and aperture switching corresponding to NA2 is performed by the aperture switching function.

[Ninth embodiment]
FIG. 21 is a diagram schematically showing a configuration of a ninth optical pickup device PU9 capable of appropriately recording / reproducing information on both the high density optical disc HD and the DVD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 405 nm, the thickness t1 of the protective layer PL1 is 0.1 mm, and the numerical aperture NA1 = 0.85. The optical specifications of the DVD are the wavelength λ2 = 650 nm and the protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.65. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

The optical pickup device PU9 is used for recording / reproducing information to / from the blue-violet semiconductor laser LD1, DVD that emits light and emits a 405 nm laser beam when recording / reproducing information on the high-density optical disk HD. A red semiconductor laser LD2 that emits a 650 nm laser beam, a photodetector PD that is shared by the high-density optical disk HD and DVD, an aberration correction element L1, and a laser beam that has passed through the aberration correction element L1 is recorded on an information recording surface RL1, Aperture STO corresponding to an objective optical system OBJ, a biaxial actuator AC, and a high-density optical disc HD having a numerical aperture NA of 0.85. , First polarization beam splitter BS1, second polarization beam splitter BS2, collimating lens COL, single axis Actuator UAC, sensor lens SEN, the beam shaping element BS, and a city.
In addition to the blue-violet semiconductor laser LD1 described above, a blue-violet SHG laser can also be used as a light source for the high-density optical disk HD.

  When information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU9, the blue-violet semiconductor laser LD1 is caused to emit light as illustrated by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is transmitted through the beam shaping element SH so that its cross-sectional shape is shaped from an ellipse to a circle, and then the first and second polarization beam splitters BS1 and BS2 are passed through. After being transmitted, the light beam is converted into a parallel light beam by the collimating lens COL, the light beam diameter is regulated by the stop STO, and the spot formed on the information recording surface RL1 via the protective layer PL1 of the high-density optical disk HD by the objective optical system OBJ. Become. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ.

  The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ and the collimating lens COL, then reflected by the second polarizing beam splitter BS2, and given astigmatism by the sensor lens SEN. And is converted into a convergent light beam and converges on the light receiving surface of the photodetector PD1. Then, information recorded on the high density optical disk HD can be read using the output signal of the photodetector PD1.

  Further, when information is recorded / reproduced with respect to the DVD in the optical pickup device PU9, the red semiconductor laser LD2 is caused to emit light as shown by the broken line in FIG. The divergent light beam emitted from the red semiconductor laser LD2 is reflected by the first polarization beam splitter BS1, passes through the second polarization beam splitter BS2, is converted into a parallel light beam by the collimator lens COL, and is converted into the objective optical system OBJ. Thus, the spot is formed on the information recording surface RL2 via the protective layer PL2 of the DVD. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ.

  The reflected light beam modulated by the information pits on the information recording surface RL2 is again transmitted through the objective optical system OBJ and the collimating lens COL, then reflected by the second polarization beam splitter BS2, and given astigmatism by the sensor lens SEN. And is converted into a convergent light beam and converges on the light receiving surface of the photodetector PD1. And the information recorded on DVD can be read using the output signal of photodetector PD1.

  Next, the configuration of the objective optical system OBJ will be described. The aberration correction element L1 is a plastic lens, and the condensing element L2 is a glass lens. In addition, the aberration correction element L1 and the light condensing element L2 are integrated via the bonding member B.

The optical functional surface S1 on the semiconductor laser light source side of the aberration correction element L1 is not shown in the figure, but is DV
This corresponds to the 32nd optical function area AREA32 including the optical axis corresponding to the area within the numerical aperture 0.65 of D, and the area from the numerical aperture 0.65 of DVD to the numerical aperture 0.85 of the high-density optical disk HD. It is divided into a thirty-third optical function area AREA33, and the thirty-second optical function area AREA32 has a structure in which a plurality of annular zones having a staircase structure formed therein are arranged around the optical axis. A type diffraction structure HOE 13 is formed.
The structure of the superposition type diffractive structure HOE 34 formed in the thirty-second optical function area AREA 32 is the same as that of the superposition type diffractive structure HOE4 in the second optical pickup device PU2, and a detailed description thereof will be omitted here.

Further, on the optical functional surface S2 on the optical disc side of the aberration correction element L1, a diffractive structure DOE14 including a plurality of annular zones whose step shape including the optical axis is stepped is formed.
The diffractive structure DOE14 is a structure for correcting the chromatic spherical aberration of the objective optical system OBJ in the blue-violet region, and the step in the optical axis direction is 100% of the + 5th order diffracted light when a light beam having a wavelength λ1 = 405 nm is incident. It is designed to be generated with a diffraction efficiency of. When a light beam having a wavelength λ2 = 650 nm is incident on the diffractive structure DOE 14, + 3rd order diffracted light is generated with a diffraction efficiency of 100%, and high diffraction efficiency is ensured for any wavelength.

The aberration correction element L1 of the present embodiment has a configuration in which the superposition type diffractive structure is formed on the optical function surface S1 on the semiconductor laser light source side and the type diffractive structure is formed on the optical function surface S2 on the optical disc side. Conversely, a configuration may be adopted in which a mold diffractive structure is formed on the optical functional surface S1 on the semiconductor laser light source side, and a superimposed diffractive structure is formed on the optical functional surface S2 on the optical disk side.
In addition, the collimating lens COL of the present embodiment is configured such that its position can be shifted in the optical axis direction by the uniaxial actuator UAC. This makes it possible to correct the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disc HD, so that good recording / reproducing characteristics can always be maintained for the high-density optical disc HD. it can.

The cause of spherical aberration to be corrected by adjusting the position of the collimating lens COL is, for example, wavelength variation due to manufacturing error of the blue-violet semiconductor laser LD1, change in refractive index or refractive index distribution of the objective optical system OBJ due to temperature change, two-layer disc These include focus jumps between layers at the time of recording / reproduction with respect to a multi-layer disc such as a four-layer disc, and thickness variations and thickness distributions due to manufacturing errors of the protective layer PL1.
In the above description, the case where the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disk HD is corrected has been described. You may make it correct | amend by position adjustment of COL.
The objective optical system OBJ in the present embodiment includes the second optical pickup device PU2, the third optical pickup device PU3, the fifth optical pickup device PU5, the seventh optical pickup device PU7, and the eighth optical pickup. Similar to the device PU8, it has an aperture switching function corresponding to the numerical aperture NA2 of the DVD, and aperture switching corresponding to NA2 is performed by this aperture switching function.

[Tenth embodiment]
FIG. 22 is a diagram schematically showing a configuration of a tenth optical pickup apparatus PU10 capable of appropriately recording / reproducing information for both the high density optical disc HD and the DVD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 407 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, the numerical aperture NA1 = 0.85, and the optical specifications of the DVD are the wavelength λ2 = 660 nm and the protection The thickness t2 of the layer PL2 is 0.6 mm and the numerical aperture NA2 is 0.65. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

The optical pickup device PU10 records / reproduces information with respect to the first light emitting point EP1 that emits a 407-nm laser beam when recording / reproducing information with respect to the high-density optical disc HD and the DVD. From a second light emitting point EP2 that emits a 660 nm laser light beam, a first light receiving unit DS1 that receives a reflected light beam from the information recording surface RL1 of the high-density optical disk HD, and a DVD information recording surface RL2. A high-density optical disk / DVD laser module LM composed of a second light receiving portion DS2 that receives the reflected light flux of the light beam and a prism PS, an aberration correction element L1, and a laser light flux that has passed through the aberration correction element L1 as an information recording surface An objective optical system OBJ having a function of condensing on RL1 and RL2, and a concentrating element L2 having aspherical surfaces on both sides. Yueta AC, diaphragm STO corresponding to numerical aperture NA0.85 of the high density optical disk HD, collimator lens COL, 1-axis actuator UAC, and a city.
In addition to the blue-violet semiconductor laser LD1 described above, a blue-violet SHG laser can also be used as a light source for the high-density optical disk HD.

  Further, when information is recorded / reproduced with respect to the high-density optical disk HD in the optical pickup device PU10, the first light emitting point EP1 is caused to emit light. The divergent light beam emitted from the first light emitting point EP1 is reflected by the prism PS and then converted into a parallel light beam by the collimating lens COL as depicted by the solid line in FIG. 22, and the objective optical system OBJ. As a result, the spots are formed on the information recording surface RL1 via the protective layer PL1 of the high-density optical disc HD. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ and the collimating lens COL, reflected twice inside the prism PS, and condensed on the light receiving unit DS1. Then, information recorded on the high density optical disk HD can be read using the output signal of the light receiving unit DS1.

  Further, in the optical pickup device PU10, when information is recorded / reproduced with respect to the DVD, the second light emitting point EP2 is caused to emit light. The divergent light beam emitted from the second light emitting point EP2 is reflected by the prism PS and passes through the collimating lens COL as shown by the broken line in FIG. Then, it is incident on the objective optical system OBJ as divergent light, and becomes a spot formed on the information recording surface RL2 by the objective optical system OBJ via the protective layer PL2 of the DVD. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC arranged around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the objective optical system OBJ and the collimator lens COL, reflected twice inside the prism PS, and condensed on the light receiving unit DS2. And the information recorded on DVD can be read using the output signal of light-receiving part DS2.

  Next, the configuration of the objective optical system OBJ will be described. The aberration correction element L1 and the condensing element L2 are both plastic lenses. Further, a flange portion FL1 formed integrally with the optical function portion around each optical function portion (region of the aberration correction element L1 and the condensing element L2 through which the laser beam from the blue-violet semiconductor laser LD1 passes). , FL2 and a part of the flange portions FL1, FL2 are joined together.

The optical functional surface S1 on the semiconductor laser light source side of the objective optical system OBJ is not shown, but the 34th optical functional area AREA34 including the optical axis corresponding to the area within the numerical aperture 0.65 of the DVD and the DVD This is divided into a 35th optical function area AREA 35 corresponding to the area from the numerical aperture 0.65 to the numerical aperture 0.85 of the high-density optical disc HD. In the thirty-fourth optical function area AREA34, there is formed a superposition type diffractive structure HOE14 having a structure in which a plurality of annular zones having step structures formed therein are arranged around the optical axis.
The structure of the superposition type diffractive structure HOE14 formed in the 34th optical function area AREA34 is:
Since it is the same as the superposition type diffractive structure HOE4 in the second optical pickup device PU2, a detailed description is omitted here.
On the optical function surface S2 on the optical disc side of the aberration correction element L1, an optical path difference providing structure NPS, which is a structure for suppressing a spherical aberration change accompanying a temperature change of the objective optical system OBJ in the blue-violet region, is formed. The step in the optical axis direction of the optical path difference providing structure NPS is set to a depth that gives a five times optical path difference with respect to the light flux having the wavelength λ1 at the design reference temperature of the objective optical system OBJ. When a light beam having the wavelength λ2 is incident on the step set to such a depth, the optical path difference given to the light beam having the wavelength λ2 is three times that of λ2, so that a high transmittance is ensured at any wavelength. Has been.

In the optical path difference providing structure NPS, the spherical aberration changes in the direction of undercorrection when the refractive index becomes low, and the spherical aberration changes in the direction of overcorrection when the refractive index becomes high. Therefore, it is possible to suppress a change in spherical aberration accompanying a change in temperature of the objective optical system OBJ in the blue-violet region.
In the aberration correction element L1 of the present embodiment, the superposition type diffractive structure HOE14 is formed on the optical function surface S1 on the semiconductor laser light source side, and the optical path difference providing structure NPS is formed on the optical function surface S2 on the optical disk side. Conversely, the optical path difference providing structure NPS may be formed on the optical functional surface S1 on the semiconductor laser light source side, and the superposition type diffractive structure HOE14 may be formed on the optical functional surface S2 on the optical disk side.
In addition, the collimating lens COL of the present embodiment is configured such that its position can be shifted in the optical axis direction by the uniaxial actuator UAC. This makes it possible to correct the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disc HD, so that good recording / reproducing characteristics can always be maintained for the high-density optical disc HD. it can.

The cause of spherical aberration to be corrected by adjusting the position of the collimating lens COL is, for example, wavelength variation due to manufacturing error of the blue-violet semiconductor laser LD1, change in refractive index or refractive index distribution of the objective optical system OBJ due to temperature change, two-layer disc These include focus jumps between layers at the time of recording / reproduction with respect to a multi-layer disc such as a four-layer disc, and thickness variations and thickness distributions due to manufacturing errors of the protective layer PL1.
In the above description, the case where the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disk HD is corrected has been described. You may make it correct | amend by position adjustment of COL.
The objective optical system OBJ in the present embodiment includes the second optical pickup device PU2, the third optical pickup device PU3, the fifth optical pickup device PU5, the seventh optical pickup device PU7, and the eighth optical pickup. Similar to the device PU8 and the ninth optical pickup device PU9, it has an aperture switching function corresponding to the numerical aperture NA2 of the DVD, and aperture switching corresponding to NA2 is performed by this aperture switching function.

[Eleventh embodiment]
FIG. 30 is a diagram schematically showing a configuration of an eleventh optical pickup device PU11 capable of appropriately recording / reproducing information on any of the high density optical disc HD, DVD, and CD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, and the numerical aperture NA1 = 0.85. The optical specification of the DVD is the wavelength λ2 = 658 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.65. The optical specification of the CD is a wavelength λ3 = 785 nm, the protective layer PL3 has a thickness t2 = 1.2 mm, and a numerical aperture NA3 = 0. .45. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

  The optical pickup device PU11 includes a first light emission point EP1 (first light source) that emits a 408 nm laser light beam (first light beam) when recording / reproducing information on the high-density optical disk HD, and a DVD. Information is recorded / reproduced with respect to the second light emitting point EP2 (second light source) that emits a laser beam (second light beam) of 658 nm and is emitted when information is recorded / reproduced. And a first light receiving portion EP3 (third light source) that emits a 785 nm laser light beam (third light beam) and a first light receiving unit that receives the reflected light beam from the information recording surface RL1 of the high-density optical disk HD. DS1, a second light receiving unit DS2 that receives the reflected light beam from the information recording surface RL2 of the DVD, a third light receiving unit DS3 that receives the reflected light beam from the information recording surface RL3 of the CD, and the prism PS. The high-density optical disk HD / DVD / CD laser module LM formed, an objective optical system (light condensing element) OBJ, DVD / CD in which a diffractive structure (phase structure) is formed on the optical surface and both surfaces are aspherical Aperture limiting element AP, biaxial actuator AC for driving the objective optical element OBJ for focusing / tracking, aperture STO corresponding to the numerical aperture NA1 of the high-density optical disk HD, collimating lens COL, and collimating lens COL in the optical axis direction A uniaxial actuator UAC for driving, a liquid crystal phase control element LCD (spherical aberration correcting means), a holding member B for integrating the objective optical system OBJ, the aperture limiting element AP, and the liquid crystal phase control element LCD. Has been. In the present embodiment, the aberration correction element having a phase structure and the first to third light beams are divided into an information recording surface RL1, a DVD information recording surface RL2, and a CD information recording surface RL3, respectively. A condensing element for condensing the light is integrated.

When recording / reproducing information with respect to the high-density optical disk HD in the optical pickup device PU11, the laser module LM is operated to emit the first light emission point EP1. The divergent light beam emitted from the first light emitting point EP1 is reflected by the prism PS as shown by the solid line in FIG. 30, and is converted into a parallel light beam through the collimator lens COL, and then the light beam is emitted by the stop STO. The diameter is regulated, the spot passes through the liquid crystal phase control element LCD and the aperture limiting element AP, and becomes a spot formed on the information recording surface RL1 via the first protective layer PL1 by the objective optical system OBJ. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC1 disposed around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ, the aperture limiting element AP, and the liquid crystal phase control element LCD, and is converged by the collimator lens COL, and twice inside the prism PS. Reflected and condensed on the light receiving unit DS1. Then, information recorded on the high density optical disk HD can be read using the output signal of the light receiving unit DS1.

  Further, when information is recorded / reproduced with respect to the DVD in the optical pickup device PU11, the objective optical system OBJ and the collimating lens COL are arranged so that the second light flux is emitted from the collimating lens COL in the state of a parallel light flux. The collimating lens COL is moved by the uniaxial actuator UAC so that the distance between the two is smaller than that when information is recorded / reproduced with respect to the high-density optical disk HD. Thereafter, the laser module LM is operated to emit the second light emission point EP2. The divergent light beam emitted from the second light emitting point EP2 is reflected by the prism PS as shown by the dotted line in FIG. 30 and converted into a parallel light beam through the collimator lens COL, and then the liquid crystal phase control element. After passing through the LCD and the light beam diameter being regulated by the aperture limiting element AP, it becomes a spot formed on the information recording surface RL2 via the second protective layer PL2 by the objective optical system OBJ. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC1 disposed around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the objective optical system OBJ, the aperture limiting element AP, and the liquid crystal phase control element LCD, and is converged by the collimator lens COL, and is twice in the prism PS. It is reflected and collected on the light receiving part DS2. And the information recorded on DVD can be read using the output signal of light-receiving part DS2.

Further, when information is recorded / reproduced with respect to the CD in the optical pickup apparatus PU11, spherical aberration due to the difference between the thickness t1 of the protective layer PL1 and the thickness t3 of the protective layer PL3 is corrected. Then, the liquid crystal phase control element LCD is operated so that spherical aberration in the direction of insufficient correction is added to the third light flux transmitted through the liquid crystal phase control element LCD. Thereafter, the laser module LM is operated to emit the third light emission point EP3. The divergent light beam emitted from the third light emitting point EP3 is reflected by the prism PS as shown by the two-dot chain line in FIG. By passing through the phase control element LCD, spherical aberration in the direction of insufficient correction is given, and the diameter of the light beam is regulated by the aperture limiting element AP, and then on the information recording surface RL3 via the third protective layer PL3 by the objective optical system OBJ. It becomes a spot formed in The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC1 disposed around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL3 is transmitted again through the objective optical system OBJ, the aperture limiting element AP, and the liquid crystal phase control element LCD, and is converged by the collimator lens COL, and is twice in the prism PS. It is reflected and collected on the light receiving part DS3. And the information recorded on CD can be read using the output signal of light-receiving part DS3.

  As in the case of DVD, the distance between the objective optical system OBJ and the collimating lens COL is such that the third light beam is emitted from the collimating lens COL in a parallel light beam state with respect to the high-density optical disk HD. The collimating lens COL may be moved by the uniaxial actuator UAC so as to be smaller than the case of recording / reproducing information.

  Next, the configuration of the objective optical element OBJ will be described. The diffractive structure DOE15 (having a sawtooth shape in cross section) formed on the optical surface on the laser module LM side has spherical aberration due to the difference between the thickness t1 of the protective layer PL1 and the thickness t2 of the protective layer PL2. This is a structure for correcting. The objective optical system OBJ converts the first-order diffracted light of the first to third light beams generated by the diffractive structure DOE 15 into the information recording surface RL1 of the high-density optical disk HD, the information recording surface RL2 of the DVD, and the information recording surface RL3 of the CD, respectively. Focus on top. The optical path difference function of the diffractive structure DOE15 is optimized so as to correct the spherical aberration due to the difference between the thickness t1 of the protective layer PL1 and the thickness t2 of the protective layer PL2, and thus the thickness of the protective layer PL1. Although the spherical aberration due to the difference between the thickness t1 and the thickness t3 of the protective layer PL3 remains without being completely corrected, in this embodiment, the residual spherical aberration is corrected by the liquid crystal phase control element LCD. As a result, compatibility between the high-density optical disc HD and the CD is achieved.

