JP3980433B2 - Optical integrated unit and optical pickup device using the same - Google Patents

Description

で演算される。
【００１９】
ここで、定数ｋは、メインビームとサブビームＡ・Ｂとの光強度の違いを補正するためのもので、光強度比が（メインビームの光強度）：（サブビームＡの光強度）：（サブビームＢの光強度）＝ａ：ｂ：ｂならば、ｋは、次式
ｋ＝ａ／（２ｂ）
で与えられる。
【００２０】
また、ピット情報が記録された光ディスクの再生時には、出力信号Ｓｈと出力信号Ｓｉとの位相差の変化を検出して、位相差（ＤＰＤ）法によるトラッキング誤差信号ＴＥＳ３も検出可能となっている。
【００２１】
そして、記録された情報信号（ＲＦ）は、次式
ＲＦ＝Ｓｈ＋Ｓｇ＋Ｓｉ ・・・・・・（４）
により検出される。
【００２２】
【発明が解決しようとする課題】
しかしながら、特開２００１−２７３６６６号公報に開示された従来の光ピックアップ装置は、問題点を有している。特開２００１−２７３６６６号公報に開示された従来の光ピックアップ装置が有する問題点について、図１７、図１９、および図２０を用いて説明する。
【００２３】
図１７（ｂ）において、半導体レーザ１０５から出射された光ビームは、図示しない光ディスク側に進行するにつれてビーム径が太くなるため、３ビーム回折格子１０６よりも光ディスク側（図の上方）においては、メインビームとサブビームＡ、Ｂがほぼ重なり合う状態で存在しており、ビームの外形が光１２０であると考えても大差はない。この旨は上記公報中にも記載されている。
【００２４】
しかしながら、ビーム径の小さい領域では、メインビームとサブビームＡ・Ｂとのずれが顕著になり、上述と異なる状況を呈す。図１９に、ホログラム光学素子１０９上のビーム形状（スポット形状）を示す。
【００２５】
図１９において、１２１ａはメインビームのスポット、１２１ｂはサブビームＡのスポット、１２１ｃはサブビームＢのスポットを示している。図１９から、サブビームＡおよびＢがメインビームからずれていることが分かる。
【００２６】
図１７（ｂ）において、ホログラム光学素子１０９と受光素子１１０との間（例えば、図中点線Ｘ’−Ｘ’断面）における光ビームの形状および位置を調べると、図１９の状態のメインビームＭ、サブビームＡ・Ｂのそれぞれがホログラム光学素子１０９の３領域１０９ａ〜１０９ｃで回折されたことによって発生する各回折光（０次光、±１次回折光）の形状および位置は、図２０に示すごとくなる。なお、図中に符号を記した光ビームは、上記従来の光ピックアップ装置においてトラッキング誤差信号やフォーカス誤差信号の生成、情報信号（再生信号）の生成等に利用される光ビームを示し、符号を記していない光ビームは、上記従来の光ピックアップ装置で利用されない光ビームを示している。ここで、光ビーム１３０ｅおよび１３０ｃはそれぞれ、サブビームＡが領域１０９ｂおよび１０９ｃで回折された＋１次回折光であり、光ビーム１３０ｆおよび１３０ｄはそれぞれ、サブビームＢが領域１０９ｂおよび１０９ｃで回折された＋１次回折光を示している。
【００２７】
図２０から、トラッキング誤差信号の生成に用いられる領域１０９ｂおよび１０９ｃで回折された＋１次回折光は、サブビームＡとサブビームＢとの間で、光量（図２０における光ビームの大きさに対応する）が異なっていることが分かる。領域１０９ｂ・１０９ｃによるサブビームＡの＋１次回折光とサブビームＢの＋１次回折光との間における光量の相違は、図１９に示したように、サブビームＡ（スポット１２１ａ）とサブビームＢ（スポット１２１ｃ）とがホログラム光学素子１０９の分割線１０９ｌによって中央で分割されないことに起因する。そして、上記従来の光ピックアップ装置では、メインビームのプッシュプル信号ＴＥＳ１と、サブビームＡのプッシュプル信号ＴＥＳ（Ａ）とサブビームＢのプッシュプル信号ＴＥＳ（Ｂ）とを用いてトラッキング誤差を検出する構成であるため、領域１０９ｂ・１０９ｃによるサブビームＡの＋１次回折光とサブビームＢの＋１次回折光との間における光量の相違によって、以下の問題が発生する。
【００２８】
サブビームＡの回折光とサブビームＢの回折光との間の光量の違いが常に一定であれば、既述したＤＰＰ法における定数ｋを適当な値に設定することにより、安定したトラッキングサーボが可能となる。
【００２９】
しかしながら、実際の光ピックアップ装置では、半導体レーザ１０５の取り付け誤差や、パッケージ、ステム、ハウジング等の筐体部分に関する製造誤差、ビームスプリッタや反射ミラー等の製造誤差および取り付け誤差、光集積ユニットの外部で光ピックアップ装置の構成部品として用いられる光学部品の製造誤差および取り付け誤差などの影響で、ホログラム光学素子１０９上のメインビームとサブビームＡ、Ｂの位置や間隔が光ピックアップ装置ごとに異なってしまう。すなわち、上述の各種製造誤差や取り付け誤差等により、▲１▼ホログラム素子１０９上におけるメインビームＭおよびサブビームＡ・Ｂの位置がずれる場合、▲２▼ホログラム素子１０９上におけるメインビームＭとサブビームＡ・Ｂとの間隔がずれる（間隔のずれに伴ってビームサイズも変化する）場合、▲３▼これらの位置および間隔の両方がずれる場合がある。
【００３０】
また、▲１▼または▲３▼の場合、メインビームＭの光軸が分割線１０９ｌ上にあっても、サブビームＡとサブビームＢとの回折光量のアンバランスは、標準状態におけるサブビームＡとサブビームＢとの回折光量のアンバランスと異なることになる。
【００３１】
そして、これらの場合、サブビームＡとサブビームＢとの回折光量のアンバランスが、標準状態におけるサブビームＡとサブビームＢとの回折光量のアンバランスと異なるために、公差の生じていない標準的ピックアップ装置で設定された定数ｋでは十分補正しきれないという問題があった。すなわち、標準的（公差の生じていない）ピックアップ装置で設定されたｋを用いると、サブビームＡとサブビームＢとの回折光量のアンバランスが標準状態と異なることに起因して、トラッキング誤差信号ＴＥＳ２に残留オフセットが生じる。このため、上記従来の光ピックアップ装置では、安定なトラッキングサーボが困難な状況が発生するという問題があった。
【００３２】
本発明は、上記従来の問題に鑑みなされたものであって、その目的は、トラッキング誤差を安定に検出することが可能な光集積化ユニットおよびそれを用いた光ピックアップ装置を提供することにある。
【００３３】
【課題を解決するための手段】
本発明の光集積化ユニットは、上記の課題を解決するために、光記録媒体上に光ビームを集光する集光手段と組み合わせて用いられ、上記集光手段へ向かって光ビームを出射するための光源と、上記光源と上記集光手段との間に配置され、上記光源から出射された光ビームを、メインビーム（主ビーム）と、トラッキング誤差信号（光記録媒体上におけるトラック中心からのメインビームの光軸のずれを表す信号）生成のための第１のサブビーム（副ビーム）および第２のサブビームとに分岐させる第１の光分岐器と、光記録媒体からの戻り光を受光するための光検出器と、上記集光手段と光検出器との間に配置され、上記戻り光を複数の光ビームに分岐させる第２の光分岐器とを備え、上記第２の光分岐器が、戻り光を異なる方向に分岐させる複数の領域からなり、該複数の領域は、光記録媒体のトラック方向に平行な第１の分割線により互いに分割された第１領域および第２領域と、第１の分割線の延長線上に位置する第３領域とを含む光集積化ユニットにおいて、第２の光分岐器と光検出器との間に、第１のサブビームおよび第２のサブビームの戻り光が第２の光分岐器で分岐された光ビームの少なくとも一部を分岐させる第３の光分岐器が設けられていることを特徴としている。
【００３４】
上記構成によれば、第３の光分岐器を設けたことにより、光集積化ユニットを構成する部品の寸法ばらつきや、光集積化ユニットの製造ばらつきが生じても、差動プッシュプル法におけるトラッキング誤差信号を安定して得ることができる。
【００３５】
なお、「戻り光」とは、光記録媒体によって反射されて光集積化ユニット内部に戻る光ビームを指す。また、トラック方向とは、トラックに沿った直線の方向を指し、トラックが同心円状に形成される場合にはトラックの接線の方向を指す。
【００３６】
本発明の光集積化ユニットの好ましい形態は、上記光検出器が、メインビームの戻り光が第１領域で分岐されてなる光ビームを受光する第１のメインビーム受光部と、メインビームの戻り光が第２領域で分岐されてなる光ビームを受光する第２のメインビーム受光部と、少なくとも、第１のサブビームの戻り光が第１領域で分岐されてなる光ビームの少なくとも一部と、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの一部とを受光する第１のサブビーム受光部と、少なくとも、第２のサブビームの戻り光が第１領域で分岐されてなる光ビームの少なくとも一部を受光する第２のサブビーム受光部と、少なくとも、第１のサブビームの戻り光が第２領域で分岐されてなる光ビームの少なくとも一部と、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの他の一部とを受光する第３のサブビーム受光部と、少なくとも、第２のサブビームの戻り光が第２領域で分岐されてなる光ビームの少なくとも一部を受光する第４のサブビーム受光部とを備え、第１のメインビーム受光部と第２のメインビーム受光部との光量差（光量を表す出力信号の差）、並びに、第１のサブビーム受光部および第２のサブビーム受光部の合計光量と第３のサブビーム受光部および第４のサブビーム受光部の合計光量との差に基づいてトラッキング誤差信号を生成するようになっており、第３の光分岐器は、第１のサブビーム受光部に入射する第１のサブビームと、第２のサブビーム受光部に入射する第２のサブビームと、第３のサブビーム受光部に入射する第１のサブビームと、第４のサブビーム受光部に入射する第２のサブビームとが、それぞれ、第２の光分岐器による第１のサブビームおよび第２のサブビームの分岐位置に関わらず（すなわち、分岐される位置が異なる場合、例えば第２の光分岐器の分割線に対する光の位置が異なる場合や、第２の光分岐器の分割線で分割された形状が異なる場合等でも）、全体として略一定の形状となるように構成されている構成である。
【００３７】
また、本発明の光集積化ユニットの好ましい形態は、上記光検出器が、メインビームの戻り光が第１領域で分岐されてなる光ビームを受光する第１のメインビーム受光部と、メインビームの戻り光が第２領域で分岐されてなる光ビームを受光する第２のメインビーム受光部と、少なくとも、第１のサブビームの戻り光が第１領域で分岐されてなる光ビームの少なくとも一部と、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの一部とを受光する第１のサブビーム受光部と、少なくとも、第２のサブビームの戻り光が第１領域で分岐されてなる光ビームの少なくとも一部を受光する第２のサブビーム受光部と、少なくとも、第１のサブビームの戻り光が第２領域で分岐されてなる光ビームの少なくとも一部と、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの他の一部とを受光する第３のサブビーム受光部と、少なくとも、第２のサブビームの戻り光が第２領域で分岐されてなる光ビームの少なくとも一部を受光する第４のサブビーム受光部とを備え、第１のメインビーム受光部と第２のメインビーム受光部との光量差、並びに、第１のサブビーム受光部および第２のサブビーム受光部の合計光量と第３のサブビーム受光部および第４のサブビーム受光部の合計光量との差に基づいてトラッキング誤差信号を生成するようになっており、第３の光分岐器は、第１のサブビーム受光部に入射する第１のサブビームと、第２のサブビーム受光部に入射する第２のサブビームと、第３のサブビーム受光部に入射する第１のサブビームと、第４のサブビーム受光部に入射する第２のサブビームとが、全体として互いに等価的に同一形状となるように構成されている構成である。また、上記構成において、好ましくは、第３の光分岐器は、第１のサブビーム受光部に入射する第１のサブビームの形状と、第２のサブビーム受光部に入射する第２のサブビームの形状とが、全体として、第１のメインビーム受光部に入射するメインビームの形状、あるいは第１のメインビーム受光部に入射するメインビームを２つ合わせた形状と等価的に同一形状となるように、かつ、第３のサブビーム受光部に入射する第１のサブビームの形状と、第４のサブビーム受光部に入射する第２のサブビームの形状とが、全体として、第２のメインビーム受光部に入射するメインビームの形状、あるいは第２のメインビーム受光部に入射するメインビームを２つ合わせた形状と等価的に同一形状となるように、構成されている。
【００３８】
上記各構成によれば、第１のサブビーム受光部および第２のサブビーム受光部の合計光量と第３のサブビーム受光部および第４のサブビーム受光部の合計光量との差が、第２の光分岐器による第１のサブビームおよび第２のサブビームの分岐位置に依存しない。それゆえ、各種の製造誤差や取り付け誤差等により第２の光分岐器の中心に対する第１および第２のサブビーム（Ａ・Ｂ）の位置や間隔に標準状態からのずれが生じても、第１のサブビームと第２のサブビームとの回折光量に、標準状態のアンバランスと異なるアンバランスが生じることがない。したがって、標準状態でメインビームとサブビームとの強度比（第１の光分岐器による分割比）により設定した定数を用いて、残留オフセットのない正確なトラッキング誤差信号を得ることができる。
【００３９】
なお、光ビームが「全体として〜形状」とは、光ビームが単一ビームである場合には、その単一ビームの第３の光分岐器上での光像が「〜形状」であることを指し、光ビームが複数のビームからなる場合には、それらの第３の光分岐器上での光像を繋ぎ合わせたものが「〜形状」であることを指すものとする。また、「略一定の形状」とは、トラッキング誤差の発生等により形状が変化する場合も含みうるものとする。また、「等価的に同一形状」とは、トラッキング誤差の発生等により形状の微差が生じる場合も含みうるものとする。
【００４０】
また、上記光検出器が、上記受光部で受光されたメインビームの戻り光（の光量や位相等）に基づいて情報信号を生成するようにすれば、光記録媒体上に記録された情報信号を再生できる。
【００４１】
第２の光分岐器においては、第１領域と第２領域とを合わせた領域が、全領域を光記録媒体におけるトラック方向に垂直な第２の分割線により２つに分割した一方の領域であり、第３領域が、他方の領域であることが好ましい。
【００４２】
上記構成によれば、より確実に、差動プッシュプル法におけるトラッキング誤差信号を安定して得ることができる。
【００４３】
第３の光分岐器は、第２の光分岐器で分割された複数の光ビームが互いに離間する光学的位置に配置されていることが好ましい。
【００４４】
上記構成によれば、第３の光分岐器の設計が容易になる。したがって、設計の容易な光集積化ユニットを提供できる。
【００４５】
本発明の光集積化ユニットの好ましい形態は、上記光検出器は、第１のサブビーム受光部としての第１の受光部および第２の受光部と、第２のサブビーム受光部としての第３の受光部と、第３のサブビーム受光部としての第４の受光部および第５の受光部と、第４のサブビーム受光部としての第６の受光部とからなり、第２の光分岐器は、第１のサブビームの中心が第３領域の内部を通るように配置されており、上記第３の光分岐器は、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの一部分を第１の受光部に分岐させる第１の光分岐部と、第１のサブビームの戻り光が第１領域で分岐されてなる光ビームの全部を第２の受光部に分岐させる第２の光分岐部と、第２のサブビームの戻り光が第１領域で分岐されてなる光ビームの一部分を第３の受光部に分岐させる第３の光分岐部と、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの他の一部分を第４の受光部に分岐させる第４の光分岐部と、第１のサブビームの戻り光が第２領域で分岐されてなる光ビームの全部を第５の受光部に分岐させる第５の光分岐部と、第２のサブビームの戻り光が第２領域で分岐されてなる光ビームの一部分を第６の受光部に分岐させる第６の光分岐部とを備え、第１の受光部に分岐される第１のサブビームと第２の受光部に分岐される第１のサブビームとを合わせたものの形状と、第３の受光部に分岐される第２のサブビームの形状と、第４の受光部に分岐される第１のサブビームと第５の受光部に分岐される第１のサブビームとを合わせたものの形状と、第６の受光部に分岐される第２のサブビームの形状とが、それぞれ、第２の光分岐器による第１のサブビームおよび第２のサブビームの分岐位置に関わらず、略一定の形状となるように、上記第１ないし第６の光分岐部が配置されている構成である。また、上記構成において、上記第１ないし第６の光分岐部（第１の光分岐部、第２の光分岐部、第３の光分岐部、第４の光分岐部、第５の光分岐部、および第６の光分岐部）は、光分岐の効率（回折効率）が互いに等しくなるように設けられていることが好ましい。
【００４６】
上記構成によれば、各種の製造誤差や取り付け誤差等により第１のサブビームおよび第２のサブビームの位置や間隔に標準状態からのずれが生じても、第１のサブビームと第２のサブビームとの回折光量に、標準状態のアンバランスと異なるアンバランスが生じることがない。したがって、光集積化ユニットを構成する部品の寸法ばらつきや、光集積化ユニットの製造ばらつきが生じても、残留オフセットのない正確なトラッキング誤差信号を得ることができる。
【００４７】
上記の好ましい形態において、第１の受光部、第２の受光部、および第３の受光部のうちの少なくとも２つ、および／または、第４の受光部、第５の受光部、および第６の受光部のうちの少なくとも２つが、同一の受光素子で構成されていることが好ましい。
【００４８】
上記構成によれば、より少ない数の受光素子で光検出器を構成することができるので、光検出器を小型化できる。その結果、より小型の光集積化ユニットを提供できる。
【００４９】
なお、上記構成において、第１の受光部、第３の受光部、および第３の受光部のうち少なくとも２つが同一の受光素子で構成され、かつ、第４の受光部、第５の受光部、および第６の受光部のうち少なくとも２つが同一の受光素子で構成されていることが好ましい。これにより、光検出器をより一層小型化でき、さらに小型の光集積化ユニットを提供できる。
【００５０】
さらに、上記構成において、第１の受光部、第２の受光部、および第３の受光部が同一の受光素子で構成され、かつ、第４の受光部、第５の受光部、および第６の受光部が同一の受光素子で構成されていることがより好ましい。これにより、光検出器をより一層小型化でき、さらに小型の光集積化ユニットを提供できる。
【００５１】
本発明の光集積化ユニットの他の好ましい形態は、上記光検出器は、第１のサブビーム受光部としての第１の受光部および第２の受光部と、第２のサブビーム受光部としての第３の受光部および第７の受光部と、第３のサブビーム受光部としての第４の受光部および第５の受光部と、第４のサブビーム受光部としての第６の受光部および第８の受光部とからなり、上記第３の光分岐器は、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの半分を第１の受光部に分岐させる第７の光分岐部と、第１のサブビームの戻り光が第１領域で分岐されてなる光ビームの全部を第２の受光部に分岐させる第２の光分岐部と、第２のサブビームの戻り光が第１領域で分岐されてなる光ビームの全部を第３の受光部に分岐させる第８の光分岐部と、第２のサブビームの戻り光が第３領域で分岐されてなる光ビームの半分を第７の受光部に分岐させる第９の光分岐部と、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの残り半分を第４の受光部に分岐させる第１０の光分岐部と、第１のサブビームの戻り光が第２領域で分岐されてなる光ビームの全部を第５の受光部に分岐させる第５の光分岐部と、第２のサブビームの戻り光が第２領域で分岐されてなる光ビームの全部を第６の受光部に分岐させる第１１の光分岐部と、第２のサブビームの戻り光が第３領域で分岐されてなる光ビームの残り半分を第８の受光部に分岐させる第１２の光分岐部とを備える構成である。また、上記構成において、第２の光分岐部、第５の光分岐部、第７の光分岐部、第８の光分岐部、第９の光分岐部、第１０の光分岐部、第１１の光分岐部、および第１２の光分岐部は、光分岐の効率（回折効率）が互いに等しくなるように設けられていることが好ましい。
【００５２】
上記構成によれば、第１の受光部および第２の受光部に分岐される第１のサブビームの形状と、第３の受光部および第７の受光部に分岐される第２のサブビームの形状と、第４の受光部および第５の受光部に分岐される第１のサブビームの形状と、第６の受光部および第８の受光部に分岐される第２のサブビームの形状とが、第２の光分岐器による第１のサブビームおよび第２のサブビームの分岐位置に関わらず、第１のサブビームまたは第２のサブビームを２等分に分割した形状と等価的に同一形状となる。したがって、各種の製造誤差や取り付け誤差等により第１のサブビームおよび第２のサブビームの位置や間隔に標準状態からのずれが生じても、第１のサブビームと第２のサブビームとの回折光量に、標準状態のアンバランスと異なるアンバランスが生じることがない。したがって、残留オフセットのない正確なトラッキング誤差信号を得ることができる。しかも、上記構成によれば、第１のサブビームおよび第２のサブビームの全域をトラッキング誤差信号の検出に用いることができるため、トラッキング誤差信号のオフセット補正がより正確に行えると共に、差動プッシュプル法によるトラッキング誤差信号の振幅が増大し、より一層安定したトラッキング誤差信号を得ることができる。
【００５３】
上記の他の好ましい形態においては、第１の受光部、第２の受光部、第３の受光部、および第７の受光部のうちの少なくとも２つ、および／または、第４の受光部、第５の受光部、第６の受光部、および第８の受光部のうちの少なくとも２つが、同一の受光素子で構成されていることが好ましい。
【００５４】
上記構成によれば、より少ない数の受光素子で光検出器を構成することができるので、光検出器を小型化できる。その結果、より小型の光集積化ユニットを提供できる。
【００５５】
なお、上記構成において、第１の受光部、第２の受光部、第３の受光部、および第７の受光部のうちの少なくとも２つが同一の受光素子で構成され、かつ、第４の受光部、第５の受光部、第６の受光部、および第８の受光部のうちの少なくとも２つが同一の受光素子で構成されていることが好ましい。これにより、光検出器をより一層小型化でき、さらに小型の光集積化ユニットを提供できる。
【００５６】
さらに、上記構成において、第１の受光部と第２の受光部とが同一の受光素子で構成され、第３の受光部と第７の受光部とが同一の受光素子で構成され、第４の受光部と第５の受光部とが同一の受光素子で構成され、かつ、第６の受光部と第８の受光部とが同一の受光素子で構成されていることが好ましい。これにより、光検出器をより一層小型化でき、さらに小型の光集積化ユニットを提供できる。
【００５７】
上記の他の好ましい形態は、上記光検出器は、第１のサブビーム受光部としての第１の受光部と、第１のサブビーム受光部としての、第１のサブビームの戻り光が第１領域で分岐されてなる光ビームを受光する第２の受光部と、第２のサブビーム受光部としての、第２のサブビームの戻り光が第１領域で分岐されてなる光ビームを受光する第３の受光部と、第３のサブビーム受光部としての第４の受光部と、第３のサブビーム受光部としての、第１のサブビームの戻り光が第２領域で分岐されてなる光ビームを受光する第５の受光部と、第４のサブビーム受光部としての、第２のサブビームの戻り光が第２領域で分岐されてなる光ビームを受光する第６の受光部とからなり、第２の光分岐器は、第１のサブビームの中心が第３領域の内部を通るように配置されており、上記第３の光分岐器は、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの一部分を第１の受光部に分岐させる第１の光分岐部と、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの他の一部分を第４の受光部に分岐させる第４の光分岐部と、第２のサブビームの戻り光が第１領域で分岐されてなる光ビームの一部分を、上記各受光部に入射する方向以外の方向に分岐させる第１３の光分岐部と、第２のサブビームの戻り光が第２領域で分岐されてなる光ビームの一部分を、上記各受光部に入射する方向以外の方向に分岐させる第１４の光分岐部とを備え、第１の受光部に分岐される第１のサブビームと第２の受光部に入射する第１のサブビームとを合わせたものの形状と、第２のサブビームの戻り光が第１領域で分岐されてなる光ビームのうちで第１３の光分岐部で分岐されることなく第３の受光部に入射する光ビームの形状と、第４の受光部に分岐される第１のサブビームと第５の受光部に入射する第１のサブビームとを合わせたものの形状と、第２のサブビームの戻り光が第２領域で分岐されてなる光ビームのうちで第１４の光分岐部で分岐されることなく第６の受光部に入射する光ビームの形状とが、それぞれ、第２の光分岐器による第１のサブビームおよび第２のサブビームの分岐位置に関わらず、略一定の形状（特に四半円形状）となるように、上記第１の光分岐部、第４の光分岐部、第１３の光分岐部、および第１４の光分岐部が配置されている構成である。
【００５８】
上記の他の好ましい形態は、上記光検出器は、第１のサブビーム受光部としての第１の受光部と、第１のサブビーム受光部としての、第１のサブビームの戻り光が第１領域で分岐されてなる光ビームを受光する第２の受光部と、第２のサブビーム受光部としての、第２のサブビームの戻り光が第１領域で分岐されてなる光ビームを受光する第３の受光部と、第３のサブビーム受光部としての第４の受光部と、第３のサブビーム受光部としての、第１のサブビームの戻り光が第２領域で分岐されてなる光ビームを受光する第５の受光部と、第４のサブビーム受光部としての、第２のサブビームの戻り光が第２領域で分岐されてなる光ビームを受光する第６の受光部とからなり、第２の光分岐器は、第１のサブビームの中心が第３領域の内部を通るように配置されており、上記第３の光分岐器は、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの一部分を第１の受光部に分岐させる第１の光分岐部と、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの他の一部分を第４の受光部に分岐させる第４の光分岐部と、第２のサブビームの戻り光が第１領域で分岐されてなる光ビームの一部を遮光する第１の遮光部と、第２のサブビームの戻り光が第２領域で分岐されてなる光ビームの一部を遮光する第２の遮光部とを備え、第１の受光部に分岐される第１のサブビームと第２の受光部に入射する第１のサブビームとを合わせたものの形状と、第２のサブビームの戻り光が第１領域で分岐されてなる光ビームのうちで第１の遮光部で遮光されることなく第３の受光部と、第４の受光部に分岐される第１のサブビームと第５の受光部に入射する第１のサブビームとを合わせたものの形状と、第２のサブビームの戻り光が第２領域で分岐されてなる光ビームのうちで第２の遮光部で遮光されることなく第６の受光部に入射する光ビームの形状とが、それぞれ、第２の光分岐器による第１のサブビームおよび第２のサブビームの分岐位置に関わらず、略一定の形状（特に四半円形状）となるように、上記第１の光分岐部、第４の光分岐部、第１の遮光部、および第２の遮光部が配置されている構成である。
【００５９】
上記各構成によれば、第３領域で分岐された第１のサブビームを用いてトラッキング誤差信号を生成することで、差動プッシュプル法におけるトラッキング誤差信号を正確に得ることが、少ない数の回折格子等の光分岐部で実現できる。したがって、容易に製造可能な光集積化ユニットを提供できる。さらに、上記各構成によれば、第１領域および第２領域に入射する第２のサブビームの戻り光の光量が、第３領域に入射する第２のサブビームの戻り光の光量より多くなっても、第２のサブビームが中央で分割されたものを検出した場合と等価とすることができる。したがって、差動プッシュプル法におけるトラッキング誤差信号をより一層安定して得ることができる。
【００６０】
上記各構成において、第１の受光部、第２の受光部、および第３の受光部のうち少なくとも２つが同一の受光素子で構成され、かつ、第４の受光部、第５の受光部、および第６の受光部のうち少なくとも２つが同一の受光素子で構成されていることが好ましく、第１の受光部と第２の受光部とが同一の受光素子で構成され、かつ、第４の受光部と第５の受光部とが同一の受光素子で構成されていることが特に好ましい。これにより、光検出器をより一層小型化でき、さらに小型の光集積化ユニットを提供できる。
【００６１】
上記第３の光分岐器は、第１のサブビームおよび第２のサブビームの戻り光が第２の光分岐器で分岐されてなる光ビームを互いに異なる方向に分岐させる複数の光分岐部を備え、これら光分岐部が回折格子で構成されている第１のサブビームの戻り光が第３領域で分岐されてなる光ビームを互いに異なる方向に分岐させる第１の光分岐部および第２の光分岐部を備え、第１の光分岐部および第２の光分岐部が回折格子で構成されていることが好ましい。
【００６２】
上記構成によれば、第３の光分岐器が容易に作製可能な構造となるので、作製が容易な光集積化ユニットを提供できる。
【００６３】
また、第２の光分岐器は、回折格子（ホログラム光学素子）で形成されていることが好ましい。これにより、前記第２の光分岐器を容易に作製できる。
【００６４】
第２の光分岐器および第３の光分岐器は、同一の透光体上に形成されていることが好ましい。
【００６５】
上記構成によれば、第２および第３の光分岐器が同一の透光体上に形成されているため、作製が容易な光集積化ユニットを提供できる。
【００６６】
第２の光分岐器、第１の遮光部、および第２の遮光部は、同一の透光体上に形成されていることが好ましい。
【００６７】
上記構成によれば、遮光部を含めた光学系が簡単な構成で配置でき、作製が容易な光集積化ユニットを提供できる。また、遮光部（マスク）を透光体と一体に形成するので、作製が容易であると共に信頼性が向上した光集積化ユニットを提供できる。
【００６８】
第１の光分岐器および第３の光分岐器は、同一の透光体上に形成されていることが好ましく、同一の透光体の同一面上に形成されていることがより好ましい。
【００６９】
上記構成によれば、第１および第３の光分岐器が同一の透光体上に形成されているため、作製が容易で、かつ、小型化が可能な光集積化ユニットを提供できる。
【００７０】
また、光分岐器を透光体上に形成した構成においては、前記光源および光検出器は、同一パッケージ内に収納され、前記パッケージ外部に前記透光体が固定されていることが好ましい。上記構成によれば、光集積化ユニットの小型化が可能となると共に、光集積化ユニットの信頼性が向上する。
【００７１】
