JP4160411B2 - Optical integrated unit and optical pickup device having the same - Google Patents

Optical integrated unit and optical pickup device having the same Download PDF

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JP4160411B2
JP4160411B2 JP2003020614A JP2003020614A JP4160411B2 JP 4160411 B2 JP4160411 B2 JP 4160411B2 JP 2003020614 A JP2003020614 A JP 2003020614A JP 2003020614 A JP2003020614 A JP 2003020614A JP 4160411 B2 JP4160411 B2 JP 4160411B2
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light
light receiving
receiving region
diffracted
hologram
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JP2004265458A (en
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錬三郎 三木
啓至 酒井
富行 沼田
徹男 上山
廣茂 牧岡
修 宮崎
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Sharp Corp
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording 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
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/13—Optical detectors therefor
    • G11B7/131—Arrangement of detectors in a multiple array
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording 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
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/123—Integrated head arrangements, e.g. with source and detectors mounted on the same substrate
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording 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
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/13—Optical detectors therefor
    • G11B7/133—Shape of individual detector elements
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording 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
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1353—Diffractive elements, e.g. holograms or gratings
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording 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
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1356—Double or multiple prisms, i.e. having two or more prisms in cooperation

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  • Optics & Photonics (AREA)
  • Optical Recording Or Reproduction (AREA)
  • Optical Head (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、情報記録媒体に光学的に情報を記録し、または情報記録媒体から光学的に情報を読み取るための光集積化ユニットおよびそれを備えた光ピックアップ装置に関する。
【０００２】
【従来の技術】
第１の先行技術の光ピックアップ装置は、小形化、薄形化および高信頼性化を図るためのホログラムを備える。前記ホログラムは、ディスク半径方向に２分割され、かつその一方は、さらにトラック方向に２分割される。この先行技術の光ピックアップ装置は、光ディスクによって反射されたレーザ光の半分でフォーカス誤差信号を、もう半分でトラック誤差信号を、全体で情報信号を検出する。この先行技術の光ピックアップ装置では、トラッキングが合っているにも拘わらず、対物レンズのシフトおよび光ディスクの傾きによってオフセットが生じ、ディトラックと判定してしまうという問題がある（たとえば特許文献１参照）。
【０００３】
このような問題を解決するための技術は、特願２００２−２４８４７９号に提案されている。図９は、第２の先行技術の光集積化ユニット１の概略的な構成を示す図である。図１０は、光集積化ユニット１におけるホログラム２、回折格子３および第１〜第６受光領域部分１１〜１６の位置関係を示す図である。光ピックアップ装置は、光集積化ユニット１と、この光集積化ユニット１からのレーザ光を光ディスク上に集光させる対物レンズ手段と含んで構成される。
【０００４】
光集積化ユニット１は、ホログラム２、回折格子３および受光部４を含む。受光部４の受光面５は、この受光面５に垂直な仮想一平面６に関して一方の受光領域７ａと他方の受光領域７ｂとに分割され、前記一方の受光領域７ａには、第１、第３および第５受光領域部分１１，１３，１５が設けられ、前記他方の受光領域７ｂには、第２、第４および第６受光領域部分１２，１４，１６が設けられる。ホログラム２は、前述の第１の先行技術のように分割され、したがって第１〜第３回折面２ａ〜２ｃを有する。第１回折面２ａは、第１受光領域部分１１および第２受光領域部分１２に向けてレーザ光を導き、第２回折面２ｂは、第３受光領域部分１３および第４受光領域部分１４に向けてレーザ光を導き、第３回折面２ｃは、第５受光領域部分１５および第６受光領域部分１６に向けてレーザ光を導く。
【０００５】
ホログラム２と受光部４との間には、ディスク半径方向に回折効率を異ならせた回折格子３が介在される。この回折格子３は、一方の受光領域７ａの、第１受光領域部分１１および第３受光領域部分１３に向けて導かれるレーザ光Ｌａ１，Ｌｂ１を回折させる。したがって第１受光領域部分１１および第３受光領域部分１３には、回折格子３によって回折されたレーザ光が導かれ、対物レンズのシフトおよび光ディスクの傾きによって生じるオフセットを補正するためのキャンセル信号が生成される。これによってプッシュプル信号のオフセット補正を行うことができ、安定したトラッキングサーボ性能を得ることができる。
【０００６】
【特許文献１】
特開平９−１６１２８２号公報
【０００７】
【発明が解決しようとする課題】
図１１は、ホログラム２からのレーザ光Ｌａ１，Ｌａ２，Ｌｂ１，Ｌｂ２，Ｌｃ１，Ｌｃ２の、回折格子３を含む仮想一平面上の透過位置を示す図である。この図１１に示されるように、回折格子３を含む仮想一平面上では、各受光領域部分１１〜１６に向けて導かれるレーザ光は充分に分離されず、第３受光領域部分１３に向けて導かれるレーザ光Ｌｂ１と第５受光領域部分１５に向けて導かれるレーザ光Ｌｃ１とは重なり合う。したがって前記第２の先行技術では、第１受光領域部分１１および第３受光領域部分１３に向けて導かれるレーザ光Ｌａ１，Ｌｂ１だけでなく、第５受光領域部分１５に向けて導かれるレーザ光Ｌｃ１までもが回折格子３によって回折されてしまう。すなわちキャンセル信号を生成するためのレーザ光だけでなく、フォーカス誤差信号を検出するためのレーザ光までもが、回折格子３によって回折されてしまう。これによってフォーカス誤差信号は、回折格子３による透過率変化の影響を受け、その影響はフォーカス誤差信号にノイズとなって現れてしまうので、フォーカスサーボが引き込めなくなったり、引き込めても充分にゲインを上げることができず、サーボの抑え込みが不充分であったりする。
【０００８】
一方の受光領域７ａの、第１受光領域部分１１および第３受光領域部分１３に向けて導かれるレーザ光Ｌａ１，Ｌｂ１ではなく、他方の受光領域７ｂの、第２受光領域部分１２および第４受光領域部分１４に向けて導かれるレーザ光Ｌａ２，Ｌｂ２を回折させるように回折格子３が設けられると、第６受光領域部分１６に向けて導かれるレーザ光Ｌｃ２までもが回折格子３によって回折されてしまい、トラック誤差信号が不安定になるとともに、情報信号のエラーレートが極端に悪くなる恐れがある。
【０００９】
前記第２の先行技術では、一方の受光領域７ａの、第１受光領域部分１１および第３受光領域部分１３に向けて導かれるレーザ光Ｌａ１，Ｌｂ１だけが回折格子３によって回折されるように回折格子３を配置することはできない。また他方の受光領域７ｂの、第２受光領域部分１２および第４受光領域部分１４に向けて導かれるレーザ光Ｌａ２，Ｌｂ２だけが回折格子３によって回折されるように回折格子３を配置することもできない。このように前記第２の先行技術では、回折格子３によって回折される必要がない回折光の光経路を避けて回折格子３を配置することができず、誤検出が生じてしまうという問題がある。
【００１０】
本発明の目的は、誤検出が生じてしまうという不具合を容易に防止することができる光集積化ユニットおよびそれを備えた光ピックアップ装置を提供することである。
【００１１】
【課題を解決するための手段】
本発明は、予め定める第１軸線に垂直な受光面を有し、この受光面を、前記予め定める第１軸線を含む仮想一平面に関して一方の受光領域と他方の受光領域とに分割し、一方の受光領域および他方の受光領域には、前記仮想一平面と受光面とが交差する第２軸線に沿って各複数の受光領域部分が設けられる受光部と、
前記一方の受光領域内の複数の受光領域部分のうち予め定める第１受光領域部分および前記他方の受光領域内の複数の受光領域部分のうち予め定める第２受光領域部分に向けてレーザ光を導く第１回折面と、前記一方の受光領域内の複数の受光領域部分のうち予め定める第３受光領域部分および前記他方の受光領域内の複数の受光領域部分のうち予め定める第４受光領域部分に向けてレーザ光を導く第２回折面と、前記一方の受光領域内の複数の受光領域部分のうち予め定める第５受光領域部分および前記他方の受光領域内の複数の受光領域部分のうち予め定める第６受光領域部分に向けてレーザ光を導く第３回折面とが、前記予め定める第１軸線に垂直にかつ受光面に臨んで設けられるホログラムと、
前記受光部とホログラムとの間に介在され、前記第２軸線に垂直な方向に沿って回折効率が変化し、ホログラムの第１回折面によって回折された回折光の一部を回折させて、前記第１受光領域部分に導き、かつホログラムの第２回折面によって回折された回折光の一部を回折させて、前記第４受光領域部分に導き、ホログラムの第３回折面によって回折された回折光の光経路を避けて配置される回折格子とを含むことを特徴とする光集積化ユニットである。