Further, the collimating lens COL of the present embodiment is configured such that its position can be shifted in the optical axis direction by the uniaxial actuator UAC, but this allows the collimating lens COL to be placed on the information recording surface RL1 of the high-density optical disc HD. It is possible to correct the spherical aberration of the formed spot. The cause of the spherical aberration to be corrected by adjusting the position of the collimator lens COL is, for example, wavelength variation due to manufacturing error of the first light source, refractive index change or refractive index distribution of the objective optical system OBJ due to temperature change, two-layer disk, 4 These include focus jumps between layers at the time of recording / reproduction with respect to a multi-layer disc such as a layer disc, and thickness variations and thickness distributions due to manufacturing errors of the protective layer PL1.
In the above description, the case where the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disk HD is corrected has been described. You may make it correct | amend by position adjustment of COL.

[Twelfth embodiment]
FIG. 31 is a diagram schematically showing a configuration of a twelfth optical pickup device PU12 capable of appropriately recording / reproducing information for any of the high-density optical disc HD, DVD, and CD. The optical specifications of the high-density optical disc HD are the wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, and the numerical aperture NA1 = 0.85. The optical specification of the DVD is the wavelength λ2 = 658 nm, protection The layer PL2 has a thickness t2 = 0.6 mm and a numerical aperture NA2 = 0.65. The optical specification of the CD is a wavelength λ3 = 785 nm, the protective layer PL3 has a thickness t2 = 1.2 mm, and a numerical aperture NA3 = 0. .45. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

  The optical pickup device PU12 includes a first light emission point EP1 (first light source) that emits a 408 nm laser light beam (first light beam) when recording / reproducing information with respect to the high-density optical disk HD, and a DVD. Information is recorded / reproduced with respect to the second light emitting point EP2 (second light source) that emits a laser beam (second light beam) of 658 nm and is emitted when information is recorded / reproduced. And a first light receiving portion EP3 (third light source) that emits a 785 nm laser light beam (third light beam) and a first light receiving unit that receives the reflected light beam from the information recording surface RL1 of the high-density optical disk HD. DS1, a second light receiving unit DS2 that receives the reflected light beam from the information recording surface RL2 of the DVD, a third light receiving unit DS3 that receives the reflected light beam from the information recording surface RL3 of the CD, and the prism PS. A high-density optical disk HD / DVD / CD laser module LM formed, an aberration correction element L1 in which a superposition type diffractive structure (phase structure) and a diffractive structure (second phase structure) are formed on its optical surface, and both surfaces Of an objective optical system OBJ composed of a condensing element L2 having an aspherical surface, an aperture limiting element AP for CD, a biaxial actuator AC for focusing / tracking driving the objective optical element OBJ, and a high-density optical disc HD A diaphragm STO corresponding to the numerical aperture NA1, a collimating lens COL, an expander lens EXP (spherical aberration correcting means) composed of a negative lens E1 and a positive lens E2, and a uniaxial actuator for driving the negative lens E1 in the optical axis direction. The UAC is composed of a holding member B for integrating the objective optical system OBJ and the aperture limiting element AP. That.

When recording / reproducing information with respect to the high-density optical disc HD in the optical pickup device PU12, the laser module LM is operated to emit the first light emission point EP1. The divergent light beam emitted from the first light emitting point EP1 is reflected by the prism PS as shown by the solid line in FIG. 31, and is converted into a parallel light beam through the collimator lens COL. The light beam diameter is enlarged by passing through, and then the light beam diameter is regulated by the stop STO, passes through the aperture limiting element AP, and is formed on the information recording surface RL1 via the first protective layer PL1 by the objective optical system OBJ. Become a spot. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC1 disposed around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective optical system OBJ, the aperture limiting element AP, and the expander lens EXP, is converted into a converged light beam by the collimator lens COL, and is reflected twice inside the prism PS. The light is condensed on the light receiving part DS1. Then, information recorded on the high density optical disk HD can be read using the output signal of the light receiving unit DS1.

  Further, when recording / reproducing information with respect to the DVD in the optical pickup device PU12, the negative lens E1 and the positive lens E2 are arranged so that the second light flux is emitted from the expander lens EXP in a parallel light flux state. The negative lens E1 is moved by the uniaxial actuator UAC so that the distance between them is larger than that when information is recorded / reproduced with respect to the high-density optical disk HD. Thereafter, the laser module LM is operated to emit the second light emission point EP2. The divergent light beam emitted from the second light emitting point EP2 is reflected by the prism PS as shown by the dotted line in FIG. 31, is converted into a substantially parallel light beam through the collimator lens COL, and then the expander lens EXP. The light beam diameter is enlarged by transmitting the light beam, and after that, after passing through the aperture limiting element AP, it becomes a spot formed on the information recording surface RL2 by the objective optical system OBJ via the second protective layer PL2. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC1 disposed around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the objective optical system OBJ, the aperture limiting element AP, and the expander lens EXP, is converted into a convergent light beam by the collimator lens COL, and is reflected twice inside the prism PS. The light is condensed on the light receiving part DS2. And the information recorded on DVD can be read using the output signal of light-receiving part DS2.

  Further, when information is recorded / reproduced with respect to the CD in the optical pickup device PU12, spherical aberration due to the difference between the thickness t1 of the protective layer PL1 and the thickness t3 of the protective layer PL3 is corrected. In addition, the negative lens E1 is moved by the uniaxial actuator UAC so that the distance between the negative lens E1 and the positive lens E2 is smaller than that in the case of recording / reproducing information with respect to the high-density optical disk HD. Thereafter, the laser module LM is operated to emit the third light emission point EP3. The divergent light beam emitted from the third light emitting point EP3 is reflected by the prism PS as shown by the two-dot chain line in FIG. 31, and is made into a substantially parallel light beam through the collimator lens COL, and then the expander. A spot formed on the information recording surface RL3 via the third protective layer PL3 by the objective optical system OBJ after being converted into a divergent light beam by passing through the lens EXP and being regulated by the aperture limiting element AP. Become. The objective optical system OBJ performs focusing and tracking by a biaxial actuator AC1 disposed around the objective optical system OBJ. The reflected light beam modulated by the information pits on the information recording surface RL3 is transmitted again through the objective optical system OBJ, the aperture limiting element AP, and the expander lens EXP, is converted into a convergent light beam by the collimator lens COL, and is reflected twice inside the prism PS. The light is condensed on the light receiving unit DS3. And the information recorded on CD can be read using the output signal of light-receiving part DS3.

  Next, the configuration of the objective optical element OBJ will be described. Both the aberration correction element L1 and the condensing element L2 are plastic lenses, and are integrated by joining flange portions FL1 and FL2 formed integrally with the optical function portion thereof. The superposition type structure HOE15 formed on the optical surface of the aberration correction element L1 on the laser module LM side corrects spherical aberration due to the difference between the thickness t1 of the protective layer PL1 and the thickness t2 of the protective layer PL2. This is the structure. Its specific structure and function are the same as those of the superposition type diffractive structure HOE4 in the second optical pickup device PU2, and therefore detailed description thereof is omitted here. Since the superposition type diffractive structure HOE15 is formed only within the numerical aperture NA2 of the DVD, the second light flux passing through the area outside the NA2 becomes a flare component on the information recording surface RL2 of the DVD, and the aperture for the DVD The restriction is automatically performed.

  Further, the objective optical system OBJ includes the fifth-order diffracted light and the second light flux of the first light beam generated by the diffractive structure DOE 16 (the cross-sectional shape of which is a step shape) formed on the optical surface of the aberration correction element L1 on the optical disk side. The third-order diffracted light and the second-order diffracted light of the third light beam are condensed on the information recording surface RL1 of the high-density optical disc HD, the information recording surface RL2 of the DVD, and the information recording surface RL3 of the CD, respectively. The diffractive structure DOE 16 is a structure for reducing spherical aberration caused by the difference between t1 and t3 by adding an optical path difference that is a half integer multiple of the third wavelength λ3 to the third light flux. As a result, the absolute value of the magnification m3 of the objective optical system OBJ with respect to the third light flux when recording / reproducing information with respect to the CD can be prevented from becoming too large, so that the amount of movement of the negative lens E1 can be small. Also, it becomes possible to improve the tracking characteristics of the objective optical system OBJ.

  In the present embodiment, the negative lens E1 is moved in the optical axis direction by the uniaxial actuator UAC to correct the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disc HD. Yes. The cause of the spherical aberration corrected by adjusting the position of the negative lens E1 is, for example, wavelength variation due to manufacturing error of the first light source, refractive index change or refractive index distribution of the objective optical system OBJ due to temperature change, two-layer disk, 4 These include a focus jump between layers at the time of recording / reproducing with respect to a multi-layer disc such as a layer disc, a thickness variation due to a manufacturing error of the protective layer PL1, and a thickness distribution.

In the above description, the case where the spherical aberration of the spot formed on the information recording surface RL1 of the high-density optical disk HD is corrected has been described. You may make it correct | amend by the position adjustment of E1. Further, the positive lens E2 may be moved instead of the negative lens E1.
Further, instead of the expander lens EXP, a collimating lens or a coupling lens that can be shifted in the optical axis direction by an actuator may be used as the spherical aberration correcting means.

Next, 8 examples (Examples 1 to 8) of optical elements suitable as the objective optical system OBJ of the optical pickup devices PU1 to PU4 and PU8 to PU10 described above, and the spherical aberration correcting element of PU12 and the objective optical system OBJ 3 examples (Examples 9 to 11) will be described.
The aspherical surface in each embodiment has a deformation amount from a plane in contact with the apex of the surface as X (mm), a height perpendicular to the optical axis as h (mm), and a radius of curvature as r (mm). The following equation 5 is expressed by a mathematical formula in which the aspheric coefficient A _2i in Tables 15 to 25 is substituted. Where κ is the conic coefficient.

In addition, the superposition type diffractive structure and the diffractive structure in each embodiment are represented by an optical path difference added to the transmitted wavefront by these structures. This optical path difference is the above number when λ is the wavelength of the incident light beam, λ _B is the production wavelength, the height in the direction perpendicular to the optical axis is h (mm), B _2j is the optical path difference function coefficient, and n is the diffraction order. 1 is represented by an optical path difference function φb (mm) defined by 1.
In Tables 15 to 25, NA1, f1, λ1, m1, and t1 are the numerical aperture of the objective optical system OBJ, the focal length of the objective optical system OBJ, and the wavelength of the objective optical system OBJ, respectively, when the high-density optical disk HD is used. The magnification of the objective optical system OBJ and the thickness of the protective layer. NA2, f2, λ2, m2, and t2 are the same values when using a DVD, and NA3, f3, λ3, m3, and t3 are when using a CD. Are similar values.
Further, r (mm) is a radius of curvature, and d1 (mm), d2 (mm), and d3 (mm) are lens intervals when using a high-density optical disc HD, using a DVD, and using a CD, respectively, Nλ1, Nλ2, Nλ3 is the refractive index of the lens with respect to wavelength λ1, wavelength λ2, and wavelength λ3, respectively, and νd is the Abbe number of the d-line lens.
Further, n1, n2, and n3 are diffraction orders of the diffracted light of the first light beam, the second light beam, and the third light beam generated in the superposition type diffractive structure or the diffractive structure, respectively.

  The optical elements of Examples 1 to 3 are a plastic lens having a numerical aperture of 0.85 and a spherical aberration correction optimized for a wavelength of 408 nm, a protective layer thickness of 0.0875 mm, and a magnification of 1 / 18.215. The optical element L2 is combined with an aberration correction element L2, which is a plastic lens in which a superposition type diffractive structure is formed on the optical function surface S1 on the semiconductor laser side and a diffractive structure is formed on the optical function surface S2 on the optical disk side.

The optical element of Example 4 is a condensing element, which is a plastic lens having a numerical aperture of 0.85, in which spherical aberration correction is optimized for a wavelength of 408 nm, a protective layer thickness of 0.0875 mm, and a magnification of 1 / 1.123. L2 is combined with an aberration correction element L2, which is a plastic lens in which a superposition type diffractive structure is formed on the optical functional surface S1 on the semiconductor laser side and a diffractive structure is formed on the optical functional surface S2 on the optical disk side.
The optical element of Example 5 is a condensing element L which is a glass lens with a wavelength of 408 nm, a protective layer thickness of 0.0875 mm, and a numerical aperture of 0.85 with spherical aberration correction optimized for a magnification of 0.
2 is combined with an aberration correction element L2 which is a plastic lens in which a superposition type diffractive structure is formed on the optical function surface S1 on the semiconductor laser side and a diffractive structure is formed on the optical function surface S2 on the optical disc side.

The optical element of Example 6 is a condensing element which is a plastic lens having a numerical aperture of 0.85, in which spherical aberration correction is optimized for a wavelength of 407 nm, a protective layer thickness of 0.1 mm, and a magnification of 1 / 114.104. L2 is combined with an aberration correction element L1 which is a plastic lens in which a superposition type diffractive structure is formed on the optical function surface S1 on the semiconductor laser side and a diffractive structure is formed on the optical function surface S2 on the optical disc side.
The optical element of Example 7 includes a condensing element L2 which is a glass lens having a wavelength of 405 nm, a protective layer thickness of 0.1 mm, and a numerical aperture of 0.85 optimized for spherical aberration correction, and a semiconductor. An aberration correcting element L1 which is a plastic lens having a superposition type diffractive structure formed on the optical function surface S1 on the laser side and a diffractive structure formed on the optical function surface S2 on the optical disc side is combined.
The optical element of Example 8 is a condensing element that is a glass lens with a numerical aperture of 0.85, in which spherical aberration correction is optimized for a wavelength of 407 nm, a protective layer thickness of 0.0875 mm, and a magnification of 1 / 1.416. L2 is combined with an aberration correction element L1 which is a plastic lens in which the optical path difference providing structure NPS is formed on the optical function surface S1 on the semiconductor laser side and the superposition type diffractive structure HOE is formed on the optical function surface S2 on the optical disc side. Yes.

The optical element of Example 1 is the optimum optical element as the objective optical system OBJ of the first optical pickup device PU1 as shown in FIG.

The thickness of the protective layer of the high-density optical disc HD and DVD while the magnification m2 with respect to the wavelength λ2 and the magnification m3 with respect to the wavelength λ3 are substantially matched by the action of the superposition type diffractive structure HOE1 formed in the first optical functional area AREA1. The spherical aberration due to the difference is corrected.
In addition, the superposition type diffractive structure HOE2 formed in the second optical function area AREA2 and the superposition type diffractive structure HOE3 formed in the third optical function area AREA3 are a dichroic filter when recording / reproducing information with respect to a DVD or CD. It functions in the same way and is automatically limited in opening.
Also, the chromatic aberration in the blue-violet region and the change in spherical aberration due to the change in incident wavelength are corrected by the action of the diffractive structure DOE1 formed in the fourth optical functional area AREA4 and the diffractive structure DOE2 formed in the fifth optical functional area AREA5. is doing.
When the wavelength change amount of the blue-violet semiconductor laser LD1 due to mode hopping is assumed to be +1 nm, when the aberration correction element L1 is combined with the condensing element L2 with respect to the defocus component change amount 151mλRMS of the condensing element L2 alone. Is 20 mλ RMS, and it can be seen that the change in the defocus component due to mode hopping is well corrected.
Further, when the wavelength variation due to the manufacturing error of the blue-violet semiconductor laser LD1 is assumed to be +10 nm, when the aberration correcting element L1 is combined with the condensing element L2 with respect to the change amount 74 mλRMS of the spherical aberration component of the condensing element L2 alone Is 4 mλ RMS, and it can be seen that the change in spherical aberration accompanying the change in incident wavelength is well corrected.

The optical element of Example 2 is an optimal optical element as the objective optical system OBJ of the second optical pickup device PU2 as shown in FIG. 3 and the fifth optical pickup device PU5 as shown in FIG. The specific numerical data is shown in Table 16.

The high-density optical disc while the magnification m1 with respect to the wavelength λ1 and the magnification m2 with respect to the wavelength λ2 are substantially matched by the action of the superposition type diffractive structure HOE4 (HOE8) formed in the sixth (18th) optical function area AREA6 (AREA18). The spherical aberration due to the difference in the thickness of the protective layer between HD and DVD is corrected.
The diffraction structure DOE3 (DOE8) formed in the eighth (20th) optical function area AREA8 (AREA20) and the diffraction structure DOE4 (DOE9) formed in the ninth (21st) optical function area AREA9 (AREA21). As a result, the chromatic aberration in the blue-violet region and the spherical aberration change accompanying the environmental temperature change are corrected.
When the wavelength change amount of the blue-violet semiconductor laser LD1 due to mode hopping is assumed to be +1 nm, when the aberration correction element L1 is combined with the condensing element L2 with respect to the defocus component change amount 151mλRMS of the condensing element L2 alone. Is 27 mλ RMS, and it can be seen that the defocus component change due to mode hopping is well corrected.
Further, when the ambient temperature rises by 30 degrees, the oscillation wavelength of the blue-violet semiconductor laser is 409.5 nm, the refractive index of the aberration correcting element L1 at that time is 1.52079, and the refractive index of the condensing element L2 is 1.55671 When the aberration correction element L1 is combined with the condensing element L2, the amount of change in spherical aberration due to the environmental temperature changes favorably, compared to the change amount 116mλRMS of the spherical aberration component of the condensing element L2 alone. You can see that it has been corrected.
Table 16 also shows numerical data obtained by combining the optical element of this embodiment with a coupling lens CUL as a coma aberration correcting element. When the amount of shift in the direction perpendicular to the optical axis of the optical element at the time of recording / reproducing information with respect to the CD is 0.2 mm, the converging element L2 has an aberration with respect to the coma aberration generation amount 51 mλRMS of the optical element alone. When the correction element L1 is combined, it becomes 20 mλRMS, and it can be seen that the coma change due to the shift of the optical element is well corrected.

The optical element of Example 3 is the optimum optical element as the objective optical system OBJ of the third optical pickup device PU3 as shown in FIG. 5, and specific numerical data thereof are shown in Table 17.

The thickness of the protective layer of the high-density optical disc HD and DVD is made different by making the action of the superposition type diffractive structure HOE5 formed in the tenth optical functional area AREA10 different from the magnification m1 for the wavelength λ1 and the magnification m2 for the wavelength λ2. The spherical aberration due to the difference is corrected.
Further, the chromatic aberration in the blue-violet region and the spherical aberration change due to the environmental temperature change are corrected by the action of the diffractive structure DOE5 formed in the twelfth optical function area AREA12 and the diffractive structure DOE6 formed in the thirteenth optical function area AREA13. is doing.
When the wavelength change amount of the blue-violet semiconductor laser LD1 due to mode hopping is assumed to be +1 nm, when the aberration correction element L1 is combined with the condensing element L2 with respect to the defocus component change amount 151mλRMS of the condensing element L2 alone. Is 32 mλRMS, and it can be seen that the defocus component change due to mode hopping is well corrected.

