JP4206705B2

JP4206705B2 - Skew detection method, skew detection device, optical pickup, and optical disk device

Info

Publication number: JP4206705B2
Application number: JP2002239452A
Authority: JP
Inventors: 徹長良; 京介宮野; 清豊田; 哲日根野
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 2002-08-20
Filing date: 2002-08-20
Publication date: 2009-01-14
Anticipated expiration: 2022-08-20
Also published as: JP2004079094A

Description

【０００１】
【発明の属する技術分野】
本発明は、光記録媒体（光ディスク）のラジアルスキュー（光ディスクの半径方向の傾き）を検出するスキュー検出方法及びスキュー検出装置並びにこのスキュー検出装置を備えた光ピックアップ及び光ディスク装置に関する。
【０００２】
【従来の技術】
光ディスクへの記録が高密度化されるに伴い、光ディスクのスキューマージンが少なくなっている。このため、光学ピックアップでは、スキューセンサを用いて光学ピックアップ（対物レンズ）の光軸に対する光ディスクの傾き量を検出し、この傾き量に応じて対物レンズの光軸が光ディスクの信号記録面に対し直交するように光学ピックアップをスキューサーボ機構により制御するようにしている。
【０００３】
このような従来のスキューセンサは、光ピックアップの本体部分に光ディスクの信号記録面に向けて光が照射されるように配置されたＬＥＤからなる発光素子と、光ピックアップの本体部分に配置され、光ディスクの信号記録面で反射されてくる光を受ける２分割のフォトダイオードとを備え、上記両フォトダイオードから光記録媒体の傾き量に応じた差信号を取り出し、この差信号をスキューエラー信号として検出するとともに、このスキューエラー信号によりスキューサーボ機構を制御することにより、光ピックアップの光軸（対物レンズの光軸）が光記録媒体の信号記録面に対し直交するようにしている。
【０００４】
【発明が解決しようとする課題】
しかし、上記のような従来のスキューセンサでは、スキュー検出専用の発光素子及びフォトダイオードが必要なため、部品点数が増えて光学ピックアップのコストが増加するという問題がある。
また、従来のスキューセンサは、２分割されたフォトダイオードの出力信号の差分を取り出すことで光ディスクの傾き量を検出するものであるため、光ディスクとスキューセンサとの間の距離が変動すると光ディスクの傾き量が同じであってもスキュー検出用フォトダイオード面上でのビームの光量分布が変わり、光ディスクの傾き量に誤差を生じてしまう。
また、光ディスクとスキューセンサとの間の距離は、ＣＤやＤＶＤ等のように光ディスクの種類、光ディスクのターンテーブルへのチャッキングの状態や光ディスクのそり方等で変わってくるため、常に変動している。そのため、このままでは光検出用素子の出力には常に誤差が含み、正確なスキュー検出が難しくなっている。
【０００５】
そこで、上述するような別構造のスキューセンサを用いることなく、記録／再生用の光学系でスキュー情報を検出できれば、実際に読み書きに使用する光学系のレンズおよび光検出素子を通してスキューエラー信号を検出することができ、誤差を含まない正確なスキュー検出が可能になる。
【０００６】
本発明は、上記のような従来の問題を解決するためになされたもので、その目的は、光記録媒体の記録／再生用の光学系を利用して光記録媒体の傾き及び量を検出できるように構成することにより、高精度のラジアルスキュー検出を可能にするとともに構成部品数を削減して低コスト化を可能にしたスキュー検出方法及びスキュー検出装置並びにこのスキュー検出装置を用いた光ピックアップ及び光ディスク装置を提供することにある。
【０００７】
【課題を解決するための手段】
上記の目的を達成するために、本発明に係るスキュー検出方法は、光源と、光検出手段と、前記光源からの光束を光記録媒体の信号記録面に照射するとともに該信号記録面から反射される反射光束が前記光検出手段に集束されるように構成された記録／再生用の光学系とを用いて、前記光記録媒体に照射される記録／再生用光束の光軸に対する前記光記録媒体の傾きであるスキューを検出するスキュー検出方法であって、前記光検出手段は、前記光記録媒体のラジアル方向に沿って分割される２以上の複数対領域に対応した複数対の分割された受光部を有し、前記受光部のうちの内側に位置する対の受光部である内側受光部対が前記反射光束の中心領域の光を受光し、且つ、前記受光部のうちの外側に位置する対の受光部である外側受光部対が前記反射光束の周辺領域の光を受光するようにすることで、前記内側受光部対が受光する反射光束に関する前記光学系の実効ＮＡ（開口数）が、前記外側受光部対が受光する反射光束に関する前記光学系の実効ＮＡもしくは前記内側受光部対が受光する反射光束と該外側受光部対が受光する反射光束との総和である反射光束に関する前記光学系の実効ＮＡより小さくなるようにし、もって、前記内側受光部対の各受光部から出力される信号の差信号であり前記光記録媒体のトラックに対する前記光記録媒体に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第１プッシュプル信号と、前記外側受光部対の各受光部から出力される信号の差信号もしくは前記外側受光部対の各受光部の出力信号に前記内側受光部対各受光部の出力信号をそれぞれ加算した後の信号の差信号であり前記光記録媒体のトラックに対する前記光記録媒体に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第２プッシュプル信号とが、互いに異なった等価的ＭＴＦ（ｍｏｄｕｌａｔｉｏｎｔｒａｎｓｆｅｒｆｕｎｃｔｉｏｎ）を持つようにして、スキューの変動により発生する前記第１プッシュプル信号のＰＴＦ（ｐｈａｓｅｔｒａｎｓｆｅｒｆｕｎｃｔｉｏｎ）の変動と前記第２プッシュプル信号のＰＴＦの変動とが互いに異なるようにし、ここで等価的ＭＴＦとは、変動信号成分の発生源の空間周波数に対するプッシュプル信号の変動信号成分の振幅を表す関数であり、前記第１プッシュプル信号の変動信号成分の位相と前記第２プッシュプル信号の変動信号成分の位相とを比較し、この比較結果として得られる位相差に基づいて、前記光記録媒体に照射される記録／再生用光束の光軸に対する前記光記録媒体の傾き方向と傾き量を含むスキューエラー信号を生成することを特徴とする。
【０００８】
本発明のスキュー検出方法によれば、光記録媒体の記録／再生用の光学系を利用して、光記録媒体に照射される記録／再生用光束の光軸に対する光記録媒体の傾き方向及び傾き量を検出でき、高精度のラジアルスキュー検出を可能にするとともに構成部品数を削減して低コスト化を可能にする。
【０００９】
また、本発明に係るスキュー検出装置は、光源と、光検出手段と、前記光源からの光束を光記録媒体の信号記録面に照射するとともに該信号記録面から反射される反射光束が前記光検出手段に集束されるように構成された記録／再生用の光学系とを用いて、前記光記録媒体に照射される記録／再生用光束の光軸に対する前記光記録媒体の傾きであるスキューを検出するスキュー検出装置であって、前記光検出手段は、前記光記録媒体のラジアル方向に沿って分割される２以上の複数対領域に対応した複数対の分割された受光部を有し、前記受光部のうちの内側に位置する対の受光部である内側受光部対が前記反射光束の中心領域の光を受光し、且つ、前記受光部のうちの外側に位置する対の受光部である外側受光部対が前記反射光束の周辺領域の光を受光するようにすることで、前記内側受光部対が受光する反射光束に関する前記光学系の実効ＮＡ（開口数）が、前記外側受光部対が受光する反射光束に関する前記光学系の実効ＮＡもしくは前記内側受光部対が受光する反射光束と該外側受光部対が受光する反射光束との総和である反射光束に関する前記光学系の実効ＮＡより小さくなるようにし、もって、前記内側受光部対の各受光部から出力される信号の差信号であり前記光記録媒体のトラックに対する前記光記録媒体に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第１プッシュプル信号と、前記外側受光部対の各受光部から出力される信号の差信号もしくは前記外側受光部対の各受光部の出力信号に前記内側受光部対各受光部の出力信号をそれぞれ加算した後の信号の差信号であり前記光記録媒体のトラックに対する前記光記録媒体に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第２プッシュプル信号とが、互いに異なった等価的ＭＴＦ（ｍｏｄｕｌａｔｉｏｎｔｒａｎｓｆｅｒｆｕｎｃｔｉｏｎ）を持つようにして、スキューの変動により発生する前記第１プッシュプル信号のＰＴＦ（ｐｈａｓｅｔｒａｎｓｆｅｒｆｕｎｃｔｉｏｎ）の変動と前記第２プッシュプル信号のＰＴＦの変動とが互いに異なるようにしてあり、ここで等価的ＭＴＦとは、変動信号成分の発生源の空間周波数に対するプッシュプル信号の変動信号成分の振幅を表す関数であり、更に、前記第１プッシュプル信号を検出する第１プッシュプル信号検出手段と、前記第２プッシュプル信号を検出する第２プッシュプル信号検出手段と、前記第１プッシュプル信号の変動信号成分の位相と前記第２プッシュプル信号の変動信号成分の位相とを比較し、この比較結果として得られる位相差に基づいて前記光記録媒体に照射される記録／再生用光束の光軸に対する前記光記録媒体の傾き方向と傾き量を含むスキューエラー信号を生成する位相比較手段とを備えることを特徴とする。
【００１０】
本発明のスキュー検出装置によれば、光記録媒体の記録／再生用の光学系を利用して、光記録媒体に照射される記録／再生用光束の光軸に対する光記録媒体の傾き方向及び傾き量を検出でき、高精度のラジアルスキュー検出を可能にするとともに構成部品数を削減して低コスト化を可能にする。
【００１１】
また、本発明に係る光ピックアップは、記録または再生用の光束を出射する光源と、前記光源からの光束を集束して光記録媒体に照射する集束手段と、前記光源から出射された前記光記録媒体への光束と前記光記録媒体からの反射光束とを分離する光分離手段と、前記光分離手段により分離された前記反射光束を受光する光検出手段と、前記光記録媒体に照射される記録／再生用光束の光軸に対する前記光記録媒体の傾きであるスキューを検出するスキュー検出装置とを有する光ピックアップであって、前記スキュー検出装置は、前記光記録媒体のラジアル方向に沿って分割される２以上の複数対領域に対応した複数対の分割された受光部を有する光検出手段を備え、前記受光部のうちの内側に位置する対の受光部である内側受光部対が前記反射光束の中心領域の光を受光し、且つ、前記受光部のうちの外側に位置する対の受光部である外側受光部対が前記反射光束の周辺領域の光を受光するようにすることで、前記内側受光部対が受光する反射光束に関する前記光学系の実効ＮＡ（開口数）が、前記外側受光部対が受光する反射光束に関する前記光学系の実効ＮＡもしくは前記内側受光部対が受光する反射光束と該外側受光部対が受光する反射光束との総和である反射光束に関する前記光学系の実効ＮＡより小さくなるようにし、もって、前記内側受光部対の各受光部から出力される信号の差信号であり前記光記録媒体のトラックに対する前記光記録媒体に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第１プッシュプル信号と、前記外側受光部対の各受光部から出力される信号の差信号もしくは前記外側受光部対の各受光部の出力信号に前記内側受光部対各受光部の出力信号をそれぞれ加算した後の信号の差信号であり前記光記録媒体のトラックに対する前記光記録媒体に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第２プッシュプル信号とが、互いに異なった等価的ＭＴＦ（ｍｏｄｕｌａｔｉｏｎｔｒａｎｓｆｅｒｆｕｎｃｔｉｏｎ）を持つようにして、スキューの変動により発生する前記第１プッシュプル信号のＰＴＦ（ｐｈａｓｅｔｒａｎｓｆｅｒｆｕｎｃｔｉｏｎ）の変動と前記第２プッシュプル信号のＰＴＦの変動とが互いに異なるようにしてあり、ここで等価的ＭＴＦとは、変動信号成分の発生源の空間周波数に対するプッシュプル信号の変動信号成分の振幅を表す関数であり、前記スキュー検出装置は、更に、前記第１プッシュプル信号を検出する第１プッシュプル信号検出手段と、前記第２プッシュプル信号を検出する第２プッシュプル信号検出手段と、前記第１プッシュプル信号の変動信号成分の位相と前記第２プッシュプル信号の変動信号成分の位相とを比較し、この比較結果として得られる位相差に基づいて前記光記録媒体に照射される記録／再生用光束の光軸に対する前記光記録媒体の傾き方向と傾き量を含むスキューエラー信号を生成する位相比較手段とを備え、更に、前記集束手段の光軸を揺動するスキュー用駆動手段と、前記位相比較手段で生成されたスキューエラー信号により前記集束手段の光軸を前記光記録媒体の信号記録面に直交するように前記スキュー用駆動手段を制御するスキューサーボ制御手段とを備えることを特徴とする。
【００１２】
本発明の光ピックアップによれば、光記録媒体の記録／再生用の光学系を利用して、光記録媒体に照射される記録／再生用光束の光軸に対する光記録媒体の傾き方向及び傾き量を検出でき、高精度のラジアルスキュー検出を可能にするとともに構成部品数を削減して低コスト化を可能にする。
【００１３】
また、本発明に係る光ディスク装置は、駆動手段により回転駆動される光記録媒体と、送り手段により前記光記録媒体の半径方向に移動される光ピックアップと、前記光記録媒体の回転と前記光ピックアップの移動とを記録及び／または再生動作に対応して制御する制御手段と、前記光ピックアップによる前記光記録媒体に対する記録及び／または再生動作の信号処理をする信号処理手段とを備える光ディスク装置であって、前記光ピックアップは、記録または再生用の光束を出射する光源と、前記光源からの光束を集束して光記録媒体に照射する集束手段と、前記光源から出射された前記光記録媒体への光束と前記光記録媒体からの反射光束とを分離する光分離手段と、前記光分離手段により分離された前記反射光束を受光する光検出手段と、前記光記録媒体に照射される記録／再生用光束の光軸に対する前記光記録媒体の傾きであるスキューを検出するスキュー検出装置とを有し、前記スキュー検出装置は、前記光記録媒体のラジアル方向に沿って分割される２以上の複数対領域に対応した複数対の分割された受光部を有する光検出手段を備え、前記受光部のうちの内側に位置する対の受光部である内側受光部対が前記反射光束の中心領域の光を受光し、且つ、前記受光部のうちの外側に位置する対の受光部である外側受光部対が前記反射光束の周辺領域の光を受光するようにすることで、前記内側受光部対が受光する反射光束に関する前記光学系の実効ＮＡ（開口数）が、前記外側受光部対が受光する反射光束に関する前記光学系の実効ＮＡもしくは前記内側受光部対が受光する反射光束と該外側受光部対が受光する反射光束との総和である反射光束に関する前記光学系の実効ＮＡより小さくなるようにし、もって、前記内側受光部対の各受光部から出力される信号の差信号であり前記光記録媒体のトラックに対する前記光記録媒体に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第１プッシュプル信号と、前記外側受光部対の各受光部から出力される信号の差信号もしくは前記外側受光部対の各受光部の出力信号に前記内側受光部対各受光部の出力信号をそれぞれ加算した後の信号の差信号であり前記光記録媒体のトラックに対する前記光記録媒体に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第２プッシュプル信号とが、互いに異なった等価的ＭＴＦ（ｍｏｄｕｌａｔｉｏｎｔｒａｎｓｆｅｒｆｕｎｃｔｉｏｎ）を持つようにして、スキューの変動により発生する前記第１プッシュプル信号のＰＴＦ（ｐｈａｓｅｔｒａｎｓｆｅｒｆｕｎｃｔｉｏｎ）の変動と前記第２プッシュプル信号のＰＴＦの変動とが互いに異なるようにしてあり、ここで等価的ＭＴＦとは、変動信号成分の発生源の空間周波数に対するプッシュプル信号の変動信号成分の振幅を表す関数であり、前記スキュー検出装置は、更に、前記第１プッシュプル信号を検出する第１プッシュプル信号検出手段と、前記第２プッシュプル信号を検出する第２プッシュプル信号検出手段と、前記第１プッシュプル信号の変動信号成分の位相と前記第２プッシュプル信号の変動信号成分の位相とを比較し、この比較結果として得られる位相差に基づいて前記光記録媒体に照射される記録／再生用光束の光軸に対する前記光記録媒体の傾き方向と傾き量を含むスキューエラー信号を生成する位相比較手段とを備え、前記光ピックアップは、更に、前記集束手段の光軸を揺動するスキュー用駆動手段と、前記位相比較手段で生成されたスキューエラー信号により前記集束手段の光軸を前記光記録媒体の信号記録面に直交するように前記スキュー用駆動手段を制御するスキューサーボ制御手段とを備えることを特徴とする。
【００１４】
本発明の光ディスク装置によれば、光記録媒体の記録／再生用の光学系を利用して、光記録媒体に照射される記録／再生用光束の光軸に対する光記録媒体の傾き方向及び傾き量を検出でき、高精度のラジアルスキュー検出を可能にするとともに構成部品数を削減して低コスト化を可能にする。
【００１５】
【発明の実施の形態】
以下、本発明によるスキュー検出方法及びスキュー検出装置並びにこのスキュー検出装置を用いた光ピックアップ及び光ディスク装置の実施の形態について、図面を参照して詳細に説明する。
図１は本発明にかかるスキュー検出装置及び光ピックアップを備えた光ディスク装置の構成を示すブロック図、図２は本発明にかかるスキュー検出機能を備える光ピックアップの構成図、図３は本発明の第１の実施の形態にけるスキュー検出装置の構成を示すブロック図、図４は本発明のラジアルスキュー検出に適用されるウォーブルグルーブと光スポットとの関係を示す説明図、図５は本発明の第１の実施の形態にけるスキュー検出装置のラジアルスキューとプッシュプル出力信号との関係を示す説明図である。なお、図１に示す光ディスク装置は、以下に説明するスキュー検出装置及び光ピックアップを搭載することが可能な記録・再生装置の一例である。
【００１６】
まず、図１に示す光ディスク装置１０１の構成について説明する。
この光ディスク装置１０１は、ＣＤ，ＤＶＤやＤＶＤ±Ｒ／ＲＷ，ＣＤ−Ｒ／ＲＷのような光記録媒体である光ディスク１０２を回転駆動する駆動手段としてのスピンドルモータ１０３と、光ピックアップ１０４と、この光ピックアップ１０４を光ディスク１０２の半径方向に移動する駆動手段としての送りモータ１０５とを備えている。
ここで、スピンドルモータ１０３及び送りモータ１０５は、システムコントローラ１０７からの指令に基づいて制御されるサーボ制御部１０９により所定の回転数で駆動制御される構成になっている。
【００１７】
図１に示す信号変復調器＆ＥＣＣブロック１０８は、信号の変調、復調及びＥＣＣ（エラー訂正符号）の付加を行う。
光ピックアップ１０４は、信号変復調器＆ＥＣＣブロック１０８の指令に従って、回転する光ディスク１０２の信号記録面に、光源からの光束を、記録／再生用の光スポットとして照射するように構成されている。さらに、光ピックアップ１０４は、光ディスク１０２の信号記録面から反射される反射光束に応じて、光ピックアップ１０４の光検出手段（後述する）から出力される各種の信号をプリアンプ１２０およびラジアルスキューエラー信号処理部１１６に対して供給するように構成されている。
【００１８】
上記プリアンプ１２０は、反射光束に従い光ピックアップ１０４の光検出手段（後述する）から出力される各種の信号に基づいてフォーカスエラー信号、トラッキングエラー信号、ＲＦ信号等を生成できるように構成されている。また、再生対象とされる記録媒体の種類に応じて、サーボ制御部１０９、信号変復調器＆ＥＣＣブロック１０８等により、これらの信号に基づく復調及び誤り訂正処理等の所定の処理が行われる。
ここで、信号変復調器＆ＥＣＣブロック１０８により復調された記録信号が、例えばコンピュータのデータストレージ用であれば、インタフェース１１１を介して外部コンピュータ１３０等に送出される。これにより、外部コンピュータ１３０等は光ディスク１０２に記録された信号を再生信号として受け取ることができるように構成されている。
【００１９】
また、信号変復調器＆ＥＣＣブロック１０８により復調された記録信号がオーディオ・ビジュアル用であれば、Ｄ／Ａ，Ａ／Ｄ変換器１１２のＤ／Ａ変換部でデジタル／アナログ変換され、オーディオ・ビジュアル処理部１１３に供給される。そして、このオーディオ・ビジュアル処理部１１３でオーディオ・ビデオ信号処理が行われ、オーディオ・ビジュアル信号入出力部１１４を介して外部の撮像・映写機器に伝送される。
【００２０】
上記光ピックアップ１０４には、例えば光ディスク１０２上の所定の記録トラックまで移動させるための送りモータ１０５が接続されている。スピンドルモータ１０３の制御と、送りモータ１０５の制御と、光ピックアップ１０４の対物レンズを保持する二軸アクチュエータのフォーカシング方向及びトラッキング方向の制御は、それぞれサーボ制御部１０９により行われる。
また、レーザ制御部１２１は、光ピックアップ１０４におけるレーザ光源２２（図２参照）を制御するものであり、レーザ光源２２の出力パワーを記録モード及び再生モードに応じて制御する構成になっている。
【００２１】
上記ラジアルスキューエラー信号処理部１１６は、光ピックアップ１０４の光検出手段（後述する）から出力される信号、すなわち光ディスク１０２に形成したウォーブルグルーブに沿いトラッキングサーボを行う時に、このウォーブルグルーブ上を移動する光スポットに対応した反射光束を上記光検出手段で受光することにより該光検出手段から出力される第１及び第２プッシュプル信号との位相差を検出し、この位相差から光ディスク１０２の傾き方向と傾き量を含むスキューエラー信号Ｓ１を生成するものである。
【００２２】
上記ラジアルスキューエラー信号処理部１１６から出力されるスキューエラー信号Ｓ１は、光ピックアップ１０４を、その光軸（対物レンズの光軸）が光ディスク１０２の信号記録面に直交するように揺動させるスキュー用駆動手段であるスキューアクチュエータ１１７に供給されるように構成され、また、このスキューアクチュエータ１１７は、ラジアルスキューエラー信号処理部１１６からのスキューエラー信号に基づいて駆動制御されるスキューサーボ制御部１１８を備える。上記スキューサーボ制御部１１８は、システムコントローラ１０７からの制御指令に基づいても制御できるように構成されている。
【００２３】
次に、図２により本発明にかかる光ピックアップ１０４の構成について説明する。
光ピックアップ１０４は、図２に示すように、記録・再生用の光束を出射するレーザ光源２２と、このレーザ光源２２の光束出射方向に配置され、この光束を平行光にするコリメータレンズ２４と、このコリメータレンズ２４の平行光束出射側に配置されたビームスプリッタ２６（請求項に記載した光分離手段に相当する）と、このビームスプリッタ２６を透過した光束を集束して光ディスク１０２に照射する対物レンズ（光集束手段）２８と、上記ビームスプリッタ２６の反射方向に対向して配置され、ビームスプリッタ２６で分離された光ディスク１０２からの反射光束を受光して電気信号に変換する光検出手段３０と、光検出手段３０の光入射側に配置され、反射光束を光検出手段３０上に集束する集光レンズ３２とを備え、これらの各光学部品は図示省略したホルダ本体にマウントされる構成になっている。
【００２４】
次に、図３により本発明にかかるスキュー検出用のラジアルスキューエラー信号処理部１１６の構成について説明する。
スキュー検出用のフォトディテクタには、トラッキングエラー信号の生成に用いられている、図２に示す光検出手段３０が使用される。
この光検出手段３０は、図３に示すように、光ディスク１０２のラジアル方向（図４に示すウォーブルグルーブを横切る方向）に沿って分割される２以上の複数対領域に対応した複数対の、すなわち内側と外側の２対に分離できるように４分割された、フォトダイオードからなる受光部３０ａ〜３０ｄを有している。
上記受光部３０ａ〜３０ｄのうち、内側の受光部３０ｂと３０ｃには反射光束ＲＳＰの中心領域が照射され、また、外側の受光部３０ａと３０ｄには反射光束ＲＳＰの周辺領域が照射されるように構成されている。
【００２５】
また、上記ラジアルスキューエラー信号処理部１１６は、図３に示すように、反射光束ＲＳＰの中心領域の光照射に応じて上記内側の受光部３０ｂ及び３０ｃのそれぞれに発生する電流を電圧に変換する別々の電流−電圧変換回路４２ｂ及び４２ｃと、反射光束ＲＳＰの周辺領域の光照射に応じて上記外側の受光部３０ａと３０ｄのそれぞれに発生する電流を電圧に変換する別々の電流−電圧変換回路４２ａ及び４２ｄと、上記電流−電圧変換回路４２ｂ及び４２ｃから出力される信号の差信号でありウォーブル信号成分（後述するように、このウォーブル信号成分は、光ディスク１０２のトラックに対するこの光ディスク１０２に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分である）を含む第１プッシュプル信号ＰＰ１を求める第１減算回路４３と、上記電流−電圧変換回路４２ａの出力電圧と電流−電圧変換回路４２ｂの出力電圧とを加算する加算回路４４と、上記電流−電圧変換回路４２ｃの出力電圧と電流−電圧変換回路４２ｄの出力電圧とを加算する加算回路４５と、上記加算回路４４と４５の差信号でありウォーブル信号成分を含む第２プッシュプル信号ＰＰ２を求める第２減算回路４６とを備える。
【００２６】
上記減算回路４３の出力側には、この減算回路４３から出力される第１プッシュプル信号ＰＰ１中のウォーブル信号成分を通過させるＢＰＦ（帯域通過フィルタ）４７が直列に接続されている。
上記減算回路４６の出力側には、この減算回路４６から出力される第２プッシュプル信号ＰＰ２中のウォーブル信号成分を通過させるＢＰＦ（帯域通過フィルタ）４８が直列に接続されている。
これらのＢＰＦ４７，４８はスキュー検出に使用するウォーブル信号成分のＳ／Ｎを向上させるものである。
【００２７】
また、ＢＰＦ４７及びＢＰＦ４８に出力側には、ＢＰＦ４７を通過した第１プッシュプル信号のウォーブル信号成分の位相とＢＰＦ４８を通過した第２プッシュプル信号のウォーブル信号成分の位相とを比較し、この比較結果として得られる位相差に基づいて、光ディスク１０２に照射される記録／再生用光束の光軸に対するこの光ディスク１０２の傾き方向と傾き量を含むスキューエラー信号Ｓ１を生成する位相比較回路４９が接続されている。このスキューエラー信号Ｓ１は、図１に示すようにスキューサーボ制御部１１８に出力される。
【００２８】
なお、上記電流−電圧変換回路４２ｂ及び４２ｃと第１減算回路４３は第１プッシュプル信号検出回路を構成し、また、上記電流−電圧変換回路４２ａ及び４２ｄと加算回路４４、４５と第２減算回路４６は第２プッシュプル信号検出回路を構成する。
【００２９】
次に、上記のように構成された第１の実施の形態に示すスキュー検出装置によるスキュー検出方法及びその動作について説明する。
光ディスク１０２のラジアルスキューエラー検出は、図１に示す光ディスク装置の光ピックアップ１０４を利用して行われる。すなわち、図４に示す光ディスク１０２のウォーブルグルーブ１０２Ａに沿いトラッキングサーボ制御を行いながら、レーザ光源２２から出射された光束をコリメータレンズ２４により平行光束に変換し、さらに、ビームスプリッタ２６を透過させた後、対物レンズ２８により集束して光ディスク１０２の信号記録面に照射する。このとき、対物レンズ２８により集束された記録または再生用の光束ＭＳＰは、図４に示すように、光ディスク１０２のウォーブルグルーブ１０２Ａ上に配置される。
また、光ディスク１０２の信号記録面で反射された反射光束ＲＳＰ（図３参照）は、図１に示す対物レンズ２８を透過した後、ビームスプリッタ２６により反射され、さらに、集光レンズ３２により光検出手段３０上に集束される。
【００３０】
すなわち、内側の受光部３０ｂと３０ｃに集束された反射光束ＲＳＰの中心領域に対応する光は電流−電圧変換回路４２ｂ，４２ｃにより電圧に変化され、さらに、この両電流−電圧変換回路４２ｂ，４２ｃから出力された電圧を第１減算回路４３に入力することにより、第１減算回路４３からは両電圧の差に相当する第１プッシュプル信号ＰＰ１が算出される。この第１プッシュプル信号ＰＰ１はＢＰＦ４７を通して位相比較回路４９に入力される。
【００３１】
また、外側の受光部３０ａと３０ｄに集束された反射光束ＲＳＰの周辺領域に対応する光は電流−電圧変換回路４２ａ，４２ｄにより電圧に変化され、さらに、この両電流−電圧変換回路４２ａ，４２ｄから出力される電圧と上記電流−電圧変換回路４２ｂ，４２ｃから出力された電圧とを加算回路４４及び加算回路４５により、それぞれ加算した後、第２減算回路４６に入力することにより、第２減算回路４６からは両加算回路４４，４５出力信号の差に相当する第２プッシュプル信号ＰＰ２が算出される。この第２プッシュプル信号ＰＰ２はＢＰＦ４８を通して位相比較回路４９に入力される。
【００３２】
ここで、集光レンズ３２により光検出手段３０上に集束された反射光束ＲＳＰは、その内側（中央領域）に空間周波数の低域成分が、外側（周辺領域）に空間周波数の高域成分が分布している。また、全受光部３０ａ〜３０ｄが受光する反射光束に関する光学系の実効ＮＡ（開口数）よりも、反射光束ＲＳＰの中心領域に対応する受光部３０ｂと３０ｃが受光する反射光束に関する光学系の実効ＮＡの方が低く（小さく）なっている。
また、光ディスク１０２にスキューの変動があった場合、ウォーブル信号成分を含む第１及び第２プッシュプル信号ＰＰ１、ＰＰ２のＰＴＦ（Phase Transfer Function）が変動するが、第１プッシュプル信号ＰＰ１と第２プッシュプル信号ＰＰ２とでは、それらの等価的ＭＴＦ（Modulation Transfer Function）が互いに異なるため、それら第１及び第２プッシュプル信号ＰＰ１、ＰＰ２はＰＴＦの変動の仕方が異なる。尚、ここで等価的ＭＴＦとは、変動信号成分（この実施の形態ではウォーブル信号成分）の発生源の空間周波数（この実施の形態ではウォーブルグルーブの空間周波数）に対するプッシュプル信号の変動信号成分（この実施の形態ではウォーブル信号成分）の振幅を表す関数である。
【００３３】
そこで、この発明の実施の形態では、上記ＰＴＦの変動の違いを利用して、光ディスク１０２のラジアルスキューエラーを検出する。すなわち、光ディスク１０２にスキューがない場合において、記録／再生用の光束ＭＳＰが光ディスク１０２のウォーブルグルーブ１０２Ａをトラバース方向に横切る時の受光部３０ｂと３０ｃの出力差である第１プッシュプル信号ＰＰ１は、図５の（Ｂ）に示す曲線５１のように０点を通るＳ字型の出力特性となる。また、受光部３０ａ及び３０ｂと受光部３０ｃ及び３０ｄの出力差である第２プッシュプル信号ＰＰ２は、図５の（Ｂ）に示す曲線５２のように０点を通るＳ字型の出力特性となる。その結果、この出力特性の第１及び第２プッシュプル信号ＰＰ１、ＰＰ２がそれぞれのＢＰＦ４７およびＢＰＦ３８を通過した後の第１プッシュプル信号ＰＰ１と第２プッシュプル信号ＰＰ２との間の位相差はゼロであるから、位相比較回路４９は光ディスク１０２にラジアルスキューエラーがないと判断し、スキューサーボ制御部１１８は動作しない。
【００３４】
一方、光ディスク１０２が図２の破線に示すように対物レンズ２８の光軸の直交面から−Δθ傾くようなラジアルスキューが生じた場合において、記録／再生用の光束ＭＳＰが光ディスク１０２のウォーブルグルーブ１０２Ａをトラバース方向に横切る時の受光部３０ｂと３０ｃの出力差である第１プッシュプル信号ＰＰ１は、図５の（Ａ）に示す曲線５３のように０点を通る以前にゼロクロスする左側へシフトしたＳ字型の出力特性となる。また、受光部３０ａ及び３０ｂと受光部３０ｃ及び３０ｄの出力差である第２プッシュプル信号ＰＰ２は、図５の（Ａ）に示す曲線５４のように０点を通るＳ字型の出力特性となる。その結果、この出力特性の第１及び第２プッシュプル信号ＰＰ１、ＰＰ２がそれぞれのＢＰＦ４７およびＢＰＦ３８を通過した後の第１プッシュプル信号ＰＰ１と第２プッシュプル信号ＰＰ２との間には、スキュー量−Δθに応じた位相差が生じる。このため、位相比較回路４９では位相差を算出するとともに、この位相差に基づいて光ディスク１０２の傾き方向と傾き量を含むスキューエラー信号Ｓ１を生成し、このスキューエラー信号Ｓ１をスキューサーボ制御部１１８に入力してスキューアクチュエータ１１７を駆動制御することにより、対物レンズ３０の光軸が光ディスク１０２の信号記録面に直交するように光ピックアップ１０４を動作させ、対物レンズ３０の光軸と光ディスク１０２の信号記録面とが直交された状態に保持する。
【００３５】
