JP3658508B2 - Tracking error signal offset correction apparatus and optical disc apparatus - Google Patents

Description

【００４３】
このことより、点（ｐ１，Ａ）、（ｐ２，Ｃ）を通る直線ＴＯ（ｘ）は、次の（数２）と表される。
【００４４】
【数２】

【００４５】
また、点（ｐ１，Ｂ）、（ｐ２，Ｄ）を通る直線ＬＥ（ｘ）は、次の（数３）と表される。
【００４６】
【数３】

【００４７】
（数３）は、次の（数４）に変形でき、
【００４８】
【数４】

【００４９】
（数４）を（数２）に代入すると、次の（数５）となり、ＴＯ（ｘ）とＬＥ（ｘ）との相関式が求まる。
【００５０】
【数５】

【００５１】
このことから、ＬＥ（ｘ）および定数Ａ、Ｂ、Ｃ、Ｄを測定し、（数５）を用いてＴＥ信号の直流オフセットであるＴＯ（ｘ）を求め、ＴＥ信号からＴＯ（ｘ）を減算することで、直流オフセット分を０に補正することができる。
【００５２】
次に、以上に述べたＴＥ信号の直流オフセットの補正を可能にする光ディスク装置について説明する。
【００５３】
図１は、本発明の第１実施形態に係る、光ディスクを再生または記録するための光ディスク装置のブロック図である。
図１において、１は光ディスク、２は対物レンズ、３は光ピックアップ、４は信号処理回路、５はフォーカスサーボ制御回路、６はフォーカス駆動回路、７はトラッキングサーボ制御回路、８は切換えスイッチ、９はトラッキング駆動回路、１０は制御回路、１１はスレッドサーボ制御回路、１２はスレッド駆動回路、１３はスレッドモータ、１４は光ピックアップ送り機構、１５はスピンドルモータ、１６はスピンドルサーボ制御回路、１７はスピンドル駆動回路、１８、１９は一定電圧出力回路、２０は切換えスイッチ、２１は振幅中心測定回路、２２〜２５は保持回路、２６は係数演算回路、２７、２９、３０は加算回路、２８は乗算回路である。
【００５４】
以下、本実施形態の光ディスク装置の動作概要について説明する。
光ディスク１には、記録層の凸凹、または反射率の差異などにより情報がディジタル的に記録されており、対物レンズ２は、レーザー光線を集光して光ディスク１の記録層に焦点を合わせる。光ピックアップ３は、対物レンズ２をレーザーの光軸方向へ駆動するフォーカスアクチュエータ、並びに、対物レンズ２をディスクの半径方向へ駆動するトラッキングアクチュエータを備えている。ここで、本実施形態においては、光ピックアップ３は、先に図２を用いて説明したプッシュプル法によるＴＥ信号を得るために必要な光検出器を備え、光ディスク１からの反射光を電気信号に変えて信号処理回路４に供給する。また、光ピックアップ３は、先に図４を用いて説明したＬＥ信号を得るために必要な光検出器を備え、ＬＥ信号を得るための信号を信号処理回路４へ供給する。
【００５５】
信号処理回路４は、光ピックアップ３からの出力信号を処理して、フォーカスのずれに対応するフォーカスエラー信号、トラッキングのずれに対応するＴＥ信号、スピンドルの回転状態を示すスピンドル信号、および、光ピックアップ３に対する対物レンズ２のディスク半径方向の位置ずれに対応するＬＥ信号を、それぞれ出力する。
【００５６】
フォーカスサーボ制御回路５は、信号処理回路４から供給されるフォーカスエラー信号を受けて、フォーカスサーボの安定性と追従性能を改善するために必要なゲインや位相の補償を行った信号を出力する。フォーカス駆動回路６は、フォーカスサーボ制御回路５の出力信号を受けてその信号を増幅し、光ピックアップ３内のフォーカスアクチュエータを駆動する信号を出力して、対物レンズ２のレーザーの光軸方向の位置を変化させる。
【００５７】
トラッキングサーボ制御回路７は、信号処理回路４から供給されるＴＥ信号から加算回路２９の出力信号を減算する加算回路３０の出力信号を受け、トラッキングサーボの安定性と追従性能を改善するために必要なゲインや位相の補償を行った信号（以下、トラッキング駆動信号と呼ぶ）を、切換えスイッチ８のａ側およびスレッドサーボ制御回路１１に供給する。
【００５８】
切換えスイッチ８は、制御回路１０から供給される切換えスイッチ８を制御する信号（以下、ＯＰＥＮ２信号と呼ぶ）がＬｏｗの場合、ａ側に切換わってトラッキングサーボループを閉じ、トラッキングサーボ制御回路７から供給されるトラッキング駆動信号を出力する。また、ＯＰＥＮ２信号がＨｉｇｈの場合は、ｂ側に切換わってトラッキングサーボループを開き、スイッチ２０から供給される信号を出力する。
【００５９】
トラッキング駆動回路９は、切換えスイッチ８から供給される信号を増幅して、光ピックアップ３内のトラッキングアクチュエータを駆動する信号を出力し、対物レンズ２のディスク半径方向の位置を変化させる。
【００６０】
制御回路１０は、切換えスイッチ８および切換えスイッチ２０を切換えたり、振幅中心測定回路２１、保持回路２２〜２５を制御する信号を出力する。
【００６１】
スレッドサーボ制御回路１１は、トラッキングサーボ制御回路７から供給されるトラッキング駆動信号を受け、スレッドサーボの追従性能を改善するためにゲインの補償を行った信号を出力する。なお、スレッドサーボ制御回路１１は、光ピックアップ３内のトラッキングアクチュエータによって移動した対物レンズ２が移動限界を超えないように、光ピックアップ３の位置を制御する。
【００６２】
スレッドモータ駆動回路１２は、スレッドサーボ制御回路１１の出力信号を増幅してスレッドモータ１３に供給し、スレッドモータ１３は、スレッドモータ駆動回路１２から供給される信号により、光ピックアップ送り機構１４を駆動する。そして、光ピックアップ送り機構１４は、光ピックアップ３を光ディスク１の内周方向、または外周方向へ移動させる。
【００６３】
スピンドルサーボ制御回路１６は、信号処理回路４から供給されるスピンドル信号を受けて、スピンドルモータ１５を所定の回転速度で回転させるための制御を行う。スピンドルモータ駆動回路１７は、スピンドルサーボ制御回路１６の出力信号を増幅してスピンドルモータ１５を回転させ、これにより、光ディスク１を回転させる。
【００６４】
一定電圧出力回路１８は、対物レンズ２を光ピックアップ３に対してディスク半径方向の任意の位置ｐ１に位置させる一定電圧を、切換えスイッチ２０のａ側に供給する。また、一定電圧出力回路１９は、対物レンズ２を光ピックアップ３に対してディスク半径方向の任意の場所ｐ２に位置させる一定電圧を、切換えスイッチ２０のｂ側に供給する。なお、一定電圧出力回路１８、１９の出力する電圧は異なるものとする。このため、任意の位置ｐ１とｐ２とは、異なる位置となる。
【００６５】
切換えスイッチ２０は、制御回路１０から供給される切換えスイッチ２０を制御する信号（以下、ＯＰＥＮ１信号と呼ぶ）がＬｏｗの場合、ａ側に切換わって、一定電圧出力回路１８から供給される信号を出力する。また、ＯＰＥＮ１信号がＨｉｇｈの場合は、ｂ側に切換わって、一定電圧出力回路１９から供給される信号を出力する。なお、切換えスイッチ２０の出力信号は、切換えスイッチ８のｂ側へ供給される。
【００６６】
振幅中心測定回路２１は、制御回路１０から供給される振幅中心測定回路２１を制御する信号（以下、ＳＴＲＴ信号と呼ぶ）が変化した後に、信号処理回路４から供給されるＴＥ信号の振幅中心を測定して、測定値を保持回路２４、２５に供給する。ＴＥ信号の振幅中心を測定する方法としては、ＴＥ信号の最大値と最小値を検出して加算し、その平均を求める方法を用いることができる。また、ＴＥ信号をローパスフィルタに通して、高域信号を除去することで、直流成分である振幅中心を得る方法等も用いることができる。なお本実施形態では、ＳＴＲＴ信号がＨｉｇｈとなってから、検出した最大値、最小値をクリアして振幅中心を測定するものとする。
【００６７】
保持回路２２は、制御回路１０から供給される保持回路２２および保持回路２４を制御する信号（以下、ＨＬＤ１信号と呼ぶ）が変化するタイミングで、信号処理回路４から供給されるＬＥ信号を保持して、加算回路２７および係数演算回路２６に供給する。なお本実施形態では、ＨＬＤ１信号がＨｉｇｈとなるタイミングでＬＥ信号を保持するものとする。
【００６８】
保持回路２３は、制御回路１０から供給される保持回路２３および保持回路２５を制御する信号（以下、ＨＬＤ２信号と呼ぶ）が変化するタイミングで、信号処理回路４から供給されるＬＥ信号を保持して、係数演算回路２６に供給する。なお本実施形態では、ＨＬＤ２信号がＨｉｇｈとなるタイミングでＬＥ信号を保持するものとする。
【００６９】
保持回路２４は、ＨＬＤ１信号がＨｉｇｈとなるタイミングで振幅中心測定回路２１から供給される振幅中心を保持して、係数演算回路２６および加算回路２９に供給する。
【００７０】
保持回路２５は、ＨＬＤ２信号がＨｉｇｈとなるタイミングで振幅中心測定回路２１から供給される振幅中心を保持して、係数演算回路２６に供給する。
【００７１】
係数演算回路２６は、保持回路２５の出力信号から保持回路２４の出力信号を減算した第１の減算信号を求める。また、保持回路２３の出力信号から保持回路２２の出力信号を減算した第２の減算信号を求める。そして、係数演算回路２６は、第１の減算信号を第２の減算信号で除した演算信号を、乗算回路２８に供給する。
【００７２】
加算回路２７は、信号処理回路４から供給されるＬＥ信号と、保持回路２２から供給される信号の極性を反転した信号とを加算して、乗算回路２８に供給する。なお、極性の反転については、保持回路２２で行ってもよいことはいうまでもない。
【００７３】
乗算回路２８は、加算回路２７の出力信号と、係数演算回路２６の出力信号を乗算して、加算回路２９に供給する。
【００７４】
加算回路２９は、乗算回路２８の出力信号と、保持回路２４の出力信号とを加算して、加算回路３０に供給する。
【００７５】
加算回路３０は、信号処理回路４から供給されるＴＥ信号と、加算回路２９の出力信号を極性反転した信号とを加算して、トラッキングサーボ制御回路７に供給する。なお、極性の反転については、加算回路２９で行ってもよいことはいうまでもない。
【００７６】
次に、上述の構成に基づき、本実施形態の信号例である図８を用いて、ＴＥ信号の直流オフセットの補正方法について説明する。
【００７７】
光ディスク１を装着した後に、フォーカスサーボ制御回路５は、信号処理回路４から供給されるフォーカスエラー信号を用いて、レーザー光の焦点が光ディスク１の記録面に合うように、レーザー光の光軸方向における対物レンズ２の位置を制御する。また、スピンドルサーボ制御回路１６は、所定の回転速度で光ディスク１を回転させる。制御回路１０は、ＯＰＥＮ１信号にＬｏｗを、ＯＰＥＮ２信号にＨｉｇｈを、ＳＴＲＴ信号にＬｏｗを、ＨＬＤ１信号にＬｏｗを、ＨＬＤ２信号にＬｏｗを、それぞれ出力している。このとき、切換えスイッチ８はｂ側に切換わっており、切換えスイッチ２０はａ側に切換わっている。そのため、一定電圧出力回路１８の出力信号が、切換えスイッチ２０、切換えスイッチ８、およびトラッキング駆動回路９を介して、光ピックアップ３内のトラッキングアクチュエータに印加されるので、対物レンズ２は、光ピックアップ３に対してディスク半径方向における任意の位置ｐ１に位置する。この位置が、図７における位置ｐ１である。
【００７８】
上記の状態から、制御回路１０は、ＳＴＲＴ信号にＨｉｇｈを出力して、振幅中心測定回路２１にＴＥ信号の振幅中心の測定を開始させた後、ＨＬＤ１信号にＨｉｇｈを出力する。このとき、保持回路２２は、信号処理回路４から供給されるＬＥ信号を保持する。また、回転している光ディスク１には偏心があるので、信号処理回路４から出力されるＴＥ信号は振幅を持った信号となる。上記の制御回路１０からの信号により、振幅中心測定回路２１はＴＥ信号の振幅中心を測定して出力し、保持回路２４は振幅中心測定回路２１の出力信号を保持する。ここで、対物レンズ２の位置はｐ１であるので、保持回路２４は図７における直流オフセットＡを保持する。また、保持回路２２は図７におけるＬＥ信号Ｂを保持する。なお本実施形態では、ＨＬＤ１信号にＨｉｇｈを出力した後、再びＬｏｗを出力しているが、Ｈｉｇｈのままでも以降の動作に影響はない。
【００７９】
制御回路１０は、ＨＬＤ１信号にＨｉｇｈを出力した後、ＯＰＥＮ１信号にＨｉｇｈを出力して、切換えスイッチ２０をｂ側に切換える。このため、一定電圧出力回路１９の出力信号が、切換えスイッチ２０、切換えスイッチ８、およびトラッキング駆動回路９を介して、光ピックアップ３内のトラッキングアクチュエータに印加される。このとき、一定電圧出力回路１９は、対物レンズ２を任意の位置ｐ２に位置させる一定電圧を出力するので、対物レンズ２のディスク半径方向の位置はｐ２となる。この位置が、図７における位置ｐ２である。
【００８０】
制御回路１０は、ＯＰＥＮ１信号にＨｉｇｈを出力した後、ＳＴＲＴ信号にＨｉｇｈを再び出力して、振幅中心測定回路２１によってＴＥ信号の振幅中心の測定を開始させた後に、ＨＬＤ２信号にＨｉｇｈを出力する。このとき、対物レンズ２の位置は図７におけるｐ２であるので、保持回路２５は図７における直流オフセットＣを保持する。また、保持回路２３は図７におけるＬＥ信号Ｄを保持する。なお本実施形態では、ＨＬＤ２信号にＨｉｇｈを出力した後、再びＬｏｗを出力しているが、Ｈｉｇｈのままでも以降の動作に影響はない。
【００８１】
そして、係数演算回路２６は、保持回路２２、２３、２４、２５から供給される信号を用いて係数を演算し、演算結果を乗算回路２８に供給する。
【００８２】
以上に説明した動作が、直流オフセット補正の準備である。
【００８３】
次に、制御回路１０は、直流オフセット補正の準備を行った後、ＯＰＥＮ２信号にＬｏｗを出力し、切換えスイッチ８をａ側に切換えてトラッキングサーボループを閉じる。ここで、信号処理回路４から出力されるＬＥ信号は、対物レンズ２の位置が変化するに従って変化するため、（数５）におけるＬＥ（ｘ）を出力する。このとき、保持回路２２は図７におけるＬＥ信号Ｂを保持しているので、加算回路２７は（数５）における、次の（数６）の値を出力する。
【００８４】
【数６】

