JP2005025873A - Optical pickup device and optical disk drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To write signals in an optical disk in an always optimum state. <P>SOLUTION: The optical pickup device comprises: a writing laser beam source 41 which writes the signal, a reading laser beam source 42 which reads the signal 21 just after being written to the optical disk by the writing laser beam source 41; a jitter amount measuring means 56 for measuring an amount of jitters which detects the amount of the jitters from a reproduction signal read by the reading laser beam source 42; and a control means 57 which controls the current to drive the writing laser beam source 42 based on the result of the measurement of the means for measuring the amount of jitters. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１８】
レーザ発光の遅れを小さくするためには、キャリア寿命τｓを小さくするか、前バイアス電流Ｉ１を閾値電流Ｉｔｈまで上げることが最も有効であり、また、前バイアス電流Ｉ１を閾値電流Ｉｔｈ以上に上げることも可能である。しかしながら、この場合、前バイアス電流Ｉ１による発光で光ディスクに書き込んでしまうことや、既に書き込んだ信号（ピット）を変形させてしまわないように注意することが必要である。また、光の立ち下がりには、いわゆるすそ引きと称されるダレＳｈ（図５（ｃ）参照）が生じ、制御しにくい要素であるが、例えば、後バイアス電流Ｉ３を制御することで微調整することは可能である。
【００１９】
レーザ光は立ち上がり後、緩和振動Ｆｍ（図５（ｃ）参照）を数回繰り返すが、この振動の大きさや減衰の程度も書き込み形状（ピット形状）に影響を与える可能性があり、うまく行えば、立ち上がりエッジを強調させる効果があるためジッターの低減には有効である。前バイアス電流Ｉ１のレベルや前バイアス電流Ｉ１と発光電流Ｉ２との間に別レベルのパルス電流（中間パルス）を挿入することやそのタイミングを制御することで効果を出せる可能性がある。一般に、戻り光が多い場合や初期にレーザ内部光が多い場合に緩和振動Ｆｍが抑制されやすいという性質があるので、前バイアス電流Ｉ１を増やすか前バイアス電流Ｉ１以上のレベルの中間パルスを挿入することで緩和振動Ｆｍの程度を抑えることが出来る。この制御もジッターの適正化に効果がある。
【００２０】
上記したように、ジッターは、例えば、設計通りの綺麗な形状のピットが形成されている等、書き込み時に如何に状態のいい信号が書き込まれているかどうかということが大きく関わっており、この信号の書き込み状態が悪ければ、その他の要因、例えば、フォーカスバイアス値を調整したり、ラジアルチルト位置を調整しても、信号の大本で、ジッターの発生要因があるわけで、いかんともし難い。
【００２１】
その意味で、特許文献２及び特許文献２は、何れも、信号の書き込みは正しく為されていることを前提に、如何に高品位の再生信号を得るかということを目的としており、信号の書き込み自体を如何に高品位に行うかという目的はそぐわないものである。しかも、高品の再生を目指すにしても、再生する光ディスクにテストパターンデータ及び該テストパターンデータの隣接トラックに記録された別のデータが必要である（特許文献２）とか、予め２つの学習領域にデータが記録された光ディスクを使用する（特許文献３）とか、特別の光ディスクを必要とし、汎用性がない。
【００２２】
特許文献１に示された技術にあっては、信号の書き込み自体を如何に高品位に行うかということを目的としていて、ジッターの根本原因を除去しようとしている点、高品位の信号の書き込みを行うために、駆動電流が大きな要因である点に着目している点で本発明の目指すところと同根である。
【００２３】
しかしながら、特許文献１に記載されて技術にあっては、予め、幾つかの異なるライトパワー毎にジッター量の測定を行い、ジッター量が最小となるライトパワーを求め、当該ライトパワーを最適ライトパワーとして記憶し、この最適ライトパワーを実際のデータ記録の時に利用するものである。つまり、予め決めたライトパワーを当該光ディスクの全域に亘って最適であると仮定して、後は、当該最適ライトパワーによって全ての領域について書き込みを行うものであって、その時々、その場所場所にとって常に最適な書き込みが行われるとは限らない。また、書き込み用レーザ光源しか持たない特許文献１の装置にあっては、ジッター量を測定し、それをフィードバック制御に利用して書き込みを行うことはできない。
【００２４】
本発明は、上記した事情に鑑みて為されたものであり、光ディスクに対して常に最良の状態の信号の書き込みを行うことを課題とする。
【００２５】
【課題を解決するための手段】
本発明光ピックアップ装置は、上記した課題を解決するために、光ディスクへの信号の書き込みを行う書き込み用レーザ光源と、上記書き込み用レーザ光源によって上記光ディスクに書き込まれた直後の信号を読み取る読取用レーザ光源と、上記読取用レーザ光源によって読み取った再生信号からジッター量を検出するジッター量測定手段と、上記ジッター量測定手段の測定結果に基づいて上記書き込み用レーザ光源を駆動する電流を制御する制御手段とを有するものである。
【００２６】