【００１２】
本発明に従えば、受光部の受光面は前記仮想一平面に関して一方の受光領域と他方の受光領域とに分割され、さらに一方の受光領域は第１、第３および第５受光領域部分に分割され、他方の受光領域は第２、第４および第６受光領域部分に分割される。ホログラムは、導かれたレーザ光を前記第１〜第３回折面によって回折し、その回折された各回折光は前記受光部の第１〜第６受光領域部分によって受光される。回折格子は、ホログラムの第１回折面によって回折された回折光の一部を回折させて、前記一方の受光領域内の第１受光領域部分に導き、かつ第２回折面によって回折された回折光の一部を回折させて、前記他方の受光領域内の第４受光領域部分に導き、さらに第３回折面によって回折された回折光の光経路を避けるように、前記受光部とホログラムとの間に設けられる。
【００１３】
このように受光部の一方の受光領域に向かう第１回折面による回折光の一部と、受光部の他方の受光領域に向かう第２回折面による回折光の一部とを回折させ、受光部の両方の受光領域に向かう第３回折面による回折光の光経路を避ける位置に前記回折格子が配置される。このとき、第１〜第３回折面によって回折された各回折光を、前記回折格子によって回折させる必要がある回折光と、前記回折格子によって回折させる必要がない回折光とに第２軸線に沿う方向に関して前後に振り分けられるようにホログラムの第１〜第３回折面の特性を適宜選択することによって、回折格子によって回折させる必要がない第３回折面による回折光の光経路を避けて回折格子を配置することが可能となる。したがって回折格子によって回折させる必要がない回折光までもが回折格子によって回折してしまい、誤検出が生じてしまうという不具合を容易に防止することができる。
【００１４】
また本発明は、前記第１回折面は、第１受光領域部分に向けては＋ｎ（ここに、ｎは１以上の正の整数）次回折光を導き、かつ第２受光領域部分に向けては−ｎ次回折光を導き、
前記第２回折面は、第３受光領域部分に向けては＋ｎ次回折光を導き、かつ第４受光領域部分に向けては−ｎ次回折光を導き、
前記第３回折面は、第５受光領域部分に向けては＋ｎ次回折光を導き、かつ第６受光領域部分に向けては−ｎ次回折光を導くことを特徴とする。
【００１５】
本発明に従えば、ホログラムの第１〜第３回折面は、＋ｎ次回折光および−ｎ次回折光を、所定の各受光領域部分に向けて導く。第１回折面からの＋ｎ次回折光および−ｎ次回折光はホログラムの近傍でも充分に分離され、第２回折面からの＋ｎ次回折光および−ｎ次回折光はホログラムの近傍でも充分に分離され、第３回折面からの＋ｎ次回折光および−ｎ次回折光はホログラムの近傍でも充分に分離されるので、回折格子によって回折させる必要がない回折光の光経路を避けて回折格子を配置することが容易となる。
【００１６】
また本発明は、前記回折格子は、ホログラムの第１回折面によって回折された前記回折光の一部の光経路上と、ホログラムの第２回折面によって回折された前記回折光の一部の光経路上とに、個別に設けられることを特徴とする。
【００１７】
本発明に従えば、ホログラムの第１回折面によって回折された前記回折光の一部の光経路上と、ホログラムの第２回折面によって回折された前記回折光の一部の光経路上とに、個別に回折格子が設けられるので、回折格子は不要な部分が削減され、第１受光領域部分および第４受光領域部分を除く残余の各受光領域部分に導かれる回折光までもが回折格子によって回折してしまうという不具合を可及的に防止することができる。
【００１８】
また本発明は、レーザ光を発生する発光部と、
発光部からのレーザ光を情報記録媒体に導き、かつ情報記録媒体によって反射されたレーザ光を前記ホログラムに導く光分岐素子とをさらに含むことを特徴とする。
【００１９】
本発明に従えば、光分岐素子は、発光部からのレーザ光を情報記録媒体に導き、かつ情報記録媒体によって反射されたレーザ光をホログラムに導く。ホログラムは、導かれたレーザ光を、前述のように受光部の各受光領域部分に導く。このような本発明の光集積化ユニットがたとえば光ピックアップ装置に用いられる場合、発光部と受光部とを個別に設ける必要がないので、信号検出系の調整が不要であり、組立て性が向上される。また発光部および受光部などを含む本発明の光集積化ユニットは１つの光学部品として扱うことができ、したがって光学部品点数が低減される。
【００２０】
また本発明は、前記光集積化ユニットと、
光集積化ユニットからのレーザ光を情報記録媒体上に集光させる対物レンズ手段とを含むことを特徴とする光ピックアップ装置である。
【００２１】
本発明に従えば、対物レンズ手段が光集積化ユニットからのレーザ光を情報記録媒体上に集光させるとともに、光集積化ユニットの受光部の各受光領域部分が情報記録媒体によって反射されたレーザ光を受光する。前記光集積化ユニットは、誤検出が生じるという不具合が防止されているので、情報記録媒体に正確に情報を記録し、または情報記録媒体から正確に情報を読み取ることができる。
【００２２】
【発明の実施の形態】
図１は、本発明の実施の一形態の光集積化ユニット２１の概略的な構成を示す図である。本実施の形態の光集積化ユニット２１は、たとえば、情報記録媒体に光学的に情報を記録し、または情報記録媒体から光学的に情報を読み取る光ピックアップ装置などに搭載される。前記情報記録媒体は、たとえばデジタルバーサタイルディスク（Digital Versatile Disc、略称ＤＶＤ）などの光ディスクである。光集積化ユニット２１は、発光部２２、ホログラム素子２３、光分岐素子２４および受光部２５を含む。
【００２３】
発光部２２は、ステム２６に設けられる。発光部２２は、レーザ光を発生する。発光部２２は、たとえばレーザダイオード（Laser Diode、略称ＬＤ）チップによって実現される。ホログラム素子２３は、ホログラム３１および光学素子３２を有する。ホログラム３１は、多分割ホログラムである。光学素子３２は、回折格子である。受光部２５には、第１〜第６受光領域部分４１〜４６（後述の図２参照）が設けられ、各受光領域部分４１〜４６は、ホログラム素子２３からのレーザ光を受光する。
【００２４】
光分岐素子２４は、発光部２２からのレーザ光を光ディスクに導き、かつ光ディスクによって反射されたレーザ光をホログラム素子２３のホログラム３１に導く。光分岐素子２４は、第１面３３および第２面３４を有する。第１面３３は、発光部２２からのレーザ光は透過させ、光ディスクによって反射されたレーザ光は反射させる。第２面３４は、第１面３３によって反射されたレーザ光を反射させる。
【００２５】
発光部２２からのレーザ光は、第１面３３を透過して光ディスクに導かれ、光ディスクによって反射されたレーザ光は、第１面３３によって反射され、さらに第２面３４によって反射されてホログラム素子２３のホログラム３１に導かれる。こうしてホログラム３１に導かれたレーザ光は、受光部２５の各受光領域部分４１〜４６で受光される。
【００２６】
本実施の形態の光集積化ユニット２１がたとえば光ピックアップ装置に用いられる場合、発光部２２と受光部２５とを個別に設ける必要がないので、信号検出系の調整が不要であり、組立て性が向上される。また発光部２２および受光部２５などを含む本実施の形態の光集積化ユニットは１つの光学部品として扱うことができ、したがって光学部品点数が低減される。
【００２７】
図２は、ホログラム３１、光学素子３２および第１〜第６受光領域部分４１〜４６の位置関係を示す図である。受光部２５は、予め定める第１軸線Ｌ１に垂直な受光面３６を有する。この受光面３６は、前記予め定める第１軸線Ｌ１を含む仮想一平面３７に関して一方の受光領域３８ａと他方の受光領域３８ｂとに分割される。ホログラム３１は、第１〜第３回折面３１ａ〜３１ｃを有する。第１〜第３回折面３１ａ〜３１ｃは、前記予め定める第１軸線Ｌ１に垂直にかつ受光面３６に臨んで設けられる。
【００２８】
ホログラム３１は円形状であり、このホログラム３１の中心は前記予め定める第１軸線Ｌ１上に配置される。第２回折面３１ｂと第３回折面３１ｃとの境界４８ａは、ホログラム３１の中心から、前記仮想一平面３７に垂直な第１方向Ｘの一方Ｘ１に向かって延びる。第１回折面３１ａと第３回折面３１ｃとの境界４８ｂは、ホログラム３１の中心から、第１方向Ｘの他方Ｘ２に向かって延びる。第１回折面３１ａと第２回折面３１ｂとの境界４８ｃは、ホログラム３１の中心から、前記予め定める第１軸線Ｌ１に垂直で、かつ第１方向Ｘに垂直な第２方向Ｙの一方Ｙ１に向かって延びる。
【００２９】
受光面３６の一方の受光領域３８ａには、前記仮想一平面３７と受光面３６とが交差する第２軸線Ｌ２に沿って、第１受光領域部分４１、第３受光領域部分４３および第５受光領域部分４５が設けられる。第５受光領域部分４５は、第２軸線Ｌ２に沿う方向、すなわち第２方向Ｙに、ホログラム３１とほぼ同一の位置に設けられる。第１受光領域部分４１は、第５受光領域部分４５よりも第２方向Ｙの一方Ｙ１に設けられる。第３受光領域部分４３は、第５受光領域部分４５よりも第２方向Ｙの他方Ｙ２に設けられる。
【００３０】
受光面３６の他方の受光領域３８ｂには、第２軸線Ｌ２に沿って、第２受光領域部分４２、第４受光領域部分４４および第６受光領域部分４６が設けられる。第６受光領域部分４６は、第２方向Ｙに、ホログラム３１とほぼ同一の位置に設けられる。第２受光領域部分４２は、第６受光領域部分４６よりも第２方向Ｙの他方Ｙ２に設けられる。第４受光領域部分４４は、第６受光領域部分４６よりも第２方向Ｙの一方Ｙ１に設けられる。
【００３１】
第１受光領域部分４１は、３つの部分４１１，４１２，４１３を有する。この３つの部分４１１，４１２，４１３は、第２軸線Ｌ２に沿って、相互に間隔をあけて設けられる。第４受光領域部分４４は、３つの部分４４１，４４２，４４３を有する。この３つの部分４４１，４４２，４４３は、第２軸線Ｌ２に沿って、相互に間隔をあけて設けられる。第５受光領域部分４５は、２つの部分４５１，４５２を有する。この２つの部分４５１，４５２は、第２軸線Ｌ２に沿って、相互に隣接して設けられる。
【００３２】
ホログラム３１の第１〜第３回折面３１ａ〜３１ｃには、相互に異なる回折格子が形成される。第１回折面３１ａは、前記一方の受光領域３８ａ内の複数の受光領域部分４１，４３，４５のうち予め定める第１受光領域部分４１および前記他方の受光領域３８ｂ内の複数の受光領域部分４２，４４，４６のうち予め定める第２受光領域部分４２に向けてレーザ光を導く。第２回折面３１ｂは、前記一方の受光領域３８ａ内の複数の受光領域部分４１，４３，４５のうち予め定める第３受光領域部分４３および前記他方の受光領域３８ｂ内の複数の受光領域部分４２，４４，４６のうち予め定める第４受光領域部分４４に向けてレーザ光を導く。第３回折面３１ｃは、前記一方の受光領域３８ａ内の複数の受光領域部分４１，４３，４５のうち予め定める第５受光領域部分４５および前記他方の受光領域３８ｂ内の複数の受光領域部分４２，４４，４６のうち予め定める第６受光領域部分４６に向けてレーザ光を導く。
【００３３】
本実施の形態においては、第１回折面３１ａは、第１受光領域部分４１に向けては＋１次回折光Ｌａ１を導き、かつ第２受光領域部分４２に向けては−１次回折光Ｌａ２を導く。第２回折面３１ｂは、第３受光領域部分４３に向けては＋１次回折光Ｌｂ１を導き、かつ第４受光領域部分４４に向けては−１次回折光Ｌｂ２を導く。第３回折面３１ｃは、第５受光領域部分４５に向けては＋１次回折光Ｌｃ１を導き、かつ第６受光領域部分４６に向けては−１次回折光Ｌｃ２を導く。
【００３４】
このようにホログラム３１の第１〜第３回折面３１ａ〜３１ｃは、＋１次回折光Ｌａ１，Ｌｂ１，Ｌｃ１および−１次回折光Ｌａ２，Ｌｂ２，Ｌｃ２を、所定の各受光領域部分４１〜４６に向けて導く。第１回折面３１ａからの＋１次回折光Ｌａ１および−１次回折光Ｌａ２はホログラム３１の近傍でも充分に分離され、第２回折面３１ｂからの＋１次回折光Ｌｂ１および−１次回折光Ｌｂ２はホログラム３１の近傍でも充分に分離され、第３回折面３１ｃからの＋１次回折光Ｌｃ１および−１次回折光Ｌｃ２はホログラム３１の近傍でも充分に分離されるので、光学素子３２を透過させる必要がない回折光Ｌａ２，Ｌｂ１，Ｌｃ１，Ｌｃ２の光経路を避けて光学素子３２を配置することが容易となる。
