JP2008171538A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device which has simple constitution and can use different kinds of optical disks. <P>SOLUTION: Since each of optical planes of a first objective lens part OL1 and a second objective lens part OL2 consists of only refraction planes, formation can be comparatively easily performed and cost can be reduced. Also, since a movable collimator COL is arranged between a laser module LM and an optical element OE, appropriate convergence spot can be formed for a CD and a DVD having different protection substrate thickness even when the same second objective lenses OL2 is used. by driving the collimator COL in the optical axis direction and by changing magnification in accordance with an optical disk. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical pickup apparatus capable of recording and / or reproducing information with respect to different types of optical information recording media (also referred to as optical disks).

  Research and development of high-density optical disc systems that can record and / or reproduce information (hereinafter, “recording and / or reproduction” is referred to as “recording / reproduction”) using a blue-violet semiconductor laser having a wavelength of about 400 nm in recent years. Development is progressing rapidly. As an example, in an optical disc for recording / reproducing information with specifications of NA 0.85 and light source wavelength 405 nm, so-called Blu-ray Disc (hereinafter referred to as BD), DVD (NA 0.6, light source wavelength 650 nm, storage capacity 4, 7 GB) Can record information of 23 to 27 GB per layer on an optical disk with a diameter of 12 cm, which is the same size as the above, and an optical disk that records and reproduces information with specifications of NA 0.65 and light source wavelength 405 nm, so-called With HD DVD (hereinafter referred to as HD), information of 15 to 20 GB per layer can be recorded on an optical disk having a diameter of 12 cm. In the BD, since coma aberration generated due to the tilt (skew) of the optical disk increases, the protective layer is designed to be thinner than in the DVD (0.1 mm with respect to 0.6 mm of the DVD) The amount of coma due to skew is reduced. Hereinafter, such an optical disc is referred to as a “high density optical disc” in the present specification.

  Also, given the reality that DVDs and CDs (compact discs) on which a wide variety of information is recorded are currently being sold, information can be appropriately recorded on as many different types of optical discs as possible with a single player. It is desired to enable reproduction. Furthermore, considering that the optical pickup device is mounted on a notebook personal computer or the like, it is not only necessary to have compatibility with a plurality of types of optical discs, but it is important to further promote downsizing.

  Thus, at present, four types of optical discs, BD, HD, DVD, and CD, are commercially available. However, it is convenient for the user to limit the number of optical discs that can be used in the optical pickup device to, for example, two types. Will be reduced. On the other hand, it is conceivable to use three or more objective lenses in order to use three or more types of optical disks. However, there is a problem that the optical system becomes complicated and the compactness is lost. Therefore, using two objective lenses, consider whether it is possible to achieve both compactness of the optical pickup device and compatible use of three or more different optical disks. In such a case, what kind of optical disk is shared by the two objective lenses becomes a problem.

One problem here is that it is technically difficult to share the objective lens in consideration of the specifications of the two types of high-density optical disks. The reason will be described below. For example, Patent Document 1 describes a pickup device that enables compatible use of BD and HD with one objective optical element by sorting light beams of the same wavelength using a diffraction effect. If such an objective lens and two commercially available objective lenses for DVD / CD compatibility are used in combination, it can be said that information can be recorded / reproduced on four different types of optical disks.
JP 2006-147069 A

  However, as in the optical pickup device described in Patent Document 1 described above, when realizing the compatible use of BD and HD using the diffraction effect, for example, the light from the light source passing through the diffraction structure to one optical disk Utilization efficiency (the utilization efficiency here is the ratio of the amount of light that contributes to the spot on the optical disk with respect to the amount of light incident on the optical surface on the light source side of the objective optical element) is 40% (diffractive distribution using a diffraction structure) (Theoretically does not exceed 50%), the utilization efficiency of light passing from the optical disk through the same diffraction structure toward the photodetector (the utilization efficiency here is the optical surface on the optical disk side of the objective optical element) The ratio of the amount of light that contributes to the spot on the photodetector with respect to the amount of light incident on the detector is 40%, so the total utilization efficiency (here, the utilization efficiency is the light source side of the objective optical element) (The ratio of the amount of light that contributes to the spot on the optical detector with respect to the amount of light incident on the optical surface) The square of 40% can only use 16% of light, and it is necessary to significantly increase the light emission intensity of the light source and put it to practical use. Is extremely difficult.

  On the other hand, the compatibility between BD or HD and DVD or CD is different in the wavelength of the light beam used, so it is possible to correct the spherical aberration due to the difference in the thickness of the protective substrate using the diffraction effect of the diffractive structure. is there. However, the diffractive structure is a fine ring-shaped structure, and advanced molding technology is required to accurately form the optical surface of a small objective lens. However, it is unavoidable that the diffractive structure is not used, and the diffraction efficiency is lowered.

  The present invention has been made in view of the problems of the prior art, and an object thereof is to provide an optical pickup device that can use different types of optical disks with a simple configuration.

  In this specification, an optical disk (also referred to as an optical information recording medium) that uses 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 NA0 In addition to a standard optical disc (for example, BD: Blu-ray Disc) in which information is recorded / reproduced by an objective optical system of .85 and the thickness of the protective layer is about 0.1 mm, NA 0.65 to 0.67 Information is recorded / reproduced by the objective optical system, and includes a standard optical disc (for example, HD DVD: also simply referred to as HD) having a protective layer thickness of about 0.6 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.