他方、光ディスク１０２が図２の１点鎖線に示すように対物レンズ２８の光軸の直交面から＋Δθ傾くようなスキューが生じた場合において、記録／再生用の光束ＭＳＰが光ディスク１０２のウォーブルグルーブ１０２Ａをトラバース方向に横切る時の受光部３０ｂと３０ｃの出力差である第１プッシュプル信号ＰＰ１は、図５の（Ｃ）に示す曲線５５のように０点を通った以後にゼロクロスする右側へシフトしたＳ字型の出力特性となる。また、受光部３０ａ及び３０ｂと受光部３０ｃ及び３０ｄの出力差である第２プッシュプル信号ＰＰ２は、図５の（Ｃ）に示す曲線５６のように０点を通るＳ字型の出力特性となる。その結果、この出力特性の第１及び第２プッシュプル信号ＰＰ１、ＰＰ２がそれぞれのＢＰＦ４７およびＢＰＦ３８を通過した後の第１プッシュプル信号ＰＰ１と第２プッシュプル信号ＰＰ２との間には、スキュー量＋Δθに応じた位相差が生じる。このため、位相比較回路４９では位相差を算出するとともに、この位相差に基づいて光ディスク１０２の傾き方向と傾き量を含むスキューエラー信号Ｓ１を生成し、このスキューエラー信号Ｓ１をスキューサーボ制御部１１８に入力してスキューアクチュエータ１１７を駆動制御することにより、対物レンズ３０の光軸が光ディスク１０２の信号記録面に直交するように光ピックアップ１０４を動作させ、対物レンズ３０の光軸と光ディスク１０２の信号記録面とが直交された状態に保持する。
【００３６】
なお、図５の（Ａ）〜（Ｃ）において、横軸は、光ディスク１０２のウォーブルグルーブの中心線を基準としたこのウォーブルグルーブのトラバース方向における光束ＭＳＰの光スポットの位置座標を表している。左側の縦軸の数値は第１プッシュプル信号ＰＰ１の相対的出力値を表し、また、右側の縦軸の数値は第２プッシュプル信号ＰＰ２の相対的出力値を表している。
【００３７】
上記第１の実施の形態に示す光ピックアップ１０４において、ＤＶＤ±Ｒ／ＲＷ，ＣＤ−Ｒ／ＲＷのような光ディスク１０２への記録時は、レーザ光源２２から記録信号に応じて変化する３０ｍＷ程度のパワーの大きい光ビームを発生させる。この光束はコリメータレンズ２４により平行光束に変換され、ビームスプリッタ２８を透過した後、対物レンズ２８により集束されて光ディスク１０２の信号記録面に照射される。これにより、光ディスク１０２の記録膜を変質して光ディスク１０２に信号を記録する。
【００３８】
また、光ディスク１０２から反射された反射光束は対物レンズ２８を透過した後、ビームスプリッタ２６により集光レンズ３２に向けて反射され、この集光レンズ３２により光検出手段３０上に集束される。光検出手段３０の主受光部（図示省略）で受光された光信号はプリアンプ１２０で電気信号に変換され、フォーカスエラー信号として取り出される。また、受光部３０ａ〜３０ｄで受光された光信号はプリアンプ１２０で電気信号に変換され、トラッキングエラー信号として取り出される。
【００３９】
また、ＤＶＤ±Ｒ／ＲＷ，ＣＤ−Ｒ／ＲＷのような光ディスク１０２の再生時には、１ｍＷ程度の一定強度の光ビームをレーザ光源２２から発生させ、この光ビームを記録時と同じ光路で光ディスク１０２に照射する。これに伴い、光ディスク１０２の信号記録面から反射された反射光束は対物レンズ２８を透過した後、ビームスプリッタ２６により集光レンズ３２に向けて反射され、この集光レンズ３２により光検出手段３０上に集束される。光検出手段３０の主受光部（図示省略）で受光された光信号はプリアンプ１２０で電気信号に変換され、ＲＦ信号やフォーカスエラー信号として取り出される。また、受光部３０ａ〜３０ｄで受光された光信号はプリアンプ１２０で電気信号に変換され、トラッキングエラー信号として取り出される。
【００４０】
このような第１の実施の形態に示すスキュー検出装置及びこれを用いた光ピックアップ１０４並びに光ディスク装置１０１によれば、光ディスク１０２のウォーブルグルーブに沿いトラッキングサーボを行う時に、記録／再生用の光ピックアップ１０４を利用して、反射光束ＲＰＳの中心領域の光を受光する受光部３０ｂと３０ｃの出力差でありウォーブル信号成分を含む第１プッシュプル信号ＰＰ１と、反射光束ＲＰＳの中心領域及び周辺領域の光を受光する受光部３０ａ及び３０ｂと受光部３０ｃ及び３０ｄとの出力差でありウォーブル信号成分を含む第２プッシュプル信号ＰＰ２をそれぞれ算出し、この第１プッシュプル信号ＰＰ１のウォーブル信号成分の位相と第２プッシュプル信号ＰＰ２のウォーブル信号成分の位相とを位相比較回路４９で比較し、この比較結果として得られる位相差に基づいて、光ディスク１０２に照射される記録／再生用光束の光軸に対するこの光ディスク１０２の傾き方向と傾き量を含むスキューエラー信号Ｓ１を生成し、スキューエラー信号Ｓ１をスキューサーボ制御部１１８に入力してスキューアクチュエータ１１７を駆動制御することにより、対物レンズ３０の光軸が光ディスク１０２の信号記録面に直交するように光ピックアップ１０４を動作させる構成にしたので、光ディスク１０２のラジアルスキューを高精度に検出することができるとともに、従来のような別構造のスキューセンサが不要になるため、構成部品数が削減され、スキュー検出装置を含めた光ピックアップ１０４及び光ディスク装置１０１を低コスト化することができる。
【００４１】
次に、図６により本発明にかかるスキュー検出方法及びスキュー検出装置の第２の実施の形態について説明する。
この図６において、図３と異なるところは、第２プッシュプル信号ＰＰ２を外側の受光部３０ａと３０ｄの差信号から得るようにしたものである。以下、図３と同一の構成要素には同一符号を付して説明する。
【００４２】
図６に示す光検出手段３０は、図３に示す場合と同様に、光ディスク１０２のラジアル方向に複数対、すなわち内側と外側の２対に分離できるように４分割された、フォトダイオードからなる受光部３０ａ〜３０ｄを有し、この受光部３０ａ〜３０ｄのうち、内側の受光部３０ｂと３０ｃには反射光束ＲＳＰの中心領域が照射され、また、外側の受光部３０ａと３０ｄには反射光束ＲＳＰの周辺領域が照射されるように構成されている。
【００４３】
また、ラジアルスキューエラー信号処理部１１６Ａは、図６に示すように、反射光束ＲＳＰの中心領域の光照射に応じて上記内側の受光部３０ｂ及び３０ｃのそれぞれに発生する電流を電圧に変換する別々の電流−電圧変換回路４２ｂ及び４２ｃと、反射光束ＲＳＰの周辺領域の光照射に応じて上記外側の受光部３０ａと３０ｄのそれぞれに発生する電流を電圧に変換する別々の電流−電圧変換回路４２ａ及び４２ｄと、上記電流−電圧変換回路４２ｂ及び４２ｃから出力される信号の差信号でありウォーブル信号成分を含む第１プッシュプル信号ＰＰ１を求める第１減算回路４３と、上記電流−電圧変換回路４２ａ及び４２ｄから出力される信号の差信号でありウォーブル信号成分を含む第２プッシュプル信号ＰＰ２を求める第２減算回路４６と、減算回路４３から出力される第１プッシュプル信号ＰＰ１中のウォーブル信号成分を通過させるＢＰＦ（帯域通過フィルタ）４７と、減算回路４６から出力される第２プッシュプル信号ＰＰ２中のウォーブル信号成分を通過させるＢＰＦ（帯域通過フィルタ）４８と、ＢＰＦ４７を通過した第１プッシュプル信号のウォーブル信号成分の位相とＢＰＦ４８を通過した第２プッシュプル信号のウォーブル信号成分の位相とを比較し、この比較結果として得られる位相差に基づいて、光ディスク１０２に照射される記録／再生用光束の光軸に対するこの光ディスク１０２の傾き方向と傾き量を含むスキューエラー信号Ｓ１を生成する位相比較回路４９とを備えている。
【００４４】
このようなスキュー検出装置において、内側の受光部３０ｂと３０ｃに集束された反射光束ＲＳＰの中心領域に対応する光は電流−電圧変換回路４２ｂ，４２ｃにより電圧に変化され、この両電流−電圧変換回路４２ｂ，４２ｃから出力された電圧は第１減算回路４３に入力されることにより、この第１減算回路４３からは両電圧の差に相当しウォーブル信号成分を含む第１プッシュプル信号ＰＰ１が算出され、この第１プッシュプル信号ＰＰ１のウォーブル信号成分はＢＰＦ４７を通して位相比較回路４９に入力される。
また、外側の受光部３０ａと３０ｄに集束された反射光束ＲＳＰの周辺領域に対応する光は電流−電圧変換回路４２ａ，４２ｄにより電圧に変化され、この両電流−電圧変換回路４２ａ，４２ｄから出力される電圧は第２減算回路４６に入力されることにより、この第２減算回路４６からは両電圧の差に相当しウォーブル信号成分を含む第２プッシュプル信号ＰＰ２が算出され、この第２プッシュプル信号ＰＰ２のウォーブル信号成分はＢＰＦ４８を通して位相比較回路４９に入力される。
【００４５】
したがって、それぞれのＢＰＦ４７及び４８を通過した第１プッシュプル信号ＰＰ１のウォーブル信号成分と第２プッシュプル信号ＰＰ２のウォーブル信号成分とが位相比較回路４９に入力されることにより、光ディスク１０２にラジアルスキューが生じている場合は、この位相比較回路４９でそれらプッシュプル信号のウォーブル信号成分の位相差が算出されるとともに、この位相差に基づいて、光ディスク１０２に照射される記録／再生用光束の光軸に対するこの光ディスク１０２の傾き方向と傾き量を含むスキューエラー信号Ｓ１が生成される。この位相差に基づいて光ディスク１０２の傾き方向と傾き量を含むスキューエラー信号Ｓ１が生成される。このスキューエラー信号Ｓ１に基づいてスキューアクチュエータ１１７をスキューサーボ制御部１１８で制御することにより、光ディスク１０２のスキューがゼロになるように対物レンズ３０の光軸を光ディスク１０２の信号記録面に直交させる。
このような第２の実施の形態に示すスキュー検出装置においても、上記第１の実施の形態に示す場合と同様な作用効果が得られる。
【００４６】
次に、図７により本発明にかかるスキュー検出方法及びスキュー検出装置の第３の実施の形態について説明する。
この図７において、図３と異なるところは、光ディスク１０２のウォーブルグルーブ（トラック）をトラバースすることにより得られる第１及び第２プッシュプル信号からスキューエラー信号を得るようにしたものである。以下、図３と同一の構成要素には同一符号を付して説明する。
【００４７】
図７に示す光検出手段３０は、図３に示す場合と同様に、光ディスク１０２のラジアル方向に複数対、すなわち内側と外側の２対に分離できるように４分割された、フォトダイオードからなる受光部３０ａ〜３０ｄを有し、この受光部３０ａ〜３０ｄのうち、内側の受光部３０ｂと３０ｃには反射光束ＲＳＰの中心領域が照射され、また、外側の受光部３０ａと３０ｄには反射光束ＲＳＰの周辺領域が照射されるように構成されている。
【００４８】
また、ラジアルスキューエラー信号処理部１１６Ｂは、図７に示すように、反射光束ＲＳＰの中心領域の光照射に応じて上記内側の受光部３０ｂ及び３０ｃのそれぞれに発生する電流を電圧に変換する別々の電流−電圧変換回路４２ｂ及び４２ｃと、反射光束ＲＳＰの周辺領域の光照射に応じて上記外側の受光部３０ａと３０ｄのそれぞれに発生する電流を電圧に変換する別々の電流−電圧変換回路４２ａ及び４２ｄと、この電流−電圧変換回路４２ａ及び４２ｄから出力される信号の差信号であり光ディスク１０２のトラックに対するこの光ディスク１０２に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分（この実施の形態では、この変動信号成分は、後述するように、光ディスク１０２に照射される記録／再生用光束の光スポットが光ディスク１０２のトラックをトラバースすることにより生成される）を含む第１プッシュプル信号ＰＰ１を求める第１減算回路４３と、上記電流−電圧変換回路４２ａの出力電圧と電流−電圧変換回路４２ｂの出力電圧とを加算する加算回路４４と、上記電流−電圧変換回路４２ｃの出力電圧と電流−電圧変換回路４２ｄの出力電圧とを加算する加算回路４５と、上記加算回路４４と４５の差信号であり光ディスク１０２のトラックに対するこの光ディスク１０２に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第２プッシュプル信号ＰＰ２を求める第２減算回路４６と、第１プッシュプル信号の変動信号成分の位相と第２プッシュプル信号の変動信号成分の位相とを比較し、この比較結果として得られる位相差に基づいて、光ディスク１０２に照射される記録／再生用光束の光軸に対するこの光ディスク１０２の傾き方向と傾き量を含むスキューエラー信号Ｓ１を生成する位相比較回路４９とを備えている。
【００４９】
このようなスキュー検出装置において、光ディスク１０２のスキューエラー検出に際しては、光ディスク装置をスキューエラー検出モードに設定し、記録／再生用の光束ＭＳＰが光ディスク１０２のウォーブルグルーブ（トラック）をトラバースするようにする。このトラバース時に、内側の受光部３０ｂと３０ｃに集束された反射光束ＲＳＰの中心領域に対応する光は電流−電圧変換回路４２ｂ，４２ｃにより電圧に変化され、この両電流−電圧変換回路４２ｂ，４２ｃから出力された電圧は第１減算回路４３に入力されることにより、この第１減算回路４３からは両電圧の差に相当し光ディスク１０２のトラックに対するこの光ディスク１０２に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第１プッシュプル信号ＰＰ１が算出され、この第１プッシュプル信号ＰＰ１は位相比較回路４９に入力される。
また、トラバース時に外側の受光部３０ａと３０ｄに集束された反射光束ＲＳＰの周辺領域に対応する光は電流−電圧変換回路４２ａ，４２ｄにより電圧に変化され、この両電流−電圧変換回路４２ａ，４２ｄから出力される電圧と電流−電圧変換回路４２ｂ，４２ｃから出力された電圧とはそれぞれの加算回路４４，４５で加算された後、第２減算回路４６に入力されることにより、この第２減算回路４６からは両出力電圧の差に相当し光ディスク１０２のトラックに対するこの光ディスク１０２に照射される記録／再生用光束の光スポットの相対位置に応じて変動する変動信号成分を含む第２プッシュプル信号ＰＰ２が算出され、この第２プッシュプル信号ＰＰ２は位相比較回路４９に入力される。
【００５０】
したがって、第１プッシュプル信号ＰＰ１と第２プッシュプル信号ＰＰ２が位相比較回路４９に入力されることにより、光ディスク１０２にラジアルスキューが生じている場合は、この位相比較回路４９でそれらプッシュプル信号の変動信号成分の位相差が算出されるとともに、この位相差に基づいて、光ディスク１０２に照射される記録／再生用光束の光軸に対するこの光ディスク１０２の傾き方向と傾き量を含むスキューエラー信号Ｓ１が生成される。このスキューエラー信号Ｓ１に基づいてスキューアクチュエータ１１７をスキューサーボ制御部１１８で制御することにより、光ディスク１０２のスキューがゼロになるように対物レンズ３０の光軸を光ディスク１０２の信号記録面に直交させる。
このような第３の実施の形態に示すスキュー検出装置においても、上記第１の実施の形態に示す場合と同様な作用効果が得られる。
【００５１】
次に、図８により本発明にかかるスキュー検出に用いられる光ピックアップの他の実施の形態について説明する。
この図８（Ａ）に示す光ピックアップ１０４は、記録・再生用の光束を出射するレーザ光源２２と、このレーザ光源２２の光束出射方向に配置され、この光束を平行光にするコリメータレンズ２４と、このコリメータレンズ２４の平行光束出射側に配置されたビームスプリッタ２６（請求項に記載した光分離手段に相当する）と、このビームスプリッタ２６を透過した光束を集束して光ディスク１０２に照射する対物レンズ（光集束手段）２８と、上記ビームスプリッタ２６の反射方向に対向して配置され、ビームスプリッタ２６で分離された光ディスク１０２からの反射光束を受光して電気信号に変換する光検出手段３０と、光検出手段３０の光入射側に配置され、反射光束を光検出手段３０上に集束する集光レンズ３２と、この集光レンズ３２と光検出手段３０との間に配置され、集光レンズ３２からの出射光束を回折し、光ディスク１０２のラジアル方向に空間的に離間して各受光部３０ａ〜３０ｄ上にそれぞれ集束させるホログラム素子３４とを備え、これらの各光学部品は図示省略したホルダ本体にマウントされる構成になっている。
【００５２】
また、上記光検出手段３０は、図８（Ｂ）に示すように、その各受光部３０ａ〜３０ｄが、上記ホログラム素子３４で回折された各分割光束３４ａ〜３４ｄがそれら各受光部３０ａ〜３０ｄ上に集束されるように、光ディスク１０２のラジアル方向に空間的に離間して配列されている。
なお、このように配列された各受光部３０ａ〜３０ｄには、上記図３、図６または図７に示す構成のラジアルスキューエラー信号処理部が接続される。
【００５３】
このような光ピックアップ１０４においては、受光部３０ａ〜３０ｄで検出され、かつラジアルスキューエラー信号処理部で処理された第１及び第２プッシュプル信号のオフセットを比較し、このオフセットが同じであれば、光ディスク１０２にラジアル方向の傾きがなく、この両フセットが異なっている場合は、光ディスク１０２にラジアルスキューがあること判定される。したがって、光ディスク１０２のラジアルスキューがゼロになるように、スキューアクチュエータ１１７をスキューサーボ制御部１１８で制御して対物レンズ３０の光軸を光ディスク１０２の信号記録面に直交させればよい。
【００５４】
このような実施の形態に示す光ピックアップ１０４によれば、ホログラム素子３４で反射光束ＭＳＰを受光部３０ａ〜３０ｄの配列方向に分割して受光部３０ａ〜３０ｄ上に離して入射させるため、対物レンズ２８の視野が変動してもプッシュプルオフセットが変動しないようにすることができるほか、上記第１の実施の形態に示す場合と同様な作用効果が得られる。
【００５５】
なお、本実施の形態では前記光記録媒体が、ＤＶＤ±Ｒ、ＤＶＤ±ＲＷである場合について説明したが、本発明は、ＣＤ，ＤＶＤ，ＣＤ−Ｒ、ＣＤ−ＲＷ、ＤＶＤ−ＲＡＭまたはＢＬＵＥ−ＲＡＹＤＩＳＣなどのその他の光ディスクにも広く適用される。
また、本発明にかかるスキューセンサ及び光ピックアップは、上記実施の形態に示す構成のものに限定されるものではなく、請求項に記載した技術的範囲を逸脱しない範囲において種々に変更し変形することは勿論である。
また、本発明における光検出手段３０の分割数は、上記実施の形態に示す４分割したものに限らず、ＰＴＦの変化が検出し易いように、光記録媒体のウォーブルグルーブの空間周波数が第１プッシュプル信号または第２プッシュプル信号の等価的ＭＴＦのカットオフ周波数の１／４以上になるような分割数としてもよい。
【００５６】
【発明の効果】
以上説明したように本発明にかかるスキュー検出方法及びスキュー検出装置並びにこのスキュー検出装置を用いた光ピックアップ及び光ディスク装置によれば、光記録媒体の記録／再生用の光学系を利用して、光記録媒体に照射される記録／再生用光束の光軸に対する光記録媒体の傾き方向及び傾き量を検出できるように構成したので、光記録媒体のラジアルスキューを高精度に検出することができるとともに、従来のような別構造のスキューセンサが不要になって構成部品数を削減でき、スキュー検出装置を含めた光ピックアップ及び光ディスク装置を低コスト化することができる。
【図面の簡単な説明】
【図１】本発明にかかるスキュー検出装置及び光ピックアップを備えた光ディスク装置の構成を示すブロック図である。
【図２】本発明にかかるスキュー検出機能を備える光ピックアップの構成図である。
【図３】本発明の第１の実施の形態に係るスキュー検出装置の構成を示すブロック図である。
【図４】本発明のラジアルスキュー検出に適用されるウォーブルグルーブと光スポットとの関係を示す説明図である。
【図５】（Ａ）〜（Ｃ）は本発明の第１の実施の形態に係るスキュー検出装置の、光ディスクのウォーブルグルーブの中心線を基準としたこのウォーブルグルーブのトラバース方向における光束ＭＳＰの光スポットの位置と、第１及び第２プッシュプル出力信号との関係を示す説明図である。
【図６】本発明にかかるスキュー検出方法及びスキュー検出装置の第２の実施の形態を示すブロック図である。
【図７】本発明にかかるスキュー検出方法及びスキュー検出装置の第３の実施の形態を示すブロック図である。
【図８】（Ａ）は本発明にかかるスキュー検出に用いられる光ピックアップの他の実施の形態を示す構成図、（Ｂ）は各受光部と分離光束との関係を示す説明図である。
【符号の説明】
１０１……光ディスク装置、１０２……光ディスク、１０３……スピンドルモータ、１０４……光ピックアップ、１０５……送りモータ、１０７……システムコントローラ、１０９……サーボ制御部、１１６……ラジアルスキューエラー信号処理部、１１７……スキューアクチュエータ、１１８……スキューサーボ制御部、４９，５１，５２……ディレー回路、５０，５３，５４……ＢＰＦ（帯域通過フィルタ）、５５，５６……位相比較回路、５９，７４……差分算出回路、７１，７３……振幅検出回路、２２……レーザ光源、２４……コリメータレンズ、２６……ビームスプリッタ、２８……対物レンズ（光集束手段）、３０……光検出手段、３０ａ〜３０ｄ……受光部。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a skew detection method and a skew detection device for detecting a radial skew (inclination in the radial direction of an optical disk) of an optical recording medium (optical disk), and an optical pickup and an optical disk device including the skew detection device.
[0002]
[Prior art]
As the recording on the optical disc is increased in density, the skew margin of the optical disc is reduced. For this reason, in the optical pickup, the skew amount of the optical disk with respect to the optical axis of the optical pickup (objective lens) is detected using a skew sensor, and the optical axis of the objective lens is orthogonal to the signal recording surface of the optical disk in accordance with the tilt amount. Thus, the optical pickup is controlled by a skew servo mechanism.
[0003]
Such a conventional skew sensor includes a light emitting element composed of an LED arranged so that light is irradiated on a main body portion of an optical pickup toward a signal recording surface of the optical disc, and an optical disc arranged on the main body portion of the optical pickup. And a two-divided photodiode that receives the light reflected by the signal recording surface. A difference signal corresponding to the tilt amount of the optical recording medium is extracted from both photodiodes, and the difference signal is detected as a skew error signal. At the same time, the skew servo mechanism is controlled by the skew error signal so that the optical axis of the optical pickup (the optical axis of the objective lens) is orthogonal to the signal recording surface of the optical recording medium.
[0004]
[Problems to be solved by the invention]
However, since the conventional skew sensor as described above requires a light emitting element and a photodiode dedicated to skew detection, there is a problem that the number of parts increases and the cost of the optical pickup increases.
In addition, since the conventional skew sensor detects the tilt amount of the optical disk by extracting the difference between the output signals of the two divided photodiodes, the tilt of the optical disk is changed when the distance between the optical disk and the skew sensor varies. Even if the amount is the same, the light quantity distribution of the beam on the skew detection photodiode surface changes, and an error occurs in the tilt amount of the optical disk.
Also, the distance between the optical disk and the skew sensor varies depending on the type of optical disk, such as CD and DVD, the state of chucking of the optical disk to the turntable, and the method of warping of the optical disk. Yes. Therefore, in this state, the output of the light detection element always includes an error, and accurate skew detection is difficult.
[0005]
Therefore, if the skew information can be detected by the recording / reproducing optical system without using the skew sensor having the different structure as described above, the skew error signal is detected through the optical lens and the light detecting element actually used for reading and writing. Therefore, accurate skew detection without error can be performed.
[0006]
The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to detect the tilt and amount of an optical recording medium using an optical system for recording / reproducing of the optical recording medium. By configuring as described above, a skew detection method, a skew detection device, an optical pickup using the skew detection device, and a skew detection method, which enables high-accuracy radial skew detection and can reduce costs by reducing the number of components are provided. To provide an optical disk device.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, a skew detection method according to the present invention irradiates a signal recording surface of an optical recording medium with a light source, light detection means, and a light beam from the light source, and is reflected from the signal recording surface. The optical recording medium with respect to the optical axis of the recording / reproducing light beam irradiated to the optical recording medium using a recording / reproducing optical system configured such that the reflected light beam is focused on the light detection means A skew detection method for detecting a skew that is a slope of the optical recording medium, wherein the light detection means includes a plurality of pairs of divided light receiving units corresponding to two or more pairs of regions divided along a radial direction of the optical recording medium. A pair of light receiving portions located on the inside of the light receiving portion receives the light in the central region of the reflected light flux and is located outside the light receiving portion. A pair of outer light-receiving parts that is a pair of light-receiving parts By receiving light in the peripheral region of the reflected light beam, the effective NA (numerical aperture) of the optical system related to the reflected light beam received by the inner light receiving unit pair is reflected light beam received by the outer light receiving unit pair. Smaller than the effective NA of the optical system with respect to the reflected light flux, which is the sum of the effective NA of the optical system or the reflected light beam received by the inner light receiving portion pair and the reflected light beam received by the outer light receiving portion pair. The difference signal between the signals output from the respective light receiving portions of the inner light receiving portion pair.Fluctuation signal that varies according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording mediumA difference signal between a first push-pull signal including a component and a signal output from each light receiving unit of the outer light receiving unit pair or an output signal of each light receiving unit of the outer light receiving unit pair It is the difference signal of the signal after adding each output signalFluctuation signal that varies according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording mediumThe second push-pull signal including the component has equivalent MTFs (modulation transfer functions) different from each other, and the variation of the PTF (phase transfer function) of the first push-pull signal generated by the variation of the skew The variation of the PTF of the second push-pull signal is different from each other, where the equivalent MTF isFluctuationsignalComponentOf the push-pull signal to the spatial frequency of the sourceFluctuation signalA function representing the amplitude of the component, and the first push-pull signalFluctuation signalThe phase of the component and the second push-pull signalFluctuation signalThe skew including the tilt direction and the tilt amount of the optical recording medium with respect to the optical axis of the recording / reproducing light beam irradiated on the optical recording medium based on the phase difference obtained as a result of the comparison An error signal is generated.
