JP3574747B2 - Optical pickup, information reproducing device and information recording device - Google Patents

Description

なお、式（１）において、「７ａ」は部分ディテクタ７ａからの出力信号の出力値を、「７ｂ」は部分ディテクタ７ｂからの出力信号の出力値を、「７ｃ」は部分ディテクタ７ｃからの出力信号の出力値を、「７ｄ」は部分ディテクタ７ｄからの出力信号の出力値を、「７ｅ」は部分ディテクタ７ｅからの出力信号の出力値を、「７ｆ」は部分ディテクタ７ｆからの出力信号の出力値を、「７ｇ」は部分ディテクタ７ｇからの出力信号の出力値を、「７ｈ」は部分ディテクタ７ｈからの出力信号の出力値を夫々示している。
【００５９】
このようにして球面エラー信号Ｓｋｅを生成すれば、図２（ａ）又は（ｂ）に示す場合には式（１）右辺第１項よりも右辺第２項の方が大きくなり、結果として負の球面エラー信号Ｓｋｅが生成される。これに対し、図２（ｄ）又は（ｅ）に示す場合には式（１）右辺第２項よりも右辺第１項の方が大きくなり、結果として正の球面エラー信号Ｓｋｅが生成される。
【００６０】
更に、図２（ｃ）の場合には式（１）右辺第２項と右辺第１項が等しくなり、結果としてゼロレベルの球面エラー信号Ｓｋｅが生成される。
【００６１】
従って、これらにより、保護層１ａの厚さｔがその理想値（０．６ｍｍ）よりも厚い場合は負の値を有する球面エラー信号Ｓｋｅが生成され、当該理想値よりも薄い場合は正の値を有する球面エラー信号Ｓｋｅが生成され、当該理想値に等しいときはゼロレベルの球面エラー信号Ｓｋｅが生成されるので、当該厚さｔの変動に起因する球面収差を補償する際の極性が判定できるのである。
【００６２】
また、当該補償の量については、図２及び図３から明らかなように、図２（ａ）の場合と図２（ｂ）の場合とで球面エラー信号Ｓｋｅの絶対値を比較すると、図２（ｂ）に示す場合の方が照射硬度分布内の各領域の濃淡の差が小さいことから、図２（ｂ）の場合の方が球面エラー信号Ｓｋｅの絶対値が小さくなる。更に、図２（ｄ）の場合と図２（ｅ）の場合とで球面エラー信号Ｓｋｅの絶対値を比較すると、図２（ｄ）に示す場合の方が照射硬度分布内の各領域の濃淡の差が小さいことから、図２（ｄ）の場合の方が球面エラー信号Ｓｋｅの絶対値が小さくなる。
【００６３】
つまり、球面エラー信号Ｓｋｅの絶対値は、実際の保護層１ａの厚さｔとその理想値との差が大きいほど大きくなることとなるので、球面エラー信号Ｓｋｅの絶対値が大きいほど必要な補償量も大きいと判断することができる。
【００６４】
以上述べた原理により、本発明によれば、球面収差の量及び極性を示す球面エラー信号Ｓｋｅがいわゆる非点収差法によるフォーカスエラー信号のようにＳ字型カーブを有することとなるので、当該球面エラー信号Ｓｋｅを用いれば、いわゆるクローズドループを有するサーボ制御系により迅速且つ正確に球面収差を補償することが可能となる。
【００６５】
なお、非点収差を与えられた光ビームＢの反射光のディテクタ７上の照射強度分布が、保護層１ａの厚さｔの変化により図２に示すように変化する理由は、本発明では、当該保護層１ａを通過することにより光ビームＢに発生した球面収差（この球面収差は、光ビームＢの光軸を対称軸として軸対称の分布形状を有し、その厚さｔにより収差量が異なる。）にシリンドリカルレンズ６により非点収差が重畳されることとなるが、このことに起因して、保護層１ａの厚さｔの変化により球面収差の極性及び量が変化すると、図２各図に示すような厚さｔに対応した照射強度分布の形状の変化が現れるものである。
【００６６】
（ＩＩ）実施形態
次に、本発明の実施形態について、具体的に図４乃至図７を用いて説明する。
【００６７】
なお、以下に説明する実施形態は、本発明により球面収差を補償すると共に非点収差法によるフォーカスサーボ制御を行いつつ光ディスク１上に記録された情報を再生する情報再生装置に対して本発明を適用した場合の実施形態である。
【００６８】
また、図４は実施形態に係る情報再生装置の概要を示すブロック図であり、図５は実施形態のディテクタの形状を示す平面図であり、図６は球面エラー信号Ｓｋｅを生成すると同時に非点収差法によるフォーカスエラー信号等も生成する信号処理部の概要構成を示すブロック図であり、図７は球面エラー信号Ｓｋｅの波形の例を示す図である。
【００６９】
更に、実施形態における光ディスク１には、再生すべき情報が予め記録されているものとする。
【００７０】
図４に示すように、実施形態の情報再生装置Ｐは、図１に示す原理説明のための光学系Ｓの構成に加えて、球面収差補償用の補償手段としての液晶パネル９と、フォーカスサーボ制御用のフォーカスサーボ手段としてのアクチュエータ１０と、生成手段及びエラー信号生成手段としての信号処理部１１と、再生手段としての再生部１２と、アンプ１３と、補償手段としてのドライバ１４と、アンプ１５と、フォーカスサーボ手段としてのドライバ１６と、により構成される。
【００７１】
ここで、液晶パネル９は、公知の技術により光ビームＢに対して球面収差を補償するための位相差を与える透過型の液晶パネルである。
【００７２】
また、ディテクタ７は、上述した原理に基づいて、図５に示すように、第２副受光手段及び第２部分受光手段としての部分ディテクタ７ａ、７ｂ、７ｃ及び７ｄと、第１副受光手段及び第１部分受光手段としての部分ディテクタ７ｅ、７ｆ、７ｇ及び７ｈに分割されている。
【００７３】
このとき、上述のように、部分ディテクタ７ｅ乃至７ｈを合わせた領域の広さは、図２に示す照射強度分布における中央部の照射強度が強くなる領域の広さとほぼ等しくなるように設定されている。
【００７４】
更に、上述の構成のうち、光学系Ｓ、液晶パネル９、アクチュエータ１０により本発明の光ピックアップＰＵが形成されている。
【００７５】
なお、図４においては、本発明に係る部分のみを示したが、実際の情報再生装置Ｓには、この他に、光ビームＢの照射位置に対していわゆるトラッキングサーボ制御を施すトラッキングサーボ制御部や、情報再生装置Ｓの動作全体を制御するＣＰＵ、或いは、必要な情報を入力するための入力操作部等が含まれている。
【００７６】
次に、情報再生装置Ｐの動作について説明する。
【００７７】
図１に示した光学系Ｓの動作によりディテクタ７に含まれる各部分ディテクタから夫々出力された受光信号Ｓｐ（なお、図４においては、実際には八つある受光信号Ｓｐを、纏めて一の受光信号Ｓｐにより示している。）は、信号処理部１１に入力される。
【００７８】
そして、信号処理部１１は、上述した原理に基づく後述する処理により、上記球面エラー信号Ｓｋｅを生成してアンプ１３に出力すると共に、光ディスク１上に記録されている再生すべき情報に対応するＲＦ信号Ｓｒｆを後述する処理により生成して再生部１２に出力し、更に非点収差法に基づくフォーカスエラー信号Ｓｆｅを後述する処理により生成してアンプ１５に出力する。
【００７９】
これにより、再生部１２は、ＲＦ信号Ｓｒｆに基づいて当該光ディスク１に記録されている情報に対応する再生信号Ｓｐｕを生成して図示しない外部のスピーカ又はディスプレイ等に出力する。
【００８０】
また、アンプ１５は、入力されたフォーカスエラー信号Ｓｆｅを所定の増幅率で増幅し、増幅エラー信号Ｓａｆを生成してドライバ１６に出力する。
【００８１】
そして、ドライバ１６は、増幅エラー信号Ｓａｆに基づいて、フォーカスサーボ制御を行うべくアクチュエータ１０を駆動するための駆動信号Ｓｄｆを生成し、当該アクチュエータ１０に出力する。
【００８２】
これにより、アクチュエータ１０は、駆動信号Ｓｄｆに基づいて、対物レンズ２を光ビームＢの光軸（図４中一点鎖線で示す。）と平行な方向に駆動し、フォーカスエラー信号Ｓｆｅがゼロレベルとなるようにフォーカスサーボ制御を行う。
【００８３】
一方、アンプ１３は、入力された球面エラー信号Ｓｋｅを所定の増幅率で増幅し、増幅エラー信号Ｓａｋを生成してドライバ１４に出力する。
【００８４】
そして、ドライバ１４は、増幅エラー信号Ｓａｋに基づいて、球面エラー信号Ｓｋｅで示される量及び極性を有する球面収差を補償すべく液晶パネル９を駆動するための駆動信号Ｓｄｋを生成し、当該液晶パネル９に出力する。
【００８５】
これにより、液晶パネル９は、駆動信号Ｓｄｋに基づき、通過する光ビームＢに対して球面エラー信号Ｓｋｅがゼロレベルとなるような位相差を与え、発生している球面収差を補償する。
【００８６】
このとき、液晶パネル９は、駆動信号Ｓｄｋで示される電圧を当該液晶パネル９内の液晶層に印加し、これにより当該液晶層の配向性を変化させて屈性率を変えることにより必要な位相差を光ビームＢに対して与えることとなる。
【００８７】
次に、信号処理部１１の細部構成及び動作について、図６及び図７を用いて説明する。
【００８８】
図６に示すように、信号処理部１１は、加算器２０乃至２８と、減算器２９及び３０と、により構成されている。
【００８９】
このとき、加算器２０に対しては、部分ディテクタ７ａからの受光信号Ｓｐと部分ディテクタ７ｃからの受光信号Ｓｐとが入力されるように、当該部分ディテクタ７ａ及び部分ディテクタ７ｃが加算器２０に接続されている。
【００９０】
また、加算器２１に対しては、部分ディテクタ７ｄからの受光信号Ｓｐと部分ディテクタ７ｂからの受光信号Ｓｐとが入力されるように、当該部分ディテクタ７ｄ及び部分ディテクタ７ｂが加算器２１に接続されている。
【００９１】
更に、加算器２２に対しては、部分ディテクタ７ｅからの受光信号Ｓｐと部分ディテクタ７ｇからの受光信号Ｓｐとが入力されるように、当該部分ディテクタ７ｅ及び部分ディテクタ７ｇが加算器２２に接続されている。