Further, when the environmental temperature rises by 30 degrees, the oscillation wavelength of the blue-violet semiconductor laser LD1 is 409.5 nm, the refractive index of the aberration correcting element L1 at that time is 1.52079, and the refractive index of the condensing element L2 is 1. When 55671 is set, the change amount 116 mλRMS of the spherical aberration component of the condensing element L2 alone is 45 mλRMS when the aberration correcting element L1 is combined with the condensing element L2, and the change in spherical aberration due to the environmental temperature change is good. It can be seen that it has been corrected.
Table 17 also shows numerical data obtained by combining the optical element of the present embodiment with a coupling lens CUL as a divergence angle conversion element.
The coupling lens CUL uses the action of the superposition type diffractive structure HOE6 formed in the fourteenth optical function area AREA14, and the laser beam having the wavelength λ2 emitted from the first emission point EP1 and the second emission. A divergence angle with a laser beam having a wavelength λ3 emitted from the point EP2 is converted into a divergence angle corresponding to a magnification m2 with respect to the wavelength λ2 and a magnification m3 with respect to the wavelength λ3 of the objective optical system OBJ, respectively, and emitted. It is an optical element.

The optical element of Example 4 is an optical element that is optimal as the objective optical system OBJ of the second optical pickup device PU2 as shown in FIG. 3 and the fifth optical pickup device PU5 as shown in FIG. Table 18 shows specific numerical data.

The high-density optical disc while the magnification m1 with respect to the wavelength λ1 and the magnification m2 with respect to the wavelength λ2 are substantially matched by the action of the superposition type diffractive structure HOE4 (HOE8) formed in the sixth (18th) optical function area AREA6 (AREA18). The spherical aberration due to the difference in the thickness of the protective layer between HD and DVD is corrected.
As a method of correcting the spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disk HD and the DVD by the action of the superposition type diffractive structure, a method of adding a correction supplemental spherical aberration to the light beam having the wavelength λ2. There is a method in which the paraxial diffraction power for the light beam having the wavelength λ2 is set to be negative. The latter has a problem that coma aberration increases when an off-axis light beam having a wavelength λ2 is incident.
In the superposition type diffractive structure HOE4 (HOE8) in this embodiment, the spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disk HD and the DVD is corrected by combining both, and the light beam having the wavelength λ2 is corrected. When determining the paraxial diffractive power, the off-axis characteristics for the light beam having the wavelength λ2 are not deteriorated excessively while mitigating the occurrence of coma due to the optical axis deviation between the aberration correcting element L1 and the condensing element L2. Noted.

The optical path difference function of the superposition type diffractive structure HOE4 (HOE8) has an inflection point within NA2 = 0.67, and the slope of the tangent of the optical path difference function is switched from positive to negative before and after the inflection point. . This corresponds to the fact that the inclination direction of the annular zone (l4 in FIG. 3) of the superposition type diffractive structure HOE4 (HOE8) is reversed halfway, but if the optical path difference function has an inflection point in this way, the annular zone. Can be secured large (Λ4 in FIG. 3). In this embodiment, the minimum value of the width of the annular zone is 70 μm.
The diffraction structure DOE3 (DOE8) formed in the eighth (20th) optical function area AREA8 (AREA20) and the diffraction structure DOE4 (DOE9) formed in the ninth (21st) optical function area AREA9 (AREA21). As a result, the chromatic aberration in the blue-violet region and the spherical aberration change accompanying the environmental temperature change are corrected.
Assuming that the wavelength variation of the blue-violet semiconductor laser due to mode hopping is +1 nm, when the aberration correction element L1 is combined with the light condensing element L2 with respect to the defocus component variation 151mλRMS of the light condensing element L2 alone. It can be seen that the change in defocus component due to mode hopping is well corrected.

  Further, when the ambient temperature rises by 30 degrees, the oscillation wavelength of the blue-violet semiconductor laser LD1 is 409.5 nm, the refractive index of the aberration correcting element L1 at that time is 1.52079, and the refractive index of the condensing element L2 is 1. When 55671 is set, the amount of change in spherical aberration component 114 mλRMS of the condensing element L2 alone is 46 mλRMS when the aberration correcting element L1 is combined with the condensing element L2, and the change in spherical aberration due to environmental temperature changes is good. It can be seen that it has been corrected.

The optical element of Example 5 is an optical element that is optimal as the objective optical system OBJ of the second optical pickup device PU2 as shown in FIG. 3 and the fifth optical pickup device PU5 as shown in FIG. Table 19 shows the specific numerical data.

The high-density optical disc while the magnification m1 with respect to the wavelength λ1 and the magnification m2 with respect to the wavelength λ2 are substantially matched by the action of the superposition type diffractive structure HOE4 (HOE8) formed in the sixth (18th) optical function area AREA6 (AREA18). The spherical aberration due to the difference in the thickness of the protective layer between HD and DVD is corrected.
In the optical element of the present embodiment, like the optical element of the fourth embodiment, the correction supplemental spherical aberration is added to the light beam with wavelength λ2, and the paraxial diffraction power for the light beam with wavelength λ2 is set negative. In combination with this method, spherical aberration due to the difference in thickness of the protective layer between the high-density optical disk HD and the DVD is corrected, and the minimum value of the width of the annular zone is 81 μm.
The diffraction structure DOE3 (DOE8) formed in the eighth (20th) optical function area AREA8 (AREA20) and the diffraction structure DOE4 (DOE9) formed in the ninth (21st) optical function area AREA9 (AREA21). As a result, the chromatic aberration in the blue-violet region and the change in spherical aberration accompanying the change in incident wavelength are corrected.

Assuming that the wavelength variation of the blue-violet semiconductor laser due to mode hopping is +1 nm, when the aberration correction element L1 is combined with the light condensing element L2 with respect to the defocus component change amount 138 mλRMS of the light condensing element L2 alone. 18 mλRMS, indicating that the change in defocus component due to mode hopping is corrected well.
Further, when the wavelength variation due to the manufacturing error of the blue-violet semiconductor laser is assumed to be +10 nm, when the aberration correction element L1 is combined with the condensing element L2 with respect to the change amount 54 mλRMS of the spherical aberration component of the condensing element L2 alone. Is 4 mλRMS, and it can be seen that the change in spherical aberration accompanying the change in incident wavelength is well corrected.
In the optical element of Example 2, the sectional view of the superposition type diffractive structure HOE4 formed in the sixth optical function area AREA6 is shown in FIG. 16, and in the optical element of Example 4, it is formed in the eighteenth optical function area AREA18. FIG. 17 shows a cross-sectional view of the superimposed diffractive structure HOE8.
In the figure, the horizontal axis indicates the height h (mm) from the optical axis, and the vertical axis indicates the height D (mm) in the direction perpendicular to the optical axis of the superposition type diffractive structure HOE4 (HOE8).

The optical element of Example 6 is the optimum optical element as the objective optical system OBJ of the eighth optical pickup device PU8 as shown in FIG. 20, and specific numerical data are shown in Table 20. FIG. 23 shows an optical path diagram.

Due to the action of the superposition type diffractive structure HOE12 formed in the 30th optical function area AREA30, spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disc HD and DVD is corrected, and the aperture limitation when using the DVD is aberration. This is automatically performed by the correction element L1.
In the optical element of the present embodiment, the second-order optical path difference function coefficient B2 and the fourth-order optical path difference function coefficient B4 of the superposition type diffractive structure HOE12 have different signs, so that correction supplementation is performed for the light flux having the wavelength λ2. Correction of spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disc HD and the DVD by combining the method of adding spherical aberration and the method of setting the diffractive power in the paraxial to the light beam of wavelength λ2 to be negative It is carried out. The minimum value of the annular zone width of the superposition type diffractive structure HOE 12 is 117.4 μm, and a sufficient annular zone width is obtained, so that the die machining is easy.
In addition, the axial chromatic aberration in the blue-violet region and the spherical aberration change accompanying the environmental temperature change are corrected by the action of the diffractive structure DOE 13 formed on the optical function surface S2 on the optical disc side of the aberration correction element L1.

Assuming that the wavelength change amount of the blue-violet semiconductor laser due to mode hopping is +1 nm, when the aberration correction element L1 is combined with the light condensing element L2 with respect to the defocus component change amount 119mλRMS of the light condensing element L2 alone, It can be seen that the defocus component change due to the mode hopping is well corrected.
Further, when the ambient temperature rises by 30 degrees, the oscillation wavelength of the blue-violet semiconductor laser is 408.5 nm, the refractive index of the aberration correcting element L1 at that time is 1.52094, and the refractive index of the condensing element L2 is 1.55687. When the aberration correction element L1 is combined with the light condensing element L2, the amount of change in the spherical aberration component of the condensing element L2 alone is 28 mλRMS. You can see that it has been corrected.

The optical element of Example 7 is the optimum optical element as the objective optical system OBJ of the ninth optical pickup device PU9 as shown in FIG. 21, and specific numerical data are shown in Table 21. FIG. 24 shows an optical path diagram.

The effect of the superposition type diffractive structure HOE13 formed in the thirty-second optical function area AREA32 corrects spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disc HD and DVD, and the aperture limitation when using the DVD is aberration. This is automatically performed by the correction element L1.
In the optical element of the present embodiment, the second-order optical path difference function coefficient B2 and the fourth-order optical path difference function coefficient B4 of the superposition type diffractive structure HOE13 have different signs, so that a supplementary correction is made for the light flux of wavelength λ2. Correction of spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disc HD and the DVD by combining the method of adding spherical aberration and the method of setting the diffractive power in the paraxial to the light beam of wavelength λ2 to be negative It is carried out. The minimum value of the annular zone width of the superposition type diffractive structure HOE 13 is 93.8 μm, and since a sufficient annular zone width is obtained, the die machining is easy.
Further, the axial chromatic aberration and the chromatic spherical aberration change in the blue-violet region are corrected by the action of the diffractive structure DOE 13 formed on the optical function surface S2 on the optical disc side of the aberration correction element L1.

Assuming that the wavelength variation of the blue-violet semiconductor laser due to mode hopping is +1 nm, when the aberration correction element L1 is combined with the light condensing element L2 with respect to the defocus component variation 114mλRMS of the light condensing element L2 alone. It can be seen that the change in defocus component due to mode hopping is well corrected.
Further, assuming that the wavelength variation due to the manufacturing error of the blue-violet semiconductor laser is +10 nm, when the aberration correcting element L1 is combined with the condensing element L2 with respect to the change amount 47 mλRMS of the spherical aberration component of the condensing element L2 alone. Is 4 mλRMS, and it can be seen that the change in spherical aberration accompanying the change in incident wavelength is well corrected.

The optical element of Example 8 is the optimum optical element as the objective optical system OBJ of the tenth optical pickup apparatus PU10 as shown in FIG. 22, and specific numerical data are shown in Table 22. FIG. 25 shows an optical path diagram.

The superposed diffractive structure HOE 14 formed in the 34th optical function area AREA 34 corrects spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disc HD and DVD, and the aperture limitation when using the DVD is aberration. This is automatically performed by the correction element L1.
In the optical element of the present embodiment, the second-order optical path difference function coefficient B2 and the fourth-order optical path difference function coefficient B4 of the superposition type diffractive structure HOE14 have different signs, so that correction supplementation is performed for the light flux having the wavelength λ2. Correction of spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disk HD and DVD by combining the method of adding spherical aberration and the method of setting the diffractive power in the paraxial to the light beam of wavelength λ2 to be negative It is carried out. The minimum value of the annular zone width of the superposed diffractive structure HOE 14 is 66.3 μm, and a sufficient annular zone width is obtained, so that the die machining is easy.
Further, the spherical aberration change accompanying the environmental temperature change in the blue-violet region is corrected by the action of the optical path difference providing structure NPS formed on the optical function surface S1 on the semiconductor laser side of the aberration correction element L1.
Further, when the ambient temperature rises by 30 degrees, the oscillation wavelength of the blue-violet semiconductor laser is 408.5 nm, the refractive index of the aberration correcting element L1 at that time is 1.52094, and the refractive index of the condensing element L2 is 1.55687. When the aberration correction element L1 is combined with the light condensing element L2, the amount of change in spherical aberration due to the environmental temperature change is favorable with respect to the amount of change 81mλRMS of the spherical aberration component of the condensing element L2 alone. You can see that it has been corrected.

In Table 22-2, “Optical path difference providing structure on the first surface”, i represents the number of the central region and each annular zone, the central region is i = 0, and the first annular zone adjacent to the outside of the central region. I = 1, and the second annular zone adjacent to the outside of the first annular zone is i = 2. h _iS represents the center region and the height of the start point of each ring zone, and h _iL represents the center region and the end point height of each ring zone. _{M i1} d represents the amount of shift in the optical axis direction of each annular zone with respect to the central region. For example, the second annular zone (i = 2) is shifted to the optical disc side by 7.761 μm with respect to the central region (i = 0), and the sixth annular zone (i = 6) is shifted to the central region (i = 6). 0) is shifted to the laser light source side by 7.761 μm. Further, m _i1 is a value representing the wavelength the optical path length difference of each ring-shaped zone to the center region λ1 (= 407nm) as a unit, m _i2 wavelength the optical path length difference of each ring-shaped zone to the center region .lambda.2 (.lambda.2 = 660 nm) as a unit. For example, the second annular zone has a short optical path length by 10 × λ1 (= 6 × λ2) with respect to the central region, and the sixth annular zone has an optical path length by 10 × λ1 (= 6 × λ2) with respect to the central region. long.

The optical system of Example 9 is composed of an expander lens composed of a negative lens and a positive lens, both of which are plastic lenses, and an objective optical system composed of an aberration correction element and a condensing element, both of which are plastic lenses. This optical system is optimal as the optical system of the twelfth optical pickup device PU12. The specific numerical data are shown in Table 23.

The objective optical system has a spherical surface due to the difference in the thickness of the protective layer between the high-density optical disc HD and the DVD by the action of the superposition type diffractive structure formed on the optical surface on the light source side of the aberration correction element (the fifth surface in Table 23). This is an HD / DVD compatible lens with corrected aberration. The condensing element is a lens in which spherical aberration correction is optimized for the high-density optical disc HD.
Further, spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disc HD and the CD is corrected by moving the negative lens of the expander lens in the optical axis direction and changing the magnification of the objective optical system.
Further, when the wavelength of the incident light beam changes, the divergence of the light beam emitted from the expander lens changes due to the influence of chromatic aberration. Therefore, at the time of recording / reproducing on DVD, the negative lens is set so that the distance between the negative lens and the positive lens is wider than that of the high-density optical disc HD so that the second light beam emitted from the expander lens becomes a parallel light beam. It is moving.
Incidentally, the diffraction efficiency of the first light beam generated by the superposition type diffractive structure is 100%, the diffraction efficiency of the first light beam of the second light beam is 87%, and the 0th order light beam (transmission) of the third light beam. The diffraction efficiency of light) is 100%, and high diffraction efficiency is obtained for any light flux.

対物光学系は、光源側の光学面（表２４において第３面）に形成した回折構造の作用により、高密度光ディスクＨＤとＤＶＤとの保護層の厚さの違いによる球面収差を補正したＨＤ／ＤＶＤ互換レンズである。
また、高密度光ディスクＨＤとＣＤとの保護層の厚さの違いによる球面収差は、コリメートレンズを光軸方向に動かして、対物光学系の倍率を変化させることで補正しているが、回折構造で、第１光束乃至第３光束の１次回折光を利用することで、高密度光ディスクＨＤとＣＤとの保護層の厚さの違いによる球面収差を低減しているため、コリメートレンズの移動量が小さくてすみ、また、対物光学系のトラッキング特性を良好なものにしている。 The optical system of Example 10 is an optical system composed of an expander lens that is a plastic lens and an objective optical system that is a plastic lens, and is optimal as an optical system of the twelfth optical pickup device PU12. Further, the objective optical system of the present embodiment is optimal as the objective optical system of the eleventh optical pickup device PU11. The specific numerical data is shown in Table 24.

The objective optical system corrects spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disc HD and the DVD by the action of the diffractive structure formed on the optical surface on the light source side (third surface in Table 24). It is a DVD compatible lens.
In addition, spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disk HD and the CD is corrected by moving the collimating lens in the optical axis direction and changing the magnification of the objective optical system. Since the spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disk HD and the CD is reduced by using the first-order diffracted light of the first light flux to the third light flux, the movement amount of the collimating lens is reduced. It is small, and the tracking characteristic of the objective optical system is improved.

When the wavelength of the incident light beam changes, the divergence of the light beam emitted from the collimating lens changes due to the influence of chromatic aberration. Therefore, at the time of recording / reproducing on DVD, the collimating lens is set so that the distance between the collimating lens and the objective optical system is narrower than that of the high-density optical disc HD so that the second light beam emitted from the collimating lens becomes a parallel light beam. Is moving.
The diffraction efficiency of the first-order diffracted light of the first light beam generated in the diffractive structure is 88%, the diffraction efficiency of the first-order diffracted light of the second light beam is 76%, and the diffraction efficiency of the first-order diffracted light of the third light beam is 50%. By setting the manufacturing wavelength λB to 480 nm, a high diffraction efficiency is obtained for high-density optical disks HD and DVD that require high speed during recording.

対物光学系は、収差補正素子の光源側の光学面（表２５において第５面）に形成した重
畳型回折構造の作用により、高密度光ディスクＨＤとＤＶＤとの保護層の厚さの違いによる球面収差を補正したＨＤ／ＤＶＤ互換レンズである。尚、集光素子は、高密度光ディスクＨＤに対して球面収差補正が最適化されたレンズである。 The optical system of Example 11 is composed of an expander lens composed of a negative lens and a positive lens, both of which are plastic lenses, and an objective optical system composed of an aberration correction element and a condensing element, both of which are plastic lenses. This optical system is optimal as the optical system of the twelfth optical pickup device PU12. Specific numerical data are shown in Table 25.

The objective optical system has a spherical surface due to the difference in the thickness of the protective layer between the high-density optical disc HD and the DVD by the action of the superposition type diffractive structure formed on the optical surface (fifth surface in Table 25) on the light source side of the aberration correction element. This is an HD / DVD compatible lens with corrected aberration. The condensing element is a lens in which spherical aberration correction is optimized for the high-density optical disc HD.

Further, spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disk HD and the CD is corrected by moving the negative lens of the expander lens in the optical axis direction and changing the magnification of the objective optical system. In the diffraction structure formed on the optical surface (sixth surface in Table 25) of the optical disc side of the aberration correction element, the fifth-order diffracted light of the first light beam, the third-order diffracted light of the second light beam, and the second-order diffracted light of the third light beam are used. As a result, the spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disc HD and the CD is reduced, so that the amount of movement of the negative lens is small, and the tracking characteristic of the objective optical system is good. I'm making things.
Further, when the wavelength of the incident light beam changes, the divergence of the light beam emitted from the expander lens changes due to the influence of chromatic aberration. Therefore, at the time of recording / reproducing on DVD, the negative lens is set so that the distance between the negative lens and the positive lens is wider than that of the high-density optical disc HD so that the second light beam emitted from the expander lens becomes a parallel light beam. It is moving.

  Incidentally, the diffraction efficiency of the first light beam generated by the superposition type diffractive structure is 100%, the diffraction efficiency of the first light beam of the second light beam is 87%, and the 0th order light beam (transmission) of the third light beam. Light) is 100%, the diffraction efficiency of the fifth-order diffracted light of the first light beam generated in the diffractive structure is 100%, the diffraction efficiency of the third-order diffracted light of the second light beam is 100%, and the second time of the third light beam. The diffraction efficiency of the folded light is 41%. The diffraction efficiency of the two diffractive structures is 100% for the first light flux, 87% for the second light flux, and 41% for the third light flux, which is higher than that for high-density optical disks HD and DVD that require high speed during recording. Diffraction efficiency is obtained.

