JP3982079B2 - Optical recording / reproducing apparatus, focus bias setting method - Google Patents

Description

により示される演算を行うことで、サンプルしたｍ個のΔＴｉ，ΔＴｉ，ΔＴｉ・・・についての平均値を得る。そして、この平均値を利用して、
【数２】

により示す演算を実行することで、ジッター値ＪＴを得る。この（数２）により示されるジッター値ＪＴは、サンプルされたｍ個のΔＴｉ，ΔＴｉ・・・間の変動幅を示すものとなる。
このようにして算出されたジッター値ＪＴは、システムコントローラ１０に対して入力される。
【００６４】
なお、上記サンプル数ｍは、ジッター値ＪＴができるだけ高精度で得られることと、ジッター値ＪＴの算出に要する時間が必要以上に長くならないようにすることを考慮して任意に設定されればよい。
また、ジッター検出回路２１を形成する各部の内部構成は各種考えられるためここでは、詳しい図示は省略する。例えば、ΔＴ検出回路３１及びジッター値算出回路３２等は、各種デジタル回路や論理回路を組み合わせることで、上記した動作を実現することが容易に可能とされるものである。
また、上記（数１）（数２）により示したジッター値ＪＴの算出方法はあくまでも一例であり、他の演算式等を利用して行われてもよいものである。
【００６５】
そして、第２例の場合においては、テスト記録としては先の第１例の場合と同様に行われるが、このテスト記録により記録されたデータを再生して信号特性を計測する際、上記のようにして得られたジッター値ＪＴをサンプル値として取り込み、テスト記録時において設定されていたフォーカスバイアスと関連づけて、例えばシステムコントローラ１０内部のＲＡＭに保持することになる。
【００６６】
ここで、図１０に上記のようにしてサンプルを行った結果として、再生信号のジッター値と、テスト記録時において設定されていたフォーカスバイアスとの関係が示されている。この図においては、横軸がフォーカスバイアスとされ、縦軸がジッター値とされる。そして、図の座標内には×印により６つのサンプルポイントＡ〜Ｆが示されている。ジッター値は、良好であるほど小さい値を示すので、先に図６に示した変調度とフォーカスバイアスとの関係に対して、逆の傾向となる。
【００６７】
例えば図１０に示すようにして、再生信号のジッター値とテスト記録時に設定されたフォーカスバイアスとの関係がサンプル情報として得られさえすれば、最適とされるフォーカスバイアスは、先に第１例で述べたと同様にして求めることができる。
つまりは、サンプルポイントのうちで、最も小さなジッター値（最良値）が得られたときのフォーカスバイアスを最適値として設定することができる。
また、最もジッター値の変化率が低いとされるサンプル領域を見いだし、この領域に対応するフォーカスバイアスを最適なフォーカスバイアスとして設定することができる。
また、ジッター値が予め設定した所定値に近く、かつ、ジッター値としての極値を挟む２つのサンプルポイントの平均値、或いは相加平均値をフォーカスバイアスの最適値として設定することができる。
更には、サンプル結果に基づいて、信号特性の極値を算出、更にこの極値に対応する推定されるフォーカスバイアスを算出するための数値演算処理を実行することで最適値としてのフォーカスバイアスを設定することができる。
【００６８】
４．処理動作
続いて、これまで説明した最適値としてのフォーカスバイアスを設定するための動作を実現するための処理動作について図１１〜図１３のフローチャートを参照して説明する。この処理動作は、システムコントローラ１０が実行するものとされる。また、以降の処理動作の説明は、第１例に則って、測定すべき再生信号特性として変調度を採用している場合を例に挙げる。
【００６９】
最適値としてのフォーカスバイアス設定のための処理動作としては、図１１に示すようにして、先ず、ステップＳ１０１においてディスクが装填されるのを待機している。そしてディスクが装填されたことが判別されるとステップＳ１０２に進んで、テスト記録レーザパワーを設定する。つまり通常記録時に設定されるレーザパワーよりも低いレベルのレーザパワーを設定する。
【００７０】
続くステップＳ１０３においては、テスト記録エリア、つまり、例えば予めテスト記録用に設定されたディスク上の記録領域に対してシークを行う。そして、シークが完了したら、ステップＳ１０４により前述したテスト記録と、テスト記録により記録されたデータを再生してサンプル情報（変更されたフォーカスバイアスごとに対応する再生信号の変調度）を取得するための処理を行う。
【００７１】
但し、本実施の形態においては、テスト記録動作として２つの方法が考えられるものである。