[0008]
  BookAccording to the skew detection method of the invention, an optical system for recording / reproducing of an optical recording medium is used., With respect to the optical axis of the recording / reproducing light beam irradiated on the optical recording mediumTilt of optical recording mediumdirectionas well asInclinationThe amount can be detected, high-accuracy radial skew detection can be performed, and the number of components can be reduced to reduce the cost.
[0009]
  Further, the skew detection apparatus according to the present invention irradiates the signal recording surface of the optical recording medium with the light source, the light detection means, and the light beam from the light source, and the reflected light beam reflected from the signal recording surface detects the light. A skew which is an inclination of the optical recording medium with respect to an optical axis of a recording / reproducing light beam irradiated on the optical recording medium, using a recording / reproducing optical system configured to be focused on the means; In the skew detection apparatus, the light detection unit includes a plurality of pairs of divided light receiving units corresponding to two or more pairs of regions divided along a radial direction of the optical recording medium. The outer side which is a pair of light receiving parts located on the outer side of the light receiving part, and the inner light receiving part pair which is a pair of light receiving parts located on the inner side of the light receiving part receives the light in the central region of the reflected light flux. A pair of light-receiving portions is a peripheral area of the reflected light flux. The effective NA (numerical aperture) of the optical system related to the reflected light beam received by the inner light receiving unit pair is the effective NA of the optical system related to the reflected light beam received by the outer light receiving unit pair. NA or smaller than the effective NA of the optical system with respect to the reflected light beam that is the sum of the reflected light beam received by the inner light receiving unit pair and the reflected light beam received by the outer light receiving unit pair, so that the inner light receiving unit pair The difference signal between the signals output from each light receiving unitFluctuation signal that varies according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording mediumA difference signal between a first push-pull signal including a component and a signal output from each light receiving unit of the outer light receiving unit pair or an output signal of each light receiving unit of the outer light receiving unit pair It is the difference signal of the signal after adding each output signalFluctuation signal that varies according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording mediumThe second push-pull signal including the component has equivalent MTFs (modulation transfer functions) different from each other, and the variation of the PTF (phase transfer function) of the first push-pull signal generated by the variation of the skew The PTF variation of the second push-pull signal is different from each other, where the equivalent MTF isFluctuationsignalComponentOf the push-pull signal to the spatial frequency of the sourceFluctuation signalA first push-pull signal detecting means for detecting the first push-pull signal; a second push-pull signal detecting means for detecting the second push-pull signal; and Push-pull signalFluctuation signalThe phase of the component and the second push-pull signalFluctuation signalThe skew error including the tilt direction and the tilt amount of the optical recording medium with respect to the optical axis of the recording / reproducing light beam irradiated to the optical recording medium based on the phase difference obtained as a result of the comparison And phase comparison means for generating a signal.
[0010]
  BookAccording to the skew detection apparatus of the invention, an optical system for recording / reproducing of an optical recording medium is used., With respect to the optical axis of the recording / reproducing light beam irradiated on the optical recording mediumTilt of optical recording mediumdirectionas well asInclinationThe amount can be detected, high-accuracy radial skew detection can be performed, and the number of components can be reduced to reduce the cost.
[0011]
  The optical pickup according to the present invention includes a light source that emits a light beam for recording or reproduction, a focusing unit that focuses the light beam from the light source and irradiates the optical recording medium, and the optical recording emitted from the light source. A light separating means for separating a light flux to the medium and a reflected light flux from the optical recording medium; a light detecting means for receiving the reflected light flux separated by the light separating means; and a recording irradiated to the optical recording medium. An optical pickup having a skew detection device that detects a skew that is an inclination of the optical recording medium with respect to the optical axis of the reproducing light beam, the skew detection device being divided along a radial direction of the optical recording medium A pair of divided light receiving units corresponding to two or more pairs of regions, and an inner light receiving unit pair, which is a pair of light receiving units located inside the light receiving unit, By receiving the light in the central region of the incident light beam and allowing the outer light receiving unit pair, which is a pair of light receiving units located outside the light receiving unit, to receive the light in the peripheral region of the reflected light beam. The effective NA (numerical aperture) of the optical system related to the reflected light beam received by the inner light receiving portion pair is received by the effective NA of the optical system related to the reflected light beam received by the outer light receiving portion pair or the inner light receiving portion pair. The reflected light beam and the reflected light beam received by the outer light receiving unit pair are smaller than the effective NA of the optical system so that the signal output from each light receiving unit of the inner light receiving unit pair is smaller than the effective NA of the optical system. Difference signalFluctuation signal that varies according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording mediumA difference signal between a first push-pull signal including a component and a signal output from each light receiving unit of the outer light receiving unit pair or an output signal of each light receiving unit of the outer light receiving unit pair It is the difference signal of the signal after adding each output signalFluctuation signal that varies according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording mediumThe second push-pull signal including the component has equivalent MTFs (modulation transfer functions) different from each other, and the variation of the PTF (phase transfer function) of the first push-pull signal generated by the variation of the skew The PTF variation of the second push-pull signal is different from each other, where the equivalent MTF isFluctuationsignalComponentOf the push-pull signal to the spatial frequency of the sourceFluctuation signalThe skew detection device further includes a first push-pull signal detection unit that detects the first push-pull signal and a second push-pull signal detection that detects the second push-pull signal. Means and the first push-pull signalFluctuation signalThe phase of the component and the second push-pull signalFluctuation signalThe skew error including the tilt direction and the tilt amount of the optical recording medium with respect to the optical axis of the recording / reproducing light beam irradiated to the optical recording medium based on the phase difference obtained as a result of the comparison A phase comparison means for generating a signal, a skew drive means for swinging the optical axis of the focusing means, and an optical axis of the focusing means by the skew error signal generated by the phase comparison means. And skew servo control means for controlling the skew drive means so as to be orthogonal to the signal recording surface of the recording medium.
[0012]
  BookAccording to the optical pickup of the invention, the optical system for recording / reproducing of the optical recording medium is utilized., With respect to the optical axis of the recording / reproducing light beam irradiated on the optical recording mediumTilt of optical recording mediumdirectionas well asInclinationThe amount can be detected, high-accuracy radial skew detection can be performed, and the number of components can be reduced to reduce the cost.
[0013]
  The optical disc apparatus according to the present invention includes an optical recording medium rotated by a driving unit, an optical pickup moved in a radial direction of the optical recording medium by a feeding unit, rotation of the optical recording medium, and the optical pickup. An optical disc apparatus comprising: control means for controlling the movement of the recording medium in response to recording and / or reproducing operations; and signal processing means for performing signal processing of recording and / or reproducing operations on the optical recording medium by the optical pickup. The optical pickup includes a light source that emits a light beam for recording or reproduction, a focusing unit that focuses the light beam from the light source and irradiates the optical recording medium, and an optical recording medium emitted from the light source to the optical recording medium. A light separating unit that separates a light beam and a reflected light beam from the optical recording medium; and a light detecting unit that receives the reflected light beam separated by the light separating unit. A skew detecting device for detecting a skew that is an inclination of the optical recording medium with respect to an optical axis of a recording / reproducing light beam irradiated on the optical recording medium, wherein the skew detecting device is a radial of the optical recording medium. Inner light receiving means comprising a light detecting means having a plurality of pairs of divided light receiving portions corresponding to two or more pairs of regions divided along a direction, and being a pair of light receiving portions located inside the light receiving portions The pair of pairs receives light in the central region of the reflected light beam, and the outer light receiving portion pair, which is a pair of light receiving portions located outside the light receiving portion, receives light in the peripheral region of the reflected light beam. Therefore, the effective NA (numerical aperture) of the optical system related to the reflected light beam received by the inner light receiving unit pair is the effective NA of the optical system related to the reflected light beam received by the outer light receiving unit pair or the inner light receiving unit. Pair receives light A signal output from each light-receiving unit of the inner light-receiving unit pair so that the reflected light beam, which is the sum of the reflected light beam and the reflected light beam received by the outer light-receiving unit pair, is smaller than the effective NA of the optical system. Is the difference signalFluctuation signal that varies according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording mediumA difference signal between a first push-pull signal including a component and a signal output from each light receiving unit of the outer light receiving unit pair or an output signal of each light receiving unit of the outer light receiving unit pair It is the difference signal of the signal after adding each output signalFluctuation signal that varies according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording mediumThe second push-pull signal including the component has equivalent MTFs (modulation transfer functions) different from each other, and the variation of the PTF (phase transfer function) of the first push-pull signal generated by the variation of the skew The PTF variation of the second push-pull signal is different from each other, where the equivalent MTF isFluctuationsignalComponentOf the push-pull signal to the spatial frequency of the sourceFluctuation signalThe skew detection device further includes a first push-pull signal detection unit that detects the first push-pull signal and a second push-pull signal detection that detects the second push-pull signal. Means and the first push-pull signalFluctuation signalThe phase of the component and the second push-pull signalFluctuation signalThe skew error including the tilt direction and the tilt amount of the optical recording medium with respect to the optical axis of the recording / reproducing light beam irradiated to the optical recording medium based on the phase difference obtained as a result of the comparison A phase comparison unit that generates a signal, and the optical pickup further includes a skew driving unit that swings the optical axis of the focusing unit, and a skew error signal generated by the phase comparison unit. And skew servo control means for controlling the skew drive means so that the optical axis is orthogonal to the signal recording surface of the optical recording medium.