また、本発明光ディスクドライブ装置は、上記した課題を解決するために、光ディスクを回転させるディスク駆動手段と、ディスク駆動手段によって回転される光ディスクの半径方向に移動しながら光ディスクへの信号の書き込み及び書き込まれた信号の読取を行う光ピックアップ装置とを備え、上記光ピックアップ装置は、信号の書き込みを行う書き込み用レーザ光源と、上記書き込み用レーザ光源によって上記光ディスクに書き込まれた直後の信号を読み取る読取用レーザ光源と、上記読取用レーザ光源によって読み取った再生信号からジッター量を検出するジッター量測定手段と、上記ジッター量測定手段の測定結果に基づいて上記書き込み用レーザ光源を駆動する電流を制御する制御手段とを有するものである。
【００２７】
従って、本発明にあっては、光ディスクに書き込まれた直後の信号の書き込み状態に基づいて決定した最適な駆動電流によって信号の書き込みを行う。
【００２８】
【発明の実施の形態】
以下に、本発明の実施の形態を添付図面を参照して説明する。
【００２９】
図１は本発明にかかる光ディスクドライブ装置１０の主要構成部を示すブロック図である。
【００３０】
光ディスクドライブ装置１０は光ディスク２０を回転させるディスク駆動手段３０と光ディスク２０に対する信号の書き込み及び読取を行う光ピックアップ装置４０を備える。
【００３１】
ディスク駆動手段３０は例えば、スピンドルモータ、スピンドルモータによって回転されるディスクテーブル、ディスクテーブルに光ディスク２０を保持するチャッキング手段等を備える。
【００３２】
ここで光ディスク２０は、光パワーによって信号の書き込みが為される記録媒体ディスクであれば良く、例えば、ＣＤ−Ｒ、ＣＤ−ＲＷ（Ｃｏｍｐａｃｔ Ｄｉｓｃ Ｒｅｗｒｉｔａｂｌｅ）、ＭＤ（Ｍｉｎｉ−Ｄｉｓｃ）、ＤＶＤ−ＲＡＭ（Ｄｉｇｉｔａｌ Ｖｅｒｓａｔｉｌｅ Ｄｉｓｃ Ｒａｎｄａｍ Ａｃｃｅｓｓ Ｍｅｍｏｒｙ）、ＤＶＤ−Ｒ、ＤＶＤ＋Ｒ、ブルーレイディスク等種々のものが使用可能である。すなわち、光パワーによって、ピット形状の形成、反射率や屈折率の異種領域の形成、ファラデー回転、カー効果等の光磁気効果を利用して検知できる領域の形成、ホログラムの領域形成等種々の手法によって信号を記録するものを含む。
【００３３】
光ディスク２０はディスク駆動手段３０によって回転され、光ピックアップ装置４０は該回転される光ディスク２０の半径方向に移動しながら光ディスク２０の記録面にレーザ光をスポット状に照射し、該スポット光によって信号の書き込みをし、また、該スポット光が光ディスク２０の記録面で反射された戻り光を検出して信号の読取を行うものである。
【００３４】
光ピックアップ装置４０は、信号の書き込みに使用される書き込み用レーザ光源４１と光ディスク２０に記録された信号の読取に使用される読取用レーザ光源４２を備える。書き込み用レーザ光源４１としては、例えば、出力３０ｍＷ（ミリワット）以上のクラスの高出力の半導体レーザが、また、読取用レーザ光源４２としては、例えば、出力３ｍＷ（ミリワット）以上のクラスの低出力半導体レーザが一般に使用されるが、勿論これらに限定されるものではない。
【００３５】
書き込み用レーザ光源４１のレーザ光は図示しない対物レンズを含む光学系４３によって光ディスク２０の記録面にスポット照射される。これによって、光ディスク２０の記録面に、例えば、信号に応じた長さのピット２１、２１、・・・が形成される。
【００３６】
読取用レーザ光源４２のレーザ光は図示しない対物レンズを含む光学系４４によって光ディスク２０の記録面にスポット照射される。この読取用レーザ光がスポット照射される位置は、上記書込用レーザ光がスポット照射される位置の僅かに下流側、すなわち、書き込み用レーザ光の照射位置から光ディスク２０の回転方向に僅かに隔たった位置とされる。これによって、書込用レーザ光源４１によって書き込まれた直後の信号（ピット２１）の読取を行うことができる。
【００３７】
光ディスク２０の記録面にスポット照射され、且つ、そこで反射された読取レーザ光の戻り光は光学系４４を経て受光器４５によって受光される。
【００３８】
光ピックアップ装置４０は光ディスク２０の半径方向に移動しながら、スポット光を光ディスク２０に照射するので、移動部分を有する。そして、少なくともレーザ光源４１、４２、レーザ光源４１、４２のレーザ光を所望の経路に通す光学系及び受光器４５、対物レンズをフォーカス方向及びトラッキング方向に駆動するレンズ駆動部が上記移動部分を構成し、その他の部分、例えば、読取用レーザ光源４２のレーザ光によって読み取った再生信号からジッター量を検出し、その検出結果に基づいて書き込み用レーザ光源４１の駆動電流を制御する制御ブロック５０等は、通常、シャーシ等の固定部に構成される。
【００３９】
上記制御ブロック５０においては、上記受光器４５で受光した再生信号は、プリアンプ５１で増幅された後、波形等化器５２によって波形干渉の小さい信号に変えられ、さらに整形器５３によって信号の有無を表すパルス信号に変換され、ＰＬＬ５４に入力される。ＰＬＬ５４に入力された信号は復調器５５で復調された後データ信号として取り出される経路と、ジッター量測定手段５６によってジッター量の計測をされる経路とに分けられ、ジッター量測定手段５６によってジッター量が計測される。ここで使用されるジッター量測定手段５６は特殊なものである必要はなく、現在実用化されているジッター量測定手段、例えば、上記特許文献１、特許文献２及び特許文献３等に具体的に示されているジッター量測定手段を使用することができる。なお、上記データ信号として取り出された信号はさらに処理した後、スピーカ、外部機器等に出力することができる。
【００４０】
ジッター量測定手段５６で計測されたジッター量に関するデータが電流制御回路５７に送られ、該電流制御回路５７において、ジッター量に応じてどのような電流制御を行うかが決定され、その決定に従って書き込み用レーザ光源４１の駆動回路５８が駆動されて、所定の電流制御が行われる。すなわち、電流制御回路５７は、書き込み用レーザ光源４１を駆動する電流を制御する制御手段とされる。
【００４１】
上記電流制御回路５７においては、ジッター量測定手段５６で計測されたジッター量に応じて、上記前バイアス電流Ｉ１、発光電流Ｉ２、後バイアス電流Ｉ３が決められ、また、必要に応じて、前バイアス電流Ｉ１と発光電流Ｉ２との間に所定のパルス電流（中間パルス）をどのようなタイミングで挿入するか等の適宜の制御方法が決定される。
【００４２】
