JP2004279191A - Inclination sensor, inclination measurement device, optical pickup device, and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inclination sensor small in size, low in price, and capable of precisely outputting a signal containing the information regarding inclination of an object. <P>SOLUTION: A light beam reflected by the object 15 is incident on a diffraction element 153, and diffracted with a diffraction efficiency corresponding to an incident angle. The diffracted rays from the diffraction element are received by an optical detector 159. If the object inclined regarding a reference surface, intensity of diffracted rays from the diffraction element varies depending on the incident angle on the diffraction element corresponding to the inclination of the object. Therefore, the output signal of the optical detector contains the information of the inclination of the object. Consequently, an allowable range about mounting position of the optical detector becomes wider than before. As a result, an assembly step, an adjusting step, and an inspection step can be simplified. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００９４】
例えば光ディスク１５がθｍだけ時計回りに傾いたときの出力信号Ｉｍは、次の（９）式で示すことができる。
【００９５】

【００９６】
上記（９）式と（８）式との差を求めると、次の（１０）式が得られる。すなわち、受光素子１５９の出力信号の変化量とチルト量とが対応することとなる。従って、予め実験等により、Ｉ０及びａ２の値を求めておくことにより、チルト量θｍを算出することができる。本実施形態では、受光素子１５９の出力信号は再生信号処理回路２８で電圧信号に変換されるので、（１０）式における電流値をＩ／Ｖアンプ２８ｆの特性に応じて電圧値に変更した次の（１１）式におけるＶ０及びＢの値（いずれも定数）が前記チルト変換情報としてメモリ２８ｍに格納されている。
【００９７】
Ｉｍ−Ｉ０＝２ａ２・θｍ ……（１０）
Ｖｍ−Ｖ０＝Ｂ・θｍ ……（１１）
【００９８】
すなわち、前記チルトセンサ信号検出回路２８ｇでは、上記（１１）式及び前記チルト変換情報に基づいてチルト量を検出する。
【００９９】
また、メモリ２８ｍには、チルト量と電気光学素子７１への印加電圧との関係がチルト補償情報として格納されている。そして、前記スポット調整信号生成回路２８ｈでは、検出されたチルト量とチルト補償情報とに基づいて電気光学素子７１への印加電圧を設定する。
【０１００】
なお、本実施形態では、受光素子１５９は、一例として＋１次回折光Ｌ_＋１を受光するように設定されている（図４参照）。図４におけるＬ_−１は−１次回折光を示している。
【０１０１】
次に、前述の光ディスク装置２０を用いて、光ディスク１５にユーザデータを記録する場合の処理動作について簡単に説明する。
【０１０２】
ＣＰＵ４０はホストから記録要求のコマンド（以下、「記録要求コマンド」という）を受信すると、指定された記録速度に基づいてスピンドルモータ２２の回転を制御するための制御信号をドライバ２７に出力するとともに、記録要求コマンドを受信した旨を再生信号処理回路２８に通知する。また、ＣＰＵ４０はホストから受信したユーザデータのバッファＲＡＭ３４への蓄積をバッファマネージャ３７に指示する。
【０１０３】
光ディスク１５の回転が所定の線速度に達すると、前記トラッキング制御及びフォーカス制御が行われる。なお、トラッキング制御及びフォーカス制御は記録処理が終了するまで随時行われる。また、再生信号処理回路２８は、受光器５９の出力信号に基づいてＡＤＩＰ情報を取得し、ＣＰＵ４０に通知する。なお、再生信号処理回路２８は、記録処理が終了するまで所定のタイミング毎にＡＤＩＰ情報を取得し、ＣＰＵ４０に通知する。
【０１０４】
ＣＰＵ４０は、ＡＤＩＰ情報に基づいて書き込み開始地点に光ピックアップ装置２３が位置するようにシークモータを制御する制御信号をドライバ２７に出力する。さらに、ＣＰＵ４０は、バッファマネージャ３７からバッファＲＡＭ３４に蓄積されたユーザデータのデータ量が所定量を超えたとの通知を受けると、エンコーダ２５に書き込み信号の生成を指示する。
【０１０５】
光ピックアップ装置２３が書き込み開始地点に到達すると、ＣＰＵ４０はチルト補正処理を行う。
【０１０６】
このチルト補正処理では、ＣＰＵ４０はチルトセンサＴＳにチルト検出を指示するとともに、再生信号処理回路２８にチルト補正処理の開始を指示する。これにより、チルトセンサＴＳでは、発光ダイオード１５１からチルト検出用光束が出射され、光ディスク１５からの反射光がホログラム素子１５３を介して受光素子１５９で受光される。受光素子１５９からは受光量に応じた信号（電流信号）が再生信号処理回路２８に出力される。
【０１０７】
再生信号処理回路２８では、チルトセンサＴＳの出力信号はＩ／Ｖアンプ２８ｆで電圧信号に変換され、チルトセンサ信号検出回路２８ｇに入力される。チルトセンサ信号検出回路２８ｇは、メモリ２８ｍに格納されているチルト変換情報（ここでは前記Ｖ０及びＢ）を読み出し、前記（１１）式を用いてチルト量を算出する。ここで算出されたチルト量はチルトセンサ信号としてスポット調整信号生成回路２８ｈに出力される。スポット調整信号生成回路２８ｈは、メモリ２８ｍに格納されているチルト補償情報を読み出し、チルトセンサ信号に基づいて、チルトによる波面収差を相殺するための光学的位相差が電気光学素子７１で付与されるように、電気光学素子７１の印加電圧を設定しドライバ２７に出力する。
【０１０８】
チルト補正処理が終了すると、ＣＰＵ４０はエンコーダ２５に対して書き込みを許可する。これにより、ユーザデータは、エンコーダ２５、レーザコントロール回路２４及び光ピックアップ装置２３を介して光ディスク１５に書き込まれる。ホストから受信したユーザデータがすべて書き込まれると記録処理を終了する。
【０１０９】
また、光ディスク装置２０を用いて、光ディスク１５に記録されているデータを再生する場合の処理動作について簡単に説明する。
【０１１０】
ＣＰＵ４０は、ホストから再生要求のコマンド（以下、「再生要求コマンド」という）を受信すると、再生速度に基づいてスピンドルモータ２２の回転を制御するための制御信号をドライバ２７に出力するとともに、再生要求コマンドを受信した旨を再生信号処理回路２８に通知する。
【０１１１】
光ディスク１５の回転が所定の線速度に達すると、前記トラッキング制御及びフォーカス制御が行われる。なお、トラッキング制御及びフォーカス制御は再生処理が終了するまで随時行われる。
【０１１２】
ＣＰＵ４０は、再生信号処理回路２８から所定のタイミング毎に出力されるＡＤＩＰ情報に基づいて、読み出し開始地点に光ピックアップ装置２３が位置するようにシークモータを制御する制御信号をドライバ２７に出力する。
【０１１３】
そして、光ピックアップ装置２３が読み出し開始地点に到達すると、ＣＰＵ４０は前述と同様にしてチルト補正処理を行う。ＣＰＵ４０はチルト補正処理が終了すると再生信号処理回路２８に通知する。これにより、再生信号処理回路２８は、受光器５９の出力信号からＲＦ信号を検出し、復号処理、誤り訂正処理等を行った後、再生データとしてバッファＲＡＭ３４に蓄積する。バッファマネージャ３７は、バッファＲＡＭ３４に蓄積された再生データがセクタデータとして揃ったときに、インターフェース３８を介してホストに転送する。
【０１１４】
以上の説明から明らかなように、本実施形態に係る光ディスク装置２０では、再生信号処理回路２８によって調整手段が実現されている。
【０１１５】
また、ＣＰＵ４０及び該ＣＰＵ４０にて実行されるプログラムとによって処理装置が実現されている。しかしながら、本発明がこれに限定されるものではないことは勿論である。すなわち、上記実施形態は一例に過ぎず、ＣＰＵ４０によるプログラムに従う上記処理によって実現した処理装置の少なくとも一部をハードウェアによって構成することとしても良いし、あるいは全てをハードウェアによって構成することとしても良い。
【０１１６】
以上説明したように、本実施形態に係るチルトセンサＴＳによると、発光ダイオード１５１から出射された光束はコリメートレンズ１５２を介して光ディスク１５に照射される。この光束は光ディスク１５で反射され、ホログラム素子１５３を介して受光素子１５９で受光される。光ディスク１５が基準面に対して傾斜すると、ホログラム素子１５３は基準面と所定の位置関係を有して配置されているために、光ディスク１５の傾斜角に応じてホログラム素子１５３に入射する光束の入射角が変化する。このホログラム素子１５３は光束の入射角に応じて回折効率が変化する特性を有しているために、光束の入射角に応じてホログラム素子１５３からの回折光の強度が変化し、それによって受光素子１５９での受光光量が変化する。すなわち、受光素子１５９から出力される光電変換信号には光ディスク１５の傾きに関する情報が含まれることとなる。このように受光素子１５９での受光光量そのものが光ディスク１５の傾きに関する情報を含んでいるために、前記従来例に比べて受光素子１５９の実装位置に関する許容範囲が広くなり、組み付け工程、調整工程及び検査工程を簡素化することが可能となる。すなわち、製造コストを低減することが可能となる。また、受光素子１５９の出力信号に及ぼす経時変化や温度変化などの影響を低減することができる。従って、小型で安価な構成で、光ディスク１５の傾きに関する情報を含む信号を精度良く出力することができる。
【０１１７】
また、受光素子１５９の出力信号に含まれるオフセット成分が極めて少ないため、高精度のチルト量を検出することが可能となる。そして、受光素子１５９の出力信号からチルト量を求めるための回路あるいは処理を簡素化することができる。
【０１１８】
また、本実施形態に係る光ディスク装置２０によると、データの記録及び再生に先だってチルトに起因する波面収差が精度良く補正されるため、光ディスクに対する記録及び再生を含むアクセスを精度良く安定して行うことが可能となる。
【０１１９】
なお、上記実施形態のチルトセンサＴＳでは、受光素子１５９がホログラム素子１５３からの＋１次回折光Ｌ_＋１を受光する場合について説明したが、これに限らず、受光素子１５９がホログラム素子１５３からの−１次回折光Ｌ_−１を受光しても良い。
【０１２０】
また、上記実施形態のチルトセンサＴＳでは、ホログラム素子１５３からの＋１次回折光のみを用いてチルト量を検出する場合について説明したが、これに限らず、＋１次回折光及び−１次回折光の両方を用いても良い。一例として図７（Ａ）に示されるように、光ディスクが傾くと、ホログラム素子１５３では＋１次回折光Ｌ_＋１とともに−１次回折光Ｌ_−１の回折効率も変化する。このとき、−１次回折光Ｌ_−１の回折効率と＋１次回折光Ｌ_＋１の回折効率との差（以下、便宜上「回折効率差」という）は、一例として図７（Ｂ）に示されるように、ホログラム素子１５３への入射角に応じて周期的に変化することとなる。そして、図７（Ｂ）の例では、入射角が−１０度と＋１０度の間において、回折効率差と入射角との関係がほぼ線形となる。このことは、上記実施形態での説明からわかるように、＋１次回折光Ｌ_＋１の光量と−１次回折光Ｌ_−１の光量との差によってホログラム素子１５３における入射角を求めることができることを示している。また、入射角が０度のときには、＋１次回折光Ｌ_＋１の回折効率と−１次回折光Ｌ_−１の回折効率とは互いに等しく、回折効率差が０となるため、処理を単純化することができる。
【０１２１】
そこで、図８（Ａ）に示されるように、＋１次回折光Ｌ_＋１を受光するための受光素子１５９ａと、−１次回折光Ｌ_−１を受光するための受光素子１５９ｂとを備えたチルトセンサＴＳａを用いても良い。但し、このときには、一例として図８（Ｂ）に示されるように、受光素子１５９ｂの出力信号と受光素子１５９ａの出力信号との差信号を生成する差信号生成手段としてのアンプＯＰａが必要となる。なお、このアンプＯＰａは、チルトセンサＴＳａ内に実装しても良いが、チルトセンサＴＳａの出力信号を処理する外部回路に実装しても良い。そして、アンプＯＰａの出力信号がほぼ０となるように電気光学素子７１への印加電圧を制御すれば良い。
【０１２２】
また、体積ホログラム素子は、溝深さ及び溝間隔などを調整することにより、一例として図９（Ａ）に示されるように、０次光Ｌ_０の最大光量、−１次回折光Ｌ_−１の最大光量及び＋１次回折光Ｌ_＋１の最大光量を互いにほぼ等しくすることができる。図９（Ａ）には、溝深さ（設計値）が６．０±１μｍ、溝間隔（設計値）が１．４±０．１μｍの周期的な凹凸格子を有する体積ホログラム素子の場合ついて示されている。この場合には、図９（Ｂ）に示されるように、入射角が０よりも小さいときに、−１次回折光Ｌ_−１と０次光Ｌ_０との光量差と、入射角との関係が広範囲でほぼ線形となる。また、図９（Ｃ）に示されるように、入射角が０よりも大きいときに、＋１次回折光Ｌ_＋１と０次光Ｌ_０との光量差と、入射角との関係が広範囲でほぼ線形となる。このことは、上記実施形態での説明からわかるように、＋１次回折光Ｌ_＋１の光量と０次光Ｌ_０の光量との差、及び−１次回折光Ｌ_−１の光量と０次光Ｌ_０の光量との差によって入射角を求めることができることを示している。
【０１２３】