[0014]
  BookAccording to the optical disk apparatus of the invention, the optical system for recording / reproducing of the optical recording medium is used., With respect to the optical axis of the recording / reproducing light beam irradiated on the optical recording mediumTilt of optical recording mediumdirectionas well asInclinationThe amount can be detected, high-accuracy radial skew detection can be performed, and the number of components can be reduced to reduce the cost.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of a skew detection method, a skew detection device, and an optical pickup and an optical disk device using the skew detection device according to the present invention will be described below in detail with reference to the drawings.
  FIG. 1 is a block diagram showing a configuration of a skew detection apparatus and an optical disc apparatus including an optical pickup according to the present invention, FIG. 2 is a configuration diagram of an optical pickup having a skew detection function according to the present invention, and FIG. FIG. 4 is a block diagram showing a configuration of a skew detection apparatus according to one embodiment, and FIG. 4 shows a wobble groove and light applied to radial skew detection according to the present invention.TheFIG. 5 is an explanatory diagram showing the relationship between the pot and FIG. 5 is an explanatory diagram showing the relationship between the radial skew and the push-pull output signal of the skew detection device according to the first embodiment of the present invention. The optical disk apparatus shown in FIG. 1 is an example of a recording / reproducing apparatus in which a skew detection apparatus and an optical pickup described below can be mounted.
[0016]
First, the configuration of the optical disc apparatus 101 shown in FIG. 1 will be described.
This optical disk device 101 includes a spindle motor 103 as a driving means for rotationally driving an optical disk 102 which is an optical recording medium such as CD, DVD, DVD ± R / RW, and CD-R / RW, an optical pickup 104, A feed motor 105 is provided as drive means for moving the optical pickup 104 in the radial direction of the optical disk 102.
Here, the spindle motor 103 and the feed motor 105 are configured to be driven and controlled at a predetermined rotational speed by a servo control unit 109 that is controlled based on a command from the system controller 107.
[0017]
  The signal modulator / demodulator & ECC block 108 shown in FIG. 1 performs signal modulation, demodulation, and addition of ECC (error correction code).
  The optical pickup 104 is placed on the signal recording surface of the rotating optical disk 102 in accordance with a command from the signal modulator / demodulator & ECC block 108.,The luminous flux from the light source,For recording / playbackLight ofspotWhenIrradiationYouIt is comprised so that. Further, the optical pickup 104 processes various signals output from the light detection means (described later) of the optical pickup 104 in accordance with the reflected light beam reflected from the signal recording surface of the optical disc 102 and the radial skew error signal processing. The unit 116 is configured to be supplied.
[0018]
The preamplifier 120 is configured to generate a focus error signal, a tracking error signal, an RF signal, and the like based on various signals output from light detection means (described later) of the optical pickup 104 according to the reflected light flux. Further, depending on the type of recording medium to be reproduced, predetermined processing such as demodulation and error correction processing based on these signals is performed by the servo control unit 109, the signal modulator / demodulator & ECC block 108, and the like.
Here, if the recording signal demodulated by the signal modulator / demodulator & ECC block 108 is for data storage of a computer, for example, it is sent to the external computer 130 or the like via the interface 111. Accordingly, the external computer 130 and the like are configured to receive a signal recorded on the optical disc 102 as a reproduction signal.
[0019]
If the recording signal demodulated by the signal modulator / demodulator & ECC block 108 is for audio / visual use, the D / A conversion unit of the D / A and A / D converter 112 performs digital / analog conversion, and audio / visual processing is performed. Supplied to the unit 113. Audio / video signal processing is performed by the audio / visual processing unit 113 and transmitted to an external imaging / projection device via the audio / visual signal input / output unit 114.
[0020]
The optical pickup 104 is connected to a feed motor 105 for moving to a predetermined recording track on the optical disk 102, for example. Control of the spindle motor 103, control of the feed motor 105, and control of the focusing direction and tracking direction of the biaxial actuator that holds the objective lens of the optical pickup 104 are performed by a servo control unit 109, respectively.
The laser control unit 121 controls the laser light source 22 (see FIG. 2) in the optical pickup 104, and is configured to control the output power of the laser light source 22 according to the recording mode and the reproduction mode.
[0021]
The radial skew error signal processing unit 116 performs a tracking servo along a signal output from a light detection means (described later) of the optical pickup 104, that is, a wobble groove formed on the optical disc 102, and performs this on the wobble groove. The reflected light beam corresponding to the moving light spot is received by the light detection means to detect the phase difference between the first and second push-pull signals output from the light detection means, and from this phase difference, the optical disc 102 The skew error signal S1 including the tilt direction and the tilt amount is generated.
[0022]
The skew error signal S1 output from the radial skew error signal processing unit 116 is used for skewing the optical pickup 104 so that its optical axis (optical axis of the objective lens) is orthogonal to the signal recording surface of the optical disk 102. The skew actuator 117 is configured to be supplied to a skew actuator 117 that is a driving unit, and includes a skew servo control unit 118 that is driven and controlled based on a skew error signal from the radial skew error signal processing unit 116. . The skew servo control unit 118 is configured to be controlled based on a control command from the system controller 107.
[0023]
Next, the configuration of the optical pickup 104 according to the present invention will be described with reference to FIG.
As shown in FIG. 2, the optical pickup 104 has a laser light source 22 that emits a light beam for recording / reproduction, a collimator lens 24 that is arranged in the light beam emission direction of the laser light source 22 and converts the light beam into parallel light, A beam splitter 26 (corresponding to the light separating means described in the claims) disposed on the collimating lens 24 on the parallel light beam emitting side, and an objective lens for focusing the light beam transmitted through the beam splitter 26 and irradiating the optical disk 102 (Light focusing means) 28, light detection means 30 that is arranged facing the reflection direction of the beam splitter 26 and receives the reflected light beam from the optical disk 102 separated by the beam splitter 26, and converts it into an electrical signal; A condenser lens 32 that is arranged on the light incident side of the light detection means 30 and focuses the reflected light flux on the light detection means 30. Optics has a structure that is mounted on the holder main body (not shown).
[0024]
Next, the configuration of the radial skew error signal processing unit 116 for skew detection according to the present invention will be described with reference to FIG.
The photodetector for skew detection uses the light detection means 30 shown in FIG. 2, which is used to generate a tracking error signal.
As shown in FIG. 3, the light detection means 30 includes a plurality of pairs corresponding to two or more pairs of regions divided along the radial direction of the optical disc 102 (the direction crossing the wobbled groove shown in FIG. 4). That is, it has light receiving portions 30a to 30d made of photodiodes that are divided into four so as to be separated into two pairs of an inner side and an outer side.
Among the light receiving portions 30a to 30d, the inner light receiving portions 30b and 30c are irradiated with the central region of the reflected light beam RSP, and the outer light receiving portions 30a and 30d are irradiated with the peripheral region of the reflected light beam RSP. It is configured.
[0025]
  Further, as shown in FIG. 3, the radial skew error signal processing unit 116 converts the current generated in each of the inner light receiving units 30b and 30c into a voltage in accordance with the light irradiation of the central region of the reflected light beam RSP. Separate current-voltage conversion circuits 42b and 42c, and separate current-voltage conversion circuits for converting the current generated in each of the outer light receiving units 30a and 30d into voltages in response to light irradiation in the peripheral region of the reflected light beam RSP. 42a and 42d and a difference signal between signals output from the current-voltage conversion circuits 42b and 42c, and a wobble signal component(As will be described later, this wobble signal component is a fluctuation signal component that varies depending on the relative position of the light spot of the recording / reproducing light beam irradiated on the optical disk 102 with respect to the track of the optical disk 102).A first subtractor circuit 43 for obtaining a first push-pull signal PP1 including, an adder circuit 44 for adding the output voltage of the current-voltage conversion circuit 42a and the output voltage of the current-voltage conversion circuit 42b, and the current-voltage An adder circuit 45 that adds the output voltage of the conversion circuit 42c and the output voltage of the current-voltage conversion circuit 42d, and a second push-pull signal PP2 that is a difference signal between the adder circuits 44 and 45 and that includes a wobble signal component. 2 subtraction circuit 46.
[0026]
  The subtraction circuit 43ofOn the output side, thisSubtraction circuit 43Is connected in series with a BPF (band pass filter) 47 that passes a wobble signal component in the first push-pull signal PP1 output from the first push-pull signal PP1.
  Subtracting circuit 46ofOn the output side, thisSubtraction circuit 46Is connected in series with a BPF (band pass filter) 48 that passes the wobble signal component in the second push-pull signal PP2 output from the.
  ThisTheyBPF 47 and 48 for skew detectionuseWobble signalImprove S / N of ingredients.
[0027]
  Further, on the output side of the BPF 47 and the BPF 48, the first push-pull signal passing through the BPF 47 is transmitted.Of the wobble signal componentOf the second push-pull signal that has passed through the phase and BPF 48Of the wobble signal componentThe result of this comparison with the phaseAsObtainedPlaceBased on phase differenceThe optical axis of the recording / reproducing light beam irradiated on the optical disk 102A phase comparison circuit 49 that generates a skew error signal S1 including the tilt direction and tilt amount of the optical disk 102 is connected. The skew error signal S1 is output to the skew servo control unit 118 as shown in FIG.
[0028]
  The current-voltage conversion circuits 42b and 42c and the first subtraction circuit 43Is the first1 push-pull signal detection circuit, and the current-voltage conversion circuits 42a and 42d, the addition circuits 44 and 45, and the second subtraction circuit 46.Is the firstA two push-pull signal detection circuit is configured.
[0029]
Next, a skew detection method and operation by the skew detection apparatus configured as described above according to the first embodiment will be described.
The radial skew error detection of the optical disc 102 is performed using the optical pickup 104 of the optical disc apparatus shown in FIG. That is, while performing tracking servo control along the wobbled groove 102A of the optical disk 102 shown in FIG. 4, the light beam emitted from the laser light source 22 is converted into a parallel light beam by the collimator lens 24, and further transmitted through the beam splitter 26. Thereafter, the light is focused by the objective lens 28 and irradiated onto the signal recording surface of the optical disk 102. At this time, the recording or reproducing beam MSP focused by the objective lens 28 is arranged on the wobbled groove 102A of the optical disc 102 as shown in FIG.
A reflected light beam RSP (see FIG. 3) reflected by the signal recording surface of the optical disk 102 passes through the objective lens 28 shown in FIG. 1, is reflected by the beam splitter 26, and is further detected by the condenser lens 32. Focused on means 30.
[0030]
That is, the light corresponding to the central region of the reflected light beam RSP focused on the inner light receiving portions 30b and 30c is changed to a voltage by the current-voltage conversion circuits 42b and 42c, and further, the both current-voltage conversion circuits 42b and 42c. The first push-pull signal PP1 corresponding to the difference between the two voltages is calculated from the first subtraction circuit 43 by inputting the voltage output from the first subtraction circuit 43. The first push-pull signal PP1 is input to the phase comparison circuit 49 through the BPF 47.
[0031]
  Further, the light corresponding to the peripheral region of the reflected light beam RSP focused on the outer light receiving portions 30a and 30d is changed to a voltage by the current-voltage conversion circuits 42a and 42d, and the current-voltage conversion circuits 42a and 42d. Are added by the adder circuit 44 and the adder circuit 45, respectively, and then input to the second subtractor circuit 46, whereby the second subtraction is performed. From the circuit 46, a second push-pull signal PP2 corresponding to the difference between the output signals of both the adder circuits 44 and 45 is calculated. The second push-pull signal PP2 is input to the phase comparison circuit 49 through the BPF 48..
[0032]