PU optical pickup device L1 superimposition type diffractive structure optical element L2 condensing element HOE superposition type diffractive structure DOE diffractive structure

Claims (264)

Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. For an optical pickup device for reproducing and / or recording information on a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) An optical element,
The optical element includes an optical functional surface on which a superposition type diffractive structure, which is a structure in which a plurality of annular zones having a plurality of steps formed therein are arranged around the optical axis, and a step in the optical axis direction. An optical element for an optical pickup device, comprising: an optical functional surface on which a diffraction structure composed of a plurality of divided annular zones is formed. Of the diffracted light generated when the light beam having the first wavelength λ1 is incident on the diffractive structure, the diffraction order of the diffracted light having the maximum diffraction efficiency is n1, and the light beam having the second wavelength λ2 is incident on the diffractive structure. When the diffraction order of the diffracted light having the maximum diffraction efficiency among the diffracted light generated in this case is n2, the depth of the step of the diffractive structure is set so as to satisfy the following expression (1) The optical element for an optical pickup device according to claim 1.
n1> n2 (1) When the first wavelength λ1 (μm) and the second wavelength λ2 (μm) satisfy the following expressions (2) and (3), respectively, and the light beam having the first wavelength λ1 is incident on the diffractive structure: Of the generated diffracted light, the diffraction order n1 of the diffracted light having the maximum diffraction efficiency and the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light beam having the second wavelength λ2 enters the diffractive structure. The combination of the diffraction orders n2 of (n1, n2) = (2,1), (3,2), (5,3), (8,5), (10,6) The optical element for an optical pickup device according to claim 1, wherein the optical element is an optical element.
0.39 <λ1 <0.42 (2)
0.63 <λ2 <0.68 (3) Among the optical elements, an element having an optical functional surface on which the diffractive structure is formed has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1, and an Abbe number at the d-line. 50
The depth d1 in the optical axis direction of the step closest to the optical axis among the steps of the diffractive structure formed of a material within a range of ˜60 satisfies any of the following formulas (4) to (8). The optical element for an optical pickup device according to claim 1, wherein the optical element is an optical element.
1.2 μm <d1 <1.7 μm (4)
2.0 μm <d1 <2.6 μm (5)
3.4 μm <d1 <4.1 μm (6)
5.6 μm <d1 <6.5 μm (7)
6.9 μm <d1 <8.1 μm (8)   5. The optical element for an optical pickup device according to claim 1, wherein a cross-sectional shape including an optical axis of the diffractive structure is a step shape.   The optical element for an optical pickup device according to any one of claims 1 to 4, wherein a cross-sectional shape including the optical axis of the diffractive structure is a sawtooth shape.   The optical element is composed of one element, the superposition type diffractive structure is formed on one optical functional surface of the optical element, and the diffractive structure is formed on the other optical functional surface of the optical element. The optical element for an optical pickup device according to claim 1, wherein the optical element is an optical element.   The superposition type diffractive structure does not substantially give an optical path difference between adjacent annular zones to the light flux having the first wavelength λ1, but gives an optical path difference to the light flux having the second wavelength λ2. An optical element for an optical pickup device according to any one of claims 1 to 7. The said 1st wavelength (lambda) 1 (micrometer) and the said 2nd wavelength (lambda) 2 (micrometer) satisfy | fill the following (2) and (3) Formula, respectively, The Claim 1 thru | or 8 characterized by the above-mentioned. Optical element for optical pickup device.
0.39 <λ1 <0.42 (2)
0.63 <λ2 <0.68 (3) Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. For an optical pickup device for reproducing and / or recording information on a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1) An optical element,
The optical element includes an optical functional surface on which a superposition type diffractive structure, which is a structure in which a plurality of annular zones having a plurality of steps formed therein are arranged around the optical axis, and a step in the optical axis direction. And an optical functional surface on which an optical path difference providing structure composed of a plurality of divided annular zones is formed.   Among the annular zones of the optical path difference providing structure, the annular zone located at a predetermined height within the maximum effective diameter is shifted in the optical axis direction so that the optical path length becomes shorter as the distance from the optical axis increases. The annular zone outside the annular zone located at a predetermined height within the maximum effective diameter is shifted in the optical axis direction so that the optical path length becomes longer as the distance from the optical axis increases. An optical element for an optical pickup device according to claim 10.   The height from the optical axis in the central part of the annular zone located at the predetermined height is a height within a range of 60% to 85% of the maximum effective diameter. Optical element for optical pickup device. The first wavelength λ1 (μm), the second wavelength λ2 (μm), the depth d2 (μm) of the step closest to the optical axis among the steps of the optical path difference providing structure, among the optical elements The refractive index Nλ _{1 of the} element having the optical function surface on which the optical path difference providing structure is formed with respect to the first wavelength λ _1.
Depending on the refractive index Nλ ₂ of the optical element with respect to the second wavelength λ1, the following (9)
And Φ1 and Φ2 represented by the formula (10) satisfy the following formulas (11) to (13): The optical element for an optical pickup device according to any one of claims 10 to 12 . Φ1 = d2 (Nλ ₁ −1) / λ1 (9)
Φ2 = d2 (Nλ ₂ −1) / λ2 (10)
INT (Φ1) ≦ 20 (11)
0 ≦ | INT (Φ1) −Φ1 | ≦ 0.4 (12)
0 ≦ | INT (Φ2) −Φ2 | ≦ 0.4 (13)
However, INT (Φi) (i = 1, 2) is an integer obtained by rounding Φi. Among the optical elements, an element having an optical function surface on which the optical path difference providing structure is formed has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and is d-line 14. The optical element for an optical pickup device according to claim 13, wherein the optical element is formed of a material having an Abbe number in the range of 50 to 60 and satisfies the following expressions (14) and (15).
INT (Φ1) = 5p (14)
INT (Φ2) = 3p (15)
However, p is an integer of 1 or more.   The optical element is composed of one element, the superposition type diffractive structure is formed on one optical functional surface of the optical element, and the optical path difference providing structure is formed on the other optical functional surface of the optical element. 15. The optical element for an optical pickup device according to any one of claims 10 to 14, wherein the optical element is formed.   The superposition type diffractive structure does not substantially give an optical path difference between adjacent annular zones to the light flux having the first wavelength λ1, but gives an optical path difference to the light flux having the second wavelength λ2. An optical element for an optical pickup device according to any one of claims 10 to 15. The said 1st wavelength (lambda) 1 (micrometer) and the said 2nd wavelength (lambda) 2 (micrometer) satisfy | fill the following (2) and (3) Formula, respectively, The Claim 10 thru | or 16 characterized by the above-mentioned. Optical element for optical pickup device.
0.39 <λ1 <0.42 (2)
0.63 <λ2 <0.68 (3) The first wavelength λ1 (μm) and the second wavelength λ2 (μm) satisfy the following expressions (2) and (3), and the light of the step formed in each annular zone in the superimposed diffraction structure: A refractive index Nλ ₁ with respect to the first wavelength λ 1 of an element having an optical functional surface on which the superposition type diffractive structure is formed is substantially the following ( The optical element for an optical pickup device according to any one of claims 1 to 17, wherein the expression (16) is satisfied.
0.39 <λ1 <0.42 (2)
0.63 <λ2 <0.68 (3)
Δ = 2m · λ1 / (Nλ 1 -1) (16)
However, N is either 3 or 4 or 5, and m is an integer of 1 or more. Among the optical elements, an element having an optical functional surface on which the superposition type diffractive structure is formed has a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and is d-line The Abbe number is made of a material in the range of 50 to 60, and in the superposition type diffractive structure, the number N of the steps formed in each annular zone and the annular zone closest to the optical axis among the annular zones. 19. The optical element for an optical pickup device according to claim 18, wherein a combination of depths D (μm) in the optical axis direction is any of the following formulas (17) to (19).
When N = 3, 4.1 ≦ D ≦ 4.8 (17)
When N = 4, 5.4 ≦ D ≦ 6.4 (18)
When N = 5, 7.0 ≦ D ≦ 7.9 (19) Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Used in an optical pickup device that reproduces and / or records information on a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1). The light beam having the first wavelength λ1 is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 is collected on the information recording surface of the second optical information recording medium. An objective optical system used for light,
10. The optical element for an optical pickup device according to claim 1, wherein the diffractive structure is configured so that the objective optical system is changed when the first wavelength λ1 changes within a range of ± 10 nm. An objective optical system having a function of suppressing chromatic aberration generated due to the wavelength dispersion of the objective lens.   The objective optical system according to claim 20, wherein the diffractive structure has a function of suppressing axial chromatic aberration of the objective optical system when the first wavelength λ1 changes within a range of ± 10 nm. .   The diffractive structure has a function of suppressing a change in spherical aberration caused by wavelength dispersion of the objective optical system when the first wavelength λ1 changes within a range of ± 10 nm. Item 22. The objective optical system according to Item 20 or 21. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Used in an optical pickup device that reproduces and / or records information on a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1). The light beam having the first wavelength λ1 is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 is collected on the information recording surface of the second optical information recording medium. An objective optical system used for light,
Including an optical element for the optical pickup device according to any one of claims 1 to 9,
The objective optical system includes a plastic lens having a positive paraxial power, and the diffractive structure suppresses a change in spherical aberration caused by a change in refractive index of the plastic lens due to a change in environmental temperature. An objective optical system characterized by having a function.   In the objective optical system, when the first wavelength λ1 changes to the long wavelength side, the spherical aberration changes in the direction of insufficient correction, and when the first wavelength λ1 changes to the short wavelength side, the spherical aberration. 24. The objective optical system according to claim 23, wherein the objective lens system has a wavelength dependency of spherical aberration that changes in an overcorrection direction. The objective optical system condenses the aberration correcting element and the light beam having the first wavelength λ1 emitted from the aberration correcting element on the information recording surface of the first optical information recording medium, and from the aberration correcting element. A condensing element used for condensing the emitted light beam having the second wavelength λ2 on the information recording surface of the second optical information recording medium,
25. The objective optical system according to claim 20, wherein the superposition type diffractive structure and the diffractive structure are formed on an optical function surface of the aberration correction element.   The objective optical system according to any one of claims 20 to 25, wherein a cross-sectional shape including an optical axis of the diffractive structure is a stepped shape.   The objective optical system according to any one of claims 20 to 25, wherein a cross-sectional shape including an optical axis of the diffractive structure is a sawtooth shape.   The superposition type diffractive structure has a function of correcting a spherical aberration generated due to a difference in thickness between a protective layer of the first optical information recording medium and a protective layer of the second optical information recording medium. The objective optical system according to any one of claims 20 to 27, wherein Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Used in an optical pickup device that reproduces and / or records information on a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1). The light beam having the first wavelength λ1 is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 is collected on the information recording surface of the second optical information recording medium. An objective optical system used for light,
An optical element for an optical pickup device according to any one of claims 10 to 17, wherein the optical path difference providing structure has the objective when the first wavelength λ1 changes within a range of ± 10 nm. An objective optical system having a function of suppressing a change in spherical aberration caused by wavelength dispersion of the optical system. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Used in an optical pickup device that reproduces and / or records information on a second optical information recording medium having a protective layer having a thickness t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1). The light beam having the first wavelength λ1 is condensed on the information recording surface of the first optical information recording medium, and the light beam having the second wavelength λ2 is collected on the information recording surface of the second optical information recording medium. An objective optical system used for light,
An optical element for an optical pickup device according to any one of claims 10 to 17, wherein the objective optical system includes a plastic lens having a positive paraxial power, and the optical path difference providing structure is An objective optical system having a function of suppressing a change in spherical aberration caused by a change in refractive index of the plastic lens due to a change in environmental temperature.   In the optical path difference providing structure, when the environmental temperature increases, the spherical aberration added to the light beam having the first wavelength λ1 changes in the direction of insufficient correction, and when the environmental temperature decreases, 31. The objective optical system according to claim 30, wherein the spherical aberration added to the light beam having the wavelength [lambda] 1 has a temperature dependency of the spherical aberration so that the spherical aberration changes in a direction of insufficient correction.   Among the annular zones of the optical path difference providing structure, the annular zone located at a predetermined height within the maximum effective diameter is shifted in the optical axis direction so that the optical path length becomes shorter as the distance from the optical axis increases. The annular zone outside the annular zone located at a predetermined height within the maximum effective diameter is shifted in the optical axis direction so that the optical path length becomes longer as the distance from the optical axis increases. The objective optical system according to claim 30 or 31.   The height from the optical axis in the central portion of the annular zone located at the predetermined height is a height within a range of 60% to 85% of the maximum effective diameter. Objective optical system. The objective optical system condenses the aberration correcting element and the light beam having the first wavelength λ1 emitted from the aberration correcting element on the information recording surface of the first optical information recording medium, and from the aberration correcting element. A condensing element used for condensing the emitted light beam having the second wavelength λ2 on the information recording surface of the second optical information recording medium,
The objective optical system according to any one of claims 29 to 33, wherein the superimposing diffraction structure and the optical path difference providing structure are formed on an optical function surface of the aberration correction element.   The superposition type diffractive structure has a function of correcting a spherical aberration generated due to a difference in thickness between a protective layer of the first optical information recording medium and a protective layer of the second optical information recording medium. The objective optical system according to any one of claims 29 to 34, wherein When the optical path difference added to the transmitted wavefront by the superposition type diffractive structure is defined by the following equation,

B ₂ and the objective optical system written in any one of claims 20 to 35 codes B ₄ is different from each other.
However, lambda is the wavelength of the incident light beam, .lambda.B production wavelength, h is the direction perpendicular to the optical axis height (mm), B _2j is the optical path difference function coefficient, n represents the diffraction order. The objective optical system includes an aberration correction element having an optical function surface on which the superposition type diffractive structure is formed, and a light beam having the first wavelength λ1 emitted from the aberration correction element. A one-group configuration for condensing on the recording surface and condensing the light beam having the second wavelength λ2 emitted from the aberration correction element onto the information recording surface of the second optical information recording medium Condensing element that is a plastic lens of
The objective optical system according to any one of claims 20 to 36, wherein a paraxial power P1 (mm ^-1 ) of the aberration correction element with respect to the first wavelength λ1 satisfies the following expression (20). system.
P1> 0 (20) The objective optical system includes an aberration correction element having an optical function surface on which the superposition type diffractive structure is formed, and a light beam having the first wavelength λ1 emitted from the aberration correction element, as information on the first optical information recording medium. A one-group configuration for condensing on the recording surface and condensing the light beam having the second wavelength λ2 emitted from the aberration correction element onto the information recording surface of the second optical information recording medium The light condensing element,
The ratio of the paraxial power P1 (mm ⁻¹ ) of the aberration correcting element to the first wavelength λ1 and the paraxial power P2 (mm ⁻¹ ) of the condensing element to the first wavelength λ1 is as follows: The objective optical system according to any one of claims 20 to 37, wherein the expression (21) is satisfied.
| P1 / P2 | ≦ 0.2 (21) The condensing element is a cyclic polyolefin-based plastic lens, and the plastic lens has a refractive index N ₄₀₅ for a wavelength of 405 nm at a temperature of 25 ° C., and an Abbe number ν _d in a d-line, −5 ° C. to 70 ° C. The objective optical system according to claim 38, wherein a refractive index change rate dN ₄₀₅ / dT with respect to a wavelength of 405 nm accompanying a temperature change within the temperature range satisfies the following formulas (22) to (24).
1.54 <N ₄₀₅ <1.58 (22)
50 <ν _d <60 (23)
−10 × 10 ⁻⁵ (° C. ⁻¹ ) <dN ₄₀₅ / dT <−8 × 10 ⁻⁵ (° C. ⁻¹ ) (24)   39. The objective optical system according to claim 38, wherein the condensing element is formed using a material in which particles having a diameter of 30 [mu] m or less are dispersed in a plastic material.   39. The objective optical system according to claim 38, wherein the condensing element is a glass lens. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. An optical pickup device that reproduces and / or records information on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1). And
An optical pickup device comprising the optical element for an optical pickup device according to any one of claims 1 to 19. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. An optical pickup device that reproduces and / or records information on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1). And
An optical pickup device comprising the objective optical system according to any one of claims 20 to 41. The optical pickup device according to claim 42 or 43 is mounted, and the following (I) to (IV):
An optical information recording / reproducing apparatus characterized in that at least one of them can be executed.
(I) Recording information on the first optical information recording medium and recording information on the second optical information recording medium (II) Recording information on the first optical information recording medium and the second optical information Reproduction of information recorded on a recording medium (III) Reproduction of information recorded on the first optical information recording medium, and recording of information on the second optical information recording medium (IV) First optical information recording medium Of information recorded on the recording medium and reproduction of information recorded on the second optical information recording medium Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2) An optical element for the device,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. An optical element for an optical pickup device, wherein a superposition type diffractive structure is formed. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2) An optical element for the device,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
A first magnification m1 when information is reproduced and / or recorded on the first optical information recording medium, and a second magnification when information is reproduced and / or recorded on the second optical information recording medium. An optical element for an optical pickup device, characterized in that the magnification m2 substantially matches.   47. The optical element for an optical pickup device according to claim 46, wherein a diffraction power at a paraxial axis of the superposition type diffractive structure with respect to the second wavelength λ2 is negative.   48. The optical element for an optical pickup device according to claim 46, wherein the superposition type diffractive structure adds an uncorrected spherical aberration to the second wavelength λ2. 49. The optical element for an optical pickup device according to any one of claims 46 to 48, wherein the first magnification m1 and the second magnification m2 satisfy the following expression (25).
m1 = m2 = 0 (25) 50. The third magnification m3 when information is reproduced and / or recorded on the third optical information recording medium satisfies the following expression (26): An optical element for the optical pickup device described.
−0.25 <m3 <−0.10 (26)   The first light source and the second light source are packaged light source modules, and the optical element emits the light beam having the first wavelength λ1 emitted from the light source module to the information recording surface of the first optical information recording medium. 51. The light beam having the second wavelength λ2 collected on the light source module and condensed on the information recording surface of the second optical information recording medium. An optical element for an optical pickup device according to one item. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2) An optical element for the device,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
A second magnification m2 when information is reproduced and / or recorded on the second optical information recording medium, and a third magnification when information is reproduced and / or recorded on the third optical information recording medium. An optical element for an optical pickup device, wherein the magnification m3 substantially matches.   53. The optical element for an optical pickup device according to claim 52, wherein a diffraction power in a paraxial axis of the superposition type diffractive structure with respect to the second wavelength [lambda] 2 is positive.   54. The optical element for an optical pickup device according to claim 52, wherein the superposition type diffractive structure adds an overcorrected spherical aberration to the second wavelength λ2. 55. The first magnification m1 when reproducing and / or recording information on the first optical information recording medium satisfies the following expression (27): 55. An optical element for the optical pickup device described.
m1 = 0 (27) The optical element for an optical pickup device according to any one of claims 52 to 55, wherein the second magnification m2 and the third magnification m3 satisfy the following expressions (28) and (29). m2 = m3 (28)
−0.25 <m2 <−0.10 (29)   The second light source and the third light source are packaged light source modules, and the optical element emits a light beam having the second wavelength λ2 emitted from the light source module to an information recording surface of the second optical information recording medium. 57. The light beam having the third wavelength λ3 emitted from the light source module and condensed on the information recording surface of the second optical information recording medium. An optical element for an optical pickup device according to one item. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2) An optical element for the device,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
The first light flux λ1 and the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps among the discontinuous steps formed in each annular zone in the superposition type diffractive structure are as follows: An optical element for an optical pickup device satisfying the expressions (30) and (31).
0.39 μm <λ1 <0.42 μm (30)
P> 3 μm (31) In the superposition type diffractive structure, the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps among the discontinuous steps formed in each annular zone satisfies the following expression (32). 59. An optical element for an optical pickup device according to claim 58.
P> 5 μm (32) In the superposition type diffractive structure, among the discontinuous steps formed in each annular zone, the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps satisfies the following expression (33). 59. An optical element for an optical pickup device according to claim 58.
P> 10 μm (33) Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2) An optical element for the device,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
When the optical path difference added to the transmitted wavefront by the superposition type diffractive structure is defined by the following equation,