また、本発明の光集積化ユニットは、光源からの光を透過させる一方、光記録媒体からの戻り光を反射させるビームスプリッタをさらに備えることが好ましい。上記ビームスプリッタとしては、偏光ビームスプリッタと１／４波長板を組み合わせたものが特に好ましい。
【００７２】
また、ビームスプリッタを備える場合、その面に平行な反射面をさらに設けて、この反射面で光記録媒体からの戻り光をさらに反射させることが好ましい。これにより、光集積化ユニットを小型化することができる。
【００７３】
上記各構成において、第３の光分岐器は、第１のサブビームの戻り光が第３領域で分岐されてなる光ビームの全部または一部を光記録媒体のトラック方向に平行な分割線（例えば、第１の光分岐部と第４の光分岐部との境界線）で２等分に分割する構成であることが好ましい。これにより、差動プッシュプル法におけるトラッキング誤差信号の精度をさらに向上できる。
【００７４】
本発明の光ピックアップ装置は、上記の課題を解決するために、前記の構成を備える光集積化ユニットと、光集積化ユニットと光記録媒体との間に配置され、光集積化ユニットから出射された光ビームを光記録媒体上に集光する集光手段とを備えることを特徴としている。
【００７５】
上記構成によれば、前述した特徴および効果を有する光集積化ユニットを用いたので、差動プッシュプル法におけるトラッキング誤差信号を安定して得ることができる光ピックアップ装置を提供できる。
【００７６】
【発明の実施の形態】
〔実施の形態１〕
本発明の実施の一形態について図１ないし図８を用いて以下に説明する。
【００７７】
図１に、本実施形態の光ピックアップ装置の光学系の側面図を示している。
【００７８】
本実施形態の光ピックアップ装置は、光集積化ユニット２０と、該光集積化ユニット２０から出射されたレーザ光（光ビーム）を、光記録媒体であるＤＶＤ等の光ディスク１０上に集光させるための集光手段としてのコリメートレンズ１２および対物レンズ１３とを備えている。光集積化ユニット２０は、コリメートレンズ１２へ向かって光ビームを出射するための光源としての半導体レーザ１１と、光ディスク１０からの戻り光を受光するための光検出器７と、半導体レーザ１１とコリメートレンズ１２との間に配置された第１の光分岐器としての３ビーム回折格子１と、コリメートレンズ１２と光検出器７との間に配置された第２の光分岐器としてのホログラム光学素子（ホログラフィック回折格子）２と、ホログラム光学素子２と光検出器７との間に配置された第３の光分岐器としての回折光学素子３と、ビームスプリッタ８と、ビームスプリッタ８の面に平行な反射面１４とを備えている。
【００７９】
本実施形態においては、ビームスプリッタ８は、偏光ビームスプリッタ（ＰＢＳ）であり、ビームスプリッタ８における光ディスク１０側には、光ビームの光軸に垂直な１／４波長板９が配置されている。
【００８０】
３ビーム回折格子１では、半導体レーザ１１から出射されたＰ偏光（直線偏光）である光ビームが、光ディスク１０のトラック接線方向（半径方向に垂直な方向）Ｙと平行な方向に回折される。これにより、上記光ビームは、０次光（非回折光）であるメインビーム、＋１次回折光である第１のサブビーム、−１次回折光である第２のサブビームの３本の光ビームに分岐される。上記回折は、図面の紙面に垂直な方向（光ディスク１０のトラック接線方向Ｙ）に沿って発生するため、ここでは図示していない。３ビーム回折格子１は、図２に示すように、直線格子状の形状を有し、溝（図面に縞で示す）の方向が光ディスク１０の半径方向（トラック接線方向に垂直な方向）Ｘに平行となるように配置されている。なお、３ビーム回折格子１では、±１次回折光より高次の回折光も僅かに発生するが、高次の回折光は、本光ピックアップ装置の機能とは無関係なので言及しない。
【００８１】
３ビーム回折格子１を通過した上記３本の光ビームは、ビームスプリッタ８を透過し、ビームスプリッタ８上の１／４波長板９により円偏光となり、コリメートレンズ１２に入射する。コリメートレンズ１２で平行光となった３本の光ビームは、対物レンズ１３で集光され、光ディスク１０上に照射される。光ディスク１０からの３本の戻り光は、対物レンズ１３、コリメートレンズ１２、および１／４波長板９を順に戻り、１／４波長板９を通過することによりＳ偏光（直線偏光）になる。Ｓ偏光（直線偏光）となった３本の戻り光は、ビームスプリッタ８で、ビームスプリッタ８へ入射する戻り光の光軸にほぼ垂直な方向（図１の右方向）に反射され、さらに、反射面１４でビームスプリッタ８へ入射する戻り光の進行方向（図１の下方向）に反射されることにより、ホログラム光学素子２に入射する。
【００８２】
ホログラム光学素子２では、上記３本の戻り光のそれぞれが＋１次回折光４および−１次回折光５に回折される。＋１次回折光４は、その一部分が光検出器７の手前に配置された回折光学素子３によりさらに回折され、回折光６となって光検出器７に入射する。＋１次回折光４の残部および−１次回折光５は、回折光学素子３で回折されることなくそのまま光検出器７に入射する。
【００８３】
光検出器７は、領域２ａで回折されたメインビームＭを受光する受光素子７Ｍａ・７Ｍａ１・７Ｍａ２（図７参照）と、領域２ｂで回折されたメインビームＭを受光する受光素子７Ｍｂと、領域２ｃで回折されたメインビームＭを受光する受光素子７Ｍｃとを備えている。また、光検出器７は、領域２ｂで回折されたサブビームＡ（光ビーム４Ａｂ）がさらに回折格子３Ａｂで回折されてなる光ビームを受光する受光部７Ａｂと、領域２ｂで回折されたサブビームＢ（光ビーム４Ｂｂ）がさらに回折格子３Ｂｂで回折されてなる光ビームを受光する受光部７Ｂｂとを備えている。また、光検出器７は、領域２ｃで回折されたサブビームＡ（光ビーム４Ａｃ）がさらに回折格子３Ａｃで回折されてなる光ビームを受光する受光部７Ａｃと、領域２ｃで回折されたサブビームＢ（光ビーム４Ｂｃ）がさらに回折格子３Ｂｃで回折されてなる光ビームを受光する受光部７Ｂｃとを備えている。
【００８４】
図３は、ホログラム光学素子２の形状ならびにホログラム光学素子２上の光の様子を示している。ホログラム光学素子２は、複数の領域からなり、戻り光を各領域で異なる方向に回折させることにより複数の光ビームに分割するものである。ホログラム光学素子２は、円形の全領域を、光ディスク１０の半径方向Ｘに平行な分割線２Ｌで２等分に分割することにより、第３領域としての半円状の領域２ａと残りの半円部分とを形成し、さらに、残りの半円部分を光ディスク１０のトラック接線方向Ｙに平行な分割線２Ｎにより第１領域としての領域２ｂおよび第２領域としての領域２ｃの２つの領域に等分に分割した３分割ホログラム光学素子となっている。なお、図３において、Ｍ、Ａ、Ｂは、光ディスク１０からの３本の戻り光を示し、Ｍはメインビーム、Ａは第１のサブビームＡ、Ｂは第２のサブビームを表す。
【００８５】
図４は、上記３本の戻り光が上記の３分割された領域２ａ〜２ｃでそれぞれ回折された各回折光の、回折光学素子３が設置された光学的位置でのビーム形状を示している。図面右側のビーム群は、ホログラム光学素子２による＋１次回折光４、左側のビーム群は−１次回折光５を示している。回折光４・５の各光ビームの符号は、その光ビームがメインビームＭ、第１のサブビームＡ、および第２のサブビームＢの何れであるかを表す符号Ｍ、Ａ、およびＢと、ホログラム光学素子２の領域２ａ、２ｂ、２ｃの何れで回折された光であるかを表す符号ａ、ｂ、ｃとを複合して示している。
【００８６】
なお、ホログラム光学素子２の各領域２ａ、２ｂ、２ｃの回折角度は、各領域２ａ、２ｂ、２ｃの回折光同士で、回折光学素子３の光学的位置において重なり合わないように設定されている。言い換えると、回折光学素子３は、ホログラム光学素子２で分割された複数の光ビームが互いに離間する光学的位置に配置されている。
【００８７】
回折光学素子３は、サブビームＡの戻り光が領域２ａで回折されてなる光ビーム４Ａａを、光ディスク１０のトラック接線方向Ｙに平行な分割線３Ｎにより分割するようになっている。回折光学素子３は、光ビーム４Ａａの一部を回折させる回折格子３Ａａ１と、光ビーム４Ａａの他の一部を回折させる回折格子３Ａａ２と、サブビームＡの戻り光が領域２ｂで分岐されてなる光ビーム４Ａｂを回折させる回折格子３Ａｂと、サブビームＢの戻り光が領域２ｂで分岐されてなる光ビーム４Ｂｂを回折させる回折格子３Ｂｂと、サブビームＡの戻り光が領域２ｃで分岐されてなる光ビーム４Ａｃを回折させる回折格子３Ａｃと、サブビームＢの戻り光が領域２ｃで分岐されてなる光ビーム４Ｂｃを回折させる回折格子３Ｂｃとを備えている。また、回折光学素子３は、サブビームＡの戻り光が領域２ａで回折されてなる光ビーム４Ａａの一部を、光ディスク１０のトラック接線方向Ｙに平行な分割線３Ｎにより２等分に分割するようになっている。
回折格子３Ａｂ・３Ｂｂ・３Ａａ１・３Ａｃ・３Ｂｃは、溝（図面に縞で示す）の方向が光ディスク１０の半径方向Ｘに平行となるように配置されている。一方、回折格子３Ａａ２は、溝（図面に縞で示す）の方向が光ディスク１０の半径方向Ｘから傾斜した方向となるように配置されており、これにより、回折格子３ＡｃでのサブビームＡの＋１次回折光に近づく方向に、サブビームＡの＋１次回折光を発生させるようになっている。
【００８８】
それと共に、図６の斜視模式図に示すように、光検出器７は、領域２ａで回折されたサブビームＡがさらに回折格子３Ａａ１で回折されてなる光ビーム４Ａａ１を受光する受光部（第１の受光部）７Ａａ１と、領域２ａで回折されたサブビームＡがさらに回折格子３Ａａ２で回折されてなる光ビーム４Ａａ２を受光する受光部（第４の受光部）７Ａａ２とをさらに備えている。
【００８９】
また、光検出器７は、回折格子３Ａｂによる＋１次回折光（光ビーム４Ａｂ）、および回折格子３Ａａ１による＋１次回折光（光ビーム４Ａａ１）をそれぞれ、光検出器７上の受光素子７Ａｂおよび受光素子７Ａａ１で検出し、受光素子７Ａｂの出力信号ＳＡｂと受光素子７Ａａ１の出力信号ＳＡａ１とを加算する。また、回折格子３Ｂｂによる＋１次回折光（光ビーム４Ｂｂ）の一部の光量を、光検出器７上の受光素子７Ｂｂで出力信号ＳＢｂとして検出する。また、回折格子３Ａｃによる＋１次回折光（光ビーム４Ａｃ）、および、回折格子３Ａａ２による＋１次回折光（光ビーム４Ａａ２）をそれぞれ、光検出器７上の受光素子７Ａｃおよび受光素子７Ａａ２で検出し、受光素子７Ａｃの出力信号ＳＡｃと受光素子７Ａａ２の出力信号ＳＡａ２とを加算する。また、回折格子３Ｂｃによる＋１次回折光（光ビーム４Ｂｃ）の一部の光量を、光検出器７上の受光素子７Ｂｃで出力信号ＳＢｃとして検出する。
【００９０】
そして、本実施形態の光集積化ユニット２０では、受光素子７Ｍｂと受光素子７Ｍｃとの間の出力信号差、および受光素子７Ａａ１・７Ａｂ・７Ｂｂと受光素子７Ａａ２・７Ａｃ・７Ｂｃとの間の出力信号差に基づいて、ＤＰＰ法によるトラッキング誤差信号を生成するようになっている。
【００９１】
ＤＰＰ法によるトラッキング誤差信号ＴＥＳ２は、これまでの説明により
ＴＥＳ２＝（ＳＭｃ−ＳＭｂ）−ｋ［[（ＳＡｂ＋ＳＡａ１）−（ＳＡｃ＋ＳＡａ２）]＋[ＳＢｂ−ＳＢｃ]］ ・・・（５）
で検出できる。
【００９２】
さらに、本実施形態の構成は、光検出器７の受光素子で検出された信号から生成される上記トラッキング誤差信号においては、上述した光量のアンバランスを補正できる構成となっている。
【００９３】
ここで、ＤＰＰ法によるトラッキング誤差信号の生成においてオフセット除去を目的として用いられる光ビーム４Ａｂと光ビーム４Ｂｂ、光ビーム４Ａｃと光ビーム４Ｂｃについてはそれぞれ、サブビームＢがホログラム光学素子２の分割線２Ｌで分割される位置がビーム径の中央からずれているため、光強度の違い（光量のアンバランス）が生じている。
【００９４】
具体的には、まず、サブビームＡがホログラム光学素子２の分割線２Ｌによりビーム径の中央で分割されていたと仮定すれば光ビーム４Ａｂおよび４Ａｃの一部となるはずの光線部分（図４に３Ａａ１および３Ａａ２で示す領域で囲まれた部分の光ビーム４Ａａ）が光ビーム４Ａａの一部となっている。また、同様に、サブビームＢがビーム径の中央で分割されていたと仮定すれば光ビーム４Ｂａの光量となるはずの光線部分（図４に３Ｂｂで示す領域で囲まれた部分以外の光ビーム４Ｂｂ、および図４に３Ｂｃで示す領域で囲まれた部分以外の光ビーム４Ｂｃ）が光ビーム４Ｂｂおよび４Ｂｃの一部となっている。
【００９５】
そこで、本実施形態では、図４に示すように、回折光学素子３の位置における光ビーム４Ａａが入射しうる領域の一部分（サブビームＡがホログラム光学素子２の分割線２Ｌによりビーム径の中央で分割されたと仮定した場合に光ビーム４Ａａが入射する領域を除く部分）に回折格子３Ａａ１および回折格子３Ａａ２を配置し、光ビーム４Ａｂが入射する領域に回折格子３Ａｂを配置し、光ビーム４Ｂｂが入射する領域の一部分（サブビームＢがホログラム光学素子２の分割線２Ｌによりビーム径の中央で分割されたと仮定した場合に光ビーム４Ｂｂが入射する領域を除く部分）に回折格子３Ｂｂを配置し、光ビーム４Ａｃが入射する領域に回折格子３Ａｃを配置し、光ビーム４Ｂｃが入射する領域の一部分（サブビームＢがホログラム光学素子２の分割線２Ｌによりビーム径の中央で分割されたと仮定した場合に光ビーム４Ｂｃが入射する領域を除く部分）に回折格子３Ｂｃを配置し、それぞれの回折光を光検出器７上の所定の受光素子に入射させる。
【００９６】
具体的には、図５に示す配置および形状の回折格子３Ａａ１・３Ａｂ・３Ｂｂ・３Ａａ２・３Ａｃ・３Ｂｃを用い、これらの回折光を図６に示すように光検出器７上の受光素子７Ａａ１・７Ａｂ・７Ｂｂ・７Ａａ２・７Ａｃ・７Ｂｃで検出する。
【００９７】
すなわち、まず、回折格子３Ａｂ・３Ａｃは、サブビームＡの回折光（光ビーム）４Ａｂ・４Ａｃの全てを受光部７Ａｂ・７Ａｃに回折させる。また、回折格子３Ａａ１・３Ａａ２は、光ビーム４Ａａのうち、一部分のみを受光素子７Ａａ１・７Ａａ２に回折させる。また、光ビーム４Ａａのうち、受光素子７Ａａ１・７Ａａ２に回折されない部分の形状は半円状となっており、受光素子７Ａａ１に回折される部分の形状と、受光素子７Ａａ２に回折される光ビーム４Ａａの形状とは、鏡像の関係にある。また、光検出器７では、サブビームＡの回折光（光ビーム）４Ａａ１・４Ａａ２のうち、回折格子３Ａａ１・３Ａａ２で回折された光のみを受光素子７Ａａ１・７Ａａ２で検出し、回折格子３Ａａ１・３Ａａ２を通らない部分は利用しない（捨てる）。また、サブビームＡの回折光（光ビーム）４Ａｂと、光ビーム４Ａａのうちの回折格子３Ａａ１で回折された光とは、光検出器７上で加算されるようになっている。同様に、サブビームＡの回折光（光ビーム）４Ａｃと、光ビーム４Ａａのうちの回折格子３Ａａ２で回折された光とは、光検出器７上で加算されるようになっている。
【００９８】
さらに、回折格子３Ｂｂ・３Ｂｃは、光ビーム４Ｂｂ・４Ｂｃのうち、一部分のみを受光素子７Ｂｂ・７Ｂｃに回折させる。また、受光素子７Ｂｂに回折される部分の形状、および受光素子７Ｂｃに回折される部分の形状は、おのおの四半円状となっている。また、光検出器７では、サブビームＢの回折光（光ビーム）４Ｂｂ・４Ｂｃのうち、回折格子３Ｂｂ・３Ｂｃで回折された光のみを受光素子７Ｂｂ・７Ｂｃで検出し、回折格子３Ｂｂ・３Ｂｃを通らない部分は利用しない（捨てる）。
【００９９】
これらによれば、サブビームＡおよびＢが分割線２Ｌによりビーム内のどの位置で分割されても、受光素子７Ａｂの出力信号ＳＡｂと受光素子７Ａａ１の出力信号ＳＡａ１とを加算した信号、および受光素子７Ａｃの出力信号ＳＡｃと受光素子７Ａａ２の出力信号ＳＡａ２とを加算した信号においては、サブビームＡおよびＢがその中央部で分割された光ビームを検出した場合と等価とすることができる。また、受光素子７Ｂｂの出力信号ＳＢｂおよび受光素子７Ｂｃの出力信号ＳＢｃについても、サブビームＡおよびＢがその中央部で分割された光ビームを検出した場合と等価とすることができる。したがって、サブビームＡおよびＢが分割線２Ｌによりビーム内のどの位置で分割されても、サブビームＡおよびＢがその中央部で分割された光ビームを検出した場合と等価なトラッキング誤差信号が得られる。したがって、既述した部品公差や製造誤差により光ピックアップ装置ごとに分割線２ＬがサブビームＡ・Ｂを分割する位置にずれが生じても、前記のオフセット除去に関わる光ビーム間の光量のアンバランスをなくすことができる。
【０１００】
すなわち、上記構成では、受光素子７Ａｂおよび受光素子７Ａａ１に入射するサブビームＡ、受光素子７Ｂｂに入射するサブビームＢ共に、サブビームＡおよびＢが分割線２Ｌによりビーム内のどの位置で分割されるかに関わらず、受光素子７Ｍｂに入射するメインビーム５Ｍｂと等価的に同一形状（ここでは略四分円形状）のビームとなる。また、受光素子７Ａｃおよび受光素子７Ａａ２に入射するサブビームＡ、受光素子７Ｂｃに入射するサブビームＢ共に、サブビームＡおよびＢが分割線２Ｌによりビーム内のどの位置で分割されるかに関わらず、受光素子７Ｍｃに入射するメインビーム５Ｍｃと等価的に同一形状（ここでは略四分円形状）のビームとなる。結局、これら４つのサブビームは、光集積化ユニットの公差（従来の技術の項で説明した▲１▼〜▲３▼）によりメインビームＭの光軸がホログラム光学素子２の中心からずれ、それに伴ってサブビームＡ・Ｂの光軸も標準位置からずれた場合であっても、常に一定の形状（ここでは略四分円形状）となる。したがって、標準状態で設定したｋを用いてトラッキング誤差信号を生成したときに残留オフセットを生じないので、正確なトラッキング誤差信号を得ることができる。
【０１０１】
上記の説明では、トラッキング誤差信号の生成に用いるメインビーム５Ｍｂ・５Ｍｃの形状は四分円形状であるものとしたが、この形状も公差により変化する可能性がある。しかしながら、分割線２Ｌに対しビームの位置が変化した時の各ビームの光量変化を考えると、トラッキング誤差信号の生成に用いる四分円形状のメインビームよりも、トラッキング誤差信号の生成に用いるサブビームＡ・Ｂの和の光量変化の方がかなり大きいので、メインビームの変化は、ピックアップ装置を動作させる上では、誤差範囲に入る。そのため、メインビームの変化は、トラッキング誤差信号の正確性にほとんど影響を与えない。そのため、上述したように、トラッキング誤差信号の生成に用いるサブビームＡ・Ｂの形状をできるだけ変化させないことが重要である。
【０１０２】
なお、ピット情報が記録された光ディスク１０の再生時には、受光素子７Ｍｃの出力信号ＳＭｃと受光素子７Ｍｂの出力信号ＳＭｂとの位相差の変化を検出して、ＤＰＤ法によるトラッキング誤差信号ＴＥＳ３を検出することもできる。
【０１０３】
また、本願明細書では、各受光素子の符号の７に代えてＳを用いた符号によって、その受光素子の出力信号を表すものとする。また、図６では、実線３１で囲まれた領域が回折光学素子３を配置する光軸方向（Ｚ方向）の位置となり、点線７１で囲まれた領域が光検出器７の受光面位置を示す。なお、図面の煩雑を防ぐために、点線７１内に記載した受光素子は、ＤＰＰ方式のトラッキング誤差信号検出に関わるもののみとしている。ここで、回折光学素子３における６つの回折格子３Ａｂ、３Ｂｂ、３Ａａ１、３Ａｃ、３Ｂｃ、３Ａａ２の回折効率は、等しく設定されている。
【０１０４】
かくして構成された光ピックアップ装置の光検出器７上の受光部の形状および配置、並びに光検出器７に入射する光線を図７に示す。図７に示す符号は、図６で用いた受光素子の符号とほとんど同様である。ただし、図７では、情報信号およびフォーカス誤差信号の検出に関わる受光素子（７Ｍａ、７Ｍａ１、および７Ｍａ２）も示している。また、必要に応じて図１、図４、図６等も引用する。
【０１０５】
光線列７２は、ホログラム光学素子２による＋１次回折光を示し、光線列７３は、ホログラム光学素子２による＋１次回折光が回折光学素子３により回折されることで発生した回折光６（＋１次回折光）を示す。光線列７４は、回折光学素子３の−１次回折光を表している。光線列７５は、ホログラム光学素子２の−１次回折光を表す。
【０１０６】
ここで、回折光学素子３は、各回折格子の断面がブレーズ化（鋸歯状に形成すること）され、光線列７３（＋１次回折光）が、光線列７４（−１次回折光）より回折効率が高く構成されるのが好ましい。
【０１０７】
なお、フォーカス誤差信号ＦＥＳは、ホログラム光学素子２の＋１次回折光のうち、光ビーム４Ｍａの＋１次回折光を受光素子７Ｍａ１と受光素子７Ｍａ２との境界の分割線上で受光し、受光素子７Ｍａ１の出力信号ＳＭａ１と受光素子７Ｍａ２の出力信号ＳＭａ２との差動により、
ＦＥＳ＝ＳＭａ１−ＳＭａ２ ・・・・・・（６）
で検出できる。
【０１０８】
光ディスク１０上に記録された情報信号（ＲＦ）は、
ＲＦ＝ＳＭｃ＋ＳＭａ＋ＳＭｂ ・・・・・・（７）
で検出できる。
【０１０９】
本実施形態では、３ビーム回折格子１、ホログラム光学素子２、および回折光学素子３は、図８に示すように、同一の光学基板（透光体）１５上に形成された構造となっている。
【０１１０】
３ビーム回折格子１と回折光学素子３とは、メインビームＭの光軸方向Ｚにおける光学的な位置（Ｚ軸座標）を同一にすることにより、図８に示すように光学基板１５の一方の同一面１５ａ上に形成できる。
【０１１１】
また、ホログラム光学素子２は、光学基板１５における回折光学素子３が形成された面の裏面上に形成されているが、光学ガラス等の硝材で該光学基板１５を構成することにより、フォトリソグラフィ等の半導体プロセスにより形成できるので、ホログラム光学素子２と回折光学素子３との位置関係を極めて高精度に作製することができる。このため、回折光学素子３で回折させたい光線部分のばらつきが極めて少なくなる。
【０１１２】
また、これらの光学素子（３ビーム回折格子１、ホログラム光学素子２、および回折光学素子３）を１つの光学基板１５上に集積的に形成することで、前記光学素子の作製ならびに光集積化ユニット２０内での配置および取り付けが容易になり、ＣＡＮ等のパッケージ１６上に載せて固定できる。また、パッケージ１６上に載せて固定した場合、半導体レーザ１１や光検出器７等の半導体素子をパッケージ１６内部に収納できるので、光集積化ユニット２０の生産性ならびに信頼性が向上する。
【０１１３】
ここで、光学基板１５は、硝材に対しフォトリソグラフィを用いて形成されるものに限らず、樹脂材料を用いて成形等で形成された透光基板であっても構わない。
【０１１４】
以上のように、本実施形態に係る光集積化ユニットは、光記録媒体（１０）上に光ビームを集光する集光手段（１２・１３）と組み合わせて用いられ、上記集光手段（１２・１３）へ向かって光ビームを出射するための光源（１１）と、上記光源（１１）と上記集光手段（１２・１３）との間に配置され、上記光源（１１）から出射された光ビームを、メインビーム（Ｍ）と、トラッキング誤差信号生成のための第１のサブビーム（Ａ）および第２のサブビーム（Ｂ）とに分岐させる第１の光分岐器（１）と、光記録媒体（１０）からの戻り光を受光するための光検出器（７）と、上記集光手段（１２・１３）と光検出器（７）との間に配置され、上記戻り光を複数の光ビームに分岐させる第２の光分岐器（２）とを備え、上記第２の光分岐器（２）が、戻り光を異なる方向に分岐させる複数の領域からなり、該複数の領域は、光記録媒体（１０）のトラック方向（Ｙ）に平行な第１の分割線（２Ｎ）により互いに分割された第１領域（２ｂ）および第２領域（２ｃ）と、第１の分割線（２Ｎ）の延長線上に位置する第３領域（２ａ）とを含む光集積化ユニットにおいて、第２の光分岐器（２）と光検出器（７）との間に、第１のサブビーム（Ａ）および第２のサブビーム（Ｂ）の戻り光が第２の光分岐器（２）で分岐された光ビームの一部を分岐させる第３の光分岐器（３）が設けられている構成である。
【０１１５】
また、本実施の形態に係る光集積化ユニットは、光検出器（７）が、メインビーム（Ｍ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ｍｂ）を受光する第１のメインビーム受光部（７Ｍｂ）と、メインビーム（Ｍ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ｍｃ）を受光する第２のメインビーム受光部（７Ｍｃ）と、第１ないし第３の受光部（７Ａｂ・７Ｂｂ・７Ａａ１）と、第４ないし第６の受光部（７Ａｃ・７Ｂｃ・７Ａａ２）とを備え、第２の光分岐器（２）は、第１のサブビーム（Ａ）の中心が第３領域（２ａ）の内部を通るように配置されており、第３の光分岐器（３）は、第１のサブビーム（Ａ）の戻り光が第３領域（２ａ）で分岐されてなる光ビーム（４Ａａ）の一部分を第１の受光部（７Ａａ１）に分岐させる第１の光分岐部（３Ａａ１）と、第１のサブビーム（Ａ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ａｂ）の全部を第２の受光部（７Ａｂ）に分岐させる第２の光分岐部（３Ａｂ）と、第２のサブビーム（Ｂ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ｂｂ）の一部分を第３の受光部（７Ｂｂ）に分岐させる第３の光分岐部（３Ｂｂ）と、第１のサブビーム（Ａ）の戻り光が第３領域（２ａ）で分岐されてなる光ビーム（４Ａａ）の他の一部分を第４の受光部（７Ａａ２）に分岐させる第４の光分岐部（３Ａａ２）と、第１のサブビーム（Ａ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ａｃ）の全部を第５の受光部（７Ａｃ）に分岐させる第５の光分岐部（３Ａｃ）と、第２のサブビーム（Ｂ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ｂｃ）の一部分を第６の受光部（７Ｂｃ）に分岐させる第６の光分岐部（３Ｂｃ）とを備え、第１のメインビーム受光部（７Ｍｂ）と第２のメインビーム受光部（７Ｍｃ）との光量差、並びに、第１ないし第３の受光部（７Ａｂ・７Ｂｂ・７Ａａ１）の合計光量と第４ないし第６の受光部（７Ａｃ・７Ｂｃ・７Ａａ２）の合計光量との差に基づいてトラッキング誤差信号を生成するようになっており、第１の受光部（７Ａａ１）に分岐される第１のサブビームと第２の受光部（７Ａｂ）に分岐される第１のサブビームとを合わせたものの形状と、第３の受光部（７Ｂｂ）に分岐される第２のサブビームの形状と、第４の受光部（７Ａａ２）に分岐される第１のサブビームと第５の受光部（７Ａｃ）に分岐される第１のサブビームとを合わせたものの形状と、第６の受光部（７Ｂｃ）に分岐される第２のサブビームの形状とが、第２の光分岐器（２）による第１のサブビーム（Ａ）および第２のサブビーム（Ｂ）の分岐位置に関わらず、略一定の形状（四半円形状）となるように、上記第１ないし第６の光分岐部が配置されている。また、第１のメインビーム受光部（７Ｍｂ）に入射するメインビーム（４Ｍｂ）の形状、および第２のメインビーム受光部（７Ｍｃ）に入射するメインビーム（４Ｍｃ）の形状も、上記の「略一定の形状」と等価的に同一形状となるように構成されている。
【０１１６】
上記構成によれば、前述したように、装置の公差によりビームの光軸が標準位置からずれた場合であっても、常に一定の形状（ここでは略四分円形状）のビームを用いてトラッキング誤差信号を生成することができるので、正確なトラッキング誤差信号を得ることができる。
【０１１７】
〔実施の形態２〕
本発明の他の実施の形態について図９および図１０を用いて以下に説明する。図９、図１０はそれぞれ本実施形態における回折光学素子３、ならびにＤＰＰ法によるトラッキング誤差信号検出に関わる各回折格子と受光部の斜視模式図を示す。実施の形態１と同種の構成要素については、同符号を引用して説明する。図１、３、４等も必要に応じて引用する。
【０１１８】
本実施形態の光ピックアップ装置は、次の２つの点のみが実施の形態と異なり、他は実施の形態１の光ピックアップ装置と同一の構成を備えている。
【０１１９】
まず、第１の相違点は、図５に示す形状の回折光学素子３に代えて、図９に示す形状の回折光学素子３、すなわち、光ディスク１０のトラック接線方向Ｙに対して、回折格子３Ａｂおよび回折格子３Ｂｃの溝方向が互いに異なる方向に傾斜しており、かつ、回折格子３Ａａ１および回折格子３Ａａ２の溝方向も互いに異なる方向に傾斜している点である。
【０１２０】
第２の相違点は、上記の第１の相違点により、図１０に示すように、回折格子３Ａｂ・３Ａａ１・３Ｂｂによる＋１次回折光のすべてを、受光素子７ｂ上に回折させて受光素子７ｂから検出すると共に、回折格子３Ａｃ、３Ａａ２、３Ｂｃによる＋１次回折光のすべてを、受光素子７ｃに回折させ受光素子７ｃから検出する構成となっている点である。したがって、本実施形態では、受光素子７ｂが、受光素子７Ａｂ・７Ｂｂ・７Ａａ１と同等の機能を備え、受光素子７ｃが、受光素子７Ａｃ・７Ｂｃ・７Ａａ２と同等の機能を備えている。
【０１２１】
これらにより、受光素子７Ｍｂ、７Ｍｃ、７ｂ、７ｃの出力信号ＳＭｂ、ＳＭｃ、Ｓｂ、Ｓｃに基づいて、ＤＰＰ法によるトラッキング誤差信号ＴＥＳ２は、次式
ＴＥＳ２＝（ＳＭｃ−ＳＭｂ）−ｋ（Ｓｂ−Ｓｃ） ・・・・・・（８）
で検出できる。また、他のサーボ信号や情報信号については、実施の形態１と同様の検出方法で検出できる。
【０１２２】
本実施形態の構成では、オフセット除去に関し同様の性質を有する光線の受光部を共通化して受光素子７ｂ・７ｃで実現することにより、受光素子の数を削減でき、光検出器７の小型化、引き出し端子の削減による光集積化ユニットの小型化、製造工程の簡略化が可能となる。
【０１２３】
〔実施の形態３〕
本発明のさらに他の実施の形態について図１１および図１２を用いて以下に説明する。実施の形態１および２と同種の構成要素については、同符号を引用して説明する。図１、３、４等も必要に応じて引用する。
【０１２４】
本実施形態は、次の２つの点のみが実施の形態２と異なり、他は実施の形態１と同一の構成を備えている。
【０１２５】
第１の相違点は、回折光学素子３が、図１１に示す形状である点である。すなわち、回折光学素子３が回折格子３Ｂａ１・Ｂａ２をさらに備え、ホログラム光学素子２の領域２ａにおけるサブビームＢの＋１次回折光である光ビーム４Ｂａを、光ディスク１０のトラック接線方向Ｙに平行な分割線３Ｍで２等分に分割し、光ビーム４Ｂａの半分を回折格子３Ｂａ１で分岐させて受光素子７Ｂ１に入射させ、光ビーム４Ｂａの残り半分を回折格子３Ｂａ２で分岐させて受光素子７Ｂ２に入射させるようになっている点である。なお、回折格子３Ａａ１・３Ａａ２・３Ａｂ・３Ａｃ・３Ｂｂ・３Ｂｃ・３Ｂａ１・３Ｂａ２の回折効率は、等しく設定されている。
【０１２６】
第２の相違点は、ホログラム光学素子２によるサブビームＡ・Ｂの＋１次回折光が、部分的に欠けることなく全て回折され、回折光（＋１次回折光）が回折光学素子３によって光検出器７の受光部に入射される点である。
【０１２７】
第３の相違点は、光検出器７が、受光素子７Ａｂおよび受光素子７Ａａ１に代えて、受光素子７Ａｂおよび受光素子７Ａａ１の両方の機能を兼ね備える受光素子７Ａ１を備え、受光素子７Ａｃおよび受光素子７Ａａ２に代えて、受光素子７Ａｃおよび受光素子７Ａａ２の両方の機能を兼ね備える受光素子７Ａ２を備える点である。
【０１２８】
