JP4193915B2 - Optical pickup device and objective optical element for optical pickup device - Google Patents

Optical pickup device and objective optical element for optical pickup device Download PDF

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JP4193915B2
JP4193915B2 JP2008529805A JP2008529805A JP4193915B2 JP 4193915 B2 JP4193915 B2 JP 4193915B2 JP 2008529805 A JP2008529805 A JP 2008529805A JP 2008529805 A JP2008529805 A JP 2008529805A JP 4193915 B2 JP4193915 B2 JP 4193915B2
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pickup device
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optical axis
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JPWO2008117663A1 (en
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英司 野村
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Konica Minolta Opto Inc
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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00Optical objectives specially designed for the purposes specified below
    • G02B13/18Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/42Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
    • G02B27/4233Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive element [DOE] contributing to a non-imaging application
    • G02B27/4238Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive element [DOE] contributing to a non-imaging application in optical recording or readout devices
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/18Diffraction gratings
    • G02B5/1814Diffraction gratings structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1365Separate or integrated refractive elements, e.g. wave plates
    • G11B7/1367Stepped phase plates
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1372Lenses
    • G11B7/1374Objective lenses
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1392Means for controlling the beam wavefront, e.g. for correction of aberration
    • G11B7/13922Means for controlling the beam wavefront, e.g. for correction of aberration passive

Description

本発明は、高密度光ディスクに対して情報の記録及び/又は再生を行える光ピックアップ装置及びそれに用いる対物光学素子に関する。   The present invention relates to an optical pickup device capable of recording and / or reproducing information with respect to a high-density optical disc and an objective optical element used therefor.

近年、波長400nm程度の青紫色半導体レーザを用いて、情報の記録及び/又は再生(以下、「記録及び/又は再生」を「記録/再生」と記載する)を行うことができる高密度光ディスクシステムの研究・開発が急速に進んでいる。一例として、NA0.85、光源波長405nmの仕様で情報の記録/再生を行う光ディスク、いわゆるBlu−rayDisc(以下、BDという)では、DVD(NA0.65、光源波長650nm、記憶容量4、7GB)と同じ大きさである直径12cmの光ディスクに対して、1層あたり23〜27GBの情報の記録が可能であり、又、NA0.65、光源波長405nmの仕様で情報の記録/再生を行う光ディスク、いわゆるHD DVD(以下、HDという)では、直径12cmの光ディスクに対して、1層あたり約15GBの情報の記録が可能である。尚、BDでは、光ディスクの傾き(スキュー)に起因して発生するコマ収差が増大するため、DVDにおける場合よりも保護層を薄く設計し(DVDの0.6mmに対して、BDでは0.1mm)、スキューによるコマ収差量を低減している。以下、本明細書では、このような光ディスクを「高密度光ディスク」と呼ぶ。   In recent years, a high-density optical disk system capable of recording and / or reproducing information (hereinafter, “recording and / or reproduction” is referred to as “recording / reproduction”) using a blue-violet semiconductor laser having a wavelength of about 400 nm. Research and development are progressing rapidly. As an example, an optical disc for recording / reproducing information with specifications of NA 0.85 and light source wavelength 405 nm, so-called Blu-ray Disc (hereinafter referred to as BD), DVD (NA 0.65, light source wavelength 650 nm, storage capacity 4, 7 GB) An optical disc capable of recording information of 23 to 27 GB per layer with respect to an optical disc having a diameter of 12 cm which is the same size as the above, and recording / reproducing information with specifications of NA 0.65 and light source wavelength 405 nm, A so-called HD DVD (hereinafter referred to as HD) can record information of about 15 GB per layer on an optical disk having a diameter of 12 cm. In BD, coma aberration generated due to the inclination (skew) of the optical disk increases. Therefore, a protective layer is designed to be thinner than in DVD (0.1 mm in BD compared to 0.6 mm in DVD). ), The amount of coma due to skew is reduced. Hereinafter, such an optical disc is referred to as a “high density optical disc” in the present specification.

ここで、特許文献1には、複数の光学素子を用いて高密度光ディスクとDVD、そしてCDに対して互換性をもち、複数種類の光ディスクに情報の記録/再生を行うことができる光ピックアップ装置が開示されている。
特開2004−319062号公報
Here, Patent Document 1 discloses an optical pickup device that is compatible with a high-density optical disc, a DVD, and a CD using a plurality of optical elements, and that can record / reproduce information on a plurality of types of optical discs. Is disclosed.
JP 2004-319062 A

ところで、特許文献1に開示された高密度光ディスク専用の対物レンズは、ガラス製であるため、一般的にはコストが高く、大量生産に不向きという問題がある。そこで、低コスト化を図るべく、高密度光ディスク専用の対物レンズをプラスチックで成形したいという要望がある。しかしながら、プラスチックはガラスに比べて温度変化に対する屈折率変化が大きいため、プラスチック製対物レンズでは環境温度変化に応じて収差劣化が生じやすいという問題がある。環境温度変化による収差劣化を緩和するために、いわゆるNPS構造を設けたプラスチック製の単玉非球面レンズも提案されている。(尚、本明細書における「NPS構造」の定義は後に詳述する。)しかしながら、NPS構造は波長依存性を有するため、光源から射出される光束の波長が変化した場合、収差劣化を招く場合がある。更に、NPS構造を用いたとしても、軸上色収差を補正するには別個の技術が必要であり、これによりコスト高を招くという問題がある。   By the way, since the objective lens for high density optical discs disclosed in Patent Document 1 is made of glass, there is a problem that it is generally expensive and unsuitable for mass production. Therefore, there is a demand for molding an objective lens dedicated to a high-density optical disc made of plastic in order to reduce costs. However, since the refractive index change with respect to the temperature change is larger than that of glass, the plastic objective lens has a problem that aberration deterioration is likely to occur according to the environmental temperature change. In order to alleviate aberration deterioration due to environmental temperature changes, a plastic single aspherical lens provided with a so-called NPS structure has also been proposed. (Note that the definition of “NPS structure” in this specification will be described in detail later.) However, since the NPS structure has wavelength dependence, if the wavelength of the light beam emitted from the light source changes, aberration deterioration may occur. There is. Furthermore, even if the NPS structure is used, a separate technique is required to correct the longitudinal chromatic aberration, which causes a problem of increasing the cost.

本発明は、かかる従来技術の問題点に鑑みてなされたものであり、プラスチック製の対物光学素子を用いながらも、温度特性と軸上色収差とを良好に維持しつつ、しかも波長特性が大きく劣化することなく、高密度光ディスクに対して情報の記録/再生を行うことができる光ピックアップ装置、及び、それに用いる対物光学素子を提供することを目的とする。   The present invention has been made in view of the problems of the prior art, and while using a plastic objective optical element, while maintaining good temperature characteristics and axial chromatic aberration, the wavelength characteristics are greatly deteriorated. An object of the present invention is to provide an optical pickup device capable of recording / reproducing information on / from a high-density optical disc, and an objective optical element used therefor.

請求項1の光ピックアップ装置は、波長λ1(380nm<λ1<420nm)の光束を射出する光源と、前記光束を光ディスクの情報記録面上に集光させるための対物光学素子と、前記光ディスクの情報記録面上で反射した光を受光する受光素子とを有し、前記光束を前記光ディスクの情報記録面上に集光させることによって情報の記録及び/又は再生を行う光ピックアップ装置において、
前記対物光学素子は、単玉のプラスチックレンズであり、
前記対物光学素子の像側開口数(NA)は0.8以上であり、
前記対物光学素子の光学面は、同心円状の複数の境界段差で区切られた、複数の領域に分けられており、
前記境界段差で区切られた各領域は、同心円状の複数の領域内段差を有し、
前記各領域のうち、光軸に近い側の領域では前記境界段差が光軸とは逆側を向いており、前記光軸から離れた側の領域では前記境界段差が光軸側を向いており、
前記各領域において、前記境界段差の段差量は、前記領域内段差の段差量よりも大きいことを特徴とする。
The optical pickup device according to claim 1 is a light source that emits a light beam having a wavelength λ1 (380 nm <λ1 <420 nm), an objective optical element that focuses the light beam on an information recording surface of the optical disk, and information on the optical disk. A light receiving element that receives light reflected on the recording surface, and records and / or reproduces information by focusing the light flux on the information recording surface of the optical disc.
The objective optical element is a single plastic lens,
The image side numerical aperture (NA) of the objective optical element is 0.8 or more,
The optical surface of the objective optical element is divided into a plurality of regions separated by a plurality of concentric boundary steps,
Each region divided by the boundary step has a plurality of concentric steps in the region,
Among the regions, the boundary step in the region closer to the optical axis faces away from the optical axis, and the boundary step in the region away from the optical axis faces the optical axis side. ,
In each of the regions, the step amount of the boundary step is larger than the step amount of the in-region step.

請求項2に記載の光ピックアップ装置は、請求項1に記載の発明において、
前記各領域のうち、光軸を含む領域において、前記領域内段差の全ての段差量d2が、以下の条件式を満たすことを特徴とする。
The optical pickup device according to claim 2 is the invention according to claim 1,
Among the regions, in the region including the optical axis, all the step amounts d2 of the step in the region satisfy the following conditional expression.

0.9・q・λ1/(n−1)≦d2(nm)≦1.1・q・λ1/(n−1) (2)
但し、qは、任意の整数を示し、nは波長λ1の前記光束における前記対物光学素子の屈折率を示す。
0.9 · q · λ1 / (n−1) ≦ d2 (nm) ≦ 1.1 · q · λ1 / (n−1) (2)
Here, q represents an arbitrary integer, and n represents the refractive index of the objective optical element in the light flux having the wavelength λ1.

請求項3に記載の光ピックアップ装置は、請求項2に記載の発明において、前記各領域のうち、光軸を含む領域において、前記光軸を含む領域とその外側の領域との前記境界段差の段差量d1が、以下の条件式を満たすことを特徴とする。 According to a third aspect of the present invention, in the optical pickup device according to the second aspect , in the region including the optical axis among the regions, the boundary step between the region including the optical axis and the region outside thereof. The step amount d1 satisfies the following conditional expression.

0.9・(p−q)・λ1/(n−1)≦d1(nm)≦1.1・p・λ1/(n−1) (3)
但し、pは、q以上の任意の整数を示す。
0.9 · (p−q) · λ1 / (n−1) ≦ d1 (nm) ≦ 1.1 · p · λ1 / (n−1) (3)
However, p shows the arbitrary integers more than q.

請求項4に記載の光ピックアップ装置は、請求項3に記載の発明において、前記各領域のうち、光軸を含む領域において、前記光軸を含む領域とその外側の領域との前記境界段差の段差量d1が、以下の条件式を満たすことを特徴とする。 According to a fourth aspect of the present invention, in the invention according to the third aspect , in the region including the optical axis, the boundary step between the region including the optical axis and the region outside thereof is included. The step amount d1 satisfies the following conditional expression.

0.9・(p−q)・λ1/(n−1)≦d1(nm)≦1.1・(p−q)・λ1/(n−1) (4)
請求項5に記載の光ピックアップ装置は、請求項3又はに記載の発明において、前記境界段差のうち、光軸側を向いている前記境界段差の光軸方向の段差量d1‘が、全て以下の条件式を満たすことを特徴とする。
0.9 · (p−q) · λ1 / (n−1) ≦ d1 (nm) ≦ 1.1 · (p−q) · λ1 / (n−1) (4)
An optical pickup device according to a fifth aspect is the invention according to the third or fourth aspect , wherein the step height d1 ′ in the optical axis direction of the boundary step facing the optical axis is all of the boundary step. The following conditional expression is satisfied.

1.0・p・λ1/(n−1)≦d1‘(nm)≦2.0・(p+q)・λ1/(n−1) (5)
請求項6に記載の光ピックアップ装置は、請求項5に記載の発明において、前記境界段差のうち、光軸側を向いている前記境界段差の光軸方向の段差量d1‘が、全て以下の条件式を満たすことを特徴とする。
1.0 · p · λ1 / (n−1) ≦ d1 ′ (nm) ≦ 2.0 · (p + q) · λ1 / (n−1) (5)
The optical pickup device according to a sixth aspect is the optical pickup device according to the fifth aspect , wherein the step height d1 ′ in the optical axis direction of the boundary step facing the optical axis among the boundary steps is less than the following. It satisfies the conditional expression.