そこで、図１０（Ａ）に示されるように、＋１次回折光Ｌ_＋１を受光するための受光素子１５９ａと、−１次回折光Ｌ_−１を受光するための受光素子１５９ｂと、０次光Ｌ_０を受光するための受光素子１５９ｃと、を備えたチルトセンサＴＳｂを用いても良い。但し、このときには、一例として図１０（Ｂ）に示されるように、受光素子１５９ａの出力信号と受光素子１５９ｃの出力信号との差信号を生成する差信号生成手段としてのアンプＯＰｂ、受光素子１５９ｂの出力信号と受光素子１５９ｃの出力信号との差信号を生成する差信号生成手段としてのアンプＯＰｃ、アンプＯＰｂの出力信号及びアンプＯＰｃの出力信号のいずれか一方を出力する切り換えスイッチＳＷ、及び受光素子１５９ａの出力信号と受光素子１５９ｂの出力信号とを比較し、切り換えスイッチＳＷを制御する選択回路ＳＥＬが必要となる。この選択回路ＳＥＬは、受光素子１５９ａの出力信号のほうが大きい場合にアンプＯＰｂの出力信号が出力され、受光素子１５９ｂの出力信号のほうが大きい場合にアンプＯＰｃの出力信号が出力されるように、切り換えスイッチＳＷを制御する。これにより、検出の分解能が高くなり、更に精度良くチルトを検出することができる。なお、アンプＯＰｂ、アンプＯＰｃ、切り換えスイッチＳＷ及び選択回路ＳＥＬは、チルトセンサＴＳｂ内に実装しても良いが、チルトセンサＴＳｂの出力信号を処理する外部回路に実装しても良い。
【０１２４】
体積ホログラム素子では、溝深さを深くすると、前述したように回折効率の入射角依存性が顕著となるため、チルト検出の分解能を上げることが可能である。しかしながら、溝深さがある程度以上深くなると、一例として図１１に示されるように、回折効率と入射角との関係がほぼ線形を示す領域（以下、便宜上「線形領域」という）内に入射角０度が含まれなくなる。このような場合には、一例として図１２に示されるように、チルト量が０のときの入射角が線形領域のほぼ中央の入射角（図１１では約６．５度）となるようにホログラム素子１５３を設定すれば良い。また、この場合に、一例として図１３に示されるように、凹凸格子の断面形状がのこぎり刃状となるように（ブレーズ化）しても良い。
【０１２５】
また、上記実施形態のチルトセンサＴＳでは、ホログラム素子１５３が偏光性を有さない場合について説明したが、一例として図１４に示されるように、ホログラム素子１５３に代えて偏光回折素子としての偏光性を有する偏光ホログラム素子１５３’を用いても良い。このチルトセンサＴＳｃには、発光ダイオード１５１に代えて、直線偏光の光束を発光する半導体レーザ１５１’が用いられ、往路と復路の光路上に位相差板としてのλ／４板１５５が配置される。例えば半導体レーザ１５１’からＰ偏光の光束が発光され、偏光ホログラム素子１５３’がＰ偏光の光束を透過し、Ｓ偏光の光束を回折するように設定されている場合について説明する。
【０１２６】
半導体レーザ１５１’から出射されたＰ偏光の光束（以下「ＬＤ光」という）は、コリメートレンズ１５２で略平行光とされ、偏光ホログラム素子１５３’に入射する。ＬＤ光の大部分は偏光ホログラム素子１５３’を透過し、λ／４板１５５で円偏光となり光ディスク１５に照射される。光ディスク１５からの反射光（以下「反射ＬＤ光」という）は往路と逆回りの円偏光であり、λ／４板１５５でＳ偏光となり、偏光ホログラム素子１５３’に入射する。偏光ホログラム素子１５３’で回折された反射ＬＤ光は受光素子１５９で受光される。これにより、光利用効率が向上し、チルトセンサの小型化を推進することができる。
【０１２７】
また、上記実施形態のチルトセンサＴＳでは、コリメートレンズ１５２を用いて発光ダイオード１５１から出射される光束を略平行光とする場合について説明したが、例えば発光ダイオード１５１から出射される光束の発散度が小さい場合には、コリメートレンズ１５２がなくても良い。
【０１２８】
また、上記実施形態のチルトセンサＴＳでは、ラジアルチルトを検出する場合について説明したが、光ディスク１５に対向してチルトセンサの配置を９０度回転することにより、タンジェンシャル方向に関するチルト（以下「タンジェンシャルチルト」という）を検出することができる。
【０１２９】
また、一例として図１５（Ａ）に示されるように、ホログラム素子１５３に代えて、互いに凹凸格子の溝方向が直交する２つの領域（Ｒ１，Ｒ２）に分割されたホログラム素子１６３を用いることにより、互いに直交する２方向におけるチルトを検出することが可能となる。例えば、図１５（Ｂ）に示されるように、領域Ｒ１（第１の領域）に入射した光束がラジアル方向に回折され、領域Ｒ２（第２の領域）に入射した光束がタンジェンシャル方向に回折されるようにホログラム素子１６３を配置し、領域Ｒ１からの＋１次回折光を受光するための受光素子１５９ｒ（第１の受光部）、及び領域Ｒ２からの＋１次回折光を受光するための受光素子１５９ｔ（第２の受光部）を、それぞれ所定位置に設けることにより、受光素子１５９ｒの出力信号に基づいてラジアルチルトを検出し、受光素子１５９ｔの出力信号に基づいてタンジェンシャルチルトを検出することができる。
【０１３０】
この場合において、図１６に示されるように、領域Ｒ１からの＋１次回折光Ｌ_＋１を受光するための受光素子１５９ｒａと、−１次回折光Ｌ_−１を受光するための受光素子１５９ｒｂと、領域Ｒ２からの＋１次回折光Ｌ_＋１を受光するための受光素子１５９ｔａと、−１次回折光Ｌ_−１を受光するための受光素子１５９ｔｂと、を備えても良い。そして、一例として図１７に示されるように、受光素子１５９ｒａの出力信号と受光素子１５９ｒｂの出力信号との差信号を生成する第１の差信号生成手段としてのアンプＯＰｄ、及び受光素子１５９ｔａの出力信号と受光素子１５９ｔｂの出力信号との差信号を生成する第２の差信号生成手段としてのアンプＯＰｅを備えても良い。なお、これらのアンプは、チルトセンサ内に実装しても良いが、チルトセンサの出力信号を処理する外部回路に実装しても良い。
【０１３１】
さらに、この場合において、図１８に示されるように、０次光Ｌ_０を受光するための受光素子１５９ｃを備えても良い。そして、一例として図１９に示されるように、受光素子１５９ｒａの出力信号と受光素子１５９ｃの出力信号との差信号を生成する第１の差信号生成手段としてのアンプＯＰｆ、受光素子１５９ｒｂの出力信号と受光素子１５９ｃの出力信号との差信号を生成する第１の差信号生成手段としてのアンプＯＰｇ、アンプＯＰｆの出力信号及びアンプＯＰｇの出力信号のいずれか一方を出力する切り換えスイッチＳＷ１、及び受光素子１５９ｒａの出力信号と受光素子１５９ｒｂの出力信号とを比較し、切り換えスイッチＳＷ１を制御する選択回路ＳＥＬ１を備えても良い。この選択回路ＳＥＬ１は、受光素子１５９ｒａの出力信号のほうが大きい場合にアンプＯＰｆの出力信号が出力され、受光素子１５９ｒｂの出力信号のほうが大きい場合にアンプＯＰｇの出力信号が出力されるように、切り換えスイッチＳＷ１を制御する。さらに、受光素子１５９ｔａの出力信号と受光素子１５９ｃの出力信号との差信号を生成する第２の差信号生成手段としてのアンプＯＰｈ、受光素子１５９ｔｂの出力信号と受光素子１５９ｃの出力信号との差信号を生成する第２の差信号生成手段としてのアンプＯＰｉ、アンプＯＰｈの出力信号及びアンプＯＰｉの出力信号のいずれか一方を出力する切り換えスイッチＳＷ２、及び受光素子１５９ｔａの出力信号と受光素子１５９ｔｂの出力信号とを比較し、切り換えスイッチＳＷ２を制御する選択回路ＳＥＬ２を備えても良い。この選択回路ＳＥＬ２は、受光素子１５９ｔａの出力信号のほうが大きい場合にアンプＯＰｈの出力信号が出力され、受光素子１５９ｔｂの出力信号のほうが大きい場合にアンプＯＰｉの出力信号が出力されるように、切り換えスイッチＳＷ２を制御する。これにより、検出の分解能が高くなり、更に精度良くチルトを検出することができる。なお、各アンプ、各切り換えスイッチ及び各選択回路は、チルトセンサ内に実装しても良いが、チルトセンサの出力信号を処理する外部回路に実装しても良い。また、一例として図２０に示されるように、複数の領域Ｒ１及び複数の領域Ｒ２を備えるホログラム素子を用いても良い。
【０１３２】
また、上記実施形態では、チルトセンサの外部でチルト量を求める場合について説明したが、これに限らず、チルトセンサの内部にチルト量を求める回路を実装しても良い。
【０１３３】
また、上記実施形態において、一例として図２１に示されるように、チルト検出用の光束として、受発光モジュール５１から出射される光束の一部を用いても良い。この場合には、コリメートレンズ５２と立上げミラー５７との間に分岐光学素子としてのビームスプリッタ５４が配置され、コリメートレンズ５２で略平行光とされた光束の一部を光ディスク１５にチルト検出用光束として照射する。そして、光ディスク１５で反射されたチルト検出用光束の光路上にホログラム素子１５３が配置される。従って、発光ダイオード１５１及びコリメートレンズ１５２は不要である。なお、ビームスプリッタ５４に代えて、ホログラム素子や反射ミラーなどを用いても良い。
【０１３４】
また、上記実施形態では、電気光学素子７１に印加する電圧を制御して記録面に形成される光スポットの形状を調整する場合について説明したが、本発明がこれに限定されるものではない。例えば、チルト量に対応して対物レンズ６０を保持しているレンズホルダ（図示省略）を回動させても良い。この場合には、レンズホルダを回動するためのアクチュエータが設けられ、該アクチュエータの駆動信号がスポット調整信号生成回路２８ｈから出力されることとなる。また、チルト量に対応して光ピックアップ装置２３自体を回動させても良い。この場合には、光ピックアップ装置２３自体を回動するためのモータが設けられ、該モータの駆動信号がスポット調整信号生成回路２８ｈから出力されることとなる。そして、これらの場合には、電気光学素子７１は不要である。
【０１３５】
さらに、上記実施形態では、再生信号処理２８でチルト補正信号及びスポット調整信号を求める場合について説明したが、これに限らず、例えばチルトセンサ信号検出回路及びスポット調整信号生成回路の少なくとも一方と同様な処理を行う回路を光ピックアップ装置に設けても良い。
【０１３６】
また、上記実施形態では、光ディスク装置がＤＶＤの規格に準拠した光ディスクに対応する場合について説明したが、これに限らず、例えばＣＤの規格に準拠した光ディスクに対応しても良い。さらに、光磁気ディスクに対応しても良い。
【０１３７】
また、上記実施形態では、光源が１つの場合について説明したが、本発明がこれに限定されるものではなく、互いに異なる波長の光を発光する複数の光源を備えても良い。例えば波長が４０５ｎｍの光束を発光する光源、波長が６６０ｎｍの光束を発光する光源及び波長が７８０ｎｍの光束を発光する光源のうちの少なくとも２つの光源を備えても良い。
【０１３８】
また、上記実施形態において、ホログラム素子５３に代えて、入射する光束の偏光方向に応じて回折効率が異なる偏光ホログラム素子を用いても良い。これにより、光利用効率が向上するので、高速化に対応できるようになる。なお、この場合には、対物レンズと偏光ホログラム素子との間にλ／４板などの位相差付与手段が必要となる。
【０１３９】
また、上記実施形態では、戻り光束を分岐するためにホログラム素子５３を用いる場合について説明したが、これに限らず、例えばビームスプリッタを用いても良い。
【０１４０】
また、上記実施形態に係る光ディスク装置は、ホストと同一の筐体内に配置される、いわゆる内蔵タイプであっても良いし、ホストとは別の筐体内に配置される、いわゆる外付けタイプであっても良い。
【０１４１】
また、上記実施形態では、情報の記録及び再生が可能な光ディスク装置について説明したが、これに限らず、情報の記録、再生及び消去のうち少なくとも再生が可能な光ディスク装置であれば良い。
【０１４２】
また、上記実施形態では、インターフェースがＡＴＡＰＩの規格に準拠する場合について説明したが、これに限らず、例えばＡＴＡ（ＡＴ Ａｔｔａｃｈｍｅｎｔ）、ＳＣＳＩ（Ｓｍａｌｌ Ｃｏｍｐｕｔｅｒ Ｓｙｓｔｅｍ Ｉｎｔｅｒｆａｃｅ）、ＵＳＢ（Ｕｎｉｖｅｒｓａｌ Ｓｅｒｉａｌ Ｂｕｓ）１．０、ＵＳＢ２．０、ＩＥＥＥ１３９４、ＩＥＥＥ８０２．３、シリアルＡＴＡ及びシリアルＡＴＡＰＩのうちのいずれかの規格に準拠しても良い。
【０１４３】
また、一例として図２２に示されるように、上記実施形態に係るチルトセンサＴＳを用いて、傾き測定装置２００を実現することができる。この傾き測定装置２００は、受光素子１５９の出力信号に含まれるチルトに関する情報を角度情報に変換する傾斜角取得手段としての角度情報変換回路２０１、及び角度情報を表示する表示器２０３を有している。すなわち、対象物の傾きに関する情報を含む信号が、チルトセンサＴＳから出力されるため、小型で安価な装置構成で、対象物の傾斜角を精度良く測定することができる。なお、角度情報を表示する必要がない場合には、表示器２０３はなくても良い。また、チルトセンサＴＳに代えて前記チルトセンサＴＳａ、ＴＳｂ及びＴＳｃのいずれかを用いても良い。さらに、前記２方向のチルト検出を行うチルトセンサを用いても良い。
【０１４４】
【発明の効果】
本発明に係る傾きセンサによれば、小型で安価な構成で、対象物の傾きに関する情報を含む信号を精度良く出力することができるという効果がある。
【０１４５】
また、本発明に係る傾き測定装置によれば、小型で安価な装置構成で、対象物の傾斜角を精度良く測定することができるという効果がある。
【０１４６】
また、本発明に係る光ピックアップ装置によれば、大型化及び高コスト化を招くことなく、光ピックアップ装置自体及び対物レンズの位置制御に必要な情報などを含む信号を精度良く出力することができるという効果がある。
【０１４７】
また、本発明に係る光ディスク装置によれば、情報記録媒体へのアクセスを精度良く安定して行うことができるという効果がある。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る光ディスク装置の概略構成を示すブロック図である。
【図２】図１における光ピックアップ装置の構成を説明するための図である。
【図３】図１における再生信号処理回路の構成を説明するためのブロック図である。
【図４】図１のチルトセンサの構成を説明するための図である。
【図５】体積ホログラムを説明するための図である。
【図６】チルトセンサに配置されたホログラム素子における回折効率の入射角依存性を説明するための図である。
【図７】図７（Ａ）及び図７（Ｂ）は、それぞれ体積ホログラムにおける＋１次回折光及び−１次回折光の特性を説明するための図である。
【図８】図８（Ａ）及び図８（Ｂ）は、それぞれ＋１次回折光と−１次回折光とを用いてチルト検出を行う場合を説明するための図である。
【図９】図９（Ａ）〜図９（Ｃ）は、それぞれ溝深さ及び溝間隔が調整された体積ホログラムにおける０次光及び±１次回折光の特性を説明するための図である。
【図１０】図１０（Ａ）及び図１０（Ｂ）は、それぞれ０次光と±１次回折光折光とを用いてチルト検出を行う場合を説明するための図である。