１つは、テスト記録エリアにおける同一の記録領域に対して、変更設定されたフォーカスバイアスによってデータ記録を行う方法（以降、第１のテスト記録もという）であり、もう１つは、フォーカスバイアスを変更するごとに、テスト記録エリアにおける同一の記録領域に対してデータ記録を行う方法（以降、第２のテスト記録もという）である。
例えば、通常のテスト記録としては、第２のテスト記録でよいものとされるが、例えばディスクによっては、記録領域によって感度にばらつきの生じる場合があるため、このようなことが想定される場合には、第１のテスト記録を採用した方が、再生信号特性としても記録領域による感度のばらつきに影響されない信頼性の高い結果を得ることが可能となる。
【００７２】
そこで、ステップＳ１０４としてのテスト記録及びサンプル取得のための制御処理として、第１のテスト記録によりサンプル情報を取得する処理と、第２のテスト記録にによりサンプル情報を取得する処理とを、それぞれ図１２と図１３のフローチャートに示す。
【００７３】
先ず、図１２に示す第１のテスト記録によりサンプルを取得するための処理から説明する。
この図に示すルーチンにおいては、先ず、ステップＳ２０１においてテスト記録エリア内の所定のアドレスにアクセスするための制御を実行する、そして、続くステップＳ２０２として最初の１回目の処理では、予めテスト記録に対応して設定された所定サンプル数に対応した複数のフォーカスバイアスのうち、最初に設定すべき所要のフォーカスバイアスを設定する。
【００７４】
そして、次のステップＳ２０３において、上記ステップＳ２０１においてアクセスしたテスト記録エリア内の所定のアドレスからデータ記録を行うようにされる。この際記録するデータとしては、予めテスト記録のために決めておいた所定パターンを記録するようにすればよい。
【００７５】
上記ステップＳ２０３におけるデータ記録を完了すると、ステップＳ２０４により記録開始したアドレスに再度アクセスし、続くステップＳ２０５において、このアクセスしたアドレスからデータを再生するための制御処理を実行する。これにより、或るフォーカスバイアスが設定された状態でテスト記録されたデータを再生することが行われることになる。
このようにして再生された信号はＲＦアンプ９、二値化回路１１を介してエンコーダ／デコーダ１２のデコーダ部に送られるが、システムコントローラ１０では、ステップＳ２０６において、このデコーダ部に入力された再生データをサンプルして変調度を測定し、この測定結果を現在設定されていたフォーカスバイアスと対応させてサンプル情報として内部ＲＡＭに保持する。
【００７６】
続くステップＳ２０７においては、全サンプル情報を取得したか否かが判別されるが、ここで全てのサンプル情報が取得されていないと判別された場合には、ステップＳ２０８にて、再度記録開始アドレス（この場合はステップＳ２０１及びＳ２０４によりアクセスしたアドレスと同一アドレス）にアクセスしてステップＳ２０２に戻る。
そして、２回目以降のステップＳ２０２の処理としては、先に設定されていたフォーカスバイアスとは異なる所定のフォーカスバイアスを設定してステップＳ２０３以降の処理を実行する。このような処理が実行されることで、全サンプル情報を取得するまで、変更設定されたフォーカスバイアスにより記録したデータを再生して変調度を測定し、この測定結果をこのとき設定されたフォーカスバイアスと対応付けて内部ＲＡＭに保持するという動作が得られることになる。また、ステップＳ２０８の処理によって、同一の記録開始アドレスに戻ってからデータ記録を行うようにされるため、フォーカスバイアスを可変しながらのデータ記録は常に同一の記録領域に対して行われることになる。
【００７７】
そして、ステップＳ２０７において全てのサンプル情報を取得したことが判別されると、図１１に示したステップＳ１０５に進むことになる。
【００７８】
次に、図１３に示す第２のテスト記録によりサンプル情報を取得するための処理を説明する。
この図に示すルーチンにおいて、ステップＳ３０１から開始され、最初の１回目に実行されるステップＳ３０２〜Ｓ３０７までの処理は、図１２に示したステップＳ２０１〜Ｓ２０７までの処理と同様となる。但し、ステップＳ３０７にて否定結果が得られて、次のサンプルを取得する必要がある場合、ステップＳ３０８において、例えば、先のステップＳ３０３におけるデータ記録を行った領域には含まれないアドレスを次の記録開始アドレスとして設定するようにされる。そして、この後ステップＳ３０２に進んで、先のフォーカスバイアスとは異なる所要のフォーカスバイアスを設定してステップＳ３０３以降に進むようにされる。このようにステップＳ３０８の処理を経て、２回目以降のステップＳ３０２〜Ｓ３０７の処理が実行されることで、フォーカスバイアスが可変設定されるごとに異なる記録領域に対してデータ記録が行われることになる。