【００９２】
次に、加算器２３に対しては、部分ディテクタ７ｈからの受光信号Ｓｐと部分ディテクタ７ｆからの受光信号Ｓｐとが入力されるように、当該部分ディテクタ７ｈ及び部分ディテクタ７ｆが加算器２３に接続されている。
【００９３】
また、加算器２４に対しては、加算器２０の出力信号と加算器２３の出力信号とが入力されるように、当該加算器２０及び２３が加算器２４に接続されている。
【００９４】
更に、加算器２５に対しては、加算器２１の出力信号と加算器２２の出力信号とが入力されるように、当該加算器２１及び２２が加算器２５に接続されている。
【００９５】
更にまた、加算器２６に対しては、加算器２０の出力信号と加算器２２の出力信号とが入力されるように、当該加算器２０及び２２が加算器２６に接続されている。
【００９６】
また、加算器２７に対しては、加算器２１の出力信号と加算器２３の出力信号とが入力されるように、当該加算器２１及び２３が加算器２７に接続されている。
【００９７】
そして、加算器２８に対しては、加算器２４の出力信号と加算器２５の出力信号とが入力されるように、当該加算器２４及び２５が加算器２８に接続されている。これにより、加算器２８からは、各部分ディテクタ７ａ乃至７ｈからの受光信号Ｓｐを全て加算した信号、すなわち、光ディスク１に記録されている情報に対応するＲＦ信号Ｓｒｆが出力されることとなる。
【００９８】
一方、減算器２９に対しては、加算器２４の出力信号が正端子に入力されると共に加算器２５の出力信号が負端子に入力されるように、当該加算器２４及び２５が減算器２９に接続されている。これにより、減算器２９からは、部分ディテクタ７ａ、７ｃ、７ｈ及び７ｆからの各受光信号Ｓｐの和信号から部分ディテクタ７ｂ、７ｄ、７ｅ及び７ｇからの各受光信号Ｓｐの和信号を減算した信号、すなわち、上述した式（１）に基づく球面エラー信号Ｓｋｅが出力されることとなる。
【００９９】
このときの球面エラー信号Ｓｋｅの波形について、図７を用いて説明すると、上記原理において説明したように、光ディスク１における保護層１ａの厚さｔの変化（上記理想値０．６ｍｍを中心とした変化）に伴って、略Ｓ字形の球面エラー信号Ｓｋｅが生成される。そして、このＳ字形の球面エラー信号Ｓｋｅを用いることにより、上述したようにいわゆるクローズドループを有するサーボ制御系により迅速且つ正確に球面収差を補償することが可能となるのである。
【０１００】
なお、図７に示す球面エラー信号Ｓｋｅは、保護層１ａの厚さｔが一の光ディスク１内の部分毎に異なっている場合においては、光ディスク１の回転に伴って図７に示す球面エラー信号Ｓｋｅの全体が出力されることとなるが、一の光ディスク１内の保護層１ａの厚さｔは当該光ディスク１内で一定であるが、その厚さｔ自体が本来の理想値からずれている場合には、図７に示す球面エラー信号Ｓｋｅのうち、一の厚さｔに対応する球面エラー信号Ｓｋｅのみが常に出力されることとなる。
【０１０１】
次に、減算器３０に対しては、加算器２６の出力信号が正端子に入力されると共に加算器２７の出力信号が負端子に入力されるように、当該加算器２６及び２７が減算器３０に接続されている。これにより、減算器３０からは、部分ディテクタ７ａ、７ｃ、７ｅ及び７ｇからの各受光信号Ｓｐの和信号から部分ディテクタ７ｂ、７ｄ、７ｈ及び７ｆからの各受光信号Ｓｐの和信号を減算した信号、すなわち、公知の非点収差法を用いたフォーカスエラー信号Ｓｆｅが出力されることとなる。その後は、上述したドライバ１６及びアクチュエータ１０の動作により、フォーカスエラー信号Ｓｆｅがゼロレベルとなるようにフォーカスサーボ制御が行なわれる。
【０１０２】
以上説明したように、実施形態の情報再生装置Ｓの動作によれば、光ビームＢの反射光に含まれる球面収差を示すと共に正又は負のいずれか一方の極性を有する球面エラー信号Ｓｋｅが生成されるので、当該球面収差の量及び極性を正確且つ即時に把握してこれを補償することができる。
【０１０３】
また、部分ディテクタ７ｅ、７ｆ、７ｇ及び７ｈを含む領域が光ビームＢの反射光のディテクタ７上における照度強度分布の保護層１ａの厚さｔの変化に起因した変化に対応する広さ（すなわち、当該照射範囲内の中央部の照射強度が強い部分を含むような広さ）を有し、且つ、各部分ディテクタが当該照射強度分布の変化に対応した形状を有しているので、各部分ディテクタから出力される八つの受光信号Ｓｐの夫々が保護層１ａの特性の変化に伴う球面収差の変化に対応して変化することとなり、当該八つの受光信号Ｓｐに基づいて光ビームＢの反射光に含まれている球面収差の量及び極性を正確に検出することができる。
【０１０４】
更に、上述した構成の信号処理部１１により球面エラー信号Ｓｋｅを生成するので、反射光に発生している球面収差の量及び極性を的確に示す球面エラー信号Ｓｋｅを生成することができる。
【０１０５】
また、球面収差を示す球面エラー信号Ｓｋｅを生成する信号処理部１１によりフォーカスエラー信号Ｓｆｅ及びＲＦ信号Ｓｒｆをも生成することができる。
【０１０６】
更にまた、部分ディテクタ７ｅ乃至７ｈにより形成される領域の形状が矩形であるので、ディテクタ７を簡易に形成することができる。
【０１０７】
また、保護層１ａの特性に起因して反射光に発生している球面収差を的確に補償して光ディスク１上の情報を正確に再生することができる。
【０１０８】
なお、上記した球面エラー信号Ｓｋｅについては、光ディスク１における情報記録面の光ビームＢの光軸に対する傾斜、対物レンズ２の瞳面における開口部内の光ビームＢの強度及び対物レンズ２の情報記録面に平行な方向の偏倚によっては影響を受けないことが実験的に確認されているが、光ビームＢの光軸の位置とディテクタ７の中心位置との間にずれが生じている場合には、球面エラー信号Ｓｋｅ全体のレベルが低下し、且つゼロクロス点もシフトすることが実験的に確認されている。
【０１０９】
（ＩＩＩ）変形形態
次に、本発明の変形形態について、図８及び図９を用いて説明する。
【０１１０】
なお、図９においては、図４と同様の構成部材については、同様の部材番号を付して細部の説明は省略する。
【０１１１】
先ず、ディテクタ７の分割形状について、図８（ａ）にディテクタ７’として示すように、部分ディテクタ７ｅ’乃至７ｈ’により構成される領域の形状を円形としても良い。
【０１１２】
この場合でも、部分ディテクタ７ｅ’乃至７ｈ’を含む領域は、光ビームＢの反射光のディテクタ７上における照度強度分布の保護層１ａの厚さｔの変化に起因した変化に対応する広さ（すなわち、当該照射範囲内の中央部の照射居度が強い部分を含むような広さ）とされる。
【０１１３】
この場合にも、上述の実施形態の効果と同様な効果が得られる他、部分ディテクタ７ｅ’乃至７ｈ’を含む領域の形状が円形であるので、光ビームＢにおけるビーム形状及びその照射強度分布に対応してより正確に球面収差の量及び極性を検出することができることとなる。
【０１１４】
また、ディテクタ７の分割形状について、図８（ｂ）にディテクタ７”として示すように、部分ディテクタ７ｅ”乃至７ｈ”により構成される領域の形状を八角形としても良い。
【０１１５】
この場合でも、図８（ａ）の場合と同様に、部分ディテクタ７ｅ”乃至７ｈ”を含む領域は、光ビームＢの反射光のディテクタ７上における照度強度分布の保護層１ａの厚さｔの変化に起因した変化に対応する広さとされる。
【０１１６】
この場合には、上述の実施形態の効果と同様な効果が得られる他、部分ディテクタ７ｅ”乃至７ｈ”を含む領域の形状が八角形であるので、光ビームＢにおけるビーム形状及びその照射強度分布に対応してより正確に球面収差の量及び極性を検出することができると共に、ディテクタ７”を簡易に形成することができる。
【０１１７】
また、上述した実施形態及び各変形形態は、本発明を情報再生装置Ｓに対して適用した場合の実施形態又は変形形態について説明したが、これ以外に、本発明は、光ディスク１に予め記録されているアドレス情報等の記録制御情報を検出し、当該検出した記録制御情報に基づいて当該光ディスク１に情報を記録するための情報記録装置に対して適用することもできる。
【０１１８】
すなわち、図９に示すように、図１に示す光学系Ｓと、図４に示す信号処理部１１、再生部１２、アンプ１３及び１５、ドライバ１４及び１６、液晶パネル９及びアクチュエータ１０とに加えて、再生部１２から出力される再生信号Ｓｐｕ（この再生信号Ｓｐｕが上記した記録制御情報を含んでいることとなる。）に基づいて記録制御を行う記録手段としてのＣＰＵ４１と、ＣＰＵ４１からの制御信号Ｓｃに基づいて外部から入力されている記録すべき記録信号Ｓｒを変調し、レーザダイオード８の出力値を当該記録信号Ｓｒに対応した値とするための変調信号Ｓｒｒを生成する記録手段としてのエンコーダ４０と、を備える情報記録装置Ｒに対しても本発明を適用することができる。
【０１１９】
この場合、レーザダイオード８の出力値（すなわち、光ビームＢの強度）が変調信号Ｓｒｒに基づいて強度変調され、当該強度変調された光ビームＢが上記記録制御情報に含まれている光ディスク１のアドレス情報に対応する位置に照射されることにより、当該照射位置に変調信号Ｓｒｒに対応した形状の情報ピットが形成されて記録信号Ｓｒが光ディスク１に記録されることとなる。
【０１２０】
この情報記録装置Ｒの動作によれば、球面収差が的確に補償されることにより記録制御情報を含む受光信号Ｓｐが正確に再生されるので、正確に記録すべき情報を光ディスク１上に記録することができる。
【０１２１】