【００８５】
また、係数演算回路２６は（数５）における、次の（数７）の値を出力する。
【００８６】
【数７】

【００８７】
また、乗算回路２８は（数５）における、次の（数８）の値を出力する。
【００８８】
【数８】

【００８９】
保持回路２４は図７における直流オフセットＡを保持しているので、加算回路２９は、（数５）におけるＴＯ(ｘ)、つまり、ＴＥ信号の直流オフセットを出力する。
【００９０】
そして、加算回路３０は、信号処理回路４から供給されるＴＥ信号から、加算回路２９の出力、つまりＴＥ信号の直流オフセットを減算することで、トラッキングサーボ制御回路７に供給されるＴＥ信号の直流オフセットを０に補正する。
【００９１】
以上に説明した本実施形態においては、光ピックアップ３に対する対物レンズ２のディスク半径方向への位置を示すＬＥ信号からＴＥ信号の直流オフセットを求めるために光ディスク１を回転させて、ＴＥ信号の直流オフセットとＬＥ信号との相関式を求める。そして、ＬＥ信号と（数５）で示した相関式を用いて算出した直流オフセットを、ＴＥ信号から減算することにより、ＴＥ信号の直流オフセット補正が可能となる。
【００９２】
なお本実施形態では、一定電圧出力回路１８が、対物レンズ２を光ピックアップ３に対してディスク半径方向の中点に位置させる電圧を出力するようにしてもよい。何となれば、本来、ディスク再生前には、対物レンズ２は、光ピックアップ３に対してディスク半径方向の中点に位置している。そのため、このようになすと、対物レンズ２が図７の位置ｐ１に移動する時間が不必要となり、短時間で図７の直流オフセットＡとＬＥ信号Ｂを測定することができる。
【００９３】
次に、本発明の第２実施形態に係る光ディスク装置を、図９のブロック図を用いて説明する。
【００９４】
本実施形態の構成が先の第１実施形態の構成と異なるのは、保持回路２２、２４、係数演算回路２６、および加算回路２９を含まない点と、一定電圧出力回路３１、３３、加算回路３２、および除算回路３４を含む点である。また、加算回路３０には、乗算回路２８の出力と加算回路３２の出力とが供給され、制御回路１０はＨＬＤ１信号を出力しない。
【００９５】
一定電圧出力回路３１は、対物レンズ２が光ピックアップ３に対してディスク半径方向の中点位置にあるときに、加算回路３２の出力が０レベルとなる一定電圧を加算回路３２に供給する。
【００９６】
加算回路３２は、信号処理回路４が出力するＴＥ信号と一定電圧出力回路３１の出力とを加算した信号を、加算回路３０と振幅中心測定回路２１に供給する。
【００９７】
一定電圧出力回路３３は、対物レンズ２が光ピックアップ３に対してディスク半径方向の中点位置にあるときに、加算回路２７の出力が０レベルとなる一定電圧を加算回路２７に供給する。
【００９８】
加算回路２７は、信号処理回路４から得られるＬＥ信号と一定電圧出力回路３３の出力とを加算した信号を、保持回路２３と乗算回路２８に供給する。
【００９９】
除算回路３４は、保持回路２５の出力を保持回路２３の出力で除算した出力を、乗算回路２８に供給する。
【０１００】
振幅中心測定回路２１は、ＳＴＲＴ信号が変化した後に、加算回路３２の出力信号の振幅中心を測定して、測定値を保持回路２５に供給する。
【０１０１】
また、一定電圧出力回路１８は、対物レンズ２が光ピックアップ３に対してディスク半径方向の中点に位置する一定電圧を、切換えスイッチ２０のａ側に供給する。
【０１０２】
このような本実施形態の構成において、対物レンズ２の位置が中点のときは、ＴＥ信号のオフセットは一定電圧出力回路３１と加算回路３２によって０レベルに補正されるので、ＴＥ信号の直流オフセットも０レベルとなる。また、ＬＥ信号のオフセットも、一定電圧出力回路３３と加算回路２７によって０レベルに補正される。
【０１０３】
図７と同様に、補正後の直流オフセットと補正後のＬＥ信号を図１０に示す。図１０において、対物レンズ位置が中点（０レベル）のときの、補正後の直流オフセットＡと補正後のＬＥ信号Ｂは、ともに０レベルである。また、対物レンズ位置が任意の位置ｐ２のときの、補正後の直流オフセットはＣ、補正後のＬＥ信号はＤである。ここで、補正後の直流オフセットをＴＯ２（ｘ）、補正後のＬＥ信号をＬＥ２（ｘ）で近似とすると、点（０，０）、（ｐ２，Ｃ）を通る直線ＴＯ２（ｘ）は、次の（数９）と表される。
【０１０４】
【数９】