1.0・(p+q)・λ1/(n−1)≦d1‘(nm)≦2.0・(p+q)・λ1/(n−1) (6)
請求項7に記載の光ピックアップ装置は、請求項2乃至のいずれかに記載の発明において、qが2又は1であることを特徴とする。
1.0 · (p + q) · λ1 / (n−1) ≦ d1 ′ (nm) ≦ 2.0 · (p + q) · λ1 / (n−1) (6)
An optical pickup device according to a seventh aspect is characterized in that q is 2 or 1 in the invention according to any one of the second to sixth aspects.

請求項8に記載の光ピックアップ装置は、請求項3乃至のいずれかに記載の発明において、pが5又は4であることを特徴とする。 An optical pickup device according to an eighth aspect is characterized in that, in the invention according to any one of the third to seventh aspects, p is 5 or 4.

請求項9に記載の光ピックアップ装置用の対物光学素子は、波長λ1(380nm<λ1<420nm)の光束を射出する光源と、前記光束を光ディスクの情報記録面上に集光させるための対物光学素子と、前記光ディスクの情報記録面上で反射した光を受光する受光素子とを有し、前記光束を前記光ディスクの情報記録面上に集光させることによって情報の記録及び/又は再生を行う光ピックアップ装置用の対物光学素子において、
前記対物光学素子は、単玉のプラスチックレンズであり、
前記対物光学素子の像側開口数(NA)は0.8以上であり、
前記対物光学素子の光学面は、同心円状の複数の境界段差で区切られた、複数の領域に分けられており、
前記境界段差で区切られた各領域は、同心円状の複数の領域内段差を有し、
前記各領域のうち、光軸に近い側の領域では前記境界段差が光軸とは逆側を向いており、前記光軸から離れた側の領域では前記境界段差が光軸側を向いており、
前記各領域において、前記境界段差の段差量は、前記領域内段差の段差量よりも大きいことを特徴とする。
The objective optical element for an optical pickup device according to claim 9 includes a light source that emits a light beam having a wavelength λ1 (380 nm <λ1 <420 nm), and an objective optical device that focuses the light beam on an information recording surface of an optical disk. And a light receiving element that receives light reflected on the information recording surface of the optical disc, and records and / or reproduces information by condensing the light flux on the information recording surface of the optical disc. In the objective optical element for the pickup device,
The objective optical element is a single plastic lens,
The image side numerical aperture (NA) of the objective optical element is 0.8 or more,
The optical surface of the objective optical element is divided into a plurality of regions separated by a plurality of concentric boundary steps,
Each region divided by the boundary step has a plurality of concentric steps in the region,
Among the regions, the boundary step in the region closer to the optical axis faces away from the optical axis, and the boundary step in the region away from the optical axis faces the optical axis side. ,
In each of the regions, the step amount of the boundary step is larger than the step amount of the in-region step.

請求項10に記載の光ピックアップ装置用の対物光学素子は、請求項9に記載の発明において、前記各領域のうち、光軸を含む領域において、前記領域内段差の全ての段差量d2が、以下の条件式を満たすことを特徴とする。 An objective optical element for an optical pickup device according to a tenth aspect is the invention according to the ninth aspect , wherein in the region including the optical axis among the regions, all the step amounts d2 of the step in the region are The following conditional expression is satisfied.

0.9・q・λ1/(n−1)≦d2(nm)≦1.1・q・λ1/(n−1) (2)
但し、qは、任意の整数を示し、nは、波長λ1の前記光束における前記対物光学素子の屈折率を示す。
0.9 · q · λ1 / (n−1) ≦ d2 (nm) ≦ 1.1 · q · λ1 / (n−1) (2)
Here, q represents an arbitrary integer, and n represents the refractive index of the objective optical element in the light beam having the wavelength λ1.

請求項11に記載の光ピックアップ装置用の対物光学素子は、請求項10に記載の発明において、前記各領域のうち、光軸を含む領域において、前記光軸を含む領域とその外側の領域の間の前記境界段差の光軸方向の段差量d1が、以下の条件式を満たすことを特徴とする。 An objective optical element for an optical pickup device according to an eleventh aspect of the present invention is the optical pickup device according to the tenth aspect , wherein the region including the optical axis and the region outside the optical axis are included in the regions including the optical axis. The step amount d1 of the boundary step in the optical axis direction satisfies the following conditional expression.

0.9・(p−q)・λ1/(n−1)≦d1(nm)≦1.1・p・λ1/(n−1) (3)
但し、pは、q以上の任意の整数を示す。
0.9 · (p−q) · λ1 / (n−1) ≦ d1 (nm) ≦ 1.1 · p · λ1 / (n−1) (3)
However, p shows the arbitrary integers more than q.

請求項12に記載の光ピックアップ装置用の対物光学素子は、請求項11に記載の発明において、前記各領域のうち、光軸を含む領域において、前記光軸を含む領域とその外側の領域との前記境界段差の段差量d1が、以下の条件式を満たすことを特徴とする。 An objective optical element for an optical pickup device according to a twelfth aspect of the invention according to the eleventh aspect includes a region including the optical axis and a region outside the optical region in the region including the optical axis. The step amount d1 of the boundary step satisfies the following conditional expression.

0.9・(p−q)・λ1/(n−1)≦d1(nm)≦1.1・(p−q)・λ1/(n−1) (4)
請求項13に記載の光ピックアップ装置用の対物光学素子は、請求項11又は12に記載の発明において、前記境界段差のうち、光軸側を向いている前記境界段差の光軸方向の段差量d1‘が、全て以下の条件式を満たすことを特徴とする。
0.9 · (p−q) · λ1 / (n−1) ≦ d1 (nm) ≦ 1.1 · (p−q) · λ1 / (n−1) (4)
The objective optical element for an optical pickup device according to claim 13 is the invention according to claim 11 or 12 , wherein, of the boundary steps, the step amount in the optical axis direction of the boundary step facing the optical axis side. All of d1 ′ satisfy the following conditional expressions.

1.0・p・λ1/(n−1)≦d1‘(nm)≦2.0・(p+q)・λ1/(n−1) (5)
請求項14に記載の光ピックアップ装置用の対物光学素子は、請求項13に記載の発明において、前記境界段差のうち、光軸側を向いている前記境界段差の光軸方向の段差量d1‘が、全て以下の条件式を満たすことを特徴とする。
1.0 · p · λ1 / (n−1) ≦ d1 ′ (nm) ≦ 2.0 · (p + q) · λ1 / (n−1) (5)
The objective optical element for an optical pickup device according to a fourteenth aspect is the invention according to the thirteenth aspect , in which the step amount d1 ′ in the optical axis direction of the boundary step facing the optical axis side among the boundary steps. Satisfy all the following conditional expressions.

1.0・(p+q)・λ1/(n−1)≦d1‘(nm)≦2.0・(p+q)・λ1/(n−1) (6)
請求項15に記載の光ピックアップ装置用の対物光学素子は、請求項10乃至14のいずれかに記載の発明において、qが2又は1であることを特徴とする。
1.0 · (p + q) · λ1 / (n−1) ≦ d1 ′ (nm) ≦ 2.0 · (p + q) · λ1 / (n−1) (6)
An objective optical element for an optical pickup device according to a fifteenth aspect is characterized in that, in the invention according to any one of the tenth to fourteenth aspects, q is 2 or 1.

請求項16に記載の光ピックアップ装置用の対物光学素子は、請求項11乃至15のいずれかに記載の発明において、pが5又は4であることを特徴とする。 An objective optical element for an optical pickup device according to a sixteenth aspect is characterized in that, in the invention according to any one of the eleventh to fifteenth aspects, p is 5 or 4.

本発明の光ピックアップ装置は、波長λ1(380nm<λ1<420nm)の光束を射出する少なくとも一つの光源を有する。また、本発明の光ピックアップ装置は、当該光束を光ディスクの情報記録面上に集光させるための対物光学素子を有する集光光学系である。また、本発明の光ピックアップ装置は、光ディスクの情報記録面からの反射光束を受光する少なくとも一つの受光素子を有する。   The optical pickup device of the present invention has at least one light source that emits a light beam having a wavelength λ1 (380 nm <λ1 <420 nm). The optical pickup device of the present invention is a condensing optical system having an objective optical element for condensing the luminous flux on the information recording surface of the optical disc. Further, the optical pickup device of the present invention has at least one light receiving element for receiving a reflected light beam from the information recording surface of the optical disc.

光ピックアップ装置は、一種類の高密度光ディスクの情報の記録/再生を行う装置であってもよいし、高密度光ディスクに加えてDVDやCDなどの複数種類の光ディスクの情報の記録/再生を行う装置であってもよい。尚、本発明の光ピックアップ装置、及び、対物光学素子は、軸上色収差を良好にできるため、特に光ディスクへの記録(又は記録及び再生)を行なう光ピックアップ装置やそれに用いられる対物レンズにおいて、特に効果が顕著となる。   The optical pickup device may be a device that records / reproduces information of one type of high-density optical disc, or records / reproduces information of a plurality of types of optical discs such as DVD and CD in addition to the high-density optical disc. It may be a device. Since the optical pickup device and the objective optical element of the present invention can improve axial chromatic aberration, particularly in an optical pickup device that performs recording (or recording and reproduction) on an optical disc and an objective lens used in the optical pickup device. The effect becomes remarkable.

本発明の光ピックアップ装置、又は、対物レンズで情報の記録/再生を行う対象となる光ディスクは高密度光ディスクである事が好ましい。高密度光ディスクは、厚さがt1の保護基板と情報記録面とを有する。なお、高密度光ディスクは、複数の情報記録面を有する複数層の光ディスクでもよい。高密度光ディスクの例としては、NA0.85の対物光学素子により情報の記録/再生が行われ、保護基板の厚さが0.1mm程度である規格の光ディスク(例えば、BD:ブルーレイディスク)が挙げられる。また、高密度光ディスクには、情報記録面上に数〜数十nm程度の厚さの保護膜(本明細書では、保護基板は保護膜も含むものとする)を有する光ディスクや、保護基板の厚さが0の光ディスクも含まれる。また、高密度光ディスクには、情報の記録/再生用の光源として、青紫色半導体レーザや青紫色SHGレーザが用いられる光磁気ディスクも含まれるものとする。本発明において、高密度光ディスクはBDである事が好ましい。   The optical pickup device of the present invention or the optical disc to be recorded / reproduced with the objective lens is preferably a high-density optical disc. A high-density optical disc has a protective substrate having a thickness t1 and an information recording surface. The high-density optical disc may be a multi-layer optical disc having a plurality of information recording surfaces. As an example of a high-density optical disc, there is a standard optical disc (for example, BD: Blu-ray Disc) in which information is recorded / reproduced by an objective optical element having a NA of 0.85 and a protective substrate has a thickness of about 0.1 mm. It is done. In addition, the high-density optical disc includes an optical disc having a protective film with a thickness of about several to several tens of nanometers on the information recording surface (in this specification, the protective substrate includes the protective film), and the thickness of the protective substrate. Also included is an optical disc with 0. The high-density optical disk includes a magneto-optical disk in which a blue-violet semiconductor laser or a blue-violet SHG laser is used as a light source for recording / reproducing information. In the present invention, the high density optical disk is preferably a BD.

なお、保護基板の厚さt1に関しては、以下の条件式(7)を満たすことが好ましいが、これに限られない。   In addition, regarding the thickness t1 of the protective substrate, it is preferable to satisfy the following conditional expression (7), but is not limited thereto.

0.070mm ≦ t1 ≦ 0.105mm (7)
光ピックアップ装置が、複数種類の光ディスクの情報の記録/再生を行う装置である場合は、更に、波長λ2(630nm<λ2<680nm)の光束や、波長λ3(750nm<λ3<820nm)の光束を射出する光源を有していてもよい。
0.070 mm ≦ t1 ≦ 0.105 mm (7)
When the optical pickup device is a device for recording / reproducing information on a plurality of types of optical discs, a light beam having a wavelength λ2 (630 nm <λ2 <680 nm) or a light beam having a wavelength λ3 (750 nm <λ3 <820 nm) is further provided. You may have the light source which inject | emits.