  Furthermore, in this specification, DVD is a generic term for DVD series optical disks such as DVD-ROM, DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW, and the like. Is a general term for CD-series optical disks such as CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW and the like. The recording density is highest in the high-density optical disc, and then decreases in the order of DVD and CD.

The optical pickup device according to claim 1 includes a plurality of light sources capable of emitting light beams having different wavelengths, a first objective lens unit, and a second objective lens unit, and any one of the plurality of light sources. The light flux from the light source is condensed on the information recording surface of the first optical information recording medium having the protective substrate thickness t1 through the first objective lens unit, thereby recording information on the information recording surface. Reproduction is possible, and second light information of a protective substrate thickness t2 (t2 ≧ t1) is converted from a light beam from any one of the plurality of light sources through the second objective lens unit. By condensing on the information recording surface of the recording medium, information can be recorded and / or reproduced on the information recording surface, and a light beam from any one of the plurality of light sources is 1st objective lens part or said 2nd objective lens part By condensing the light on the information recording surface of the third optical information recording medium having a protective substrate thickness t3 (t3 ≧ t2), the light can be recorded and / or reproduced on the information recording surface. A pickup device,
Each of the first objective lens unit and the second objective lens unit has an optical surface composed only of a refractive surface,
Aberration correction means is arranged between the light source and the optical element.

  According to the present invention, only the first objective lens unit and the second objective lens unit are provided for recording / reproducing information with respect to three or more different types of optical information recording media. The optical system directed to the information recording medium can be simplified, and the optical surfaces of the first objective lens unit and the second objective lens unit are each composed of only a refractive surface. The optical element can be molded relatively easily, and the cost can be reduced. In addition, since an aberration correction unit is disposed between the light source and the optical element, the optical surfaces of the first objective lens unit and the second objective lens unit are respectively formed only from refractive surfaces. Even in this case, spherical aberration due to the thickness of the protective substrate of the optical information recording medium can be effectively corrected. Aberration correction means corrects spherical aberration that occurs based on the difference in substrate thickness and / or wavelength when recording / reproducing on different optical information recording media, and different optical information is obtained by one objective lens unit. Means that enable compatible use of recording media. Preferably, the aberration correcting means corrects spherical aberration caused by a difference in thickness or wavelength of the protective substrate between the second optical information recording medium and the third optical information recording medium and / or the fourth optical information recording medium. . One of the third optical information recording medium and the fourth optical information recording medium may change the magnification by changing the optical path length depending on the arrangement of the light source, without using the aberration correcting means.

  There is no particular limitation on the target optical information recording medium. However, when a first objective lens unit dedicated to HD and a second objective lens unit compatible with BD / DVD / CD are provided, or a first objective lens unit dedicated to BD When providing a second objective lens unit compatible with HD / DVD / CD, when providing a first objective lens unit compatible with BD / HD and a second objective lens unit compatible with DVD / CD, the first objective dedicated to BD For example, when a lens unit and a second objective lens unit compatible with DVD / CD are provided, a first objective lens unit dedicated for HD and a second objective lens unit compatible with DVD / CD can be used.

  According to a second aspect of the present invention, there is provided the optical pickup device according to the first aspect, wherein a light beam from any one of the plurality of light sources is transmitted through the first objective lens or the second objective lens. Thus, by focusing on the information recording surface of the fourth optical information recording medium having the protective substrate thickness t4, information can be recorded and / or reproduced on the information recording surface.

  According to a third aspect of the present invention, in the optical pickup device according to the first or second aspect, the light source includes a first light source that emits a first light flux having a wavelength λ1, and a second light source having a wavelength λ2 (λ1 <λ2). A second light source that emits a light beam; and a third light source that emits a third light beam having a wavelength of λ3 (λ2 <λ3), wherein the first objective lens unit transmits the first light beam with the first thickness of the protective substrate t1. Condensing on the information recording surface of one optical information recording medium, the second objective lens unit condenses the first light flux on the information recording surface of the second optical information recording medium having a protective substrate thickness t2, The second light beam is condensed on the information recording surface of the third optical information recording medium having a protective substrate thickness t3 (t2 = t3), and the third light beam is a fourth light beam having a protective substrate thickness t4 (t3 <t4). The light is condensed on the information recording surface of the optical information recording medium, and the aberration correction means includes the second objective lens unit, the light source, Characterized in that provided between.

  For example, one objective lens unit condenses on the information recording surfaces of the first optical information recording medium, the third optical information recording medium, and the fourth optical information recording medium having different protective substrate thicknesses t1, t3, and t4. However, in order to correct the spherical aberration due to the difference between the protective substrate thicknesses t1, t3, and t4, it is necessary to ensure a large difference in magnification, which leads to an increase in the size of the structure. However, there is a problem that the tracking shift characteristic in the optical information recording medium becomes worse. On the other hand, as in the present invention, the second objective lens unit focuses the light onto the information recording surfaces of the second optical information recording medium, the third optical information recording medium, and the fourth optical information recording medium. In this case, the second optical information recording medium and the third optical information recording medium have the same protective substrate thickness (t2 = t3). Therefore, it is sufficient to correct only the chromatic aberration with the magnification difference. And good tracking shift characteristics can be secured. The aberration correction means is provided in the optical path between the second objective lens unit and the light source. As a result, even if the aberration correction unit is arranged in the optical path between the first objective lens unit and the light source. Alternatively, it may not be disposed in the optical path between the first objective lens unit and the light source.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the aberration correction unit is a magnification conversion unit.