仮に、前バイアス電流Ｉ１の制御を行う場合を例にとって、その制御のフローを図２及び図３に示す。
【００４３】
光ディスク２０への信号の書き込み動作が開始される（スタート）と、先ず、予め設定されている標準設定値の前バイアス電流Ｉ１を有する駆動電流で書き込みを開始し（ステップ１（Ｓ１））、ステップ２（Ｓ２）へ進む。
【００４４】
ステップ２（Ｓ２）でジッター量を測定し、ステップ３（Ｓ３）にて上記測定されたジッター量が基準ジッター量（例えば、７％以下）より小さいか否かの判断をする。
【００４５】
ステップ３（Ｓ３）で基準ジッター量より小さい（ＹＥＳ）と判断された場合はステップ４（Ｓ４）に進み、基準ジッター量より小さくない（ＮＯ）と判断されたときはステップ５に進む。
【００４６】
ステップ４（Ｓ４）では書き込みが満足に行われていると判断してそのままの電流値で書き込みを続行する。
【００４７】
ステップ５（Ｓ５）では前回の前バイアス電流Ｉ１より値を上げた前バイアス電流Ｉ１によって書き込みを行いステップ６（Ｓ６）に進む。
【００４８】
ステップ６（Ｓ６）ではジッター量の測定を行いステップ７（Ｓ７）においてはステップ６（Ｓ６）にて測定した結果を前回のジッター量と比較し、前回より少ないか変わらない場合はステップ８（Ｓ８）に進み、前回より大きい場合にはステップ９（Ｓ９）に進む。
【００４９】
ステップ８（Ｓ８）の場合、すなわち、ジッター量が前回より少ないか変わらない場合はステップ１０（Ｓ１０）でジッター量が基準ジッター以下であるか否かの判断が為され、基準ジッター量以下の場合（ＹＥＳ）はステップ１１（Ｓ１１）に進んで、そのまま書き込みを実行し、基準ジッター量以下でない場合（ＮＯ）にはステップ５（Ｓ５）に戻る。
【００５０】
ステップ７（Ｓ７）で、ジッター量が前回より大きかったと判断された場合は、前バイアス電流Ｉ１の値を標準設定値より下げて書き込みを行い（ステップ９（Ｓ９））、ステップ１２（Ｓ１２）へと進む。
【００５１】
ステップ１２（Ｓ１２）ではジッター量の測定を行い、次いで、ステップ１３（Ｓ１３）でステップ１２（Ｓ１２）で測定したジッター量と前回のジッター量との比較を行い、前回のジッター量と同じか少ない場合にはステップ１４に進み、ジッター量が前回より大きい場合にはステップ１５（Ｓ１５）に進む。
【００５２】
ステップ１３（Ｓ１３）で測定したジッター量が前回のジッター量と同じか少ない場合（ステップ１４（Ｓ１４））ではステップ１６（Ｓ１６）でジッター量（ステップ１２（Ｓ１２）で測定した）が基準ジッター量以下であるか否かの判断が為され、基準ジッター量以下であれば（ＹＥＳ）そのまま書き込みを実行し、基準ジッター量以下でなければ（ＮＯ）ステップ９（Ｓ９）に戻る。
【００５３】
ステップ１３（Ｓ１３）での判断の結果、ジッター量が前回より大きくなっているとされた場合は、ステップ１５（Ｓ１５）で前バイアス電流Ｉ１を基準値に戻し、書き込み動作を終了する。
【００５４】
この図２及び図３のフローチャートでは、ジッター量が基準ジッター量より大きかった場合、まず、前バイアス電流Ｉ１を増加させる制御を行うようにした手順を示したが、始めに、前バイアス電流Ｉ１を下げる制御を行う手順としても良い。要するに、前バイアス電流を上げたり下げたりしながらジッター量が基準値以下になるまで制御を行う。
【００５５】
上記したフローチャートに示したジッター量の測定と判断、そして、前バイアス電流Ｉ１の制御は光ディスク２０への書き込みを行っている最中に継続的に為される。このジッター適正化の動作の設定は、自由に決めることができ、例えば、５分ごとに行うというように設定しておけば、５分ごとにジッター適正化の動作が為されることになる。あるいは、書き込みはじめと書き込み終了前に行うと設定しておけば、２度ジッター適正化の動作が行われることになる。
【００５６】
図２及び図３ではジッター量測定の結果に基づいて前バイアス電流Ｉ１の値を制御する場合を示したが、本発明における駆動電流の制御が、前バイアス電流Ｉ１の制御のみを為すものでないことは前記したとおりである。しかしながら、前バイアス電流Ｉ１の制御がジッター量の減少にとって有効な手段であることを図４に示す。
【００５７】
図４は、前バイアス電流Ｉ１を変化させ、その都度ジッター量を測定した結果をプロットした（中抜き丸印で示す）ものであるが、プロットした点をつないだ曲線で分かるように、ほぼ舟形の形状を示す。すなわち、前バイアス電流Ｉ１は適正値から大きすぎても少なすぎてもジッター量は増加し、書き込み品位は低下するものである。
【００５８】
本発明にあっては、光ディスクへの書き込みが為された直後の書き込み信号を再生して、該再生信号からジッター量を測定し、その測定結果に基づいて書き込み用レーザ光源の駆動電流を制御するものであるので、実時間（ｒｅａｌ−ｔｉｍｅ）での書き込み最適条件を設定することができる。そのため、光ディスクに予め、ジッター測定のための特定のトラックや記録領域を設けておく必要がなく、一般に市販されている光ディスクを使用して、当該光ディスクに関しての最適条件で書き込みを為すことができる。
【００５９】
また、書き込み中にリアルタイムで書き込み状態を確認することができるため、無駄な記録をすることがなくなる。
【００６０】
さらに、現実にはジッターが多くて記録が不可能であるといわれていた高速での高品位な信号の記録を実現することができ、超高速での記録を可能にすることができる。
【００６１】
さらにまた、ＣＤ系からＤＶＤ系へ、さらに、ブルーレイディスク系へと展開してきている高密度記録において、ますます厳しくなるジッター管理を容易にし、失敗の少ない記録が可能になる。
【００６２】
なお、上記した実施の形態では、書き込み用レーザ光源の駆動電流を制御することについてのみ説明したが、ジッターの悪化は、この（書き込みパルス電流波形）ほかにも、光ディスクの光ピックアップの光軸とのチルト角やスピンドルモータの回転揺らぎ（回転サーボ揺れ）等にも依存する。そこで、上記した駆動電流の制御に加えて、ジッター測定の結果をチルトサーボ回路やスピンドル制御回路等にフィードバックすれば、さらなるジッターの低減が可能になる。
【００６３】
その他、上記した実施の形態において示した各部の形状及び構造並びに手法は、何れも本発明を実施するに際して行う具体化のほんの一例を示したものにすぎず、これらによって本発明の技術的範囲が限定的に解釈されるようなことがあってはならないものである。
