WO2009147942A1

WO2009147942A1 - Objective lens and optical pickup device

Info

Publication number: WO2009147942A1
Application number: PCT/JP2009/059170
Authority: WO
Inventors: 満三森
Original assignee: Konica Minolta Opto Inc
Current assignee: Konica Minolta Opto Inc
Priority date: 2008-06-04
Filing date: 2009-05-19
Publication date: 2009-12-10
Anticipated expiration: 2010-12-04
Also published as: JPWO2009147942A1

Abstract

An optical pickup device and an objective lens which are capable of appropriately recording and/or reproducing information into/from three types of disks which are different in recording density, the configurations of which can be simplified and the costs of which can be reduced. Since the combination for diffraction orders of diffracted light generated from a circumferential optical path difference giving structure is (x, y, z) = (1, 1, 2), (1, 1, 0), (4, 2, 2), (4, 2, 0), (2, 1, 2) or (2, 1, 0), first and second luminous fluxes having passed through the circumferential optical path difference giving structure effectively form condensing spots on information recording surfaces of first and second optical disks, respectively, while a third luminous flux having passed through the circumferential optical path difference giving structure is not effectively condensed on an information recording surface of a third optical disk but flares. This eliminates the necessity of providing individual aperture stops and ensures cost reduction and downsizing of the optical pickup device.

Description

Objective lens and optical pickup device

　本発明は、異なる種類の光ディスクに対して互換可能に情報の記録及び／又は再生を行える光ピックアップ装置及びそれに用いる対物レンズに関する。 The present invention relates to an optical pickup apparatus capable of recording and / or reproducing information interchangeably for different types of optical discs and an objective lens used therefor.

　近年、光ピックアップ装置において、光ディスクに記録された情報の再生や、光ディスクへの情報の記録のための光源として使用されるレーザ光源の短波長化が進み、例えば、青紫色半導体レーザや、第２高調波を利用して赤外半導体レーザの波長変換を行う青色ＳＨＧレーザ等、波長４００～４２０ｎｍのレーザ光源が実用化されつつある。これら青紫色レーザ光源を使用すると、ＤＶＤ（デジタルバーサタイルディスク）と同じ開口数（ＮＡ）の対物レンズを使用する場合で、直径１２ｃｍの光ディスクに対して、１５～２０ＧＢの情報の記録が可能となり、対物レンズのＮＡを０．８５にまで高めた場合には、直径１２ｃｍの光ディスクに対して、２３～２５ＧＢの情報の記録が可能となる。以下、本明細書では、青紫色レーザ光源を使用する光ディスク及び光磁気ディスクを総称して「高密度光ディスク」という。 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, Laser light sources with wavelengths of 400 to 420 nm, such as blue SHG lasers that perform wavelength conversion of infrared semiconductor lasers using harmonics, are being put into practical use. When these blue-violet laser light sources are used, it is possible to record 15 to 20 GB of information 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”.

　尚、ＮＡ０．８５の対物レンズを使用する高密度光ディスクでは、光ディスクの傾き（スキュー）に起因して発生するコマ収差が増大するため、ＤＶＤにおける場合よりも保護層を薄く設計し（ＤＶＤの０．６ｍｍに対して、０．１ｍｍ）、スキューによるコマ収差量を低減しているものがある。ところで、かかるタイプの高密度光ディスクに対して適切に情報の記録／再生ができると言うだけでは、光ディスクプレーヤ／レコーダ（光情報記録再生装置）の製品としての価値は十分なものとはいえない。現在において、多種多様な情報を記録したＤＶＤやＣＤ（コンパクトディスク）が販売されている現実をふまえると、高密度光ディスクに対して情報の記録／再生ができるだけでは足らず、例えばユーザが所有しているＤＶＤやＣＤに対しても同様に適切に情報の記録／再生ができるようにすることが、高密度光ディスク用の光ディスクプレーヤ／レコーダとしての商品価値を高めることに通じるのである。このような背景から、高密度光ディスク用の光ディスクプレーヤ／レコーダに搭載される光ピックアップ装置は、高密度光ディスクとＤＶＤ、更にはＣＤとの何れに対しても互換性を維持しながら適切に情報を記録／再生できる性能を有することが望まれる。 In a high-density optical disk using an NA 0.85 objective lens, 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). Some have reduced the amount of coma due to skew. By the way, it can not be said that the value of an optical disc player / recorder (optical information recording / reproducing device) as a product is sufficient only by appropriately recording / reproducing information on such a high-density optical disc. In light of the reality that DVDs and CDs (compact discs) on which a wide 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 / recorder for high-density optical discs. From such a background, an optical pickup device mounted on an optical disc player / recorder for high density optical discs can appropriately receive information while maintaining compatibility with both high density optical discs, DVDs, and even CDs. It is desired to have a performance capable of recording / reproducing.

　高密度光ディスクとＤＶＤ、更にはＣＤとの何れに対しても互換性を維持しながら適切に情報を記録／再生できるようにする方法として、高密度光ディスク用の光学系とＤＶＤやＣＤ用の光学系とを情報を記録／再生する光ディスクの記録密度に応じて選択的に切り替える方法が考えられるが、複数の光学系が必要となるので、小型化に不利であり、またコストが増大する。 As a method for recording / reproducing information appropriately while maintaining compatibility with both high-density optical discs and DVDs, and even CDs, optical systems for high-density optical discs and optical systems for DVDs and CDs are used. A method of selectively switching the system to and from the recording density of an optical disk for recording / reproducing information is conceivable, but a plurality of optical systems are required, which is disadvantageous for miniaturization and increases the cost.

　従って、光ピックアップ装置の構成を簡素化し、低コスト化を図るためには、互換性を有する光ピックアップ装置においても、高密度光ディスク用の光学系とＤＶＤやＣＤ用の光学系とを共通化して、光ピックアップ装置を構成する光学部品点数を極力減らすのが好ましい。そして、光ディスクに対向して配置される対物レンズを共通化することが光ピックアップ装置の構成の簡素化、低コスト化に最も有利となる。尚、記録／再生波長が互いに異なる複数種類の光ディスクに対して共通に使用可能な対物レンズを得るためには、球面収差の波長依存性を有する光路差付与構造を対物光学系に形成することで、波長の違いや保護層の厚みの違いにより発生する球面収差を低減する必要がある。 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. And, it is most advantageous to simplify the configuration of the optical pickup device and to reduce the cost to make the objective lens arranged facing the optical disc in common. In order to obtain an objective lens that can be used in common for a plurality of types of optical disks having different recording / reproducing wavelengths, an optical path difference providing structure having wavelength dependency of spherical aberration is formed in the objective optical system. It is necessary to reduce the spherical aberration that occurs due to the difference in wavelength and the thickness of the protective layer.

　特許文献１には、光路差付与構造を有し、高密度光ディスクと従来のＤＶＤ及びＣＤに対して共通に使用可能な対物レンズに用いる光学素子が記載されている。 Patent Document 1 describes an optical element that has an optical path difference providing structure and is used for an objective lens that can be used in common with high-density optical discs and conventional DVDs and CDs.

特開２００６－１８５５７６号公報JP 2006-185576 A

　ところで、高密度光ディスク、ＤＶＤ及びＣＤに対して共通に使用する一般的な光ピックアップ装置において、各光ディスク使用時の有効径が異なるので、それぞれ光束を制限する可変の開口絞りを設けている。これに対し、回折構造を用いて、例えばＣＤの有効径外を通過する光束を、ＣＤの情報記録面上でフレアにするような回折光に変換すれば、機械的な開口絞りを設けずに済むという問題がある。そこで本発明者は、鋭意研究の結果、高密度光ディスク及びＤＶＤの情報記録面には適切な集光スポットを形成すると共に、ＣＤの情報記録面では適切なフレアを発生できる回折次数の組み合わせを得ることに成功した。ところが、一般的なブレーズ型或いは階段型の回折構造で、得られた回折次数の組み合わせを実現しようとすると、実用に適さないほどに回折効率が低下するという問題があることが判明した。 By the way, in a general optical pickup device that is commonly used for high-density optical discs, DVDs, and CDs, since effective diameters when using each optical disc are different, variable aperture stops for limiting the light flux are provided. On the other hand, if a diffractive structure is used to convert, for example, a light beam passing outside the effective diameter of a CD into diffracted light that flares on the information recording surface of the CD, a mechanical aperture stop is not provided. There is a problem that it will end. Therefore, as a result of diligent research, the present inventor has obtained a combination of diffraction orders capable of forming an appropriate condensing spot on the information recording surface of a high-density optical disc and DVD and generating an appropriate flare on the information recording surface of the CD. Succeeded. However, it has been found that there is a problem that the diffraction efficiency is lowered to such an extent that it is not suitable for practical use when trying to realize a combination of the obtained diffraction orders with a general blazed or stepped diffraction structure.

　これに対し、特許文献１に開示された技術によれば、第１の光路差関数を第２の光路差関数に足し合わせて形成される光路差付与構造を対物レンズに形成しているので、高密度光ディスク用の光束、ＤＶＤ用の光束及びＣＤ用の光束が入射した場合、高い回折効率を維持しつつ任意の次数の回折光を発生させることができるという特徴がある。 On the other hand, according to the technique disclosed in Patent Document 1, since the optical path difference providing structure formed by adding the first optical path difference function to the second optical path difference function is formed in the objective lens, When a light beam for a high density optical disc, a light beam for DVD, and a light beam for CD are incident, there is a feature that diffracted light of an arbitrary order can be generated while maintaining high diffraction efficiency.

　ところが、第１の光路差関数と第２の光路差関数とを関係づけないで足し合わせた場合、最終的な光路差付与構造において、特許文献１の図３に示すように、谷底に小突起が生じたり、山頂に窪みが生じるなど複雑な構造となり、成形金型の構成が困難になると共に、成形時に金型の奥まで素材が入り込みにくくなり、成形された対物レンズの光学面が理想形状で転写されにくく、所望の光学特性を得ることが困難となる。 However, when the first optical path difference function and the second optical path difference function are added without being related, in the final optical path difference providing structure, as shown in FIG. And a complex structure such as a depression at the top of the mountain, making it difficult to configure the mold, making it difficult for the material to enter the mold at the time of molding, and the optical surface of the molded objective lens to be ideal Therefore, it is difficult to obtain desired optical characteristics.

　本発明は、上述の問題を考慮してなされたものであり、対物レンズとして単玉のレンズを用いたとしても、高密度光ディスク（特にＢＤ）とＤＶＤとＣＤ等の、記録密度が異なる３種類のディスクに対して情報の記録及び／又は再生を適切に行うことができる光ピックアップ装置及び対物レンズであって、所望の光学特性を発揮できると共に、成形金型の構成が複雑なものになりすぎる事を防止し、転写性を良好にでき、その構成の簡素化、低コスト化を実現可能な対物レンズ及びそれを用いた光ピックアップ装置を提供することを目的とする。 The present invention has been made in consideration of the above-mentioned problems. Even if a single lens is used as an objective lens, the recording density of the high-density optical disc (particularly BD), DVD, and CD is different. An optical pickup device and an objective lens capable of appropriately recording and / or reproducing information with respect to a disc of the above, and exhibiting desired optical characteristics, and the configuration of a molding die becomes too complicated It is an object of the present invention to provide an objective lens that can prevent this, improve transferability, simplify the configuration, and reduce the cost, and an optical pickup device using the objective lens.

以上の課題を解決するために、請求項１記載の発明は、第１光源から出射される波長λ１（μｍ）の第１光束を用いて厚さｔ１の保護層を有する第１光ディスクの情報記録面に対して集光スポット形成を行い、第２光源から出射される波長λ２（λ１＜λ２）の第２光束を用いて厚さｔ２（ｔ１≦ｔ２）の保護層を有する第２光ディスクの情報記録面に対して集光スポット形成を行い、第３光源から出射される波長λ３（λ２＜λ３）の第３光束を用いて厚さｔ３（ｔ２＜ｔ３）の保護層を有する第３光ディスクの情報記録面に対して集光スポット形成を行う対物レンズを備えた光ピックアップ装置の対物レンズにおいて、
　前記対物レンズの光学面は、少なくとも、光軸を含む中央領域と、前記中央領域の周囲に形成された輪帯状の周辺領域とを有し、
　前記中央領域と前記周辺領域とを通過した前記第１光束が、前記第１光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、
　前記中央領域と前記周辺領域とを通過した前記第２光束が、前記第２光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、
　前記中央領域を通過した前記第３光束が、前記第３光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、前記周辺領域を通過した前記第３光束が、前記第３光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光されず、
　前記周辺領域には、第２光路差付与構造が形成されており、
　前記第２光路差付与構造は、ブレーズ型構造である第１基礎構造と、階段型構造である第２基礎構造とを、前記第１基礎構造の全ての段差部の位置と前記第２基礎構造の段差部の位置が一致するように重畳させてなり、
　ｘ、ｙ、ｚを任意の整数としたときに、前記第２光路差付与構造に前記第１光束が入射した場合に発生する回折光のうち、ｘ次回折光が最大の回折効率を有し、前記第２光路差付与構造に前記第２光束が入射した場合に発生する回折光のうち、ｙ次回折光が最大の回折効率を有し、前記第２光路差付与構造に前記第３光束が入射した場合に発生する回折光のうち、ｚ次回折光が最大の回折効率を有することを特徴とする。 In order to solve the above problems, the invention according to claim 1 is directed to information recording on a first optical disc having a protective layer having a thickness t1 using a first light beam having a wavelength λ1 (μm) emitted from a first light source. Information on a second optical disc having a protective layer having a thickness t2 (t1 ≦ t2) using a second light flux having a wavelength λ2 (λ1 <λ2) emitted from the second light source by forming a condensed spot on the surface. A third optical disk having a protective layer with a thickness t3 (t2 <t3) is formed on the recording surface by using a third light flux having a wavelength λ3 (λ2 <λ3) emitted from the third light source. In the objective lens of the optical pickup device provided with the objective lens that performs the condensing spot formation on the information recording surface,
The optical surface of the objective lens has at least a central region including an optical axis, and a ring-shaped peripheral region formed around the central region,
The first light flux that has passed through the central region and the peripheral region is condensed so that information can be recorded and / or reproduced on the information recording surface of the first optical disc,
The second light flux that has passed through the central region and the peripheral region is condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc,
The third light flux that has passed through the central region is condensed so that information can be recorded and / or reproduced on the information recording surface of the third optical disc, and the third light flux that has passed through the peripheral region is 3 It is not condensed so that information can be recorded and / or reproduced on the information recording surface of the optical disc,
A second optical path difference providing structure is formed in the peripheral region,
The second optical path difference providing structure includes a first basic structure that is a blaze type structure and a second basic structure that is a staircase type structure, the positions of all the step portions of the first basic structure, and the second basic structure. Is superimposed so that the position of the step part of
Of the diffracted light generated when the first light flux is incident on the second optical path difference providing structure when x, y, z are arbitrary integers, the x-order diffracted light has the maximum diffraction efficiency, Of the diffracted light generated when the second light beam enters the second optical path difference providing structure, the y-order diffracted light has the maximum diffraction efficiency, and the third light beam enters the second optical path difference providing structure. Among the diffracted light generated in this case, the z-th order diffracted light has the maximum diffraction efficiency.

　例えばブレーズ型形状の回折構造又は階段形状の回折構造のいずれかのみを互換用の対物レンズに形成する場合、回折効率が高い第１光束と第２光束と第３光束の回折次数の組み合わせが定まってしまうため、設計の自由度が低下するという問題がある。本発明の第２光路差付与構造のように第１基礎構造と第２基礎構造とを重畳させることで、任意の回折次数の選択を行うことが出来、設計の自由度が向上すると共に、単一の光路差関数を使用して設計することが可能なため、設計がしやすくなる。加えて、前記第１基礎構造の全ての段差部の位置と前記第２基礎構造の段差部の位置が一致するように重畳させることにより、前記光路差付与構造をシンプルにすることができ、対物レンズの成形金型の加工が容易になり、対物レンズの成形時に樹脂やガラスが金型の末端まで入り込みやすく、製造精度を高めることが出来、設計値に近い光量を得る事が可能となり、光量ロスを減らすことが可能となる。 For example, when only a blazed diffraction structure or a staircase diffraction structure is formed on a compatible objective lens, the combination of the diffraction orders of the first, second, and third light beams with high diffraction efficiency is determined. Therefore, there is a problem that the degree of freedom in design is reduced. By overlapping the first basic structure and the second basic structure as in the second optical path difference providing structure of the present invention, it is possible to select an arbitrary diffraction order, and the degree of freedom in design is improved. Since it is possible to design using one optical path difference function, the design is facilitated. In addition, the optical path difference providing structure can be simplified by overlapping the positions of all the step portions of the first foundation structure so that the positions of the step portions of the second foundation structure coincide with each other. Processing of the lens mold becomes easy, resin and glass can easily reach the end of the mold when forming the objective lens, the manufacturing accuracy can be improved, and the light quantity close to the design value can be obtained. Loss can be reduced.

　請求項２に記載の対物レンズは、請求項１に記載の発明において、前記第２基礎構造は３分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 According to a second aspect of the present invention, there is provided the objective lens according to the first aspect, wherein the second basic structure is a three-step staircase structure, and the optical axis direction of the small step of the stepped structure of the second basic structure. Length d21 (μm), the length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and the length in the optical axis of the step portion of the first basic structure d1 (μm) satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３λ１＋０．２λ１）／（ｎ－１）
　　（６λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（６λ１＋０．２λ１）／（ｎ－１）
　ただし、ｎは、前記第１光束における前記対物レンズの屈折率を表す。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(6λ1-0.2λ1) / (n−1) ≦ d22 ≦ (6λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

　請求項３に記載の対物レンズは、請求項２に記載の発明において、前記第２光路差付与構造は、３分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 According to a third aspect of the present invention, there is provided the objective lens according to the second aspect, wherein the second optical path difference providing structure is a three-part blazed stepped structure, and has the largest step difference of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５λ１＋０．２λ１）／（ｎ－１）
　請求項４に記載の対物レンズは、請求項１～３のいずれかに記載の発明において、
　｜ｘ｜＝１、｜ｙ｜＝１、｜ｚ｜＝２
であることを特徴とする。 (5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1)
The objective lens according to claim 4 is the invention according to any one of claims 1 to 3,
| X | = 1, | y | = 1, | z | = 2
It is characterized by being.

　請求項５に記載の対物レンズは、請求項１に記載の発明において、前記第２基礎構造は２分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 According to a fifth aspect of the present invention, there is provided the objective lens according to the first aspect, wherein the second basic structure is a two-step staircase structure, and the optical axis direction of a small step of the stepped structure of the second basic structure. Length d21 (μm), the length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and the length in the optical axis of the step portion of the first basic structure d1 (μm) satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（５λ１＋０．２λ１）／（ｎ－１）
　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（５λ１＋０．２λ１）／（ｎ－１）
　ただし、ｎは、前記第１光束における前記対物レンズの屈折率を表す。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(5λ1-0.2λ1) / (n−1) ≦ d21 ≦ (5λ1 + 0.2λ1) / (n−1)
(5λ1-0.2λ1) / (n−1) ≦ d22 ≦ (5λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

　請求項６に記載の対物レンズは、請求項２に記載の発明において、前記第２光路差付与構造は、２分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 The objective lens according to claim 6 is the objective lens according to claim 2, wherein the second optical path difference providing structure is a two-part blazed stepped structure, and has the largest step difference of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５λ１＋０．２λ１）／（ｎ－１）
　請求項７に記載の対物レンズは、請求項１、５又は６のいずれかに記載の発明において、
　｜ｘ｜＝１、｜ｙ｜＝１、｜ｚ｜＝０
であることを特徴とする。 (5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1)
The objective lens according to claim 7 is the invention according to any one of claims 1, 5 and 6,
| X | = 1, | y | = 1, | z | = 0
It is characterized by being.

　請求項８に記載の対物レンズは、請求項１に記載の発明において、前記第２基礎構造は２分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 An objective lens according to an eighth aspect of the present invention is the optical system according to the first aspect, wherein the second basic structure is a two-step staircase structure, and the optical axis direction of the small step of the stepped structure of the second basic structure. Length d21 (μm), the length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and the length in the optical axis of the step portion of the first basic structure d1 (μm) satisfies the following conditional expression.

　　（４．１λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（４．１λ１＋０．４λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３λ１＋０．２λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（３λ１＋０．２λ１）／（ｎ－１）
　ただし、ｎは、前記第１光束における前記対物レンズの屈折率を表す。 (4.1λ1-0.4λ1) / (n−1) ≦ d1 ≦ (4.1λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

　請求項９に記載の対物レンズは、請求項８に記載の発明において、前記第２光路差付与構造は、２分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 The objective lens according to claim 9 is the objective lens according to claim 8, wherein the second optical path difference providing structure is a two-part blazed stepped structure, and has the largest step difference of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（７．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（７．１λ１＋０．２λ１）／（ｎ－１）
　請求項１０に記載の対物レンズは、請求項１、８又は９のいずれかに記載の発明において、
　｜ｘ｜＝４、｜ｙ｜＝２、｜ｚ｜＝３
であることを特徴とする。 (7.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (7.1λ1 + 0.2λ1) / (n−1)
The objective lens according to claim 10 is the invention according to any one of claims 1, 8 and 9,
| X | = 4, | y | = 2, | z | = 3
It is characterized by being.

　請求項１１に記載の対物レンズは、請求項１に記載の発明において、前記第２基礎構造は２分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 An objective lens according to an eleventh aspect is the optical system according to the first aspect, wherein the second basic structure is a two-step staircase structure, and the optical axis direction of the small step of the stepped structure of the second basic structure. Length d21 (μm), the length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and the length in the optical axis of the step portion of the first basic structure d1 (μm) satisfies the following conditional expression.

　　（４λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（４λ１＋０．４λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３λ１＋０．２λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（３λ１＋０．２λ１）／（ｎ－１）
　ただし、ｎは、前記第１光束における前記対物レンズの屈折率を表す。 (4λ1-0.4λ1) / (n−1) ≦ d1 ≦ (4λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

　請求項１２に記載の対物レンズは、請求項１１に記載の発明において、前記第２光路差付与構造は、２分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 The objective lens according to claim 12 is the objective lens according to claim 11, wherein the second optical path difference providing structure is a two-part blazed stepped structure, and has the largest step difference of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（７λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（７λ１＋０．２λ１）／（ｎ－１）
　請求項１３に記載の対物レンズは、請求項１、１１又は１２のいずれかに記載の発明において、
　｜ｘ｜＝４、｜ｙ｜＝２、｜ｚ｜＝１
であることを特徴とする。 (7λ1-0.2λ1) / (n−1) ≦ d0 ≦ (7λ1 + 0.2λ1) / (n−1)
The objective lens according to claim 13 is the invention according to any one of claims 1, 11 and 12,
| X | = 4, | y | = 2, | z | = 1
It is characterized by being.

　請求項１４に記載の対物レンズは、請求項１に記載の発明において、前記第２基礎構造は２分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 The objective lens according to claim 14 is the invention according to claim 1, wherein the second base structure is a two-step staircase structure, and the optical axis direction of a small step of the step structure of the second base structure Length d21 (μm), the length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and the length in the optical axis of the step portion of the first basic structure d1 (μm) satisfies the following conditional expression.

　　（２．１λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（２．１λ１＋０．４λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３λ１＋０．２λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（３λ１＋０．２λ１）／（ｎ－１）
　ただし、ｎは、前記第１光束における前記対物レンズの屈折率を表す。 (2.1λ1-0.4λ1) / (n−1) ≦ d1 ≦ (2.1λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

　請求項１５に記載の対物レンズは、請求項１４に記載の発明において、前記第２光路差付与構造は、２分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 The objective lens according to claim 15 is the objective lens according to claim 14, wherein the second optical path difference providing structure is a two-part blazed stepped structure, and has the largest step difference of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（５．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５．１λ１＋０．２λ１）／（ｎ－１）
　請求項１６に記載の対物レンズは、請求項１、１４又は１５のいずれかに記載の発明において、
　｜ｘ｜＝２、｜ｙ｜＝１、｜ｚ｜＝２
であることを特徴とする。 (5.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5.1λ1 + 0.2λ1) / (n−1)
The objective lens according to claim 16 is the invention according to any one of claims 1, 14 and 15,
| X | = 2, | y | = 1, | z | = 2
It is characterized by being.