【図１１】溝深さがある程度深い体積ホログラムにおける回折効率の入射角依存性を説明するための図である。
【図１２】図１１の体積ホログラムを用いたチルトセンサを説明するための図である。
【図１３】体積ホログラムにおけるブレーズを説明するための図である。
【図１４】偏光ホログラムを用いたチルトセンサを説明するための図である。
【図１５】図１５（Ａ）及び図１５（Ｂ）は、それぞれ２方向のチルト検出を行うチルトセンサを説明するための図である。
【図１６】図１５（Ｂ）において、＋１次回折光と−１次回折光とを受光する場合を説明するための図である。
【図１７】図１６における差信号生成回路を説明するための図である。
【図１８】図１６において、更に０次光を受光する場合を説明するための図である。
【図１９】図１８における差信号生成回路を説明するための図である。
【図２０】図１５（Ａ）のホログラム素子の変形例を説明するための図である。
【図２１】受発光モジュールから出射された光束の一部をチルト検出用に用いる場合を説明するための図である。
【図２２】本発明の一実施形態に係る傾き測定装置の構成を説明するための図である。
【図２３】レーザオートコリメータを説明するための図である。
【符号の説明】
１５…光ディスク（情報記録媒体、対象物）、２０…光ディスク装置、２３…光ピックアップ装置、２８…再生信号処理回路（調整手段）、４０…ＣＰＵ（処理装置）、５１ａ…半導体レーザ（レーザ光源）、５４…ビームスプリッタ（分岐光学素子）、５９…受光器（信号光検出器）、６０…対物レンズ、１５１…発光ダイオード（光源）、１５２…コリメートレンズ（光学素子）、１５３…ホログラム素子（回折素子）、１５３’…偏光ホログラム素子（偏光回折素子）、１５５…λ／４板（位相差板）、１５９…受光素子（光検出器）、１５９ｃ…受光素子（第３の受光部）、１５９ｒ…受光素子（第１の受光部）、１５９ｔ…受光素子（第２の受光部）、１６３…ホログラム素子（回折素子）、２００…傾き測定装置、２０１…角度情報変換回路（傾斜角取得手段）、ＯＰａ，ＯＰｂ，ＯＰｃ…アンプ（差信号生成手段）、ＯＰｄ，ＯＰｆ，ＯＰｇ…アンプ（第１の差信号生成手段）、ＯＰｅ，ＯＰｈ，ＯＰｉ…アンプ（第２の差信号生成手段）、Ｒ１…領域（第１の領域）、Ｒ２…領域（第２の領域）、ＴＳ…チルトセンサ（傾きセンサ）。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tilt sensor, a tilt measuring device, an optical pickup device, and an optical disk device, and more specifically, a tilt sensor for detecting a tilt of an object with respect to a predetermined reference plane, a tilt measuring device using the tilt sensor, The present invention relates to an optical pickup device that irradiates a recording surface of an information recording medium with light and receives reflected light from the recording surface, and an optical disk device including the optical pickup device.
[0002]
[Prior art]
Personal computers (hereinafter abbreviated as "PCs") have been able to handle AV (Audio-Visual) information such as music and video as their functions have improved. Since the information amount of these AV information is very large, large-capacity optical discs such as CD (compact disc) and DVD (digital versatile disc) have attracted attention as information recording media. An optical disk device for accessing a personal computer has become popular as one of peripheral devices of a personal computer.
[0003]
In an optical disk device, information is recorded by forming a small spot of laser light on a recording surface of an optical disk on which spiral or concentric tracks are formed, and information is reproduced based on light reflected from the recording surface. Is going. The optical disc device is provided with an optical pickup device as a device for irradiating the recording surface with laser light and receiving reflected light from the recording surface.
[0004]
Generally, an optical pickup device includes an objective lens, guides a light beam emitted from a light source to a recording surface, and arranges an optical system that guides a return light beam reflected by the recording surface to a predetermined light receiving position, and a light receiving position. Light receiving element and the like. The light receiving element outputs a signal including not only reproduction information of data recorded on the recording surface but also information (servo information) necessary for controlling the position of the optical pickup device itself and the objective lens. The optical disk device performs various servo controls based on an output signal from the light receiving element so that a light spot having a predetermined shape is formed at a predetermined position on the recording surface.
[0005]
In order to accurately form a predetermined light spot at a predetermined position on the recording surface, and to accurately detect reproduction information, servo information, and the like, it is desirable that the recording surface and the optical axis of the objective lens be substantially orthogonal to each other. . However, for example, the recording surface may be inclined with respect to a plane perpendicular to the optical axis of the objective lens due to, for example, warpage or eccentricity of the information recording medium. There is a possibility that a signal including servo information or the like may be deteriorated. Hereinafter, the inclination of the information recording medium with respect to a plane perpendicular to the optical axis of the objective lens will be simply referred to as “the inclination of the information recording medium” for convenience.
[0006]
A laser autocollimator is known as a device that detects the inclination of an object using light. In general, as shown in FIG. 23 as an example, a laser autocollimator includes an objective lens L, a light source LD having a focal position of the objective lens L as a laser light emitting point, and a laser light emitted from the light source LD. A polarizing beam splitter PBS that is disposed on the optical path at a distance b from the light source LD and that splits reflected light from the object M via the objective lens L, and is disposed between the polarizing beam splitter PBS and the objective lens L. A λ / 4 plate PX and a position detector PSD disposed at a distance b from the polarizing beam splitter PBS on the optical path of the laser beam split by the polarizing beam splitter PBS. Laser light emitted from the light source LD is applied to the object M via the polarizing beam splitter PBS, the λ / 4 plate PX, and the objective lens L. Here, for example, when the object M is inclined by an angle θ with respect to a plane perpendicular to the optical axis of the objective lens L, the reflected light reflected by the object M is shifted by an angle 2θ with respect to the outward path and the object M The light enters the lens L. The reflected light incident on the objective lens L is incident on the position detector PSD via the λ / 4 plate PX and the polarizing beam splitter PBS. Then, the angle θ is calculated from the light receiving position d detected by the position detector PSD and the focal length f (= a + b) of the objective lens L based on the following equation (1).
[0007]
θ = d / 2f (1)
[0008]
However, in a laser autocollimator, the position detector PSD is expensive, and an objective lens having a long focal length f must be used to obtain the required detection accuracy. In addition, there is a disadvantage that the cost and size of the optical disk device are hindered.
[0009]
Therefore, various devices have been proposed for detecting the inclination of the information recording medium without hindering cost reduction and miniaturization (for example, see Patent Document 1).
