JP3759037B2 - Optical pickup device and optical disk device - Google Patents

Description

【００９６】
上記（４）式におけるλは光の波長、Ｌは第１のホログラム素子５７と第１の受光器５９の受光面との距離、ｎは第１のホログラム素子５７の屈折率、ｄは回折領域の幅（Ｔ方向の長さ）である。
【００９７】
そこで、例えば図６（Ｂ）に示されるように、±１次回折光を含む回折光を受光する場合には、第１の受光器５９の受光面のＴ方向の長さを２Ｐ_１よりも若干長くすることにより、±１次回折光による光スポットも受光でき、その結果受光量が増加するため、第１の受光器５９からの出力信号におけるＳ／Ｎ比が向上する。すなわち、トラックエラーに関する情報を含む信号を精度良く求めることが可能となる。また、第１の受光器５９の形状を、例えばＲ方向の長さをＴ方向の長さよりも小さくすることにより、その受光面で受光する回折光の次数に応じて最適な形状に設計することが可能なため、光ピックアップ装置の小型化を促進することができる。
【００９８】
なお、上記第１の実施形態では、第２のビームスプリッタ６４で偏向した反射光束を第１のホログラム素子５７に入射しているが、一例として図７に示されるように、第１のビームスプリッタ５４と対物レンズ６０との間に第１のホログラム素子５７を配置し、対物レンズ６０からの反射光束を直接、第１のホログラム素子５７に入射しても良い。これにより、第２のビームスプリッタ６４及び集光レンズ５８が不要となり、光ピックアップ装置の小型化及び低コスト化を促進することができる。
【００９９】
また、上記第１の実施形態では、第１のホログラム素子５７と第１の受光器５９とが個別に配置されている場合について説明したが、これに限らず、第１のホログラム素子５７と第１の受光器５９とを一体化しても良い。これにより、第１のホログラム素子５７と第１の受光器５９との間隔が狭くなり、光ピックアップ装置２３の小型化を促進することが可能となる。また、予め第１のホログラム素子５７と第１の受光器５９との位置関係が最適化されているために、組み付け及び調整作業を簡略化することができる。従って、作業コストが低下し、低コスト化を促進することができる。
【０１００】
また、上記第１の実施形態では、第１のホログラム素子５７が複数の第１回折領域５７ａ及び第２回折領域５７ｂとから構成されている場合について説明したが、これに限らず、一例として図８（Ａ）〜図８（Ｃ）に示されるように、１つの第１回折領域５７ａと１つの第２回折領域５７ｂとから構成されるホログラム素子５７’でも良い。
【０１０１】
この場合に、例えば、ホログラム素子５７’の受光面における反射光束の光スポットのアスペクト比（Ｒ方向のスポット径／Ｔ方向のスポット径）が０．５以上、すなわち、（２×Ｒ方向のスポット径）≧（Ｔ方向のスポット径）であれば、各回折領域のアスペクト比（Ｒ方向の長さＬｒ／Ｔ方向の長さＬｔ）が１以上、すなわち、（Ｒ方向の長さＬｒ）≧（Ｔ方向の長さＬｔ）とすることにより、ホログラム素子５７’の大きさをビーム形状ギリギリまで小さくすることが可能となる。なお、（Ｒ方向の長さＬｒ）＝（Ｔ方向の長さＬｔ）の場合が図８（Ｃ）に示されている。
【０１０２】
《第２の実施形態》
次に、本発明の第２の実施形態を図９及び図１０に基づいて説明する。
【０１０３】
この第２の実施形態は、前述した第１のホログラム素子５７の代わりに、図９（Ａ）に示されるように、その受光面をＴ方向の分割線（トラック分割線）ＴＤによって分割し、分割線ＴＤの＋Ｒ側の領域と−Ｒ側の領域とで回折方向が異なるように設計された第３のホログラム素子６７を用いる点に特徴を有する。その他、光ピックアップ装置、光ディスク装置の構成などは、前述した第１の実施形態と同様である。従って、以下においては、第１の実施形態との相違点を中心に説明するとともに、前述した第１の実施形態と同一若しくは同等の構成部分については同一の符号を用い、その説明を簡略化し若しくは省略するものとする。
【０１０４】
第３のホログラム素子６７は、図９（Ａ）に示されるように、波長が６５０ｎｍの光束に対して選択的に高い回折効率を有する第３回折領域６７ａ及び第４回折領域６７ｂと、波長が７８０ｎｍの光束に対して選択的に高い回折効率を有する第５回折領域６７ｃ及び第６回折領域６７ｄとから構成されている。ここでは、トラック分割線ＴＤの＋Ｒ側に複数個の第３回折領域６７ａ及び第５回折領域６７ｃがＲ方向を境界線として配置されている。そして、トラック分割線ＴＤの−Ｒ側に複数個の第４回折領域６７ｂ及び第６回折領域６７ｄがＲ方向を境界線として配置されている。また、第３回折領域６７ａと第４回折領域６７ｂとはトラック分割線ＴＤを介して隣接し、第５回折領域６７ｃと第６回折領域６７ｄとはトラック分割線ＴＤを介して隣接している。なお、以下では、第３回折領域６７ａと第５回折領域６７ｃとを合わせて第１領域ＨＡ、第４回折領域６７ｂと第６回折領域７ｄとを合わせて第２領域ＨＢという。
【０１０５】
第３回折領域６７ａと第４回折領域６７ｂは、波長が６５０ｎｍの光束に対して選択的に高い回折効率を有する点では共通しているが、回折方向がそれぞれ異なるように設定されている。同様に、第５回折領域６７ｃと第６回折領域６７ｄは、波長が７８０ｎｍの光束に対して選択的に高い回折効率を有する点では共通しているが、回折方向がそれぞれ異なるように設定されている。従って、本第２の実施形態では、前述した第１の実施形態における第１の受光器５９の代わりに、図９（Ｂ）に示されるように、第１領域ＨＡからの回折光を受光する第４の受光器７０ａと第２領域ＨＢからの回折光を受光する第５の受光器７０ｂとが用いられる。この場合には、第４の受光器７０ａ及び第５の受光器７０ｂを構成する各受光素子は、２分割受光素子でなくとも良い。
【０１０６】
次に、本第２の実施形態に係る光ピックアップ装置２３を備えた光ディスク装置２０を用いて光ディスク１５をアクセスする際のトラッキング制御について簡単に説明する。
【０１０７】
先ず、光ディスク１５がＤＶＤの場合について説明する。
【０１０８】
光ディスク１５が光ディスク装置本体の所定位置に挿入されると、ＣＰＵ４０は、光ディスク１５の記録面の反射率に基づいて光ディスク１５の種類を判別し、ＤＶＤであることを確認すると、レーザコントロール回路２４に制御対象の光源として６５０ｎｍ半導体レーザ５１ａの選択を指示する。
【０１０９】
６５０ｎｍ半導体レーザ５１ａから出射された光束は、第１のカップリングレンズ５２で略平行光となり、第１のビームスプリッタ５４及び第２のビームスプリッタ６４を透過し、対物レンズ６０を介して光ディスク１５の記録面に微小スポットとして集光される。
【０１１０】
光ディスク１５の記録面からの反射光束は、対物レンズ６０で再び略平行光とされ、第２のビームスプリッタ６４で偏向され、集光レンズ５８を介して第３のホログラム素子６７に入射される。そして、この反射光束のうち第３のホログラム素子６７の第１領域ＨＡに入射された部分は、第３回折領域６７ａにて回折され、その回折光は第４の受光器７０ａにて受光される。また、反射光束のうち第３のホログラム素子６７の第２領域ＨＢに入射された部分は、第４回折領域６７ｂにて回折され、その回折光は第５の受光器７０ｂにて受光される。第４の受光器７０ａ及び第５の受光器７０ｂからは、それぞれの受光量に応じた電流信号が再生信号処理回路２８に出力される。
【０１１１】
再生信号処理回路２８では、第４の受光器７０ａ及び第５の受光器７０ｂからの電流信号を電圧信号に変換し、次の（５）式に基づいてトラックエラー信号ＴＥを検出する。
【０１１２】
TE=(S70a-S70b)/(S70a+S70b) ……（５）
【０１１３】
上記（５）式におけるＳ７０ａは第４の受光器７０ａの出力信号であり、Ｓ７０ｂは第５の受光器７０ｂの出力信号である。
【０１１４】
そして、再生信号処理回路２８では、そのトラックエラー信号ＴＥをサーボコントローラ３３に出力する。サーボコントローラ３３は、再生信号処理回路２８からのトラックエラー信号ＴＥに基づいて、モータドライバ２７を介して光ピックアップ装置２３のトラッキングアクチュエータを駆動し、トラックずれを補正する。
【０１１５】
次に、光ディスク１５がＣＤの場合について説明する。
【０１１６】
光ディスク１５が光ディスク装置本体の所定位置に挿入されると、ＣＰＵ４０は、光ディスク１５の記録面の反射率に基づいて光ディスク１５の種類を判別し、ＣＤであることを確認すると、レーザコントロール回路２４に制御対象の光源として７８０ｎｍ半導体レーザ６１ａの選択を指示する。
【０１１７】
７８０ｎｍ半導体レーザ６１ａから出射された光束は、第２のカップリングレンズ６２で略平行光となり、第１のビームスプリッタ５４でその光軸を＋Ｘ方向に折り曲げられた後、第２のビームスプリッタ６４を透過し、対物レンズ６０を介して光ディスク１５の記録面に微小スポットとして集光される。
【０１１８】
光ディスク１５からの反射光束は、対物レンズ６０で再び略平行光とされ、第２のビームスプリッタ６４で偏向され、集光レンズ５８を介して第３のホログラム素子６７に入射される。そして、この反射光束のうち第３のホログラム素子６７の第１領域ＨＡに入射された部分は、第５回折領域６７ｃにて回折され、その回折光は第４の受光器７０ａにて受光される。また、反射光束のうち第３のホログラム素子６７の第２領域ＨＢに入射された部分は、第６回折領域６７ｄにて回折され、その回折光は第５の受光器７０ｂにて受光される。第４の受光器７０ａ及び第５の受光器７０ｂからは、それぞれの受光量に応じた電流信号が再生信号処理回路２８に出力される。
【０１１９】
再生信号処理回路２８では、上述したＤＶＤの場合と同様にして、上記（５）式に基づいて、トラックエラー信号ＴＥを検出する。そして、そのトラックエラー信号ＴＥに基づいて、サーボコントローラ３３及びモータドライバ２７を介して光ピックアップ装置２３のトラッキングアクチュエータが駆動され、トラックずれが補正される。
【０１２０】
また、本第２の実施形態に係る光ディスク装置２０を用いて、前述した第１の実施形態と同様にして、光ディスク１５に対する記録処理及び再生処理を行うことができる。
【０１２１】
以上説明したように、本第２の実施形態に係る光ピックアップ装置によると、第３のホログラム素子６７では、その受光面をＴ方向のトラック分割線ＴＤによって分割され、トラック分割線ＴＤの＋Ｒ側と−Ｒ側とで回折方向が異なるように設定されているため、第４の受光器７０ａ及び第５の受光器７０ｂの位置精度はそれほど厳密なものである必要はなく、組み付け及び調整作業を簡略化することができ、作業コストを低減することが可能となる。
【０１２２】
また、本第２の実施形態に係る光ディスク装置によると、光ピックアップ装置からの出力信号に基づいて、複数種類の情報記録媒体に対してトラックエラー信号を精度良く検出することができるので、前述した第１の実施形態と同様な効果が得られる。
【０１２３】
なお、上記第２の実施形態では、第１の反射光束に対するトラック分割線と第２の反射光束に対するトラック分割線とが等しい場合について説明したが、本発明がこれに限定されるものではない。例えば、第１の反射光束の光軸と第２の反射光束の光軸とが一致していない場合には、一例として図１０（Ａ）に示されるように、第１の反射光束に対するトラック分割線（ＴＤ１とする）と第２の反射光束に対するトラック分割線（ＴＤ２とする）とが異なっている第４のホログラム素子６７‘を用いても良い。この場合には、第１の反射光束に対しては、第４のホログラム素子６７‘における、トラック分割線ＴＤ１の＋Ｒ側の領域が第１領域（ＨＡ１とする）、−Ｒ側の領域が第２領域（ＨＢ１とする）となる。第２の反射光束に対しては、第４のホログラム素子６７‘における、トラック分割線ＴＤ２の＋Ｒ側の領域が第１領域（ＨＡ２とする）、−Ｒ側の領域が第２領域（ＨＢ２とする）となる。
【０１２４】
すなわち、光ディスク１５がＤＶＤの場合は、一例として図１０（Ｂ）に示されるように、ＴＤ１がトラック分割線となり、第１領域ＨＡ１からの回折光は第４の受光器７０ａで受光され、第２領域ＨＢ１からの回折光は第５の受光器７０ｂで受光される。
【０１２５】
一方、光ディスク１５がＣＤの場合は、一例として図１０（Ｃ）に示されるように、ＴＤ２がトラック分割線となり、第１領域ＨＡ２からの回折光は第４の受光器７０ａで受光され、第２領域ＨＢ２からの回折光は第５の受光器７０ｂで受光される。
【０１２６】
すなわち、例えばいわゆる１Ｃａｎ２ＬＤ方式の半導体レーザユニットを用いる場合のように、複数の光源を備え、各光源での発光点が異なる場合であっても、受光器からの出力信号にオフセットが生じるのを防止することができる。従って、複数種類の情報記録媒体に対して、トラックエラーに関する情報を含む信号を精度良く求めることが可能である。
【０１２７】
《第３の実施形態》
次に、本発明の第３の実施形態を図１１に基づいて説明する。
【０１２８】
この第３の実施形態は、一例として図１１（Ａ）に示されるように、６５０ｎｍ半導体レーザ５１ａと７８０ｎｍ半導体レーザ６１ａとを、１つの半導体レーザユニット６５内に配置している点に特徴を有する。以下においては、第１の実施形態との相違点を中心に説明するとともに、前述した第１の実施形態と同一若しくは同等の構成部分については同一の符号を用い、その説明を簡略化し若しくは省略するものとする。
【０１２９】
半導体レーザユニット６５は、図１１（Ａ）に示されるように、光源としての６５０ｎｍ半導体レーザ５１ａと７８０ｎｍ半導体レーザ６１ａ、それら光源を保持するステム６５ｂ、光源からのレーザ光を外部に出射するための出射窓を有し、光源を保護するカバー６５ｃなどを含んで構成されている。
【０１３０】
それに伴い、第１のカップリングレンズ５２の代わりに、６５０ｎｍ及び７８０ｎｍの２波長に対して色消しされた第３のカップリングレンズ５２’が用いられる。
【０１３１】
また、図１１（Ｂ）に示されるように、第１のホログラム素子５７は、半導体レーザユニット６５と第３のカップリングレンズ５２’との間に配置され、第１の受光器５９は、第１のホログラム素子５７からの回折光の受光位置に配置されている。
【０１３２】
次に、本第３の実施形態に係る光ピックアップ装置２３を備えた光ディスク装置２０を用いて光ディスク１５をアクセスする際のトラッキング制御について簡単に説明する。ここでは、光ディスク１５がＤＶＤの場合についてのみ説明する。
【０１３３】
光ディスク１５が光ディスク装置本体の所定位置に挿入されると、ＣＰＵ４０は、光ディスク１５の記録面の反射率に基づいて光ディスク１５の種類を判別し、ＤＶＤであることを確認すると、レーザコントロール回路２４に制御対象の光源として６５０ｎｍ半導体レーザ５１ａの選択を指示する。
【０１３４】
６５０ｎｍ半導体レーザ５１ａから出射された光束は、第１のホログラム５７を透過し、第１のカップリングレンズ５２で略平行光となり、対物レンズ６０を介して光ディスク１５の記録面に微小スポットとして集光される。
【０１３５】
光ディスク１５の記録面からの反射光束は、対物レンズ６０で再び略平行光とされ、第３のカップリングレンズ５２’を介して第１のホログラム素子５７に入射される。そして、この反射光束は第１のホログラム素子５７の第１回折領域５７ａにて回折され、その回折光は第１の受光器５９で受光される。第１の受光器５９の第１部分受光素子５９ａと第２部分受光素子５９ｂからは、それぞれの受光量に応じた電流信号が再生信号処理回路２８に出力される。
【０１３６】