  According to the present invention, the magnification conversion means changes the magnification of the light beam incident on the objective lens unit in accordance with the optical information recording medium, so that one objective lens unit can change the information recording surface of a different optical information recording medium. On the other hand, an appropriate condensing spot can be formed.

  According to a fifth aspect of the present invention, in the optical pickup device according to the fourth aspect of the present invention, the magnification conversion means includes an optical element that is movable in the optical axis direction.

  In the case where the magnification conversion means has an optical element that can move in the optical axis direction, there is no particular limitation on the target optical information recording medium, but preferably a BD / HD compatible first objective lens unit and DVD / CD A compatible second objective lens unit is provided, a first objective lens unit dedicated to HD and a second objective lens unit compatible with BD / DVD / CD, or a first objective lens unit dedicated to BD and HD / DVD A second objective lens unit for CD compatibility may be provided.

  According to a sixth aspect of the present invention, in the invention according to the fourth or fifth aspect, the magnification conversion unit includes an optical element having a diffractive structure.

  As an optical element having a diffractive structure, for example, a collimator lens or a coupling lens may be provided with a diffractive structure, or a flat plate may be provided with a diffractive structure. For example, in the optical element DO having a form as shown in FIG. 3, an optical element that transmits a light beam for DVD and diffracts and diverges a light beam for CD is given as an example. In this case, in the optical element DO of the form shown in FIG. 3, the amount DP of one step is preferably equal to the wavelength of the DVD light flux.

  When the magnification conversion means has an optical element having a diffractive structure, there is no particular limitation on the target optical information recording medium, but preferably the optical element is used for DVD / CD compatibility with the first objective lens unit dedicated to BD. It is preferable that the optical element has a second objective lens part or an optical element having a first objective lens part dedicated to HD and a second objective lens part compatible with DVD / CD.

  According to a seventh aspect of the present invention, in the invention according to any one of the first to sixth aspects, the aberration correction unit includes a liquid crystal element.

  The liquid crystal element performs aberration correction by giving a phase to the wavefront. When the aberration correction means has a liquid crystal element, there is no particular limitation on the target optical information recording medium.

  Note that the aberration correction means may be a combination of any two or all of the magnification conversion means such as the movable optical element and the optical element having the diffractive structure described above, and the liquid crystal element.

  Further, preferably, a first objective lens unit dedicated to HD and a second objective lens unit compatible with BD / DVD / CD are provided, or a first objective lens unit dedicated to BD and a second objective lens unit compatible with HD / DVD / CD are provided. An objective lens unit may be provided.

  An optical pickup device according to an eighth aspect is the invention according to any one of the first to seventh aspects, wherein the first objective lens portion and the second objective lens portion are integrally formed. And

  By adopting the configuration as described above, in the compatible optical pickup device, it is possible to achieve both “common” and “compact” of the objective lens and obtain preferable optical performance. The composite optical element formed integrally as described above has an advantage that the interval between the lenses can be narrowed since the flange portion can be made common as compared with the case of using two individually molded lenses. There is also an advantage that assembly adjustment can be simplified and cost can be reduced.

  An optical pickup device according to a ninth aspect is the invention according to any one of the first to seventh aspects, wherein the first objective lens portion and the second objective lens portion are separate optical elements. It is characterized by being. The first objective lens portion and the second objective lens portion having a highly accurate shape can be formed by independent molding.

  According to the present invention, it is possible to provide an optical pickup device that can use different types of optical disks with a simple configuration.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The optical pickup device PU1 according to the present embodiment can be incorporated in an optical disk drive device. FIG. 1 is a diagram showing a schematic configuration of the optical pickup device PU1. FIG. 2 is a side view of the optical element OE. In the present embodiment, the first objective lens section OL1 and the second objective lens section OL2 are integrally molded to form the optical element OE.

  The optical pick-up device PU1 emits a 407 nm blue-violet laser beam (first beam) and emits a 407 nm blue-violet laser beam (first beam) when recording / reproducing information with respect to the BD and HD, and Second emission point EP2 (second light source) that emits a 655 nm laser beam (second beam) when recording / reproducing information on a DVD, and BD and HD information recording surfaces RL1 and RL2 A laser module LM and a CD including a first light receiving unit DS1 that receives a reflected light beam from the first light receiving unit DS2, a second light receiving unit DS2 that receives a reflected light beam from the information recording surface RL3 of the DVD, and a prism PS. A light source / light receiving unit integrated light source unit in which a third light source that emits a 785 nm laser beam (third beam) and a photodetector are integrated when information is recorded / reproduced. It has a hologram laser HL, and collimator COL is the magnification converting means driven in the optical axis direction by uniaxial actuator AC2, and an optical element OE, which is driven by an actuator AC1. The optical element OE includes a first objective lens section OL1 and a second objective lens section OL2 each having an optical surface composed only of a refractive surface, and is held by the bobbin BB.

  When recording / reproducing information with respect to the HD in the optical pickup device PU1, the bobbin BB is moved together with the actuator AC1 to the position shown in FIG. 1, and the first objective lens unit OL1 is inserted into the optical path. The first light emission point EP1 is caused to emit light. The divergent light beam emitted from the first light emitting point EP1 is converted into a parallel light beam by the collimator COL moved to the first position by the uniaxial actuator AC2, as illustrated by the solid line in FIG. After passing through the beam splitter BS and entering the first objective lens section OL1 in the state of parallel light, it becomes a spot formed on the information recording surface RL1 via the HD protective substrate PL1. The first objective lens section OL1 is driven together with the bobbin BB by the actuator AC1 to perform focusing and tracking.