  Here, the reflected light beam RSP focused on the light detection means 30 by the condenser lens 32 has a low frequency component of the spatial frequency on the inner side (center region) and a high frequency component of the spatial frequency on the outer side (peripheral region). Distributed. In addition, the effective optical system related to the reflected light beam received by the light receiving units 30b and 30c corresponding to the central region of the reflected light beam RSP is more than the effective NA (numerical aperture) of the optical system related to the reflected light beam received by all the light receiving units 30a to 30d. NA is lower (smaller).
  In addition, when the skew of the optical disc 102 varies, the PTF (Phase Transfer Function) of the first and second push-pull signals PP1 and PP2 including the wobble signal component varies, but the first push-pull signal PP1 and the second push-pull signal PP1 and second Push-pull signal PP2soThoseEquivalentSince the MTFs (Modulation Transfer Functions) are different from each other, the first and second push-pull signals PP1 and PP2 have different ways of changing the PTF. Here, the equivalent MTF isFluctuation signal component (in this embodimentWobble signalIngredients)Source spatial frequency (In this embodimentPush-pull signal to the wobble groove spatial frequency)FluctuationSignal component(Wobble signal component in this embodiment)This is a function representing the amplitude of.
[0033]
Therefore, in the embodiment of the present invention, the radial skew error of the optical disk 102 is detected using the difference in the variation of the PTF. That is, when there is no skew in the optical disc 102, the first push-pull signal PP1 that is the output difference between the light receiving portions 30b and 30c when the recording / reproducing beam MSP crosses the wobble groove 102A of the optical disc 102 in the traverse direction is As shown by a curve 51 shown in FIG. 5B, an S-shaped output characteristic passing through the 0 point is obtained. Further, the second push-pull signal PP2 which is an output difference between the light receiving units 30a and 30b and the light receiving units 30c and 30d has an S-shaped output characteristic passing through the 0 point as indicated by a curve 52 shown in FIG. Become. As a result, the phase difference between the first push-pull signal PP1 and the second push-pull signal PP2 after the first and second push-pull signals PP1 and PP2 having the output characteristics have passed through the BPF 47 and BPF 38, respectively, is zero. Therefore, the phase comparison circuit 49 determines that the optical disk 102 has no radial skew error, and the skew servo control unit 118 does not operate.
[0034]
On the other hand, when the optical disc 102 has a radial skew that is inclined by −Δθ from the plane orthogonal to the optical axis of the objective lens 28 as indicated by a broken line in FIG. The first push-pull signal PP1, which is the output difference between the light receiving portions 30b and 30c when traversing 102A in the traverse direction, is shifted to the left which crosses zero before passing through the zero point as shown by the curve 53 shown in FIG. S-shaped output characteristics. Further, the second push-pull signal PP2 which is an output difference between the light receiving units 30a and 30b and the light receiving units 30c and 30d has an S-shaped output characteristic passing through the 0 point as shown by a curve 54 in FIG. Become. As a result, there is a skew amount between the first push-pull signal PP1 and the second push-pull signal PP2 after the first and second push-pull signals PP1 and PP2 having the output characteristics pass through the BPF 47 and the BPF 38, respectively. A phase difference corresponding to −Δθ occurs. Therefore, the phase comparison circuit 49 calculates the phase difference, generates a skew error signal S1 including the tilt direction and the tilt amount of the optical disk 102 based on the phase difference, and uses the skew error signal S1 as the skew servo control unit 118. And the skew actuator 117 is driven and controlled to operate the optical pickup 104 so that the optical axis of the objective lens 30 is orthogonal to the signal recording surface of the optical disc 102, and the optical axis of the objective lens 30 and the signal of the optical disc 102 are controlled. The recording surface is kept orthogonal.
[0035]
On the other hand, when the optical disk 102 is skewed by + Δθ from the plane orthogonal to the optical axis of the objective lens 28 as indicated by the one-dot chain line in FIG. The first push-pull signal PP1, which is the output difference between the light receiving portions 30b and 30c when traversing 102A in the traverse direction, passes to the right side after zero passing as shown by the curve 55 shown in FIG. A shifted S-shaped output characteristic is obtained. Further, the second push-pull signal PP2, which is the output difference between the light receiving portions 30a and 30b and the light receiving portions 30c and 30d, has an S-shaped output characteristic passing through the 0 point as indicated by a curve 56 shown in FIG. Become. As a result, there is a skew amount between the first push-pull signal PP1 and the second push-pull signal PP2 after the first and second push-pull signals PP1 and PP2 having the output characteristics pass through the BPF 47 and the BPF 38, respectively. A phase difference corresponding to + Δθ occurs. Therefore, the phase comparison circuit 49 calculates the phase difference, generates a skew error signal S1 including the tilt direction and the tilt amount of the optical disk 102 based on the phase difference, and uses the skew error signal S1 as the skew servo control unit 118. And the skew actuator 117 is driven and controlled to operate the optical pickup 104 so that the optical axis of the objective lens 30 is orthogonal to the signal recording surface of the optical disc 102, and the optical axis of the objective lens 30 and the signal of the optical disc 102 are controlled. The recording surface is kept orthogonal.
[0036]
  In FIGS. 5A to 5C, the horizontal axis isThe position coordinates of the light spot of the light beam MSP in the traverse direction of the wobble groove with respect to the center line of the wobble groove of the optical disc 102 are shown.The numerical value on the left vertical axis represents the relative output value of the first push-pull signal PP1, and the numerical value on the right vertical axis represents the relative output value of the second push-pull signal PP2.
[0037]
In the optical pickup 104 shown in the first embodiment, at the time of recording on the optical disk 102 such as DVD ± R / RW, CD-R / RW, about 30 mW that changes according to the recording signal from the laser light source 22. Generate a light beam with high power. This light beam is converted into a parallel light beam by the collimator lens 24, passes through the beam splitter 28, is focused by the objective lens 28, and is irradiated onto the signal recording surface of the optical disk 102. As a result, the recording film of the optical disc 102 is altered to record a signal on the optical disc 102.
[0038]
The reflected light beam reflected from the optical disk 102 passes through the objective lens 28, is reflected toward the condenser lens 32 by the beam splitter 26, and is focused on the light detection means 30 by the condenser lens 32. An optical signal received by a main light receiving unit (not shown) of the light detecting means 30 is converted into an electric signal by the preamplifier 120 and is taken out as a focus error signal. The optical signals received by the light receiving units 30a to 30d are converted into electrical signals by the preamplifier 120 and extracted as tracking error signals.
[0039]
Further, when reproducing the optical disk 102 such as DVD ± R / RW or CD-R / RW, a light beam having a constant intensity of about 1 mW is generated from the laser light source 22, and this light beam is transmitted along the same optical path as that during recording. Irradiate. Accordingly, the reflected light beam reflected from the signal recording surface of the optical disk 102 is transmitted through the objective lens 28 and then reflected toward the condenser lens 32 by the beam splitter 26, and is reflected on the light detection means 30 by the condenser lens 32. Focused on. An optical signal received by a main light receiving unit (not shown) of the light detection means 30 is converted into an electrical signal by the preamplifier 120 and is taken out as an RF signal or a focus error signal. The optical signals received by the light receiving units 30a to 30d are converted into electrical signals by the preamplifier 120 and extracted as tracking error signals.
[0040]
  According to the skew detection apparatus, the optical pickup 104 using the skew detection apparatus, and the optical disk apparatus 101 shown in the first embodiment, when performing tracking servo along the wobble groove of the optical disk 102, the recording / reproducing light is used. This is the output difference between the light receiving portions 30b and 30c that receive the light in the central region of the reflected light beam RPS using the pickup 104.Includes wobble signal componentThis is an output difference between the first push-pull signal PP1 and the light receiving units 30a and 30b and the light receiving units 30c and 30d that receive the light in the central region and the peripheral region of the reflected light beam RPS.Includes wobble signal componentThe second push-pull signal PP2 is calculated, and the first push-pull signal PP1Of the wobble signal componentPhase and second push-pull signal PP2Of the wobble signal componentThe phase comparison circuit 49 compares the phase and the comparison resultAsObtainedPlaceBased on phase differenceThe optical axis of the recording / reproducing light beam irradiated on the optical disk 102The skew error signal S1 including the tilt direction and the tilt amount of the optical disk 102 is generated, and the skew error signal S1 is input to the skew servo control unit 118 to drive and control the skew actuator 117, whereby the optical axis of the objective lens 30 is changed to the optical disk. Since the optical pickup 104 is configured to operate so as to be orthogonal to the signal recording surface 102, the radial skew of the optical disc 102 can be detected with high accuracy, and a conventional skew sensor having a different structure becomes unnecessary. Therefore, the number of components can be reduced, and the cost of the optical pickup 104 and the optical disc apparatus 101 including the skew detection apparatus can be reduced.
[0041]
Next, a second embodiment of the skew detection method and skew detection apparatus according to the present invention will be described with reference to FIG.
6 differs from FIG. 3 in that the second push-pull signal PP2 is obtained from the difference signal between the outer light receiving portions 30a and 30d. In the following description, the same components as those in FIG.
[0042]
As in the case shown in FIG. 3, the light detection means 30 shown in FIG. 6 receives light consisting of photodiodes that are divided into a plurality of pairs in the radial direction of the optical disk 102, that is, two pairs of inner and outer sides. Among the light receiving portions 30a to 30d, the inner light receiving portions 30b and 30c are irradiated with the central region of the reflected light beam RSP, and the outer light receiving portions 30a and 30d are reflected with the reflected light beam RSP. The peripheral area is irradiated.
[0043]
  Further, as shown in FIG. 6, the radial skew error signal processing unit 116A separately converts the current generated in each of the inner light receiving units 30b and 30c into a voltage in response to light irradiation in the central region of the reflected light beam RSP. Current-voltage conversion circuits 42b and 42c, and separate current-voltage conversion circuits 42a for converting the current generated in each of the outer light receiving units 30a and 30d into voltages in response to light irradiation in the peripheral region of the reflected light beam RSP. And 42d and a difference signal between signals output from the current-voltage conversion circuits 42b and 42c.Includes wobble signal componentA difference signal between the first subtraction circuit 43 for obtaining the first push-pull signal PP1 and the signals output from the current-voltage conversion circuits 42a and 42d.Includes wobble signal componentA second subtraction circuit 46 for obtaining the second push-pull signal PP 2, a BPF (band pass filter) 47 that passes the wobble signal component in the first push-pull signal PP 1 output from the subtraction circuit 43, and an output from the subtraction circuit 46 BPF (band pass filter) 48 that passes the wobble signal component in the second push-pull signal PP2 and the first push-pull signal that has passed through the BPF 47Of the wobble signal componentOf the second push-pull signal that has passed through the phase and BPF 48Of the wobble signal componentThe result of this comparison with the phaseAsObtainedPlaceBased on phase differenceThe optical axis of the recording / reproducing light beam irradiated on the optical disk 102A phase comparison circuit 49 that generates a skew error signal S1 including the tilt direction and tilt amount of the optical disc 102;.
[0044]
  In such a skew detection device, the light corresponding to the central region of the reflected light beam RSP focused on the inner light receiving portions 30b and 30c is changed to a voltage by the current-voltage conversion circuits 42b and 42c, and both current-voltage conversions are performed. The voltage output from the circuits 42b and 42c is input to the first subtracting circuit 43, which corresponds to the difference between the two voltages from the first subtracting circuit 43.Includes wobble signal componentA first push-pull signal PP1 is calculated, and this first push-pull signal PP1Wobble signal component ofIs input to the phase comparison circuit 49 through the BPF 47.
  Further, the light corresponding to the peripheral region of the reflected light beam RSP focused on the outer light-receiving portions 30a and 30d is changed to a voltage by the current-voltage conversion circuits 42a and 42d, and is output from both the current-voltage conversion circuits 42a and 42d. The input voltage is input to the second subtracting circuit 46, which corresponds to the difference between the two voltages from the second subtracting circuit 46.Includes wobble signal componentA second push-pull signal PP2 is calculated, and this second push-pull signal PP2Wobble signal component ofIs input to the phase comparison circuit 49 through the BPF 48.