[0010]
[Patent Document 1]
Japanese Patent No. 1787274
[0011]
[Problems to be solved by the invention]
In an optical disk device disclosed in Patent Document 1 (described as an optical disk player in Patent Document 1), a two-divided light receiving element in which a light receiving area of a reflected light from an information recording medium is divided into two parts. The tilt of the information recording medium is detected based on the difference signal between the photoelectric conversion signals output for each light receiving area. However, it is difficult to accurately mount the two-segment light receiving element at a designed position, and an offset due to an assembly error is added to the difference signal, and the accuracy of detecting the inclination may be reduced. Further, there is a possibility that an offset due to a change over time or a change in temperature is added to the difference signal.
[0012]
The present invention has been made under such circumstances, and a first object of the present invention is to provide a small and inexpensive tilt sensor that can accurately output a signal including information on the tilt of an object. .
[0013]
A second object of the present invention is to provide a small and inexpensive tilt measuring device capable of accurately measuring the tilt angle of an object.
[0014]
A third object of the present invention is to provide an optical pickup capable of outputting a signal including information necessary for controlling the position of an optical pickup device itself and an objective lens with high accuracy without increasing the size and cost. It is to provide a device.
[0015]
A fourth object of the present invention is to provide an optical disk device capable of performing stable and accurate access to an information recording medium.
[0016]
[Means for Solving the Problems]
The invention according to claim 1 is a tilt sensor for detecting information about a tilt of an object with respect to a predetermined reference plane, wherein the predetermined positional relationship between the reference plane and an optical path of a light beam passing through the target object is provided. And a light detector that receives the diffracted light from the diffraction element and outputs a photoelectric conversion signal, the diffraction element being configured to diffract the light with a diffraction efficiency corresponding to the incident angle of the light. It is.
[0017]
In the present specification, the “information about the tilt” includes not only the tilt angle itself, but also information that can be converted into a tilt angle, information that changes according to a change in the tilt angle, and the like.
[0018]
According to this, the light beam passing through the object enters the diffraction element and is diffracted with a diffraction efficiency corresponding to the incident angle. Diffracted light from the diffraction element is received by the photodetector, and a photoelectric conversion signal corresponding to the amount of received light is output from the photodetector. For example, when the object is inclined with respect to a predetermined reference plane, the diffraction element is disposed in a predetermined positional relationship with the reference plane, so that the incident angle of the light beam incident on the diffraction element according to the inclination angle of the object is Change. Since this diffraction element has the characteristic that the diffraction efficiency changes according to the incident angle of the light beam, the intensity of the diffracted light from the diffraction element changes according to the incident angle of the light beam, and as a result, the photodetector Of the received light changes. That is, the photoelectric conversion signal output from the photodetector includes information regarding the tilt of the target object. As described above, since the amount of light received by the photodetector itself includes information on the inclination of the object, the permissible range regarding the mounting position of the photodetector is wider than in the conventional example, and the assembling step, the adjusting step, and the like. The inspection process can be simplified. That is, the manufacturing cost can be reduced. In addition, it is possible to reduce the influence of a change over time or a change in temperature on the output signal of the photodetector. Therefore, it is possible to accurately output a signal including information on the inclination of the object with a small and inexpensive configuration.
[0019]
In this case, as in the tilt sensor according to the second aspect, the diffracted light received by the photodetector can be the diffracted light of the order having the highest intensity.
[0020]
In each of the inclination sensors according to the first and second aspects, as in the inclination sensor according to the third aspect, the diffraction element is configured to determine a difference between an intensity of the diffracted light received by the photodetector and an incident angle of the light beam. The relationship can be set to be substantially linear in a predetermined section. In such a case, it is possible to simplify the processing and circuit for extracting information regarding the tilt of the target object from the output signal of the tilt sensor.
[0021]
In each of the tilt sensors according to the first to third aspects, as in the tilt sensor according to the fourth aspect, the photodetector further receives the zero-order light from the diffraction element separately from the diffracted light. May further include difference signal generating means for generating a difference signal between the photoelectric conversion signal of the diffracted light output from the photodetector and the photoelectric conversion signal of the zero-order light. In such a case, it is possible to cope with a relatively large inclination.
[0022]
In the tilt sensor according to the first aspect, as in the tilt sensor according to the fifth aspect, when the photodetector receives + 1st-order and -1st-order diffracted light from the diffractive element, respectively, The image processing apparatus may further include a difference signal generating unit that generates a difference signal between the photoelectric conversion signal of the + 1st-order diffracted light and the photoelectric conversion signal of the −1st-order diffracted light output from the detector. In such a case, the difference signal becomes 0 when the incident angle is 0 degrees, and the processing and circuit for extracting information on the tilt of the target object from the output signal of the tilt sensor can be simplified.
[0023]
7. The tilt sensor according to claim 1, wherein, as in the tilt sensor according to claim 6, the diffractive element includes a first region in which a concave-convex grating in a first groove direction is formed and the first groove direction. In the case where each of the second regions includes a second region in which a concave-convex grating in a second groove direction orthogonal to the first region is formed, the photodetector includes a first light receiving unit that receives diffracted light from the first region. And a second light receiving unit that receives the diffracted light from the second region. In such a case, it is possible to output signals including information on the tilt of the object in two directions orthogonal to each other.
[0024]
In this case, as in the tilt sensor according to the seventh aspect, the diffracted lights received by the first and second light receiving units can be the highest-order diffracted lights, respectively.
[0025]
In each of the tilt sensors according to the sixth and seventh aspects, as in the tilt sensor according to the eighth aspect, the diffractive element includes an intensity of the diffracted light received by the first light receiving unit and the first area. The relationship between the incident angle of the light beam and the incident angle becomes substantially linear in the first section, and the intensity of the diffracted light received by the second light receiving unit and the incident angle of the light beam into the second region Is set to be substantially linear in the second section.
[0026]
In each of the tilt sensors according to the sixth to eighth aspects, as in the tilt sensor according to the ninth aspect, the photodetector further includes a third light receiving unit that receives zero-order light from the diffraction element. May further include first difference signal generating means for generating a difference signal between the photoelectric conversion signal from the first light receiving unit and the photoelectric conversion signal from the third light receiving unit.
[0027]
In this case, a second difference signal for generating a difference signal between a photoelectric conversion signal from the second light receiving unit and a photoelectric conversion signal from the third light receiving unit, as in the tilt sensor according to claim 10. It may further include a generation unit.
[0028]
In the tilt sensor according to the sixth aspect, as in the tilt sensor according to the eleventh aspect, when the first light receiving unit receives + 1st-order diffracted light and -1st-order diffracted light from the first region, respectively. Further includes first difference signal generating means for generating a difference signal between the photoelectric conversion signal of the + 1st-order diffracted light and the photoelectric conversion signal of the -1st-order diffracted light output from the first light receiving unit. be able to.
[0029]
In this case, as in the tilt sensor according to claim 12, when the second light receiving unit receives the + 1st-order diffracted light and the -1st-order diffracted light from the second area, respectively, the second light receiving unit is used. And a second difference signal generating unit that generates a difference signal between the photoelectric conversion signal of the + 1st-order diffracted light and the photoelectric conversion signal of the −1st-order diffracted light output from the unit.
[0030]
In each of the tilt sensors according to the first to twelfth aspects, as in the tilt sensor according to the thirteenth aspect, in the diffraction element, the cross-sectional shape of the formed uneven lattice is a saw-tooth shape. it can.
[0031]
In each of the tilt sensors according to the first to thirteenth aspects, the light beam passing through the object may be a light beam passing through the object or a light beam emitted from the object. As in the tilt sensor according to item 14, the light beam passing through the target object may be reflected light reflected by the target object.
[0032]
In this case, as in the tilt sensor according to claim 15, further comprising a light source that emits a light beam in a direction forming a predetermined angle with respect to the reference plane, wherein the reflection light emitted from the light source is reflected by the object. The diffraction element may be arranged on an optical path of light.
[0033]
In this case, as in the tilt sensor according to claim 16, an optical element further arranged on the optical path of a light beam emitted from the light source and traveling toward the object, and making the light beam emitted from the light source substantially parallel light is further provided. Can be provided.
[0034]
In each of the tilt sensors according to claims 15 and 16, as in the tilt sensor according to claim 17, the diffractive element is a polarization diffractive element having a different diffractive action depending on a polarization state of an incident light beam. A phase difference plate for shifting the polarization direction of the reflected light incident on the polarization diffraction element by approximately 90 degrees with respect to the polarization direction of the light beam emitted from the light source may be further provided. In such a case, since the light use efficiency is improved, the size can be further reduced.
[0035]
An invention according to claim 18 is a tilt measuring device for measuring a tilt angle of an object with respect to a predetermined reference plane, wherein the tilt sensor according to any one of claims 15 to 17; A tilt angle obtaining unit configured to obtain a tilt angle of the object with respect to the reference plane based on the output signal.
[0036]
According to this, the inclination angle of the object with respect to the reference plane is acquired by the inclination angle acquisition means based on the output signal of the inclination sensor according to any one of claims 15 to 17, and as a result, the size is small. With an inexpensive apparatus configuration, the inclination angle of the object can be measured with high accuracy.
[0037]
The invention according to claim 19 is an optical pickup device that irradiates light to a recording surface of an information recording medium and receives light reflected from the recording surface, wherein the information recording medium is the object. The tilt sensor according to any one of 15 to 17, a laser light source that emits laser light having a wavelength corresponding to the information recording medium, and an objective lens that condenses the laser light on the recording surface, An optical system for guiding a return light beam of the laser beam reflected by a recording surface through the objective lens to a predetermined light receiving position; and a signal light detector arranged at the light receiving position and receiving the return light beam. It is a pickup device.
[0038]
According to this, the laser light emitted from the laser light source is condensed on the recording surface of the information recording medium via the objective lens, and the returning light flux of the laser light reflected by the recording surface and passing through the objective lens is a signal light detector. Is received at. In the tilt sensor according to any one of claims 15 to 17, a light beam emitted from a light source and reflected by an information recording medium is received by a photodetector via a diffraction element, and a photoelectric beam corresponding to the amount of received light is received. A converted signal is output. That is, a signal including information on the inclination of the information recording medium is output with high accuracy by the inclination sensor according to any one of claims 15 to 17, and as a result, the signal is increased without increasing the size and cost. It is possible to output a signal including information necessary for controlling the position of the optical pickup device itself and the objective lens from the photodetector with high accuracy.
[0039]
The invention according to claim 20 is an optical pickup device that irradiates light onto a recording surface of an information recording medium and receives light reflected from the recording surface, wherein laser light having a wavelength corresponding to the information recording medium is provided. A laser light source that emits light; an optical system including an objective lens that focuses the laser light on the recording surface, and guides a return light beam of the laser light reflected by the recording surface and passing through the objective lens to a predetermined light receiving position. A signal light detector disposed at the light receiving position and receiving the return light beam; and disposed on an optical path of a light beam emitted from the laser light source toward the objective lens, and a part of the laser light is transmitted to the information recording medium. An optical element that branches toward the optical element; and the diffractive element is disposed on an optical path of a laser beam that is branched by the optical element and reflected by the information recording medium, and the information recording medium is the object. An optical pickup apparatus provided with; a tilt sensor according to Motomeko 14.
[0040]
According to this, the laser light emitted from the laser light source is condensed on the recording surface of the information recording medium via the objective lens, and the returning light flux of the laser light reflected by the recording surface and passing through the objective lens is a signal light detector. Is received at. At this time, a part of the laser light emitted from the laser light source is branched toward the information recording medium by the branching optical element, and the reflected light of the branched laser light from the information recording medium is tilted according to claim 14. The light is incident on a diffraction element constituting the sensor. That is, a signal including information on the inclination of the information recording medium is accurately output by the inclination sensor according to the fourteenth aspect. Therefore, it is possible to output a signal including information necessary for controlling the position of the optical pickup device itself and the objective lens from the signal light detector with high accuracy without increasing the size and cost.
[0041]
According to a twenty-first aspect of the present invention, there is provided an optical disc apparatus that irradiates light onto a recording surface of an information recording medium to perform at least reproduction of information recording, reproduction, and erasure. An optical pickup device; adjusting means for adjusting the shape of a light spot formed on the recording surface based on an output signal of the tilt sensor; recording, reproduction, and reproduction of information using the output signal of the optical pickup device; And a processing device that performs at least reproduction among erasure and erasure.