  The reflected light flux modulated by the information pits on the information recording surface RL1 is transmitted again through the first objective lens section OL1, the beam splitter BS, and the collimator COL, and then enters the laser module LM, and then is reflected twice in the prism. Then, the light converges to the first light receiving unit DS1. And the information recorded on HD can be read using the output signal of 1st light-receiving part DS1. Spherical aberration caused by temperature changes during HD recording / reproduction and spherical aberration caused by using a two-layer disc are corrected by driving the collimator COL.

  When recording / reproducing information with respect to the BD in the optical pickup device PU1, the bobbin BB is moved upward from the position shown in FIG. 1, and the second objective lens portion OL2 is inserted into the optical path. One light emission point EP1 is caused to emit light. The divergent light beam emitted from the first light emission point EP1 is converted into a parallel light beam by the collimator COL moved to the first position by the uniaxial actuator AC2, although the light beam path is omitted in FIG. After passing through the beam splitter BS and entering the second objective lens section OL2 in the state of parallel light, it becomes a spot formed on the information recording surface RL2 via the protective substrate PL2 of the BD. The second objective lens section OL2 is driven by the actuator AC1 together with the bobbin BB to perform focusing and tracking.

  The reflected light flux modulated by the information pits on the information recording surface RL2 is again transmitted through the second objective lens section OL2, the beam splitter BS, and the collimator COL, then enters the laser module LM, and then is reflected twice in the prism. Then, the light converges to the first light receiving unit DS1. And the information recorded on BD can be read using the output signal of 1st light-receiving part DS1.

  In the optical pickup device PU1, when recording / reproducing information with respect to a DVD, the bobbin BB is moved upward from the position shown in FIG. 1, the second objective lens portion OL2 is inserted into the optical path, and The collimator COL is moved to the second position by the single-axis actuator AC2, and the second light emission point EP2 is caused to emit light. The divergent light beam emitted from the second light emitting point EP2 is converted into a weak divergent light beam by the collimator COL so that the light beam path is represented by a two-dot chain line in FIG. The luminous flux becomes flare light. The weakly divergent light beam passes through the beam splitter BS and is incident on the second objective lens section OL2 in the state of a finite divergent light beam, and then becomes a spot formed on the information recording surface RL3 via the protective substrate PL3 of the DVD. . The second objective lens section OL2 is driven by the actuator AC1 together with the bobbin BB to perform focusing and tracking.

  The reflected light flux modulated by the information pits on the information recording surface RL3 is again transmitted through the second objective lens section OL2, the beam splitter BS, and the collimator COL, then enters the laser module LM, and then is reflected twice in the prism. Then, the light converges to the second light receiving unit DS2. Then, information recorded on the DVD can be read using the output signal of the second light receiving unit DS2.

  In the optical pickup device PU1, when recording / reproducing information on a CD, the bobbin BB is moved upward in the drawing from the position shown in FIG. 1, and the second objective lens portion OL2 is inserted into the optical path. Then, the hologram laser HL is caused to emit light. The divergent light beam emitted from the hologram laser HL is reflected by the beam splitter BS and drawn in the state of a finite divergent light beam in the state of a finite divergent light beam as depicted in FIG. From there, the spot is formed on the information recording surface RL4 via the CD protective substrate PL4. The second objective lens section OL2 is driven by the actuator AC1 together with the bobbin BB to perform focusing and tracking.

  The reflected light flux modulated by the information pits on the information recording surface RL4 is reflected again by the second objective lens section OL2 and the beam splitter BS, then enters the hologram laser HL, and converges on the light receiving surface of the photodetector. And the information recorded on CD can be read using the output signal of a photodetector.

  According to the present embodiment, since the optical surfaces of the first objective lens portion OL1 and the second objective lens portion OL2 are each composed of only a refractive surface, the optical element OE can be molded relatively easily. Cost can be reduced. In addition, since a movable collimator COL is disposed as an aberration correction unit between the laser module LM and the optical element OE, the magnification is changed according to the optical disk by driving the collimator COL in the optical axis direction. Thus, even when the same second objective lens portion OL2 is used, it is possible to form an appropriate light condensing spot for BD and DVD having different protective substrate thicknesses. A condensing spot may be formed on any one or more of BD, HD, DVD, and CD using the first objective lens section OL1, and BD, HD, You may form a condensing spot in any one or more of DVD and CD.

  Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. The optical pickup device PU2 according to the present embodiment can be incorporated in an optical disk drive device. FIG. 4 is a diagram showing a schematic configuration of the optical pickup device PU2. FIG. 3 is a side view of the optical element DO as in the first embodiment. In the present embodiment, as shown in FIG. 2, the first objective lens section OL1 and the second objective lens section OL2 are integrally molded to form the optical element OE.

  The optical pickup device PU2 includes a first light source BLD that emits a 407-nm laser beam (first beam) emitted when information is recorded / reproduced on the BD, and a photodetector PD for the first beam. A first emission point EP1 (second light source) that emits a 655 nm laser beam (second beam) when recording / reproducing information on a DVD, and records / records information on a CD. A second light emitting point EP2 (third light source) that emits a 780 nm laser beam (third beam) when reproducing, and a first light receiving unit DS1 that receives a reflected beam from the information recording surface of the CD. A laser module LM composed of a second light receiving unit DS2 that receives a reflected light beam from an information recording surface of a DVD, a prism PS, a collimator COL, and a diffractive structure that is a magnification conversion means and a flat plate shape Has a Manabu element DO, and an optical element OE, which is driven by an actuator AC1. The optical element OE includes a first objective lens section OL1 and a second objective lens section OL2 each having an optical surface composed only of a refractive surface, and is held by the bobbin BB.