【００３５】
光学素子３２は、受光部２５とホログラム３１との間に介在される。この光学素子３２は、ホログラム３１の第１回折面３１ａによって回折された回折光の一部である＋１次回折光Ｌａ１をさらに回折させ、＋１次、０次および−１次の回折光Ｌａ１１〜Ｌａ１３を、第１受光領域部分４１の３つの部分４１１，４１２，４１３にそれぞれ導く。またこの光学素子３２は、ホログラム３１の第２回折面３１ｂによって回折された回折光の一部である−１次回折光Ｌｂ２をさらに回折させ、＋１次、０次および−１次の回折光Ｌｂ２１〜Ｌｂ２３を、第４受光領域部分４４の３つの部分４４１，４４２，４４３にそれぞれ導く。
【００３６】
図３は、ホログラム３１からの回折光Ｌａ１，Ｌａ２，Ｌｂ１，Ｌｂ２，Ｌｃ１，Ｌｃ２の、光学素子３２を含む仮想一平面上の透過位置を示す図である。光学素子３２は、第１受光領域部分４１に向けて導かれる回折光Ｌａ１の光経路上と、第４受光領域部分４４に向けて導かれる回折光Ｌｂ２の光経路上とに配置される。
【００３７】
第３受光領域部分４３に向けて導かれる回折光Ｌｂ１および第５受光領域部分４５に向けて導かれる回折光Ｌｃ１は、光学素子３２を含む仮想一平面上では一部が重なり合っている。また第２受光領域部分４２に向けて導かれる回折光Ｌａ２および第６受光領域部分４６に向けて導かれる回折光Ｌｃ２は、光学素子３２を含む仮想一平面上では一部が重なり合っている。
【００３８】
これに対して、第１受光領域部分４１に向けて導かれる回折光Ｌａ１は、光学素子３２を含む仮想一平面上では、第１受光領域部分４１を除く残余の各受光領域部分４２〜４６に向けて導かれる回折光Ｌａ２，Ｌｂ１，Ｌｂ２，Ｌｃ１，Ｌｃ２と重なり合わず、それらから充分に分離されている。また第４受光領域部分４４に向けて導かれる回折光Ｌｂ２は、光学素子３２を含む仮想一平面上では、第４受光領域部分４４を除く残余の各受光領域部分４１〜４３，４５，４６に向けて導かれる回折光Ｌａ１，Ｌａ２，Ｌｂ１，Ｌｃ１，Ｌｃ２と重なり合わず、それらから充分に分離されている。
【００３９】
本実施の形態では、光学素子３２は、ホログラム３１の第１回折面３１ａによって回折された回折光の一部Ｌａ１を透過させて、一方の受光領域３８ａ内の第１受光領域部分４１に導き、かつ第２回折面３１ｂによって回折された回折光の一部Ｌｂ２を透過させて、他方の受光領域３８ｂ内の第４受光領域部分４４に導くように、受光部２５とホログラム３１との間に設けられる。
【００４０】
このように受光部２５の一方の受光領域３８ａに向かう第１回折面３１ａによる回折光の一部Ｌａ１と、受光部２５の他方の受光領域３８ｂに向かう第２回折面３１ｂによる回折光の一部Ｌｂ２とが透過する位置に前記光学素子３２が配置されるので、前述のように第１〜第３回折面３１ａ〜３１ｃによって回折された各回折光Ｌａ１，Ｌａ２，Ｌｂ１，Ｌｂ２，Ｌｃ１，Ｌｃ２を、前記光学素子３２を透過させる必要がある回折光Ｌａ１，Ｌｂ２と、前記光学素子３２を透過させる必要がない回折光Ｌａ２，Ｌｂ１，Ｌｃ１，Ｌｃ２とに第２軸線Ｌ２に沿う方向（第２方向Ｙ）に関して前後に振り分けられるようにホログラム３１の第１〜第３回折面３１ａ〜３１ｃの特性を選択することによって、光学素子３２を透過させる必要がない回折光Ｌａ２，Ｌｂ１，Ｌｃ１，Ｌｃ２の光経路を避けて光学素子３２を配置することが可能となる。したがって第１受光領域部分４１および第４受光領域部分４４を除く残余の各受光領域部分４２，４３，４５，４６に導かれる回折光Ｌａ２，Ｌｂ１，Ｌｃ１，Ｌｃ２までもが光学素子３２を透過してしまい、誤検出が生じてしまうという不具合を容易に防止することができる。
【００４１】
図４は、光学素子３２の一部を概略的に示す平面図である。図５は、第１受光領域部分４１に向けて導かれる回折光Ｌａ１の、光学素子３２上の透過位置を示す図である。光学素子３２は、透過率が第１方向Ｘに変化する。本実施の形態では、光学素子３２は回折格子であり、したがって回折効率が第１方向Ｘに変化する。光学素子３２には、第１方向Ｘに沿って、複数の溝５１が形成される。光学素子３２の格子間ピッチＰは、第１方向Ｘの位置に拘わらず一定である。
【００４２】
光学素子３２のデューティＤは、第１方向Ｘに連続的に変化する。前記デューディＤは、グルーブ幅をＷＧ、ランド幅をＷＬとすると、次式、
Ｄ＝ＷＬ／（ＷＧ＋ＷＬ） …（１）
で表される。
【００４３】
光学素子３２のデューティＤは、第１方向Ｘの一方Ｘ１に進むにつれて徐々に増加する。デューティＤの初期値を０．５以上に設定した場合、デューティＤが増加するにつれて、光学素子３２によって回折された＋１次回折光および−１次回折光の回折効率は低くなり、光学素子３２によって回折された０次回折光の回折効率は高くなる。
【００４４】
光学素子３２の第１方向Ｘの他方Ｘ２の端部のデューティＤ１は、たとえば０．６に選ばれ、光学素子３２の第１方向Ｘの一方Ｘ１の端部のデューティＤ２は、たとえば０．９に選ばれる。光学素子３２の第１方向Ｘの両端部間の中央部のデューティＤ３は、たとえば０．７５に選ばれる。前記光学素子３２の第１方向Ｘの両端部間の中央部と、ホログラム３１の中心とは、第１方向Ｘに同一の位置である（前述の図３参照）。
【００４５】
第１受光領域部分４１に向けて導かれる回折光Ｌａ１の、光学素子３２上の透過位置が、所定位置５２から図５の仮想線５３で示される位置へ移動した場合、すなわち第１方向Ｘの一方Ｘ１へ移動した場合、光学素子３２によって回折された＋１次回折光Ｌａ１１および−１次回折光Ｌａ１３の光量が低下し、０次回折光Ｌａ１２の光量が増加する。第１受光領域部分４１に向けて導かれる回折光Ｌａ１の、光学素子３２上の透過位置が、所定位置５２から図５の仮想線５４で示される位置へ移動した場合、すなわち第１方向Ｘの他方Ｘ２へ移動した場合、光学素子３２によって回折された＋１次回折光Ｌａ１１および−１次回折光Ｌａ１３の光量が増加し、０次回折光Ｌａ１２の光量が低下する。
【００４６】
第４受光領域部分４４に向けて導かれる回折光Ｌｂ２の、光学素子３２上の透過位置が、第１方向Ｘの一方Ｘ１へ移動した場合、光学素子３２によって回折された＋１次回折光Ｌｂ２１および−１次回折光Ｌｂ２３の光量が低下し、０次回折光Ｌｂ２２の光量が増加する。第４受光領域部分４４に向けて導かれる回折光Ｌｂ２の、光学素子３２上の透過位置が、第１方向Ｘの他方Ｘ２へ移動した場合、光学素子３２によって回折された＋１次回折光Ｌｂ２１および−１次回折光Ｌｂ２３の光量が増加し、０次回折光Ｌｂ２２の光量が低下する。
【００４７】
本発明の実施の他の形態の光ピックアップ装置は、前述の実施の形態の光集積化ユニット２１と、この光集積化ユニット２１からのレーザ光を光ディスク上に集光させる対物レンズ手段とを含む。本実施の形態においては、第１方向Ｘは、光ディスクの予め定める半径方向に対応し、第２方向Ｙは、光ディスクの前記半径方向に垂直なトラック方向に対応する。本実施の形態の光ピックアップ装置では、光集積化ユニット２１の受光部２５の各受光領域部分４１〜４６からの出力信号に基づいて、情報信号ＲＦ、フォーカス誤差信号ＦＥＳおよびトラック誤差信号ＴＥＳが生成される。
【００４８】
第１受光領域部分４１の３つの部分４１１〜４１３からの各出力信号をＳ１１〜Ｓ１３とし、第２受光領域部分４２からの出力信号をＳ２とし、第３受光領域部分４３からの出力信号をＳ３とし、第４受光領域部分４４の３つの部分４４１〜４４３からの各出力信号をＳ４１〜Ｓ４３とし、第５受光領域部分４５の２つの部分４５１，４５２からの各出力信号をＳ５１，Ｓ５２とし、第６受光領域部分４６からの出力信号をＳ６とする。このとき、情報信号ＲＦ、フォーカス誤差信号ＦＥＳおよびトラック誤差信号ＴＥＳは、以下の式２〜式４、

Figure 0004160411
に基づいてそれぞれ生成される。
【００４９】
式４において、右辺の第１項はプッシュプル信号（ＰＰ信号）であり、右辺の第２項の係数α１以降はキャンセル信号である。係数α１は、対物レンズのシフト量および光ディスクの傾き量をプッシュプル信号におけるオフセット量に換算するための係数である。キャンセル信号は、対物レンズのシフトおよび光ディスクの傾きなどによってプッシュプル信号に生じるオフセットを補正するための信号である。
【００５０】
また式４において、係数β１は、光学素子３２の溝５１の深さによって決まる係数である。この係数β１は、光学素子３２によって回折された＋１次回折光Ｌａ１１，Ｌｂ２１および−１次回折光Ｌａ１３，Ｌｂ２３と、光学素子３２によって回折された０次回折光Ｌａ１２，Ｌｂ２２との回折効率の差を調整する係数である。この係数β１は、ホログラム３１の第１回折面３１ａによって回折された＋１次回折光Ｌａ１およびホログラム３１の第２回折面３１ｂによって回折された−１次回折光Ｌｂ２が光学素子３２上の所定位置をそれぞれ透過するときに、次式、
（Ｓ１２＋Ｓ４２）
−β１×（Ｓ１１＋Ｓ１３＋Ｓ４１＋Ｓ４３）＝０ …（５）
を満たすように決定される。前記光学素子３２上の所定位置は、ホログラム３１の第１回折面３１ａによって回折された＋１次回折光Ｌａ１およびホログラム３１の第２回折面３１ｂによって回折された−１次回折光Ｌｂ２の、対物レンズのシフトおよび光ディスクの傾きがないとき、すなわちオフセットがないときの、光学素子３２上の透過位置である。
【００５１】
本実施の形態では、係数α１以降の演算においては、光学素子３２によって回折された＋１次回折光Ｌａ１１，Ｌｂ２１および−１次回折光Ｌａ１３，Ｌｂ２３と、光学素子３２によって回折された０次回折光Ｌａ１２，Ｌｂ２２との差動を演算している。光学素子３２によって回折された＋１次回折光Ｌａ１１，Ｌｂ２１および−１次回折光Ｌａ１３，Ｌｂ２３と、光学素子３２によって回折された０次回折光Ｌａ１２，Ｌｂ２２とは、前述のように光量の変化の方向が反対である。したがって対物レンズのシフトおよび光ディスクの傾きに対する感度は高くなる。
【００５２】
以上のようにして本実施の形態の光ピックアップ装置では、いわゆる１ビームＰＰ法を用いて、情報信号ＲＦ、フォーカス誤差信号ＦＥＳおよびトラック誤差信号ＴＥＳを生成する。１ビームＰＰ法を用いる場合、記録光量を大きくして、記録スピードを大きくすることができる。この光ピックアップ装置は、光ディスクにおけるスポットおよびピット間の光軸のずれ、すなわちトラッキング方向のずれだけを抽出して、そのずれを補正することができる。したがってこの光ピックアップ装置では、対物レンズのシフトおよび光ディスクの傾きに拘わらず、安定したトラッキングサーボ性能を達成することができる。
【００５３】
本実施の形態では、対物レンズ手段が光集積化ユニット２１からのレーザ光を光ディスク上に集光させるとともに、光集積化ユニット２１の受光部２５の各受光領域部分４１〜４６が光ディスクによって反射されたレーザ光を受光する。前記光集積化ユニット２１は、誤検出が生じるという不具合が防止されているので、光ディスクに正確に情報を記録し、または光ディスクから正確に情報を読み取ることができ、信頼性が向上される。
【００５４】
図６は、本発明の実施のさらに他の形態の光集積化ユニット６１の概略的な構成を示す図である。図７は、ホログラム３１、光学素子６２および第１〜第６受光領域部分４１〜４６の位置関係を示す図である。図８は、ホログラム３１からの回折光Ｌａ１，Ｌａ２，Ｌｂ１，Ｌｂ２，Ｌｃ１，Ｌｃ２の、光学素子６２を含む仮想一平面上の透過位置を示す図である。本実施の形態の光集積化ユニット６１は、前述の実施の形態の光集積化ユニット２１と類似するので、同様の部分は同一の参照符を付して説明を省略する。
【００５５】
本実施の形態においては、光学素子６２は、第１受光領域部分４１に向けて導かれる回折光Ｌａ１の光経路上と、第４受光領域部分４４に向けて導かれる回折光Ｌｂ２の光経路上とに、個別に設けられる。光学素子６２は、第１受光領域部分４１に向けて導かれる回折光Ｌａ１の光経路上に設けられる第１部分６２ａと、第４受光領域部分４４に向けて導かれる回折光Ｌｂ２の光経路上に設けられる第２部分６２ｂとを有する。