そして、この場合にも、ステップＳ３０７において全てのサンプル情報を取得したことが判別されると、図１１に示したステップＳ１０５に進むことになる。
【００７９】
図１１に示すステップＳ１０５では、ステップＳ１０４の処理によって得られたサンプル情報を利用して、図６により説明した各種算出方法の何れかを用いるなどして最適値としてのフォーカスバイアスを求めるようにされる。そして、算出された最適値としてのフォーカスバイアスをシステムコントローラ１０の内部ＲＡＭに保持するようにされる。
このようにして、ステップＳ１０５にて算出され、内部ＲＡＭに保持された最適値としてのフォーカスバイアスは、この後のディスク再生時において再生されるべき領域に応じて読み出され、これまで説明したようにして目標値制御回路４１（図５参照）に対して設定が行われる。これにより、実際の再生時においては、装填されたディスクごとに適合して設定されたフォーカスバイアスが与えられた状態の下で閉ループによるフォーカスサーボ制御が実行される。つまり、適正なフォーカスサーボ制御動作が得られることになる。
【００８０】
なお、第２例のようにしてジッター値を信号特性として扱う場合には、上記図１１，図１２，及び図１３に示した処理動作において、変調度に代えてジッター値を取り込むようにして制御処理を実行すれば、同様の処理手順によってフォーカスバイアスを設定することが可能とされるものである。
また、例えばディスクのばらつきや各種条件の相違によっては、ステップＳ１０２において設定したテスト記録レーザパワーが弱すぎて、どのサンプルについてもフォーカスバイアス設定に必要なだけの所要の変調度が得られなかったり、或るいは、テスト記録レーザパワーが強すぎてサンプルごとの変調度にあまり変化が見られないような場合が起こり得る。そこで、このような状態であることが上記図１１（及び図１２、図１３）に示す処理動作中において判別されたときには、再度ステップＳ１０２に戻って、テスト記録レーザパワーを強めに、或いは弱めに設定し直すように構成することが考えられる。
【００８１】
また、本発明はこれまで説明した構成に限定されるものではない。例えば、図１のディスクドライブ装置は或る程度汎用的な構成を示すにとどまっており、実際に対応するディスク種別に応じて必要となる機能回路部が追加若しくは削除されるなど、各部は適宜変更されるものである。
また、フォーカスバイアスを求めるための信号特性として変調度又はジッター値を採用しているが、記録時のデフォーカス状態に応じた記録ピットの品質に依存して変化するとされる再生信号特性であれば、例えば他の信号特性が採用されて構わないものである。
【００８２】
【発明の効果】
以上説明したように本発明は、通常記録時のレーザパワーよりも低い試行記録用のレーザパワーにより、フォーカスバイアスを可変しながら試行記録を行い、このようにして記録されたデータを再生して得られる所定の信号特性に基づいて最適とされるフォーカスバイアスを設定するようにされる。
この構成に依れば、第１にフォーカスバイアスは、装填されたディスクごとに適合して設定される。つまり、光学系の経時変化やディスクごとのばらつきの兼ね合いによる条件のばらつきに関わらず、装填されたディスクごとに最適とされるフォーカスバイアスを得ることが可能となる。従って、どのようなディスクが装填されたとしても適正なフォーカスサーボ制御を実行することができる。
また、再生信号を利用することで、例えば精度の高いフォーカスバイアス値を得ることが可能となり、特に、高記録密度のメディアに対応することでデフォーカスのマージンが小さいとされるシステムであっても高い信頼性が得られる。更には、再生信号を利用することで、特にフォーカスバイアスを求めるための機能回路部等を追加する必要もなく、比較的簡易な構成で実現されるものである。
また、書き換え可能とされるディスク領域にデータが全く記録されていない状態であるとしても、本発明では試行記録を行ってデータ記録を行うという手順を含むため、適切にフォーカスバイアスを求めることができるものである。
【００８３】
また、信号特性に基づいてフォーカスバイアスを求めるのにあたっては、所定の信号特性が最良とされるとき、又はその変化率が最小となったときに設定されていたフォーカスバイアスを最適なフォーカスバイアスとして設定するとすれば、比較的単純な処理でもってフォーカスバイアスを求めることができる。