  In the optical pickup device PU2, when recording / reproducing information with respect to the BD, the bobbin BB is moved together with the actuator AC1 to the position shown in FIG. 4, and the first objective lens unit OL1 is inserted into the optical path. The first light source BLD is caused to emit light. The divergent light beam emitted from the first light source BLD passes through the beam splitter BS2, is reflected by the beam splitter BS1, and has an infinite parallel light beam reflected on the first objective lens section OL1, as illustrated in FIG. After being incident in a state, it becomes a spot formed on the information recording surface through the protective substrate of the BD.

  The reflected light beam modulated by the information pits on the information recording surface is reflected again by the first objective lens section OL1 and the beam splitter BS1, then reflected by the beam splitter BS2, and converges on the light receiving surface of the photodetector PD. And the information recorded on BD can be read using the output signal of a photodetector.

  When information is recorded / reproduced with respect to the DVD in the optical pickup device PU2, the bobbin BB is moved together with the actuator AC1 from the position shown in FIG. 4, and the second objective lens portion OL2 is inserted into the optical path. Then, the first light emission point EP1 is caused to emit light. The divergent light beam emitted from the first light emitting point EP1 is converted into a parallel light beam by the collimator COL as shown by the solid line in FIG. 4, and is applied to the optical element DO having a diffractive structure as magnification conversion means. Incident.

  The optical element DO is an optical element having a form as shown in FIG. 3, and the amount DP of one step of the diffractive structure is substantially equal to the wavelength of the DVD light flux. Therefore, the DVD light flux passes through the optical element DO, and the CD light flux is diffracted and emitted as a divergent light flux.

  Accordingly, the parallel light beam incident on the optical element DO is emitted from the optical element DO as the parallel light beam. The parallel light beam transmitted through the beam splitter BS1 becomes a spot formed on the information recording surface via the protective substrate of the DVD after entering the second objective lens portion OL2 in the state of parallel light. The second objective lens section OL2 is driven by the actuator AC1 together with the bobbin BB to perform focusing and tracking.

  The reflected light beam modulated by the information pits on the information recording surface is again transmitted through the second objective lens section OL2, the beam splitter BS1, the optical element DO, and the collimator COL, and then enters the laser module LM. After being reflected twice, it converges to the first light receiving part DS1. Then, information recorded on the DVD can be read using the output signal of the first light receiving unit DS1.

  When information is recorded / reproduced with respect to the CD in the optical pickup device PU2, the bobbin BB is moved upward from the position shown in FIG. 1, and the second objective lens portion OL2 is inserted into the optical path. The second light emission point EP2 is caused to emit light. The divergent light beam emitted from the second light emitting point EP2 is converted into a parallel light beam by the collimator COL as depicted by the two-dot chain line in FIG. 4, and has an diffractive structure as magnification conversion means. Incident on DO.

  As described above, in the optical element DO, the DVD light flux passes through the optical element DO, and the CD light flux is diffracted and emitted as a divergent light flux.

  Accordingly, the parallel light beam incident on the optical element DO is emitted from the optical element DO as a divergent light beam. The divergent light beam transmitted through the beam splitter BS1 becomes a spot formed on the information recording surface via the protective substrate of the DVD after entering the second objective lens portion OL2 in the form of divergent light. The second objective lens section OL2 is driven by the actuator AC1 together with the bobbin BB to perform focusing and tracking.

  The reflected light beam modulated by the information pits on the information recording surface RL3 is again transmitted through the second objective lens section OL2, the beam splitter BS1, the optical element DO, and the collimator COL, and then enters the laser module LM. And then converges on the second light receiving part DS2. The information recorded on the CD can be read using the output signal of the second light receiving unit DS2.

  According to the present embodiment, since the optical surfaces of the first objective lens portion OL1 and the second objective lens portion OL2 are each composed of only a refractive surface, the optical element OE can be molded relatively easily. Cost can be reduced. Further, since the optical element DO having a diffractive structure is arranged between the laser module LM and the optical element OE, the same second can be obtained by changing the magnification according to the optical disk without moving the optical element. Even when the objective lens section OL2 is used, it is possible to form an appropriate condensing spot for DVDs and CDs having different protective substrate thicknesses. A condensing spot may be formed on any one or more of BD, HD, DVD, and CD using the first objective lens section OL1, and BD, HD, You may form a condensing spot in any one or more of DVD and CD.

  The third embodiment of the present invention will be described below with reference to the drawings. Note that the optical pickup device according to the present embodiment can be incorporated in an optical disk drive device. FIG. 6 is a diagram illustrating a schematic configuration of the optical pickup device. In the present embodiment, as shown in FIG. 6, the first objective lens section OL1 and the second objective lens section OL2 are separate optical elements.

  FIG. 6 shows that information can be appropriately recorded and / or reproduced on the first optical disc BD, the second optical disc HD, the third optical disc DVD, and the fourth optical disc CD. It is a figure which shows schematically the structure of the optical pick-up apparatus of this Embodiment. FIG. 5 is a perspective view of an objective lens actuator device used in the optical pickup device of the present embodiment. The optical pickup device according to the present embodiment can be mounted on an optical information recording / reproducing device. The present invention is not limited to the present embodiment.