[0042]
According to this, when at least reproduction among information recording, reproduction, and erasure is performed by using the output signal of the pickup device by the processing device, the adjustment unit forms the information on the recording surface based on the output signal of the tilt sensor. The shape of the light spot is adjusted. Therefore, it is possible to accurately and stably perform an access including at least reproduction among information recording, reproduction, and erasure on the information recording medium.
[0043]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an optical disk device 20 according to an embodiment of the present invention.
[0044]
The optical disk device 20 shown in FIG. 1 includes a spindle motor 22 for rotating and driving an optical disk 15 as an information recording medium (object), an optical pickup device 23, a laser control circuit 24, an encoder 25, a driver 27, a reproduction signal, It includes a processing circuit 28, a servo controller 33, a buffer RAM 34, a buffer manager 37, an interface 38, a flash memory 39, a CPU 40, a RAM 41, and the like. Note that the connection lines in FIG. 1 show typical flows of signals and information, and do not represent all of the connection relationships between the blocks. In the present embodiment, an information recording medium conforming to the DVD standard is used for the optical disc 15 as an example.
[0045]
The optical pickup device 23 is a device for irradiating a recording surface on which a spiral or concentric track of the optical disk 15 is formed with laser light and receiving reflected light from the recording surface, as shown in FIG. As described above, the light emitting / receiving module 51, the collimating lens 52, the hologram element 53, the rising mirror 57, the electro-optical element 71, the objective lens 60, the tilt sensor TS as a tilt sensor and the driving system (a focusing actuator, a tracking actuator, and a seek motor) (All are not shown)).
[0046]
The light receiving / emitting module 51 includes a semiconductor laser 51a as a laser light source and a light receiver 59 as a signal light detector.
[0047]
The semiconductor laser 51a emits a light beam (laser light) having a wavelength of 660 nm. Here, the maximum intensity emission direction of the light beam emitted from the light emitting / receiving module 51 (hereinafter also referred to as “emitted light beam” for convenience) is defined as the + X direction.
[0048]
The light receiver 59 is disposed near the semiconductor laser 51a, and receives the reflected light (hereinafter, referred to as “return light beam”) of the emitted light beam applied to the recording surface of the optical disk 15. The light receiver 59 includes a plurality of light receiving elements that output signals including wobble signal information, reproduction data information, focus error information, track error information, and the like, similarly to a normal optical disk device.
[0049]
On the + X side of the light emitting / receiving module 51, the hologram element 53 is arranged integrally with the light emitting / receiving module 51. The hologram element 53 splits the return light beam from the common optical path of the forward path and the return path in the direction of the light receiving surface of the light receiver 59.
[0050]
The collimating lens 52 is disposed on the + X side of the hologram element 53, and makes the outgoing light flux transmitted through the hologram element 53 into substantially parallel light.
[0051]
On the + X side of the collimating lens 52, the rising mirror 57 is disposed, and reflects substantially parallel light from the collimating lens 52 in the + Z direction.
[0052]
On the + Z side of the rising mirror 57, the electro-optical element 71 is arranged. A voltage is applied to the electro-optical element 71 from the driver 27, and an optical phase difference corresponding to the applied voltage is given to the incident light flux.
[0053]
The objective lens 60 is arranged on the + Z side of the electro-optical element 71, condenses a light beam transmitted through the electro-optical element 71, and forms a light spot on the recording surface of the optical disk 15.
[0054]
The tilt sensor TS is arranged in the vicinity of the objective lens 60 and outputs a signal including information on the tilt of the optical disc 15 with respect to a plane (reference plane) perpendicular to the optical axis of the objective lens 60 (hereinafter, also referred to as “tilt” for convenience). I do. The configuration and the like of the tilt sensor TS will be described later in detail.
[0055]
Here, the operation of the optical pickup device 23 configured as described above will be briefly described. A light beam (emitted light beam) emitted from the light receiving / emitting module 51 enters the hologram element 53. The emitted light beam transmitted through the hologram element 53 is converted into substantially parallel light by the collimator lens 52, and is reflected by the rising mirror 57 in the + Z direction. The emitted light beam is condensed on the recording surface of the optical disk 15 via the objective lens 60 after an optical phase difference corresponding to the applied voltage is given by the electro-optical element 71.
[0056]
The reflected light reflected on the recording surface of the optical disk 15 is converted into a substantially parallel light again by the objective lens 60 as a return light beam, and an electro-optical element 71 gives an optical phase difference corresponding to the applied voltage. It is incident on 57. This return light beam is reflected by the rising mirror 57 in the −X direction, and enters the hologram element 53 via the collimator lens 52. The return light beam diffracted by the hologram element 53 is received by the light receiver 59. Each light receiving element constituting the light receiver 59 outputs a signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0057]
Further, the tilt sensor TS outputs a signal including information on tilt to the reproduction signal processing circuit 28 as described above.
[0058]
As shown in FIG. 3, the reproduction signal processing circuit 28 includes an I / V amplifier 28a, a servo signal detection circuit 28b, a wobble signal detection circuit 28c, an RF signal detection circuit 28d, a decoder 28e, an I / V amplifier 28f, a tilt It comprises a sensor signal detection circuit 28g, a spot adjustment signal generation circuit 28h, a memory 28m, and the like.
[0059]
The I / V amplifier 28a converts a current signal, which is an output signal of the light receiver 59, into a voltage signal and amplifies the voltage signal with a predetermined gain. The servo signal detection circuit 28b detects a servo signal (such as a focus error signal and a track error signal) based on the output signal of the I / V amplifier 28a. The servo signal detected here is output to the servo controller 33. The wobble signal detection circuit 28c detects a wobble signal based on the output signal of the I / V amplifier 28a. The RF signal detection circuit 28d detects an RF signal based on the output signal of the I / V amplifier 28a.
[0060]
The decoder 28e extracts ADIP (Address In Pregroove) information, a synchronization signal, and the like from the wobble signal detected by the wobble signal detection circuit 28c. The extracted ADIP information is output to the CPU 40, and the synchronization signal is output to the encoder 25. Further, the decoder 28e performs decoding processing, error correction processing, and the like on the RF signal detected by the RF signal detection circuit 28d, and then stores the reproduced data in the buffer RAM 34 via the buffer manager 37. If the reproduction data is music data, it is output to an external audio device or the like.
[0061]
The I / V amplifier 28f converts a current signal, which is an output signal of the tilt sensor TS, into a voltage signal and amplifies the voltage signal with a predetermined gain.
[0062]
The memory 28m stores various information including tilt conversion information and tilt compensation information to be described later.
[0063]
The tilt sensor signal detection circuit 28g calculates an inclination angle of the optical disc 15 with respect to the reference plane (hereinafter referred to as “tilt amount” for convenience) based on the output signal of the I / V amplifier 28f and the tilt conversion information stored in the memory 28m. Is detected.
[0064]
The spot adjustment signal generation circuit 28h is a signal for adjusting the shape of the light spot formed on the recording surface of the optical disk 15 to an optimum shape based on the tilt sensor signal and the tilt compensation information stored in the memory 28m. (Hereinafter abbreviated as “spot adjustment signal”). Here, a signal corresponding to a voltage applied to the electro-optical element 71 for giving an optical phase difference by the electro-optical element 71 to offset the wavefront aberration caused by the tilt is output to the driver 27 as a spot adjustment signal. You.
[0065]
Returning to FIG. 1, the servo controller 33 generates a focus control signal for correcting a focus shift based on the focus error signal from the reproduction signal processing circuit 28, and corrects the track shift based on the track error signal. To generate the tracking control signal. Each control signal generated here is output to the driver 27.
[0066]
The driver 27 outputs a driving signal of the focusing actuator to the optical pickup device 23 based on the focus control signal, and outputs a driving signal of the tracking actuator to the optical pickup device 23 based on the tracking control signal. That is, tracking control and focus control are performed by the servo signal detection circuit 28b, the servo controller 33, and the driver 27. Further, the driver 27 outputs a voltage applied to the electro-optical element 71 to the optical pickup device 23 based on the spot adjustment signal from the spot adjustment signal generation circuit 28g. Further, the driver 27 outputs a drive signal to each of the spindle motor 22 and the seek motor based on a control signal from the CPU 40.
[0067]
The buffer RAM 34 temporarily stores data to be recorded on the optical disk 15, data read from the optical disk 15, and the like.
[0068]
The buffer manager 37 manages the input and output of data to and from the buffer RAM 34, and notifies the CPU 40 when the accumulated data amount reaches a predetermined amount.
[0069]
The encoder 25 extracts the data stored in the buffer RAM 34 via the buffer manager 37 based on an instruction from the CPU 40, modulates the data, adds an error correction code, and the like, and generates a write signal to the optical disk 15. At the same time, the write signal is output to the laser control circuit 24 in synchronization with the synchronization signal from the reproduction signal processing circuit 28.
[0070]
The laser control circuit 24 outputs a control signal for controlling the emission power of the semiconductor laser 51 a to the optical pickup device 23 based on a write signal from the encoder 25 and an instruction from the CPU 40.
[0071]
The interface 38 is a bidirectional communication interface with a host (for example, a personal computer), and conforms to the ATAPI (AT Attachment Packet Interface) standard as an example.
[0072]
The flash memory 39 stores a program described in a code decodable by the CPU 40.
[0073]
The CPU 40 controls the operation of each unit according to the program stored in the flash memory 39, and temporarily stores data and the like necessary for the control in the RAM 41.
[0074]
Next, the configuration and the like of the tilt sensor TS will be described with reference to FIGS. As shown in FIG. 4, the tilt sensor TS includes a light emitting diode 151 as a light source, a collimating lens 152 as an optical element, a hologram element 153 as a diffractive element, a light receiving element 159 as a photodetector, and the like. I have.
[0075]
The light emitting diode 151 emits a light beam (hereinafter also referred to as a “tilt detecting light beam” for convenience) for detecting information about tilt in a direction at a predetermined angle with respect to the reference plane based on an instruction from the CPU 40. Emit.
[0076]
The collimating lens 152 is disposed on the optical path of the tilt detection light beam emitted from the light emitting diode 151 and traveling toward the optical disc 15, and converts the tilt detection light beam emitted from the light emitting diode 151 into substantially parallel light.
[0077]
The hologram element 153 has a predetermined positional relationship with the reference surface, and is arranged on an optical path of a tilt detection light beam reflected on the optical disk 15 (hereinafter, referred to as “tilt detection reflected light beam” for convenience), and detects the tilt. Diffracts the reflected light beam. The hologram element 153 is a so-called volume hologram element, and has a periodic concave / convex grating having a groove depth of 3.7 ± 1 μm and a groove interval (pitch) of 1.4 ± 0.1 μm as design values. .
[0078]
Here, the volume hologram will be described. For example, as described in "Optical Electron Optics" by Koyama and Nishihara (Corona Corp.), pp. 117-132, holograms generally include a planar hologram and a volume hologram. Whether it is a plane hologram or a volume hologram is determined by the value (Q value) of the parameter Q calculated by the following equation (2). Here, λ is the wavelength of the incident light, T is the groove depth of the concave and convex grating, n is the refractive index, and P is the groove interval.
[0079]
Q = 2πλT / (nP ² …… (2)
[0080]
Usually, the case where Q ≦ 0.5 is called a plane hologram, and the case where Q ≧ 5 is called a volume hologram. One of the differences between the properties of the plane hologram and the volume hologram is whether or not the diffraction efficiency depends on the incident angle. For example, as shown in FIG. 5, the diffraction efficiency of a plane hologram is almost constant irrespective of the angle of incidence of light, but the diffraction efficiency of a volume hologram greatly changes depending on the angle of incidence of light, and the specific incidence angle θ _B (Bragg angle), the diffraction efficiency is maximized.