受光素子としては、フォトダイオードなどの光検出器が好ましく用いられる。光ディスクの情報記録面上で反射した光が受光素子へ入射し、その出力信号を用いて、光ディスクに記録された情報の読み取り信号が得られる。さらに、受光素子上のスポットの形状変化や位置変化によって生じる光量変化を検出して、合焦検出やトラック検出を行い、この検出に基づいて、合焦、トラッキングのために対物光学素子を移動する。受光素子は、複数の光検出器からなっていてもよい。受光素子は、メインの光検出器とサブの光検出器を有していてもよい。例えば、情報の記録/再生に用いられるメイン光を受光する光検出器の両脇に2つのサブの光検出器を設け、当該2つのサブの光検出器によってトラッキング調整用のサブ光を受光するような受光素子としてもよい。また、受光素子は各光源に対応した複数の受光素子を有していてもよい。また、光ピックアップ装置が、複数種類の光ディスクの情報の記録/再生を行う装置である場合は、波長λ2の光束や、波長λ3の光束を受光する受光素子を有していてもよい。   As the light receiving element, a photodetector such as a photodiode is preferably used. Light reflected on the information recording surface of the optical disc enters the light receiving element, and a read signal of information recorded on the optical disc is obtained using the output signal. Further, a change in the amount of light caused by a change in the shape or position of the spot on the light receiving element is detected, and focus detection and track detection are performed. Based on this detection, the objective optical element is moved for focusing and tracking. . The light receiving element may comprise a plurality of photodetectors. The light receiving element may have a main photodetector and a sub photodetector. For example, two sub-photodetectors are provided on both sides of a photodetector that receives main light used for recording / reproducing information, and the sub-light for tracking adjustment is received by the two sub-detectors. Such a light receiving element may be used. The light receiving element may have a plurality of light receiving elements corresponding to the respective light sources. In addition, when the optical pickup device is a device that records / reproduces information on a plurality of types of optical disks, it may have a light receiving element that receives a light beam having a wavelength λ2 or a light beam having a wavelength λ3.

光ピックアップ装置の集光光学系は、対物光学素子を有する。集光光学系は、対物光学素子のみを有していても良いが、対物光学素子の他にコリメートレンズ等のカップリングレンズを有していてもよい。カップリングレンズとは、対物光学素子と光源の間に配置され、光束の発散角を変える単レンズ又はレンズ群のことをいう。コリメートレンズは、カップリングレンズの一種で、入射した光束を平行光束として射出するレンズである。更に、集光光学系は光源から射出された光束を、情報の記録/再生に用いられるメイン光束と、トラッキング調整用に用いられる二つのサブ光束とに分割する回折光学素子などの光学素子を有していてもよい。本明細書において、対物光学素子とは、光ピックアップ装置において光ディスクを装填した状態において、最も光ディスク側の位置で、光ディスクと対向する位置に配置され、光源から射出された光束を光ディスクの情報記録面上に集光する機能を有する光学素子を指す。   The condensing optical system of the optical pickup device has an objective optical element. The condensing optical system may include only the objective optical element, but may include a coupling lens such as a collimator lens in addition to the objective optical element. The coupling lens is a single lens or a lens group that is disposed between the objective optical element and the light source and changes the divergence angle of the light beam. The collimating lens is a type of coupling lens, and is a lens that emits an incident light beam as a parallel light beam. Furthermore, the condensing optical system has an optical element such as a diffractive optical element that splits the light beam emitted from the light source into a main light beam used for recording / reproducing information and two sub-light beams used for tracking adjustment. You may do it. In this specification, the objective optical element is an optical recording device that is arranged at the position closest to the optical disc in the state where the optical disc is loaded in the optical pickup device and is opposed to the optical disc. An optical element having a function of condensing on the top.

対物光学素子は、対物光学素子を通過する光束を、高密度光ディスクの情報記録面上に情報の記録/再生が出来るように集光する。本発明の対物光学素子は、好ましくは高密度光ディスク専用の単玉のプラスチックレンズである。光ピックアップ装置が、複数種類の光ディスクの情報の記録/再生を行う装置である場合は、本発明の対物光学素子の他に、波長λ2の光束及び/又は波長λ3の光束を光ディスクの情報記録面上に集光するための対物光学素子を有していてもよい。本発明の高密度光ディスク専用の対物光学素子と他の光ディスク用の対物光学素子を並列して一体化した光学素子も本発明の単玉の光学素子に含まれるものとする。対物光学素子は、屈折面が非球面であることが好ましい。また、対物光学素子は、光路差付与構造が設けられるベース面が非球面であることが好ましい。   The objective optical element condenses the light beam passing through the objective optical element so that information can be recorded / reproduced on the information recording surface of the high-density optical disk. The objective optical element of the present invention is preferably a single plastic lens dedicated to a high-density optical disc. When the optical pickup device is a device for recording / reproducing information on a plurality of types of optical discs, in addition to the objective optical element of the present invention, a light flux having a wavelength λ2 and / or a light flux having a wavelength λ3 is used as an information recording surface of the optical disc. You may have the objective optical element for condensing on. The single optical element of the present invention also includes an optical element in which the objective optical element dedicated to the high density optical disk of the present invention and the objective optical element for another optical disk are integrated in parallel. The objective optical element preferably has an aspheric refractive surface. In the objective optical element, the base surface on which the optical path difference providing structure is provided is preferably an aspherical surface.

なお、対物光学素子を形成するプラスチックは、ポリオレフィン系の樹脂である事が好ましいが、これに限られるものではない。また、波長405nmでの対物光学素子の屈折率nは、1.5以上、1.75以下であることが好ましい。   The plastic forming the objective optical element is preferably a polyolefin-based resin, but is not limited thereto. The refractive index n of the objective optical element at a wavelength of 405 nm is preferably 1.5 or more and 1.75 or less.

本発明の対物光学素子には、少なくとも1つの光学面に光路差付与構造が設けられている。光路差付与構造は、対物光学素子の光学面の面積の70%以上の領域に設けられていることが好ましく、90%以上がより好ましい。より好ましくは、光路差付与構造が、光学面の有効径内領域の全面に設けられていることである。また、光路差付与構造は、対物光学素子の光学面のうち、曲率が大きい方の光学面に設けられていることが好ましい。   In the objective optical element of the present invention, an optical path difference providing structure is provided on at least one optical surface. The optical path difference providing structure is preferably provided in a region of 70% or more of the area of the optical surface of the objective optical element, and more preferably 90% or more. More preferably, the optical path difference providing structure is provided on the entire surface of the effective diameter area of the optical surface. Moreover, it is preferable that the optical path difference providing structure is provided on the optical surface having the larger curvature among the optical surfaces of the objective optical element.

本明細書でいう光路差付与構造は、入射光束に対して光路差を付加する構造の総称である。一般に、光路差付与構造には、位相差を付与する位相差付与構造も含まれる。また、位相差付与構造には広義の回折構造が含まれる。ここでいう広義の回折構造とは、回折構造を通過した光束が回折作用によって発散又は収束される構造をいう。光路差付与構造は、段差を有し、好ましくは段差を複数有する。この段差により入射光束に光路差及び/又は位相差が付加される。NPS構造も光路差付与構造の一種と捉えることができ、また、広義の回折構造の一種と捉える事もできる。   The optical path difference providing structure referred to in this specification is a general term for structures that add an optical path difference to an incident light beam. In general, the optical path difference providing structure includes a phase difference providing structure for providing a phase difference. Further, the phase difference providing structure includes a diffractive structure in a broad sense. The diffractive structure in a broad sense here refers to a structure in which a light beam that has passed through the diffractive structure is diverged or converged by a diffraction action. The optical path difference providing structure has a step, preferably a plurality of steps. This step adds an optical path difference and / or phase difference to the incident light flux. The NPS structure can also be regarded as a kind of optical path difference providing structure, and can also be regarded as a kind of diffractive structure in a broad sense.

本発明の光路差付与構造は、NPS構造と狭義の回折構造を重ね合わせた構造である。(明細書の以降の記載において「回折構造」という場合、広義の回折構造と明記しない場合は、基本的に狭義の回折構造を表すものとする。)ここで、本明細書でいうNPS構造と回折構造の効果について、図1を用いて説明する。図1の横軸は対物光学素子の入射瞳における入射高さhを示し、縦軸は光軸を通過する光線と入射高さhを通過する光線との光路差を示している。曲線と横軸とで囲まれた部分の面積を収差の量と捉える事ができる。対物光学素子に入射する光束の波長x、環境温度25℃において、非球面の屈折面のみを有し、光軸を通過する光線といずれの入射高さhを通過する光線との光路差が0である(即ち横軸に重なる直線)対物光学素子を基準として考える。当該非球面の対物光学素子では、環境温度を、例えば55℃とした際には、ASで示されるように、光軸を通過する光線と入射高さhを通過する光線とでは光路差が生じ、ASと横軸で囲まれた面積に相当する収差が発生する。次に、当該非球面の対物光学素子に、波長xに最適化した輪帯状の段差構造Xを複数設ける。環境温度を55℃とし、波長xが当該段差構造Xを有する対物光学素子に入射した際に、曲線ASから全体的に横軸に近づいた滑らかな曲線DSとなる場合、当該段差構造Xは、本明細書でいう回折構造である。回折構造を設けることにより、光路差を示す曲線が全体的に横軸に近づくため、曲線と横軸で囲まれる面積が減少し、温度変化により生じる収差が減っている事が分かる。次に、前述の非球面の対物光学素子に、波長xに最適化した、前述とは異なる複数の輪帯状の段差構造Yを設ける。環境温度を55℃とし、波長xが当該段差構造Yを有する光学素子に入射した際に、曲線ASから不連続部を有する断続的なNPSで示す曲線となる場合、当該段差構造Yは、本明細書でいうNPS構造である。尚、NPS構造と回折構造とを組み合わせた場合、図1でNPS+DSで示す曲線となり、ハッチングで示すような面積に相当する収差となる。
表1を用いて、回折構造とNPS構造とを重ね合わせた光路差付与構造を設けた対物光学素子の特徴について説明する。温度が設計温度から+30℃変化した状態をA状態、波長が設計波長から+5nm変化した状態をB状態とすると、非球面形状の対物光学素子(以下、非球面レンズ)と回折構造を設けた対物光学素子(以下、回折レンズ)において、A状態での球面収差発生量を2つのレンズで同じにしたとき、表1のようにB状態で発生する球面収差量はそれぞれ異なり、回折レンズの方が多くなる。一方、温度特性(温度変化による収差劣化)が向上するNPS構造をそれぞれの対物光学素子に設けることで、A状態とB状態のどちらの状態でもアンダー(補正不足)となる方向に球面収差は変化する。球面収差の変化量はNSP構造の段差による位相シフト量で決定され、後述する実施例1の材料においては、NPS構造の一つの段差により、B状態の位相シフト量はA状態の3倍程度となり、B状態の方が球面収差はアンダー方向に過剰に補正される。表1のように、非球面レンズと回折レンズにNPS構造を付加することで、ともにA状態では−0.027λ、B状態では−0.162λ変化する。NPS構造の段差による位相シフト量で球面収差の変化量は変わるが、A状態とB状態の変化比率はほぼ同じとなる。非球面レンズと回折レンズにNPS構造を付加したとき、回折レンズにNPS構造を重ね合わせた方がB状態での球面収差発生量の絶対量は小さくなっているが、これはNPS構造を付加する前のB状態において、非球面レンズよりも回折レンズの方がオーバー方向(補正過剰)に大きいためである。以上のことから、回折構造とNPS構造とを重ね合わせた構造を設けた対物光学素子では波長特性(入射光束の波長変化による収差劣化)は良好となる。
The optical path difference providing structure of the present invention is a structure in which an NPS structure and a narrowly defined diffraction structure are overlapped. (In the following description of the specification, “diffractive structure” refers to a diffractive structure in a narrow sense unless otherwise specified as a diffractive structure in a broad sense.) Here, the NPS structure referred to in this specification and The effect of the diffractive structure will be described with reference to FIG. The horizontal axis of FIG. 1 indicates the incident height h at the entrance pupil of the objective optical element, and the vertical axis indicates the optical path difference between the light beam passing through the optical axis and the light beam passing through the incident height h. The area surrounded by the curve and the horizontal axis can be regarded as the amount of aberration. At the wavelength x of the light beam incident on the objective optical element and the environmental temperature of 25 ° C., the optical path difference between the light beam having only an aspherical refracting surface and passing through the optical axis and the light beam passing through any incident height h is 0. (Ie, a straight line overlapping the horizontal axis) is considered as a reference. In the aspheric objective optical element, when the environmental temperature is 55 ° C., for example, an optical path difference occurs between the light beam passing through the optical axis and the light beam passing through the incident height h as shown by AS. Aberration corresponding to the area surrounded by AS and the horizontal axis occurs. Next, a plurality of annular zone step structures X optimized for the wavelength x are provided on the aspheric objective optical element. When the ambient temperature is 55 ° C. and the wavelength x is incident on the objective optical element having the step structure X, when the curve DS becomes a smooth curve DS that approaches the horizontal axis as a whole, the step structure X is It is a diffractive structure as used in this specification. By providing the diffractive structure, since the curve indicating the optical path difference approaches the horizontal axis as a whole, the area surrounded by the curve and the horizontal axis is reduced, and it can be seen that the aberration caused by the temperature change is reduced. Next, a plurality of annular zone step structures Y different from those described above, which are optimized for the wavelength x, are provided on the aspheric objective optical element described above. When the ambient temperature is 55 ° C. and the wavelength x is incident on the optical element having the step structure Y, when the curve AS is a curve indicated by intermittent NPS having discontinuous portions, the step structure Y is It is an NPS structure as used in the specification. When the NPS structure and the diffractive structure are combined, a curve indicated by NPS + DS in FIG. 1 is obtained, and an aberration corresponding to the area indicated by hatching is obtained.
The characteristics of the objective optical element provided with the optical path difference providing structure obtained by superimposing the diffraction structure and the NPS structure will be described with reference to Table 1. When the temperature is changed from the design temperature by + 30 ° C. to the A state, and the wavelength is changed from the design wavelength by +5 nm to the B state, the objective optical element having an aspherical shape (hereinafter referred to as an aspherical lens) and a diffractive structure is provided. In an optical element (hereinafter referred to as a diffractive lens), when the amount of spherical aberration generated in the A state is the same for the two lenses, the amount of spherical aberration generated in the B state is different as shown in Table 1, and the diffractive lens is different. Become more. On the other hand, by providing each objective optical element with an NPS structure that improves temperature characteristics (aberration degradation due to temperature change), spherical aberration changes in the direction of under (undercorrection) in either state A or B. To do. The amount of change in spherical aberration is determined by the amount of phase shift due to the step of the NSP structure. In the material of Example 1 described later, the phase shift amount of the B state is about three times that of the A state due to one step of the NPS structure. In the B state, spherical aberration is excessively corrected in the under direction. As shown in Table 1, when an NPS structure is added to the aspherical lens and the diffractive lens, both change by −0.027λ in the A state and −0.162λ in the B state. Although the amount of change in spherical aberration varies with the amount of phase shift due to the level difference of the NPS structure, the change ratio between the A state and the B state is substantially the same. When the NPS structure is added to the aspherical lens and the diffractive lens, the absolute amount of the spherical aberration generated in the B state is smaller when the NPS structure is superimposed on the diffractive lens, but this adds the NPS structure. This is because, in the previous B state, the diffractive lens is larger in the over direction (overcorrection) than the aspherical lens. From the above, the objective optical element provided with a structure in which the diffractive structure and the NPS structure are overlapped has good wavelength characteristics (aberration deterioration due to wavelength change of incident light beam).