また、所定の特性が最良としての極値に近く、かつ、この極値を挟む２サンプル以上に対応して設定されていたフォーカスバイアスの相加平均又は平均値を最適なフォーカスバイアスとして設定する、更にはサンプル値に基づいて、信号特性の極値に対応するとされるフォーカスバイアスを得るための数値演算処理を実行することで最適値としてのフォーカスバイアスを求めるようにすれば、必要最小限とされる少ないサンプル数によっても高い精度でフォーカスバイアスを得ることができる。
【００８４】
そして、最適とされるフォーカスバイアスを求めるために利用する再生信号特性として、信号変調度或いはジッターの変化量を検出するように構成した場合、例えば本来のディスクドライブ装置の機能として、変調度やジッターの変化量を検出する構成が備えられる場合にはこれを流用すればよいことにもなり、機能回路部の追加は必要ないため、コストの削減を図ることができるものである。また、本発明に対応してこのような機能を追加するとしても、回路規模の拡大やコストアップは小さくて済むものである。
【００８５】
また、テスト記録時において、フォーカスバイアスを可変設定しながら光学記録媒体の同一の所定領域に対してデータ記録を行うようにすれば、記録領域よっては存在する感度のばらつきに影響されずにデフォーカスに応じたピット品質を得ることができる。従って、再生信号特性としても記録領域によるする感度のばらつきに依存しない測定結果が得られ、この測定結果に基づいて得られるフォーカスバイアスとしても信頼性の高い結果が得られることになる。
【図面の簡単な説明】
【図１】本発明の実施の形態のディスクドライブ装置の構成を示すブロック図である。
【図２】光学ピックアップの光学系の構造例を概念的に示す構造図である。
【図３】光学ピックアップのフォトディテクタによる検出動作を示す説明図である。
【図４】フォトディテクタにおいて受光するビームスポット形状をフォーカス状態に応じて示す説明図である。
【図５】本実施の形態のフォーカスサーボ系を示すブロック図である。
【図６】テスト記録時のフォーカスバイアスと再生信号の変調度との関係例を示す説明図である。
【図７】本実施の形態のジッター検出回路の構成例を示すブロック図である。
【図８】本実施の形態のジッター検出に際して必要となる二値化信号と再生クロックとの位相差の検出動作を説明するためのタイミングチャートである。
【図９】本実施の形態のジッター検出に際して必要となる二値化信号と再生クロックとの位相差の検出動作を説明するためのタイミングチャートである。
【図１０】テスト記録時のフォーカスバイアスと再生信号のジッター値との関係例を示す説明図である。
【図１１】最適値としてのフォーカスバイアスを求めるための処理動作を示すフローチャートである。
【図１２】第１のテスト記録によりサンプルを得るための処理動作を示すフローチャートである。
【図１３】第２のテスト記録によりサンプルを得るための処理動作を示すフローチャートである。
【図１４】ディスク信号面に照射されるレーザ光の様子を概念的に示す説明図である。
【符号の説明】
１ 光学ピックアップ、２ 対物レンズ、３ 二軸機構、４ レーザダイオード、５ フォトディテクタ、５ａ 分割ディテクタ、５ｂ 差動アンプ、６ スピンドルモータ、７ ターンテーブル、８ スレッド機構、９ ＲＦアンプ、１０ システムコントローラ、１１ 二値化回路、１２ デコーダ、１３ インターフェース部、１４ サーボプロセッサ、１５ スレッドドライバ、１６ 二軸ドライバ、１６ａ フォーカスコイルドライバ、１６ｂ トラッキングコイルドライバ、１７ スピンドルモータドライバ、１８ レーザドライバ、２０ ＰＬＬ回路、２１ ジッター検出回路、２２ 磁気ヘッドドライバ、２３ 磁気ヘッド、３０ 逓倍器、３１ ΔＴ検出回路、３２ ジッター値算出回路、５１ コリメータレンズ、５２ ビームスプリッタ、５３ 集光レンズ、３６ 円筒レンズ、４１ 目標値制御回路、４２ 差動アンプ、４３ 位相補償回路、Ｄディスク、[0001]
BACKGROUND OF THE INVENTION
  The present invention is optimal as a focus bias for giving an offset to the focal position of the converged laser beam when irradiating the converged laser beam to perform recording or reproduction corresponding to an optical recording medium, for example. To set the focus biasOptical recording / reproducing deviceThe present invention relates to a focus bias setting method.