An optical element for an optical pickup device, wherein B ₂ and B ₄ have different signs.
Where λ is the wavelength of the incident light beam, λ _B is the manufacturing wavelength, h is the height (mm) in the direction perpendicular to the optical axis,
B _2j is an optical path difference function coefficient, and n is a diffraction order.   A first magnification m1 when information is reproduced and / or recorded on the first optical information recording medium, and a second magnification when information is reproduced and / or recorded on the second optical information recording medium. 62. The magnification m2 and the third magnification m3 when information is reproduced and / or recorded on the third optical information recording medium are different from each other. Optical element for optical pickup apparatus. 63. The optical for an optical pickup device according to claim 62, wherein the first magnification m1, the second magnification m2, and the third magnification m3 satisfy the following expressions (34) to (36). element. m1 = 0 (34)
-0.08 <m2 <-0.01 (35)
−0.25 <m3 <−0.10 (36) Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2) An optical element for the device,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function areas, at least two optical function areas are provided with a plurality of ring zones each having a predetermined number of discontinuous steps formed continuously around the optical axis. A superposed diffractive structure is formed,
In the superposition type diffractive structure, one of the number N of the discontinuous steps formed in each annular zone and the depth Δ (μm) of the discontinuous steps in the optical axis direction is determined for each optical function region. An optical element for an optical pickup device, characterized by being different. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2) An optical element for the device,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is formed with a diffractive structure composed of a plurality of annular zones divided by a step around the optical axis. Optical element for pickup device.   The depth of the step of the diffractive structure is such that the second wavelength λ2 is greater than the diffraction order n1 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the first wavelength λ1 is incident. Of the diffracted light generated when the light beam is incident, the diffraction order n2 of the diffracted light having the maximum diffraction efficiency and the maximum diffraction efficiency of the diffracted light generated when the light beam of the third wavelength λ3 is incident. 66. The optical element for an optical pickup device according to claim 65, wherein both of the diffraction orders n3 of the diffracted light are designed to be lower orders. The first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm) satisfy the following expressions (37) to (39), respectively, and the diffraction order n1 and the diffraction The combination of the order n2 and the diffraction order n3 is (n1, n2, n3) = (2,1,1), (4,2,2), (6,4,3), (8,5,4) 67. The optical element for an optical pickup device according to claim 66, wherein the optical element is any one of (10, 6, 5).
0.39 <λ1 <0.42 (37)
0.63 <λ2 <0.68 (38)
0.75 <λ3 <0.85 (39) The aberration correction element is formed of a material having a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and an Abbe number in the range of 50 to 60 at the d-line, and 68. The light according to claim 66 or 67, wherein a depth d1 of the step closest to the optical axis among the steps of the structure satisfies any one of the following formulas (40) to (44): Optical element for pickup device.
1.2 μm <d1 <1.7 μm (40)
2.6 μm <d1 <3.0 μm (41)
4.4 μm <d1 <5.0 μm (42)
5.6 μm <d1 <6.5 μm (43)
6.9 μm <d1 <8.1 μm (44)   The diffractive structure has a function of suppressing a focus position shift that occurs due to chromatic aberration of the light collecting element when the first wavelength λ1 changes within a range of ± 10 nm. 70. An optical element for an optical pickup device according to any one of 65 to 68.   The diffractive structure has a function of suppressing axial chromatic aberration that occurs due to chromatic aberration of the light collecting element when the first wavelength λ1 changes within a range of ± 10 nm. 69. An optical element for an optical pickup device according to 69.   The diffractive structure has a function of suppressing a spherical aberration change caused by chromatic aberration of the light collecting element when the first wavelength λ1 changes within a range of ± 10 nm. 69. An optical element for an optical pickup device according to 69 or 70.   The condensing element is a plastic lens, and in the diffractive structure, when the first wavelength λ1 changes to the long wavelength side, the spherical aberration changes in the direction of insufficient correction, and the first wavelength λ1 is short. Spherical aberration change caused by change in refractive index of condensing element due to environmental temperature change by having wavelength dependency of spherical aberration that changes spherical aberration in the overcorrection direction when it changes to the wavelength side 72. The optical element for an optical pickup device according to any one of claims 65 to 71, wherein the optical element has a function of suppressing the above.   Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a central optical functional region including an optical axis and a peripheral optical functional region surrounding the central optical functional region. The optical element for an optical pickup device according to claim 72, wherein the diffractive structure is formed only in the functional region.   74. The optical element for an optical pickup device according to any one of claims 65 to 73, wherein a cross-sectional shape including the optical axis of the diffractive structure is a stepped shape.   74. The optical element for an optical pickup device according to any one of claims 65 to 73, wherein a cross-sectional shape including the optical axis of the diffractive structure is a sawtooth shape.   66. The superimposed diffraction structure is formed on one optical functional surface of the aberration correction element, and the diffraction structure is formed on the other optical functional surface of the aberration correction element. 75. An optical element for an optical pickup device according to any one of 75. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2) An optical element for the device,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
At least one of the optical functional surfaces of the aberration correction element has an optical path difference providing structure comprising a central region including the optical axis and a plurality of annular zones divided by steps on the outside of the central region. An optical element for an optical pickup device, characterized in that is formed.   The condensing element and the aberration correcting element are both plastic lenses, and the optical path difference providing structure is such that when the environmental temperature rises, the spherical aberration added to the first wavelength λ1 is in the direction of insufficient correction. When the ambient temperature decreases, the spherical aberration added to the first wavelength λ1 has a temperature dependency of the spherical aberration that changes in the overcorrection direction. 78. The optical element for an optical pickup device according to claim 77, which has a function of suppressing a change in spherical aberration caused by a change in refractive index of the condensing element.   In the optical path difference providing structure, the annular zone adjacent to the outside of the central region is formed by shifting in the optical axis direction so as to shorten the optical path length with respect to the central region, and the ring at the maximum effective diameter position. The band is formed by shifting in the optical axis direction so that the optical path length is longer with respect to the ring zone adjacent to the inner side thereof, and the ring zone at a position of 75% of the maximum effective diameter is adjacent to the inner side. 79. The optical element for an optical pickup device according to claim 78, wherein the optical element is formed so as to be shifted in the optical axis direction so that the optical path length becomes shorter with respect to the annular zone and the annular zone adjacent to the outer zone. . Of the steps of the first wavelength λ1 (μm), the second wavelength λ3 (μm), the third wavelength λ3 (μm) and the optical path difference providing structure, the depth d2 in the optical axis direction of the step closest to the optical axis (μm), the refractive index Nλ _{1 of} the aberration correction element with respect to the first wavelength λ1, the refractive index Nλ _{2 of} the aberration correction element with respect to the second wavelength λ1, and the refractive index Nλ of the aberration correction element with respect to the third wavelength λ3. by _3, .phi.1 are expressed by the following (45) to (47) below, .phi.2, any Φ3 is, but the claims 77 to 79, characterized by satisfying the following (48) to (51) below An optical element for an optical pickup device according to claim 1.
Φ1 = d2 (Nλ ₁ −1) / λ1 (45)
Φ2 = d2 (Nλ ₂ −1) / λ2 (46)
Φ3 = d2 (Nλ ₃ −1) / λ3 (47)
INT (Φ1) ≦ 10 (48)
0 ≦ | INT (Φ1) −Φ1 | ≦ 0.4 (49)
0 ≦ | INT (Φ2) −Φ2 | ≦ 0.4 (50)
0 ≦ | INT (Φ3) −Φ3 | ≦ 0.4 (51)
However, INT (Φi) (i = 1, 2, 3) is an integer obtained by rounding Φi.   The superposition type diffractive structure is formed on one optical functional surface of the aberration correction element, and the optical path difference providing structure is formed on the other optical functional surface of the aberration correction element. 81. An optical element for an optical pickup device according to any one of 77 to 80. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2) An optical element for the device,
The optical element includes an aberration correction element and a light condensing for focusing the light beam emitted from the aberration correction element on each information recording surface of the first optical information recording medium to the third optical information recording medium. Consisting of elements,
The condensing element is a plastic lens having one lens element per group,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposition type diffractive structure is formed,
An optical element for an optical pickup device, wherein a power P1 (mm ⁻¹ ) in the paraxial axis of the aberration correction element with respect to the first wavelength λ1 satisfies the following expression (52).
P1> 0 (52) 85. The aberration correction element is a plastic lens, and a refractive power PR (mm ⁻¹ ) in the paraxial axis of the aberration correction element with respect to the first wavelength λ1 satisfies the following expression (53): An optical element for the optical pickup device described in 1.
PR> 0 (53)   84. The optical element for an optical pickup device according to any one of claims 45 to 83, wherein the optical functional region in which the superposition type diffractive structure is formed is an optical functional region including an optical axis. In the superposition type diffractive structure formed in the optical function region including the first wavelength λ1 (μm), the second wavelength λ3 (μm), the third wavelength λ3 (μm), and the optical axis, The number N of the discontinuous steps formed in the optical axis, the depth Δ (μm) of the discontinuous steps in the optical axis direction, the refractive index Nλ _{1 of} the aberration correction element with respect to the first wavelength λ1, the aberration correction element refractive index N [lambda ₂ to the second wavelength λ1 of the refractive index N [lambda ₃ with respect to the third wavelength λ3 of the aberration correcting element, .phi.1 are expressed by the following (54) to (56) below, .phi.2, .phi.3 is 85. The optical element for an optical pickup device according to claim 84, wherein: satisfies the following expressions (57) to (59).
φ1 = Δ (Nλ ₁ −1) (N + 1) / λ1 (54)
φ2 = Δ (Nλ ₂ −1) (N + 1) / λ2 (55)
φ3 = Δ (Nλ ₃ −1) (N + 1) / λ3 (56)
0 ≦ | INT (φ1) −φ1 | ≦ 0.4 (57)
0 ≦ | INT (φ2) −φ2 | ≦ 0.4 (58)
0 ≦ | INT (φ3) −φ3 | ≦ 0.4 (59)
However, INT (φi) (i = 1, 2, 3) is an integer obtained by rounding off φi. 86. The optical for an optical pickup device according to claim 85, wherein the φ1 and the number N of the discontinuous steps formed in each annular zone satisfy the following expressions (60) and (61). element. φ1 ≦ 24 (60)
3 ≦ N ≦ 11 (61)   The superposition type diffractive structure formed in the optical function region including the optical axis gives an equivalent first optical action to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3, and 87. The light for an optical pickup device according to claim 84, wherein a second optical action different from the first optical action is given to a light beam having two wavelengths [lambda] 2. Optical element for pickup device.   The first optical action is zero-order diffraction that does not substantially give an optical path difference between adjacent annular zones with respect to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. 88. The optical element for an optical pickup device according to claim 87, wherein the two-optical action is a first-order diffraction that diffracts the light flux having the second wavelength λ2 in the first-order direction. The aberration correction element is made of a material having a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and an Abbe number in the range of 50 to 60 at the d-line, One wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm) satisfy the following expressions (62) to (64), respectively, and are in an optical functional region including the optical axis. In the superimposed diffractive structure thus formed, combinations of the number N of the discontinuous steps formed in each annular zone and the depth D (μm) of the annular zone in the optical axis direction are as follows: The optical element for an optical pickup device according to claim 88, which is any one of formulas (65) to (68).
0.39 <λ1 <0.42 (62)
0.63 <λ2 <0.68 (63)
0.75 <λ3 <0.85 (64)
When N = 3, 4.1 ≦ D ≦ 4.8 (65)
When N = 4, 5.4 ≦ D ≦ 6.4 (66)
When N = 5, 7.0 ≦ D ≦ 7.9 (67)
When N = 6, 8.4 ≦ D ≦ 9.0 (68)   The first optical action is zero-order diffraction that does not substantially give an optical path difference between adjacent annular zones with respect to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. 88. The optical element for an optical pickup device according to claim 87, wherein the two-optical action is second-order diffraction that diffracts the light beam having the second wavelength [lambda] 2 in the second-order direction. The aberration correction element is made of a material having a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and an Abbe number in the range of 50 to 60 at the d-line, One wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm) satisfy the following expressions (69) to (71), respectively, and are in an optical functional region including the optical axis. In the superimposed diffractive structure thus formed, the number N of the discontinuous steps formed in each annular zone and the depth D (μm) in the optical axis direction of the annular zone are respectively the following (72) The optical element for an optical pickup device according to claim 90, wherein the optical element is any one of formulas (75) to (75).
0.39 <λ1 <0.42 (69)
0.63 <λ2 <0.68 (70)
0.75 <λ3 <0.85 (71)
When N = 8, 11.3 ≦ D ≦ 12.7 (72)
When N = 9, 12.8 ≦ D ≦ 14.1 (73)
When N = 10, 14.2 ≦ D ≦ 15.6 (74)
When N = 11, 15.7 ≦ D ≦ 17.2 (75)   92. The optical element for an optical pickup device according to claim 84, wherein the superposition type diffractive structure is formed in all of the plurality of optical function regions.   The optical pickup device according to any one of claims 45 to 91, wherein the superposition type diffractive structure is not formed in at least one of the plurality of optical function regions. Optical elements.   94. The optical element for an optical pickup device according to claim 45, wherein the superposition type diffractive structure is formed on a plurality of optical functional surfaces of the aberration correction element. 95. The thickness t1 of the protective layer of the first optical information recording medium and the thickness t2 of the protective layer of the second optical information recording medium satisfy the following expression (76). An optical element for an optical pickup device according to any one of the above.
0.8 ≦ t1 / t2 ≦ 1.2 (76)   The plurality of optical function areas are two optical function areas, and the light flux of the first wavelength λ1 to the third wavelength λ3 incident on the optical function area including the optical axis of the two optical function areas. Each of the light beams forms a good wavefront on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, and the optical functional area that does not include the optical axis of the two optical functional areas. The light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 incident on the light form a good wavefront on the information recording surfaces of the first optical information recording medium and the second optical information recording medium, respectively. 96. An optical element for an optical pickup device according to claim 95.   Of the two optical function regions, the superposition type diffractive structure is formed in an optical function region that does not include the optical axis, and the light beam having the third wavelength λ3 is incident on the superposition type diffractive structure. The optical element for an optical pickup device according to claim 96, wherein diffraction efficiency η3 of diffracted light having the maximum diffraction efficiency among the diffracted light generated is 40% or less.   The superposition type diffractive structure is formed in an optical function region that does not include the optical axis of the two optical function regions, and the superposition type diffractive structure includes the light flux having the first wavelength λ1 and the second wavelength. An equivalent optical action is given to the light beam of λ2, and the light beam having the third wavelength λ3 is transmitted through the superposition type diffractive structure by giving an optical action different from the optical action. 98. The optical pickup device according to claim 96 or 97, wherein the light flux having the third wavelength λ3 is a flare component that does not contribute to spot formation on the information recording surface of the third optical information recording medium. Optical element.   The plurality of optical function areas are three optical function areas, and the light flux having the first wavelength λ1 to the third wavelength λ3 incident on the optical function area including the optical axis among the three optical function areas. Each of the light beams forms a good wavefront on the information recording surface of the first optical information recording medium to the third optical information recording medium, and of the three optical functional areas, an optical functional area including the previous optical axis. The light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 incident on the optical function area adjacent to the outside of the optical information area are information recording surfaces of the first optical information recording medium and the second optical information recording medium, respectively. A light wave of the first wavelength λ1 that forms a good wavefront on the top and is incident on the outermost optical function area among the three optical function areas is excellent on the information recording surface of the first optical information recording medium. Characterized by forming a smooth wavefront 96. An optical element for an optical pickup device according to claim 95.   Of the three optical function regions, the superposition type diffractive structure is formed in an optical function region adjacent to the outside of the optical function region including the optical axis, and the superposition type diffractive structure includes the third wavelength λ3. 101. The optical element for an optical pickup device according to claim 99, wherein a diffraction efficiency η3 of a diffracted light having the maximum diffraction efficiency among diffracted lights generated when the light beam enters is 40% or less.   The superposition type diffractive structure is formed in the optical function region adjacent to the outside of the optical function region including the optical axis among the three optical function regions, and the superposition type diffractive structure has the first wavelength λ1. By giving an equivalent optical action to the light flux of the second wavelength λ2 and giving an optical action different from the optical action to the light flux of the third wavelength λ3, The light beam having the third wavelength λ3 transmitted through the superposition type diffractive structure is a flare component that does not contribute to spot formation on the information recording surface of the third optical information recording medium. An optical element for the optical pickup device described.   Of the three optical function regions, the superposition type diffractive structure is formed in the outermost optical function region, and the light beam having the second wavelength λ2 is incident on the superposition type diffractive structure. Of the diffracted light, the diffracted light having the maximum diffraction efficiency is 40% or less, and the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light flux having the third wavelength λ3 is incident. 102. The optical element for an optical pickup device according to any one of claims 99 to 101, wherein a diffraction efficiency η3 of the optical pickup device is 40% or less.   Of the three optical function regions, the superposition type diffractive structure is formed in the outermost optical function region, and the superposition type diffractive structure exerts an optical action on the light flux having the first wavelength λ1. By giving the second wavelength λ2 and the third wavelength λ3 an optical action different from that of the second wavelength λ2 and the third wavelength λ3 transmitted through the superposition type diffractive structure, The flare component which does not contribute to spot formation on the information recording surface of the second optical information recording medium and the third optical information recording medium, respectively, is described in any one of claims 99 to 102. Optical element for optical pickup apparatus. 95. The thickness t1 of the protective layer of the first optical information recording medium and the thickness t2 of the protective layer of the second optical information recording medium satisfy the following expression (77). An optical element for an optical pickup device according to any one of the above.
t1 / t2 ≦ 0.4 (77)   The plurality of optical function areas are three optical function areas, and the light flux having the first wavelength λ1 to the third wavelength λ3 incident on the optical function area including the optical axis among the three optical function areas. Each of the light beams forms a good wavefront on the information recording surface of the first optical information recording medium to the third optical information recording medium, and of the three optical functional areas, an optical functional area including the previous optical axis. The light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 incident on the optical function area adjacent to the outside of the optical information area are information recording surfaces of the first optical information recording medium and the second optical information recording medium, respectively. A light wave of the first wavelength λ1 that forms a good wavefront on the top and is incident on the outermost optical function area among the three optical function areas is excellent on the information recording surface of the first optical information recording medium. Characterized by forming a smooth wavefront 105. An optical element for an optical pickup device according to claim 104.   Of the three optical function regions, the superposition type diffractive structure is formed in an optical function region adjacent to the outside of the optical function region including the optical axis, and the superposition type diffractive structure includes the third wavelength λ3. 106. The optical element for an optical pickup device according to claim 105, wherein the diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam is incident is 40% or less.   The superposition type diffractive structure is formed in the optical function region adjacent to the outside of the optical function region including the optical axis among the three optical function regions, and the superposition type diffractive structure has the first wavelength λ1. By giving an equivalent optical action to the light flux of the second wavelength λ2 and giving an optical action different from the optical action to the light flux of the third wavelength λ3, 105. The light flux having the third wavelength λ3 that has passed through the superposition type diffractive structure is a flare component that does not contribute to spot formation on the information recording surface of the third optical information recording medium. An optical element for the optical pickup device described.   Of the three optical function regions, the superposition type diffractive structure is formed in the outermost optical function region, and the light beam having the second wavelength λ2 is incident on the superposition type diffractive structure. Of the diffracted light, the diffracted light having the maximum diffraction efficiency is 40% or less, and the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light flux having the third wavelength λ3 is incident. 108. The optical element for an optical pickup device according to any one of claims 105 to 107, wherein the diffraction efficiency η3 of the optical pickup device is 40% or less.   Of the three optical function regions, the superposition type diffractive structure is formed in the outermost optical function region, and the superposition type diffractive structure exerts an optical action on the light flux having the first wavelength λ1. By giving the second wavelength λ2 and the third wavelength λ3 an optical action different from that of the second wavelength λ2 and the third wavelength λ3 transmitted through the superposition type diffractive structure, 109. The flare component that does not contribute to spot formation on the information recording surface of the second optical information recording medium and the third optical information recording medium, respectively. Optical element for optical pickup apparatus. The paraxial power P1 (mm ⁻¹ ) of the aberration correcting element with respect to the first wavelength λ1 and the paraxial power P2 (mm ⁻¹ ) of the condensing element with respect to the first wavelength λ1 are expressed by the following (78 110. The optical element for an optical pickup device according to any one of claims 45 to 109, wherein:
| P1 / P2 | ≦ 0.2 (78)   111. The optical element for an optical pickup device according to claim 45, wherein the aberration correction element is a plastic lens.   The optical element for an optical pickup device according to any one of claims 45 to 111, wherein the condensing element is a plastic lens.   The optical element for an optical pickup device according to any one of claims 45 to 111, wherein the condensing element is a glass lens.   The optical pickup device according to any one of claims 45 to 111, wherein the condensing element is formed using a material in which particles having a diameter of 30 nm or less are dispersed in a plastic material. Optical elements.   2. The aberration correction of the light condensing element with respect to the first wavelength λ1 and a thickness t1 of a protective layer of the first optical information recording medium so as to be equal to or less than a Marshall limit. 115. An optical element for an optical pickup device according to any one of 45 to 114. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). Because
The optical pickup device has an objective for condensing the light beams of the first wavelength λ1 to the third wavelength λ3 on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, respectively. Having an optical system,
116. An optical pickup device using the optical element according to any one of claims 45 to 115 as the objective optical system.   116. The optical pickup device according to claim 116 is mounted, information recording on the first optical information recording medium to the third optical information recording medium, and the first optical information recording medium to the third optical information recording. An optical information recording / reproducing apparatus capable of executing at least one of reproducing information on a medium. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). An aberration correction element for an apparatus,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. An aberration correction element for an optical pickup device, wherein a superposition type diffractive structure is formed.   The optical function region in which the superposition type diffractive structure is formed is an optical function region including an optical axis, and the diffractive power at the paraxial axis of the superposition type diffractive structure with respect to the second wavelength λ2 is negative. The aberration correction element for an optical pickup device according to claim 118.   The optical function region in which the superposition type diffractive structure is formed is an optical function region including an optical axis, and the superposition type diffractive structure adds an undercorrected spherical aberration to the second wavelength λ2. 120. The aberration correction element for an optical pickup device according to claim 118 or 119.   The optical function region in which the superposition type diffractive structure is formed is an optical function region including an optical axis, and the diffractive power at the paraxial axis of the superposition type diffractive structure with respect to the second wavelength λ2 is positive. The aberration correction element for an optical pickup device according to claim 118.   The optical function region in which the superposition type diffractive structure is formed is an optical function region including an optical axis, and the superposition type diffractive structure adds an overcorrected spherical aberration to the second wavelength λ2. 122. The aberration correction element for an optical pickup device according to claim 118 or 121. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). An aberration correction element for an apparatus,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
The first light flux λ1 and the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps among the discontinuous steps formed in each annular zone in the superposition type diffractive structure are as follows: An aberration correction element for an optical pickup device, which satisfies the expressions (79) and (80).
0.39 μm <λ1 <0.42 μm (79)
P> 3 μm (80) In the superposition type diffractive structure, among the discontinuous steps formed in each annular zone, the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps satisfies the following expression (81). 124. An aberration correction element for an optical pickup device according to claim 123.
P> 5 μm (81) In the superposition type diffractive structure, among the discontinuous steps formed in each annular zone, the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps satisfies the following formula (82). The aberration correction element for an optical pickup device according to claim 124, wherein:
P> 10 μm (82) Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). An aberration correction element for an apparatus,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
When the optical path difference added to the transmitted wavefront by the superposition type diffractive structure is defined by the following equation,