更に、上述の実施形態及び各変形形態では、球面収差を補償する方法として液晶パネル９を用いた場合について説明したが、これ以外に、例えば、対物レンズを二つの独立したレンズを用いて構成し、当該二つのレンズ間の間隙を制御しすることにより発生している球面収差を補償する方法や、コリメータレンズ３を光ビームＢの光軸と平行な方向に移動することにより球面収差を補償する方法に対しても、本発明により得られた球面エラー信号Ｓｋｅを用いたクローズドループのサーボ制御を適用することにより、迅速且つ確実に球面収差を補償することができる。
【０１２２】
また、上述した実施形態及び変形形態においては、保護層１ａの厚さｔの変化に起因して発生する球面収差を検出してこれを補償する場合について説明したが、これ以外に、保護層１ａにおける屈折率のばらつき（一枚の光ディスク１内におけるばらつき又は複数の光ディスク１間におけるばらつき）に起因して発生する球面収差を検出してこれを補償する場合に、当該屈折率にばらつきがある時におけるディテクタ７上の光ビームＢの反射光の照射強度分布も当該ばらつきの量及び極性に応じ図２に示した場合に準じて変化するので、この場合にも本発明を適用して当該球面収差を検出し補償することが可能である。
【０１２３】
【発明の効果】
以上説明したように、請求項１に記載の発明によれば、球面収差を示すと共に極性を有する球面エラー信号が生成されるので、反射光に発生している球面収差の量及び極性を、正確且つ即時に把握してこれを補償することができる。
【０１２４】
従って、保護層の特性が変化したことにより反射光に発生する球面収差が変化しても、当該球面収差の量及び極性を正確且つ即時に把握してこれを補償し、記録媒体に対して正確に情報を記録再生することが可能になる。
【０１２５】
また、非点収差が与えられた反射光を受光して球面エラー信号を生成するので、反射光に発生している球面収差の量及び極性を正確且つ即時に把握してこれを補償することができる。
【０１２６】
また、第１副受光手段が反射光の受光手段上における照度強度分布の保護層の特性に起因した変化に対応した広さを有するので、各副受光手段から出力される各受光信号の夫々が、保護層の特性の変化に伴う球面収差の変化に対応して変化することとなり、当該各受光信号に基づいて反射光に含まれている球面収差の量及び極性を正確に検出することができる。
【０１２７】
また、第１副受光手段及び第２副受光手段が当該照射強度分布に対応した形状の分割線により夫々複数の第１部分受光手段と複数の第２部分受光手段とに分割されているので、各部分受光手段から出力される各受光信号の夫々が、保護層の特性の変化に伴う球面収差の変化に対応して変化することとなり、当該各受光信号に基づいて反射光に含まれている球面収差の量及び極性を正確に検出することができる。
【０１２８】
さらに、各第１分布方向受光手段から夫々出力される受光信号と各第２分布方向受光手段から夫々出力される受光信号との和信号と、各第１部分受光手段のうち第１分布方向受光手段以外の複数の第１部分受光手段から夫々出力される受光信号と各第２部分受光手段のうち第２分布方向受光手段以外の複数の第２部分受光手段から出力される複数の受光信号との和信号との差信号を球面エラー信号として出力するので、反射光に発生している球面収差の量及び極性を的確に示す球面エラー信号を生成することができる。
【０１２９】
請求項２に記載の発明によれば、請求項１に記載の発明の効果に加えて、非点収差発生手段を球面エラー信号の生成用とフォーカスエラー信号の生成用とで兼用できるので、光ピックアップ自体を小型化しつつ球面エラー信号とフォーカスエラー信号とを生成することができる。
【０１３０】
請求項３に記載の発明によれば、請求項２に記載の発明の効果に加えて、各第１分布方向受光手段から夫々出力される受光信号と各第２部分受光手段のうち第２分布方向受光手段以外の複数の第２部分受光手段から夫々出力される受光信号との和信号と、各第１部分受光手段のうち第１分布方向受光手段以外の複数の第１部分受光手段から夫々出力される受光信号と各第２分布方向受光手段から夫々出力される受光信号との和信号との差信号をフォーカスエラー信号として出力するので、球面エラー信号を生成する受光手段によりフォーカスエラー信号をも生成することができる。
【０１３１】
請求項４に記載の発明によれば、請求項１乃至請求項３のいずれか一項に記載の発明の効果に加えて、各第１部分受光手段から夫々出力される受光信号の和信号と各第２部分受光手段から夫々出力される受光信号の和信号との和信号を検出信号として更に出力するので、球面エラー信号を生成する受光手段により記録されている情報に対応する検出信号をも生成することができる。
【０１３２】
請求項５に記載の発明によれば、請求項１乃至請求項４のいずれか一項に記載の発明の効果に加えて、第１副受光手段の形状が円形であるので、光ビームにおけるビーム形状及びその照射強度分布に対応してより正確に球面収差の量及び極性を検出することができる。
【０１３３】
請求項６に記載の発明によれば、請求項１乃至請求項４のいずれか一項に記載の発明の効果に加えて、第１副受光手段の形状が矩形であるので、第１副受光手段及び第２副受光手段を簡易に形成することができる。
【０１３４】
請求項７に記載の発明によれば、請求項１乃至請求項４のいずれか一項に記載の発明の効果に加えて、第１副受光手段の形状が八角形であるので、光ビームにおけるビーム形状及びその照射強度分布に対応して正確に球面収差を検出することができると共に、第１副受光手段及び第２副受光手段を簡易に形成することができる。
【０１３５】
請求項８に記載の発明によれば、請求項４に記載の発明の効果に加えて、保護層の特性に起因して反射光に発生している球面収差を的確に補償して正確に情報を再生することができる。
【０１３６】
請求項９に記載の発明によれば、請求項４に記載の発明の効果に加えて、保護層の特性に起因して反射光に発生している球面収差を的確に補償して正確に情報を記録することができる。
【図面の簡単な説明】
【図１】本発明の原理を示す光学系の概要構成を示すブロック図である。
【図２】本発明の原理を説明する図であり、（ａ）は保護層の厚さが０．７ｍｍのときのディテクタ上における光ビームの照射強度分布を示す模式図であり、（ｂ）は保護層の厚さが０．６５ｍｍのときのディテクタ上における光ビームの照射強度分布を示す模式図であり、（ｃ）は保護層の厚さが０．６ｍｍのときのディテクタ上における光ビームの照射強度分布を示す模式図であり、（ｄ）は保護層の厚さが０．５５ｍｍのときのディテクタ上における光ビームの照射強度分布を示す模式図であり、（ｅ）は保護層の厚さが０．５ｍｍのときのディテクタ上における光ビームの照射強度分布を示す模式図である。
【図３】ディテクタの分割形状の例を示す平面図である。
【図４】実施形態の情報再生装置の概要構成を示すブロック図である。
【図５】実施形態のディテクタの形状を示す平面図である。
【図６】信号処理部の細部構成を示すブロック図である。
【図７】球面収差を示す球面エラー信号の波形例を示す図である。
【図８】ディテクタの分割形状の変形形態を示す平面図であり、（ａ）は第１の変形形態を示す平面図であり、（ｂ）は第２の変形形態を示す平面図である。
【図９】変形形態の情報記録装置の概要構成を示すブロック図である。
【符号の説明】
１…光ディスク
１ａ…保護層
１ｂ…情報記録面
２…対物レンズ
３…コリメータレンズ
４…偏向ビームスプリッタ
５…集光レンズ
６…シリンドリカルレンズ
７、７’、７”…ディテクタ
７ａ、７ｂ、７ｃ、７ｄ、７ｅ、７ｆ、７ｇ、７ｈ、７ａ’、７ｂ’、７ｃ’、７ｄ’、７ｅ’、７ｆ’、７ｇ’、７ｈ’、７ａ”、７ｂ”、７ｃ”、７ｄ”、７ｅ”、７ｆ”、７ｇ”、７ｈ”…部分ディテクタ
８…レーザダイオード
９…液晶パネル
１０…アクチュエータ
１１…信号処理部
１２…再生部
１３、１５…アンプ
１４、１６…ドライバ
２０、２１、２２、２３、２４、２５、２６、２７、２８…加算器
２９、３０…減算器
４０…エンコーダ
４１…ＣＰＵ
４５…λ／４板
Ｓｄｆ、Ｓｄｋ…駆動信号
Ｓａｆ、Ｓａｋ…増幅エラー信号
Ｓｐ…受光信号
Ｓｆｅ…フォーカスエラー信号
Ｓｋｅ…球面エラー信号
Ｓｒｆ…ＲＦ信号
Ｓｐｕ…再生信号
Ｓｃ…制御信号
Ｓｒ…記録信号
Ｓｒｒ…変調信号
Ｓ…光学系
Ｒ…情報記録装置
Ｐ…情報再生装置
ＰＵ…光ピックアップ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field of an optical pickup that optically records and reproduces information on a recording medium, and an information reproducing apparatus and an information recording apparatus including the optical pickup, and more specifically, a protective layer of the recording medium. The present invention belongs to the technical field of an optical pickup for recording and reproducing information while compensating for spherical aberration generated due to a change in thickness, and an information reproducing apparatus and an information recording apparatus including the optical pickup.
