JP2006092720A - Objective optical device, optical pickup device, and optical disk driving device - Google Patents

Objective optical device, optical pickup device, and optical disk driving device Download PDF

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JP2006092720A
JP2006092720A JP2005242988A JP2005242988A JP2006092720A JP 2006092720 A JP2006092720 A JP 2006092720A JP 2005242988 A JP2005242988 A JP 2005242988A JP 2005242988 A JP2005242988 A JP 2005242988A JP 2006092720 A JP2006092720 A JP 2006092720A
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optical element
optical
objective optical
light
phase structure
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Kenji Ogiwara
賢治 荻原
Toru Kimura
徹 木村
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Konica Minolta Opto Inc
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Konica Minolta Opto Inc
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an objective optical device permitting to correct a spherical aberration or the like caused by differences of protective layer thickness among a high density optical disk, a DVD, and a CD by a phase structure function, permitting to obtain a high light utilization factor in any of the wavelength areas in the vicinity of 400nm, 650nm, and 780nm, and further having an excellent temperature characteristic, and also to provide an optical pickup device comprising this objective optical device, and an optical disk driving device mounted with this optical pickup device. <P>SOLUTION: The objective optical device of this invention comprises: a 1st phase structure for compensating for degradation of a condensing spot forming performance to an information recording surface of a 1st optical information recording medium produced by variation in temperature; a 2nd phase structure for offsetting the spherical aberration based on a difference in protective substrate thickness or an operating wavelength difference between the 1st optical information recording medium and the 2nd optical information recording medium; and a 3rd phase structure for offsetting the spherical aberration based on a difference in protective substrate thickness between the 1st optical information recording medium and the 3rd optical information recording medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、対物光学素子、光ピックアップ装置及び光ディスクドライブ装置に関する。   The present invention relates to an objective optical element, an optical pickup device, and an optical disk drive device.

従来より、青紫色レーザ光源を使用することで記録密度を高めた高密度光ディスク、ＤＶＤ（赤色レーザ光源を使用）、及びＣＤ（赤外レーザ光源を使用）とに対して互換性を有する光ピックアップ装置及びこのような光ピックアップ装置に用いられる対物光学素子が知られている（例えば、非特許文献１を参照）。
非特許文献１には、プラスチック製の補正素子とガラス製の集光光学素子とからなる２群２枚構成の対物光学素子の１つの光学面に１つの位相構造を設けることで、この位相構造の作用により、高密度光ディスクとＤＶＤの保護層厚みの差による球面収差を補正する技術が開示されている。
"TECHNICAL DIGEST", INTERNATIONAL SYMPOSIUM ON OPTICAL MEMORY 2003(ISOM 2003),NOVEMBER 3-7,2003 P230,231 Conventionally, an optical pickup compatible with a high density optical disc, a DVD (using a red laser light source), and a CD (using an infrared laser light source) whose recording density is increased by using a blue-violet laser light source. Devices and objective optical elements used in such optical pickup devices are known (see, for example, Non-Patent Document 1).
Non-Patent Document 1 discloses that this phase structure is provided by providing one phase structure on one optical surface of a two-group objective optical element composed of a plastic correction element and a glass condensing optical element. A technique for correcting spherical aberration due to the difference in the thickness of the protective layer between the high-density optical disk and the DVD is disclosed.
"TECHNICAL DIGEST", INTERNATIONAL SYMPOSIUM ON OPTICAL MEMORY 2003 (ISOM 2003), NOVEMBER 3-7,2003 P230,231

ところが、非特許文献１のように、対物光学素子を構成する光学素子の一部をガラス製とした場合、ガラスはプラスチックと比較して比重が大きいため、対物光学素子の総重量が重くなり、駆動機構（フォーカシング及びトラッキング用のアクチュエータ）への負担が増大するという問題が生じるため、この問題を解消すべく、高性能で大型のアクチュエータを配置する必要が生じ、結果として光ピックアップ装置の省スペース化や製造コストの増大という新たな問題が生じる。   However, as in Non-Patent Document 1, when a part of the optical element constituting the objective optical element is made of glass, since the specific gravity is larger than that of plastic, the total weight of the objective optical element becomes heavy. Since the load on the driving mechanism (focusing and tracking actuator) increases, it is necessary to arrange a high-performance and large actuator to solve this problem. As a result, space saving of the optical pickup device is required. A new problem arises in that the cost and manufacturing cost increase.

また、ガラスでは射出成形ができず製造が困難なため、対物光学素子を大量生産することができず、製造コストの増加という問題も生じる。
また、対物光学素子を構成する光学素子の一部を、比重が小さく且つ射出成形可能なプラスチック製とした場合であっても、光ピックアップ装置の動作中には、アクチュエータからの放熱や環境温度の変化に伴ってプラスチック製の光学素子の温度が変化し、この温度変化に伴い屈折率が大きく変化する結果、安定した記録／再生特性が得られない虞がある。 Further, since glass cannot be injection-molded and is difficult to manufacture, objective optical elements cannot be mass-produced, resulting in an increase in manufacturing cost.
In addition, even when a part of the optical elements constituting the objective optical element is made of a plastic having a small specific gravity and can be injection-molded, during the operation of the optical pickup device, heat radiation from the actuator and environmental temperature The temperature of the plastic optical element changes with the change, and as a result of the refractive index changing greatly with this temperature change, there is a possibility that stable recording / reproducing characteristics cannot be obtained.

本発明の課題は、上記の課題を鑑みてなされたものであり、位相構造の作用により、高密度光ディスクとＤＶＤとＣＤとの保護層厚みの差による球面収差、或いは、高密度光ディスクとＤＶＤとＣＤとの使用波長の差による球面収差を良好に補正することができるとともに、４００ｎｍ近傍の青紫色波長領域と、６５０ｎｍ近傍の赤色波長領域と、７８０ｎｍ近傍の赤外波長領域との何れの波長領域においても高い光利用効率が得ることができ、更には、温度特性に優れた対物光学素子、この対物光学素子を有する光ピックアップ装置、及び、この光ピックアップ装置を搭載した光ディスクドライブ装置を提供することである。   An object of the present invention has been made in view of the above-described problems. Due to the action of the phase structure, spherical aberration due to a difference in protective layer thickness between a high-density optical disk and a DVD and a CD, or a high-density optical disk and a DVD Spherical aberration due to the difference in wavelength used with CD can be corrected well, and any wavelength region of a blue-violet wavelength region near 400 nm, a red wavelength region near 650 nm, and an infrared wavelength region near 780 nm In addition, an objective optical element having excellent temperature characteristics, an optical pickup device having the objective optical element, and an optical disc drive apparatus equipped with the optical pickup device can be provided. It is.

本明細書においては、ＮＡ＝０．８５の対物レンズを使用し保護層厚さが０．０８７５ｍｍであるブルーレイディスク（「ＢＤ」と略記する）や、ＮＡ＝０．６５乃至０．６７の対物レンズを使用し保護層厚さが０．６ｍｍであるＨＤ ＤＶＤの如き、青紫色レーザ光源を使用する光ディスクを総称して「高密度光ディスク」といい、「ＨＤ」で略記する。上述したブルーレイディスクＢＤやＨＤ ＤＶＤ以外にも、光磁気ディスクや、情報記録面上に数〜数十ｎｍ程度の厚さの保護膜を有する光ディスクや、保護層或いは保護膜の厚さがゼロの光ディスクも高密度光ディスクに含むものとする。
また、本明細書においては、ＤＶＤ（デジタルバーサタイルディスク）とは、ＤＶＤ−ＲＯＭ、ＤＶＤ−Ｖｉｄｅｏ、ＤＶＤ−Ａｕｄｉｏ、ＤＶＤ−ＲＡＭ、ＤＶＤ−Ｒ、ＤＶＤ−ＲＷ、ＤＶＤ＋Ｒ、ＤＶＤ＋ＲＷ等のＤＶＤ系列の光ディスクの総称であり、ＣＤ（コンパクトディスク）とは、ＣＤ−ＲＯＭ、ＣＤ−Ａｕｄｉｏ、ＣＤ−Ｖｉｄｅｏ、ＣＤ−Ｒ、ＣＤ−ＲＷ等のＣＤ系列の光ディスクの総称である。 In this specification, an objective lens with NA = 0.85 and a protective layer thickness of 0.0875 mm, a Blu-ray disc (abbreviated as “BD”), and an objective with NA = 0.65 to 0.67 are used. An optical disk using a blue-violet laser light source, such as an HD DVD using a lens and a protective layer thickness of 0.6 mm, is collectively referred to as a “high density optical disk” and is abbreviated as “HD”. In addition to the Blu-ray Disc BD and HD DVD described above, a magneto-optical disc, an optical disc having a protective film with a thickness of several to several tens of nanometers on the information recording surface, a protective layer or a protective film having a thickness of zero An optical disk is also included in a high density optical disk.
In this specification, DVD (Digital Versatile Disc) means DVD series optical discs such as DVD-ROM, DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW, etc. CD (compact disc) is a generic term for CD-series optical discs such as CD-ROM, CD-Audio, CD-Video, CD-R, and CD-RW.

また、本明細書において、「集光光学素子」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レンズを指す。
更に、本明細書において、「対物光学素子」とは、上述の集光光学素子と、この集光光学素子と一体となってアクチュエータによりトラッキング及びフォーカシングを行う収差補正レンズ群とから構成される光学系を指す。ここでいう収差補正レンズ群は、１つのレンズ群から構成されていても良いし、２つ以上のレンズ群から構成されていても良い。
また、「温度変化によって生じる前記第１光情報記録媒体の情報記録面に対する集光スポット形成性能の劣化を補償する」とは、対物光学素子と第１光情報記録媒体の保護基板を介して波長λ１の第１光束を集光させた場合の波面収差が０．０５λ１ＲＭＳ以下であることをいうものとする。 In the present specification, the “condensing optical element” 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 on the information recording surface of the optical disk. Refers to the lens.
Further, in the present specification, the “objective optical element” means an optical element composed of the above-described condensing optical element and an aberration correction lens group that is integrated with the condensing optical element and performs tracking and focusing by an actuator. Refers to the system. The aberration correction lens group here may be composed of one lens group, or may be composed of two or more lens groups.
Further, “compensates for degradation of the condensed spot forming performance with respect to the information recording surface of the first optical information recording medium caused by temperature change” means that the wavelength is passed through the objective optical element and the protective substrate of the first optical information recording medium. It is assumed that the wavefront aberration when the first light flux of λ1 is condensed is 0.05λ1 RMS or less.

請求項１記載の発明は、波長λ１の第１光源から出射される第１光束を用いて、保護基板厚ｔ１の第１光情報記録媒体に対して情報の再生および／または記録を行い、波長λ２（λ１＜λ２）の第２光源から出射される第２光束を用いて、保護基板厚ｔ２（ｔ１≦ｔ２）の第２光情報記録媒体に対して情報の再生および／または記録を行い、波長λ３（λ２＜λ３）の第３光源から出射される第３光束を用いて、保護基板厚ｔ３（ｔ２＜ｔ３）の第３光情報記録媒体に対して情報の再生および／または記録を行う光ピックアップ装置に用いられ、前記各光情報記録媒体の情報記録面に集光スポットを形成する対物光学素子において、前記対物光学素子の有する光学面のうちいずれかに、温度変化によって生じる前記第１光情報記録媒体の情報記録面に対する集光スポット形成性能の劣化を補償する第１位相構造と、前記保護基板厚ｔ１と前記保護基板厚ｔ２或いは前記波長λ１と前記波長λ２との差に基づく球面収差を解消するための第２位相構造と、前記保護基板厚ｔ１と前記保護基板厚ｔ３との差に基づく球面収差を解消するための第３位相構造を備えることを特徴とする。   According to the first aspect of the present invention, information is reproduced and / or recorded on the first optical information recording medium having the protective substrate thickness t1 by using the first light beam emitted from the first light source having the wavelength λ1, and the wavelength is increased. Information is reproduced and / or recorded on the second optical information recording medium having the protective substrate thickness t2 (t1 ≦ t2) using the second light flux emitted from the second light source having λ2 (λ1 <λ2). Information is reproduced and / or recorded on a third optical information recording medium having a protective substrate thickness t3 (t2 <t3) using a third light beam emitted from a third light source having a wavelength λ3 (λ2 <λ3). In the objective optical element that is used in an optical pickup device and forms a condensing spot on the information recording surface of each optical information recording medium, the first surface generated by a temperature change on any one of the optical surfaces of the objective optical element. Information recording on optical information recording media A first phase structure that compensates for deterioration of the focusing spot formation performance with respect to the second, and a second phase for eliminating spherical aberration based on the difference between the protective substrate thickness t1 and the protective substrate thickness t2 or the wavelength λ1 and the wavelength λ2. A third phase structure for eliminating spherical aberration based on a phase structure and a difference between the protective substrate thickness t1 and the protective substrate thickness t3 is provided.

請求項１に記載の発明によれば、第１位相構造において第１光情報記録媒体に対して情報の再生および／または記録を行なう際の温度特性を補償し、第２位相構造において第１光情報記録媒体と第２光情報記録媒体の再生および／または記録の互換を達成し、第３位相構造において第１光情報記録媒体と第３光情報記録媒体の再生および／または記録の互換を達成できるので、対物光学素子がこれら３つの位相構造を持つことにより、第１光情報記録媒体としてのＨＤ／第２光情報記録媒体としてのＤＶＤ／第３光情報記録媒体としてのＣＤ間での互換を達成でき、さらに、特にＮＡの大きい第１光情報記録媒体としてのＢＤでは顕著になる温度変化による球面収差の発生を抑えられる。   According to the first aspect of the present invention, the temperature characteristic when information is reproduced and / or recorded on the first optical information recording medium in the first phase structure is compensated, and the first light is recorded in the second phase structure. Reproduction and / or recording compatibility between the information recording medium and the second optical information recording medium is achieved, and reproduction and / or recording compatibility between the first optical information recording medium and the third optical information recording medium is achieved in the third phase structure. Since the objective optical element has these three phase structures, compatibility between HD as the first optical information recording medium / DVD as the second optical information recording medium / CD as the third optical information recording medium is possible. Further, it is possible to suppress the occurrence of spherical aberration due to a temperature change that is particularly noticeable in the BD as the first optical information recording medium having a large NA.

第１乃至第３の各位相構造は図１乃至４に概略的に示すように様々な断面形状をとり得る。図１は鋸歯状である場合であり、図２は全ての段差が同じ方向とされた階段状である場合である。本明細書では、入射光束に対して所定の位相差を付与することにより、この光束に対して特定の作用を与える構造を「位相差付与構造」とし、例えば、図１や図２のように、光軸を含む平面でその断面をみた場合に鋸歯状あるいは光軸方向に沿った階段状となった構造などを指す。また、図３は段差の方向が途中で反対となる階段状である場合、つまり、請求項２に記載したような、光軸を含む断面形状が、光軸から所定の高さまでは、光軸から離れるに従って光路長が長くなり、前記光軸から所定の高さ以降は、光軸から離れるに従って光路長が短くなる階段構造（位相差付与構造）、或いは、光軸から所定の高さまでは、光軸から離れるに従って光路長が短くなり、前記光軸から所定の高さ以降は、光軸から離れるに従って光路長が長くなる階段構造（位相差付与構造）である場合を示している。   Each of the first to third phase structures can take various cross-sectional shapes as schematically shown in FIGS. FIG. 1 shows a case of a sawtooth shape, and FIG. 2 shows a case of a step shape in which all the steps are in the same direction. In the present specification, a structure that gives a specific action to a light beam by giving a predetermined phase difference to the incident light beam is referred to as a “phase difference providing structure”. For example, as shown in FIGS. In addition, it refers to a structure having a sawtooth shape or a stepped shape along the optical axis direction when the cross section is viewed in a plane including the optical axis. Further, FIG. 3 shows a case where the direction of the step is a stepped shape that is opposite in the middle, that is, when the cross-sectional shape including the optical axis as defined in claim 2 is at a predetermined height from the optical axis. The optical path length increases as the distance from the optical axis increases, and after a predetermined height from the optical axis, a staircase structure (phase difference providing structure) where the optical path length decreases as the distance from the optical axis, or at a predetermined height from the optical axis, The figure shows a case of a staircase structure (phase difference providing structure) in which the optical path length decreases as the distance from the optical axis decreases, and after the predetermined height from the optical axis, the optical path length increases as the distance from the optical axis increases.

また、図４は、請求項８に記載したような、光軸を含む断面形状が階段状とされたパターンを同心円状に配列し、所定のレベル面数（図４では５レベル面）の個数毎に、そのレベル面数に対応した段数分（図４では４段）の高さだけ段をシフトさせた場合を示している（本明細書では、「マルチレベル型」ともいう）。
図１では各鋸歯の向きが同一である場合を示し、図４では断面形状が階段状とされた各パターンの向きが同一である場合を示したが、図５や図６のように、位相反転部分ＰＲや、位相反転部分ＰＲよりも光軸に近い側にある鋸歯とは向きが反対の鋸歯や、位相反転部分ＰＲよりも光軸に近い側にあるパターンとは向きが反対のパターンを含む場合もある。なお、図１乃至６は、各構造を平面上に形成した場合を示した場合であるが、各構造は球面上或いは非球面上に形成しても良い。また、図４や図６では、所定のレベル面数を５としているが、これに限られるものではない。 FIG. 4 shows the number of predetermined level planes (five level planes in FIG. 4) arranged in a concentric pattern in which the cross-sectional shape including the optical axis is stepped. Each case shows a case where the level is shifted by the height corresponding to the number of level surfaces (4 levels in FIG. 4) (also referred to as “multi-level type” in this specification).
FIG. 1 shows the case where the directions of the saw blades are the same, and FIG. 4 shows the case where the directions of the patterns whose sectional shapes are stepped are the same. However, as shown in FIGS. A sawtooth whose direction is opposite to the sawtooth on the side closer to the optical axis than the inversion part PR or the phase inversion part PR, or a pattern whose direction is opposite to that of the pattern closer to the optical axis than the phase inversion part PR is used. May include. 1 to 6 show a case where each structure is formed on a plane, but each structure may be formed on a spherical surface or an aspherical surface. In FIG. 4 and FIG. 6, the predetermined number of level faces is set to 5, but the present invention is not limited to this.

請求項２記載の発明は、請求項１に記載の対物光学素子において、前記第１位相構造の光軸を含む断面形状は、光軸から所定の高さまでは、光軸から離れるに従って光路長が長くなり、前記光軸から所定の高さ以降は、光軸から離れるに従って光路長が短くなる位相差付与構造、或いは、光軸から所定の高さまでは、光軸から離れるに従って光路長が短くなり、前記光軸から所定の高さ以降は、光軸から離れるに従って光路長が長くなる位相差付与構造であることを特徴とする。   According to a second aspect of the present invention, in the objective optical element according to the first aspect, the cross-sectional shape including the optical axis of the first phase structure has an optical path length as the distance from the optical axis increases at a predetermined height from the optical axis. A phase difference providing structure in which the optical path length becomes shorter as the distance from the optical axis becomes longer after the predetermined height from the optical axis, or the optical path length becomes shorter as the distance from the optical axis increases from the optical axis at a predetermined height. The phase difference providing structure is characterized in that the optical path length becomes longer as the distance from the optical axis increases from a predetermined height from the optical axis.