更に、NPS構造と回折構造とを、同一の光学面に設けられることにより、製造時の偏芯誤差を少なくすることが可能となる。また、光路差付与構造は、対物光学素子の光ディスク側の面よりも、対物光学素子の光源側の面に設けられることが好ましい。即ち、光路差付与構造は、対物光学素子の対向する2つの光学面において、曲率半径がより小さい方の光学面に設けられることが好ましい。光源側の面においては、入射する光の入射角は比較的小さくなる。そうすると、回折構造における光学面でない面に光が入射することによる光量損が少ないからである。   Furthermore, by providing the NPS structure and the diffractive structure on the same optical surface, it is possible to reduce the eccentricity error during manufacturing. The optical path difference providing structure is preferably provided on the light source side surface of the objective optical element rather than the surface of the objective optical element on the optical disk side. That is, it is preferable that the optical path difference providing structure is provided on an optical surface having a smaller radius of curvature in two optical surfaces facing each other of the objective optical element. On the light source side surface, the incident angle of incident light is relatively small. This is because there is little loss of light amount due to light entering a surface that is not an optical surface in the diffractive structure.

NPS構造は、NPS構造を通過した光束のp次の回折光量を他のいかなる次数の回折光量よりも大きくする構造であり、回折構造は、回折構造を通過した光束のq次の回折光量を他のいかなる次数の回折光量よりも大きくする構造であって、以下の条件式を満たすことが好ましい。   The NPS structure is a structure in which the p-order diffracted light amount of the light beam that has passed through the NPS structure is made larger than any other order diffracted light amount. It is preferable that the diffracted light quantity of any order is greater than the order, and the following conditional expression is satisfied.

p≧q (1)
尚、pは5又は4である事が好ましい。pを5又は4とすることで、環境温度変化時、及び/または、波長変化時に、NPS構造で生じる回折効率変化を小さく抑えることができるとともに、一方で、NPS構造の輪帯のピッチが細かくなりすぎる事も抑えられ、製造しやすい対物光学素子となるため好ましい。また、qは2又は1である事が好ましい。特に、(p、q)=(5,2)又は(4,2)であると回折効率が高まるので好ましい。
p ≧ q (1)
Note that p is preferably 5 or 4. By setting p to 5 or 4, it is possible to suppress a change in diffraction efficiency that occurs in the NPS structure when the environmental temperature changes and / or when the wavelength changes, and on the other hand, the ring pitch of the NPS structure is fine. It is preferable because it becomes an objective optical element that can be easily manufactured and can be suppressed. Further, q is preferably 2 or 1. In particular, (p, q) = (5, 2) or (4, 2) is preferable because the diffraction efficiency is increased.

回折構造の段差の光軸方向の段差量が、NPS構造の段差量よりも小さい事が好ましい。また、NPS構造の光軸方向における各々の段差量は、0.9・p・λ1/(n−1)以上、2.0・p・λ1/(n−1)以下を満たす事が好ましい。また、回折構造の全ての段差量は、0.9・q・λ1/(n−1)以上、2.0・q・λ1/(n−1)以下であることが好ましい。特に、NPS構造の段差量は、NA0.45以内において、0.9・p・λ1/(n−1)以上、1.1・p・λ1/(n−1)以下を満たす事が好ましい。また、回折構造の段差量は、NA0.45以内において、0.9・q・λ1/(n−1)以上、1.1・q・λ1/(n−1)以下であることが好ましい。   It is preferable that the step amount in the optical axis direction of the step of the diffractive structure is smaller than the step amount of the NPS structure. Moreover, it is preferable that each step amount in the optical axis direction of the NPS structure satisfies 0.9 · p · λ1 / (n−1) or more and 2.0 · p · λ1 / (n−1) or less. Moreover, it is preferable that all the steps of the diffractive structure are 0.9 · q · λ1 / (n-1) or more and 2.0 · q · λ1 / (n-1) or less. In particular, the step amount of the NPS structure preferably satisfies 0.9 · p · λ1 / (n−1) or more and 1.1 · p · λ1 / (n−1) or less within NA of 0.45. Further, the step height of the diffractive structure is preferably 0.9 · q · λ1 / (n-1) or more and 1.1 · q · λ1 / (n-1) or less within NA of 0.45.

NPS構造と回折構造を重ね合わせた光路差付与構造の全ての段差量は、以下の条件式(8)〜(11)に示すdA、dB、dC、dDの少なくとも3つからなることが好ましい。特に好ましくは、全ての段差量が、dA、dC、dDの3つのみからなることである。NPS構造の段差の位置が回折構造の段差の位置と一致する様に、NPS構造と回折構造とを重ねる事により、本構成が達成できる。   It is preferable that all the steps in the optical path difference providing structure in which the NPS structure and the diffractive structure are overlapped consist of at least three of dA, dB, dC, and dD shown in the following conditional expressions (8) to (11). Particularly preferably, all the steps are composed of only three of dA, dC, and dD. This configuration can be achieved by overlapping the NPS structure and the diffractive structure so that the position of the step of the NPS structure coincides with the position of the step of the diffractive structure.

0.9・q・λ1/(n−1)≦dA≦2.0・q・λ1/(n−1) (8)
0.9・p・λ1/(n−1)≦dB≦2.0・p・λ1/(n−1) (9)
0.9・(p−q)・λ1/(n−1)≦dC≦2.0・(p−q)・λ1/(n−1) (10)
0.9・(p+q)・λ1/(n−1)≦dD≦2.0・(p+q)・λ1/(n−1) (11)
但し、nはλ1の光束における対物光学素子の屈折率を示す。
0.9 · q · λ1 / (n-1) ≦ dA ≦ 2.0 · q · λ1 / (n-1) (8)
0.9 · p · λ1 / (n−1) ≦ dB ≦ 2.0 · p · λ1 / (n−1) (9)
0.9 · (p−q) · λ1 / (n−1) ≦ dC ≦ 2.0 · (pq) · λ1 / (n−1) (10)
0.9 · (p + q) · λ1 / (n−1) ≦ dD ≦ 2.0 · (p + q) · λ1 / (n−1) (11)
However, n shows the refractive index of the objective optical element in the light beam of λ1.

また、光路差付与構造の段差量は、NA0.45以内において全ての段差量が、以下の条件式(12)〜(15)に示す、dA‘、dB’、dC‘、dD’の少なくとも2つからなることが好ましい。特に好ましくは、NA0.45以内において全ての段差量がdA‘、dC’の2つのみからなることである。   Further, the level difference of the optical path difference providing structure is such that all level differences within NA of 0.45 are at least two of dA ′, dB ′, dC ′, and dD ′ shown in the following conditional expressions (12) to (15). Preferably it consists of one. Particularly preferably, all the step amounts are only two of dA ′ and dC ′ within NA of 0.45.

0.9・q・λ1/(n−1)≦dA‘≦1.1・q・λ1/(n−1) (12)
0.9・p・λ1/(n−1)≦dB‘≦1.1・p・λ1/(n−1) (13)
0.9・(p−q)・λ1/(n−1)≦dC‘≦1.1・(p−q)・λ1/(n−1) (14)
0.9・(p+q)・λ1/(n−1)≦dD‘≦1.1・(p+q)・λ1/(n−1) (15)
例えば、p=5のNPS構造と、q=2の回折構造を重ね合わせた光路差付与構造である場合、光路差付与構造の全ての段差量が、以下の条件式(16)〜(19)に示すdA、dB、dC、dDの少なくとも3つからなる事が好ましい。特に好ましくは、全ての段差量がdA、dC及びdDのみからなるような光路差付与構造とする事である。
0.9 · q · λ1 / (n−1) ≦ dA ′ ≦ 1.1 · q · λ1 / (n−1) (12)
0.9 · p · λ1 / (n−1) ≦ dB ′ ≦ 1.1 · p · λ1 / (n−1) (13)
0.9 · (p−q) · λ1 / (n−1) ≦ dC ′ ≦ 1.1 · (p−q) · λ1 / (n−1) (14)
0.9 · (p + q) · λ1 / (n−1) ≦ dD ′ ≦ 1.1 · (p + q) · λ1 / (n−1) (15)
For example, in the case of an optical path difference providing structure in which an NPS structure with p = 5 and a diffraction structure with q = 2 are overlapped, all the step amounts of the optical path difference providing structure are expressed by the following conditional expressions (16) to (19). It is preferable to consist of at least three of dA, dB, dC and dD shown in FIG. Particularly preferred is an optical path difference providing structure in which all the steps are composed only of dA, dC and dD.

0.9・2・λ1/(n−1)≦dA≦2.0・2・λ1/(n−1) (16)
0.9・5・λ1/(n−1)≦dB≦2.0・5・λ1/(n−1) (17)
0.9・(5−2)・λ1/(n−1)≦dC≦2.0・(5−2)・λ1/(n−1) (18)
0.9・(5+2)・λ1/(n−1)≦dD≦2.0・(5+2)・λ1/(n−1) (19)
また、p=5のNPS構造と、q=2の回折構造を重ね合わせた光路差付与構造である場合、その段差量は、NA0.45以内において、以下の条件式(20)〜(22)に示すdA‘、dB’、dC‘、dD’の少なくとも2つからなることが好ましい。特に好ましくは、NPS構造と回折構造の段差位置を合わせる事によって、NA0.45以内における光路差付与構造の全ての段差量がdA‘及びdC’のみからなるような光路差付与構造とする事である。
0.9 · 2 · λ1 / (n−1) ≦ dA ≦ 2.0 · 2 · λ1 / (n−1) (16)
0.9 · 5 · λ1 / (n−1) ≦ dB ≦ 2.0 · 5 · λ1 / (n−1) (17)
0.9 · (5-2) · λ1 / (n−1) ≦ dC ≦ 2.0 · (5-2) · λ1 / (n−1) (18)
0.9 · (5 + 2) · λ1 / (n−1) ≦ dD ≦ 2.0 · (5 + 2) · λ1 / (n−1) (19)
In addition, in the case of an optical path difference providing structure in which an NPS structure with p = 5 and a diffraction structure with q = 2 are overlapped, the level difference is within the condition of NA 0.45, and the following conditional expressions (20) to (22) It is preferably composed of at least two of dA ′, dB ′, dC ′, and dD ′ shown in FIG. Particularly preferably, by aligning the step positions of the NPS structure and the diffractive structure, an optical path difference providing structure in which all the steps of the optical path difference providing structure within NA 0.45 are composed only of dA ′ and dC ′. is there.