【０１０５】
また、点（０，０）、（ｐ２，Ｄ）を通る直線ＬＥ２（ｘ）は、次の（数１０）と表される。
【０１０６】
【数１０】

【０１０７】
（数１０）は、次の（数１１）に変形でき、
【０１０８】
【数１１】

【０１０９】
（数１１）を（数９）に代入すると、次の（数１２）となり、ＴＯ２（ｘ）とＬＥ２（ｘ）との相関式が求まる。
【０１１０】
【数１２】

【０１１１】
図１１に、本実施形態の制御回路１０の出力信号波形を示す。
光ディスク１を装着してフォーカス制御が定常的に動作しており、光ディスク１が回転している状態で、制御回路１０は、ＯＰＥＮ１信号、ＳＴＲＴ信号、ＨＬＤ２信号にそれぞれＬｏｗを出力し、ＯＰＥＮ２信号にＨｉｇｈを出力している。このため、一定電圧出力回路１８の出力が、切換えスイッチ２０、切換えスイッチ８、およびトラッキング駆動回路９を介して、光ピックアップ３内のトラッキングアクチュエータに印加され、対物レンズ２は光ピックアップ３に対して、ディスク半径方向の中点に位置する。
【０１１２】
ここで、制御回路１０は、ＯＰＥＮ１信号にＨｉｇｈを出力して切換えスイッチ２０をｂ側に切換えて、一定電圧出力回路１９の出力を光ピックアップ３内のトラッキングアクチュエータに印加する。一定電圧出力回路１９は、対物レンズ２を光ピックアップ３に対してディスク半径方向の所定の位置ｐ２に移動させるため、対物レンズ２は位置ｐ２に移動する。この位置ｐ２が、図１０の位置ｐ２である。
【０１１３】
対物レンズ２が位置ｐ２に移動するのに十分な時間が経過した後、制御回路１０はＳＴＲＴ信号にＨｉｇｈを出力して、振幅中心測定回路２１にＴＥ信号の振幅中心の測定を開始させる。ＳＴＲＴ信号にＨｉｇｈを出力した後、制御回路１０はＨＬＤ２信号にＨｉｇｈを出力して、保持回路２３に加算回路２７の出力を、保持回路２５に振幅中心測定回路２１の出力を、それぞれ保持させる。このとき、対物レンズ２は図１０における位置ｐ２にあるため、保持回路２５は、図１０の補正後の直流オフセットＣを保持する。また、保持回路２３は、図１０の補正後のＬＥ信号Ｄを保持する。
【０１１４】
その後、制御回路１０は、ＯＰＥＮ２信号にＬｏｗを出力して切換えスイッチ８をａ側に切換えて、トラッキングサーボループを閉じる。
【０１１５】
ここで、保持回路２５は図１０におけるＣを、保持回路２３は図１０におけるＤを保持しており、除算回路３４はＣをＤで除した信号を出力する。このため、乗算回路２８は、（数１２）と等価である信号を出力する。そして、加算回路３０は、加算回路３２が出力する補正後のＴＥ信号から、乗算回路２８が出力する（数１２）と等価な信号を減算することで、ＴＥ信号の直流オフセットを０に補正する。
【０１１６】
本実施形態では、ディスク再生前には、対物レンズ２は光ピックアップ３に対してディスク半径方向の中点に位置している。そのため、対物レンズ２が図１０の位置ｐ１に移動する時間が不必要であり、短時間で図１０の補正後の直流オフセットＡと補正後のＬＥ信号Ｂを測定することができる。
【０１１７】
以上に説明した本実施形態においては、光ピックアップ３に対する対物レンズ２のディスク半径方向への位置を示すＬＥ信号からＴＥ信号の直流オフセットを求めるために光ディスク１を回転させて、対物レンズ２が光ピックアップ３に対してディスク半径方向の中点に位置する際の、補正後のＴＥ信号の直流オフセットと補正後のＬＥ信号との相関式を求める。そして、補正後のＬＥ信号と（数１２）で示した相関式を用いて算出した直流オフセットを、補正後のＴＥ信号から減算することにより、ＴＥ信号の直流オフセット補正が可能となる。
【０１１８】
次に、本発明の第３実施形態に係る光ディスク装置を、図１２のブロック図を用いて説明する。
【０１１９】
本実施形態の構成が先の第１実施形態の構成と異なるのは、回転角度測定回路３５および半回転検出回路３６が含まれている点である。
【０１２０】
回転角度測定回路３５は、スピンドルモータ１５の回転角度を測定して測定角度を半回転検出回路３６に供給する。
【０１２１】
半回転検出回路３６は、回転角度測定回路３５から供給される測定角度の変化から、光ディスク１の半回転を検出する信号（以下、ＨＦＲ信号と呼ぶ）を制御回路１０に供給する。なお本実施形態では、光ディスク１の半回転を検出したら、半回転検出回路３６はＨｉｇｈを出力する。
【０１２２】
他の構成、およびその動作については、第１実施形態と同じである。
【０１２３】
フォーカス制御が定常的に動作している状態から対物レンズ２のディスク半径方向の位置を任意の位置に固定して、偏心がある光ディスク１を回転させた場合のレーザー光の焦点の軌跡を図１３に示す。図１３の実線は、レーザー光の焦点の軌跡で、点線で示すらせんは、光ディスク１のトラックの中心である。
【０１２４】
ここで、らせんの中心は、レーザー焦点の軌跡の中心に対して、光ディスク１の偏心のために、ＯＦで示すずれが生じている。このことにより、光ディスク１の回転前にはＡに位置していたレーザー光の焦点は、光ディスク１の回転に伴って、点Ｂから点Ｈまでの各位置でトラックの中心を横切る。このときに得られるＴＥ信号を図１４に示す。なお、図１４中のＡ〜Ｈは、図１３中のＡ〜Ｈに対応している。
【０１２５】
図１４の点Ｄから点Ｅまでの期間においては、ＴＥ信号は最小レベルまで到達する前に折り返る。振幅中心測定回路２１を用いてＴＥ信号の振幅中心を測定するときに、例えば図１４の期間Ｔで測定を行うと、測定した振幅中心はレベルＶとなり、正しい振幅中心を測定することができない。このようなＴＥ信号の折り返りはディスクの半回転に一回現れるので、ＴＥ信号の振幅中心を測定するときは、少なくとも光ディスク１が半回転する期間中について測定を行えば、正しいＴＥ信号の振幅中心を測定することができる。本実施形態は、この点を考慮に入れたものである。
【０１２６】
図８と同様に、本実施形態の各信号の波形を図１５に示す。図１５において、ＨＦＲ信号は半回転検出回路３６の出力信号である。
【０１２７】
制御回路１０は、第１実施形態と同様に、ＯＰＥＮ１信号にＬｏｗを、ＯＰＥＮ２信号にＨｉｇｈを出力して、対物レンズ２を図７におけるｐ１に位置させる。この状態で制御回路１０は、半回転検出回路３６から供給されるＨＦＲ信号がＨｉｇｈになったことを検知し、ＳＴＲＴ信号にＨｉｇｈを出力して、振幅中心測定回路２１によるＴＥ信号の振幅中心の測定を開始させる。そして、ＨＦＲ信号が次にＨｉｇｈになることを検知したら、つまり光ディスク１が半回転したら、ＨＬＤ１信号にＨｉｇｈを出力する。また、ＯＰＥＮ１信号にＨｉｇｈを出力して、対物レンズ１の位置を図７における位置ｐ２にした後、ＨＦＲ信号がＨｉｇｈになったことを検知し、ＳＴＲＴ信号にＨｉｇｈを再び出力して、振幅中心測定回路２１によるＴＥ信号の振幅中心の測定を開始させる。そして、ＨＦＲ信号の変化から光ディスク１の半回転を検知して、ＨＬＤ２信号にＨｉｇｈを出力した後、ＯＰＥＮ２信号にＬｏｗを出力して、切換えスイッチ８をａ側に切換えてトラッキングサーボループを閉じる。
【０１２８】
以上の方法により、保持回路２４、２２、２５、２３はそれぞれ図７におけるＡ、Ｂ、Ｃ、Ｄを保持するので、加算回路２９の出力は、第１実施形態における図１の加算回路２９と同等である。このため、加算回路３０の出力は、ＴＥ信号の直流オフセットを０に補正したものとなる。
【０１２９】
なお本実施形態では、半回転検出回路３６を用いて光ディスク１の半回転を検出するが、半回転検出回路３６を設けない場合は、ＳＴＲＴ信号にＨｉｇｈを出力したときの回転角度測定回路３５の測定角度を保持しておき、その保持角度と回転角度測定回路３５の測定角度を比較することで、光ディスク１が半回転したことを検知してもよい。
【０１３０】
以上に説明した本実施形態においては、光ピックアップ３に対する対物レンズ２のディスク半径方向への位置を示すＬＥ信号からＴＥ信号の直流オフセットを求めるために光ディスク１を回転させて、ＴＥ信号の直流オフセットとＬＥ信号との相関式を求める。そして、ＬＥ信号と前述の相関式を用いて算出した直流オフセットをＴＥ信号から減算することにより、ＴＥ信号の直流オフセット補正が可能となる。
【０１３１】
さらに、相関式を求めるために対物レンズ２を光ピックアップ３に対して任意の位置ｐ１に移動させて、光ディスク１が半回転する期間におけるＴＥ信号の直流オフセットおよびＬＥ信号を測定する。また、対物レンズ２を光ピックアップ３に対して任意の位置ｐ２に移動させて、光ディスク１が半回転する期間におけるＴＥ信号の直流オフセットおよびＬＥ信号を測定する。このことから、相関式を求める時間は、光ディスク１が半回転を２回行う時間と、光ピックアップ３が位置ｐ１から位置ｐ２への移動する時間の総和であるので、短時間でＴＥ信号の直流オフセットとＬＥ信号の相関式を求めることができる。
【０１３２】
また、本実施形態では光ディスク１の半回転を検出する方法を用いているが、半回転の整数倍を検出することでも、ＴＥ信号の直流オフセット補正が可能であることはいうまでもない。
【０１３３】
次に、本発明の第４実施形態に係る光ディスク装置を、図１６のブロック図を用いて説明する。
【０１３４】
本実施形態の構成が第１実施形態の構成と異なるのは、振幅中心測定回路３７、サイン波出力回路３８、および加算回路３９が含まれている点であり、動作が異なるのは、直流オフセット補正の準備において光ディスク１を回転させずに、対物レンズ２を振動させる点である。
【０１３５】
偏心成分のない光ディスク１を回転させた場合、レーザー光の焦点はトラックを横切らないので、図１４に示したような振幅を持ったＴＥ信号を得ることができない。つまり、相関式を決定するために必要なＴＥ信号の振幅中心を求めることができない。しかし、対物レンズ２を振動させることによって、図１４と同様な振幅を持ったＴＥ信号を得ることができる。以上に述べた理由から、本実施形態では、対物レンズ２を微少量だけ振動させることによって、第１実施形態と同様に振幅を持ったＴＥ信号を得る。
【０１３６】
振幅中心測定回路３７は、制御回路１０から供給されるＳＴＲＴ信号が変化した後に、信号処理回路４から供給されるＬＥ信号の振幅中心を測定して、測定値を保持回路２２および保持回路２３に供給する。ＬＥ信号の振幅中心を測定する方法は、ＴＥ信号の振幅中心を測定する振幅中心測定回路２１と同様である。
【０１３７】
サイン波出力回路３８は、０レベルを基準としたサイン波を加算回路３９に供給する。
【０１３８】
加算回路３９は、切換えスイッチ２０の出力信号とサイン波出力回路３８の出力信号とを加算して、切換えスイッチ８のｂ側に供給する。
【０１３９】
他の構成、およびその動作については第１実施形態と同じである。また、制御回路１０が出力する各制御信号の波形は、第１実施形態で示した図８と同様である。
【０１４０】
フォーカス制御が定常的に動作しており光ディスク１が停止している状態から、制御回路１０は、第１実施形態と同様に各信号を出力する。このとき、加算回路３９によって、切換えスイッチ２０の出力信号とサイン波出力回路３８の出力信号とが加算される。このことから、切換えスイッチ２０がａ側に切換わっている場合、対物レンズ２が図７における位置ｐ１となるレベルを基準としたサイン波が、光ピックアップ３内のトラッキングアクチュエータに印加される。つまり、対物レンズ２は位置ｐ１を中心として振動するので、レーザー光の焦点は光ディスク１のトラックを横切り、光ディスク１を回転させなくても、ＴＥ信号は振幅を持った信号となる。なお、サイン波出力回路３８が出力する信号によって対物レンズ２が振動する振幅は、図７における位置ｐ１、ｐ２に比べて十分小さいものとする。
【０１４１】
一方、切換えスイッチ２０がｂ側に切換わっている場合、対物レンズ２が図７における位置ｐ２となるレベルを基準としたサイン波が、光ピックアップ３内のトラッキングアクチュエータに印加される。そのため、対物レンズ２は位置ｐ２を中心として振動するので、ＴＥ信号は振幅を持った信号となる。
【０１４２】
ここで、対物レンズ２が振動するので、第１実施形態では直流成分であったＬＥ信号は振幅を持つ。そのため、振幅中心測定回路３７を設け、ＴＥ信号と同様にＬＥ信号の振幅中心を測定する。
【０１４３】
つまり、光ディスク１を回転させる代わりに、対物レンズ２を振動させることによって、第１実施形態と同様に、図７におけるＡ、Ｂ、Ｃ、Ｄの各信号を測定することができる。
【０１４４】
なお、本実施形態では、対物レンズ２を振動させるためにサイン波出力回路３８が出力するサイン波を用いたが、三角波等の他の信号を用いてもよいことはいうまでもない。
【０１４５】
以上に説明した本実施形態においては、光ピックアップ３に対する対物レンズ２のディスク半径方向への位置を示すＬＥ信号からＴＥ信号の直流オフセットを求めるために、対物レンズ２を光ピックアップ３に対してディスク半径方向へ振動させて、ＴＥ信号の直流オフセットとＬＥ信号との相関式を求める。そして、ＬＥ信号と相関式とを用いて算出した直流オフセットを、ＴＥ信号から減算することにより、ＴＥ信号の直流オフセット補正が可能となる。
【０１４６】
さらに、対物レンズ２を振動させることにより、偏心成分がない光ディスク１においても、ＴＥ信号の直流オフセットとＬＥ信号との相関式を求めることができる。
【０１４７】
【発明の効果】
以上のように本発明に依れば、回路誤差やディスク毎の反射率の差等によって、トラッキングエラー信号の直流オフセットと、光ピックアップに対するディスク半径方向への対物レンズの位置を示す信号とが一致しない場合であっても、トラッキングエラー信号の直流オフセットを補正できるトラッキングエラー信号補正機能を実現することが可能となる。さらに、かようなトラッキングエラー信号オフセット補正機能を用いてトラッキング制御を行うことにより、情報の読み取りまたは書き込みの信頼性を向上させた光ディスク装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態に係る光ディスク装置のブロック図である。
【図２】プッシュプル法の概要を説明するための図である。
【図３】トラッキングエラー信号の波形図である。
【図４】レンズ位置信号の生成手段を説明するための図である。
【図５】直流オフセットとレンズ位置信号の波形摸式図である。
【図６】従来方式における直流オフセット補正の波形図である。
【図７】直流オフセットとレンズ位置信号の波形摸式図である。
【図８】本発明の第１実施形態の信号波形を示す説明図である。
【図９】本発明の第２実施形態に係る光ディスク装置のブロック図である。
【図１０】補正後の直流オフセットと補正後のレンズ位置信号の波形摸式図である。
【図１１】本発明の第２実施形態の信号波形を示す説明図である。
【図１２】本発明の第３実施形態に係る光ディスク装置のブロック図である。
【図１３】偏心がある場合のレーザー光焦点の軌跡模式図である。
【図１４】偏心がある場合のトラッキングエラー信号の波形摸式図である。
【図１５】本発明の第３実施形態の信号波形を示す説明図である。
【図１６】本発明の第４実施形態に係る光ディスク装置のブロック図である。
【符号の説明】
１ 光ディスク
２ 対物レンズ
３ 光ピックアップ
４ 信号処理回路
５ フォーカスサーボ制御回路
６ フォーカス駆動回路
７ トラッキングサーボ制御回路
８ 切換えスイッチ
９ トラッキング駆動回路
１０ 制御回路
１１ スレッドサーボ制御回路
１２ スレッド駆動回路
１３ スレッドモータ
１４ 光ピックアップ送り機構
１５ スピンドルモータ
１６ スピンドルサーボ制御回路
１７ スピンドル駆動回路
１８ 一定電圧出力回路
１９ 一定電圧出力回路
２０ 切換えスイッチ
２１ 振幅中心測定回路
２２ 保持回路
２３ 保持回路
２４ 保持回路
２５ 保持回路
２６ 係数演算回路
２７ 加算回路
２８ 乗算回路
２９ 加算回路
３０ 加算回路
３１ 一定電圧出力回路
３２ 加算回路
３３ 一定電圧出力回路
３４ 除算回路
３５ 回転角度測定回路
３６ 半回転検出回路
３７ 振幅中心測定回路
３８ サイン波出力回路
３９ 加算回路
４０ レーザーダイオード
４１ ビームスプリッタ
４２ 対物レンズ
４３ 光ディスク
４４ グルーブ
４５ ランド
４６ 光検出器
４７ 光検出器
４８ 差分増幅器
４９ 揺動竿
５０ 発光ダイオード
５１ 回動軸
５２ 固定部
５３ａ 光検出器
５３ｂ 光検出器
５４ 対物レンズ位置検知器
５５ 差分増幅器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tracking error signal offset correction apparatus and an optical disk apparatus, and more particularly to a technique related to an optical disk system that can correct a DC offset of a tracking error signal to improve information reading accuracy and recording accuracy. About.
[0002]
[Prior art]
In an optical disk apparatus, information is recorded by irradiating a laser onto a disk on which information is optically recorded (hereinafter referred to as an optical disk), or the recorded information is read from a difference in reflected light of the laser. Here, as a means for obtaining a tracking error signal (hereinafter referred to as a TE signal) indicating a laser focus shift with respect to a track on the optical disk, a push-pull method, a DPD (Differential Phase Detection) method, or the like. It is known that is used.
[0003]
As an example, an outline of the push-pull method will be described with reference to FIG.
The laser light emitted from the laser diode 40 is focused on the recording surface of the optical disk 43 by reflection by the beam splitter 41 and condensing by the objective lens 42. Here, a groove-shaped groove 44 is provided on the recording surface of the optical disc 43. A portion other than the groove on the recording surface is a land 45. Information is recorded on a track which is an area of each of the land 45 and the groove 44 using a difference in reflectance.
[0004]
The laser light reflected from the optical disk 43 passes through the objective lens 42 and the beam splitter 41 and then enters the photodetectors 46 and 47, respectively. The output signal of the photodetector 46 is supplied to the inverting input terminal of the difference amplifier 48, and the output signal of the photodetector 47 is supplied to the non-inverting input terminal of the difference amplifier 48.
[0005]
In a state where the focus of the laser beam is in the center of the track, the amount of laser light incident on the photodetectors 46 and 47 is the same, so the TE signal output from the differential amplifier 48 is at 0 level. When the objective lens 42 moves in the inner circumferential direction of the optical disc 43 from the state where the focus of the laser beam is in the center of the track, light detection is performed due to light interference due to the difference in groove depth of the land 45 and the groove 44. The amount of laser light incident on the detector 46 is smaller than the amount of laser light incident on the photodetector 47, and the TE signal output from the differential amplifier 48 has a positive polarity. On the other hand, when the objective lens 42 moves in the outer circumferential direction of the optical disc 43, the amount of laser light incident on the photodetector 47 is smaller than the amount of laser light incident on the photodetector 46, contrary to the above phenomenon. The TE signal output from the differential amplifier 48 has a negative polarity.
[0006]
The waveform of the TE signal obtained by the push-pull method described above is shown in FIG. In the tracking control, the position of the objective lens 42 is adjusted in a direction perpendicular to the track in the radial direction of the optical disc 43 so that the TE signal becomes 0 level that is the control center.
[0007]
By the way, a drawback of this push-pull method is that a DC offset occurs in the TE signal when the center of the objective lens 42 does not coincide with the optical axis of the laser beam. A problem when an offset occurs in the TE signal will be described with reference to FIG.
[0008]
In FIG. 3B, a DC offset indicated by A is generated in the TE signal. In this case, since the tracking control adjusts the position of the objective lens 42 so that the TE signal becomes 0 level, which is the control center, a control error indicated by B occurs between the track center and the control center. That is, the laser is focused at a position B away from the track center. For this reason, the reading accuracy and recording accuracy of information are reduced. Note that when the tracking control is steadily operating, the TE signal is in the vicinity of the 0 level, so the direct current offset cannot be measured directly.
[0009]
Conventionally, various measures have been considered in order to solve this problem. As described in Japanese Patent Laid-Open No. 7-235064, a TE signal DC offset correction method using position information of the objective lens 42 is known. Is commonly used. This will be described with reference to FIG.
[0010]
4A is a view of the objective lens 42 viewed from the optical disk 43 in the optical axis direction of the laser in FIG. 2, and FIG. 4B is a view of FIG. 4A viewed from the right side. FIG.
[0011]