【００５６】
第１部分６２ａの、第１方向Ｘの他方Ｘ２の端部のデューティＤ１ａは、たとえば０．６に選ばれ、第１方向Ｘの一方Ｘ１の端部のデューティＤ２ａは、たとえば０．９に選ばれる。また第２部分６２ｂの、第１方向Ｘの他方Ｘ２の端部のデューティＤ１ｂは、たとえば０．６に選ばれ、第１方向Ｘの一方Ｘ１の端部のデューティＤ２ｂは、たとえば０．９に選ばれる。
【００５７】
本実施の形態では、第１受光領域部分４１に向けて導かれる回折光Ｌａ１の光経路上と、第４受光領域部分４４に向けて導かれる回折光Ｌｂ２の光経路上とに、個別に光学素子６２が設けられるので、光学素子６２は不要な部分が削減され、第１受光領域部分４１および第４受光領域部分４４を除く残余の各受光領域部分４２，４３，４５，４６に導かれる回折光Ｌａ２，Ｌｂ１，Ｌｃ１，Ｌｃ２までもが光学素子６２を透過してしまうということを可及的に防止することができる。
【００５８】
また前述のように第１受光領域部分４１および第４受光領域部分４４に向けて導かれる回折光Ｌａ１，Ｌｂ２の、光学素子６２上の透過位置に応じた光量の変化を大きくすることができ、たとえば光ピックアップ装置に本実施の形態の光集積化ユニット６１が用いられた場合、対物レンズのシフトおよび光ディスクの傾きによって生じるオフセットを補正するためのキャンセル信号の感度を向上することができる。
【００５９】
本実施の形態の光集積化ユニット６１と、光集積化ユニット６１からのレーザ光を光ディスク上に集光させる対物レンズ手段とを組み合せることによって、本発明の実施のさらに他の形態の光ピックアップ装置が実現される。この光ピックアップ装置は、前述の実施の形態の光ピックアップ装置と同様の効果を達成することができる。
【００６０】
前述の実施の各形態の光ピックアップ装置では、トラック誤差信号ＴＥＳは式４に基づいて生成されるが、本発明の実施のさらに他の形態の光ピックアップ装置では、トラック誤差信号ＴＥＳは、次式、
Figure 0004160411
に基づいて生成される。
【００６１】
式６において、右辺の第１項はプッシュプル信号（ＰＰ信号）であり、右辺の第２項の係数α２以降はキャンセル信号である。係数α２は、対物レンズのシフト量および光ディスクの傾き量をプッシュプル信号におけるオフセット量に換算するための係数である。係数β２は、ホログラム３１の第１回折面３１ａによって回折された＋１次回折光Ｌａ１およびホログラム３１の第２回折面３１ｂによって回折された−１次回折光Ｌｂ２が光学素子３２，６２上の所定位置をそれぞれ透過するときに、次式、
（Ｓ２＋Ｓ３）
−β２×（Ｓ１１＋Ｓ１３＋Ｓ４１＋Ｓ４３）＝０ …（７）
を満たすように決定される。
【００６２】
式６に基づいてトラック誤差信号ＴＥＳを生成する本実施の形態の光ピックアップ装置では、情報信号ＲＦ、フォーカス誤差信号ＦＥＳおよびトラック誤差信号ＴＥＳを生成するにあたって、前述の各出力信号Ｓ１１〜Ｓ１３，Ｓ２，Ｓ３，Ｓ４１〜Ｓ４３，Ｓ５１，Ｓ５２，Ｓ６のうち、出力信号Ｓ１２，Ｓ４２が不要である。したがって光集積化ユニット内の演算回路規模を小さくすることができ、かつピン数も少なくすることができる。これによって光集積化ユニット２１をさらに小形化することができ、したがって光ピックアップ装置をさらに小形化することができる。
【００６３】
前述の実施の各形態の光ピックアップ装置では、トラック誤差信号ＴＥＳは式４または式６に基づいて生成されるが、本発明の実施のさらに他の形態の光ピックアップ装置では、トラック誤差信号ＴＥＳは、次式、
Figure 0004160411
に基づいて生成される。
【００６４】
式８において、右辺の第１項はプッシュプル信号（ＰＰ信号）であり、右辺の第２項の係数α３以降はキャンセル信号である。係数α３は、対物レンズのシフト量および光ディスクの傾き量をプッシュプル信号におけるオフセット量に換算するための係数である。係数β３は、ホログラム３１の第１回折面３１ａによって回折された＋１次回折光Ｌａ１およびホログラム３１の第２回折面３１ｂによって回折された−１次回折光Ｌｂ２が光学素子３２，６２上の所定位置をそれぞれ透過するときに、次式、
（Ｓ２＋Ｓ３）−β３×（Ｓ１２＋Ｓ４２）＝０ …（９）
を満たすように決定される。
【００６５】
式８に基づいてトラック誤差信号ＴＥＳを生成する本実施の形態の光ピックアップ装置では、情報信号ＲＦ、フォーカス誤差信号ＦＥＳおよびトラック誤差信号ＴＥＳを生成するにあたって、前述の各出力信号Ｓ１１〜Ｓ１３，Ｓ２，Ｓ３，Ｓ４１〜Ｓ４３，Ｓ５１，Ｓ５２，Ｓ６のうち、出力信号Ｓ１１，Ｓ１３，Ｓ４１，Ｓ４３が不要である。したがって光集積化ユニット２１内の演算回路規模を小さくすることができ、かつピン数も少なくすることができる。これによって光集積化ユニットをさらに小形化することができ、したがって光ピックアップ装置をさらに小形化することができる。
【００６６】
【発明の効果】
以上のように本発明によれば、回折格子は、受光部の一方の受光領域に向かう第１回折面による回折光の一部と、受光部の他方の受光領域に向かう第２回折面による回折光の一部とを回折させ、受光部の両方の受光領域に向かう第３回折面による回折光の光経路を避ける位置に配置される。このように回折格子が配置される本発明では、第１〜第３回折面によって回折された各回折光を、前記回折格子によって回折させる必要がある回折光と、前記回折格子によって回折させる必要がない回折光とに第２軸線に沿う方向に関して前後に振り分けられるようにホログラムの第１〜第３回折面の特性を適宜選択することによって、回折格子によって回折させる必要がない第３回折面による回折光の光経路を避けて回折格子を配置することが可能となる。したがって回折格子によって回折させる必要がない回折光までもが回折格子によって回折してしまい、誤検出が生じてしまうという不具合を容易に防止することができる。
【００６７】
また本発明によれば、ホログラムの第１〜第３回折面は、＋ｎ次回折光および−ｎ次回折光を、所定の各受光領域部分に向けて導く。第１回折面からの＋ｎ次回折光および−ｎ次回折光はホログラムの近傍でも充分に分離され、第２回折面からの＋ｎ次回折光および−ｎ次回折光はホログラムの近傍でも充分に分離され、第３回折面からの＋ｎ次回折光および−ｎ次回折光はホログラムの近傍でも充分に分離されるので、回折格子によって回折させる必要がない回折光の光経路を避けて回折格子を配置することが容易となる。
【００６８】
また本発明によれば、回折格子が、ホログラムの第１回折面によって回折された前記回折光の一部の光経路上と、ホログラムの第２回折面によって回折された前記回折光の一部の光経路上とに個別に設けられるので、回折格子は不要な部分が削減され、これによって第１受光領域部分および第４受光領域部分を除く残余の各受光領域部分に導かれる回折光までもが回折格子によって回折してしまうという不具合を可及的に防止することができる。
【００６９】
また本発明によれば、光分岐素子が発光部からのレーザ光を情報記録媒体に導き、また光分岐素子が情報記録媒体によって反射されたレーザ光をホログラムに導き、ホログラムがその導かれたレーザ光を、受光部の各受光領域部分に導く。このような本発明の光集積化ユニットがたとえば光ピックアップ装置に用いられる場合、発光部と受光部とを個別に設ける必要がないので、信号検出系の調整が不要であり、組立て性が向上される。また発光部および受光部などを含む本発明の光集積化ユニットは１つの光学部品として扱うことができ、したがって光学部品点数が低減される。
【００７０】
また本発明によれば、対物レンズ手段が光集積化ユニットからのレーザ光を情報記録媒体上に集光させるとともに、光集積化ユニットの受光部の各受光領域部分が情報記録媒体によって反射されたレーザ光を受光する。前記光集積化ユニットは誤検出が生じるという不具合が防止されているので、情報記録媒体に正確に情報を記録し、または情報記録媒体から正確に情報を読み取ることができ、信頼性が向上される。
【図面の簡単な説明】
【図１】本発明の実施の一形態の光集積化ユニット２１の概略的な構成を示す図である。
【図２】ホログラム３１、光学素子３２および第１〜第６受光領域部分４１〜４６の位置関係を示す図である。
【図３】ホログラム３１からの回折光Ｌａ１，Ｌａ２，Ｌｂ１，Ｌｂ２，Ｌｃ１，Ｌｃ２の、光学素子３２を含む仮想一平面上の透過位置を示す図である。
【図４】光学素子３２の一部を概略的に示す平面図である。
【図５】第１受光領域部分４１に向けて導かれる回折光Ｌａ１の、光学素子３２上の透過位置を示す図である。
【図６】本発明の実施のさらに他の形態の光集積化ユニット６１の概略的な構成を示す図である。
【図７】ホログラム３１、光学素子６２および第１〜第６受光領域部分４１〜４６の位置関係を示す図である。
【図８】ホログラム３１からの回折光Ｌａ１，Ｌａ２，Ｌｂ１，Ｌｂ２，Ｌｃ１，Ｌｃ２の、光学素子６２を含む仮想一平面上の透過位置を示す図である。
【図９】第２の先行技術の光集積化ユニット１の概略的な構成を示す図である。
【図１０】光集積化ユニット１におけるホログラム２、回折格子３および第１〜第６受光領域部分１１〜１６の位置関係を示す図である。
【図１１】ホログラム２からのレーザ光Ｌａ１，Ｌａ２，Ｌｂ１，Ｌｂ２，Ｌｃ１，Ｌｃ２の、回折格子３を含む仮想一平面上の透過位置を示す図である。
【符号の説明】
２１，６１ 光集積化ユニット
２２ 発光部
２３ ホログラム素子
２４ 光分岐素子
２５ 受光部
３１ ホログラム
３１ａ 第１回折面
３１ｂ 第２回折面
３１ｃ 第３回折面
３２，６２ 光学素子
３６ 受光面
３８ａ 一方の受光領域
３８ｂ 他方の受光領域
４１ 第１受光領域部分
４２ 第２受光領域部分
４３ 第３受光領域部分
４４ 第４受光領域部分
４５ 第５受光領域部分
４６ 第６受光領域部分[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical integrated unit for optically recording information on an information recording medium or optically reading information from an information recording medium, and an optical pickup apparatus including the same.
[0002]
[Prior art]
The first prior art optical pickup device includes a hologram for miniaturization, thinning, and high reliability. The hologram is divided into two in the disk radial direction, and one of the holograms is further divided into two in the track direction. This prior art optical pickup device detects a focus error signal with half of the laser light reflected by the optical disc, a track error signal with the other half, and an information signal as a whole. In this prior art optical pickup device, there is a problem that an offset is generated due to the shift of the objective lens and the tilt of the optical disc, even though the tracking is correct, and it is determined as a detrack (see, for example, Patent Document 1). .
