JP2012226816A - Optical pickup device - Google Patents

Optical pickup device Download PDF

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JP2012226816A
JP2012226816A JP2011095771A JP2011095771A JP2012226816A JP 2012226816 A JP2012226816 A JP 2012226816A JP 2011095771 A JP2011095771 A JP 2011095771A JP 2011095771 A JP2011095771 A JP 2011095771A JP 2012226816 A JP2012226816 A JP 2012226816A
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light
laser light
light source
pickup device
optical
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JP5565371B2 (en
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Yasushi Kobayashi
靖史 小林
Kenji Matsumura
健二 松村
Katsuhiko Yasuda
勝彦 安田
Kenji Kono
賢二 河野
Yoshiaki Kaneuma
慶明 金馬
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Panasonic Corp
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Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device which can get a desired spot quality without an aberration occurrence caused by a phase step and at low cost.SOLUTION: An optical pickup device comprises: laser sources 1,2 to emit laser beams; objective lenses 9,13 to condense laser beams emitted from the laser sources 1,2 to a record layer of an optical disk; and a diffraction element 4 placed on a light path between the laser sources 1,2 and objective lenses 9,13. The diffraction element 4 changes zeroth-order light transmittance by reducing duties of a diffraction grating comprising shields stepwise towards the outside from the center.

Description

本発明はＢＤやＤＶＤ、ＣＤのように、記録密度の異なる複数の光ディスクに対応した記録再生用光ピックアップ装置、並びに該光ピックアップ装置を搭載した光ディスク装置に関するものである。 The present invention relates to an optical pickup device for recording / reproduction corresponding to a plurality of optical discs having different recording densities such as BD, DVD, and CD, and an optical disc device equipped with the optical pickup device.

ＤＶＤ、ＣＤに比べて、ＢＤは極めて高密度に信号を記録するため、良好な記録・再生特性を得るためには、光ディスク上の光スポットサイズを十分に小さく絞る必要がある。ここで光スポットのサイズを小さく絞るためには対物レンズの開口数を大きくするか、ＢＤ光学系の倍率を高く設定する必要がある。なお、ここにいう倍率とは図１０に示すように、符号３０に示す集光光学系における焦点距離に対する、符号３１に示すコリメート光学系における焦点距離の比である。以降、集光光学系の焦点距離に対するコリメート光学系の焦点距離の比を単に倍率と述べる事にする。また図１０には図示しないが、コリメート光学系は単一のレンズだけに限定されず、複数のレンズを用いて構成しても良い。この場合は、これら複数のレンズによる合成焦点距離がコリメート光学系の焦点距離となる。
従来、ＢＤ光学系の倍率は略１４．０倍、ＤＶＤ光学系の倍率は略６．０倍が最適な設計値とされており、ＢＤ／ＤＶＤでコリメートレンズを共有化する場合、少なくともどちらか一方に合成焦点距離を補正するレンズを用いることで異なる倍率を実現していた。
前記合成焦点距離を補正するレンズを搭載した光学構成に対して、誘電体多層膜フィルタもしくは矩形断面回折格子の採用により、焦点距離補正レンズを必要としないコリメート光学系が提案されている。例えば特許文献１等参照。 Compared to DVD and CD, BD records signals at a very high density, and therefore, in order to obtain good recording / reproduction characteristics, it is necessary to reduce the light spot size on the optical disk sufficiently small. Here, in order to reduce the size of the light spot, it is necessary to increase the numerical aperture of the objective lens or set the magnification of the BD optical system high. The magnification referred to here is the ratio of the focal length in the collimating optical system indicated by reference numeral 31 to the focal length in the condensing optical system indicated by reference numeral 30 as shown in FIG. Hereinafter, the ratio of the focal length of the collimating optical system to the focal length of the condensing optical system is simply referred to as magnification. Although not shown in FIG. 10, the collimating optical system is not limited to a single lens, and may be configured using a plurality of lenses. In this case, the combined focal length of the plurality of lenses becomes the focal length of the collimating optical system.
Conventionally, the optimum design value is approximately 14.0 times the magnification of the BD optical system and approximately 6.0 times of the DVD optical system, and at least one of the collimating lenses is shared by BD / DVD. On the other hand, a different magnification was realized by using a lens for correcting the composite focal length.
A collimating optical system that does not require a focal length correction lens has been proposed by adopting a dielectric multilayer filter or a rectangular cross-section diffraction grating for an optical configuration equipped with a lens for correcting the combined focal length. For example, see Patent Document 1 and the like.