0.9・2・λ1/(n−1)≦dA‘≦1.1・2・λ1/(n−1) (20)
0.9・5・λ1/(n−1)≦dB‘≦1.1・5・λ1/(n−1) (21)
0.9・(5−2)・λ1/(n−1)≦dC‘≦1.1・(5−2)・λ1/(n−1) (22)
0.9・(5+2)・λ1/(n−1)≦dD‘≦1.1・(5+2)・λ1/(n−1) (23)
従って、p=5、q=2の場合は、NA0.45以内において、2種類の段差量のみを有することが好ましいといえる。
0.9 · 2 · λ1 / (n−1) ≦ dA ′ ≦ 1.1 · 2 · λ1 / (n−1) (20)
0.9 · 5 · λ1 / (n−1) ≦ dB ′ ≦ 1.1 · 5 · λ1 / (n−1) (21)
0.9 · (5-2) · λ1 / (n−1) ≦ dC ′ ≦ 1.1 · (5-2) · λ1 / (n−1) (22)
0.9 · (5 + 2) · λ1 / (n−1) ≦ dD ′ ≦ 1.1 · (5 + 2) · λ1 / (n−1) (23)
Therefore, in the case of p = 5 and q = 2, it can be said that it is preferable to have only two kinds of steps within NA 0.45.

また、p=4のNPS構造と、q=2の回折構造を重ね合わせた光路差付与構造である場合、光路差付与構造の全ての段差量が、以下の条件式(24)〜(27)に示すdA、dB、dC、dDの少なくとも3つからなる事が好ましい。特に好ましくは、全ての段差量がdA、dC及びdDのみからなるような光路差付与構造とする事である。但し、dAとdCは実質的に等しくなる。   Further, in the case of an optical path difference providing structure in which an NPS structure with p = 4 and a diffraction structure with q = 2 are overlapped, all the step amounts of the optical path difference providing structure are expressed by the following conditional expressions (24) to (27). It is preferable to consist of at least three of dA, dB, dC and dD shown in FIG. Particularly preferred is an optical path difference providing structure in which all the steps are composed only of dA, dC and dD. However, dA and dC are substantially equal.

0.9・2・λ1/(n−1)≦dA≦2.0・2・λ1/(n−1) (24)
0.9・4・λ1/(n−1)≦dB≦2.0・4・λ1/(n−1) (25)
0.9・(4−2)・λ1/(n−1)≦dC≦2.0・(4−2)・λ1/(n−1) (26)
0.9・(4+2)・λ1/(n−1)≦dD≦2.0・(4+2)・λ1/(n−1) (27)
また、p=4のNPS構造と、q=2の回折構造を重ね合わせた光路差付与構造である場合、その段差量は、NA0.45以内において全ての段差量が、以下の条件式(28)〜(31)に示すdA‘、dB’、dC‘、dD’の少なくとも2つからなることが好ましい。特に好ましくは、NPS構造と回折構造の段差位置を合わせる事によって、NA0.45以内における光路差付与構造の全ての段差量がdA‘及びdC’のみからなるような光路差付与構造、即ち、段差量が実質1種類のみである光路差付与構造とする事である。
0.9 · 2 · λ1 / (n−1) ≦ dA ≦ 2.0 · 2 · λ1 / (n−1) (24)
0.9 · 4 · λ1 / (n−1) ≦ dB ≦ 2.0 · 4 · λ1 / (n−1) (25)
0.9 · (4-2) · λ1 / (n−1) ≦ dC ≦ 2.0 · (4-2) · λ1 / (n−1) (26)
0.9 · (4 + 2) · λ1 / (n−1) ≦ dD ≦ 2.0 · (4 + 2) · λ1 / (n−1) (27)
Further, in the case of an optical path difference providing structure in which an NPS structure with p = 4 and a diffraction structure with q = 2 are overlapped, the level difference is within the range of NA 0.45, and all level differences are equal to the following conditional expression (28 ) To (31), and preferably comprises at least two of dA ′, dB ′, dC ′, and dD ′. Particularly preferably, by aligning the step positions of the NPS structure and the diffractive structure, the optical path difference providing structure in which all the step amounts of the optical path difference providing structure within NA 0.45 are composed only of dA ′ and dC ′, ie, the step The optical path difference providing structure has only one kind of amount.

0.9・2・λ1/(n−1)≦dA‘≦1.1・2・λ1/(n−1) (28)
0.9・4・λ1/(n−1)≦dB‘≦1.1・4・λ1/(n−1) (29)
0.9・(4−2)・λ1/(n−1)≦dC‘≦1.1・(4−2)・λ1/(n−1) (30)
0.9・(4+2)・λ1/(n−1)≦dD‘≦1.1・(4+2)・λ1/(n−1) (31)
従って、p=4、q=2の場合は、NA0.45以内において、1種類の段差量のみを有することが好ましいといえる。
0.9 · 2 · λ1 / (n−1) ≦ dA ′ ≦ 1.1 · 2 · λ1 / (n−1) (28)
0.9 · 4 · λ1 / (n−1) ≦ dB ′ ≦ 1.1 · 4 · λ1 / (n−1) (29)
0.9 · (4-2) · λ1 / (n−1) ≦ dC ′ ≦ 1.1 · (4-2) · λ1 / (n−1) (30)
0.9 · (4 + 2) · λ1 / (n−1) ≦ dD ′ ≦ 1.1 · (4 + 2) · λ1 / (n−1) (31)
Therefore, in the case of p = 4 and q = 2, it can be said that it is preferable to have only one type of step amount within NA 0.45.

また、NPS構造と回折構造とを重ね合わせた光路差付与構造を、形状の観点から、以下の様に捉える事もできる。   Further, the optical path difference providing structure in which the NPS structure and the diffractive structure are superposed can be grasped as follows from the viewpoint of the shape.

即ち、対物光学素子の光学面が、同心円状の複数の境界段差で区切られた複数の領域に分けられており、境界段差で区切られた各領域が、同心円状の複数の領域内段差を有している、という捉え方である。ここでいう境界段差が、前述のNPS構造の段差のことであり、領域内段差は、回折構造の段差のことである。尚、境界段差は、NPS構造の段差と回折構造の段差が重なっている場合もあり得る。   In other words, the optical surface of the objective optical element is divided into a plurality of regions divided by a plurality of concentric boundary steps, and each region divided by the boundary steps has a plurality of concentric in-region steps. It is a way of thinking that it is doing. The boundary step here is a step of the above-mentioned NPS structure, and the in-region step is a step of the diffractive structure. Note that the boundary step may be the case where the step of the NPS structure and the step of the diffraction structure overlap.

なお、各領域のうち、光軸に近い側の領域では境界段差が光軸とは逆側を向いており、光軸から離れた側の領域では前記境界段差が光軸側を向いていることが好ましい。本明細書において「境界段差が光軸とは逆側を向いている」とは、図2における1,2,3のように、段差を構成する面が光軸とは逆の方向(矢印方向)を向いていることをいう。また、「境界段差が光軸側を向いている」とは、図2における4,5,6のように、段差を構成する面が光軸の方向(矢印方向)を向いていることをいう。即ち、NPS構造は、図2に示すような構造である事が好ましい。また、光軸とは逆側を向いている段差の数と、光軸側を向いている段差の数とが等しい事が好ましい。   In each region, the boundary step is facing away from the optical axis in the region near the optical axis, and the boundary step is facing the optical axis in the region away from the optical axis. Is preferred. In this specification, “the boundary step is facing the opposite side of the optical axis” means that the surface constituting the step is the direction opposite to the optical axis (in the direction of the arrow) as shown in FIGS. ). Further, “the boundary step faces the optical axis side” means that the surface constituting the step faces the direction of the optical axis (arrow direction) as in FIGS. . That is, the NPS structure is preferably a structure as shown in FIG. Moreover, it is preferable that the number of steps facing the opposite side of the optical axis is equal to the number of steps facing the optical axis.

また、領域内段差は、全て光軸側を向いていることが好ましい。即ち、回折構造は、図3に示すような構造である事が好ましい。   Moreover, it is preferable that all the steps in the region face the optical axis side. That is, the diffractive structure is preferably a structure as shown in FIG.

従って、NPS構造と回折構造とを重ね合わせた光路差付与構造は、一例として、図4に示す様に、同心円状の複数の境界段差A,B,C,D,E、Fで区切られた複数の領域10,11,12,13,14,15,16に分けられており、境界段差A,B,C,D、E、Fで区切られた各領域10,11,12,13,14,15,16は、同心円状の複数の領域内段差a〜nを有している、という捉え方ができる。
また、各領域においては、境界段差の段差量は、領域内段差の段差量よりも大きいことが好ましい。
Therefore, the optical path difference providing structure in which the NPS structure and the diffractive structure are overlapped, as an example, is divided by a plurality of concentric boundary steps A, B, C, D, E, and F as shown in FIG. It is divided into a plurality of regions 10, 11, 12, 13, 14, 15, 16 and each region 10, 11, 12, 13, 14 divided by boundary steps A, B, C, D, E, F. , 15, 16 can be understood as having a plurality of concentric in-region steps a to n.
Further, in each region, the step amount of the boundary step is preferably larger than the step amount of the in-region step.

境界段差で区切られた各領域のうち、光軸を含む領域において(例えば、図4における領域16)、領域内段差(例えば、図4におけるm,n)の全ての段差量d2が、以下の条件式(2)を満たすことが好ましい。   Among the regions divided by the boundary step, in the region including the optical axis (for example, the region 16 in FIG. 4), all the step amounts d2 of the in-region steps (for example, m and n in FIG. 4) are as follows: It is preferable to satisfy conditional expression (2).

0.9・q・λ1/(n−1)≦d2(nm)≦1.1・q・λ1/(n−1) (2)
但し、qは、任意の整数を示し、nは、波長λ1の光束における対物光学素子の屈折率を示す。より好ましくは、qは、前述した様に、回折構造が、回折構造を通過した光束のq次の回折光量を他のいかなる次数の回折光量よりも大きくする構造であるとしたときのq次のqである事が好ましい。
0.9 · q · λ1 / (n−1) ≦ d2 (nm) ≦ 1.1 · q · λ1 / (n−1) (2)
Here, q represents an arbitrary integer, and n represents the refractive index of the objective optical element in the light flux having the wavelength λ1. More preferably, as described above, q is a q-th order when the diffractive structure is a structure that makes the q-order diffracted light quantity of the light beam that has passed through the diffractive structure larger than any other order diffracted light quantity. q is preferred.

また、各領域のうち、光軸を含む領域(例えば、図4における16)において、光軸を含む領域とその外側の領域(例えば、図4における15)の間の境界段差(例えば、図4におけるF)の段差量d1が、以下の条件式(3)を満たすことが好ましい。   In each region, in a region including the optical axis (for example, 16 in FIG. 4), a boundary step (for example, FIG. 4) between the region including the optical axis and the outer region (for example, 15 in FIG. 4). It is preferable that the step amount d1 of F) satisfies the following conditional expression (3).

0.9・(p−q)・λ1/(n−1)≦d1(nm)≦1.1・p・λ1/(n−1) (3)
但し、pは、q以上の任意の整数を示す。より好ましくは、pは、前述した様に、NPS構造が、NPS構造を通過した光束のp次の回折光量を他のいかなる次数の回折光量よりも大きくする構造であるとしたときのp次のpである事が好ましい。
0.9 · (p−q) · λ1 / (n−1) ≦ d1 (nm) ≦ 1.1 · p · λ1 / (n−1) (3)
However, p shows the arbitrary integers more than q. More preferably, as described above, p is a p-th order when the NPS structure is a structure in which the p-order diffracted light amount of the light beam that has passed through the NPS structure is larger than any other order diffracted light amount. p is preferred.