請求項２のように決定された第１位相構造の輪帯構造による温度収差の補正の原理を説明する。
図７中の線（Ａ）は、非球面である２つの光学面を有する単レンズの、設計基準温度から温度が上昇した場合の波面の様子を表すものであり、横軸が光学面の有効半径を表し、縦軸が光路差を表す。
単レンズは、温度上昇に伴う屈折率変化の影響で球面収差が発生し、線（Ａ）のように波面が変化する。特に単レンズが樹脂製の場合、温度変化に伴う屈折率変化が大きいため、球面収差の発生量は大きくなる。 The principle of correction of temperature aberration by the ring structure of the first phase structure determined as in claim 2 will be described.
The line (A) in FIG. 7 represents the state of the wave front when the temperature rises from the design reference temperature of a single lens having two aspherical optical surfaces, and the horizontal axis is the effective optical surface. The radius is represented, and the vertical axis represents the optical path difference.
In the single lens, spherical aberration occurs due to the influence of the refractive index change accompanying the temperature rise, and the wavefront changes as shown by the line (A). In particular, when the single lens is made of resin, the amount of spherical aberration is increased because the refractive index change with temperature change is large.

また、線（Ｂ）は、請求項２のように決定された輪帯構造により透過波面に付加される光路差であり、線（Ｃ）は、設計基準温度から温度が上昇した場合の、かかる輪帯構造と単レンズとを透過した波面の様子を表す図である。線（Ｂ）及び線（Ｃ）から、かかる輪帯構造を透過した波面と、設計基準温度から温度が上昇した場合の単レンズの波面とが打ち消しあうことで、光ディスクの情報記録面上に集光されたレーザ光の波面は、巨視的にみると光路差のない良好な波面となり、かかる輪帯構造により単レンズの温度収差が補正されることが理解できる。   The line (B) is an optical path difference added to the transmitted wavefront by the annular structure determined as in claim 2, and the line (C) is obtained when the temperature rises from the design reference temperature. It is a figure showing the mode of the wave front which permeate | transmitted the annular zone structure and the single lens. From the line (B) and the line (C), the wave front transmitted through the annular structure and the wave front of the single lens when the temperature rises from the design reference temperature cancel each other, so that they are collected on the information recording surface of the optical disc. When viewed macroscopically, the wavefront of the emitted laser beam has a good wavefront with no optical path difference, and it can be understood that the temperature aberration of the single lens is corrected by such an annular structure.

請求項３記載の発明は、請求項２に記載の対物光学素子において、前記第１位相構造の前記所定の高さの位置での位相と同位相となる領域が、前記第１光束の有効光束径の７０％の位置を含むことを特徴とする。   According to a third aspect of the present invention, in the objective optical element according to the second aspect, an area having the same phase as the phase at the position of the predetermined height of the first phase structure is an effective light flux of the first light flux. It includes 70% of the diameter.

温度変化に伴う波面の変化は、有効光束径の７０％付近で最大となるので、請求項３のように位相構造の折り返し地点である輪帯、即ち所定の高さの位置での位相（光路差）と同位相を持つ領域が有効光束径の７０％の位置を含むように設定すると、温度特性改善の効果を最も期待できる。   The wavefront change accompanying the temperature change becomes maximum near 70% of the effective light beam diameter. Therefore, as in claim 3, the phase at the position where the phase structure is turned, that is, the position of a predetermined height (optical path). If the region having the same phase as (difference) is set so as to include a position of 70% of the effective light beam diameter, the effect of improving the temperature characteristic can be most expected.

請求項４記載の発明は、請求項１に記載の対物光学素子において、前記第１位相構造は、前記第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であるα１次の回折光を発生し、前記第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であるβ１（β１＜α１）次の回折光を発生し、前記第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であるγ１（γ１≦β１）次の回折光を発生する位相差付与構造であることを特徴とする。   According to a fourth aspect of the present invention, in the objective optical element according to the first aspect, the first phase structure has an α1 order which is the maximum diffraction efficiency of the diffracted light generated when the first light beam is incident. When diffracted light is generated and diffracted light of β1 (β1 <α1) order, which is the maximum diffraction efficiency, is generated among the diffracted light generated when the second light flux is incident, and when the third light flux is incident It is characterized in that it is a phase difference providing structure that generates diffracted light of γ1 (γ1 ≦ β1) order, which is the maximum diffraction efficiency among generated diffracted light.

請求項４に記載の発明によれば、第１位相構造に請求項１のような効果（温度特性補償）を持たせることが可能となり、かつ３つの光束に対して高い透過率が確保できる。尚、このような回折特性を有する位相差付与構造は、光軸を含む断面形状が鋸歯型でもよいし、光軸から離れるに従って光路長が長くなる階段構造、或いは、光軸から離れるに従って光路長が短くなる階段構造でもよい。   According to the fourth aspect of the present invention, the first phase structure can have the effect (temperature characteristic compensation) as in the first aspect, and high transmittance can be secured for the three light beams. The phase difference providing structure having such diffraction characteristics may have a sawtooth shape in cross section including the optical axis, a step structure in which the optical path length increases as the distance from the optical axis increases, or the optical path length increases as the distance from the optical axis increases. A staircase structure that shortens the length may be used.

請求項５記載の発明は、請求項２〜４のいずれか一項に記載の対物光学素子において、前記位相差付与構造は、断面形状が階段構造であることを特徴とする。   According to a fifth aspect of the present invention, in the objective optical element according to any one of the second to fourth aspects, the phase difference imparting structure has a stepped structure in cross section.

請求項５に記載の発明によれば、請求項１のような効果を持つ対物光学素子を高精度且つ容易に成形することができ、低コストで光利用効率も高い対物光学素子を得ることが可能になる。   According to the fifth aspect of the present invention, the objective optical element having the effect as in the first aspect can be easily shaped with high accuracy, and an objective optical element with low cost and high light utilization efficiency can be obtained. It becomes possible.

請求項６記載の発明は、請求項５に記載の対物光学素子において、前記第１位相構造において、ｐ＝INT（ｄ（ｎ１−１）／λ１）、ｑ＝INT（ｄ（ｎ３−１）／λ３）としたとき、ｐ＞ｑを満たすことを特徴とする。
ただし、
ｄ：第１位相構造の段差量
ｎ１：第１位相構造を持つ媒質の波長λ１での屈折率
ｎ３：第１位相構造を持つ媒質の波長λ３での屈折率
INT（X）：Ｘにもっとも近い整数 According to a sixth aspect of the present invention, in the objective optical element according to the fifth aspect, in the first phase structure, p = INT (d (n1-1) / λ1), q = INT (d (n3-1)) / Λ3), p> q is satisfied.
However,
d: Step amount of the first phase structure n1: Refractive index of the medium having the first phase structure at the wavelength λ1 n3: Refractive index of the medium having the first phase structure at the wavelength λ3
INT (X): Integer closest to X

請求項６に記載の発明によれば、第１位相構造が上記条件を満たすことにより、３つの光束に対して高い透過率を確保できる。   According to the sixth aspect of the invention, when the first phase structure satisfies the above condition, high transmittance can be secured for the three light beams.

請求項７記載の発明は、請求項１に記載の対物光学素子において、前記第２位相構造は、前記第１光束及び前記第３光束を回折せず、前記第２光束を回折する回折構造であることを特徴とする。   The invention according to claim 7 is the objective optical element according to claim 1, wherein the second phase structure is a diffractive structure that does not diffract the first light flux and the third light flux but diffracts the second light flux. It is characterized by being.

請求項７のように、前記第２位相構造を第２光束のみを選択的に回折する回折構造とすることで、第２光束に対する収差を独立に制御することが可能となり、第１情報記録媒体と第２情報記録媒体の両方に対して良好な集光特性が得られる。   According to a seventh aspect of the present invention, the second phase structure is a diffractive structure that selectively diffracts only the second light beam, whereby the aberration with respect to the second light beam can be independently controlled, and the first information recording medium Good condensing characteristics can be obtained for both the first information recording medium and the second information recording medium.

請求項８記載の発明は、請求項７に記載の対物光学素子において、前記第２位相構造は、光軸を含む断面形状が階段状とされたパターンが同心円状に配列された構造であって、所定のレベル面の個数Ａ毎に、そのレベル面数に対応した段数分の高さだけ段をシフトさせた構造であることを特徴とする。   The invention according to claim 8 is the objective optical element according to claim 7, wherein the second phase structure is a structure in which patterns having a stepped cross-sectional shape including an optical axis are arranged concentrically. The structure is characterized in that for each predetermined number of level surfaces A, the steps are shifted by a height corresponding to the number of steps corresponding to the number of level surfaces.

請求項８に記載の発明によれば、請求項７にあるような回折特性を第２位相構造に持たせることが可能になる。   According to the invention described in claim 8, it is possible to give the second phase structure the diffraction characteristics as in claim 7.

請求項９記載の発明は、請求項８に記載の対物光学素子において、前記所定のレベル面の個数Ａは、４、５、６の何れかであることを特徴とする。   According to a ninth aspect of the present invention, in the objective optical element according to the eighth aspect, the number A of the predetermined level surfaces is any one of 4, 5, and 6.

請求項９に記載の発明によれば、３つの光束に対して高い透過率が確保できる。なお、３つの光束に透過率を最も高く確保するためには、所定のレベル面の個数Ａを５とするのがより好ましい。   According to the ninth aspect of the invention, high transmittance can be secured for the three light beams. In order to secure the highest transmittance for the three light beams, the number A of predetermined level surfaces is more preferably 5.

請求項１０記載の発明は、請求項８又は９に記載の対物光学素子において、前記階段の１つの段差により生じる光路差は前記波長λ１の２倍であることを特徴とする。   According to a tenth aspect of the present invention, in the objective optical element according to the eighth or ninth aspect, an optical path difference caused by one step of the step is twice the wavelength λ1.

請求項１０に記載の発明によれば、３つの光束に対して高い透過率が確保できる。ここで、「前記階段の１つの段差により生じる光路差は前記波長λ１の２倍」とは、前記光路差が前記波長λ１のちょうど２倍の場合だけでなく、前記波長λ１の１．９〜２．１倍の場合も含む。   According to the invention described in claim 10, high transmittance can be secured for the three light beams. Here, “the optical path difference caused by one step of the staircase is twice the wavelength λ1” means not only the case where the optical path difference is exactly twice the wavelength λ1, but also the wavelength λ1 of 1.9 to Including the case of 2.1 times.

請求項１１記載の発明は、請求項７〜１０のいずれか一項に記載の対物光学素子において、前記第２位相構造を備える媒質のアッベ数をνｄ２としたとき、４０＜νｄ２＜７０を満たすことを特徴とする。   An eleventh aspect of the present invention is the objective optical element according to any one of the seventh to tenth aspects, wherein 40 <νd2 <70 is satisfied when an Abbe number of the medium including the second phase structure is νd2. It is characterized by that.

請求項１１に記載の発明によれば、３つの光束に対して高い透過率が確保できる。   According to the eleventh aspect of the present invention, high transmittance can be secured for the three light beams.

請求項１２記載の発明は、請求項１に記載の対物光学素子において、前記第２位相構造は、前記第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であるα２次の回折光を発生し、前記第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であるβ２（β２＜α２）次の回折光を発生し、前記第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であるγ２（γ２≦β２）次の回折光を発生する回折構造であることを特徴とする。   According to a twelfth aspect of the present invention, in the objective optical element according to the first aspect, the second phase structure has an α2nd order which is the maximum diffraction efficiency of the diffracted light generated when the first light flux is incident. When diffracted light is generated and diffracted light of β2 (β2 <α2) order, which is the maximum diffraction efficiency, is generated from the diffracted light generated when the second light flux is incident, and the third light flux is incident It is characterized by a diffractive structure that generates γ2 (γ2 ≦ β2) order diffracted light, which is the maximum diffraction efficiency among the generated diffracted light.

請求項１２に記載の発明によれば、第２位相構造に請求項１のような効果を持たせることが出来、かつ３つの光束に対して高い透過率を確保出来る。尚、このような回折特性を有する回折構造は、光軸を含む断面形状が鋸歯型でもよいし、光軸から離れるに従って光路長が長くなる階段構造、或いは、光軸から離れるに従って光路長が短くなる階段構造でもよい。   According to the twelfth aspect of the present invention, the second phase structure can have the effect as in the first aspect, and a high transmittance can be secured for the three light beams. The diffractive structure having such diffraction characteristics may have a sawtooth shape in cross section including the optical axis, a staircase structure in which the optical path length increases as the distance from the optical axis increases, or the optical path length decreases as the distance from the optical axis increases. It may be a staircase structure.

請求項１３記載の発明は、請求項１に記載の対物光学素子において、前記第３位相構造は、前記第１光束及び前記第２光束を回折せず、前記第３光束を回折する回折構造であることを特徴とする。   According to a thirteenth aspect of the present invention, in the objective optical element according to the first aspect, the third phase structure is a diffractive structure that diffracts the third light flux without diffracting the first light flux and the second light flux. It is characterized by being.

請求項１３に記載の発明によれば、前記第３位相構造を第３光束のみを選択的に回折する回折構造とすることで、第３光束に対する収差を独立に制御することが可能となり、第１情報記録媒体と第３情報記録媒体の両方に対して良好な集光特性が得られる。   According to the invention described in claim 13, by making the third phase structure a diffractive structure that selectively diffracts only the third light beam, it becomes possible to independently control the aberration with respect to the third light beam. Good condensing characteristics can be obtained for both the one information recording medium and the third information recording medium.

請求項１４記載の発明は、請求項１３に記載の対物光学素子において、前記第３位相構造は、光軸を含む断面形状が階段状とされたパターンが同心円状に配列された構造であって、所定のレベル面の個数Ｂ毎に、そのレベル面数に対応した段数分の高さだけ段をシフトさせた構造であることを特徴とする。   According to a fourteenth aspect of the present invention, in the objective optical element according to the thirteenth aspect, the third phase structure is a structure in which patterns whose cross-sectional shape including the optical axis is stepped are arranged concentrically. Each of the predetermined number of level faces B has a structure in which the steps are shifted by a height corresponding to the number of steps corresponding to the number of level faces.

請求項１４に記載の発明によれば、請求項１３にあるような回折特性を第３位相構造に持たせることが可能になる。   According to the fourteenth aspect of the present invention, the third phase structure can have the diffraction characteristics as in the thirteenth aspect.

請求項１５記載の発明は、請求項１４に記載の対物光学素子において、前記第３位相構造を備える媒質のアッベ数をνｄ３としたとき、４０＜νｄ３＜７０を満たし、前記所定のレベル面の個数Ｂは２であることを特徴とする。   According to a fifteenth aspect of the present invention, in the objective optical element according to the fourteenth aspect, when the Abbe number of the medium having the third phase structure is νd3, 40 <νd3 <70 is satisfied, and the predetermined level surface The number B is two.

請求項１６記載の発明は、請求項１５に記載の対物光学素子において、前記階段の１つの段差により生じる光路差は前記波長λ１の５倍であることを特徴とする。ここで、「前記階段の１つの段差により生じる光路差は前記波長λ１の５倍」とは、前記光路差が前記波長λ１のちょうど５倍の場合だけでなく、前記波長λ１の４．９〜５．１倍の場合も含む。   A sixteenth aspect of the present invention is the objective optical element according to the fifteenth aspect, wherein an optical path difference caused by one step of the steps is five times the wavelength λ1. Here, “the optical path difference caused by one step of the staircase is five times the wavelength λ1” means not only when the optical path difference is exactly five times the wavelength λ1, but also from 4.9 to 4.9 of the wavelength λ1. Including the case of 5.1 times.

請求項１５に記載の発明によれば、記録／再生速度の高速化が要求される第１光情報記録媒体と第２光情報記録媒体とに対して高い透過率を確保できる。そして、請求項１６のように、階段の１つの段差により生じる光路差を波長λ１の５倍にすることで、この効果がより顕著となる。   According to the fifteenth aspect of the present invention, it is possible to ensure a high transmittance for the first optical information recording medium and the second optical information recording medium that are required to increase the recording / reproducing speed. Then, as in the sixteenth aspect, this effect becomes more conspicuous by setting the optical path difference caused by one step of the steps to five times the wavelength λ1.

請求項１７記載の発明は、請求項１４に記載の対物光学素子において、前記第３位相構造を備える媒質のアッベ数をνｄ３としたとき、２４＜νｄ３＜４０を満たし、前記所定のレベル面の個数Ｂは３であることを特徴とする。
請求項１８記載の発明は、請求項１７に記載の対物光学素子において、前記階段の１つの段差により生じる光路差は前記波長λ１の５倍又は７倍であることを特徴とする。
請求項１７に記載の発明によれば、３つの光束に対して高い透過率が確保できる。そして、請求項１８のように、階段の１つの段差により生じる光路差を波長λ１の５倍もしくは７倍にすることで、この効果がより顕著となる。 According to a seventeenth aspect of the present invention, in the objective optical element according to the fourteenth aspect, when the Abbe number of the medium having the third phase structure is νd3, 24 <νd3 <40 is satisfied, and the predetermined level surface The number B is three.
According to an eighteenth aspect of the present invention, in the objective optical element according to the seventeenth aspect, an optical path difference caused by one step of the steps is 5 or 7 times the wavelength λ1.
According to the seventeenth aspect of the present invention, high transmittance can be secured for the three light beams. Then, as in the eighteenth aspect, this effect becomes more conspicuous by setting the optical path difference generated by one step of the steps to 5 times or 7 times the wavelength λ1.

請求項１９記載の発明は、請求項１４に記載の対物光学素子において、前記第３位相構造を備える媒質のアッベ数をνｄ３としたとき、２０＜νｄ３＜２６を満たし、前記所定のレベル面の個数Ｂは４であることを特徴とする。   According to a nineteenth aspect of the present invention, in the objective optical element according to the fourteenth aspect, when the Abbe number of the medium having the third phase structure is νd3, 20 <νd3 <26 is satisfied, and the predetermined level surface The number B is four.

請求項２０記載の発明は、請求項１９に記載の対物光学素子において、前記階段の１つの段差により生じる光路差は前記波長λ１の７倍であることを特徴とする。   According to a twentieth aspect of the present invention, in the objective optical element according to the nineteenth aspect, an optical path difference caused by one step of the steps is seven times the wavelength λ1.

請求項１９に記載の発明によれば、３つの光束に対して高い透過率が確保できる。そして、請求項２０のように、階段の１つの段差により生じる光路差を波長λ１の７倍にすることで、この効果がより顕著となる。   According to the nineteenth aspect of the present invention, high transmittance can be secured for the three light beams. Then, as in the twentieth aspect, this effect becomes more conspicuous by setting the optical path difference caused by one step of the steps to 7 times the wavelength λ1.

請求項２１記載の発明は、請求項１に記載の対物光学素子において、前記第３位相構造は、前記第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であるα３次の回折光を発生し、前記第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であるβ３（β３＜α３）次の回折光を発生し、前記第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であるγ３（γ３≦β３）次の回折光を発生する回折構造であることを特徴とする。   According to a twenty-first aspect of the present invention, in the objective optical element according to the first aspect, the third phase structure has an α 3rd order which is the maximum diffraction efficiency of the diffracted light generated when the first light beam is incident. When diffracted light is generated and diffracted light of β3 (β3 <α3) order, which is the maximum diffraction efficiency, is generated from the diffracted light generated when the second light flux is incident, and the third light flux is incident It is characterized by a diffractive structure that generates γ3 (γ3 ≦ β3) order diffracted light, which is the maximum diffraction efficiency among the generated diffracted light.

請求項２１に記載の発明によれば、第３位相構造にこのような回折特性を持たせることにより、第３位相構造に請求項１のような効果を持たせることが出来、かつ３つの光束に対して高い透過率を確保出来る。尚、このような回折特性を有する回折構造は、光軸を含む断面形状が鋸歯型でもよいし、光軸から離れるに従って光路長が長くなる階段構造、或いは、光軸から離れるに従って光路長が短くなる階段構造でもよい。   According to the twenty-first aspect of the present invention, the third phase structure can have the effect as in the first aspect by providing the third phase structure with such diffraction characteristics, and three light beams can be obtained. High transmittance can be secured. The diffractive structure having such diffraction characteristics may have a sawtooth shape in cross section including the optical axis, a staircase structure in which the optical path length increases as the distance from the optical axis increases, or the optical path length decreases as the distance from the optical axis increases. It may be a staircase structure.