[0002]
[Prior art]
2. Description of the Related Art In recent years, research and development on an optical information recording medium having an increased recording capacity, such as a so-called DVD (an optical disk having an increased recording capacity about seven times as compared with a conventional CD (Compact Disk)), has been actively conducted. is there.
[0003]
Here, when optically recording / reproducing information with respect to the information recording medium having the high recording density, it is necessary to narrow the light beam for recording / reproduction to an extremely small amount on the information recording surface of the information recording medium. For this purpose, it is necessary to perform the focusing using an objective lens having a high NA (aperture ratio).
[0004]
On the other hand, when a light beam is condensed on the information recording surface using such an objective lens, it is necessary to transmit the light beam through a transparent protective layer of the information recording medium. Spherical aberration occurs in the reflected light of the light beam from the information recording surface.
[0005]
Here, for example, in a conventional CD or the like, the information recording density was not so high and the information pits to be read were not so small, so that the generated spherical aberration could be neglected. In an information recording medium having a high surface area, when the thickness of the protective layer is different due to the increase in the NA of the objective lens described above, the amount of spherical aberration generated by the light beam passing through the protective layer is not negligible. It will be.
[0006]
Therefore, as a method for compensating the spherical aberration, for example, a phase difference for compensating for the generated spherical aberration is previously given to the light beam before irradiating the information recording medium by the liquid crystal panel. And a method of compensating for the spherical aberration generated by controlling the gap between the two lenses by configuring the objective lens using two independent lenses, and the like. Was.
[0007]
Further, as a method of detecting the spherical aberration, the point at which the amplitude becomes maximum is monitored by monitoring the amplitude of an RF (Radio Frequency) signal generated based on the reflected light of the light beam. The spherical aberration is compensated by detecting this point as being a point that has been detected, and controlling the voltage applied to the liquid crystal panel or the gap between the lenses so that the amplitude is maximized.
[0008]
[Problems to be solved by the invention]
However, according to the above-described method of obtaining the maximum value of the amplitude of the RF signal and compensating for the spherical aberration, it is necessary to monitor the RF signal at every predetermined interval timing to find the maximum value of the amplitude. Cannot be speeded up.
[0009]
This problem is, for example, when the thickness of the protective layer is different for each part in one information recording medium due to a manufacturing error, the operation of compensating for the spherical aberration is caused by the movement of the information recording medium. This leads to a problem that it may not be possible to follow the speed of change of the aberration.
[0010]
On the other hand, although the thickness of the protective layer in one information recording medium is constant in the information recording medium, even if the thickness itself is deviated from the original thickness, the generated spherical surface This leads to a problem that aberration cannot be compensated quickly.
[0011]
In the method of detecting spherical aberration from the maximum value of the amplitude of the RF signal described above, since the signal indicating the spherical aberration has no polarity, the polarity of correction of spherical aberration (for example, in the case of compensation by a liquid crystal panel, It is not possible to determine whether the voltage value applied to the liquid crystal panel should be increased or decreased in order to compensate for the generated spherical aberration). In this case, for example, an S-shaped curve is required. There is also a problem that quick and accurate compensation control by forming a so-called closed loop such as focus servo control using a focus error signal cannot be performed.
[0012]
Therefore, the present invention has been made in view of the above-described problems, and the problem is that the characteristics of the protective layer, represented by the thickness of the protective layer, are different in one information recording medium or a plurality of information recording media. Even if the spherical aberration generated in the reflected light changes due to a change between recording media, the amount and polarity of the spherical aberration are accurately and immediately grasped and compensated, and information is accurately written to the recording medium. An object of the present invention is to provide an optical pickup capable of recording and reproducing, and an information reproducing apparatus and an information recording apparatus including the optical pickup.
[0013]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 is directed to an optical pickup that irradiates the recording medium having at least a protective layer transparent to a light beam with the light beam by transmitting the protective layer through the protective layer. Emitting means for emitting the light beam; astigmatism generating means for generating astigmatism in the reflected light of the light beam from the recording medium; receiving the reflected light having the astigmatism; Light-receiving means for generating, and based on the light-receiving signalA spherical error signal indicating the spherical aberration occurring in the reflected light due to the characteristics of the protective layer and having a polarity.And a compensator for compensating the spherical aberration based on the generated spherical error signal, wherein the light receiving means occupies a central portion of the light receiving means. The first sub-light receiving means is divided into a sub-light receiving means and a second sub-light receiving means occupying a peripheral portion of the first sub-light receiving means, and the first sub-light receiving means transmits the reflected light having astigmatism on the light receiving means. The irradiation intensity distribution has a width corresponding to a change caused by the characteristics of the protective layer, and includes a plurality of dividing lines each having a direction corresponding to the irradiation intensity distribution passing through the center of the first sub-light receiving unit. The first sub-light receiving means is divided into a plurality of first partial light-receiving means, and the second sub-light-receiving means is divided into a plurality of second partial light-receiving means by each of the dividing lines. Partial light receiver Among the plurality of first partial light receiving means being the first distribution direction light receiving means, which are the plurality of first partial light receiving means, which are opposite to the irradiation intensity distribution direction corresponding to the irradiation intensity distribution. Sum signals of the light receiving signals respectively output from the second distribution direction light receiving means, which are a plurality of second partial light receiving means, which are opposed to each other in a direction perpendicular to the irradiation intensity distribution direction; The light receiving signals respectively output from the plurality of first partial light receiving means other than the first distribution direction light receiving means among the light receiving means and the plurality of light receiving signals other than the second distribution direction light receiving means among the respective second partial light receiving means. A difference signal from a sum signal of the plurality of light receiving signals respectively output from the second partial light receiving unit is output as the spherical error signal.
[0014]
Therefore,Since the spherical error signal indicating the spherical aberration and having the polarity is generated, the amount and the polarity of the spherical aberration occurring in the reflected light can be accurately and immediately grasped and compensated.
[0015]
Also, since the reflected light with astigmatism is received to generate a spherical error signal, it is possible to accurately and immediately grasp the amount and polarity of the spherical aberration generated in the reflected light and compensate for it. it can.
[0016]
Also, since the first sub-light receiving means has a width corresponding to the change of the illuminance intensity distribution on the light receiving means of the reflected light due to the characteristics of the protective layer, each of the light receiving signals output from each of the sub-light receiving means is Changes in accordance with the change in the spherical aberration associated with the change in the characteristics of the protective layer, and the amount and polarity of the spherical aberration contained in the reflected light can be accurately detected based on the respective light receiving signals. .
[0017]
Further, since the first sub-light receiving means and the second sub-light receiving means are respectively divided into a plurality of first partial light receiving means and a plurality of second partial light receiving means by dividing lines having a shape corresponding to the irradiation intensity distribution, Each of the light receiving signals output from each of the partial light receiving means changes in accordance with the change in the spherical aberration accompanying the change in the characteristic of the protective layer, and the spherical surface included in the reflected light based on each of the light receiving signals. The amount and polarity of the aberration can be accurately detected.
[0018]
Also, a sum signal of a light receiving signal output from each of the first distribution direction light receiving means and a light receiving signal output from each of the second distribution direction light receiving means, and a first distribution direction light receiving means among the first partial light receiving means. A light receiving signal output from each of the plurality of first partial light receiving means other than the means and a plurality of light receiving signals output from a plurality of second partial light receiving means other than the second distribution direction light receiving means among the second partial light receiving means; Is output as a spherical error signal, it is possible to generate a spherical error signal that accurately indicates the amount and polarity of the spherical aberration generated in the reflected light.
[0019]
Claims to solve the above problems2The invention described in2. The optical pickup according to claim 1, wherein the error signal generating unit further outputs a focus error signal based on an astigmatism method based on the light receiving signal.
[0020]
Therefore, the astigmatism generating means can be used both for generating the spherical error signal and for generating the focus error signal.
[0021]
Claims to solve the above problems3The invention described in claim2In the optical pickup described in the above,The error signal generation means includes a plurality of the second partial light receiving means other than the second distribution direction light receiving means among the light receiving signals respectively output from the first distribution direction light receiving means and the second partial light receiving means. And the sum signal of the light receiving signals respectively output from the plurality of first partial light receiving means other than the first distribution direction light receiving means among the first partial light receiving means. A difference signal between the received light signal and the sum signal output from the second distribution direction light receiving means is output as the focus error signal.
[0022]
Therefore,The focus error signal can also be generated by the light receiving means for generating the spherical error signal.
[0023]
Claims to solve the above problems4The invention described in claim1 to 3The optical pickup according to any one of the above,The information to be reproduced is recorded on the recording medium, and the error signal generating means includes a sum signal of the light receiving signals output from each of the first partial light receiving means and a signal from each of the second partial light receiving means. A sum signal of the output light reception signal and the sum signal is further output as a detection signal corresponding to the information.
[0024]
Therefore,A detection signal corresponding to the information recorded by the light receiving means for generating the spherical error signal can also be generated.
[0025]
Claims to solve the above problems5The invention described in claim1 to Claim 4The optical pickup according to any one of the above,The shape of the first sub-light receiving means is circular.
[0026]
Therefore,It is possible to more accurately detect the amount and polarity of spherical aberration in accordance with the beam shape of the light beam and its irradiation intensity distribution.