特開２００４−２９５９５４号公報JP 2004-295594 A

しかしながら，誘電体多層膜フィルタの場合，素子内部で領域を分割して多層膜を形成する必要があり，非常に高コストになる。また，矩形断面回折格子の場合には格子幅を変化させることによって位相段差が生じ，収差が発生してしまう。従来のＤＶＤ／ＣＤであれば位相段差によって発生する収差量についても許容できたが、より高精度が要求されるＢＤにおいては性能を満足できるレベルに収まらない。 However, in the case of a dielectric multilayer filter, it is necessary to form a multilayer film by dividing a region inside the element, which is very expensive. Further, in the case of a rectangular cross-section diffraction grating, a phase step is generated by changing the grating width, and aberration is generated. With conventional DVD / CD, the amount of aberration caused by the phase step can be allowed, but in a BD that requires higher accuracy, the level of performance cannot be satisfied.

そこで、本発明は、上記の問題を解決すべく、低コストで位相段差による収差発生のなく、所望のスポット品質を得ることができる光ピックアップ装置を提供することを目的とする。   SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical pickup device that can obtain a desired spot quality at low cost without causing aberration due to a phase step, in order to solve the above-described problems.

上記目的を達成するために、本発明の光ピックアップ装置は、レーザ光を出射するレーザ光源と、前記レーザ光源から出射されるレーザ光を光ディスクの記録層に集光させる対物レンズと、前記レーザ光源と前記対物レンズとの間の光路上に配置された回折素子とを備え、前記回折素子は、遮蔽物で構成される回折格子のデューティを中心部から外側に向かって階段状に小さくすることで、０次光透過率を変化させる、ことを特徴とする光ピックアップ装置である。また、前記回折素子の格子方向θは、３０ｄｅｇ≦｜θ｜≦９０ｄｅｇであることが望ましい。
本発明の光ピックアップ装置は、互いに発振波長の異なる第１のレーザ光源および第２のレーザ光源と、第１のレーザ光源から出射した第１の光ビームまたは第２のレーザ光源から出射した第２の光ビームを光ディスクに集光させる対物レンズとを搭載した光ピックアップ装置において、第１のレーザ光源を出射した第１の光ビームが光ディスクに向かう光路中に、前記光ビームの中心部近傍が通過する領域に比べて前記光ビームの外縁部近傍が通過する領域の０次光の透過率が高くなるよう、中心部から外縁部に向けて回折格子のデューティを小さくし、かつ前記回折格子は金属膜のような遮光体で形成された回折素子を搭載する。 In order to achieve the above object, an optical pickup device of the present invention includes a laser light source that emits laser light, an objective lens that focuses the laser light emitted from the laser light source on a recording layer of an optical disc, and the laser light source. And a diffractive element disposed on the optical path between the objective lens and the diffractive element. An optical pickup device characterized in that the 0th-order light transmittance is changed. The grating direction θ of the diffraction element is preferably 30 deg ≦ | θ | ≦ 90 deg.
The optical pickup device of the present invention includes a first laser light source and a second laser light source having different oscillation wavelengths, and a first light beam emitted from the first laser light source or a second laser light source emitted from the second laser light source. In an optical pickup apparatus equipped with an objective lens for condensing the light beam on the optical disk, the vicinity of the center of the light beam passes through the optical path of the first light beam emitted from the first laser light source toward the optical disk. The duty of the diffraction grating is reduced from the center toward the outer edge so that the transmittance of the zero-order light in the area where the vicinity of the outer edge of the light beam passes is higher than the area where the light beam passes. A diffractive element formed of a light shielding body such as a film is mounted.