　請求項１７に記載の対物レンズは、請求項１に記載の発明において、前記第２基礎構造は２分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 The objective lens according to claim 17 is the objective lens according to claim 1, wherein the second basic structure is a two-stage stepped structure, and the optical axis direction of the small step of the stepped structure of the second basic structure Length d21 (μm), the length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and the length in the optical axis of the step portion of the first basic structure d1 (μm) satisfies the following conditional expression.

　　（２λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（２λ１＋０．４λ１）／（ｎ－１）
　　（３．０５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３．０５λ１＋０．２λ１）／（ｎ－１）
　　（３．０５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（３．０５λ１＋０．２λ１）／（ｎ－１）
　ただし、ｎは、前記第１光束における前記対物レンズの屈折率を表す。 (2λ1−0.4λ1) / (n−1) ≦ d1 ≦ (2λ1 + 0.4λ1) / (n−1)
(3.05λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3.05λ1 + 0.2λ1) / (n−1)
(3.05λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3.05λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

　請求項１８に記載の対物レンズは、請求項１７に記載の発明において、前記第２光路差付与構造は、２分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 The objective lens according to claim 18 is the objective lens according to claim 17, wherein the second optical path difference providing structure is a two-part blazed stepped structure, and has the largest step difference of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（５．０５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５．０５λ１＋０．２λ１）／（ｎ－１）
　請求項１９に記載の対物レンズは、請求項１、１７又は１８のいずれかに記載の発明において、
　｜ｘ｜＝２、｜ｙ｜＝１、｜ｚ｜＝０
であることを特徴とする。 (5.05λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5.05λ1 + 0.2λ1) / (n−1)
The objective lens according to claim 19 is the invention according to any one of claims 1, 17 or 18,
| X | = 2, | y | = 1, | z | = 0
It is characterized by being.

　請求項２０に記載の対物レンズは、請求項１～１９のいずれかに記載の発明において、
　前記対物レンズは、前記周辺領域の周囲に形成された輪帯状の最周辺領域を有し、
　前記中央領域と前記周辺領域と前記最周辺領域を通過した前記第１光束が、前記第１光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、
　前記中央領域と前記周辺領域とを通過した前記第２光束が、前記第２光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、前記最周辺領域を通過した前記第２光束が、前記第２光ディスクの情報記録面上に情報の記録及び／又は再生ができるように集光されず、
　前記中央領域を通過した前記第３光束が、前記第３光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、前記周辺領域と前記最周辺領域を通過した前記第３光束が、前記第３光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光されないことを特徴とする。 The objective lens according to claim 20 is the invention according to any one of claims 1 to 19,
The objective lens has a ring-shaped outermost peripheral region formed around the peripheral region,
The first light flux that has passed through the central area, the peripheral area, and the most peripheral area is condensed so that information can be recorded and / or reproduced on the information recording surface of the first optical disc,
The second light flux that has passed through the central area and the peripheral area is condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc, and the second light flux that has passed through the outermost peripheral area. Two light beams are not condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc,
The third light flux that has passed through the central area is condensed so that information can be recorded and / or reproduced on the information recording surface of the third optical disc, and the third light flux that has passed through the peripheral area and the most peripheral area. The light beam is not focused on the information recording surface of the third optical disc so that information can be recorded and / or reproduced.

　請求項２１に記載の光ピックアップ装置は、第１光源から出射される波長λ１（μｍ）の第１光束を用いて厚さｔ１の保護層を有する第１光ディスクの情報記録面に対して集光スポット形成を行い、第２光源から出射される波長λ２（λ１＜λ２）の第２光束を用いて厚さｔ２（ｔ１≦ｔ２）の保護層を有する第２光ディスクの情報記録面に対して集光スポット形成を行い、第３光源から出射される波長λ３（λ２＜λ３）の第３光束を用いて厚さｔ３（ｔ２＜ｔ３）の保護層を有する第３光ディスクの情報記録面に対して集光スポット形成を行う対物レンズを備えた光ピックアップ装置において、
　前記対物レンズの光学面は、少なくとも、光軸を含む中央領域と、前記中央領域の周囲に形成された輪帯状の周辺領域とを有し、
　前記中央領域と前記周辺領域とを通過した前記第１光束が、前記第１光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、
　前記中央領域と前記周辺領域とを通過した前記第２光束が、前記第２光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、
　前記中央領域を通過した前記第３光束が、前記第３光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、前記周辺領域を通過した前記第３光束が、前記第３光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光されず、
　前記周辺領域には、第２光路差付与構造が形成されており、
　前記第２光路差付与構造は、ブレーズ型構造である第１基礎構造と、階段型構造である第２基礎構造とを、前記第１基礎構造の全ての段差部の位置と前記第２基礎構造の段差部の位置が一致するように重畳させてなり、
　ｘ、ｙ、ｚを任意の整数としたときに、前記第２光路差付与構造に前記第１光束が入射した場合に発生する回折光のうち、ｘ次回折光が最大の回折効率を有し、前記第２光路差付与構造に前記第２光束が入射した場合に発生する回折光のうち、ｙ次回折光が最大の回折効率を有し、前記第２光路差付与構造に前記第３光束が入射した場合に発生する回折光のうち、ｚ次回折光が最大の回折効率を有することを特徴とする。 The optical pickup device according to claim 21 is focused on an information recording surface of a first optical disc having a protective layer having a thickness of t1 using a first light beam having a wavelength λ1 (μm) emitted from a first light source. Spot formation is performed on the information recording surface of the second optical disc having a protective layer having a thickness t2 (t1 ≦ t2) using a second light flux having a wavelength λ2 (λ1 <λ2) emitted from the second light source. With respect to the information recording surface of the third optical disk having a protective layer having a thickness t3 (t2 <t3) using a third light beam having a wavelength λ3 (λ2 <λ3) emitted from the third light source. In an optical pickup device equipped with an objective lens for forming a condensed spot,
The optical surface of the objective lens has at least a central region including an optical axis, and a ring-shaped peripheral region formed around the central region,
The first light flux that has passed through the central region and the peripheral region is condensed so that information can be recorded and / or reproduced on the information recording surface of the first optical disc,
The second light flux that has passed through the central region and the peripheral region is condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc,
The third light flux that has passed through the central region is condensed so that information can be recorded and / or reproduced on the information recording surface of the third optical disc, and the third light flux that has passed through the peripheral region is 3 It is not condensed so that information can be recorded and / or reproduced on the information recording surface of the optical disc,
A second optical path difference providing structure is formed in the peripheral region,
The second optical path difference providing structure includes a first basic structure that is a blaze type structure and a second basic structure that is a staircase type structure, the positions of all the step portions of the first basic structure, and the second basic structure. Is superimposed so that the position of the step part of
Of the diffracted light generated when the first light flux is incident on the second optical path difference providing structure when x, y, z are arbitrary integers, the x-order diffracted light has the maximum diffraction efficiency, Of the diffracted light generated when the second light beam enters the second optical path difference providing structure, the y-order diffracted light has the maximum diffraction efficiency, and the third light beam enters the second optical path difference providing structure. Among the diffracted light generated in this case, the z-th order diffracted light has the maximum diffraction efficiency.

　請求項２２に記載の光ピックアップ装置は、請求項２１に記載の発明において、前記第２基礎構造は３分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 According to a twenty-second aspect of the present invention, in the invention according to the twenty-first aspect, the second basic structure is a three-stage stepped structure, and the optical axis of a small step of the stepped structure of the second basic structure. Length d21 (μm) in the direction, length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and length in the optical axis direction of the step portion of the first basic structure The length d1 (μm) satisfies the following conditional expression.

　請求項２３に記載の光ピックアップ装置は、請求項２２に記載の発明において、前記第２光路差付与構造は、３分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 The optical pickup device according to a twenty-third aspect is the invention according to the twenty-second aspect, wherein the second optical path difference providing structure is a three-part blazed stepped structure, and the largest step of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５λ１＋０．２λ１）／（ｎ－１）。 (5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1).

　請求項２４に記載の光ピックアップ装置は、請求項２１～２３のいずれかに記載の発明において、
　｜ｘ｜＝１、｜ｙ｜＝１、｜ｚ｜＝２
であることを特徴とする。 An optical pickup device according to a twenty-fourth aspect is the invention according to any one of the twenty-first to twenty-third aspects,
| X | = 1, | y | = 1, | z | = 2
It is characterized by being.

　請求項２５に記載の光ピックアップ装置は、請求項２１に記載の発明において、前記第２基礎構造は２分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 An optical pickup device according to a twenty-fifth aspect is the optical pickup apparatus according to the twenty-first aspect, wherein the second basic structure is a two-step staircase structure, and the optical axis of a small step of the stepped structure of the second basic structure. Length d21 (μm) in the direction, length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and length in the optical axis direction of the step portion of the first basic structure The length d1 (μm) satisfies the following conditional expression.

　請求項２６に記載の光ピックアップ装置は、請求項２５に記載の発明において、前記第２光路差付与構造は、２分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 An optical pickup device according to a twenty-sixth aspect is the optical pickup apparatus according to the twenty-fifth aspect, wherein the second optical path difference providing structure is a two-part blazed stepped structure, and the largest step of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５λ１＋０．２λ１）／（ｎ－１）
　請求項２７に記載の光ピックアップ装置は、請求項２１、２５又は２６のいずれかに記載の発明において、
　｜ｘ｜＝１、｜ｙ｜＝１、｜ｚ｜＝０
であることを特徴とする。 (5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1)
The optical pickup device according to claim 27 is the invention according to any one of claims 21, 25, or 26,
| X | = 1, | y | = 1, | z | = 0
It is characterized by being.

　請求項２８に記載の光ピックアップ装置は、請求項２１に記載の発明において、前記第２基礎構造は２分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 An optical pickup device according to a twenty-eighth aspect is the optical pickup device according to the twenty-first aspect, wherein the second basic structure is a two-stage stepped structure, and the optical axis of a small step of the stepped structure of the second basic structure. Length d21 (μm) in the direction, length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and length in the optical axis direction of the step portion of the first basic structure The length d1 (μm) satisfies the following conditional expression.

　請求項２９に記載の光ピックアップ装置は、請求項２８に記載の発明において、前記第２光路差付与構造は、２分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 An optical pickup device according to a twenty-ninth aspect is the invention according to the twenty-eighth aspect, wherein the second optical path difference providing structure is a two-part blazed stepped structure, and the largest step of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（７．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（７．１λ１＋０．２λ１）／（ｎ－１）
　請求項３０に記載の光ピックアップ装置は、請求項２１、２８又は２９のいずれかに記載の発明において、
　｜ｘ｜＝４、｜ｙ｜＝２、｜ｚ｜＝３
であることを特徴とする。 (7.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (7.1λ1 + 0.2λ1) / (n−1)
The optical pickup device according to claim 30 is the invention according to any one of claims 21, 28, or 29,
| X | = 4, | y | = 2, | z | = 3
It is characterized by being.

　請求項３１に記載の光ピックアップ装置は、請求項２１に記載の発明において、前記第２基礎構造は２分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 An optical pickup device according to a thirty-first aspect is the optical pickup device according to the twenty-first aspect, wherein the second basic structure is a two-stage stepped structure, and the optical axis of a small step of the stepped structure of the second basic structure. Length d21 (μm) in the direction, length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and length in the optical axis direction of the step portion of the first basic structure The length d1 (μm) satisfies the following conditional expression.

　請求項３２に記載の光ピックアップ装置は、請求項３１に記載の発明において、前記第２光路差付与構造は、２分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 An optical pickup device according to a thirty-second aspect is the invention according to the thirty-first aspect, wherein the second optical path difference providing structure is a two-part blazed stepped structure, and the largest step of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（７λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（７λ１＋０．２λ１）／（ｎ－１）
　請求項３３に記載の光ピックアップ装置は、請求項２１、３１又は３２のいずれかに記載の発明において、
　｜ｘ｜＝４、｜ｙ｜＝２、｜ｚ｜＝１
であることを特徴とする。 (7λ1-0.2λ1) / (n−1) ≦ d0 ≦ (7λ1 + 0.2λ1) / (n−1)
An optical pickup device according to a thirty-third aspect is the invention according to any one of the twenty-first, thirty-one or thirty-second aspects,
| X | = 4, | y | = 2, | z | = 1
It is characterized by being.

　請求項３４に記載の光ピックアップ装置は、請求項２１に記載の発明において、前記第２基礎構造は２分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 An optical pickup device according to a thirty-fourth aspect is the invention according to the twenty-first aspect, wherein the second basic structure is a two-step staircase structure, and the optical axis of a small step of the stepped structure of the second basic structure. Length d21 (μm) in the direction, length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and length in the optical axis direction of the step portion of the first basic structure The length d1 (μm) satisfies the following conditional expression.

　請求項３５に記載の光ピックアップ装置は、請求項３４に記載の発明において、前記第２光路差付与構造は、２分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 In an optical pickup device according to a thirty-fifth aspect, in the invention according to the thirty-fourth aspect, the second optical path difference providing structure is a two-part blazed stepped structure, and the largest step of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（５．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５．１λ１＋０．２λ１）／（ｎ－１）
　請求項３６に記載の光ピックアップ装置は、請求項２１、３４又は３５のいずれかに記載の発明において、
　｜ｘ｜＝２、｜ｙ｜＝１、｜ｚ｜＝２
であることを特徴とする。 (5.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5.1λ1 + 0.2λ1) / (n−1)
An optical pickup device according to a thirty-sixth aspect is the invention according to any one of the twenty-first, thirty-four and thirty-fifth aspects,
| X | = 2, | y | = 1, | z | = 2
It is characterized by being.

　請求項３７に記載の光ピックアップ装置は、請求項２１に記載の発明において、前記第２基礎構造は２分割の階段型構造であり、前記第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と前記第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、前記第１基礎構造の前記段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たすことを特徴とする。 An optical pickup device according to a thirty-seventh aspect is the optical pickup device according to the twenty-first aspect, wherein the second basic structure is a two-stage stepped structure, and the optical axis of a small step of the stepped structure of the second basic structure. Length d21 (μm) in the direction, length d22 (μm) in the optical axis direction of the large step of the stepped structure of the second basic structure, and length in the optical axis direction of the step portion of the first basic structure The length d1 (μm) satisfies the following conditional expression.

　請求項３８に記載の光ピックアップ装置は、請求項３７に記載の発明において、前記第２光路差付与構造は、２分割のブレーズ階段型構造であり、前記第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）が以下の条件式を満たすことを特徴とする。 The optical pickup device according to a thirty-eighth aspect is the invention according to the thirty-seventh aspect, wherein the second optical path difference providing structure is a two-part blazed stepped structure, and the largest step of the second optical path difference providing structure. The length d0 (μm) in the optical axis direction satisfies the following conditional expression.

　　（５．０５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５．０５λ１＋０．２λ１）／（ｎ－１）
　請求項３９に記載の光ピックアップ装置は、請求項２１、３７又は３８のいずれかに記載の発明において、
　｜ｘ｜＝２、｜ｙ｜＝１、｜ｚ｜＝０
であることを特徴とする。 (5.05λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5.05λ1 + 0.2λ1) / (n−1)
The optical pickup device according to claim 39 is the invention according to any one of claims 21, 37, or 38,
| X | = 2, | y | = 1, | z | = 0
It is characterized by being.

　請求項４０に記載の光ピックアップ装置は、請求項２１～３９のいずれかに記載の発明において、
　前記対物レンズは、前記周辺領域の周囲に形成された輪帯状の最周辺領域を有し、
　前記中央領域と前記周辺領域と前記最周辺領域を通過した前記第１光束が、前記第１光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、
　前記中央領域と前記周辺領域とを通過した前記第２光束が、前記第２光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、前記最周辺領域を通過した前記第２光束が、前記第２光ディスクの情報記録面上に情報の記録及び／又は再生ができるように集光されず、
　前記中央領域を通過した前記第３光束が、前記第３光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光され、前記周辺領域と前記最周辺領域を通過した前記第３光束が、前記第３光ディスクの情報記録面に情報の記録及び／又は再生ができるように集光されないことを特徴とする。
前記第１光束が前記対物レンズに入射する時の、前記対物レンズの結像倍率ｍ１が、下記の式（１）を満たし、前記第２光束が前記対物レンズに入射する時の、前記対物レンズの結像倍率ｍ２が、下記の式（２）を満たし、前記第３光束が前記対物レンズに入射する時の、前記対物レンズの結像倍率ｍ３が、下記の式（３）を満たすことを特徴とする。 The optical pickup device according to claim 40, in the invention according to any one of claims 21 to 39,
The objective lens has a ring-shaped outermost peripheral region formed around the peripheral region,
The first light flux that has passed through the central area, the peripheral area, and the most peripheral area is condensed so that information can be recorded and / or reproduced on the information recording surface of the first optical disc,
The second light flux that has passed through the central area and the peripheral area is condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc, and the second light flux that has passed through the outermost peripheral area. Two light beams are not condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc,
The third light flux that has passed through the central area is condensed so that information can be recorded and / or reproduced on the information recording surface of the third optical disc, and the third light flux that has passed through the peripheral area and the most peripheral area. The light beam is not focused on the information recording surface of the third optical disc so that information can be recorded and / or reproduced.
The objective lens when the imaging magnification m1 of the objective lens satisfies the following expression (1) when the first light beam is incident on the objective lens, and the second light beam is incident on the objective lens. The imaging magnification m2 of the objective lens satisfies the following formula (2), and the imaging magnification m3 of the objective lens when the third light beam enters the objective lens satisfies the following formula (3). Features.

　ｍ１＜０　　　　　（１）
　ｍ２＜０　　　　　（２）
　０＜ｍ３　　　　　（３）
　本発明に係る光ピックアップ装置は、第１光源、第２光源、第３光源の少なくとも３つの光源を有する。さらに、本発明の光ピックアップ装置は、第１光束を第１光ディスクの情報記録面上に集光させ、第２光束を第２光ディスクの情報記録面上に集光させ、第３光束を第３光ディスクの情報記録面上に集光させるための集光光学系を有する。また、本発明の光ピックアップ装置は、第１光ディスク、第２光ディスク又は第３光ディスクの情報記録面からの反射光束を受光する受光素子を有する。このときの第１光ディスクはＢＤ（Ｂｌｕ－ｒａｙ　Ｄｉｓｃ）又はＨＤ　ＤＶＤ（以下、ＨＤと記載）、第２光ディスクはＤＶＤである事が好ましく、第３光ディスクはＣＤであることが好ましいが、これに限られない。第１光ディスク、第２光ディスク、又は第３光ディスクは、複数の情報記録面を有する複数層の光ディスクでもよい。 m1 <0 (1)
m2 <0 (2)
0 <m3 (3)
The optical pickup device according to the present invention has at least three light sources: a first light source, a second light source, and a third light source. Furthermore, the optical pickup device of the present invention condenses the first light flux on the information recording surface of the first optical disc, condenses the second light flux on the information recording surface of the second optical disc, and causes the third light flux to be third. It has a condensing optical system for condensing on the information recording surface of the optical disc. The optical pickup device of the present invention includes a light receiving element that receives a reflected light beam from the information recording surface of the first optical disc, the second optical disc, or the third optical disc. At this time, the first optical disc is preferably a BD (Blu-ray Disc) or HD DVD (hereinafter referred to as HD), the second optical disc is preferably a DVD, and the third optical disc is preferably a CD. Not limited. The first optical disc, the second optical disc, or the third optical disc may be a multi-layer optical disc having a plurality of information recording surfaces.

　ＢＤは、ＮＡ０．８５の対物レンズにより情報の記録／再生が行われ、保護基板の厚さが０．１ｍｍ程度である。また、ＨＤは、ＮＡ０．６５乃至０．６７の対物レンズにより情報の記録／再生が行われ、保護基板の厚さが０．６ｍｍ程度である。更に、ＤＶＤとは、ＮＡ０．６０～０．６７程度の対物レンズにより情報の記録／再生が行われ、保護基板の厚さが０．６ｍｍ程度であるＤＶＤ系列光ディスクの総称であり、ＤＶＤ－ＲＯＭ、ＤＶＤ－Ｖｉｄｅｏ、ＤＶＤ－Ａｕｄｉｏ、ＤＶＤ－ＲＡＭ、ＤＶＤ－Ｒ、ＤＶＤ－ＲＷ、ＤＶＤ＋Ｒ、ＤＶＤ＋ＲＷ等を含む。また、本明細書においては、ＣＤとは、ＮＡ０．４５～０．５３程度の対物レンズにより情報の記録／再生が行われ、保護基板の厚さが１．２ｍｍ程度であるＣＤ系列光ディスクの総称であり、ＣＤ－ＲＯＭ、ＣＤ－Ａｕｄｉｏ、ＣＤ－Ｖｉｄｅｏ、ＣＤ－Ｒ、ＣＤ－ＲＷ等を含む。尚、記録密度については、ＢＤの記録密度が最も高く、次いでＨＤ、ＤＶＤ、ＣＤの順に低くなる。 BD records and reproduces information with an objective lens with NA of 0.85, and the thickness of the protective substrate is about 0.1 mm. In the HD, information is recorded / reproduced by an objective lens having NA of 0.65 to 0.67, and the thickness of the protective substrate is about 0.6 mm. Further, DVD is a general term for DVD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.60 to 0.67, and the thickness of the protective substrate is about 0.6 mm. DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW, and the like. In this specification, CD is a generic name for CD-series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.45 to 0.53, and the thickness of the protective substrate is about 1.2 mm. Including CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW and the like. As for the recording density, the recording density of BD is the highest, followed by HD, DVD, and CD in that order.

　なお、保護基板の厚さｔ１、ｔ２、ｔ３に関しては、以下の条件式（４）、（５）、（６）を満たすことが好ましいが、これに限られない。 In addition, regarding the thicknesses t1, t2, and t3 of the protective substrate, it is preferable to satisfy the following conditional expressions (4), (5), and (6), but is not limited thereto.

　０．０７５０ｍｍ≦ｔ１≦０．１１２５ｍｍ　又は　０．５ｍｍ≦ｔ１≦０．７ｍｍ　　　　　　　　　　　　　　　　（４）
　０．５ｍｍ≦ｔ２≦０．７ｍｍ　　　　　　（５）
　１．０ｍｍ≦ｔ３≦１．３ｍｍ　　　　　　（６）
　本明細書において、第１光源、第２光源、第３光源は、好ましくはレーザ光源である。
レーザ光源としては、好ましくは半導体レーザ、シリコンレーザ等を用いることが出来る。第１光源から出射される第１光束の第１波長λ１、第２光源から出射される第２光束の第２波長λ２（λ２＞λ１）、第３光源から出射される第３光束の第３波長λ３（λ３＞λ２）は以下の条件式（７）、（８）を満たすことが好ましい。 0.0750 mm ≦ t1 ≦ 0.1125 mm or 0.5 mm ≦ t1 ≦ 0.7 mm (4)
0.5mm ≦ t2 ≦ 0.7mm (5)
1.0mm ≦ t3 ≦ 1.3mm (6)
In the present specification, the first light source, the second light source, and the third light source are preferably laser light sources.
As the laser light source, a semiconductor laser, a silicon laser, or the like can be preferably used. The first wavelength λ1 of the first light beam emitted from the first light source, the second wavelength λ2 (λ2> λ1) of the second light beam emitted from the second light source, and the third of the third light beam emitted from the third light source. The wavelength λ3 (λ3> λ2) preferably satisfies the following conditional expressions (7) and (8).

　１．５×λ１＜λ２＜１．７×λ１　　　　（７）
　１．９×λ１＜λ３＜２．１×λ１　　　　（８）
　また、第１光ディスク、第２光ディスク、第３光ディスクとして、それぞれ、ＢＤ又はＨＤ、ＤＶＤ及びＣＤが用いられる場合、第１光源の第１波長λ１は好ましくは、０．３５μｍ以上、０．４４μｍ以下、より好ましくは、０．３８μｍ以上、０．４１５μｍ以下であって、第２光源の第２波長λ２は好ましくは０．５７μｍ以上、０．６８μｍ以下、より好ましくは０．６３μｍ以上、０．６７μｍ以下であって、第３光源の第３波長λ３は好ましくは、０．７５μｍ以上、０．８８μｍ以下、より好ましくは、０．７６μｍ以上、０．８２μｍ以下である。 1.5 × λ1 <λ2 <1.7 × λ1 (7)
1.9 × λ1 <λ3 <2.1 × λ1 (8)
In addition, when BD or HD, DVD, and CD are used as the first optical disc, the second optical disc, and the third optical disc, respectively, the first wavelength λ1 of the first light source is preferably 0.35 μm or more and 0.44 μm or less. More preferably, it is 0.38 μm or more and 0.415 μm or less, and the second wavelength λ2 of the second light source is preferably 0.57 μm or more and 0.68 μm or less, more preferably 0.63 μm or more and 0.67 μm. The third wavelength λ3 of the third light source is preferably 0.75 μm or more and 0.88 μm or less, more preferably 0.76 μm or more and 0.82 μm or less.