【００６４】
【発明の効果】
以上に記載したところから明らかなように、本発明光ピックアップ装置は、光ディスクに光パワーによって信号の書き込みをする光ピックアップ装置であって、信号の書き込みを行う書き込み用レーザ光源と、上記書き込み用レーザ光源によって上記光ディスクに書き込まれた直後の信号を読み取る読取用レーザ光源と、上記読取用レーザ光源によって読み取った再生信号からジッター量を検出するジッター量測定手段と、上記ジッター量測定手段の測定結果に基づいて上記書き込み用レーザ光源を駆動する電流を制御する制御手段とを有することを特徴とする。
【００６５】
また、本発明光ディスクドライブ装置は、光ディスクに光パワーによって信号の書き込み及び書き込まれた信号の読取を行う光ディスクドライブ装置であって、光ディスクを回転させるディスク駆動手段と、ディスク駆動手段によって回転される光ディスクの半径方向に移動しながら光ディスクへの信号の書き込み及び書き込まれた信号の読取を行う光ピックアップ装置とを備え、上記光ピックアップ装置は、信号の書き込みを行う書き込み用レーザ光源と、上記書き込み用レーザ光源によって上記光ディスクに書き込まれた直後の信号を読み取る読取用レーザ光源と、上記読取用レーザ光源によって読み取った再生信号からジッター量を検出するジッター量測定手段と、上記ジッター量測定手段の測定結果に基づいて上記書き込み用レーザ光源を駆動する電流を制御する制御手段とを有することを特徴とする。
【００６６】
従って、本発明にあっては、光ディスクに書き込まれた直後の信号を再生してジッター量を測定し、該ジッター量の測定結果に基づいて決定した最適な駆動電流によって信号の書き込みを行う。そのため、ジッター量を低減した常に最適な状態での信号の書き込みを行うことができる。よって、記録の高速化及び記録の高密度化に対応することができる。
【００６７】
また、光ディスクに予め特別の学習領域やテストパターンデータ等を記録しておく必要がなく、そのため、一般に市販されている光ディスクに対して常に最適な状態での信号の記録を行うことができ、汎用性の高いものとなる。
【図面の簡単な説明】
【図１】本発明の実施の形態の主要構成部を示すブロック図である。
【図２】本発明実施の形態にかかるフローチャートである。
【図３】図２示した手順に続く手順を示すフローチャート図である。
【図４】前バイアス電流とジッター量との相関関係を示すグラフ図である。
【図５】書き込み用レーザの駆動電流と光ディスクに書き込まれた波形との関係を示すグラフ図である。
【符号の説明】
１０…光ディスクドライブ装置、２０…光ディスク、２１…ピット（光ディスクに書き込まれた信号）、３０…ディスク駆動手段、４０…光ピックアップ装置、４１…書き込み用レーザ光源、４２…読取用レーザ光源、５６…ジッター量測定手段、５７…電流制御回路（制御手段）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel optical pickup device and optical disc drive device. More specifically, the present invention relates to a technology that enables high-quality signal recording on an optical disc.
[0002]
[Prior art]
Various optical discs such as CD-R (Compact Disc Recordable), DVD-R (Digital Versatile Disc Recordable), and Blu-ray Disc (Bru-ray Disc) have become widespread, and further double-speed recording competition has intensified, exceeding 40 times speed. Ultra high-speed recording devices have been proposed.
[0003]
However, when various optical discs are used for high-speed recording, deterioration of the writing quality has become a problem, and even when satisfactory writing cannot be performed, it frequently occurs.
[0004]
Further, regarding sound source recording and video recording that require high quality, there has been an increasing dissatisfaction that the quality of optical disks is poor and difficult to use.
[0005]
The cause of the above problems cannot be simply narrowed down to one, but in most cases, the write signal jitter failure is the majority, and the disk drive device supports various disks to optimize jitter. Therefore, it is possible to improve the writing quality. In particular, when recording on a high-density recording optical disc such as a Blu-ray disc or a multilayer disc, the pit shape is finer than that of a conventional optical disc and the standard becomes stricter. Therefore, jitter management is very important. It becomes.