上記の構成によれば、低コストで位相段差による収差発生なく所望のスポット品質を得ることができる光ピックアップ装置を提供できる。 According to said structure, the optical pick-up apparatus which can obtain desired spot quality at low cost without the aberration generation by a phase level | step difference can be provided.

光ピックアップ装置の概略図Schematic diagram of optical pickup device 遮光型回折素子４の通過前後に於ける光ビームの強度分布を示す特性図Characteristic diagram showing the intensity distribution of the light beam before and after passing through the light-shielding diffraction element 4 遮光型回折素子４の通過有無に於ける光スポットの光強度分布を示す特性図A characteristic diagram showing the light intensity distribution of a light spot with or without passing through the light-shielding diffraction element 4 遮光型回折格子の一パターンとして階段状の遮光型回折格子を示す図Figure showing a stair-shaped light-shielding diffraction grating as a pattern of light-shielding diffraction grating 検出器２０における受光パターンを示す図The figure which shows the light reception pattern in the detector 20 ＡＰＰ（Advanced Push-Pull）方式の場合の光学構成図Optical configuration diagram for the APP (Advanced Push-Pull) method 検出器のレイアウト例を示す図Diagram showing an example of the layout of the detector 遮光型回折格子の他パターンとして２次元セルパターンを示す図A diagram showing a two-dimensional cell pattern as another pattern of the light-shielding diffraction grating 遮光型回折格子の他パターンとして遮光格子を途中で間引いたパターンを示す図The figure which shows the pattern which thinned out the shading grating on the way as other patterns of the shading type diffraction grating 集光光学系の焦点距離に対するコリメート光学系の焦点距離の比を説明ずる図Diagram explaining the ratio of the focal length of the collimating optical system to the focal length of the condensing optical system

［１．光ピックアップの構成］
図１は光ピックアップ装置の概略図である。符号１は発振波長が４０５ｎｍ帯の半導体レーザ光源、符号２は発振波長６５０ｎｍ帯の半導体レーザ光源を表している。
半導体レーザ光源１を出射した光ビームは、３スポット用回折格子３を通過した後、本発明の遮光型回折格子４に入射する。この遮光型回折格子４は、光ビームの中心部近傍が通過する領域に比べて光ビームの外縁部近傍が通過する領域の０次光の透過率が高くなるよう、中心部から外縁部に向けて回折格子のデューティを小さくし、かつ回折格子はＣｒなどの金属膜のような遮光体で形成された回折素子である。
遮光型回折格子４によって光強度分布を補正された光ビームはビームスプリッタ５を反射して、コリメートレンズ６に入射する。コリメートレンズ６によって略平行光となった光ビームは立ち上げミラー７を透過した後、立ち上げミラー８ を反射して、４０５ｎｍ用対物レンズ９に入射する。対物レンズ９によってディスク１４に集光された光ビームは、ディスク１４の情報面で反射され往路で反射したビームスプリッタ５を透過した後、ビームスプリッタ１０、検出レンズ１１を透過して、検出器２０に入射する。
半導体レーザ光源２を出射した光ビームは３スポット用回折格子１２を通過した後、ビームスプリッタ１０を反射、ビームスプリッタ５を透過してコリメートレンズ６に入射する。コリメートレンズによって略平行光となった光ビームは立ち上げミラー７で反射して、６５０ｎｍ用対物レンズ１３に入射する。対物レンズ１３によってディスク１５に集光された光ビームはディスク１５の情報面で反射され往路で反射したビームスプリッタ１０を透過した後、検出レンズ１１を透過して、検出器２０に入射する。 [1. Configuration of optical pickup]
FIG. 1 is a schematic diagram of an optical pickup device. Reference numeral 1 denotes a semiconductor laser light source having an oscillation wavelength of 405 nm band, and reference numeral 2 denotes a semiconductor laser light source having an oscillation wavelength of 650 nm band.
The light beam emitted from the semiconductor laser light source 1 passes through the three-spot diffraction grating 3 and then enters the light-shielding diffraction grating 4 of the present invention. This light-shielding diffraction grating 4 is directed from the center to the outer edge so that the transmittance of the zero-order light in the region where the vicinity of the outer edge of the light beam passes is higher than the region where the vicinity of the center of the light beam passes. Thus, the duty of the diffraction grating is reduced, and the diffraction grating is a diffraction element formed of a light shielding body such as a metal film such as Cr.
The light beam whose light intensity distribution is corrected by the light-shielding diffraction grating 4 is reflected by the beam splitter 5 and enters the collimating lens 6. The light beam that has become substantially parallel light by the collimator lens 6 passes through the rising mirror 7, then reflects off the rising mirror 8, and enters the objective lens 9 for 405 nm. The light beam focused on the disk 14 by the objective lens 9 passes through the beam splitter 5 reflected on the information surface of the disk 14 and reflected on the forward path, and then passes through the beam splitter 10 and the detection lens 11 to be detected by the detector 20. Is incident on.
The light beam emitted from the semiconductor laser light source 2 passes through the three-spot diffraction grating 12, then reflects off the beam splitter 10, passes through the beam splitter 5, and enters the collimating lens 6. The light beam that has become substantially parallel light by the collimator lens is reflected by the rising mirror 7 and enters the objective lens 13 for 650 nm. The light beam focused on the disk 15 by the objective lens 13 passes through the beam splitter 10 reflected on the information surface of the disk 15 and reflected on the forward path, then passes through the detection lens 11 and enters the detector 20.