第４の相違点は、光検出器７が、受光素子７Ｂｂに代えて、回折格子３Ｂｂから光ビーム４Ｂｂの＋１次回折光を受光すると共に回折格子３Ｂａ１から第３の分割ビーム（光ビーム４Ｂａの＋１次回折光）を受光する受光素子７Ｂ１を備え、受光素子７Ｂｃに代えて、回折格子３Ｂｃから光ビーム４Ｂｃの＋１次回折光を受光すると共に回折格子３Ｂａ２から第４の分割ビーム（光ビーム４Ｂａの＋１次回折光）を受光する受光素子７Ｂ２を備え、受光素子７Ｍｂと受光素子７Ｍｃとの間の出力信号差、受光素子７Ａ１と受光素子Ａ２との間の出力信号差、および受光素子７Ｂ１と受光素子Ｂ２との間の出力信号差に基づいて、トラッキング誤差信号を生成するようになっている点である。
【０１２９】
図１２に、本実施形態におけるＤＰＰ法によるトラッキング誤差信号検出に関わる各回折格子と受光素子の斜視模式図を示す。回折格子３Ａａ１の回折光と回折格子３Ａｂの回折光とが同一の受光素子７Ａ１で検出され、回折格子３Ａａ２の回折光と回折格子３Ａｃの回折光とが同一の受光素子７Ａ２で検出され、回折格子３Ｂａ１の回折光と回折格子３Ｂｂの回折光とが同一の受光素子７Ｂ１で検出され、回折格子３Ｂａ２の回折光と回折格子３Ｂｃの回折光とが同一の受光素子７Ｂ２で検出される。
【０１３０】
ここで、回折光学素子３は、サブビームＡ・Ｂの各々の＋１次回折光を、部分的に欠けることなく全て、所定の受光部に入射させるようになっている。それゆえ、受光素子７Ａ１、７Ａ２で検出される信号を合せるとすれば、サブビームＡそのものの信号と等価となり、同様に受光素子７Ｂ１、７Ｂ２で検出される信号を合せるとすれば、サブビームＢそのものの信号と等価となる。
【０１３１】
ＤＰＰ法によるトラッキング誤差信号ＴＥＳ２は、

で表される。
【０１３２】
ここで、回折光学素子３は、サブビームＡ・Ｂの各々の＋１次回折光を、部分的に欠けることなく全て、所定の受光部に入射させるようになっている。それゆえ、受光素子７Ａ１、７Ａ２で検出される信号を合せるとすれば、サブビームＡそのものの信号と等価となり、同様に受光素子７Ｂ１、７Ｂ２で検出される信号を合せるとすれば、サブビームＢそのものの信号と等価となる。
【０１３３】
すなわち、上記構成では、サブビームＡについては、回折格子３Ａｂおよび３Ａａ１で回折されるサブビームＡを光検出器７上で加算する（共に受光素子７Ａ１で受光する）と共に、回折格子３Ａｃおよび３Ａａ２で回折されるサブビームＡを光検出器７上で加算する（共に受光素子７Ａ２で受光する）。また、サブビームＢについては、回折格子３Ｂｂと３Ｂａ１で回折されるサブビームＢを光検出器７上で加算（共に受光素子７Ｂ１で受光する）すると共に、回折格子３Ｂｃおよび３Ｂａ２で回折されるサブビームＢを光検出器７上で加算する（共に受光素子７Ｂ２で受光する）。これらにより、受光素子７Ａ１で受光されるサブビームＡ、受光素子７Ａ２で受光されるサブビームＡ、受光素子７Ｂ１で受光されるサブビームＢ、受光素子７Ｂ２で受光されるサブビームＢの全てが、トラックに平行な分割線で分割された半円形状のビームと等価的に同一形状のビームとなる。したがって、サブビームＡ・Ｂについては、ビームが分割線２Ｌによってどこで分割されても、常に一定形状（ここでは半円状）となる。したがって、サブビームＡ・Ｂについては、光集積化ユニットが公差（従来の技術の項で説明した▲１▼〜▲３▼）を有する場合でも、常に一定形状（ここでは半円状）のビームをトラッキング誤差信号の生成に利用することになる。したがって、標準状態で設定したｋ’を用いてトラッキング誤差信号を生成したときに残留オフセットを生じないので、正確なトラッキング誤差信号を得ることができる。
【０１３４】
ここで、上式（９）の第２項は、サブビームＡ・Ｂによるプッシュプル信号和を表している。これらは、上述のようにサブビームＡ・Ｂを丸ごと用いたプッシュプル信号と等価である。このため、サブビームＡ・Ｂの一部を用いる実施の形態１の構成と比較して、サブビームによるプッシュプル信号の振幅の強度が増大し、Ｓ／Ｎ比が向上する。すなわち、トラッキング誤差信号のオフセット除去が安定して行えると共に、上式（９）で表されるトラッキング誤差信号ＴＥＳ２の振幅も増大する。
【０１３５】
なお、回折格子３Ａａ１の回折光と回折格子３Ａｂの回折光、回折格子３Ａａ２の回折光と回折格子３Ａｃの回折光、回折格子３Ｂａ１の回折光と回折格子３Ｂｂの回折光、回折格子３Ｂａ２の回折光と回折格子３Ｂｃの回折光は、別々の受光素子で検出された後、加算されても構わない。なお、他のサーボ信号や情報信号の検出方法については、実施の形態１と同様である。
【０１３６】
以上のように、本実施形態に係る光集積化ユニットは、上記光検出器（７）は、メインビーム（Ｍ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（５Ｍｂ）を受光する第１のメインビーム受光部（７Ｍｂ）と、メインビーム（Ｍ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（５Ｍｃ）を受光する第２のメインビーム受光部（７Ｍｃ）と、第１および第２の受光部（７Ａ１）と、第３および第７の受光部（７Ｂ１）と、第４および第５の受光部（７Ａ２）と、第６および第８の受光部（７Ｂ２）とを備え、上記第３の光分岐器（３）は、第１のサブビーム（Ａ）の戻り光が第３領域（２ａ）で分岐されてなる光ビーム（４Ａａ）の半分を第１の受光部（７Ａ１）に分岐させる第７の光分岐部（３Ａａ１）と、第１のサブビーム（Ａ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ａｂ）の全部を第２の受光部（７Ａ１）に分岐させる第２の光分岐部（３Ａｂ）と、第２のサブビーム（Ｂ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ｂｂ）の全部を第３の受光部（７Ｂ１）に分岐させる第８の光分岐部（３Ｂｂ）と、第２のサブビーム（Ｂ）の戻り光が第３領域（２ａ）で分岐されてなる光ビーム（４Ｂａ）の半分を第７の受光部（７Ｂ１）に分岐させる第９の光分岐部（３Ｂａ１）と、第１のサブビーム（Ａ）の戻り光が第３領域（２ａ）で分岐されてなる光ビーム（４Ａａ）の残り半分を第４の受光部（７Ａ２）に分岐させる第１０の光分岐部（３Ａａ２）と、第１のサブビーム（Ａ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ａｃ）の全部を第５の受光部（７Ａ２）に分岐させる第５の光分岐部（３Ａｃ）と、第２のサブビーム（Ｂ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ｂｃ）の全部を第６の受光部（７Ｂ２）に分岐させる第１１の光分岐部（３Ｂｃ）と、第２のサブビーム（Ｂ）の戻り光が第３領域（２ａ）で分岐されてなる光ビーム（４Ｂａ）の残り半分を第８の受光部（７Ｂ２）に分岐させる第１２の光分岐部（３Ｂａ２）とを備え、第１のメインビーム受光部（７Ｍｂ）と第２のメインビーム受光部（７Ｍｃ）との光量差、並びに、第１および第２の受光部（７Ａ１）並びに第３および第７の受光部（７Ｂ１）の合計光量と第４および第５の受光部（７Ａ２）および第６および第８の受光部（７Ｂ２）の合計光量との差に基づいてトラッキング誤差信号を生成するようになっている構成である。
【０１３７】
〔実施の形態４〕
本発明のさらに他の実施の形態について図１３および図１４を用いて説明する。図１３、１４は、本実施形態における回折光学素子３ならびに、ＤＰＰ法によるトラッキング誤差信号検出に関わる各回折格子と受光素子の斜視模式図を示す。実施の形態１ないし３と同種の構成要素については、同符号を引用して説明する。図１、３、４等も必要に応じて引用する。
【０１３８】
本実施形態は、次の５つの点のみが実施の形態１と異なり、他は実施の形態１と同一の構成を備えている。
【０１３９】
第１の相違点は、回折光学素子３が、図１３に示すように、回折格子３Ａｂおよび回折格子３Ａｃを備えておらず、４つの回折格子３Ｂｂ、３Ｂｃ、３Ａａ１、および３Ａａ２で構成されている点である。
【０１４０】
第２の相違点は、受光素子７Ａｂおよび受光素子７Ａｃが、光ビーム４Ａｂおよび光ビーム４Ａｃを、回折光学素子３で回折されることなく直接受光するようになっており、受光素子７Ｂｂおよび受光素子７Ｂｃが、光ビーム４Ｂｂおよび光ビーム４Ｂｃの一部を、回折光学素子３で回折されることなく直接受光するようになっている点である。
【０１４１】
第３の相違点は、図１４に示すように、回折格子３Ｂｂが、光ビームを受光素子７Ｂｂに入射させるものではなく、サブビームＢの戻り光が領域２ｂで回折されてなる光ビーム４Ｂｂの一部を、各受光素子７Ａｂ・７Ａｃ・７Ｂｂ・７Ｂｃ以外の領域８０に（各受光素子７Ａｂ・７Ａｃ・７Ｂｂ・７Ｂｃ部に入射する方向以外の方向に）回折させる第１３の光分岐部として機能し、回折格子３Ｂｃが、光ビームを受光素子７Ｂｃに入射させるものではなく、サブビームＢの戻り光が領域２ｃで回折されてなる光ビーム４Ｂｃの一部を、各受光素子７Ａｂ・７Ａｃ・７Ｂｂ・７Ｂｃ以外の領域８０に（各受光素子７Ａｂ・７Ａｃ・７Ｂｂ・７Ｂｃ部に入射する方向以外の方向に）回折させる第１４の光分岐部として機能する点である。
【０１４２】
第４の相違点は、回折格子３Ａａ１がその回折光を光ビーム４Ａｂを検出する受光素子７Ａｂに回折させ、回折格子３Ａａ２がその回折光を光ビーム４Ａｃを検出する受光素子７Ａｃに回折させる点である。すなわち、受光素子７Ａｂが、回折格子３Ａａ１で回折されたサブビームＡを受光する第１の受光部としての機能を兼ね備え、受光素子７Ａｃが、回折格子３Ａａ２で回折されたサブビームＡを受光する第１の受光部としての機能を兼ね備えている。
【０１４３】
第５の相違点は、各回折格子３Ｂｂ・３Ｂｃ・３Ａａ１・３Ａａ２の回折効率が略１００％になっている点である。
【０１４４】
上記の構成により、光ビーム４Ａａのうち回折格子３Ａａ１に入射する光ビームの信号すべてを光ビーム４Ａｂの信号に加算すると共に、光ビーム４Ａａのうち回折格子３Ａａ２に入射する光ビームの信号すべてを光ビーム４Ａｃの信号に加算する。また、光ビーム４Ｂｂのうち回折格子３Ｂｂに入射する光ビームのすべておよび、光ビーム４Ｂｃのうち回折格子３Ｂｃに入射する光ビームのすべてを不要な方向に回折させ、信号検出から除外している。
【０１４５】
これにより、サブビームＡ・Ｂがホログラム光学素子２によりアンバランスに分割されることに起因するサブビームＡ・Ｂの回折光のアンバランスを、より少ない数（４つ）の回折格子で補正できる。
【０１４６】
ＤＰＰ法によるトラッキング誤差信号ＴＥＳ２は、次式

で検出できる。他のサーボ信号や情報信号の検出方法については、実施の形態１と同様である。
【０１４７】
なお、本実施形態で用いた回折格子３Ｂｂ・３Ｂｃ・３Ａａ１・３Ａａ２は、ブレーズ化等の手法によって形成される。
【０１４８】
以上のように、本実施形態に係る光集積化ユニットは、上記光検出器（７）は、メインビーム（Ｍ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（５Ｍｂ）を受光する第１のメインビーム受光部（７Ｍｂ）と、メインビーム（Ｍ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（５Ｍｃ）を受光する第２のメインビーム受光部（７Ｍｃ）と、第１の受光部（７Ａｂ）と、第１のサブビーム（Ａ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ａｂ）を受光する第２の受光部（７Ａｂ）と、第２のサブビーム（Ｂ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ｂｂ）を受光する第３の受光部（７Ｂｂ）と、第４の受光部（７Ａｃ）と、第１のサブビーム（Ａ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ａｃ）を受光する第５の受光部（７Ａｃ）と、第２のサブビーム（Ｂ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ｂｃ）を受光する第６の受光部（７Ｂｃ）と備え、第２の光分岐器（２）は、第１のサブビーム（Ａ）の中心が第３領域（２ａ）の内部を通るように配置されており、上記第３の光分岐器（３）は、第１のサブビーム（Ａ）の戻り光が第３領域（２ａ）で分岐されてなる光ビームの一部分を第１の受光部（７Ａｂ）に分岐させる第１の光分岐部（３Ａａ１）と、第１のサブビーム（Ａ）の戻り光が第３領域（２ａ）で分岐されてなる光ビーム（４Ａａ）の他の一部分を第４の受光部（７Ａｃ）に分岐させる第４の光分岐部（３Ａａ２）と、第２のサブビーム（Ｂ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ｂｂ）の一部分を、上記各受光部に入射する方向以外の方向に分岐させる第１３の光分岐部（３Ｂｂ）と、第２のサブビーム（Ｂ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ｂｃ）の一部分を、上記各受光部に入射する方向以外の方向に分岐させる第１４の光分岐部（３Ｂｃ）とを備え、第１のメインビーム受光部（７Ｍｂ）と第２のメインビーム受光部（７Ｍｃ）との光量差、並びに、第１ないし第３の受光部（７Ａｂ・７Ｂｂ・７Ａａ１）の合計光量と第４ないし第６の受光部（７Ａｃ・７Ｂｃ・７Ａａ２）の合計光量との差に基づいてトラッキング誤差信号を生成するようになっており、第１の受光部（７Ａｂ）に分岐される第１のサブビームと第２の受光部（７Ａｂ）に入射する第１のサブビームとを合わせたものの形状と、第２のサブビーム（Ｂ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビームのうちで第１３の光分岐部（３Ｂｂ）で分岐されることなく第３の受光部（７Ｂｂ）に入射する光ビームの形状と、第４の受光部（７Ａｃ）に分岐される第１のサブビームと第５の受光部（７Ａｃ）に入射する第１のサブビームとを合わせたものの形状と、第２のサブビーム（Ｂ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビームのうちで第１４の光分岐部（３Ｂｃ）で分岐されることなく第６の受光部（７Ｂｃ）に入射する光ビームの形状とが、第２の光分岐器（２）による第１のサブビーム（Ａ）および第２のサブビーム（Ｂ）の分岐位置に関わらず、略一定の形状（四半円形状）となるように、上記第１の光分岐部（３Ａａ１）、第４の光分岐部（３Ａａ２）、第１３の光分岐部（３Ｂｂ）、および第１４の光分岐部（３Ｂｃ）が配置されている。また、第１のメインビーム受光部（７Ｍｂ）に入射するメインビーム（５Ｍｂ）の形状、および第２のメインビーム受光部（７Ｍｃ）に入射するメインビーム（５Ｍｃ）の形状も、上記の「略一定の形状」と等価的に同一形状となるように構成されている。
【０１４９】
上記構成によれば、第２の光分岐器の中心に対する第１および第２のサブビーム（Ａ・Ｂ）の位置や間隔に標準状態からのずれが生じた場合においても、第１および第２の受光部（７Ａｂ）に入射する第１のサブビームを合わせたものの形状と、第３の受光部（７Ｂｂ）に入射する第２のサブビームの形状と、第４および第５の受光部（７Ａｃ）に入射する第１のサブビームを合わせたものの形状と、第６の受光部（７Ｂｃ）に入射する第２のサブビームの形状とを、常に略一定の形状にすることができるので、これら光ビームの光量に標準状態と異なるアンバランスが生じることを避けることができる。その結果、残留オフセットのない正確なトラッキング誤差信号を得ることが可能となる。
【０１５０】
〔実施の形態５〕
本発明のさらに他の実施の形態について図１５および図１６を用いて説明する。実施の形態１ないし４のいずれかと同種の構成要素については、同符号を引用して説明する。図１、３、４等も必要に応じて引用する。
【０１５１】
本実施形態は、次の点のみが実施の形態４と異なり、他は実施の形態１と同一の構成を備えている。すなわち、実施の形態１との相違点は、図１５に示すように、実施の形態４において、回折光４Ｂｂおよび４Ｂｃの一部分を受光素子以外の方向に回折させていた回折格子３Ｂｂ、３Ｂｃのそれぞれの代わりに、回折格子３Ｂｂと同じ位置に第１の遮光部としての遮光膜（マスク）を設け、回折格子３Ｂｃと同じ位置に第２の遮光部としての遮光膜（マスク）を設けている点である。
【０１５２】
上記の構成により、実施の形態４と同様に、光ビーム４Ａａのうち回折格子３Ａａ１に入射する光ビームの信号すべてを光ビーム４Ａｂの信号に加算すると共に、光ビーム４Ａａのうち回折格子３Ａａ２に入射する光ビームの信号すべてを光ビーム４Ａｃの信号に加算する。また、光ビーム４Ｂｂのうち回折格子３Ｂｂに入射する光ビームのすべておよび、光ビーム４Ｂｃのうち回折格子３Ｂｃに入射する光ビームのすべてを遮光することにより信号検出から除外している。
【０１５３】
これにより、サブビームＡ・Ｂがホログラム光学素子２によりアンバランスに分割されることに起因するサブビームＡ・Ｂの回折光のアンバランスを、さらに少ない数（２つ）の回折格子と遮光膜とで補正できる。
【０１５４】
ＤＰＰ法によるトラッキング誤差信号ＴＥＳ２は、実施の形態４と同様で、次式

で検出できる。他のサーボ信号や情報信号の検出方法については、実施の形態１と同様である。
【０１５５】
図１６に、遮光膜３Ｄｂ・３Ｄｃが形成された光学基板１５を裏面（光検出器７側の面）から見た斜視図を示す。遮光膜３Ｄｂ・３Ｄｃは、遮光性を有するものであれば特に限定されるものではないが、クロム等の金属からなる膜が、遮光性に優れていることから、好ましい。金属からなる遮光膜３Ｄｂ・３Ｄｃは、例えば、光学基板（透光体）における回折光学素子３が形成される面上に、金属を蒸着することにより形成できる。遮光膜３Ｄｂ・３Ｄｃは、フォトリソグラフ等の手法で形成されるので、回折格子３Ａａ１・３Ａａおよびホログラム光学素子２（図示しない）との位置精度は極めて良く、所定の光線部分を正確に遮光できる。本実施形態の遮光膜３Ｄｂ・３Ｄｃは、金属蒸着膜であり、遮光率は１００％に設定されている。
【０１５６】
このように、遮光部である遮光膜３Ｄｂ・３Ｄｃを光学基板１５と一体に形成することで、光集積化ユニット２０の作製が容易になると共に信頼性が向上する。
【０１５７】
以上のように、本実施形態に係る光集積化ユニットは、上記光検出器（７）は、メインビーム（Ｍ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ｍｂ）を受光する第１のメインビーム受光部（７Ｍｂ）と、メインビーム（Ｍ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ｍｃ）を受光する第２のメインビーム受光部（７Ｍｃ）と、第１の受光部（７Ａｂ）と、第１のサブビーム（Ａ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ａｂ）を受光する第２の受光部（７Ａｂ）と、第２のサブビーム（Ｂ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ｂｂ）を受光する第３の受光部（７Ｂｂ）と、第４の受光部（７Ａｃ）と、第１のサブビーム（Ａ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ａｃ）を受光する第５の受光部（７Ａｃ）と、第２のサブビーム（Ｂ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ｂｃ）を受光する第６の受光部（７Ｂｃ）と備え、第２の光分岐器（２）は、第１のサブビーム（Ａ）の中心が第３領域（２ａ）の内部を通るように配置されており、上記第３の光分岐器（３）は、第１のサブビーム（Ａ）の戻り光が第３領域（２ａ）で分岐されてなる光ビームの一部分を第１の受光部（７Ａｂ）に分岐させる第１の光分岐部（３Ａａ１）と、第１のサブビーム（Ａ）の戻り光が第３領域（２ａ）で分岐されてなる光ビーム（４Ａａ）の他の一部分を第４の受光部（７Ａｃ）に分岐させる第４の光分岐部（３Ａａ２）と、 第２のサブビーム（Ｂ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ｂｂ）の一部を遮光する第１の遮光部（３Ｄｂ）と、第２のサブビーム（Ｂ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ｂｃ）の一部を遮光する第２の遮光部（３Ｄｃ）とを備え、第１のメインビーム受光部（７Ｍｂ）と第２のメインビーム受光部（７Ｍｃ）との光量差、並びに、第１ないし第３の受光部（７Ａｂ・７Ｂｂ・７Ａａ１）の合計光量と第４ないし第６の受光部（７Ａｃ・７Ｂｃ・７Ａａ２）の合計光量との差に基づいてトラッキング誤差信号を生成するようになっており、第１の受光部（７Ａｂ）に分岐される第１のサブビームと第２の受光部（７Ａｂ）に入射する第１のサブビームとを合わせたものの形状と、第２のサブビーム（Ｂ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビームのうちで第１の遮光部（３Ｄｂ）で遮光されることなく第３の受光部（７Ｂｂ）に入射する光ビームの形状と、第４の受光部（７Ａｃ）に分岐される第１のサブビームと第５の受光部（７Ａｃ）に入射する第１のサブビームとを合わせたものの形状と、第２のサブビーム（Ｂ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビームのうちで第２の遮光部（３Ｄｃ）で遮光されることなく第６の受光部（７Ｂｃ）に入射する光ビームの形状とが、第２の光分岐器（２）による第１のサブビーム（Ａ）および第２のサブビーム（Ｂ）の分岐位置に関わらず、略一定の形状（四半円形状）となるように、上記第１の光分岐部（３Ａａ１）、第４の光分岐部（３Ａａ２）、第１３の光分岐部（３Ｂｂ）、および第１４の光分岐部（３Ｂｃ）が配置されている。また、第１のメインビーム受光部（７Ｍｂ）に入射するメインビーム（４Ｍｂ）の形状、および第２のメインビーム受光部（７Ｍｃ）に入射するメインビーム（４Ｍｃ）の形状も、上記の「略一定の形状」と等価的に同一形状となるように構成されている。
【０１５８】
上記構成によれば、第２の光分岐器の中心に対する第１および第２のサブビーム（Ａ・Ｂ）の位置や間隔に標準状態からのずれが生じた場合においても、第１および第２の受光部（７Ａｂ）に入射する第１のサブビームを合わせたものの形状と、第３の受光部（７Ｂｂ）に入射する第２のサブビームの形状と、第４および第５の受光部（７Ａｃ）に入射する第１のサブビームを合わせたものの形状と、第６の受光部（７Ｂｃ）に入射する第２のサブビームの形状とを、常に略一定の形状にすることができるので、これら光ビームの光量に標準状態と異なるアンバランスが生じることを避けることができる。その結果、残留オフセットのない正確なトラッキング誤差信号を得ることが可能となる。
【０１５９】
また、以上のように、上記各実施の形態に係る光集積化ユニットは、光記録媒体（１０）上に光ビームを集光する集光手段（１２・１３）と組み合わせて用いられ、上記集光手段（１２・１３）へ向かって光ビームを出射するための光源（１１）と、上記光源（１１）と上記集光手段（１２・１３）との間に配置され、上記光源（１１）から出射された光ビームを、メインビーム（Ｍ）と、トラッキング誤差信号生成のための第１のサブビーム（Ａ）および第２のサブビーム（Ｂ）とに分岐させる第１の光分岐器（１）と、光記録媒体（１０）からの戻り光を受光するための光検出器（７）と、上記集光手段（１２・１３）と光検出器（７）との間に配置され、上記戻り光を複数の光ビームに分岐させる第２の光分岐器（２）とを備え、上記第２の光分岐器（２）が、戻り光を異なる方向に分岐させる複数の領域からなり、該複数の領域は、光記録媒体（１０）のトラック方向（Ｙ）に平行な第１の分割線（２Ｎ）により互いに分割された第１領域（２ｂ）および第２領域（２ｃ）と、第１の分割線（２Ｎ）の延長線上に位置する第３領域（２ａ）とを含む光集積化ユニットにおいて、第２の光分岐器（２）と光検出器（７）との間に、第１のサブビーム（Ａ）および第２のサブビーム（Ｂ）の戻り光が第２の光分岐器（２）で分岐された光ビームの一部を分岐させる第３の光分岐器（３）が設けられている構成である。
【０１６０】
また、上記各実施の形態に係る光集積化ユニットは、上記光検出器（７）が、メインビーム（Ｍ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ｍｂ）を受光する第１のメインビーム受光部（７Ｍｂ）と、メインビーム（Ｍ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ｍｃ）を受光する第２のメインビーム受光部（７Ｍｃ）と、少なくとも、第１のサブビーム（Ａ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ａｂ）の少なくとも一部と、第１のサブビーム（Ａ）の戻り光が第３領域（２ａ）で分岐されてなる光ビーム（４Ａａ）の一部とを受光する第１のサブビーム受光部（７Ａｂ・７Ａａ１、７ｂ、７Ａ１、または７Ａｂ）と、少なくとも、第２のサブビーム（Ｂ）の戻り光が第１領域（２ｂ）で分岐されてなる光ビーム（４Ｂｂ）の少なくとも一部を受光する第２のサブビーム受光部（７Ｂｂ、７ｂ、または７Ｂ１）と、少なくとも、第１のサブビーム（Ａ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ａｃ）の少なくとも一部と、第１のサブビーム（Ａ）の戻り光が第３領域（２ａ）で分岐されてなる光ビーム（４Ａａ）の他の一部とを受光する第３のサブビーム受光部（７Ａｃ・７Ａａ２、７ｃ、７Ａ２、または７Ａｃ）と、少なくとも、第２のサブビーム（Ｂ）の戻り光が第２領域（２ｃ）で分岐されてなる光ビーム（４Ｂｃ）の少なくとも一部を受光する第４のサブビーム受光部（７Ｂｃ、７ｃ、または７Ｂ２）とを備え、第１のメインビーム受光部（７Ｍｂ）と第２のメインビーム受光部（７Ｍｃ）との光量差、並びに、第１のサブビーム受光部（７Ａｂ・７Ａａ１、７ｂ、７Ａ１、または７Ａｂ）および第２のサブビーム受光部（７Ｂｂ、７ｂ、または７Ｂ１）の合計光量と第３のサブビーム受光部（７Ａｃ・７Ａａ２、７ｃ、７Ａ２、または７Ａｃ）および第４のサブビーム受光部（７Ｂｃ、７ｃ、または７Ｂ２）の合計光量との差に基づいてトラッキング誤差信号を生成するようになっており、第３の光分岐器（３）は、第１のサブビーム受光部（７Ａｂ・７Ａａ１、７ｂ、７Ａ１、または７Ａｂ）に入射する第１のサブビーム（以下、光ビームαと称する）と、第２のサブビーム受光部（７Ｂｂ、７ｂ、または７Ｂ１）に入射する第２のサブビーム（以下、光ビームβと称する）と、第３のサブビーム受光部（７Ａｃ・７Ａａ２、７ｃ、７Ａ２、または７Ａｃ）に入射する第１のサブビーム（以下、光ビームγと称する）と、第４のサブビーム受光部（７Ｂｃ、７ｃ、または７Ｂ２）に入射する第２のサブビーム（以下、光ビームδと称する）とが、それぞれ、第２の光分岐器（２）による第１のサブビーム（Ａ）および第２のサブビーム（Ｂ）の分岐位置に関わらず、全体として略一定の形状となるように構成されている。また、第３の光分岐器（３）は、光ビームαと、光ビームβと、光ビームγと、光ビームδとが、全体として互いに等価的に同一形状となるように構成されている。また、第３の光分岐器（３）は、光ビームαの形状と、光ビームβの形状とが、全体として、第１のメインビーム受光部（７Ｍｂ）に入射するメインビーム（４Ｍｂ）の形状、あるいはその入射メインビーム（４Ｍｂ）を２つ合わせた形状と等価的に同一形状となるように、かつ、光ビームγの形状と、光ビームδの形状とが、全体として、第２のメインビーム受光部（７Ｍｃ）に入射するメインビーム（４Ｍｃ）の形状、あるいはその入射メインビーム（４Ｍｃ）を２つ合わせた形状と等価的に同一形状となるように、構成されている。
【０１６１】
上記構成によれば、第２の光分岐器の中心に対する第１および第２のサブビーム（Ａ・Ｂ）の位置や間隔に標準状態からのずれが生じた場合においても、光ビームαと、光ビームβと、光ビームγと、光ビームδとを、常に略一定の形状にすることができるので、これら光ビームの光量に標準状態と異なるアンバランスが生じることを避けることができる。その結果、残留オフセットのない正確なトラッキング誤差信号を得ることが可能となる。
【０１６２】
なお、上記各実施の形態で用いたホログラム光学素子２は、光ディスク１０の半径方向Ｘに平行な分割線２Ｌで第３領域としての半円状の領域２ａを形成し、さらに残りの半円部分（第２の領域）をトラック接線方向Ｙに平行な分割線２Ｎにより、第１領域および第２領域としての四分円状の２つの領域２ｂ・２ｃに分割した３分割ホログラム光学素子であった。しかしながら、本発明に用いるホログラム光学素子の形状は、これに限るものではない。ホログラム光学素子は、例えば、ホログラム光学素子２におけるトラック接線方向Ｙに平行な分割線２Ｎが光線の全域に延在し、四分円状の４つの領域に分割された４分割ホログラム光学素子であっても構わない。
【０１６３】
４分割ホログラム素子は、実施の形態３等のようにサブビームＡ・Ｂを等価的に丸ごと用いる構成の場合に、特に好ましい。この場合、メインビームの片側半円形状同士の差動をとることにより、メインビームＭによるトラッキング誤差信号の生成についても、光ビーム（メインビームＭ）を等価的に丸ごと利用できる。それゆえ、メインビームが分割線２Ｌによってどこで分割されても、トラッキング誤差信号生成に用いるメインビームと、トラッキング誤差信号生成に用いるサブビームＡ・Ｂとを、常に同一形状にすることができる。
【０１６４】
【発明の効果】
本発明によれば、第３の光分岐器を設けたことにより、光集積化ユニットを構成する部品の寸法ばらつきや、光集積化ユニットの製造ばらつきが生じても、差動プッシュプル法におけるトラッキング誤差信号を安定して得ることができる。したがって、本発明は、トラッキング誤差を安定に検出することが可能な光集積化ユニットおよびそれを用いた光ピックアップ装置を提供することができるという効果を奏する。
【図面の簡単な説明】
【図１】本発明の実施の一形態に係る光ピックアップ装置の概略構成を示す側面図である。
【図２】上記光ピックアップ装置が備える３ビーム回折格子を示す平面図である。
【図３】上記光ピックアップ装置が備えるホログラム光学素子の概略構成を光ビームと共に示す平面図である。
【図４】上記光ピックアップ装置が備える回折光学素子の概略構成を光ビームと共に示す平面図である。
【図５】上記回折光学素子の概略構成を示す平面図である。
【図６】上記光ピックアップ装置が備える回折光学素子および光検出器の構成を、回折光学素子による回折光と共に示す図である。
【図７】上記光ピックアップ装置が備える光検出器の構成を入射する光線と共に示す図である。
【図８】上記光ピックアップ装置が備える、３ビーム回折格子、ホログラム光学素子、および回折光学素子が形成された光学基板を示す斜視図である。
【図９】本発明の他の実施の形態に係る光ピックアップ装置が備える回折光学素子の概略構成を示す平面図である。
【図１０】本発明の他の実施の形態に係る光ピックアップ装置が備える回折光学素子および光検出器の構成を、回折光学素子による回折光と共に示す図である。
【図１１】本発明のさらに他の実施の形態に係る光ピックアップ装置が備える回折光学素子の概略構成を示す平面図である。
【図１２】本発明のさらに他の実施の形態に係る光ピックアップ装置が備える回折光学素子および光検出器の構成を、回折光学素子による回折光と共に示す図である。