[0003]
A technique for solving such a problem is proposed in Japanese Patent Application No. 2002-248479. FIG. 9 is a diagram showing a schematic configuration of the optical integrated unit 1 of the second prior art. FIG. 10 is a diagram showing a positional relationship between the hologram 2, the diffraction grating 3, and the first to sixth light receiving region portions 11 to 16 in the optical integrated unit 1. The optical pickup device includes an optical integrated unit 1 and objective lens means for condensing the laser light from the optical integrated unit 1 on an optical disk.
[0004]
The optical integrated unit 1 includes a hologram 2, a diffraction grating 3, and a light receiving unit 4. The light-receiving surface 5 of the light-receiving unit 4 is divided into one light-receiving region 7a and the other light-receiving region 7b with respect to a virtual plane 6 perpendicular to the light-receiving surface 5, and the first light-receiving region 7a includes first and first light-receiving regions 7a. 3 and 5 light receiving area portions 11, 13, and 15 are provided, and the other light receiving area 7b is provided with second, fourth, and sixth light receiving area portions 12, 14, and 16. The hologram 2 is divided as in the first prior art described above, and thus has first to third diffractive surfaces 2a to 2c. The first diffractive surface 2 a guides laser light toward the first light receiving region portion 11 and the second light receiving region portion 12, and the second diffractive surface 2 b faces the third light receiving region portion 13 and the fourth light receiving region portion 14. The third diffractive surface 2 c guides the laser light toward the fifth light receiving region portion 15 and the sixth light receiving region portion 16.
[0005]
Between the hologram 2 and the light receiving unit 4, a diffraction grating 3 having different diffraction efficiencies in the disc radial direction is interposed. The diffraction grating 3 diffracts the laser beams La1 and Lb1 guided toward the first light receiving region portion 11 and the third light receiving region portion 13 in one light receiving region 7a. Accordingly, the laser beam diffracted by the diffraction grating 3 is guided to the first light receiving region portion 11 and the third light receiving region portion 13, and a cancel signal for correcting the offset caused by the shift of the objective lens and the tilt of the optical disc is generated. Is done. Thereby, offset correction of the push-pull signal can be performed, and stable tracking servo performance can be obtained.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-161282
[0007]
[Problems to be solved by the invention]
FIG. 11 is a diagram illustrating transmission positions of the laser beams La1, La2, Lb1, Lb2, Lc1, and Lc2 from the hologram 2 on a virtual plane including the diffraction grating 3. As shown in FIG. 11, on the virtual plane including the diffraction grating 3, the laser light guided toward the light receiving region portions 11 to 16 is not sufficiently separated, and toward the third light receiving region portion 13. The guided laser beam Lb1 and the laser beam Lc1 guided toward the fifth light receiving region portion 15 overlap. Therefore, in the second prior art, not only the laser beams La1 and Lb1 guided toward the first light receiving region portion 11 and the third light receiving region portion 13, but also the laser light Lc1 guided toward the fifth light receiving region portion 15. Will be diffracted by the diffraction grating 3. That is, not only the laser beam for generating the cancel signal but also the laser beam for detecting the focus error signal is diffracted by the diffraction grating 3. As a result, the focus error signal is affected by a change in transmittance by the diffraction grating 3 and the influence appears as noise in the focus error signal. The servo cannot be raised and the servo is not sufficiently suppressed.
[0008]
Not the laser beams La1 and Lb1 guided toward the first light receiving region portion 11 and the third light receiving region portion 13 in one light receiving region 7a, but the second light receiving region portion 12 and the fourth light receiving in the other light receiving region 7b. When the diffraction grating 3 is provided so as to diffract the laser beams La2 and Lb2 guided toward the region portion 14, even the laser light Lc2 guided toward the sixth light receiving region portion 16 is also diffracted by the diffraction grating 3. As a result, the track error signal becomes unstable and the error rate of the information signal may be extremely deteriorated.
[0009]
In the second prior art, diffraction is performed so that only the laser beams La 1 and Lb 1 guided toward the first light receiving region portion 11 and the third light receiving region portion 13 of one light receiving region 7 a are diffracted by the diffraction grating 3. The grid 3 cannot be arranged. In addition, the diffraction grating 3 may be arranged so that only the laser beams La2 and Lb2 guided toward the second light receiving region portion 12 and the fourth light receiving region portion 14 in the other light receiving region 7b are diffracted by the diffraction grating 3. Can not. As described above, in the second prior art, there is a problem that the diffraction grating 3 cannot be arranged avoiding the optical path of the diffracted light that does not need to be diffracted by the diffraction grating 3, and erroneous detection occurs. .
[0010]
An object of the present invention is to provide an optical integrated unit that can easily prevent a problem that erroneous detection occurs, and an optical pickup device including the same.
[0011]
[Means for Solving the Problems]
The present invention has a light receiving surface perpendicular to a predetermined first axis, and the light receiving surface is divided into one light receiving region and the other light receiving region with respect to a virtual one plane including the predetermined first axis, A light-receiving portion provided with a plurality of light-receiving region portions along a second axis where the virtual plane and the light-receiving surface intersect,
Laser light is directed toward a predetermined first light receiving region portion among the plurality of light receiving region portions in the one light receiving region and a predetermined second light receiving region portion among the plurality of light receiving region portions in the other light receiving region. A first diffractive surface and a predetermined third light receiving region portion of the plurality of light receiving region portions in the one light receiving region and a predetermined fourth light receiving region portion of the plurality of light receiving region portions in the other light receiving region. A second diffractive surface for directing the laser beam toward a predetermined direction, a predetermined fifth light receiving region portion among a plurality of light receiving region portions in the one light receiving region, and a predetermined one among a plurality of light receiving region portions in the other light receiving region. A hologram provided with a third diffractive surface for directing laser light toward the sixth light receiving region, perpendicular to the predetermined first axis and facing the light receiving surface;
Interposed between the light receiving portion and the hologram, The diffraction efficiency changes along a direction perpendicular to the second axis; Part of the diffracted light diffracted by the first diffraction surface of the hologram diffraction A portion of the diffracted light that is guided to the first light receiving region and diffracted by the second diffraction surface of the hologram. diffraction To the fourth light receiving region. And a diffraction grating arranged to avoid the optical path of the diffracted light diffracted by the third diffraction surface of the hologram This is an optical integrated unit.
[0012]
According to the present invention, the light receiving surface of the light receiving unit is divided into one light receiving region and the other light receiving region with respect to the virtual plane, and the one light receiving region is further divided into first, third and fifth light receiving region portions. The other light receiving area is divided into second, fourth and sixth light receiving area portions. The hologram diffracts the guided laser beam by the first to third diffraction surfaces, and each diffracted diffracted beam is received by the first to sixth light receiving region portions of the light receiving unit. Diffraction grating Is a part of the diffracted light diffracted by the first diffraction surface of the hologram diffraction A portion of the diffracted light that is guided to the first light receiving region in the one light receiving region and diffracted by the second diffraction surface. diffraction To the fourth light receiving area in the other light receiving area. Furthermore, avoid the optical path of the diffracted light diffracted by the third diffraction surface , Provided between the light receiving unit and the hologram.
[0013]
Thus, a part of the diffracted light by the first diffractive surface toward one light receiving region of the light receiving unit and a part of the diffracted light by the second diffractive surface toward the other light receiving region of the light receiving unit Diffracting the light, avoiding the optical path of the diffracted light by the third diffraction surface toward both light receiving areas of the light receiving unit Said position Diffraction grating Is placed . At this time , Each diffracted light diffracted by the first to third diffraction surfaces, Diffraction by diffraction grating Diffracted light that needs to be Diffraction by diffraction grating By appropriately selecting the characteristics of the first to third diffractive surfaces of the hologram so as to be distributed back and forth with respect to the direction along the second axis to the diffracted light that does not need to be Diffraction by diffraction grating I need to let No. Avoid the optical path of diffracted light by the three diffractive surfaces Diffraction grating Can be arranged. Therefore Diffraction by diffraction grating Even diffracted light that does not need to be Diffraction by diffraction grating Therefore, it is possible to easily prevent a problem that erroneous detection occurs.
[0014]
According to the present invention, the first diffractive surface guides + n (where n is a positive integer of 1 or more) order diffracted light toward the first light receiving region, and is directed toward the second light receiving region. -Guide the nth order diffracted light,
The second diffractive surface guides + n-order diffracted light toward the third light-receiving region portion, and guides -n-order diffracted light toward the fourth light-receiving region portion,
The third diffractive surface guides + n-order diffracted light toward the fifth light-receiving region and directs -n-order diffracted light toward the sixth light-receiving region.
[0015]
According to the present invention, the first to third diffraction surfaces of the hologram guide + n-order diffracted light and −n-order diffracted light toward each predetermined light receiving region. The + nth order diffracted light and the −nth order diffracted light from the first diffractive surface are sufficiently separated even in the vicinity of the hologram, and the + nth order diffracted light and the −nth order diffracted light from the second diffractive surface are sufficiently separated also in the vicinity of the hologram. Since + n order diffracted light and −n order diffracted light from the diffraction surface are sufficiently separated even in the vicinity of the hologram, Diffraction by diffraction grating Avoid the optical path of diffracted light that does not need to be Diffraction grating It becomes easy to arrange.
[0016]
The present invention also provides the above-mentioned Diffraction grating Are individually provided on an optical path of a part of the diffracted light diffracted by the first diffraction surface of the hologram and on an optical path of a part of the diffracted light diffracted by the second diffraction surface of the hologram It is characterized by being able to.
[0017]
According to the present invention, on a part of the optical path of the diffracted light diffracted by the first diffraction surface of the hologram and on a part of the optical path of the diffracted light diffracted by the second diffraction surface of the hologram ,Individually Diffraction grating Is provided, Diffraction grating The unnecessary portion is reduced, and even the diffracted light guided to the remaining light receiving region portions excluding the first light receiving region portion and the fourth light receiving region portion is stripped. Diffraction by diffraction grating It is possible to prevent as much as possible the problem of being lost.
[0018]
The present invention also includes a light emitting unit that generates laser light,
It further includes an optical branching element that guides the laser light from the light emitting unit to the information recording medium and guides the laser light reflected by the information recording medium to the hologram.
[0019]
According to the present invention, the optical branching element guides the laser beam from the light emitting unit to the information recording medium, and guides the laser beam reflected by the information recording medium to the hologram. The hologram guides the guided laser beam to each light receiving region of the light receiving unit as described above. When such an optical integrated unit of the present invention is used in, for example, an optical pickup device, it is not necessary to provide a light emitting part and a light receiving part separately, so that adjustment of the signal detection system is unnecessary, and the assembling property is improved. The Further, the optical integrated unit of the present invention including the light emitting unit and the light receiving unit can be handled as one optical component, and thus the number of optical components is reduced.
[0020]
The present invention also provides the optical integrated unit;
And an objective lens means for condensing the laser light from the optical integrated unit on the information recording medium.
[0021]
According to the present invention, the objective lens means condenses the laser light from the optical integrated unit on the information recording medium, and each light receiving area portion of the light receiving portion of the optical integrated unit is reflected by the information recording medium. Receives light. Since the optical integrated unit is prevented from the problem of erroneous detection, information can be accurately recorded on or read from the information recording medium.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a schematic configuration of an optical integrated unit 21 according to an embodiment of the present invention. The optical integrated unit 21 of the present embodiment is mounted on, for example, an optical pickup device that optically records information on an information recording medium or optically reads information from the information recording medium. The information recording medium is an optical disc such as a digital versatile disc (abbreviated as DVD). The optical integrated unit 21 includes a light emitting unit 22, a hologram element 23, a light branching element 24, and a light receiving unit 25.