また、各領域のうち、光軸を含む領域において、光軸を含む領域とその外側の領域の間の境界段差の段差量d1が、以下の条件式(4)を満たすことが好ましい。   In each region including the optical axis, it is preferable that the step amount d1 of the boundary step between the region including the optical axis and the region outside thereof satisfies the following conditional expression (4).

0.9・(p−q)・λ1/(n−1)≦d1(nm)≦1.1・(p−q)・λ1/(n−1) (4)
また、境界段差のうち、光軸側を向いている全ての境界段差(例えば、図4におけるA,B,C)の光軸方向の段差量d1‘が、全て以下の条件式(5)を満たすことが好ましい。
0.9 · (p−q) · λ1 / (n−1) ≦ d1 (nm) ≦ 1.1 · (p−q) · λ1 / (n−1) (4)
Further, among the boundary steps, all the step amounts d1 ′ in the optical axis direction of all the boundary steps (for example, A, B, C in FIG. 4) facing the optical axis side all satisfy the following conditional expression (5). It is preferable to satisfy.

1.0・p・λ1/(n−1)≦d1‘(nm)≦2.0・(p+q)・λ1/(n−1) (5)
更に好ましくは、境界段差のうち、光軸側を向いている全ての境界段差の光軸方向の段差量d1‘が、全て以下の条件式(6)を満たすことが好ましい。
1.0 · p · λ1 / (n−1) ≦ d1 ′ (nm) ≦ 2.0 · (p + q) · λ1 / (n−1) (5)
More preferably, all the step heights d1 ′ in the optical axis direction of all the boundary steps facing the optical axis side among the boundary steps satisfy all of the following conditional expression (6).

1.0・(p+q)・λ1/(n−1)≦d1‘(nm)≦2.0・(p+q)・λ1/(n−1) (6)
尚、pとqは、前述のpとqと同様に、pが5又は4であり、qが2又は1であることが特に好ましいが、これに限られるものではない。
1.0 · (p + q) · λ1 / (n−1) ≦ d1 ′ (nm) ≦ 2.0 · (p + q) · λ1 / (n−1) (6)
In addition, as for p and q, it is especially preferable that p is 5 or 4 and q is 2 or 1 like the above-mentioned p and q, However, it is not restricted to this.

NPS構造と回折構造とを重ね合わせた光路差付与構造の設計方法としては、例えば、以下の様に設計することができる。まず、NPS構造の回折次数であるpを決め、そして、光学面をいくつの領域に分割するかを決めた後、非球面係数を用いた非球面の式に基づいて、NPS構造を設計することができる。次に、回折構造の回折次数であるqを決め、NPS構造の各領域において、位相差関数を用いて回折構造を設計することにより、NPS構造と回折構造が重ね合わせた光路差付与構造を得ることができる。位相差関数に基づいて回折構造を設計するので、位相差関数の位相差がm・2π毎(mは整数)に回折構造のピッチが対応するように設定される。この事により、回折構造のピッチは周期的であると捉えることができる。但し、NPS構造の各領域において光路差関数を用いて回折構造を設計する際に、NPS構造の段差(境界段差)と、各領域における回折構造の最も外側の段差の位置とが一致するように回折構造やNPS構造のピッチを若干ずらすなどの微調整を行うことも可能である。なお、本発明の光学素子の設計方法は上記に限定されるものではなく、結果として本発明の光学素子を得られればよく、いかなる設計方法であっても用いることが可能である。   As a design method of the optical path difference providing structure in which the NPS structure and the diffractive structure are superposed, for example, the design can be performed as follows. First, p, which is the diffraction order of the NPS structure, is determined, and after determining how many regions the optical surface is divided into, the NPS structure is designed based on the aspherical expression using the aspheric coefficient. Can do. Next, the diffraction order q of the diffractive structure is determined, and the diffractive structure is designed using a phase difference function in each region of the NPS structure, thereby obtaining an optical path difference providing structure in which the NPS structure and the diffractive structure are superimposed. be able to. Since the diffractive structure is designed based on the phase difference function, the phase difference of the phase difference function is set so that the pitch of the diffractive structure corresponds to every m · 2π (m is an integer). Accordingly, it can be understood that the pitch of the diffractive structure is periodic. However, when designing the diffractive structure using the optical path difference function in each region of the NPS structure, the step (boundary step) of the NPS structure and the position of the outermost step of the diffractive structure in each region match. It is also possible to perform fine adjustment such as slightly shifting the pitch of the diffractive structure or the NPS structure. In addition, the design method of the optical element of the present invention is not limited to the above, and any optical design method may be used as long as the optical element of the present invention can be obtained as a result.

尚、光路差付与構造は、一般的に光軸を中心とする同心円状の複数の輪帯からなることが好ましい。また、光路差付与構造は、様々な断面形状(光軸を含む面での断面形状)をとり得る。好ましくは、図4に示すような形状である。   In addition, it is preferable that the optical path difference providing structure is generally composed of a plurality of concentric ring zones centered on the optical axis. In addition, the optical path difference providing structure can have various cross-sectional shapes (cross-sectional shapes in a plane including the optical axis). Preferably, the shape is as shown in FIG.

高密度光ディスクに対して情報の記録/再生のために必要な開口数をNA1とする。NA1は、0.8以上、0.9以下であることが好ましい。したがって、対物光学素子の像側開口数(NA)も、0.8以上、0.9以下であることが好ましい。   The numerical aperture necessary for recording / reproducing information with respect to the high-density optical disk is NA1. NA1 is preferably 0.8 or more and 0.9 or less. Therefore, the image-side numerical aperture (NA) of the objective optical element is preferably 0.8 or more and 0.9 or less.

また、対物光学素子は、以下の式(32)を満たす場合に、良好な軸上色収差を得ることができるという本発明の効果がより重要となる。
0.88 ≦ f(mm) ≦ 2.35 (32)
fは、波長λ1の光束における対物光学素子の焦点距離を指す。
また、対物光学素子は、以下の式(33)を満たす場合に、ワーキングディスタンスを十分確保し、かつ、温度特性が良好であるという本発明の効果がより重要となる。
0.7 ≦ d/f ≦ 1.5 (33)
dは、対物光学素子の光軸上の厚さ(mm)を指す。
Further, when the objective optical element satisfies the following expression (32), the effect of the present invention that a good axial chromatic aberration can be obtained becomes more important.
0.88 ≦ f (mm) ≦ 2.35 (32)
f indicates the focal length of the objective optical element in the light beam having the wavelength λ1.
Further, when the objective optical element satisfies the following expression (33), the effect of the present invention that a sufficient working distance is ensured and the temperature characteristics are good becomes more important.
0.7 ≦ d / f ≦ 1.5 (33)
d indicates the thickness (mm) on the optical axis of the objective optical element.

また、対物光学素子は、以下の式(34)を満たす場合に、温度特性が良好であるという本発明の効果がより重要となる。
1.5 ≦ Φ(mm) ≦ 4.0 (34)
Φは、対物光学素子の光源側の有効径を指す。
Further, when the objective optical element satisfies the following expression (34), the effect of the present invention that the temperature characteristics are good becomes more important.
1.5 ≦ Φ (mm) ≦ 4.0 (34)
Φ refers to the effective diameter of the objective optical element on the light source side.

波長λ1の光束は、平行光として対物光学素子に入射してもよいし、発散光若しくは収束光として対物光学素子に入射してもよい。好ましくは、光束の、対物光学素子への入射光束の倍率m1が、下記の式(35)を満たすことである。
−0.02<m1<0.02 (35)
本発明の光ピックアップ装置は、対物光学素子がNPS構造と回折構造を重ね合わせた光路差付与構造を設けることで、軸上色収差が良好になっている。具体的には、光源からの光束の波長変化に伴う集光位置の変化が、−0.15μm/nm以上、+0.15μm/nm以下である事が好ましい。なお、集光位置とは、光源から射出された光束が対物レンズに入射して集光する際に、スポット径が最小となるベストフォーカス位置とする。
The light beam having the wavelength λ1 may be incident on the objective optical element as parallel light, or may be incident on the objective optical element as divergent light or convergent light. Preferably, the magnification m1 of the light beam incident on the objective optical element satisfies the following formula (35).
−0.02 <m1 <0.02 (35)
In the optical pickup device of the present invention, the objective optical element has an optical path difference providing structure in which the NPS structure and the diffractive structure are overlapped, so that the axial chromatic aberration is good. Specifically, it is preferable that the change in the condensing position accompanying the change in wavelength of the light beam from the light source is −0.15 μm / nm or more and +0.15 μm / nm or less. The condensing position is the best focus position at which the spot diameter is minimum when the light beam emitted from the light source is incident on the objective lens and condensed.

本発明の光路差付与構造は、NPS構造と回折構造を重ね合わせた構造であり、回折光を発生させる構造である。本発明の、NPS構造と回折構造を重ね合わせた光路差付与構造を有する対物光学素子は、軸外特性も良好になっている。具体的には、0.5°の軸外光線が対物光学素子に入射した場合に、発生するコマ収差の量は20μm以下である事が好ましい。好ましくは、10μm以下である。更に、3次より高次のコマ収差(5次、7次、9次など)ができるだけ発生しない様にする事が好ましい。具体的には、3次より高次のコマ収差の量が、いずれも0.010λrms未満である事が好ましい。より好ましくは、0.005λrms以下である。   The optical path difference providing structure of the present invention is a structure in which an NPS structure and a diffractive structure are overlapped, and is a structure that generates diffracted light. The objective optical element of the present invention having an optical path difference providing structure in which an NPS structure and a diffractive structure are superimposed has excellent off-axis characteristics. Specifically, when a 0.5 ° off-axis ray is incident on the objective optical element, the amount of coma generated is preferably 20 μm or less. Preferably, it is 10 μm or less. Further, it is preferable to prevent coma aberration higher than the third order (5th order, 7th order, 9th order, etc.) from occurring as much as possible. Specifically, it is preferable that the amount of coma higher than the third order is less than 0.010 λrms. More preferably, it is 0.005λrms or less.

また、対物光学素子が単玉のプラスチックレンズである場合、波長特性と温度特性で良好なバランスを保つことが好ましい。この様な特性を満たすために、下記の条件式(4)及び(5)を満たすことが好ましい。   When the objective optical element is a single plastic lens, it is preferable to maintain a good balance between wavelength characteristics and temperature characteristics. In order to satisfy such characteristics, it is preferable to satisfy the following conditional expressions (4) and (5).

+0.0001 ≦ δSAT1/f(WFEλrms/(℃・mm))
≦ +0.0020 (4)
−0.020 ≦ δSAλ/f(WFEλrms/(nm・mm))
≦ −0.002 (5)
但し、δSAT1は、使用波長(この場合、温度変化に伴う波長変動がないとする)における光ディスクの情報の記録/再生を行う際の対物光学素子のδSA3/δT(3次球面収差の温度変化率)を表す。使用波長とは、対物光学素子を有する光ピックアップ装置で用いられている光源の波長をいう。好ましくは、使用波長は、400nm以上、415nm以下の範囲の波長であって、対物光学素子を介して、光ディスクの情報の記録/再生を行うことができる波長である。使用波長を上述のように設定できない場合は、405nmを使用波長として、対物光学素子のδSAT1及び後述するδSAT2、δSAT3を求めてもよい。なお、WFEは、3次球面収差が波面収差で表現されていることを示している。また、δSAλは、使用波長における光ディスクの情報の記録/再生を行う際の対物光学素子のδSA3/δλ(3次球面収差の波長変化率)を表す。尚、環境温度は室温である事が好ましい。室温とは、10℃以上、40℃以下であり、好ましくは、25℃である。fは、波長λ1の光束(好ましくは405nm)における対物光学素子の焦点距離を指す。
+ 0.0001 ≦ δSAT1 / f (WFEλrms / (° C./mm))
≦ +0.0020 (4)
−0.020 ≦ δSAλ / f (WFEλrms / (nm · mm))
≤ -0.002 (5)
However, δSAT1 is δSA3 / δT (temperature change rate of the third-order spherical aberration) of the objective optical element when recording / reproducing information on the optical disk at the used wavelength (in this case, there is no wavelength variation due to temperature change). ). The used wavelength refers to the wavelength of a light source used in an optical pickup device having an objective optical element. Preferably, the wavelength used is a wavelength in the range of not less than 400 nm and not more than 415 nm, and can record / reproduce information on the optical disc via the objective optical element. When the use wavelength cannot be set as described above, δSAT1 of the objective optical element and δSAT2 and δSAT3 described later may be obtained using 405 nm as the use wavelength. Note that WFE indicates that the third-order spherical aberration is expressed by wavefront aberration. Further, δSAλ represents δSA3 / δλ (wavelength change rate of third-order spherical aberration) of the objective optical element when recording / reproducing information on the optical disk at the used wavelength. The ambient temperature is preferably room temperature. The room temperature is 10 ° C. or more and 40 ° C. or less, and preferably 25 ° C. f indicates a focal length of the objective optical element in a light beam having a wavelength λ1 (preferably 405 nm).