[0045]
  Therefore, the first push-pull signal PP1 that has passed through the BPFs 47 and 48, respectively.Wobble signal component ofAnd the second push-pull signal PP2Wobble signal component andIs input to the phase comparison circuit 49, and the optical disc 102 has a radial skew,thisIn the phase comparison circuit 49ThemPush-pull signalOf the wobble signal componentPhase differenceCalculatedAnd based on this phase differenceThe optical axis of the recording / reproducing light beam irradiated on the optical disk 102A skew error signal S1 including the tilt direction and tilt amount of the optical disk 102 is generated. Based on this phase difference, a skew error signal S1 including the tilt direction and tilt amount of the optical disk 102 is generated. By controlling the skew actuator 117 by the skew servo control unit 118 based on the skew error signal S1, the optical axis of the objective lens 30 is made orthogonal to the signal recording surface of the optical disk 102 so that the skew of the optical disk 102 becomes zero.
  Also in the skew detection apparatus shown in the second embodiment, the same operational effects as in the case of the first embodiment can be obtained.
[0046]
Next, a third embodiment of the skew detection method and skew detection apparatus according to the present invention will be described with reference to FIG.
7 differs from FIG. 3 in that a skew error signal is obtained from the first and second push-pull signals obtained by traversing the wobbled groove (track) of the optical disk 102. In the following description, the same components as those in FIG.
[0047]
As in the case shown in FIG. 3, the light detection means 30 shown in FIG. 7 receives light consisting of photodiodes divided into a plurality of pairs in the radial direction of the optical disk 102, that is, two pairs of the inner side and the outer side. Among the light receiving portions 30a to 30d, the inner light receiving portions 30b and 30c are irradiated with the central region of the reflected light beam RSP, and the outer light receiving portions 30a and 30d are reflected with the reflected light beam RSP. The peripheral area is irradiated.
[0048]
  Further, as shown in FIG. 7, the radial skew error signal processing unit 116B separately converts the current generated in each of the inner light receiving units 30b and 30c into a voltage in response to light irradiation in the central region of the reflected light beam RSP. Current-voltage conversion circuits 42b and 42c, and separate current-voltage conversion circuits 42a for converting the current generated in each of the outer light receiving units 30a and 30d into voltages in response to light irradiation in the peripheral region of the reflected light beam RSP. And 42d and a difference signal between the signals output from the current-voltage conversion circuits 42a and 42d.Fluctuations that vary according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical disk 102 with respect to the track of the optical disk 102Signal component(In this embodiment, the fluctuation signal component is generated by traversing the track of the optical disk 102 by the light spot of the recording / reproducing light beam irradiated on the optical disk 102, as will be described later).A first subtractor circuit 43 for obtaining a first push-pull signal PP1 including, an adder circuit 44 for adding the output voltage of the current-voltage conversion circuit 42a and the output voltage of the current-voltage conversion circuit 42b, and the current-voltage An addition circuit 45 for adding the output voltage of the conversion circuit 42c and the output voltage of the current-voltage conversion circuit 42d, and a difference signal between the addition circuits 44 and 45.Fluctuations that vary according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical disk 102 with respect to the track of the optical disk 102A second subtraction circuit 46 for obtaining a second push-pull signal PP2 including a signal component;FluctuationThe phase of the signal component and the second push-pull signalFluctuationThe skew error signal including the tilt direction and the tilt amount of the optical disk 102 with respect to the optical axis of the recording / reproducing light beam irradiated to the optical disk 102 based on the phase difference obtained as a result of the comparison by comparing the phase of the signal component And a phase comparison circuit 49 for generating S1.
[0049]
  In such a skew detection apparatus, when detecting a skew error of the optical disk 102, the optical disk apparatus is set to the skew error detection mode so that the recording / reproducing light beam MSP traverses the wobble groove (track) of the optical disk 102. To do. During this traverse, the light corresponding to the central region of the reflected light beam RSP focused on the inner light receiving portions 30b and 30c is changed to a voltage by the current-voltage conversion circuits 42b and 42c, and both the current-voltage conversion circuits 42b and 42c. The voltage output from the first subtracting circuit 43 is input to the first subtracting circuit 43, which corresponds to the difference between the two voltages.Fluctuations that vary according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical disk 102 with respect to the track of the optical disk 102A first push-pull signal PP1 including a signal component is calculated, and the first push-pull signal PP1 is input to the phase comparison circuit 49.
  Further, the light corresponding to the peripheral region of the reflected light beam RSP focused on the outer light receiving portions 30a and 30d during the traverse is changed into a voltage by the current-voltage conversion circuits 42a and 42d, and both the current-voltage conversion circuits 42a and 42d. And the voltage output from the current-voltage conversion circuits 42b and 42c are added by the addition circuits 44 and 45, and then input to the second subtraction circuit 46, whereby the second subtraction is performed. From circuit 46, it corresponds to the difference between both output voltages.Fluctuations that vary according to the relative position of the light spot of the recording / reproducing light beam irradiated on the optical disk 102 with respect to the track of the optical disk 102A second push-pull signal PP2 including a signal component is calculated, and the second push-pull signal PP2 is input to the phase comparison circuit 49.
[0050]
  Therefore, when the first push-pull signal PP1 and the second push-pull signal PP2 are input to the phase comparison circuit 49 and a radial skew occurs in the optical disc 102, the phase comparison circuit 49 uses these push-pull signals.FluctuationThe phase difference of the signal component is calculated, and a skew error signal S1 including the tilt direction and the tilt amount of the optical disk 102 with respect to the optical axis of the recording / reproducing light beam irradiated on the optical disk 102 is generated based on the phase difference. Is done. By controlling the skew actuator 117 by the skew servo control unit 118 based on the skew error signal S1, the optical axis of the objective lens 30 is made orthogonal to the signal recording surface of the optical disk 102 so that the skew of the optical disk 102 becomes zero.
  Also in the skew detection apparatus shown in the third embodiment, the same operational effects as in the case of the first embodiment can be obtained.
[0051]
Next, another embodiment of an optical pickup used for skew detection according to the present invention will be described with reference to FIG.
The optical pickup 104 shown in FIG. 8A includes a laser light source 22 that emits a recording / reproducing light beam, a collimator lens 24 that is arranged in the light beam emission direction of the laser light source 22 and converts the light beam into parallel light, and A beam splitter 26 (corresponding to the light separating means described in the claims) disposed on the collimating lens 24 on the side of the parallel light beam, and an object for focusing the light beam transmitted through the beam splitter 26 and irradiating the optical disk 102 A lens (light focusing means) 28; and a light detection means 30 that is arranged facing the reflection direction of the beam splitter 26 and receives a reflected light beam from the optical disk 102 separated by the beam splitter 26 and converts it into an electric signal; A condensing lens 32 that is arranged on the light incident side of the light detection means 30 and focuses the reflected light beam on the light detection means 30; The hologram element is disposed between the light detection unit 30 and the light detection unit 30 and diffracts the light beam emitted from the condensing lens 32 and spatially separates it in the radial direction of the optical disk 102 and focuses it on the light receiving units 30a to 30d. 34, and each of these optical components is mounted on a holder body (not shown).
[0052]
  In addition, as shown in FIG.ThatEach light receiving part 30a-30dButThe divided light beams 34a to 34d diffracted by the hologram element 34 areThemFocused on each light receiving part 30a-30dThisAs shown, the optical disks 102 are arrayed spatially apart in the radial direction.
  The light receiving units 30a to 30d arranged in this way are connected to the radial skew error signal processing unit having the configuration shown in FIG. 3, FIG. 6, or FIG.
[0053]
In such an optical pickup 104, the offsets of the first and second push-pull signals detected by the light receiving units 30a to 30d and processed by the radial skew error signal processing unit are compared. If the optical disc 102 has no radial inclination and the two offsets are different, it is determined that the optical disc 102 has a radial skew. Therefore, the skew actuator 117 is controlled by the skew servo control unit 118 so that the radial skew of the optical disk 102 becomes zero, and the optical axis of the objective lens 30 may be orthogonal to the signal recording surface of the optical disk 102.
[0054]
  According to the optical pickup 104 shown in this embodiment, the hologram element 34 divides the reflected light beam MSP in the arrangement direction of the light receiving portions 30a to 30d and separates it on the light receiving portions 30a to 30d.Make it incidentTherefore, it is possible to prevent the push-pull offset from fluctuating even if the field of view of the objective lens 28 fluctuates, and the same operational effects as those shown in the first embodiment can be obtained.
[0055]
  In the present embodiment, the case where the optical recording medium is DVD ± R or DVD ± RW has been described. However, the present invention is not limited to CD, DVD, CD-R, CD-RW, DVD-RAM, or BLUE-. It is widely applied to other optical discs such as RAY DISC.
  Further, the skew sensor and the optical pickup according to the present invention are not limited to the configurations shown in the above-described embodiments, and various modifications and changes can be made without departing from the technical scope described in the claims. Of course.
  In addition, the number of divisions of the light detection means 30 in the present invention is not limited to the four divisions shown in the above embodiment, and the wobble groove of the optical recording medium is easily detected so that a change in PTF can be easily detected.Spatial frequencyButEquivalent of first push-pull signal or second push-pull signalTo be more than 1/4 of the cutoff frequency of MTFNumber of divisionsMay be.
[0056]
【The invention's effect】
  As described above, according to the skew detection method, the skew detection device, the optical pickup and the optical disk device using the skew detection device, the optical system for recording / reproducing the optical recording medium is used., With respect to the optical axis of the recording / reproducing light beam irradiated on the optical recording mediumTilt of optical recording mediumdirectionas well asInclinationSince it is configured to detect the amount, it can detect the radial skew of the optical recording medium with high accuracy and eliminate the need for a separate skew sensor as in the past, reducing the number of components and detecting skew. The optical pickup including the device and the optical disk device can be reduced in cost.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an optical disc apparatus including a skew detection apparatus and an optical pickup according to the present invention.
FIG. 2 is a configuration diagram of an optical pickup having a skew detection function according to the present invention.
FIG. 3 shows the first embodiment of the present invention.Person in charge1 is a block diagram illustrating a configuration of a skew detection device.
FIG. 4 shows wobble grooves and light applied to the radial skew detection of the present invention.TheIt is explanatory drawing which shows the relationship with a pot.
FIGS. 5A to 5C show the first embodiment of the present invention.Person in chargeThe skew detectorThe position of the light spot of the light flux MSP in the traverse direction of the wobble groove with respect to the center line of the wobble groove of the optical diskWhen, First and secondIt is explanatory drawing which shows the relationship with a push pull output signal.
FIG. 6 is a block diagram showing a second embodiment of a skew detection method and a skew detection apparatus according to the present invention.
FIG. 7 is a block diagram showing a third embodiment of a skew detection method and a skew detection apparatus according to the present invention.
8A is a configuration diagram illustrating another embodiment of an optical pickup used for skew detection according to the present invention, and FIG. 8B is an explanatory diagram illustrating a relationship between each light receiving unit and a separated light beam.
[Explanation of symbols]
  DESCRIPTION OF SYMBOLS 101 ... Optical disk apparatus, 102 ... Optical disk, 103 ... Spindle motor, 104 ... Optical pick-up, 105 ... Feed motor, 107 ... System controller, 109 ... Servo control part, 116 ... Radial skewerrorSignal processing unit, 117 ... skew actuator, 118 ... skew servo control unit, 49, 51, 52 ... delay circuit, 50, 53, 54 ... BPF (band pass filter), 55, 56 ... phase comparison circuit , 59, 74... Difference calculation circuit, 71, 73... Amplitude detection circuit, 22... Laser light source, 24... Collimator lens, 26. ... light detecting means, 30a to 30d.