　また、第１光源、第２光源、第３光源のうち少なくとも２つの光源をユニット化してもよい。ユニット化とは、例えば第１光源と第２光源とが１パッケージに固定収納されているようなものをいう。また、光源に加えて、後述する受光素子を１パッケージ化してもよい。 Also, at least two of the first light source, the second light source, and the third light source may be unitized. The unitization means that the first light source and the second light source are fixedly housed in one package, for example. In addition to the light source, a light receiving element to be described later may be packaged.

　受光素子としては、フォトダイオードなどの光検出器が好ましく用いられる。光ディスクの情報記録面上で反射した光が受光素子へ入射し、その出力信号を用いて、各光ディスクに記録された情報の読み取り信号が得られる。さらに、受光素子上のスポットの形状変化、位置変化による光量変化を検出して、合焦検出やトラック検出を行い、この検出に基づいて、合焦、トラッキングのために対物レンズを移動させることが出来る。受光素子は、複数の光検出器からなっていてもよい。受光素子は、メインの光検出器とサブの光検出器を有していてもよい。例えば、情報の記録再生に用いられるメイン光を受光する光検出器の両脇に２つのサブの光検出器を設け、当該２つのサブの光検出器によってトラッキング調整用のサブ光を受光するような受光素子としてもよい（いわゆる３ビーム法）。また、受光素子は各光源に対応した複数の受光素子を有していてもよい。 As the light receiving element, a photodetector such as a photodiode is preferably used. Light reflected on the information recording surface of the optical disc enters the light receiving element, and a read signal of information recorded on each optical disc is obtained using the output signal. Furthermore, it detects the change in the light amount due to the spot shape change and position change on the light receiving element, performs focus detection and track detection, and based on this detection, the objective lens can be moved for focusing and tracking I can do it. The light receiving element may comprise a plurality of photodetectors. The light receiving element may have a main photodetector and a sub photodetector. For example, two sub photodetectors are provided on both sides of a photodetector that receives main light used for recording and reproducing information, and the sub light for tracking adjustment is received by the two sub photodetectors. A light receiving element may be used (so-called three beam method). The light receiving element may have a plurality of light receiving elements corresponding to the respective light sources.

　集光光学系は、対物レンズを有する。集光光学系は、対物レンズのみを有していても良いが、集光光学系は、対物レンズの他にコリメータ等のカップリングレンズを有していてもよい。カップリングレンズとは、対物レンズと光源の間に配置され、光束の発散角を変える単レンズ又はレンズ群のことをいう。コリメータは、カップリングレンズの一種で、コリメータに入射した光を平行光にして出射するレンズである。更に集光光学系は、光源から射出された光束を、情報の記録再生に用いられるメイン光束と、トラッキング等に用いられる二つのサブ光束とに分割する回折光学素子などの光学素子を有していてもよい。本明細書において、対物レンズとは、光ピックアップ装置において光ディスクに対向する位置に配置され、光源から射出された光束を光ディスクの情報記録面上に集光する機能を有する光学系を指す。好ましくは、対物レンズとは、光ピックアップ装置において光ディスクに対向する位置に配置され、光源から射出された光束を光ディスクの情報記録面上に集光する機能を有する光学系であって、更に、アクチュエータにより少なくとも光軸方向に一体的に変位可能とされた光学系を指す。対物レンズは、好ましくは単玉の対物レンズであるが、複数の光学素子から形成されていても良い。また、対物レンズは、ガラスレンズであってもプラスチックレンズであっても、又は、ガラスレンズの上に光硬化性樹脂などで光路差付与構造などを設けたハイブリッドレンズであってもよい。また、対物レンズは、屈折面が非球面であることが好ましい。また、対物レンズは、光路差付与構造が設けられるベース面が非球面であることが好ましい。 The condensing optical system has an objective lens. The condensing optical system may include only the objective lens, but the condensing optical system may include a coupling lens such as a collimator in addition to the objective lens. The coupling lens is a single lens or a lens group that is disposed between the objective lens and the light source and changes the divergence angle of the light beam. The collimator is a type of coupling lens, and is a lens that emits light incident on the collimator as parallel light. Further, the condensing optical system has an optical element such as a diffractive optical element that divides the light beam emitted from the light source into a main light beam used for recording and reproducing information and two sub light beams used for tracking and the like. May be. In this specification, the objective lens refers to an optical system that is disposed at a position facing the optical disk in the optical pickup device and has a function of condensing the light beam emitted from the light source onto the information recording surface of the optical disk. Preferably, the objective lens is an optical system which is disposed at a position facing the optical disk in the optical pickup device and has a function of condensing a light beam emitted from the light source on the information recording surface of the optical disk, and further includes an actuator An optical system that can be integrally displaced at least in the optical axis direction. The objective lens is preferably a single objective lens, but may be formed of a plurality of optical elements. The objective lens may be a glass lens, a plastic lens, or a hybrid lens in which an optical path difference providing structure or the like is provided on a glass lens with a photocurable resin or the like. The objective lens preferably has a refractive surface that is aspheric. In the objective lens, the base surface on which the optical path difference providing structure is provided is preferably an aspherical surface.

　また、対物レンズをガラスレンズとする場合は、ガラス転移点Ｔｇが４００℃以下であるガラス材料を使用することが好ましい。ガラス転移点Ｔｇが４００℃以下であるガラス材料を使用することにより、比較的低温での成形が可能となるので、金型の寿命を延ばすことが出来る。このようなガラス転移点Ｔｇが低いガラス材料としては、例えば（株）住田光学ガラス製のＫ－ＰＧ３２５や、Ｋ－ＰＧ３７５（共に製品名）がある。 Further, when the objective lens is a glass lens, it is preferable to use a glass material having a glass transition point Tg of 400 ° C. or lower. By using a glass material having a glass transition point Tg of 400 ° C. or lower, molding at a relatively low temperature becomes possible, so that the life of the mold can be extended. 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.

　ところで、ガラスレンズは一般的に樹脂レンズよりも比重が大きいため、対物レンズをガラスレンズとすると、重量が大きくなり対物レンズを駆動するアクチュエータに負担がかかる。そのため、対物レンズをガラスレンズとする場合には、比重が小さいガラス材料を使用するのが好ましい。具体的には、比重が３．０以下であるのが好ましく、２．８以下であるのがより好ましい。 By the way, since the specific gravity of the glass lens is generally larger than that of the resin lens, if the objective lens is a glass lens, the weight increases and a load is imposed on the actuator that drives the objective lens. Therefore, when the objective lens is a glass lens, it is preferable to use a glass material having a small specific gravity. Specifically, the specific gravity is preferably 3.0 or less, and more preferably 2.8 or less.

　また、対物レンズをプラスチックレンズとする場合は、環状オレフィン系の樹脂材料を使用するのが好ましく、環状オレフィン系の中でも、波長４０５ｎｍに対する温度２５℃での屈折率が１．５２乃至１．６０の範囲内であって、－５℃から７０℃の温度範囲内での温度変化に伴う波長４０５ｎｍに対する屈折率変化率ｄＮ／ｄＴ（℃^-1）が－２０×１０^-5乃至－５×１０^-5（より好ましくは、－１０×１０^-5乃至－８×１０^-5）の範囲内である樹脂材料を使用するのがより好ましい。また、対物レンズをプラスチックレンズとする場合、カップリングレンズもプラスチックレンズとすることが好ましい。 When the objective lens is a plastic lens, it is preferable to use a cyclic olefin-based resin material. Among the cyclic olefin-based materials, the refractive index at a temperature of 25 ° C. with respect to a wavelength of 405 nm is 1.52 to 1.60. The refractive index change rate dN / dT (° C. ⁻¹ ) is −20 × 10 ^{−5 to} −5 × 10 ^{− with} respect to the wavelength of 405 nm accompanying the temperature change within the range of −5 ° C. to 70 ° C. ^It is more preferable to use a resin material in the range of ⁵ (more preferably, −10 × 10 ^{−5 to} −8 × 10 ⁻⁵ ). When the objective lens is a plastic lens, the coupling lens is preferably a plastic lens.

　対物レンズについて、以下に記載する。対物レンズの少なくとも一つの光学面が、中央領域と、中央領域の周りの周辺領域とを有する。対物レンズの少なくとも一つの光学面が、周辺領域の周りに最周辺領域を有していてもよい。中央領域は、対物レンズの光軸を含む領域であることが好ましいが、含まない領域であってもよい。中央領域、周辺領域、及び最周辺領域は同一の光学面上に設けられていることが好ましい。図１に示されるように、中央領域ＣＮ、周辺領域ＭＤ、最周辺領域ＯＴは、同一の光学面上に、光軸を中心とする同心円状に設けられていることが好ましい。また、対物レンズの中央領域には第１光路差付与構造が設けられることが好ましい。また、周辺領域には第２光路差付与構造が設けられていてもよい。最周辺領域を有する場合、最周辺領域は屈折面であってもよいし、最周辺領域に第３光路差付与構造が設けられていてもよい。中央領域、周辺領域、最周辺領域はそれぞれ隣接していることが好ましいが、間に僅かに隙間があっても良い。 The objective lens is described below. At least one optical surface of the objective lens has a central region and a peripheral region around the central region. At least one optical surface of the objective lens may have an outermost peripheral region around the peripheral region. The central region is preferably a region including the optical axis of the objective lens, but may be a region not including the optical axis. It is preferable that the central region, the peripheral region, and the most peripheral region are provided on the same optical surface. As shown in FIG. 1, the central region CN, the peripheral region MD, and the most peripheral region OT are preferably provided concentrically around the optical axis on the same optical surface. Moreover, it is preferable that a first optical path difference providing structure is provided in the central region of the objective lens. Further, a second optical path difference providing structure may be provided in the peripheral region. In the case of having the outermost peripheral region, the outermost peripheral region may be a refractive surface, or the third optical path difference providing structure may be provided in the outermost peripheral region. The central region, the peripheral region, and the outermost peripheral region are preferably adjacent to each other, but there may be a slight gap between them.

　第１光路差付与構造は、対物レンズの中央領域の面積の７０％以上の領域に設けられていることが好ましく、９０％以上がより好ましい。より好ましくは、第１光路差付与構造が、中央領域の全面に設けられていることである。第２光路差付与構造は、対物レンズの周辺領域の面積の７０％以上の領域に設けられていることが好ましく、９０％以上がより好ましい。より好ましくは、第２光路差付与構造が、周辺領域の全面に設けられていることである。第３光路差付与構造は、対物レンズの最周辺領域の面積の７０％以上の領域に設けられていることが好ましく、９０％以上がより好ましい。より好ましくは、第３光路差付与構造が、最周辺領域の全面に設けられていることである。 The first optical path difference providing structure is preferably provided in a region of 70% or more of the area of the central region of the objective lens, and more preferably 90% or more. More preferably, the first optical path difference providing structure is provided on the entire surface of the central region. The second optical path difference providing structure is preferably provided in a region of 70% or more of the area of the peripheral region of the objective lens, and more preferably 90% or more. More preferably, the second optical path difference providing structure is provided on the entire surface of the peripheral region. The third optical path difference providing structure is preferably provided in a region of 70% or more of the area of the outermost peripheral region of the objective lens, and more preferably 90% or more. More preferably, the third optical path difference providing structure is provided on the entire surface of the outermost peripheral region.

　なお、本明細書でいう光路差付与構造とは、入射光束に対して光路差を付加する構造の総称である。光路差付与構造には、位相差を付与する位相差付与構造も含まれる。また、位相差付与構造には回折構造が含まれる。本願発明の光路差付与構造は、回折構造であるといえる。光路差付与構造は、段差を有し、好ましくは段差を複数有する。この段差により入射光束に光路差及び／又は位相差が付加される。光路差付与構造により付加される光路差は、入射光束の波長の整数倍であっても良いし、入射光束の波長の非整数倍であっても良い。段差は、光軸垂直方向に周期的な間隔をもって配置されていてもよいし、光軸垂直方向に非周期的な間隔をもって配置されていてもよい。 In addition, the optical path difference providing structure referred to in this specification is a general term for structures that add an optical path difference to an incident light beam. The optical path difference providing structure also includes a phase difference providing structure for providing a phase difference. The phase difference providing structure includes a diffractive structure. It can be said that the optical path difference providing structure of the present invention is a diffractive structure. The optical path difference providing structure has a step, preferably a plurality of steps. This step adds an optical path difference and / or phase difference to the incident light flux. The optical path difference added by the optical path difference providing structure may be an integer multiple of the wavelength of the incident light beam or a non-integer multiple of the wavelength of the incident light beam. The steps may be arranged with a periodic interval in the direction perpendicular to the optical axis, or may be arranged with a non-periodic interval in the direction perpendicular to the optical axis.

　光路差付与構造は、光軸を中心とする同心円状の複数の輪帯を有することが好ましい。また、光路差付与構造は、様々な断面形状（光軸を含む面での断面形状）をとり得る。特に、第２光路差付与構造は、光軸を含む断面形状がブレーズ型構造である第１基礎構造と、光軸を含む断面形状が階段型構造である第２基礎構造とを重畳させたものが好ましい。 It is preferable that the optical path difference providing structure has a plurality of concentric annular zones centered on the optical axis. In addition, the optical path difference providing structure can have various cross-sectional shapes (cross-sectional shapes in a plane including the optical axis). In particular, the second optical path difference providing structure is obtained by superimposing the first basic structure whose cross-sectional shape including the optical axis is a blazed structure and the second basic structure whose cross-sectional shape including the optical axis is a stepped structure. Is preferred.

　ブレーズ型構造とは、図２（ａ）、（ｂ）に示されるように、光路差付与構造を有する光学素子の光軸を含む断面形状が、鋸歯状の形状ということであり、別の言い方としては、光路差付与構造がベース面に対して、直角でも平行でもない、斜めの面を有するということである。また、階段型構造とは、図２（ｃ）に示されるように、光路差付与構造を有する光学素子の光軸を含む断面形状が、小階段状のものを複数有するということであり、別の言い方としては、光路差付与構造がベース面に対して平行な面と光軸に対して平行な面のみを有し、ベース面に対して斜めの面を有さず、ベース面の方向に進むに従って、段階的に光軸方向の長さが変化する小構造を複数有するということである。また、基礎構造が階段型構造である場合、ベース面が曲率を有する面であると、ベース面において光線が屈折するため光軸からの距離ごとに屈折角度が異なるという現象が生じる。そのため、ベース面を光軸方向に平行にシフトすることにより階段型構造を得るよりも、光線の進む方向にベース面を同じ光路長分シフトすることにより階段型構造を得る事が好ましい。尚、本明細書中、「Ｘ分割」とは、１つの階段型構造の光軸垂直方向に対応する（向いた）輪帯状の面が、段差によって区分けされＸ個に分割されていることをいい、「小さい段差」とは、１つの階段型構造において、最も小さな光軸方向の段差をいい、「大きな段差」とは、１つの階段型構造において、最も大きな光軸方向の段差をいうものとする。 As shown in FIGS. 2 (a) and 2 (b), the blazed structure means that the cross-sectional shape including the optical axis of an optical element having an optical path difference providing structure is a sawtooth shape. In other words, the optical path difference providing structure has an oblique surface that is neither perpendicular nor parallel to the base surface. Further, as shown in FIG. 2 (c), the staircase structure means that the cross-sectional shape including the optical axis of the optical element having the optical path difference providing structure has a plurality of small staircase shapes. In other words, the optical path difference providing structure has only a surface parallel to the base surface and a surface parallel to the optical axis, and does not have an oblique surface with respect to the base surface. This means that it has a plurality of small structures whose length in the optical axis direction changes step by step. Further, when the base structure is a stepped structure, if the base surface is a surface having a curvature, a light beam is refracted on the base surface, so that a refraction angle varies depending on the distance from the optical axis. For this reason, it is preferable to obtain a stepped structure by shifting the base surface by the same optical path length in the light traveling direction, rather than shifting the base surface parallel to the optical axis direction. In the present specification, “X division” means that a ring-shaped surface corresponding to (or facing) the vertical direction of the optical axis of one staircase structure is divided by steps and divided into X pieces. “Small step” means the smallest step in the optical axis direction in one staircase structure, and “large step” means the largest step in the optical axis direction in one staircase structure. And

　第１基礎構造と第２基礎構造とを重畳する場合、第１基礎構造に、第１基礎構造とは異なる第２基礎構造を、第１基礎構造の全ての段差部の位置と第２基礎構造の段差部の位置が一致するように重畳することが好ましい。好ましい態様としては、図３（ａ）に示すブレーズ型構造の最も深くなる位置Ｐ１と、図３（ｂ）に示す階段型構造の最も深くなる位置Ｐ２とを一致させて重畳することをいう。これにより、図３（ｃ）に示す第１光路差付与構造を得ることができる。このように、ブレーズ型構造と階段型構造とをブレーズ型の段差の位置と階段型構造の大きな段差の位置とを一致させて重畳させて得られる図３（ｃ）のような構造を、本明細書においてブレーズ型階段構造と称する。ブレーズ型階段構造は、光路差付与構造がベース面に対して斜めの面と光軸に対して平行な面を有し、ベース面の方向に進むに従って、段階的に光軸方向の長さが変化する小構造を複数有する構造である。なお、第１基礎構造の一単位の輪帯に対して、第２基礎構造の複数単位の輪帯を重畳させても良い。また、第２基礎構造の段差部の全ての位置が第１基礎構造の段差部の位置と一致していなくてもよい。即ち、第２基礎構造の段差部の中には、第１基礎構造の段差部の位置と一致しないものがあってもよい。第１光路差付与構造及び第３光路差付与構造は、基礎構造を重畳させても重畳させなくても良く、この場合には図２や図３に示す任意の形状の構造を採りうる。 When the first foundation structure and the second foundation structure are overlapped, the second foundation structure different from the first foundation structure is placed on the first foundation structure, the positions of all the step portions of the first foundation structure, and the second foundation structure. It is preferable to superimpose so that the position of the level | step-difference part matches. As a preferred mode, the deepest position P1 of the blaze structure shown in FIG. 3A and the deepest position P2 of the staircase structure shown in FIG. Thereby, the 1st optical path difference providing structure shown in FIG.3 (c) can be obtained. Thus, the structure as shown in FIG. 3C obtained by superimposing the blaze type structure and the staircase type structure with the position of the blaze type step and the position of the large step of the staircase structure being coincident with each other is obtained. In the specification, it is referred to as a blaze-type step structure. The blazed staircase structure has an optical path difference providing structure that has an oblique surface with respect to the base surface and a surface parallel to the optical axis. A structure having a plurality of small structures that change. Note that a plurality of unit zones of the second foundation structure may be superimposed on one unit zone of the first foundation structure. Further, not all the positions of the step portions of the second foundation structure need to coincide with the positions of the step portions of the first foundation structure. That is, some of the step portions of the second foundation structure may not coincide with the position of the step portion of the first foundation structure. The first optical path difference providing structure and the third optical path difference providing structure may or may not overlap the basic structure. In this case, a structure having an arbitrary shape shown in FIGS. 2 and 3 can be adopted.

　尚、光路差付与構造又は基礎構造は、ある単位形状が周期的に繰り返されている構造であることが好ましい。ここでいう「単位形状が周期的に繰り返されている」とは、同一の形状が同一の周期で繰り返されている形状は当然含む。さらに、周期の１単位となる単位形状が、規則性を持って、周期が徐々に長くなったり、徐々に短くなったりする形状も、「単位形状が周期的に繰り返されている」ものに含まれているとする。 It should be noted that the optical path difference providing structure or the basic structure is preferably a structure in which a certain unit shape is periodically repeated. As used herein, “unit shape is periodically repeated” naturally includes shapes in which the same shape is repeated in the same cycle. In addition, the unit shape that is one unit of the cycle has regularity, and the shape in which the cycle gradually increases or decreases gradually is also included in the “unit shape is periodically repeated”. Suppose that

　光路差付与構造又は基礎構造が、ブレーズ型構造を有する場合、単位形状である鋸歯状の形状が繰り返された形状となる。図２（ａ）に示されるように、同一の鋸歯状形状が繰り返されてもよいし、図２（ｂ）に示されるように、ベース面の方向に進むに従って、徐々に鋸歯状形状の大きさが大きくなっていく形状、又は、小さくなっていく形状であってもよい。また、徐々に鋸歯状形状の大きさが大きくなった形状と、徐々に鋸歯状形状の大きさが小さくなっていく形状を組み合わせた形状としてもよい。但し、鋸歯状形状の大きさが徐々に変化する場合であっても、鋸歯状形状において、光軸方向（又は通過する光線の方向）の大きさはほとんど変化しないことが好ましい。なお、ブレーズ型構造において、１つの鋸歯状形状の光軸方向の長さ（鋸歯状形状を通過する光線の方向の長さとしてもよい）を、ピッチ深さといい、１つの鋸歯状形状の光軸垂直方向の長さをピッチ幅という。加えて、ある領域においては、ブレーズ型構造の段差が光軸（中心）側とは逆を向いている形状とし、他の領域においては、ブレーズ型構造の段差が光軸（中心）側を向いている形状とし、その間に、ブレーズ型構造の段差の向きを切り替えるために必要な遷移領域が設けられている形状としてもよい。この遷移領域は、光路差付与構造である光路差付与構造により付加される光路差を光路差関数で表現した時、光路差関数の極値となる点に相当する領域である。なお、光路差関数が極値となる点を持つと、光路差関数の傾きが小さくなるので、輪帯ピッチを広げることが可能となり、光路差付与構造の形状誤差による透過率低下を抑制できる。 When the optical path difference providing structure or the basic structure has a blazed structure, the sawtooth shape as a unit shape is repeated. As shown in FIG. 2 (a), the same sawtooth shape may be repeated, and as shown in FIG. 2 (b), the size of the sawtooth shape gradually increases as it goes in the direction of the base surface. It may be a shape that increases in size or a shape that decreases. Moreover, it is good also as a shape which combined the shape where the magnitude | size of the serrated shape became large gradually and the shape where the magnitude | size of a serrated shape becomes small gradually. However, even in the case where the size of the serrated shape changes gradually, it is preferable that the size in the optical axis direction (or the direction of the passing light beam) hardly changes in the serrated shape. In the blazed structure, the length in the optical axis direction of one sawtooth shape (may be the length in the direction of the light beam passing through the sawtooth shape) is referred to as the pitch depth, and one sawtooth shape light. The length in the direction perpendicular to the axis is called the pitch width. In addition, in some areas, the blazed structure has a step opposite to the optical axis (center) side, and in other areas, the blazed structure has a step toward the optical axis (center). It is good also as a shape in which the transition area | region required in order to switch the direction of the level | step difference of a blaze | braze type | mold structure is provided in the meantime. This transition region is a region corresponding to a point that becomes an extreme value of the optical path difference function when the optical path difference added by the optical path difference providing structure, which is an optical path difference providing structure, is expressed by an optical path difference function. If the optical path difference function has an extreme point, the inclination of the optical path difference function becomes small, so that the annular zone pitch can be widened, and the decrease in transmittance due to the shape error of the optical path difference providing structure can be suppressed.

　光路差付与構造又は基礎構造が、階段型構造を有する場合、単位形状である、階段形状が繰り返された形状となる。図２（ｃ）で示されるような数段（例えば、図２（ｃ）に示す様に５分割の構造）の同一の小階段形状が、繰り返されるような形状等があり得る。さらに、ベース面の方向に進むに従って、徐々に階段の大きさが大きくなっていく形状や、徐々に階段の大きさが小さくなっていく形状であってもよいが、光軸方向（又は通過する光線の方向）の長さはほとんど変化しないことが好ましい。 When the optical path difference providing structure or the basic structure has a staircase structure, the shape is a unit shape, which is a repeated staircase shape. There may be a shape in which the same small staircase shape of several stages (for example, a structure of five divisions as shown in FIG. 2C) is repeated as shown in FIG. Furthermore, the shape of the staircase may gradually increase in size as it proceeds in the direction of the base surface, or the shape of the staircase may gradually decrease in size. It is preferable that the length of the direction of light) hardly changes.