  First, the objective lens actuator device will be described. The objective lens actuator device 10 shown in FIG. 5 is disposed in the optical pickup device PU1 shown in FIG. 6, and is a separate component that condenses laser light from a semiconductor laser, which will be described later, on information recording surfaces of different optical disks. The first objective lens section OL1, the second objective lens section OL2, the lens holder 13 that holds the optical axes of these objective lens sections OL1 and OL2 on the same circumference 13A, and the lens holder 13 A chassis 15 that holds the lens holder 13 in a direction along the support shaft 14 so as to be rotatable through a support shaft 14 provided at the center axis of 13A and reciprocally movable along the rotation center axis. A focusing actuator (not shown) for reciprocating movement, and a trap for urging the lens holder 13 to rotate and positioning the objective lens portions OL1 and OL2. And a ring actuator 20. The objective lens actuator device 10 is provided with an operation control circuit (not shown) that controls the operation of each actuator.

  The objective lens portions OL1 and OL2 are respectively provided in holes penetrating the flat plate surface of the disk-shaped lens holder 13, and are disposed at equal distances from the center of the lens holder 13. The lens holder 13 is rotatably engaged with an upper end portion of a support shaft 14 erected from the chassis 15 at the center thereof, and a focusing actuator (not shown) is disposed below the support shaft 14. It is installed.

  In other words, the focusing actuator includes an electromagnetic solenoid composed of a permanent magnet provided at the lower end portion of the support shaft 14 and a coil provided therearound, and by adjusting the current flowing through the coil, the support shaft 14 and the lens. The holder 13 is urged to reciprocate in a minute unit in the direction along the support shaft 14 (vertical direction in FIG. 5), and the focal length is adjusted.

  Further, as described above, the lens holder 13 is rotated by the tracking actuator 20 around the support shaft 14 having an axis parallel to the optical axis. The tracking actuator 20 includes a pair of tracking coils 21 </ b> A and 21 </ b> B that are symmetrically provided on the edge of the lens holder 13 with the support shaft 14 interposed therebetween, and a support on the chassis 15 that is close to the edge of the lens holder 13. There are two pairs of magnets 22A, 22B, 23A, and 23B provided at symmetrical positions with the shaft 14 in between.

  When the tracking coils 21A and 21B are individually opposed to one pair of magnets 22A and 22B, the first objective lens section OL1 rises on the optical path of the laser beam reflected by the rising mirror RP (FIG. 1). The positions of the magnets 22A and 22B are set so that the second objective lens portion OL2 is on the optical path of the laser beam when facing the magnets 23A and 23B individually. , 23B are set.

  Further, the lens holder 13 described above has a stopper (not shown) that limits the rotation range so that the tracking coil 21A and the magnet 22B or magnet 23B and the tracking coil 21B and the magnet 22A or magnet 23A do not face each other. Is provided.

  Further, the tracking actuator 20 is arranged so that the tangential direction of the outer periphery of the circular lens holder 13 is orthogonal to the tangential direction of the track of the optical disk, and the lens holder 13 is biased to rotate in minute units. This is for correcting the deviation of the irradiation position with respect to the track of the laser beam. Therefore, in order to perform this tracking operation, for example, it is necessary to slightly bias the lens holder 13 while keeping the tracking coils 21A and 21B facing the magnets 22A and 22B.

  In order to perform such tracking operation, each tracking coil 21A, 21B is equipped with an iron piece on the inside thereof, and this iron piece is attracted to each magnet so that a delicate repulsive force is generated between these magnets. In addition, the operation control circuit controls the flow of current through the tracking coils 21A and 21B.

  Next, the optical pickup device main body will be described. The optical pickup device PU1 has a first objective lens portion OL1 dedicated to BD consisting only of a refracting surface, an objective lens actuator device 10, a second objective lens portion OL2 commonly used for HD / DVD / CD consisting of only a refracting surface, and a startup. Mirror RP, λ / 4 wavelength plate QWP, coupling lens CL composed of negative lens L1 and positive lens L2, actuator ACT for displacing positive lens L2 in the optical axis direction, polarization beam splitter PBS, wavelength λ1 = 405 nm A semiconductor laser LD1 (first light source) that emits a laser beam (first beam), a semiconductor laser (second light source) that emits a laser beam (second beam) with a wavelength λ2 = 650 nm, and a laser beam with a wavelength λ3 = 785 nm 2 lasers 1 package in which a semiconductor laser (third light source) emitting (third light flux) is housed in a common package Having 2L1P, sensor lens SL, and a light receiving element PD for receiving the light beam reflected from the BD information recording surface RL1, HD information recording surface RL2, DVD information recording surface RL3, CD information recording surface RL4.

  A case of recording / reproducing BD will be described. First, when recording and / or reproducing information with respect to the BD, the lens holder 13 of the objective lens actuator mechanism 10 shown in FIG. 5 is rotated, and the first objective lens section OL1 is placed in the optical path as shown in FIG. Shall be inserted. Further, after moving the positive lens L2 in the optical axis direction by the actuator ACT to a position where the first light beam emitted to the first objective lens section OL1 becomes a parallel light beam, the blue-violet semiconductor laser LD1 emits light ( The position of the positive lens L2 at this time is the first position). The divergent light beam of the first light beam (λ1 = 405 nm) emitted from the blue-violet semiconductor laser LD1 passes through the dichroic prism DP and the polarization beam splitter PBS, and is converted into a parallel light beam by the coupling lens CL, and then λ / 4 wavelength. The linearly polarized light is converted into circularly polarized light by the plate QWP, reflected by the rising mirror RP, the diameter of the light beam is regulated by a diaphragm (not shown), and the protective substrate PL1 having a thickness t1 = 0.1 mm is formed by the first objective lens unit OL1. And the spot formed on the information recording surface RL1 of the BD.