Claims

A light source, a light detection unit, and a recording unit configured to irradiate a light beam from the light source onto a signal recording surface of an optical recording medium and to focus a reflected light beam reflected from the signal recording surface on the light detection unit A skew detection method for detecting a skew, which is an inclination of the optical recording medium with respect to an optical axis of a recording / reproducing light beam irradiated to the optical recording medium, using a reproducing optical system,
The light detection means includes a plurality of pairs of divided light receiving units corresponding to two or more pairs of regions divided along a radial direction of the optical recording medium,
An inner light receiving unit pair, which is a pair of light receiving units located inside the light receiving unit, receives light in a central region of the reflected light beam, and is a pair of light receiving units located outside the light receiving unit. A certain outer light receiving unit pair receives light in the peripheral region of the reflected light beam, so that the effective NA (numerical aperture) of the optical system related to the reflected light beam received by the inner light receiving unit pair is the outer light receiving unit. From the effective NA of the optical system related to the reflected light beam received by the pair or the effective NA of the optical system related to the reflected light beam that is the sum of the reflected light beam received by the inner light receiving unit pair and the reflected light beam received by the outer light receiving unit pair Accordingly, a difference signal between signals output from the respective light receiving portions of the inner light receiving portion pair, and a light spot of a recording / reproducing light beam irradiated on the optical recording medium with respect to a track of the optical recording medium. relative A first push-pull signal including a varying signal component which varies as a function of location, the output signal of the light receiving portions of the difference signal or the outer light receiving portions pair of signals output from the light receiving portions of the outer light receiving portion pairs This is a difference signal between signals obtained by adding the output signals of the inner light receiving unit to the respective light receiving units , depending on the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording medium PTF (phase transfer) of the first push-pull signal generated by the fluctuation of the skew so that the second push-pull signal including the fluctuation signal component that fluctuates in the same manner has different equivalent MTF (modulation transfer function). variation in function) and variation in PTF of the second push-pull signal are different from each other. , Here, the equivalent MTF, a function representing the amplitude of the fluctuation signal component of the push-pull signal with respect to the spatial frequency of the sources of variation signal component,
The phase of the fluctuation signal component of the first push-pull signal is compared with the phase of the fluctuation signal component of the second push-pull signal, and the optical recording medium is irradiated based on the phase difference obtained as a result of this comparison A skew error signal including a tilt direction and a tilt amount of the optical recording medium with respect to an optical axis of a recording / reproducing light beam;
And a skew detection method.