　光路差付与構造が、図２（ｄ）に示されるようにバイナリ状の形状（この様な構造は、２分割の階段型構造とも言える）を有する場合、ベース面の方向に進むに従って、徐々にバイナリの大きさが大きくなっていく形状や、徐々に階段の大きさが小さくなっていく形状であってもよいが、通過する光線の方向の長さはほとんど変化しないことが好ましい。 When the optical path difference providing structure has a binary shape as shown in FIG. 2D (such a structure can be said to be a two-step staircase structure), the optical path difference providing structure gradually increases in the direction of the base surface. A shape in which the size of the binary increases or a shape in which the size of the staircase gradually decreases may be used, but it is preferable that the length of the light beam passing through hardly changes.

　次に、様々な第２光路差付与構造の例について、図６～図２６を用い、より詳細に説明する。第１光路差付与構造として２種類の基礎構造を重畳させたものを用いる場合、以下に詳述する第２光路差付与構造の説明を、第１光路差付与構造にも適用することが出来る。尚、以下の例で示すｘ、ｙ、ｚとは、第２光路差付与構造に第１光束が入射した場合に発生する回折光のうち、最大の回折効率を有する回折光の回折次数をｘ次、第２光路差付与構造に第２光束が入射した場合に発生する回折光のうち、最大の回折効率を有する回折光の回折次数をｙ次、第２光路差付与構造に第３光束が入射した場合に発生する回折光のうち、最大の回折効率を有する回折光の回折次数をｚ次としたときの整数ｘ、ｙ、ｚを表している。 Next, examples of various second optical path difference providing structures will be described in more detail with reference to FIGS. When a structure in which two types of basic structures are superimposed is used as the first optical path difference providing structure, the description of the second optical path difference providing structure described in detail below can be applied to the first optical path difference providing structure. In the following examples, x, y, and z are diffraction orders of diffracted light having the maximum diffraction efficiency among diffracted lights generated when the first light flux is incident on the second optical path difference providing structure x. Next, among the diffracted light generated when the second light beam enters the second optical path difference providing structure, the diffraction order of the diffracted light having the maximum diffraction efficiency is set to the yth order, and the third light beam is applied to the second optical path difference providing structure. Of the diffracted light generated when incident, the integers x, y, and z are expressed when the diffraction order of the diffracted light having the maximum diffraction efficiency is the zth order.

　（第２光路差付与構造　例１）
　例１においては、図６（ｂ）に示すように階段型構造である第２基礎構造は４分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図６（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 1)
In Example 1, as shown in FIG.6 (b), the 2nd foundation structure which is a staircase type structure is a 4 stepped staircase structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 6A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having a blaze structure satisfies the following conditional expression.

　　（１．２λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（１．２λ１＋０．４λ１）／（ｎ－１）
　　（１．２５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．２５λ１＋０．２λ１）／（ｎ－１）
　　（３．７５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（３．７５λ１＋０．２λ１）／（ｎ－１）
　ただし、ｎは、第１光束における対物レンズの屈折率を表す。 (1.2λ1-0.4λ1) / (n−1) ≦ d1 ≦ (1.2λ1 + 0.4λ1) / (n−1)
(1.25λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.25λ1 + 0.2λ1) / (n−1)
(3.75λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3.75λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

　尚、上記の式は、第１基礎構造の光軸方向の段差量ｄ１が第１光束の波長λ１に対して、１．２λ１±０．４・λ１の光路差を与えるような段差量であることを意味しているとも言える。また、第２基礎構造の小さな光軸方向の段差量ｄ２１が第１光束の波長λ１に対して、１．２５λ１±０．２・λ１の光路差を与えるような段差量であって、第２基礎構造の大きな光軸方向の段差量ｄ２２が第１光束の波長λ１に対して、３．７５λ１±０．２・λ１の光路差を与えるような段差量であることを意味しているとも言える。 Note that the above equation is such a step amount that the step amount d1 in the optical axis direction of the first basic structure gives an optical path difference of 1.2λ1 ± 0.4 · λ1 with respect to the wavelength λ1 of the first light flux. It can be said that it means. Further, the small step amount d21 in the optical axis direction of the second basic structure is a step amount that gives an optical path difference of 1.25λ1 ± 0.2 · λ1 to the wavelength λ1 of the first light flux, It can be said that the step amount d22 in the optical axis direction having a large basic structure is a step amount that gives an optical path difference of 3.75λ1 ± 0.2 · λ1 to the wavelength λ1 of the first light flux. .

　尚、第１基礎構造のようなブレーズ型構造の光路差付与構造において、回折効率は以下の数１に示すような式に基づいて計算することが可能である。 In the blazed optical path difference providing structure such as the first basic structure, the diffraction efficiency can be calculated based on the following equation (1).

　尚、ηm：回折次数ｍでの回折効率、λ：波長、n(λ) ：λでの屈折率、ｍ：回折次数、λB：基準波長（ブレーズ化波長）、n(λB)：λBでの屈折率、ｍB：ブレーズ化の回折次数を表す。また、段差の光軸方向の段差量ｄと回折次数ｍの関係は、ｍ＝（ｎ－１）・ｄ／λで表すことが可能である。 Ηm: diffraction efficiency at diffraction order m, λ: wavelength, n (λ): refractive index at λ, m: diffraction order, λB: reference wavelength (blazed wavelength), n (λB): at λB Refractive index, mB: represents the diffraction order of blazing. The relationship between the step amount d in the optical axis direction of the step and the diffraction order m can be expressed as m = (n−1) · d / λ.

　更に、第２基礎構造のような階段型構造において、回折効率は以下の数２に示すような式に基づいて計算することが可能である。 Furthermore, in a stepped structure such as the second basic structure, the diffraction efficiency can be calculated based on the following equation (2).

　尚、ηm：回折次数ｍでの回折効率、λ：波長、n(λ) ：λでの屈折率、ｍ：回折次数、λB：位相シフトの基準波長、n(λB)：λBでの屈折率、d：位相シフト量(単位：λB)、N：ステップ数（分割数）を表す。 Ηm: diffraction efficiency at diffraction order m, λ: wavelength, n (λ): refractive index at λ, m: diffraction order, λB: reference wavelength for phase shift, n (λB): refractive index at λB , D: phase shift amount (unit: λB), N: number of steps (number of divisions).

　また、本例においては、図６（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを同じ向きで重畳している。「同じ向き」とは、対物レンズの光軸を含む断面において、光軸を縦軸とし光軸直交方向を横軸としたときに、ブレーズ型構造の斜めの面の傾きの方向（右下がりか左下がりか）と、階段型構造の各段の包絡面である斜めの面の傾きの方向が同じであることをいう。 In this example, as shown in FIGS. 6A and 6B, the directions of the first basic structure and the second basic structure are overlapped in the same direction. “Same orientation” means the direction of inclination of the slanted surface of the blazed structure (decreasing to the right) when the optical axis is the vertical axis and the optical axis orthogonal direction is the horizontal axis in the cross section including the optical axis of the objective lens. It means that the direction of the inclination of the slanted surface which is the envelope surface of each step of the staircase structure is the same.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図６（ｃ）に示す様に４分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 The second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a four-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is curved. The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（４．９５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（４．９５λ１＋０．２λ１）／（ｎ－１）
　　（１．２５λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．２５λ１＋０．２λ１）／（ｎ－１）
　また、上記の式は、第２光路差付与構造の小さな光軸方向の段差量ｄ００が第１光束の波長λ１に対して、１．２５λ１±０．２・λ１の光路差を与えるような段差量であって、第２光路差付与構造の大きな光軸方向の段差量ｄ０が第１光束の波長λ１に対して、４．９５λ１±０．２・λ１の光路差を与えるような段差量であることを意味しているとも言える。 (4.95λ1-0.2λ1) / (n−1) ≦ d0 ≦ (4.95λ1 + 0.2λ1) / (n−1)
(1.25λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.25λ1 + 0.2λ1) / (n−1)
In addition, the above equation shows that the step d00 in the small optical axis direction of the second optical path difference providing structure gives an optical path difference of 1.25λ1 ± 0.2 · λ1 with respect to the wavelength λ1 of the first light flux. The step amount d0 having a large optical axis direction of the second optical path difference providing structure gives an optical path difference of 4.95λ1 ± 0.2 · λ1 with respect to the wavelength λ1 of the first light flux. It can be said that it means something.

　また、本例においては、｜ｘ｜＝２、ｙ＝０、｜ｚ｜＝１を満たし、ｘとｚの正負の符号が異なる。ｘが正であることが好ましい。 In this example, | x | = 2, y = 0, and | z | = 1 are satisfied, and the signs of x and z are different. It is preferable that x is positive.

　なお、第２光路差付与構造を通過した第１光束は光軸から離れる程、位相が進み、且つ、第２光路差付与構造を通過した第３光束は光軸から離れる程、位相が遅れるような場合、又は、第２光路差付与構造を通過した第１光束は光軸から離れる程、位相が遅れ、且つ、第２光路差付与構造を通過した第３光束は光軸から離れる程、位相が進むような場合、ｘとｚの正負の符号が異なると言える。尚、第２光路差付与構造が、階段形状の繰り返し構造である場合は、単位構造である一つの階段形状の中で、上記の位相の進みと位相の遅れが起きている事が好ましい。 Note that the phase of the first light flux that has passed through the second optical path difference providing structure increases as it moves away from the optical axis, and the phase of the third light flux that has passed through the second optical path difference providing structure is delayed as it moves away from the optical axis. In such a case, the phase of the first light flux that has passed through the second optical path difference providing structure is delayed as the distance from the optical axis increases, and the phase of the third light flux that has passed through the second optical path difference providing structure is increased as the distance from the optical axis increases. Can be said to be different in the sign of x and z. In addition, when the second optical path difference providing structure is a staircase-shaped repeating structure, it is preferable that the above-described phase advance and phase delay occur in one staircase shape that is a unit structure.

　例１の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約７７％、第２光束において約６８％、第３光束において約５７％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 1, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 77% for the first beam, about 68% for the second beam, and about 57% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　尚、光路差付与構造において、回折効率は以下の数３に示すような式に基づいても計算することが可能である。 In the optical path difference providing structure, the diffraction efficiency can also be calculated based on the following equation (3).

尚、f(x)は、光路差付与構造による位相差を現す関数を表す。 Note that f (x) represents a function representing the phase difference due to the optical path difference providing structure.

　（第２光路差付与構造　例２）
　例２においては、図７（ｂ）に示すように階段型構造である第２基礎構造は６分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図７（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 2)
In Example 2, as shown in FIG.7 (b), the 2nd foundation structure which is a staircase type structure is a 6-step staircase type structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 7A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having a blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（１．２λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．２λ１＋０．２λ１）／（ｎ－１）
　　（６λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（６λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図７（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。「異なる向き」とは、対物レンズの光軸を含む断面において、光軸を縦軸とし光軸直交方向を横軸としたときに、ブレーズ型構造の斜めの面の傾きの方向（右下がりか左下がりか）と、階段型構造の各段の包絡面である斜めの面の傾きの方向が逆であることをいう。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(1.2λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.2λ1 + 0.2λ1) / (n−1)
(6λ1-0.2λ1) / (n−1) ≦ d22 ≦ (6λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 7 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction. “Different orientation” refers to the direction of inclination of a slanted surface of a blazed structure (decrease to the right) when the optical axis is the vertical axis and the optical axis orthogonal direction is the horizontal axis in the cross section including the optical axis of the objective lens. It means that the inclination direction of the slanted surface, which is the envelope surface of each step of the staircase structure, is reversed.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図７（ｃ）に示す様に６分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Also, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a 6-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５λ１＋０．２λ１）／（ｎ－１）
　　（１．２λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．２λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、ｘ＝０、｜ｙ｜＝２、｜ｚ｜＝３を満たし、ｙとｚの正負の符号が等しい。ｙとｚが共に正であることが好ましい。 (5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1)
(1.2λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.2λ1 + 0.2λ1) / (n−1)
In this example, x = 0, | y | = 2, | z | = 3 are satisfied, and the signs of y and z are equal. It is preferable that y and z are both positive.

　なお、第２光路差付与構造を通過した第２光束は光軸から離れる程、位相が進み、且つ、第２光路差付与構造を通過した第３光束も光軸から離れる程、位相が進むような場合、又は、第２光路差付与構造を通過した第２光束は光軸から離れる程、位相が遅れ、且つ、第２光路差付与構造を通過した第３光束も光軸から離れる程、位相が遅れるような場合、ｘとｚの正負の符号が等しいと言える。尚、第２光路差付与構造が、階段形状の繰り返し構造である場合は、単位構造である一つの階段形状の中で、上記の位相の進みと位相の遅れが起きている事が好ましい。 Note that the phase of the second light beam that has passed through the second optical path difference providing structure advances as the distance from the optical axis increases, and the phase of the third light beam that has passed through the second optical path difference providing structure also advances as it separates from the optical axis. In such a case, the phase of the second light beam that has passed through the second optical path difference providing structure is delayed as the distance from the optical axis increases, and the phase of the third light beam that has passed through the second optical path difference providing structure is also separated from the optical axis. Is delayed, it can be said that the signs of x and z are equal. In addition, when the second optical path difference providing structure is a staircase-shaped repeating structure, it is preferable that the above-described phase advance and phase delay occur in one staircase shape that is a unit structure.

　例２の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約８０％、第２光束において約６２％、第３光束において約５４％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 2, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 80% for the first beam, about 62% for the second beam, and about 54% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例３）
　例３においては、図８（ｂ）に示すように階段型構造である第２基礎構造は７分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図８（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 3)
In Example 3, as shown in FIG.8 (b), the 2nd foundation structure which is a staircase type structure is a 7-step staircase type structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 8A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having a blaze structure satisfies the following conditional expression.

　　（３λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（３λ１＋０．４λ１）／（ｎ－１）
　　（１．３１λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．３１λ１＋０．２λ１）／（ｎ－１）
　　（７．８６λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（７．８６λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図８（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (3λ1-0.4λ1) / (n−1) ≦ d1 ≦ (3λ1 + 0.4λ1) / (n−1)
(1.31λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.31λ1 + 0.2λ1) / (n−1)
(7.86λ1-0.2λ1) / (n−1) ≦ d22 ≦ (7.86λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 8 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図８（ｃ）に示す様に７分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a seven-part blaze step structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（４．８６λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（４．８６λ１＋０．２λ１）／（ｎ－１）
　　（１．３１λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．３１λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝１、｜ｙ｜＝３、｜ｚ｜＝４を満たし、ｘとｙとｚの正負の符号が等しい。また、ｘとｙとｚが共に正であることが好ましい。 (4.86λ1-0.2λ1) / (n−1) ≦ d0 ≦ (4.86λ1 + 0.2λ1) / (n−1)
(1.31λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.31λ1 + 0.2λ1) / (n−1)
In this example, | x | = 1, | y | = 3, and | z | = 4 are satisfied, and the signs of x, y, and z are equal. Moreover, it is preferable that x, y, and z are all positive.

　例３の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約６９％、第２光束において約６５％、第３光束において約６４％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 3, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 69% for the first beam, about 65% for the second beam, and about 64% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例４）
　例４においては、図９（ｂ）に示すように階段型構造である第２基礎構造は７分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図９（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 4)
In Example 4, as shown in FIG. 9B, the second basic structure having a stepped structure is a seven-stage stepped structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 9A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（４λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（４λ１＋０．４λ１）／（ｎ－１）
　　（１．２８λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．２８λ１＋０．２λ１）／（ｎ－１）
　　（７．６８λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（７．６８λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図９（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (4λ1-0.4λ1) / (n−1) ≦ d1 ≦ (4λ1 + 0.4λ1) / (n−1)
(1.28λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.28λ1 + 0.2λ1) / (n−1)
(7.68λ1-0.2λ1) / (n−1) ≦ d22 ≦ (7.68λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 9 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図９（ｃ）に示す様に７分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a seven-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（３．６８λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（３．６８λ１＋０．２λ１）／（ｎ－１）
　　（１．２８λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．２８λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝２、｜ｙ｜＝４、｜ｚ｜＝５を満たし、ｘとｙとｚの正負の符号が等しい。また、ｘとｙとｚが共に正であることが好ましい。 (3.68λ1-0.2λ1) / (n−1) ≦ d0 ≦ (3.68λ1 + 0.2λ1) / (n−1)
(1.28λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.28λ1 + 0.2λ1) / (n−1)
In this example, | x | = 2, | y | = 4, and | z | = 5 are satisfied, and the signs of x, y, and z are equal. Moreover, it is preferable that x, y, and z are all positive.

　例４の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約６７％、第２光束において約６８％、第３光束において約６０％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 4, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 67% for the first beam, about 68% for the second beam, and about 60% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例５）
　例５においては、図１０（ｂ）に示すように階段型構造である第２基礎構造は５分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図１０（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 5)
In Example 5, as shown in FIG.10 (b), the 2nd foundation structure which is a staircase type structure is a 5-step staircase type structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 10A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having a blaze structure satisfies the following conditional expression.

　　（２λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（２λ１＋０．４λ１）／（ｎ－１）
　　（１．２λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．２λ１＋０．２λ１）／（ｎ－１）
　　（４．８λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（４．８λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図１０（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを同じ向きで重畳している。 (2λ1−0.4λ1) / (n−1) ≦ d1 ≦ (2λ1 + 0.4λ1) / (n−1)
(1.2λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.2λ1 + 0.2λ1) / (n−1)
(4.8λ1-0.2λ1) / (n−1) ≦ d22 ≦ (4.8λ1 + 0.2λ1) / (n−1)
Moreover, in this example, as shown to Fig.10 (a), (b), the direction of the 1st foundation structure and the 2nd foundation structure is overlapped with the same direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図１０（ｃ）に示す様に５分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a five-part blazed staircase structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（６．８λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（６．８λ１＋０．２λ１）／（ｎ－１）
　　（１．２λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．２λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝３、ｙ＝０、｜ｚ｜＝１を満たし、ｘとｚの正負の符号が異なる。また、ｘが正であることが好ましい。 (6.8λ1-0.2λ1) / (n−1) ≦ d0 ≦ (6.8λ1 + 0.2λ1) / (n−1)
(1.2λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.2λ1 + 0.2λ1) / (n−1)
In this example, | x | = 3, y = 0, | z | = 1 is satisfied, and the signs of x and z are different. Moreover, it is preferable that x is positive.

　例５の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約８８％、第２光束において約７０％、第３光束において約５７％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 5, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 88% for the first beam, about 70% for the second beam, and about 57% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例６）
　例６においては、図１１（ｂ）に示すように階段型構造である第２基礎構造は２分割の階段型構造（バイナリ構造）である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図１１（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。ここでは、ｄ２１＝ｄ２２の場合を含む（例７，８，１８，１９も同じ）。 (Second optical path difference providing structure example 6)
In Example 6, as shown in FIG. 11B, the second basic structure having a stepped structure is a two-step stepped structure (binary structure). Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 11A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression. Here, the case where d21 = d22 is included (examples 7, 8, 18, and 19 are the same).

　　　　　　　（４λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（４λ１＋０．４λ１）／（ｎ－１）
　　（１．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．１λ１＋０．２λ１）／（ｎ－１）
　　（１．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（１．１λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図１１（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (4λ1-0.4λ1) / (n−1) ≦ d1 ≦ (4λ1 + 0.4λ1) / (n−1)
(1.1λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.1λ1 + 0.2λ1) / (n−1)
(1.1λ1-0.2λ1) / (n−1) ≦ d22 ≦ (1.1λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 11 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図１１（ｃ）に示す様に２分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 The second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a two-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（２．９λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（２．９λ１＋０．２λ１）／（ｎ－１）
　　（１．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．１λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝４、｜ｙ｜＝３、｜ｚ｜＝３を満たし、ｘとｙとｚの正負の符号が等しい。また、ｘ、ｙ、ｚが正であることが好ましい。 (2.9λ1-0.2λ1) / (n−1) ≦ d0 ≦ (2.9λ1 + 0.2λ1) / (n−1)
(1.1λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.1λ1 + 0.2λ1) / (n−1)
In this example, | x | = 4, | y | = 3, and | z | = 3 are satisfied, and the signs of x, y, and z are equal. Moreover, it is preferable that x, y, and z are positive.

　例６の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約９７％、第２光束において約７４％、第３光束において約４５％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 6, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 97% for the first beam, about 74% for the second beam, and about 45% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例７）
　例７においては、図１２（ｂ）に示すように階段型構造である第２基礎構造は２分割の階段型構造（バイナリ構造）である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図１２（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 7)
In Example 7, as shown in FIG. 12B, the second basic structure having a stepped structure is a two-stage stepped structure (binary structure). Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 12A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having a blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（２λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（２λ１＋０．２λ１）／（ｎ－１）
　　（２λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（２λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図１２（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを同じ向きで重畳している。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(2λ1−0.2λ1) / (n−1) ≦ d21 ≦ (2λ1 + 0.2λ1) / (n−1)
(2λ1−0.2λ1) / (n−1) ≦ d22 ≦ (2λ1 + 0.2λ1) / (n−1)
Moreover, in this example, as shown to Fig.12 (a), (b), the direction of the 1st foundation structure and the 2nd foundation structure is overlapped with the same direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図１２（ｃ）に示す様に２分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 The second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a two-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（３λ１＋０．２λ１）／（ｎ－１）
　　（２λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（２λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝１、｜ｙ｜＝１、｜ｚ｜＝１を満たし、ｘとｙとｚの正負の符号が等しい。また、ｘ、ｙ、ｚが正であることが好ましい。 (3λ1-0.2λ1) / (n−1) ≦ d0 ≦ (3λ1 + 0.2λ1) / (n−1)
(2λ1−0.2λ1) / (n−1) ≦ d00 ≦ (2λ1 + 0.2λ1) / (n−1)
In this example, | x | = 1, | y | = 1, | z | = 1, and the signs of x, y, and z are equal. Moreover, it is preferable that x, y, and z are positive.

　例７の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約８２％、第２光束において約９１％、第３光束において約５７％とできる。本例によれば、ブレーズ型構造に比べ、高い回折効率を得ることができる。 In the second optical path difference providing structure of Example 7, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 82% for the first beam, about 91% for the second beam, and about 57% for the third beam. According to this example, higher diffraction efficiency can be obtained as compared with the blazed structure.

　（第２光路差付与構造　例８）
　例８においては、図１３（ｂ）に示すように階段型構造である第２基礎構造は２分割の階段型構造（バイナリ構造）である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図１３（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 8)
In Example 8, as shown in FIG. 13B, the second basic structure having a stepped structure is a two-stage stepped structure (binary structure). Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 13A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having a blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（３．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３．１λ１＋０．２λ１）／（ｎ－１）
　　（３．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（３．１λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図１３（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(3.1λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3.1λ1 + 0.2λ1) / (n−1)
(3.1λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3.1λ1 + 0.2λ1) / (n−1)
Moreover, in this example, as shown to Fig.13 (a), (b), the direction of the 1st foundation structure and the 2nd foundation structure is overlapped with a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図１３（ｃ）に示す様に２分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a two-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（３．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（３．１λ１＋０．２λ１）／（ｎ－１）
　　（２．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（２．１λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝１、｜ｙ｜＝１、｜ｚ｜＝１を満たし、ｘとｙとｚの正負の符号が等しい。また、ｘ、ｙ、ｚが正であることが好ましい。 (3.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (3.1λ1 + 0.2λ1) / (n−1)
(2.1λ1-0.2λ1) / (n−1) ≦ d00 ≦ (2.1λ1 + 0.2λ1) / (n−1)
In this example, | x | = 1, | y | = 1, | z | = 1, and the signs of x, y, and z are equal. Moreover, it is preferable that x, y, and z are positive.

　例８の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約９０％、第２光束において約８５％、第３光束において約５０％とできる。本例によれば、ブレーズ型構造に比べ、高い回折効率を得ることができる。 In the second optical path difference providing structure of Example 8, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 90% for the first beam, about 85% for the second beam, and about 50% for the third beam. According to this example, higher diffraction efficiency can be obtained as compared with the blazed structure.