［２．遮光型回折格子の機能］
ここで図２（ａ）に示すように、例えば半導体レーザ光源１を出射する光ビームの強度分布はガウス分布であるため、光学フィルタ素子４（遮光型回折格子４）に入射する光ビームの強度分布もガウス分布となり、その模式図を符号５０で示す。本実施例において遮光型回折素子４は、光ビームが通過する中心部から外縁部にむけて段階的に格子幅を小さくしており、中心部付近に比べて外縁部付近の０次光透過率を高く設定している。そのため遮光型回折素子４を通過した光ビームの強度分布は、図２（ｃ）の符号５１に示すように中心部付近の光強度が低くなる。なお中心部付近の光強度を低くする事で、遮光型回折素子４を通過した後の光ビームの光強度分布は、通過する前に比べてフラットな状態に近づく。なお遮光型回折素子４の０次光透過率の領域分割は図２（ｂ）に示すように、多段階的に透過率を変えるものであっても構わないし、または連続的に変化しても構わない。 [2. Function of light-shielding diffraction grating]
Here, as shown in FIG. 2A, for example, the intensity distribution of the light beam emitted from the semiconductor laser light source 1 is a Gaussian distribution, so the intensity of the light beam incident on the optical filter element 4 (light-shielding diffraction grating 4). The distribution is also a Gaussian distribution, and a schematic diagram thereof is indicated by reference numeral 50. In the present embodiment, the light-shielding diffractive element 4 has a grating width that is gradually reduced from the central part through which the light beam passes to the outer edge part, and the 0th-order light transmittance in the vicinity of the outer edge part as compared with the vicinity of the central part. Is set high. Therefore, the intensity distribution of the light beam that has passed through the light-shielding diffraction element 4 has a lower light intensity near the center as indicated by reference numeral 51 in FIG. By reducing the light intensity in the vicinity of the central portion, the light intensity distribution of the light beam after passing through the light-shielding diffraction element 4 becomes closer to a flat state than before passing through. The area division of the 0th-order light transmittance of the light-shielding diffractive element 4 may change the transmittance in multiple steps as shown in FIG. 2B, or may change continuously. I do not care.