【図１３】本発明のさらに他の実施の形態に係る光ピックアップ装置が備える回折光学素子の概略構成を示す平面図である。
【図１４】本発明のさらに他の実施の形態に係る光ピックアップ装置が備える回折光学素子および光検出器の構成を、回折光学素子による回折光と共に示す図である。
【図１５】本発明のさらに他の実施の形態に係る光ピックアップ装置が備える回折光学素子および光検出器の構成を、回折光学素子による回折光と共に示す図である。
【図１６】本発明のさらに他の実施の形態に係る光ピックアップ装置が備える、遮光膜が形成された光学基板を示す斜視図である。
【図１７】従来の光ピックアップ装置の一例を示す図であり、（ａ）は上面図、（ｂ）は側面図である。
【図１８】上記従来の光ピックアップ装置が備えるホログラム光学素子および受光素子の構成を、ホログラム光学素子の各領域による回折光と共に示す図である。
【図１９】上記従来の光ピックアップ装置が備えるホログラム光学素子の概略構成を光ビームと共に示す平面図である。
【図２０】図１９のホログラム光学素子による回折光の形状および位置を示す図である。
【符号の説明】
１ ３ビーム回折格子
２ ホログラム光学素子
２Ｌ・２Ｎ 分割線
２ａ〜２ｃ 領域
３ 回折光学素子
３Ａａ１・３Ａａ２・３Ａｂ・３Ａｃ・３Ｂｂ・３Ｂｃ 回折格子
３Ｂａ１・３Ｂａ２ 回折格子
３Ｄｂ・３Ｄｃ 遮光膜
３Ｍ・３Ｎ 分割線
４ ＋１次回折光
４Ａａ・４Ａｂ・４Ａｃ・４Ｂａ・４Ｂｂ・４Ｂｃ 光ビーム
４Ｍａ・４Ｍｂ・４Ｍｃ 回折格子
５ −１次回折光
６ 回折光
７ 光検出器
７Ａａ１・７Ａａ２・７Ａｂ・７Ａｃ・７Ｂｂ・７Ｂｃ 受光素子
７Ｍａ１・７Ｍａ２・７Ｍａ・７Ｍｂ・７Ｍｃ 受光素子
７ｂ・７ｃ 受光素子
７Ａ１・７Ａ２・７Ｂ１・７Ｂ２ 受光素子
７Ｍａ１・７Ｍａ２・７Ｍａ・７Ｍｂ・７Ｍｃ 受光素子
８ ビームスプリッタ
９ １／４波長板
１０ 光ディスク
１１ 半導体レーザ
１２ コリメートレンズ
１３ 対物レンズ
１５ 光学基板
２０ 光集積化ユニット
８０ 領域
Ａ・Ｂ サブビーム
Ｍ メインビーム
Ｘ 半径方向
Ｙ トラック接線方向
Ｚ 光軸方向[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup device that optically records or reproduces information on an information recording medium such as an optical disk, and an optical integrated unit used therefor, and more particularly, to accurately detect a tracking error in the optical pickup device. It is related with the structure for performing stably.
[0002]
[Prior art]
In an optical disk device, tracking servo that controls the position of the light beam along the radial direction of the optical disk is essential so that the light beam does not deviate from the track on the optical disk. As a tracking servo system in an optical disk apparatus, there are mainly a 3-beam method and a push-pull method. However, when these methods are used in an optical disc apparatus, an offset occurs due to recording / reproduction, access, or disc tilt.
[0003]
As a method for removing this offset, the differential push-pull method (hereinafter referred to as DPP (Differential Push-Pull) as appropriate) is proposed in the Optical Memory Symposium '86 “New Tracking Servo Method Differential Push-Pull Method” (announced on December 18, 1986). ) Is abbreviated as law. The DPP method is a combination of the three-beam method and the one-pull push-pull method. The DPP method divides a light beam into three beams of a main beam and two sub-beams, and divides each beam in the track tangential direction. This is a method for detecting a tracking error from a difference signal of divided light beams.
[0004]
In recent years, an optical pickup device using the DPP method is used in an apparatus for recording or reproducing a high density optical disk such as a DVD (Digital Versatile Disc) player.
[0005]
Further, the applicant of the present application has proposed an optical pickup device using an optical integrated unit capable of using the DPP method in Japanese Patent Laid-Open No. 2001-273666.
[0006]
FIG. 17 shows a conventional example of the optical pickup device disclosed in the above publication. FIG. 17A shows a top view and FIG. 17B shows a side view. FIG. 17 is a concise redraw of the portion of the optical integrated unit shown in FIG. 2 in the above publication, and the reference numerals and the like in the figure are different from those in the publication.
[0007]
The light beam 120 emitted from the semiconductor laser 105 is divided into a main beam (0th-order light) and two sub-beams (± 1st-order diffracted light) by the three-beam diffraction grating 106, and the polarization beam splitter (hereinafter referred to as appropriate) of the composite prism 107. , Abbreviated as PBS) through the surface 107a, through the quarter-wave plate 108, and toward a collimator lens (not shown). Note that the sub-beam is not shown in order to avoid complication of the drawing.
[0008]
Here, the light beam emitted from the semiconductor laser 105 is linearly polarized light (P-polarized light; vibration direction is parallel to the incident surface) in a direction parallel to the radial direction (direction perpendicular to the track tangential direction on the optical disk) of the optical disk. ). The linearly polarized light is transmitted through the PBS surface 107a, is circularly polarized by the quarter wavelength plate 108, and travels to a collimator lens (not shown). This circularly polarized light is converted into parallel light by a collimator lens, condensed by an objective lens (not shown), and incident on an optical disc (not shown). Then, the return light 121 from the optical disc is incident on the quarter-wave plate 108 again, and is transmitted through the quarter-wave plate 108 so that it is linearly polarized in a direction parallel to the track tangential direction (circumferential direction) Y of the optical disc. (S polarized light; polarized light whose vibration direction is perpendicular to the incident surface), reflected by the PBS surface 107 a and the reflecting mirror surface 107 b of the composite prism 107, and enters the hologram optical element 109. The return light 121 incident on the hologram optical element 109 is diffracted and incident on the light receiving element 110.
[0009]
Therefore, almost all of the light emitted from the semiconductor laser 105 can be guided to the optical disc in both the main beam and the sub beam, and almost all of the return light can be guided to the photodetector side, so that the light utilization efficiency is improved. ing.
[0010]
Next, the hologram optical element 109, the light receiving element 110, and the servo signal detection method are as follows. FIG. 18 shows the element shapes of the hologram optical element 109 and the light receiving element 110 and in which area of the light receiving element 110 the light diffracted by each area of the hologram optical element 109 is received.
[0011]
The hologram optical element 109 is divided into three areas 109a to 109c by a dividing line 109l parallel to the radial direction X of the optical disk and a dividing line 109m parallel to the track tangential direction Y of the optical disk. At 109c, diffracted light is generated in different directions. The light receiving element 110 includes six light receiving regions 110a to 110f that receive the + 1st order diffracted light from the hologram optical element 109 and three light receiving regions 110g to 110i that receive the −1st order diffracted light from the hologram optical element 109. The output signals Sa to Si are output from the light receiving regions 110a to 110i, respectively.
[0012]
Of the return light of the main beam, the + 1st order diffracted light diffracted by the region 109a of the hologram optical element 109 is detected on the dividing line 110l of the regions 110a and 110b of the light receiving element 110, and the −1st order diffracted light is detected by the region 110g. It is configured to be. Further, the −1st order diffracted light in the region 109b of the hologram optical element 109 is detected in the region 110h of the light receiving element 110, and the −1st order diffracted light in the region 109c is detected in the region 110i.
[0013]
Further, if one sub-beam (+ 1st order diffracted light) is represented by A and the other subbeam (−1st order diffracted light) is represented by B, the + 1st order diffracted light diffracted in the region 109b is converted into the region 110e for the return light of the subbeam A. + 1st order diffracted light detected in step 119 and diffracted in the region 109c is detected in the region 110c. For the sub-beam B, the + 1st order diffracted light diffracted in the region 109b is detected in the region 110f, and the + 1st order diffracted light diffracted in the region 109c is detected in the region 110d.
[0014]
Based on the output signals Sa to Si detected by the hologram optical element 109 and the light receiving element 110 configured as described above, arithmetic processing of various signals is performed as follows.
[0015]
A focus error signal (a signal representing a deviation from the optical disc surface at the position (focal position) where the light beam is converged by the objective lens) FES is expressed by the following equation using the output signal Sa and the output signal Sb.
FES = Sa-Sb (1)
Is calculated by
[0016]
The tracking error signal TES1 based on the push-pull method is expressed by the following equation using the output signal Si of the region 110i and the output signal Sh of the region 110h.
TES1 = Sh-Si (2)
Calculated with
[0017]
In an apparatus for recording or reproducing a high density optical disc, for the reasons described above, a tracking error signal based on the differential push-pull method is mainly used as a tracking error signal rather than a tracking error signal based on the push-pull method. It is like that. In addition to the tracking error signal based on the push-pull method, the tracking error signal based on the differential push-pull method includes the push-pull signal TES (A) (sub-beam A obtained from the output signal Sc of the region 110c and the output signal Se of the region 110e. = Sc-Se) and the push-pull signal TES (B) (= Sd-Sf) of the sub beam B obtained from the output signal Sd of the region 110c and the output signal Sf of the region 110f.
[0018]
The tracking error signal TES2 by the differential push-pull method is given by

Calculated with
[0019]
Here, the constant k is for correcting the difference in light intensity between the main beam and the sub beams A and B, and the light intensity ratio is (light intensity of the main beam) :( light intensity of the sub beam A) :( sub beam) If the light intensity of B) = a: b: b, then k is
k = a / (2b)
Given in.
[0020]
Further, when reproducing an optical disc on which pit information is recorded, a change in phase difference between the output signal Sh and the output signal Si can be detected, and a tracking error signal TES3 by the phase difference (DPD) method can also be detected.
[0021]
The recorded information signal (RF) is expressed by the following equation:
RF = Sh + Sg + Si (4)
Is detected.
[0022]
[Problems to be solved by the invention]
However, the conventional optical pickup device disclosed in Japanese Patent Laid-Open No. 2001-273666 has a problem. The problems of the conventional optical pickup device disclosed in Japanese Patent Laid-Open No. 2001-273666 will be described with reference to FIGS. 17, 19, and 20. FIG.
[0023]
In FIG. 17B, the light beam emitted from the semiconductor laser 105 becomes thicker as it travels toward the optical disk (not shown). Therefore, on the optical disk side (upper side in the figure) than the three-beam diffraction grating 106, The main beam and the sub-beams A and B exist in a substantially overlapping state, and there is no significant difference even when the outer shape of the beam is considered to be the light 120. This fact is also described in the above publication.
[0024]
However, in the region where the beam diameter is small, the deviation between the main beam and the sub-beams A and B becomes remarkable, and the situation is different from the above. FIG. 19 shows a beam shape (spot shape) on the hologram optical element 109.
[0025]
In FIG. 19, 121a indicates a spot of the main beam, 121b indicates a spot of the sub beam A, and 121c indicates a spot of the sub beam B. It can be seen from FIG. 19 that the sub beams A and B are deviated from the main beam.
[0026]
In FIG. 17B, when the shape and position of the light beam between the holographic optical element 109 and the light receiving element 110 (for example, the cross section along the dotted line X′-X ′ in the figure) are examined, the main beam M in the state of FIG. The shape and position of each diffracted light (0th order light and ± 1st order diffracted light) generated by diffracting each of the sub-beams A and B by the three regions 109a to 109c of the hologram optical element 109 are as shown in FIG. Become. Note that the light beam indicated by a reference numeral in the figure indicates a light beam used for generating a tracking error signal, a focus error signal, an information signal (reproduction signal), etc. in the conventional optical pickup device. A light beam not shown represents a light beam that is not used in the conventional optical pickup device. Here, the light beams 130e and 130c are + 1st order diffracted lights in which the sub-beam A is diffracted in the areas 109b and 109c, respectively, and the light beams 130f and 130d are + 1st order diffracted lights in which the subbeam B is diffracted in the areas 109b and 109c, respectively. Is shown.
[0027]
From FIG. 20, the + 1st order diffracted light diffracted in the regions 109b and 109c used for generating the tracking error signal has a light quantity (corresponding to the size of the light beam in FIG. 20) between the sub beam A and the sub beam B. You can see that they are different. As shown in FIG. 19, the difference in the amount of light between the + 1st order diffracted light of the sub beam A and the + 1st order diffracted light of the sub beam B by the regions 109b and 109c is the difference between the sub beam A (spot 121a) and the sub beam B (spot 121c). This is because the hologram optical element 109 is not divided at the center by the dividing line 109l. In the conventional optical pickup apparatus, the tracking error is detected using the push-pull signal TES1 of the main beam, the push-pull signal TES (A) of the sub beam A, and the push-pull signal TES (B) of the sub beam B. Therefore, the following problem occurs due to the difference in the amount of light between the + 1st order diffracted light of the sub beam A and the + 1st order diffracted light of the sub beam B by the regions 109b and 109c.