The fluctuation signal component of the first and second push-pull signals is generated by traversing a track of the optical recording medium with a light spot of a recording / reproducing light beam irradiated on the optical recording medium. The skew detection method according to claim 1.

The optical recording medium has a wobble groove, and the fluctuation signal components of the first and second push-pull signals are such that a light spot of a recording / reproducing light beam irradiated on the optical recording medium follows the wobble groove. 3. The skew detection method according to claim 2, wherein the skew detection signal is a wobble signal component generated by tracking control.

The number of divisions of the light detection means is a number of divisions such that the spatial frequency of the wobble groove is ¼ or more of the cutoff frequency of the equivalent MTF of the first push-pull signal or the second push-pull signal. 4. The skew detection method according to claim 3, wherein there is a skew detection method.

A light source, a light detection unit, and a recording unit configured to irradiate a light beam from the light source onto a signal recording surface of an optical recording medium and to focus a reflected light beam reflected from the signal recording surface on the light detection unit A skew detection device that detects a skew that is an inclination of the optical recording medium with respect to an optical axis of a recording / reproducing light beam irradiated to the optical recording medium using a reproducing optical system;
The light detection means includes a plurality of pairs of divided light receiving units corresponding to two or more pairs of regions divided along a radial direction of the optical recording medium,
An inner light receiving unit pair, which is a pair of light receiving units located inside the light receiving unit, receives light in a central region of the reflected light beam, and is a pair of light receiving units located outside the light receiving unit. A certain outer light receiving unit pair receives light in the peripheral region of the reflected light beam, so that the effective NA (numerical aperture) of the optical system related to the reflected light beam received by the inner light receiving unit pair is the outer light receiving unit. From the effective NA of the optical system related to the reflected light beam received by the pair or the effective NA of the optical system related to the reflected light beam that is the sum of the reflected light beam received by the inner light receiving unit pair and the reflected light beam received by the outer light receiving unit pair Accordingly, a difference signal between signals output from the respective light receiving portions of the inner light receiving portion pair, and a light spot of a recording / reproducing light beam irradiated on the optical recording medium with respect to a track of the optical recording medium. relative A first push-pull signal including a varying signal component which varies as a function of location, the output signal of the light receiving portions of the difference signal or the outer light receiving portions pair of signals output from the light receiving portions of the outer light receiving portion pairs This is a difference signal between signals obtained by adding the output signals of the inner light receiving unit to the respective light receiving units , depending on the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording medium PTF (phase transfer) of the first push-pull signal generated by the fluctuation of the skew so that the second push-pull signal including the fluctuation signal component that fluctuates in the same manner has different equivalent MTF (modulation transfer function). variation in function) and variation in PTF of the second push-pull signal are different from each other. Te Yes, wherein the equivalent MTF is a function representing the amplitude of the fluctuation signal component of the push-pull signal with respect to the spatial frequency of the sources of variation signal component,
A first push-pull signal detecting means for detecting the first push-pull signal;
Second push-pull signal detection means for detecting the second push-pull signal;
The phase of the fluctuation signal component of the first push-pull signal is compared with the phase of the fluctuation signal component of the second push-pull signal, and recording is performed on the optical recording medium based on the phase difference obtained as a result of this comparison Phase comparison means for generating a skew error signal including the tilt direction and tilt amount of the optical recording medium with respect to the optical axis of the reproducing light beam,
A skew detection apparatus.

The fluctuation signal component of the first and second push-pull signals is generated by traversing a track of the optical recording medium with a light spot of a recording / reproducing light beam irradiated on the optical recording medium. The skew detection device according to claim 5.

The optical recording medium has a wobble groove, and the fluctuation signal components of the first and second push-pull signals are such that a light spot of a recording / reproducing light beam irradiated on the optical recording medium follows the wobble groove. 6. The skew detection apparatus according to claim 5, wherein the skew detection signal is a wobble signal component generated by tracking control.

The number of divisions of the light detection means is a number of divisions such that the spatial frequency of the wobble groove is ¼ or more of the cutoff frequency of the equivalent MTF of the first push-pull signal or the second push-pull signal. The skew detection apparatus according to claim 7 , wherein the skew detection apparatus is provided.

Each of the light receiving portions is arranged spatially spaced in the radial direction of the optical recording medium, and the reflected light beams are spatially separated in the radial direction of the optical recording medium and focused on the light receiving portions, respectively. The skew detection apparatus according to claim 5, further comprising an element.

A light source that emits a light beam for recording or reproduction;
Focusing means for focusing the light beam from the light source and irradiating the optical recording medium;
A light separating means for separating a light beam emitted from the light source to the optical recording medium and a reflected light beam from the optical recording medium;
A light detection means for receiving the reflected light beam separated by the light separation means;
An optical pickup having a skew detection device that detects a skew that is an inclination of the optical recording medium with respect to an optical axis of a recording / reproducing light beam irradiated on the optical recording medium,
The skew detection apparatus includes a light detection unit including a plurality of pairs of divided light receiving portions corresponding to two or more pairs of regions divided along a radial direction of the optical recording medium,
An inner light receiving unit pair, which is a pair of light receiving units located inside the light receiving unit, receives light in a central region of the reflected light beam, and is a pair of light receiving units located outside the light receiving unit. A certain outer light receiving unit pair receives light in the peripheral region of the reflected light beam, so that the effective NA (numerical aperture) of the optical system related to the reflected light beam received by the inner light receiving unit pair is the outer light receiving unit. From the effective NA of the optical system related to the reflected light beam received by the pair or the effective NA of the optical system related to the reflected light beam that is the sum of the reflected light beam received by the inner light receiving unit pair and the reflected light beam received by the outer light receiving unit pair Accordingly, a difference signal between signals output from the respective light receiving portions of the inner light receiving portion pair, and a light spot of a recording / reproducing light beam irradiated on the optical recording medium with respect to a track of the optical recording medium. relative A first push-pull signal including a varying signal component which varies as a function of location, the output signal of the light receiving portions of the difference signal or the outer light receiving portions pair of signals output from the light receiving portions of the outer light receiving portion pairs This is a difference signal between signals obtained by adding the output signals of the inner light receiving unit to the respective light receiving units , depending on the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording medium PTF (phase transfer) of the first push-pull signal generated by the fluctuation of the skew so that the second push-pull signal including the fluctuation signal component that fluctuates in the same manner has different equivalent MTF (modulation transfer function). variation in function) and variation in PTF of the second push-pull signal are different from each other. Te Yes, wherein the equivalent MTF is a function representing the amplitude of the fluctuation signal component of the push-pull signal with respect to the spatial frequency of the sources of variation signal component,
The skew detection device further includes first push-pull signal detection means for detecting the first push-pull signal, second push-pull signal detection means for detecting the second push-pull signal, and the first push-pull signal. The phase of the fluctuation signal component of the second push-pull signal is compared with the phase of the fluctuation signal component of the second push-pull signal, and the light of the recording / reproducing light beam irradiated on the optical recording medium based on the phase difference obtained as a result of the comparison A phase comparison unit that generates a skew error signal including a tilt direction and a tilt amount of the optical recording medium with respect to an axis;
Further, a skew driving means for swinging the optical axis of the focusing means;
A skew servo control means for controlling the skew drive means so that the optical axis of the focusing means is orthogonal to the signal recording surface of the optical recording medium by a skew error signal generated by the phase comparison means;
An optical pickup characterized by that.

The fluctuation signal component of the first and second push-pull signals is generated by traversing a track of the optical recording medium with a light spot of a recording / reproducing light beam irradiated on the optical recording medium. The optical pickup according to claim 10.

The optical recording medium has a wobble groove, and the fluctuation signal components of the first and second push-pull signals are such that a light spot of a recording / reproducing light beam irradiated on the optical recording medium follows the wobble groove. 11. The optical pickup according to claim 10, wherein the optical pickup is a wobble signal component generated by tracking control.

The number of divisions of the light detection means is a number of divisions such that the spatial frequency of the wobble groove is ¼ or more of the cutoff frequency of the equivalent MTF of the first push-pull signal or the second push-pull signal. The optical pickup according to claim 12 , wherein the optical pickup is provided.

Each of the light receiving portions is arranged spatially spaced in the radial direction of the optical recording medium, and the reflected light beams are spatially separated in the radial direction of the optical recording medium and focused on the light receiving portions, respectively. The optical pickup according to claim 10, further comprising an element.

An optical recording medium that is rotationally driven by a driving means;
An optical pickup moved in the radial direction of the optical recording medium by a feeding means;
Control means for controlling the rotation of the optical recording medium and the movement of the optical pickup in accordance with a recording and / or reproducing operation;
An optical disc device comprising: signal processing means for performing signal processing of recording and / or reproducing operations on the optical recording medium by the optical pickup;
The optical pickup is
A light source that emits a light beam for recording or reproduction;
Focusing means for focusing the light beam from the light source and irradiating the optical recording medium;
A light separating means for separating a light beam emitted from the light source to the optical recording medium and a reflected light beam from the optical recording medium;
A light detection means for receiving the reflected light beam separated by the light separation means;
A skew detection device that detects a skew that is an inclination of the optical recording medium with respect to an optical axis of a recording / reproducing light beam irradiated on the optical recording medium;
The skew detection apparatus includes a light detection unit including a plurality of pairs of divided light receiving portions corresponding to two or more pairs of regions divided along a radial direction of the optical recording medium,
An inner light receiving unit pair, which is a pair of light receiving units located inside the light receiving unit, receives light in a central region of the reflected light beam, and is a pair of light receiving units located outside the light receiving unit. A certain outer light receiving unit pair receives light in the peripheral region of the reflected light beam, so that the effective NA (numerical aperture) of the optical system related to the reflected light beam received by the inner light receiving unit pair is the outer light receiving unit. From the effective NA of the optical system related to the reflected light beam received by the pair or the effective NA of the optical system related to the reflected light beam that is the sum of the reflected light beam received by the inner light receiving unit pair and the reflected light beam received by the outer light receiving unit pair Accordingly, a difference signal between signals output from the respective light receiving portions of the inner light receiving portion pair, and a light spot of a recording / reproducing light beam irradiated on the optical recording medium with respect to a track of the optical recording medium. relative A first push-pull signal including a varying signal component which varies as a function of location, the output signal of the light receiving portions of the difference signal or the outer light receiving portions pair of signals output from the light receiving portions of the outer light receiving portion pairs This is a difference signal between signals obtained by adding the output signals of the inner light receiving unit to the respective light receiving units , depending on the relative position of the light spot of the recording / reproducing light beam irradiated on the optical recording medium with respect to the track of the optical recording medium PTF (phase transfer) of the first push-pull signal generated by the fluctuation of the skew so that the second push-pull signal including the fluctuation signal component that fluctuates in the same manner has different equivalent MTF (modulation transfer function). variation in function) and variation in PTF of the second push-pull signal are different from each other. Te Yes, wherein the equivalent MTF is a function representing the amplitude of the fluctuation signal component of the push-pull signal with respect to the spatial frequency of the sources of variation signal component,
The skew detection device further includes first push-pull signal detection means for detecting the first push-pull signal, second push-pull signal detection means for detecting the second push-pull signal, and the first push-pull signal. The phase of the fluctuation signal component of the second push-pull signal is compared with the phase of the fluctuation signal component of the second push-pull signal, and the light of the recording / reproducing light beam irradiated on the optical recording medium based on the phase difference obtained as a result of the comparison A phase comparison unit that generates a skew error signal including a tilt direction and a tilt amount of the optical recording medium with respect to an axis;
The optical pickup further includes a skew driving unit that swings the optical axis of the focusing unit, and a skew error signal generated by the phase comparison unit to shift the optical axis of the focusing unit to the signal recording surface of the optical recording medium. Skew servo control means for controlling the skew drive means so as to be orthogonal to
An optical disc device characterized by the above.

The fluctuation signal component of the first and second push-pull signals is generated by traversing a track of the optical recording medium with a light spot of a recording / reproducing light beam irradiated on the optical recording medium. The optical disc apparatus according to claim 15.

The optical recording medium has a wobble groove, and the fluctuation signal components of the first and second push-pull signals are such that a light spot of a recording / reproducing light beam irradiated on the optical recording medium follows the wobble groove. 16. The optical disk apparatus according to claim 15, wherein the optical disk apparatus is a wobble signal component generated by tracking control.

The number of divisions of the light detection means is a number of divisions such that the spatial frequency of the wobble groove is ¼ or more of the cutoff frequency of the equivalent MTF of the first push-pull signal or the second push-pull signal. 18. The optical disk apparatus according to claim 17, wherein there is an optical disk apparatus.

Each of the light receiving portions is arranged spatially spaced in the radial direction of the optical recording medium, and the reflected light beams are spatially separated in the radial direction of the optical recording medium and focused on the light receiving portions, respectively. 16. The optical disc apparatus according to claim 15, further comprising an element.