[0081]
The diffraction efficiency of the hologram element 153 has a large incident angle dependence as shown in FIG. 6 as an example. FIG. 6 shows the case of + 1st-order diffracted light. When the incident angle is between -5 degrees and +5 degrees, the diffraction efficiency and the incident angle have a substantially linear relationship. Here, the relationship between the diffraction efficiency Df and the incident angle θ is represented by the following equation (3) as an example. Here, a1 and k1 are constants.
[0082]
Df = a1 · θ + k1 (3)
[0083]
Therefore, assuming that the incident angle when the inclination of the optical disc 15 with respect to the reference plane is 0 degrees is θ0, the diffraction efficiency Df0 at that time is expressed by the following equation (4).
[0084]
Df0 = a1 · θ0 + k1 (4)
[0085]
Here, for example, when the optical disk 15 is inclined clockwise by an angle θm with respect to the reference plane, the incident angle becomes θ0 + 2θm. The diffraction efficiency Dfm at this time is expressed by the following equation (5).
[0086]
Dfm = a1 (θ0 + 2θm) + k1 (5)
[0087]
When the difference between the above equations (5) and (4) is obtained, the following equation (6) is obtained. That is, the amount of change in the diffraction efficiency corresponds to the amount of tilt.
[0088]
Dfm−Df0 = 2a1 · θm (6)
[0089]
In the present embodiment, as an example, when the optical disk 15 is tilted in a direction (hereinafter, also referred to as “radial direction”) orthogonal to a tangential direction of a track (hereinafter, also referred to as “tangential direction”), the diffraction efficiency of the hologram element 153 changes. Is set to That is, a signal including information on radial tilt is output from the tilt sensor TS. The hologram element 153 is arranged such that when the tilt amount is zero, the incident angle of the reflected light beam for tilt detection becomes substantially zero.
[0090]
The light receiving element 159 receives the diffracted light from the hologram element 153 and outputs a photoelectric conversion signal to the reproduction signal processing circuit 28. Therefore, the output signal of the light receiving element 159 changes according to the diffraction efficiency of the hologram element 153. Therefore, the output signal I of the light receiving element 159 can be expressed by the following equation (7) using the diffraction efficiency Df of the hologram element 153. Note that a2 and k2 are constants.
[0091]
I = a2 · Df + k2 (7)
[0092]
The output signal I0 when the tilt amount is 0 can be expressed by the following equation (8). Note that A = a1 · a2 and K = a2 · k1 + k2.
[0093]

[0094]
For example, the output signal Im when the optical disk 15 is tilted clockwise by θm can be expressed by the following equation (9).
[0095]

[0096]
When the difference between the above equations (9) and (8) is obtained, the following equation (10) is obtained. That is, the amount of change in the output signal of the light receiving element 159 corresponds to the amount of tilt. Therefore, the tilt amount θm can be calculated by obtaining the values of I0 and a2 in advance through experiments and the like. In the present embodiment, since the output signal of the light receiving element 159 is converted into a voltage signal by the reproduction signal processing circuit 28, the current value in the equation (10) is changed to a voltage value according to the characteristics of the I / V amplifier 28f. The values (both constants) of V0 and B in equation (11) are stored in the memory 28m as the tilt conversion information.
[0097]
Im−I0 = 2a2 · θm (10)
Vm−V0 = B · θm (11)
[0098]
That is, the tilt sensor signal detection circuit 28g detects the amount of tilt based on the equation (11) and the tilt conversion information.
[0099]
Further, the relationship between the amount of tilt and the voltage applied to the electro-optical element 71 is stored in the memory 28m as tilt compensation information. Then, the spot adjustment signal generation circuit 28h sets a voltage to be applied to the electro-optical element 71 based on the detected tilt amount and the tilt compensation information.
[0100]
In the present embodiment, the light receiving element 159 is, for example, a + 1st-order diffracted light L ₊₁ (See FIG. 4). L in FIG. _-1 Indicates -1st-order diffracted light.
[0101]
Next, a processing operation when user data is recorded on the optical disk 15 using the above-described optical disk device 20 will be briefly described.
[0102]
Upon receiving a recording request command (hereinafter, referred to as a “recording request command”) from the host, the CPU 40 outputs a control signal for controlling the rotation of the spindle motor 22 to the driver 27 based on the designated recording speed, and The reproduction signal processing circuit 28 is notified that the recording request command has been received. Further, the CPU 40 instructs the buffer manager 37 to store the user data received from the host in the buffer RAM 34.
[0103]
When the rotation of the optical disk 15 reaches a predetermined linear velocity, the tracking control and the focus control are performed. Note that the tracking control and the focus control are performed as needed until the recording process ends. Further, the reproduction signal processing circuit 28 acquires the ADIP information based on the output signal of the light receiver 59 and notifies the CPU 40 of the information. Note that the reproduction signal processing circuit 28 acquires ADIP information at predetermined timings until the recording processing ends, and notifies the CPU 40 of the ADIP information.
[0104]
The CPU 40 outputs a control signal for controlling the seek motor to the driver 27 based on the ADIP information so that the optical pickup device 23 is located at the writing start point. Further, upon receiving from the buffer manager 37 that the data amount of the user data stored in the buffer RAM 34 has exceeded a predetermined amount, the CPU 40 instructs the encoder 25 to generate a write signal.
[0105]
When the optical pickup device 23 reaches the writing start point, the CPU 40 performs a tilt correction process.
[0106]
In this tilt correction processing, the CPU 40 instructs the tilt sensor TS to detect tilt, and instructs the reproduction signal processing circuit 28 to start tilt correction processing. Thus, in the tilt sensor TS, the light beam for tilt detection is emitted from the light emitting diode 151, and the reflected light from the optical disk 15 is received by the light receiving element 159 via the hologram element 153. From the light receiving element 159, a signal (current signal) corresponding to the amount of received light is output to the reproduction signal processing circuit 28.
[0107]
In the reproduction signal processing circuit 28, the output signal of the tilt sensor TS is converted into a voltage signal by the I / V amplifier 28f and input to the tilt sensor signal detection circuit 28g. The tilt sensor signal detection circuit 28g reads out the tilt conversion information (here, V0 and B) stored in the memory 28m, and calculates the amount of tilt using the equation (11). The calculated tilt amount is output to the spot adjustment signal generation circuit 28h as a tilt sensor signal. The spot adjustment signal generation circuit 28h reads the tilt compensation information stored in the memory 28m, and the electro-optical element 71 gives an optical phase difference for canceling the wavefront aberration due to the tilt based on the tilt sensor signal. Thus, the voltage applied to the electro-optical element 71 is set and output to the driver 27.
[0108]
When the tilt correction process ends, the CPU 40 permits the encoder 25 to perform writing. Thus, the user data is written to the optical disk 15 via the encoder 25, the laser control circuit 24, and the optical pickup device 23. When all the user data received from the host is written, the recording process ends.
[0109]
In addition, a brief description will be given of a processing operation when reproducing data recorded on the optical disk 15 using the optical disk device 20.
[0110]
Upon receiving a reproduction request command (hereinafter, referred to as a “reproduction request command”) from the host, the CPU 40 outputs a control signal for controlling rotation of the spindle motor 22 to the driver 27 based on the reproduction speed, and The reproduction signal processing circuit 28 is notified that the command has been received.
[0111]
When the rotation of the optical disk 15 reaches a predetermined linear velocity, the tracking control and the focus control are performed. Note that the tracking control and the focus control are performed as needed until the reproduction process ends.
[0112]
The CPU 40 outputs a control signal to the driver 27 for controlling the seek motor so that the optical pickup device 23 is located at the reading start point, based on the ADIP information output at every predetermined timing from the reproduction signal processing circuit 28.
[0113]
Then, when the optical pickup device 23 reaches the reading start point, the CPU 40 performs the tilt correction processing in the same manner as described above. When the tilt correction processing is completed, the CPU 40 notifies the reproduction signal processing circuit 28. Thus, the reproduction signal processing circuit 28 detects the RF signal from the output signal of the light receiver 59, performs decoding processing, error correction processing, and the like, and then accumulates the reproduction data in the buffer RAM 34. The buffer manager 37 transfers the reproduced data stored in the buffer RAM 34 to the host via the interface 38 when the data is prepared as sector data.
[0114]
As is clear from the above description, in the optical disc device 20 according to the present embodiment, the adjustment means is realized by the reproduction signal processing circuit 28.
[0115]
A processing device is realized by the CPU 40 and a program executed by the CPU 40. However, it goes without saying that the present invention is not limited to this. That is, the above embodiment is merely an example, and at least a part of the processing device realized by the above processing according to the program by the CPU 40 may be configured by hardware, or may be entirely configured by hardware. .
[0116]
As described above, according to the tilt sensor TS according to the present embodiment, the light flux emitted from the light emitting diode 151 is applied to the optical disc 15 via the collimator lens 152. This light beam is reflected by the optical disk 15 and received by the light receiving element 159 via the hologram element 153. When the optical disc 15 is tilted with respect to the reference plane, the hologram element 153 is disposed with a predetermined positional relationship with the reference plane. The angle changes. Since the hologram element 153 has a characteristic that the diffraction efficiency changes in accordance with the incident angle of the light beam, the intensity of the diffracted light from the hologram element 153 changes in accordance with the incident angle of the light beam. The amount of received light at 159 changes. That is, the photoelectric conversion signal output from the light receiving element 159 includes information on the tilt of the optical disc 15. As described above, since the amount of light received by the light receiving element 159 itself includes information on the tilt of the optical disk 15, the allowable range of the mounting position of the light receiving element 159 is wider than in the conventional example, and the assembling step, the adjusting step, The inspection process can be simplified. That is, the manufacturing cost can be reduced. Further, it is possible to reduce the influence of a change over time or a change in temperature on the output signal of the light receiving element 159. Therefore, a signal including information on the tilt of the optical disk 15 can be accurately output with a small and inexpensive configuration.
[0117]
Further, since the offset component included in the output signal of the light receiving element 159 is extremely small, it is possible to detect the tilt amount with high accuracy. Then, a circuit or a process for obtaining the amount of tilt from the output signal of the light receiving element 159 can be simplified.
[0118]
In addition, according to the optical disc device 20 of the present embodiment, the wavefront aberration caused by the tilt is accurately corrected prior to the recording and the reproduction of the data, so that the access including the recording and the reproduction with respect to the optical disc can be accurately and stably performed. Becomes possible.
[0119]
In the tilt sensor TS of the above embodiment, the light receiving element 159 is the + 1st-order diffracted light L from the hologram element 153. ₊₁ However, the present invention is not limited to this, and the light receiving element 159 may be configured such that the -1st-order diffracted light L _-1 May be received.
[0120]
Further, in the tilt sensor TS of the above-described embodiment, the case where the tilt amount is detected using only the + 1st-order diffracted light from the hologram element 153 has been described. However, the present invention is not limited to this. May be used. As an example, as shown in FIG. 7A, when the optical disk is tilted, the hologram element 153 causes the + 1st-order diffracted light L ₊₁ With the -1st order diffracted light L _-1 Also changes the diffraction efficiency. At this time, the -1st-order diffracted light L _-1 Diffraction efficiency and + 1st order diffracted light L ₊₁ (Hereinafter referred to as “diffraction efficiency difference” for convenience), as shown in FIG. 7B as an example, changes periodically according to the angle of incidence on the hologram element 153. . In the example of FIG. 7B, when the incident angle is between −10 degrees and +10 degrees, the relationship between the diffraction efficiency difference and the incident angle becomes almost linear. This means that the + 1st-order diffracted light L ₊₁ And the -1st order diffracted light L _-1 It is shown that the angle of incidence on the hologram element 153 can be obtained from the difference between the hologram element 153 and the light amount. When the incident angle is 0 degree, the + 1st-order diffracted light L ₊₁ Diffraction efficiency and -1st order diffracted light L _-1 Since the diffraction efficiencies are equal to each other and the diffraction efficiency difference is 0, the processing can be simplified.