[0006]
Therefore, some proposals have been made to detect a jitter amount and control parameters affecting the jitter amount such as write power, focus servo, and radial tilt so that the jitter amount is reduced.
[0007]
For example, in Patent Document 1, the jitter amount is measured for several different write powers, the write power that minimizes the jitter amount is obtained, the write power is stored as the optimum write power, and the optimum write power is stored. The power is stored by the memory means and used for actual data recording.
[0008]
In Patent Document 2, test pattern data and other data are recorded on an adjacent optical disk to be reproduced, and the test pattern data is reproduced while changing the focus bias. Find the focus bias value that minimizes the amount. A signal obtained by adding a focus error signal to the focus bias value is used as an optimum focus servo signal, and reproduction of the optical disc is performed using the optimum focus servo signal, thereby improving the reproduction characteristics of the optical disc.
[0009]
Further, in Patent Document 3, when an optical disk in which data is recorded in two learning areas is used in advance, and the optical disk is mounted on an optical disk apparatus (optical disk drive apparatus), the optical disk apparatus reproduces the learning area. Start. Measure the jitter amount from the playback signal in the learning area, find the radial tilt position that minimizes the jitter amount in the inner and outer peripheral learning areas while changing the radial tilt position, and determine it as the optimum radial tilt position in each area . Reproduction with high reliability is performed by performing reproduction of the optical disc at the optimum radial tilt position.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-273078 (paragraph [0035], FIG. 5 and FIG. 6)
[Patent Document 2]
JP 11-273097 A (paragraphs [0001], [0008], [0012])
[Patent Document 3]
JP-A-8-45081 (paragraphs [0031], [0043] to [0051])
[0011]
[Problems to be solved by the invention]
By the way, the causes of jitter include crosstalk due to reflected diffracted light from adjacent tracks due to radial tilt (tilt in the disc radial direction), off-track (deviation from the track center of the spot light), and tangential tilt (recording). There are various things such as track tangential inclination), defocus (defocus), disc aging, decrease in playback signal amplitude due to circuit noise, waveform interference, etc. First of all, recording (writing) itself is solid For example, if the pit shape (including the length) is accurately formed, it is known that a considerable part of the jitter is eliminated. In order to perform accurate recording, the driving current of the writing laser occupies a large factor.
[0012]
FIG. 5 shows the relationship between the drive current of the writing laser and the waveform written on the optical disc (the waveform reproduced from the pit shape formed on the optical disc). In each drawing of FIG. 5, the horizontal axis represents the time axis, and the vertical axis represents each numerical value, which is expressed as increasing in the arrow direction.
[0013]
5A shows the driving current I supplied to the writing semiconductor laser, and FIG. 5B shows the carrier N injected into the semiconductor laser by supplying the driving current of FIG. 5A. 5 (c) shows the emission waveform S of the semiconductor laser by the carrier injection of FIG. 5 (b), and FIG. 5 (d) shows the reproduction waveform P by the pits formed on the optical disk with the laser light having the waveform of FIG. Are shown respectively.
[0014]
First, consider driving a semiconductor laser with a current waveform as shown in FIG. Actually, it is often driven with a pulse waveform, but here, in order to explain the principle, the simplest basic waveform will be considered. This current waveform is a waveform having a shape similar to a pit shape to be recorded, and an I1 level current is initially supplied as a pre-bias current, and a laser light output can be obtained during recording. Then, after laser driving (writing operation) is performed for a desired length, the current is lowered to a post-bias current at the I3 level.
[0015]
By driving with current as shown in FIG. 5A, the carriers injected into the semiconductor laser change as shown in FIG. 5B, and as a result, the laser emission operation as shown in FIG. 5C is performed. Is called.
[0016]
The relationship between the drive current and the light emission waveform described above is known by rate equation analysis of a semiconductor laser. At this time, the problem is the oscillation delay of laser emission. The oscillation delay Td (see FIG. 5C) when the current is increased from I1 to I2 at time t = 0 occurs because it takes time until the number of injected carriers n reaches the threshold value nth. This oscillation time The delay Td is expressed by equation (1).
[0017]
[Expression 1]

[0018]
In order to reduce the delay in laser emission, it is most effective to reduce the carrier lifetime τs or increase the pre-bias current I1 to the threshold current Ith, and to increase the pre-bias current I1 to the threshold current Ith or more. Is also possible. However, in this case, it is necessary to be careful not to write on the optical disc by light emission by the pre-bias current I1 or to change the already written signal (pit). In addition, the fall of the light causes sagging Sh (referring to FIG. 5C), which is so-called trailing, and is an element that is difficult to control. For example, fine adjustment is performed by controlling the rear bias current I3. It is possible to do.
[0019]
After the laser beam rises, the relaxation vibration Fm (see FIG. 5C) is repeated several times. The magnitude of the vibration and the degree of attenuation may affect the writing shape (pit shape). Since it has the effect of enhancing the rising edge, it is effective in reducing jitter. There is a possibility that an effect can be obtained by inserting another level of pulse current (intermediate pulse) between the level of the pre-bias current I1 or between the pre-bias current I1 and the light emission current I2 and controlling the timing thereof. In general, since there is a property that the relaxation oscillation Fm is easily suppressed when there is a large amount of return light or when there is a large amount of laser internal light in the initial stage, the pre-bias current I1 is increased or an intermediate pulse having a level equal to or higher than the pre-bias current I1 is inserted. Thus, the degree of relaxation vibration Fm can be suppressed. This control is also effective in optimizing jitter.