[0023]
The light emitting unit 22 is provided on the stem 26. The light emitting unit 22 generates laser light. The light emitting unit 22 is realized by, for example, a laser diode (abbreviated as LD) chip. The hologram element 23 includes a hologram 31 and an optical element 32. The hologram 31 is a multi-division hologram. The optical element 32 is a diffraction grating. The light receiving unit 25 is provided with first to sixth light receiving region portions 41 to 46 (see FIG. 2 described later), and each light receiving region portion 41 to 46 receives laser light from the hologram element 23.
[0024]
The light branching element 24 guides the laser light from the light emitting unit 22 to the optical disk and guides the laser light reflected by the optical disk to the hologram 31 of the hologram element 23. The optical branching element 24 has a first surface 33 and a second surface 34. The first surface 33 transmits the laser light from the light emitting unit 22 and reflects the laser light reflected by the optical disk. The second surface 34 reflects the laser light reflected by the first surface 33.
[0025]
The laser light from the light emitting unit 22 is guided to the optical disk through the first surface 33, and the laser light reflected by the optical disk is reflected by the first surface 33 and further reflected by the second surface 34 to be a hologram element. 23 holograms 31 are guided. The laser light thus guided to the hologram 31 is received by the light receiving region portions 41 to 46 of the light receiving unit 25.
[0026]
When the optical integrated unit 21 according to the present embodiment is used in, for example, an optical pickup device, it is not necessary to provide the light emitting unit 22 and the light receiving unit 25 separately, so that adjustment of the signal detection system is unnecessary, and assemblability is improved. Be improved. Further, the optical integrated unit of the present embodiment including the light emitting unit 22 and the light receiving unit 25 can be handled as one optical component, and thus the number of optical components is reduced.
[0027]
FIG. 2 is a diagram showing a positional relationship among the hologram 31, the optical element 32, and the first to sixth light receiving region portions 41 to 46. As shown in FIG. The light receiving unit 25 has a light receiving surface 36 perpendicular to the predetermined first axis L1. The light receiving surface 36 is divided into one light receiving region 38a and the other light receiving region 38b with respect to a virtual one plane 37 including the predetermined first axis L1. The hologram 31 has first to third diffraction surfaces 31a to 31c. The first to third diffractive surfaces 31 a to 31 c are provided perpendicular to the predetermined first axis L <b> 1 and facing the light receiving surface 36.
[0028]
The hologram 31 has a circular shape, and the center of the hologram 31 is arranged on the predetermined first axis L1. A boundary 48 a between the second diffractive surface 31 b and the third diffractive surface 31 c extends from the center of the hologram 31 toward one X 1 in the first direction X perpendicular to the virtual one plane 37. A boundary 48b between the first diffraction surface 31a and the third diffraction surface 31c extends from the center of the hologram 31 toward the other X2 in the first direction X. A boundary 48c between the first diffractive surface 31a and the second diffractive surface 31b extends from the center of the hologram 31 to one Y1 of the second direction Y perpendicular to the predetermined first axis L1 and perpendicular to the first direction X. Extend toward.
[0029]
One light-receiving region 38a of the light-receiving surface 36 has a first light-receiving region portion 41, a third light-receiving region portion 43, and a fifth light-receiving portion along a second axis L2 where the virtual plane 37 and the light-receiving surface 36 intersect. A region portion 45 is provided. The fifth light receiving region portion 45 is provided at the same position as the hologram 31 in the direction along the second axis L2, that is, in the second direction Y. The first light receiving region portion 41 is provided in one Y1 in the second direction Y more than the fifth light receiving region portion 45. The third light receiving region portion 43 is provided on the other side Y <b> 2 in the second direction Y with respect to the fifth light receiving region portion 45.
[0030]
In the other light receiving region 38b of the light receiving surface 36, a second light receiving region portion 42, a fourth light receiving region portion 44, and a sixth light receiving region portion 46 are provided along the second axis L2. The sixth light receiving region portion 46 is provided in the second direction Y at substantially the same position as the hologram 31. The second light receiving region portion 42 is provided on the other side Y <b> 2 in the second direction Y with respect to the sixth light receiving region portion 46. The fourth light receiving region portion 44 is provided in one Y1 in the second direction Y with respect to the sixth light receiving region portion 46.
[0031]
The first light receiving region portion 41 has three portions 411, 412 and 413. The three portions 411, 412 and 413 are provided along the second axis L2 with a space therebetween. The fourth light receiving region portion 44 includes three portions 441, 442, and 443. The three portions 441, 442, and 443 are provided at intervals from each other along the second axis L2. The fifth light receiving region portion 45 has two portions 451 and 452. The two portions 451 and 452 are provided adjacent to each other along the second axis L2.
[0032]
Different diffraction gratings are formed on the first to third diffraction surfaces 31 a to 31 c of the hologram 31. The first diffractive surface 31a includes a predetermined first light receiving region portion 41 of the plurality of light receiving region portions 41, 43, and 45 in the one light receiving region 38a and a plurality of light receiving region portions 42 in the other light receiving region 38b. , 44, 46 lead the laser beam toward the predetermined second light receiving region portion 42. The second diffractive surface 31b includes a predetermined third light receiving region portion 43 among the plurality of light receiving region portions 41, 43, and 45 in the one light receiving region 38a and a plurality of light receiving region portions 42 in the other light receiving region 38b. , 44, 46 lead the laser beam toward a predetermined fourth light receiving region 44. The third diffractive surface 31c includes a predetermined fifth light receiving region portion 45 among the plurality of light receiving region portions 41, 43, 45 in the one light receiving region 38a and a plurality of light receiving region portions 42 in the other light receiving region 38b. , 44 and 46, the laser beam is guided toward a predetermined sixth light receiving region portion 46.
[0033]
In the present embodiment, the first diffractive surface 31 a guides the + 1st order diffracted light La1 toward the first light receiving region portion 41 and the −1st order diffracted light La2 toward the second light receiving region portion 42. The second diffractive surface 31 b guides the + 1st order diffracted light Lb1 toward the third light receiving region portion 43 and guides the −1st order diffracted light Lb2 toward the fourth light receiving region portion 44. The third diffractive surface 31 c guides the + 1st order diffracted light Lc1 toward the fifth light receiving region portion 45 and guides the −1st order diffracted light Lc2 toward the sixth light receiving region portion 46.
[0034]
As described above, the first to third diffraction surfaces 31a to 31c of the hologram 31 direct the + 1st order diffracted beams La1, Lb1, and Lc1 and the −1st order diffracted beams La2, Lb2, and Lc2 toward predetermined light receiving region portions 41 to 46, respectively. Lead. The + 1st order diffracted light La1 and the −1st order diffracted light La2 from the first diffractive surface 31a are sufficiently separated even in the vicinity of the hologram 31, and the + 1st order diffracted light Lb1 and the −1st order diffracted light Lb2 from the second diffractive surface 31b are in the vicinity of the hologram 31. However, since the + 1st order diffracted light Lc1 and the −1st order diffracted light Lc2 from the third diffraction surface 31c are sufficiently separated even in the vicinity of the hologram 31, the diffracted lights La2 and Lb1 that do not need to be transmitted through the optical element 32 are sufficiently separated. , Lc1 and Lc2 can be avoided and the optical element 32 can be easily arranged.
[0035]
The optical element 32 is interposed between the light receiving unit 25 and the hologram 31. The optical element 32 further diffracts the + 1st order diffracted light La1 that is a part of the diffracted light diffracted by the first diffractive surface 31a of the hologram 31, and converts the + 1st order, 0th order and −1st order diffracted lights La11 to La13. The first light receiving region portion 41 is led to three portions 411, 412 and 413, respectively. Further, the optical element 32 further diffracts the −1st order diffracted light Lb2 that is a part of the diffracted light diffracted by the second diffracting surface 31b of the hologram 31, and the + 1st order, 0th order, and −1st order diffracted light Lb21˜ Lb23 is guided to the three portions 441, 442, and 443 of the fourth light receiving region portion 44, respectively.
[0036]
FIG. 3 is a diagram illustrating transmission positions of the diffracted lights La1, La2, Lb1, Lb2, Lc1, and Lc2 from the hologram 31 on a virtual plane including the optical element 32. The optical element 32 is disposed on the optical path of the diffracted light La1 guided toward the first light receiving region portion 41 and on the optical path of the diffracted light Lb2 guided toward the fourth light receiving region portion 44.
[0037]
The diffracted light Lb1 guided toward the third light receiving region portion 43 and the diffracted light Lc1 guided toward the fifth light receiving region portion 45 are partially overlapped on a virtual plane including the optical element 32. Further, the diffracted light La2 guided toward the second light receiving region portion 42 and the diffracted light Lc2 guided toward the sixth light receiving region portion 46 are partially overlapped on a virtual plane including the optical element 32.
[0038]
On the other hand, the diffracted light La1 guided toward the first light receiving region portion 41 is transmitted to the remaining light receiving region portions 42 to 46 excluding the first light receiving region portion 41 on a virtual one plane including the optical element 32. It does not overlap with the diffracted beams La2, Lb1, Lb2, Lc1, and Lc2 that are directed toward it, and is sufficiently separated from them. Further, the diffracted light Lb 2 guided toward the fourth light receiving region portion 44 is transmitted to the remaining light receiving region portions 41 to 43, 45, 46 excluding the fourth light receiving region portion 44 on the virtual plane including the optical element 32. It does not overlap with the diffracted beams La1, La2, Lb1, Lc1, and Lc2 that are directed toward it, and is sufficiently separated from them.
[0039]
In the present embodiment, the optical element 32 transmits a part La1 of the diffracted light diffracted by the first diffraction surface 31a of the hologram 31, and guides it to the first light receiving region portion 41 in the one light receiving region 38a. In addition, a part Lb2 of the diffracted light diffracted by the second diffractive surface 31b is transmitted and guided to the fourth light receiving region portion 44 in the other light receiving region 38b, and is provided between the light receiving unit 25 and the hologram 31. It is done.
[0040]
Thus, a part La1 of the diffracted light by the first diffractive surface 31a toward the one light receiving region 38a of the light receiving unit 25 and a part of the diffracted light by the second diffractive surface 31b toward the other light receiving region 38b of the light receiving unit 25. Since the optical element 32 is disposed at a position where Lb2 is transmitted, the diffracted beams La1, La2, Lb1, Lb2, Lc1, and Lc2 diffracted by the first to third diffraction surfaces 31a to 31c as described above are provided. A direction along the second axis L2 (second direction) to the diffracted light La1, Lb2 that needs to pass through the optical element 32 and the diffracted light La2, Lb1, Lc1, Lc2 that does not need to pass through the optical element 32 Y) By selecting the characteristics of the first to third diffractive surfaces 31a to 31c of the hologram 31 so as to be distributed back and forth with respect to Y), it is not necessary to transmit the optical element 32. It is possible to arrange the optical element 32 away from light path of the light La2, Lb1, Lc1, Lc2. Accordingly, even the diffracted beams La2, Lb1, Lc1, and Lc2 guided to the remaining light receiving region portions 42, 43, 45, and 46 except the first light receiving region portion 41 and the fourth light receiving region portion 44 are transmitted through the optical element 32. Therefore, it is possible to easily prevent a problem that erroneous detection occurs.
[0041]
FIG. 4 is a plan view schematically showing a part of the optical element 32. FIG. 5 is a diagram showing a transmission position on the optical element 32 of the diffracted light La1 guided toward the first light receiving region portion 41. As shown in FIG. The transmittance of the optical element 32 changes in the first direction X. In the present embodiment, the optical element 32 is a diffraction grating, and therefore the diffraction efficiency changes in the first direction X. A plurality of grooves 51 are formed in the optical element 32 along the first direction X. The interstitial pitch P of the optical element 32 is constant regardless of the position in the first direction X.