The objective lens 42 is fixed to one end of the swing rod 49, the light emitting diode 50 is fixed to the other end of the swing rod 49, and a rotation shaft 51 is provided at the center of the swing rod 49. . The rotation shaft 51 is fixed to the fixed portion 52. The swing rod 49 can be rotated about the rotation shaft 51. Further, in the state where the objective lens 42 is positioned at the middle point, an objective lens position detector 54 composed of the two-divided photodetectors 53a and 53b arranged so as to be evenly opposed to the light emitting surface of the light emitting diode 50, It is installed in the fixed part 52.
[0012]
The output signal of the photodetector 53a is supplied to the inverting input terminal of the difference amplifier 55, and the output signal of the photodetector 53b is supplied to the non-inverting input terminal of the difference amplifier 55. The difference amplifier 55 amplifies the difference between the two input signals and outputs a lens position signal (hereinafter referred to as LE signal) indicating the position of the objective lens 42 in the disk radial direction.
[0013]
In the above configuration, when the objective lens 42 is positioned at the midpoint, the received light amount from the light emitting diode 50 in each of the photodetectors 53a and 53b is equal, and the LE signal is at the 0 level. From this state, when the objective lens 42 moves in the inner circumferential direction, the amount of light received by the photodetector 53b is larger than the amount of light received by the photodetector 53a, so that the LE signal is positive. On the other hand, when the objective lens 42 moves in the outer circumferential direction, the amount of light received by the photodetector 53a is larger than the amount of light received by the photodetector 53b, so the LE signal has a negative polarity.
[0014]
The LE signal described above is a DC component signal corresponding to the DC offset of the TE signal. 5A shows the DC offset of the TE signal depending on the position of the objective lens, and FIG. 5B shows the LE signal based on the position of the objective lens. Here, when the objective lens is located at the middle point, the two signals are both at 0 level, and the two signals change in the same manner as the position of the objective lens moves in the outer circumferential direction and the inner circumferential direction. . That is, since the LE signal is a signal equivalent to a DC offset, the DC offset of the TE signal can be corrected to 0 by subtracting the LE signal from the TE signal.
[0015]
However, the DC offset correction method described above cannot correct the DC offset of the TE signal when a DC offset occurs in the LE signal due to a change in temperature, a change over time, or the like. As a solution to this problem, as disclosed in Japanese Patent Laid-Open No. 7-233504, as shown in FIG. 6A, when the position of the objective lens 42 is at the midpoint position, the LE signal offset is measured and the LE signal is 0. Is corrected so that the DC offset of the TE signal matches the corrected LE signal.
[0016]
[Problems to be solved by the invention]
However, when the method according to the above-mentioned prior application publication is used, when the change rate of the LE signal changes due to the difference in the amplification factor of the differential amplifier 55 in FIG. ), The DC offset of the TE signal due to the position of the objective lens and the corrected LE signal do not match, so the DC offset of the TE signal cannot be corrected correctly.
[0017]
The present invention has been made in consideration of this problem, and an object of the present invention is to reduce the TE signal DC offset depending on the position of the objective lens due to a circuit error, a difference in reflectance of each disk, and the like. Even if the LE signals do not match, the tracking error signal correction function that can correct the DC offset of the TE signal is realized, thereby improving the reliability of reading and writing of information. An object of the present invention is to provide an improved optical disk device.
[0018]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention provides an objective lens that is movable in a substantially radial direction of a disk, an optical detection means that includes the objective lens and outputs a tracking error signal, and the objective for the optical detection means. In a tracking error signal offset correction apparatus for an optical disc apparatus, comprising: a lens position detection unit that detects a lens position; and a lens driving unit that drives the objective lens to a predetermined position with respect to the optical detection unit.
Using the tracking error signal and the output of the lens position detecting means when the objective lens is at a predetermined position of at least two points before reproducing the disk, and the output of the lens position detecting means during reproducing or recording the disk An offset calculating means for calculating a DC offset of the tracking error signal, and a subtracting means for subtracting a calculated value of the offset calculating means from the tracking error signal, so as to correct the DC offset of the tracking error signal, Composed.
[0019]
Further, the offset calculation means includes offset detection means for detecting a DC offset of the tracking error signal before reproduction of the disk, and the objective lens is rotated relative to the optical detection means by rotating the disk before reproduction. The output of the offset detection means (A) and the output of the lens position detection means (B) when positioned at a predetermined position 1, and the objective lens becomes the optical detection means by rotating the disk before reproduction. On the other hand, the output (C) of the offset detection means and the output (D) of the lens position detection means when positioned at the second predetermined position, and the output (D) of the lens position detection means during disk reproduction or recording ( L) and the offset calculating means uses the output signal (of1) as
of1 = {(C−A) × (LB) / (D−B)} + A
Is output.
[0020]
Here, one of the first predetermined position and the second predetermined position is a position where the objective lens is a midpoint with respect to the optical detection means.
[0021]
In order to achieve the above-described object, the present invention provides an objective lens that is movable in a substantially radial direction of the disk, an optical detection means that includes the objective lens and outputs a tracking error signal, and the optical detection means. In a tracking error signal offset correction apparatus for an optical disc apparatus, comprising: a lens position detection unit that detects a position of the objective lens; and a lens driving unit that drives the objective lens to a predetermined position with respect to the optical detection unit.
Tracking error signal correcting means for correcting a DC offset of the tracking error signal to zero when the objective lens is located at a midpoint with respect to the optical detecting means, and the objective lens with respect to the optical detecting means Lens position signal correction means for correcting the output of the lens position detection means to 0 when positioned at the middle point, output of the tracking error signal correction means when the objective lens is at a predetermined position before disk reproduction, and An offset calculating means for calculating a DC offset of the tracking error signal using an output of the lens position signal correcting means and an output of the lens position signal correcting means during disk reproduction or recording, and the tracking error signal correcting means Subtracting means for subtracting the calculated value of the offset calculating means from the output of Configured so as to correct the DC offset of the tracking error signal.
[0022]
Further, the offset calculating means includes offset detecting means for detecting a DC offset of a signal output from the tracking error signal correcting means before reproducing the disk, and the objective lens is rotated by rotating the disk before reproducing. The output (E) of the offset detection means and the output (F) of the lens position correction means when positioned at a predetermined position with respect to the detection means, and the output of the lens position correction means during disk reproduction or recording ( L) and the offset calculating means uses the output signal (of2) as
of2 = E × L / F
Is output.
[0023]
In order to achieve the above-described object, the present invention provides an objective lens that is movable in a substantially radial direction of the disk, an optical detection means that includes the objective lens and outputs a tracking error signal, and the optical detection means. In a tracking error signal offset correction apparatus for an optical disc apparatus, comprising: a lens position detection unit that detects a position of the objective lens; and a lens driving unit that drives the objective lens to a predetermined position with respect to the optical detection unit.
Rotation angle detection means for detecting the rotation angle of the disk and a period during which the disk rotates more than half a rotation from the output of the rotation angle detection means when the objective lens is at at least two predetermined positions before the disk reproduction. Then, the offset calculation for calculating the DC offset of the tracking error signal using the tracking error signal and the output of the lens position detection means during the period and the output of the lens position detection means during disk reproduction or recording And subtracting means for subtracting the calculated value of the offset calculating means from the tracking error signal, and configured to correct the DC offset of the tracking error signal.
[0024]
Further, the offset calculation means includes offset detection means for detecting a DC offset of the tracking error signal before reproduction of the disk, and the objective lens is rotated relative to the optical detection means by rotating the disk before reproduction. An output (G) of the offset detection means and an output (H) of the lens position detection means when a half rotation of the disk is detected from the output of the rotation angle detection means after being positioned at a predetermined position 1, and the disk Is detected before a half rotation of the disk is detected from the output of the rotation angle detection means after the objective lens is positioned at a second predetermined position with respect to the optical detection means. Output (I) of the means and output (J) of the lens position detecting means, and the lens position detection during disk reproduction or recording. By using the output of the means (L), said offset calculation means as an output signal (OF3),
of3 = {(I−G) × (L−H) / (J−H)} + G
Output.
[0025]
In order to achieve the above-described object, the present invention provides an objective lens that is movable in a substantially radial direction of the disk, an optical detection means that includes the objective lens and outputs a tracking error signal, and the optical detection means. An optical disc apparatus comprising: lens position detection means for detecting the position of the objective lens; and lens vibration means for causing the optical detection means to vibrate the objective lens in a disc radial direction about a predetermined position by a minute amount. In the tracking error signal offset correction device of
Using the tracking error signal and the output of the lens position detecting means when the objective lens vibrates at at least two predetermined positions before reproducing the disk, and the output of the lens position detecting means during reproducing or recording the disk. Offset calculating means for calculating the DC offset of the tracking error signal, and subtracting means for subtracting the calculated value of the offset calculating means from the tracking error signal, so as to correct the DC offset of the tracking error signal. Configured.
[0026]