[0020]
As described above, jitter is greatly related to how well a signal is written at the time of writing, for example, a pit having a beautiful shape as designed is formed. If the writing state is bad, even if other factors, for example, the focus bias value or the radial tilt position are adjusted, there is a factor in generating jitter in a large signal, and it is difficult to do so.
[0021]
In that sense, both Patent Document 2 and Patent Document 2 are aimed at how to obtain a high-quality reproduction signal on the assumption that signal writing is performed correctly. The purpose of how to do it with high quality is not appropriate. Moreover, even if high quality reproduction is aimed, test pattern data and other data recorded on the adjacent track of the test pattern data are necessary on the optical disc to be reproduced (Patent Document 2), or two learning areas in advance. In other words, an optical disk on which data is recorded is used (Patent Document 3) or a special optical disk is required, and there is no versatility.
[0022]
The technique disclosed in Patent Document 1 aims to remove the root cause of jitter for the purpose of how to perform signal writing itself with high quality, and to write high quality signals. In order to do this, it is the same as the target of the present invention in that the drive current is a major factor.
[0023]
However, in the technique described in Patent Document 1, the jitter amount is measured in advance for each of several different write powers, the write power that minimizes the jitter amount is obtained, and the write power is determined as the optimum write power. And the optimum write power is used at the time of actual data recording. In other words, assuming that the predetermined write power is optimal over the entire area of the optical disk, the entire area is written with the optimal write power. Optimal writing is not always performed. Further, in the apparatus of Patent Document 1 having only a writing laser light source, writing cannot be performed by measuring the jitter amount and using it for feedback control.
[0024]
The present invention has been made in view of the above circumstances, and an object of the present invention is to always write a signal in the best state on an optical disc.
[0025]
[Means for Solving the Problems]
In order to solve the above-described problems, an optical pickup device of the present invention includes a writing laser light source for writing a signal to an optical disk, and a reading laser for reading a signal immediately after being written to the optical disk by the writing laser light source. A light source, a jitter amount measuring means for detecting a jitter amount from a reproduction signal read by the reading laser light source, and a control means for controlling a current for driving the writing laser light source based on a measurement result of the jitter amount measuring means It has.
[0026]
Further, in order to solve the above-described problems, the optical disk drive apparatus of the present invention writes and writes signals to the optical disk while moving in the radial direction of the optical disk rotated by the disk driving means and the disk driving means rotating the optical disk. An optical pickup device that reads the read signal, and the optical pickup device reads the signal immediately after being written on the optical disc by the writing laser light source for writing the signal and the writing laser light source. A laser light source, a jitter amount measuring means for detecting a jitter amount from a reproduction signal read by the reading laser light source, and a control for controlling a current for driving the writing laser light source based on a measurement result of the jitter amount measuring means Means.
[0027]
Therefore, in the present invention, the signal is written with the optimum driving current determined based on the signal writing state immediately after being written on the optical disk.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0029]
FIG. 1 is a block diagram showing the main components of an optical disk drive apparatus 10 according to the present invention.
[0030]
The optical disk drive device 10 includes a disk drive unit 30 that rotates the optical disk 20 and an optical pickup device 40 that writes and reads signals to and from the optical disk 20.
[0031]
The disk drive means 30 includes, for example, a spindle motor, a disk table rotated by the spindle motor, chucking means for holding the optical disk 20 on the disk table, and the like.
[0032]
Here, the optical disk 20 may be a recording medium disk on which signals are written by optical power. For example, CD-R, CD-RW (Compact Disc Rewriteable), MD (Mini-Disc), DVD-RAM ( Various types such as Digital Versatile Disc Random Access Memory), DVD-R, DVD + R, and Blu-ray Disc can be used. That is, various methods such as formation of pit shapes, formation of heterogeneous regions of reflectivity and refractive index, formation of regions that can be detected using magneto-optical effects such as Faraday rotation, Kerr effect, hologram region formation, etc. Including those that record signals.
[0033]
The optical disk 20 is rotated by the disk drive means 30, and the optical pickup device 40 irradiates the recording surface of the optical disk 20 in a spot shape while moving in the radial direction of the rotated optical disk 20. Writing is performed, and a signal is read by detecting the return light reflected from the recording surface of the optical disc 20 by the spot light.
[0034]
The optical pickup device 40 includes a writing laser light source 41 used for signal writing and a reading laser light source 42 used for reading a signal recorded on the optical disc 20. The writing laser light source 41 is, for example, a high-power semiconductor laser of a class having an output of 30 mW (milliwatt) or more, and the reading laser light source 42 is, for example, a low-power semiconductor of a class having an output of 3 mW (milliwatt) or more. Lasers are commonly used, but of course are not limited to these.
[0035]
The laser beam of the writing laser light source 41 is spot-irradiated on the recording surface of the optical disc 20 by an optical system 43 including an objective lens (not shown). As a result, for example, pits 21, 21,... Having a length corresponding to a signal are formed on the recording surface of the optical disc 20.
[0036]
The laser beam of the reading laser light source 42 is spot-irradiated on the recording surface of the optical disc 20 by an optical system 44 including an objective lens (not shown). The position where the reading laser beam is irradiated with the spot is slightly downstream of the position where the writing laser beam is irradiated with the spot, that is, slightly spaced from the irradiation position of the writing laser beam in the rotation direction of the optical disc 20. It is considered as the only position. As a result, the signal (pit 21) immediately after being written by the writing laser light source 41 can be read.
[0037]
The return light of the reading laser beam that is irradiated with the spot on the recording surface of the optical disc 20 and reflected there is received by the light receiver 45 through the optical system 44.