　（第２光路差付与構造　例９）
　例９においては、図１４（ｂ）に示すように階段型構造である第２基礎構造は７分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図１４（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 9)
In Example 9, as shown in FIG. 14B, the second basic structure having a stepped structure is a seven-step stepped structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 14A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having a blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（１．２９λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．２９λ１＋０．２λ１）／（ｎ－１）
　　（７．７４λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（７．７４λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図１４（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(1.29λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.29λ1 + 0.2λ1) / (n−1)
(7.74λ1-0.2λ1) / (n−1) ≦ d22 ≦ (7.74λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 14 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図１４（ｃ）に示す様に７分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a seven-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is curved. The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（６．７４λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（６．７４λ１＋０．２λ１）／（ｎ－１）
　　（１．２９λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．２９λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝１、｜ｙ｜＝２、｜ｚ｜＝３を満たし、正負の符号については、ｘの符号と、ｙ及びｚの符号が異なり、ｙとｚの符号が等しい。また、ｘが負であることが好ましい。 (6.74λ1-0.2λ1) / (n−1) ≦ d0 ≦ (6.74λ1 + 0.2λ1) / (n−1)
(1.29λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.29λ1 + 0.2λ1) / (n−1)
In this example, | x | = 1, | y | = 2, and | z | = 3 are satisfied, and the signs of x and y and z are different for positive and negative signs. The signs are equal. Moreover, it is preferable that x is negative.

　例９の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約７６％、第２光束において約７６％、第３光束において約６４％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 9, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 76% for the first beam, about 76% for the second beam, and about 64% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例１０）
　例１０においては、図１５（ｂ）に示すように階段型構造である第２基礎構造は８分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図１５（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 10)
In Example 10, as shown in FIG.15 (b), the 2nd foundation structure which is a step type structure is a step type structure of 8 divisions. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 15A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（１．１３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．１３λ１＋０．２λ１）／（ｎ－１）
　　（７．９１λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（７．９１λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図１５（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(1.13λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.13λ1 + 0.2λ1) / (n−1)
(7.91λ1-0.2λ1) / (n−1) ≦ d22 ≦ (7.91λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 15 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図１５（ｃ）に示す様に８分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is an eight-divided blaze step structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（６．９１λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（６．９１λ１＋０．２λ１）／（ｎ－１）
　　（１．１３λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．１３λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝２、｜ｙ｜＝２、｜ｚ｜＝３を満たし、正負の符号については、ｘの符号と、ｙ及びｚの符号が異なり、ｙとｚの符号が等しい。また、ｘが正であることが好ましい。 (6.91λ1-0.2λ1) / (n−1) ≦ d0 ≦ (6.91λ1 + 0.2λ1) / (n−1)
(1.13λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.13λ1 + 0.2λ1) / (n−1)
In this example, | x | = 2, | y | = 2, | z | = 3 are satisfied, and the sign of x is different from the sign of y and z with respect to the sign of positive and negative. The signs are equal. Moreover, it is preferable that x is positive.

　例１０の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約９５％、第２光束において約７０％、第３光束において約５１％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 10, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 95% for the first beam, about 70% for the second beam, and about 51% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例１１）
　例１１においては、図１６（ｂ）に示すように階段型構造である第２基礎構造は８分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図１６（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 11)
In Example 11, as shown in FIG.16 (b), the 2nd foundation structure which is a step type structure is a step type structure of 8 divisions. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 16A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（３λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（３λ１＋０．４λ１）／（ｎ－１）
　　（１．３７λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．３７λ１＋０．２λ１）／（ｎ－１）
　　（９．５９λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（９．５９λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図１６（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (3λ1-0.4λ1) / (n−1) ≦ d1 ≦ (3λ1 + 0.4λ1) / (n−1)
(1.37λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.37λ1 + 0.2λ1) / (n−1)
(9.59λ1-0.2λ1) / (n−1) ≦ d22 ≦ (9.59λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 16 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図１６（ｃ）に示す様に８分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is an eight-divided blaze step structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is curved. The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（６．５９λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（６．５９λ１＋０．２λ１）／（ｎ－１）
　　（１．３７λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．３７λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、ｘ＝０、｜ｙ｜＝３、｜ｚ｜＝４を満たし、ｙ及びｚの正負の符号が等しい。また、ｙ、ｚが正であることが好ましい。 (6.59λ1-0.2λ1) / (n−1) ≦ d0 ≦ (6.59λ1 + 0.2λ1) / (n−1)
(1.37λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.37λ1 + 0.2λ1) / (n−1)
In this example, x = 0, | y | = 3, | z | = 4 is satisfied, and the positive and negative signs of y and z are equal. Moreover, it is preferable that y and z are positive.

　例１１の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約６１％、第２光束において約８１％、第３光束において約７１％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 11, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 61% for the first beam, about 81% for the second beam, and about 71% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例１２）
　例１２においては、図１７（ｂ）に示すように階段型構造である第２基礎構造は９分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図１７（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 12)
In Example 12, as shown in FIG. 17 (b), the second basic structure having a stepped structure is a nine-stage stepped structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 17A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（２λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（２λ１＋０．４λ１）／（ｎ－１）
　　（１．１１λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．１１λ１＋０．２λ１）／（ｎ－１）
　　（８．８８λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（８．８８λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図１７（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (2λ1−0.4λ1) / (n−1) ≦ d1 ≦ (2λ1 + 0.4λ1) / (n−1)
(1.11λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.11λ1 + 0.2λ1) / (n−1)
(8.88λ1-0.2λ1) / (n−1) ≦ d22 ≦ (8.88λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 17 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図１７（ｃ）に示す様に９分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a nine-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is curved. The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（６．８８λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（６．８８λ１＋０．２λ１）／（ｎ－１）
　　（１．１１λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．１１λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝１、｜ｙ｜＝４、｜ｚ｜＝５を満たし、ｘ、ｙ及びｚの正負の符号が等しい。また、ｘ、ｙ、ｚが正であることが好ましい。 (6.88λ1-0.2λ1) / (n−1) ≦ d0 ≦ (6.88λ1 + 0.2λ1) / (n−1)
(1.11λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.11λ1 + 0.2λ1) / (n−1)
In this example, | x | = 1, | y | = 4, | z | = 5 is satisfied, and the positive and negative signs of x, y, and z are equal. Moreover, it is preferable that x, y, and z are positive.

　例１２の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約９１％、第２光束において約６６％、第３光束において約４８％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 12, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 91% for the first beam, about 66% for the second beam, and about 48% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例１３）
　例１３においては、図１８（ｂ）に示すように階段型構造である第２基礎構造は１０分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図１８（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 13)
In Example 13, as shown in FIG.18 (b), the 2nd basic structure which is a staircase type structure is a 10-step staircase type structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 18A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（２λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（２λ１＋０．４λ１）／（ｎ－１）
　　（１．２λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．２λ１＋０．２λ１）／（ｎ－１）
　　（１０．８λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（１０．８λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図１８（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (2λ1−0.4λ1) / (n−1) ≦ d1 ≦ (2λ1 + 0.4λ1) / (n−1)
(1.2λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.2λ1 + 0.2λ1) / (n−1)
(10.8λ1-0.2λ1) / (n−1) ≦ d22 ≦ (10.8λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 18 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図１８（ｃ）に示す様に１０分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a 10-divided blaze step structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（８．８λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（８．８λ１＋０．２λ１）／（ｎ－１）
　　（１．２λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．２λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、ｘ＝０、｜ｙ｜＝４、｜ｚ｜＝５を満たし、ｙ及びｚの正負の符号が等しい。また、ｙ、ｚが正であることが好ましい。 (8.8λ1-0.2λ1) / (n−1) ≦ d0 ≦ (8.8λ1 + 0.2λ1) / (n−1)
(1.2λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.2λ1 + 0.2λ1) / (n−1)
In this example, x = 0, | y | = 4, | z | = 5 are satisfied, and the signs of y and z are equal. Moreover, it is preferable that y and z are positive.

　例１３の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約８８％、第２光束において約７６％、第３光束において約５７％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 13, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 88% for the first beam, about 76% for the second beam, and about 57% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例１４）
　例１４においては、図１９（ｂ）に示すように階段型構造である第２基礎構造は１０分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図１９（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 14)
In Example 14, as shown in FIG. 19B, the second basic structure having a stepped structure is a ten-step divided structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 19A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having a blaze structure satisfies the following conditional expression.

　　（３λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（３λ１＋０．４λ１）／（ｎ－１）
　　（１．３３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．３３λ１＋０．２λ１）／（ｎ－１）
　　（１１．９７λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（１１．９７λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図１９（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (3λ1-0.4λ1) / (n−1) ≦ d1 ≦ (3λ1 + 0.4λ1) / (n−1)
(1.33λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.33λ1 + 0.2λ1) / (n−1)
(11.97λ1-0.2λ1) / (n−1) ≦ d22 ≦ (11.97λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 19 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図１９（ｃ）に示す様に１０分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a blazed stepped structure with 10 divisions as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is curved. The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（８．９７λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（８．９７λ１＋０．２λ１）／（ｎ－１）
　　（１．３３λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．３３λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、ｘ＝０、｜ｙ｜＝４、｜ｚ｜＝５を満たし、ｙ及びｚの正負の符号が等しい。また、ｙ、ｚが正であることが好ましい。 (8.97λ1-0.2λ1) / (n−1) ≦ d0 ≦ (8.97λ1 + 0.2λ1) / (n−1)
(1.33λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.33λ1 + 0.2λ1) / (n−1)
In this example, x = 0, | y | = 4, | z | = 5 are satisfied, and the signs of y and z are equal. Moreover, it is preferable that y and z are positive.

　例１４の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約７４％、第２光束において約８５％、第３光束において約６５％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 14, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 74% for the first beam, about 85% for the second beam, and about 65% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例１５）
　例１５においては、図２０（ｂ）に示すように階段型構造である第２基礎構造は６分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図２０（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 15)
In Example 15, as shown in FIG. 20B, the second basic structure that is a stepped structure is a six-step staircase structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 20A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（１．１９λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（１．１９λ１＋０．２λ１）／（ｎ－１）
　　（５．９５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（５．９５λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図２０（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを同じ向きで重畳している。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(1.19λ1-0.2λ1) / (n−1) ≦ d21 ≦ (1.19λ1 + 0.2λ1) / (n−1)
(5.95λ1-0.2λ1) / (n−1) ≦ d22 ≦ (5.95λ1 + 0.2λ1) / (n−1)
Moreover, in this example, as shown to FIG. 20 (a), (b), the direction of the 1st foundation structure and the 2nd foundation structure is overlapped with the same direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図２０（ｃ）に示す様に６分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a 6-divided blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（６．９５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（６．９５λ１＋０．２λ１）／（ｎ－１）
　　（１．１９λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（１．１９λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝２、｜ｙ｜＝１、｜ｚ｜＝２を満たし、正負の符号について、ｘの符号と、ｙ及びｚの符号が異なり、ｙとｚの符号が等しい。また、ｘが正であることが好ましい。 (6.95λ1-0.2λ1) / (n−1) ≦ d0 ≦ (6.95λ1 + 0.2λ1) / (n−1)
(1.19λ1-0.2λ1) / (n−1) ≦ d00 ≦ (1.19λ1 + 0.2λ1) / (n−1)
Further, in this example, | x | = 2, | y | = 1, | z | = 2, and the sign of x is different from the sign of y and z for positive and negative signs, and the signs of y and z Are equal. Moreover, it is preferable that x is positive.

　例１５の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約８６％、第２光束において約７４％、第３光束において約５４％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 15, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 86% for the first beam, about 74% for the second beam, and about 54% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例１６）
　例１６においては、図２１（ｂ）に示すように階段型構造である第２基礎構造は４分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図２１（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 16)
In Example 16, as shown in FIG. 21 (b), the second basic structure having a stepped structure is a four-step stepped structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 21A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（３．２５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３．２５λ１＋０．２λ１）／（ｎ－１）
　　（９．７５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（９．７５λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図２１（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(3.25λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3.25λ1 + 0.2λ1) / (n−1)
(9.75λ1-0.2λ1) / (n−1) ≦ d22 ≦ (9.75λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 21 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図２１（ｃ）に示す様に４分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a four-part blazed staircase structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is curved. The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（８．７５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（８．７５λ１＋０．２λ１）／（ｎ－１）
　　（３．２５λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（３．２５λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、ｘ＝０、｜ｙ｜＝１、｜ｚ｜＝２を満たし、ｙとｚの正負の符号が等しい。また、ｙ、ｚが正であることが好ましい。 (8.75λ1-0.2λ1) / (n−1) ≦ d0 ≦ (8.75λ1 + 0.2λ1) / (n−1)
(3.25λ1-0.2λ1) / (n−1) ≦ d00 ≦ (3.25λ1 + 0.2λ1) / (n−1)
In this example, x = 0, | y | = 1, and | z | = 2 are satisfied, and the signs of y and z are equal. Moreover, it is preferable that y and z are positive.

　例１６の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約８１％、第２光束において約８９％、第３光束において約６１％とできる。本例によれば、階段型構造に比べ、高い回折効率を得ることができる。 In the second optical path difference providing structure of Example 16, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 81% for the first beam, about 89% for the second beam, and about 61% for the third beam. According to this example, higher diffraction efficiency can be obtained as compared with the stepped structure.

　（第２光路差付与構造　例１７）
　例１７においては、図２２（ｂ）に示すように階段型構造である第２基礎構造は４分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図２２（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 17)
In Example 17, as shown in FIG.22 (b), the 2nd foundation structure which is a staircase type structure is a 4 stepped staircase type structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 22A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（３．２２λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３．２２λ１＋０．２λ１）／（ｎ－１）
　　（９．６６λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（９．６６λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図２２（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを同じ向きで重畳している。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(3.22λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3.22λ1 + 0.2λ1) / (n−1)
(9.66λ1-0.2λ1) / (n−1) ≦ d22 ≦ (9.66λ1 + 0.2λ1) / (n−1)
Moreover, in this example, as shown to Fig.22 (a), (b), the direction of the 1st foundation structure and the 2nd foundation structure is overlapped with the same direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図２２（ｃ）に示す様に４分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a four-part blazed staircase structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is curved. The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（１０．６６λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（１０．６６λ１＋０．２λ１）／（ｎ－１）
　　（３．２２λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（３．２２λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝２、ｙ＝０、｜ｚ｜＝１を満たし、ｘとｚの正負の符号が異なる。また、ｘが正であることが好ましい。 (10.66λ1-0.2λ1) / (n−1) ≦ d0 ≦ (10.66λ1 + 0.2λ1) / (n−1)
(3.22λ1-0.2λ1) / (n−1) ≦ d00 ≦ (3.22λ1 + 0.2λ1) / (n−1)
In this example, | x | = 2, y = 0, and | z | = 1 are satisfied, and the signs of x and z are different. Moreover, it is preferable that x is positive.

　例１７の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約７８％、第２光束において約７２％、第３光束において約５８％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 17, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 78% for the first beam, about 72% for the second beam, and about 58% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例１８）
　例１８においては、図２３（ｂ）に示すように階段型構造である第２基礎構造は２分割の階段型構造（バイナリ構造）である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図２３（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 18)
In Example 18, as shown in FIG. 23B, the second basic structure having a stepped structure is a two-step staircase structure (binary structure). Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 23A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（２λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（２λ１＋０．４λ１）／（ｎ－１）
　　（３．０５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３．０５λ１＋０．２λ１）／（ｎ－１）
　　（３．０５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（３．０５λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図２３（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを同じ向きで重畳している。 (2λ1−0.4λ1) / (n−1) ≦ d1 ≦ (2λ1 + 0.4λ1) / (n−1)
(3.05λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3.05λ1 + 0.2λ1) / (n−1)
(3.05λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3.05λ1 + 0.2λ1) / (n−1)
Moreover, in this example, as shown to FIG. 23 (a), (b), the direction of the 1st foundation structure and the 2nd foundation structure is overlapped with the same direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図２３（ｃ）に示す様に２分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 The second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a two-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（５．０５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５．０５λ１＋０．２λ１）／（ｎ－１）
　　（３．０５λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（３．０５λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝２、｜ｙ｜＝１、ｚ＝０を満たし、ｘとｙの正負の符号が等しい。また、ｘ、ｙが正であることが好ましい。 (5.05λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5.05λ1 + 0.2λ1) / (n−1)
(3.05λ1-0.2λ1) / (n−1) ≦ d00 ≦ (3.05λ1 + 0.2λ1) / (n−1)
In this example, | x | = 2, | y | = 1, z = 0 are satisfied, and the signs of x and y are equal. Moreover, it is preferable that x and y are positive.

　例１８の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約９８％、第２光束において約９１％、第３光束において約４１％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 18, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 98% for the first beam, about 91% for the second beam, and about 41% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例１９）
　例１９においては、図２４（ｂ）に示すように階段型構造である第２基礎構造は２分割の階段型構造（バイナリ構造）である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図２４（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 19)
In Example 19, as shown in FIG. 24B, the second basic structure having a stepped structure is a two-stage stepped structure (binary structure). Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 24A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（５λ１＋０．２λ１）／（ｎ－１）
　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（５λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図２４（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(5λ1-0.2λ1) / (n−1) ≦ d21 ≦ (5λ1 + 0.2λ1) / (n−1)
(5λ1-0.2λ1) / (n−1) ≦ d22 ≦ (5λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 24 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図２４（ｃ）に示す様に２分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 The second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a two-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is curved. The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５λ１＋０．２λ１）／（ｎ－１）
　　（４λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（４λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝１、｜ｙ｜＝１、ｚ＝０を満たし、ｘとｙの正負の符号が等しい。また、ｘ、ｙが正であることが好ましい。 (5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1)
(4λ1−0.2λ1) / (n−1) ≦ d00 ≦ (4λ1 + 0.2λ1) / (n−1)
In this example, | x | = 1, | y | = 1, and z = 0 are satisfied, and the signs of x and y are equal. Moreover, it is preferable that x and y are positive.

　例１９の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約８２％、第２光束において約８３％、第３光束において約５４％とできる。本例によれば、階段型構造に比べ、高い回折効率を得ることができる。 In the second optical path difference providing structure of Example 19, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 82% for the first beam, about 83% for the second beam, and about 54% for the third beam. According to this example, higher diffraction efficiency can be obtained as compared with the stepped structure.

　（第２光路差付与構造　例２０）
　例２０においては、図２５（ｂ）に示すように階段型構造である第２基礎構造は３分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図２５（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 20)
In Example 20, as shown in FIG.25 (b), the 2nd foundation structure which is a staircase type structure is a three-step staircase type structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 25A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（２λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（２λ１＋０．２λ１）／（ｎ－１）
　　（４λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（４λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図２５（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(2λ1−0.2λ1) / (n−1) ≦ d21 ≦ (2λ1 + 0.2λ1) / (n−1)
(4λ1-0.2λ1) / (n−1) ≦ d22 ≦ (4λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 25 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図２５（ｃ）に示す様に３分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 The second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a three-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（３λ１＋０．２λ１）／（ｎ－１）
　　（２λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（２λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝１、ｙ＝０、｜ｚ｜＝１を満たし、ｘとｚの正負の符号が等しい。また、ｘ、ｚが正であることが好ましい。 (3λ1-0.2λ1) / (n−1) ≦ d0 ≦ (3λ1 + 0.2λ1) / (n−1)
(2λ1−0.2λ1) / (n−1) ≦ d00 ≦ (2λ1 + 0.2λ1) / (n−1)
In this example, | x | = 1, y = 0, | z | = 1 is satisfied, and the positive and negative signs of x and z are equal. Moreover, it is preferable that x and z are positive.

　例２０の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約１００％、第２光束において約８８％、第３光束において約４４％とできる。本例によれば、階段型構造に比べ、高い回折効率を得ることができる。 In the second optical path difference providing structure of Example 20, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 100% for the first beam, about 88% for the second beam, and about 44% for the third beam. According to this example, higher diffraction efficiency can be obtained as compared with the stepped structure.

　（第２光路差付与構造　例２１）
　例２１においては、図２６（ｂ）に示すように階段型構造である第２基礎構造は３分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図２６（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 21)
In Example 21, as shown in FIG.26 (b), the 2nd foundation structure which is a staircase type structure is a three-step staircase type structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 26 (a), the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（λ１＋０．４λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３λ１＋０．２λ１）／（ｎ－１）
　　（６λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（６λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図２６（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを異なる向きで重畳している。 (Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(6λ1-0.2λ1) / (n−1) ≦ d22 ≦ (6λ1 + 0.2λ1) / (n−1)
In this example, as shown in Drawing 26 (a) and (b), the direction of the 1st foundation structure and the 2nd foundation structure is piled up in a different direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図２６（ｃ）に示す様に３分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 The second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a three-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. Note that it is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（５λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５λ１＋０．２λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（３λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝１、｜ｙ｜＝１、｜ｚ｜＝２を満たし、ｘ、ｙ、ｚの正負の符号が等しい。また、ｘ、ｙ、ｚが正であることが好ましい。 (5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d00 ≦ (3λ1 + 0.2λ1) / (n−1)
In this example, | x | = 1, | y | = 1, | z | = 2 are satisfied, and the positive and negative signs of x, y, and z are equal. Moreover, it is preferable that x, y, and z are positive.

　例２１の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約１００％、第２光束において約８０％、第３光束において約４０％とできる。本例によれば、通常のブレーズ型構造や、階段型構造の回折構造では得られない次数を最大の回折効率とすることが可能となる。 In the second optical path difference providing structure of Example 21, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 100% for the first beam, about 80% for the second beam, and about 40% for the third beam. According to this example, the order that cannot be obtained with a normal blazed structure or a diffractive structure with a staircase structure can be set to the maximum diffraction efficiency.

　（第２光路差付与構造　例２２）
　例２２においては、図２７（ｂ）に示すように階段型構造である第２基礎構造は２分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図２７（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 22)
In Example 22, as shown in FIG.27 (b), the 2nd foundation structure which is a staircase type structure is a two-step staircase type structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 27A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（４．１λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（４．１λ１＋０．４λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３λ１＋０．２λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（３λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図２７（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを同じ向きで重畳している。 (4.1λ1-0.4λ1) / (n−1) ≦ d1 ≦ (4.1λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
Moreover, in this example, as shown to Fig.27 (a), (b), the direction of the 1st foundation structure and the 2nd foundation structure is overlapped with the same direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図２７（ｃ）に示す様に２分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 The second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a two-part blazed staircase structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（７．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（７．１λ１＋０．２λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（３λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝４、｜ｙ｜＝２、｜ｚ｜＝３を満たし、ｘ、ｙ、ｚの正負の符号が等しい。また、ｘ、ｙ、ｚが正であることが好ましい。 (7.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (7.1λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d00 ≦ (3λ1 + 0.2λ1) / (n−1)
In this example, | x | = 4, | y | = 2, | z | = 3 is satisfied, and the positive and negative signs of x, y, and z are equal. Moreover, it is preferable that x, y, and z are positive.

　例２２の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約９７％、第２光束において約８４％、第３光束において約４３％とできる。本例によれば、階段型構造に比べ、高い回折効率を得ることができる。 In the second optical path difference providing structure of Example 22, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 97% for the first beam, about 84% for the second beam, and about 43% for the third beam. According to this example, higher diffraction efficiency can be obtained as compared with the stepped structure.

　（第２光路差付与構造　例２３）
　例２３においては、図２８（ｂ）に示すように階段型構造である第２基礎構造は２分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図２８（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 23)
In Example 23, as shown in FIG. 28 (b), the second basic structure having a stepped structure is a two-stage stepped structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 28A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（４λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（４λ１＋０．４λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３λ１＋０．２λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（３λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図２８（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを同じ向きで重畳している。 (4λ1-0.4λ1) / (n−1) ≦ d1 ≦ (4λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
Moreover, in this example, as shown to Fig.28 (a), (b), the direction of the 1st foundation structure and the 2nd foundation structure is overlapped with the same direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図２８（ｃ）に示す様に２分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 Further, the second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a two-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is curved. The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（７λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（７λ１＋０．２λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（３λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝４、｜ｙ｜＝２、｜ｚ｜＝１を満たし、ｘ、ｙ、ｚの正負の符号が等しい。また、ｘ、ｙ、ｚが正であることが好ましい。 (7λ1-0.2λ1) / (n−1) ≦ d0 ≦ (7λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d00 ≦ (3λ1 + 0.2λ1) / (n−1)
In this example, | x | = 4, | y | = 2, | z | = 1 is satisfied, and the positive and negative signs of x, y, and z are equal. Moreover, it is preferable that x, y, and z are positive.

　例２３の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約１００％、第２光束において約８８％、第３光束において約４２％とできる。本例によれば、階段型構造に比べ、高い回折効率を得ることができる。 In the second optical path difference providing structure of Example 23, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 100% for the first beam, about 88% for the second beam, and about 42% for the third beam. According to this example, higher diffraction efficiency can be obtained as compared with the stepped structure.