  The reflected light flux modulated by the information pits on the information recording surface RL1 is transmitted again through the first objective lens section OL1 and the diaphragm, then reflected by the rising mirror RP, and linearly reflected from the circularly polarized light by the λ / 4 wavelength plate QWP. After being converted into polarized light and converted into a convergent light beam by the coupling lens CL and reflected by the polarization beam splitter PBS, astigmatism is given by the sensor lens SL and converges on the light receiving surface of the light receiving element PD. The information recorded on the BD can be read by using the output signal of the light receiving element PD to cause the objective lens actuator device 10 to focus and track the first objective lens portion OL1.

  Next, a case where HD recording / reproduction is performed will be described. When recording and / or reproducing information with respect to the HD, the lens holder 13 of the objective lens actuator mechanism 10 shown in FIG. 5 is rotated, and the second objective lens section OL2 is inserted into the optical path. Further, after the positive lens L2 is moved to the first position by the actuator ACT, the blue-violet semiconductor laser LD1 is caused to emit light. The divergent light beam of the first light beam (λ1 = 405 nm) emitted from the blue-violet semiconductor laser LD1 passes through the dichroic prism DP and the polarization beam splitter PBS, and is converted into a parallel light beam by the coupling lens CL, and then λ / 4 wavelength. The linearly polarized light is converted into circularly polarized light by the plate QWP, reflected by the rising mirror RP, the diameter of the light beam is regulated by a diaphragm (not shown), and the protective substrate PL2 having a thickness t2 = 0.6 mm is formed by the second objective lens unit OL2. The spot is formed on the HD information recording surface RL2.

  The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the second objective lens section OL2 and the diaphragm, then reflected by the rising mirror RP, and linearly reflected from the circularly polarized light by the λ / 4 wavelength plate QWP. After being converted into polarized light and converted into a convergent light beam by the coupling lens CL and reflected by the polarization beam splitter PBS, astigmatism is given by the sensor lens SL and converges on the light receiving surface of the light receiving element PD. Then, using the output signal of the light receiving element PD, the information recorded in the HD can be read by causing the objective lens actuator device 10 to focus and track the second objective lens portion OL2.

  Next, a case where DVD recording / reproduction is performed will be described. When recording and / or reproducing information with respect to a DVD, the lens holder 13 of the objective lens actuator mechanism 10 shown in FIG. 5 is rotated, and the second objective lens section OL2 is inserted into the optical path. Further, the positive lens L2 is moved in the direction of the optical axis by the actuator ACT so that the second light beam (λ2 = 650 nm) emitted from the red semiconductor laser of the two lasers 1 package 2L1P passes through the positive lens L2 and becomes a divergent light beam having an angle θ1. (The position of the positive lens L2 at this time is set as the second position), and the red semiconductor laser of the two-laser one package 2L1P is caused to emit light. The divergent light beam of the second light beam (λ1 = 650 nm) emitted from the red laser diode of 2 lasers 1 package 2L1P is reflected by the dichroic prism DP, passes through the polarization beam splitter PBS, and diverges at an angle θ1 by the coupling lens CL. After being converted into a light beam, it is converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, reflected by the rising mirror RP, the diameter of the light beam is regulated by a diaphragm (not shown), and thickened by the second objective lens unit OL2. The spot is formed on the information recording surface RL3 of the DVD through the protective substrate PL3 having a length t3 = 0.6 mm.

  The reflected light beam modulated by the information pits on the information recording surface RL3 is transmitted again through the second objective lens section OL2 and the diaphragm, then reflected by the rising mirror RP, and linearly reflected from the circularly polarized light by the λ / 4 wavelength plate QWP. After being converted into polarized light and converted into a convergent light beam by the coupling lens CL and reflected by the polarization beam splitter PBS, astigmatism is given by the sensor lens SL and converges on the light receiving surface of the light receiving element PD. Then, the information recorded on the DVD can be read by using the output signal of the light receiving element PD to cause the objective lens actuator device 10 to focus and track the second objective lens section OL2.

  Next, a case where CD recording / reproduction is performed will be described. When recording and / or reproducing information on a CD, the lens holder 13 of the objective lens actuator mechanism 10 shown in FIG. 5 is rotated, and the second objective lens section OL2 is inserted into the optical path. Further, the positive lens L2 is moved to the actuator so that the third light beam (λ3 = 785 nm) emitted from the red laser diode of the two laser 1 package 2L1P passes through the positive lens L2 and becomes a divergent light beam having an angle θ2 (θ1 ≠ θ2). After being displaced in the optical axis direction by ACT (the position of the positive lens L2 at this time is taken as the third position), the infrared laser diode of the two lasers one package 2L1P is caused to emit light. Note that the third position of the positive lens L2 is closer to the rising mirror RP than the second position. The divergent light beam of the third light beam (λ3 = 785 nm) emitted from the red laser diode of the 2 laser 1 package 2L1P is reflected by the dichroic prism DP, passes through the polarization beam splitter PBS, and is angled θ2 (θ2) by the coupling lens CL. > Θ1), and then converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP, reflected by the rising mirror RP, and the diameter of the light beam is regulated by the stop (not shown), so that the second objective It becomes a spot formed on the information recording surface RL4 of the CD via the protective substrate PL4 having a thickness t4 = 1.2 mm by the lens portion OL2.