[0121]
Therefore, as shown in FIG. 8A, the + 1st-order diffracted light L ₊₁ Light-receiving element 159a for receiving light, and -1st-order diffracted light L _-1 A tilt sensor TSa provided with a light receiving element 159b for receiving light. However, at this time, as shown in FIG. 8B as an example, an amplifier OPa is required as a difference signal generating means for generating a difference signal between the output signal of the light receiving element 159b and the output signal of the light receiving element 159a. . The amplifier OPa may be mounted in the tilt sensor TSa, or may be mounted in an external circuit that processes an output signal of the tilt sensor TSa. Then, the voltage applied to the electro-optical element 71 may be controlled so that the output signal of the amplifier OPa becomes substantially zero.
[0122]
In addition, the volume hologram element adjusts the groove depth, the groove interval, and the like, as shown in FIG. ₀ Maximum light quantity, -1st order diffracted light L _-1 And the + 1st-order diffracted light L ₊₁ Can be made substantially equal to each other. FIG. 9A shows the case of a volume hologram element having a periodic concave / convex grating with a groove depth (design value) of 6.0 ± 1 μm and a groove interval (design value) of 1.4 ± 0.1 μm. It is shown. In this case, as shown in FIG. 9B, when the incident angle is smaller than 0, the -1st-order diffracted light L _-1 And zero-order light L ₀ Is substantially linear over a wide range. Further, as shown in FIG. 9C, when the incident angle is larger than 0, the + 1st-order diffracted light L ₊₁ And zero-order light L ₀ Is substantially linear over a wide range. This means that the + 1st-order diffracted light L ₊₁ Light intensity and zero-order light L ₀ And the -1st-order diffracted light L _-1 Light intensity and zero-order light L ₀ It is shown that the angle of incidence can be obtained from the difference from the amount of light.
[0123]
Therefore, as shown in FIG. 10A, the + 1st-order diffracted light L ₊₁ Light-receiving element 159a for receiving light, and -1st-order diffracted light L _-1 Light-receiving element 159b for receiving the zero-order light L ₀ And a light receiving element 159c for receiving light. However, at this time, as shown in FIG. 10B as an example, an amplifier OPb as a difference signal generating means for generating a difference signal between the output signal of the light receiving element 159a and the output signal of the light receiving element 159c, and the light receiving element 159b OPc, a changeover switch SW for outputting one of the output signal of the amplifier OPb and the output signal of the amplifier OPc as a difference signal generating means for generating a difference signal between the output signal of the light receiving element 159c and the light receiving element. A selection circuit SEL for comparing the output signal of the element 159a with the output signal of the light receiving element 159b and controlling the changeover switch SW is required. The selection circuit SEL switches so that the output signal of the amplifier OPb is output when the output signal of the light receiving element 159a is larger, and the output signal of the amplifier OPc is output when the output signal of the light receiving element 159b is larger. Control the switch SW. As a result, the resolution of detection is increased, and tilt can be detected with higher accuracy. Note that the amplifier OPb, the amplifier OPc, the changeover switch SW, and the selection circuit SEL may be mounted in the tilt sensor TSb, or may be mounted in an external circuit that processes an output signal of the tilt sensor TSb.
[0124]
In the volume hologram element, when the groove depth is increased, the incident angle dependence of the diffraction efficiency becomes remarkable as described above, so that the resolution of tilt detection can be increased. However, when the groove depth is increased to a certain degree or more, as shown in FIG. 11 as an example, the incident angle becomes 0 within a region where the relationship between the diffraction efficiency and the incident angle shows a substantially linear shape (hereinafter referred to as “linear region” for convenience). The degree is not included. In such a case, as shown in FIG. 12 as an example, the hologram is set so that the incident angle when the tilt amount is 0 is substantially the center of the linear region (approximately 6.5 degrees in FIG. 11). The element 153 may be set. Further, in this case, as shown in FIG. 13 as an example, the cross-sectional shape of the concave-convex lattice may be a saw-tooth shape (blazed).
[0125]
In the tilt sensor TS of the above embodiment, the case where the hologram element 153 has no polarization has been described. However, as an example, as shown in FIG. May be used. In the tilt sensor TSc, a semiconductor laser 151 ′ that emits a linearly polarized light beam is used instead of the light emitting diode 151, and a λ / 4 plate 155 as a phase difference plate is arranged on the optical path of the forward path and the return path. . For example, a case will be described where a P-polarized light beam is emitted from the semiconductor laser 151 ′, and the polarization hologram element 153 ′ is set to transmit the P-polarized light beam and diffract the S-polarized light beam.
[0126]
A P-polarized light beam (hereinafter, referred to as “LD light”) emitted from the semiconductor laser 151 ′ is converted into substantially parallel light by the collimator lens 152 and enters the polarization hologram element 153 ′. Most of the LD light passes through the polarization hologram element 153 ′, becomes circularly polarized light by the λ / 4 plate 155, and is irradiated on the optical disc 15. The reflected light from the optical disk 15 (hereinafter, referred to as “reflected LD light”) is circularly polarized light in the opposite direction to the outward path, becomes S-polarized light by the λ / 4 plate 155, and enters the polarization hologram element 153 ′. The reflected LD light diffracted by the polarization hologram element 153 ′ is received by the light receiving element 159. As a result, light use efficiency is improved, and downsizing of the tilt sensor can be promoted.
[0127]
Further, in the tilt sensor TS of the above-described embodiment, a case has been described in which the light flux emitted from the light emitting diode 151 is made substantially parallel light by using the collimating lens 152. However, for example, the divergence of the light flux emitted from the light emitting diode 151 is reduced. If smaller, the collimating lens 152 may not be necessary.
[0128]
Further, in the tilt sensor TS of the above-described embodiment, the case where the radial tilt is detected has been described. However, by rotating the tilt sensor by 90 degrees in opposition to the optical disk 15, the tilt in the tangential direction (hereinafter referred to as “tangential Tilt)) can be detected.
[0129]
As an example, as shown in FIG. 15A, instead of using hologram element 153, hologram element 163 divided into two regions (R1, R2) in which the groove directions of the uneven lattice are orthogonal to each other is used. , It is possible to detect tilt in two directions orthogonal to each other. For example, as shown in FIG. 15B, the light beam incident on the region R1 (first region) is diffracted in the radial direction, and the light beam incident on the region R2 (second region) is diffracted in the tangential direction. The hologram element 163 is arranged such that the light receiving element 159r (first light receiving unit) for receiving the + 1st-order diffracted light from the region R1 and the light receiving element 159t for receiving the + 1st-order diffracted light from the region R2 By providing the (second light receiving unit) at predetermined positions, a radial tilt can be detected based on an output signal of the light receiving element 159r, and a tangential tilt can be detected based on an output signal of the light receiving element 159t. .
[0130]
In this case, as shown in FIG. 16, the + 1st-order diffracted light L from the region R1 ₊₁ Light receiving element 159ra for receiving light, and -1st-order diffracted light L _-1 Light-receiving element 159rb for receiving light, and + 1st-order diffracted light L from region R2 ₊₁ Light-receiving element 159ta for receiving light, and -1st-order diffracted light L _-1 And a light receiving element 159tb for receiving light. As an example, as shown in FIG. 17, an amplifier OPd as first difference signal generating means for generating a difference signal between the output signal of the light receiving element 159ra and the output signal of the light receiving element 159rb, and the output of the light receiving element 159ta An amplifier OPe may be provided as second difference signal generation means for generating a difference signal between the signal and the output signal of the light receiving element 159tb. Note that these amplifiers may be mounted in the tilt sensor, or may be mounted in an external circuit that processes the output signal of the tilt sensor.
[0131]
Further, in this case, as shown in FIG. ₀ May be provided with a light receiving element 159c for receiving light. As an example, as shown in FIG. 19, an amplifier OPf as first difference signal generating means for generating a difference signal between an output signal of the light receiving element 159ra and an output signal of the light receiving element 159c, and an output signal of the light receiving element 159rb. OPg serving as first difference signal generating means for generating a difference signal between the output signal of the light receiving element 159c and the changeover switch SW1 for outputting one of the output signal of the amplifier OPf and the output signal of the amplifier OPg; A selection circuit SEL1 for comparing the output signal of the element 159ra with the output signal of the light receiving element 159rb and controlling the changeover switch SW1 may be provided. The selection circuit SEL1 switches so that the output signal of the amplifier OPf is output when the output signal of the light receiving element 159ra is larger, and the output signal of the amplifier OPg is output when the output signal of the light receiving element 159rb is larger. The switch SW1 is controlled. Further, an amplifier OPh as second difference signal generating means for generating a difference signal between the output signal of the light receiving element 159ta and the output signal of the light receiving element 159c, the difference between the output signal of the light receiving element 159tb and the output signal of the light receiving element 159c. An amplifier OPi as a second difference signal generating means for generating a signal, a changeover switch SW2 for outputting one of an output signal of the amplifier OPh and an output signal of the amplifier OPi, and an output signal of the light receiving element 159ta and a signal of the light receiving element 159tb. A selection circuit SEL2 for comparing the output signal and controlling the changeover switch SW2 may be provided. The selection circuit SEL2 switches so that the output signal of the amplifier OPh is output when the output signal of the light receiving element 159ta is larger, and the output signal of the amplifier OPi is output when the output signal of the light receiving element 159tb is larger. The switch SW2 is controlled. As a result, the resolution of detection is increased, and tilt can be detected with higher accuracy. Each amplifier, each changeover switch, and each selection circuit may be mounted in the tilt sensor, or may be mounted in an external circuit that processes an output signal of the tilt sensor. As an example, as shown in FIG. 20, a hologram element including a plurality of regions R1 and a plurality of regions R2 may be used.
[0132]
In the above embodiment, the case where the tilt amount is obtained outside the tilt sensor has been described. However, the present invention is not limited to this, and a circuit for obtaining the tilt amount may be mounted inside the tilt sensor.
[0133]
In the above embodiment, as shown in FIG. 21 as an example, a part of the light beam emitted from the light emitting / receiving module 51 may be used as the light beam for tilt detection. In this case, a beam splitter 54 as a branching optical element is disposed between the collimating lens 52 and the rising mirror 57, and a part of the light beam that has been made substantially parallel by the collimating lens 52 is used for tilt detection on the optical disk 15. Irradiate as a light beam. Then, the hologram element 153 is arranged on the optical path of the tilt detection light beam reflected by the optical disk 15. Therefore, the light emitting diode 151 and the collimating lens 152 are unnecessary. Note that a hologram element, a reflection mirror, or the like may be used instead of the beam splitter 54.
[0134]
Further, in the above embodiment, the case where the voltage applied to the electro-optical element 71 is controlled to adjust the shape of the light spot formed on the recording surface has been described, but the present invention is not limited to this. For example, a lens holder (not shown) holding the objective lens 60 may be rotated according to the amount of tilt. In this case, an actuator for rotating the lens holder is provided, and a drive signal of the actuator is output from the spot adjustment signal generation circuit 28h. Further, the optical pickup device 23 itself may be rotated according to the tilt amount. In this case, a motor for rotating the optical pickup device 23 itself is provided, and a drive signal of the motor is output from the spot adjustment signal generation circuit 28h. In these cases, the electro-optical element 71 is unnecessary.
[0135]
Further, in the above-described embodiment, the case where the tilt correction signal and the spot adjustment signal are obtained in the reproduction signal processing 28 has been described. However, the present invention is not limited to this, and is similar to at least one of the tilt sensor signal detection circuit and the spot adjustment signal generation circuit. A circuit for performing the processing may be provided in the optical pickup device.
[0136]
Further, in the above-described embodiment, a case has been described in which the optical disk device is compatible with an optical disk compliant with the DVD standard. However, the present invention is not limited to this, and may be an optical disk compliant with the CD standard, for example. Further, it may correspond to a magneto-optical disk.
[0137]
Further, in the above embodiment, the case where the number of light sources is one has been described. However, the present invention is not limited to this, and a plurality of light sources that emit light of different wavelengths may be provided. For example, at least two light sources of a light source emitting a light beam having a wavelength of 405 nm, a light source emitting a light beam having a wavelength of 660 nm, and a light source emitting a light beam having a wavelength of 780 nm may be provided.