請求項２２記載の発明は、請求項２１に記載の対物光学素子において、前記第３位相構造を備える媒質のアッベ数をνｄ３としたとき、２０＜νｄ３＜４０を満たすことを特徴とする。   According to a twenty-second aspect of the present invention, in the objective optical element according to the twenty-first aspect, when the Abbe number of the medium having the third phase structure is νd3, 20 <νd3 <40 is satisfied.

請求項２２に記載の発明によれば、３つの光束に対して高い透過率が確保できる。   According to the twenty-second aspect of the present invention, high transmittance can be secured for the three light beams.

請求項２３記載の発明は、請求項２２に記載の対物光学素子において、前記α３が奇数であることを特徴とする。   According to a twenty-third aspect of the present invention, in the objective optical element according to the twenty-second aspect, the α3 is an odd number.

請求項２３に記載の発明によれば、３つの光束に対して高い透過率が確保できる。   According to the twenty-third aspect of the present invention, high transmittance can be secured for the three light beams.

請求項２４記載の発明は、請求項１〜２３のいずれか一項に記載の対物光学素子において、少なくとも1枚の集光光学素子と、収差補正レンズ群とを備えることを特徴とする。   According to a twenty-fourth aspect of the present invention, in the objective optical element according to any one of the first to twenty-third aspects, the objective optical element includes at least one condensing optical element and an aberration correction lens group.

請求項２４に記載の発明によれば、対物光学素子に請求項１のような効果を持たせることが可能になる。   According to the twenty-fourth aspect, the objective optical element can be provided with the effect as in the first aspect.

請求項２５記載の発明は、請求項１〜２４のいずれか一項に記載の対物光学素子において、少なくとも１枚の集光光学素子を備えた２群２枚構成であることを特徴とする。   According to a twenty-fifth aspect of the present invention, in the objective optical element according to any one of the first to twenty-fourth aspects, a two-group two-element configuration including at least one condensing optical element is provided.

請求項２５に記載の発明によれば、対物光学素子に請求項１のような効果を持たせることが可能になる。   According to the invention described in claim 25, the objective optical element can be provided with the effect as in claim 1.

請求項２６記載の発明は、請求項１〜２４のいずれか一項に記載の対物光学素子において、少なくとも１枚の集光光学素子を備えた２群３枚構成であり、それら２群のうちの１群は２枚の互いに異なる媒質からなる光学素子を接合して成ることを特徴とする。   The invention according to claim 26 is the objective optical element according to any one of claims 1 to 24, wherein the objective optical element is a two-group three-element configuration including at least one condensing optical element. One group is formed by joining two optical elements made of different media.

請求項２６に記載の発明によれば、対物光学素子に請求項１のような効果を持たせることが可能になる。さらに、接合された光学素子の光学面に効果的に位相構造を配置することによって、３つの光束に対してより高い透過率が確保できる。   According to the twenty-sixth aspect, the objective optical element can be provided with the effect as in the first aspect. Furthermore, by effectively arranging the phase structure on the optical surface of the bonded optical element, higher transmittance can be secured for the three light beams.

請求項２７記載の発明は、請求項１〜２４のいずれか一項に記載の対物光学素子において、少なくとも１枚の集光光学素子を備えた３群３枚構成であることを特徴とする。   A twenty-seventh aspect of the present invention is the objective optical element according to any one of the first to twenty-fourth aspects, wherein the objective optical element has a three-group three-element configuration including at least one condensing optical element.

請求項２７に記載の発明によれば、対物光学素子に請求項１のような効果を持たせることが可能になる。さらに、３群の光学素子のそれぞれの光学面に効果的に位相構造を配置することによって、３つの光束に対してより高い透過率が確保できる。   According to the twenty-seventh aspect, the objective optical element can be provided with the effect as in the first aspect. Further, by effectively arranging the phase structure on each optical surface of the three groups of optical elements, a higher transmittance can be secured for the three light beams.

請求項２８記載の発明は、請求項２４〜２７のいずれか一項に記載の対物光学素子において、少なくとも前記集光光学素子が樹脂から構成されていることを特徴とする。   A twenty-eighth aspect of the present invention is the objective optical element according to any one of the twenty-fourth to twenty-seventh aspects, wherein at least the condensing optical element is made of a resin.

請求項２９記載の発明は、請求項２４〜２７のいずれか一項に記載の対物光学素子において、前記対物光学素子を構成するすべての光学素子が樹脂から構成されていることを特徴とする。   A twenty-ninth aspect of the invention is the objective optical element according to any one of the twenty-fourth to twenty-seventh aspects, wherein all the optical elements constituting the objective optical element are made of a resin.

請求項２８に記載の発明によれば、対物光学素子を構成する光学素子のうち集光光学素子を、ガラスと比較して一般的に比重が小さい樹脂製とすることで、対物光学素子全体の重量が軽くなり、当該対物光学素子のフォーカシングやトラッキング動作のためのアクチュエータへの負担を軽減でき、結果として光ピックアップ装置の小型化や低コスト化を実現できる。
また、樹脂製の光学素子は射出成形が可能となるので、大量生産による製造コストの低下を実現できる。 According to the invention described in claim 28, the condensing optical element among the optical elements constituting the objective optical element is made of a resin whose specific gravity is generally smaller than that of glass. The weight is reduced, and the burden on the actuator for focusing and tracking operations of the objective optical element can be reduced. As a result, the optical pickup device can be reduced in size and cost.
In addition, since the resin optical element can be injection-molded, the manufacturing cost can be reduced by mass production.

さらに、請求項２９に記載の発明のように、対物光学素子を構成するすべての光学素子を樹脂製とすることでより大きな効果を得られる。
また、樹脂製の光学素子は、アクチュエータからの放熱や、光ピックアップ装置の外部温度の変化による屈折率変化や形状変化が大きく、温度変化による球面収差発生量が大きいというデメリットがあるが、本発明では、第１位相構造において第１光情報記録媒体に対して情報の再生および／または記録を行なう際の温度特性を補償することから、これらデメリットを解消することができる。 Furthermore, as in the invention described in claim 29, a greater effect can be obtained by making all the optical elements constituting the objective optical element made of resin.
In addition, the resin-made optical element has a demerit that the refractive index change and the shape change due to the heat radiation from the actuator and the change in the external temperature of the optical pickup device are large, and the amount of spherical aberration generated due to the temperature change is large. Then, since the temperature characteristics when information is reproduced and / or recorded on the first optical information recording medium in the first phase structure are compensated, these disadvantages can be eliminated.

請求項３０記載の発明は、光ピックアップ装置において、保護基板厚ｔ１の第１光情報記録媒体に対して情報の再生または記録を行う波長λ１の第１光束を出射する第１光源と、保護基板厚ｔ２（ｔ１≦ｔ２）の第２光情報記録媒体に対して情報の再生または記録を行う波長λ２（λ１＜λ２）の第２光束を出射する第２光源と、保護基板厚ｔ３（ｔ２＜ｔ３）の第３光情報記録媒体に対して情報の再生または記録を行う波長λ３（λ２＜λ３）の第３光束を出射する第３光源と、請求項１〜２９のいずれか一項に記載の対物光学素子とを搭載したことを特徴とする。   A thirty-first aspect of the present invention is the optical pickup device, wherein the first light source that emits the first light flux having the wavelength λ1 for reproducing or recording information on the first optical information recording medium having the protective substrate thickness t1, and the protective substrate A second light source that emits a second light flux of wavelength λ2 (λ1 <λ2) for reproducing or recording information on a second optical information recording medium of thickness t2 (t1 ≦ t2), and a protective substrate thickness t3 (t2 < 30. A third light source that emits a third light beam having a wavelength of λ3 (λ2 <λ3) for reproducing or recording information on the third optical information recording medium at t3), and any one of claims 1 to 29. The objective optical element is mounted.

請求項３０に記載の発明によれば、請求項１〜２９のいずれか一項と同様の効果を得られる。   According to the invention of claim 30, the same effect as that of any one of claims 1 to 29 can be obtained.

請求項３１記載の発明は、光ディスクドライブ装置において、請求項３０に記載の光ピックアップ装置と、前記光ピックアップ装置を光情報記録媒体の半径方向に移動させる移動装置とを搭載したことを特徴とする。   A thirty-first aspect of the invention is an optical disc drive device, wherein the optical pickup device according to the thirty-third aspect and a moving device that moves the optical pickup device in the radial direction of the optical information recording medium are mounted. .

請求項３１に記載の発明によれば、請求項３０と同様の効果を得られる。   According to the invention of claim 31, the same effect as that of claim 30 can be obtained.

本発明によれば、位相構造の作用により、高密度光ディスクとＤＶＤとＣＤとの保護層厚みの差による球面収差、或いは、高密度光ディスクとＤＶＤとＣＤとの使用波長の差による球面収差を良好に補正することができるとともに、４００ｎｍ近傍の青紫色波長領域と、６５０ｎｍ近傍の赤色波長領域と、７８０ｎｍ近傍の赤外波長領域との何れの波長領域においても高い光利用効率を得ることができ、更には、温度特性に優れた対物光学素子、この対物光学素子を有する光ピックアップ装置、及び、この光ピックアップ装置を搭載した光ディスクドライブ装置を得られる。   According to the present invention, spherical aberration due to the difference in the protective layer thickness between the high-density optical disc and the DVD and CD, or spherical aberration due to the difference in use wavelength between the high-density optical disc and the DVD and CD is good due to the action of the phase structure. And a high light utilization efficiency can be obtained in any wavelength region of a blue-violet wavelength region near 400 nm, a red wavelength region near 650 nm, and an infrared wavelength region near 780 nm, Furthermore, an objective optical element having excellent temperature characteristics, an optical pickup device having the objective optical element, and an optical disk drive device equipped with the optical pickup device can be obtained.

[第１の実施の形態]
以下、本発明の第１の実施の形態について図面を用いて説明する。まず、図８を用いて本発明の対物光学素子及びこの対物光学素子を用いた光ピックアップ装置について説明する。
図８は、高密度光ディスクＨＤ（第１光情報記録媒体）とＤＶＤ（第２光情報記録媒体）とＣＤ（第３光情報記録媒体）との何れに対しても適切に情報の記録／再生を行える光ピックアップ装置ＰＵの構成を概略的に示す図である。ＨＤの光学的仕様は、第１波長λ１＝４０８ｎｍ、保護層ＰＬ１の厚さ（保護基板厚）ｔ１＝０．０８７５ｍｍ、開口数ＮＡ１＝０．８５であり、ＤＶＤの光学的仕様は、第２波長λ２＝６５８ｎｍ、保護層ＰＬ２の厚さ（保護基板厚）ｔ２＝０．６ｍｍ、開口数ＮＡ２＝０．６０であり、ＣＤの光学的仕様は、第３波長λ３＝７８５ｎｍ、保護層ＰＬ３の厚さ（保護基板厚）ｔ３＝１．２ｍｍ、開口数ＮＡ３＝０．４７である。但し、波長、保護層の厚さ、及び開口数の組合せはこれに限られない。 [First embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. First, the objective optical element of the present invention and an optical pickup device using the objective optical element will be described with reference to FIG.
FIG. 8 shows recording / reproduction of information appropriately for any of the high-density optical disc HD (first optical information recording medium), DVD (second optical information recording medium), and CD (third optical information recording medium). It is a figure which shows schematically the structure of optical pick-up apparatus PU which can perform. The optical specifications of the HD are the first wavelength λ1 = 408 nm, the thickness of the protective layer PL1 (protective substrate thickness) t1 = 0.0875 mm, the numerical aperture NA1 = 0.85, and the optical specifications of the DVD are the second The wavelength λ2 = 658 nm, the thickness of the protective layer PL2 (protective substrate thickness) t2 = 0.6 mm, the numerical aperture NA2 = 0.60, and the optical specifications of the CD are the third wavelength λ3 = 785 nm, the protective layer PL3 The thickness (protective substrate thickness) t3 = 1.2 mm and the numerical aperture NA3 = 0.47. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

光ピックアップ装置ＰＵは、ＨＤに対して情報の記録／再生を行う場合に発光され４０８ｎｍの青紫色レーザ光束（第１光束）を射出する青紫色半導体レーザ（第１光源）ＬＤ１、ＤＶＤに対して情報の記録／再生を行う場合に発光され６５８ｎｍの赤色レーザ光束（第２光束）を射出する第１の発光点（第２光源）ＥＰ１と、ＣＤに対して情報の記録／再生を行う場合に発光され７８５ｎｍの赤外レーザ光束（第３光束）を射出する第２の発光点（第３光源）ＥＰ２とを一つのチップ上に形成したＤＶＤ／ＣＤ用レーザ光源ユニットＬＵ、ＨＤ／ＤＶＤ／ＣＤ共用の光検出器ＰＤ、第１収差補正レンズＬ１と、この第１収差補正レンズＬ１を透過したレーザ光束を情報記録面ＲＬ１、ＲＬ２、ＲＬ３上に集光させる機能を有する両面が非球面とされた集光光学素子ＯＬとから構成された対物レンズユニットＯＵ（対物光学素子）、２軸アクチュエータＡＣ１、１軸アクチュエータＡＣ２、近軸における屈折力が負である第１レンズＥＸＰ１と近軸における屈折力が正である第２レンズＥＸＰ２とから構成されたエキスパンダーレンズＥＸＰ、第１偏光ビームスプリッタＢＳ１、第２偏光ビームスプリッタＢＳ２、第１コリメートレンズＣＯＬ１、第２コリメートレンズＣＯＬ２、第３コリメートレンズＣＯＬ３、情報記録面ＲＬ１、ＲＬ２及びＲＬ３からの反射光束に対して非点収差を付加するためのセンサーレンズＳＥＮとから構成されている。尚、ＨＤ用の光源として、上述の青紫色半導体レーザＬＤ１の他に青紫色ＳＨＧレーザを使用することもできる。   The optical pickup device PU is used for blue-violet semiconductor laser (first light source) LD1 and DVD that emits a 408 nm blue-violet laser beam (first beam) when information is recorded / reproduced with respect to HD. When recording / reproducing information to / from a first light emitting point (second light source) EP1 that emits a 658 nm red laser beam (second light beam) when recording / reproducing information and a CD. DVD / CD laser light source unit LU, HD / DVD / CD having a second light emitting point (third light source) EP2 that emits a 785 nm infrared laser light beam (third light beam) emitted on one chip. Shared photo detector PD, first aberration correction lens L1, and both surfaces having a function of condensing the laser beam transmitted through the first aberration correction lens L1 on the information recording surfaces RL1, RL2, RL3 are aspherical Objective lens unit OU (objective optical element) composed of a condensing optical element OL, a biaxial actuator AC1, a monoaxial actuator AC2, a first lens EXP1 having a negative refractive power in the paraxial and a paraxial An expander lens EXP including a second lens EXP2 having a positive refractive power, a first polarizing beam splitter BS1, a second polarizing beam splitter BS2, a first collimating lens COL1, a second collimating lens COL2, and a third collimating lens COL3 And a sensor lens SEN for adding astigmatism to the reflected light beams from the information recording surfaces RL1, RL2 and RL3. In addition to the blue-violet semiconductor laser LD1 described above, a blue-violet SHG laser can also be used as the HD light source.

光ピックアップ装置ＰＵにおいて、ＨＤに対して情報の記録／再生を行う場合には、図８において実線でその光線経路を描いたように、まず青紫色半導体レーザＬＤ１を発光させる。青紫色半導体レーザＬＤ１から射出された発散光束は、第１コリメートレンズＣＯＬ１により平行光束に変換された後、第１偏光ビームスプリッタＢＳ１により反射され、第２偏光ビームスプリッタＢＳ２を通過し、第１レンズＥＸＰ１、第２レンズＥＸＰ２を透過することにより拡径された後、図示しない絞りＳＴＯにより光束径が規制され、対物レンズユニットＯＵによってＨＤの保護層ＰＬ１を介して情報記録面ＲＬ１上に形成されるスポットとなる。対物レンズユニットＯＵは、その周辺に配置された２軸アクチュエータＡＣ１によってフォーカシングやトラッキングを行う。   When recording / reproducing information with respect to the HD in the optical pickup device PU, first, the blue-violet semiconductor laser LD1 is caused to emit light, as shown by the solid line in FIG. The divergent light beam emitted from the blue-violet semiconductor laser LD1 is converted into a parallel light beam by the first collimating lens COL1, then reflected by the first polarizing beam splitter BS1, passes through the second polarizing beam splitter BS2, and passes through the first lens. After being expanded by passing through EXP1 and the second lens EXP2, the diameter of the light beam is regulated by a stop STO (not shown) and formed on the information recording surface RL1 by the objective lens unit OU via the HD protective layer PL1. Become a spot. The objective lens unit OU performs focusing and tracking by a biaxial actuator AC1 disposed in the periphery thereof.

情報記録面ＲＬ１で情報ピットにより変調された反射光束は、再び対物レンズユニットＯＵ、第２レンズＥＸＰ２、第１レンズＥＸＰ１、第２偏光ビームスプリッタＢＳ２、第１偏光ビームスプリッタＢＳ１を透過した後、第３コリメートレンズＣＯＬ３を通過する際に収斂光束となり、センサーレンズＳＥＮにより非点収差が付加され、光検出器ＰＤの受光面上に収束する。そして、光検出器ＰＤの出力信号を用いてＨＤに記録された情報を読み取ることができる。   The reflected light flux modulated by the information pits on the information recording surface RL1 passes through the objective lens unit OU, the second lens EXP2, the first lens EXP1, the second polarizing beam splitter BS2, and the first polarizing beam splitter BS1 again, When passing through the three collimating lens COL3, it becomes a convergent light beam, is added with astigmatism by the sensor lens SEN, and converges on the light receiving surface of the photodetector PD. And the information recorded on HD can be read using the output signal of photodetector PD.

また、光ピックアップ装置ＰＵにおいて、ＤＶＤに対して情報の記録／再生を行う場合には、発光点ＥＰ１を発光させる。発光点ＥＰ１から射出された発散光束は、図８において破線でその光線経路を描いたように、第２コリメートレンズＣＯＬ２により平行光束に変換された後、第２偏光ビームスプリッタＢＳ２により反射され、第１レンズＥＸＰ１、第２レンズＥＸＰ２を透過することにより拡径され、対物レンズユニットＯＵによってＤＶＤの保護層ＰＬ２を介して情報記録面ＲＬ２上に形成されるスポットとなる。対物レンズユニットＯＵは、その周辺に配置された２軸アクチュエータＡＣ１によってフォーカシングやトラッキングを行う。   In addition, when the optical pickup device PU records / reproduces information with respect to a DVD, the light emitting point EP1 is caused to emit light. The divergent light beam emitted from the light emitting point EP1 is converted into a parallel light beam by the second collimating lens COL2 as depicted by the broken line in FIG. 8, and then reflected by the second polarization beam splitter BS2, The diameter is increased by transmitting through the first lens EXP1 and the second lens EXP2, and becomes a spot formed on the information recording surface RL2 via the protective layer PL2 of the DVD by the objective lens unit OU. The objective lens unit OU performs focusing and tracking by a biaxial actuator AC1 disposed in the periphery thereof.