[0028]
If the difference in the amount of light between the diffracted light of sub-beam A and the diffracted light of sub-beam B is always constant, stable tracking servo can be performed by setting the constant k in the DPP method described above to an appropriate value. Become.
[0029]
However, in an actual optical pickup device, an installation error of the semiconductor laser 105, a manufacturing error related to a housing portion such as a package, a stem, and a housing, a manufacturing error and an installation error of a beam splitter, a reflection mirror, etc. The position and interval of the main beam and the sub beams A and B on the hologram optical element 109 differ from one optical pickup device to another due to the influence of manufacturing errors and mounting errors of optical components used as components of the optical pickup device. That is, (1) When the positions of the main beam M and the sub beams A and B on the hologram element 109 are shifted due to the above-mentioned various manufacturing errors and mounting errors, etc., and (2) the main beam M and the sub beams A and B on the hologram element 109 are shifted. When the distance from B is deviated (the beam size also changes as the distance deviates), (3) both of these positions and intervals may deviate.
[0030]
In the case of {circle around (1)} or {circle around (3)}, even if the optical axis of the main beam M is on the dividing line 109l, the diffracted light quantity unbalance between the sub beam A and the sub beam B is the sub beam A and the sub beam B in the standard state. This is different from the unbalance of the diffracted light quantity.
[0031]
In these cases, since the unbalance of the diffracted light amount between the sub beam A and the sub beam B is different from the unbalanced diffracted light amount between the sub beam A and the sub beam B in the standard state, a standard pickup device having no tolerance is used. There is a problem that the set constant k cannot be corrected sufficiently. That is, if k set by a standard (no tolerance) pickup device is used, the tracking error signal TES2 is generated due to the difference in the diffracted light amount between the sub beam A and the sub beam B being different from the standard state. A residual offset occurs. For this reason, the conventional optical pickup device has a problem that a stable tracking servo is difficult.
[0032]
The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an optical integrated unit capable of stably detecting a tracking error and an optical pickup device using the same. .
[0033]
[Means for Solving the Problems]
In order to solve the above problems, the optical integrated unit of the present invention is used in combination with a condensing unit that condenses a light beam on an optical recording medium, and emits the light beam toward the condensing unit. And a light beam disposed between the light source and the condensing means, the light beam emitted from the light source is divided into a main beam (main beam) and a tracking error signal (from the track center on the optical recording medium). A first optical branching device for branching into a first sub-beam (secondary beam) and a second sub-beam for generating a signal representing a deviation of the optical axis of the main beam, and a return light from the optical recording medium is received. And a second optical branching device arranged between the light condensing means and the photodetector for branching the return light into a plurality of light beams, and the second optical branching device. But the return light is split in different directions A plurality of regions, wherein the plurality of regions are on a first region and a second region separated from each other by a first parting line parallel to the track direction of the optical recording medium, and on an extension line of the first parting line In the optical integrated unit including the third region positioned, the return light of the first sub-beam and the second sub-beam is branched by the second optical splitter between the second optical splitter and the photodetector. Light beam at least A third optical branching device for branching a part is provided.
[0034]
According to the above configuration, even if there is a variation in the dimensions of components constituting the optical integrated unit or a manufacturing variation in the optical integrated unit due to the provision of the third optical branching device, tracking in the differential push-pull method is performed. An error signal can be obtained stably.
[0035]
The “return light” refers to a light beam that is reflected by the optical recording medium and returns to the inside of the optical integrated unit. The track direction refers to the direction of a straight line along the track, and refers to the direction of the track tangent when the track is formed concentrically.
[0036]
In a preferred embodiment of the optical integrated unit of the present invention, the photodetector includes a first main beam light receiving unit that receives a light beam obtained by branching the return light of the main beam in the first region, and a return of the main beam. A second main beam receiving unit that receives a light beam that is branched in the second region, and at least a part of the light beam in which the return light of the first sub-beam is branched in the first region; A first sub-beam receiving unit that receives a part of the light beam in which the return light of the first sub-beam is branched in the third region; and at least the return light of the second sub-beam is branched in the first region. A second sub-beam receiving unit that receives at least a part of the light beam, at least a part of the light beam obtained by branching the return light of the first sub-beam in the second region, and the return of the first sub-beam. A third sub-beam receiving unit that receives the other part of the light beam branched in the third region, and at least a light beam formed by branching the return light of the second sub-beam in the second region. A fourth sub-beam light receiving unit that receives at least a part of the light; a light amount difference between the first main beam light-receiving unit and the second main beam light-receiving unit (a difference in an output signal indicating the light amount); A tracking error signal is generated based on the difference between the total light amount of the sub beam light receiving unit and the second sub beam light receiving unit and the total light amount of the third sub beam light receiving unit and the fourth sub beam light receiving unit. The optical branching device includes a first sub-beam incident on the first sub-beam receiving unit, a second sub-beam incident on the second sub-beam receiving unit, and a first sub-beam incident on the third sub-beam receiving unit. The second sub-beam incident on the fourth sub-beam receiving unit is different regardless of the branch position of the first sub-beam and the second sub-beam by the second optical splitter (that is, the branch position is different). In this case, for example, when the position of the light with respect to the dividing line of the second optical branching device is different, or when the shape divided by the dividing line of the second optical branching device is different), the overall shape is substantially constant. It is the structure comprised as follows.
[0037]
In a preferred embodiment of the optical integrated unit according to the present invention, the photodetector includes a first main beam receiving unit that receives a light beam obtained by branching return light of the main beam in the first region, and a main beam. A second main beam receiving unit that receives a light beam that is branched from the return light of the first region, and at least a part of the light beam that is branched from the return light of the first sub-beam at the first region. A first sub-beam receiving unit that receives a part of the light beam obtained by branching the return light of the first sub-beam in the third region, and at least the return light of the second sub-beam branches in the first region. A second sub-beam receiving unit that receives at least a part of the light beam formed, at least a part of the light beam that is branched from the return light of the first sub-beam in the second region, and the first sub-beam A third sub-beam light receiving unit that receives the other part of the light beam branched in the third region, and at least light obtained by branching the return light of the second sub-beam in the second region A fourth sub-beam light receiving unit that receives at least a part of the beam, a light amount difference between the first main beam light-receiving unit and the second main beam light-receiving unit, and the first sub-beam light receiving unit and the second sub-beam light receiving unit. A tracking error signal is generated based on the difference between the total light amount of the sub-beam light receiving unit and the total light amount of the third sub-beam light receiving unit and the fourth sub-beam light receiving unit. A first sub-beam incident on one sub-beam receiving unit, a second sub-beam incident on a second sub-beam receiving unit, a first sub-beam incident on a third sub-beam receiving unit, and a fourth sub-beam A second sub-beam incident on the optical unit is a configuration that is configured to be equivalent to same shape as a whole. In the above configuration, preferably, the third optical branching unit includes a shape of the first sub-beam incident on the first sub-beam light receiving unit and a shape of the second sub-beam incident on the second sub-beam light receiving unit. However, as a whole, the shape of the main beam incident on the first main beam light receiving unit or the shape of the two main beams incident on the first main beam light receiving unit is equivalently the same shape. In addition, the shape of the first sub beam incident on the third sub beam light receiving unit and the shape of the second sub beam incident on the fourth sub beam light receiving unit are incident on the second main beam light receiving unit as a whole. The shape is equivalent to the shape of the main beam or the shape of the two main beams incident on the second main beam light receiving unit.
[0038]
According to each of the above configurations, the difference between the total light amount of the first sub-beam light receiving unit and the second sub-beam light receiving unit and the total light amount of the third sub-beam light receiving unit and the fourth sub-beam light receiving unit is the second light branching. It does not depend on the branch position of the first sub-beam and the second sub-beam by the detector. Therefore, even if the position and interval of the first and second sub-beams (A / B) with respect to the center of the second optical branching device are deviated from the standard state due to various manufacturing errors, mounting errors, etc., the first The diffracted light quantity of the sub-beam and the second sub-beam does not cause an unbalance different from the unbalance in the standard state. Therefore, an accurate tracking error signal without a residual offset can be obtained by using a constant set by the intensity ratio between the main beam and the sub beam (division ratio by the first optical splitter) in the standard state.
[0039]
When the light beam is a single beam, the light image on the third optical branching device of the single beam is “to shape”. In the case where the light beam is composed of a plurality of beams, it means that a combination of the optical images on the third optical branching device is “˜shape”. The “substantially constant shape” can include a case where the shape changes due to the occurrence of a tracking error or the like. In addition, “equivalently the same shape” can include a case where a slight difference in shape occurs due to generation of a tracking error or the like.
[0040]
Further, if the light detector generates an information signal based on the return light (the light amount, phase, etc.) of the main beam received by the light receiving unit, the information signal recorded on the optical recording medium Can be played.
[0041]
In the second optical splitter, the total area of the first area and the second area is one area obtained by dividing the entire area into two by a second dividing line perpendicular to the track direction in the optical recording medium. It is preferable that the third region is the other region.
[0042]
According to the above configuration, the tracking error signal in the differential push-pull method can be obtained more reliably and stably.
[0043]
The third optical branching unit is preferably disposed at an optical position where the plurality of light beams divided by the second optical branching unit are separated from each other.
[0044]
According to the above configuration, the third optical branching device can be easily designed. Therefore, an optical integrated unit that is easy to design can be provided.
[0045]
In a preferred embodiment of the optical integrated unit according to the present invention, the photodetector includes a first light receiving unit and a second light receiving unit as a first sub beam light receiving unit, and a third sub beam receiving unit. It comprises a light receiving part, a fourth light receiving part and a fifth light receiving part as a third sub-beam light receiving part, and a sixth light receiving part as a fourth sub-beam light receiving part. The center of the first sub-beam is arranged so as to pass through the inside of the third region, and the third optical branching unit is a part of the light beam obtained by branching the return light of the first sub-beam in the third region. And a second light for branching all of the light beam formed by branching the return light of the first sub-beam in the first region to the second light receiver. An optical beam formed by branching the return light of the second sub-beam in the first region. A third light branching part for branching a part of the light beam to the third light receiving part, and another part of the light beam obtained by branching the return light of the first sub-beam in the third region to the fourth light receiving part. A fourth light branching section, a fifth light branching section for branching all of the light beam obtained by branching the return light of the first sub-beam in the second region to the fifth light-receiving section, and a second sub-beam A sixth light branching part for branching a part of the light beam branched from the return light in the second region to the sixth light receiving part, and the first sub beam and the second branching to the first light receiving part. And the shape of the second sub-beam branched to the third light-receiving unit, and the first sub-beam branched to the fourth light-receiving unit The shape of the first sub-beam branched to the fifth light-receiving unit and the sixth receiver The shape of the second sub-beam branched into the first and second sub-beams is substantially constant regardless of the branch position of the first sub-beam and the second sub-beam by the second optical splitter. In this configuration, first to sixth optical branching portions are arranged. In the above configuration, the first to sixth optical branching units (first optical branching unit, second optical branching unit, third optical branching unit, fourth optical branching unit, and fifth optical branching unit). And the sixth light branching section) are preferably provided so that the light branching efficiency (diffraction efficiency) is equal to each other.
[0046]
According to the above configuration, even if the positions and intervals of the first sub-beam and the second sub-beam are deviated from the standard state due to various manufacturing errors and attachment errors, the first sub-beam and the second sub-beam The amount of diffracted light does not cause an unbalance different from the unbalance in the standard state. Therefore, an accurate tracking error signal having no residual offset can be obtained even if there are variations in dimensions of parts constituting the optical integrated unit or manufacturing variations in the optical integrated unit.
[0047]
In the preferred embodiment, at least two of the first light receiving unit, the second light receiving unit, and the third light receiving unit, and / or the fourth light receiving unit, the fifth light receiving unit, and the sixth light receiving unit. It is preferable that at least two of the light receiving portions are formed of the same light receiving element.
[0048]
According to the above configuration, since the photodetector can be configured with a smaller number of light receiving elements, the photodetector can be reduced in size. As a result, a smaller optical integrated unit can be provided.
[0049]
In the above configuration, at least two of the first light receiving unit, the third light receiving unit, and the third light receiving unit are configured by the same light receiving element, and the fourth light receiving unit and the fifth light receiving unit are provided. In addition, it is preferable that at least two of the sixth light receiving parts are formed of the same light receiving element. As a result, the photodetector can be further reduced in size, and an even smaller optical integrated unit can be provided.
[0050]
Further, in the above configuration, the first light receiving unit, the second light receiving unit, and the third light receiving unit are configured by the same light receiving element, and the fourth light receiving unit, the fifth light receiving unit, and the sixth light receiving unit are configured. It is more preferable that the light receiving portions are formed of the same light receiving element. As a result, the photodetector can be further reduced in size, and an even smaller optical integrated unit can be provided.
[0051]
In another preferred embodiment of the optical integrated unit of the present invention, the photodetector includes a first light receiving unit and a second light receiving unit as a first sub beam light receiving unit, and a second sub beam receiving unit as the second sub beam receiving unit. 3 light receiving parts and 7th light receiving part, 4th light receiving part and 5th light receiving part as 3rd sub-beam light receiving part, 6th light receiving part and 8th as 4th sub beam light receiving part The seventh optical branching unit includes a light receiving unit, and the third optical branching unit branches a half of the light beam obtained by branching the return light of the first sub-beam into the third region to the first light receiving unit. A second light branching unit for branching all of the light beam obtained by branching the return light of the first sub-beam into the first region to the second light-receiving unit, and the return light of the second sub-beam being the first region An eighth optical branch for branching all of the light beam branched at the third light receiving section A ninth light branching portion for branching a half of the light beam obtained by branching the return light of the second sub beam into the third region to the seventh light receiving portion, and the return light of the first sub beam for the third region. A tenth light branching portion for branching the remaining half of the light beam branched in step 4 to the fourth light receiving portion, and a fifth light beam formed by branching the return light of the first sub beam in the second region to the fifth region. A fifth light branching portion that branches to the light receiving portion, and an eleventh light branching portion that branches all of the light beams obtained by branching the return light of the second sub-beam in the second region to the sixth light receiving portion. And a twelfth light branching unit for branching the remaining half of the light beam obtained by branching the return light of the second sub-beam into the third region to the eighth light receiving unit. In the above configuration, the second optical branching unit, the fifth optical branching unit, the seventh optical branching unit, the eighth optical branching unit, the ninth optical branching unit, the tenth optical branching unit, the eleventh optical branching unit, The optical branching section and the twelfth optical branching section are preferably provided so that the optical branching efficiency (diffraction efficiency) is equal to each other.
[0052]
According to the above configuration, the shape of the first sub beam branched to the first light receiving unit and the second light receiving unit, and the shape of the second sub beam branched to the third light receiving unit and the seventh light receiving unit. And the shape of the first sub beam branched to the fourth light receiving portion and the fifth light receiving portion and the shape of the second sub beam branched to the sixth light receiving portion and the eighth light receiving portion are Regardless of the branching position of the first sub-beam and the second sub-beam by the two optical splitters, the first sub-beam or the second sub-beam has the same shape equivalent to the shape divided into two equal parts. Therefore, even if the position and interval of the first sub-beam and the second sub-beam are deviated from the standard state due to various manufacturing errors and mounting errors, the amount of diffracted light between the first sub-beam and the second sub-beam is An unbalance different from the unbalance in the standard state does not occur. Therefore, an accurate tracking error signal without residual offset can be obtained. In addition, according to the above configuration, since the entire area of the first sub-beam and the second sub-beam can be used for detection of the tracking error signal, offset correction of the tracking error signal can be performed more accurately, and the differential push-pull method As a result, the amplitude of the tracking error signal is increased, and a more stable tracking error signal can be obtained.
[0053]
In another preferable embodiment, at least two of the first light receiving unit, the second light receiving unit, the third light receiving unit, and the seventh light receiving unit, and / or the fourth light receiving unit, It is preferable that at least two of the fifth light receiving unit, the sixth light receiving unit, and the eighth light receiving unit are configured by the same light receiving element.
[0054]
According to the above configuration, since the photodetector can be configured with a smaller number of light receiving elements, the photodetector can be reduced in size. As a result, a smaller optical integrated unit can be provided.
[0055]
In the above configuration, at least two of the first light receiving unit, the second light receiving unit, the third light receiving unit, and the seventh light receiving unit are configured by the same light receiving element, and the fourth light receiving unit is used. It is preferable that at least two of the first light receiving unit, the fifth light receiving unit, the sixth light receiving unit, and the eighth light receiving unit are configured by the same light receiving element. As a result, the photodetector can be further reduced in size, and an even smaller optical integrated unit can be provided.
[0056]
Further, in the above configuration, the first light receiving unit and the second light receiving unit are configured by the same light receiving element, and the third light receiving unit and the seventh light receiving unit are configured by the same light receiving element, The light receiving unit and the fifth light receiving unit are preferably formed of the same light receiving element, and the sixth light receiving unit and the eighth light receiving unit are preferably formed of the same light receiving element. As a result, the photodetector can be further reduced in size, and an even smaller optical integrated unit can be provided.
[0057]
In another preferred embodiment, the photodetector includes a first light-receiving unit as a first sub-beam light-receiving unit and a return light of the first sub-beam as a first sub-beam light-receiving unit in the first region. A second light receiving unit that receives the branched light beam, and a third light receiving unit that receives the light beam obtained by branching the return light of the second sub beam in the first region as the second sub beam receiving unit. , A fourth light-receiving unit as a third sub-beam light-receiving unit, and a fifth sub-light-receiving unit that receives a light beam that is branched from the return light of the first sub-beam in the second region. And a sixth light receiving unit for receiving a light beam obtained by branching the return light of the second sub beam in the second region as a fourth sub beam receiving unit, and a second optical splitter. Means that the center of the first sub-beam passes through the interior of the third region. The third optical branching device is arranged so that the first optical branching unit branches a part of the light beam obtained by branching the return light of the first sub-beam in the third region to the first light receiving unit. A fourth optical branching unit for branching another part of the light beam obtained by branching the return light of the first sub-beam in the third region to the fourth light-receiving unit, and the return light of the second sub-beam A thirteenth light branching portion for branching a part of the light beam branched in the first region in a direction other than the direction incident on each light receiving portion, and the return light of the second sub beam is branched in the second region. And a fourteenth light branching part for branching a part of the light beam in a direction other than the direction incident on each of the light receiving parts, and the first sub beam and the second light receiving part branched to the first light receiving part. And a shape of a combination of the first sub beam incident on the second portion and the second sub beam. The shape of the light beam incident on the third light receiving part without being branched by the thirteenth light branching part among the light beams branched from the return light of the first region, and the fourth light receiving part Among the light beams formed by combining the branched first sub-beam and the first sub-beam incident on the fifth light receiving unit and the return light of the second sub-beam branched in the second region, The shape of the light beam incident on the sixth light receiving portion without being branched by the 14 light branching portions is independent of the branch positions of the first sub-beam and the second sub-beam by the second optical branching device, respectively. The first light branching portion, the fourth light branching portion, the thirteenth light branching portion, and the fourteenth light branching portion are arranged so as to have a substantially constant shape (particularly, a quadrant shape). It is a configuration.
[0058]
In another preferred embodiment, the photodetector includes a first light-receiving unit as a first sub-beam light-receiving unit and a return light of the first sub-beam as a first sub-beam light-receiving unit in the first region. A second light receiving unit that receives the branched light beam, and a third light receiving unit that receives the light beam obtained by branching the return light of the second sub beam in the first region as the second sub beam receiving unit. , A fourth light-receiving unit as a third sub-beam light-receiving unit, and a fifth sub-light-receiving unit that receives a light beam that is branched from the return light of the first sub-beam in the second region. And a sixth light receiving unit for receiving a light beam obtained by branching the return light of the second sub beam in the second region as a fourth sub beam receiving unit, and a second optical splitter. Means that the center of the first sub-beam passes through the interior of the third region. The third optical branching device is arranged so that the first optical branching unit branches a part of the light beam obtained by branching the return light of the first sub-beam in the third region to the first light receiving unit. A fourth optical branching unit for branching another part of the light beam obtained by branching the return light of the first sub-beam in the third region to the fourth light-receiving unit, and the return light of the second sub-beam A first light-shielding portion for shielding a part of the light beam branched in the first region, and a second light-shielding part for shielding a part of the light beam branched from the return light of the second sub-beam in the second region. A light shielding portion, the shape of a combination of the first sub beam branched to the first light receiving portion and the first sub beam incident on the second light receiving portion, and the return light of the second sub beam is the first Among the light beams branched in the region, the third light beam is not shielded by the first light shielding part. The shape of the optical part, the first sub beam branched to the fourth light receiving part, and the first sub beam incident on the fifth light receiving part, and the return light of the second sub beam in the second region Of the branched light beams, the shapes of the light beams that are incident on the sixth light receiving unit without being blocked by the second light blocking unit are respectively the first sub beam and the first light beam by the second optical branching unit. The first light branching portion, the fourth light branching portion, the first light shielding portion, and the second light guide portion so as to have a substantially constant shape (particularly, a quadrant shape) regardless of the branch position of the two sub beams. It is the structure by which the light-shielding part is arrange | positioned.
[0059]
According to each of the above configurations, it is possible to accurately obtain a tracking error signal in the differential push-pull method by generating a tracking error signal using the first sub-beam branched in the third region. This can be realized by an optical branching unit such as a grating. Therefore, an optical integrated unit that can be easily manufactured can be provided. Furthermore, according to each of the above configurations, even if the amount of return light of the second sub-beam incident on the first region and the second region is greater than the amount of return light of the second sub-beam incident on the third region. This can be equivalent to the case where the second sub-beam is split at the center. Therefore, the tracking error signal in the differential push-pull method can be obtained more stably.
[0060]
In each of the above configurations, at least two of the first light receiving unit, the second light receiving unit, and the third light receiving unit are configured by the same light receiving element, and the fourth light receiving unit, the fifth light receiving unit, It is preferable that at least two of the sixth light receiving units are configured by the same light receiving element, the first light receiving unit and the second light receiving unit are configured by the same light receiving element, and the fourth It is particularly preferable that the light receiving unit and the fifth light receiving unit are formed of the same light receiving element. As a result, the photodetector can be further reduced in size, and an even smaller optical integrated unit can be provided.
[0061]
The third optical branching unit includes a plurality of optical branching units that branch light beams obtained by branching the return light of the first sub-beam and the second sub-beam in the second optical branching unit in different directions, The first optical branching unit and the second optical branching unit branch the light beams obtained by branching the return light of the first sub-beam, in which the optical branching unit is formed of a diffraction grating, in the third region in different directions. It is preferable that the first light branching portion and the second light branching portion are constituted by diffraction gratings.
[0062]
According to the above configuration, since the third optical branching device can be easily manufactured, an optical integrated unit that can be easily manufactured can be provided.
[0063]
The second optical branching unit is preferably formed of a diffraction grating (hologram optical element). Thereby, the second optical branching device can be easily manufactured.
[0064]
It is preferable that the second optical branching device and the third optical branching device are formed on the same light transmitting body.
[0065]
According to the above configuration, since the second and third optical branching devices are formed on the same light transmitting body, an optical integrated unit that can be easily manufactured can be provided.
[0066]
It is preferable that the second light branching unit, the first light shielding unit, and the second light shielding unit are formed on the same light transmitting body.
[0067]
According to the above configuration, it is possible to provide an optical integrated unit that can be arranged with a simple configuration of the optical system including the light shielding portion and can be easily manufactured. Further, since the light shielding portion (mask) is formed integrally with the light transmitting body, an optical integrated unit that is easy to manufacture and has improved reliability can be provided.
[0068]
The first optical branching device and the third optical branching device are preferably formed on the same light transmitting body, and more preferably formed on the same surface of the same light transmitting body.
[0069]
According to the above configuration, since the first and third optical branching devices are formed on the same light transmitting body, it is possible to provide an optical integrated unit that can be easily manufactured and can be downsized.
[0070]
Moreover, in the structure which formed the optical branching device on the translucent body, it is preferable that the said light source and a photodetector are accommodated in the same package, and the said translucent body is being fixed to the exterior of the said package. According to the above configuration, the optical integrated unit can be downsized and the reliability of the optical integrated unit is improved.
[0071]
The optical integrated unit of the present invention preferably further comprises a beam splitter that transmits light from the light source and reflects return light from the optical recording medium. As the beam splitter, a combination of a polarizing beam splitter and a quarter wave plate is particularly preferable.
[0072]
Further, when a beam splitter is provided, it is preferable to further provide a reflecting surface parallel to the surface, and to further reflect the return light from the optical recording medium by this reflecting surface. Thereby, an optical integrated unit can be reduced in size.
[0073]
In each of the above-described configurations, the third optical branching unit converts all or part of the light beam obtained by branching the return light of the first sub-beam in the third region into a dividing line parallel to the track direction of the optical recording medium (eg, It is preferable to divide into two equal parts at the boundary line between the first light branching portion and the fourth light branching portion. Thereby, the accuracy of the tracking error signal in the differential push-pull method can be further improved.
[0074]
In order to solve the above problems, an optical pickup device of the present invention is disposed between an optical integrated unit having the above-described configuration, and the optical integrated unit and the optical recording medium, and is emitted from the optical integrated unit. And a light collecting means for condensing the light beam on the optical recording medium.
[0075]
According to the above configuration, since the optical integrated unit having the above-described features and effects is used, it is possible to provide an optical pickup device that can stably obtain a tracking error signal in the differential push-pull method.
[0076]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS.
[0077]
FIG. 1 shows a side view of the optical system of the optical pickup device of the present embodiment.
[0078]
The optical pickup device according to the present embodiment collects an optical integrated unit 20 and a laser beam (light beam) emitted from the optical integrated unit 20 on an optical disc 10 such as a DVD as an optical recording medium. A collimating lens 12 and an objective lens 13 are provided. The optical integrated unit 20 includes a semiconductor laser 11 as a light source for emitting a light beam toward the collimating lens 12, a photodetector 7 for receiving return light from the optical disk 10, and the semiconductor laser 11 and the collimator. A three-beam diffraction grating 1 as a first optical splitter disposed between the lens 12 and a hologram optical element as a second optical splitter disposed between the collimator lens 12 and the photodetector 7 (Holographic diffraction grating) 2, a diffractive optical element 3 as a third optical splitter disposed between the hologram optical element 2 and the photodetector 7, a beam splitter 8, and a beam splitter 8 And a parallel reflecting surface 14.
[0079]
In the present embodiment, the beam splitter 8 is a polarization beam splitter (PBS), and a quarter wavelength plate 9 perpendicular to the optical axis of the light beam is disposed on the optical splitter 10 side of the beam splitter 8.
[0080]
In the three-beam diffraction grating 1, the light beam that is P-polarized light (linearly polarized light) emitted from the semiconductor laser 11 is diffracted in a direction parallel to the track tangential direction (direction perpendicular to the radial direction) Y of the optical disk 10. As a result, the light beam is branched into three light beams: a main beam that is 0th-order light (non-diffracted light), a first subbeam that is + 1st-order diffracted light, and a second subbeam that is -1st-order diffracted light. The The diffraction is not shown here because it occurs along a direction perpendicular to the paper surface of the drawing (track tangent direction Y of the optical disk 10). As shown in FIG. 2, the three-beam diffraction grating 1 has a linear lattice shape, and the direction of the groove (shown by stripes in the drawing) is the radial direction (direction perpendicular to the track tangential direction) X of the optical disk 10. They are arranged in parallel. The 3-beam diffraction grating 1 generates slightly higher-order diffracted light than ± first-order diffracted light, but the higher-order diffracted light is irrelevant to the function of the optical pickup device and will not be described.