再生信号処理回路２８では、前述した第１の実施形態と同様にして、トラックエラー信号ＴＥを検出する。そして、そのトラックエラー信号ＴＥに基づいてサーボコントローラ３３及びモータドライバ２７を介して光ピックアップ装置２３のトラッキングアクチュエータが駆動され、トラックずれが補正される。
【０１３７】
また、本第３の実施形態に係る光ディスク装置２０を用いて、前述した第１の実施形態と同様にして、光ディスク１５に対する記録処理及び再生処理を行うことができる。
【０１３８】
以上説明したように、本第３の実施形態に係る光ピックアップ装置によると、前述した第１の実施形態と比べて、半導体レーザユニットが２個から１個に削減されるとともに、第１のビームスプリッタ５４、第２のカップリングレンズ６２、第２のビームスプリッタ６４及び集光レンズ５８が不要となる。従って、光ピックアップ装置の小型化及び低コスト化を促進することが可能となる。さらに、組み付け及び調整作業などが簡略化できるため、作業コストを低減させることが可能となる。
【０１３９】
また、本第３の実施形態に係る光ディスク装置によると、光ピックアップ装置からの出力信号に基づいて、複数種類の情報記録媒体に対してトラックエラー信号を精度良く検出することができるので、前述した第１の実施形態と同様な効果が得られる。
【０１４０】
なお、上記第３の実施形態では、第１のホログラム素子５７は、半導体レーザユニット６５と第３のカップリングレンズ５２’との間に配置されているが、これに限らず、例えば、第３のカップリングレンズ５２’と対物レンズ６０との間に配置されても良い。
【０１４１】
また、上記第３の実施形態では、光源と第１のホログラム素子５７と第１の受光器５９とは、それぞれ個別に配置されているが、一例として図１２（Ａ）に示されるように、光源と第１のホログラム素子５７と第１の受光器５９とを一体化した、半導体レーザユニット６６を用いても良い。この半導体レーザユニット６６では、ステム６６ｂを介して６５０ｎｍ半導体レーザ５１ａ、７８０ｎｍ半導体レーザ６１ａ及び第１の受光器５９が所定の位置関係で配置され、カバー６６ｃの開口部に接して第１のホログラム素子５７が配置されている。
【０１４２】
この場合に、６５０ｎｍ半導体レーザ５１ａ及び７８０ｎｍ半導体レーザ６１ａから出射された光束は、一例として図１２（Ｂ）に示されるように、第１のホログラム素子５７、第３のカップリングレンズ５２’及び対物レンズ６０を介して光ディスク１５の記録面に集光され、光ディスク１５の記録面からの反射光束は往路と同一の光路を通って第１のホログラム素子５７に入射される。そして、その反射光束は前述した第１の実施形態と同様にして第１のホログラム素子５７で回折され、第１の受光器５９で受光される。第１の受光器５９からは、その受光量に応じた電流信号が再生信号処理回路２８に出力される。
【０１４３】
これによって、光源、第１のホログラム５７及び第１の受光器５９それぞれの間隔を狭くすることができ、光ピックアップ装置の小型化を促進することが可能となる。また、組み付け及び調整作業などを簡略化することができるため、作業コストが低減され、低コスト化を促進することが可能となる。
【０１４４】
なお、上記各実施形態では、光源が２波長の場合について説明しているが、本発明がこれに限定されるものではなく、３波長以上の光源を備える場合であっても良い。その場合には、勿論、波長毎に対応する回折領域が配置されたホログラム素子が用いられることとなる。
【０１４５】
また、上記各実施形態では、ホログラム素子として、例えば有機系の延伸膜からなる薄い位相差膜にエッチング等で格子が形成され、偏光方向によって回折効率が異なるように設定された偏光ホログラムを用いても良い。例えば図１３に示されるように、上述した第３の実施形態において、ホログラム素子５７の代わりに偏光ホログラム素子７１を用い、そして、第３のカップリングレンズ５２’と対物レンズ６０との間の光路上に、光束の偏光方向を変換するためのλ／４板５５を配置しても良い。ここで、一例として、偏光ホログラム素子７１はＳ偏光の光束に対しては低い回折効率を有し、Ｐ偏光の光束に対しては高い回折効率を有し、光源からＳ偏光の光束が出射される場合について簡単に説明する。
【０１４６】
半導体レーザユニット６５から出射されたＳ偏光の光束は、偏光ホログラム素子７１がＳ偏光の光束に対して低い回折効率を有するため、その殆どは偏光ホログラム素子７１を透過し、第３のカップリングレンズ５２’にて略平行光とされ、さらにλ／４板５５にて円偏光とされた後、対物レンズ６０を介して光ディスク１５の記録面に微小スポットとして集光される。
【０１４７】
光ディスク１５の記録面にて反射した反射光は、往路とは反対回りの円偏光となり、対物レンズ６０で再び略平行光とされ、λ／４板５５にて円偏光からＰ偏光に変換された後、第３のカップリングレンズ５２’を介して偏光ホログラム素子７１に照射される。偏光ホログラム素子７１はＰ偏光の光束に対しては高い回折効率を有するため、反射光は偏光ホログラム素子７１にて選択的に回折される。そして、その回折光は第１の受光器５９で受光される。
【０１４８】
このように、光源から出射される光束の偏光方向に対して低い回折効率を有する偏光ホログラム素子を用いることにより、光源から出射された光束は偏光ホログラム素子を高効率で透過するため、光ディスク１５の記録面に照射される光の光量低下が極めて少なくなる。従って、記録速度の高速化に対応することが容易となる。
【０１４９】
また、戻り光束の偏光方向に対して高い回折効率を有する偏光ホログラム素子を用いることにより、戻り光束の回折時における光量のロスが減少するため、第１の受光器５９での受光量が増加し、結果として信号のＳ／Ｎ比を向上させることができる。従って、トラックエラーに関する情報を含む信号を精度良く求めることが可能となる。
【０１５０】
一般に偏光ホログラム素子は複屈折性を有する材料を格子形状に加工することにより、あるいは波長よりピッチの小さい格子を加工することにより製造することができる。複屈折性を有する材料としてはＬｉＮｂＯ_３結晶や液晶があるが、薄い膜で複屈折性を有する透明な有機材料の延伸膜、例えばポリイミドやＰＥＴは、Δｎ＝０．０６〜０．１程度の複屈折性を有し、屈折率が１．６程度であるため、格子加工後のオーバーコート材料も安価なものを用いることができ、低コスト化が容易である。
【０１５１】
【発明の効果】
以上説明したように、本発明に係る光ピックアップ装置によれば、大型化及び高コスト化を招くことなく、複数種類の情報記録媒体に対応可能で、トラックエラーに関する情報を精度良く安定して求めることができるという効果がある。
【０１５２】
また、本発明に係る光ディスク装置によれば、大型化及び高コスト化を招くことなく、複数種類の情報記録媒体に対応可能で、正確なアクセスを安定して行うことができるという効果がある。
【図面の簡単な説明】
【図１】本発明の第１の実施形態の光ディスク装置の構成を示すブロック図である。
【図２】図１の光ピックアップ装置における光学系の概略構成を示す図である。
【図３】図２における半導体レーザユニットを説明するための図である。
【図４】図４（Ａ）〜図４（Ｃ）は、それぞれ第１のホログラム素子の構成を説明するための図であり、図４（Ｄ）は第１の受光器の構成を説明するための図である。
【図５】第１の受光器からの出力信号に基づいて検出されるトラックエラー信号ＴＥと回折領域の幅Ｄとの関係を説明するための図である。
【図６】図６（Ａ）は第１のホログラム素子での回折方向が波長によって異なる場合を説明するための図であり、図６（Ｂ）は±１次光を含む回折光を受光する場合の受光器の大きさを説明するための図である。
【図７】第１のホログラム素子をビームスプリッタと対物レンズとの間に配置した場合の一例を説明するための図である。
【図８】図８（Ａ）〜図８（Ｃ）は、それぞれ回折領域の形状と光スポットの形状との関係を説明するための図である。
【図９】図９（Ａ）及び図９（Ｂ）は、それぞれ第２の実施形態におけるホログラム素子を説明するための図である。
【図１０】図１０（Ａ）〜図１０（Ｃ）は、それぞれホログラム素子が２つのトラック分割線を有する場合の一例を説明するための図である。
【図１１】図１１（Ａ）及び図１１（Ｂ）は、それぞれ６５０ｎｍ半導体レーザと７８０ｎｍ半導体レーザとが１つの半導体レーザユニットに一体化されている一例を説明するための図である。
【図１２】図１２（Ａ）及び図１２（Ｂ）は、それぞれ２つの半導体レーザと受光器とホログラム素子とが一体化されている一例を説明するための図である。
【図１３】ホログラム素子として偏光ホログラムを用いた一例を説明するための図である。
【図１４】従来例におけるトラックエラー信号ＴＥとホログラムの幅Ｄとの関係を説明するための図である。
【符号の説明】
１５…光ディスク（情報記録媒体）、２０…光ディスク装置、２３…光ピックアップ装置、４０…ＣＰＵ（処理装置）、５７…第１のホログラム素子（ホログラム素子）、５９…第１の受光素子（光検出器）、６０…対物レンズ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup device and an optical disk device, and more specifically, irradiates a recording surface with light to a plurality of types of information recording media, receives reflected light from the recording surface, and reproduces information. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device suitable for performing and an optical disk device provided with the optical pickup device.
[0002]
[Prior art]
In an optical disk device, information is recorded on an information recording medium such as an optical disk by irradiating a recording surface on which a spiral or concentric track is formed with a small spot of laser light, and reflection from the recording surface is performed. Information is reproduced based on light. The optical disk device is provided with an optical pickup device for irradiating the recording surface of the information recording medium with laser light and receiving reflected light from the recording surface.
[0003]
The optical pickup device includes a light source and an objective lens, guides the light beam emitted from the light source to the recording surface of the information recording medium, and guides the return light beam reflected by the recording surface to a predetermined light receiving position, and light receiving The light receiving element etc. which are arrange | positioned are provided. This light receiving element outputs not only the reproduction information of the data recorded on the recording surface but also a signal including information necessary for position control of the optical pickup device itself and the objective lens. For example, in so-called tracking control in which the objective lens is driven in a direction (tracking direction) perpendicular to the tangential direction of the track in order to accurately irradiate a predetermined position on the recording surface with a minute spot, the groove of the track is detected from the output signal of the light receiving element The intensity difference between two diffraction patterns (hereinafter referred to as “track pattern”) generated due to the above is detected as a track error signal (track servo signal) and fed back to the position control of the objective lens.
[0004]
In recent years, a DVD (Digital Versatile Disc) having a recording capacity that is dramatically larger than a CD (Compact Disc) has been generalized as an information recording medium. A laser beam having a wavelength of 780 nm is used to perform recording and reproduction on a CD, and a laser beam having a wavelength of 650 nm is used to perform recording and reproduction on a DVD. The optical disc apparatus of DVD and the optical disc apparatus for DVD are used independently as peripheral devices of information equipment such as personal computers.
[0005]