Further, the offset calculating means includes first offset detecting means for detecting a DC offset of the tracking error signal before disc reproduction, and second offset detecting means for detecting a DC offset of an output of the lens position detecting means. The output (K) of the first offset detecting means and the second when the objective lens vibrates around the first predetermined position with respect to the optical detecting means before reproducing the disc. The output (M) of the first offset detection means and the output of the first offset detection means when the objective lens vibrates around the second predetermined position with respect to the optical detection means before reproducing the disk. (N) and the output (O) of the second offset detecting means and the output of the lens position detecting means during disk reproduction or recording. With (L), said offset calculation means as an output signal (OF4),
of4 = {(N−K) × (LM) / (OM)} + K
Is output.
[0027]
In order to achieve the above-mentioned object, the present invention provides an objective lens that is movable in a substantially radial direction of the disc, an optical detection means including the objective lens, and the objective lens for the optical detection means in the optical disc apparatus. A lens position detecting means for detecting the position of the lens, a lens driving means for driving the objective lens to a predetermined position with respect to the optical detecting means, and when the objective lens is at a predetermined position of at least two points before disc reproduction. The tracking error signal obtained from the optical detection means, the output of the lens position detection means, and the output of the lens position detection means during disk reproduction or recording are used to calculate a DC offset of the tracking error signal Offset calculating means, and the offset calculating means from the tracking error signal And a subtraction means for subtracting the calculated value, so as to perform tracking control by using the output of said subtracting means constituted.
[0028]
Further, the offset calculation means includes offset detection means for detecting a DC offset of the tracking error signal before reproduction of the disk, and the objective lens is rotated relative to the optical detection means by rotating the disk before reproduction. The output of the offset detection means (A) and the output of the lens position detection means (B) when positioned at a predetermined position 1, and the objective lens becomes the optical detection means by rotating the disk before reproduction. On the other hand, the output (C) of the offset detection means and the output (D) of the lens position detection means when positioned at the second predetermined position, and the output (D) of the lens position detection means during disk reproduction or recording ( L) and the offset calculating means uses the output signal (of5) as
of5 = {(C−A) × (LB) / (D−B)} + A
Output.
[0029]
Here, one of the first predetermined position and the second predetermined position is a position where the objective lens is a midpoint with respect to the optical detection means.
[0030]
In order to achieve the above-mentioned object, the present invention provides an objective lens that is movable in a substantially radial direction of the disc, an optical detection means including the objective lens, and the objective lens for the optical detection means in the optical disc apparatus. Lens position detecting means for detecting the position of the lens, lens driving means for driving the objective lens to a predetermined position with respect to the optical detecting means, and the objective lens being positioned at a midpoint with respect to the optical detecting means. The tracking error signal correcting means for correcting the DC offset of the tracking error signal to zero, and the output of the lens position detecting means when the objective lens is positioned at the midpoint with respect to the optical detecting means. Lens position signal correction means for correcting, and the tracking error signal when the objective lens is at a predetermined position before disk reproduction. An offset calculating means for calculating a DC offset of the tracking error signal using the output of the correcting means and the output of the lens position signal correcting means and the output of the lens position signal correcting means during disk reproduction or recording; Subtracting means for subtracting the calculated value of the offset calculating means from the output of the tracking error signal correcting means, and configured to perform tracking control using the output of the subtracting means.
[0031]
Further, the offset calculating means includes offset detecting means for detecting a DC offset of a signal output from the tracking error signal correcting means before reproducing the disk, and the objective lens is rotated by rotating the disk before reproducing. The output (E) of the offset detection means and the output (F) of the lens position correction means when positioned at a predetermined position with respect to the detection means, and the output of the lens position correction means during disk reproduction or recording ( L) and the offset calculating means uses the output signal (of6) as
of6 = E × L / F
Is output.
[0032]
In order to achieve the above-mentioned object, the present invention provides an objective lens that is movable in a substantially radial direction of the disc, an optical detection means including the objective lens, and the objective lens for the optical detection means in the optical disc apparatus. Lens position detecting means for detecting the position of the optical disk, lens driving means for driving the objective lens to a predetermined position with respect to the optical detecting means, rotation angle detecting means for detecting the rotation angle of the disk, and before reproducing the disk. When the objective lens is at a predetermined position of at least two points, a tracking error signal obtained from the optical detection means during the period is detected from the output of the rotation angle detection means, and a period during which the disk rotates more than half rotation is detected. Output of the lens position detection means and output of the lens position detection means during disk reproduction or recording Using an offset calculating means for calculating a DC offset of the tracking error signal and a subtracting means for subtracting a calculated value of the offset calculating means from the tracking error signal, and using the output of the subtracting means for tracking control Configured to do.
[0033]
Further, the offset calculation means includes offset detection means for detecting a DC offset of the tracking error signal before reproduction of the disk, and the objective lens is rotated relative to the optical detection means by rotating the disk before reproduction. An output (G) of the offset detection means and an output (H) of the lens position detection means when a half rotation of the disk is detected from the output of the rotation angle detection means after being positioned at a predetermined position 1, and the disk Is detected before a half rotation of the disk is detected from the output of the rotation angle detection means after the objective lens is positioned at a second predetermined position with respect to the optical detection means. Output (I) of the means and output (J) of the lens position detecting means, and the lens position detection during disk reproduction or recording. By using the output of the means (L), said offset calculation means as the output signal (OF7),
of7 = {(I−G) × (L−H) / (J−H)} + G
Is output.
[0034]
In order to achieve the above-mentioned object, the present invention provides an objective lens that is movable in a substantially radial direction of the disc, an optical detection means including the objective lens, and the objective lens for the optical detection means in the optical disc apparatus. A lens position detecting means for detecting the position of the lens, a lens vibrating means for vibrating the objective lens in the radial direction of the disc around a predetermined position with respect to the optical detecting means, and the objective lens before reproducing the disc. Using the tracking error signal obtained from the optical detection means when it vibrates at at least two predetermined positions, the output of the lens position detection means, and the output of the lens position detection means during disk reproduction or recording Offset calculating means for calculating a DC offset of the tracking error signal; And a subtraction means for subtracting the calculated value of the offset calculating means from King error signal, so as to perform tracking control by using the output of said subtracting means constituted.
[0035]
Further, the offset calculating means includes first offset detecting means for detecting a DC offset of the tracking error signal before disc reproduction, and second offset detecting means for detecting a DC offset of an output of the lens position detecting means. The output (K) of the first offset detecting means and the second when the objective lens vibrates around the first predetermined position with respect to the optical detecting means before reproducing the disc. The output (M) of the first offset detection means and the output of the first offset detection means when the objective lens vibrates around the second predetermined position with respect to the optical detection means before reproducing the disk. (N) and the output (O) of the second offset detecting means and the output of the lens position detecting means during disk reproduction or recording. By using the (L), said offset calculation means as an output signal (OF8),
of8 = {(N−K) × (LM) / (OM)} + K
Is output.
[0036]
All the offset detection means described so far include a maximum value detection means for detecting the maximum value of the input signal, a minimum value detection means for detecting the minimum value of the input signal, a detection value of the maximum value detection means, and the Center calculating means for calculating the center value of the detected value of the minimum value detecting means and outputting the center of amplitude of the input signal.
[0037]
Or all the offset detection means described so far removes a high frequency component by passing an input signal through a low-pass filter and outputs a DC offset component.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, a method for correcting the DC offset of the TE signal when the DC offset of the TE signal and the LE signal do not match due to a circuit error, a difference in reflectivity for each disk, or the like will be described.
[0039]
FIG. 7 is a waveform diagram of the DC offset of the TE signal and the LE signal depending on the position of the objective lens, and shows a case where the DC offset of the TE signal and the LE signal do not match. When the position of the objective lens with respect to the optical pickup is an arbitrary position p1, the DC offset is A, and the LE signal is B. Further, when the position of the objective lens is an arbitrary position p2, the DC offset is C, and the LE signal is D.
[0040]
When the position of the objective lens approaches the limit of movement with respect to the optical pickup, the DC offset and the change rate of the LE signal become smaller, but in other cases, both change while maintaining linearity. In actual operation, since the moving range of the objective lens is near the midpoint, the DC offset can be approximated by a straight line TO (x). Here, x is the position of the objective lens in the disc radial direction with respect to the optical pickup. Similarly, the LE signal can be approximated by a straight line LE (x).
[0041]
Generally, a straight line y passing through the points (x1, y1) and (x2, y2) is expressed as the following (Equation 1).
[0042]
[Expression 1]