更に言えば、温度変化による対物光学素子の球面収差変化に加えて、温度変化に伴う光源の波長変化を考慮することが好ましい。好ましくは、以下の条件式(6)を満たすことである。   Furthermore, it is preferable to consider the wavelength change of the light source accompanying the temperature change in addition to the spherical aberration change of the objective optical element due to the temperature change. Preferably, the following conditional expression (6) is satisfied.

0 ≦ δSAT2/f(WFEλrms/(℃・mm)) ≦ +0.0020 (6)
但し、δSAT2は、温度変化に伴う波長変動が005nm/℃である光源において、光ディスクの情報の記録/再生を行う際の対物光学素子のδSA3/δTを指す。
0 ≦ δSAT2 / f (WFEλrms / (° C. mm)) ≦ + 0.0020 (6)
However, δSAT2 refers to δSA3 / δT of the objective optical element when recording / reproducing information on the optical disc in a light source whose wavelength variation with temperature change is 005 nm / ° C.

より好ましくは、下記の条件式(7)を満たすことである。   More preferably, the following conditional expression (7) is satisfied.

0 ≦ δSAT2/f(WFEλrms/(℃・mm)) ≦ +0.0015 (7)
また、光ピックアップ装置の集光光学系がコリメートレンズ等のカップリングレンズを有し、そのカップリングレンズがプラスチックレンズである場合、以下の条件式(8)を満たすことが好ましい。
0 ≦ δSAT2 / f (WFEλrms / (° C. mm)) ≦ + 0.0015 (7)
Moreover, when the condensing optical system of an optical pick-up apparatus has coupling lenses, such as a collimating lens, and the coupling lens is a plastic lens, it is preferable to satisfy the following conditional expressions (8).

0 ≦ δSAT3/f(WFEλrms/(℃・mm)) ≦ +0.0015 (8)
但し、δSAT3は、温度変化に伴う波長変動が0.05nm/℃である光源において、高密度光ディスクの情報の記録/再生を行う際のカップリングレンズと対物光学素子を含んだ光学系全体のδSA3/δTを指す。
0 ≦ δSAT3 / f (WFEλrms / (° C. mm)) ≦ + 0.0015 (8)
However, δSAT3 is δSA3 of the entire optical system including a coupling lens and an objective optical element when recording / reproducing information on a high-density optical disk in a light source whose wavelength variation with temperature change is 0.05 nm / ° C. / ΔT.

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

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

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

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

本発明によれば、プラスチック製の対物光学素子を用いながらも、温度特性と軸上色収差とを良好に維持しつつ、しかも、波長特性が大きく劣化することなく、高密度光ディスクに対して情報の記録/再生を行える光ピックアップ装置、及び、それに用いる対物光学素子を提供することができる。   According to the present invention, while using a plastic objective optical element, while maintaining good temperature characteristics and axial chromatic aberration, and without greatly degrading wavelength characteristics, it is possible to record information on a high-density optical disk. An optical pickup device capable of recording / reproducing and an objective optical element used therefor can be provided.

横軸は対物光学素子の入射瞳における光線高さを示し、縦軸は光軸を通過する光線と光線高さhを通過する光線との光路差を示すグラフである。The horizontal axis represents the light ray height at the entrance pupil of the objective optical element, and the vertical axis represents the optical path difference between the light ray passing through the optical axis and the light ray passing through the light ray height h. 光路差付与構造の概略断面図である。It is a schematic sectional drawing of an optical path difference providing structure. 回折構造の例を示す断面図である。It is sectional drawing which shows the example of a diffraction structure. 同心円状の複数の境界段差で区切られた複数の領域を含む回折構造の例を示す断面図である。It is sectional drawing which shows the example of the diffraction structure containing the some area | region divided by the concentric circle-like boundary level | step difference. 光ピックアップ装置PUの概略構成を示す図である。It is a figure which shows schematic structure of optical pick-up apparatus PU.

符号の説明Explanation of symbols

AC アクチュエータ
AP 絞り
LD 半導体レーザ
COL コリメートレンズ
OBJ 対物レンズ
PD 受光素子
PBS 偏光ビームスプリッタ
PU 光ピックアップ装置
QWP λ/4波長板
SN センサレンズ
AC Actuator AP Aperture LD Semiconductor laser COL Collimating lens OBJ Objective lens PD Light receiving element PBS Polarizing beam splitter PU Optical pickup device QWP λ / 4 wave plate SN Sensor lens

以下、本発明の実施の形態を、図を用いて説明する。図5は、高密度光ディスクであるBDに対して適切に情報の記録/再生を行うことができる本実施の形態の光ピックアップ装置PUの構成を概略的に示す図である。かかる光ピックアップ装置PUは、光情報記録再生装置に搭載できる。なお、本発明は、本実施の形態に限られるものではない。本実施の形態の対物光学素子OBJは、例えば図4に示すように、NPS構造と回折構造とを重ね合わせた光路差付与構造を有する単玉のプラスチックレンズである。   Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 5 is a diagram schematically showing a configuration of the optical pickup device PU of the present embodiment that can appropriately record / reproduce information to / from a BD that is a high-density optical disc. Such an optical pickup device PU can be mounted on an optical information recording / reproducing device. The present invention is not limited to the present embodiment. The objective optical element OBJ of this embodiment is a single plastic lens having an optical path difference providing structure in which an NPS structure and a diffractive structure are superimposed as shown in FIG.

図5に示す光ピックアップ装置PUにおいて、高密度光ディスクであるBDに対して情報の記録/再生を行う場合には、半導体レーザLDを発光させる。半導体レーザLDから射出された波長λ1=405nmの発散光束は、一点鎖線でその光線経路を描いたように、偏光ビームスプリッタPBSを通過し、コリメートレンズCOLにより平行光束に変換され、λ/4波長板QWP及び絞りAPを通過し、対物光学素子OBJに平行光の状態で入射して、BDの情報記録面上に集光される。対物光学素子OBJは、アクチュエータACによって駆動されフォーカシングやトラッキングが行われる。   In the optical pickup device PU shown in FIG. 5, when information is recorded / reproduced with respect to a BD that is a high-density optical disc, the semiconductor laser LD is caused to emit light. A divergent light beam having a wavelength of λ1 = 405 nm emitted from the semiconductor laser LD passes through the polarization beam splitter PBS and is converted into a parallel light beam by a collimator lens COL, as depicted by the dashed line, and has a wavelength of λ / 4. The light passes through the plate QWP and the aperture AP, enters the objective optical element OBJ in a parallel light state, and is condensed on the information recording surface of the BD. The objective optical element OBJ is driven by the actuator AC to perform focusing and tracking.

BDの情報記録面で情報ピットにより変調された反射光束は、再び対物光学素子OBJ、絞りAP、λ/4波長板QWP及びコリメートレンズCOLを透過した後、偏光ビームスプリッタPBSで反射されて、センサレンズSNを介して受光素子PDに集光する。そして、受光素子PDの出力信号を用いてBDに記録された情報を読み取ることができる。
<実施例>
次に、上述の実施の形態に用いることができる実施例について説明する。以下の実施例1において、対物光学素子は、単玉のポリオレフィン系のプラスチックレンズである。対物光学素子には、図4に示した構成に近い光路差付与構造を有しており、当該光路差付与構造は、NPS構造と回折構造を重ねあわせた構造である。本実施例において、NPS構造は、NPS構造を通過した光束の5次の回折光量を他のいかなる次数の回折光量よりも大きくする構造であり、回折構造は、回折構造を通過した光束の2次の回折光量を他のいかなる次数の回折光量よりも大きくする構造である。尚、図4では、理解しやすい様に段差が誇張して描かれている。
The reflected light beam modulated by the information pits on the information recording surface of the BD is again transmitted through the objective optical element OBJ, the aperture AP, the λ / 4 wavelength plate QWP, and the collimator lens COL, and then reflected by the polarization beam splitter PBS, and the sensor. The light is condensed on the light receiving element PD through the lens SN. And the information recorded on BD can be read using the output signal of light receiving element PD.
<Example>
Next, examples that can be used in the above-described embodiment will be described. In Example 1 below, the objective optical element is a single polyolefin plastic lens. The objective optical element has an optical path difference providing structure similar to the configuration shown in FIG. 4, and the optical path difference providing structure is a structure in which an NPS structure and a diffraction structure are overlapped. In the present embodiment, the NPS structure is a structure in which the fifth-order diffracted light amount of the light beam that has passed through the NPS structure is larger than any other order diffracted light amount, and the diffractive structure is the second order of the light beam that has passed through the diffractive structure. In this structure, the amount of diffracted light is larger than that of any other order. In FIG. 4, the steps are exaggerated for easy understanding.

表2から表5に本実施例のレンズデータを示す。尚、これ以降(表のレンズデータ含む)において、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。Tables 2 to 5 show lens data of this example. In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 −3 ) is represented by using E (for example, 2.5E-3).

対物光学素子の光学面は、それぞれ数1式に、表2から表5に示す係数を代入した数式で規定される、光軸の周りに軸対称な非球面に形成されている。   The optical surface of the objective optical element is formed as an aspherical surface that is axisymmetric about the optical axis and is defined by mathematical formulas obtained by substituting the coefficients shown in Tables 2 to 5 into Formula 1.

ここで、X(h)は光軸方向の軸(光の進行方向を正とする)、κは円錐係数、A2iは非球面係数、hは光軸からの高さである。Here, X (h) is an axis in the optical axis direction (the light traveling direction is positive), κ is a conical coefficient, A 2i is an aspherical coefficient, and h is a height from the optical axis.

また、光路差付与構造により各波長の光束に対して与えられる光路長は、数2式の光路差関数に、表3と表4に示す係数を代入した数式で規定される。   Further, the optical path length given to the light flux of each wavelength by the optical path difference providing structure is defined by a mathematical formula in which the coefficients shown in Tables 3 and 4 are substituted into the optical path difference function of Formula 2.

λは入射光束の波長、λBは製造波長(ブレーズ化波長)、dorは回折次数、C2iは光路差関数の係数である。
本実施例の収差特性は以下の通りである。なお、実施例で用いた材料の温度変化による屈折率変化は−9.0E−5/℃である。また、SAは球面収差、ASは非点収差、CMはコマ収差を意味し、その後の数字は次数である(例SA3:3次球面収差)。
(1)軸上色収差:0.06μm/nm
(2)波長特性(光束の波長が+5nm変化)
SA TOTAL:0.068λrms
SA3:−0.062λrms
SA5:−0.026λrms
SA7:−0.007λrms
SA9:−0.002λrms
この場合、δSAλ/f=−0.0088となり、式(5)を満たす。
(3)温度特性(環境温度が+30℃上昇、但し波長シフトなし)
SA TOTAL:0.043λrms
SA3:0.042λrms
SA5:0.006λrms
SA7:0.000λrms
SA9:0.000λrms
この場合、δSAT1/f=0.00099となり、式(4)を満たす。
(4)軸外特性(光軸に対する入射角度:0.5°)
SA TOTAL:0.010λrms
AS TOTAL:0.011λrms
CM TOTAL:0.011λrms
CM3:−0.010λrms
CM5:0.002λrms
CM7:0.003λrms
CM9:0.001λrms
λ is the wavelength of the incident light beam, λB is the manufacturing wavelength (blazed wavelength), dor is the diffraction order, and C 2i is the coefficient of the optical path difference function.
The aberration characteristics of the present example are as follows. In addition, the refractive index change due to the temperature change of the material used in the examples is −9.0E−5 / ° C. SA represents spherical aberration, AS represents astigmatism, CM represents coma, and the subsequent numbers are orders (example SA3: third-order spherical aberration).
(1) Axial chromatic aberration: 0.06 μm / nm
(2) Wavelength characteristics (wavelength of light beam changes +5 nm)
SA TOTAL: 0.068λrms
SA3: -0.062λrms
SA5: -0.026λrms
SA7: -0.007λrms
SA9: -0.002λrms
In this case, δSAλ / f = −0.0088, which satisfies Expression (5).
(3) Temperature characteristics (environmental temperature increases by + 30 ° C, but no wavelength shift)
SA TOTAL: 0.043λrms
SA3: 0.042λrms
SA5: 0.006λrms
SA7: 0.000λrms
SA9: 0.000λrms
In this case, δSAT1 / f = 0.00099, which satisfies Expression (4).
(4) Off-axis characteristics (incident angle with respect to optical axis: 0.5 °)
SA TOTAL: 0.010λrms
AS TOTAL: 0.011λrms
CM TOTAL: 0.011λrms
CM3: -0.010λrms
CM5: 0.002λrms
CM7: 0.003λrms
CM9: 0.001λrms