Thereafter, with the downsizing and weight reduction of information equipment, the need for an optical disc apparatus capable of accessing both CDs and DVDs has increased. In this case, the optical pickup device emits a laser beam having a wavelength of 650 nm as a light source (hereinafter referred to as “650 nm light source”) and a laser beam having a wavelength of 780 nm in order to support both DVD and CD. A semiconductor laser (hereinafter referred to as “780 nm light source”), and an optical system for detecting each laser beam. However, if the optical system for 650 nm and the optical system for 780 nm are individually arranged, the optical pickup device becomes large, which is one of the factors that hinder the miniaturization of the optical disk device. Hereinafter, an optical pickup device provided with a plurality of light sources having different wavelengths is also referred to as a “multi-wavelength optical pickup device”.
[0006]
Therefore, development for reducing the size of the multi-wavelength optical pickup device has been actively carried out, and as one of them, a hologram element constituting an optical system for guiding the return light beam reflected by the recording surface to the light receiving element described above. Japanese Patent Application Laid-Open No. 2000-76688 discloses a technique for reducing the number of components and reducing the cost by making the light flux common to the light fluxes of the respective wavelengths.
[0007]
In Japanese Patent Application Laid-Open No. 2000-76688, by using one hologram element in which a plurality of holograms optimized for each wavelength are combined, a returning light beam is guided to a light receiving element even for light beams having different wavelengths. A multi-wavelength optical pickup device capable of achieving the above has been disclosed.
[0008]
[Problems to be solved by the invention]
However, in the multi-wavelength optical pickup device disclosed in Japanese Patent Laid-Open No. 2000-76688 described above, a plurality of holograms optimized for each wavelength are mutually tangential to the track as shown in FIG. Hologram elements arranged so as to be adjacent to a direction corresponding to a direction orthogonal to the so-called radial direction are used. Even if the size (spot diameter) of the light spot on the light receiving surface of the hologram element is constant, When the width D of the hologram changes, the area of the hologram corresponding to the wavelength in the light spot changes, so that the amount of light received by the light receiving element changes greatly. In some cases, the amount of received light becomes extremely small. Therefore, for example, as shown in FIG. 14, the track error signal TE detected based on the output signal of the light receiving element greatly varies depending on the width D of the hologram. Conversely, even if the hologram width D is constant, if the spot diameter on the light receiving surface of the hologram element changes, the amount of light received by the light receiving element similarly changes, and the detected track error signal TE changes greatly. Is meant to do. In general, the spot diameter depends on the groove spacing and depth of the track, and is constantly changing. Therefore, the detection accuracy of the track error signal is lowered, and the tracking control may become unstable. .
[0009]
The present invention has been made under such circumstances, and a first object of the present invention is to deal with a plurality of types of information recording media without incurring an increase in size and cost, and accurately information on track errors. An object of the present invention is to provide an optical pickup device that can be obtained stably.
[0010]
A second object of the present invention is to provide an optical disc apparatus that can deal with a plurality of types of information recording media and can perform accurate access stably without increasing the size and cost. It is in.
[0011]
[Means for Solving the Problems]
According to the first aspect of the present invention, the light used for performing at least reproduction of information recording, reproduction, and erasing with respect to a plurality of types of information recording media having a recording surface on which spiral or concentric tracks are formed. A plurality of light sources that are individually associated with the plurality of information recording media and selectively emit light beams having different wavelengths; and a recording surface of the information recording medium that corresponds to each of the light beams. An objective lens that focuses light on the recording surface, and is disposed on an optical path of each return light beam that is reflected by the recording surface and passes through the objective lens, the light receiving surface of the objective lens along a first direction corresponding to the tangential direction of the track. An optical system including a hologram element in which a plurality of diffraction regions corresponding to each wavelength are arranged in a predetermined order; and light detection for receiving diffracted light from the hologram element at a predetermined light receiving position When; an optical pickup apparatus comprising a.
[0012]
According to this, the light beam emitted from the light source alternatively selected according to the type of the information recording medium is condensed on the recording surface of the information recording medium via the objective lens or the like. The return light beam reflected by the recording surface is incident on the hologram element. The return light beam is diffracted in a predetermined direction by at least one diffraction region corresponding to the wavelength of the return light beam (hereinafter also referred to as “corresponding diffraction region” as appropriate) among a plurality of diffraction regions constituting the hologram element. . Here, since the diffractive region is arranged along the first direction in the hologram element, even if the beam diameter of the return light beam changes due to changes in the groove interval and depth of the track, The change in the area of the corresponding diffraction region is small, and as a result, the change in the amount of light received by the photodetector is extremely small. That is, the information regarding the track error included in the output signal of the photodetector is stabilized. Moreover, since it is possible to deal with a plurality of return light beams having different wavelengths with one hologram element, it is possible to reduce the component cost. Furthermore, since work such as assembly and adjustment can be simplified, work costs can be reduced. Therefore, it is possible to deal with a plurality of types of information recording media without causing an increase in size and cost, and information relating to track errors can be obtained accurately and stably.