図２（ｃ）に示すように、対物レンズに入射する光ビームの光強度分布をフラットな状態にすると、対物レンズのＲＩＭ強度（対物レンズ中心部における光強度に対する、対物レンズ外縁部における光強度の比）が高くなる。ＲＩＭ強度が高いほど対物レンズによって絞られた光スポット径は小さくなることから、図２の符号５０で示す光強度分布のとき図３の符号６０で示す光スポットの光強度分布であったものが、遮光型回折素子４を通過させ符号５１で示すフラットな光強度分布にすることで、符号６１で示すように光スポットの光強度分布を小さく絞ることができる。
本実施例では例えば図２に示したように、遮光型回折素子４の格子幅を中心部から外縁部にむけて段階的に小さくする事で、中心部付近に比べて外縁部付近の０次光透過率を高く設定することで、位相段差を発生させることなく、対物レンズに入射する光ビームの光強度分布をフラットに近づけ、ＢＤ側における光ディスク上の光スポットを小さく絞る事を特徴としている。これによって光学系の倍率が低くても、位相段差による収差発生なく、ＢＤ側における光ディスク上の光スポットサイズを十分に小さく絞る事ができる。 As shown in FIG. 2C, when the light intensity distribution of the light beam incident on the objective lens is made flat, the RIM intensity of the objective lens (the light intensity at the outer edge of the objective lens with respect to the light intensity at the center of the objective lens). Ratio) increases. As the RIM intensity is higher, the diameter of the light spot focused by the objective lens is smaller. Therefore, the light intensity distribution indicated by reference numeral 50 in FIG. 2 is the light intensity distribution of the light spot indicated by reference numeral 60 in FIG. The light intensity distribution of the light spot can be narrowed down as indicated by reference numeral 61 by passing through the light-shielding diffraction element 4 and forming a flat light intensity distribution indicated by reference numeral 51.
In this embodiment, for example, as shown in FIG. 2, the grating width of the light-shielding diffraction element 4 is gradually reduced from the central portion toward the outer edge portion, so that the 0th order near the outer edge portion is compared with the vicinity of the central portion. By setting the light transmittance high, the light intensity distribution of the light beam incident on the objective lens is made to be flat without causing a phase step, and the light spot on the optical disk on the BD side is narrowed down. . As a result, even when the magnification of the optical system is low, the light spot size on the optical disk on the BD side can be sufficiently reduced without generating aberration due to a phase step.

［３．遮光型回折格子の構成］
図４に遮光型回折格子４のパターン例を示している。光ピックアップのトラッキングサーボ方式が３スポットによるＤＰＰ（Differential Push-Pull）方式の場合、透過型の矩形断面形状を有する３スポット用回折格子によって３スポットが生成されるため、検出器２０における受光パターンは図５のようになる。このとき、遮光型回折格子４の格子角度θを０ｄｅｇとすると、遮光型回折格子４によって回折した回折迷光の発生角度φは０ｄｅｇと１８０ｄｅｇ方向になり、Ｔａｎ方向に配置したＤＰＰ検出器に回折迷光が入り光ピックアップの特性上望ましくない。このとき、遮光型回折素子４の格子ピッチを非常に狭くする（≦３μｍ）ことで理論的には回折迷光を検出器の外側に飛ばすことが可能だが、形成できる遮光型格子の幅の限度が１μｍであることを考慮すると、与えられる透過率分布に適切な設計解が無く現実的ではない。このため回折迷光の検出器への混入を避けるため、３スポットによるＤＰＰ方式を採用する場合には、遮光型回折格子の格子方向θは、
３０ｄｅｇ≦｜θ｜≦９０ｄｅｇ
でなければならない。 [3. Configuration of light-shielding diffraction grating]
FIG. 4 shows a pattern example of the light-shielding diffraction grating 4. When the tracking servo method of the optical pickup is a three-spot DPP (Differential Push-Pull) method, three spots are generated by a three-spot diffraction grating having a rectangular rectangular cross-sectional shape. As shown in FIG. At this time, if the grating angle θ of the light-shielding diffraction grating 4 is 0 deg, the generation angle φ of the diffracted stray light diffracted by the light-shielding diffraction grating 4 is 0 deg and 180 deg. Is not desirable due to the characteristics of the optical pickup. At this time, the grating pitch of the light-shielding diffractive element 4 can be made very narrow (≦ 3 μm), theoretically, it is possible to fly the diffracted stray light to the outside of the detector. Considering that the thickness is 1 μm, there is no appropriate design solution for the given transmittance distribution, which is not realistic. Therefore, in order to avoid mixing of diffracted stray light into the detector, when adopting the DPP method with three spots, the grating direction θ of the light-shielding diffraction grating is:
30deg ≦ | θ | ≦ 90deg
Must.