　（第２光路差付与構造　例２４）
　例２４においては、図２９（ｂ）に示すように階段型構造である第２基礎構造は２分割の階段型構造である。また、第２基礎構造の階段型構造の小さい段差の光軸方向の長さｄ２１（μｍ）と第２基礎構造の階段型構造の大きな段差の光軸方向の長さｄ２２（μｍ）、及び、図２９（ａ）に示すようにブレーズ型構造である第１基礎構造の段差部の光軸方向の長さｄ１（μｍ）が以下の条件式を満たす。 (Second optical path difference providing structure example 24)
In Example 24, as shown in FIG. 29B, the second basic structure having a stepped structure is a two-stage stepped structure. Further, the length d21 (μm) of the small step of the stepped structure of the second basic structure in the optical axis direction, the length d22 (μm) of the large step of the stepped structure of the second basic structure, and As shown in FIG. 29A, the length d1 (μm) in the optical axis direction of the step portion of the first basic structure having the blaze structure satisfies the following conditional expression.

　　（２．１λ１－０．４λ１）／（ｎ－１）　≦　ｄ１　≦　（２．１λ１＋０．４λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２１　≦　（３λ１＋０．２λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ２２　≦　（３λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、図２９（ａ）、（ｂ）に示すように第１基礎構造と第２基礎構造の向きを同じ向きで重畳している。 (2.1λ1-0.4λ1) / (n−1) ≦ d1 ≦ (2.1λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
Moreover, in this example, as shown to Fig.29 (a), (b), the direction of the 1st foundation structure and the 2nd foundation structure is overlapped with the same direction.

　また、第１基礎構造と第２基礎構造を重畳して得られた第２光路差付与構造は、図２９（ｃ）に示す様に２分割のブレーズ階段型構造であり、第２光路差付与構造の最も大きな段差の光軸方向の長さｄ０（μｍ）と、第２光路差付与構造の小さな段差の光軸方向の長さｄ００（μｍ）が以下の条件式を満たす。尚、周辺領域の第２光路差付与構造の全ての段差量ｄ０、ｄ００が以下の条件式を満たすことがより好ましいが、光軸から離れた段差の場合、対物レンズの非球面形状の曲面を考慮した段差量にしなければならず、光軸から離れた段差の段差量ｄ０、ｄ００が徐々に大きくなって行く傾向があり、以下の条件式よりも若干大きな段差が存在することもある。従って、第２光路差付与構造の光軸に最も近いｄ０とｄ００が少なくとも以下の条件式を満たすことが好ましい。 The second optical path difference providing structure obtained by superimposing the first basic structure and the second basic structure is a two-part blazed stepped structure as shown in FIG. The length d0 (μm) in the optical axis direction of the largest step of the structure and the length d00 (μm) in the optical axis direction of the small step of the second optical path difference providing structure satisfy the following conditional expression. It is more preferable that all the step amounts d0 and d00 of the second optical path difference providing structure in the peripheral region satisfy the following conditional expression. However, in the case of a step away from the optical axis, the aspheric surface of the objective lens is The amount of step must be taken into consideration, and the step amounts d0 and d00 of the step away from the optical axis tend to increase gradually, and a step slightly larger than the following conditional expression may exist. Therefore, it is preferable that d0 and d00 closest to the optical axis of the second optical path difference providing structure satisfy at least the following conditional expression.

　　（５．１λ１－０．２λ１）／（ｎ－１）　≦　ｄ０　≦　（５．１λ１＋０．２λ１）／（ｎ－１）
　　（３λ１－０．２λ１）／（ｎ－１）　≦　ｄ００　≦　（３λ１＋０．２λ１）／（ｎ－１）
　また、本例においては、｜ｘ｜＝２、｜ｙ｜＝１、｜ｚ｜＝２を満たし、ｘ、ｙ、ｚの正負の符号が等しい。また、ｘ、ｙ、ｚが正であることが好ましい。 (5.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5.1λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d00 ≦ (3λ1 + 0.2λ1) / (n−1)
In this example, | x | = 2, | y | = 1, | z | = 2 are satisfied, and the positive and negative signs of x, y, and z are equal. Moreover, it is preferable that x, y, and z are positive.

　例２３の第２光路差付与構造においては、第１光束の第１波長を約４０５ｎｍとし、第２光束の第２波長を約６５５ｎｍとし、第３光束の第３波長を約７８５ｎｍとした場合の回折効率を、第１光束において約９７％、第２光束において約８９％、第３光束において約４４％とできる。本例によれば、階段型構造に比べ、高い回折効率を得ることができる。 In the second optical path difference providing structure of Example 23, the first wavelength of the first light beam is about 405 nm, the second wavelength of the second light beam is about 655 nm, and the third wavelength of the third light beam is about 785 nm. The diffraction efficiency can be about 97% for the first beam, about 89% for the second beam, and about 44% for the third beam. According to this example, higher diffraction efficiency can be obtained as compared with the stepped structure.

　また、対物レンズの周辺領域に設けられた第２光路差付与構造に加え、中央領域に設けられた第１光路差付与構造を設ける場合、対物レンズの異なる光学面に設けてもよいが、同一の光学面に設けることが好ましい。同一の光学面に設けることにより、製造時の偏芯誤差を少なくすることが可能となるため好ましい。また、第１光路差付与構造及び第２光路差付与構造は、対物レンズの光ディスク側の面よりも、対物レンズの光源側の面に設けられることが好ましい。 In addition to the second optical path difference providing structure provided in the peripheral area of the objective lens, when the first optical path difference providing structure provided in the central area is provided, it may be provided on a different optical surface of the objective lens, but the same It is preferably provided on the optical surface. Providing them on the same optical surface is preferable because it makes it possible to reduce eccentricity errors during manufacturing. Moreover, it is preferable that the first optical path difference providing structure and the second optical path difference providing structure are provided on the light source side surface of the objective lens rather than the optical disk side surface of the objective lens.

　対物レンズは、対物レンズの第１光路差付与構造が設けられた中央領域を通過する第１光束、第２光束及び第３光束を、それぞれ集光スポットを形成するように集光する。好ましくは、対物レンズは、対物レンズの第１光路差付与構造が設けられた中央領域を通過する第１光束を、第１光ディスクの情報記録面上に情報の記録及び／又は再生ができるように集光する。また、対物レンズは、対物レンズの第１光路差付与構造が設けられた中央領域を通過する第２光束を、第２光ディスクの情報記録面上に情報の記録及び／又は再生ができるように集光する。さらに、対物レンズは、対物レンズの第１光路差付与構造が設けられた中央領域を通過する第３光束を、第３光ディスクの情報記録面上に情報の記録及び／又は再生ができるように集光する。また、第１光ディスクの保護基板の厚さｔ１と第２光ディスクの保護基板の厚さｔ２が異なる場合、第１光路差付与構造は、第１光路差付与構造を通過する第１光束及び第２光束に対して、第１光ディスクの保護基板の厚さｔ１と第２光ディスクの保護基板の厚さｔ２の違いにより発生する球面収差及び／又は第１光束と第２光束の波長の違いにより発生する球面収差を補正することが好ましい。さらに、第１光路差付与構造は、第１光路差付与構造を通過した第１光束及び第３光束に対して、第１光ディスクの保護基板の厚さｔ１と第３光ディスクの保護基板の厚さｔ３との違いにより発生する球面収差及び／又は第１光束と第３光束の波長の違いにより発生する球面収差を補正することが好ましい。 The objective lens condenses the first light beam, the second light beam, and the third light beam that pass through the central region where the first optical path difference providing structure of the objective lens is provided so as to form a condensed spot. Preferably, the objective lens is capable of recording and / or reproducing information on the information recording surface of the first optical disc, with the first light beam passing through the central region provided with the first optical path difference providing structure of the objective lens. Condensate. In addition, the objective lens collects the second light flux that passes through the central region where the first optical path difference providing structure of the objective lens is provided so that information can be recorded and / or reproduced on the information recording surface of the second optical disc. Shine. Further, the objective lens collects the third light flux that passes through the central region where the first optical path difference providing structure of the objective lens is provided so that information can be recorded and / or reproduced on the information recording surface of the third optical disc. Shine. In addition, when the thickness t1 of the protective substrate of the first optical disc and the thickness t2 of the protective substrate of the second optical disc are different, the first optical path difference providing structure includes the first light flux passing through the first optical path difference providing structure and the second optical flux. It occurs due to the spherical aberration generated by the difference between the thickness t1 of the protective substrate of the first optical disk and the thickness t2 of the protective substrate of the second optical disk and / or the difference in the wavelengths of the first and second light beams. It is preferable to correct spherical aberration. Further, the first optical path difference providing structure has a thickness t1 of the protective substrate of the first optical disc and a thickness of the protective substrate of the third optical disc with respect to the first light beam and the third light beam that have passed through the first optical path difference providing structure. It is preferable to correct spherical aberration generated due to a difference from t3 and / or spherical aberration generated due to a difference in wavelength between the first light flux and the third light flux.

　対物レンズの第１光束における焦点距離をｆ１（ｍｍ）とし、対物レンズの光軸上の中心厚さをｄ（ｍｍ）とした際に、下記の式（９）を満たすことが好ましい。 When the focal length of the first light beam of the objective lens is f1 (mm) and the center thickness on the optical axis of the objective lens is d (mm), it is preferable to satisfy the following formula (9).

　０．７≦ｄ／ｆ１≦２．０　　　　　　　（９）
　なお、下記の式（１０）を満たすことがより好ましい。 0.7 ≦ d / f1 ≦ 2.0 (9)
In addition, it is more preferable to satisfy | fill following formula (10).

　１．０≦ｄ／ｆ１≦１．５　　　　　　　（１０）
　上記構成により、光路差付与構造のピッチを小さくすることなく、第３光ディスクとしてのＣＤのワーキングディスタンスを確保でき、対物レンズの製造も容易にする事が出来、加えて、光の利用効率を高く維持することが可能となる。 1.0 ≦ d / f1 ≦ 1.5 (10)
With the above configuration, the working distance of the CD as the third optical disk can be secured without reducing the pitch of the optical path difference providing structure, and the objective lens can be easily manufactured. In addition, the light use efficiency is increased. Can be maintained.

　また、以下の条件式を満たすことが好ましい。 Moreover, it is preferable that the following conditional expression is satisfied.

　2.1mm≦φ≦4.2mm
尚、Φは、第１光ディスク使用時の対物レンズの有効径を表す。上記範囲を満たすことにより、第３光ディスクとしてのCDのワーキングディスタンスを実使用上問題ないレベルの距離を確保しつつ、例え、対物レンズがプラスチックレンズであったとしても、温度変化時における収差変化を問題ないレベルに維持することができる。 2.1mm ≦ φ ≦ 4.2mm
Φ represents the effective diameter of the objective lens when the first optical disk is used. By satisfying the above range, the working distance of the CD as the third optical disk is secured at a distance that does not cause any problem in practical use, and even if the objective lens is a plastic lens, for example, the aberration change when the temperature changes It can be maintained at a problem-free level.

　また、対物レンズは、対物レンズに設けられた第２光路差付与構造を用いて周辺領域を通過する第１光束及び第２光束を、それぞれ集光スポットを形成するように集光する。好ましくは、対物レンズは、対物レンズの第２光路差付与構造が設けられた周辺領域を通過する第１光束を、第１光ディスクの情報記録面上に情報の記録及び／又は再生ができるように集光する。また、対物レンズは、対物レンズの第２光路差付与構造が設けられた周辺領域を通過する第２光束を、第２光ディスクの情報記録面上に情報の記録及び／又は再生ができるように集光する。また第２光路差付与構造は、第２光路差付与構造を通過する第１光束及び第２光束の波長の違いにより発生する色球面収差を補正することが好ましい。 Further, the objective lens condenses the first light flux and the second light flux that pass through the peripheral region by using the second optical path difference providing structure provided in the objective lens so as to form a condensed spot. Preferably, the objective lens is capable of recording and / or reproducing information on the information recording surface of the first optical disc, with the first light flux passing through the peripheral region provided with the second optical path difference providing structure of the objective lens. Condensate. In addition, the objective lens collects the second light flux that passes through the peripheral area where the second optical path difference providing structure of the objective lens is provided so that information can be recorded and / or reproduced on the information recording surface of the second optical disc. Shine. Further, it is preferable that the second optical path difference providing structure corrects chromatic spherical aberration caused by a difference in wavelength between the first light beam and the second light beam that pass through the second optical path difference providing structure.

　また、好ましい態様として、対物レンズの第２光路差付与構造が設けられた周辺領域を通過した第３光束は、第３光ディスクの記録及び／又は再生に用いられない態様が挙げられる。第２光路差付与構造が設けられた周辺領域を通過した第３光束が、第３光ディスクの情報記録面上で集光スポットの形成に寄与しないようにすることが好ましい。つまり、第２光路差付与構造が設けられた周辺領域を通過する第３光束は、第３光ディスクの情報記録面上でフレアを形成することが好ましい。図４に示すように、対物レンズを通過した第３光束が第３光ディスクの情報記録面上で形成するスポットにおいて、光軸側（又はスポット中心部）から外側へ向かう順番で、光量密度が高いスポット中心部ＳＣＮ、光量密度がスポット中心部より低いスポット中間部ＳＭＤ、光量密度がスポット中間部よりも高くスポット中心部よりも低いスポット周辺部ＳＯＴを有する。スポット中心部が、光ディスクの情報の記録及び／又は再生に用いられ、スポット中間部及びスポット周辺部は、光ディスクの情報の記録及び／又は再生には用いられない。上記において、このスポット周辺部をフレアと言っている。しかしながら、上述のようなフレアでなくても、光量密度が高いスポット中心部の周りに、スポット中間部がなく、光量密度がスポット中心部より低いスポット周辺部がある場合もあり得、この場合は、当該スポット周辺部をフレアと言う。つまり、対物レンズの第２光路差付与構造が設けられた周辺領域を通過した第３光束は、第３光ディスクの情報記録面上でスポット周辺部を形成する。 Further, as a preferable mode, a mode in which the third light flux that has passed through the peripheral region provided with the second optical path difference providing structure of the objective lens is not used for recording and / or reproduction of the third optical disk can be mentioned. It is preferable that the third light flux that has passed through the peripheral region provided with the second optical path difference providing structure does not contribute to the formation of a focused spot on the information recording surface of the third optical disc. That is, it is preferable that the third light flux passing through the peripheral region provided with the second optical path difference providing structure forms a flare on the information recording surface of the third optical disc. As shown in FIG. 4, in the spot formed on the information recording surface of the third optical disc by the third light flux that has passed through the objective lens, the light amount density is high in the order from the optical axis side (or the spot center) to the outside. The spot center portion SCN, the spot intermediate portion SMD whose light intensity density is lower than that of the spot center portion, and the spot peripheral portion SOT whose light intensity density is higher than that of the spot intermediate portion and lower than that of the spot center portion. The center portion of the spot is used for recording and / or reproducing information on the optical disc, and the spot intermediate portion and the spot peripheral portion are not used for recording and / or reproducing information on the optical disc. In the above, this spot peripheral part is called flare. However, even if the flare is not as described above, there may be a spot peripheral portion around the spot center portion where the light density is high and there is no spot middle portion, and the light spot density is lower than the spot center portion. The periphery of the spot is called flare. That is, the third light flux that has passed through the peripheral area where the second optical path difference providing structure of the objective lens is provided forms a spot peripheral portion on the information recording surface of the third optical disc.

　また、最周辺領域を有する場合の好ましい態様として、最周辺領域を通過した第１光束は、第１光ディスクの記録及び／又は再生に用いられ、最周辺領域を通過した第２光束及び第３光束は、第２光ディスク及び第３光ディスクの記録及び／又は再生に用いられない態様が挙げられる。最周辺領域を通過した第２光束及び第３光束が、それぞれ第２光ディスク及び第３光ディスクの情報記録面上での集光スポットの形成に寄与しないようにすることが好ましい。つまり、対物レンズが最周辺領域を有する場合、対物レンズの最周辺領域を通過する第２光束及び第３光束は、第２光ディスク及び第３光ディスクの情報記録面上でフレアを形成することが好ましい。言い換えると、対物レンズの最周辺領域を通過した第２光束及び第３光束は、第２光ディスク及び第３光ディスクの情報記録面上でスポット周辺部を形成することが好ましい。 Moreover, as a preferable aspect in the case of having the outermost peripheral area, the first light flux that has passed through the outermost peripheral area is used for recording and / or reproduction of the first optical disc, and the second and third light fluxes that have passed through the outermost peripheral area. Includes an aspect that is not used for recording and / or reproduction of the second optical disc and the third optical disc. It is preferable that the second light flux and the third light flux that have passed through the outermost peripheral region do not contribute to the formation of a condensed spot on the information recording surfaces of the second optical disc and the third optical disc, respectively. That is, when the objective lens has the outermost peripheral area, the second light flux and the third light flux that pass through the outermost peripheral area of the objective lens preferably form a flare on the information recording surfaces of the second optical disc and the third optical disc. . In other words, it is preferable that the second light flux and the third light flux that have passed through the most peripheral area of the objective lens form a spot peripheral portion on the information recording surface of the second optical disc and the third optical disc.

　最周辺領域が第３光路差付与構造を有する場合、第３光路差付与構造が、第３光路差付与構造を通過した第１光束に対して、第１光源の波長の僅かな変動によって発生するスフェロクロマティズム（色球面収差）を補正するようにしてもよい。波長の僅かな変動とは、±１０ｎｍ以内の変動を指す。例えば、第１光束が波長λ１より±５ｎｍ変化した際に、第３光路差付与構造によって、最周辺領域を通過した第１光束の球面収差の変動を補償し、第１光ディスクの情報記録面上での波面収差の変化量が０．００１λ２ｒｍｓ以上、０．０７０λ２ｒｍｓ以下となるようにすることが好ましい。 When the outermost peripheral region has the third optical path difference providing structure, the third optical path difference providing structure is generated by a slight variation in the wavelength of the first light source with respect to the first light flux that has passed through the third optical path difference providing structure. Spherochromatism (chromatic spherical aberration) may be corrected. A slight change in wavelength refers to a change within ± 10 nm. For example, when the first light beam changes by ± 5 nm from the wavelength λ1, the third optical path difference providing structure compensates for the variation in spherical aberration of the first light beam that has passed through the most peripheral region, and on the information recording surface of the first optical disc. It is preferable that the amount of change in the wavefront aberration at 0.001λ2 rms or more and 0.070λ2 rms or less.

　なお、第１の基礎構造と第２の基礎構造を重ね併せて第２光路差付与構造を形成することにより、第２光路差付与構造を通過した第１光束、第２光束、第３光束全ての出射光の方向を異ならせることが可能となるため、第１光束、第２光束、第３光束の全ての光束が同じ結像倍率（例えば、全て平行光束）で対物レンズに入射したとしても、異なる種類の光ディスクを用いていることに起因して発生する収差を補正でき、互換が可能となる。 In addition, all of the first light flux, the second light flux, and the third light flux that have passed through the second optical path difference providing structure are formed by overlapping the first basic structure and the second basic structure to form the second optical path difference providing structure. The directions of the emitted light beams can be made different, so even if all the first, second, and third light beams enter the objective lens with the same imaging magnification (for example, all parallel light beams). Aberrations caused by using different types of optical discs can be corrected, and compatibility is possible.

　対物レンズがプラスチックレンズである場合、温度特性補正用構造として第３の基礎構造を、第１の基礎構造及び第２の基礎構造にさらに重ねたものを第２光路差付与構造としてもよい。但し、第１光ディスクがＨＤである場合は、温度変化の影響がそれ程大きくないため、対物レンズに温度特性補正用構造としての基礎構造は設けなくてもよい。具体的には、第３の基礎構造の光軸方向の段差量は、第１光束に対して第１波長の略１０波長分の光路差を与え、第２光束に対して第２波長の略６波長分の光路差を与え、第３光束に対して第３波長の略５波長分の光路差を与えるような段差量であるか、第１光束に対して第１波長の略５波長分の光路差を与え、第２光束に対して第２波長の略３波長分の光路差を与え、第３光束に対して第３波長の略２波長分の光路差を与えるような段差量である事が好ましい。 When the objective lens is a plastic lens, the third basic structure as the temperature characteristic correcting structure may be further overlapped with the first basic structure and the second basic structure as the second optical path difference providing structure. However, when the first optical disc is an HD, the influence of temperature change is not so great, so that the objective lens does not have to be provided with a basic structure as a temperature characteristic correcting structure. Specifically, the level difference in the optical axis direction of the third basic structure gives an optical path difference corresponding to approximately 10 wavelengths of the first wavelength to the first light flux, and approximately the second wavelength relative to the second light flux. The optical path difference for 6 wavelengths is given, and the step amount is such that the optical path difference for about 5 wavelengths of the third wavelength is given to the third light flux, or about 5 wavelengths of the first wavelength for the first light flux. The difference in level is such that an optical path difference corresponding to approximately three wavelengths of the second wavelength is applied to the second light flux, and an optical path difference corresponding to approximately two wavelengths of the third wavelength is applied to the third light flux. Something is preferable.

　また、対物レンズがプラスチックレンズである場合、温度特性補正用構造として基礎構造を、重ねたものを第１光路差付与構造としてもよい。但し、第１光ディスクがＨＤである場合は、温度変化の影響がそれ程大きくないため、対物レンズに温度特性補正用構造としての基礎構造は設けなくてもよい。具体的には、第３の基礎構造の光軸方向の段差量は、第１光束に対して第１波長の略１０波長分の光路差を与え、第２光束に対して第２波長の略６波長分の光路差を与え、第３光束に対して第３波長の略５波長分の光路差を与えるような段差量である事が好ましい。 Further, when the objective lens is a plastic lens, the basic structure may be used as the temperature characteristic correcting structure, and the stacked structure may be used as the first optical path difference providing structure. However, when the first optical disc is an HD, the influence of temperature change is not so great, so that the objective lens does not have to be provided with a basic structure as a temperature characteristic correcting structure. Specifically, the level difference in the optical axis direction of the third basic structure gives an optical path difference corresponding to approximately 10 wavelengths of the first wavelength to the first light flux, and approximately the second wavelength relative to the second light flux. It is preferable that the level difference be such that an optical path difference for six wavelengths is given and an optical path difference for about five wavelengths of the third wavelength is given to the third light flux.

　また、最周辺領域を設け、対物レンズがプラスチックである場合は、さらに最周辺領域に第３光路差付与構造を設けることが好ましいが、その場合は、第３光路差付与構造は、少なくとも第３の基礎構造を有する構造としてもよい。 In the case where the outermost peripheral region is provided and the objective lens is plastic, it is preferable to further provide the third optical path difference providing structure in the outermost peripheral region. In this case, the third optical path difference providing structure is at least the third optical path difference providing structure. It is good also as a structure which has the following basic structure.

　前述したように、段差量は大きすぎない方が好ましい。基礎構造を複数重ね合わせて得た基礎となる光路差付与構造のある輪帯の段差量が基準の値より高い場合、輪帯の段差量を１０・λＢ／（ｎ－１）（μｍ）だけ低くすることにより、光学性能に影響を及ぼすことなく、大きすぎる段差量を減らすことが可能となる。なお、基準の値としては、任意の値を設定する事ができるが、１０・λＢ／（ｎ－１）（μｍ）を基準値とする事が好ましい。 As described above, it is preferable that the level difference is not too large. If the level difference of the annular zone with the optical path difference providing structure that is the basis obtained by superimposing multiple foundation structures is higher than the reference value, the level difference of the annular zone is only 10 · λB / (n-1) (μm) By making it low, it becomes possible to reduce an excessively large step amount without affecting the optical performance. An arbitrary value can be set as the reference value, but it is preferable to set 10 · λB / (n−1) (μm) as the reference value.

　また、細長い輪帯が少ない方が製造上好ましいという観点から、第１光路差付与構造の全ての輪帯において、（段差量／ピッチ幅）の値が、１以下である事が好ましく、更に好ましくは０．８以下である事である。更に好ましくは、全ての光路差付与構造の全ての輪帯において、（段差量／ピッチ幅）の値が、１以下である事が好ましく、更に好ましくは０．８以下である事である。 Further, from the viewpoint that it is preferable from the viewpoint of production that the number of elongated ring zones is small, it is preferable that the value of (step amount / pitch width) is 1 or less in all the ring zones of the first optical path difference providing structure, and more preferable. Is 0.8 or less. More preferably, the value of (step difference / pitch width) is preferably 1 or less, and more preferably 0.8 or less, in all annular zones of all optical path difference providing structures.