  The reflected light beam modulated by the information pits on the information recording surface RL4 is transmitted again through the second objective lens section OL2 and the diaphragm, then reflected by the rising mirror RP, and linearly reflected from the circularly polarized light by the λ / 4 wavelength plate QWP. After being converted into polarized light and converted into a convergent light beam by the coupling lens CL and reflected by the polarization beam splitter PBS, astigmatism is given by the sensor lens SL and converges on the light receiving surface of the light receiving element PD. Then, by using the output signal of the light receiving element PD to focus or track the second objective lens unit OL2 by the objective lens actuator device 10, information recorded on the CD can be read.

  According to the present embodiment, since the optical surfaces of the first objective lens portion OL1 and the second objective lens portion OL2 which are separate members are each composed of only a refractive surface, it is relatively easy to mold the objective lens portion. This can be done and the cost can be reduced. In addition, since a movable collimator COL is disposed as an aberration correction unit between the laser module LM and the optical element OE, the magnification is changed according to the optical disk by driving the collimator COL in the optical axis direction. As a result, even when the same second objective lens section OL2 is used, it is possible to form an appropriate condensing spot for CDs and DVDs having different protective substrate thicknesses. A condensing spot may be formed on any one or more of BD, HD, DVD, and CD using the first objective lens section OL1, and BD, HD, You may form a condensing spot in any one or more of DVD and CD.

It is a figure which shows schematically the structure of optical pick-up apparatus PU1. It is a side view of optical element OE. It is a side view of optical element DO. It is a figure which shows schematically the structure of optical pick-up apparatus PU2. It is a perspective view of the objective lens actuator apparatus used for the optical pick-up apparatus of this Embodiment. It is a figure which shows schematically the structure of the optical pick-up apparatus of other embodiment.

Explanation of symbols

AC1 Actuator AC2 Single-axis actuator BB Bobbin BS Beam splitter CL Coil COL Collimator DS1 First light receiving part DS2 Second light receiving part EP1 First light emitting point EP2 Second light emitting point HL Hologram laser LM Laser module OL1 First objective lens Part OL2 Second objective lens part PL1 Protective substrate PL2 Protective substrate PL3 Protective substrate PL4 Protective substrate PS Prism PU1, PU2 Optical pickup device RL1 Information recording surface RL2 Information recording surface RL3 Information recording surface RL4 Information recording surface 10 Objective lens actuator device 13 Lens Holder 13A Circumference 14 Support shaft 15 Chassis 20 Tracking actuator 21A Tracking coil 21B Tracking coil 22A Magnet 22B Magnet 23A Magnet 23B, Ma Net

Claims (9)

A plurality of light sources capable of emitting light beams having different wavelengths, and a first objective lens unit and a second objective lens unit, wherein the light beams from any one of the plurality of light sources are By focusing on the information recording surface of the first optical information recording medium having the protective substrate thickness t1 through the objective lens portion, information can be recorded and / or reproduced on the information recording surface. A light beam from any one of the plurality of light sources is condensed on an information recording surface of a second optical information recording medium having a protective substrate thickness t2 (t2 ≧ t1) through the second objective lens unit. Thus, information can be recorded and / or reproduced on the information recording surface, and a light beam from any one of the plurality of light sources is used as the first objective lens unit or the second object lens unit. The thickness of the protective substrate t3 (t3 ≧ t2) through the objective lens unit 3 by focused on the information recording surface of the optical information recording medium, a recording and / or an optical pickup apparatus reproducing is made possible for information to the information recording surface,
Each of the first objective lens unit and the second objective lens unit has an optical surface composed only of a refractive surface,
An optical pickup device, wherein an aberration correction unit is disposed between the light source and the optical element.   In the optical pickup device, information on a fourth optical information recording medium having a protective substrate thickness t4 is obtained by using a light beam from any one of the plurality of light sources via the first objective lens or the second objective lens. 2. The optical pickup device according to claim 1, wherein information can be recorded and / or reproduced on the information recording surface by condensing on the recording surface. The light source emits a first light source that emits a first light flux with a wavelength λ1, a second light source that emits a second light flux with a wavelength λ2 (λ1 <λ2), and a third light flux with a wavelength λ3 (λ2 <λ3). And a third light source
The first objective lens unit condenses the first light flux on an information recording surface of the first optical information recording medium having a protective substrate thickness t1,
The second objective lens part condenses the first light beam on the information recording surface of the second optical information recording medium having a protective substrate thickness t2, and the second light beam is protected substrate thickness t3 (t2 = t3). Condensing on the information recording surface of the third optical information recording medium, condensing the third light flux on the information recording surface of the fourth optical information recording medium having a protective substrate thickness t4 (t3 <t4),
The optical pickup device according to claim 1, wherein the aberration correcting unit is provided between the second objective lens unit and the light source.   4. The optical pickup device according to claim 1, wherein the aberration correction unit is a magnification conversion unit.   The optical pickup device according to claim 4, wherein the magnification conversion unit includes an optical element movable in an optical axis direction.   6. The optical pickup device according to claim 4, wherein the magnification conversion unit includes an optical element having a diffractive structure.   The optical pickup device according to claim 1, wherein the aberration correction unit includes a liquid crystal element.   The optical pickup device according to claim 1, wherein the first objective lens unit and the second objective lens unit are integrally formed.   The optical pickup device according to claim 1, wherein the first objective lens unit and the second objective lens unit are separate optical elements.

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