[0043]
From this, the straight line TO (x) passing through the points (p1, A) and (p2, C) is expressed as the following (Equation 2).
[0044]
[Expression 2]

[0045]
The straight line LE (x) passing through the points (p1, B) and (p2, D) is expressed as the following (Equation 3).
[0046]
[Equation 3]

[0047]
(Equation 3) can be transformed into the following (Equation 4),
[0048]
[Expression 4]

[0049]
When (Equation 4) is substituted into (Equation 2), the following (Equation 5) is obtained, and a correlation equation between TO (x) and LE (x) is obtained.
[0050]
[Equation 5]

[0051]
From this, LE (x) and constants A, B, C, and D are measured, and TO (x), which is a DC offset of the TE signal, is obtained using (Equation 5), and TO (x) is obtained from the TE signal. By subtracting, the DC offset can be corrected to zero.
[0052]
Next, an optical disk apparatus that enables correction of the DC offset of the TE signal described above will be described.
[0053]
FIG. 1 is a block diagram of an optical disc apparatus for reproducing or recording an optical disc according to the first embodiment of the present invention.
In FIG. 1, 1 is an optical disk, 2 is an objective lens, 3 is an optical pickup, 4 is a signal processing circuit, 5 is a focus servo control circuit, 6 is a focus drive circuit, 7 is a tracking servo control circuit, 8 is a changeover switch, 9 Is a tracking drive circuit, 10 is a control circuit, 11 is a sled servo control circuit, 12 is a sled drive circuit, 13 is a sled motor, 14 is an optical pickup feed mechanism, 15 is a spindle motor, 16 is a spindle servo control circuit, and 17 is a spindle. Drive circuit, 18 and 19 are constant voltage output circuits, 20 is a changeover switch, 21 is an amplitude center measurement circuit, 22 to 25 are holding circuits, 26 is a coefficient calculation circuit, 27, 29 and 30 are addition circuits, and 28 is a multiplication circuit It is.
[0054]
Hereinafter, an outline of the operation of the optical disc apparatus of the present embodiment will be described.
Information is digitally recorded on the optical disc 1 due to unevenness of the recording layer or a difference in reflectance. The objective lens 2 focuses the laser beam to focus on the recording layer of the optical disc 1. The optical pickup 3 includes a focus actuator that drives the objective lens 2 in the direction of the optical axis of the laser, and a tracking actuator that drives the objective lens 2 in the radial direction of the disk. Here, in the present embodiment, the optical pickup 3 includes a photodetector necessary for obtaining the TE signal by the push-pull method described above with reference to FIG. 2, and reflects the reflected light from the optical disc 1 as an electrical signal. To the signal processing circuit 4 instead. The optical pickup 3 includes a photodetector necessary for obtaining the LE signal described above with reference to FIG. 4, and supplies a signal for obtaining the LE signal to the signal processing circuit 4.
[0055]
The signal processing circuit 4 processes an output signal from the optical pickup 3 to produce a focus error signal corresponding to the focus shift, a TE signal corresponding to the tracking shift, a spindle signal indicating the rotation state of the spindle, and the optical pickup. LE signals corresponding to the displacement of the objective lens 2 in the disk radial direction with respect to 3 are output.
[0056]
The focus servo control circuit 5 receives the focus error signal supplied from the signal processing circuit 4 and outputs a signal that has been subjected to gain and phase compensation necessary to improve the stability and tracking performance of the focus servo. The focus drive circuit 6 receives the output signal of the focus servo control circuit 5 and amplifies the signal, outputs a signal for driving the focus actuator in the optical pickup 3, and the position of the objective lens 2 in the optical axis direction of the laser To change.
[0057]
The tracking servo control circuit 7 receives the output signal of the adder circuit 30 that subtracts the output signal of the adder circuit 29 from the TE signal supplied from the signal processing circuit 4, and is necessary to improve the stability and tracking performance of the tracking servo. A signal (hereinafter referred to as a tracking drive signal) that has been compensated for a large gain and phase is supplied to the a side of the changeover switch 8 and the sled servo control circuit 11.
[0058]
When the signal for controlling the changeover switch 8 supplied from the control circuit 10 (hereinafter referred to as OPEN2 signal) is Low, the changeover switch 8 is switched to the a side to close the tracking servo loop, and from the tracking servo control circuit 7 The supplied tracking drive signal is output. When the OPEN2 signal is High, the tracking servo loop is opened by switching to the b side, and the signal supplied from the switch 20 is output.
[0059]
The tracking drive circuit 9 amplifies the signal supplied from the changeover switch 8 and outputs a signal for driving the tracking actuator in the optical pickup 3 to change the position of the objective lens 2 in the disk radial direction.
[0060]
The control circuit 10 switches the changeover switch 8 and the changeover switch 20 and outputs a signal for controlling the amplitude center measurement circuit 21 and the holding circuits 22 to 25.
[0061]
The sled servo control circuit 11 receives the tracking drive signal supplied from the tracking servo control circuit 7 and outputs a signal that has been compensated for gain in order to improve the tracking performance of the sled servo. The sled servo control circuit 11 controls the position of the optical pickup 3 so that the objective lens 2 moved by the tracking actuator in the optical pickup 3 does not exceed the movement limit.
[0062]
The sled motor drive circuit 12 amplifies the output signal of the sled servo control circuit 11 and supplies the amplified signal to the sled motor 13. The sled motor 13 drives the optical pickup feeding mechanism 14 by the signal supplied from the sled motor drive circuit 12. To do. Then, the optical pickup feeding mechanism 14 moves the optical pickup 3 in the inner peripheral direction or the outer peripheral direction of the optical disc 1.
[0063]
The spindle servo control circuit 16 receives the spindle signal supplied from the signal processing circuit 4 and performs control for rotating the spindle motor 15 at a predetermined rotational speed. The spindle motor drive circuit 17 amplifies the output signal of the spindle servo control circuit 16 and rotates the spindle motor 15, thereby rotating the optical disc 1.
[0064]
The constant voltage output circuit 18 supplies a constant voltage for positioning the objective lens 2 at an arbitrary position p1 in the disk radial direction with respect to the optical pickup 3 to the a side of the changeover switch 20. The constant voltage output circuit 19 supplies a constant voltage for positioning the objective lens 2 at an arbitrary position p2 in the disk radial direction with respect to the optical pickup 3 to the b side of the changeover switch 20. Note that the voltages output from the constant voltage output circuits 18 and 19 are different. For this reason, arbitrary positions p1 and p2 are different positions.
[0065]
When the signal for controlling the changeover switch 20 supplied from the control circuit 10 (hereinafter referred to as the OPEN1 signal) is Low, the changeover switch 20 is switched to the a side, and the signal supplied from the constant voltage output circuit 18 is changed. Output. When the OPEN1 signal is High, the signal is switched to the b side and the signal supplied from the constant voltage output circuit 19 is output. The output signal of the changeover switch 20 is supplied to the b side of the changeover switch 8.
[0066]
The amplitude center measurement circuit 21 changes the amplitude center of the TE signal supplied from the signal processing circuit 4 after the signal (hereinafter referred to as STRT signal) for controlling the amplitude center measurement circuit 21 supplied from the control circuit 10 changes. Measure and supply the measured value to the holding circuits 24 and 25. As a method of measuring the amplitude center of the TE signal, a method of detecting and adding the maximum value and the minimum value of the TE signal and obtaining an average thereof can be used. Also, a method of obtaining an amplitude center that is a direct current component by passing the TE signal through a low-pass filter and removing the high-frequency signal can be used. In this embodiment, after the STRT signal becomes High, the detected maximum value and minimum value are cleared and the amplitude center is measured.
[0067]
The holding circuit 22 holds the LE signal supplied from the signal processing circuit 4 at a timing when a signal for controlling the holding circuit 22 and the holding circuit 24 (hereinafter referred to as the HLD1 signal) supplied from the control circuit 10 changes. And supplied to the addition circuit 27 and the coefficient calculation circuit 26. In the present embodiment, the LE signal is held at the timing when the HLD1 signal becomes High.
[0068]
The holding circuit 23 holds the LE signal supplied from the signal processing circuit 4 at a timing when a signal for controlling the holding circuit 23 and the holding circuit 25 supplied from the control circuit 10 (hereinafter referred to as an HLD2 signal) changes. To the coefficient calculation circuit 26. In the present embodiment, the LE signal is held at the timing when the HLD2 signal becomes High.
[0069]
The holding circuit 24 holds the amplitude center supplied from the amplitude center measurement circuit 21 at the timing when the HLD1 signal becomes High, and supplies the amplitude center to the coefficient calculation circuit 26 and the addition circuit 29.
[0070]
The holding circuit 25 holds the amplitude center supplied from the amplitude center measuring circuit 21 at the timing when the HLD2 signal becomes High, and supplies it to the coefficient calculation circuit 26.
[0071]
The coefficient calculation circuit 26 obtains a first subtraction signal obtained by subtracting the output signal of the holding circuit 24 from the output signal of the holding circuit 25. Further, a second subtraction signal obtained by subtracting the output signal of the holding circuit 22 from the output signal of the holding circuit 23 is obtained. Then, the coefficient calculation circuit 26 supplies a calculation signal obtained by dividing the first subtraction signal by the second subtraction signal to the multiplication circuit 28.
[0072]
The addition circuit 27 adds the LE signal supplied from the signal processing circuit 4 and the signal obtained by inverting the polarity of the signal supplied from the holding circuit 22 and supplies the result to the multiplication circuit 28. It goes without saying that the polarity inversion may be performed by the holding circuit 22.
[0073]
The multiplication circuit 28 multiplies the output signal of the addition circuit 27 and the output signal of the coefficient calculation circuit 26 and supplies the result to the addition circuit 29.
[0074]
The addition circuit 29 adds the output signal of the multiplication circuit 28 and the output signal of the holding circuit 24 and supplies the result to the addition circuit 30.
[0075]
The adder circuit 30 adds the TE signal supplied from the signal processing circuit 4 and a signal obtained by inverting the polarity of the output signal of the adder circuit 29 and supplies the sum to the tracking servo control circuit 7. Needless to say, the polarity inversion may be performed by the adder circuit 29.
[0076]
Next, based on the above configuration, a method for correcting the DC offset of the TE signal will be described with reference to FIG. 8 which is a signal example of the present embodiment.
[0077]
After mounting the optical disc 1, the focus servo control circuit 5 uses the focus error signal supplied from the signal processing circuit 4 so that the laser beam is focused on the recording surface of the optical disc 1 in the optical axis direction of the laser beam. The position of the objective lens 2 is controlled. The spindle servo control circuit 16 rotates the optical disc 1 at a predetermined rotation speed. The control circuit 10 outputs Low to the OPEN1 signal, High to the OPEN2 signal, Low to the STRT signal, Low to the HLD1 signal, and Low to the HLD2 signal. At this time, the changeover switch 8 is switched to the b side, and the changeover switch 20 is switched to the a side. Therefore, the output signal of the constant voltage output circuit 18 is applied to the tracking actuator in the optical pickup 3 via the changeover switch 20, the changeover switch 8, and the tracking drive circuit 9, so that the objective lens 2 is connected to the optical pickup 3. Is located at an arbitrary position p1 in the disk radial direction. This position is the position p1 in FIG.
[0078]
From the above state, the control circuit 10 outputs High to the STRT signal, causes the amplitude center measurement circuit 21 to start measuring the amplitude center of the TE signal, and then outputs High to the HLD1 signal. At this time, the holding circuit 22 holds the LE signal supplied from the signal processing circuit 4. Further, since the rotating optical disk 1 is eccentric, the TE signal output from the signal processing circuit 4 is a signal having an amplitude. The amplitude center measuring circuit 21 measures and outputs the amplitude center of the TE signal based on the signal from the control circuit 10, and the holding circuit 24 holds the output signal of the amplitude center measuring circuit 21. Here, since the position of the objective lens 2 is p1, the holding circuit 24 holds the DC offset A in FIG. The holding circuit 22 holds the LE signal B in FIG. In this embodiment, after outputting High to the HLD1 signal, Low is output again, but even if it remains High, the subsequent operation is not affected.
[0079]
The control circuit 10 outputs High to the HLD1 signal, then outputs High to the OPEN1 signal, and switches the changeover switch 20 to the b side. For this reason, the output signal of the constant voltage output circuit 19 is applied to the tracking actuator in the optical pickup 3 via the changeover switch 20, the changeover switch 8, and the tracking drive circuit 9. At this time, since the constant voltage output circuit 19 outputs a constant voltage for positioning the objective lens 2 at an arbitrary position p2, the position of the objective lens 2 in the disc radial direction is p2. This position is the position p2 in FIG.
[0080]
The control circuit 10 outputs High to the OPEN1 signal, then outputs High again to the STRT signal, starts the measurement of the amplitude center of the TE signal by the amplitude center measurement circuit 21, and then outputs High to the HLD2 signal. . At this time, since the position of the objective lens 2 is p2 in FIG. 7, the holding circuit 25 holds the DC offset C in FIG. The holding circuit 23 holds the LE signal D in FIG. In the present embodiment, Low is output again after High is output to the HLD2 signal. However, even if High is maintained, subsequent operations are not affected.
[0081]
The coefficient calculation circuit 26 calculates a coefficient using the signals supplied from the holding circuits 22, 23, 24, and 25 and supplies the calculation result to the multiplication circuit 28.
[0082]
The operation described above is preparation for DC offset correction.
[0083]
Next, after preparing for the DC offset correction, the control circuit 10 outputs Low to the OPEN2 signal, switches the changeover switch 8 to the a side, and closes the tracking servo loop. Here, since the LE signal output from the signal processing circuit 4 changes as the position of the objective lens 2 changes, LE (x) in (Expression 5) is output. At this time, since the holding circuit 22 holds the LE signal B in FIG. 7, the adder circuit 27 outputs the next value of (Formula 6) in (Formula 5).
[0084]
[Formula 6]

[0085]
The coefficient calculation circuit 26 outputs the next value of (Expression 7) in (Expression 5).
[0086]
[Expression 7]

[0087]
The multiplication circuit 28 outputs the next value of (Equation 8) in (Equation 5).
[0088]
[Equation 8]

[0089]
Since the holding circuit 24 holds the DC offset A in FIG. 7, the adding circuit 29 outputs TO (x) in (Equation 5), that is, the DC offset of the TE signal.
[0090]
Then, the adder circuit 30 subtracts the output of the adder circuit 29, that is, the direct current offset of the TE signal, from the TE signal supplied from the signal processing circuit 4, so that the direct current of the TE signal supplied to the tracking servo control circuit 7 is obtained. Correct the offset to zero.
[0091]
In the present embodiment described above, the optical disc 1 is rotated in order to obtain the DC offset of the TE signal from the LE signal indicating the position of the objective lens 2 in the disc radial direction with respect to the optical pickup 3, and the DC offset of the TE signal is obtained. And a correlation equation of LE signals. Then, the DC offset of the TE signal can be corrected by subtracting the DC offset calculated from the LE signal and the correlation equation shown in (Equation 5) from the TE signal.
[0092]
In the present embodiment, the constant voltage output circuit 18 may output a voltage for positioning the objective lens 2 at the midpoint in the disk radial direction with respect to the optical pickup 3. In any case, the objective lens 2 is originally positioned at the midpoint of the optical disc 3 in the radial direction of the disc before the disc reproduction. Therefore, when this is done, it is not necessary to move the objective lens 2 to the position p1 in FIG. 7, and the DC offset A and the LE signal B in FIG. 7 can be measured in a short time.
[0093]
Next, an optical disc device according to a second embodiment of the present invention will be described with reference to the block diagram of FIG.
[0094]
The configuration of the present embodiment is different from the configuration of the first embodiment in that it does not include the holding circuits 22 and 24, the coefficient calculation circuit 26, and the addition circuit 29, and the constant voltage output circuits 31 and 33 and the addition circuit. 32, and a division circuit 34. Further, the adder circuit 30 is supplied with the output of the multiplier circuit 28 and the output of the adder circuit 32, and the control circuit 10 does not output the HLD1 signal.
[0095]
The constant voltage output circuit 31 supplies the addition circuit 32 with a constant voltage at which the output of the addition circuit 32 becomes 0 level when the objective lens 2 is at the midpoint position in the disk radial direction with respect to the optical pickup 3.
[0096]
The adder circuit 32 supplies a signal obtained by adding the TE signal output from the signal processing circuit 4 and the output of the constant voltage output circuit 31 to the adder circuit 30 and the amplitude center measuring circuit 21.
[0097]
The constant voltage output circuit 33 supplies the addition circuit 27 with a constant voltage at which the output of the addition circuit 27 becomes 0 level when the objective lens 2 is at the midpoint position in the disk radial direction with respect to the optical pickup 3.
[0098]
The adder circuit 27 supplies a signal obtained by adding the LE signal obtained from the signal processing circuit 4 and the output of the constant voltage output circuit 33 to the holding circuit 23 and the multiplier circuit 28.
[0099]
The division circuit 34 supplies an output obtained by dividing the output of the holding circuit 25 by the output of the holding circuit 23 to the multiplication circuit 28.
[0100]
After the STRT signal changes, the amplitude center measurement circuit 21 measures the amplitude center of the output signal of the addition circuit 32 and supplies the measurement value to the holding circuit 25.
[0101]
The constant voltage output circuit 18 supplies a constant voltage at which the objective lens 2 is positioned at the midpoint of the disk radial direction with respect to the optical pickup 3 to the a side of the changeover switch 20.
[0102]
In such a configuration of the present embodiment, when the position of the objective lens 2 is the midpoint, the offset of the TE signal is corrected to 0 level by the constant voltage output circuit 31 and the adder circuit 32. Becomes 0 level. The offset of the LE signal is also corrected to 0 level by the constant voltage output circuit 33 and the addition circuit 27.
[0103]
Similarly to FIG. 7, the corrected DC offset and the corrected LE signal are shown in FIG. In FIG. 10, when the objective lens position is the middle point (0 level), both the corrected DC offset A and the corrected LE signal B are at 0 level. Further, when the objective lens position is an arbitrary position p2, the corrected DC offset is C, and the corrected LE signal is D. Here, when the corrected DC offset is approximated by TO2 (x) and the corrected LE signal is approximated by LE2 (x), a straight line TO2 (x) passing through the points (0, 0) and (p2, C) is The following (Equation 9) is expressed.
[0104]
[Equation 9]

[0105]
A straight line LE2 (x) passing through the points (0, 0) and (p2, D) is expressed as the following (Equation 10).
[0106]
[Expression 10]

[0107]
(Equation 10) can be transformed into the following (Equation 11),
[0108]
[Expression 11]

[0109]
When (Equation 11) is substituted into (Equation 9), the following (Equation 12) is obtained, and a correlation equation between TO2 (x) and LE2 (x) is obtained.
[0110]
[Expression 12]