[0138]
Further, in the above embodiment, instead of the hologram element 53, a polarization hologram element having a different diffraction efficiency depending on the polarization direction of the incident light beam may be used. As a result, the light use efficiency is improved, so that it is possible to cope with a higher speed. In this case, a phase difference providing means such as a λ / 4 plate is required between the objective lens and the polarization hologram element.
[0139]
In the above embodiment, the case where the hologram element 53 is used to split the return light beam has been described. However, the present invention is not limited to this, and a beam splitter may be used, for example.
[0140]
The optical disk device according to the above embodiment may be a so-called built-in type, which is arranged in the same housing as the host, or a so-called external type, which is arranged in a housing different from the host. May be.
[0141]
Further, in the above-described embodiment, the optical disk device capable of recording and reproducing information has been described. However, the present invention is not limited to this, and any optical disk device capable of at least reproducing among information recording, reproducing, and erasing may be used.
[0142]
In the above embodiment, the case where the interface complies with the ATAPI standard has been described. However, the present invention is not limited to this. , USB 2.0, IEEE 1394, IEEE 802.3, serial ATA, and serial ATAPI.
[0143]
As an example, as shown in FIG. 22, the tilt measuring device 200 can be realized using the tilt sensor TS according to the above embodiment. The tilt measuring device 200 includes an angle information conversion circuit 201 as tilt angle obtaining means for converting information regarding tilt included in an output signal of the light receiving element 159 into angle information, and a display 203 for displaying angle information. I have. That is, since a signal including information on the tilt of the target is output from the tilt sensor TS, the tilt angle of the target can be measured accurately with a small and inexpensive device configuration. If there is no need to display angle information, the display 203 need not be provided. Further, any of the tilt sensors TSa, TSb, and TSc may be used instead of the tilt sensor TS. Further, a tilt sensor for detecting the tilt in the two directions may be used.
[0144]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the inclination sensor which concerns on this invention, there exists an effect that the signal containing the information regarding the inclination of a target object can be output with high precision with a small and cheap structure.
[0145]
Further, according to the tilt measuring device according to the present invention, there is an effect that the tilt angle of the object can be measured accurately with a small and inexpensive device configuration.
[0146]
Further, according to the optical pickup device of the present invention, it is possible to accurately output a signal including information necessary for controlling the position of the optical pickup device itself and the objective lens without increasing the size and cost. This has the effect.
[0147]
Further, according to the optical disc device of the present invention, there is an effect that access to the information recording medium can be performed stably with high accuracy.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of an optical disc device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration of an optical pickup device in FIG.
FIG. 3 is a block diagram for explaining a configuration of a reproduction signal processing circuit in FIG. 1;
FIG. 4 is a diagram for explaining a configuration of the tilt sensor of FIG. 1;
FIG. 5 is a diagram for explaining a volume hologram.
FIG. 6 is a diagram for explaining the dependence of the diffraction efficiency on the incident angle in the hologram element arranged in the tilt sensor.
FIGS. 7A and 7B are diagrams for explaining the characteristics of + 1st-order diffracted light and −1st-order diffracted light in a volume hologram, respectively.
FIGS. 8A and 8B are diagrams illustrating a case where tilt detection is performed using + 1st-order diffracted light and −1st-order diffracted light, respectively.
FIGS. 9A to 9C are diagrams for explaining the characteristics of zero-order light and ± first-order diffracted light in a volume hologram in which the groove depth and the groove interval are adjusted, respectively.
FIGS. 10A and 10B are diagrams for explaining a case where tilt detection is performed using 0-order light and ± 1st-order diffracted light folded light, respectively.
FIG. 11 is a diagram for describing the dependence of the diffraction efficiency on the incident angle in a volume hologram having a somewhat deep groove depth.
FIG. 12 is a diagram for explaining a tilt sensor using the volume hologram of FIG. 11;
FIG. 13 is a diagram for explaining blaze in a volume hologram.
FIG. 14 is a diagram for explaining a tilt sensor using a polarization hologram.
FIGS. 15A and 15B are diagrams for explaining a tilt sensor that detects tilt in two directions, respectively.
FIG. 16 is a diagram for explaining a case of receiving + 1st-order diffracted light and −1st-order diffracted light in FIG.
17 is a diagram for explaining the difference signal generation circuit in FIG.
FIG. 18 is a diagram for describing a case where zero-order light is further received in FIG.
19 is a diagram for explaining the difference signal generation circuit in FIG.
FIG. 20 is a view for explaining a modified example of the hologram element of FIG. 15 (A).
FIG. 21 is a diagram for describing a case where a part of a light beam emitted from a light receiving / emitting module is used for tilt detection.
FIG. 22 is a diagram illustrating a configuration of a tilt measuring device according to an embodiment of the present invention.
FIG. 23 is a diagram for explaining a laser autocollimator.
[Explanation of symbols]
15 optical disk (information recording medium, object), 20 optical disk device, 23 optical pickup device, 28 reproduction signal processing circuit (adjustment means), 40 CPU (processing device), 51a semiconductor laser (laser light source) 54, a beam splitter (branching optical element), 59, a light receiver (signal light detector), 60, an objective lens, 151, a light emitting diode (light source), 152, a collimating lens (optical element), 153, a hologram element (diffraction) Elements), 153 ': polarization hologram element (polarization diffraction element), 155: λ / 4 plate (phase difference plate), 159: light receiving element (photodetector), 159c: light receiving element (third light receiving section), 159r .., Light receiving element (first light receiving section), 159t, light receiving element (second light receiving section), 163, hologram element (diffraction element), 200, tilt measuring device, 201, angular information Conversion circuits (inclination angle obtaining means), OPa, OPb, OPc... Amplifiers (difference signal generation means), OPd, OPf, OPg... Amplifiers (first difference signal generation means), OPe, OPh, OPi. R1... Area (first area), R2... Area (second area), TS... Tilt sensor (tilt sensor).

Claims (21)

A tilt sensor for detecting information about the tilt of the object with respect to a predetermined reference plane,
A diffraction element arranged on the optical path of the light beam passing through the object in a predetermined positional relationship with the reference plane, and diffracting the light beam at a diffraction efficiency according to an incident angle of the light beam;
A photodetector that receives the diffracted light from the diffractive element and outputs a photoelectric conversion signal. The tilt sensor according to claim 1, wherein the diffracted light received by the photodetector is a diffracted light of the highest order. The said diffraction element is set so that the relationship between the intensity of the diffracted light received by the photodetector and the incident angle of the light beam may be substantially linear in a predetermined section. The tilt sensor according to 1. The photodetector further receives 0-order light from the diffraction element separately from the diffracted light,
4. The apparatus according to claim 1, further comprising a difference signal generating unit configured to generate a difference signal between a photoelectric conversion signal of the diffracted light from the photodetector and a photoelectric conversion signal of the zero-order light. The tilt sensor according to the item. The photodetector receives + 1st-order diffracted light and -1st-order diffracted light from the diffraction element, respectively.
The tilt according to claim 1, further comprising a difference signal generating unit configured to generate a difference signal between a photoelectric conversion signal of the + 1st-order diffracted light and a photoelectric conversion signal of the −1st-order diffracted light from the photodetector. Sensors. The diffraction element includes a first region in which a concave-convex lattice in a first groove direction is formed and a second region in which a concave-convex lattice in a second groove direction orthogonal to the first groove direction is formed. ,
The photodetector includes a first light receiving unit that receives the diffracted light from the first region, and a second light receiving unit that receives the diffracted light from the second region. The tilt sensor according to claim 1. The tilt sensor according to claim 6, wherein the diffracted lights received by the first and second light receiving units are the highest-order diffracted lights, respectively. In the diffraction element, the relationship between the intensity of the diffracted light received by the first light receiving unit and the angle of incidence of the light beam on the first region becomes substantially linear in a first section, and the second The relationship between the intensity of the diffracted light received by the light receiving unit and the angle of incidence of the light beam on the second area is set to be substantially linear in the second section. 8. The tilt sensor according to 6 or 7. The light detector further includes a third light receiving unit that receives the zero-order light from the diffraction element,
9. The image forming apparatus according to claim 6, further comprising: first difference signal generating means for generating a difference signal between a photoelectric conversion signal from the first light receiving unit and a photoelectric conversion signal from the third light receiving unit. The tilt sensor according to any one of the above. 10. The apparatus according to claim 9, further comprising a second difference signal generating unit configured to generate a difference signal between a photoelectric conversion signal from the second light receiving unit and a photoelectric conversion signal from the third light receiving unit. Tilt sensor. The first light receiving unit receives + 1st-order diffracted light and -1st-order diffracted light from the first region, respectively.
It further comprises a first difference signal generating means for generating a difference signal between the photoelectric conversion signal of the + 1st-order diffracted light and the photoelectric conversion signal of the -1st-order diffracted light output from the first light receiving unit. The tilt sensor according to claim 6. The second light receiving unit receives + 1st-order diffracted light and -1st-order diffracted light from the second region, respectively,
It further comprises a second difference signal generating means for generating a difference signal between the photoelectric conversion signal of the + 1st-order diffracted light and the photoelectric conversion signal of the -1st-order diffracted light output from the second light receiving unit. The tilt sensor according to claim 11. The tilt sensor according to any one of claims 1 to 12, wherein in the diffraction element, a cross-sectional shape of the formed concavo-convex grating is a saw-tooth shape. The tilt sensor according to any one of claims 1 to 13, wherein the light beam passing through the object is reflected light reflected by the object. A light source that emits a light beam in a direction that forms a certain angle with respect to the reference plane,
The tilt sensor according to claim 14, wherein the diffraction element is disposed on an optical path of light reflected from the object and emitted from the light source. The tilt sensor according to claim 15, further comprising: an optical element disposed on an optical path of a light beam emitted from the light source toward the object, and configured to make the light beam emitted from the light source substantially parallel light. The diffraction element is a polarization diffraction element having a different diffraction effect according to the polarization state of the incident light beam,
17. A phase difference plate for shifting the polarization direction of the reflected light incident on the polarization diffraction element by approximately 90 degrees with respect to the polarization direction of a light beam emitted from the light source. The tilt sensor according to 1. A tilt measuring device that measures a tilt angle of an object with respect to a predetermined reference plane,
A tilt sensor according to any one of claims 15 to 17;
A tilt angle obtaining unit configured to obtain a tilt angle of the object with respect to the reference plane based on an output signal of the tilt sensor. An optical pickup device that irradiates light to a recording surface of an information recording medium and receives reflected light from the recording surface,
The inclination sensor according to any one of claims 15 to 17, wherein the information recording medium is the object.
A laser light source that emits laser light having a wavelength corresponding to the information recording medium;
An optical system including an objective lens for condensing the laser light on the recording surface, and guiding a return light beam of the laser light reflected by the recording surface and passing through the objective lens to a predetermined light receiving position;
A signal light detector arranged at the light receiving position and receiving the return light beam. An optical pickup device that irradiates light to a recording surface of an information recording medium and receives reflected light from the recording surface,
A laser light source that emits laser light having a wavelength corresponding to the information recording medium;
An optical system including an objective lens for condensing the laser light on the recording surface, and guiding a return light beam of the laser light reflected by the recording surface and passing through the objective lens to a predetermined light receiving position;
A signal light detector arranged at the light receiving position and receiving the return light beam;
A branch optical element that is disposed on an optical path of a light beam emitted from the laser light source and that travels toward the objective lens, and that branches a part of the laser light toward the information recording medium;
15. The tilt sensor according to claim 14, wherein the diffraction element is arranged on an optical path of a laser beam branched by the branch optical element and reflected by the information recording medium, and the information recording medium is used as the object. Optical pickup device. An optical disc device that irradiates light onto a recording surface of an information recording medium and performs at least reproduction of information recording, reproduction, and erasing,
An optical pickup device according to claim 19 or 20;
Adjusting means for adjusting the shape of a light spot formed on the recording surface based on an output signal of the tilt sensor;
A processing device that performs at least reproduction of information recording, reproduction, and erasure using an output signal of the optical pickup device.

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