また、図４に示す格子パターンでは光強度分布の補正がＴａｎ方向のみで、Ｒａｄ方向には透過率分布が変化しない構成になっている。これはレーザの光強度分布を考慮したものである。一般的に半導体レーザの光強度分布は楕円であり、今回の設計例ではレーザ強度分布の短手方向をＴａｎ方向に向けた場合の設計例を示している。つまり、レーザ強度分布の長手になるＲａｄ方向は十分なＲＩＭ強度が確保できるため透過率分布の補正無しに所望のスポット径にまで絞ることができるが、短手になるＴａｎ方向はＲＩＭ強度が低いためにそのままでは所望のスポット径が得られない。このため、レーザ強度分布の短手になるＴａｎ方向にのみ透過率分布を付与することで、Ｔａｎ方向の光強度分布の補正を行っている。   Further, the grating pattern shown in FIG. 4 is configured such that the correction of the light intensity distribution is only in the Tan direction and the transmittance distribution does not change in the Rad direction. This is in consideration of the light intensity distribution of the laser. In general, the light intensity distribution of a semiconductor laser is an ellipse, and this design example shows a design example in which the short side direction of the laser intensity distribution is directed to the Tan direction. That is, the Rad direction, which is the length of the laser intensity distribution, can secure a sufficient RIM intensity, so that it can be narrowed down to a desired spot diameter without correcting the transmittance distribution, but the tan direction, which is short, has a low RIM intensity. Therefore, a desired spot diameter cannot be obtained as it is. For this reason, the light intensity distribution in the Tan direction is corrected by providing the transmittance distribution only in the Tan direction where the laser intensity distribution is short.

［４．まとめ］
本実施の形態の光ピックアップは、互いに発振波長の異なる第１のレーザ光源１および第２にレーザ光源２と、レーザ光源１から出射したレーザ光を３スポットにするための３スポット用回折格子３と、位相段差の発生なしに外縁部に比べて中心部の０次光透過率を低下させられる遮光型回折格子４と、遮光型回折格子４を透過した透過光を反射させるビームスプリッタ５と、レーザ光を略平行光に変換するコリメートレンズ６と、コリメートレンズ６によって略平行光になった光ビームを反射させる立ち上げミラー８と、光ディスク上に光ビームを集光させる対物レンズ９と、光ディスクから反射した信号光を受光する検出器２０からなる。
これにより、位相段差の発生なしに低コストで所望のスポット品質を得ることができる。 [4. Summary]
The optical pickup according to the present embodiment includes a first laser light source 1 and a second laser light source 2 having different oscillation wavelengths, and a three-spot diffraction grating 3 for making laser light emitted from the laser light source 1 into three spots. A light-shielding diffraction grating 4 that can reduce the 0th-order light transmittance at the center compared to the outer edge without the occurrence of a phase step, and a beam splitter 5 that reflects the transmitted light that has passed through the light-shielding diffraction grating 4. A collimating lens 6 that converts laser light into substantially parallel light, a rising mirror 8 that reflects a light beam that has become substantially parallel light by the collimating lens 6, an objective lens 9 that focuses the light beam on the optical disk, and an optical disk It comprises a detector 20 that receives the signal light reflected from.
Thereby, desired spot quality can be obtained at low cost without the occurrence of a phase step.