[0081]
The three light beams that have passed through the three-beam diffraction grating 1 pass through the beam splitter 8, become circularly polarized by the quarter-wave plate 9 on the beam splitter 8, and enter the collimating lens 12. The three light beams converted into parallel light by the collimator lens 12 are condensed by the objective lens 13 and irradiated onto the optical disk 10. The three return lights from the optical disk 10 sequentially return through the objective lens 13, the collimating lens 12, and the quarter wavelength plate 9 and pass through the quarter wavelength plate 9 to become S-polarized light (linearly polarized light). The three return lights that have become S-polarized light (linearly polarized light) are reflected by the beam splitter 8 in a direction substantially perpendicular to the optical axis of the return light incident on the beam splitter 8 (right direction in FIG. 1). The light is reflected by the reflecting surface 14 in the traveling direction of the return light incident on the beam splitter 8 (the lower direction in FIG. 1), and enters the hologram optical element 2.
[0082]
In the hologram optical element 2, each of the three return lights is diffracted into the + 1st order diffracted light 4 and the −1st order diffracted light 5. A part of the + 1st order diffracted light 4 is further diffracted by the diffractive optical element 3 disposed in front of the photodetector 7, and becomes diffracted light 6 and enters the photodetector 7. The remainder of the + 1st order diffracted light 4 and the −1st order diffracted light 5 enter the photodetector 7 as they are without being diffracted by the diffractive optical element 3.
[0083]
The photodetector 7 includes light receiving elements 7Ma, 7Ma1, and 7Ma2 (see FIG. 7) that receive the main beam M diffracted in the region 2a, a light receiving element 7Mb that receives the main beam M diffracted in the region 2b, And a light receiving element 7Mc that receives the main beam M diffracted by 2c. The photodetector 7 includes a light receiving unit 7Ab that receives a light beam obtained by further diffracting the sub beam A (light beam 4Ab) diffracted in the region 2b by the diffraction grating 3Ab, and a sub beam B (diffracted in the region 2b). The light beam 4Bb) is further provided with a light receiving portion 7Bb for receiving the light beam diffracted by the diffraction grating 3Bb. The photodetector 7 includes a light receiving unit 7Ac that receives a light beam obtained by further diffracting the sub beam A (light beam 4Ac) diffracted in the region 2c by the diffraction grating 3Ac, and a sub beam B (diffracted in the region 2c). The light beam 4Bc) is further provided with a light receiving portion 7Bc for receiving the light beam diffracted by the diffraction grating 3Bc.
[0084]
FIG. 3 shows the shape of the hologram optical element 2 and the state of light on the hologram optical element 2. The hologram optical element 2 is composed of a plurality of regions, and divides the return light into a plurality of light beams by diffracting the return light in different directions in each region. The hologram optical element 2 divides the entire circular area into two equal parts by a dividing line 2L parallel to the radial direction X of the optical disc 10, so that a semicircular area 2a as a third area and the remaining semicircle Furthermore, the remaining semicircular portion is equally divided into two regions, a region 2b as a first region and a region 2c as a second region, by a dividing line 2N parallel to the track tangential direction Y of the optical disk 10 This is a three-part hologram optical element divided into two. In FIG. 3, M, A, and B represent three return lights from the optical disc 10, M represents the main beam, A represents the first sub beam A, and B represents the second sub beam.
[0085]
FIG. 4 shows the beam shape at the optical position where the diffractive optical element 3 is installed, for each diffracted light obtained by diffracting the three return lights in the three divided regions 2a to 2c. . The beam group on the right side of the drawing shows the + 1st order diffracted light 4 by the hologram optical element 2, and the beam group on the left side shows the −1st order diffracted light 5. The signs of the light beams of the diffracted lights 4 and 5 are the signs M, A, and B indicating whether the light beam is the main beam M, the first sub-beam A, or the second sub-beam B, and the hologram. Symbols a, b, and c representing the light diffracted in the regions 2a, 2b, and 2c of the optical element 2 are shown in combination.
[0086]
The diffraction angles of the regions 2a, 2b, and 2c of the hologram optical element 2 are set so that the diffracted lights of the regions 2a, 2b, and 2c do not overlap at the optical position of the diffractive optical element 3. . In other words, the diffractive optical element 3 is disposed at an optical position where a plurality of light beams divided by the hologram optical element 2 are separated from each other.
[0087]
The diffractive optical element 3 divides the light beam 4Aa obtained by diffracting the return light of the sub beam A in the region 2a by a dividing line 3N parallel to the track tangential direction Y of the optical disc 10. The diffractive optical element 3 includes a diffraction grating 3Aa1 that diffracts a part of the light beam 4Aa, a diffraction grating 3Aa2 that diffracts another part of the light beam 4Aa, and light obtained by branching the return light of the sub beam A in the region 2b. A diffraction grating 3Ab that diffracts the beam 4Ab, a diffraction grating 3Bb that diffracts the light beam 4Bb in which the return light of the sub beam B is branched in the region 2b, and a light beam 4Ac in which the return light of the sub beam A is branched in the region 2c. And a diffraction grating 3Bc that diffracts the light beam 4Bc obtained by branching the return light of the sub beam B in the region 2c. Further, the diffractive optical element 3 divides a part of the light beam 4Aa obtained by diffracting the return light of the sub beam A in the region 2a into two equal parts by a dividing line 3N parallel to the track tangential direction Y of the optical disk 10. It has become.
The diffraction gratings 3Ab, 3Bb, 3Aa1, 3Ac, and 3Bc are arranged so that the direction of the grooves (indicated by stripes in the drawing) is parallel to the radial direction X of the optical disc 10. On the other hand, the diffraction grating 3Aa2 is arranged such that the direction of the groove (shown by stripes in the drawing) is inclined from the radial direction X of the optical disk 10, and thereby the sub beam A at the diffraction grating 3Ac is +1 next time. The + 1st order diffracted light of the sub beam A is generated in a direction approaching the folding light.
[0088]
At the same time, as shown in the schematic perspective view of FIG. 6, the photodetector 7 receives a light beam 4Aa1 obtained by further diffracting the sub beam A diffracted in the region 2a by the diffraction grating 3Aa1 (first (Light receiving part) 7Aa1 and a light receiving part (fourth light receiving part) 7Aa2 for receiving the light beam 4Aa2 obtained by further diffracting the sub beam A diffracted in the region 2a by the diffraction grating 3Aa2.
[0089]
In addition, the photodetector 7 receives the + 1st order diffracted light (light beam 4Ab) by the diffraction grating 3Ab and the + 1st order diffracted light (light beam 4Aa1) by the diffraction grating 3Aa1, respectively, on the light detector 7Ab and light receiving element 7Aa1. And the output signal SAb of the light receiving element 7Ab and the output signal SAa1 of the light receiving element 7Aa1 are added. Further, a part of the light amount of the + 1st order diffracted light (light beam 4Bb) by the diffraction grating 3Bb is detected as an output signal SBb by the light receiving element 7Bb on the photodetector 7. Further, the + 1st order diffracted light (light beam 4Ac) by the diffraction grating 3Ac and the + 1st order diffracted light (light beam 4Aa2) by the diffraction grating 3Aa2 are detected by the light receiving element 7Ac and the light receiving element 7Aa2 on the photodetector 7, respectively. The output signal SAc of the element 7Ac and the output signal SAa2 of the light receiving element 7Aa2 are added. Further, a part of the light amount of the + 1st order diffracted light (light beam 4Bc) by the diffraction grating 3Bc is detected as an output signal SBc by the light receiving element 7Bc on the photodetector 7.
[0090]
In the optical integrated unit 20 of this embodiment, the output signal difference between the light receiving element 7Mb and the light receiving element 7Mc, and the output signal between the light receiving elements 7Aa1, 7Ab, 7Bb and the light receiving elements 7Aa2, 7Ac, 7Bc. Based on the difference, a tracking error signal by the DPP method is generated.
[0091]
The tracking error signal TES2 according to the DPP method is as described above.
TES2 = (SMc−SMb) −k [[(SAb + SAa1) − (SAc + SAa2)] + [SBb−SBc]] (5)
Can be detected.
[0092]
Furthermore, the configuration of the present embodiment is configured to correct the above-described light quantity imbalance in the tracking error signal generated from the signal detected by the light receiving element of the photodetector 7.
[0093]
Here, with respect to the light beam 4Ab and the light beam 4Bb, and the light beam 4Ac and the light beam 4Bc used for the purpose of removing the offset in the generation of the tracking error signal by the DPP method, the sub-beam B is the dividing line 2L of the hologram optical element 2 respectively. Since the position to be divided is shifted from the center of the beam diameter, a difference in light intensity (unbalance in light amount) occurs.
[0094]
Specifically, first, assuming that the sub-beam A is divided at the center of the beam diameter by the dividing line 2L of the hologram optical element 2, a light beam portion (3Aa1 in FIG. 4) that should be a part of the light beams 4Ab and 4Ac. And a portion of the light beam 4Aa) surrounded by a region indicated by 3Aa2 is a part of the light beam 4Aa. Similarly, if it is assumed that the sub-beam B is divided at the center of the beam diameter, the light beam portion that should be the light amount of the light beam 4Ba (the light beam 4Bb other than the portion surrounded by the region indicated by 3Bb in FIG. 4) And the light beam 4Bc) other than the portion surrounded by the region indicated by 3Bc in FIG. 4 is a part of the light beams 4Bb and 4Bc.
[0095]
Therefore, in the present embodiment, as shown in FIG. 4, a part of the region where the light beam 4Aa can enter at the position of the diffractive optical element 3 (the sub beam A is divided at the center of the beam diameter by the dividing line 2L of the hologram optical element 2). If it is assumed that the diffraction grating 3Aa1 and the diffraction grating 3Aa2 are disposed in a portion excluding the region where the light beam 4Aa is incident), the diffraction grating 3Ab is disposed in the region where the light beam 4Ab is incident, and the light beam 4Bb is incident. The diffraction grating 3Bb is arranged in a part of the region (a portion excluding the region where the light beam 4Bb is incident when it is assumed that the sub beam B is divided at the center of the beam diameter by the dividing line 2L of the hologram optical element 2), and the light beam 4Ac The diffraction grating 3Ac is arranged in a region where the light beam 4B is incident, and a part of the region where the light beam 4Bc is incident (the sub beam B is a hologram optical). When it is assumed that the light beam 4Bc is divided by the dividing line 2L of the child 2 at the center of the beam diameter, the diffraction grating 3Bc is disposed in a portion excluding a region where the light beam 4Bc is incident. Is incident on the light receiving element.
[0096]
Specifically, diffraction gratings 3Aa1, 3Ab, 3Bb, 3Aa2, 3Ac, and 3Bc having the arrangement and shape shown in FIG. 5 are used, and these diffracted lights are received as light receiving elements 7Aa1 and 7A on the photodetector 7 as shown in FIG. 7Ab, 7Bb, 7Aa2, 7Ac, and 7Bc are detected.
[0097]
That is, first, the diffraction gratings 3Ab and 3Ac diffract all the diffracted light (light beams) 4Ab and 4Ac of the sub beam A to the light receiving portions 7Ab and 7Ac. The diffraction gratings 3Aa1 and 3Aa2 diffract only a part of the light beam 4Aa to the light receiving elements 7Aa1 and 7Aa2. In addition, in the light beam 4Aa, the shape of the portion that is not diffracted by the light receiving elements 7Aa1 and 7Aa2 is semicircular, the shape of the portion that is diffracted by the light receiving element 7Aa1, and the light beam 4Aa that is diffracted by the light receiving element 7Aa2. Is in a mirror image relationship. The photodetector 7 detects only the light diffracted by the diffraction gratings 3Aa1 and 3Aa2 out of the diffracted lights (light beams) 4Aa1 and 4Aa2 of the sub beam A by the light receiving elements 7Aa1 and 7Aa2, and detects the diffraction gratings 3Aa1 and 3Aa2. Do not use (throw away) the parts that do not pass. The diffracted light (light beam) 4Ab of the sub beam A and the light diffracted by the diffraction grating 3Aa1 of the light beam 4Aa are added on the photodetector 7. Similarly, the diffracted light (light beam) 4Ac of the sub beam A and the light diffracted by the diffraction grating 3Aa2 of the light beam 4Aa are added on the photodetector 7.
[0098]
Further, the diffraction gratings 3Bb and 3Bc diffract only a part of the light beams 4Bb and 4Bc to the light receiving elements 7Bb and 7Bc. In addition, the shape of the portion diffracted by the light receiving element 7Bb and the shape of the portion diffracted by the light receiving element 7Bc are each a quadrant. The photodetector 7 detects only the light diffracted by the diffraction gratings 3Bb and 3Bc among the diffracted lights (light beams) 4Bb and 4Bc of the sub beam B by the light receiving elements 7Bb and 7Bc, and detects the diffraction gratings 3Bb and 3Bc. Do not use (throw away) the parts that do not pass.
[0099]
According to these, even if the sub-beams A and B are divided by the dividing line 2L at any position in the beam, the signal obtained by adding the output signal SAb of the light receiving element 7Ab and the output signal SAa1 of the light receiving element 7Aa1 and the light receiving element 7Ac The signal obtained by adding the output signal SAc of the light receiving element 7Aa2 and the output signal SAa2 of the light receiving element 7Aa2 can be equivalent to the case where the light beams obtained by dividing the sub-beams A and B at the center are detected. Further, the output signal SBb of the light receiving element 7Bb and the output signal SBc of the light receiving element 7Bc can be equivalent to the case where the sub beams A and B are detected by the light beam divided at the center. Therefore, even if sub-beams A and B are divided at any position in the beam by dividing line 2L, a tracking error signal equivalent to the case where sub-beams A and B detect a light beam divided at the center is obtained. Therefore, even if the position where the dividing line 2L divides the sub-beams A and B is shifted for each optical pickup device due to the component tolerances and manufacturing errors described above, the light quantity imbalance between the light beams related to the offset removal described above can be reduced. Can be eliminated.
[0100]
That is, in the above configuration, both the sub-beam A incident on the light-receiving element 7Ab and the light-receiving element 7Aa1 and the sub-beam B incident on the light-receiving element 7Bb are related to where the sub-beams A and B are divided by the dividing line 2L. In other words, the beam is equivalent to the main beam 5Mb incident on the light receiving element 7Mb (here, substantially quadrant). Further, both of the sub beam A incident on the light receiving element 7Ac and the light receiving element 7Aa2 and the sub beam B incident on the light receiving element 7Bc, regardless of where the sub beams A and B are divided by the dividing line 2L. The main beam 5Mc incident on 7Mc is equivalent to a beam having the same shape (here, substantially quadrant). Eventually, these four sub-beams are shifted in the optical axis of the main beam M from the center of the hologram optical element 2 due to the tolerance of the optical integrated unit ((1) to (3) described in the section of the prior art). Even if the optical axes of the sub beams A and B are also deviated from the standard position, they always have a constant shape (here, a substantially quadrant shape). Therefore, no residual offset is generated when the tracking error signal is generated using k set in the standard state, so that an accurate tracking error signal can be obtained.
[0101]
In the above description, the shapes of the main beams 5Mb and 5Mc used for generating the tracking error signal are assumed to be quadrants, but this shape may also change due to tolerances. However, considering the change in the light amount of each beam when the beam position changes with respect to the dividing line 2L, the sub beam A used for generating the tracking error signal rather than the quadrant main beam used for generating the tracking error signal. -Since the change in the amount of light of the sum of B is much larger, the change in the main beam falls within the error range when operating the pickup device. For this reason, the change in the main beam hardly affects the accuracy of the tracking error signal. Therefore, as described above, it is important not to change the shapes of the sub beams A and B used for generating the tracking error signal as much as possible.
[0102]
When reproducing the optical disk 10 on which pit information is recorded, a change in phase difference between the output signal SMc of the light receiving element 7Mc and the output signal SMb of the light receiving element 7Mb is detected, and a tracking error signal TES3 by the DPD method is detected. You can also.
[0103]
In the present specification, the output signal of the light receiving element is represented by a code using S instead of 7 of the light receiving element. In FIG. 6, the region surrounded by the solid line 31 is the position in the optical axis direction (Z direction) where the diffractive optical element 3 is disposed, and the region surrounded by the dotted line 71 indicates the position of the light receiving surface of the photodetector 7. . In order to prevent the drawing from being complicated, the light receiving elements described within the dotted line 71 are only those related to DPP tracking error signal detection. Here, the diffraction efficiencies of the six diffraction gratings 3Ab, 3Bb, 3Aa1, 3Ac, 3Bc, and 3Aa2 in the diffractive optical element 3 are set to be equal.
[0104]
FIG. 7 shows the shape and arrangement of the light receiving section on the photodetector 7 of the optical pickup device thus configured, and the light rays incident on the photodetector 7. The reference numerals shown in FIG. 7 are almost the same as the reference numerals of the light receiving elements used in FIG. However, FIG. 7 also shows the light receiving elements (7Ma, 7Ma1, and 7Ma2) involved in the detection of the information signal and the focus error signal. Moreover, FIG.1, FIG.4, FIG.6 etc. are quoted as needed.
[0105]
A ray train 72 indicates + 1st order diffracted light by the hologram optical element 2, and a ray train 73 indicates diffracted light 6 (+ 1st order diffracted light) generated by diffracting the + 1st order diffracted light by the hologram optical element 2 by the diffractive optical element 3. Indicates. The light beam 74 represents the −1st order diffracted light of the diffractive optical element 3. The light beam 75 represents the −1st order diffracted light of the hologram optical element 2.
[0106]
Here, in the diffractive optical element 3, the cross section of each diffraction grating is blazed (formed in a sawtooth shape), and the light beam 73 (+ 1st order diffracted light) has a diffraction efficiency higher than that of the light beam row 74 (−1st order diffracted light). It is preferable that the height is high.
[0107]
The focus error signal FES receives the + 1st order diffracted light of the light beam 4Ma out of the + 1st order diffracted light of the hologram optical element 2 on the dividing line at the boundary between the light receiving element 7Ma1 and the light receiving element 7Ma2 and outputs the output signal of the light receiving element 7Ma1. Due to the differential between SMa1 and the output signal SMa2 of the light receiving element 7Ma2,
FES = SMa1-SMa2 (6)
Can be detected.
[0108]
An information signal (RF) recorded on the optical disc 10 is
RF = SMc + SMa + SMb (7)
Can be detected.
[0109]
In the present embodiment, the three-beam diffraction grating 1, the hologram optical element 2, and the diffractive optical element 3 have a structure formed on the same optical substrate (translucent body) 15, as shown in FIG. .
[0110]
The three-beam diffraction grating 1 and the diffractive optical element 3 have the same optical position (Z-axis coordinate) in the optical axis direction Z of the main beam M, so that one of the optical substrates 15 as shown in FIG. It can be formed on the same surface 15a.
[0111]
The hologram optical element 2 is formed on the rear surface of the surface on which the diffractive optical element 3 is formed on the optical substrate 15, and the optical substrate 15 is made of a glass material such as optical glass so that photolithography or the like can be performed. Therefore, the positional relationship between the hologram optical element 2 and the diffractive optical element 3 can be manufactured with extremely high accuracy. For this reason, the variation of the light beam portion desired to be diffracted by the diffractive optical element 3 is extremely reduced.
[0112]
Further, these optical elements (three-beam diffraction grating 1, hologram optical element 2, and diffractive optical element 3) are formed on one optical substrate 15 in an integrated manner, thereby producing the optical element and the optical integration unit. Placement and mounting within the unit 20 are facilitated and can be fixed on a package 16 such as CAN. Further, when mounted on the package 16 and fixed, semiconductor elements such as the semiconductor laser 11 and the photodetector 7 can be accommodated in the package 16, so that the productivity and reliability of the optical integrated unit 20 are improved.
[0113]
Here, the optical substrate 15 is not limited to the one formed by photolithography on the glass material, and may be a light transmitting substrate formed by molding or the like using a resin material.
[0114]
As described above, the optical integrated unit according to the present embodiment is used in combination with the condensing means (12, 13) for condensing the light beam on the optical recording medium (10). The light source (11) for emitting a light beam toward (13) and the light source (11) and the light collecting means (12, 13) are arranged and emitted from the light source (11). A first optical splitter (1) for splitting the optical beam into a main beam (M) and a first sub beam (A) and a second sub beam (B) for generating a tracking error signal; and optical recording A light detector (7) for receiving return light from the medium (10), and the light collecting means (12, 13) and a light detector (7) are arranged between the light detector (7) and the light detector (7). A second optical branching device (2) for branching the light beam, and the second optical branching device. (2) is composed of a plurality of areas for branching the return light in different directions, and the plurality of areas are mutually connected by a first dividing line (2N) parallel to the track direction (Y) of the optical recording medium (10). In the optical integrated unit including the divided first region (2b) and second region (2c) and the third region (2a) located on the extension line of the first dividing line (2N), The return light of the first sub-beam (A) and the second sub-beam (B) is branched between the optical splitter (2) and the photodetector (7) by the second optical splitter (2). A third optical branching device (3) for branching a part of the light beam is provided.
[0115]
In the optical integrated unit according to the present embodiment, the photodetector (7) receives the light beam (4Mb) obtained by branching the return light of the main beam (M) in the first region (2b). The first main beam receiving unit (7Mb) and the second main beam receiving unit (7Mc) that receives the light beam (4Mc) obtained by branching the return light of the main beam (M) in the second region (2c). And first to third light receiving portions (7Ab, 7Bb, 7Aa1) and fourth to sixth light receiving portions (7Ac, 7Bc, 7Aa2), and the second optical branching device (2) includes: The center of one sub-beam (A) is arranged so as to pass through the inside of the third region (2a), and the third optical branching device (3) is configured such that the return light of the first sub-beam (A) is third. A part of the light beam (4Aa) branched in the region (2a) is converted into a first light receiving unit (7A). 1) the first light branching portion (3Aa1) to be branched to the first sub-beam (A) and the entire light beam (4Ab) obtained by branching the return light of the first sub-beam (A) in the first region (2b). A second light branching portion (3Ab) for branching to the portion (7Ab) and a third portion of the light beam (4Bb) formed by branching the return light of the second sub-beam (B) in the first region (2b). The third light branching portion (3Bb) for branching to the light receiving portion (7Bb) of the light beam and the other light beam (4Aa) obtained by branching the return light of the first sub-beam (A) in the third region (2a) A fourth light branching portion (3Aa2) for branching a part to the fourth light receiving portion (7Aa2), and a light beam (4Ac) obtained by branching the return light of the first sub-beam (A) in the second region (2c) ) Is branched to the fifth light receiving portion (7Ac), and the fifth light branching portion (3Ac) A sixth light branching section (3Bc) for branching a part of the light beam (4Bc) obtained by branching the return light of the second sub-beam (B) in the second region (2c) to the sixth light receiving section (7Bc) And a difference in light amount between the first main beam light receiving unit (7Mb) and the second main beam light receiving unit (7Mc), and a total light amount of the first to third light receiving units (7Ab, 7Bb, 7Aa1). The tracking error signal is generated based on the difference between the total light quantity of the fourth to sixth light receiving parts (7Ac, 7Bc, 7Aa2) and branched to the first light receiving part (7Aa1). The shape of a combination of the first sub-beam and the first sub-beam branched to the second light receiving unit (7Ab), the shape of the second sub-beam branched to the third light receiving unit (7Bb), and the fourth The first branched to the light receiving part (7Aa2) The shape of the sub beam and the first sub beam branched to the fifth light receiving portion (7Ac) and the shape of the second sub beam branched to the sixth light receiving portion (7Bc) are the second Regardless of the branching position of the first sub-beam (A) and the second sub-beam (B) by the optical branching device (2), the first to sixth shapes described above are formed so as to have a substantially constant shape (quadric shape). Are arranged. In addition, the shape of the main beam (4Mb) incident on the first main beam light-receiving unit (7Mb) and the shape of the main beam (4Mc) incident on the second main beam light-receiving unit (7Mc) are also the above-mentioned “abbreviations”. It is configured to be equivalent in shape to “a certain shape”.
[0116]
According to the above configuration, as described above, even when the optical axis of the beam deviates from the standard position due to the tolerance of the apparatus, tracking is always performed using a beam having a constant shape (here, substantially quadrant). Since an error signal can be generated, an accurate tracking error signal can be obtained.
[0117]
[Embodiment 2]
Another embodiment of the present invention will be described below with reference to FIGS. FIGS. 9 and 10 are perspective schematic views of the diffractive optical element 3 according to the present embodiment, and each diffraction grating and a light receiving portion related to tracking error signal detection by the DPP method. Constituent elements of the same type as in the first embodiment will be described with reference to the same reference numerals. Figures 1, 3, 4, etc. are also cited as necessary.
[0118]
The optical pickup device of the present embodiment is different from the embodiment only in the following two points, and the rest has the same configuration as the optical pickup device of the first embodiment.
[0119]
First, the first difference is that the diffractive optical element 3 having the shape shown in FIG. 9 instead of the diffractive optical element 3 having the shape shown in FIG. In addition, the groove directions of the diffraction grating 3Bc are inclined in different directions, and the groove directions of the diffraction grating 3Aa1 and the diffraction grating 3Aa2 are also inclined in different directions.
[0120]
The second difference is that, as shown in FIG. 10, all of the + 1st order diffracted light beams from the diffraction gratings 3Ab, 3Aa1, and 3Bb are diffracted on the light receiving element 7b and the light receiving element 7b is moved. In addition to detection, all of the + 1st order diffracted light beams from the diffraction gratings 3Ac, 3Aa2, and 3Bc are diffracted by the light receiving element 7c and detected from the light receiving element 7c. Therefore, in the present embodiment, the light receiving element 7b has the same function as the light receiving elements 7Ab, 7Bb, and 7Aa1, and the light receiving element 7c has the same function as the light receiving elements 7Ac, 7Bc, and 7Aa2.
[0121]
Thus, based on the output signals SMb, SMc, Sb, Sc of the light receiving elements 7Mb, 7Mc, 7b, 7c, the tracking error signal TES2 by the DPP method is expressed by the following equation:
TES2 = (SMc−SMb) −k (Sb−Sc) (8)
Can be detected. Other servo signals and information signals can be detected by the same detection method as in the first embodiment.
[0122]
In the configuration of this embodiment, the number of the light receiving elements can be reduced by reducing the number of the light receiving elements by realizing the light receiving elements 7b and 7c by sharing a light receiving unit having a similar property with respect to offset removal. The optical integrated unit can be reduced in size and the manufacturing process can be simplified by reducing the number of lead terminals.
[0123]
[Embodiment 3]
Still another embodiment of the present invention will be described below with reference to FIGS. Constituent elements of the same type as in the first and second embodiments will be described with reference to the same reference numerals. Figures 1, 3, 4, etc. are also cited as necessary.
[0124]
This embodiment is different from the second embodiment only in the following two points, and the other configuration is the same as that of the first embodiment.