[0002]
[Prior art]
Disc-shaped optical recording media such as CD (Compact Disc) and CD-ROM (Compact Disc-Read Only Memory) are widely used. When these CDs and CD-ROMs are manufactured, minute concave portions (physical pits) are formed on the surface of the plastic substrate, and information is recorded by the pit rows. The pit row itself is used as a track, and the light beam spot for signal reproduction traces the track formed by the pit row.
That is, media such as CDs and CD-ROMs are for reproduction only, and information cannot be added or rewritten after manufacture.
[0003]
On the other hand, in recent years, discs capable of recording and reproducing data, such as write-once type CD-R (Recordable) and rewritable type CD-RW (ReWritable), have become widespread. In these recording media, grooves as guide grooves are formed in the manufacturing process so that the light beam spot can be appropriately traced in the recording area.
Data recording is performed by forming a physical pit by deforming the recording layer on the groove by modulating the intensity of a light beam spot in the case of a CD-R. In the case of CD-RW, the phase pit is formed by a so-called phase change method.
[0004]
In recent years, reproduction-only discs such as DVDs (Digital Versataile Discs or Digital Video Discs) and DVD-ROMs, which have a larger recording capacity than CDs, are also known. A recordable disc medium having a substantially equivalent recording capacity has also been proposed.
[0005]
In a disk drive device corresponding to these disk media, a disk rotated by a spindle motor is irradiated with a laser beam from an optical pickup to a track on the disk, and the reflected light is detected to detect data. Is read, or data is recorded by irradiating a laser beam modulated by the recording data.
[0006]
In order to perform a recording or reproducing operation with a laser beam, the spot of the laser beam must be kept in focus on the recording surface of the disk. For this reason, the disk drive device has an output end of the laser beam. A focus servo circuit system is mounted for controlling the focus state by moving the objective lens in the direction of contact with and away from the disk. As this focus servo circuit system, normally, a biaxial mechanism having a focus coil that moves the objective lens in the direction of moving toward and away from the disk and a tracking coil that can move in the disk radial direction, and reflected light information from the disk A focus servo control system that generates a focus error signal (that is, a signal of a deviation amount from the in-focus state), generates a focus drive signal based on the focus error signal, and applies the focus drive signal to the focus coil of the biaxial mechanism. Has been.
[0007]
The basic operation of the focus servo circuit system is to adjust the distance between the objective lens and the signal surface by applying a focus drive signal to the focus coil of the biaxial mechanism so that the focus error signal level becomes zero. To be. That is, in a state where the focus error signal level is 0, the objective lens is focused on the signal surface, that is, the best imaging state is obtained with respect to the laser light irradiated on the signal surface. It is said.
[0008]
[Problems to be solved by the invention]
By the way, in an actual disk drive apparatus, the best focus state may not always be obtained when the focus error signal level is 0.
This is caused by, for example, a change in position and characteristics due to a change with time of a laser light source, a photodetector that detects laser light as reflected light from a disk, and other optical system components.
In addition, the disc-shaped recording medium is used, for example, for the purpose of ensuring proper recording / reproduction even if there is dust or scratches on the surface of the medium and protecting the signal surface. As shown as a partial sectional view), the signal surface 201 is usually formed on the back surface of the transparent layer 202 formed of resin or the like.