[0111]
FIG. 11 shows an output signal waveform of the control circuit 10 of the present embodiment.
When the optical disc 1 is mounted and the focus control is operating steadily, and the optical disc 1 is rotating, the control circuit 10 outputs Low to the OPEN1 signal, the STRT signal, and the HLD2 signal, respectively. High is output. Therefore, the output of the constant voltage output circuit 18 is applied to the tracking actuator in the optical pickup 3 via the changeover switch 20, the changeover switch 8, and the tracking drive circuit 9, and the objective lens 2 is applied to the optical pickup 3. , Located at the midpoint of the disk radial direction.
[0112]
Here, the control circuit 10 outputs High to the OPEN1 signal, switches the changeover switch 20 to the b side, and applies the output of the constant voltage output circuit 19 to the tracking actuator in the optical pickup 3. The constant voltage output circuit 19 moves the objective lens 2 to the position p2 in order to move the objective lens 2 to the predetermined position p2 in the disk radial direction with respect to the optical pickup 3. This position p2 is the position p2 in FIG.
[0113]
After a sufficient time has passed for the objective lens 2 to move to the position p2, the control circuit 10 outputs High to the STRT signal and causes the amplitude center measurement circuit 21 to start measuring the amplitude center of the TE signal. After outputting High to the STRT signal, the control circuit 10 outputs High to the HLD2 signal, causing the holding circuit 23 to hold the output of the adder circuit 27 and the holding circuit 25 to hold the output of the amplitude center measuring circuit 21. At this time, since the objective lens 2 is at the position p2 in FIG. 10, the holding circuit 25 holds the corrected DC offset C in FIG. The holding circuit 23 holds the corrected LE signal D in FIG.
[0114]
Thereafter, the control circuit 10 outputs Low to the OPEN2 signal, switches the changeover switch 8 to the a side, and closes the tracking servo loop.
[0115]
Here, the holding circuit 25 holds C in FIG. 10, the holding circuit 23 holds D in FIG. 10, and the dividing circuit 34 outputs a signal obtained by dividing C by D. Therefore, the multiplication circuit 28 outputs a signal equivalent to (Equation 12). The adder circuit 30 corrects the DC offset of the TE signal to 0 by subtracting a signal equivalent to the output from the multiplier circuit 28 (Equation 12) from the corrected TE signal output from the adder circuit 32. .
[0116]
In the present embodiment, the objective lens 2 is positioned at the midpoint of the radial direction of the disc with respect to the optical pickup 3 before reproducing the disc. Therefore, it is unnecessary to move the objective lens 2 to the position p1 in FIG. 10, and the corrected DC offset A and the corrected LE signal B in FIG. 10 can be measured in a short time.
[0117]
In the present embodiment described above, the optical disk 1 is rotated in order to obtain the DC offset of the TE signal from the LE signal indicating the position of the objective lens 2 in the radial direction of the disk with respect to the optical pickup 3, and the objective lens 2 emits light. A correlation equation between the DC offset of the corrected TE signal and the corrected LE signal when it is positioned at the midpoint of the disk radial direction with respect to the pickup 3 is obtained. Then, the DC offset of the TE signal can be corrected by subtracting the DC offset calculated using the corrected LE signal and the correlation equation shown in (Equation 12) from the corrected TE signal.
[0118]
Next, an optical disc device according to a third embodiment of the present invention will be described with reference to the block diagram of FIG.
[0119]
The configuration of this embodiment is different from the configuration of the first embodiment in that a rotation angle measurement circuit 35 and a half-rotation detection circuit 36 are included.
[0120]
The rotation angle measurement circuit 35 measures the rotation angle of the spindle motor 15 and supplies the measurement angle to the half-rotation detection circuit 36.
[0121]
The half-rotation detection circuit 36 supplies a signal (hereinafter referred to as an HFR signal) for detecting half-rotation of the optical disc 1 to the control circuit 10 based on a change in the measurement angle supplied from the rotation angle measurement circuit 35. In the present embodiment, when half rotation of the optical disk 1 is detected, the half rotation detection circuit 36 outputs High.
[0122]
Other configurations and operations thereof are the same as those in the first embodiment.
[0123]
FIG. 13 shows the locus of the focal point of the laser beam when the optical disk 1 with eccentricity is rotated while the position of the objective lens 2 in the disk radial direction is fixed to an arbitrary position from the state in which the focus control is constantly operating. Shown in The solid line in FIG. 13 is the locus of the focal point of the laser beam, and the helix indicated by the dotted line is the center of the track of the optical disc 1.
[0124]
Here, due to the eccentricity of the optical disc 1 with respect to the center of the locus of the laser focal point, the center of the spiral has a deviation indicated by OF. As a result, the focal point of the laser beam located at A before the rotation of the optical disc 1 crosses the center of the track at each position from point B to point H as the optical disc 1 rotates. The TE signal obtained at this time is shown in FIG. Note that A to H in FIG. 14 correspond to A to H in FIG. 13.
[0125]
In the period from point D to point E in FIG. 14, the TE signal is folded before reaching the minimum level. When the amplitude center of the TE signal is measured using the amplitude center measurement circuit 21, for example, if measurement is performed in the period T in FIG. 14, the measured amplitude center becomes level V, and the correct amplitude center cannot be measured. Such folding of the TE signal appears once in a half rotation of the disk. Therefore, when measuring the amplitude center of the TE signal, if the measurement is performed at least during the half rotation of the optical disk 1, the correct amplitude of the TE signal is obtained. The center can be measured. The present embodiment takes this point into consideration.
[0126]
Similarly to FIG. 8, the waveforms of the signals of this embodiment are shown in FIG. In FIG. 15, the HFR signal is an output signal of the half-rotation detection circuit 36.
[0127]
As in the first embodiment, the control circuit 10 outputs Low to the OPEN1 signal and High to the OPEN2 signal, and positions the objective lens 2 at p1 in FIG. In this state, the control circuit 10 detects that the HFR signal supplied from the half-rotation detection circuit 36 has become High, outputs High to the STRT signal, and outputs the amplitude center of the TE signal by the amplitude center measurement circuit 21. Start measurement. When it is detected that the HFR signal becomes High next time, that is, when the optical disc 1 is rotated halfway, High is output to the HLD1 signal. Further, after outputting High to the OPEN1 signal and setting the position of the objective lens 1 to the position p2 in FIG. 7, it is detected that the HFR signal has become High, and High is output again to the STRT signal, so that the amplitude center is obtained. Measurement of the amplitude center of the TE signal by the measurement circuit 21 is started. Then, the half rotation of the optical disk 1 is detected from the change in the HFR signal, and High is output to the HLD2 signal, then Low is output to the OPEN2 signal, the changeover switch 8 is switched to the a side, and the tracking servo loop is closed.
[0128]
With the above method, the holding circuits 24, 22, 25, and 23 hold A, B, C, and D in FIG. 7, respectively. Therefore, the output of the adding circuit 29 is the same as that of the adding circuit 29 of FIG. 1 in the first embodiment. It is equivalent. For this reason, the output of the adder circuit 30 is obtained by correcting the DC offset of the TE signal to zero.
[0129]
In this embodiment, half rotation of the optical disc 1 is detected using the half rotation detection circuit 36. However, when the half rotation detection circuit 36 is not provided, the rotation angle measurement circuit 35 when High is output to the STRT signal. It may be detected that the optical disk 1 has been rotated halfway by holding the measurement angle and comparing the held angle with the measurement angle of the rotation angle measurement circuit 35.
[0130]
In the present embodiment described above, the optical disc 1 is rotated in order to obtain the DC offset of the TE signal from the LE signal indicating the position of the objective lens 2 in the disc radial direction with respect to the optical pickup 3, and the DC offset of the TE signal is obtained. And a correlation equation of LE signals. Then, the DC offset of the TE signal can be corrected by subtracting the DC offset calculated using the LE signal and the above-described correlation equation from the TE signal.
[0131]
Further, in order to obtain the correlation equation, the objective lens 2 is moved to an arbitrary position p1 with respect to the optical pickup 3, and the direct current offset of the TE signal and the LE signal during the half rotation of the optical disk 1 are measured. Further, the objective lens 2 is moved to an arbitrary position p2 with respect to the optical pickup 3, and the direct current offset of the TE signal and the LE signal during the half rotation of the optical disc 1 are measured. From this, the time for obtaining the correlation equation is the sum of the time for the optical disk 1 to perform half rotation twice and the time for the optical pickup 3 to move from the position p1 to the position p2. A correlation equation between the offset and the LE signal can be obtained.
[0132]
In the present embodiment, the method of detecting half rotation of the optical disk 1 is used. Needless to say, the DC offset correction of the TE signal can be performed by detecting an integral multiple of half rotation.
[0133]
Next, an optical disc device according to a fourth embodiment of the present invention will be described with reference to the block diagram of FIG.
[0134]
The configuration of the present embodiment is different from the configuration of the first embodiment in that an amplitude center measurement circuit 37, a sine wave output circuit 38, and an addition circuit 39 are included. The objective lens 2 is vibrated without rotating the optical disc 1 in preparation for correction.
[0135]
When the optical disk 1 having no eccentric component is rotated, the focal point of the laser beam does not cross the track, so that a TE signal having an amplitude as shown in FIG. 14 cannot be obtained. That is, the amplitude center of the TE signal necessary for determining the correlation equation cannot be obtained. However, a TE signal having the same amplitude as that shown in FIG. 14 can be obtained by vibrating the objective lens 2. For the reasons described above, in this embodiment, the TE lens having an amplitude is obtained in the same manner as in the first embodiment by vibrating the objective lens 2 by a minute amount.
[0136]
The amplitude center measurement circuit 37 measures the amplitude center of the LE signal supplied from the signal processing circuit 4 after the STRT signal supplied from the control circuit 10 has changed, and sends the measurement value to the holding circuit 22 and the holding circuit 23. Supply. The method for measuring the amplitude center of the LE signal is the same as that of the amplitude center measuring circuit 21 for measuring the amplitude center of the TE signal.
[0137]
The sine wave output circuit 38 supplies a sine wave with the 0 level as a reference to the adder circuit 39.
[0138]
The adder circuit 39 adds the output signal of the changeover switch 20 and the output signal of the sine wave output circuit 38 and supplies the sum to the b side of the changeover switch 8.
[0139]
Other configurations and operations thereof are the same as those in the first embodiment. The waveforms of the control signals output from the control circuit 10 are the same as those in FIG. 8 shown in the first embodiment.
[0140]
From the state in which the focus control is steadily operating and the optical disc 1 is stopped, the control circuit 10 outputs each signal as in the first embodiment. At this time, the adder circuit 39 adds the output signal of the changeover switch 20 and the output signal of the sine wave output circuit 38. For this reason, when the changeover switch 20 is switched to the a side, a sine wave based on the level at which the objective lens 2 is at the position p1 in FIG. 7 is applied to the tracking actuator in the optical pickup 3. That is, since the objective lens 2 vibrates around the position p1, the focal point of the laser light crosses the track of the optical disc 1, and the TE signal becomes a signal having an amplitude without rotating the optical disc 1. It is assumed that the amplitude at which the objective lens 2 is vibrated by the signal output from the sine wave output circuit 38 is sufficiently smaller than the positions p1 and p2 in FIG.
[0141]
On the other hand, when the changeover switch 20 is switched to the b side, a sine wave based on the level at which the objective lens 2 is at the position p2 in FIG. 7 is applied to the tracking actuator in the optical pickup 3. Therefore, since the objective lens 2 vibrates around the position p2, the TE signal becomes a signal having an amplitude.
[0142]
Here, since the objective lens 2 vibrates, the LE signal, which is a direct current component in the first embodiment, has an amplitude. Therefore, an amplitude center measurement circuit 37 is provided to measure the amplitude center of the LE signal in the same manner as the TE signal.
[0143]
That is, by rotating the objective lens 2 instead of rotating the optical disc 1, the signals A, B, C, and D in FIG. 7 can be measured as in the first embodiment.
[0144]
In the present embodiment, the sine wave output from the sine wave output circuit 38 is used to vibrate the objective lens 2, but it goes without saying that other signals such as a triangular wave may be used.
[0145]
In the present embodiment described above, in order to obtain a DC offset of the TE signal from the LE signal indicating the position of the objective lens 2 in the radial direction of the disc with respect to the optical pickup 3, the objective lens 2 is placed on the disc with respect to the optical pickup 3. A correlation equation between the direct current offset of the TE signal and the LE signal is obtained by vibrating in the radial direction. Then, the DC offset of the TE signal can be corrected by subtracting the DC offset calculated using the LE signal and the correlation equation from the TE signal.
[0146]
Furthermore, by oscillating the objective lens 2, it is possible to obtain a correlation formula between the DC offset of the TE signal and the LE signal even in the optical disc 1 having no eccentric component.
[0147]
【The invention's effect】
As described above, according to the present invention, the DC offset of the tracking error signal coincides with the signal indicating the position of the objective lens in the disk radial direction with respect to the optical pickup due to a circuit error, a difference in reflectance of each disk, and the like. Even if not, a tracking error signal correction function capable of correcting the DC offset of the tracking error signal can be realized. Furthermore, by performing tracking control using such a tracking error signal offset correction function, it is possible to provide an optical disc apparatus with improved information reading or writing reliability.
[Brief description of the drawings]
FIG. 1 is a block diagram of an optical disc apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining an outline of a push-pull method.
FIG. 3 is a waveform diagram of a tracking error signal.
FIG. 4 is a diagram for explaining a lens position signal generation unit;
FIG. 5 is a waveform diagram of a DC offset and a lens position signal.
FIG. 6 is a waveform diagram of DC offset correction in the conventional method.
FIG. 7 is a waveform diagram of a DC offset and a lens position signal.
FIG. 8 is an explanatory diagram showing signal waveforms according to the first embodiment of the present invention.
FIG. 9 is a block diagram of an optical disc apparatus according to a second embodiment of the present invention.
FIG. 10 is a waveform diagram of a corrected DC offset and a corrected lens position signal.
FIG. 11 is an explanatory diagram showing signal waveforms according to the second embodiment of the present invention.
FIG. 12 is a block diagram of an optical disc apparatus according to a third embodiment of the present invention.
FIG. 13 is a schematic diagram of a locus of a laser beam focus when there is an eccentricity.
FIG. 14 is a schematic waveform diagram of a tracking error signal when there is eccentricity.
FIG. 15 is an explanatory diagram showing signal waveforms according to a third embodiment of the present invention.
FIG. 16 is a block diagram of an optical disc apparatus according to a fourth embodiment of the present invention.
[Explanation of symbols]
1 Optical disc
2 Objective lens
3 Optical pickup
4 signal processing circuit
5 Focus servo control circuit
6 Focus drive circuit
7 Tracking servo control circuit
8 changeover switch
9 Tracking drive circuit
10 Control circuit
11 Thread servo control circuit
12 Thread drive circuit
13 Thread motor
14 Optical pickup feeding mechanism
15 Spindle motor
16 Spindle servo control circuit
17 Spindle drive circuit
18 Constant voltage output circuit
19 Constant voltage output circuit
20 changeover switch
21 Amplitude center measurement circuit
22 Holding circuit
23 Holding circuit
24 holding circuit
25 Holding circuit
26 Coefficient calculation circuit
27 Adder circuit
28 Multiplier circuit
29 Adder circuit
30 Adder circuit
31 Constant voltage output circuit
32 Adder circuit
33 Constant voltage output circuit
34 Division circuit
35 Rotation angle measurement circuit
36 Half rotation detection circuit
37 Amplitude center measurement circuit
38 Sine wave output circuit
39 Adder circuit
40 Laser diode
41 Beam splitter
42 Objective lens
43 Optical disc
44 Groove
45 rand
46 Photodetector
47 Photodetector
48 differential amplifier
49 Oscillating rod
50 Light emitting diode
51 Rotating shaft
52 fixed part
53a Photodetector
53b Photodetector
54 Objective lens position detector
55 Differential Amplifier