[0125]
The first difference is that the diffractive optical element 3 has a shape shown in FIG. That is, the diffractive optical element 3 further includes diffraction gratings 3Ba1 and Ba2, and a light beam 4Ba, which is the + 1st order diffracted light of the sub-beam B in the region 2a of the hologram optical element 2, is divided into a dividing line 3M parallel to the track tangential direction Y of the optical disc 10. So that half of the light beam 4Ba is branched by the diffraction grating 3Ba1 and incident on the light receiving element 7B1, and the other half of the light beam 4Ba is branched by the diffraction grating 3Ba2 and incident on the light receiving element 7B2. It is a point. The diffraction efficiencies of the diffraction gratings 3Aa1, 3Aa2, 3Ab, 3Ac, 3Bb, 3Bc, 3Ba1, and 3Ba2 are set equal.
[0126]
The second difference is that the + 1st order diffracted light of the sub-beams A and B by the hologram optical element 2 is all diffracted without being partially lost, and the diffracted light (+ 1st order diffracted light) is It is a point incident on the light receiving part.
[0127]
The third difference is that the photodetector 7 includes a light receiving element 7A1 having both functions of the light receiving element 7Ab and the light receiving element 7Aa1 instead of the light receiving element 7Ab and the light receiving element 7Aa1, and the light receiving element 7Ac and the light receiving element 7Aa2. Instead of this, a light receiving element 7A2 having both functions of the light receiving element 7Ac and the light receiving element 7Aa2 is provided.
[0128]
The fourth difference is that the photodetector 7 receives the + 1st order diffracted light of the light beam 4Bb from the diffraction grating 3Bb instead of the light receiving element 7Bb, and also receives the third split beam (+1 of the light beam 4Ba from the diffraction grating 3Ba1). A light receiving element 7B1 that receives (the next-order diffracted light). Instead of the light-receiving element 7Bc, the light receiving element 7Bc receives the + 1st order diffracted light of the light beam 4Bc from the diffraction grating 3Bc and the fourth divided beam (the +1 next time of the light beam 4Ba) from the diffraction grating 3Ba2. A light-receiving element 7B2 that receives light), an output signal difference between the light-receiving element 7Mb and the light-receiving element 7Mc, an output signal difference between the light-receiving element 7A1 and the light-receiving element A2, and the light-receiving element 7B1 and the light-receiving element B2. The tracking error signal is generated based on the output signal difference between the two.
[0129]
FIG. 12 is a schematic perspective view of each diffraction grating and a light receiving element involved in tracking error signal detection by the DPP method in this embodiment. The diffraction light of the diffraction grating 3Aa1 and the diffraction light of the diffraction grating 3Ab are detected by the same light receiving element 7A1, and the diffraction light of the diffraction grating 3Aa2 and the diffraction light of the diffraction grating 3Ac are detected by the same light receiving element 7A2. The diffracted light of 3Ba1 and the diffracted light of the diffraction grating 3Bb are detected by the same light receiving element 7B1, and the diffracted light of the diffraction grating 3Ba2 and the diffracted light of the diffraction grating 3Bc are detected by the same light receiving element 7B2.
[0130]
Here, the diffractive optical element 3 makes all the + 1st-order diffracted lights of the sub-beams A and B enter a predetermined light receiving part without being partially lost. Therefore, if the signals detected by the light receiving elements 7A1 and 7A2 are combined, it is equivalent to the signal of the sub beam A itself. Similarly, if the signals detected by the light receiving elements 7B1 and 7B2 are combined, the sub beam B itself It is equivalent to a signal.
[0131]
Tracking error signal TES2 by the DPP method is

It is represented by
[0132]
Here, the diffractive optical element 3 makes all the + 1st-order diffracted lights of the sub-beams A and B enter a predetermined light receiving part without being partially lost. Therefore, if the signals detected by the light receiving elements 7A1 and 7A2 are combined, it is equivalent to the signal of the sub beam A itself. Similarly, if the signals detected by the light receiving elements 7B1 and 7B2 are combined, the sub beam B itself It is equivalent to a signal.
[0133]
That is, in the above configuration, for the sub beam A, the sub beam A diffracted by the diffraction gratings 3Ab and 3Aa1 is added on the photodetector 7 (both are received by the light receiving element 7A1) and diffracted by the diffraction gratings 3Ac and 3Aa2. The sub-beams A are added on the photodetector 7 (both are received by the light receiving element 7A2). For the sub-beam B, the sub-beam B diffracted by the diffraction gratings 3Bb and 3Ba1 is added on the photodetector 7 (both are received by the light receiving element 7B1), and the sub-beam B diffracted by the diffraction gratings 3Bc and 3Ba2 is added. Addition is performed on the photodetector 7 (both are received by the light receiving element 7B2). Accordingly, the sub beam A received by the light receiving element 7A1, the sub beam A received by the light receiving element 7A2, the sub beam B received by the light receiving element 7B1, and the sub beam B received by the light receiving element 7B2 are all parallel to the track. The beam is equivalent in shape to the semicircular beam divided by the dividing line. Therefore, the sub-beams A and B always have a constant shape (here, semicircular) regardless of where the beam is divided by the dividing line 2L. Therefore, for the sub-beams A and B, even if the optical integrated unit has tolerances ((1) to (3) described in the section of the prior art), a beam having a constant shape (here semicircular shape) is always used. This is used to generate a tracking error signal. Therefore, when a tracking error signal is generated using k ′ set in the standard state, no residual offset is generated, so that an accurate tracking error signal can be obtained.
[0134]
Here, the second term of the above equation (9) represents the push-pull signal sum by the sub-beams A and B. These are equivalent to push-pull signals using the whole sub-beams A and B as described above. For this reason, compared with the structure of Embodiment 1 which uses a part of sub beam A * B, the intensity | strength of the amplitude of the push pull signal by a sub beam increases, and S / N ratio improves. That is, the offset removal of the tracking error signal can be stably performed, and the amplitude of the tracking error signal TES2 expressed by the above equation (9) is also increased.
[0135]
The diffraction light of the diffraction grating 3Aa1, the diffraction light of the diffraction grating 3Ab, the diffraction light of the diffraction grating 3Aa2, the diffraction light of the diffraction grating 3Ac, the diffraction light of the diffraction grating 3Ba1, the diffraction light of the diffraction grating 3Bb, and the diffraction light of the diffraction grating 3Ba2 And the diffracted light of the diffraction grating 3Bc may be added after being detected by separate light receiving elements. Other servo signal and information signal detection methods are the same as those in the first embodiment.
[0136]
As described above, in the optical integrated unit according to the present embodiment, the photodetector (7) has the light beam (5Mb) obtained by branching the return light of the main beam (M) in the first region (2b). The first main beam receiving unit (7Mb) for receiving the light and the second main beam receiving unit for receiving the light beam (5Mc) obtained by branching the return light of the main beam (M) in the second region (2c) (7Mc), first and second light receiving parts (7A1), third and seventh light receiving parts (7B1), fourth and fifth light receiving parts (7A2), sixth and eighth The third optical branching unit (3) includes a light receiving unit (7B2), and the third optical branching unit (3) is half of the light beam (4Aa) formed by branching the return light of the first sub-beam (A) in the third region (2a). A first light branching section (3Aa1) for branching the first light receiving section (7A1) A second light branching portion (3Ab) for branching the entire light beam (4Ab) formed by branching the return light of the beam (A) into the first region (2b) to the second light receiving portion (7A1); An eighth light branching section (3Bb) for branching all of the light beam (4Bb) obtained by branching the return light of the second sub-beam (B) in the first region (2b) to the third light receiving section (7B1) And a ninth optical branching section (for branching half of the light beam (4Ba) obtained by branching the return light of the second sub-beam (B) in the third region (2a) to the seventh light receiving section (7B1). 3Ba1) and the tenth light for branching the remaining half of the light beam (4Aa) obtained by branching the return light of the first sub-beam (A) into the third region (2a) to the fourth light receiving section (7A2) The return light of the branch part (3Aa2) and the first sub beam (A) is branched in the second region (2c). A fifth light branching portion (3Ac) for branching the entire light beam (4Ac) to the fifth light receiving portion (7A2), and the return light of the second sub-beam (B) branches in the second region (2c) An eleventh light branching portion (3Bc) for branching the entire light beam (4Bc) to the sixth light receiving portion (7B2), and the return light of the second sub beam (B) is the third region (2a). And a twelfth light branching portion (3Ba2) for branching the remaining half of the light beam (4Ba) branched at the eighth light receiving portion (7B2), and the first main beam light receiving portion (7Mb) and the first light receiving portion (7Mb) The difference in the amount of light from the two main beam light receiving units (7Mc), the total light amount of the first and second light receiving units (7A1) and the third and seventh light receiving units (7B1), and the fourth and fifth light receiving units. Part (7A2) and the sixth and eighth light receiving parts (7B2) The tracking error signal is generated based on the difference between the two.
[0137]
[Embodiment 4]
Still another embodiment of the present invention will be described with reference to FIGS. FIGS. 13 and 14 are perspective schematic views of the diffractive optical element 3 and the diffraction gratings and light receiving elements involved in tracking error signal detection by the DPP method in this embodiment. Constituent elements of the same type as in the first to third embodiments will be described with reference to the same reference numerals. Figures 1, 3, 4, etc. are also cited as necessary.
[0138]
This embodiment is different from the first embodiment only in the following five points, and the other configuration is the same as that of the first embodiment.
[0139]
The first difference is that the diffractive optical element 3 does not include the diffraction grating 3Ab and the diffraction grating 3Ac, as shown in FIG. 13, and includes four diffraction gratings 3Bb, 3Bc, 3Aa1, and 3Aa2. Is a point.
[0140]
The second difference is that the light receiving element 7Ab and the light receiving element 7Ac directly receive the light beam 4Ab and the light beam 4Ac without being diffracted by the diffractive optical element 3, and the light receiving element 7Bb and the light receiving element 7Bc is such that the light beam 4Bb and a part of the light beam 4Bc are directly received without being diffracted by the diffractive optical element 3.
[0141]
As shown in FIG. 14, the third difference is that the diffraction grating 3Bb does not cause the light beam to be incident on the light receiving element 7Bb, but one part of the light beam 4Bb formed by diffracting the return light of the sub beam B in the region 2b. Function as a thirteenth optical branching portion that diffracts the light in the region 80 other than the light receiving elements 7Ab, 7Ac, 7Bb, and 7Bc (in a direction other than the direction incident on the light receiving elements 7Ab, 7Ac, 7Bb, and 7Bc). The diffraction grating 3Bc does not cause the light beam to enter the light receiving element 7Bc, but a part of the light beam 4Bc obtained by diffracting the return light of the sub beam B in the region 2c is converted into each light receiving element 7Ab, 7Ac, 7Bb, 7Bc. This is a point that functions as a fourteenth light branching portion that diffracts the region 80 other than (in a direction other than the direction incident on the light receiving elements 7Ab, 7Ac, 7Bb, and 7Bc).
[0142]
The fourth difference is that the diffraction grating 3Aa1 diffracts the diffracted light to the light receiving element 7Ab that detects the light beam 4Ab, and the diffraction grating 3Aa2 diffracts the diffracted light to the light receiving element 7Ac that detects the light beam 4Ac. is there. That is, the light receiving element 7Ab also functions as a first light receiving unit that receives the sub beam A diffracted by the diffraction grating 3Aa1, and the light receiving element 7Ac receives the first sub beam A diffracted by the diffraction grating 3Aa2. It also has a function as a light receiving part.
[0143]
The fifth difference is that the diffraction efficiencies of the diffraction gratings 3Bb, 3Bc, 3Aa1, and 3Aa2 are approximately 100%.
[0144]
With the above configuration, all the light beam signals incident on the diffraction grating 3Aa1 in the light beam 4Aa are added to the light beam 4Ab signals, and all the light beam signals incident on the diffraction grating 3Aa2 in the light beam 4Aa It adds to the signal of beam 4Ac. Also, all of the light beams incident on the diffraction grating 3Bb in the light beam 4Bb and all of the light beams incident on the diffraction grating 3Bc in the light beam 4Bc are diffracted in unnecessary directions and excluded from signal detection.
[0145]
Thereby, the unbalance of the diffracted light of the sub-beams A and B caused by the sub-beams A and B being split in an unbalanced manner by the hologram optical element 2 can be corrected with a smaller number (four) of diffraction gratings.
[0146]
The tracking error signal TES2 by the DPP method is given by

Can be detected. Other servo signal and information signal detection methods are the same as those in the first embodiment.
[0147]
The diffraction gratings 3Bb, 3Bc, 3Aa1, and 3Aa2 used in the present embodiment are formed by a technique such as blazing.
[0148]
As described above, in the optical integrated unit according to the present embodiment, the photodetector (7) has the light beam (5Mb) obtained by branching the return light of the main beam (M) in the first region (2b). The first main beam receiving unit (7Mb) for receiving the light and the second main beam receiving unit for receiving the light beam (5Mc) obtained by branching the return light of the main beam (M) in the second region (2c) (7Mc), the first light receiving part (7Ab), and the second light receiving part for receiving the light beam (4Ab) obtained by branching the return light of the first sub-beam (A) in the first region (2b) (7Ab), a third light receiving part (7Bb) for receiving the light beam (4Bb) obtained by branching the return light of the second sub-beam (B) in the first region (2b), and a fourth light receiving part (7Ac) and the return light of the first sub-beam (A) branches in the second region (2c) A fifth light receiving portion (7Ac) that receives the light beam (4Ac) and a light beam (4Bc) obtained by branching the return light of the second sub beam (B) in the second region (2c). The second light splitter (2) is arranged so that the center of the first sub-beam (A) passes through the inside of the third region (2a), and the sixth light receiver (7Bc). The third optical branching device (3) branches a part of the light beam obtained by branching the return light of the first sub-beam (A) in the third region (2a) to the first light receiving unit (7Ab). Another part of the light beam (4Aa) formed by branching the return light of the first light beam (3Aa1) and the first sub-beam (A) in the third region (2a) is used as the fourth light receiving unit (7Ac). ), And the return light of the second sub beam (B) is reflected in the first region (3Aa2). b) a thirteenth light branching portion (3Bb) for branching a part of the light beam (4Bb) branched in the direction other than the direction incident on each light receiving portion, and the return of the second sub beam (B). A fourteenth light branching section (3Bc) for branching a part of the light beam (4Bc) obtained by branching the light in the second region (2c) in a direction other than the direction incident on each light receiving section; The difference in the amount of light between the first main beam receiver (7Mb) and the second main beam receiver (7Mc), the total amount of light of the first to third receivers (7Ab, 7Bb, 7Aa1) and the fourth to fourth The tracking error signal is generated based on a difference from the total light quantity of the six light receiving units (7Ac, 7Bc, 7Aa2), and the first sub-beam branched to the first light receiving unit (7Ab) and the first sub beam 2 incident on the light receiving part (7Ab) Of the light beam formed by combining the shape of the first sub-beam and the return light of the second sub-beam (B) in the first region (2b), it is branched in the thirteenth light branch (3Bb). The shape of the light beam incident on the third light receiving part (7Bb) without being transmitted, the first sub beam branched to the fourth light receiving part (7Ac), and the first light incident on the fifth light receiving part (7Ac) Among the light beams formed by combining the shape of the first sub-beam and the return light of the second sub-beam (B) in the second region (2c), it is branched in the fourteenth light branching section (3Bc). The shape of the light beam incident on the sixth light receiving section (7Bc) without any change is at the branch position of the first sub-beam (A) and the second sub-beam (B) by the second optical splitter (2). Regardless, the above-mentioned first so as to have a substantially constant shape (quadric shape). Of the optical branching section (3Aa1), the fourth optical splitter (3Aa2), the light branching unit of the 13 (3Bb), and an optical branching portion of the 14 (3Bc) is arranged. In addition, the shape of the main beam (5Mb) incident on the first main beam light receiving unit (7Mb) and the shape of the main beam (5Mc) incident on the second main beam light receiving unit (7Mc) are also described above. It is configured to be equivalent in shape to “a certain shape”.
[0149]
According to the above configuration, the first and second sub-beams (A · B) with respect to the center of the second optical branching device can be moved even if the positions and intervals of the first and second sub-beams (A · B) are deviated from the standard state. The shape of the combined first sub-beams incident on the light-receiving unit (7Ab), the shape of the second sub-beams incident on the third light-receiving unit (7Bb), and the fourth and fifth light-receiving units (7Ac) Since the shape of the combination of the incident first sub-beams and the shape of the second sub-beam incident on the sixth light receiving portion (7Bc) can always be substantially constant, the light quantity of these light beams It is possible to avoid the occurrence of an unbalance different from the standard state. As a result, an accurate tracking error signal without residual offset can be obtained.
[0150]
[Embodiment 5]
Still another embodiment of the present invention will be described with reference to FIGS. 15 and 16. Constituent elements of the same type as in any of Embodiments 1 to 4 will be described with reference to the same reference numerals. Figures 1, 3, 4, etc. are also cited as necessary.
[0151]
This embodiment is different from the fourth embodiment only in the following points, and the other configuration is the same as that of the first embodiment. That is, the difference from the first embodiment is that each of the diffraction gratings 3Bb and 3Bc in which a part of the diffracted beams 4Bb and 4Bc is diffracted in a direction other than the light receiving element in the fourth embodiment as shown in FIG. Instead, a light shielding film (mask) as a first light shielding part is provided at the same position as the diffraction grating 3Bb, and a light shielding film (mask) as a second light shielding part is provided at the same position as the diffraction grating 3Bc. It is.
[0152]
With the above configuration, in the same manner as in the fourth embodiment, all the signals of the light beam incident on the diffraction grating 3Aa1 in the light beam 4Aa are added to the signal of the light beam 4Ab, and the light beam 4Aa is incident on the diffraction grating 3Aa2. All signals of the light beam to be added are added to the signal of the light beam 4Ac. Further, all of the light beams incident on the diffraction grating 3Bb in the light beam 4Bb and all of the light beams incident on the diffraction grating 3Bc in the light beam 4Bc are excluded from the signal detection.
[0153]
As a result, the unbalanced diffracted light of the sub-beams A and B caused by the sub-beams A and B being unbalanced by the hologram optical element 2 can be further reduced by using a smaller number (two) of diffraction gratings and light shielding films. Can be corrected.
[0154]
The tracking error signal TES2 by the DPP method is the same as that of the fourth embodiment, and

Can be detected. Other servo signal and information signal detection methods are the same as those in the first embodiment.
[0155]
FIG. 16 is a perspective view of the optical substrate 15 on which the light shielding films 3Db and 3Dc are formed as seen from the back surface (the surface on the photodetector 7 side). The light shielding films 3Db and 3Dc are not particularly limited as long as they have a light shielding property, but a film made of a metal such as chromium is preferable because it is excellent in the light shielding property. The light shielding films 3Db and 3Dc made of metal can be formed, for example, by vapor-depositing metal on the surface of the optical substrate (translucent body) on which the diffractive optical element 3 is formed. Since the light shielding films 3Db and 3Dc are formed by a technique such as photolithography, the positional accuracy with the diffraction gratings 3Aa1 and 3Aa and the hologram optical element 2 (not shown) is very good, and a predetermined light beam portion can be shielded accurately. The light shielding films 3Db and 3Dc of this embodiment are metal vapor deposition films, and the light shielding rate is set to 100%.
[0156]
Thus, by forming the light shielding films 3Db and 3Dc, which are light shielding portions, integrally with the optical substrate 15, the fabrication of the optical integrated unit 20 is facilitated and the reliability is improved.
[0157]
As described above, in the optical integrated unit according to the present embodiment, the photodetector (7) has the light beam (4Mb) obtained by branching the return light of the main beam (M) in the first region (2b). The first main beam receiving unit (7Mb) that receives the light beam and the second main beam receiving unit that receives the light beam (4Mc) obtained by branching the return light of the main beam (M) in the second region (2c) (7Mc), the first light receiving part (7Ab), and the second light receiving part for receiving the light beam (4Ab) obtained by branching the return light of the first sub-beam (A) in the first region (2b) (7Ab), a third light receiving part (7Bb) for receiving the light beam (4Bb) obtained by branching the return light of the second sub-beam (B) in the first region (2b), and a fourth light receiving part (7Ac) and the return light of the first sub-beam (A) branches in the second region (2c) A fifth light receiving portion (7Ac) that receives the light beam (4Ac) and a light beam (4Bc) obtained by branching the return light of the second sub beam (B) in the second region (2c). The second light splitter (2) is arranged so that the center of the first sub-beam (A) passes through the inside of the third region (2a), and the sixth light receiver (7Bc). The third optical branching device (3) branches a part of the light beam obtained by branching the return light of the first sub-beam (A) in the third region (2a) to the first light receiving unit (7Ab). Another part of the light beam (4Aa) formed by branching the return light of the first light beam (3Aa1) and the first sub-beam (A) in the third region (2a) is used as the fourth light receiving unit (7Ac). ) And the return light of the second sub-beam (B) in the first region (3Aa2). The first light shielding part (3Db) that shields a part of the light beam (4Bb) branched in b) and the return light of the second sub beam (B) are branched in the second region (2c). A second light-shielding part (3Dc) that shields a part of the light beam (4Bc), and a light quantity difference between the first main beam light-receiving part (7Mb) and the second main beam light-receiving part (7Mc); The tracking error signal is generated based on the difference between the total light amount of the first to third light receiving units (7Ab, 7Bb, and 7Aa1) and the total light amount of the fourth to sixth light receiving units (7Ac, 7Bc, and 7Aa2). The shape of a combination of the first sub-beam branched to the first light-receiving unit (7Ab) and the first sub-beam incident on the second light-receiving unit (7Ab), and the second sub-beam The return light of (B) is separated in the first region (2b). Of the light beam thus formed, the light beam is incident on the third light receiving part (7Bb) without being shielded by the first light shielding part (3Db), and branched to the fourth light receiving part (7Ac). The shape of the first sub-beam and the first sub-beam incident on the fifth light receiving portion (7Ac) and the return light of the second sub-beam (B) are branched in the second region (2c). The shape of the light beam incident on the sixth light receiving part (7Bc) without being shielded by the second light shielding part (3Dc) is the first light beam by the second light splitter (2). Regardless of the branch position of the sub beam (A) and the second sub beam (B), the first light branch portion (3Aa1) and the fourth light branch are formed so as to have a substantially constant shape (quadric shape). Section (3Aa2), thirteenth light branching section (3Bb), and fourteenth light branching section (3Bc) is arranged. In addition, the shape of the main beam (4Mb) incident on the first main beam light-receiving unit (7Mb) and the shape of the main beam (4Mc) incident on the second main beam light-receiving unit (7Mc) are also the above-mentioned “abbreviations”. It is configured to be equivalent in shape to “a certain shape”.
[0158]
According to the above configuration, the first and second sub-beams (A · B) with respect to the center of the second optical branching device can be moved even if the positions and intervals of the first and second sub-beams (A · B) are deviated from the standard state. The shape of the combined first sub-beams incident on the light-receiving unit (7Ab), the shape of the second sub-beams incident on the third light-receiving unit (7Bb), and the fourth and fifth light-receiving units (7Ac) Since the shape of the combination of the incident first sub-beams and the shape of the second sub-beam incident on the sixth light receiving portion (7Bc) can always be substantially constant, the light quantity of these light beams It is possible to avoid the occurrence of an unbalance different from the standard state. As a result, an accurate tracking error signal without residual offset can be obtained.
[0159]
Further, as described above, the optical integrated unit according to each of the above embodiments is used in combination with the condensing means (12, 13) for condensing the light beam on the optical recording medium (10). A light source (11) for emitting a light beam toward the light means (12, 13), disposed between the light source (11) and the light collecting means (12, 13), and the light source (11) A first optical branching device (1) for branching the light beam emitted from the main beam (M) into a first sub beam (A) and a second sub beam (B) for generating a tracking error signal And a photodetector (7) for receiving return light from the optical recording medium (10), and between the light collecting means (12, 13) and the photodetector (7), and the return A second optical branching device (2) for branching the light into a plurality of light beams, The two optical splitters (2) are composed of a plurality of regions for branching the return light in different directions, and the plurality of regions are first dividing lines parallel to the track direction (Y) of the optical recording medium (10). An optical integrated unit including a first region (2b) and a second region (2c) divided by (2N) and a third region (2a) located on an extension line of the first dividing line (2N) , The return light of the first sub-beam (A) and the second sub-beam (B) is transferred between the second optical splitter (2) and the photodetector (7). ) Is provided with a third optical branching device (3) for branching a part of the light beam branched.
[0160]
In the optical integrated unit according to each of the above embodiments, the photodetector (7) generates a light beam (4Mb) obtained by branching the return light of the main beam (M) in the first region (2b). A first main beam receiving unit (7Mb) for receiving light and a second main beam receiving unit (4Mc) for receiving a light beam (4Mc) obtained by branching return light of the main beam (M) in the second region (2c). 7Mc), at least a part of the light beam (4Ab) obtained by branching the return light of the first sub-beam (A) in the first region (2b), and the return light of the first sub-beam (A) A first sub-beam receiving unit (7Ab, 7Aa1, 7b, 7A1, or 7Ab) that receives a part of the light beam (4Aa) branched in the third region (2a), and at least a second sub-beam ( The return light of B) is the first region (2 ) And the second sub-beam light receiving unit (7Bb, 7b, or 7B1) that receives at least a part of the light beam (4Bb) branched by at least the second sub-beam (A), and at least the return light of the first sub-beam (A) is in the second region. At least a part of the light beam (4Ac) branched in (2c) and the other one of the light beam (4Aa) in which the return light of the first sub-beam (A) is branched in the third region (2a) A third sub-beam light receiving portion (7Ac, 7Aa2, 7c, 7A2, or 7Ac) that receives light from the light receiving portion and light obtained by branching at least the return light of the second sub-beam (B) in the second region (2c) A fourth sub-beam receiving unit (7Bc, 7c, or 7B2) that receives at least a part of the beam (4Bc), and a first main beam receiving unit (7Mb) and a second main beam receiving unit (7Mc). When The difference between the light amounts, the total light amount of the first sub-beam light receiving unit (7Ab / 7Aa1, 7b, 7A1, or 7Ab) and the second sub-beam light receiving unit (7Bb, 7b, or 7B1) and the third sub-beam light receiving unit (7Ac) 7Aa2, 7c, 7A2, or 7Ac) and the fourth sub-beam light receiving unit (7Bc, 7c, or 7B2) are configured to generate a tracking error signal based on the difference between the total light amounts, and the third light The branching unit (3) includes a first sub-beam light receiving unit (7Ab, 7Aa1, 7b, 7A1, or 7Ab) incident on the first sub-beam (hereinafter referred to as a light beam α) and a second sub-beam light receiving unit ( 7Bb, 7b, or 7B1) and a third sub-beam light receiving unit (7Ac, 7Aa2, 7c). 7A2 or 7Ac) and a second sub-beam (hereinafter referred to as light beam δ) incident on a fourth sub-beam receiving part (7Bc, 7c or 7B2). Each of the first sub-beam (A) and the second sub-beam (B) by the second optical splitter (2), regardless of the branch position of the first sub-beam (B). It is configured. The third optical splitter (3) is configured such that the light beam α, the light beam β, the light beam γ, and the light beam δ are equivalently identical in shape as a whole. . Further, the third optical splitter (3) has a main beam (4Mb) in which the shape of the light beam α and the shape of the light beam β are incident on the first main beam receiving part (7Mb) as a whole. The shape, or the shape of the light beam γ and the shape of the light beam δ as a whole so as to be equivalently the same shape as the shape obtained by combining two of the incident main beams (4 Mb). The main beam receiving portion (7Mc) is configured to have the same shape as the main beam (4Mc) that is incident on the main beam receiving portion (7Mc) or the shape of the two incident main beams (4Mc).