　第１光ディスクに対して情報を再生及び／又は記録するために必要な対物レンズの像側開口数をＮＡ１とし、第２光ディスクに対して情報を再生及び／又は記録するために必要な対物レンズの像側開口数をＮＡ２（ＮＡ１≧ＮＡ２）とし、第３光ディスクに対して情報を再生及び／又は記録するために必要な対物レンズの像側開口数をＮＡ３（ＮＡ２＞ＮＡ３）とする。ＮＡ１は、０．６以上、０．９以下であることが好ましい。特にＮＡ１は０．８５であることが好ましい。ＮＡ２は、０．５５以上、０．７以下であることが好ましい。特にＮＡ２は０．６０又は０．６５であることが好ましい。また、ＮＡ３は、０．４以上、０．５５以下であることが好ましい。特にＮＡ３は０．４５又は０．５３であることが好ましい。 The objective-side numerical aperture of the objective lens necessary for reproducing and / or recording information on the first optical disk is NA1, and the objective lens necessary for reproducing and / or recording information on the second optical disk The image-side numerical aperture is NA2 (NA1 ≧ NA2), and the image-side numerical aperture of the objective lens necessary for reproducing and / or recording information on the third optical disk is NA3 (NA2> NA3). NA1 is preferably 0.6 or more and 0.9 or less. In particular, NA1 is preferably 0.85. NA2 is preferably 0.55 or more and 0.7 or less. In particular, NA2 is preferably 0.60 or 0.65. NA3 is preferably 0.4 or more and 0.55 or less. In particular, NA3 is preferably 0.45 or 0.53.

　対物レンズの中央領域と周辺領域の境界は、第３光束の使用時において、０．９・ＮＡ３以上、１．２・ＮＡ３以下（より好ましくは、０．９５・ＮＡ３以上、１．１５・ＮＡ３以下）の範囲に相当する部分に形成されていることが好ましい。より好ましくは、対物レンズの中央領域と周辺領域の境界が、ＮＡ３に相当する部分に形成されていることである。また、対物レンズの周辺領域と最周辺領域の境界は、第２光束の使用時において、０．９・ＮＡ２以上、１．２・ＮＡ２以下（より好ましくは、０．９５・ＮＡ２以上、１．１５・ＮＡ２以下）の範囲に相当する部分に形成されていることが好ましい。より好ましくは、対物レンズの周辺領域と最周辺領域の境界が、ＮＡ２に相当する部分に形成されていることである。 The boundary between the central region and the peripheral region of the objective lens is 0.9 · NA3 or more and 1.2 · NA3 or less (more preferably 0.95 · NA3 or more, 1.15 · NA3) when the third light flux is used. It is preferably formed in a portion corresponding to the following range. More preferably, the boundary between the central region and the peripheral region of the objective lens is formed in a portion corresponding to NA3. The boundary between the peripheral area and the most peripheral area of the objective lens is 0.9 · NA 2 or more and 1.2 · NA 2 or less (more preferably 0.95 · NA 2 or more, 1. 15 · NA2 or less) is preferable. More preferably, the boundary between the peripheral region and the most peripheral region of the objective lens is formed in a portion corresponding to NA2.

　対物レンズを通過した第３光束を第３光ディスクの情報記録面上に集光する場合に、球面収差が少なくとも１箇所の不連続部を有することが好ましい。その場合、不連続部は、第３光束の使用時において、０．９・ＮＡ３以上、１．２・ＮＡ３以下（より好ましくは、０．９５・ＮＡ３以上、１．１５・ＮＡ３以下）の範囲に存在することが好ましい。 When the third light flux that has passed through the objective lens is condensed on the information recording surface of the third optical disc, it is preferable that the spherical aberration has at least one discontinuous portion. In that case, the discontinuous portion has a range of 0.9 · NA 3 or more and 1.2 · NA 3 or less (more preferably 0.95 · NA 3 or more and 1.15 · NA 3 or less) when the third light flux is used. It is preferable that it exists in.

　また、球面収差が連続していて、不連続部を有さない場合であって、対物レンズを通過した第３光束を第３光ディスクの情報記録面上に集光する場合に、ＮＡ２では、縦球面収差の絶対値が０．０３μｍ以上であって、ＮＡ３では縦球面収差の絶対値が０．０２μｍ以下であることが好ましい。より好ましくは、ＮＡ２では、縦球面収差の絶対値が０．０８μｍ以上であって、ＮＡ３では縦球面収差の絶対値が０．０１μｍ以下である。 In addition, when spherical aberration is continuous and does not have a discontinuous portion and the third light flux that has passed through the objective lens is condensed on the information recording surface of the third optical disc, NA2 It is preferable that the absolute value of the spherical aberration is 0.03 μm or more, and in NA3, the absolute value of the longitudinal spherical aberration is 0.02 μm or less. More preferably, in NA2, the absolute value of longitudinal spherical aberration is 0.08 μm or more, and in NA3, the absolute value of longitudinal spherical aberration is 0.01 μm or less.

　また、光ピックアップ装置の用途に応じて、中央領域の各波長に対する回折効率を適宜設定可能である。例えば、第１光ディスクに対して記録及び再生を行い、第２、第３光ディスクに対して再生のみ行う光ピックアップ装置の場合には、中央領域及び／又は周辺領域の回折効率を、第１光束を重視して設定するのが好ましい。一方、第１光ディスクに対して再生のみを行い、第２、第３光ディスクに対して記録及び再生を行う光ピックアップ装置の場合には、中央領域の回折効率を、第２、第３光束を重視して設定し、周辺領域の回折効率を第２光束を重視して設定するのが好ましい。 Also, the diffraction efficiency for each wavelength in the central region can be set as appropriate according to the use of the optical pickup device. For example, in the case of an optical pickup device that performs recording and reproduction on the first optical disc and only reproduction on the second and third optical discs, the diffraction efficiency of the central region and / or the peripheral region is expressed as It is preferable to set with emphasis. On the other hand, in the case of an optical pickup device that performs only reproduction with respect to the first optical disc and performs recording and reproduction with respect to the second and third optical discs, the second and third light fluxes are emphasized with respect to the diffraction efficiency of the central region. It is preferable to set the diffraction efficiency of the peripheral region with the second light flux as important.

　何れの場合でも、下記条件式（１１）を満たすようにすることで、各領域の面積加重平均により計算される第１光束の回折効率を高く確保することが可能となる。 In any case, by satisfying the following conditional expression (11), it is possible to ensure high diffraction efficiency of the first light flux calculated by the area weighted average of each region.

　η１１≦η２１　　　　（１１）
　但し、η１１は中央領域における第１光束の回折効率を表し、η２１は周辺領域における第１光束の回折効率を表す。なお、中央領域の回折効率を第２、第３波長の光束重視とした場合には、中央領域の第１光束の回折効率は低くなるが、第１光ディスクの開口数が第３光ディスクの開口数に比べて大きい場合は、第１光束の有効径全体で考えると中央領域の回折効率低下はそれほど大きな影響を与えない。 η11 ≦ η21 (11)
However, η11 represents the diffraction efficiency of the first light flux in the central region, and η21 represents the diffraction efficiency of the first light flux in the peripheral region. When the diffraction efficiency of the central region is focused on the light fluxes of the second and third wavelengths, the diffraction efficiency of the first light flux of the central region is low, but the numerical aperture of the first optical disc is the numerical aperture of the third optical disc. If it is larger than, the lowering of the diffraction efficiency in the central region does not have a significant effect when considering the entire effective diameter of the first light flux.

　なお、本明細書における回折効率は、以下のように定義することができる。
［１］同一の焦点距離、レンズ厚さ、開口数を有し、同一の材料で形成され、第１及び第２光路差付与構造が形成されない対物レンズの透過率を、中央領域、周辺領域に分けて測定する。この際、中央領域の透過率は、周辺領域に入射する光束を遮断して測定し、周辺領域の透過率は中央領域に入射する光束を遮断して測定する。
［２］第１及び第２光路差付与構造を有する対物レンズの透過率を、中央領域と周辺領域に分けて測定する。
［３］上記［２］の結果を［１］の結果で割った値を各領域の回折効率とする。 In addition, the diffraction efficiency in this specification can be defined as follows.
[1] The transmittance of an objective lens that has the same focal length, lens thickness, and numerical aperture, is formed of the same material, and does not have the first and second optical path difference providing structures is formed in the central region and the peripheral region. Separately measure. At this time, the transmittance of the central region is measured by blocking the light beam incident on the peripheral region, and the transmittance of the peripheral region is measured by blocking the light beam incident on the central region.
[2] The transmittance of the objective lens having the first and second optical path difference providing structures is measured separately for the central region and the peripheral region.
[3] The value obtained by dividing the result of [2] by the result of [1] is the diffraction efficiency of each region.

　また、第１光束乃至第３光束の何れか二つの光束の光利用効率が７０％以上であって、残りの一つの光束の光利用効率を３０％以上、７０％以下にするようにしてもよい。残りの一つの光束の光利用効率を４０％以上、６０％以下にするようにしてもよい。この場合、光利用効率を３０％以上、７０％以下（または４０％以上、６０％以下）とする光束は、第３光束であることが好ましい。 The light utilization efficiency of any two of the first to third light fluxes is 70% or more, and the light utilization efficiency of the remaining one light flux is 30% or more and 70% or less. Good. The light utilization efficiency of the remaining one light beam may be 40% or more and 60% or less. In this case, it is preferable that the light beam having the light use efficiency of 30% or more and 70% or less (or 40% or more and 60% or less) is the third light beam.

　なお、ここでいう光利用効率とは、第１光路差付与構造が形成された対物レンズ（第２光路差付与構造及び第３光路差付与構造が形成されていてもよい）により光ディスクの情報記録面上に形成された集光スポットのエアリーディスク内の光量をＡとし、同一の材料から形成され、且つ、同一の焦点距離、軸上厚さ、開口数、波面収差を有し、第１光路差付与構造、第２光路差付与構造及び第３光路差付与構造が形成されない対物レンズにより、光情報記録媒体の情報記録面上に形成された集光スポットのエアリーディスク内の光量をＢとしたとき、Ａ／Ｂにより算出するものとする。なお、ここでいうエアリーディスクとは、集光スポットの光軸を中心とする半径ｒ’の円をいう。ｒ’＝０．６１・λ／ＮＡで表される。 Here, the light utilization efficiency is the information recording on the optical disk by the objective lens in which the first optical path difference providing structure is formed (the second optical path difference providing structure and the third optical path difference providing structure may be formed). The amount of light in the Airy disk of the focused spot formed on the surface is A, and the first optical path is formed from the same material and has the same focal length, axial thickness, numerical aperture, and wavefront aberration. The amount of light in the Airy disk of the focused spot formed on the information recording surface of the optical information recording medium by the objective lens in which the difference providing structure, the second optical path difference providing structure, and the third optical path difference providing structure are not formed is defined as B. When calculating by A / B. Here, the Airy disk refers to a circle having a radius r ′ centered on the optical axis of the focused spot. r ′ = 0.61 · λ / NA.

　第１光束、第２光束及び第３光束は、平行光として対物レンズに入射してもよいし、発散光若しくは収束光として対物レンズに入射してもよい。好ましくは、第１光束が対物レンズに入射する時の、対物レンズの結像倍率ｍ１が、下記の式（１２）を満たすことである。
－０．０２＜ｍ１＜０．０２　　　　　（１２）
　一方で、第１光束を発散光として対物レンズに入射する場合、第１光束が対物レンズへ入射する時の、対物レンズの結像倍率ｍ１が、下記の式（１２‘）を満たすことが好ましい。
－０．１０＜ｍ１＜０　　　　　（１２‘）
　また、第２光束を平行光又は略平行光として対物レンズに入射させる場合、第２光束が対物レンズへ入射する時の、対物レンズの結像倍率ｍ２が、下記の式（１３）を満たすことが好ましい。 The first light beam, the second light beam, and the third light beam may be incident on the objective lens as parallel light, or may be incident on the objective lens as divergent light or convergent light. Preferably, the imaging magnification m1 of the objective lens when the first light beam enters the objective lens satisfies the following formula (12).
-0.02 <m1 <0.02 (12)
On the other hand, when the first light beam is incident on the objective lens as diverging light, the imaging magnification m1 of the objective lens when the first light beam is incident on the objective lens preferably satisfies the following expression (12 ′). .
-0.10 <m1 <0 (12 ')
Further, when the second light flux is incident on the objective lens as parallel light or substantially parallel light, the imaging magnification m2 of the objective lens when the second light flux enters the objective lens satisfies the following expression (13). Is preferred.

　－０．０２＜ｍ２＜０．０２　　　　　（１３）
　一方で、第２光束を発散光として対物レンズに入射させる場合、第２光束が対物レンズへ入射する時の、対物レンズの結像倍率ｍ２が、下記の式（１３‘）を満たすことが好ましい。 -0.02 <m2 <0.02 (13)
On the other hand, when the second light beam is incident on the objective lens as diverging light, the imaging magnification m2 of the objective lens when the second light beam is incident on the objective lens preferably satisfies the following expression (13 ′). .

　－０．１０＜ｍ２＜０　　　　　（１３‘）
　また、第３光束を平行光又は略平行光として対物レンズに入射させる場合、第３光束が対物レンズへ入射する時の、対物レンズの結像倍率ｍ３が、下記の式（１４）を満たすことが好ましい。第３光束が平行光である場合、トラッキングにおいて問題が発生しやすくなるが、本発明は第３光束が平行光であっても、良好なトラッキング特性を得ることを可能とし、３つの異なる光ディスクに対して記録及び／又は再生を適切に行う事を可能とする。 -0.10 <m2 <0 (13 ')
When the third light beam is incident on the objective lens as parallel light or substantially parallel light, the imaging magnification m3 of the objective lens when the third light beam enters the objective lens satisfies the following expression (14). Is preferred. When the third light flux is parallel light, a problem easily occurs in tracking. However, even if the third light flux is parallel light, the present invention can obtain good tracking characteristics, and can be used for three different optical disks. On the other hand, recording and / or reproduction can be appropriately performed.

　－０．０２＜ｍ３＜０．０２　　　　　（１４）
　一方で、第３光束を発散光として対物レンズに入射させる場合、第３光束が対物レンズへ入射する時の、対物レンズの結像倍率ｍ３が、下記の式（１４‘）を満たすことが好ましい。 -0.02 <m3 <0.02 (14)
On the other hand, when the third light beam is incident on the objective lens as diverging light, the imaging magnification m3 of the objective lens when the third light beam is incident on the objective lens preferably satisfies the following expression (14 ′). .

　－０．１０＜ｍ３＜０　　　　　（１４‘）
　また、第３光ディスクを用いる際の対物レンズのワーキングディスタンス（ＷＤ）は、０．２０ｍｍ以上、１．５ｍｍ以下であることが好ましい。好ましくは、０．３ｍｍ以上、１．２０ｍｍ以下である。次に、第２光ディスクを用いる際の対物レンズのＷＤは、０．４ｍｍ以上、１．３ｍｍ以下であることが好ましい。さらに、第１光ディスクを用いる際の対物レンズのＷＤは、０．４ｍｍ以上、１．２ｍｍ以下であることが好ましい。 -0.10 <m3 <0 (14 ')
Further, the working distance (WD) of the objective lens when using the third optical disk is preferably 0.20 mm or more and 1.5 mm or less. Preferably, it is 0.3 mm or more and 1.20 mm or less. Next, the WD of the objective lens when using the second optical disk is preferably 0.4 mm or more and 1.3 mm or less. Further, the WD of the objective lens when using the first optical disk is preferably 0.4 mm or more and 1.2 mm or less.

　本発明に係る光情報記録再生装置は、上述の光ピックアップ装置を有する光ディスクドライブ装置を有する。 An optical information recording / reproducing apparatus according to the present invention includes an optical disc drive apparatus having the above-described optical pickup apparatus.

　ここで、光情報記録再生装置に装備される光ディスクドライブ装置に関して説明すると、光ディスクドライブ装置には、光ピックアップ装置等を収納している光情報記録再生装置本体から光ディスクを搭載した状態で保持可能なトレイのみが外部に取り出される方式と、光ピックアップ装置等が収納されている光ディスクドライブ装置本体ごと、外部に取り出される方式とがある。 Here, the optical disk drive apparatus provided in the optical information recording / reproducing apparatus will be described. The optical disk drive apparatus can hold an optical disk mounted from the optical information recording / reproducing apparatus main body containing the optical pickup apparatus or the like. There are a system in which only the tray is taken out, and a system in which the optical disc drive apparatus main body in which the optical pickup device is stored is taken out to the outside.

　上述した各方式を用いる光情報記録再生装置には、概ね、次の構成部材が装備されているがこれに限られるものではない。　ハウジング等に収納された光ピックアップ装置、光ピックアップ装置をハウジングごと光ディスクの内周あるいは外周に向けて移動させるシークモータ等の光ピックアップ装置の駆動源、光ピックアップ装置のハウジングを光ディスクの内周あるいは外周に向けてガイドするガイドレールなどを有した光ピックアップ装置の移送手段及び、光ディスクの回転駆動を行うスピンドルモータ等である。 The optical information recording / reproducing apparatus using each method described above is generally equipped with the following components, but is not limited thereto. An optical pickup device housed in a housing or the like, a drive source of an optical pickup device such as a seek motor that moves the optical pickup device together with the housing toward the inner periphery or outer periphery of the optical disc, and the optical pickup device housing the inner periphery or outer periphery of the optical disc These include a transfer means of an optical pickup device having a guide rail or the like that guides toward the head, a spindle motor that rotates the optical disk, and the like.

　前者の方式には、これら各構成部材の他に、光ディスクを搭載した状態で保持可能なトレイおよびトレイを摺動させるためのローディング機構等が設けられ、後者の方式にはトレイおよびローディング機構がなく、各構成部材が外部に引き出し可能なシャーシに相当するドロワーに設けられていることが好ましい。 In addition to these components, the former method is provided with a tray that can be held in a state in which an optical disk is mounted and a loading mechanism for sliding the tray, and the latter method has no tray and loading mechanism. It is preferable that each component is provided in a drawer corresponding to a chassis that can be pulled out to the outside.

　本発明によれば、所望の光学特性を発揮できると共に、成形金型の構成が複雑なものになりすぎる事を防止し、転写性を良好にでき、その構成の簡素化、低コスト化を実現可能な対物レンズ及びそれを用いた光ピックアップ装置を提供することが可能になる。 According to the present invention, the desired optical characteristics can be exhibited, the molding die configuration can be prevented from becoming too complicated, the transferability can be improved, and the configuration can be simplified and reduced in cost. It is possible to provide a possible objective lens and an optical pickup device using the same.

（ａ）は、本発明に係る対物レンズＯＢＪの一例を、光軸方向から見た図であり、（ｂ）は断面図である。(A) is the figure which looked at an example of objective-lens OBJ which concerns on this invention from the optical axis direction, (b) is sectional drawing. 本発明に係る対物レンズＯＢＪに設けられる光路差付与構造の幾つかの例（ａ）～（ｄ）を模式的に示す断面図である。FIG. 3 is a cross-sectional view schematically showing several examples (a) to (d) of an optical path difference providing structure provided in the objective lens OBJ according to the present invention. 光路差付与構造の重畳を示す図である。It is a figure which shows the superimposition of the optical path difference providing structure. 本発明に係る対物レンズによるスポットの形状を示した図である。It is the figure which showed the shape of the spot by the objective lens which concerns on this invention. 本発明に係る光ピックアップ装置の構成を概略的に示す図である。It is a figure which shows schematically the structure of the optical pick-up apparatus which concerns on this invention. 例１にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 1, (a) a cross section of a first basic structure, (b) a cross section of a second basic structure, and (c) a cross section of a superimposed second optical path difference providing structure. 例２にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 2, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例３にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 3, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例４にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 4, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例５にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 5, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例６にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 6, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例７にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 7, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例８にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 8, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例９にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 9, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, (c) a cross section of the superimposed second optical path difference providing structure. 例１０にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 10, (a) a cross section of a first basic structure, (b) a cross section of a second basic structure, and (c) a cross section of a superimposed second optical path difference providing structure. 例１１にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 11, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, (c) a cross section of the superimposed second optical path difference providing structure. 例１２にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 12, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例１３にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 13, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例１４にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 14, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, (c) a cross section of the superimposed second optical path difference providing structure. 例１５にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 15, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed optical path difference providing structure. 例１６にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 16, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例１７にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 17, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例１８にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 18, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, (c) a cross section of the superimposed second optical path difference providing structure. 例１９にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 19, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例２０にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 20, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例２１にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 21, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例２２にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 22, (a) a cross section of a first basic structure, (b) a cross section of a second basic structure, and (c) a cross section of a superimposed second optical path difference providing structure. 例２３にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 23, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure. 例２４にかかる光路差付与構造において、（ａ）第１基礎構造の断面、（ｂ）第２基礎構造の断面、（ｃ）重畳された第２光路差付与構造の断面を示す図である。In the optical path difference providing structure according to Example 24, (a) a cross section of the first basic structure, (b) a cross section of the second basic structure, and (c) a cross section of the superimposed second optical path difference providing structure.

　以下、本発明の実施の形態を図面を参照して説明する。図５は、異なる光ディスクであるＢＤとＤＶＤとＣＤに対して適切に情報の記録及び／又は再生を行うことができる本実施の形態の光ピックアップ装置ＰＵ１の構成を概略的に示す図である。かかる光ピックアップ装置ＰＵ１は、光情報記録再生装置に搭載できる。ここでは、第１光ディスクをＢＤとし、第２光ディスクをＤＶＤとし、第３光ディスクをＣＤとする。なお、本発明は、本実施の形態に限られるものではない。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 5 is a diagram schematically showing a configuration of the optical pickup device PU1 of the present embodiment that can appropriately record and / or reproduce information on BD, DVD, and CD, which are different optical disks. Such an optical pickup device PU1 can be mounted on an optical information recording / reproducing device. Here, the first optical disc is a BD, the second optical disc is a DVD, and the third optical disc is a CD. The present invention is not limited to the present embodiment.

　光ピックアップ装置ＰＵ１は、対物レンズＯＢＪ、絞りＳＴ、コリメートレンズＣＬ偏光ダイクロイックプリズムＰＰＳ、ＢＤに対して情報の記録／再生を行う場合に発光され波長λ１＝４０５ｎｍのレーザ光束（第１光束）を射出する第１半導体レーザＬＤ１（第１光源）と、ＢＤの情報記録面ＲＬ１からの反射光束を受光する第１の受光素子ＰＤ１とを一体化したユニットＭＤ１、レーザモジュールＬＭ等を有する。 The optical pickup device PU1 emits a laser beam (first beam) having a wavelength λ1 = 405 nm that is emitted when information is recorded / reproduced with respect to the objective lens OBJ, the aperture stop ST, and the collimator lens CL polarization dichroic prism PPS, BD. A unit MD1, a laser module LM, and the like in which a first semiconductor laser LD1 (first light source) and a first light receiving element PD1 that receives a reflected light beam from the information recording surface RL1 of the BD are integrated.

　また、レーザモジュールＬＭは、ＤＶＤに対して情報の記録／再生を行う場合に発光され波長λ２＝６５８ｎｍのレーザ光束（第２光束）を射出する第２半導体レーザＥＰ１（第２光源）と、ＣＤに対して情報の記録／再生を行う場合に発光され波長λ３＝７８５ｎｍのレーザ光束（第３光束）を射出する第３半導体レーザＥＰ２（第３光源）と、ＤＶＤの情報記録面ＲＬ２からの反射光束を受光する第２の受光素子ＤＳ１と、ＣＤの情報記録面ＲＬ３からの反射光束を受光する第３の受光素子ＤＳ２と、プリズムＰＳと、を有している。 The laser module LM includes a second semiconductor laser EP1 (second light source) that emits a laser beam (second beam) having a wavelength λ2 = 658 nm and is emitted when information is recorded / reproduced with respect to a DVD, and a CD. A third semiconductor laser EP2 (third light source) that emits a laser beam (third beam) having a wavelength λ3 = 785 nm and is reflected from the information recording surface RL2 of the DVD. It has a second light receiving element DS1 that receives the light beam, a third light receiving element DS2 that receives the reflected light beam from the information recording surface RL3 of the CD, and a prism PS.