An aberration correction element for an optical pickup device, wherein B ₂ and B ₄ have different signs.
Where λ is the wavelength of the incident light beam, λ _B is the manufacturing wavelength, h is the height (mm) in the direction perpendicular to the optical axis,
B _2j is an optical path difference function coefficient, and n is a diffraction order. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). An aberration correction element for an apparatus,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function areas, at least two optical function areas are provided with a plurality of ring zones each having a predetermined number of discontinuous steps formed continuously around the optical axis. A superposed diffractive structure is formed,
In the superposition type diffractive structure, one of the number N of the discontinuous steps formed in each annular zone and the depth Δ (μm) of the discontinuous steps in the optical axis direction is determined for each optical function region. An aberration correction element for an optical pickup device, which is different. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). An aberration correction element for an apparatus,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is formed with a diffractive structure composed of a plurality of annular zones divided by a step around the optical axis. An aberration correction element for a pickup device.   The depth of the step of the diffractive structure is such that the second wavelength λ2 is greater than the diffraction order n1 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the first wavelength λ1 is incident. Of the diffracted light generated when the light beam is incident, the diffraction order n2 of the diffracted light having the maximum diffraction efficiency and the maximum diffraction efficiency of the diffracted light generated when the light beam of the third wavelength λ3 is incident. 129. The aberration correction element for an optical pickup device according to claim 128, wherein both of the diffraction orders n3 of the diffracted light are designed to be lower. The first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm) satisfy the following equations (83) to (85), respectively, and the diffraction order n1 and the diffraction The combination of the order n2 and the diffraction order n3 is (n1, n2, n3) = (2,1,1), (4,2,2,), (6,4,3), (8,5,4). 131. The aberration correction element for an optical pickup device according to claim 129, wherein the aberration correction element is any one of (10, 6, 5).
0.39 <λ1 <0.42 (83)
0.63 <λ2 <0.68 (84)
0.75 <λ3 <0.85 (85) The aberration correction element is formed of a material having a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and an Abbe number in the range of 50 to 60 at the d-line, and 131. The light according to claim 129 or 130, wherein the depth d1 in the optical axis direction of the step closest to the optical axis among the steps of the structure satisfies any one of the following formulas (86) to (90): An aberration correction element for a pickup device.
1.2 μm <d1 <1.7 μm (86)
2.6 μm <d1 <3.0 μm (87)
4.4 μm <d1 <5.0 μm (88)
5.6 μm <d1 <6.5 μm (89)
6.9 μm <d1 <8.1 μm (90) Diffraction power PD0 (mm ⁻¹ ) on the paraxial axis of the diffractive structure with respect to the first wavelength λ1, and diffractive power PD1 (mm ⁻¹ ) on the paraxial axis of the diffractive structure with respect to a wavelength 10 nm longer than the first wavelength λ1. 132. The paraxial diffraction power PD2 (mm ⁻¹ ) of the diffractive structure with respect to a wavelength shorter by 10 nm than the first wavelength λ1 satisfies the following expression (91): An aberration correction element for an optical pickup device according to one item. PD2 <PD0 <PD1 (91)   In the diffractive structure, when the first wavelength λ1 changes to the long wavelength side, the spherical aberration changes in the direction of insufficient correction, and when the first wavelength λ1 changes to the short wavelength side, the spherical aberration changes. The aberration correction element for an optical pickup device according to any one of claims 128 to 132, wherein the spherical aberration has a wavelength dependency that changes in an overcorrection direction.   Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a central optical functional region including an optical axis and a peripheral optical functional region surrounding the central optical functional region. 134. The aberration correction element for an optical pickup device according to claim 133, wherein the diffraction structure is formed only in the functional region.   135. The aberration correction element for an optical pickup device according to any one of claims 128 to 134, wherein a cross-sectional shape including the optical axis of the diffractive structure is a step shape.   135. The aberration correction element for an optical pickup device according to any one of claims 128 to 134, wherein a cross-sectional shape including the optical axis of the diffractive structure is a sawtooth shape.   128. The superposition type diffractive structure is formed on one optical functional surface of the aberration correction element, and the diffractive structure is formed on the other optical functional surface of the aberration correction element. 136. An aberration correction element for an optical pickup device according to any one of 136. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). An aberration correction element for an apparatus,
The aberration correction element includes the first light source to the third light source, and the first wavelength λ1 emitted from the first light source to the third wavelength λ3 emitted from the third light source, respectively. 1 optical information recording medium to the third optical information recording medium is disposed in the optical path between the light condensing elements for condensing on the information recording surface of the third optical information recording medium,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is divided into a plurality of annular optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
At least one of the optical functional surfaces of the aberration correction element has an optical path difference providing structure comprising a central region including the optical axis and a plurality of annular zones divided by steps on the outside of the central region. An aberration correction element for an optical pickup device, wherein:   In the optical path difference providing structure, when the environmental temperature rises, the spherical aberration added to the first wavelength λ1 changes in the direction of insufficient correction, and when the environmental temperature decreases, the first wavelength λ1. 139. The aberration correction element for an optical pickup device according to claim 138, wherein the spherical aberration to be added has a temperature dependency of the spherical aberration so that the spherical aberration to be changed changes in an overcorrection direction.   In the optical path difference providing structure, the annular zone adjacent to the outside of the central region is formed by shifting in the optical axis direction so as to shorten the optical path length with respect to the central region, and the ring at the maximum effective diameter position. The band is formed by shifting in the optical axis direction so that the optical path length is longer with respect to the ring zone adjacent to the inner side thereof, and the ring zone at a position of 75% of the maximum effective diameter is adjacent to the inner side. 140. Aberration correction for optical pickup device according to claim 139, characterized in that it is formed by shifting in the optical axis direction so that the optical path length is shorter with respect to the annular zone and the annular zone adjacent to the outer zone. element. Of the steps of the first wavelength λ1 (μm), the second wavelength λ3 (μm), the third wavelength λ3 (μm) and the optical path difference providing structure, the depth d2 in the optical axis direction of the step closest to the optical axis (μm), the refractive index Nλ _{1 of} the aberration correction element with respect to the first wavelength λ1, the refractive index Nλ _{2 of} the aberration correction element with respect to the second wavelength λ1, and the refractive index Nλ of the aberration correction element with respect to the third wavelength λ3. by _3, .phi.1 are expressed by the following (92) to (94) below, .phi.2, any Φ3 is, but of claims 138 to 140 and satisfying the following (95) to (98) below An aberration correction element for an optical pickup device according to claim 1.
Φ1 = d2 · (Nλ ₁ −1) / λ1 (92)
Φ2 = d2 · (Nλ ₂ −1) / λ2 (93)
Φ3 = d2 · (Nλ ₃ −1) / λ3 (94)
INT (Φ1) ≦ 10 (95)
0 ≦ | INT (Φ1) −Φ1 | ≦ 0.4 (96)
0 ≦ | INT (Φ2) −Φ2 | ≦ 0.4 (97)
0 ≦ | INT (Φ3) −Φ3 | ≦ 0.4 (98)
However, INT (Φi) (i = 1, 2, 3) is an integer obtained by rounding Φi.   The superposition type diffractive structure is formed on one optical functional surface of the aberration correction element, and the optical path difference providing structure is formed on the other optical functional surface of the aberration correction element. 144. An aberration correction element for an optical pickup device according to any one of 138 to 141.   143. The aberration correction element for an optical pickup device according to any one of claims 118 to 142, wherein the optical function region in which the superposition type diffractive structure is formed is an optical function region including an optical axis. In the superposition type diffractive structure formed in the optical function region including the first wavelength λ1 (μm), the second wavelength λ3 (μm), the third wavelength λ3 (μm), and the optical axis, The number N of the discontinuous steps formed in the optical axis, the depth Δ (μm) of the discontinuous steps in the optical axis direction, the refractive index Nλ _{1 of} the aberration correction element with respect to the first wavelength λ1, the aberration correction element refractive index N [lambda ₂ to the second wavelength λ1 of the refractive index N [lambda ₃ with respect to the third wavelength λ3 of the aberration correcting element, .phi.1 are expressed by the following (99) to (101) below, .phi.2, .phi.3 is 144. The aberration correction element for an optical pickup device according to claim 143, wherein: satisfies the following expressions (102) to (104):
φ1 = Δ · (Nλ ₁ −1) · (N + 1) / λ1 (99)
φ2 = Δ · (Nλ ₂ −1) · (N + 1) / λ2 (100)
φ3 = Δ · (Nλ ₃ −1) · (N + 1) / λ3 (101)
0 ≦ | INT (φ1) −φ1 | ≦ 0.4 (102)
0 ≦ | INT (φ2) −φ2 | ≦ 0.4 (103)
0 ≦ | INT (φ3) −φ3 | ≦ 0.4 (104)
However, INT (φi) (i = 1, 2, 3) is an integer obtained by rounding off φi. 145. The aberration for an optical pickup device according to claim 144, wherein the φ1 and the number N of the discontinuous steps formed in each annular zone satisfy the following expressions (105) and (106): Correction element.
φ1 ≦ 24 (105)
3 ≦ N ≦ 11 (106)   The superposition type diffractive structure formed in the optical function region including the optical axis gives an equivalent first optical action to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3, and 146. The light for an optical pickup device according to any one of claims 143 to 145, wherein a second optical action different from the first optical action is applied to a light beam having two wavelengths [lambda] 2. Aberration correction element for pickup device.   The first optical action is zero-order diffraction that does not substantially give an optical path difference between adjacent annular zones with respect to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. 147. The aberration correction element for an optical pickup device according to claim 146, wherein the two-optical action is a first-order diffraction that diffracts the light beam having the second wavelength λ2 in the first-order direction. The aberration correction element is made of a material having a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and an Abbe number in the range of 50 to 60 at the d-line, One wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm) satisfy the following expressions (107) to (109), respectively, and are in an optical functional region including the optical axis. In the superimposed diffractive structure thus formed, combinations of the number N of the discontinuous steps formed in each annular zone and the depth D (μm) of the annular zone in the optical axis direction are as follows: 149. The aberration correction element for an optical pickup device according to claim 147, which is any one of equations (110) to (113).
0.39 <λ1 <0.42 (107)
0.63 <λ2 <0.68 (108)
0.75 <λ3 <0.85 (109)
When N = 3, 4.1 ≦ D ≦ 4.8 (110)
When N = 4, 5.4 ≦ D ≦ 6.4 (111)
When N = 5, 7.0 ≦ D ≦ 7.9 (112)
When N = 6, 8.4 ≦ D ≦ 9.0 (113)   The first optical action is zero-order diffraction that does not substantially give an optical path difference between adjacent annular zones with respect to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. 147. The aberration correction element for an optical pickup device according to claim 146, wherein the two-optical action is second-order diffraction that diffracts the light beam having the second wavelength λ2 in the second-order direction. The aberration correction element is made of a material having a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and an Abbe number in the range of 50 to 60 at the d-line, One wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm) satisfy the following expressions (114) to (116), respectively, and are in an optical functional region including the optical axis. In the superimposed diffractive structure thus formed, the number N of the discontinuous steps formed in each annular zone and the depth D (μm) in the optical axis direction of the annular zone are respectively the following (117): 150. The aberration correction element for an optical pickup device according to claim 149, wherein the aberration correction element is any one of formulas (120) to (120).
0.39 <λ1 <0.42 (114)
0.63 <λ2 <0.68 (115)
0.75 <λ3 <0.85 (116)
When N = 8, 11.3 ≦ D ≦ 12.7 (117)
When N = 9, 12.8 ≦ D ≦ 14.1 (118)
When N = 10, 14.2 ≦ D ≦ 15.6 (119)
When N = 11, 15.7 ≦ D ≦ 17.2 (120)   The aberration correction element for an optical pickup device according to any one of claims 143 to 150, wherein the superposition type diffractive structure is formed in all of the plurality of optical function regions.   The optical pickup device according to any one of claims 118 to 150, wherein the superposition type diffractive structure is not formed in at least one of the plurality of optical function regions. Aberration correction element.   The aberration correction element for an optical pickup device according to any one of claims 118 to 152, wherein the superposition type diffractive structure is formed on a plurality of optical functional surfaces of the aberration correction element.   The plurality of optical function areas are two optical function areas, and the superposition type diffractive structure is formed in an optical function area that does not include the optical axis, and the superposition type diffraction structure is formed. The diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the third wavelength λ3 is incident on the diffractive structure is 40% or less. An aberration correction element for an optical pickup device according to any one of the above.   The plurality of optical function areas are two optical function areas, and the superposition type diffractive structure is formed in an optical function area that does not include the optical axis, and the superposition type diffraction structure is formed. The diffractive structure gives an equivalent optical action to the light flux of the first wavelength λ1 and the light flux of the second wavelength λ2, and is different from the optical action for the light flux of the third wavelength λ3. By providing an optical action, the light beam having the third wavelength λ3 transmitted through the superposition type diffractive structure is used as a flare component that does not contribute to spot formation on the information recording surface of the third optical information recording medium. The aberration correction element for an optical pickup device according to any one of claims 118 to 154, wherein   The plurality of optical function areas are three optical function areas, and the superposition type diffractive structure is formed in an optical function area adjacent to the outside of the optical function area including the optical axis among the three optical function areas. The diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the third wavelength λ3 is incident on the superposition type diffractive structure is 40% or less. The aberration correction element for an optical pickup device according to any one of claims 118 to 153.   The plurality of optical function areas are three optical function areas, and the superposition type diffractive structure is formed in an optical function area adjacent to the outside of the optical function area including the optical axis among the three optical function areas. The superposition type diffractive structure gives an equivalent optical action to the light flux of the first wavelength λ1 and the light flux of the second wavelength λ2, and for the light flux of the third wavelength λ3, By providing an optical action different from the optical action, the light beam having the third wavelength λ3 transmitted through the superposition type diffractive structure contributes to spot formation on the information recording surface of the third optical information recording medium. 156. The aberration correction element for an optical pickup device according to any one of claims 118 to 153, 156, wherein a flare component is not used.   The plurality of optical function areas are three optical function areas, and the superposition type diffractive structure is formed in the outermost optical function area among the three optical function areas. In addition, the diffraction efficiency η2 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the second wavelength λ2 is incident is 40% or less, and the light beam having the third wavelength λ3 is incident. The optical pickup according to any one of claims 118 to 153, 156, and 157, wherein the diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated in the case is 40% or less. Aberration correction element for equipment.   The plurality of optical function areas are three optical function areas, and the superposition type diffractive structure is formed in the outermost optical function area among the three optical function areas. Is transmitted through the superposition type diffractive structure by giving an optical action different from the optical action given to the light flux of the first wavelength λ1 to the light flux of the second wavelength λ2 and the third wavelength λ3. The light fluxes having the second wavelength λ2 and the third wavelength λ3 are flare components that do not contribute to spot formation on the information recording surfaces of the second optical information recording medium and the third optical information recording medium, respectively. 159. The aberration correcting element for an optical pickup device according to any one of claims 118 to 153, 156 to 158.   160. The aberration correction element for an optical pickup device according to any one of claims 118 to 159, wherein the aberration correction element is a plastic lens. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). Because
The optical pickup device converts the first wavelength λ1 to the third wavelength λ3 emitted from the first light source to the first optical information recording medium to the third optical information, respectively. Having a condensing element for condensing on the information recording surface of the recording medium;
161. An optical pickup device comprising the aberration correction element according to any one of claims 118 to 160 disposed in an optical path between the first light source to the third light source and the condensing element.   162. The information pickup on the first optical information recording medium to the third optical information recording medium and the first optical information recording medium to the third optical information recording mounted with the optical pickup device according to claim 161. An optical information recording / reproducing apparatus capable of executing at least one of reproducing information on a medium. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A light collecting element for the device,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A condensing element for an optical pickup device, wherein a superposition type diffractive structure is formed. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A light collecting element for the device,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
A first magnification m1 when information is reproduced and / or recorded on the first optical information recording medium, and a second magnification when information is reproduced and / or recorded on the second optical information recording medium. A condensing element for an optical pickup device, characterized in that the magnification m2 substantially coincides.   165. The condensing element for an optical pickup device according to claim 164, wherein the superposition type diffractive structure adds an uncorrected spherical aberration to the second wavelength λ2. 166. The condensing element for an optical pickup device according to claim 164 or 165, wherein the first magnification m1 and the second magnification m2 satisfy the following expression (121).
m1 = m2 = 0 (121) 170. The third magnification m3 when reproducing and / or recording information on the third optical information recording medium satisfies the following expression (122). The light condensing element for optical pickup apparatuses as described.
−0.25 <m3 <−0.10 (122)   The first light source and the second light source are packaged light source modules, and the condensing element records information on the first optical information recording medium by using the light beam having the first wavelength λ1 emitted from the light source module. 167. The light beam having the second wavelength λ2 that is condensed on the surface and emitted from the light source module is condensed on the information recording surface of the second optical information recording medium. A condensing element for an optical pickup device according to claim 1. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A light collecting element for the device,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
A second magnification m2 when information is reproduced and / or recorded on the second optical information recording medium, and a third magnification when information is reproduced and / or recorded on the third optical information recording medium. A condensing element for an optical pickup device, characterized in that the magnification m3 substantially coincides.   170. The condensing element for an optical pickup device according to claim 169, wherein the superposition type diffractive structure adds overcorrected spherical aberration to the second wavelength [lambda] 2. 171. The optical pickup device according to claim 169 or 170, wherein the first magnification m1 when reproducing and / or recording information on the first optical information recording medium satisfies the following expression (123): Concentrating element for use.
m1 = 0 (123) The condensing element for an optical pickup device according to any one of claims 169 to 171, wherein the second magnification m2 and the third magnification m3 satisfy the following expressions (124) and (125): .
m2 = m3 (124)
−0.25 <m2 <−0.10 (125)   The second light source and the third light source are packaged light source modules, and the condensing element records the light beam having the second wavelength λ2 emitted from the light source module on the second optical information recording medium. 173. The light beam having the third wavelength λ3 emitted from the light source module and condensed on the information recording surface of the second optical information recording medium. A condensing element for an optical pickup device according to claim 1. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A light collecting element for the device,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
The first light flux λ1 and the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps among the discontinuous steps formed in each annular zone in the superposition type diffractive structure are as follows: (126) and (127) are satisfied, A condensing element for an optical pickup device.
0.39 μm <λ1 <0.42 μm (126)
P> 3 μm (127) In the superposition type diffractive structure, the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps among the discontinuous steps formed in each annular zone satisfies the following expression (128). 175. A light condensing element for an optical pickup device according to claim 174.
P> 5 μm (128) In the superposition type diffractive structure, among the discontinuous steps formed in each annular zone, the minimum value P of the interval in the direction perpendicular to the optical axis between adjacent steps satisfies the following expression (129). 175. The condensing element for an optical pickup device according to claim 175.
P> 10 μm (129) Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A light collecting element for the device,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
When the optical path difference added to the transmitted wavefront by the superposition type diffractive structure is defined by the following equation,