Claims (10)

An objective lens movable in a substantially radial direction of the disk;
Optical detection means for providing a tracking error signal with the objective lens;
Lens position detection means for detecting the position of the objective lens relative to the optical detection means;
Lens driving means for driving the objective lens to a predetermined position with respect to the optical detection means;
Tracking error signal correcting means for correcting a DC offset of the tracking error signal to zero when the objective lens is positioned at a midpoint with respect to the optical detecting means;
Lens position signal correction means for correcting the output of the lens position detection means to 0 when the objective lens is positioned at a midpoint with respect to the optical detection means;
The DC offset of the output of the tracking error signal correction means when the objective lens is in a predetermined position before disk reproduction and the output of the lens position signal correction means, and the lens position signal correction means during disk reproduction or recording Offset calculating means for calculating a DC offset of the tracking error signal using an output; and
Subtracting means for subtracting the calculated value of the offset calculating means from the output of the tracking error signal correcting means,
Further, the offset calculation means includes an offset detection means for detecting a DC offset of a signal output from the tracking error signal correction means before disk reproduction,
An output (E) of the offset detection means and an output (F) of the lens position correction means when the objective lens is positioned at a predetermined position with respect to the optical detection means by rotating the disk before reproduction;
Using the output (L) of the lens position correction means during disk playback or recording,
The offset calculation means outputs the output signal (of2) as
of2 = E × L / F
Output
A tracking error signal offset correction apparatus for correcting a DC offset of the tracking error signal. An objective lens movable in a substantially radial direction of the disk;
Optical detection means for providing a tracking error signal with the objective lens;
Lens position detection means for detecting the position of the objective lens relative to the optical detection means;
Lens driving means for driving the objective lens to a predetermined position with respect to the optical detection means;
When the objective lens is at two predetermined positions before the disk reproduction, a period in which the disk rotates more than half rotation passes, and the DC offset of the tracking error signal and the output of the lens position detection means in that period Offset calculating means for calculating a DC offset of the tracking error signal using the output of the lens position detecting means during disk reproduction or recording;
Subtracting means for subtracting the calculated value of the offset calculating means from the tracking error signal,
Further, the offset calculation means includes offset detection means for detecting a DC offset of the tracking error signal before disk reproduction,
The output (G) of the offset detection unit when the rotation of the disc has passed half or more after the disc is rotated before reproduction and the objective lens is positioned at the first predetermined position with respect to the optical detection unit. ) And the output (H) of the lens position detecting means,
The output (I) of the offset detection means when the rotation of the disk has passed half or more after the disk is rotated before reproduction and the objective lens is positioned at the second predetermined position with respect to the optical detection means. ) And the output (J) of the lens position detecting means,
Using the output (L) of the lens position detection means during disk playback or recording,
The offset calculating means outputs the output signal (of3) as
of3 = {(I−G) × (L−H) / (J−H)} + G
Output
A tracking error signal offset correction apparatus for correcting a DC offset of the tracking error signal. An objective lens movable in a substantially radial direction of the disk;
Optical detection means for providing a tracking error signal with the objective lens;
Lens position detection means for detecting the position of the objective lens relative to the optical detection means;
Lens vibration means for vibrating the objective lens in the radial direction of the disc around a predetermined position with respect to the optical detection means;
DC offset of the tracking error signal when the objective lens vibrates at two predetermined positions before disk reproduction and the output of the lens position detection means, and the output of the lens position detection means during disk reproduction or recording Offset calculating means for calculating a DC offset of the tracking error signal,
Subtracting means for subtracting the calculated value of the offset calculating means from the tracking error signal,
Further, the offset calculating means includes first offset detecting means for detecting a DC offset of the tracking error signal before disc reproduction, and second offset detecting means for detecting a DC offset of the output of the lens position detecting means. With
Output (K) of the first offset detecting means and the second offset detecting means when the objective lens vibrates around the first predetermined position with respect to the optical detecting means before reproducing the disc. Output (M) of
The output (N) of the first offset detecting means and the second offset detecting means when the objective lens vibrates around the second predetermined position with respect to the optical detecting means before reproducing the disc. Output (O) of
Using the output (L) of the lens position detection means during disk playback or recording,
The offset calculating means outputs the output signal (of4) as
of4 = {(N−K) × (LM) / (OM)} + K
Output
A tracking error signal offset correction apparatus for correcting a DC offset of the tracking error signal. The claim 1, 2 or 3,
The offset detection means includes a maximum value detection means for detecting a maximum value of the input signal, a minimum value detection means for detecting a minimum value of the input signal, a detection value of the maximum value detection means, and a detection of the minimum value detection means. A center calculating means for calculating a center value with the value,
A tracking error signal offset correction apparatus for outputting an amplitude center of an input signal. The claim 1, 2 or 3,
The tracking error signal offset correction apparatus, wherein the offset detection means removes a high frequency component by passing an input signal through a low-pass filter and outputs a DC offset component. An optical pickup having an objective lens movable in a substantially radial direction of the optical disc;
Optical detection means for providing a tracking error signal with the objective lens;
Lens position detection means for detecting the position of the objective lens relative to the optical detection means;
Lens driving means for driving the objective lens to a predetermined position with respect to the optical detection means;
Tracking error signal correcting means for correcting a DC offset of the tracking error signal to zero when the objective lens is positioned at a midpoint with respect to the optical detecting means;
Lens position signal correction means for correcting the output of the lens position detection means to 0 when the objective lens is positioned at a midpoint with respect to the optical detection means;
A direct current offset of the output of the tracking error signal correcting means and an output of the lens position signal correcting means when the objective lens is in a predetermined position before reproducing or recording information on the optical disc by the optical pickup; Offset calculating means for calculating a DC offset of the tracking error signal using the output of the lens position signal correcting means during reproduction or recording of the optical disc by:
Subtracting means for subtracting the calculated value of the offset calculating means from the output of the tracking error signal correcting means,
Further, the offset calculation means includes an offset detection means for detecting a DC offset of a signal output by the tracking error signal correction means before reproducing or recording information on the optical disc by the optical pickup,
The output (E) of the offset detection means when the objective lens is positioned at a predetermined position with respect to the optical detection means by rotating the optical disk before reproducing or recording information on the optical disk by the optical pickup. And the output (F) of the lens position correction means and the output (L) of the lens position correction means during reproduction or recording of the optical disk by the optical pickup,
The offset calculation means outputs the output signal (of2) as
of2 = E × L / F
Optical disk device that outputs An optical pickup having an objective lens movable in a substantially radial direction of the optical disc;
Optical detection means for providing a tracking error signal with the objective lens;
Lens position detection means for detecting the position of the objective lens relative to the optical detection means;
Lens driving means for driving the objective lens to a predetermined position with respect to the optical detection means;
When the objective lens is at two predetermined positions before the information on the optical disk is reproduced or recorded by the optical pickup, a period in which the optical disk rotates more than half rotation elapses, and the tracking error signal in that period Offset calculating means for calculating the DC offset of the tracking error signal using the direct current offset of the lens and the output of the lens position detecting means and the output of the lens position detecting means during reproduction or recording of the optical disk by the optical pickup. When,
Subtracting means for subtracting the calculated value of the offset calculating means from the tracking error signal,
Further, the offset calculation means includes an offset detection means for detecting a DC offset of a signal output by the tracking error signal correction means before reproducing or recording information on the optical disc by the optical pickup,
Before reproducing or recording information on the optical disk by the optical pickup, the optical disk is rotated, and the objective lens is positioned at a first predetermined position with respect to the optical detection means. The output (G) of the offset detection means and the output (H) of the lens position detection means when elapsed,
Before the information on the optical disk is reproduced or recorded by the optical pickup, the optical disk is rotated and the objective lens is positioned at a second predetermined position with respect to the optical detection means. The output (I) of the offset detection means and the output (J) of the lens position detection means when elapsed,
Using the output (L) of the lens position detecting means during reproduction or recording of the optical disc by the optical pickup,
The offset calculating means outputs the output signal (of3) as
of3 = {(I−G) × (L−H) / (J−H)} + G
Optical disk device that outputs An optical pickup having an objective lens movable in a substantially radial direction of the optical disc;
Optical detection means for providing a tracking error signal with the objective lens;
Lens position detection means for detecting the position of the objective lens relative to the optical detection means;
Lens vibration means for vibrating the objective lens in the radial direction of the disc around a predetermined position with respect to the optical detection means;
Before reproducing or recording information on the optical disc by the optical pickup, a DC offset of the tracking error signal when the objective lens vibrates at two predetermined positions and an output of the lens position detecting means, and by the optical pickup Offset calculating means for calculating a DC offset of the tracking error signal using the output of the lens position detecting means during reproduction or recording of the optical disc;
Subtracting means for subtracting the calculated value of the offset calculating means from the tracking error signal,
Further, the offset calculation means includes a first offset detection means for detecting a DC offset of the tracking error signal before reproducing or recording information on the optical disc by the optical pickup, and a direct current output from the lens position detection means. Second offset detecting means for detecting an offset,
The output of the first offset detection means when the objective lens vibrates around the first predetermined position with respect to the optical detection means before reproducing or recording information on the optical disk by the optical pickup. (K) and the output (M) of the second offset detecting means;
The output of the first offset detecting means when the objective lens vibrates around the second predetermined position with respect to the optical detecting means before reproducing or recording information on the optical disc by the optical pickup. (N) and the output (O) of the second offset detecting means;
Using the output (L) of the lens position detecting means during reproduction or recording of the optical disc by the optical pickup,
The offset calculating means outputs the output signal (of4) as
of4 = {(N−K) × (LM) / (OM)} + K
Optical disk device that outputs Claim 6 or 7 or 8
The offset detection means includes a maximum value detection means for detecting a maximum value of the input signal, a minimum value detection means for detecting a minimum value of the input signal, a detection value of the maximum value detection means, and a detection of the minimum value detection means. A center calculating means for calculating a center value with the value,
An optical disc apparatus that outputs the center of amplitude of an input signal. Claim 6 or 7 or 8
The offset detecting means is an optical disc apparatus that removes a high frequency component by passing an input signal through a low-pass filter and outputs a DC offset component.

Images