[0013]
In this case, as in the optical pickup device according to claim 2, the length in the first direction in each diffraction region is equal to or shorter than the length in the second direction orthogonal to the first direction. It can be. In such a case, the size of the hologram element can be made as small as possible in accordance with the shape of the light spot.
[0014]
In the optical pickup device according to any one of claims 1 and 2, as in the optical pickup device according to claim 3, the beam diameter at the light receiving surface is minimized at the center of the light receiving surface of the hologram element. It can be assumed that a diffraction region corresponding to the wavelength of the light beam is arranged. In such a case, even if a return light beam having a small spot diameter is incident, the photodetector can obtain a diffracted light beam having a light quantity necessary for obtaining information on the track error. That is, it is possible to obtain a diffracted light with a stable light amount regardless of the beam diameter of the return light beam.
[0015]
In each of the optical pickup devices according to claims 1 to 3, the length of the photodetector in the third direction corresponding to the first direction is diffracted as in the optical pickup device according to claim 4. The order m of light (≧ 1), the wavelength λ of the return beam, the distance L between the hologram element and the light receiving surface of the photodetector, the refractive index n of the hologram element, and the length of the diffraction region in the third direction By using the length d, it can be set to be not less than twice the value represented by mλL / (2nd). In such a case, diffracted light including not only 0th-order diffracted light but also higher-order diffracted light can be received. As a result, the amount of received light is increased, so that the S / N ratio of the signal is improved. In other words, it is possible to accurately obtain a signal including information on track errors. In addition, since the shape of the photodetector can be designed to an optimum shape according to the order of the diffracted light received by the light receiving surface, the downsizing of the optical pickup device can be promoted.
[0016]
In this case, as in the optical pickup device according to claim 5, the length of the photodetector in the third direction is longer than the length in the fourth direction orthogonal to the third direction. can do.
[0017]
6. The optical pickup device according to claim 1, wherein the hologram element includes an optical path of light from the light source toward the information recording medium, and the information recording medium, as in the optical pickup device according to claim 6. It can be assumed that it is arranged on the common optical path of the optical path of the return light reflected by. In such a case, the number of parts constituting the optical system can be reduced, and the downsizing and cost reduction of the optical pickup device can be promoted.
[0018]
In this case, as in the optical pickup device according to claim 7, a polarization direction of light directed from the light source toward the information recording medium is different from a polarization direction of return light reflected by the information recording medium, The hologram element can be a hologram element having different diffraction efficiency depending on the polarization direction of incident light. In such a case, for example, when the diffraction efficiency of the hologram element is set to be low with respect to the polarization direction of the light beam emitted from the light source and high with respect to the polarization direction of the return light beam, the light is emitted from the light source. Since the emitted light beam passes through the hologram element with high efficiency, the amount of light irradiated onto the recording surface of the information recording medium is extremely reduced. Therefore, it becomes easy to cope with an increase in recording speed. Further, since the return light beam is efficiently diffracted by the hologram element, the loss of light quantity at the hologram element is reduced, and as a result, the amount of light received by the photodetector is increased, and the S / S in the output signal from the photodetector is increased. The N ratio can be improved. Therefore, it is possible to accurately obtain a signal including information regarding the track error.
[0019]
In each of the optical pickup devices according to any one of claims 1 to 7, as in the optical pickup device according to claim 8, the hologram element causes the return light beams to pass through substantially the same position on a detection surface of the photodetector. It can be diffracted toward. In such a case, since the photodetector can be made small, it is possible to promote downsizing and cost reduction of the optical pickup device.
[0020]
In this case, as in the optical pickup device according to claim 9, the photodetector includes at least a two-divided light receiving element divided into two by a dividing line in a direction corresponding to the first direction. Can do.
[0021]
Each optical pickup device according to any one of claims 1 to 7, wherein the hologram element diffracts each return light beam in at least two different directions according to the wavelength thereof, as in the optical pickup device according to claim 10. Can be. In such a case, it is not necessary to make the position accuracy of the photodetector strict, and operations such as assembly and adjustment can be simplified, and the operation cost can be reduced.
[0022]
In this case, as in the optical pickup device according to claim 11, the photodetector includes a plurality of light receiving elements that respectively receive the diffracted lights diffracted in the different directions, and each of the light receiving elements is at least A two-divided light receiving element divided into two by a dividing line in a direction corresponding to the first direction can be included.
[0023]
The optical pickup device according to any one of claims 1 to 7, wherein, as in the optical pickup device according to claim 12, the hologram element includes two light receiving regions each having a diffraction line divided by a dividing line in the first direction. The diffraction direction of the return light beam may be different for each light receiving region. In such a case, it is not necessary to make the position accuracy of the photodetector strict, and operations such as assembly and adjustment can be simplified, and the operation cost can be reduced.
[0024]
In this case, as in the optical pickup device according to the thirteenth aspect, each of the diffraction regions can be divided corresponding to the optical axis position of the return light beam having the corresponding wavelength. In such a case, for example, when a so-called 1Can2LD type semiconductor laser unit is used, even if a plurality of light sources are provided and the light emission points of the respective light sources are different, there is an offset in the output signal from the photodetector. It can be prevented from occurring. Therefore, it is possible to accurately obtain a signal including information regarding a track error for a plurality of types of information recording media.
[0025]
14. Each optical pickup device according to claim 12 and claim 13, wherein the optical detector receives a plurality of diffracted lights diffracted in the different directions as in the optical pickup device according to claim 14. An element can be provided.
[0026]
15. Each optical pickup device according to claim 1-14, wherein the photodetector is housed in the same housing as the plurality of light sources and packaged, as in the optical pickup device according to claim 15. Can be. In such a case, the intervals between the light source, the hologram element, and the photodetector can be reduced, and the downsizing of the optical pickup device can be promoted. In addition, since assembly and adjustment operations can be simplified, the operation cost is reduced, and cost reduction can be promoted.
[0027]
In each of the optical pickup devices according to claims 1 to 14, the hologram element and the photodetector can be integrated as in the optical pickup device according to claim 16. In such a case, the distance between the hologram element and the photodetector can be narrowed, and the downsizing of the optical pickup device can be promoted. In addition, since assembly and adjustment operations can be simplified, the operation cost is reduced, and cost reduction can be promoted.
[0028]
Each optical pickup device according to any one of claims 1 to 14, wherein the hologram element and the photodetector are housed in the same housing as the plurality of light sources and packaged, as in the optical pickup device according to claim 17. Can be that. In such a case, the intervals between the light source, the hologram element, and the photodetector can be reduced, and the downsizing of the optical pickup device can be promoted. In addition, since assembly and adjustment operations can be simplified, the operation cost is reduced, and cost reduction can be promoted.
[0029]
The invention described in claim 18 is an optical disk apparatus that performs at least reproduction among information recording, reproduction, and erasure on a plurality of types of optical disks, and the optical pickup apparatus according to any one of claims 1 to 17; And a processing device that performs at least reproduction among recording, reproduction, and erasing of the information using an output signal of the photodetector constituting the optical pickup device.
[0030]
According to this, since the optical pickup device according to any one of claims 1 to 17 can stably obtain information regarding accurate track errors with respect to a plurality of types of optical recording media, the processing device includes the optical pickup device. Tracking control can be performed with high accuracy. Accordingly, as a result, it is possible to deal with a plurality of types of optical recording media, and it is possible to stably reproduce accurate information. Further, the downsizing of the optical pickup device can also promote the downsizing of the optical disk device itself and the reduction of power consumption. For example, when it is used as a portable device, it is easy to carry and can be used for a long time. It becomes possible.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
<< First Embodiment >>
[0032]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
[0033]
FIG. 1 shows a schematic configuration of an optical disc device 20 according to a first embodiment provided with an optical pickup device according to the present invention.
[0034]
The optical disk apparatus 20 shown in FIG. 1 includes a spindle motor 22, an optical pickup apparatus 23, a laser control circuit 24, an encoder 25, a motor driver 27, a reproduction signal processing circuit 28, a servo controller 33, and the like. A buffer RAM 34, a buffer manager 37, an interface 38, a ROM 39, a CPU 40, a RAM 41, and the like are provided. Note that the arrows in FIG. 1 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block.
[0035]
The optical pickup device 23 is a device for irradiating a recording surface on which a spiral or concentric track of the optical disk 15 is formed with laser light and receiving reflected light from the recording surface. The configuration of the optical pickup device 23 will be described in detail later.
[0036]
The reproduction signal processing circuit 28 converts a current signal, which is an output signal of the optical pickup device 23, into a voltage signal, and based on the voltage signal, a wobble signal, an RF signal including reproduction information, and a servo signal (focus error signal, track Error signal). Then, the reproduction signal processing circuit 28 extracts address information, a synchronization signal, and the like from the wobble signal. The address information extracted here is output to the CPU 40, and the synchronization signal is output to the encoder 25. Further, the reproduction signal processing circuit 28 performs error correction processing or the like on the RF signal and then stores it in the buffer RAM 34 via the buffer manager 37. The servo signal is output from the reproduction signal processing circuit 28 to the servo controller 33.
[0037]
The servo controller 33 generates a control signal for controlling the optical pickup device 23 based on the servo signal. The control signal is output from the servo controller 33 to the motor driver 27.
[0038]
The buffer manager 37 manages input / output of data to / from the buffer RAM 34, and notifies the CPU 40 when the accumulated data amount reaches a predetermined value.
[0039]
The motor driver 27 controls the optical pickup device 23 based on an instruction from the CPU 40 and a control signal from the servo controller 33. Further, the motor driver 27 controls the spindle motor 22 so that the linear velocity of the optical disk 15 is constant based on an instruction from the CPU 40.
[0040]
The encoder 25 takes out data stored in the buffer RAM 34 based on an instruction from the CPU 40 via the buffer manager 37, adds an error correction code, etc., and creates write data to the optical disk 15. The encoder 25 outputs write data to the laser control circuit 24 in synchronization with the synchronization signal from the reproduction signal processing circuit 28 based on an instruction from the CPU 40.
[0041]
The laser control circuit 24 controls the output of the laser light emitted from the optical pickup device 23 based on the write data from the encoder 25. Note that, in the laser control circuit 24, one of two light sources of the optical pickup device 23, which will be described later, is controlled based on an instruction from the CPU 40.
[0042]
The interface 38 is a bidirectional communication interface with a host (for example, a personal computer) and conforms to standard interfaces such as ATAPI (AT Attachment Packet Interface) and SCSI (Small Computer System Interface).
[0043]
The ROM 39 stores a program written in a code readable by the CPU 40.
[0044]
The CPU 40 controls the operation of each unit according to the program stored in the ROM 39 and temporarily stores data necessary for the control in the RAM 41.
[0045]
Next, the configuration and the like of the optical pickup device 23 will be described with reference to FIGS.