[0042]
The duty D of the optical element 32 continuously changes in the first direction X. When the groove width is WG and the land width is WL,
D = WL / (WG + WL) (1)
It is represented by
[0043]
The duty D of the optical element 32 gradually increases as it proceeds to one side X1 in the first direction X. When the initial value of the duty D is set to 0.5 or more, the diffraction efficiency of the + 1st order diffracted light and the −1st order diffracted light diffracted by the optical element 32 decreases as the duty D increases, and is diffracted by the optical element 32. In addition, the diffraction efficiency of the 0th order diffracted light is increased.
[0044]
The duty D1 of the end of the other X2 in the first direction X of the optical element 32 is selected to be 0.6, for example, and the duty D2 of the end of one X1 of the optical element 32 in the first direction X is, for example, 0.9 Chosen. For example, 0.75 is selected as the duty D3 at the center between both ends of the optical element 32 in the first direction X. The central portion between both end portions in the first direction X of the optical element 32 and the center of the hologram 31 are the same position in the first direction X (see FIG. 3 described above).
[0045]
When the transmission position on the optical element 32 of the diffracted light La1 guided toward the first light receiving region portion 41 is moved from the predetermined position 52 to the position indicated by the virtual line 53 in FIG. 5, that is, in the first direction X. On the other hand, when moving to X1, the light amounts of the + 1st order diffracted light La11 and the −1st order diffracted light La13 diffracted by the optical element 32 decrease, and the light amount of the 0th order diffracted light La12 increases. When the transmission position of the diffracted light La1 guided toward the first light receiving region portion 41 on the optical element 32 moves from the predetermined position 52 to the position indicated by the imaginary line 54 in FIG. 5, that is, in the first direction X. On the other hand, when moving to X2, the light amounts of the + 1st order diffracted light La11 and the −1st order diffracted light La13 diffracted by the optical element 32 increase, and the light amount of the 0th order diffracted light La12 decreases.
[0046]
When the transmission position on the optical element 32 of the diffracted light Lb2 guided toward the fourth light receiving region portion 44 moves to one X1 in the first direction X, the + 1st order diffracted light Lb21 diffracted by the optical element 32 and − The light quantity of the first-order diffracted light Lb23 decreases, and the light quantity of the zero-order diffracted light Lb22 increases. When the transmission position on the optical element 32 of the diffracted light Lb2 guided toward the fourth light receiving region portion 44 moves to the other X2 in the first direction X, the + 1st order diffracted light Lb21 diffracted by the optical element 32 and − The light amount of the first-order diffracted light Lb23 increases, and the light amount of the zero-order diffracted light Lb22 decreases.
[0047]
An optical pickup device according to another embodiment of the present invention includes the optical integrated unit 21 according to the above-described embodiment, and objective lens means for condensing the laser light from the optical integrated unit 21 on an optical disk. . In the present embodiment, the first direction X corresponds to a predetermined radial direction of the optical disc, and the second direction Y corresponds to a track direction perpendicular to the radial direction of the optical disc. In the optical pickup device of the present embodiment, the information signal RF, the focus error signal FES, and the track error signal TES are generated based on the output signals from the light receiving area portions 41 to 46 of the light receiving unit 25 of the optical integrated unit 21. Is done.
[0048]
The output signals from the three portions 411 to 413 of the first light receiving region portion 41 are S11 to S13, the output signal from the second light receiving region portion 42 is S2, and the output signal from the third light receiving region portion 43 is S3. The output signals from the three portions 441 to 443 of the fourth light receiving region portion 44 are S41 to S43, the output signals from the two portions 451 and 452 of the fifth light receiving region portion 45 are S51 and S52, An output signal from the sixth light receiving region portion 46 is S6. At this time, the information signal RF, the focus error signal FES, and the track error signal TES are expressed by the following equations 2 to 4,
Figure 0004160411
Is generated based on each.
[0049]
In Equation 4, the first term on the right side is a push-pull signal (PP signal), and the coefficient α1 and later on the second term on the right side is a cancel signal. The coefficient α1 is a coefficient for converting the shift amount of the objective lens and the tilt amount of the optical disk into the offset amount in the push-pull signal. The cancel signal is a signal for correcting an offset generated in the push-pull signal due to the shift of the objective lens and the tilt of the optical disk.
[0050]
In Expression 4, the coefficient β1 is a coefficient determined by the depth of the groove 51 of the optical element 32. This coefficient β1 adjusts the difference in diffraction efficiency between the + 1st order diffracted lights La11 and Lb21 and the −1st order diffracted lights La13 and Lb23 diffracted by the optical element 32 and the 0th order diffracted lights La12 and Lb22 diffracted by the optical element 32. It is a coefficient. The coefficient β1 is such that the + 1st order diffracted light La1 diffracted by the first diffracting surface 31a of the hologram 31 and the −1st order diffracted light Lb2 diffracted by the second diffracting surface 31b of the hologram 31 pass through predetermined positions on the optical element 32, respectively. When the following formula,
(S12 + S42)
−β1 × (S11 + S13 + S41 + S43) = 0 (5)
It is determined to satisfy. The predetermined position on the optical element 32 is the shift of the objective lens of the + 1st order diffracted light La1 diffracted by the first diffracting surface 31a of the hologram 31 and the −1st order diffracted light Lb2 diffracted by the second diffracting surface 31b of the hologram 31. And the transmission position on the optical element 32 when the optical disk is not tilted, that is, when there is no offset.
[0051]
In the present embodiment, in the calculation after the coefficient α1, the + 1st order diffracted lights La11 and Lb21 and the −1st order diffracted lights La13 and Lb23 diffracted by the optical element 32 and the 0th order diffracted lights La12 and Lb22 diffracted by the optical element 32 are used. And the differential. As described above, the + 1st order diffracted light La11, Lb21 and -1st order diffracted light La13, Lb23 diffracted by the optical element 32 and the 0th order diffracted light La12, Lb22 diffracted by the optical element 32 are opposite in the direction of change in the light amount. It is. Therefore, the sensitivity to the shift of the objective lens and the tilt of the optical disk is increased.
[0052]
As described above, in the optical pickup device of the present embodiment, the information signal RF, the focus error signal FES, and the track error signal TES are generated using the so-called 1-beam PP method. When the 1-beam PP method is used, the recording light amount can be increased and the recording speed can be increased. This optical pickup device can extract only the shift of the optical axis between spots and pits on the optical disc, that is, the shift in the tracking direction, and correct the shift. Therefore, in this optical pickup device, stable tracking servo performance can be achieved regardless of the shift of the objective lens and the tilt of the optical disk.
[0053]
In the present embodiment, the objective lens means condenses the laser light from the optical integrated unit 21 on the optical disc, and the light receiving area portions 41 to 46 of the light receiving unit 25 of the optical integrated unit 21 are reflected by the optical disc. The laser beam is received. Since the optical integrated unit 21 is prevented from a problem that erroneous detection occurs, information can be accurately recorded on or read from the optical disk, and reliability is improved.
[0054]
FIG. 6 is a diagram showing a schematic configuration of an optical integrated unit 61 according to still another embodiment of the present invention. FIG. 7 is a diagram showing the positional relationship between the hologram 31, the optical element 62, and the first to sixth light receiving region portions 41 to 46. As shown in FIG. FIG. 8 is a diagram illustrating transmission positions of the diffracted lights La1, La2, Lb1, Lb2, Lc1, and Lc2 from the hologram 31 on a virtual plane including the optical element 62. Since the optical integrated unit 61 of this embodiment is similar to the optical integrated unit 21 of the above-described embodiment, the same parts are denoted by the same reference numerals and the description thereof is omitted.
[0055]
In the present embodiment, the optical element 62 is on the optical path of the diffracted light La1 guided toward the first light receiving region portion 41 and on the optical path of the diffracted light Lb2 guided toward the fourth light receiving region portion 44. And provided separately. The optical element 62 includes a first portion 62a provided on the optical path of the diffracted light La1 guided toward the first light receiving region portion 41, and an optical path of the diffracted light Lb2 guided toward the fourth light receiving region portion 44. And a second portion 62b.
[0056]
The duty D1a at the end of the other X2 in the first direction X of the first portion 62a is selected as 0.6, for example, and the duty D2a at the end of one X1 in the first direction X is selected as 0.9, for example. It is. In addition, the duty D1b of the second portion 62b at the end of the other X2 in the first direction X is selected to 0.6, for example, and the duty D2b at the end of the first direction X in the first direction X is set to 0.9, for example. To be elected.
[0057]
In the present embodiment, the optical signals are individually applied to the optical path of the diffracted light La1 guided toward the first light receiving region portion 41 and the optical path of the diffracted light Lb2 guided toward the fourth light receiving region portion 44. Since the element 62 is provided, unnecessary portions of the optical element 62 are reduced, and diffraction guided to the remaining light receiving region portions 42, 43, 45, 46 excluding the first light receiving region portion 41 and the fourth light receiving region portion 44. It is possible to prevent the light La2, Lb1, Lc1, and Lc2 from passing through the optical element 62 as much as possible.
[0058]
Further, as described above, the change in the amount of light according to the transmission position on the optical element 62 of the diffracted light La1 and Lb2 guided toward the first light receiving region portion 41 and the fourth light receiving region portion 44 can be increased. For example, when the optical integrated unit 61 of this embodiment is used in an optical pickup device, the sensitivity of a cancel signal for correcting an offset caused by the shift of the objective lens and the tilt of the optical disk can be improved.
[0059]
An optical pickup according to still another embodiment of the present invention is obtained by combining the optical integrated unit 61 of the present embodiment and the objective lens means for condensing the laser light from the optical integrated unit 61 on the optical disk. A device is realized. This optical pickup device can achieve the same effect as the optical pickup device of the above-described embodiment.
[0060]
In the optical pickup device of each of the above-described embodiments, the track error signal TES is generated based on Equation 4, but in the optical pickup device of still another embodiment of the present invention, the track error signal TES is expressed by the following equation: ,
Figure 0004160411
Is generated based on
[0061]
In Equation 6, the first term on the right side is a push-pull signal (PP signal), and the coefficient after α2 in the second term on the right side is a cancel signal. The coefficient α2 is a coefficient for converting the shift amount of the objective lens and the tilt amount of the optical disk into the offset amount in the push-pull signal. The coefficient β2 indicates that the + 1st order diffracted light La1 diffracted by the first diffracting surface 31a of the hologram 31 and the −1st order diffracted light Lb2 diffracted by the second diffracting surface 31b of the hologram 31 are located at predetermined positions on the optical elements 32 and 62, respectively. When transmitting, the following equation:
(S2 + S3)
−β2 × (S11 + S13 + S41 + S43) = 0 (7)
It is determined to satisfy.
[0062]
In the optical pickup device of the present embodiment that generates the track error signal TES based on Expression 6, when generating the information signal RF, the focus error signal FES, and the track error signal TES, the output signals S11 to S13, S2 described above are generated. , S3, S41 to S43, S51, S52, and S6, the output signals S12 and S42 are unnecessary. Therefore, the arithmetic circuit scale in the optical integrated unit can be reduced, and the number of pins can be reduced. As a result, the optical integrated unit 21 can be further miniaturized, and thus the optical pickup device can be further miniaturized.