（他の実施の形態）
本発明の実施の形態として、実施の形態１を例示した。しかし、本発明はこれには限らない。そこで、本発明の他の実施の形態を以下まとめて説明する。なお、本発明は、これらには限定されず、適宜修正された実施の形態に対しても適用可能である。 (Other embodiments)
Embodiment 1 was illustrated as embodiment of this invention. However, the present invention is not limited to this. Therefore, other embodiments of the present invention will be described collectively below. In addition, this invention is not limited to these, It is applicable also to embodiment modified suitably.

実施の形態１において、トラッキングサーボ方式として３スポットによるＤＰＰ方式に対する最適な格子パターンを示したが、これには限らない。例えば、１ビームでホログラムを用いたＡＰＰ（Advanced Push-Pull）方式の場合の光学構成図を図６に、検出器のレイアウト例を図７（ａ）（ｂ）に示す。ＡＰＰ方式の場合では３スポット用回折格子３を用いず、例えば図６で示すようにＡＰＰ用ホログラム１６を配置する。このときの検出器レイアウトは自由度が高く、例えば図７（ａ）や（ｂ）で示すようなＡＰＰ検出器２０のレイアウトがあり、それぞれで最適な遮光型回折格子の角度が異なる。   In the first embodiment, the optimum lattice pattern for the DPP method using three spots is shown as the tracking servo method. However, the present invention is not limited to this. For example, FIG. 6 shows an optical configuration diagram in the case of an APP (Advanced Push-Pull) system using a hologram with one beam, and FIGS. 7A and 7B show layout examples of detectors. In the case of the APP system, the three-spot diffraction grating 3 is not used, and for example, an APP hologram 16 is arranged as shown in FIG. The detector layout at this time has a high degree of freedom. For example, there is a layout of the APP detector 20 as shown in FIGS. 7A and 7B, and the optimum angle of the light-shielding diffraction grating is different.

図７（ａ） ｜θ｜≦１５ｄｅｇ
図７（ｂ） ２０ｄｅｇ≦｜θ｜≦７０ｄｅｇ
このことから、遮光形回折格子の角度θは検出器のレイアウトも鑑みて最適化すべきであり、その制約は特に設けない。 FIG. 7 (a) | θ | ≦ 15 deg
FIG. 7B: 20 deg ≦ | θ | ≦ 70 deg
For this reason, the angle θ of the light-shielding diffraction grating should be optimized in view of the layout of the detector, and there is no particular limitation.

また、実施の形態１では階段状の回折格子としたが、これに限らない。図８で示すような２次元セルパターンや、図９で示すような遮光格子を途中で間引いたようなパターンであっても構わない。要するに、遮光部の面積比をＳとしたとき０次光透過率Ｔは、
Ｔ＝（１−Ｓ）＾２×１００ ［％］
で表され、所望の０次光透過率が得られ、検出器上の迷光が考慮されていれば格子パターンに特に制約はない。 In the first embodiment, a staircase diffraction grating is used, but the present invention is not limited to this. A two-dimensional cell pattern as shown in FIG. 8 or a pattern in which a light shielding grid as shown in FIG. 9 is thinned out may be used. In short, when the area ratio of the light shielding portion is S, the zero-order light transmittance T is
T = (1-S) ^ 2 × 100 [%]
If the desired 0th-order light transmittance is obtained and stray light on the detector is taken into consideration, there is no particular limitation on the grating pattern.

本発明は光ピックアップ装置に関し、特に、互いに発振波長の異なる光源を有する光ピックアップにおいて、位相段差による収差の発生なく低コストで所望のスポット品質を得ることができる。 The present invention relates to an optical pickup device, and in particular, in an optical pickup having light sources having different oscillation wavelengths, desired spot quality can be obtained at low cost without occurrence of aberration due to a phase step.