[0046]
As shown in FIG. 2, the optical pickup device 23 includes a first semiconductor laser unit 51, a second semiconductor laser unit 61, a first coupling lens 52, a second coupling lens 62, and a first beam. The splitter 54, the second beam splitter 64, the objective lens 60, the condenser lens 58, the first hologram element 57, the first light receiver 59 as a light detector, and the drive system (focusing actuator, tracking actuator and seek motor). (Both are not shown).
[0047]
As shown in FIG. 3 as an example, the first semiconductor laser unit 51 includes a semiconductor laser chip (hereinafter referred to as “650 nm semiconductor laser”) 51 a and a 650 nm semiconductor laser that emits laser light having a wavelength of 650 nm as a light source. It includes a stem 51b that holds 51a, a cover 51c that has an opening for emitting laser light from the 650 nm semiconductor laser 51a to the outside (hereinafter referred to as an “emission window”), and protects the 650 nm semiconductor laser 51a. Has been.
[0048]
The second semiconductor laser unit 61 includes a semiconductor laser chip (hereinafter referred to as “780 nm semiconductor laser”) that emits laser light having a wavelength of 780 nm as a light source, a stem that holds a 780 nm semiconductor laser, and a laser from the 780 nm semiconductor laser. It has an opening for emitting light to the outside, and includes a cover (not shown) for protecting the 780 nm semiconductor laser.
[0049]
In FIG. 2, for the sake of convenience, the emission direction of the laser light from the first semiconductor laser unit 51 is taken as the X-axis direction, and the emission direction of the laser light from the second semiconductor laser unit 61 is taken as the Z-axis direction. Further, the light beam emitted from the first semiconductor laser unit 51 is also referred to as “first outgoing light beam”, and the light beam emitted from the second semiconductor laser unit 61 is also referred to as “second outgoing light beam”.
[0050]
As shown in FIG. 4A, in the light beam (reflected light beam) RB reflected by the recording surface of the optical disc 15, the direction corresponding to the tangential direction of the track TR is set in the tangential direction of the reflected light beam (first Direction, third direction), and the direction orthogonal to the tangential direction are referred to as radial directions (second direction, fourth direction). Hereinafter, the radial direction of the reflected light beam is referred to as “R direction”, and the tangential direction of the reflected light beam is referred to as “T direction”. Further, the reflected light beam reflected from the recording surface by the first outgoing light beam is also referred to as “first reflected light beam”, and the reflected light beam from the second outgoing light beam reflected from the recording surface is also referred to as “second reflected light beam”.
[0051]
As an example, as shown in FIG. 4B, the first hologram element 57 includes a plurality of first diffraction regions 57a having high diffraction efficiency selectively with respect to a light beam having a wavelength of 650 nm, and a wavelength of 780 nm. A plurality of second diffraction regions 57b having high diffraction efficiency selectively with respect to the light beam are arranged with the R direction as a boundary line. Further, the diffracted light of the first reflected light beam diffracted by the first diffractive region 57a (hereinafter referred to as “first diffracted light” as appropriate) and the second reflected light beam diffracted by the second diffractive region 57b. The hologram patterns of the diffraction regions 57a and 57b are formed so that light (hereinafter referred to as “second diffracted light” as appropriate) is received at the same position on the light receiving surface of the light receiver 59.
[0052]
Furthermore, in this embodiment, as shown in FIG. 4B and FIG. 4C as an example, the light spot DS1 by the first diffracted light has a spot diameter that is larger than the light spot DS2 by the second diffracted light. Since it is small, the first diffraction region 57 a is arranged in the central portion of the first hologram element 57.
[0053]
As shown in FIG. 4D, the first light receiver 59 is divided into two by a T-direction dividing line and is divided into two divided light receiving elements for detecting a track error (first partial light receiving element 59a, second partial light receiving). An element 59b) is included.
[0054]
Next, tracking control when accessing the optical disk 15 using the optical disk apparatus 20 configured as described above will be described.
[0055]
First, the case where the optical disk 15 is a DVD will be described.
[0056]
When the optical disk 15 is inserted into a predetermined position of the optical disk apparatus main body, the CPU 40 determines the type of the optical disk 15 based on the reflectance of the recording surface of the optical disk 15 and confirms that it is a DVD. The selection of the 650 nm semiconductor laser 51a as the light source to be controlled is instructed.
[0057]
The light beam emitted from the 650 nm semiconductor laser 51 a becomes substantially parallel light by the first coupling lens 52, passes through the first beam splitter 54 and the second beam splitter 64, and passes through the objective lens 60 to the optical disk 15. It is condensed as a minute spot on the recording surface.
[0058]
The reflected light beam from the recording surface of the optical disk 15 is converted into substantially parallel light again by the objective lens 60, its optical axis is bent in the −Z direction by the second beam splitter 64, and then the first light beam is passed through the condenser lens 58. 1 is incident on one hologram element 57. The reflected light beam is selectively diffracted by the first diffraction region 57 a of the first hologram 57, and the diffracted light is received by the first light receiver 59. From the first partial light receiving element 59 a and the second partial light receiving element 59 b of the first light receiver 59, currents (current signals) corresponding to the respective received light amounts are output to the reproduction signal processing circuit 28.
[0059]
In the reproduction signal processing circuit 28, the current signals from the first partial light receiving element 59a and the second partial light receiving element 59b are converted into voltage signals, and the track error signal TE is detected based on the following equation (1).
[0060]
TE = (Sa-Sb) / (Sa + Sb) ...... (1)
[0061]
In the above equation (1), Sa is an output signal of the first partial light receiving element 59a, and Sb is an output signal of the second partial light receiving element 59b.
[0062]
Then, the reproduction signal processing circuit 28 outputs the track error signal TE to the servo controller 33. The servo controller 33 drives the tracking actuator of the optical pickup device 23 via the motor driver 27 based on the track error signal TE from the reproduction signal processing circuit 28 to correct the track deviation.
[0063]
Next, the case where the optical disk 15 is a CD will be described.
[0064]
When the optical disc 15 is inserted into a predetermined position of the optical disc apparatus main body, the CPU 40 determines the type of the optical disc 15 based on the reflectance of the recording surface of the optical disc 15 and confirms that it is a CD. The selection of the 780 nm semiconductor laser 61a as the light source to be controlled is instructed.
[0065]
The light beam emitted from the 780 nm semiconductor laser 61a becomes substantially parallel light by the second coupling lens 62, and its optical axis is bent in the + X direction by the first beam splitter 54, and then the second beam splitter 64 is passed through. The light passes through and is condensed as a minute spot on the recording surface of the optical disc 15 through the objective lens 60.
[0066]
The reflected light beam from the recording surface of the optical disk 15 is incident on the first hologram element 57 in the same manner as in the above-described DVD. The reflected light beam is diffracted by the second diffraction region 57 b of the first hologram 57, and the diffracted light is received by the first light receiver 59. From the first partial light receiving element 59 a and the second partial light receiving element 59 b of the first light receiver 59, current signals corresponding to the respective received light amounts are output to the reproduction signal processing circuit 28.
[0067]
The reproduction signal processing circuit 28 detects the track error signal TE based on the above equation (1) in the same manner as in the case of the DVD described above. Based on the track error signal TE, the tracking actuator of the optical pickup device 23 is driven via the servo controller 33 and the motor driver 27 to correct the track deviation.
[0068]
Next, a processing operation when data is recorded on the optical disk 15 using the optical disk device 20 described above will be briefly described.
[0069]
When receiving a recording request from the host, the CPU 40 outputs a control signal for controlling the rotation of the spindle motor 22 to the motor driver 27 based on the recording speed, and also indicates that the recording request has been received from the host. 28 is notified. When the rotation of the optical disk 15 reaches a predetermined linear velocity, an output signal from the optical pickup device 23 is output to the reproduction signal processing circuit 28.
[0070]
The reproduction signal processing circuit 28 acquires address information based on the output signal from the optical pickup device 23 and notifies the CPU 40 of the address information. Further, the reproduction signal processing circuit 28 detects the track error signal TE as described above based on the output signal from the optical pickup device 23. Based on the track error signal TE, tracking control is performed as described above. Further, the reproduction signal processing circuit 28 detects a focus error signal based on the output signal from the optical pickup device 23 and outputs it to the servo controller 33. The servo controller 33 drives the focusing actuator of the optical pickup device 23 via the motor driver 27 based on the focus error signal from the reproduction signal processing circuit 28, and corrects the focus shift. That is, so-called focus control is performed.
[0071]
When receiving data from the host, the CPU 40 stores the data in the buffer RAM 34 via the buffer manager 37. When the amount of data stored in the buffer RAM 34 exceeds a predetermined value, the buffer manager 37 notifies the CPU 40.
[0072]
Upon receiving the notification from the buffer manager 37, the CPU 40 instructs the encoder 25 to create write data. Based on the address information from the reproduction signal processing circuit 28, the CPU 40 outputs a signal that instructs the seek operation of the optical pickup 23 to the motor driver 27 so that the optical pickup 23 is positioned at a predetermined writing start point.
[0073]
When the CPU 40 determines that the position of the optical pickup device 23 is the writing start point based on the address information from the reproduction signal processing circuit 28, the CPU 40 notifies the encoder 25. The encoder 25 records write data on the optical disk 15 via the laser control circuit 24 and the optical pickup device 23. Until the recording process is completed, the reproduction signal processing circuit 28 detects the focus error signal and the track error signal TE based on the output signal from the optical pickup device 23 as described above, and the servo controller 33 and the motor driver 27. The focus shift and the track shift are corrected at any time via the.
[0074]
Next, a processing operation when reproducing data recorded on the optical disc 15 using the optical disc apparatus 20 described above will be briefly described.
[0075]
When receiving a reproduction request from the host, the CPU 40 outputs a control signal for controlling the rotation of the spindle motor 22 to the motor driver 27 based on the reproduction speed, and also indicates that the reproduction request has been received from the host. 28 is notified. When the rotation of the optical disk 15 reaches a predetermined linear velocity, an output signal from the optical pickup device 23 is output to the reproduction signal processing circuit 28.
[0076]
The reproduction signal processing circuit 28 acquires address information based on the output signal from the optical pickup device 23 and notifies the CPU 40 of the address information. Further, the reproduction signal processing circuit 28 detects the track error signal TE as described above based on the output signal from the optical pickup device 23. Based on the track error signal TE, tracking control is performed as described above. Further, the reproduction signal processing circuit 28 detects a focus error signal based on the output signal from the optical pickup device 23. Based on the focus error signal, focus control is performed as described above.
[0077]
Based on the address information from the reproduction signal processing circuit 28, the CPU 40 outputs a signal for instructing a seek operation so that the optical pickup device 23 is positioned at a predetermined reading start point to the motor driver 27.