[0027]
Claims to solve the above problems6The invention described in claim1 to Claim 4The optical pickup according to any one of the above,The shape of the first sub-light receiving means is rectangular.
[0028]
Therefore,The first sub-light receiving unit and the second sub-light receiving unit can be easily formed.
[0029]
Claims to solve the above problems7The invention described in claim1 to Claim 4The optical pickup according to any one of the above,The shape of the first sub-light receiving means is octagonal.
[0030]
Therefore, according to the beam shape and the irradiation intensity distribution of the light beam,The spherical aberration can be accurately detected, and the first and second sub-light receiving units can be easily formed.
[0031]
Claims to solve the above problems8The invention described in5. An optical pickup according to claim 4, comprising: focus servo means for controlling a focal position of the light beam based on the focus error signal; and reproducing means for reproducing the information based on the detection signal. Features.
[0032]
Therefore,Information can be accurately reproduced by accurately compensating for the spherical aberration occurring in the reflected light due to the characteristics of the protective layer.
[0033]
Claims to solve the above problems9The invention described inAn optical pickup according to claim 4, a focus servo means for controlling a focal position of the light beam based on the focus error signal, and a reproducing means for reproducing the information based on the detection signal and outputting a reproduced signal. Recording means for controlling the light beam based on the output reproduced signal and recording information to be recorded on the recording medium, and recording the recording information on the information recording surface. .
[0034]
Therefore,Information can be accurately recorded by accurately compensating for spherical aberration occurring in the reflected light due to the characteristics of the protective layer.
[0039]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, a preferred embodiment of the present invention will be described.
[0040]
(I)The principle of the present invention
First, before a specific description of the embodiment, the principle of the present invention will be described.
[0041]
The thickness or refractive index of a protective layer (a protective layer that is transparent to a light beam for protecting an information recording surface of an optical disk) that was considered when designing the optical pickup has a protective layer of an actual optical disk. If the thickness or refractive index of the light beam is different from that of the light source, when a light beam for recording / reproducing information passes through the actual protective layer, a so-called spherical aberration occurs in the light beam. When astigmatism is given to the reflected light, which is reflected from the optical disk as a recording medium and passes through the actual protective layer before and after the reflection and has the spherical aberration, after the reflection, the reflected light is reflected. The shape of the irradiation intensity distribution on the light detector corresponds to a change in the thickness or the refractive index of the protective layer (that is, a change in the amount and polarity of the spherical aberration generated in the light beam as the light passes through the protective layer). Change.
[0042]
In the present invention, using this, a spherical error signal indicating the amount and polarity of the spherical aberration is generated, and the spherical aberration is compensated using the generated spherical error signal.
[0043]
Next, the principle of the present invention will be described more specifically.
[0044]
First, the configuration of an optical system used for explaining the principle will be described with reference to FIG.
[0045]
As shown in FIG. 1, an optical system S for explaining the principle includes a laser diode 8 as an emitting means for emitting a recording / reproducing light beam B, and a deflection beam splitter 4 for reflecting the emitted light beam B. A collimator lens 3 for converting the reflected light beam B into parallel light, and a λ / for rotating the plane of polarization of the light beam B that has become parallel light and the plane of polarization of the light beam B reflected from the optical disc 1. Four plates 45, an objective lens 2 for condensing the light beam B on the information recording surface in the optical disc 1, an optical disc 1 as a recording medium having a protective layer 1a transparent to the light beam B, and reflection from the optical disc 1 As the deflecting surface rotates, the condensing lens 5 condenses the light beam B transmitted through the objective lens 2, the collimator lens 3 and the deflecting beam splitter 4 onto the detector 7, A cylindrical lens 6 as generating means and astigmatism generating means for generating astigmatism with respect to the reflected light beam B, and a detector 7 as a light receiving means for receiving the light beam B given astigmatism, It is comprised by.
[0046]
In this configuration, when the light beam B is emitted from the laser diode 8, it is applied to the optical disc 1 via the deflection beam splitter 4, the collimator lens 3, the λ / 4 plate 45, and the objective lens 2. Then, the irradiated light beam B passes through the protective layer 1a of the optical disk 1, is reflected by the information recording surface 1b, passes through the protective layer 1a again, and thereafter, the objective lens 2, the λ / 4 plate 45, the collimator The light is irradiated onto a detector 7 via a lens 3, a deflection beam splitter 4, a condenser lens 5, and a cylindrical lens 6.
[0047]
Next, in the optical system S having such a configuration, when the thickness t of the protective layer 1a is changed (that is, the amount and polarity of the spherical aberration generated in the light beam B by passing through the protective layer 1a) FIG. 2 illustrates how the irradiation intensity distribution of the light beam B on the detector 7 changes when the light beam B is in a focused state on the information recording surface 1b. .
[0048]
In each of FIGS. 2A to 2E, the irradiation intensity distribution of the light beam B on the detector 7 having a square of 0.16 mm on a side has a thickness t ( The unit schematically shows how the thickness changes when mm) is changed in the case where the thickness of the protective layer 1a is changed from 0.7 mm to 0.5 mm. Here, in each drawing, it is shown that the intensity of the irradiation intensity is higher in a region where the black spots are denser.
[0049]
Further, in FIG. 2, parameters other than the thickness t of the protective layer 1a are fixed. Further, the ideal value of the thickness t is set to 0.6 mm which is a value used in a general optical disc or the like, and the spherical aberration generated by the optical disc 1 having the ideal value of the thickness t causes the spherical aberration. The reference value for compensating the aberration (ie, the shape of the objective lens 2, the position of the collimator lens 3 (the distance between the objective lens 2 and the collimator lens 3), etc. so that the spherical aberration having the reference value can be optimally compensated) Is set as a value).
[0050]
As is clear from FIGS. 2A to 2E, when the thickness of the protective layer 1a is changed, the irradiation intensity distribution of the reflected light of the light beam B on the detector 7 changes according to a certain law.
[0051]
That is, as the thickness t becomes thicker than the ideal value (that is, as the amount of spherical aberration generated by the protective layer 1a increases from the reference value), the entire irradiation intensity distribution becomes upper left and lower right in FIG. 2 and a region where the irradiation intensity is high extends in the lower left direction and the upper right direction in FIG. 2 near the center of the detector 7 (see FIGS. 2A and 2B).
[0052]
On the other hand, as the thickness t becomes smaller than the ideal value (that is, as the amount of spherical aberration generated by the protective layer 1a becomes smaller than the reference value), the entire irradiation intensity distribution is shifted upward and downward in FIG. Around the center of the detector 7, a region where the irradiation intensity is high and extends in the lower right direction and the upper left direction in FIG. 2 appears (see FIGS. 2D and 2E).
[0053]
When the thickness t is an ideal value, the irradiation intensity distribution as described above is not broadened, and a substantially circular irradiation intensity distribution is obtained (see FIG. 2C).
In view of this, the present invention focuses on the change in the irradiation intensity distribution, and responds to the change in the shape of each irradiation intensity distribution (particularly, the width of the region where the irradiation intensity is increased in the central portion and the direction of the change in the irradiation intensity distribution). Then, the detector 7 is divided into partial detectors 7a to 7h as shown in FIG. 3, and a spherical error signal having a positive or negative polarity and showing a spherical aberration is obtained based on an output signal from each of the partial detectors. The spherical aberration is compensated by a servo system including a closed loop based on the spherical error signal.
[0054]
At this time, the width of the region including the partial detectors 7e to 7h is set to be substantially equal to the width of the region where the irradiation intensity at the central portion in the irradiation intensity distribution is high.
[0055]
More specifically, in the case of FIGS. 2A and 2B, in the detector 7 shown in FIG. 3, the output signal levels of the partial detectors 7e and 7g are equal to those of the partial detectors 7f and 7h. The output signal level becomes higher than the output signal level, and the output signal level of the partial detectors 7d and 7b becomes higher than the output signal level of the partial detectors 7a and 7c.
[0056]
On the other hand, in the case shown in FIGS. 2D and 2E, in the detector 7 shown in FIG. 3, the output signal levels of the partial detectors 7e and 7g become lower than the output signal levels of the partial detectors 7f and 7h. The output signal levels of the partial detectors 7d and 7b are lower than the output signal levels of the partial detectors 7a and 7c.
[0057]
Further, in the case shown in FIG. 2C, the output signals of the partial detectors 7a to 7d become substantially zero, and the output signals of the partial detectors 7e to 7h have substantially the same value.
[0058]
Then, in the present invention, a spherical error signal Ske (hereinafter, simply referred to as a spherical error signal Ske) indicating the amount and polarity of spherical aberration is generated by the following equation. That is,
(Equation 1)

In equation (1), “7a” represents the output value of the output signal from the partial detector 7a, “7b” represents the output value of the output signal from the partial detector 7b, and “7c” represents the output value of the partial detector 7c. The output value of the signal, "7d" is the output value of the output signal from the partial detector 7d, "7e" is the output value of the output signal from the partial detector 7e, and "7f" is the output value of the partial detector 7f. The output value, “7g” indicates the output value of the output signal from the partial detector 7g, and “7h” indicates the output value of the output signal from the partial detector 7h.
[0059]
When the spherical error signal Ske is generated in this manner, in the case shown in FIG. 2A or 2B, the second term on the right side is larger than the first term on the right side of the equation (1), and as a result, the negative value is obtained. Is generated. On the other hand, in the case shown in FIG. 2D or 2E, the first term on the right side is larger than the second term on the right side of Equation (1), and as a result, a positive spherical error signal Ske is generated. .
[0060]
Further, in the case of FIG. 2C, the second term on the right side of the equation (1) is equal to the first term on the right side, and as a result, a spherical error signal Ske of zero level is generated.