情報記録面ＲＬ２で情報ピットにより変調された反射光束は、再び対物レンズユニットＯＵ、第２レンズＥＸＰ２、第１レンズＥＸＰ１、第２偏光ビームスプリッタＢＳ２、第１偏光ビームスプリッタＢＳ１を透過した後、第３コリメートレンズＣＯＬ３を通過する際に収斂光束となり、センサーレンズＳＥＮにより非点収差が付加され、光検出器ＰＤの受光面上に収束する。そして、光検出器ＰＤ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。   The reflected light beam modulated by the information pits on the information recording surface RL2 passes through the objective lens unit OU, the second lens EXP2, the first lens EXP1, the second polarizing beam splitter BS2, and the first polarizing beam splitter BS1 again, When passing through the three collimating lens COL3, it becomes a convergent light beam, is added with astigmatism by the sensor lens SEN, and converges on the light receiving surface of the photodetector PD. And the information recorded on DVD can be read using the output signal of photodetector PD.

また、光ピックアップ装置ＰＵにおいて、ＣＤに対して情報の記録／再生を行う場合には、第１レンズＥＸＰ１と第２レンズＥＸＰ２の間隔がＨＤに対する情報の記録／再生時によりも狭くなるように、１軸アクチュエータＡＣ２により光軸方向に第１レンズＥＸＰ１を駆動させた後、発光点ＥＰ２を発光させる。発光点ＥＰ２から射出された発散光束は、図８において一点鎖線でその光線経路を描いたように、第２コリメートレンズＣＯＬ２により緩い発散光束に変換された後、第２偏光ビームスプリッタＢＳ２により反射され、第１レンズＥＸＰ１、第２レンズＥＸＰ２を透過することにより拡径されるとともに発散光束に変換され、対物レンズユニットＯＵによってＣＤの保護層ＰＬ３を介して情報記録面ＲＬ３上に形成されるスポットとなる。対物レンズユニットＯＵは、その周辺に配置された２軸アクチュエータＡＣ１によってフォーカシングやトラッキングを行う。   In the optical pickup device PU, when information is recorded / reproduced with respect to a CD, the interval between the first lens EXP1 and the second lens EXP2 is narrower than that during recording / reproduction of information with respect to HD. After the first lens EXP1 is driven in the optical axis direction by the uniaxial actuator AC2, the light emitting point EP2 is caused to emit light. The divergent light beam emitted from the light emitting point EP2 is converted into a loose divergent light beam by the second collimating lens COL2, as shown by the dashed line in FIG. 8, and then reflected by the second polarization beam splitter BS2. A spot which is enlarged by passing through the first lens EXP1 and the second lens EXP2 and converted into a divergent light beam and formed on the information recording surface RL3 by the objective lens unit OU via the protective layer PL3 of the CD. Become. The objective lens unit OU performs focusing and tracking by a biaxial actuator AC1 disposed in the periphery thereof.

情報記録面ＲＬ２で情報ピットにより変調された反射光束は、再び対物レンズユニットＯＵ、第２レンズＥＸＰ２、第１レンズＥＸＰ１、第２偏光ビームスプリッタＢＳ２、第１偏光ビームスプリッタＢＳ１を透過した後、第３コリメートレンズＣＯＬ３を通過する際に収斂光束となり、センサーレンズＳＥＮにより非点収差が付加され、光検出器ＰＤの受光面上に収束する。そして、光検出器ＰＤ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。   The reflected light beam modulated by the information pits on the information recording surface RL2 passes through the objective lens unit OU, the second lens EXP2, the first lens EXP1, the second polarizing beam splitter BS2, and the first polarizing beam splitter BS1 again, When passing through the three collimating lens COL3, it becomes a convergent light beam, is added with astigmatism by the sensor lens SEN, and converges on the light receiving surface of the photodetector PD. And the information recorded on CD can be read using the output signal of photodetector PD.

本実施形態における対物レンズユニットＯＵは、図９に概略的に示すように、樹脂製の第１収差補正レンズＬ１と、第１波長λ１とＨＤの保護層ＰＬ１の厚さｔ１とに対して球面収差が最小となるようにその非球面形状が設計された樹脂製の集光光学素子ＯＬが、鏡枠Ｂを介して同軸で一体化された２群２枚構成を有する。具体的には、円筒状の鏡枠Ｂの一端に第１収差補正レンズＬ１を嵌合固定し、他端に集光光学素子ＯＬを嵌合固定して、これらを光軸Ｘに沿って同軸に一体化した構成となっている。   As schematically shown in FIG. 9, the objective lens unit OU in the present embodiment is spherical with respect to the resin-made first aberration correction lens L1, the first wavelength λ1, and the thickness t1 of the HD protective layer PL1. A condensing optical element OL made of resin whose aspherical shape is designed so as to minimize aberration has a two-group two-element configuration in which the lens is integrated coaxially through a lens frame B. Specifically, the first aberration correction lens L1 is fitted and fixed to one end of the cylindrical lens frame B, and the condensing optical element OL is fitted and fixed to the other end, and these are coaxial along the optical axis X. It has a configuration integrated with.

また、第１収差補正レンズＬ１は、ｄ線におけるアッベ数νd（νｄ２、νｄ３）＝５５．０、ｄ線における屈折率ｎd＝１．５５であり、集光光学素子ＯＬは、ｄ線におけるアッベ数νd＝５５．０、ｄ線における屈折率ｎd＝１．５５である。
また、集光光学素子ＯＬの光源側の光学面には第１位相構造ＰＳ１が形成されており、第１収差補正レンズＬ１の光源側の光学面には第２位相構造ＰＳ２が形成されており、第１収差補正レンズＬ１の光ディスク側の光学面には第３位相構造ＰＳ３が形成されている。 The first aberration correction lens L1 has an Abbe number ν d (νd2, νd3) = 55.0 in the d-line and a refractive index n d = 1.55 in the d -line, and the condensing optical element OL has the d-line Abbe number ν d = 55.0, and refractive index n d = 1.55 at the d -line.
The first phase structure PS1 is formed on the optical surface on the light source side of the condensing optical element OL, and the second phase structure PS2 is formed on the optical surface on the light source side of the first aberration correction lens L1. The third phase structure PS3 is formed on the optical surface of the first aberration correction lens L1 on the optical disc side.

第２位相構造ＰＳ２は第１光束及び第３光束を回折せず、第２光束を回折する回折構造であり、光軸Ｘを含む断面形状が階段状とされたパターンが同心円状に配列された構造であって、所定のレベル面（本実施の形態では５レベル面）の個数毎に、そのレベル面数に対応した段数分の高さだけ段をシフトさせた構造（本実施の形態においては４段シフトさせた構造）となっている。
階段構造の各段差Δ１は、Δ１＝２・λ１／（ｎ１−１）＝１．４４μｍを満たす高さに設定されている。ここで、ｎ１は波長λ１（本実施の形態ではλ１＝４０８ｎｍ）における第１収差補正レンズＬ１の屈折率である。 The second phase structure PS2 is a diffractive structure that does not diffract the first light beam and the third light beam but diffracts the second light beam, and a pattern in which the cross-sectional shape including the optical axis X is stepped is arranged concentrically. A structure in which a level is shifted by a height corresponding to the number of level planes for each predetermined number of level planes (5 level planes in the present embodiment) (in the present embodiment, The structure is shifted by four stages.
Each step Δ1 of the staircase structure is set to a height that satisfies Δ1 = 2 · λ1 / (n1-1) = 1.44 μm. Here, n1 is the refractive index of the first aberration correction lens L1 at the wavelength λ1 (λ1 = 408 nm in the present embodiment).

段差Δ１により第１光束に付加される光路差は２×λ１であるので、第１光束は第２位相構造ＰＳ２により何ら作用を受けずにそのまま透過する。
また、段差Δ１により第３光束に付加される光路差は１×λ３（本実施の形態ではλ３＝７８５ｎｍ）であるので、第３光束も第２位相構造ＰＳ２により何ら作用を受けずにそのまま透過する。
一方、段差Δ１により第２光束に付加される光路差は１．２０×λ２（本実施の形態ではλ２＝６５８ｎｍ）であり、段差Δ１の前後のレベル面を通過する第２光束の位相は２π／５だけずれることになる。１つの鋸歯は５分割されているため、鋸歯１つ分ではちょうど第２光束の位相のずれは５×２π／５＝２πとなり、１次回折光が発生する。 Since the optical path difference added to the first light flux by the step Δ1 is 2 × λ1, the first light flux is transmitted as it is without being affected by the second phase structure PS2.
Further, since the optical path difference added to the third light flux by the step Δ1 is 1 × λ3 (λ3 = 785 nm in the present embodiment), the third light flux is also transmitted as it is without being affected by the second phase structure PS2. To do.
On the other hand, the optical path difference added to the second light flux by the step Δ1 is 1.20 × λ2 (λ2 = 658 nm in the present embodiment), and the phase of the second light flux passing through the level surface before and after the step Δ1 is 2π. Will be shifted by / 5. Since one sawtooth is divided into five, the phase shift of the second light beam is exactly 5 × 2π / 5 = 2π for one sawtooth, and first-order diffracted light is generated.

このように、第２位相構造ＰＳ２は第２光束のみを選択的に回折させることにより、ＨＤの保護層厚さとＤＶＤの保護層厚さの違いによる球面収差を補正する。
尚、第２位相構造ＰＳ２で発生する第１光束の０次回折光（透過光）の回折効率は１００％、第２光束の１次回折光の回折効率は８７．５％、第３光束の０次回折光（透過光）の回折効率は１００％であり、何れの光束に対しても高い回折効率を得ている。 As described above, the second phase structure PS2 selectively diffracts only the second light beam, thereby correcting the spherical aberration due to the difference between the HD protective layer thickness and the DVD protective layer thickness.
The diffraction efficiency of the first-order diffracted light (transmitted light) of the first light beam generated by the second phase structure PS2 is 100%, the diffraction efficiency of the first-order diffracted light of the second light beam is 87.5%, and the zero-next time of the third light beam. The diffraction efficiency of the folded light (transmitted light) is 100%, and a high diffraction efficiency is obtained for any light flux.

第３位相構造ＰＳ３は第１光束及び第２光束を回折せず、第３光束を回折する回折構造であり、光軸Ｘを含む断面形状が階段状とされたパターンが同心円状に配列された構造であって、所定のレベル面（本実施の形態では２レベル面）の個数毎に、そのレベル面数に対応した段数分の高さだけ段をシフトさせた構造（本実施の形態においては１段シフトさせた構造）となっている。
階段構造の各段差Δ２は、Δ２＝５・λ１／（ｎ１−１）＝３．６０μｍを満たす高さに設定されている。ここで、ｎ１は波長λ１における第１収差補正レンズＬ１の屈折率である。 The third phase structure PS3 is a diffractive structure that does not diffract the first light beam and the second light beam but diffracts the third light beam, and a pattern in which the cross-sectional shape including the optical axis X is stepped is arranged concentrically. A structure in which for each predetermined number of level planes (two level planes in the present embodiment), the level is shifted by a height corresponding to the number of level planes (in this embodiment, in this embodiment) 1-stage shifted structure).
Each step Δ2 of the staircase structure is set to a height that satisfies Δ2 = 5 · λ1 / (n1-1) = 3.60 μm. Here, n1 is the refractive index of the first aberration correction lens L1 at the wavelength λ1.

段差Δ２により第１光束に付加される光路差は５×λ１であるので、第１光束は第３位相構造ＰＳ３により何ら作用を受けずにそのまま透過する。
また、段差Δ２により第２光束に付加される光路差は３×λ２であるので、第２光束も第３位相構造ＰＳ３によりほとんど作用を受けずにそのまま透過する。
一方、段差Δ２によりにより第３光束に付加される光路差は約２．５×λ３であり、段差Δ２の前後のレベル面を通過する第３光束の位相は約π／２だけずれることになる。１つの鋸歯は２分割されているため、鋸歯１つ分ではちょうど第３光束の位相のずれは２×π／２＝πとなるので、第３位相構造ＰＳ３に入射する第３光束はその光量の殆どが１次回折光と−１次回折光とに振り分けられる。第３位相構造ＰＳ３は、このうち１次回折光をＣＤの情報記録面ＲＬ３上に集光させるように設計されている。 Since the optical path difference added to the first light flux by the step Δ2 is 5 × λ1, the first light flux is transmitted as it is without being affected by the third phase structure PS3.
Further, since the optical path difference added to the second light flux by the step Δ2 is 3 × λ2, the second light flux is transmitted as it is with little effect by the third phase structure PS3.
On the other hand, the optical path difference added to the third light beam by the step Δ2 is about 2.5 × λ3, and the phase of the third light beam passing through the level surface before and after the step Δ2 is shifted by about π / 2. . Since one saw blade is divided into two parts, the phase shift of the third light beam is exactly 2 × π / 2 = π in one saw blade, so the third light beam incident on the third phase structure PS3 has its light quantity. Most of the light is distributed into first-order diffracted light and −1st-order diffracted light. Of these, the third phase structure PS3 is designed to focus the first-order diffracted light on the information recording surface RL3 of the CD.

このように、第３位相構造ＰＳ３は第３光束のみを選択的に回折させることにより、ＨＤの保護層厚さとＣＤの保護層厚さの違いによる球面収差を補正する。
尚、第３位相構造ＰＳ３で発生する第１光束の０次回折光（透過光）の回折効率は１００％、第２光束の０次回折光（透過光）の回折効率は１００％、第３光束の１次回折光の回折効率は４０．５％であり、記録／再生速度の高速化が要求されるＨＤとＤＶＤとに対して高い回折効率を得ている。 As described above, the third phase structure PS3 selectively diffracts only the third light beam, thereby correcting the spherical aberration due to the difference between the HD protective layer thickness and the CD protective layer thickness.
Note that the diffraction efficiency of the 0th-order diffracted light (transmitted light) of the first light flux generated in the third phase structure PS3 is 100%, the diffraction efficiency of the 0th-order diffracted light (transmitted light) of the second light flux is 100%, and the third light flux The diffraction efficiency of the first-order diffracted light is 40.5%, and a high diffraction efficiency is obtained for HD and DVD that require high recording / reproducing speed.

第１位相構造ＰＳ１は、光軸Ｘを含む断面形状が鋸歯状の位相差付与構造であり、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であるα１＝２次の回折光を発生させるように設定されている。これにより、２軸アクチュエータＡＣ１からの放熱や環境温度の変化に伴って位相構造が形成されたプラスチック製の集光光学素子ＯＬの温度が変化し、この温度変化に伴い屈折率が大きく変化した場合であっても、第１光束のα１＝２次回折光を利用して安定した記録／再生特性が得られるようになっている。   The first phase structure PS1 is a phase difference providing structure having a sawtooth cross section including the optical axis X, and α1 = 2nd order which is the maximum diffraction efficiency of the diffracted light generated when the first light flux is incident. It is set to generate diffracted light. As a result, the temperature of the plastic condensing optical element OL formed with the phase structure changes with the heat radiation from the biaxial actuator AC1 and the change of the environmental temperature, and the refractive index changes greatly with this temperature change. Even so, stable recording / reproducing characteristics can be obtained by using α1 = 2nd order diffracted light of the first light flux.

また、第１位相構造ＰＳ１は、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であるβ１＝１（β１＜α１）次の回折光を発生させ、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であるγ１＝１（γ１≦β１）次の回折光を発生させるように設定されている。
第１光束のα１＝２次回折光、第２光束のβ１＝１次回折光、第３光束のγ１＝１次回折光の回折効率はそれぞれ１００％、８７．８％、１００％であり、何れの光束に対しても高い回折効率を得ている。
尚、このような回折特性を有する位相差付与構造は、光軸を含む断面形状が鋸歯型でもよいし、光軸から離れるに従って光路長が長くなる階段構造、或いは、光軸から離れるに従って光路長が短くなる階段構造でもよい。 Further, the first phase structure PS1 generates diffracted light of β1 = 1 (β1 <α1) order, which is the maximum diffraction efficiency, among the diffracted light generated when the second light flux is incident, and the third light flux is incident. In this case, γ1 = 1 (γ1 ≦ β1) order diffracted light, which is the maximum diffraction efficiency, is generated.
The diffraction efficiencies of α1 = 2nd order diffracted light of the first light flux, β1 = 1st order diffracted light of the second light flux, and γ1 = 1st order diffracted light of the third light flux are 100%, 87.8%, and 100%, respectively. High diffraction efficiency is also obtained.
The phase difference providing structure having such diffraction characteristics may have a sawtooth shape in cross section including the optical axis, a step structure in which the optical path length increases as the distance from the optical axis increases, or the optical path length increases as the distance from the optical axis increases. It may be a staircase structure that shortens.

以上のように、本実施の形態に係る対物光学素子及び光ピックアップ装置によれば、第１位相構造ＰＳ１においてＨＤに対する温度特性を補償し、第２位相構造ＰＳ２においてＨＤ／ＤＶＤ間の互換を達成し、第３位相構造ＰＳ３においてＨＤ／ＣＤ間の互換を達成でき、さらに、特にＮＡの大きい第１光情報記録媒体としてのＢＤでは顕著になる温度変化による球面収差の発生を抑えられる。
なお、例えば、第２位相構造ＰＳ２を、ＤＶＤの開口数ＮＡ２内にのみに形成すると、ＮＡ２より外側の領域を通過する光束はＤＶＤの情報記録面ＲＬ２上でフレア成分となり、ＤＶＤに対する開口制限が自動的に行われる構成とすることができる。 As described above, according to the objective optical element and the optical pickup device of the present embodiment, the first phase structure PS1 compensates for the temperature characteristics with respect to HD, and the second phase structure PS2 achieves compatibility between HD / DVD. In addition, compatibility between HD / CD can be achieved in the third phase structure PS3, and the occurrence of spherical aberration due to temperature change that is particularly noticeable in the BD as the first optical information recording medium having a large NA can be suppressed.
For example, if the second phase structure PS2 is formed only within the numerical aperture NA2 of the DVD, the light flux that passes through the area outside the NA2 becomes a flare component on the information recording surface RL2 of the DVD, and the aperture restriction on the DVD is limited. It can be configured to be performed automatically.

また、例えば、第３位相構造ＰＳ３を、ＣＤの開口数ＮＡ３内にのみ形成すると、ＮＡ３より外側の領域を通過する光束はＣＤの情報記録面ＲＬ３上でフレア成分となり、ＣＤに対する開口制限が自動的に行われる構成とすることができる。   For example, when the third phase structure PS3 is formed only within the numerical aperture NA3 of the CD, the light beam passing through the area outside the NA3 becomes a flare component on the information recording surface RL3 of the CD, and the aperture restriction on the CD is automatically performed. It can be set as the structure performed automatically.

なお、ビームエキスパンダーＥＸＰの負レンズＥＸＰ１を１軸アクチュエータＵＡＣにより光軸方向に駆動させることで、ＨＤの情報記録面ＲＬ１上に形成されたスポットの球面収差を補正できる。負レンズＥＸＰ１の位置調整により補正する球面収差の発生原因は、例えば、第１光源ＬＤ１の製造誤差による波長ばらつき、温度変化に伴う対物レンズ系の屈折率変化や屈折率分布、２層ディスク、４層ディスク等の多層ディスクの情報記録層間のフォーカスジャンプ、次世代ＤＶＤの保護層の製造誤差による厚みばらつきや厚み分布、等である。   Incidentally, the spherical aberration of the spot formed on the HD information recording surface RL1 can be corrected by driving the negative lens EXP1 of the beam expander EXP in the optical axis direction by the uniaxial actuator UAC. The cause of the occurrence of spherical aberration to be corrected by adjusting the position of the negative lens EXP1 is, for example, wavelength variation due to manufacturing error of the first light source LD1, refractive index change or refractive index distribution of the objective lens system due to temperature change, double-layer disk, 4 Focus jump between information recording layers of a multilayer disc such as a layer disc, thickness variation and thickness distribution due to manufacturing error of a protective layer of a next generation DVD, and the like.