[0078]
Based on the address information from the reproduction signal processing circuit 28, the CPU 40 checks whether or not it is a reading start point. If the CPU 40 determines that the position of the optical pickup device 23 is a reading start point, the CPU 40 notifies the reproduction signal processing circuit 28. Notice. The reproduction signal processing circuit 28 detects an RF signal from the output signal of the optical pickup device 23, performs error correction processing, etc., and then stores it in the buffer RAM 34.
[0079]
The buffer manager 37 transfers the data stored in the buffer RAM 34 to the host via the interface 38 when the data is prepared as sector data.
[0080]
Until the reproduction process is completed, the reproduction signal processing circuit 28 detects the focus error signal and the track error signal TE based on the output signal from the optical pickup device 23 as described above, and the servo controller 33 and the motor driver 27. The focus shift and the track shift are corrected at any time via the.
[0081]
As is apparent from the above description, in the optical disc apparatus according to the first embodiment, the reproduction signal processing circuit 28 and the CPU 40 constitute a processing apparatus.
[0082]
As described above, according to the optical pickup device according to the first embodiment, the first hologram element 57 includes a plurality of first diffraction regions that selectively have high diffraction efficiency with respect to a light beam having a wavelength of 650 nm. 57a and a plurality of second diffraction regions 57b having a high diffraction efficiency selectively with respect to a light beam having a wavelength of 780 nm, and each diffraction region is arranged such that the boundary line is parallel to the R direction. ing. Thereby, as shown in FIG. 5 as an example, even if the width (length in the T direction) D of the diffraction region changes, there is little change in the area of the diffraction region corresponding to the wavelength of the returning light beam in the light spot, As a result, the change in the amount of light received by the first light receiver 59 is extremely small, and the track error signal TE detected by the reproduction signal processing circuit 28 is substantially constant. That is, even if the beam diameter of the return light beam changes due to changes in the track groove spacing and depth, the first light receiver 59 stably outputs a signal including information on the track error.
[0083]
In the first embodiment, the first hologram element 57 can handle both a light beam having a wavelength of 650 nm and a light beam having a wavelength of 780 nm, so that the number of optical components can be reduced. It becomes possible to promote downsizing and cost reduction of the optical pickup device.
[0084]
Furthermore, in the first embodiment, since the diffraction area corresponding to the light beam having a small beam diameter is arranged at the central portion of the first hologram element 57, the beam diameter of the first hologram element 57 is set in the first hologram element 57. Even when a small return light beam is incident, the first light receiver 59 can obtain a diffracted light beam having a light quantity necessary for obtaining a signal including information on track errors. That is, it is possible to obtain a stable amount of diffracted light from the first hologram element 57 regardless of the size of the return beam.
[0085]
Further, in the first embodiment, the hologram pattern of the diffraction area is formed so that the first diffracted light and the second diffracted light are received at substantially the same position on the light receiving surface of the first light receiver 59, respectively. Therefore, even for light sources having different wavelengths, it is possible to obtain a signal including information on track errors with a single light receiving element. Therefore, the number of optical components can be reduced, and the downsizing and cost reduction of the optical pickup device can be promoted.
[0086]
Furthermore, according to the optical disc apparatus according to the first embodiment, since a track error signal can be accurately detected for a plurality of types of optical discs based on an output signal from the optical pickup device, a plurality of types can be obtained as a result. Therefore, accurate access to the information recording medium can be performed stably.
[0087]
In the above-described embodiment, the case where the arithmetic processing of the above expression (1) is performed by the reproduction signal processing circuit 28 is described. However, the present invention is not limited to this, and the optical pickup device 23 has the above expression (1). An arithmetic circuit for performing arithmetic processing may be added. As a result, the reproduction signal processing circuit 28 can be simplified, wiring work at the time of assembly can be facilitated, and workability can be improved and work cost can be reduced.
[0088]
In the first embodiment, the case where the first diffracted light and the second diffracted light are received by the first hologram element 57 at substantially the same position on the light receiving surface of the light receiver 59 has been described. However, the present invention is not limited to this. For example, as shown in FIG. 6A, instead of the first hologram element 57, a second hologram element 57 ′ having different diffraction directions of the first diffracted light and the second diffracted light may be used. In this case, instead of the first light receiver 59, a second light receiver 69a for receiving the first diffracted light and a third light receiver 69b for receiving the second diffracted light are arranged. The Rukoto. The second light receiver 69a and the third light receiver 69b, like the first light receiver 59, each include a two-divided light receiving element for track error detection divided into two by a dividing line in the T direction. It is configured. In this case, in the reproduction signal processing circuit 28, when the optical disk 15 is a DVD, the following signals are output from the above-mentioned two-divided light receiving elements constituting the second light receiver 69a (referred to as S1a and S2a). The track error signal TEa is detected from the equation (2).
[0089]
TEa = (S1a-S2a) / (S1a + S2a) (2)
[0090]
Further, in the reproduction signal processing circuit 28, when the optical disc 15 is a CD, the following (3) is based on the output signals (referred to as S1b and S2b) from the above-mentioned two-divided light receiving element constituting the third light receiving device 69b. The track error signal TEb is detected from the equation.
[0091]
TEb = (S1b-S2b) / (S1b + S2b) (3)
[0092]
This facilitates the design of the hologram pattern and the like of the diffraction area constituting the second hologram element 57 ′.
[0093]
In the first embodiment, only the 0th-order diffracted light from the first hologram element 57 is received by the first light receiver 59. However, the present invention is not limited to this, and ± Diffracted light including m (m ≧ 1) order diffracted light may be received.
[0094]
In the first hologram element 57, since a plurality of diffraction regions are arranged with the R direction as a boundary line, ± mth order diffracted light is generated in the T direction of 0th order diffracted light. In this case, the distance P between the light spot by the 0th order diffracted light and the light spot by the ± mth order diffracted light on the light receiving surface of the first light receiver 59. _m Is expressed by the following equation (4).
[0095]
[Expression 1]

[0096]
In the above equation (4), λ is the wavelength of light, L is the distance between the first hologram element 57 and the light receiving surface of the first light receiver 59, n is the refractive index of the first hologram element 57, and d is the diffraction region. (Width in the T direction).
[0097]
Therefore, for example, as shown in FIG. 6B, when receiving diffracted light including ± first-order diffracted light, the length of the light receiving surface of the first light receiver 59 in the T direction is set to 2P. ₁ By making the length slightly longer than that, it is possible to receive a light spot by ± first-order diffracted light, and as a result, the amount of light received increases, so the S / N ratio in the output signal from the first light receiver 59 is improved. In other words, it is possible to accurately obtain a signal including information on track errors. In addition, the shape of the first light receiver 59 is designed to be an optimum shape according to the order of the diffracted light received by the light receiving surface, for example, by making the length in the R direction smaller than the length in the T direction. Therefore, downsizing of the optical pickup device can be promoted.
[0098]
In the first embodiment, the reflected light beam deflected by the second beam splitter 64 is incident on the first hologram element 57. As an example, as shown in FIG. 7, the first beam splitter is used. The first hologram element 57 may be disposed between the objective lens 60 and the objective lens 60, and the reflected light beam from the objective lens 60 may be directly incident on the first hologram element 57. This eliminates the need for the second beam splitter 64 and the condenser lens 58, and can promote downsizing and cost reduction of the optical pickup device.
[0099]
In the first embodiment, the case where the first hologram element 57 and the first light receiver 59 are individually arranged has been described. However, the present invention is not limited to this, and the first hologram element 57 and the first light receiver 59 are arranged separately. One light receiver 59 may be integrated. As a result, the distance between the first hologram element 57 and the first light receiver 59 is narrowed, and it is possible to promote downsizing of the optical pickup device 23. In addition, since the positional relationship between the first hologram element 57 and the first light receiver 59 is optimized in advance, assembly and adjustment operations can be simplified. Accordingly, the work cost is reduced, and cost reduction can be promoted.
[0100]
In the first embodiment, the case where the first hologram element 57 includes a plurality of first diffraction regions 57a and second diffraction regions 57b has been described. However, the present invention is not limited to this and is illustrated as an example. As shown in FIGS. 8A to 8C, a hologram element 57 ′ composed of one first diffraction region 57a and one second diffraction region 57b may be used.
[0101]
In this case, for example, the aspect ratio (spot diameter in the R direction / spot diameter in the T direction) of the light spot of the reflected light beam on the light receiving surface of the hologram element 57 ′ is 0.5 or more, that is, (spot in the 2 × R direction). If (diameter) ≧ (spot diameter in the T direction), the aspect ratio (length Lr in the R direction / length Lt in the T direction) of each diffraction region is 1 or more, that is, (length Lr in the R direction) ≧ By setting (the length Lt in the T direction), it is possible to reduce the size of the hologram element 57 ′ to the limit of the beam shape. Note that FIG. 8C shows the case of (R direction length Lr) = (T direction length Lt).
[0102]
<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIGS.
[0103]
In the second embodiment, instead of the first hologram element 57 described above, as shown in FIG. 9A, the light receiving surface is divided by a T-direction dividing line (track dividing line) TD, The third hologram element 67 is characterized in that the third hologram element 67 designed to have different diffraction directions in the + R side region and the −R side region of the dividing line TD is used. Other configurations of the optical pickup device and the optical disk device are the same as those in the first embodiment. Accordingly, the following description will be focused on differences from the first embodiment, and the same reference numerals will be used for the same or equivalent components as in the first embodiment described above, and the description will be simplified or Shall be omitted.
[0104]
As shown in FIG. 9A, the third hologram element 67 has a third diffraction region 67a and a fourth diffraction region 67b that have a selectively high diffraction efficiency for a light beam having a wavelength of 650 nm, It is composed of a fifth diffraction region 67c and a sixth diffraction region 67d that have a high diffraction efficiency selectively with respect to a light beam of 780 nm. Here, a plurality of third diffraction regions 67a and fifth diffraction regions 67c are arranged on the + R side of the track dividing line TD with the R direction as a boundary line. A plurality of fourth diffraction regions 67b and sixth diffraction regions 67d are arranged on the −R side of the track dividing line TD with the R direction as a boundary line. The third diffraction region 67a and the fourth diffraction region 67b are adjacent to each other via the track division line TD, and the fifth diffraction region 67c and the sixth diffraction region 67d are adjacent to each other via the track division line TD. Hereinafter, the third diffraction region 67a and the fifth diffraction region 67c are collectively referred to as a first region HA, and the fourth diffraction region 67b and the sixth diffraction region 7d are collectively referred to as a second region HB.