The thickness TH of the transparent layer 202 may be slightly different for each recording medium even if they are the same type. Due to the variation in the thickness TH of the transparent layer 202, even if the detected focus error signal level is 0, the signal surface 202 is the best laser light actually irradiated from the objective lens 300. It has been found that a phenomenon in which the image state is not obtained can occur.
[0009]
Considering these circumstances, it is necessary to set the target value of the focus error signal level not to be 0 but to be shifted by another appropriate value. That is, it is necessary to give an offset (bias) to the focus error signal. Further, this bias is not fixed, and it is necessary to set it appropriately in accordance with a change with time of the optical system and a variation from disk to disk.
[0010]
Further, in a large-capacity and high recording density disk medium such as the DVD system described above, the groove interval (track pitch) and the pit length are as small as the order of the wavelength of the light source. In order to trace a land formed and accurately record or reproduce data, the light beam spot needs to have a so-called diffraction-limited quality. For this reason, since the above-described focus servo circuit system is also required to have high accuracy, a high-accuracy value must be obtained as the bias as described above.
[0011]
[Means for Solving the Problems]
  In view of the above-described problems, the present invention performs a recording / reproduction by irradiating the optical recording medium with a converged laser beam, and provides a focus bias for providing an offset with respect to the focal position of the converged laser beam. Set toAn optical recording / reproducing device, wherein the laser power is set lower than the laser power set during normal recording, andTrial recording means for executing trial recording for performing data recording on the optical recording medium while variably setting the focus bias, data reading means for reading the recording data recorded by the trial recording from the optical recording medium, and the data reading means Measuring the predetermined signal characteristics of the recording data read out by, and obtaining the measurement result as sample information in correspondence with the focus bias set at the time of the trial recording, and obtained by the sample means Focus bias setting means for setting an optimum focus bias based on the sample information.It was.
  AlsoFocus bias for applying an offset to the focal position of the converged laser light, which is performed in a recording / reproducing apparatus capable of performing recording / reproduction by irradiating the converged laser light onto an optical recording medium Focus bias setting method for settingBecause,Set the laser power lower than the laser power set during normal recording, andA trial recording procedure for performing trial recording in which data is recorded on the optical recording medium while variably setting the focus bias, a data reading procedure for reading the recording data recorded by the trial recording from the optical recording medium, and a data reading procedure. Based on the sample procedure obtained by measuring the predetermined signal characteristics of the recorded data and obtaining the sample results as sample information by associating the measurement result with the focus bias set at the time of trial recording. Thus, the focus bias setting procedure for setting the optimum focus bias is executed.
[0012]
In trial recording under the invention with the above configuration, the focus state of the laser light changes depending on the focus bias that is changed, but pits formed as recording data by performing recording with a laser power lower than that during normal recording The quality of the image depends more on the focus state than during normal recording. In the present invention, the focus bias is set based on a predetermined signal characteristic obtained by reproducing the data recorded by the trial recording. The signal characteristic is a change in the focus state during the trial recording. Corresponding remarkable fluctuations will be seen.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described. As the focus bias setting device of the present embodiment, for example, a case where it is mounted on a disc drive device that is connected to a personal computer as a host and can record and reproduce a predetermined type of disc is taken as an example. .
The following description will be given in the following order.
1. Disk drive device
2. Focus bias setting (first example)
3. Focus bias setting (second example)
4). Processing action
[0014]
1. Disk drive device
FIG. 1 is a block diagram showing a configuration of a main part of the disk drive device according to the present embodiment.
The disk D shown in this figure is placed on the turntable 7 and rotated at a constant linear velocity (CLV) or a constant angular velocity (CAV) by the spindle motor 6 during the reproducing operation. Then, the data recorded on the signal surface of the disk D is read by the optical pickup 1.
[0015]
The optical pickup 1 includes a laser diode 4 serving as a laser light source, an optical system including a deflection beam splitter and an objective lens 2, a photodetector 5 for detecting the laser light reflected on the disk, and the like. Yes. Here, the objective lens 2 is supported by the biaxial mechanism 3 so as to be movable in the tracking direction and the focus direction.
[0016]
FIG. 2 shows a structural example of an optical system in the optical pickup 1.
In the optical system shown in this figure, the laser beam output from the laser diode 4 is collimated by the collimator lens 51, then reflected 90 degrees toward the disk D by the beam splitter 52, and is reflected from the objective lens 2 to the disk D. Is irradiated.