Claims (16)

波長λ1(380nm<λ1<420nm)の光束を射出する光源と、前記光束を光ディスクの情報記録面上に集光させるための対物光学素子と、前記光ディスクの情報記録面上で反射した光を受光する受光素子とを有し、前記光束を前記光ディスクの情報記録面上に集光させることによって情報の記録及び/又は再生を行う光ピックアップ装置において、A light source that emits a light beam having a wavelength λ1 (380 nm <λ1 <420 nm), an objective optical element that focuses the light beam on the information recording surface of the optical disc, and light that is reflected on the information recording surface of the optical disc In an optical pickup device that records and / or reproduces information by condensing the light flux on the information recording surface of the optical disc,
前記対物光学素子は、単玉のプラスチックレンズであり、The objective optical element is a single plastic lens,
前記対物光学素子の像側開口数(NA)は0.8以上であり、The image side numerical aperture (NA) of the objective optical element is 0.8 or more,
前記対物光学素子の光学面は、同心円状の複数の境界段差で区切られた、複数の領域に分けられており、The optical surface of the objective optical element is divided into a plurality of regions separated by a plurality of concentric boundary steps,
前記境界段差で区切られた各領域は、同心円状の複数の領域内段差を有し、Each region divided by the boundary step has a plurality of concentric steps in the region,
前記各領域のうち、光軸に近い側の領域では前記境界段差が光軸とは逆側を向いており、前記光軸から離れた側の領域では前記境界段差が光軸側を向いており、Among the regions, the boundary step in the region closer to the optical axis faces away from the optical axis, and the boundary step in the region away from the optical axis faces the optical axis side. ,
前記各領域において、前記境界段差の段差量は、前記領域内段差の段差量よりも大きいことを特徴とする光ピックアップ装置。In each of the regions, the step amount of the boundary step is larger than the step amount of the in-region step.
前記各領域のうち、光軸を含む領域において、前記領域内段差の全ての段差量d2が、以下の条件式を満たすことを特徴とする請求項1に記載の光ピックアップ装置。2. The optical pickup device according to claim 1, wherein among the respective regions, in the region including the optical axis, all the step amounts d <b> 2 of the step within the region satisfy the following conditional expression.
0.9・q・λ1/(n−1)≦d2(nm)≦1.1・q・λ1/(n−1)0.9 · q · λ1 / (n−1) ≦ d2 (nm) ≦ 1.1 · q · λ1 / (n−1) (2)(2)
但し、qは、任意の整数を示し、nは波長λ1の前記光束における前記対物光学素子の屈折率を示す。Here, q represents an arbitrary integer, and n represents the refractive index of the objective optical element in the light flux having the wavelength λ1.
前記光軸を含む領域とその外側の領域との前記境界段差の段差量d1が、以下の条件式を満たすことを特徴とする請求項2に記載の光ピックアップ装置。3. The optical pickup device according to claim 2, wherein a step amount d <b> 1 of the boundary step between the region including the optical axis and the outer region satisfies the following conditional expression.
0.9・(p−q)・λ1/(n−1)≦d1(nm)≦1.1・p・λ1/(n−1)0.9 · (p−q) · λ1 / (n−1) ≦ d1 (nm) ≦ 1.1 · p · λ1 / (n−1) (3)(3)
但し、pは、q以上の任意の整数を示す。However, p shows the arbitrary integers more than q.
前記光軸を含む領域とその外側の領域との前記境界段差の段差量d1が、以下の条件式を満たすことを特徴とする請求項3に記載の光ピックアップ装置。4. The optical pickup device according to claim 3, wherein a step amount d <b> 1 of the boundary step between the region including the optical axis and the outer region satisfies the following conditional expression.
0.9・(p−q)・λ1/(n−1)≦d1(nm)≦1.1・(p−q)・λ1/(n−1)0.9 · (pq) · λ1 / (n-1) ≦ d1 (nm) ≦ 1.1 · (pq) · λ1 / (n−1) (4)(4)
前記境界段差のうち、光軸側を向いている前記境界段差の光軸方向の段差量d1‘が、全て以下の条件式を満たすことを特徴とする請求項3又は4に記載の光ピックアップ装置。5. The optical pickup device according to claim 3, wherein, of the boundary steps, step amounts d <b> 1 ′ in the optical axis direction of the boundary steps facing the optical axis side all satisfy the following conditional expression. .
1.0・p・λ1/(n−1)≦d1‘(nm)≦2.0・(p+q)・λ1/(n−1)1.0 · p · λ1 / (n−1) ≦ d1 ′ (nm) ≦ 2.0 · (p + q) · λ1 / (n−1) (5)(5)
前記境界段差のうち、光軸側を向いている前記境界段差の光軸方向の段差量d1‘が、全て以下の条件式を満たすことを特徴とする請求項5に記載の光ピックアップ装置。6. The optical pickup device according to claim 5, wherein among the boundary steps, step amounts d <b> 1 ′ in the optical axis direction of the boundary steps facing the optical axis side satisfy all of the following conditional expressions.
1.0・(p+q)・λ1/(n−1)≦d1‘(nm)≦2.0・(p+q)・λ1/(n−1)1.0 · (p + q) · λ1 / (n−1) ≦ d1 ′ (nm) ≦ 2.0 · (p + q) · λ1 / (n−1) (6)(6)
qが2又は1であることを特徴とする請求項2乃至6のいずれかに記載の光ピックアップ装置。7. The optical pickup device according to claim 2, wherein q is 2 or 1. pが5又は4であることを特徴とする請求項3乃至7のいずれかに記載の光ピックアップ装置。8. The optical pickup device according to claim 3, wherein p is 5 or 4. 波長λ1(380nm<λ1<420nm)の光束を射出する光源と、前記光束を光ディスクの情報記録面上に集光させるための対物光学素子と、前記光ディスクの情報記録面上で反射した光を受光する受光素子とを有し、前記光束を前記光ディスクの情報記録面上に集光させることによって情報の記録及び/又は再生を行う光ピックアップ装置用の対物光学素子において、A light source that emits a light beam having a wavelength of λ1 (380 nm <λ1 <420 nm), an objective optical element that focuses the light beam on the information recording surface of the optical disc, and light reflected on the information recording surface of the optical disc In an objective optical element for an optical pickup device that records and / or reproduces information by condensing the light flux on the information recording surface of the optical disc,
前記対物光学素子は、単玉のプラスチックレンズであり、The objective optical element is a single plastic lens,
前記対物光学素子の像側開口数(NA)は0.8以上であり、The image side numerical aperture (NA) of the objective optical element is 0.8 or more,
前記対物光学素子の光学面は、同心円状の複数の境界段差で区切られた、複数の領域に分けられており、The optical surface of the objective optical element is divided into a plurality of regions separated by a plurality of concentric boundary steps,
前記境界段差で区切られた各領域は、同心円状の複数の領域内段差を有し、Each region divided by the boundary step has a plurality of concentric steps in the region,
前記各領域のうち、光軸に近い側の領域では前記境界段差が光軸とは逆側を向いており、前記光軸から離れた側の領域では前記境界段差が光軸側を向いており、Among the regions, the boundary step in the region closer to the optical axis faces away from the optical axis, and the boundary step in the region away from the optical axis faces the optical axis side. ,
前記各領域において、前記境界段差の段差量は、前記領域内段差の段差量よりも大きいことを特徴とする光ピックアップ装置用の対物光学素子。The objective optical element for an optical pickup device according to claim 1, wherein in each of the regions, a step amount of the boundary step is larger than a step amount of the step in the region.
前記各領域のうち、光軸を含む領域において、前記領域内段差の全ての段差量d2が、以下の条件式を満たすことを特徴とする請求項9に記載の光ピックアップ装置用の対物光学素子。10. The objective optical element for an optical pickup device according to claim 9, wherein in the region including the optical axis among the regions, all the step amounts d <b> 2 of the step in the region satisfy the following conditional expression. .
0.9・q・λ1/(n−1)≦d2(nm)≦1.1・q・λ1/(n−1)0.9 · q · λ1 / (n−1) ≦ d2 (nm) ≦ 1.1 · q · λ1 / (n−1)
(2)(2)
但し、qは、任意の整数を示し、nは、波長λ1の前記光束における前記対物光学素子の屈折率を示す。Here, q represents an arbitrary integer, and n represents the refractive index of the objective optical element in the light beam having the wavelength λ1.
前記各領域のうち、光軸を含む領域において、前記光軸を含む領域とその外側の領域の間の前記境界段差の光軸方向の段差量d1が、以下の条件式を満たすことを特徴とする請求項10に記載の光ピックアップ装置用の対物光学素子。Among the regions, in the region including the optical axis, the step amount d1 in the optical axis direction of the boundary step between the region including the optical axis and the region outside the region satisfies the following conditional expression: An objective optical element for an optical pickup device according to claim 10.
0.9・(p−q)・λ1/(n−1)≦d1(nm)≦1.1・p・λ1/(n−1)0.9 · (p−q) · λ1 / (n−1) ≦ d1 (nm) ≦ 1.1 · p · λ1 / (n−1) (3)(3)
但し、pは、q以上の任意の整数を示す。However, p shows the arbitrary integers more than q.
前記各領域のうち、光軸を含む領域において、前記光軸を含む領域とその外側の領域との前記境界段差の段差量d1が、以下の条件式を満たすことを特徴とする請求項11に記載の光ピックアップ装置用の対物光学素子。12. The step amount d1 of the boundary step between the region including the optical axis and the region outside the region in the region including the optical axis among the regions satisfies the following conditional expression. The objective optical element for optical pickup apparatuses as described.
0.9・(p−q)・λ1/(n−1)≦d1(nm)≦1.1・(p−q)・λ1/(n−1)0.9 · (pq) · λ1 / (n-1) ≦ d1 (nm) ≦ 1.1 · (pq) · λ1 / (n−1) (4)(4)
前記境界段差のうち、光軸側を向いている前記境界段差の光軸方向の段差量d1‘が、全て以下の条件式を満たすことを特徴とする請求項11又は12に記載の光ピックアップ装置用の対物光学素子。13. The optical pickup device according to claim 11, wherein step heights d <b> 1 ′ in the optical axis direction of the boundary steps facing the optical axis side among the boundary steps satisfy all the following conditional expressions. Objective optical element.
1.0・p・λ1/(n−1)≦d1‘(nm)≦2.0・(p+q)・λ1/(n−1)1.0 · p · λ1 / (n−1) ≦ d1 ′ (nm) ≦ 2.0 · (p + q) · λ1 / (n−1) (5)(5)
前記境界段差のうち、光軸側を向いている前記境界段差の光軸方向の段差量d1‘が、全て以下の条件式を満たすことを特徴とする請求項13に記載の光ピックアップ装置用の対物光学素子。14. The optical pickup device for an optical pickup device according to claim 13, wherein among the boundary steps, step amounts d <b> 1 ′ in the optical axis direction of the boundary steps facing the optical axis side all satisfy the following conditional expression: Objective optical element.
1.0・(p+q)・λ1/(n−1)≦d1‘(nm)≦2.0・(p+q)・λ1/(n−1)1.0 · (p + q) · λ1 / (n−1) ≦ d1 ′ (nm) ≦ 2.0 · (p + q) · λ1 / (n−1) (6)(6)
qが2又は1であることを特徴とする請求項10乃至14のいずれかに記載の光ピックアップ装置用の対物光学素子。The objective optical element for an optical pickup device according to claim 10, wherein q is 2 or 1. pが5又は4であることを特徴とする請求項11乃至15のいずれかに記載の光ピックアップ装置用の対物光学素子。The objective optical element for an optical pickup device according to claim 11, wherein p is 5 or 4.
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