[0105]
The third diffraction region 67a and the fourth diffraction region 67b are common in that they have high diffraction efficiency selectively with respect to a light beam having a wavelength of 650 nm, but are set so that the diffraction directions are different from each other. Similarly, the fifth diffraction region 67c and the sixth diffraction region 67d are common in that they have high diffraction efficiency selectively with respect to a light beam with a wavelength of 780 nm, but are set so that the diffraction directions are different from each other. Yes. Therefore, in the second embodiment, instead of the first light receiver 59 in the first embodiment described above, diffracted light from the first region HA is received as shown in FIG. 9B. A fourth light receiver 70a and a fifth light receiver 70b that receives the diffracted light from the second region HB are used. In this case, each light receiving element constituting the fourth light receiver 70a and the fifth light receiver 70b may not be a two-part light receiving element.
[0106]
Next, tracking control when accessing the optical disc 15 using the optical disc apparatus 20 including the optical pickup device 23 according to the second embodiment will be briefly described.
[0107]
First, the case where the optical disk 15 is a DVD will be described.
[0108]
When the optical disk 15 is inserted into a predetermined position of the optical disk apparatus main body, the CPU 40 determines the type of the optical disk 15 based on the reflectance of the recording surface of the optical disk 15 and confirms that it is a DVD. The selection of the 650 nm semiconductor laser 51a as the light source to be controlled is instructed.
[0109]
The light beam emitted from the 650 nm semiconductor laser 51 a becomes substantially parallel light by the first coupling lens 52, passes through the first beam splitter 54 and the second beam splitter 64, and passes through the objective lens 60 to the optical disk 15. It is condensed as a minute spot on the recording surface.
[0110]
The reflected light beam from the recording surface of the optical disk 15 is converted into substantially parallel light again by the objective lens 60, deflected by the second beam splitter 64, and enters the third hologram element 67 through the condenser lens 58. The portion of the reflected light beam that is incident on the first area HA of the third hologram element 67 is diffracted by the third diffraction area 67a, and the diffracted light is received by the fourth light receiver 70a. . Further, the portion of the reflected light beam that is incident on the second region HB of the third hologram element 67 is diffracted by the fourth diffraction region 67b, and the diffracted light is received by the fifth light receiver 70b. From the fourth light receiver 70a and the fifth light receiver 70b, current signals corresponding to the respective amounts of received light are output to the reproduction signal processing circuit 28.
[0111]
The reproduction signal processing circuit 28 converts the current signal from the fourth light receiver 70a and the fifth light receiver 70b into a voltage signal, and detects the track error signal TE based on the following equation (5).
[0112]
TE = (S70a-S70b) / (S70a + S70b) ...... (5)
[0113]
In the above equation (5), S70a is an output signal of the fourth light receiver 70a, and S70b is an output signal of the fifth light receiver 70b.
[0114]
Then, the reproduction signal processing circuit 28 outputs the track error signal TE to the servo controller 33. The servo controller 33 drives the tracking actuator of the optical pickup device 23 via the motor driver 27 based on the track error signal TE from the reproduction signal processing circuit 28, and corrects the track deviation.
[0115]
Next, the case where the optical disk 15 is a CD will be described.
[0116]
When the optical disc 15 is inserted into a predetermined position of the optical disc apparatus main body, the CPU 40 determines the type of the optical disc 15 based on the reflectance of the recording surface of the optical disc 15 and confirms that it is a CD. The selection of the 780 nm semiconductor laser 61a as the light source to be controlled is instructed.
[0117]
The light beam emitted from the 780 nm semiconductor laser 61a becomes substantially parallel light by the second coupling lens 62, and its optical axis is bent in the + X direction by the first beam splitter 54, and then the second beam splitter 64 is passed through. The light passes through and is condensed as a minute spot on the recording surface of the optical disc 15 through the objective lens 60.
[0118]
The reflected light beam from the optical disk 15 is converted into substantially parallel light again by the objective lens 60, deflected by the second beam splitter 64, and enters the third hologram element 67 through the condenser lens 58. Then, the portion of the reflected light beam incident on the first area HA of the third hologram element 67 is diffracted by the fifth diffraction area 67c, and the diffracted light is received by the fourth light receiver 70a. . Further, the portion of the reflected light beam that has entered the second region HB of the third hologram element 67 is diffracted by the sixth diffraction region 67d, and the diffracted light is received by the fifth light receiver 70b. From the fourth light receiver 70a and the fifth light receiver 70b, current signals corresponding to the respective amounts of received light are output to the reproduction signal processing circuit 28.
[0119]
In the reproduction signal processing circuit 28, the track error signal TE is detected based on the equation (5) in the same manner as in the case of the DVD described above. Based on the track error signal TE, the tracking actuator of the optical pickup device 23 is driven via the servo controller 33 and the motor driver 27 to correct the track deviation.
[0120]
Further, by using the optical disc apparatus 20 according to the second embodiment, the recording process and the reproduction process with respect to the optical disc 15 can be performed in the same manner as the first embodiment described above.
[0121]
As described above, according to the optical pickup device of the second embodiment, in the third hologram element 67, the light receiving surface is divided by the track dividing line TD in the T direction, and the + R side of the track dividing line TD. Since the diffraction directions are set to be different on the −R side and the −R side, the positional accuracy of the fourth light receiver 70a and the fifth light receiver 70b does not need to be so strict, and assembly and adjustment operations are performed. It is possible to simplify the operation cost.
[0122]
In addition, according to the optical disk device according to the second embodiment, since the track error signal can be detected with high accuracy for a plurality of types of information recording media based on the output signal from the optical pickup device, it has been described above. The same effect as in the first embodiment can be obtained.
[0123]
In the second embodiment, the case where the track dividing line for the first reflected light beam is equal to the track dividing line for the second reflected light beam has been described. However, the present invention is not limited to this. For example, when the optical axis of the first reflected light beam does not coincide with the optical axis of the second reflected light beam, as shown in FIG. 10A as an example, track division for the first reflected light beam is performed. A fourth hologram element 67 ′ having a different line (referred to as TD1) and a track dividing line (referred to as TD2) for the second reflected light beam may be used. In this case, with respect to the first reflected light beam, the region on the + R side of the track dividing line TD1 in the fourth hologram element 67 ′ is the first region (referred to as HA1), and the region on the −R side is the first region. There are two regions (referred to as HB1). For the second reflected light beam, in the fourth hologram element 67 ′, the + R side region of the track dividing line TD2 is the first region (HA2), and the −R side region is the second region (HB2 and HB2). ).
[0124]
That is, when the optical disk 15 is a DVD, as shown in FIG. 10B as an example, TD1 serves as a track dividing line, and diffracted light from the first area HA1 is received by the fourth light receiver 70a. The diffracted light from the two regions HB1 is received by the fifth light receiver 70b.
[0125]
On the other hand, when the optical disk 15 is a CD, as shown in FIG. 10C as an example, TD2 becomes a track dividing line, and the diffracted light from the first area HA2 is received by the fourth light receiver 70a. The diffracted light from the second region HB2 is received by the fifth light receiver 70b.
[0126]
That is, even when a plurality of light sources are provided and the light emission points of the respective light sources are different, as in the case of using a so-called 1Can2LD semiconductor laser unit, for example, the output signal from the light receiver is prevented from being offset. can do. Therefore, it is possible to accurately obtain a signal including information regarding a track error for a plurality of types of information recording media.
[0127]
<< Third Embodiment >>
Next, a third embodiment of the present invention will be described with reference to FIG.
[0128]
This third embodiment is characterized in that a 650 nm semiconductor laser 51a and a 780 nm semiconductor laser 61a are arranged in one semiconductor laser unit 65 as shown in FIG. 11A as an example. . In the following description, differences from the first embodiment will be mainly described, and the same reference numerals are used for the same or equivalent components as those in the first embodiment, and the description thereof is simplified or omitted. Shall.
[0129]
As shown in FIG. 11A, the semiconductor laser unit 65 includes a 650 nm semiconductor laser 51a and a 780 nm semiconductor laser 61a as light sources, a stem 65b that holds these light sources, and a laser beam emitted from the light sources to the outside. It has an exit window and includes a cover 65c for protecting the light source.
[0130]
Accordingly, instead of the first coupling lens 52, a third coupling lens 52 ′ achromatic for two wavelengths of 650 nm and 780 nm is used.
[0131]
In addition, as shown in FIG. 11B, the first hologram element 57 is disposed between the semiconductor laser unit 65 and the third coupling lens 52 ′. It is arranged at the light receiving position of the diffracted light from one hologram element 57.
[0132]
Next, tracking control when accessing the optical disc 15 using the optical disc apparatus 20 including the optical pickup device 23 according to the third embodiment will be briefly described. Here, only the case where the optical disk 15 is a DVD will be described.
[0133]
When the optical disk 15 is inserted into a predetermined position of the optical disk apparatus main body, the CPU 40 determines the type of the optical disk 15 based on the reflectance of the recording surface of the optical disk 15 and confirms that it is a DVD. The selection of the 650 nm semiconductor laser 51a as the light source to be controlled is instructed.
[0134]
The light beam emitted from the 650 nm semiconductor laser 51 a passes through the first hologram 57, becomes substantially parallel light by the first coupling lens 52, and is condensed as a minute spot on the recording surface of the optical disk 15 through the objective lens 60. Is done.
[0135]
The reflected light beam from the recording surface of the optical disk 15 is converted into substantially parallel light again by the objective lens 60 and is incident on the first hologram element 57 via the third coupling lens 52 ′. The reflected light beam is diffracted by the first diffraction region 57 a of the first hologram element 57, and the diffracted light is received by the first light receiver 59. From the first partial light receiving element 59 a and the second partial light receiving element 59 b of the first light receiver 59, current signals corresponding to the respective received light amounts are output to the reproduction signal processing circuit 28.
[0136]
The reproduction signal processing circuit 28 detects the track error signal TE in the same manner as in the first embodiment described above. Based on the track error signal TE, the tracking actuator of the optical pickup device 23 is driven via the servo controller 33 and the motor driver 27 to correct the track deviation.
[0137]
Further, by using the optical disc apparatus 20 according to the third embodiment, the recording process and the reproduction process with respect to the optical disc 15 can be performed in the same manner as the first embodiment described above.
[0138]
As described above, according to the optical pickup device of the third embodiment, the number of semiconductor laser units is reduced from two to one as compared with the first embodiment described above, and the first beam is reduced. The splitter 54, the second coupling lens 62, the second beam splitter 64, and the condenser lens 58 are not necessary. Therefore, it is possible to promote downsizing and cost reduction of the optical pickup device. Furthermore, since assembly and adjustment operations can be simplified, the operation cost can be reduced.
[0139]
In addition, according to the optical disk device according to the third embodiment, since the track error signal can be detected with high accuracy for a plurality of types of information recording media based on the output signal from the optical pickup device, it has been described above. The same effect as in the first embodiment can be obtained.
[0140]
In the third embodiment, the first hologram element 57 is disposed between the semiconductor laser unit 65 and the third coupling lens 52 ′. However, the present invention is not limited to this. It may be arranged between the coupling lens 52 ′ and the objective lens 60.