The reflected light reflected by the disk D enters the beam splitter 52 via the objective lens 2, passes through as it is, and reaches the condenser lens 53. Then, after being condensed by the condenser lens 53, it is incident on the photodetector 5 through a cylindrical lens (cylindrical lens) 54.
[0017]
Here, the center wavelength of the laser diode 4 is set corresponding to the disc type to be actually reproduced, and the aperture ratio NA of the objective lens 2 is also set corresponding to the disc type to be actually reproduced. .
[0018]
The laser light reflected from the disk D by the reproduction operation of the disk drive device is detected by the photodetector 5 as a light receiving current. The received light current is output to the RF amplifier 9 as an information signal read from the disk.
The RF amplifier 9 includes a current-voltage conversion circuit, an amplifier circuit, a matrix operation circuit (RF matrix amplifier), and the like, and generates a necessary signal based on a signal from the photodetector 5. For example, an RF signal that is reproduction data, a push-pull signal PP for servo control, a focus error signal FE, a tracking error signal TE, a pull-in signal PI that is a so-called sum signal, and the like are generated.
[0019]
The photodetector 5 is provided with a four-divided detector 5a composed of detectors A, B, C, and D in the direction as shown in FIG. 3A. In this case, the focus error signal FE is detected by the detectors A, B, and C. , D are generated by the calculation of FE = (A + C) − (B + D).
[0020]
FIG. 4 shows a pattern example of a beam spot SP as reflected light obtained by the four-divided detector 5a according to the focus state of the objective lens 2 with respect to the disk signal surface.
For example, when the focus state with respect to the disc signal surface of the objective lens 2 is assumed to be a just focus state, the beam is received by the light receiving elements A, B, C, and D as shown in FIG. The spot SP is received. That is, a substantially equal amount of received light can be obtained for the light receiving elements A, B, C, and D.
On the other hand, when the focus state with respect to the disc signal surface of the objective lens 2 is closer to the focused state, the light receiving element than the light receiving elements B and D as shown in FIG. The beam spot SP is received so that a large amount of received light can be obtained at A and C. Further, when the position is far from the focused state, as shown in FIG. 4C, the light receiving elements B and D can obtain a larger amount of received light than the light receiving elements A and C. The beam spot SP is received.
[0021]
In this way, the light receiving areas in the light receiving elements A, B, C, and D change according to the focus state. As a result of performing the above-described calculation for such light receiving elements A, B, C, and D, a focus error signal is obtained. FE will be obtained. In this case, depending on the defocus if it is closer than the just focus state, it fluctuates in a positive region with respect to the reference value corresponding to the 0 level. Conversely, if it is farther than the just focus state, it depends on the defocus. The signal fluctuates in a negative region with respect to the reference value.
[0022]
For the pull-in signal PI, PI = (A + B + C + D).
When the push-pull signal PP is generated by the quadrant detector 5a, the output of the detectors A, B, C, D of the detector 5a is (A + D) with respect to the outputs of the detectors A, B, C, D of the detector 5a as shown in FIG. ) − (B + C).
If the so-called three-beam system is considered, the tracking error signal TE may be generated by calculating side-by-side detectors E and F separately from the quadrant detector shown in FIG.
[0023]
Returning to FIG.
Various signals generated by the RF amplifier 9 are supplied to the binarization circuit 11 and the servo processor 14. That is, the reproduction RF signal from the RF amplifier 9 is supplied to the binarization circuit 11, and the push-pull signal PP, focus error signal FE, tracking error signal TE, and pull-in signal PI are supplied to the servo processor 14.
[0024]
The reproduction RF signal output from the RF amplifier 9 is binarized by the binarization circuit 11
And a binarized signal (for example, an EFM signal (8-14 modulation signal) or an EFM + signal (8-16 modulation signal)), an encoder / decoder 12, a PLL (Phase Locked Loop) circuit 20, and a jitter detection circuit. 21 is branched and supplied.
[0025]
The PLL circuit 20 generates a reproduction clock PLCK synchronized with the channel bit frequency of the input binary signal. The reproduction clock PLCK is used as a reference clock for signal processing or the like at the time of reproduction, and is supplied to the encoder / decoder 12 as shown in the figure, for example, as a reference for reproduction signal processing timing in the encoder / decoder 12. . In the present embodiment, the recovered clock PLCK is also supplied to the jitter detection circuit 21.