[0061]
Accordingly, the spherical error signal Ske having a negative value is generated when the thickness t of the protective layer 1a is thicker than its ideal value (0.6 mm), and a positive value when the thickness t is thinner than the ideal value. Is generated, and when it is equal to the ideal value, the spherical error signal Ske at zero level is generated. Therefore, the polarity at the time of compensating for the spherical aberration caused by the variation of the thickness t can be determined. It is.
[0062]
2 and FIG. 3 show that the absolute value of the spherical error signal Ske in the case of FIG. 2A and the case of FIG. 2B, the absolute value of the spherical error signal Ske is smaller in the case of FIG. 2B because the difference in shading of each region in the irradiation hardness distribution is smaller. Further, comparing the absolute values of the spherical error signal Ske in the case of FIG. 2D and the case of FIG. 2E, the case of FIG. 2D shows the density of each region in the irradiation hardness distribution. 2D, the absolute value of the spherical error signal Ske is smaller in the case of FIG. 2D.
[0063]
That is, since the absolute value of the spherical error signal Ske increases as the difference between the actual thickness t of the protective layer 1a and its ideal value increases, the necessary compensation increases as the absolute value of the spherical error signal Ske increases. The amount can be determined to be large.
[0064]
According to the present invention, the spherical error signal Ske indicating the amount and polarity of the spherical aberration has an S-shaped curve like a focus error signal according to the so-called astigmatism method according to the present invention. The use of the error signal Ske makes it possible to quickly and accurately compensate for spherical aberration by a servo control system having a so-called closed loop.
[0065]
The reason why the irradiation intensity distribution of the reflected light of the light beam B given astigmatism on the detector 7 changes as shown in FIG. 2 due to the change in the thickness t of the protective layer 1a is that in the present invention, Spherical aberration generated in the light beam B by passing through the protective layer 1a (this spherical aberration has an axially symmetric distribution shape with the optical axis of the light beam B as a symmetric axis, and the amount of aberration depends on the thickness t). 2), the astigmatism is superimposed by the cylindrical lens 6. Due to this, if the polarity and the amount of the spherical aberration change due to the change in the thickness t of the protective layer 1 a, each of FIGS. The change in the shape of the irradiation intensity distribution corresponding to the thickness t as shown in the figure appears.
[0066]
(II)Embodiment
Next, an embodiment of the present invention will be specifically described with reference to FIGS.
[0067]
The embodiment described below applies the present invention to an information reproducing apparatus that reproduces information recorded on the optical disc 1 while performing focus servo control by the astigmatism method while compensating for spherical aberration by the present invention. This is an embodiment in the case of application.
[0068]
FIG. 4 is a block diagram showing an outline of the information reproducing apparatus according to the embodiment. FIG. 5 is a plan view showing the shape of the detector of the embodiment. FIG. FIG. 7 is a block diagram illustrating a schematic configuration of a signal processing unit that also generates a focus error signal and the like by an aberration method, and FIG. 7 is a diagram illustrating an example of a waveform of a spherical error signal Ske.
[0069]
Further, it is assumed that information to be reproduced is recorded on the optical disc 1 in the embodiment in advance.
[0070]
As shown in FIG. 4, in addition to the configuration of the optical system S for explaining the principle shown in FIG. 1, the information reproducing apparatus P of the embodiment includes a liquid crystal panel 9 as a compensating means for spherical aberration compensation, and a focus servo. Actuator 10 as control focus servo means, signal processing section 11 as generating means and error signal generating means, reproducing section 12 as reproducing means, amplifier 13, driver 14 as compensating means, amplifier 15 And a driver 16 as focus servo means.
[0071]
Here, the liquid crystal panel 9 is a transmission type liquid crystal panel that gives a phase difference to the light beam B for compensating spherical aberration by a known technique.
[0072]
Further, based on the principle described above, the detector 7 includes, as shown in FIG. 5, partial detectors 7a, 7b, 7c and 7d as second sub-light receiving means and second partial light-receiving means, and first sub-light receiving means It is divided into partial detectors 7e, 7f, 7g and 7h as first partial light receiving means.
[0073]
At this time, as described above, the width of the region including the partial detectors 7e to 7h is set so as to be substantially equal to the width of the region where the irradiation intensity at the center in the irradiation intensity distribution shown in FIG. I have.
[0074]
Furthermore, the optical pickup PU of the present invention is formed by the optical system S, the liquid crystal panel 9, and the actuator 10 in the above-described configuration.
[0075]
In FIG. 4, only the portion according to the present invention is shown. However, the actual information reproducing apparatus S additionally includes a tracking servo control section that performs so-called tracking servo control on the irradiation position of the light beam B. And a CPU for controlling the entire operation of the information reproducing apparatus S, or an input operation unit for inputting necessary information.
[0076]
Next, the operation of the information reproducing apparatus P will be described.
[0077]
The light receiving signals Sp output from the respective partial detectors included in the detector 7 by the operation of the optical system S shown in FIG. 1 (note that in FIG. 4, eight light receiving signals Sp are actually collected into one The light receiving signal Sp is input to the signal processing unit 11.
[0078]
Then, the signal processing unit 11 generates and outputs the spherical error signal Ske to the amplifier 13 by the processing described below based on the above-described principle, and also outputs the RF corresponding to the information to be reproduced recorded on the optical disc 1. The signal Srf is generated by a process described later and output to the reproducing unit 12, and the focus error signal Sfe based on the astigmatism method is generated by the process described later and output to the amplifier 15.
[0079]
Thereby, the reproducing unit 12 generates a reproduced signal Spu corresponding to the information recorded on the optical disc 1 based on the RF signal Srf, and outputs the signal to an external speaker or display (not shown).
[0080]
The amplifier 15 amplifies the input focus error signal Sfe at a predetermined amplification rate, generates an amplified error signal Saf, and outputs the amplified error signal Saf to the driver 16.
[0081]
Then, the driver 16 generates a drive signal Sdf for driving the actuator 10 to perform focus servo control based on the amplification error signal Saf, and outputs the drive signal Sdf to the actuator 10.
[0082]
Accordingly, the actuator 10 drives the objective lens 2 in a direction parallel to the optical axis of the light beam B (indicated by a dashed line in FIG. 4) based on the drive signal Sdf, and the focus error signal Sfe becomes zero level. Focus servo control is performed so that
[0083]
On the other hand, the amplifier 13 amplifies the input spherical error signal Ske at a predetermined amplification factor, generates an amplified error signal Sak, and outputs the amplified error signal Sak to the driver 14.
[0084]
Then, the driver 14 generates a drive signal Sdk for driving the liquid crystal panel 9 to compensate for the spherical aberration having the amount and polarity indicated by the spherical error signal Ske based on the amplified error signal Sak. 9 is output.
[0085]
Thereby, the liquid crystal panel 9 gives a phase difference to the passing light beam B such that the spherical error signal Ske becomes zero level based on the driving signal Sdk, and compensates for the generated spherical aberration.
[0086]
At this time, the liquid crystal panel 9 applies a voltage indicated by the drive signal Sdk to the liquid crystal layer in the liquid crystal panel 9, thereby changing the orientation of the liquid crystal layer and changing the refractive index to a necessary level. The phase difference is given to the light beam B.
[0087]
Next, the detailed configuration and operation of the signal processing unit 11 will be described with reference to FIGS.
[0088]
As shown in FIG. 6, the signal processing unit 11 includes adders 20 to 28 and subtracters 29 and 30.
[0089]
At this time, the partial detector 7a and the partial detector 7c are connected to the adder 20 so that the received light signal Sp from the partial detector 7a and the received light signal Sp from the partial detector 7c are input to the adder 20. Have been.
[0090]
In addition, the partial detector 7d and the partial detector 7b are connected to the adder 21 so that the light receiving signal Sp from the partial detector 7d and the light receiving signal Sp from the partial detector 7b are input to the adder 21. ing.
[0091]
Further, the partial detector 7e and the partial detector 7g are connected to the adder 22 so that the light receiving signal Sp from the partial detector 7e and the light receiving signal Sp from the partial detector 7g are input to the adder 22. ing.
[0092]
Next, the partial detector 7h and the partial detector 7f are connected to the adder 23 so that the received light signal Sp from the partial detector 7h and the received light signal Sp from the partial detector 7f are input to the adder 23. Have been.
[0093]
The adders 20 and 23 are connected to the adder 24 so that the output signal of the adder 20 and the output signal of the adder 23 are input to the adder 24.
[0094]
Further, the adders 21 and 22 are connected to the adder 25 such that the output signal of the adder 21 and the output signal of the adder 22 are input to the adder 25.
[0095]
Furthermore, the adders 20 and 22 are connected to the adder 26 so that the output signal of the adder 20 and the output signal of the adder 22 are input to the adder 26.
[0096]
The adders 21 and 23 are connected to the adder 27 so that the output signal of the adder 21 and the output signal of the adder 23 are input to the adder 27.
[0097]
The adders 24 and 25 are connected to the adder 28 such that the output signal of the adder 24 and the output signal of the adder 25 are input to the adder 28. As a result, the adder 28 outputs a signal obtained by adding all the light receiving signals Sp from the respective partial detectors 7a to 7h, that is, an RF signal Srf corresponding to the information recorded on the optical disc 1.
[0098]
On the other hand, the adders 24 and 25 are connected to the subtractor 29 such that the output signal of the adder 24 is input to the positive terminal and the output signal of the adder 25 is input to the negative terminal. It is connected to the. As a result, a signal obtained by subtracting the sum signal of the respective light receiving signals Sp from the partial detectors 7b, 7d, 7e and 7g from the sum signal of the respective light receiving signals Sp from the partial detectors 7a, 7c, 7h and 7f is output from the subtractor 29. That is, the spherical error signal Ske based on the above equation (1) is output.