[0141]
Moreover, in the said 3rd Embodiment, although the light source, the 1st hologram element 57, and the 1st light receiver 59 are each arrange | positioned separately, as shown in FIG. 12 (A) as an example, A semiconductor laser unit 66 in which the light source, the first hologram element 57 and the first light receiver 59 are integrated may be used. In the semiconductor laser unit 66, the 650 nm semiconductor laser 51a, the 780 nm semiconductor laser 61a, and the first light receiver 59 are arranged in a predetermined positional relationship via the stem 66b, and are in contact with the opening of the cover 66c to be in contact with the first hologram element. 57 is arranged.
[0142]
In this case, light beams emitted from the 650 nm semiconductor laser 51a and the 780 nm semiconductor laser 61a are, for example, as shown in FIG. 12B, the first hologram element 57, the third coupling lens 52 ′, and the objective. The light is condensed on the recording surface of the optical disk 15 via the lens 60, and the reflected light beam from the recording surface of the optical disk 15 is incident on the first hologram element 57 through the same optical path as the forward path. The reflected light beam is diffracted by the first hologram element 57 and received by the first light receiver 59 in the same manner as in the first embodiment. A current signal corresponding to the amount of received light is output from the first light receiver 59 to the reproduction signal processing circuit 28.
[0143]
As a result, the intervals between the light source, the first hologram 57 and the first light receiver 59 can be narrowed, and the downsizing of the optical pickup device can be promoted. In addition, since assembly and adjustment operations can be simplified, the operation cost is reduced, and cost reduction can be promoted.
[0144]
In addition, although each said embodiment demonstrated the case where a light source is 2 wavelengths, this invention is not limited to this, The case where a light source of 3 wavelengths or more is provided may be sufficient. In that case, of course, a hologram element having a diffraction region corresponding to each wavelength is used.
[0145]
In each of the above embodiments, a polarization hologram in which a grating is formed by etching or the like on a thin retardation film made of, for example, an organic stretched film and the diffraction efficiency is set to be different depending on the polarization direction is used as the hologram element. Also good. For example, as shown in FIG. 13, in the third embodiment described above, a polarization hologram element 71 is used instead of the hologram element 57, and the light between the third coupling lens 52 ′ and the objective lens 60 is used. A λ / 4 plate 55 for converting the polarization direction of the light beam may be disposed on the road. As an example, the polarization hologram element 71 has a low diffraction efficiency for an S-polarized light beam and a high diffraction efficiency for a P-polarized light beam, and an S-polarized light beam is emitted from the light source. A brief description will be given of the case.
[0146]
Since the polarization hologram element 71 has a lower diffraction efficiency than the S-polarized light beam, most of the S-polarized light beam emitted from the semiconductor laser unit 65 is transmitted through the polarization hologram element 71 and the third coupling lens. After being made substantially parallel light at 52 ′ and further circularly polarized by the λ / 4 plate 55, it is condensed as a minute spot on the recording surface of the optical disk 15 through the objective lens 60.
[0147]
The reflected light reflected from the recording surface of the optical disk 15 becomes circularly polarized light opposite to the outward path, and is converted into substantially parallel light again by the objective lens 60 and converted from circularly polarized light to P-polarized light by the λ / 4 plate 55. Thereafter, the polarization hologram element 71 is irradiated through the third coupling lens 52 ′. Since the polarization hologram element 71 has a high diffraction efficiency for a P-polarized light beam, the reflected light is selectively diffracted by the polarization hologram element 71. The diffracted light is received by the first light receiver 59.
[0148]
In this way, by using the polarization hologram element having a low diffraction efficiency with respect to the polarization direction of the light beam emitted from the light source, the light beam emitted from the light source passes through the polarization hologram element with high efficiency. A decrease in the amount of light applied to the recording surface is extremely reduced. Therefore, it becomes easy to cope with an increase in recording speed.
[0149]
In addition, by using a polarization hologram element having a high diffraction efficiency with respect to the polarization direction of the return light beam, the loss of the light amount when the return light beam is diffracted decreases, so that the amount of light received by the first light receiver 59 increases. As a result, the S / N ratio of the signal can be improved. Therefore, it is possible to accurately obtain a signal including information regarding the track error.
[0150]
In general, a polarization hologram element can be manufactured by processing a birefringent material into a grating shape, or by processing a grating having a pitch smaller than the wavelength. As a material having birefringence, LiNbO ₃ Although there are crystals and liquid crystals, a stretched film of a transparent organic material having a thin film and birefringence, such as polyimide and PET, has a birefringence of about Δn = 0.06 to 0.1 and a refractive index. Since it is about 1.6, an inexpensive overcoat material after lattice processing can be used, and cost reduction is easy.
[0151]
【The invention's effect】
As described above, according to the optical pickup device of the present invention, it is possible to deal with a plurality of types of information recording media without incurring an increase in size and cost, and information regarding track errors can be obtained accurately and stably. There is an effect that can be.
[0152]
In addition, the optical disk apparatus according to the present invention has an effect that it can be used for a plurality of types of information recording media without causing an increase in size and cost, and accurate access can be performed stably.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an optical disc apparatus according to a first embodiment of the present invention.
2 is a diagram showing a schematic configuration of an optical system in the optical pickup device of FIG. 1;
3 is a diagram for explaining the semiconductor laser unit in FIG. 2; FIG.
FIGS. 4A to 4C are diagrams for explaining the configuration of the first hologram element, respectively, and FIG. 4D explains the configuration of the first light receiver. FIG.
FIG. 5 is a diagram for explaining a relationship between a track error signal TE detected based on an output signal from a first light receiver and a width D of a diffraction region.
FIG. 6A is a diagram for explaining a case where the diffraction direction of the first hologram element differs depending on the wavelength, and FIG. 6B receives diffracted light including ± first-order light. It is a figure for demonstrating the magnitude | size of the light receiver in a case.
FIG. 7 is a diagram for explaining an example in which a first hologram element is disposed between a beam splitter and an objective lens.
8A to 8C are diagrams for explaining the relationship between the shape of the diffraction region and the shape of the light spot, respectively.
FIGS. 9A and 9B are diagrams for explaining a hologram element in the second embodiment, respectively.
FIGS. 10A to 10C are diagrams for explaining an example in which each hologram element has two track dividing lines.
FIGS. 11A and 11B are diagrams for explaining an example in which a 650 nm semiconductor laser and a 780 nm semiconductor laser are integrated into one semiconductor laser unit, respectively.
FIGS. 12A and 12B are diagrams for explaining an example in which two semiconductor lasers, a light receiver, and a hologram element are integrated, respectively.
FIG. 13 is a diagram for explaining an example using a polarization hologram as a hologram element;
FIG. 14 is a diagram for explaining a relationship between a track error signal TE and a hologram width D in a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 15 ... Optical disk (information recording medium), 20 ... Optical disk apparatus, 23 ... Optical pick-up apparatus, 40 ... CPU (processing apparatus), 57 ... 1st hologram element (hologram element), 59 ... 1st light receiving element (light detection) Instrument), 60... Objective lens.

Claims (18)

An optical pickup device used for performing at least reproduction of information recording, reproduction, and erasing with respect to a plurality of types of information recording media having a recording surface on which spiral or concentric tracks are formed,
A plurality of light sources provided individually corresponding to the plurality of information recording media and selectively emitting light beams having different wavelengths;
An objective lens for condensing each light beam on the recording surface of the corresponding information recording medium, and an optical path of each return light beam reflected by the recording surface and passing through the objective lens, the light receiving surface of which is tangent to the track An optical system including a hologram element in which a plurality of diffraction regions corresponding to each wavelength are arranged in a predetermined order along a first direction corresponding to a direction;
And a photodetector that receives diffracted light from the hologram element at a predetermined light receiving position. 2. The optical pickup device according to claim 1, wherein a length in the first direction in each diffraction region is equal to or shorter than a length in a second direction orthogonal to the first direction. The diffraction region corresponding to the wavelength of the return light beam having a minimum beam diameter on the light receiving surface is disposed at the center of the light receiving surface of the hologram element. Optical pickup device. The length of the photodetector in the third direction corresponding to the first direction is the order m (≧ 1) of diffracted light, the wavelength λ of the return beam, the hologram element and the light receiving surface of the photodetector , L, the refractive index n of the hologram element, and the length d of the diffraction region in the third direction, which is at least twice the value represented by mλL / (2nd). Item 4. The optical pickup device according to any one of Items 1 to 3. 5. The optical pickup device according to claim 4, wherein a length of the photodetector in the third direction is longer than a length in a fourth direction orthogonal to the third direction. The hologram element is disposed on a common optical path of an optical path of light from the light source toward the information recording medium and an optical path of return light reflected by the information recording medium. 5. The optical pickup device according to claim 5. The polarization direction of the light traveling from the light source toward the information recording medium is different from the polarization direction of the return light reflected by the information recording medium, and the hologram element has different diffraction efficiency depending on the polarization direction of the incident light. The optical pickup device according to claim 6, wherein the optical pickup device is a hologram element. The optical pickup device according to claim 1, wherein the hologram element diffracts each return light beam toward substantially the same position on a detection surface of the photodetector. 9. The optical pickup device according to claim 8, wherein the photodetector includes a two-divided light receiving element that is divided into two by a dividing line in a direction corresponding to at least the first direction. The optical pickup device according to claim 1, wherein the hologram element diffracts each return light beam in at least two different directions according to the wavelength. The photodetector includes a plurality of light receiving elements that respectively receive the diffracted lights diffracted in the different directions, and each of the light receiving elements is divided into two by a dividing line in a direction corresponding to at least the first direction. The optical pickup device according to claim 10, further comprising a two-divided light receiving element. 2. The hologram element according to claim 1, wherein each of the diffraction regions is divided into two light receiving regions by a dividing line in the first direction, and the diffraction direction of the return light beam is different for each light receiving region. The optical pickup device according to claim 7. 13. The optical pickup device according to claim 12, wherein each of the diffraction regions is divided corresponding to the optical axis position of the return light beam having a corresponding wavelength. 14. The optical pickup device according to claim 12, wherein the photodetector includes a plurality of light receiving elements that respectively receive the diffracted lights diffracted in the different directions. 15. The optical pickup device according to claim 1, wherein the photodetector is housed in a same housing as the plurality of light sources and packaged. The optical pickup device according to claim 1, wherein the hologram element and the photodetector are integrated. The optical pickup device according to claim 1, wherein the hologram element and the photodetector are housed and packaged in the same housing as the plurality of light sources. An optical disc apparatus that performs at least reproduction of information recording, reproduction, and erasure on a plurality of types of optical discs,
An optical pickup device according to claim 1;
An optical disk device comprising: a processing device that performs at least reproduction of recording, reproduction, and erasing of the information using an output signal of the photodetector constituting the optical pickup device.

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