　図１（ａ）及び（ｂ）に示されるように、本実施の形態の対物レンズＯＢＪにおいて、光源側の非球面光学面に光軸を含む中央領域ＣＮと、その周囲に配置された周辺領域ＭＤと、更にその周囲に配置された最周辺領域ＯＴとが、光軸を中心とする同心円状に形成されている。図示していないが、中央領域ＣＮには第１光路差付与構造が形成され、周辺領域ＭＤには第１基礎構造と第２基礎構造とを重畳した第２光路差付与構造が形成されている。また、最周辺領域ＯＴには、第３光路差付与構造が形成されているものと第３光路差付与構造が形成されず屈折面のものとがある。 As shown in FIGS. 1A and 1B, in the objective lens OBJ of the present embodiment, a central region CN including the optical axis on the aspherical optical surface on the light source side, and a peripheral region disposed around the central region CN The MD and the outermost peripheral region OT disposed around the MD are formed concentrically around the optical axis. Although not shown, the first optical path difference providing structure is formed in the central region CN, and the second optical path difference providing structure in which the first basic structure and the second basic structure are overlapped is formed in the peripheral region MD. . In the outermost peripheral region OT, there are a structure in which the third optical path difference providing structure is formed and a structure in which the third optical path difference providing structure is not formed and a refractive surface.

　第１光路差付与構造は、例えば、通過した第１光束の１次の回折効率を他のいかなる次数の回折効率よりも大きくし、第２光束の－１次の回折効率を他のいかなる次数の回折効率よりも大きくし、第３光束の－２次の回折効率を他のいかなる次数の回折効率よりも大きくする構造などを用いる事ができる。また、第２光路差付与構造の例１～２１のいずれかを第１光路差付与構造として用いてもよい。このとき、第２光路差付与構造は、例えば、通過した第１光束のｘ次の回折効率を他のいかなる次数の回折効率よりも大きくし、第２光束のｙ次の回折効率を他のいかなる次数の回折効率よりも大きくし、第３光束のｚ次の回折効率を他のいかなる次数の回折効率よりも大きくする構造などを用いる事ができ、（ｘ、ｙ、ｚ）＝（１，１，２）、（１，１，０）、（４，２，３）、（４，２，１）、（２，１，２）又は（２，１，０）とできるが、本明細書の第２光路差付与構造の例１～２４に記載されたものであれば何れも用いることができる。 The first optical path difference providing structure, for example, makes the first-order diffraction efficiency of the passed first light beam larger than any other order diffraction efficiency, and makes the -1st-order diffraction efficiency of the second light beam any other order. It is possible to use a structure that is larger than the diffraction efficiency and makes the second-order diffraction efficiency of the third light beam larger than the diffraction efficiency of any other order. Further, any one of Examples 1 to 21 of the second optical path difference providing structure may be used as the first optical path difference providing structure. At this time, the second optical path difference providing structure, for example, makes the x-order diffraction efficiency of the first light flux that has passed through larger than any other order diffraction efficiency, and makes the y-order diffraction efficiency of the second light flux any other It is possible to use a structure in which the diffraction efficiency of the third light beam is larger than the diffraction efficiency of the third light beam and the diffraction efficiency of the third light beam is larger than that of any other order. (X, y, z) = (1, 1 , 2), (1, 1, 0), (4, 2, 3), (4, 2, 1), (2, 1, 2) or (2, 1, 0). Any of those described in Examples 1 to 24 of the second optical path difference providing structure can be used.

　更に、第３光路差付与構造は、第１光路差付与構造及び第２光路差付与構造に合わせて、任意に選択することができる。また、第３光路差付与構造を有する場合、第３光路差付与構造は、第７基礎構造のみにより形成されていることが好ましい。第７基礎構造は、ブレーズ型構造であって、通過した第１光束の２次の回折効率を他のいかなる次数の回折効率よりも大きくし、第２光束の１次の回折効率を他のいかなる次数の回折効率よりも大きくし、第３光束の１次の回折効率を他のいかなる次数の回折効率よりも大きくする。なお、図１（ａ）及び（ｂ）の中央領域、周辺領域、最周辺領域の面積などの比率は正確には表されていない。 Furthermore, the third optical path difference providing structure can be arbitrarily selected according to the first optical path difference providing structure and the second optical path difference providing structure. Moreover, when it has a 3rd optical path difference providing structure, it is preferable that the 3rd optical path difference providing structure is formed only by the 7th foundation structure. The seventh basic structure is a blazed structure in which the second-order diffraction efficiency of the passed first light beam is made larger than any other order diffraction efficiency, and the first-order diffraction efficiency of the second light beam is made to be any other The first order diffraction efficiency of the third light beam is made larger than the diffraction efficiency of any other order. Note that the ratios of the areas of the central region, the peripheral region, and the outermost peripheral region in FIGS. 1A and 1B are not accurately represented.

　青紫色半導体レーザＬＤ１から射出された第１光束（λ１＝４０５ｎｍ）の発散光束は、偏光ダイクロイックプリズムＰＰＳを透過し、コリメートレンズＣＬにより平行光束とされた後、図示しないλ１／４板により直線偏光から円偏光に変換され、絞りＳＴによりその光束径が規制され、対物レンズＯＢＪに入射する。ここで、対物レンズＯＢＪの中央領域と周辺領域と最周辺領域により集光された光束は、厚さ０．１ｍｍの保護基板ＰＬ１を介して、ＢＤの情報記録面ＲＬ１上に形成されるスポットとなる。 The divergent light beam of the first light beam (λ1 = 405 nm) emitted from the blue-violet semiconductor laser LD1 is transmitted through the polarization dichroic prism PPS, converted into a parallel light beam by the collimator lens CL, and then linearly polarized by a λ1 / 4 plate (not shown). To circularly polarized light, the diameter of the light beam is regulated by the stop ST, and enters the objective lens OBJ. Here, the light beam condensed by the central region, the peripheral region, and the outermost peripheral region of the objective lens OBJ is a spot formed on the information recording surface RL1 of the BD via the protective substrate PL1 having a thickness of 0.1 mm. Become.

　情報記録面ＲＬ１上で情報ピットにより変調された反射光束は、再び対物レンズＯＢＪ、絞りＳＴを透過した後、図示しないλ１／４板により円偏光から直線偏光に変換され、コリメートレンズＣＬにより収斂光束とされ、偏光ダイクロイックプリズムＰＰＳを透過した後、第１の受光素子ＰＤ１の受光面上に収束する。そして、第１の受光素子ＰＤ１の出力信号を用いて、２軸アクチュエータＡＣにより対物レンズＯＢＪをフォーカシングやトラッキングさせることで、ＢＤに記録された情報を読み取ることができる。 The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the objective lens OBJ and the aperture stop ST, then converted from circularly polarized light to linearly polarized light by a λ1 / 4 plate (not shown), and converged by the collimating lens CL. After passing through the polarization dichroic prism PPS, it converges on the light receiving surface of the first light receiving element PD1. Then, by using the output signal of the first light receiving element PD1 to focus or track the objective lens OBJ by the biaxial actuator AC, it is possible to read information recorded on the BD.

　赤色半導体レーザＥＰ１から射出された第２光束（λ２＝６５８ｎｍ）の発散光束は、プリズムＰＳで反射された後、偏光ダイクロイックプリズムＰＰＳにより反射され、コリメートレンズＣＬにより平行光束とされた後、図示しないλ１／４板により偏光変換され、対物レンズＯＢＪに入射する。ここで、対物レンズＯＢＪの中央領域と周辺領域により集光された光束（最周辺領域を通過した光束はフレア化され、スポット周辺部を形成する）は、厚さ０．６ｍｍの保護基板ＰＬ２を介して、ＤＶＤの情報記録面ＲＬ２に形成されるスポットとなり、スポット中心部を形成する。 The divergent light beam of the second light beam (λ2 = 658 nm) emitted from the red semiconductor laser EP1 is reflected by the prism PS, then reflected by the polarization dichroic prism PPS, converted into a parallel light beam by the collimator lens CL, and is not shown in the figure. Polarized light is converted by the λ1 / 4 plate and enters the objective lens OBJ. Here, the light beam condensed by the central region and the peripheral region of the objective lens OBJ (the light beam that has passed through the most peripheral region is flared and forms a spot peripheral portion) is passed through the protective substrate PL2 having a thickness of 0.6 mm Thus, a spot is formed on the information recording surface RL2 of the DVD, and the center of the spot is formed.

　情報記録面ＲＬ２上で情報ピットにより変調された反射光束は、再び対物レンズＯＢＪ、絞りＳＴを透過した後、図示しないλ１／４板により偏光変換され、コリメートレンズＣＬにより収斂光束とされ、偏光ダイクロイックプリズムＰＰＳにより反射された後、その後、プリズム内で２回反射された後、第２の受光素子ＤＳ１に収束する。そして、第２の受光素子ＤＳ１の出力信号を用いてＤＶＤに記録された情報を読み取ることができる。なお、往復路でλ１／４板で偏光変換されることで、λ１／４板がない場合に比較して光利用効率を高くすることができる。 The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the objective lens OBJ and the aperture stop ST, and then is converted in polarization by a λ1 / 4 plate (not shown), and is converted into a convergent light beam by the collimator lens CL. After being reflected by the prism PPS, then after being reflected twice in the prism, it converges on the second light receiving element DS1. The information recorded on the DVD can be read using the output signal of the second light receiving element DS1. It should be noted that light conversion efficiency can be increased compared with the case where there is no λ1 / 4 plate by performing polarization conversion with a λ1 / 4 plate in the round trip path.

　赤外半導体レーザＥＰ２から射出された第３光束（λ３＝７８５ｎｍ）の発散光束は、プリズムＰＳで反射された後、偏光ダイクロイックプリズムＰＰＳにより反射され、コリメートレンズＣＬにより平行光束とされた後、図示しないλ１／４板により偏光変換され、対物レンズＯＪＴに入射する。ここで、対物レンズＯＢＪの中央領域により集光された（周辺領域及び最周辺領域を通過した光束はフレア化され、スポット周辺部を形成する）光束は、厚さ１．２ｍｍの保護基板ＰＬ３を介して、ＣＤの情報記録面ＲＬ３上に形成されるスポットとなる。 The divergent light beam of the third light beam (λ3 = 785 nm) emitted from the infrared semiconductor laser EP2 is reflected by the prism PS, then reflected by the polarization dichroic prism PPS, converted into a parallel light beam by the collimator lens CL, and then shown in the figure. The polarized light is converted by the λ1 / 4 plate that does not enter and enters the objective lens OJT. Here, the light beam condensed by the central region of the objective lens OBJ (the light beam that has passed through the peripheral region and the most peripheral region is flared and forms a spot peripheral part) is passed through the protective substrate PL3 having a thickness of 1.2 mm. Thus, the spot is formed on the information recording surface RL3 of the CD.

　情報記録面ＲＬ３上で情報ピットにより変調された反射光束は、再び対物レンズＯＢＪ、絞りＳＴを透過した後、図示しないλ１／４波長板により偏光変換され、コリメートレンズＣＬにより収斂光束とされ、偏光ダイクロイックプリズムＰＰＳにより反射された後、その後、プリズム内で２回反射された後、第３の受光素子ＤＳ２に収束する。そして、第３の受光素子ＤＳ２の出力信号を用いてＣＤに記録された情報を読み取ることができる。なお、往復路でλ１／４板で偏光変換されることで、λ１／４板がない場合に比較して光利用効率を高くすることができる。 The reflected light beam modulated by the information pits on the information recording surface RL3 is again transmitted through the objective lens OBJ and the aperture stop ST, and is then polarized and converted by a λ1 / 4 wavelength plate (not shown), and is converted into a convergent light beam by the collimator lens CL. After being reflected by the dichroic prism PPS, then after being reflected twice in the prism, it converges on the third light receiving element DS2. The information recorded on the CD can be read using the output signal of the third light receiving element DS2. It should be noted that light conversion efficiency can be increased compared with the case where there is no λ1 / 4 plate by performing polarization conversion with a λ1 / 4 plate in the round trip path.

　ＡＣ　二軸アクチュエータ
　ＰＰＳ　偏光ダイクロイックプリズム
　ＣＬ　コリメートレンズ
　ＬＤ１　青紫色半導体レーザ
　ＬＭ　レーザモジュール
　ＯＢＪ　対物レンズ
　ＰＬ１　保護基板
　ＰＬ２　保護基板
　ＰＬ３　保護基板
　ＰＵ１　光ピックアップ装置
　ＲＬ１　情報記録面
　ＲＬ２　情報記録面
　ＲＬ３　情報記録面
　ＣＮ　中央領域
　ＭＤ　周辺領域
　ＯＴ　最周辺領域 AC biaxial actuator PPS polarization dichroic prism CL collimating lens LD1 blue-violet semiconductor laser LM laser module OBJ objective lens PL1 protective substrate PL2 protective substrate PL3 protective substrate PU1 optical pickup device RL1 information recording surface RL2 information recording surface RL3 information recording surface CN central area MD peripheral area OT most peripheral area

Claims

Using a first light beam having a wavelength λ1 (μm) emitted from the first light source, a condensing spot is formed on the information recording surface of the first optical disc having a protective layer having a thickness t1, and emitted from the second light source. Using a second light beam having a wavelength λ2 (λ1 <λ2), a condensing spot is formed on the information recording surface of the second optical disc having a protective layer having a thickness t2 (t1 ≦ t2) and emitted from the third light source And an objective lens for forming a condensing spot on the information recording surface of the third optical disk having a protective layer having a thickness of t3 (t2 <t3) using a third light beam of wavelength λ3 (λ2 <λ3). In the objective lens of the optical pickup device,
The optical surface of the objective lens has at least a central region including an optical axis, and a ring-shaped peripheral region formed around the central region,
The first light flux that has passed through the central region and the peripheral region is condensed so that information can be recorded and / or reproduced on the information recording surface of the first optical disc,
The second light flux that has passed through the central region and the peripheral region is condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc,
The third light flux that has passed through the central region is condensed so that information can be recorded and / or reproduced on the information recording surface of the third optical disc, and the third light flux that has passed through the peripheral region is 3 It is not condensed so that information can be recorded and / or reproduced on the information recording surface of the optical disc,
A second optical path difference providing structure is formed in the peripheral region,
The second optical path difference providing structure includes a first basic structure that is a blaze type structure and a second basic structure that is a staircase type structure, the positions of all the step portions of the first basic structure, and the second basic structure. Is superimposed so that the position of the step part of
Of the diffracted light generated when the first light flux is incident on the second optical path difference providing structure when x, y, z are arbitrary integers, the x-order diffracted light has the maximum diffraction efficiency, Of the diffracted light generated when the second light beam enters the second optical path difference providing structure, the y-order diffracted light has the maximum diffraction efficiency, and the third light beam enters the second optical path difference providing structure. Among the diffracted lights generated in this case, the z-order diffracted light has the maximum diffraction efficiency.

The second foundation structure is a three-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure is large and the step structure of the second foundation structure is large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. Objective lens described in 1.
(Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(6λ1-0.2λ1) / (n−1) ≦ d22 ≦ (6λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a three-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: The objective lens according to claim 2, characterized in that:
(5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1)

| X | = 1, | y | = 1, | z | = 2
The objective lens according to any one of claims 1 to 3, wherein:

The second foundation structure is a two-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure and the step structure of the second foundation structure are large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. Objective lens described in 1.
(Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(5λ1-0.2λ1) / (n−1) ≦ d21 ≦ (5λ1 + 0.2λ1) / (n−1)
(5λ1-0.2λ1) / (n−1) ≦ d22 ≦ (5λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a two-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: The objective lens according to claim 2, characterized in that:
(5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1)

| X | = 1, | y | = 1, | z | = 0
The objective lens according to claim 1, wherein the objective lens is any one of the following.

The second foundation structure is a two-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure and the step structure of the second foundation structure are large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. Objective lens described in 1.
(4.1λ1-0.4λ1) / (n−1) ≦ d1 ≦ (4.1λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a two-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: The objective lens according to claim 8, characterized in that:
(7.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (7.1λ1 + 0.2λ1) / (n−1)

| X | = 4, | y | = 2, | z | = 3
The objective lens according to claim 1, wherein the objective lens is any one of the following.

The second foundation structure is a two-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure and the step structure of the second foundation structure are large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. Objective lens described in 1.
(4λ1-0.4λ1) / (n−1) ≦ d1 ≦ (4λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a two-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: The objective lens according to claim 11, wherein
(7λ1-0.2λ1) / (n−1) ≦ d0 ≦ (7λ1 + 0.2λ1) / (n−1)

| X | = 4, | y | = 2, | z | = 1
The objective lens according to claim 1, wherein the objective lens is any one of the following.

The second foundation structure is a two-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure and the step structure of the second foundation structure are large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. Objective lens described in 1.
(2.1λ1-0.4λ1) / (n−1) ≦ d1 ≦ (2.1λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a two-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: The objective lens according to claim 14, characterized in that:
(5.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5.1λ1 + 0.2λ1) / (n−1)

| X | = 2, | y | = 1, | z | = 2
The objective lens according to claim 1, wherein the objective lens is any one of the following.

The second foundation structure is a two-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure and the step structure of the second foundation structure are large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. Objective lens described in 1.
(2λ1−0.4λ1) / (n−1) ≦ d1 ≦ (2λ1 + 0.4λ1) / (n−1)
(3.05λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3.05λ1 + 0.2λ1) / (n−1)
(3.05λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3.05λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a two-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: The objective lens according to claim 17, characterized in that:
(5.05λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5.05λ1 + 0.2λ1) / (n−1)

| X | = 2, | y | = 1, | z | = 0
The objective lens according to claim 1, wherein the objective lens is any one of the following.

The objective lens has a ring-shaped outermost peripheral region formed around the peripheral region,
The first light flux that has passed through the central area, the peripheral area, and the most peripheral area is condensed so that information can be recorded and / or reproduced on the information recording surface of the first optical disc,
The second light flux that has passed through the central area and the peripheral area is condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc, and the second light flux that has passed through the outermost peripheral area. Two light beams are not condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc,
The third light flux that has passed through the central area is condensed so that information can be recorded and / or reproduced on the information recording surface of the third optical disc, and the third light flux that has passed through the peripheral area and the most peripheral area. The objective lens according to any one of claims 1 to 19, wherein the light beam is not condensed so that information can be recorded and / or reproduced on an information recording surface of the third optical disc.

Using a first light beam having a wavelength λ1 (μm) emitted from the first light source, a condensing spot is formed on the information recording surface of the first optical disc having a protective layer having a thickness t1, and emitted from the second light source. Using a second light beam having a wavelength λ2 (λ1 <λ2), a condensing spot is formed on the information recording surface of the second optical disc having a protective layer having a thickness t2 (t1 ≦ t2) and emitted from the third light source. And an objective lens for forming a condensing spot on the information recording surface of the third optical disk having a protective layer having a thickness of t3 (t2 <t3) using a third light beam of wavelength λ3 (λ2 <λ3). In the optical pickup device,
The optical surface of the objective lens has at least a central region including an optical axis, and a ring-shaped peripheral region formed around the central region,
The first light flux that has passed through the central region and the peripheral region is condensed so that information can be recorded and / or reproduced on the information recording surface of the first optical disc,
The second light flux that has passed through the central region and the peripheral region is condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc,
The third light flux that has passed through the central region is condensed so that information can be recorded and / or reproduced on the information recording surface of the third optical disc, and the third light flux that has passed through the peripheral region is 3 It is not condensed so that information can be recorded and / or reproduced on the information recording surface of the optical disc,
A second optical path difference providing structure is formed in the peripheral region,
The second optical path difference providing structure includes a first basic structure that is a blaze type structure and a second basic structure that is a staircase type structure, the positions of all the step portions of the first basic structure, and the second basic structure. Is superimposed so that the position of the step part of
Of the diffracted light generated when the first light flux is incident on the second optical path difference providing structure when x, y, z are arbitrary integers, the x-order diffracted light has the maximum diffraction efficiency, Of the diffracted light generated when the second light beam enters the second optical path difference providing structure, the y-order diffracted light has the maximum diffraction efficiency, and the third light beam enters the second optical path difference providing structure. Of the diffracted light generated in this case, the z-order diffracted light has the maximum diffraction efficiency.

The second foundation structure is a three-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure is large and the step structure of the second foundation structure is large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. The optical pickup device described in 1.
(Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(6λ1-0.2λ1) / (n−1) ≦ d22 ≦ (6λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a three-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: The optical pickup device according to claim 22, characterized in that:
(5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1)

| X | = 1, | y | = 1, | z | = 2
The optical pickup device according to any one of claims 21 to 23, wherein:

The second foundation structure is a two-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure and the step structure of the second foundation structure are large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. The optical pickup device described in 1.
(Λ1−0.4λ1) / (n−1) ≦ d1 ≦ (λ1 + 0.4λ1) / (n−1)
(5λ1-0.2λ1) / (n−1) ≦ d21 ≦ (5λ1 + 0.2λ1) / (n−1)
(5λ1-0.2λ1) / (n−1) ≦ d22 ≦ (5λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a two-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: 26. The optical pickup device according to claim 25, wherein
(5λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5λ1 + 0.2λ1) / (n−1)

| X | = 1, | y | = 1, | z | = 0
27. The optical pickup device according to claim 21, 25, or 26.

The second foundation structure is a two-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure and the step structure of the second foundation structure are large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. The optical pickup device described in 1.
(4.1λ1-0.4λ1) / (n−1) ≦ d1 ≦ (4.1λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a two-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: The optical pickup device according to claim 28, characterized in that:
(7.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (7.1λ1 + 0.2λ1) / (n−1)

| X | = 4, | y | = 2, | z | = 3
30. The optical pickup device according to claim 21, 28, or 29.

The second foundation structure is a two-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure and the step structure of the second foundation structure are large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. The optical pickup device described in 1.
(4λ1-0.4λ1) / (n−1) ≦ d1 ≦ (4λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a two-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: 32. The optical pickup device according to claim 31, wherein
(7λ1-0.2λ1) / (n−1) ≦ d0 ≦ (7λ1 + 0.2λ1) / (n−1)

| X | = 4, | y | = 2, | z | = 1
The optical pickup device according to any one of claims 21, 31, and 32, wherein:

The second foundation structure is a two-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure and the step structure of the second foundation structure are large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. The optical pickup device described in 1.
(2.1λ1-0.4λ1) / (n−1) ≦ d1 ≦ (2.1λ1 + 0.4λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3λ1 + 0.2λ1) / (n−1)
(3λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a two-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: The optical pickup device according to claim 34, wherein the optical pickup device is characterized in that:
(5.1λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5.1λ1 + 0.2λ1) / (n−1)

| X | = 2, | y | = 1, | z | = 2
36. The optical pickup device according to claim 21, 34, or 35.

The second foundation structure is a two-step staircase structure, and the length d21 (μm) of a small step in the optical axis direction of the step structure of the second foundation structure and the step structure of the second foundation structure are large. The length d22 (μm) in the optical axis direction of the step and the length d1 (μm) in the optical axis direction of the step portion of the first basic structure satisfy the following conditional expression. The optical pickup device described in 1.
(2λ1−0.4λ1) / (n−1) ≦ d1 ≦ (2λ1 + 0.4λ1) / (n−1)
(3.05λ1-0.2λ1) / (n−1) ≦ d21 ≦ (3.05λ1 + 0.2λ1) / (n−1)
(3.05λ1-0.2λ1) / (n−1) ≦ d22 ≦ (3.05λ1 + 0.2λ1) / (n−1)
However, n represents the refractive index of the objective lens in the first light flux.

The second optical path difference providing structure is a two-part blazed staircase structure, and the length d0 (μm) in the optical axis direction of the largest step of the second optical path difference providing structure satisfies the following conditional expression: The optical pickup device according to claim 37, characterized in that:
(5.05λ1-0.2λ1) / (n−1) ≦ d0 ≦ (5.05λ1 + 0.2λ1) / (n−1)

| X | = 2, | y | = 1, | z | = 0
The optical pickup device according to any one of claims 21, 37 and 38, wherein:

The objective lens has a ring-shaped outermost peripheral region formed around the peripheral region,
The first light flux that has passed through the central area, the peripheral area, and the most peripheral area is condensed so that information can be recorded and / or reproduced on the information recording surface of the first optical disc,
The second light flux that has passed through the central area and the peripheral area is condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc, and the second light flux that has passed through the outermost peripheral area. Two light beams are not condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disc,
The third light flux that has passed through the central region is condensed so that information can be recorded and / or reproduced on the information recording surface of the third optical disc, and the third light beam that has passed through the peripheral region and the most peripheral region. The optical pickup device according to any one of claims 21 to 39, wherein the light beam is not collected so that information can be recorded and / or reproduced on an information recording surface of the third optical disc.