なお、負レンズＥＸＰ１の代わりに、第１コリメートレンズＣＯＬ１を光軸方向に駆動させる構成としても、ＨＤの情報記録面ＲＬ１上に形成されたスポットの球面収差を補正できる。   Note that the spherical aberration of the spot formed on the HD information recording surface RL1 can be corrected even if the first collimating lens COL1 is driven in the optical axis direction instead of the negative lens EXP1.

また、本実施の形態においては、第１の発光点ＥＰ１と第２の発光点ＥＰ２とを一つのチップ上に形成したＤＶＤ／ＣＤ用レーザ光源ユニットＬＵを用いることとしたが、これに限らず、更にＨＤ用の波長４０８ｎｍのレーザ光束を射出する発光点も同一のチップ上に形成したＨＤ／ＤＶＤ／ＣＤ用レーザ光源ユニットを用いても良い。あるいは、青紫色半導体レーザと赤色半導体レーザと赤外半導体レーザの３つのレーザ光源を１つの筐体内に納めたＨＤ／ＤＶＤ／ＣＤ用レーザ光源ユニットを用いても良い。   In the present embodiment, the DVD / CD laser light source unit LU in which the first light emission point EP1 and the second light emission point EP2 are formed on one chip is used. However, the present invention is not limited to this. Further, an HD / DVD / CD laser light source unit having a light emitting point for emitting a laser beam having a wavelength of 408 nm for HD formed on the same chip may be used. Alternatively, an HD / DVD / CD laser light source unit in which three laser light sources of a blue-violet semiconductor laser, a red semiconductor laser, and an infrared semiconductor laser are housed in one housing may be used.

また、本実施の形態においては、光源と光検出器ＰＤとを別体に配置する構成としたが、これに限らず、光源と光検出器とを集積化したレーザ光源モジュールを用いても良い。
また、本実施形態においては、第１収差補正レンズＬ１と集光光学素子ＯＬとを鏡枠Ｂを介して一体化したが、第１収差補正レンズＬ１と集光光学素子ＯＬを一体化する場合には、第１収差補正レンズＬ１と集光光学素子ＯＬとの、互いの相対的な位置関係が不変となるように保持されていればよく、上述のように鏡枠Ｂを介する方法以外に、第１収差補正レンズＬ１と集光光学素子ＯＬのそれぞれのフランジ部同士を嵌合固定する方法であってもよい。 In the present embodiment, the light source and the photodetector PD are arranged separately. However, the present invention is not limited to this, and a laser light source module in which the light source and the photodetector are integrated may be used. .
In the present embodiment, the first aberration correction lens L1 and the condensing optical element OL are integrated via the lens frame B. However, the first aberration correction lens L1 and the condensing optical element OL are integrated. Need only be held so that the relative positional relationship between the first aberration correction lens L1 and the condensing optical element OL is not changed, and other than the method using the lens frame B as described above. A method of fitting and fixing the flange portions of the first aberration correction lens L1 and the condensing optical element OL may be used.

このように第１収差補正レンズＬ１と集光光学素子ＯＬとの、互いの相対的な位置関係が不変となるように保持されていることで、フォーカシングやトラッキングの際の収差の発生を抑制でき、良好なフォーカシング特性、或いはトラッキング特性を得ることができる。   Since the relative positional relationship between the first aberration correction lens L1 and the condensing optical element OL is kept unchanged as described above, the occurrence of aberration during focusing and tracking can be suppressed. Good focusing characteristics or tracking characteristics can be obtained.

[第２の実施の形態]
以下、本発明の第２の実施の形態について図面を用いて説明するが、上記第１の実施の形態と同一の構成となる箇所については説明を省略する。
本実施の形態におけるＨＤの光学的仕様は、第１波長λ１＝４０８ｎｍ、保護層ＰＬ１の厚さｔ１＝０．０８７５ｍｍ、開口数ＮＡ１＝０．８５であり、ＤＶＤの光学的仕様は、第２波長λ２＝６５８ｎｍ、保護層ＰＬ２の厚さｔ２＝０．６ｍｍ、開口数ＮＡ２＝０．６０であり、ＣＤの光学的仕様は、第３波長λ３＝７８５ｎｍ、保護層ＰＬ３の厚さｔ３＝１．２ｍｍ、開口数ＮＡ３＝０．４５である。但し、波長、保護層の厚さ、及び開口数の組合せはこれに限られない。 [Second Embodiment]
Hereinafter, the second embodiment of the present invention will be described with reference to the drawings. However, description of portions having the same configuration as that of the first embodiment will be omitted.
The optical specifications of the HD in this embodiment are the first wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, and the numerical aperture NA1 = 0.85. The optical specifications of the DVD are the second The wavelength λ2 = 658 nm, the thickness t2 of the protective layer PL2 = 0.6 mm, the numerical aperture NA2 = 0.60, and the optical specifications of the CD are the third wavelength λ3 = 785 nm and the thickness t3 = 1 of the protective layer PL3. .2 mm and numerical aperture NA3 = 0.45. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

本実施形態における対物レンズユニットＯＵは、図１０に概略的に示すように、樹脂製の第１収差補正レンズＬ１と樹脂製の第２収差補正レンズＬ２と接合してなるレンズ群と、第１波長λ１とＨＤの保護層ＰＬ１の厚さｔ１とに対して球面収差が最小となるようにその非球面形状が設計された樹脂製の集光光学素子ＯＬが、鏡枠Ｂを介して同軸で一体化された２群３枚構成を有する。具体的には、円筒状の鏡枠Ｂの一端に第１収差補正レンズＬ１と第２収差補正レンズＬ２とを接合した状態で嵌合固定し、他端に集光光学素子ＯＬを嵌合固定して、これらを光軸Ｘに沿って同軸に一体化した構成となっている。   As schematically shown in FIG. 10, the objective lens unit OU in the present embodiment includes a first lens group formed by bonding a resin-made first aberration correction lens L1 and a resin-made second aberration correction lens L2, and a first lens unit OU. A resin condensing optical element OL whose aspherical shape is designed so that the spherical aberration is minimized with respect to the wavelength λ1 and the thickness t1 of the HD protective layer PL1 is coaxially connected via the lens frame B. It has a two-group, three-element configuration. Specifically, the first aberration correction lens L1 and the second aberration correction lens L2 are fitted and fixed to one end of the cylindrical lens frame B, and the condensing optical element OL is fitted and fixed to the other end. Thus, these are integrated along the optical axis X coaxially.

また、第１収差補正レンズは、ｄ線におけるアッベ数νd（νｄ２）＝５５．０、ｄ線における屈折率ｎd＝１．５５であり、第２収差補正レンズは、ｄ線におけるアッベ数νd（νｄ３）＝２３．０、ｄ線における屈折率ｎd＝１．６０であり、集光光学素子ＯＬは、ｄ線におけるアッベ数νd＝５５．０、ｄ線における屈折率ｎd＝１．５５である。
また、集光光学素子ＯＬの光源側の光学面には第１位相構造ＰＳ１が形成されており、第１収差補正レンズＬ１の光源側の光学面には第２位相構造ＰＳ２が形成されており、第２収差補正レンズＬ２の光ディスク側の光学面には第３位相構造ＰＳ３が形成されている。
なお、第１及び第２位相構造ＰＳ１及びＰＳ２の形状及び機能は、上記第１の実施の形態と同様であるため説明を省略する。 The first aberration correction lens has an Abbe number ν d (νd2) = 55.0 at the d line, and the refractive index n d = 1.55 at the d line, and the second aberration correction lens has an Abbe number at the d line. ν d (νd3) = 23.0, refractive index n d = 1.60 at the d -line, and the condensing optical element OL has an Abbe number ν d = 55.0 at the d-line, and a refractive index n d at the d-line. = 1.55.
The first phase structure PS1 is formed on the optical surface on the light source side of the condensing optical element OL, and the second phase structure PS2 is formed on the optical surface on the light source side of the first aberration correction lens L1. The third phase structure PS3 is formed on the optical surface of the second aberration correction lens L2 on the optical disc side.
Note that the shapes and functions of the first and second phase structures PS1 and PS2 are the same as those in the first embodiment, and a description thereof will be omitted.

第３位相構造ＰＳ３は第１光束及び第２光束を回折せず、第３光束を回折する回折構造であり、光軸Ｘを含む断面形状が階段状とされたパターンが同心円状に配列された構造であって、所定のレベル面（本実施の形態では４レベル面）の個数毎に、そのレベル面数に対応した段数分の高さだけ段をシフトさせた構造（本実施の形態においては３段シフトさせた構造）となっている。
階段構造の各段差Δ２は、Δ２＝７・λ１／（ｎ１−１）＝４．４１μｍを満たす高さに設定されている。ここで、ｎ１は波長λ１における第２収差補正レンズＬ２の屈折率である。 The third phase structure PS3 is a diffractive structure that does not diffract the first light beam and the second light beam but diffracts the third light beam, and a pattern in which the cross-sectional shape including the optical axis X is stepped is arranged concentrically. A structure in which for each predetermined number of level surfaces (four level surfaces in this embodiment), the steps are shifted by a height corresponding to the number of level surfaces (in this embodiment, in this embodiment). The structure is shifted by three stages.
Each step Δ2 of the staircase structure is set to a height that satisfies Δ2 = 7 · λ1 / (n1-1) = 4.41 μm. Here, n1 is the refractive index of the second aberration correction lens L2 at the wavelength λ1.

段差Δ２により第１光束に付加される光路差は７×λ１であるので、第１光束は第３位相構造ＰＳ３により何ら作用を受けずにそのまま透過する。
また、段差Δ２により第２光束に付加される光路差は約４×λ２であるので、第２光束も第３位相構造ＰＳ３によりほとんど作用を受けずにそのまま透過する。
一方、段差Δ２によりにより第３光束に付加される光路差は約３．２５×λ３であり、段差Δ２の前後のレベル面を通過する第３光束の位相は２π／４だけずれることになる。１つの鋸歯は４分割されているため、鋸歯１つ分ではちょうど第３光束の位相のずれは４×２π／４＝２πとなり、１次回折光が発生する。 Since the optical path difference added to the first light flux by the step Δ2 is 7 × λ1, the first light flux is transmitted as it is without being affected by the third phase structure PS3.
Further, since the optical path difference added to the second light beam by the step Δ2 is about 4 × λ2, the second light beam is transmitted as it is without being affected by the third phase structure PS3.
On the other hand, the optical path difference added to the third light beam by the step Δ2 is about 3.25 × λ3, and the phase of the third light beam passing through the level surface before and after the step Δ2 is shifted by 2π / 4. Since one saw tooth is divided into four parts, the phase shift of the third light beam is exactly 4 × 2π / 4 = 2π for one saw tooth, and the first-order diffracted light is generated.

このように、第３位相構造ＰＳ３は第３光束のみを選択的に回折させることにより、ＨＤの保護層厚さとＣＤの保護層厚さの違いによる球面収差を補正する。
尚、第３位相構造ＰＳ３で発生する第１光束の０次回折光（透過光）の回折効率は１００％、第２光束の０次回折光（透過光）の回折効率は９５．８％、第３光束の１次回折光の回折効率は７７．５％であり、何れの光束に対しても高い回折効率を得ている。 As described above, the third phase structure PS3 selectively diffracts only the third light beam, thereby correcting the spherical aberration due to the difference between the HD protective layer thickness and the CD protective layer thickness.
The diffraction efficiency of the 0th-order diffracted light (transmitted light) of the first light beam generated in the third phase structure PS3 is 100%, the diffraction efficiency of the 0th-order diffracted light (transmitted light) of the second light beam is 95.8%, the third The diffraction efficiency of the first-order diffracted light of the light beam is 77.5%, and a high diffraction efficiency is obtained for any light beam.

[第３の実施の形態]
以下、本発明の第３の実施の形態について図面を用いて説明するが、上記第１及び第２の実施の形態と同一の構成となる箇所については説明を省略する。
本実施の形態におけるＨＤの光学的仕様は、第１波長λ１＝４０８ｎｍ、保護層ＰＬ１の厚さｔ１＝０．０８７５ｍｍ、開口数ＮＡ１＝０．８５であり、ＤＶＤの光学的仕様は、第２波長λ２＝６５８ｎｍ、保護層ＰＬ２の厚さｔ２＝０．６ｍｍ、開口数ＮＡ２＝０．６０であり、ＣＤの光学的仕様は、第３波長λ３＝７８５ｎｍ、保護層ＰＬ３の厚さｔ３＝１．２ｍｍ、開口数ＮＡ３＝０．４７である。但し、波長、保護層の厚さ、及び開口数の組合せはこれに限られない。 [Third embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. However, description of portions having the same configurations as those of the first and second embodiments will be omitted.
The optical specifications of the HD in this embodiment are the first wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, and the numerical aperture NA1 = 0.85. The optical specifications of the DVD are the second The wavelength λ2 = 658 nm, the thickness t2 of the protective layer PL2 = 0.6 mm, the numerical aperture NA2 = 0.60, and the optical specifications of the CD are the third wavelength λ3 = 785 nm and the thickness t3 = 1 of the protective layer PL3. .2 mm and numerical aperture NA3 = 0.47. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

本実施形態における対物レンズユニットＯＵは、図１１に概略的に示すように、樹脂製の第１収差補正レンズＬ１、樹脂製の第２収差補正レンズＬ２、第１波長λ１とＨＤの保護層ＰＬ１の厚さｔ１とに対して球面収差が最小となるようにその非球面形状が設計された樹脂製の集光光学素子ＯＬが、鏡枠Ｂを介して同軸で一体化された３群３枚構成を有する。具体的には、円筒状の鏡枠Ｂの一端に第１収差補正レンズＬ１と第２収差補正レンズＬ２とを離間した状態で嵌合固定し、他端に集光光学素子ＯＬを嵌合固定して、これらを光軸Ｘに沿って同軸に一体化した構成となっている。   As schematically shown in FIG. 11, the objective lens unit OU in the present embodiment includes a first aberration correction lens L1 made of resin, a second aberration correction lens L2 made of resin, and a protective layer PL1 of the first wavelength λ1 and HD. A three-group three-piece optical element OL in which the aspherical shape is designed so that the spherical aberration is minimized with respect to the thickness t1 of the lens unit 3 is coaxially integrated through the lens frame B. It has a configuration. Specifically, the first aberration correction lens L1 and the second aberration correction lens L2 are fitted and fixed to one end of a cylindrical lens frame B in a separated state, and the condensing optical element OL is fitted and fixed to the other end. Thus, these are integrated along the optical axis X coaxially.

また、第１収差補正レンズＬ１は、ｄ線におけるアッベ数νd（νｄ２）＝５５．０、ｄ線における屈折率ｎd＝１．５５であり、第２収差補正レンズＬ２は、ｄ線におけるアッベ数νd（νｄ３）＝２３．０、ｄ線における屈折率ｎd＝１．６０であり、集光光学素子ＯＬは、ｄ線におけるアッベ数νd＝５５．０、ｄ線における屈折率ｎd＝１．５５である。
また、第１収差補正レンズＬ１の光ディスク側の光学面には第１位相構造ＰＳ１が形成されており、第１収差補正レンズＬ１の光源側の光学面には第２位相構造ＰＳ２が形成されており、第２収差補正レンズＬ２の光源側の光学面には第３位相構造ＰＳ３が形成されている。
なお、第２及び第３位相構造ＰＳ２及びＰＳ３の形状及び機能は、上記第２の実施の形態と同様であるため説明を省略する。 The first aberration correction lens L1 has an Abbe number ν d (νd2) = 55.0 at the d-line and a refractive index n d = 1.55 at the d -line, and the second aberration correction lens L2 is at the d-line Abbe number ν d (νd3) = 23.0, refractive index n d = 1.60 for d -line, and condensing optical element OL has Abbe number ν d = 55.0 for d-line, refractive index for d-line n d = 1.55.
The first phase structure PS1 is formed on the optical surface of the first aberration correction lens L1 on the optical disc side, and the second phase structure PS2 is formed on the optical surface of the first aberration correction lens L1 on the light source side. The third phase structure PS3 is formed on the optical surface of the second aberration correction lens L2 on the light source side.
Note that the shapes and functions of the second and third phase structures PS2 and PS3 are the same as those in the second embodiment, and a description thereof will be omitted.

第１位相構造ＰＳ１は第１光束乃至第３光束を回折する回折構造であり、光軸Ｘを含む断面形状が階段状となっている。この第１位相構造ＰＳ１は、２軸アクチュエータＡＣ１からの放熱や環境温度の変化により、第１波長λ１の微小変化に伴う近軸像点位置の移動と、球面収差の変化を抑制するための構造である。
階段構造の各段差Δ３は、Δ３＝１０・λ１／（ｎ１−１）＝７．２０μｍを満たす高さに設定されている。
第１位相構造ＰＳ１を通過することで、第１光束の１０次回折光、第２光束の６次回折光、第３光束の５次回折光が発生する。 The first phase structure PS1 is a diffractive structure that diffracts the first to third light beams, and the cross-sectional shape including the optical axis X is stepped. The first phase structure PS1 is a structure for suppressing the movement of the paraxial image point position and the change of the spherical aberration due to the minute change of the first wavelength λ1 due to the heat radiation from the biaxial actuator AC1 and the change of the environmental temperature. It is.
Each step Δ3 of the staircase structure is set to a height that satisfies Δ3 = 10 · λ1 / (n1-1) = 7.20 μm.
By passing through the first phase structure PS1, the 10th-order diffracted light of the first light beam, the 6th-order diffracted light of the second light beam, and the fifth-order diffracted light of the third light beam are generated.

第１位相構造ＰＳ１を通過する際に第１光束に付加される光路差は１０．０×λ１であり、第１光束の１０次回折光が最大の回折効率を有する。
また、第１位相構造ＰＳ１を通過する際に第２光束に付加される光路差は５．９９×λ２≒６×λ２であり、第２光束の６次回折光が最大の回折効率を有する。 The optical path difference added to the first light flux when passing through the first phase structure PS1 is 10.0 × λ1, and the 10th-order diffracted light of the first light flux has the maximum diffraction efficiency.
The optical path difference added to the second light flux when passing through the first phase structure PS1 is 5.99 × λ2≈6 × λ2, and the sixth-order diffracted light of the second light flux has the maximum diffraction efficiency.

また、第１位相構造ＰＳ１を通過する際に第３光束に付加される光路差は４．９８×λ３≒５×λ３であり、第３光束の５次回折光が最大の回折効率を有する。
第１光束の１０次回折光、第２光束の６次回折光、第３光束の５次回折光の回折効率はそれぞれ１００％、９９．９％、９９．９％であり、何れの光束に対しても高い回折効率を得ている。
また、第１位相構造ＰＳ１の第１波長に対する近軸回折パワーと、第１収差補正レンズＬ１の光ディスク側の光学面の第１波長に対する近軸屈折パワーを逆符号とし、かつその絶対値を同じとすることで、第１収差補正レンズＬ１の光ディスク側の光学面を通過する第１光束の光束径が変わらないようにしている。 Further, the optical path difference added to the third light beam when passing through the first phase structure PS1 is 4.98 × λ3≈5 × λ3, and the fifth-order diffracted light of the third light beam has the maximum diffraction efficiency.
The diffraction efficiencies of the 10th-order diffracted light of the first light flux, the 6th-order diffracted light of the second light flux, and the fifth-order diffracted light of the third light flux are 100%, 99.9%, and 99.9%, respectively. High diffraction efficiency is obtained.
Also, the paraxial diffraction power for the first wavelength of the first phase structure PS1 and the paraxial refraction power for the first wavelength of the optical surface on the optical disc side of the first aberration correction lens L1 have opposite signs, and the absolute values thereof are the same. By doing so, the beam diameter of the first beam passing through the optical surface on the optical disc side of the first aberration correction lens L1 is kept unchanged.