１，２ 半導体レーザ光源
４ 遮光型回折格子
９，１３ 対物レンズ
１４，１５ ディスク
１６ ＡＰＰ用ホログラム
２０ 検出器 DESCRIPTION OF SYMBOLS 1, 2 Semiconductor laser light source 4 Light-shielding type diffraction grating 9,13 Objective lens 14,15 Disk 16 APP hologram 20 Detector

Claims (4)

レーザ光を出射するレーザ光源と、
前記レーザ光源から出射されるレーザ光を光ディスクの記録層に集光させる対物レンズと、
前記レーザ光源と前記対物レンズとの間の光路上に配置された回折素子とを備え、
前記回折素子は、遮蔽物で構成される回折格子のデューティを中心部から外側に向かって階段状に小さくすることで、０次光透過率を変化させる、
ことを特徴とする光ピックアップ装置。 A laser light source for emitting laser light;
An objective lens for condensing the laser light emitted from the laser light source onto the recording layer of the optical disc;
A diffractive element disposed on an optical path between the laser light source and the objective lens;
The diffraction element changes the zero-order light transmittance by decreasing the duty of a diffraction grating formed of a shielding object in a stepped manner from the center to the outside.
An optical pickup device characterized by that. 前記回折素子の格子方向θは、３０ｄｅｇ≦｜θ｜≦９０ｄｅｇである、請求項１に記載の光ピックアップ装置。 The optical pickup device according to claim 1, wherein a grating direction θ of the diffraction element is 30 deg ≦ | θ | ≦ 90 deg. 前記レーザ光源は、複数のレーザ波長を有するレーザ光を出射する、請求項１に記載の光ピックアップ装置。 The optical pickup apparatus according to claim 1, wherein the laser light source emits laser light having a plurality of laser wavelengths. 互いに発振波長の異なる第１のレーザ光源および第２のレーザ光源と、第１のレーザ光源から出射した第１の光ビームまたは第２のレーザ光源から出射した第２の光ビームを光ディスクに集光させる対物レンズとを搭載した光ピックアップ装置において、第１のレーザ光源を出射した第１の光ビームが光ディスクに向かう光路中に、前記光ビームの中心部近傍が通過する領域に比べて前記光ビームの外縁部近傍が通過する領域の０次光の透過率が高くなるよう、中心部から外縁部に向けて回折格子のデューティを小さくし、かつ前記回折格子は金属膜のような遮光体で形成された回折素子を搭載する光ピックアップ装置。 The first laser light source and the second laser light source having different oscillation wavelengths and the first light beam emitted from the first laser light source or the second light beam emitted from the second laser light source are condensed on the optical disk. In the optical pickup device equipped with the objective lens to be operated, the light beam is compared with a region where the vicinity of the center of the light beam passes in the optical path of the first light beam emitted from the first laser light source toward the optical disk. The duty of the diffraction grating is reduced from the center to the outer edge so that the transmittance of the zero-order light in the region through which the vicinity of the outer edge passes is increased, and the diffraction grating is formed of a light shielding body such as a metal film. Pickup device on which the diffractive element is mounted.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3252773A4 (en) * 2015-01-30 2018-01-31 Panasonic Intellectual Property Management Co., Ltd. Optical pickup device and optical drive device

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JPH01119929A (en) * 1987-11-02 1989-05-12 Seiko Epson Corp Optical pickup
JPH0650717A (en) * 1992-07-30 1994-02-25 Ntn Corp Focal point error detector
JP2004295954A (en) * 2003-03-26 2004-10-21 Hitachi Ltd Optical pickup device and optical disk device

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JPH01119929A (en) * 1987-11-02 1989-05-12 Seiko Epson Corp Optical pickup
JPH0650717A (en) * 1992-07-30 1994-02-25 Ntn Corp Focal point error detector
JP2004295954A (en) * 2003-03-26 2004-10-21 Hitachi Ltd Optical pickup device and optical disk device

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3252773A4 (en) * 2015-01-30 2018-01-31 Panasonic Intellectual Property Management Co., Ltd. Optical pickup device and optical drive device
US10049695B2 (en) 2015-01-30 2018-08-14 Panasonic Intellectual Property Management Co., Ltd. Optical pickup device and optical drive device

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