[0099]
The waveform of the spherical error signal Ske at this time will be described with reference to FIG. 7. As described in the above principle, the change in the thickness t of the protective layer 1a in the optical disc 1 (centering around the ideal value 0.6 mm). ), A substantially S-shaped spherical error signal Ske is generated. Then, by using the S-shaped spherical error signal Ske, it is possible to quickly and accurately compensate spherical aberration by the servo control system having a so-called closed loop as described above.
[0100]
Note that, when the thickness t of the protective layer 1a is different for each part in one optical disc 1, the spherical error signal Ske shown in FIG. Although the entire Ske is output, the thickness t of the protective layer 1a in one optical disc 1 is constant in the optical disc 1, but the thickness t itself deviates from the original ideal value. In this case, of the spherical error signals Ske shown in FIG. 7, only the spherical error signal Ske corresponding to one thickness t is always output.
[0101]
Next, the adders 26 and 27 are connected to the subtractor 30 such that the output signal of the adder 26 is input to the positive terminal and the output signal of the adder 27 is input to the negative terminal. 30. As a result, a signal obtained by subtracting the sum signal of the respective light receiving signals Sp from the partial detectors 7b, 7d, 7h and 7f from the subtractor 30 from the sum signal of the respective light receiving signals Sp from the partial detectors 7a, 7c, 7e and 7g. That is, the focus error signal Sfe using the known astigmatism method is output. Thereafter, the focus servo control is performed by the operation of the driver 16 and the actuator 10 so that the focus error signal Sfe becomes zero level.
[0102]
As described above, according to the operation of the information reproducing apparatus S of the embodiment, the spherical error signal Ske indicating the spherical aberration included in the reflected light of the light beam B and having one of positive and negative polarities is generated. Therefore, the amount and polarity of the spherical aberration can be accurately and immediately grasped and compensated.
[0103]
Further, the area including the partial detectors 7e, 7f, 7g, and 7h has a width corresponding to the change of the illuminance intensity distribution on the detector 7 of the reflected light of the light beam B due to the change in the thickness t of the protective layer 1a (that is, the width). , The width of the central portion within the irradiation range includes a portion where the irradiation intensity is high), and since each of the partial detectors has a shape corresponding to the change of the irradiation intensity distribution, Each of the eight light receiving signals Sp output from the detector changes in accordance with the change in the spherical aberration accompanying the change in the characteristics of the protective layer 1a, and the reflected light of the light beam B is based on the eight light receiving signals Sp. Can accurately detect the amount and polarity of the spherical aberration included in.
[0104]
Furthermore, since the spherical error signal Ske is generated by the signal processing unit 11 having the above-described configuration, the spherical error signal Ske that accurately indicates the amount and polarity of the spherical aberration generated in the reflected light can be generated.
[0105]
Further, the focus error signal Sfe and the RF signal Srf can be generated by the signal processing unit 11 that generates the spherical error signal Ske indicating the spherical aberration.
[0106]
Furthermore, since the shape of the region formed by the partial detectors 7e to 7h is rectangular, the detector 7 can be easily formed.
[0107]
Further, the spherical aberration occurring in the reflected light due to the characteristics of the protective layer 1a can be accurately compensated for, and the information on the optical disc 1 can be accurately reproduced.
[0108]
The spherical error signal Ske described above includes the inclination of the information recording surface of the optical disc 1 with respect to the optical axis of the light beam B, the intensity of the light beam B in the aperture on the pupil plane of the objective lens 2, and the information recording surface of the objective lens 2. Has been experimentally confirmed to be unaffected by the deviation in the direction parallel to the direction, but if there is a deviation between the position of the optical axis of the light beam B and the center position of the detector 7, It has been experimentally confirmed that the level of the entire spherical error signal Ske decreases and the zero-cross point also shifts.
[0109]
(III)Deformation form
Next, a modified embodiment of the present invention will be described with reference to FIGS.
[0110]
In FIG. 9, the same components as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0111]
First, as for the divided shape of the detector 7, as shown as a detector 7 'in FIG. 8A, the shape of a region formed by the partial detectors 7e' to 7h 'may be circular.
[0112]
Even in this case, the area including the partial detectors 7e 'to 7h' has a width corresponding to a change in the illuminance intensity distribution on the detector 7 of the reflected light of the light beam B due to the change in the thickness t of the protective layer 1a ( That is, the width is set to include a portion where the irradiation intensity is high at the center of the irradiation range.
[0113]
In this case as well, the same effect as that of the above-described embodiment can be obtained. In addition, since the shape of the region including the partial detectors 7e 'to 7h' is circular, the beam shape of the light beam B and the irradiation intensity distribution thereof are different. Correspondingly, the amount and polarity of the spherical aberration can be detected more accurately.
[0114]
Further, as for the divided shape of the detector 7, as shown as a detector 7 "in FIG. 8B, the shape of a region formed by the partial detectors 7e" to 7h "may be an octagon.
[0115]
Also in this case, as in the case of FIG. 8A, the region including the partial detectors 7e ″ to 7h ″ has the thickness t of the protective layer 1a of the illuminance intensity distribution on the detector 7 of the reflected light of the light beam B. The width is set to correspond to the change caused by the change.
[0116]
In this case, an effect similar to that of the above-described embodiment can be obtained, and since the shape of the region including the partial detectors 7e ″ to 7h ″ is octagonal, the beam shape of the light beam B and its irradiation intensity distribution , The amount and polarity of spherical aberration can be detected more accurately, and the detector 7 ″ can be easily formed.
[0117]
Although the above-described embodiment and each of the modifications have been described with reference to the embodiment or the modification in which the present invention is applied to the information reproducing apparatus S, the present invention is also applicable to a case in which the present invention is recorded on the optical disc 1 in advance. The present invention can also be applied to an information recording device for detecting recording control information such as address information and recording information on the optical disc 1 based on the detected recording control information.
[0118]
That is, as shown in FIG. 9, in addition to the optical system S shown in FIG. 1, the signal processing unit 11, the reproducing unit 12, the amplifiers 13 and 15, the drivers 14 and 16, the liquid crystal panel 9, and the actuator 10 shown in FIG. The CPU 41 as recording means for performing recording control based on a reproduction signal Spu output from the reproduction unit 12 (this reproduction signal Spu includes the above-described recording control information), and a control from the CPU 41. A recording means for modulating a recording signal Sr to be recorded input from the outside based on the signal Sc and generating a modulation signal Srr for setting the output value of the laser diode 8 to a value corresponding to the recording signal Sr. The present invention can also be applied to an information recording device R including the encoder 40.
[0119]
In this case, the output value of the laser diode 8 (that is, the intensity of the light beam B) is intensity-modulated based on the modulation signal Srr, and the intensity-modulated light beam B of the optical disc 1 included in the recording control information is recorded. By irradiating a position corresponding to the address information, an information pit having a shape corresponding to the modulation signal Srr is formed at the irradiation position, and the recording signal Sr is recorded on the optical disc 1.
[0120]
According to the operation of the information recording device R, the light receiving signal Sp including the recording control information is accurately reproduced by accurately compensating for the spherical aberration, so that the information to be recorded accurately is recorded on the optical disc 1. be able to.
[0121]
Further, in the above-described embodiment and each modified example, the case where the liquid crystal panel 9 is used as a method of compensating for the spherical aberration has been described. In addition, for example, the objective lens may be configured using two independent lenses. A method of compensating for the spherical aberration generated by controlling the gap between the two lenses, or compensating for the spherical aberration by moving the collimator lens 3 in a direction parallel to the optical axis of the light beam B. By applying closed-loop servo control using the spherical error signal Ske obtained by the present invention to the method, spherical aberration can be quickly and reliably compensated.
[0122]
In addition, in the above-described embodiments and modified examples, the case where the spherical aberration generated due to the change in the thickness t of the protective layer 1a is detected and compensated is described. When the spherical aberration generated due to the variation of the refractive index (variation in one optical disc 1 or variation between a plurality of optical discs 1) is detected and compensated, when the refractive index varies, The irradiation intensity distribution of the reflected light of the light beam B on the detector 7 in the above also changes according to the amount and polarity of the variation in accordance with the case shown in FIG. Can be detected and compensated for.
[0123]
【The invention's effect】
As described above, according to the first aspect of the present invention, since a spherical error signal indicating a spherical aberration and having a polarity is generated, the amount and the polarity of the spherical aberration generated in the reflected light are determined.,This can be accurately and immediately grasped and compensated.
[0124]
Therefore, even if the spherical aberration generated in the reflected light changes due to a change in the characteristics of the protective layer, the amount and polarity of the spherical aberration can be accurately and immediately grasped and compensated for, and the recording medium can be accurately corrected. Record and play back informationWill be possible.
[0125]
Also,Since the reflected light with astigmatism is received to generate a spherical error signal, the amount and polarity of the spherical aberration generated in the reflected light can be accurately and immediately grasped and compensated.
[0126]
Also,Since the first sub-light receiving means has a width corresponding to the change of the illuminance intensity distribution on the light receiving means of the reflected light due to the characteristics of the protective layer, each of the light receiving signals output from each of the sub-light receiving means is protected. It changes in response to the change in spherical aberration associated with the change in the characteristics of the layer, and the amount and polarity of the spherical aberration contained in the reflected light can be accurately detected based on the respective light receiving signals.
[0127]
Also,Each of the first sub-light receiving unit and the second sub-light receiving unit is divided into a plurality of first partial light receiving units and a plurality of second partial light receiving units by dividing lines having a shape corresponding to the irradiation intensity distribution. Each of the light receiving signals output from the light receiving means changes according to the change of the spherical aberration accompanying the change of the characteristic of the protective layer, and the spherical aberration included in the reflected light based on each of the light receiving signals. And the polarity can be accurately detected.