[0161]
According to the above configuration, even when the positions and intervals of the first and second sub beams (A and B) with respect to the center of the second optical branching device are deviated from the standard state, the light beam α and the light Since the beam β, the light beam γ, and the light beam δ can always be in a substantially constant shape, it is possible to avoid the occurrence of an imbalance different from the standard state in the light amount of these light beams. As a result, an accurate tracking error signal without residual offset can be obtained.
[0162]
The hologram optical element 2 used in each of the above embodiments forms a semicircular region 2a as a third region by a dividing line 2L parallel to the radial direction X of the optical disc 10, and the remaining semicircular portion. It was a three-segment hologram optical element in which (second region) was divided into two quadrant-shaped regions 2b and 2c as a first region and a second region by a dividing line 2N parallel to the track tangential direction Y . However, the shape of the hologram optical element used in the present invention is not limited to this. The hologram optical element is, for example, a quadrant hologram optical element in which a dividing line 2N parallel to the track tangential direction Y in the hologram optical element 2 extends over the entire region of the light beam and is divided into four quadrant regions. It doesn't matter.
[0163]
The quadrant hologram element is particularly preferable when the sub-beams A and B are equivalently used as a whole as in the third embodiment. In this case, the entire light beam (main beam M) can be used equivalently for the generation of the tracking error signal by the main beam M by taking the difference between the semicircular shapes on one side of the main beam. Therefore, wherever the main beam is divided by the dividing line 2L, the main beam used for generating the tracking error signal and the sub beams A and B used for generating the tracking error signal can always have the same shape.
[0164]
【The invention's effect】
According to the present invention, the provision of the third optical branching device enables tracking in the differential push-pull method even if the dimensional variation of parts constituting the optical integrated unit or the manufacturing variation of the optical integrated unit occurs. An error signal can be obtained stably. Therefore, the present invention can provide an optical integrated unit capable of stably detecting a tracking error and an optical pickup device using the same.
[Brief description of the drawings]
FIG. 1 is a side view showing a schematic configuration of an optical pickup device according to an embodiment of the present invention.
FIG. 2 is a plan view showing a three-beam diffraction grating provided in the optical pickup device.
FIG. 3 is a plan view showing a schematic configuration of a hologram optical element provided in the optical pickup device together with a light beam.
FIG. 4 is a plan view showing a schematic configuration of a diffractive optical element provided in the optical pickup device together with a light beam.
FIG. 5 is a plan view showing a schematic configuration of the diffractive optical element.
FIG. 6 is a diagram showing a configuration of a diffractive optical element and a photodetector included in the optical pickup device, together with diffracted light by the diffractive optical element.
FIG. 7 is a diagram showing a configuration of a photodetector included in the optical pickup device together with incident light rays.
FIG. 8 is a perspective view showing a three-beam diffraction grating, a hologram optical element, and an optical substrate on which the diffractive optical element is formed, provided in the optical pickup device.
FIG. 9 is a plan view showing a schematic configuration of a diffractive optical element included in an optical pickup device according to another embodiment of the present invention.
FIG. 10 is a diagram showing a configuration of a diffractive optical element and a photodetector included in an optical pickup device according to another embodiment of the present invention, together with diffracted light by the diffractive optical element.
FIG. 11 is a plan view showing a schematic configuration of a diffractive optical element provided in an optical pickup device according to still another embodiment of the present invention.
FIG. 12 is a diagram showing a configuration of a diffractive optical element and a photodetector included in an optical pickup device according to still another embodiment of the present invention, together with diffracted light by the diffractive optical element.
FIG. 13 is a plan view showing a schematic configuration of a diffractive optical element included in an optical pickup device according to still another embodiment of the present invention.
FIG. 14 is a diagram showing a configuration of a diffractive optical element and a photodetector included in an optical pickup device according to still another embodiment of the present invention, together with diffracted light by the diffractive optical element.
FIG. 15 is a diagram showing a configuration of a diffractive optical element and a photodetector included in an optical pickup device according to still another embodiment of the present invention, together with diffracted light by the diffractive optical element.
FIG. 16 is a perspective view showing an optical substrate on which a light shielding film is formed, which is provided in an optical pickup device according to still another embodiment of the present invention.
17A and 17B are diagrams showing an example of a conventional optical pickup device, where FIG. 17A is a top view and FIG. 17B is a side view.
FIG. 18 is a diagram showing a configuration of a hologram optical element and a light receiving element included in the conventional optical pickup device, together with diffracted light by each region of the hologram optical element.
FIG. 19 is a plan view showing a schematic configuration of a hologram optical element included in the conventional optical pickup device together with a light beam.
20 is a diagram showing the shape and position of diffracted light by the hologram optical element of FIG.
[Explanation of symbols]
1 3 beam diffraction grating
2 Hologram optical element
2L ・ 2N dividing line
2a-2c region
3 Diffractive optical elements
3Aa1, 3Aa2, 3Ab, 3Ac, 3Bb, 3Bc diffraction grating
3Ba1, 3Ba2 diffraction grating
3Db / 3Dc light-shielding film
3M / 3N dividing line
4 + 1st order diffracted light
4Aa ・ 4Ab ・ 4Ac ・ 4Ba ・ 4Bb ・ 4Bc Light beam
4Ma ・ 4Mb ・ 4Mc Diffraction grating
5-1st order diffracted light
6 Diffracted light
7 Photodetector
7Aa1, 7Aa2, 7Ab, 7Ac, 7Bb, 7Bc
7Ma1, 7Ma2, 7Ma, 7Mb, 7Mc
7b ・ 7c Light receiving element
7A1, 7A2, 7B1, 7B2 Light receiving element
7Ma1, 7Ma2, 7Ma, 7Mb, 7Mc
8 Beam splitter
9 1/4 wave plate
10 Optical disc
11 Semiconductor laser
12 Collimating lens
13 Objective lens
15 Optical substrate
20 Optical integrated unit
80 areas
A / B sub beam
M main beam
X Radial direction
Y track tangential direction
Z Optical axis direction

Claims (27)

Used in combination with a condensing means for condensing a light beam on an optical recording medium,
A light source for emitting a light beam toward the condensing means;
A first beam that is arranged between the light source and the condensing means and splits a light beam emitted from the light source into a main beam and a first sub-beam and a second sub-beam for generating a tracking error signal. With an optical splitter
A photodetector for receiving the return light from the optical recording medium;
A second optical branching device disposed between the condensing means and the photodetector and branching the return light into a plurality of light beams;
The second optical branching unit includes a plurality of regions for branching the return light in different directions, and the plurality of regions are divided by a first dividing line parallel to the track direction of the optical recording medium. In an optical integrated unit including a region and a second region, and a third region located on an extension of the first dividing line,
A return light of the first sub-beam and the second sub-beam splits at least part of the light beam branched by the second optical splitter between the second optical splitter and the photodetector. An optical splitter is provided,
The photodetector is
A first main beam receiving unit that receives a light beam obtained by branching back light of the main beam in the first region;
A second main beam light receiving unit for receiving a light beam in which the return light of the main beam is branched in the second region;
At least a part of the light beam obtained by branching the return light of the first sub-beam in the first region and a part of the light beam obtained by branching the return light of the first sub-beam in the third region are received. A first sub-beam light receiving unit,
A second sub-beam light receiving unit that receives at least a part of the light beam formed by branching the return light of the second sub-beam in the first region;
At least a part of the light beam obtained by branching the return light of the first sub-beam in the second region, and another part of the light beam obtained by branching the return light of the first sub-beam in the third region A third sub-beam light receiving portion for receiving light;
And a fourth sub-beam light receiving unit that receives at least a part of the light beam formed by branching the return light of the second sub-beam in the second region,
The light amount difference between the first main beam light receiving unit and the second main beam light receiving unit, the total light amount of the first sub beam light receiving unit and the second sub beam light receiving unit, and the third sub beam light receiving unit and the fourth sub beam. A tracking error signal is generated based on the difference from the total light amount of the light receiving unit,
The third optical branching unit includes a first sub-beam incident on the first sub-beam light receiving unit, a second sub-beam incident on the second sub-beam light receiving unit, and a first sub-beam incident on the third sub-beam light receiving unit. The sub-beam and the second sub-beam incident on the fourth sub-beam receiving unit are substantially constant in shape as a whole regardless of the branch positions of the first sub-beam and the second sub-beam by the second optical splitter. An optical integrated unit characterized by being configured as follows.   In the second optical splitter, the total area of the first area and the second area is one area obtained by dividing the entire area into two by a second dividing line perpendicular to the track direction in the optical recording medium. The optical integrated unit according to claim 1, wherein the third region is the other region.   2. The optical integrated unit according to claim 1, wherein the third optical branching unit is disposed at an optical position where a plurality of light beams branched by the second optical branching unit are separated from each other. The photodetector includes a first light receiving portion and a second light receiving portion as a first sub beam light receiving portion, a third light receiving portion as a second sub beam light receiving portion, and a third sub beam light receiving portion. It consists of a fourth light receiving part and a fifth light receiving part, and a sixth light receiving part as a fourth sub-beam light receiving part,
The second optical splitter is arranged such that the center of the first sub-beam passes through the inside of the third region,
The third optical splitter is
A first light branching unit for branching a part of the light beam obtained by branching the return light of the first sub-beam in the third region to the first light receiving unit;
A second light branching unit for branching all of the light beam obtained by branching the return light of the first sub-beam into the first region to the second light receiving unit;
A third light branching unit for branching a part of the light beam obtained by branching the return light of the second sub-beam in the first region to the third light receiving unit;
A fourth light branching part for branching the other part of the light beam obtained by branching the return light of the first sub-beam to the third region to the fourth light receiving part;
A fifth light branching unit for branching all of the light beam obtained by branching the return light of the first sub-beam into the second region to the fifth light receiving unit;
A sixth light branching unit for branching a part of the light beam obtained by branching the return light of the second sub-beam in the second region to the sixth light receiving unit;
The shape of a combination of the first sub-beam branched to the first light-receiving unit and the first sub-beam branched to the second light-receiving unit, and the shape of the second sub-beam branched to the third light-receiving unit And the shape of a combination of the first sub-beam branched to the fourth light-receiving unit and the first sub-beam branched to the fifth light-receiving unit, and the second sub-beam branched to the sixth light-receiving unit So that the first to sixth optical branching portions have substantially the same shape regardless of the branch positions of the first sub-beam and the second sub-beam by the second optical splitter. The optical integrated unit according to claim 1, wherein the optical integrated unit is arranged.   The first optical branching unit, the second optical branching unit, the third optical branching unit, the fourth optical branching unit, the fifth optical branching unit, and the sixth optical branching unit have the same ratio of optical branching. 5. The optical integrated unit according to claim 4, wherein the optical integrated unit is set.   At least two of the first light receiving unit, the second light receiving unit, and the third light receiving unit, and / or of the fourth light receiving unit, the fifth light receiving unit, and the sixth light receiving unit. 5. The optical integrated unit according to claim 4, wherein at least two of the light receiving elements are the same. The photodetector includes a first light receiving portion and a second light receiving portion as first sub beam light receiving portions, a third light receiving portion and a seventh light receiving portion as second sub beam light receiving portions, and a third light receiving portion. A fourth light receiving portion and a fifth light receiving portion as the sub beam light receiving portion, and a sixth light receiving portion and an eighth light receiving portion as the fourth sub beam light receiving portion,
The third optical splitter is
A seventh light branching unit for branching a half of the light beam obtained by branching the return light of the first sub-beam into the third region to the first light receiving unit;
A second light branching unit for branching all of the light beam obtained by branching the return light of the first sub-beam into the first region to the second light receiving unit;
An eighth light branching unit for branching all of the light beam obtained by branching the return light of the second sub-beam into the first region to the third light receiving unit;
A ninth light branching unit for branching half of the light beam obtained by branching the return light of the second sub-beam into the third region to the seventh light receiving unit;
A tenth light branching unit for branching the remaining half of the light beam obtained by branching the return light of the first sub-beam into the third region to the fourth light receiving unit;
A fifth light branching unit for branching all of the light beam obtained by branching the return light of the first sub-beam into the second region to the fifth light receiving unit;
An eleventh light branching section for branching all of the light beam obtained by branching the return light of the second sub-beam into the second region to the sixth light receiving section;
2. The light according to claim 1, further comprising a twelfth light branching portion for branching the remaining half of the light beam obtained by branching the return light of the second sub beam into the third region to the eighth light receiving portion. Integrated unit.   A second optical branch, a fifth optical branch, a seventh optical branch, an eighth optical branch, a ninth optical branch, a tenth optical branch, an eleventh optical branch, and 8. The optical integrated unit according to claim 7, wherein the twelfth optical branching unit has the same optical branching ratio.   At least two of the first light receiving unit, the second light receiving unit, the third light receiving unit, and the seventh light receiving unit, and / or the fourth light receiving unit, the fifth light receiving unit, the sixth light receiving unit, 8. The optical integrated unit according to claim 7, wherein at least two of the light receiving unit and the eighth light receiving unit are formed of the same light receiving element. The photodetector receives a first light-receiving unit as a first sub-beam light-receiving unit and a light beam obtained by branching back light of the first sub-beam as a first sub-beam light-receiving unit in a first region. A second light-receiving unit, a third light-receiving unit as a second sub-beam light-receiving unit, a third light-receiving unit that receives a light beam branched from the return light of the second sub-beam in the first region, and a third sub-beam light-receiving unit A fourth light-receiving unit as a part, a fifth light-receiving unit as a third sub-beam light-receiving part, which receives a light beam obtained by branching the return light of the first sub-beam in the second region, As a sub-beam light receiving unit, the return light of the second sub-beam comprises a sixth light receiving unit that receives the light beam branched in the second region
The second optical splitter is arranged such that the center of the first sub-beam passes through the inside of the third region,
The third optical splitter is
A first light branching unit for branching a part of the light beam obtained by branching the return light of the first sub-beam in the third region to the first light receiving unit;
A fourth light branching part for branching the other part of the light beam obtained by branching the return light of the first sub-beam to the third region to the fourth light receiving part;
A thirteenth light branching portion for branching a part of the light beam obtained by branching the return light of the second sub-beam in the first region in a direction other than the direction incident on each light receiving portion;
A fourteenth light branching part for branching a part of the light beam obtained by branching the return light of the second sub-beam in the second region in a direction other than the direction incident on each light receiving part;
The shape of a combination of the first sub-beam branched to the first light-receiving unit and the first sub-beam incident on the second light-receiving unit and the return light of the second sub-beam are branched in the first region. Among the light beams, the shape of the light beam incident on the third light receiving unit without being branched by the thirteenth light branching unit, and the first sub beam and the fifth light receiving unit branched to the fourth light receiving unit Of the first sub-beam incident on the second sub-beam and the sixth sub-beam of the light beam obtained by branching the return light of the second sub-beam in the second region without being branched in the fourteenth optical branching section. The shape of the light beam incident on the light receiving portion of the first sub-beam is approximately the same as the first sub-beam regardless of the branch position of the first sub-beam and the second sub-beam by the second optical splitter. Optical branching unit, fourth optical branching unit, and thirteenth optical branching unit And fourteenth optical integrated unit according to claim 1, wherein the light branching unit is disposed of. The photodetector receives a first light-receiving unit as a first sub-beam light-receiving unit and a light beam obtained by branching back light of the first sub-beam as a first sub-beam light-receiving unit in a first region. A second light-receiving unit, a third light-receiving unit as a second sub-beam light-receiving unit, a third light-receiving unit that receives a light beam branched from the return light of the second sub-beam in the first region, and a third sub-beam light-receiving unit A fourth light-receiving unit as a part, a fifth light-receiving unit as a third sub-beam light-receiving part, which receives a light beam obtained by branching the return light of the first sub-beam in the second region, As a sub-beam light receiving unit, the return light of the second sub-beam comprises a sixth light receiving unit that receives the light beam branched in the second region
The second optical splitter is arranged such that the center of the first sub-beam passes through the inside of the third region,
The third optical splitter is
A first light branching unit for branching a part of the light beam obtained by branching the return light of the first sub-beam in the third region to the first light receiving unit;
A fourth light branching part for branching the other part of the light beam obtained by branching the return light of the first sub-beam to the third region to the fourth light receiving part;
A first light-shielding portion that shields a part of the light beam obtained by branching the return light of the second sub-beam in the first region;
A second light shielding portion for shielding a part of the light beam obtained by branching the return light of the second sub-beam in the second region;
The shape of a combination of the first sub-beam branched to the first light-receiving unit and the first sub-beam incident on the second light-receiving unit and the return light of the second sub-beam are branched in the first region. Of the light beam, the third light receiving unit is not shielded by the first light shielding unit, the first sub beam branched to the fourth light receiving unit, and the first sub beam incident on the fifth light receiving unit, And the light beam incident on the sixth light receiving unit without being blocked by the second light blocking unit among the light beams obtained by branching the return light of the second sub beam in the second region. The first light branching unit and the fourth light are shaped so that the shapes thereof are substantially constant regardless of the branching positions of the first sub-beam and the second sub-beam by the second optical splitter. A branching portion, a first light shielding portion, and a second light shielding portion are disposed. Optical integrated unit according to claim 1, wherein the door.   12. The optical integrated unit according to claim 11, wherein the first light shielding part, the second light shielding part, and the third optical branching unit are formed on the same light transmitting body. The third optical branching unit includes a plurality of optical branching units that branch light beams obtained by branching the return light of the first sub-beam and the second sub-beam in the second optical branching unit in different directions,
2. The optical integrated unit according to claim 1, wherein these optical branching portions are constituted by diffraction gratings.   2. The optical integrated unit according to claim 1, wherein the second optical branching device and the third optical branching device are formed on the same light transmitting body.   2. The optical integrated unit according to claim 1, wherein the first optical branching device and the third optical branching device are formed on the same light transmitting body. Used in combination with a condensing means for condensing a light beam on an optical recording medium,
A light source for emitting a light beam toward the condensing means;
A first beam disposed between the light source and the light condensing means and splitting the light beam emitted from the light source into a main beam and a first sub-beam and a second sub-beam related to tracking error signal generation. An optical splitter,
A photodetector for receiving the return light from the optical recording medium;
A second optical branching device disposed between the condensing means and the photodetector and branching the return light into a plurality of light beams;
The second optical splitter includes a plurality of regions for branching the return light in different directions, and the plurality of regions are divided by a first dividing line parallel to the track direction of the optical recording medium . In an optical integrated unit including one region and a second region, and a third region located on an extension of the first dividing line ,
A third beam between the second optical branching device and the photodetector diffracts at least a part of the light beam branched by the second optical branching device by the return light of at least the first subbeam and the second subbeam. Is provided with
The photodetector is
A first main beam receiving unit that receives a light beam obtained by branching back light of the main beam in the first region;
A second main beam light receiving unit for receiving a light beam in which the return light of the main beam is branched in the second region;
At least a part of the light beam obtained by branching the return light of the first sub-beam in the first region and a part of the light beam obtained by branching the return light of the first sub-beam in the third region are received. A first sub-beam light receiving unit,
A second sub-beam light receiving unit that receives at least a part of the light beam formed by branching the return light of the second sub-beam in the first region;
At least a part of the light beam obtained by branching the return light of the first sub-beam in the second region, and another part of the light beam obtained by branching the return light of the first sub-beam in the third region A third sub-beam light receiving portion for receiving light;
And a fourth sub-beam light receiving unit that receives at least a part of the light beam formed by branching the return light of the second sub-beam in the second region,
The light amount difference between the first main beam light receiving unit and the second main beam light receiving unit, the total light amount of the first sub beam light receiving unit and the second sub beam light receiving unit, and the third sub beam light receiving unit and the fourth sub beam. A tracking error signal is generated based on the difference from the total light amount of the light receiving unit,
The third optical branching unit includes a first sub-beam incident on the first sub-beam light receiving unit, a second sub-beam incident on the second sub-beam light receiving unit, and a first sub-beam incident on the third sub-beam light receiving unit. The sub-beam and the second sub-beam incident on the fourth sub-beam receiving unit are substantially constant in shape as a whole regardless of the branch positions of the first sub-beam and the second sub-beam by the second optical splitter. An optical integrated unit characterized by being configured as follows.   The second optical splitter is divided into four quadrants by a first dividing line parallel to the track direction of the optical recording medium and a second dividing line perpendicular to the track direction of the optical recording medium. 17. The optical integrated unit according to claim 16, which is a four-part hologram optical element.   The optical integrated unit according to claim 16, wherein the third optical branching unit includes a plurality of diffraction gratings having different diffraction characteristics.   17. The optical integrated unit according to claim 16, wherein the third optical branching unit includes a plurality of diffraction gratings having different diffraction characteristics and adjacent to each other.   17. The optical integrated unit according to claim 16, wherein the third optical branching unit includes a plurality of diffraction gratings that diffract and guide the light beam to the same light receiving portion of the photodetector. The third optical branching unit includes a plurality of adjacent diffraction gratings that diffract the same light beam and guide it to the light receiving unit of the photodetector,
The optical integrated unit according to claim 16, wherein the plurality of adjacent diffraction gratings have different diffraction characteristics. The third optical branching unit is formed on an optical substrate,
The optical substrate is branched by a diffraction grating that diffracts the light beam branched by the second optical splitter and the second optical splitter at the optical position where the third optical splitter is installed. 17. The optical integrated unit according to claim 16, further comprising a region through which the transmitted light beam is transmitted without being diffracted. An optical integrated unit according to any one of claims 1 to 22,
An optical pickup device comprising: a light collecting unit disposed between the optical integrated unit and the optical recording medium, and condensing the light beam emitted from the optical integrated unit on the optical recording medium. Used in combination with a condensing means for condensing a light beam on an optical recording medium,
A light source for emitting a light beam toward the condensing means;
A first beam that is arranged between the light source and the condensing means and splits a light beam emitted from the light source into a main beam and a first sub-beam and a second sub-beam for generating a tracking error signal. With an optical splitter
A photodetector for receiving the return light from the optical recording medium;
A second optical branching device disposed between the condensing means and the photodetector and branching the return light into a plurality of light beams;
The second optical branching unit includes a plurality of regions for branching the return light in different directions, and the plurality of regions are divided by a first dividing line parallel to the track direction of the optical recording medium. In an optical integrated unit including a region and a second region, and a third region located on an extension of the first dividing line,
A return light of the first sub-beam and the second sub-beam splits at least part of the light beam branched by the second optical splitter between the second optical splitter and the photodetector. An optical splitter is provided,
The photodetector is
A first main beam receiving unit that receives a light beam obtained by branching back light of the main beam in the first region;
A second main beam light receiving unit for receiving a light beam in which the return light of the main beam is branched in the second region;
At least a part of the light beam obtained by branching the return light of the first sub-beam in the first region and a part of the light beam obtained by branching the return light of the first sub-beam in the third region are received. A first sub-beam light receiving unit,
A second sub-beam light receiving unit that receives at least a part of the light beam formed by branching the return light of the second sub-beam in the first region;
At least a part of the light beam obtained by branching the return light of the first sub-beam in the second region, and another part of the light beam obtained by branching the return light of the first sub-beam in the third region A third sub-beam light receiving portion for receiving light;
And a fourth sub-beam light receiving unit that receives at least a part of the light beam formed by branching the return light of the second sub-beam in the second region,
The light amount difference between the first main beam light receiving unit and the second main beam light receiving unit, the total light amount of the first sub beam light receiving unit and the second sub beam light receiving unit, and the third sub beam light receiving unit and the fourth sub beam. A tracking error signal is generated based on the difference from the total light amount of the light receiving unit,
The third optical branching unit includes a first sub-beam incident on the first sub-beam light receiving unit, a second sub-beam incident on the second sub-beam light receiving unit, and a first sub-beam incident on the third sub-beam light receiving unit. An optical integrated unit, wherein the sub-beam and the second sub-beam incident on the fourth sub-beam light receiving section are configured to be equivalently identical in shape as a whole. The third optical splitter is
The main beam incident on the first main beam receiving unit as a whole is formed by the shape of the first sub beam incident on the first sub beam receiving unit and the shape of the second sub beam incident on the second sub beam receiving unit. Or a shape equivalent to the shape of two main beams incident on the first main beam light receiving portion, and
The main beam incident on the second main beam receiving unit as a whole is formed by the shape of the first sub beam incident on the third sub beam receiving unit and the shape of the second sub beam incident on the fourth sub beam receiving unit. 25. The optical integration according to claim 24, wherein the optical integration is configured to have the same shape as that of the two main beams incident on the second main beam light receiving portion. unit. Used in combination with a condensing means for condensing a light beam on an optical recording medium,
A light source for emitting a light beam toward the condensing means;
A first beam disposed between the light source and the light condensing means and splitting the light beam emitted from the light source into a main beam and a first sub-beam and a second sub-beam related to tracking error signal generation. An optical splitter,
A photodetector for receiving the return light from the optical recording medium;
A second optical branching device disposed between the condensing means and the photodetector and branching the return light into a plurality of light beams;
The second optical splitter includes a plurality of regions for branching the return light in different directions, and the plurality of regions are divided by a first dividing line parallel to the track direction of the optical recording medium . In an optical integrated unit including one region and a second region, and a third region located on an extension of the first dividing line ,
A third beam between the second optical branching device and the photodetector diffracts at least a part of the light beam branched by the second optical branching device by the return light of at least the first subbeam and the second subbeam. Is provided with
The photodetector is
A first main beam receiving unit that receives a light beam obtained by branching back light of the main beam in the first region;
A second main beam light receiving unit for receiving a light beam in which the return light of the main beam is branched in the second region;
At least a part of the light beam obtained by branching the return light of the first sub-beam in the first region and a part of the light beam obtained by branching the return light of the first sub-beam in the third region are received. A first sub-beam light receiving unit,
A second sub-beam light receiving unit that receives at least a part of the light beam formed by branching the return light of the second sub-beam in the first region;
At least a part of the light beam obtained by branching the return light of the first sub-beam in the second region, and another part of the light beam obtained by branching the return light of the first sub-beam in the third region A third sub-beam light receiving portion for receiving light;
And a fourth sub-beam light receiving unit that receives at least a part of the light beam formed by branching the return light of the second sub-beam in the second region,
The light amount difference between the first main beam light receiving unit and the second main beam light receiving unit, the total light amount of the first sub beam light receiving unit and the second sub beam light receiving unit, and the third sub beam light receiving unit and the fourth sub beam. A tracking error signal is generated based on the difference from the total light amount of the light receiving unit,
The third optical branching unit includes a first sub-beam incident on the first sub-beam light receiving unit, a second sub-beam incident on the second sub-beam light receiving unit, and a first sub-beam incident on the third sub-beam light receiving unit. An optical integrated unit, wherein the sub-beam and the second sub-beam incident on the fourth sub-beam light receiving section are configured to be equivalently identical in shape as a whole. The third optical splitter is
The main beam incident on the first main beam receiving unit as a whole is formed by the shape of the first sub beam incident on the first sub beam receiving unit and the shape of the second sub beam incident on the second sub beam receiving unit. Or a shape equivalent to the shape of two main beams incident on the first main beam light receiving portion, and
The main beam incident on the second main beam receiving unit as a whole is formed by the shape of the first sub beam incident on the third sub beam receiving unit and the shape of the second sub beam incident on the fourth sub beam receiving unit. 27. The optical integration according to claim 26, wherein the optical integration is configured to have the same shape as that of the two main beams incident on the second main beam light receiving portion. unit.

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