[第４の実施の形態]
以下、本発明の第４の実施の形態について図面を用いて説明するが、上記第１〜第３の実施の形態と同一の構成となる箇所については説明を省略する。
本実施の形態におけるＨＤの光学的仕様は、第１波長λ１＝４０８ｎｍ、保護層ＰＬ１の厚さｔ１＝０．０８７５ｍｍ、開口数ＮＡ１＝０．８５であり、ＤＶＤの光学的仕様は、第２波長λ２＝６５８ｎｍ、保護層ＰＬ２の厚さｔ２＝０．６ｍｍ、開口数ＮＡ２＝０．６０であり、ＣＤの光学的仕様は、第３波長λ３＝７８５ｎｍ、保護層ＰＬ３の厚さｔ３＝１．２ｍｍ、開口数ＮＡ３＝０．４５である。但し、波長、保護層の厚さ、及び開口数の組合せはこれに限られない。 [Fourth embodiment]
Hereinafter, the fourth embodiment of the present invention will be described with reference to the drawings. However, description of portions having the same configurations as those of the first to third embodiments will be omitted.
The optical specifications of the HD in this embodiment are the first wavelength λ1 = 408 nm, the thickness t1 of the protective layer PL1 is 0.0875 mm, and the numerical aperture NA1 = 0.85. The optical specifications of the DVD are the second The wavelength λ2 = 658 nm, the thickness t2 of the protective layer PL2 = 0.6 mm, the numerical aperture NA2 = 0.60, and the optical specifications of the CD are the third wavelength λ3 = 785 nm and the thickness t3 = 1 of the protective layer PL3. .2 mm and numerical aperture NA3 = 0.45. However, the combination of the wavelength, the thickness of the protective layer, and the numerical aperture is not limited to this.

本実施形態における対物レンズユニットＯＵは、図１２に概略的に示すように、樹脂製の第１収差補正レンズＬ１と樹脂製の第２収差補正レンズＬ２と接合してなるレンズ群と、第１波長λ１とＨＤの保護層ＰＬ１の厚さｔ１とに対して球面収差が最小となるようにその非球面形状が設計された樹脂製の集光光学素子ＯＬが、鏡枠Ｂを介して同軸で一体化された２群３枚構成を有する。具体的には、円筒状の鏡枠Ｂの一端に第１収差補正レンズＬ１と第２収差補正レンズＬ２とを接合した状態で嵌合固定し、他端に集光光学素子ＯＬを嵌合固定して、これらを光軸Ｘに沿って同軸に一体化した構成となっている。   As schematically shown in FIG. 12, the objective lens unit OU in the present embodiment includes a first lens group formed by bonding a first aberration correction lens L1 made of resin and a second aberration correction lens L2 made of resin, and a first lens unit OU. A resin condensing optical element OL whose aspherical shape is designed so that the spherical aberration is minimized with respect to the wavelength λ1 and the thickness t1 of the HD protective layer PL1 is coaxially connected via the lens frame B. It has a two-group, three-element configuration. Specifically, the first aberration correction lens L1 and the second aberration correction lens L2 are fitted and fixed to one end of the cylindrical lens frame B, and the condensing optical element OL is fitted and fixed to the other end. Thus, these are integrated along the optical axis X coaxially.

また、第１収差補正レンズは、ｄ線におけるアッベ数νd（νｄ２）＝５５．０、ｄ線における屈折率ｎd＝１．５５であり、第２収差補正レンズは、ｄ線におけるアッベ数νd（νｄ３）＝３５．０、ｄ線における屈折率ｎd＝１．６０であり、集光光学素子ＯＬは、ｄ線におけるアッベ数νd＝５５．０、ｄ線における屈折率ｎd＝１．５５である。
また、集光光学素子ＯＬの光源側の光学面には第１位相構造ＰＳ１が形成されており、第１収差補正レンズＬ１の光源側の光学面には第２位相構造ＰＳ２が形成されており、第２収差補正レンズＬ２の光ディスク側の光学面には第３位相構造ＰＳ３が形成されている。
なお、第１及び第２位相構造ＰＳ１及びＰＳ２の形状及び機能は、上記第１の実施の形態と同様であるため説明を省略する。 The first aberration correction lens has an Abbe number ν d (νd2) = 55.0 at the d line, and the refractive index n d = 1.55 at the d line, and the second aberration correction lens has an Abbe number at the d line. ν d (νd3) = 35.0, refractive index n d = 1.60 for the d -line, and the condensing optical element OL has an Abbe number ν d = 55.0 for the d-line, and a refractive index n d for the d-line. = 1.55.
The first phase structure PS1 is formed on the optical surface on the light source side of the condensing optical element OL, and the second phase structure PS2 is formed on the optical surface on the light source side of the first aberration correction lens L1. The third phase structure PS3 is formed on the optical surface of the second aberration correction lens L2 on the optical disc side.
Note that the shapes and functions of the first and second phase structures PS1 and PS2 are the same as those in the first embodiment, and a description thereof will be omitted.

第３位相構造ＰＳ３は第１光束及び第２光束を回折せず、第３光束を回折する回折構造であり、光軸Ｘを含む断面形状が階段状とされたパターンが同心円状に配列された構造であって、所定のレベル面（本実施の形態では３レベル面）の個数毎に、そのレベル面数に対応した段数分の高さだけ段をシフトさせた構造（本実施の形態においては２段シフトさせた構造）となっている。
階段構造の各段差Δ２は、Δ２＝５・λ１／（ｎ１−１）＝３．２４μｍ、もしくはΔ２＝７・λ１／（ｎ１−１）＝４．５３μｍを満たす高さに設定される。ここで、ｎ１は波長λ１における第２収差補正レンズＬ２の屈折率である。 The third phase structure PS3 is a diffractive structure that does not diffract the first light beam and the second light beam but diffracts the third light beam, and a pattern in which the cross-sectional shape including the optical axis X is stepped is arranged concentrically. A structure in which for each predetermined number of level planes (three level planes in this embodiment), the level is shifted by a height corresponding to the number of level planes (in this embodiment, in this embodiment) The structure is shifted by two stages.
Each step Δ2 of the staircase structure is set to a height that satisfies Δ2 = 5 · λ1 / (n1-1) = 3.24 μm, or Δ2 = 7 · λ1 / (n1-1) = 4.53 μm. Here, n1 is the refractive index of the second aberration correction lens L2 at the wavelength λ1.

段差Δ２が Δ２＝５・λ１／（ｎ１−１）＝３．２４μｍ に設定されている場合は、段差Δ２により第１光束に付加される光路差は５×λ１であるので、第１光束は第３位相構造ＰＳ３により何ら作用を受けずにそのまま透過する。
また、段差Δ２により第２光束に付加される光路差は約３×λ２であるので、第２光束も第３位相構造ＰＳ３によりほとんど作用を受けずにそのまま透過する。
一方、段差Δ２により第３光束に付加される光路差は２．４×λ３であり、段差Δ２の前後のレベル面を通過する第３光束の位相は約２π／３だけずれることになる。１つの鋸歯は３分割されているため、鋸歯１つ分ではちょうど第３光束の位相のずれは３×２π／３＝２πとなり、１次回折光が発生する。
段差Δ２が Δ２＝７・λ１／（ｎ１−１）＝４．５３μｍ に設定されている場合は、段差Δ２により第１光束に付加される光路差は７×λ１であるので、第１光束は第３位相構造ＰＳ３により何ら作用を受けずにそのまま透過する。
また、段差Δ２により第２光束に付加される光路差は約４×λ２であるので、第２光束も第３位相構造ＰＳ３によりほとんど作用を受けずにそのまま透過する。
一方、段差Δ２により第３光束に付加される光路差は３．４×λ３であり、段差Δ２の前後のレベル面を通過する第３光束の位相は約２π／３だけずれることになる。１つの鋸歯は３分割されているため、鋸歯１つ分ではちょうど第３光束の位相のずれは３×２π／３＝２πとなり、１次回折光が発生する。 When the step Δ2 is set to Δ2 = 5 · λ1 / (n1-1) = 3.24 μm, the optical path difference added to the first light flux by the step Δ2 is 5 × λ1, and therefore the first light flux The third phase structure PS3 is transmitted as it is without any action.
Further, since the optical path difference added to the second light flux by the step Δ2 is about 3 × λ2, the second light flux is transmitted as it is with little effect by the third phase structure PS3.
On the other hand, the optical path difference added to the third light flux by the step Δ2 is 2.4 × λ3, and the phase of the third light flux passing through the level surface before and after the step Δ2 is shifted by about 2π / 3. Since one saw tooth is divided into three, the phase shift of the third light beam is exactly 3 × 2π / 3 = 2π for one saw tooth, and the first-order diffracted light is generated.
When the step Δ2 is set to Δ2 = 7 · λ1 / (n1-1) = 4.53 μm, the optical path difference added to the first light flux by the step Δ2 is 7 × λ1, and therefore the first light flux The third phase structure PS3 is transmitted as it is without any action.
Further, since the optical path difference added to the second light beam by the step Δ2 is about 4 × λ2, the second light beam is transmitted as it is without being affected by the third phase structure PS3.
On the other hand, the optical path difference added to the third light flux by the step Δ2 is 3.4 × λ3, and the phase of the third light flux passing through the level surface before and after the step Δ2 is shifted by about 2π / 3. Since one saw tooth is divided into three, the phase shift of the third light beam is exactly 3 × 2π / 3 = 2π for one saw tooth, and the first-order diffracted light is generated.

このように、第３位相構造ＰＳ３は第３光束のみを選択的に回折させることにより、ＨＤの保護層厚さとＣＤの保護層厚さの違いによる球面収差を補正する。
尚、段差Δ２が Δ２＝５・λ１／（ｎ１−１）＝３．２４μｍ に設定されている場合は、第３位相構造ＰＳ３で発生する第１光束の０次回折光（透過光）の回折効率は１００％、第２光束の０次回折光（透過光）の回折効率は８７．１％、第３光束の１次回折光の回折効率は５３．１％であり、何れの光束に対しても高い回折効率を得ている。
また、段差Δ２が Δ２＝７・λ１／（ｎ１−１）＝４．５３μｍ に設定されている場合、第３位相構造ＰＳ３で発生する第１光束の０次回折光（透過光）の回折効率は１００％、第２光束の０次回折光（透過光）の回折効率は７６．４％、第３光束の１次回折光の回折効率は６０．４％であり、何れの光束に対しても高い回折効率を得ている。 As described above, the third phase structure PS3 selectively diffracts only the third light beam, thereby correcting the spherical aberration due to the difference between the HD protective layer thickness and the CD protective layer thickness.
When the step Δ2 is set to Δ2 = 5 · λ1 / (n1-1) = 3.24 μm, the diffraction efficiency of the 0th-order diffracted light (transmitted light) of the first light beam generated by the third phase structure PS3 Is 100%, the diffraction efficiency of the 0th-order diffracted light (transmitted light) of the second light flux is 87.1%, and the diffraction efficiency of the first-order diffracted light of the third light flux is 53.1%, which is high for any light flux. Diffraction efficiency is obtained.
When the step Δ2 is set to Δ2 = 7 · λ1 / (n1-1) = 4.53 μm, the diffraction efficiency of the 0th-order diffracted light (transmitted light) of the first light beam generated in the third phase structure PS3 is 100%, the diffraction efficiency of the 0th-order diffracted light (transmitted light) of the second light beam is 76.4%, and the diffraction efficiency of the 1st-order diffracted light of the third light beam is 60.4%. Has gained efficiency.

なお、図示は省略するが、上記各実施の形態に示した光ピックアップ装置ＰＵと、前記光ピックアップ装置を光情報記録媒体の半径方向に移動させる移動装置、光ディスクを回転自在に保持する回転駆動装置、これら各種装置の駆動を制御する制御装置を搭載することで、光ディスクに対する光情報の記録及び光ディスクに記録された情報の再生のうち少なくとも一方の実行が可能な光ディスクドライブ装置を得ることが出来る。   Although not shown, the optical pickup device PU shown in each of the above embodiments, a moving device that moves the optical pickup device in the radial direction of the optical information recording medium, and a rotational drive device that rotatably holds the optical disk. By mounting a control device for controlling the driving of these various devices, an optical disc drive device capable of executing at least one of recording optical information on the optical disc and reproducing information recorded on the optical disc can be obtained.

次に、図９に示した対物光学素子ＯＵの具体的な数値実施例（実施例１）を例示する。
本実施例の対物光学素子ＯＵは、樹脂製の第１収差補正レンズＬ１と樹脂製の集光光学素子ＯＬの２群２枚構成である。
本実施例のレンズデータを表１に示す。本数値実施例では、第１〜第３位相構造ＰＳ１〜ＰＳ３により入射光束に付加される光路差を光路差関数で表している。

Figure 2006092720
Next, a specific numerical example (Example 1) of the objective optical element OU shown in FIG. 9 will be exemplified.
The objective optical element OU of the present embodiment has a two-group two-element configuration including a resin-made first aberration correction lens L1 and a resin-made condensing optical element OL.
Table 1 shows lens data of this example. In this numerical example, the optical path difference added to the incident light beam by the first to third phase structures PS1 to PS3 is represented by an optical path difference function.
Figure 2006092720

本実施例の対物光学素子は、ＨＤ／ＤＶＤ／ＣＤ互換用の対物光学素子であり、波長λ１＝４０８ｎｍのときの焦点距離ｆ＝２．２０ｍｍ、開口数ＮＡ１＝０．８５、倍率ｍ＝０に設定されており、波長λ２＝６５８ｎｍのときの焦点距離ｆ＝２．２８ｍｍ、開口数ＮＡ２＝０．６０、倍率ｍ＝０に設定されており、波長λ３＝７８５ｎｍのときの焦点距離ｆ＝２．３７ｍｍ、開口数ＮＡ３＝０．４７、倍率ｍ＝０に設定されている。   The objective optical element of the present embodiment is an objective optical element compatible with HD / DVD / CD, and has a focal length f = 2.20 mm at a wavelength λ1 = 408 nm, a numerical aperture NA1 = 0.85, and a magnification m = 0. The focal length f = 2.28 mm when the wavelength λ2 = 658 nm, the numerical aperture NA2 = 0.60, the magnification m = 0, and the focal length f = wavelength λ3 = 785 nm. 2.37 mm, numerical aperture NA3 = 0.47, and magnification m = 0.

表１において、ｒ（ｍｍ）は曲率半径、ｄ（ｍｍ）はレンズ間隔、ｎ408、ｎ658、ｎ785は、それぞれ、第１波長λ１（＝４０８ｎｍ）、第２波長λ２（＝６５８ｎｍ）、第３波長λ３（＝７８５ｎｍ）に対するレンズ・素子の屈折率、ｎｄはｄ線におけるレンズ・素子の屈折率、νdはｄ線におけるレンズ・素子のアッベ数、ＭHD、ＭDVD、ＭCDは、それぞれ、ＨＤに対する記録／再生に使用する回折光の回折次数、ＤＶＤに対する記録／再生に使用する回折光の回折次数、ＣＤに対する記録／再生に使用する回折光の回折次数である。また、１０のべき乗数（例えば ２．５×１０-3）を、Ｅ（例えば ２．５Ｅ―３）を用いて表すものとする。 In Table 1, r (mm) is a radius of curvature, d (mm) is a lens interval, n 408 , n 658 , and n 785 are a first wavelength λ1 (= 408 nm) and a second wavelength λ2 (= 658 nm), respectively. the third wavelength [lambda] 3 (= 785 nm) refractive index of the lens element with respect to, n d is the refractive index of the lens element at the d-line, [nu d is Abbe number of the lens element at the d-line, M HD, M DVD, M CD Are the diffraction order of the diffracted light used for recording / reproducing for the HD, the diffraction order of the diffracted light used for recording / reproducing for the DVD, and the diffraction order of the diffracted light used for recording / reproducing for the CD, respectively. Further, a power of 10 (for example, 2.5 × 10 −3 ) is expressed using E (for example, 2.5E-3).

第１収差補正レンズＬ１の光源側の光学面（第１面）及び光ディスク側の光学面（第２面）は平面である。また、集光光学素子ＯＬの光源側の光学面（第３面）及び光ディスク側の光学面（第４面）はそれぞれ非球面形状であり、この非球面は、次の非球面形状式に表中の係数を代入した数式で表される。

Figure 2006092720
ｘ（ｈ）：非球面形状（非球面の面頂点に接する平面から光軸に沿った方向の距離）
ｈ：光軸からの距離
ｒ：曲率半径
ｋ：コーニック係数
Ａ2i：非球面係数 The optical surface (first surface) on the light source side and the optical surface (second surface) on the optical disc side of the first aberration correction lens L1 are flat. The optical surface on the light source side (third surface) and the optical surface on the optical disc side (fourth surface) of the condensing optical element OL are each aspherical, and this aspherical surface is expressed by the following aspherical shape formula. It is expressed by a mathematical formula with the coefficient inside.
Figure 2006092720
 x (h): aspherical shape (distance in the direction along the optical axis from the plane in contact with the apex of the aspherical surface)
h: distance from the optical axis r: radius of curvature k: conic coefficient A 2i : aspheric coefficient

また、第１面の第２位相構造ＰＳ２、第２面の第３位相構造ＰＳ３、第３面の第１位相構造ＰＳ１は、各位相構造により入射光束に付加される光路差で表される。かかる光路差は、次の光路差関数を表す式に表中の係数を代入した光路差関数φ（ｍｍ）で表される。

Figure 2006092720
φ（ｈ）：光路差関数
λ：位相構造に入射する光束の波長
λB：製造波長
ｎ：光ディスクに対する記録／再生に使用する回折光の回折次数
ｈ：光軸からの距離
Ｂ2i：回折面係数 Further, the second phase structure PS2 on the first surface, the third phase structure PS3 on the second surface, and the first phase structure PS1 on the third surface are represented by optical path differences added to the incident light flux by each phase structure. Such an optical path difference is represented by an optical path difference function φ (mm) obtained by substituting a coefficient in the table into an expression representing the next optical path difference function.
Figure 2006092720
 φ (h): optical path difference function λ: wavelength of light beam incident on the phase structure λ B : manufacturing wavelength n: diffraction order of diffracted light used for recording / reproducing on optical disc h: distance from optical axis B 2i : diffraction surface coefficient

次に、図１０に示した対物光学素子ＯＵの具体的な数値実施例（実施例２）を例示する。
本実施例の対物光学素子ＯＵは、樹脂製の第１収差補正レンズＬ１と樹脂製の第２収差補正レンズＬ２と集光光学素子ＯＬの２群３枚構成である。
本実施例のレンズデータを表２に示す。

Figure 2006092720
Next, a specific numerical example (Example 2) of the objective optical element OU shown in FIG. 10 will be illustrated.
The objective optical element OU of the present embodiment has a two-group three-element configuration including a resin-made first aberration correction lens L1, a resin-made second aberration correction lens L2, and a condensing optical element OL.
Table 2 shows lens data of this example.
Figure 2006092720

本実施例の対物光学素子は、ＨＤ／ＤＶＤ／ＣＤ互換用の対物光学素子であり、波長λ１＝４０８ｎｍのときの焦点距離ｆ＝２．２０ｍｍ、開口数ＮＡ１＝０．８５、倍率ｍ＝０に設定されており、波長λ２＝６５８ｎｍのときの焦点距離ｆ＝２．２７ｍｍ、開口数ＮＡ２＝０．６０、倍率ｍ＝０に設定されており、波長λ３＝７８５ｎｍのときの焦点距離ｆ＝２．６３ｍｍ、開口数ＮＡ３＝０．４５、倍率ｍ＝０に設定されている。
第１収差補正レンズＬ１の光源側の光学面（第１面）及び第２収差補正レンズＬ２の光ディスク側の光学面（第３面）は平面である。また、集光光学素子ＯＬの光源側の光学面（第４面）及び光ディスク側の光学面（第５面）はそれぞれ非球面形状であり、この非球面は、上記非球面形状式に表中の係数を代入した数式で表される。 The objective optical element of the present embodiment is an objective optical element compatible with HD / DVD / CD, and has a focal length f = 2.20 mm at a wavelength λ1 = 408 nm, a numerical aperture NA1 = 0.85, and a magnification m = 0. The focal length f = 2.27 mm when the wavelength λ2 = 658 nm, the numerical aperture NA2 = 0.60, the magnification m = 0, and the focal length f = wavelength λ3 = 785 nm. 2.63 mm, numerical aperture NA3 = 0.45, and magnification m = 0.
The optical surface (first surface) on the light source side of the first aberration correction lens L1 and the optical surface (third surface) on the optical disk side of the second aberration correction lens L2 are flat surfaces. The optical surface on the light source side (fourth surface) and the optical surface on the optical disc side (fifth surface) of the condensing optical element OL are each aspherical, and this aspherical surface is represented in the above aspherical shape formula. It is expressed by a mathematical formula with the coefficient of.