[0038]
Since the optical pickup device 40 irradiates the optical disc 20 with the spot light while moving in the radial direction of the optical disc 20, it has a moving portion. Then, at least the laser light sources 41 and 42, the optical system that passes the laser light of the laser light sources 41 and 42 through a desired path, the light receiver 45, and the lens driving unit that drives the objective lens in the focus direction and the tracking direction constitute the moving part. A control block 50 or the like that detects the jitter amount from the reproduction signal read by the laser beam of the reading laser light source 42, for example, and controls the drive current of the writing laser light source 41 based on the detection result is provided. Usually, it is configured in a fixed part such as a chassis.
[0039]
In the control block 50, the reproduction signal received by the light receiver 45 is amplified by the preamplifier 51, converted to a signal having a small waveform interference by the waveform equalizer 52, and the presence / absence of the signal is further detected by the shaper 53. It is converted into a pulse signal to be expressed and input to the PLL 54. The signal input to the PLL 54 is divided into a path to be taken out as a data signal after being demodulated by the demodulator 55, and a path in which the jitter amount is measured by the jitter amount measuring means 56. The jitter amount measuring means 56 Is measured. The jitter amount measuring means 56 used here does not need to be special, and is specifically described in the jitter amount measuring means currently in practical use, for example, Patent Document 1, Patent Document 2, Patent Document 3, and the like. The means for measuring the amount of jitter shown can be used. The signal extracted as the data signal can be further processed and output to a speaker, an external device, or the like.
[0040]
Data relating to the jitter amount measured by the jitter amount measuring means 56 is sent to the current control circuit 57, where the current control circuit 57 determines what kind of current control is performed in accordance with the jitter amount, and writes according to the determination. The drive circuit 58 of the laser light source 41 is driven, and predetermined current control is performed. That is, the current control circuit 57 is a control unit that controls a current for driving the writing laser light source 41.
[0041]
In the current control circuit 57, the pre-bias current I1, the light emission current I2, and the post-bias current I3 are determined according to the jitter amount measured by the jitter amount measuring means 56, and, if necessary, the pre-bias An appropriate control method is determined such as at what timing a predetermined pulse current (intermediate pulse) is inserted between the current I1 and the light emission current I2.
[0042]
As an example, the control flow of the pre-bias current I1 is shown in FIGS. 2 and 3. FIG.
[0043]
When a signal writing operation to the optical disc 20 is started (start), first, writing is started with a drive current having a pre-bias current I1 having a preset standard setting value (step 1 (S1)). Go to 2 (S2).
[0044]
In step 2 (S2), the jitter amount is measured, and in step 3 (S3), it is determined whether or not the measured jitter amount is smaller than a reference jitter amount (for example, 7% or less).
[0045]
If it is determined in step 3 (S3) that the amount is smaller than the reference jitter amount (YES), the process proceeds to step 4 (S4). If it is determined that the amount is not smaller than the reference jitter amount (NO), the process proceeds to step 5.
[0046]
In step 4 (S4), it is determined that the writing is performed satisfactorily, and the writing is continued with the current value as it is.
[0047]
In step 5 (S5), writing is performed with the previous bias current I1 whose value is higher than the previous previous bias current I1, and the process proceeds to step 6 (S6).
[0048]
In step 6 (S6), the amount of jitter is measured. In step 7 (S7), the result measured in step 6 (S6) is compared with the previous amount of jitter. ), And if larger than the previous time, proceed to Step 9 (S9).
[0049]
In the case of step 8 (S8), that is, when the jitter amount is less than or not changed from the previous time, it is determined in step 10 (S10) whether or not the jitter amount is less than the reference jitter. In (YES), it progresses to step 11 (S11), and writing is performed as it is, and when it is not below a reference | standard jitter amount (NO), it returns to step 5 (S5).
[0050]
If it is determined in step 7 (S7) that the amount of jitter is larger than the previous time, writing is performed by lowering the value of the previous bias current I1 from the standard setting value (step 9 (S9)), and then to step 12 (S12). Proceed with
[0051]
In step 12 (S12), the jitter amount is measured, and then in step 13 (S13), the jitter amount measured in step 12 (S12) is compared with the previous jitter amount, which is equal to or less than the previous jitter amount. If so, the process proceeds to step 14, and if the jitter amount is larger than the previous time, the process proceeds to step 15 (S15).
[0052]
When the jitter amount measured in step 13 (S13) is the same as or less than the previous jitter amount (step 14 (S14)), the jitter amount (measured in step 12 (S12)) is the reference jitter amount in step 16 (S16). It is determined whether or not it is less than the reference jitter amount (YES), the writing is executed as it is, and if it is not less than the reference jitter amount (NO), the process returns to Step 9 (S9).
[0053]
If the result of determination in step 13 (S13) is that the amount of jitter is greater than the previous time, the previous bias current I1 is returned to the reference value in step 15 (S15), and the write operation is terminated.
[0054]
In the flowcharts of FIG. 2 and FIG. 3, when the jitter amount is larger than the reference jitter amount, the procedure for performing the control to increase the pre-bias current I1 is shown first. It is good also as a procedure which performs control to lower. In short, control is performed until the amount of jitter falls below the reference value while increasing or decreasing the pre-bias current.
[0055]
The measurement and determination of the jitter amount shown in the flowchart and the control of the pre-bias current I1 are continuously performed while writing to the optical disc 20 is being performed. The setting of the jitter optimizing operation can be freely determined. For example, if it is set to be performed every 5 minutes, the jitter optimizing operation is performed every 5 minutes. Alternatively, if it is set to be performed at the beginning of writing and before the end of writing, an operation for optimizing the jitter is performed twice.