A condensing element for an optical pickup device, wherein B ₂ and B ₄ have different signs.
Where λ is the wavelength of the incident light beam, λ _B is the manufacturing wavelength, h is the height (mm) in the direction perpendicular to the optical axis,
B _2j is an optical path difference function coefficient, and n is a diffraction order.   A first magnification m1 when information is reproduced and / or recorded on the first optical information recording medium, and a second magnification when information is reproduced and / or recorded on the second optical information recording medium. 178. The magnification m2 and the third magnification m3 when information is reproduced and / or recorded on the third optical information recording medium are different from each other. Condensing element for optical pickup device. 179. The optical pickup device assembly according to claim 178, wherein the first magnification m1, the second magnification m2, and the third magnification m3 satisfy the following expressions (130) to (132). Optical element.
m1 = 0 (130)
−0.08 <m2 <−0.01 (131)
−0.25 <m3 <−0.10 (132) Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A light collecting element for the device,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function areas, at least two optical function areas are provided with a plurality of ring zones each having a predetermined number of discontinuous steps formed continuously around the optical axis. A superposed diffractive structure is formed,
In the superposition type diffractive structure, one of the number N of the discontinuous steps formed in each annular zone and the depth Δ (μm) of the discontinuous steps in the optical axis direction is determined for each optical function region. A condensing element for an optical pickup device characterized by being different. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A light collecting element for the device,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
Of the optical functional surfaces of the aberration correction element, at least one optical functional surface is formed with a diffractive structure composed of a plurality of annular zones divided by a step around the optical axis. Condensing element for pickup device.   The depth of the step of the diffractive structure is such that the second wavelength λ2 is greater than the diffraction order n1 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam having the first wavelength λ1 is incident. Of the diffracted light generated when the light beam is incident, the diffraction order n2 of the diffracted light having the maximum diffraction efficiency and the maximum diffraction efficiency of the diffracted light generated when the light beam of the third wavelength λ3 is incident. The condensing element for an optical pickup device according to claim 181, wherein both of the diffraction orders n3 of the diffracted light are designed to be lower. The first wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm) satisfy the following equations (133) to (135), respectively, and the diffraction order n1 and the diffraction The combination of the order n2 and the diffraction order n3 is (n1, n2, n3) = (2,1,1), (4,2,2,), (6,4,3), (8,5,4). 185, (10, 6, 5), The condensing element for an optical pickup device according to claim 182.
0.39 <λ1 <0.42 (133)
0.63 <λ2 <0.68 (134)
0.75 <λ3 <0.85 (135) The condensing element is formed of a material having a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and an Abbe number in the range of 50 to 60 in the d-line. 184. The light according to claim 182 or 183, wherein the depth d1 of the step closest to the optical axis among the steps of the structure satisfies any one of the following formulas (136) to (140): Condensing element for pickup device.
1.2 μm <d1 <1.7 μm (136)
2.6 μm <d1 <3.0 μm (137)
4.4 μm <d1 <5.0 μm (138)
5.6 μm <d1 <6.5 μm (139)
6.9 μm <d1 <8.1 μm (140)   The diffractive structure has a function of suppressing a focus position shift that occurs due to chromatic aberration of the light collecting element when the first wavelength λ1 changes within a range of ± 10 nm. The condensing element for optical pick-up apparatuses as described in any one of 181 thru | or 184. Diffraction power PD0 (mm ⁻¹ ) in the paraxial direction with respect to the first first wavelength λ1 of the diffractive structure, and diffractive power PD1 (mm ⁻¹ ) in the paraxial direction with respect to a wavelength 10 nm longer than the first first wavelength λ1 of the diffractive structure. 187. The optical pickup according to claim 185, wherein a diffractive power PD2 (mm ⁻¹ ) in the paraxial axis with respect to a wavelength shorter by 10 nm than the first first wavelength λ1 of the diffractive structure satisfies the following expression (141): Condensing element for equipment.
PD2 <PD0 <PD1 (141)   In the diffractive structure, when the first wavelength λ1 changes to the long wavelength side, the spherical aberration changes in the direction of insufficient correction, and when the first wavelength λ1 changes to the short wavelength side, the spherical aberration changes. 187. The condensing element for an optical pickup device according to claim 185 or 186, wherein the concentrating element has a wavelength dependency of spherical aberration that changes in an overcorrected direction.   The condensing element is a plastic lens, and in the diffractive structure, when the first wavelength λ1 changes to the long wavelength side, the spherical aberration changes in the direction of insufficient correction, and the first wavelength λ1 is short. Spherical aberration change caused by change in refractive index of condensing element due to environmental temperature change by having wavelength dependency of spherical aberration that changes spherical aberration in the overcorrection direction when it changes to the wavelength side 188. The light condensing element for an optical pickup device according to any one of claims 181 to 187, wherein the light condensing element has a function of suppressing light.   At least one of the optical functional surfaces of the condensing element is divided into a central optical functional region including an optical axis and a peripheral optical functional region surrounding the central optical functional region, and the peripheral optical 189. The light condensing element for an optical pickup device according to claim 188, wherein the diffractive structure is formed only in a functional region.   190. The condensing element for an optical pickup device according to any one of claims 181 to 189, wherein a cross-sectional shape including an optical axis of the diffractive structure is a sawtooth shape.   181 to 181, wherein the superposition type diffractive structure is formed on one optical functional surface of the light collecting element, and the diffractive structure is formed on the other optical functional surface of the light collecting element. 190. A condensing element for an optical pickup device according to any one of 190. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A light collecting element for the device,
The condensing element is disposed at a position facing the first optical information recording medium to the third optical information recording medium,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface is divided into a plurality of annular optical functional regions centered on the optical axis,
Among the plurality of ring-shaped optical function regions, at least one optical function region has a plurality of ring zones in which a predetermined number of discontinuous steps are formed continuously arranged around the optical axis. A superposed diffractive structure is formed,
Of the optical functional surfaces of the light collecting element, at least one optical functional surface includes an optical path difference providing structure including a central region including an optical axis and a plurality of annular zones divided by steps on the outer side of the central region. A condensing element for an optical pickup device, wherein:   The condensing element is a plastic lens, and the optical path difference providing structure is such that when the environmental temperature rises, the spherical aberration added to the first wavelength λ1 changes in the direction of insufficient correction, and the environmental temperature is When it decreases, the spherical aberration added to the first wavelength λ1 has the temperature dependency of the spherical aberration so that the spherical aberration changes in the overcorrection direction, so that the refractive index of the condensing element with the environmental temperature change 193. The condensing element for an optical pickup device according to claim 192, which has a function of suppressing a change in spherical aberration caused by the change.   In the optical path difference providing structure, the annular zone adjacent to the outside of the central region is formed by shifting in the optical axis direction so as to shorten the optical path length with respect to the central region, and the ring at the maximum effective diameter position. The band is formed by shifting in the optical axis direction so that the optical path length is longer with respect to the ring zone adjacent to the inner side thereof, and the ring zone at a position of 75% of the maximum effective diameter is adjacent to the inner side. 194. The light collecting device for an optical pickup device according to claim 193, wherein the light collecting device is formed by shifting in the optical axis direction so that the optical path length is shorter with respect to the annular zone and the annular zone adjacent to the outer zone. element. Of the steps of the first wavelength λ1 (μm), the second wavelength λ3 (μm), the third wavelength λ3 (μm) and the optical path difference providing structure, the depth d2 in the optical axis direction of the step closest to the optical axis (μm), the refractive index Nλ _{1 of} the light collecting element with respect to the first wavelength λ1, the refractive index Nλ _{2 of} the light collecting element with respect to the second wavelength λ1, and the refractive index Nλ of the light collecting element with respect to the third wavelength λ3. by _3, .phi.1 are expressed by the following (142) to (144) below, .phi.2, any Φ3 is, but of claims 192 to 194 and satisfying the following (145) to (148) below A condensing element for an optical pickup device according to claim 1.
Φ1 = d2 · (Nλ ₁ −1) / λ1 (142)
Φ2 = d2 · (Nλ ₂ −1) / λ2 (143)
Φ3 = d2 · (Nλ ₃ −1) / λ3 (144)
INT (Φ1) ≦ 10 (145)
0 ≦ | INT (Φ1) −Φ1 | ≦ 0.4 (146)
0 ≦ | INT (Φ2) −Φ2 | ≦ 0.4 (147)
0 ≦ | INT (Φ3) −Φ3 | ≦ 0.4 (148)
However, INT (Φi) (i = 1, 2, 3) is an integer obtained by rounding Φi.   The superposition type diffractive structure is formed on one optical functional surface of the light collecting element, and the optical path difference providing structure is formed on the other optical functional surface of the light collecting element. 192. A condensing element for an optical pickup device according to any one of 192 to 195.   197. The condensing element for an optical pickup device according to any one of claims 163 to 196, wherein the optical functional region in which the superposition type diffractive structure is formed is an optical functional region including an optical axis. In the superposition type diffractive structure formed in the optical function region including the first wavelength λ1 (μm), the second wavelength λ3 (μm), the third wavelength λ3 (μm), and the optical axis, The number N of the discontinuous steps formed on the optical axis, the depth Δ (μm) of the discontinuous steps in the optical axis direction, the refractive index Nλ _{1 of} the light collecting element with respect to the first wavelength λ1, the light collecting element refractive index N [lambda ₂ to the second wavelength λ2 of the refractive index N [lambda ₃ with respect to the third wavelength λ3 of the light converging element, .phi.1 are expressed by the following (149) to (151) below, .phi.2, .phi.3 is 199. The condensing element for an optical pickup device according to claim 197, wherein the following expressions (152) to (154) are satisfied.
φ1 = Δ · (Nλ ₁ −1) · (N−1) / λ1 (149)
φ2 = Δ · (Nλ ₂ −1) · (N−1) / λ2 (150)
φ3 = Δ · (Nλ ₃ −1) · (N−1) / λ3 (151)
0 ≦ | INT (φ1) −φ1 | ≦ 0.4 (152)
0 ≦ | INT (φ2) −φ2 | ≦ 0.4 (153)
0 ≦ | INT (φ3) −φ3 | ≦ 0.4 (154)
However, INT (φi) (i = 1, 2, 3) is an integer obtained by rounding off φi. 199. The optical pickup device assembly according to claim 198, wherein the φ1 and the number N of the discontinuous steps formed in each annular zone satisfy the following expressions (155) and (156). Optical element.
φ1 ≦ 24 (155)
3 ≦ N ≦ 11 (156)   The superposition type diffractive structure formed in the optical function region including the optical axis gives an equivalent first optical action to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3, and 200. The light for an optical pickup device according to claim 197, wherein a second optical action different from the first optical action is applied to a light beam having two wavelengths [lambda] 2. Condensing element for pickup device.   The first optical action is zero-order diffraction that does not substantially give an optical path difference between adjacent annular zones with respect to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. The condensing element for an optical pickup device according to claim 200, wherein the two-optical action is a first-order diffraction that diffracts the light beam having the second wavelength λ2 in a first-order direction. The condensing element is formed of a material having a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and an Abbe number in the range of 50 to 60 in the d-line, The one wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm) satisfy the following expressions (157) to (159), respectively, and in the optical function region including the optical axis: In the superimposed diffractive structure thus formed, combinations of the number N of the discontinuous steps formed in each annular zone and the depth D (μm) of the annular zone in the optical axis direction are as follows: The condensing element for an optical pickup device according to claim 201, which is any one of formulas (160) to (163).
0.39 <λ1 <0.42 (157)
0.63 <λ2 <0.68 (158)
0.75 <λ3 <0.85 (159)
When N = 3, 4.1 ≦ D ≦ 4.8 (160)
When N = 4, 5.4 ≦ D ≦ 6.4 (161)
When N = 5, 7.0 ≦ D ≦ 7.9 (162)
When N = 6, 8.4 ≦ D ≦ 9.0 (163)   The first optical action is zero-order diffraction that does not substantially give an optical path difference between adjacent annular zones with respect to the light flux having the first wavelength λ1 and the light flux having the third wavelength λ3. The condensing element for an optical pickup device according to claim 200, wherein the two-optical action is second-order diffraction that diffracts the light beam having the second wavelength λ2 in the second-order direction. The condensing element is formed of a material having a refractive index in the range of 1.5 to 1.6 at the first wavelength λ1 and an Abbe number in the range of 50 to 60 in the d-line, One wavelength λ1 (μm), the second wavelength λ3 (μm), and the third wavelength λ3 (μm) satisfy the following expressions (164) to (166), respectively, and are in an optical function region including the optical axis. In the superimposed diffractive structure thus formed, the number N of the discontinuous steps formed in each annular zone and the depth D (μm) in the optical axis direction of the annular zone are as follows (167): 204. The condensing element for an optical pickup device according to claim 203, wherein the condensing element is any one of formulas (170) to (170).
0.39 <λ1 <0.42 (164)
0.63 <λ2 <0.68 (165)
0.75 <λ3 <0.85 (166)
When N = 8, 11.3 ≦ D ≦ 12.7 (167)
When N = 9, 12.8 ≦ D ≦ 14.1 (168)
When N = 10, 14.2 ≦ D ≦ 15.6 (169)
When N = 11, 15.7 ≦ D ≦ 17.2 (170)   The condensing element for an optical pickup device according to any one of claims 197 to 204, wherein the superposition type diffractive structure is formed in all of the plurality of optical function regions.   The optical pickup device according to any one of claims 163 to 204, wherein the superposition type diffractive structure is not formed in at least one of the plurality of optical function regions. Condensing element.   The condensing element for an optical pickup device according to any one of claims 163 to 206, wherein the superposition type diffractive structure is formed on a plurality of optical functional surfaces of the aberration correction element. 163 to 207, wherein the thickness t1 of the protective layer of the first optical information recording medium and the thickness t2 of the protective layer of the second optical information recording medium satisfy the following expression (171). The condensing element for optical pick-up apparatuses as described in any one of these.
0.8 ≦ t1 / t2 ≦ 1.2 (171)   The plurality of optical function areas are two optical function areas, and the light flux of the first wavelength λ1 to the third wavelength λ3 incident on the optical function area including the optical axis of the two optical function areas. Each of the light beams forms a good wavefront on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, and the optical functional area that does not include the optical axis of the two optical functional areas. The light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 incident on the light form a good wavefront on the information recording surfaces of the first optical information recording medium and the second optical information recording medium, respectively. 211. A light condensing element for an optical pickup device according to claim 208.   Of the two optical function regions, the superposition type diffractive structure is formed in an optical function region that does not include the optical axis, and the light beam having the third wavelength λ3 is incident on the superposition type diffractive structure. 209. The condensing element for an optical pickup device according to claim 209, wherein the diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the generated diffracted light is 40% or less.   The superposition type diffractive structure is formed in an optical function region that does not include the optical axis of the two optical function regions, and the superposition type diffractive structure includes the light flux having the first wavelength λ1 and the second wavelength. An equivalent optical action is given to the light beam of λ2, and the light beam having the third wavelength λ3 is transmitted through the superposition type diffractive structure by giving an optical action different from the optical action. The optical pickup device for an optical pickup device according to claim 209 or 210, wherein the light flux having the third wavelength λ3 is a flare component that does not contribute to spot formation on the information recording surface of the third optical information recording medium. Condensing element.   The plurality of optical function areas are three optical function areas, and the light flux having the first wavelength λ1 to the third wavelength λ3 incident on the optical function area including the optical axis among the three optical function areas. Each of the light beams forms a good wavefront on the information recording surface of the first optical information recording medium to the third optical information recording medium, and of the three optical functional areas, an optical functional area including the previous optical axis. The light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 incident on the optical function area adjacent to the outside of the optical information area are information recording surfaces of the first optical information recording medium and the second optical information recording medium, respectively. A light wave of the first wavelength λ1 that forms a good wavefront on the top and is incident on the outermost optical function area among the three optical function areas is excellent on the information recording surface of the first optical information recording medium. Characterized by forming a smooth wavefront The condensing element for optical pick-up apparatuses of Claim 208.   Of the three optical function regions, the superposition type diffractive structure is formed in an optical function region adjacent to the outside of the optical function region including the optical axis, and the superposition type diffractive structure includes the third wavelength λ3. 213. The condensing element for an optical pickup device according to claim 212, wherein the diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency among the diffracted light generated when the light beam enters is 40% or less .   The superposition type diffractive structure is formed in the optical function region adjacent to the outside of the optical function region including the optical axis among the three optical function regions, and the superposition type diffractive structure has the first wavelength λ1. By giving an equivalent optical action to the light flux of the second wavelength λ2 and giving an optical action different from the optical action to the light flux of the third wavelength λ3, 213. The flare component that does not contribute to spot formation on the information recording surface of the third optical information recording medium is the light beam having the third wavelength λ3 that has passed through the superposition type diffractive structure. The light condensing element for optical pickup apparatuses as described.   Of the three optical function regions, the superposition type diffractive structure is formed in the outermost optical function region, and the light beam having the second wavelength λ2 is incident on the superposition type diffractive structure. Of the diffracted light, the diffracted light having the maximum diffraction efficiency is 40% or less, and the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light flux having the third wavelength λ3 is incident. The light condensing element for an optical pickup device according to any one of claims 212 to 214, wherein the diffraction efficiency η3 of the optical pickup device is 40% or less.   Of the three optical function regions, the superposition type diffractive structure is formed in the outermost optical function region, and the superposition type diffractive structure exerts an optical action on the light flux having the first wavelength λ1. By giving the second wavelength λ2 and the third wavelength λ3 an optical action different from that of the second wavelength λ2 and the third wavelength λ3 transmitted through the superposition type diffractive structure, The flare components that do not contribute to spot formation on the information recording surface of the second optical information recording medium and the third optical information recording medium, respectively, are described in any one of claims 212 to 215. Condensing element for optical pickup device. 163 to 207, wherein the thickness t1 of the protective layer of the first optical information recording medium and the thickness t2 of the protective layer of the second optical information recording medium satisfy the following expression (172). The condensing element for optical pick-up apparatuses as described in any one of these.