また、第１面の第２位相構造ＰＳ２、第３面の第３位相構造ＰＳ３、第４面の第１位相構造ＰＳ１は、各位相構造により入射光束に付加される光路差で表される。かかる光路差は、上記光路差関数を表す式に表中の係数を代入した光路差関数φ（ｍｍ）で表される。   Further, the second phase structure PS2 on the first surface, the third phase structure PS3 on the third surface, and the first phase structure PS1 on the fourth surface are represented by optical path differences added to the incident light flux by each phase structure. Such an optical path difference is represented by an optical path difference function φ (mm) obtained by substituting the coefficient in the table into the formula representing the optical path difference function.

次に、図１１に示した対物光学素子ＯＵの具体的な数値実施例（実施例３）を例示する。
本実施例の対物光学素子ＯＵは、樹脂製の第１収差補正レンズＬ１と樹脂製の第２収差補正レンズＬ２と集光光学素子の３群３枚構成である。
本実施例のレンズデータを表３に示す。

Figure 2006092720
Next, specific numerical value examples (Example 3) of the objective optical element OU shown in FIG. 11 will be exemplified.
The objective optical element OU of the present embodiment has a three-group three-element configuration including a first aberration correction lens L1 made of resin, a second aberration correction lens L2 made of resin, and a condensing optical element.
Table 3 shows lens data of this example.
Figure 2006092720

本実施例の対物光学素子は、ＨＤ／ＤＶＤ／ＣＤ互換用の対物光学素子であり、波長λ１＝４０８ｎｍのときの焦点距離ｆ＝２．２０ｍｍ、開口数ＮＡ１＝０．８５、倍率ｍ＝０に設定されており、波長λ２＝６５８ｎｍのときの焦点距離ｆ＝２．２５ｍｍ、開口数ＮＡ２＝０．６０、倍率ｍ＝０に設定されており、波長λ３＝７８５ｎｍのときの焦点距離ｆ＝２．３７ｍｍ、開口数ＮＡ３＝０．４７、倍率ｍ＝０に設定されている。
第１収差補正レンズＬ１の光源側の光学面（第１面）、第２収差補正レンズＬ２の光源側の光学面（第３面）及び光ディスク側の光学面（第４面）は平面である。また、第１収差補正レンズＬ１の光ディスク側の光学面（第２面）、集光光学素子ＯＬの光源側の光学面（第５面）及び光ディスク側の光学面（第６面）はそれぞれ非球面形状であり、この非球面は、上記非球面形状式に表中の係数を代入した数式で表される。 The objective optical element of the present embodiment is an objective optical element compatible with HD / DVD / CD, and has a focal length f = 2.20 mm at a wavelength λ1 = 408 nm, a numerical aperture NA1 = 0.85, and a magnification m = 0. The focal length f = 2.25 mm when the wavelength λ2 = 658 nm, the numerical aperture NA2 = 0.60, the magnification m = 0, and the focal length f = wavelength λ3 = 785 nm. 2.37 mm, numerical aperture NA3 = 0.47, and magnification m = 0.
The optical surface on the light source side (first surface) of the first aberration correction lens L1, the optical surface on the light source side (third surface) and the optical surface on the optical disc side (fourth surface) of the second aberration correction lens L2 are flat. . The optical surface (second surface) on the optical disc side of the first aberration correction lens L1, the optical surface on the light source side (fifth surface), and the optical surface on the optical disc side (sixth surface) of the condensing optical element OL are non-existent, respectively. The aspherical surface is represented by an equation obtained by substituting the coefficient in the table into the aspherical shape equation.

また、第１面の第２位相構造ＰＳ２、第２面の第１位相構造ＰＳ１、第３面の第３位相構造ＰＳ３は、各位相構造により入射光束に付加される光路差で表される。かかる光路差は、上記光路差関数を表す式に表中の係数を代入した光路差関数φ（ｍｍ）で表される。   Further, the second phase structure PS2 on the first surface, the first phase structure PS1 on the second surface, and the third phase structure PS3 on the third surface are represented by optical path differences added to the incident light flux by each phase structure. Such an optical path difference is represented by an optical path difference function φ (mm) obtained by substituting the coefficient in the table into the formula representing the optical path difference function.

次に、図１２に示した対物光学素子ＯＵの具体的な数値実施例（実施例４）を例示する。
本実施例の対物光学素子ＯＵは、樹脂製の第１収差補正レンズＬ１と樹脂製の第２収差補正レンズＬ２と集光光学素子ＯＬの２群３枚構成である。
本実施例のレンズデータを表４に示す。尚、本実施例では、第４の実施の形態において段差Δ２が Δ２＝５・λ１／（ｎ１−１）＝３．２４μｍ とΔ２＝７・λ１／（ｎ１−１）＝４．５３μｍ とのどちらに設定されている場合でも、同様のレンズデータを使用するものとする。

Figure 2006092720
Next, specific numerical value examples (Example 4) of the objective optical element OU shown in FIG. 12 will be exemplified.
The objective optical element OU of the present embodiment has a two-group three-element configuration including a resin-made first aberration correction lens L1, a resin-made second aberration correction lens L2, and a condensing optical element OL.
Table 4 shows lens data of this example. In this example, the step Δ2 in the fourth embodiment is Δ2 = 5 · λ1 / (n1-1) = 3.24 μm and Δ2 = 7 · λ1 / (n1-1) = 4.53 μm. In either case, the same lens data is used.
Figure 2006092720

本実施例の対物光学素子は、ＨＤ／ＤＶＤ／ＣＤ互換用の対物光学素子であり、波長λ１＝４０８ｎｍのときの焦点距離ｆ＝２．２０ｍｍ、開口数ＮＡ１＝０．８５、倍率ｍ＝０に設定されており、波長λ２＝６５８ｎｍのときの焦点距離ｆ＝２．２７ｍｍ、開口数ＮＡ２＝０．６０、倍率ｍ＝０に設定されており、波長λ３＝７８５ｎｍのときの焦点距離ｆ＝２．６３ｍｍ、開口数ＮＡ３＝０．４５、倍率ｍ＝０に設定されている。
第１収差補正レンズＬ１の光源側の光学面（第１面）及び第２収差補正レンズＬ２の光ディスク側の光学面（第３面）は平面である。また、集光光学素子ＯＬの光源側の光学面（第４面）及び光ディスク側の光学面（第５面）はそれぞれ非球面形状であり、この非球面は、上記非球面形状式に表中の係数を代入した数式で表される。 The objective optical element of the present embodiment is an objective optical element compatible with HD / DVD / CD, and has a focal length f = 2.20 mm at a wavelength λ1 = 408 nm, a numerical aperture NA1 = 0.85, and a magnification m = 0. The focal length f = 2.27 mm when the wavelength λ2 = 658 nm, the numerical aperture NA2 = 0.60, the magnification m = 0, and the focal length f = wavelength λ3 = 785 nm. 2.63 mm, numerical aperture NA3 = 0.45, and magnification m = 0.
The optical surface (first surface) on the light source side of the first aberration correction lens L1 and the optical surface (third surface) on the optical disk side of the second aberration correction lens L2 are flat surfaces. The optical surface on the light source side (fourth surface) and the optical surface on the optical disc side (fifth surface) of the condensing optical element OL are each aspherical, and this aspherical surface is represented in the above aspherical shape formula. It is expressed by a mathematical formula in which the coefficient is substituted.

また、第１面の第２位相構造ＰＳ２、第３面の第３位相構造ＰＳ３、第４面の第１位相構造ＰＳ１は、各位相構造により入射光束に付加される光路差で表される。かかる光路差は、上記光路差関数を表す式に表中の係数を代入した光路差関数φ（ｍｍ）で表される。   Further, the second phase structure PS2 on the first surface, the third phase structure PS3 on the third surface, and the first phase structure PS1 on the fourth surface are represented by optical path differences added to the incident light flux by each phase structure. Such an optical path difference is represented by an optical path difference function φ (mm) obtained by substituting the coefficient in the table into the formula representing the optical path difference function.

図１３は、上記実施例１における、第１位相構造によるＨＤでの温度特性の補償の効果を示すグラフである。
図１３において、グラフの横軸Δｔ[℃]は基準温度からの温度変化量を表し、縦軸ΔＳＡ[λ１ｒｍｓ]は温度変化に伴う球面収差の変化量を表す。
ここで、温度変化に伴う集光光学素子ＯＬの屈折率の変化量ｄｎd１／ｄｔを、ｄｎd１／ｄｔ＝−１．２×１０-4［１／℃］とし、温度変化に伴う第１光源の波長変化量ｄλ１／ｄｔを、ｄλ１／ｄｔ＝５．０×１０-2［ｎｍ／℃］としたときに、例えば温度が基準温度よりも３０℃上がったときには第１光源の波長は４０８＋１．５＝４０９．５ｎｍとなり、そのとき集光光学素子ＯＬの屈折率は１．５６２６８となる。これらの値を用いて温度特性を算出した。 FIG. 13 is a graph showing the effect of compensation of temperature characteristics in HD by the first phase structure in the first embodiment.
In FIG. 13, the horizontal axis Δt [° C.] of the graph represents the temperature change amount from the reference temperature, and the vertical axis ΔSA [λ1 rms] represents the change amount of the spherical aberration accompanying the temperature change.
Here, the amount of change dn d 1 / dt of the refractive index of the condensing optical element OL accompanying a temperature change is set to dn d 1 / dt = −1.2 × 10 −4 [1 / ° C.], and the temperature changes. When the wavelength change amount dλ1 / dt of the first light source is dλ1 / dt = 5.0 × 10 −2 [nm / ° C.], for example, when the temperature rises 30 ° C. above the reference temperature, the wavelength of the first light source 408 + 1.5 = 409.5 nm, and at this time, the refractive index of the condensing optical element OL is 1.56268. Using these values, temperature characteristics were calculated.

また、第１位相構造が無い場合の温度特性は、集光光学素子ＯＬと同スペックで第１位相構造を持たないレンズを用いて算出した。
なお、実施例２における、第１位相構造によるＨＤでの温度特性の補償の効果を示すグラフも図１３に示すものと同様であった。
また、実施例４における、第１位相構造によるＨＤでの温度特性の補償の効果を示すグラフも図１３に示すものと同様であった。 Further, the temperature characteristics when there is no first phase structure was calculated using a lens having the same specifications as the condensing optical element OL and not having the first phase structure.
Note that the graph showing the effect of compensation of the temperature characteristic in HD by the first phase structure in Example 2 was also the same as that shown in FIG.
Further, the graph showing the effect of compensation of the temperature characteristic in HD by the first phase structure in Example 4 was also the same as that shown in FIG.

図１４は、上記実施例３における、第１位相構造によるＨＤでの温度特性の補償の効果を示すグラフである。
温度特性の算出方法は上記実施例１の場合と同様であり、第１位相構造が無い場合の温度特性は、第１収差補正レンズＬ１の光ディスク側の光学面（第２面）を平面にしたレンズを用いて算出した。
図１３及び図１４より、対物光学素子ＯＵに第１位相構造ＰＳ１を設けることで、温度変化による球面収差の変化量を抑えることができることが分かる。 FIG. 14 is a graph showing the effect of compensation of temperature characteristics in HD by the first phase structure in the third embodiment.
The calculation method of the temperature characteristic is the same as in the case of the first embodiment, and the temperature characteristic when the first phase structure is not provided is a flat optical surface (second surface) on the optical disc side of the first aberration correction lens L1. Calculated using a lens.
From FIG. 13 and FIG. 14, it can be seen that by providing the first phase structure PS1 in the objective optical element OU, the amount of change in spherical aberration due to temperature change can be suppressed.

なお、本発明における樹脂製の対物光学素子（集光光学素子、収差補正レンズ等）には、レンズ等の光学用途に通常使用可能な種々の樹脂を用いることができる。特に、脂環式構造を有する重合体を含有する樹脂を用いることが好まく、その中でも、環状オレフィン系樹脂を用いることがより好ましい。   In the resin-made objective optical element (condensing optical element, aberration correction lens, etc.) in the present invention, various resins that can be normally used for optical applications such as a lens can be used. In particular, it is preferable to use a resin containing a polymer having an alicyclic structure, and among them, it is more preferable to use a cyclic olefin resin.

また、以上のような樹脂の材料として、以下に示すようなアサーマル樹脂を用いることもできる。
母材となる樹脂に３０ｎｍ以下の粒子を分散させた材料として、アサーマル樹脂が知られている。アサーマル樹脂は、通常の光学用途との樹脂に比べ、温度変化に対する屈折率変化が小さいという特徴を有するので、位相構造による温度特性の改善効果を控えめにすることが可能となり、それによって、位相構造による波長特性の劣化を低減したり、光学素子の設計自由度を拡げたり、製造誤差や組立精度の許容範囲を拡大したりすることができる。
一般に、透明な樹脂材料に粉末を混合させると、光の散乱が生じ、透過率が低下するため、光学材料として使用することは困難であったが、微粉末を透過光束の波長より小さい平均粒径が３０ｎｍ以下の微粒子とすることにより、散乱が事実上発生しないようにできることがわかってきた。ここで、このような樹脂材料としては、母材となる樹脂の温度変化に伴う屈折率変化率よりも大きい屈折率変化率を有する平均粒径が３０ｎｍ以下の微粒子を分散させた樹脂材料であることが好ましい。尚、屈折率変化率が大きいとは、母材となる樹脂の屈折率変化率の符号が負である場合には、それよりもゼロに近い、負の屈折率変化率であるもの及び符号が正である屈折率変化率であるものの両者を含むものである。 Moreover, as a resin material as described above, an athermal resin as shown below can be used.
An athermal resin is known as a material in which particles of 30 nm or less are dispersed in a resin as a base material. Athermal resin has a feature that the refractive index change with respect to temperature change is small compared to a resin for ordinary optical use, so that the effect of improving the temperature characteristics by the phase structure can be conserved, and thereby the phase structure It is possible to reduce the deterioration of the wavelength characteristics due to the above, to increase the degree of freedom in designing the optical element, and to increase the allowable range of manufacturing error and assembly accuracy.
In general, when powder is mixed with a transparent resin material, light scattering occurs and the transmittance decreases, so that it has been difficult to use as an optical material. It has been found that by using fine particles having a diameter of 30 nm or less, scattering can be virtually prevented. Here, such a resin material is a resin material in which fine particles having a refractive index change rate larger than a refractive index change rate accompanying a temperature change of a resin serving as a base material and having an average particle size of 30 nm or less are dispersed. It is preferable. In addition, when the sign of the refractive index change rate of the resin serving as the base material is negative, the refractive index change rate is large. It includes both of positive refractive index change rates.

さて樹脂材料は、温度が上昇することにより、屈折率が低下してしまうが、無機粒子を分散、混合することにより、屈折率変化を低減しうるようにすることも知られている。具体的には、従来は−１．２×１０−４程度であった屈折率変化Ａを、絶対値で８×１０−５未満に抑えることが好ましく、より好ましくは絶対値で６×１０−５未満にすることがよい。
そして、さらに好ましくは絶対値で４×１０−５未満にするのがよい。光学素子の材料として、母材となる樹脂に３０ｎｍ以下、好ましくは２０ｎｍ以下、さらに好ましくは１０〜１５ｎｍの微粒子を分散させた材料を利用することで、屈折率の温度依存性が無いか、あるいは温度依存性を低減した光学素子を提供できる。 It is also known that the resin material has a lower refractive index as the temperature rises, but it is also possible to reduce the refractive index change by dispersing and mixing inorganic particles. Specifically, the conventionally -1.2 × 10 -4 about a a refractive index change A, it is preferable to suppress to less than 8 × 10 -5 in an absolute value, more preferably the absolute value 6 × 10 - It is good to make it less than 5 .
More preferably, the absolute value is less than 4 × 10 −5 . By using a material in which fine particles of 30 nm or less, preferably 20 nm or less, more preferably 10 to 15 nm are dispersed in a resin as a base material as the material of the optical element, there is no temperature dependence of the refractive index, or An optical element with reduced temperature dependence can be provided.

たとえば、アクリル樹脂に、酸化ニオブ（Ｎｂ2Ｏ5）の微粒子を分散させる。体積比で、母材となる樹脂は８０、酸化ニオブは２０程度の割合であり、これらを均一に混合する。微粒子は凝集しやすいという問題があるが、粒子表面に電荷を与えて分散させる等の技術により、必要な分散状態を生じさせることが出来る。酸化ニオブの代わりに、酸化シリコン（ＳｉＯ2）の微粒子を用いても良い。
母材となる樹脂と粒子との混合・分散は、光学素子の射出成形時にインラインで行うことが好ましい。いいかえると、混合・分散した後は、光学素子（レンズ）に成形される迄、冷却・固化されないようにすることが好ましい。 For example, fine particles of niobium oxide (Nb 2 O 5 ) are dispersed in an acrylic resin. The volume ratio of the resin as the base material is 80, and the ratio of niobium oxide is about 20, and these are uniformly mixed. Although the fine particles tend to aggregate, a necessary dispersion state can be generated by a technique such as applying a charge to the particle surface to disperse the particles. Instead of niobium oxide, fine particles of silicon oxide (SiO 2 ) may be used.
It is preferable to mix and disperse the resin as the base material and the particles in-line at the time of injection molding of the optical element. In other words, after mixing and dispersing, it is preferable not to be cooled and solidified until formed into an optical element (lens).

なお、上記の体積比率は、屈折率の温度に対する変化の割合をコントロールするために、適宜増減できるし、複数種類の微粒子をブレンドして分散させることも可能である。
上記の例では、比率は８０：２０、すなわち４：１であるが、９０：１０（９：１）から６０：４０（３：２）までの間で適宜調整可能である。９：１よりも微粒子の量を多くすることにより温度変化抑制の効果が大きくなり、逆に３：２よりも微粒子の量を少なくすることにより光学素子の成形性に問題が生じることがなく好ましい。 The volume ratio can be appropriately increased or decreased in order to control the rate of change of the refractive index with respect to temperature, and a plurality of types of fine particles can be blended and dispersed.
In the above example, the ratio is 80:20, that is, 4: 1, but can be adjusted as appropriate from 90:10 (9: 1) to 60:40 (3: 2). Increasing the amount of fine particles more than 9: 1 increases the effect of suppressing temperature change, and conversely, reducing the amount of fine particles less than 3: 2 is preferable without causing problems in moldability of the optical element. .