[0056]
FIGS. 2 and 3 show the case where the value of the pre-bias current I1 is controlled based on the result of jitter amount measurement, but the drive current control in the present invention does not only control the pre-bias current I1. Is as described above. However, FIG. 4 shows that the control of the pre-bias current I1 is an effective means for reducing the amount of jitter.
[0057]
FIG. 4 is a plot of the results of measuring the amount of jitter each time the pre-bias current I1 is changed (indicated by a hollow circle). As shown by the curve connecting the plotted points, The shape of is shown. That is, if the pre-bias current I1 is too large or too small from an appropriate value, the amount of jitter increases and the writing quality decreases.
[0058]
In the present invention, the write signal immediately after writing to the optical disk is reproduced, the jitter amount is measured from the reproduction signal, and the drive current of the writing laser light source is controlled based on the measurement result. Therefore, it is possible to set the optimum write condition in real-time. Therefore, it is not necessary to provide a specific track or recording area for jitter measurement in advance on the optical disc, and writing can be performed under the optimum conditions for the optical disc using a commercially available optical disc.
[0059]
In addition, since the writing state can be confirmed in real time during writing, useless recording is not performed.
[0060]
Furthermore, it is possible to realize high-quality signal recording at a high speed, which is said to be impossible to record due to a large amount of jitter, and to enable super-high-speed recording.
[0061]
Furthermore, in high-density recording that has been developed from the CD system to the DVD system and further to the Blu-ray Disc system, it becomes easier to manage jitters that are becoming increasingly severe, and recording with fewer failures becomes possible.
[0062]
In the above-described embodiment, only the control of the drive current of the writing laser light source has been described. However, in addition to this (write pulse current waveform), the deterioration of the jitter is related to the optical axis of the optical pickup of the optical disc. This also depends on the tilt angle of the motor and the rotational fluctuation (rotational servo fluctuation) of the spindle motor. Therefore, in addition to the control of the drive current described above, the jitter can be further reduced by feeding back the result of jitter measurement to a tilt servo circuit, a spindle control circuit, or the like.
[0063]
In addition, the shapes, structures, and methods of the respective parts shown in the above-described embodiments are merely examples of implementations in carrying out the present invention, and the technical scope of the present invention is thereby limited. It should not be interpreted in a limited way.
[0064]
【The invention's effect】
As is apparent from the above description, the optical pickup device of the present invention is an optical pickup device for writing a signal to an optical disk by optical power, and includes a writing laser light source for writing a signal and the writing laser. A reading laser light source for reading a signal immediately after being written on the optical disk by a light source, a jitter amount measuring means for detecting a jitter amount from a reproduction signal read by the reading laser light source, and a measurement result of the jitter amount measuring means And a control means for controlling a current for driving the writing laser light source.
[0065]
The optical disk drive apparatus of the present invention is an optical disk drive apparatus for writing a signal to the optical disk and reading the signal written by optical power, and a disk driving means for rotating the optical disk, and an optical disk rotated by the disk driving means. An optical pickup device that writes a signal to an optical disc and reads the written signal while moving in the radial direction of the optical disk, and the optical pickup device includes a writing laser light source that writes a signal and the writing laser. A reading laser light source for reading a signal immediately after being written on the optical disk by a light source, a jitter amount measuring means for detecting a jitter amount from a reproduction signal read by the reading laser light source, and a measurement result of the jitter amount measuring means Based on the above writing laser And having a control means for controlling a current for driving the source.
[0066]
Therefore, in the present invention, the signal immediately after being written on the optical disk is reproduced to measure the jitter amount, and the signal is written with the optimum driving current determined based on the measurement result of the jitter amount. Therefore, signal writing can be performed in an always optimal state with a reduced amount of jitter. Therefore, it is possible to cope with higher recording speed and higher recording density.
[0067]
In addition, it is not necessary to record special learning areas, test pattern data, etc. in advance on the optical disc, so that it is possible to always record signals in an optimal state with respect to generally available optical discs. It becomes a high quality thing.
[Brief description of the drawings]
FIG. 1 is a block diagram showing main components of an embodiment of the present invention.
FIG. 2 is a flowchart according to the embodiment of the present invention.
FIG. 3 is a flowchart showing a procedure following the procedure shown in FIG. 2;
FIG. 4 is a graph showing a correlation between a pre-bias current and a jitter amount.
FIG. 5 is a graph showing a relationship between a driving current of a writing laser and a waveform written on an optical disc.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Optical disk drive apparatus, 20 ... Optical disk, 21 ... Pit (signal written in optical disk), 30 ... Disk drive means, 40 ... Optical pick-up apparatus, 41 ... Write laser light source, 42 ... Read laser light source, 56 ... Jitter amount measuring means, 57... Current control circuit (control means)

Claims (2)

An optical pickup device for writing a signal to an optical disc by optical power,
A writing laser light source for writing a signal;
A reading laser light source for reading a signal immediately after being written on the optical disc by the writing laser light source;
A jitter amount measuring means for detecting a jitter amount from a reproduction signal read by the reading laser light source;
An optical pickup apparatus comprising: control means for controlling a current for driving the writing laser light source based on a measurement result of the jitter amount measuring means. An optical disc drive apparatus for writing a signal to an optical disc by optical power and reading the written signal,
Disk drive means for rotating the optical disk;
An optical pickup device for writing a signal to the optical disc and reading the written signal while moving in the radial direction of the optical disc rotated by the disc driving means,
The optical pickup device includes a writing laser light source for writing a signal, a reading laser light source for reading a signal immediately after being written on the optical disc by the writing laser light source, and a reproduction signal read by the reading laser light source. An optical disk drive device comprising: a jitter amount measuring means for detecting a jitter amount from the jitter amount; and a control means for controlling a current for driving the writing laser light source based on a measurement result of the jitter amount measuring means.

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