[0063]
In the optical pickup device of each of the embodiments described above, the track error signal TES is generated based on Equation 4 or Equation 6, but in the optical pickup device of still another embodiment of the present invention, the track error signal TES is ,
Figure 0004160411
Is generated based on
[0064]
In Equation 8, the first term on the right side is a push-pull signal (PP signal), and the coefficient α3 and later on the second term on the right side is a cancel signal. The coefficient α3 is a coefficient for converting the shift amount of the objective lens and the tilt amount of the optical disk into the offset amount in the push-pull signal. The coefficient β3 indicates that the + 1st order diffracted light La1 diffracted by the first diffracting surface 31a of the hologram 31 and the −1st order diffracted light Lb2 diffracted by the second diffracting surface 31b of the hologram 31 are located at predetermined positions on the optical elements 32 and 62, respectively. When transmitting, the following equation:
(S2 + S3) −β3 × (S12 + S42) = 0 (9)
It is determined to satisfy.
[0065]
In the optical pickup device of the present embodiment that generates the track error signal TES based on Expression 8, when generating the information signal RF, the focus error signal FES, and the track error signal TES, the output signals S11 to S13, S2 described above are generated. , S3, S41 to S43, S51, S52, and S6, the output signals S11, S13, S41, and S43 are unnecessary. Therefore, the scale of the arithmetic circuit in the optical integrated unit 21 can be reduced, and the number of pins can be reduced. As a result, the optical integrated unit can be further reduced in size, and thus the optical pickup device can be further reduced in size.
[0066]
【The invention's effect】
As described above, according to the present invention, Diffraction grating Are a part of the diffracted light by the first diffractive surface toward one light receiving region of the light receiving unit and a part of the diffracted light by the second diffractive surface toward the other light receiving region of the light receiving unit; Diffracting the light, avoiding the optical path of the diffracted light by the third diffraction surface toward both light receiving areas of the light receiving unit It is arranged at the position. in this way Diffraction grating In the present invention in which each of the diffracted lights diffracted by the first to third diffraction surfaces is Diffraction by diffraction grating Diffracted light that needs to be Diffraction by diffraction grating By appropriately selecting the characteristics of the first to third diffractive surfaces of the hologram so as to be distributed back and forth with respect to the direction along the second axis to the diffracted light that does not need to be Diffraction by diffraction grating I need to let No. Avoid the optical path of diffracted light by the three diffractive surfaces Diffraction grating Can be arranged. Therefore Diffraction by diffraction grating Even diffracted light that does not need to be Diffraction by diffraction grating Therefore, it is possible to easily prevent a problem that erroneous detection occurs.
[0067]
According to the invention, the first to third diffraction surfaces of the hologram guide + n-order diffracted light and -n-order diffracted light toward each predetermined light receiving region. The + nth order diffracted light and the −nth order diffracted light from the first diffractive surface are sufficiently separated even in the vicinity of the hologram, and the + nth order diffracted light and the −nth order diffracted light from the second diffractive surface are sufficiently separated also in the vicinity of the hologram. Since + n order diffracted light and −n order diffracted light from the diffraction surface are sufficiently separated even in the vicinity of the hologram, Diffraction by diffraction grating Avoid the optical path of diffracted light that does not need to be Diffraction grating It becomes easy to arrange.
[0068]
Also according to the invention, Diffraction grating Are individually provided on the optical path of a part of the diffracted light diffracted by the first diffraction surface of the hologram and on the optical path of a part of the diffracted light diffracted by the second diffraction surface of the hologram So Diffraction grating The unnecessary portion is reduced, and thus, even the diffracted light guided to the remaining light receiving region portions excluding the first light receiving region portion and the fourth light receiving region portion is covered. Diffraction by diffraction grating It is possible to prevent as much as possible the problem of being lost.
[0069]
According to the invention, the light branching element guides the laser light from the light emitting section to the information recording medium, the light branching element guides the laser light reflected by the information recording medium to the hologram, and the hologram is guided by the laser. The light is guided to each light receiving area of the light receiving unit. When such an optical integrated unit of the present invention is used in, for example, an optical pickup device, it is not necessary to provide a light emitting part and a light receiving part separately, so that adjustment of the signal detection system is unnecessary, and the assembling property is improved. The Further, the optical integrated unit of the present invention including the light emitting unit and the light receiving unit can be handled as one optical component, and thus the number of optical components is reduced.
[0070]
According to the invention, the objective lens means condenses the laser light from the optical integrated unit on the information recording medium, and each light receiving area portion of the light receiving unit of the optical integrated unit is reflected by the information recording medium. Receives laser light. Since the optical integrated unit is prevented from a problem that erroneous detection occurs, information can be accurately recorded on or read from the information recording medium, and reliability is improved. .
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an optical integrated unit 21 according to an embodiment of the present invention.
FIG. 2 is a diagram showing a positional relationship between a hologram 31, an optical element 32, and first to sixth light receiving region portions 41 to 46;
FIG. 3 is a diagram illustrating transmission positions of diffracted lights La1, La2, Lb1, Lb2, Lc1, and Lc2 from a hologram 31 on a virtual plane including the optical element 32;
4 is a plan view schematically showing a part of an optical element 32. FIG.
5 is a diagram showing a transmission position on the optical element 32 of diffracted light La1 guided toward the first light receiving region portion 41. FIG.
FIG. 6 is a diagram showing a schematic configuration of an optical integrated unit 61 according to still another embodiment of the present invention.
7 is a diagram showing a positional relationship between a hologram 31, an optical element 62, and first to sixth light receiving region portions 41 to 46; FIG.
8 is a diagram showing transmission positions of diffracted lights La1, La2, Lb1, Lb2, Lc1, and Lc2 from a hologram 31 on a virtual plane including the optical element 62. FIG.
FIG. 9 is a diagram showing a schematic configuration of a second prior art optical integrated unit 1;
10 is a diagram showing a positional relationship between the hologram 2, the diffraction grating 3, and the first to sixth light receiving region portions 11 to 16 in the optical integrated unit 1. FIG.
11 is a diagram showing transmission positions of laser beams La1, La2, Lb1, Lb2, Lc1, and Lc2 from hologram 2 on a virtual plane including diffraction grating 3. FIG.
[Explanation of symbols]
21, 61 Optical integrated unit
22 Light emitting part
23 Hologram element
24 Optical branching element
25 Light receiver
31 hologram
31a First diffraction surface
31b Second diffraction surface
31c Third diffraction surface
32, 62 optical elements
36 Photosensitive surface
38a One light receiving area
38b The other light receiving area
41 First light receiving area
42 Second light receiving area
43 Third light receiving area
44 Fourth light receiving area
45 Fifth light receiving area
46 6th light-receiving area part

Claims (5)

予め定める第１軸線に垂直な受光面を有し、この受光面を、前記予め定める第１軸線を含む仮想一平面に関して一方の受光領域と他方の受光領域とに分割し、一方の受光領域および他方の受光領域には、前記仮想一平面と受光面とが交差する第２軸線に沿って各複数の受光領域部分が設けられる受光部と、
前記一方の受光領域内の複数の受光領域部分のうち予め定める第１受光領域部分および前記他方の受光領域内の複数の受光領域部分のうち予め定める第２受光領域部分に向けてレーザ光を導く第１回折面と、前記一方の受光領域内の複数の受光領域部分のうち予め定める第３受光領域部分および前記他方の受光領域内の複数の受光領域部分のうち予め定める第４受光領域部分に向けてレーザ光を導く第２回折面と、前記一方の受光領域内の複数の受光領域部分のうち予め定める第５受光領域部分および前記他方の受光領域内の複数の受光領域部分のうち予め定める第６受光領域部分に向けてレーザ光を導く第３回折面とが、前記予め定める第１軸線に垂直にかつ受光面に臨んで設けられるホログラムと、
前記受光部とホログラムとの間に介在され、前記第２軸線に垂直な方向に沿って回折効率が変化し、ホログラムの第１回折面によって回折された回折光の一部を回折させて、前記第１受光領域部分に導き、かつホログラムの第２回折面によって回折された回折光の一部を回折させて、前記第４受光領域部分に導き、ホログラムの第３回折面によって回折された回折光の光経路を避けて配置される回折格子とを含むことを特徴とする光集積化ユニット。A light-receiving surface perpendicular to a predetermined first axis, and the light-receiving surface is divided into one light-receiving region and the other light-receiving region with respect to a virtual plane including the predetermined first axis; In the other light receiving region, a light receiving unit in which a plurality of light receiving region portions are provided along a second axis line where the virtual one plane and the light receiving surface intersect,
Laser light is directed toward a predetermined first light receiving region portion among the plurality of light receiving region portions in the one light receiving region and a predetermined second light receiving region portion among the plurality of light receiving region portions in the other light receiving region. A first diffractive surface and a predetermined third light receiving region portion of the plurality of light receiving region portions in the one light receiving region and a predetermined fourth light receiving region portion of the plurality of light receiving region portions in the other light receiving region. A second diffractive surface for directing the laser beam toward a predetermined direction, a predetermined fifth light receiving region portion among a plurality of light receiving region portions in the one light receiving region, and a predetermined one among a plurality of light receiving region portions in the other light receiving region. A hologram provided with a third diffractive surface for directing laser light toward the sixth light receiving region, perpendicular to the predetermined first axis and facing the light receiving surface;
The diffraction efficiency is changed along a direction perpendicular to the second axis , interposed between the light receiving unit and the hologram, and a part of the diffracted light diffracted by the first diffraction surface of the hologram is diffracted , directing the first light receiving area portion, and diffracts a part of the diffracted light diffracted by the second diffractive surface of the hologram,-out guide to the fourth light receiving area portions, diffraction diffracted by the third diffraction plane of the hologram An optical integrated unit comprising: a diffraction grating arranged to avoid an optical path of light . 前記第１回折面は、第１受光領域部分に向けては＋ｎ（ここに、ｎは１以上の正の整数）次回折光を導き、かつ第２受光領域部分に向けては−ｎ次回折光を導き、
前記第２回折面は、第３受光領域部分に向けては＋ｎ次回折光を導き、かつ第４受光領域部分に向けては−ｎ次回折光を導き、
前記第３回折面は、第５受光領域部分に向けては＋ｎ次回折光を導き、かつ第６受光領域部分に向けては−ｎ次回折光を導くことを特徴とする請求項１記載の光集積化ユニット。The first diffractive surface guides + n (where n is a positive integer greater than or equal to 1) order diffracted light toward the first light receiving region, and −n order diffracted light toward the second light receiving region. Guiding,
The second diffractive surface guides + n-order diffracted light toward the third light-receiving region portion, and guides -n-order diffracted light toward the fourth light-receiving region portion,
2. The optical integrated circuit according to claim 1, wherein the third diffractive surface guides + n-order diffracted light toward the fifth light-receiving region and guides −n-order diffracted light toward the sixth light-receiving region. Unit. 前記回折格子は、ホログラムの第１回折面によって回折された前記回折光の一部の光経路上と、ホログラムの第２回折面によって回折された前記回折光の一部の光経路上とに、個別に設けられることを特徴とする請求項１または２記載の光集積化ユニット。The diffraction grating is on a part of the optical path of the diffracted light diffracted by the first diffraction surface of the hologram and on a part of the optical path of the diffracted light diffracted by the second diffraction surface of the hologram, 3. The optical integrated unit according to claim 1, wherein the optical integrated unit is provided separately. レーザ光を発生する発光部と、
発光部からのレーザ光を情報記録媒体に導き、かつ情報記録媒体によって反射されたレーザ光を前記ホログラムに導く光分岐素子とをさらに含むことを特徴とする請求項１〜３のうちのいずれか１つに記載の光集積化ユニット。A light emitting unit for generating laser light;
4. An optical branching element for guiding a laser beam from the light emitting section to the information recording medium and guiding a laser beam reflected by the information recording medium to the hologram. The optical integrated unit according to one. 前記請求項４記載の光集積化ユニットと、
光集積化ユニットからのレーザ光を情報記録媒体上に集光させる対物レンズ手段とを含むことを特徴とする光ピックアップ装置。The optical integrated unit according to claim 4,
And an objective lens means for condensing the laser light from the optical integrated unit on the information recording medium.
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