また、以上の微粒子は無機物であることが好ましく、さらに酸化物であることがより好ましい。そして酸化状態が飽和していて、それ以上酸化しない酸化物であることが更に好ましい。
無機物であることは、高分子有機化合物である母材となる樹脂との反応が低く抑えられるために好ましく、また酸化物であることによって、レーザ光照射等の実使用に伴う劣化を防ぐことが出来る。特に高温化や、レーザ光を照射されるという過酷な条件において、樹脂の酸化が促進されやすくなるが、このような無機酸化物の微粒子であれば、酸化による劣化を防ぐことが出来る。
また、その他の要因による樹脂の酸化を防止するために、酸化防止剤を樹脂材料中に添加することも勿論可能である。 The fine particles are preferably inorganic and more preferably oxide. Further, it is more preferable that the oxide is saturated and does not oxidize any more.
An inorganic substance is preferable because the reaction with the base resin, which is a polymer organic compound, can be suppressed to a low level, and the oxide can prevent deterioration due to actual use such as laser light irradiation. I can do it. In particular, oxidation of the resin is easily promoted under severe conditions such as high temperature and irradiation with laser light. However, such inorganic oxide fine particles can prevent deterioration due to oxidation.
Of course, an antioxidant may be added to the resin material in order to prevent the resin from being oxidized by other factors.

ちなみに、母材となる樹脂は、特開２００４−１４４９５１号公報、特開２００４−１４４９５３号公報、特開２００４−１４４９５４号公報等に記載されているような樹脂を適宜好ましく採用することができる。   Incidentally, as the base resin, resins such as those described in Japanese Patent Application Laid-Open Nos. 2004-144951, 2004-144953, and 2004-144554 can be preferably used as appropriate.

位相構造を示す要部平面図である。It is a principal part top view which shows a phase structure. 位相構造を示す要部平面図である。It is a principal part top view which shows a phase structure. 位相構造を示す要部平面図である。It is a principal part top view which shows a phase structure. 位相構造を示す要部平面図である。It is a principal part top view which shows a phase structure. 位相構造を示す要部平面図である。It is a principal part top view which shows a phase structure. 位相構造を示す要部平面図である。It is a principal part top view which shows a phase structure. 第１位相構造の輪帯構造による温度収差の補正の原理を説明するためのグラフである。It is a graph for demonstrating the principle of correction | amendment of the temperature aberration by the ring zone structure of a 1st phase structure. 光ピックアップ装置を示す要部平面図である。It is a principal part top view which shows an optical pick-up apparatus. 対物光学素子の構造を示す要部平面図である。It is a principal part top view which shows the structure of an objective optical element. 対物光学素子の構造を示す要部平面図である。It is a principal part top view which shows the structure of an objective optical element. 対物光学素子の構造を示す要部平面図である。It is a principal part top view which shows the structure of an objective optical element. 対物光学素子の構造を示す要部平面図である。It is a principal part top view which shows the structure of an objective optical element. 第１位相構造によるＨＤでの温度特性の補償の効果を示すグラフである。It is a graph which shows the effect of compensation of the temperature characteristic in HD by the 1st phase structure. 第１位相構造によるＨＤでの温度特性の補償の効果を示すグラフである。It is a graph which shows the effect of compensation of the temperature characteristic in HD by the 1st phase structure.

符号の説明Explanation of symbols

Ｌ１ 第１収差補正レンズ
Ｌ２ 第２収差補正レンズ
ＯＬ 集光光学素子
ＯＵ 対物レンズユニット
ＰＳ１ 第１位相構造
ＰＳ２ 第２位相構造
ＰＳ３ 第３位相構造
ＰＵ 光ピックアップ装置 L1 First aberration correction lens L2 Second aberration correction lens OL Condensing optical element OU Objective lens unit PS1 First phase structure PS2 Second phase structure PS3 Third phase structure PU Optical pickup device

Claims (31)

波長λ１の第１光源から出射される第１光束を用いて、保護基板厚ｔ１の第１光情報記録媒体に対して情報の再生および／または記録を行い、波長λ２（λ１＜λ２）の第２光源から出射される第２光束を用いて、保護基板厚ｔ２（ｔ１≦ｔ２）の第２光情報記録媒体に対して情報の再生および／または記録を行い、波長λ３（λ２＜λ３）の第３光源から出射される第３光束を用いて、保護基板厚ｔ３（ｔ２＜ｔ３）の第３光情報記録媒体に対して情報の再生および／または記録を行う光ピックアップ装置に用いられ、前記各光情報記録媒体の情報記録面に集光スポットを形成する対物光学素子において、
前記対物光学素子の有する光学面のうちいずれかに、温度変化によって生じる前記第１光情報記録媒体の情報記録面に対する集光スポット形成性能の劣化を補償する第１位相構造と、前記保護基板厚ｔ１と前記保護基板厚ｔ２或いは前記波長λ１と前記波長λ２との差に基づく球面収差を解消するための第２位相構造と、前記保護基板厚ｔ１と前記保護基板厚ｔ３との差に基づく球面収差を解消するための第３位相構造を備えることを特徴とする対物光学素子。 Information is reproduced and / or recorded on the first optical information recording medium having the protective substrate thickness t1 using the first light flux emitted from the first light source having the wavelength λ1, and the first light having the wavelength λ2 (λ1 <λ2) is obtained. Using the second light flux emitted from the two light sources, information is reproduced and / or recorded on the second optical information recording medium having the protective substrate thickness t2 (t1 ≦ t2), and the wavelength λ3 (λ2 <λ3) is reached. Using the third light beam emitted from the third light source, the optical pickup device performs reproduction and / or recording of information on a third optical information recording medium having a protective substrate thickness t3 (t2 <t3), In the objective optical element that forms a focused spot on the information recording surface of each optical information recording medium,
A first phase structure that compensates for deterioration of a condensed spot forming performance with respect to the information recording surface of the first optical information recording medium caused by a temperature change on any one of the optical surfaces of the objective optical element, and the protective substrate thickness a second phase structure for eliminating spherical aberration based on the difference between t1 and the protective substrate thickness t2 or the wavelength λ1 and the wavelength λ2, and a spherical surface based on the difference between the protective substrate thickness t1 and the protective substrate thickness t3. An objective optical element comprising a third phase structure for eliminating aberration. 前記第１位相構造の光軸を含む断面形状は、光軸から所定の高さまでは、光軸から離れるに従って光路長が長くなり、前記光軸から所定の高さ以降は、光軸から離れるに従って光路長が短くなる位相差付与構造、或いは、光軸から所定の高さまでは、光軸から離れるに従って光路長が短くなり、前記光軸から所定の高さ以降は、光軸から離れるに従って光路長が長くなる位相差付与構造であることを特徴とする請求項１に記載の対物光学素子。   In the cross-sectional shape including the optical axis of the first phase structure, the optical path length increases as the distance from the optical axis increases from the optical axis at a predetermined height, and as the distance from the optical axis increases from the optical axis after the predetermined height. A phase difference providing structure that shortens the optical path length, or at a predetermined height from the optical axis, the optical path length decreases as the distance from the optical axis increases. After the predetermined height from the optical axis, the optical path length increases as the distance from the optical axis increases. The objective optical element according to claim 1, wherein the objective optical element has a phase difference imparting structure in which the length becomes longer. 前記第１位相構造の前記所定の高さの位置での位相と同位相となる領域が、前記第１光束の有効光束径の７０％の位置を含むことを特徴とする請求項２に記載の対物光学素子。   The region having the same phase as the phase at the position of the predetermined height of the first phase structure includes a position of 70% of the effective light beam diameter of the first light beam. Objective optical element. 前記第１位相構造は、前記第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であるα１次の回折光を発生し、前記第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であるβ１（β１＜α１）次の回折光を発生し、前記第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であるγ１（γ１≦β１）次の回折光を発生する位相差付与構造であることを特徴とする請求項１に記載の対物光学素子。   The first phase structure generates α1 order diffracted light having the maximum diffraction efficiency among diffracted light generated when the first light flux is incident, and diffracted light generated when the second light flux is incident. Diffracted light of β1 (β1 <α1) order which is the maximum diffraction efficiency is generated, and γ1 (γ1 ≦ β1) order which is the maximum diffraction efficiency among the diffracted light generated when the third light beam is incident. The objective optical element according to claim 1, wherein the objective optical element is a phase difference imparting structure that generates diffracted light. 前記位相差付与構造は、断面形状が階段構造であることを特徴とする請求項２〜４のいずれか一項に記載の対物光学素子。   The objective optical element according to claim 2, wherein the phase difference providing structure has a stepped structure in cross section. 前記第１位相構造において、ｐ＝INT（ｄ（ｎ１−１）／λ１）、ｑ＝INT（ｄ（ｎ３−１）／λ３）としたとき、ｐ＞ｑを満たすことを特徴とする請求項５に記載の対物光学素子。
ただし、
ｄ：第１位相構造の段差量
ｎ１：第１位相構造を持つ媒質の波長λ１での屈折率
ｎ３：第１位相構造を持つ媒質の波長λ３での屈折率
INT（X）：Ｘにもっとも近い整数 In the first phase structure, when p = INT (d (n1-1) / λ1) and q = INT (d (n3-1) / λ3), p> q is satisfied. 5. The objective optical element according to 5.
However,
d: Step amount of the first phase structure n1: Refractive index of the medium having the first phase structure at the wavelength λ1 n3: Refractive index of the medium having the first phase structure at the wavelength λ3
INT (X): Integer closest to X 前記第２位相構造は、前記第１光束及び前記第３光束を回折せず、前記第２光束を回折する回折構造であることを特徴とする請求項１に記載の対物光学素子。   2. The objective optical element according to claim 1, wherein the second phase structure is a diffractive structure that does not diffract the first light flux and the third light flux but diffracts the second light flux. 前記第２位相構造は、光軸を含む断面形状が階段状とされたパターンが同心円状に配列された構造であって、所定のレベル面の個数Ａ毎に、そのレベル面数に対応した段数分の高さだけ段をシフトさせた構造であることを特徴とする請求項７に記載の対物光学素子。   The second phase structure is a structure in which patterns whose cross-sectional shape including the optical axis is stepped are arranged concentrically, and the number of steps corresponding to the number of level planes for each predetermined number A of the level planes The objective optical element according to claim 7, wherein the objective optical element has a structure in which a step is shifted by a height of a minute. 前記所定のレベル面の個数Ａは、４、５、６の何れかであることを特徴とする請求項８に記載の対物光学素子。   The objective optical element according to claim 8, wherein the number A of the predetermined level surfaces is any one of 4, 5, and 6. 前記階段の１つの段差により生じる光路差は前記波長λ１の２倍であることを特徴とする請求項８又は９に記載の対物光学素子。   10. The objective optical element according to claim 8, wherein an optical path difference caused by one step of the staircase is twice the wavelength λ1. 前記第２位相構造を備える媒質のアッベ数をνｄ２としたとき、４０＜νｄ２＜７０を満たすことを特徴とする請求項７〜１０のいずれか一項に記載の対物光学素子。   11. The objective optical element according to claim 7, wherein 40 <νd2 <70 is satisfied, where νd2 is an Abbe number of the medium having the second phase structure. 前記第２位相構造は、前記第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であるα２次の回折光を発生し、前記第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であるβ２（β２＜α２）次の回折光を発生し、前記第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であるγ２（γ２≦β２）次の回折光を発生する回折構造であることを特徴とする請求項１に記載の対物光学素子。   The second phase structure generates α-order diffracted light having the maximum diffraction efficiency among diffracted lights generated when the first light flux is incident, and diffracted light generated when the second light flux is incident. Diffracted light of β2 (β2 <α2) order which is the maximum diffraction efficiency is generated, and γ2 (γ2 ≦ β2) order which is the maximum diffraction efficiency of the diffracted light generated when the third light beam is incident. The objective optical element according to claim 1, wherein the objective optical element has a diffractive structure that generates 前記第３位相構造は、前記第１光束及び前記第２光束を回折せず、前記第３光束を回折する回折構造であることを特徴とする請求項１に記載の対物光学素子。   The objective optical element according to claim 1, wherein the third phase structure is a diffractive structure that does not diffract the first light flux and the second light flux but diffracts the third light flux. 前記第３位相構造は、光軸を含む断面形状が階段状とされたパターンが同心円状に配列された構造であって、所定のレベル面の個数Ｂ毎に、そのレベル面数に対応した段数分の高さだけ段をシフトさせた構造であることを特徴とする請求項１３に記載の対物光学素子。   The third phase structure is a structure in which a pattern whose cross-sectional shape including the optical axis is stepped is arranged concentrically, and the number of steps corresponding to the number of level surfaces for each predetermined number of level surfaces B The objective optical element according to claim 13, wherein the objective optical element has a structure in which a step is shifted by a height of a minute. 前記第３位相構造を備える媒質のアッベ数をνｄ３としたとき、４０＜νｄ３＜７０を満たし、前記所定のレベル面の個数Ｂは２であることを特徴とする請求項１４に記載の対物光学素子。   The objective optical system according to claim 14, wherein when the Abbe number of the medium having the third phase structure is νd3, 40 <νd3 <70 is satisfied, and the number B of the predetermined level surfaces is two. element. 前記階段の１つの段差により生じる光路差は前記波長λ１の５倍であることを特徴とする請求項１５に記載の対物光学素子。   The objective optical element according to claim 15, wherein an optical path difference caused by one step of the staircase is five times the wavelength λ1. 前記第３位相構造を備える媒質のアッベ数をνｄ３としたとき、２４＜νｄ３＜４０を満たし、前記所定のレベル面の個数Ｂは３であることを特徴とする請求項１４に記載の対物光学素子。   The objective optical system according to claim 14, wherein when the Abbe number of the medium having the third phase structure is νd3, 24 <νd3 <40 is satisfied, and the number B of the predetermined level surfaces is 3. element. 前記階段の１つの段差により生じる光路差は前記波長λ１の５倍又は７倍であることを特徴とする請求項１７に記載の対物光学素子。   18. The objective optical element according to claim 17, wherein an optical path difference caused by one step of the staircase is 5 times or 7 times the wavelength λ1. 前記第３位相構造を備える媒質のアッベ数をνｄ３としたとき、２０＜νｄ３＜２６を満たし、前記所定のレベル面の個数Ｂは４であることを特徴とする請求項１４に記載の対物光学素子。   The objective optical system according to claim 14, wherein when the Abbe number of the medium having the third phase structure is νd3, 20 <νd3 <26 is satisfied, and the number B of the predetermined level surfaces is four. element. 前記階段の１つの段差により生じる光路差は前記波長λ１の７倍であることを特徴とする請求項１９に記載の対物光学素子。   The objective optical element according to claim 19, wherein an optical path difference caused by one step of the staircase is seven times the wavelength λ1. 前記第３位相構造は、前記第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であるα３次の回折光を発生し、前記第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であるβ３（β３＜α３）次の回折光を発生し、前記第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であるγ３（γ３≦β３）次の回折光を発生する回折構造であることを特徴とする請求項１に記載の対物光学素子。   The third phase structure generates α-order diffracted light having the maximum diffraction efficiency among diffracted lights generated when the first light flux is incident, and diffracted light generated when the second light flux is incident. Diffracted light of β3 (β3 <α3) order which is the maximum diffraction efficiency is generated, and γ3 (γ3 ≦ β3) order which is the maximum diffraction efficiency among the diffracted light generated when the third light beam is incident. The objective optical element according to claim 1, wherein the objective optical element has a diffractive structure that generates 前記第３位相構造を備える媒質のアッベ数をνｄ３としたとき、２０＜νｄ３＜４０を満たすことを特徴とする請求項２１に記載の対物光学素子。   The objective optical element according to claim 21, wherein 20 <νd3 <40 is satisfied when an Abbe number of the medium having the third phase structure is νd3. 前記α３が奇数であることを特徴とする請求項２２に記載の対物光学素子。   The objective optical element according to claim 22, wherein α3 is an odd number. 少なくとも1枚の集光光学素子と、収差補正レンズ群とを備えることを特徴とする請求項１〜２３のいずれか一項に記載の対物光学素子。   The objective optical element according to claim 1, comprising at least one condensing optical element and an aberration correction lens group. 少なくとも１枚の集光光学素子を備えた２群２枚構成であることを特徴とする請求項１〜２４のいずれか一項に記載の対物光学素子。   The objective optical element according to any one of claims 1 to 24, wherein the objective optical element has a two-group two-element configuration including at least one condensing optical element. 少なくとも１枚の集光光学素子を備えた２群３枚構成であり、それら２群のうちの１群は２枚の互いに異なる媒質からなる光学素子を接合して成ることを特徴とする請求項１〜２４のいずれか一項に記載の対物光学素子。   2. A two-group three-element configuration comprising at least one condensing optical element, wherein one of the two groups is formed by joining two optical elements made of different media. The objective optical element according to any one of 1 to 24. 少なくとも１枚の集光光学素子を備えた３群３枚構成であることを特徴とする請求項１〜２４のいずれか一項に記載の対物光学素子。   The objective optical element according to any one of claims 1 to 24, wherein the objective optical element has a three-group three-element configuration including at least one condensing optical element. 少なくとも前記集光光学素子が樹脂から構成されていることを特徴とする請求項２４〜２７のいずれか一項に記載の対物光学素子。   The objective optical element according to any one of claims 24 to 27, wherein at least the condensing optical element is made of a resin. 前記対物光学素子を構成するすべての光学素子が樹脂から構成されていることを特徴とする請求項２４〜２７のいずれか一項に記載の対物光学素子。   All the optical elements which comprise the said objective optical element are comprised from resin, The objective optical element as described in any one of Claims 24-27 characterized by the above-mentioned. 保護基板厚ｔ１の第１光情報記録媒体に対して情報の再生または記録を行う波長λ１の第１光束を出射する第１光源と、保護基板厚ｔ２（ｔ１≦ｔ２）の第２光情報記録媒体に対して情報の再生または記録を行う波長λ２（λ１＜λ２）の第２光束を出射する第２光源と、保護基板厚ｔ３（ｔ２＜ｔ３）の第３光情報記録媒体に対して情報の再生または記録を行う波長λ３（λ２＜λ３）の第３光束を出射する第３光源と、請求項１〜２９のいずれか一項に記載の対物光学素子とを搭載したことを特徴とする光ピックアップ装置。   A first light source that emits a first light beam having a wavelength λ1 for reproducing or recording information on a first optical information recording medium having a protective substrate thickness t1, and a second optical information recording having a protective substrate thickness t2 (t1 ≦ t2). Information for a second light source that emits a second light beam having a wavelength λ2 (λ1 <λ2) for reproducing or recording information on the medium and a third optical information recording medium having a protective substrate thickness t3 (t2 <t3) 30. A third light source that emits a third light beam having a wavelength λ3 (λ2 <λ3) for reproducing or recording the light and an objective optical element according to any one of claims 1 to 29 are mounted. Optical pickup device. 請求項３０に記載の光ピックアップ装置と、前記光ピックアップ装置を光情報記録媒体の半径方向に移動させる移動装置とを搭載したことを特徴とする光ディスクドライブ装置。   31. An optical disk drive device comprising the optical pickup device according to claim 30 and a moving device for moving the optical pickup device in a radial direction of an optical information recording medium.
JP2005242988A 2004-08-25 2005-08-24 Objective optical device, optical pickup device, and optical disk driving device Pending JP2006092720A (en)

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