[0128]
further,The sum signal of the light receiving signal output from each of the first distribution direction light receiving means and the light receiving signal output from each of the second distribution direction light receiving means, and the first partial light receiving means other than the first distribution direction light receiving means Of the light receiving signals respectively output from the plurality of first partial light receiving means and the plurality of light receiving signals output from the plurality of second partial light receiving means other than the second distribution direction light receiving means among the second partial light receiving means. Since the difference signal from the signal is output as a spherical error signal, it is possible to generate a spherical error signal that accurately indicates the amount and polarity of the spherical aberration generated in the reflected light.
[0129]
Claim2According to the invention described in (1), the claims1In addition to the effects of the invention described in the above, since the astigmatism generating means can be used for both generation of the spherical error signal and generation of the focus error signal, the optical pickup itself can be reduced in size while the spherical error signal and the focus error signal are generated. Can be generated.
[0130]
Claim3According to the invention described in (1), the claims2In addition to the effects of the invention described in the above, the light receiving signal output from each of the first distribution direction light receiving means and the plurality of second partial light receiving means other than the second distribution direction light receiving means among the respective second partial light receiving means are respectively provided. The sum signal of the output light receiving signal and the light receiving signal output from each of the plurality of first partial light receiving means other than the first distribution direction light receiving means among the first partial light receiving means and the second distribution direction light receiving means Since a difference signal between the output signal and the sum signal is output as a focus error signal, the focus error signal can also be generated by the light receiving unit that generates the spherical error signal.
[0131]
Claim4According to the invention described in (1), the claims1 to 3In addition to the effect of the invention described in any one of the above, in addition to the sum signal of the light receiving signal output from each of the first partial light receiving means and the sum signal of the light receiving signal output from each of the second partial light receiving means Since the sum signal is further output as a detection signal, a detection signal corresponding to the information recorded by the light receiving unit that generates the spherical error signal can also be generated.
[0132]
Claim5According to the invention described in (1), the claims1 to Claim 4In addition to the effect of the invention described in any one of the above, since the shape of the first sub-light receiving means is circular, the amount of spherical aberration and the amount of spherical aberration more accurately corresponding to the beam shape of the light beam and its irradiation intensity distribution Polarity can be detected.
[0133]
Claim6According to the invention described in (1), the claims1 to Claim 4In addition to the effect of the invention described in any one of the above, since the shape of the first sub-light receiving unit is rectangular, the first sub-light receiving unit and the second sub-light receiving unit can be easily formed.
[0134]
Claim7According to the invention described in (1), the claims1 to Claim 4In addition to the effect of the invention described in any one of the above, since the shape of the first sub-light receiving means is an octagon, the spherical aberration is accurately detected in accordance with the beam shape of the light beam and its irradiation intensity distribution. In addition to this, the first sub-light receiving unit and the second sub-light receiving unit can be easily formed.
[0135]
Claim8According to the invention described in (1), the claims4In addition to the effects of the invention described in (1), information can be accurately reproduced by accurately compensating for the spherical aberration generated in the reflected light due to the characteristics of the protective layer.
[0136]
Claim9According to the invention described in (1), the claims4In addition to the effects of the invention described in (1), information can be accurately recorded by accurately compensating for the spherical aberration occurring in the reflected light due to the characteristics of the protective layer.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an optical system illustrating the principle of the present invention.
FIGS. 2A and 2B are diagrams for explaining the principle of the present invention, wherein FIG. 2A is a schematic diagram showing an irradiation intensity distribution of a light beam on a detector when a protective layer has a thickness of 0.7 mm, and FIG. FIG. 4 is a schematic diagram showing an irradiation intensity distribution of a light beam on a detector when the thickness of the protective layer is 0.65 mm, and FIG. 4C is a schematic diagram showing a light beam on the detector when the thickness of the protective layer is 0.6 mm. FIG. 3D is a schematic diagram showing an irradiation intensity distribution of (a), (d) is a schematic diagram showing an irradiation intensity distribution of a light beam on a detector when the thickness of the protective layer is 0.55 mm, and (e) is a schematic diagram of the protective layer. It is a schematic diagram which shows the irradiation intensity distribution of a light beam on a detector when thickness is 0.5 mm.
FIG. 3 is a plan view showing an example of a divided shape of a detector.
FIG. 4 is a block diagram illustrating a schematic configuration of the information reproducing apparatus according to the embodiment.
FIG. 5 is a plan view illustrating a shape of a detector according to the embodiment.
FIG. 6 is a block diagram illustrating a detailed configuration of a signal processing unit.
FIG. 7 is a diagram illustrating a waveform example of a spherical error signal indicating a spherical aberration.
FIG. 8 is a plan view showing a modified form of the divided shape of the detector, wherein (a) is a plan view showing a first modified form, and (b) is a plan view showing a second modified form.
FIG. 9 is a block diagram illustrating a schematic configuration of an information recording apparatus according to a modified embodiment.
[Explanation of symbols]
1: Optical disk
1a: protective layer
1b Information recording surface
2. Objective lens
3. Collimator lens
4: Deflection beam splitter
5. Condensing lens
6. Cylindrical lens
7, 7 ', 7 "... detector
7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h, 7a ', 7b', 7c ', 7d', 7e ', 7f', 7g ', 7h', 7a ", 7b", 7c ", 7d ", 7e", 7f ", 7g", 7h "... Partial detector
8 ... Laser diode
9 ... LCD panel
10. Actuator
11 ... Signal processing unit
12 ... Reproduction unit
13, 15… Amplifier
14, 16 ... driver
20, 21, 22, 23, 24, 25, 26, 27, 28 ... adders
29, 30 ... subtractor
40 ... Encoder
41 ... CPU
45 ... λ / 4 plate
Sdf, Sdk ... drive signal
Saf, Sak ... Amplification error signal
Sp: light receiving signal
Sfe: Focus error signal
Ske: spherical error signal
Srf RF signal
Spu: playback signal
Sc: control signal
Sr: recording signal
Srr: modulated signal
S: Optical system
R: Information recording device
P ... information reproducing device
PU… Optical pickup

Claims (9)

In an optical pickup that irradiates the light beam by transmitting the protective layer to a recording medium having at least a protective layer transparent to a light beam,
Emitting means for emitting the light beam;
Astigmatism generating means for generating astigmatism in reflected light of the light beam from the recording medium, receiving the reflected light having the astigmatism, and receiving light to generate a light receiving signal; and Generating means having an error signal generating means for generating a spherical error signal having a polarity and showing a spherical aberration occurring in the reflected light due to the characteristics of the protective layer based on the
Compensation means for compensating the spherical aberration based on the generated spherical error signal,
With
The light receiving means is divided into a first sub light receiving means occupying a central part of the light receiving means and a second sub light receiving means occupying a peripheral part of the first sub light receiving means. The irradiation intensity distribution of the reflected light having the astigmatism on the light receiving unit has a width corresponding to a change caused by the characteristic of the protective layer, and passes through the center of the first sub light receiving unit. The plurality of first partial light receiving units are divided by a plurality of dividing lines having directions corresponding to the irradiation intensity distribution, and the second sub-light receiving unit is divided into a plurality of second partial light receiving units by each of the dividing lines. Has been
The error signal generating unit includes a first distribution direction light receiving unit that is a plurality of the first partial light receiving units that opposes an irradiation intensity distribution direction that is a direction corresponding to the irradiation intensity distribution among the first partial light receiving units. The light receiving signals respectively output and the second distribution direction light receiving means, which are a plurality of the second partial light receiving means, of the second partial light receiving means, which are opposed to each other in a direction perpendicular to the irradiation intensity distribution direction, are respectively output. A sum signal with the light receiving signal, the light receiving signal output from each of the plurality of first partial light receiving means other than the first distribution direction light receiving means among the first partial light receiving means, and the second partial light receiving means A difference signal between a sum signal of the plurality of light receiving signals output from the plurality of second partial light receiving means other than the second distribution direction light receiving means among the means is output as the spherical error signal. The optical pick-up to be. The optical pickup according to claim 1,
The optical pickup, wherein the error signal generating means further outputs a focus error signal based on an astigmatism method based on the light receiving signal. The optical pickup according to claim 2,
The error signal generation means includes a plurality of the second partial light receiving means other than the second distribution direction light receiving means among the light receiving signals respectively output from the first distribution direction light receiving means and the second partial light receiving means. And the sum signal of the light receiving signals respectively output from the plurality of first partial light receiving means other than the first distribution direction light receiving means among the first partial light receiving means. An optical pickup, wherein a difference signal between a sum signal of the light receiving signal and a sum signal output from the second distribution direction light receiving means is output as the focus error signal. The optical pickup according to any one of claims 1 to 3,
Information to be reproduced is recorded on the recording medium,
The error signal generating means, a sum signal of the sum signal of the light receiving signal output from each of the first partial light receiving means and the sum signal of the light receiving signal output from each of the second partial light receiving means, An optical pickup further outputting a detection signal corresponding to the information. The optical pickup according to any one of claims 1 to 4,
An optical pickup characterized in that the shape of the first sub-light receiving means is circular. The optical pickup according to any one of claims 1 to 4,
An optical pickup characterized in that the shape of the first sub-light receiving means is rectangular. The optical pickup according to any one of claims 1 to 4,
An optical pickup characterized in that the shape of the first sub-light receiving means is an octagon. An optical pickup according to claim 4,
Focus servo means for controlling a focus position of the light beam based on the focus error signal,
Reproducing means for reproducing the information based on the detection signal;
An information reproducing apparatus comprising: An optical pickup according to claim 4,
Focus servo means for controlling a focus position of the light beam based on the focus error signal,
Reproducing means for reproducing the information based on the detection signal and outputting a reproduced signal;
Recording means for controlling the light beam based on the output reproduction signal and recording information to be recorded on the recording medium, and recording the recording information on the information recording surface;
An information recording device comprising:

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