t1 / t2 ≦ 0.4 (172)   The plurality of optical function areas are three optical function areas, and the light flux having the first wavelength λ1 to the third wavelength λ3 incident on the optical function area including the optical axis among the three optical function areas. Each of the light beams forms a good wavefront on the information recording surface of the first optical information recording medium to the third optical information recording medium, and of the three optical functional areas, an optical functional area including the previous optical axis. The light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 incident on the optical function area adjacent to the outside of the optical information area are information recording surfaces of the first optical information recording medium and the second optical information recording medium, respectively. A light wave of the first wavelength λ1 that forms a good wavefront on the top and is incident on the outermost optical function area among the three optical function areas is excellent on the information recording surface of the first optical information recording medium. Characterized by forming a smooth wavefront 217. A light condensing element for an optical pickup device according to claim 217.   Of the three optical function regions, the superposition type diffractive structure is formed in an optical function region adjacent to the outside of the optical function region including the optical axis, and the superposition type diffractive structure includes the third wavelength λ3. 219. The condensing element for an optical pickup device according to claim 218, wherein the diffraction efficiency η3 of the diffracted light having the maximum diffraction efficiency out of the diffracted light generated when the light beam is incident is 40% or less .   The superposition type diffractive structure is formed in the optical function region adjacent to the outside of the optical function region including the optical axis among the three optical function regions, and the superposition type diffractive structure has the first wavelength λ1. By giving an equivalent optical action to the light flux of the second wavelength λ2 and giving an optical action different from the optical action to the light flux of the third wavelength λ3, 218 or 219, wherein the light beam having the third wavelength λ3 transmitted through the superposition type diffractive structure is used as a flare component that does not contribute to spot formation on the information recording surface of the third optical information recording medium. The light condensing element for optical pickup apparatuses as described.   Of the three optical function regions, the superposition type diffractive structure is formed in the outermost optical function region, and the light beam having the second wavelength λ2 is incident on the superposition type diffractive structure. Of the diffracted light, the diffracted light having the maximum diffraction efficiency is 40% or less, and the diffracted light having the maximum diffraction efficiency among the diffracted lights generated when the light flux having the third wavelength λ3 is incident. The light condensing element for an optical pickup device according to any one of claims 218 to 220, wherein the diffraction efficiency η3 of the optical pickup device is 40% or less.   Of the three optical function regions, the superposition type diffractive structure is formed in the outermost optical function region, and the superposition type diffractive structure exerts an optical action on the light flux having the first wavelength λ1. By giving the second wavelength λ2 and the third wavelength λ3 an optical action different from that of the second wavelength λ2 and the third wavelength λ3 transmitted through the superposition type diffractive structure, The flare components that do not contribute to spot formation on the information recording surfaces of the second optical information recording medium and the third optical information recording medium, respectively, are described in any one of claims 218 to 221. Condensing element for optical pickup device.   The said condensing element is a plastic lens, The condensing element for optical pick-up apparatuses as described in any one of Claims 163 thru | or 222 characterized by the above-mentioned.   The said condensing element is a glass lens whose glass transition point Tg is 400 degrees C or less, The condensing element for optical pick-up apparatuses as described in any one of Claims 163 thru | or 222 characterized by the above-mentioned.   The optical pickup device according to any one of claims 163 to 223, wherein the condensing element is formed using a material in which particles having a diameter of 30 nm or less are dispersed in a plastic material. Condensing element. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). Because
The optical pickup device has an objective for condensing the light beams of the first wavelength λ1 to the third wavelength λ3 on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, respectively. Having an optical system,
262. An optical pickup device using the condensing element according to any one of claims 163 to 225 as the objective optical system.   273. The optical pickup device according to claim 226 is mounted, information recording on the first optical information recording medium to the third optical information recording medium, and the first optical information recording medium to the third optical information recording An optical information recording / reproducing apparatus capable of executing at least one of reproducing information on a medium. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A device,
The optical pickup device includes an objective for condensing the light beams having the first wavelength λ1 to the third wavelength λ3 on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, respectively. An optical system, a diaphragm, and a driving device that integrally drives the objective optical system and the diaphragm in a direction perpendicular to the optical axis;
In the objective optical system, at least one of the optical functional surfaces is divided into a plurality of ring-shaped optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
Furthermore, it has a configuration in which at least one light beam among the light beam having the first wavelength λ1 to the light beam having the third wavelength λ3 is incident on the objective optical system in a non-parallel state,
Among the first light source to the third light source, in the optical path between the objective optical system and at least one light source that emits the light beam incident in a non-parallel state to the objective optical system In addition, a coma aberration correcting element having a function of reducing coma generated when the objective optical system is driven in a direction perpendicular to the optical axis by the driving device is disposed.   The coma aberration correcting element has an effective diameter within which the light beam incident in a non-parallel state passes through the objective optical system when the objective optical system is not driven in a direction perpendicular to the optical axis by the driving device. The optical pickup device according to claim 228, wherein the spherical aberration is corrected to be equal to or less than a diffraction limit, and has a spherical aberration in an overcorrected direction outside the effective diameter.   229. The optical pickup device according to claim 229, wherein the light beam incident in a non-parallel state with respect to the objective optical system is a divergent light beam.   230. The optical pickup device according to claim 229 or 230, wherein the light beam incident in a non-parallel state on the objective optical system is a light beam having the third wavelength [lambda] 3.   230. The optical pickup device according to claim 229, wherein the light beam incident in a non-parallel state with respect to the objective optical system is a light beam having the second wavelength λ2.   231. The light beam incident on the objective optical system in a non-parallel state is a light beam having the second wavelength λ2 and a light beam having the third wavelength λ3. The optical pickup device according to Item. The coma aberration correcting element is disposed in a common optical path of the light beam having the second wavelength λ2 and the light beam having the third wavelength λ3,
When the objective optical system is not driven in the direction perpendicular to the optical axis by the driving device, the wavelength is within an effective diameter through which the second wavelength λ2 incident in a non-parallel state to the objective optical system passes. The spherical aberration of λ2 is corrected so as to be equal to or less than the diffraction limit, the spherical aberration of the wavelength λ2 is set in an overcorrected direction outside the effective diameter, and the objective optical system is perpendicular to the optical axis by the driving device. When the lens is not driven in any direction, the spherical aberration of the wavelength λ3 is corrected to be equal to or less than the diffraction limit within the effective diameter through which the third wavelength λ3 incident in a non-parallel state with respect to the objective optical system passes. 234. The optical pickup device of claim 233, wherein the spherical aberration of the wavelength [lambda] 3 is in an overcorrected direction outside the effective diameter.   233 or 234, wherein at least one optical functional surface of the coma aberration correcting element is formed with a diffractive structure composed of a plurality of annular zones divided by a step around the optical axis. The optical pickup device described.   236. The optical pickup device according to any one of claims 233 to 235, wherein the second light source and the third light source are packaged light source modules. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A device,
The optical pickup device has an objective for condensing the light beams of the first wavelength λ1 to the third wavelength λ3 on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, respectively. Having an optical system,
In the objective optical system, at least one of the optical functional surfaces is divided into a plurality of ring-shaped optical functional regions around the optical axis,
Among the plurality of ring-shaped optical function regions, in the optical function region including the optical axis, a plurality of ring zones in which a predetermined number of discontinuous steps are formed are continuously arranged around the optical axis. A superposed diffractive structure is formed,
Further, among the light beams having the first wavelength λ1 to the light beams having the third wavelength λ3, at least two light beams are incident on the objective optical system at different magnifications.
Among the first light source to the third light source, the light source that emits the at least two light beams that are incident on the objective optical system at different magnifications is a packaged light source module,
A superposition type diffractive structure, which is a structure in which a plurality of annular zones having a predetermined number of discontinuous steps formed therein is continuously arranged around the optical axis, is formed on at least one optical functional surface. A divergence angle conversion element for converting a divergence angle of at least one light beam out of the light beams emitted from the light source module and guiding it to the objective optical system, an optical path between the light source module and the objective optical system An optical pickup device characterized by being disposed inside.   The superposition type diffractive structure formed in the divergence angle conversion element gives a first optical action to a certain light beam out of the light beams emitted from the light source module, and to light beams of other wavelengths. 237. The optical pickup device according to claim 237, wherein a second optical action different from the first optical action is applied.   238. The light beam emitted from the light source module is two light beams, and the two light beams are a light beam having the first wavelength λ1 and a light beam having the second wavelength λ2. Optical pickup device.   238. The light beam emitted from the light source module is two light beams, and the two light beams are a light beam having the second wavelength λ2 and a light beam having the second wavelength λ3. Optical pickup device.   A wavelength selective filter is formed on at least one of the optical functional surfaces of the optical element, and the optical functional surface on which the wavelength selective filter is formed includes an optical functional region including an optical axis and a periphery thereof. The wavelength selection filter transmits the light flux of the first wavelength λ1 to the light flux of the third wavelength λ3 in the optical function region including the optical axis, and In the optical function region, the light beam has a wavelength selectivity such that the light beam having the third wavelength λ3 is blocked or reflected, and the light beam having the first wavelength λ1 and the light beam having the second wavelength λ2 are transmitted. The optical element for an optical pickup device according to any one of claims 45 to 115.   A wavelength selective filter is formed on at least one of the optical functional surfaces of the optical element, and the optical functional surface on which the wavelength selective filter is formed includes an optical functional region including an optical axis and a periphery thereof. Is divided into a first peripheral optical functional region surrounding the periphery and a second peripheral optical functional region surrounding the periphery, and the wavelength selective filter includes the first wavelength in the optical functional region including the optical axis. The light beam having the wavelength λ1 to the light beam having the third wavelength λ3 is transmitted, and the light beam having the third wavelength λ3 is blocked or reflected in the first peripheral optical function region. Transmits the light beam having the two wavelengths λ2, blocks or reflects the light beam having the second wavelength λ2 and the light beam having the third wavelength λ3, and transmits the light beam having the first wavelength λ1 in the second peripheral optical function region. Transmittance 116. The optical element for an optical pickup device according to any one of claims 45 to 115, which has a wavelength selectivity of:   243. The optical element for an optical pickup device according to claim 241, wherein the wavelength selection filter is formed on at least one optical function surface of the aberration correction element.   The optical element for an optical pickup device according to claim 241, wherein the wavelength selection filter is formed on at least one optical function surface of the light condensing element.   The optical pickup device includes an aperture limiting element disposed on a light incident surface side of the objective optical system, and a wavelength selection filter is formed on at least one optical function surface of the aperture limiting element, and the wavelength selection The optical functional surface on which the filter is formed is divided into an optical functional area including an optical axis and a peripheral optical functional area surrounding the optical axis, and the wavelength selection filter includes the optical functional area including the optical axis in the optical functional area including the optical axis. The light beam having the first wavelength λ1 to the light beam having the third wavelength λ3 is transmitted, and the light beam having the third wavelength λ3 is blocked or reflected in the peripheral optical function region, and the light beam having the first wavelength λ1 and the second light beam are transmitted. 117. The optical pickup device according to claim 116, wherein the optical pickup device has a wavelength selectivity of a transmittance that transmits a light beam having a wavelength [lambda] 2.   The optical pickup device includes an aperture limiting element disposed on a light incident surface side of the objective optical system, and a wavelength selection filter is formed on at least one optical function surface of the aperture limiting element, and the wavelength selection The optical functional surface on which the filter is formed is divided into an optical functional region including the optical axis, a first peripheral optical functional region surrounding the periphery, and a second peripheral optical functional region surrounding the periphery. The wavelength selection filter transmits the light flux having the first wavelength λ1 to the light flux having the third wavelength λ3 in the optical function area including the optical axis, and the first wavelength optical filter in the first peripheral optical function area. Blocks or reflects the light beam having the third wavelength λ3, transmits the light beam having the first wavelength λ1 and the light beam having the second wavelength λ2, and transmits the light beam having the second wavelength λ2 and the light beam in the second peripheral optical function region. Third wavelength λ Of a light beam blocking or reflecting optical pickup apparatus of claim 116, characterized in that it comprises a wavelength selectivity of the transmittance, such as to transmit light beams of said first wavelength .lambda.1.   The optical pickup device includes a drive device for driving the objective optical system in a direction at least perpendicular to the optical axis, and the aperture limiting element is integrated with the objective optical system by the drive device. 247. The optical pickup device according to claim 245 or 246, which is driven in a direction perpendicular to the axis. Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). Because
The optical pickup device has a structure in which a plurality of annular zones having a predetermined number of discontinuous steps formed therein are continuously arranged around the optical axis, and the first light flux and the third light flux Includes a diffractive lens having at least one optical surface on which a superposition type diffractive structure that gives a phase difference only to the second light flux is provided, and the first wavelength that has passed through the diffractive lens. a condensing element for condensing the light beams of λ1 to the third wavelength λ3 on the information recording surfaces of the first optical information recording medium to the third optical information recording medium, respectively.
The magnification of the optical system composed of the diffractive lens and the condensing element with respect to the light beam having the first wavelength λ1 is m1, and the second wavelength λ2 of the optical system composed of the diffractive lens and the condensing element. The following equation (173) is satisfied, where m2 is the magnification with respect to the luminous flux of m, and m3 is the magnification with respect to the luminous flux of the third wavelength λ3 of the optical system constituted by the diffractive lens and the condenser element. Optical pickup device.
m1 ≧ m2> m3 (173) 249. The optical pickup device according to claim 248, wherein the following equation (174) is satisfied.
m1 = m2 (174) 249. The optical pickup device according to claim 248, wherein the following expressions (175) and (176) are satisfied.
m1 = m2 = 0 (175)
−0.25 <m3 <−0.10 (176) Information is reproduced and / or recorded on a first optical information recording medium having a protective layer having a thickness t1 using a light beam having a first wavelength λ1 emitted from the first light source, and emitted from the second light source. Information is reproduced and / or recorded on a second optical information recording medium having a protective layer having a thickness of t2 (t2 ≧ t1) using a light beam having a second wavelength λ2 (λ2> λ1), and then from a third light source. An optical pickup that reproduces and / or records information on a third optical information recording medium having a protective layer having a thickness of t3 (t3> t2) using an emitted light beam having a third wavelength λ3 (λ3> λ2). A device,
The optical pickup device collects the light beams of the first wavelength λ1 to the third wavelength λ3 on the information recording surfaces of the first information recording medium to the third information recording medium, respectively. And an aberration correction element having a phase structure, and spherical aberration correction means,
The aberration correction element corrects spherical aberration caused by the condensing element and / or spherical aberration caused by the difference between t1 and t2 due to the difference between the first wavelength λ1 and the second wavelength λ2. Has function,
2. The optical pickup device according to claim 1, wherein the spherical aberration correcting unit has a function of correcting spherical aberration caused by the difference between the thickness t1 and the thickness t3.   The optical pickup device according to claim 251, wherein the phase structure is any one of a superposition type diffractive structure, a diffractive structure, and an optical path difference providing structure.   253. The optical pickup device of claim 252, wherein the optical path difference added to the first light flux by the phase structure is an integral multiple of the first wavelength λ1.   254. The optical pickup device of claim 253, wherein the optical path difference added to the first light flux by the phase structure is an even multiple of the first wavelength [lambda] 1.   The optical pickup device further includes a second aberration correction element having a second phase structure that is either a diffractive structure or an optical path difference providing structure, and is added to the first light flux by the second phase structure. 254. The optical pickup device of claim 254, wherein the optical path difference is an odd multiple of the first wavelength λ1.   256. The magnification m1 with respect to the first wavelength λ1 and the magnification m2 with respect to the second wavelength λ2 of the optical system including the condensing element and the aberration correction element substantially coincide with each other. The optical pick-up apparatus as described in any one.   256. The spherical light aberration correction of the condensing element is optimized for the first wavelength λ1 and the protective layer having the thickness t1. Optical pickup device.   257. The optical pickup device according to any one of claims 251 to 257, wherein the condensing element and the aberration correcting element are held so that their relative positional relationship does not change.   The spherical aberration correction means includes a liquid crystal phase control element including a liquid crystal layer that causes a phase change with respect to a light beam transmitted through application of a voltage, and electrode layers facing each other for applying a voltage to the liquid crystal element. The liquid crystal phase control element corrects the spherical aberration caused by the difference between the thickness t1 and the thickness t3 by performing phase control of the third light flux. 252. The optical pickup device according to any one of items 251 to 258.   260. The optical pickup apparatus according to claim 259, wherein the liquid crystal phase control element selectively performs only phase control of the third light flux.   The spherical aberration correcting means is a movable lens unit including an actuator and a movable lens group that can be moved at least in the optical axis direction by the actuator, and the movable lens unit changes a magnification of the light collecting element. 260. The optical pickup device according to claim 25, wherein spherical aberration caused by the difference between the thickness t1 and the thickness t3 is corrected. The optical pickup device according to claim 261, wherein a magnification m3 of the condensing element with respect to the third wavelength λ3 satisfies the following expression (177).
−0.15 <m3 <−0.02 (177)   263. The optical pickup device according to any one of claims 251 to 262, wherein at least two of the first light source to the third light source are integrated.   263. The optical pickup device of claim 263, wherein all of the first light source to the third light source are integrated.

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