[0026]
At the time of reproduction, the decoding unit of the encoder / decoder 12 reproduces information read from the disk D by performing EFM demodulation or EFM + demodulation and error correction processing (RS-PC method, CIRC method, etc.) according to a predetermined method. I do. The data decoded by the encoder / decoder 12 is supplied to a host computer (not shown) or the like via the interface unit 13.
Further, the encoder / decoder 12 obtains disk rotation speed information from the reproduction clock PLCK. This disk rotation information indicates the relative speed between the laser spot output from the optical pickup 1 and the track on which the recording pit is formed.
[0027]
The jitter detection circuit 21 detects the jitter amount of the binarized signal using the input binarized signal and the reproduction clock PLCK as will be described later, and uses this jitter amount information as the jitter value. This is output to the system controller 10 as JT. The jitter here refers to the fluctuation of the binarized signal along the time axis direction.
The jitter value JT obtained by the jitter detection circuit 21 can be used when the system controller 10 is required for various control processes. However, in the configuration of the focus bias setting as a second example to be described later. This is treated as a signal characteristic to be measured when setting the focus bias as an optimum value.
[0028]
When data is recorded on the disk D, for example, data supplied from a host computer (not shown) is sent to the encoding unit of the encoder / decoder 12 via the interface unit 13.
[0029]
In this encoding unit, the data input from the interface unit 13 is subjected to error correction code addition and encoding processing according to a predetermined method, and further subjected to predetermined modulation processing for recording on the disk D for recording. Data WD is generated.
Here, for example, assuming that the overwrite area Aov of the disk D corresponds to the magneto-optical method, if recording is performed by the optical modulation overwrite method, the recording data WD is output to the laser driver 18. The laser driver 18 generates a laser diode drive voltage modulated based on the supplied recording data, and drives the laser diode 4 of the optical pickup 1. As a result, the laser diode 4 emits pulsed light modulated by the recording data WD. On the other hand, for example, the system controller 10 controls the magnetic head driver 22 to generate, for example, a required constant level magnetic field from the magnetic head 23 and apply it to the disk D. In this way, data recording by the light modulation overwrite method is realized.
[0030]
If recording is performed by a magnetic field modulation overwrite method (here, a simple magnetic field modulation method is taken as an example), recording data WD generated by an encoding unit of the encoder / decoder 12 is supplied to the magnetic head driver 22. To be done. The magnetic head driver 22 outputs a drive signal corresponding to the input recording data WD to the magnetic head 23, so that the magnetic head 23 generates an N or S magnetic field corresponding to the recording data and applies it to the disk. To do. At the same time, the system controller 10 generates laser drive control data in which the laser power corresponding to the required recording level is set, and outputs it to the laser driver 18 as a laser drive signal via the servo processor 14, for example. Thereby, the laser diode 4 emits light with the laser power corresponding to the recording level.
In this way, recording by the magnetic field modulation overwrite method is possible by applying an external magnetic field modulated by the recording data and irradiating the laser beam with the laser power at the recording level.
As a magnetic field modulation overwrite method, a so-called laser strobe magnetic field modulation method has been proposed in which a higher recording density than a simple magnetic field modulation method has been proposed, but when performing data recording according to this method, depending on the recording data, The system controller 10 may perform control so that a modulated external magnetic field is applied and laser light is pulsed according to the clock timing of the recording data.
[0031]
As can be said with any of the magneto-optical recording systems described above, the laser diode 4 of the optical pickup 3 at the time of recording is a laser beam having a power sufficient to raise the temperature on the recording surface of the disk D to a so-called Curie point. The magnetic head 23 applies a magnetic field to the recording surface of the disk D whose temperature has been raised to the Curie point by the laser beam, and then the temperature of the recording surface decreases as the disk D rotates. As a result, the applied magnetic field remains, thereby recording.
[0032]
Further, assuming that the overwrite area Aov of the disk D corresponds to the phase change method, when recording is performed on the overwrite area Aov, for example, the recording data WD generated by the encoding unit of the encoder / decoder 12 is recorded. Is supplied to the laser driver 18. In this case, for example, the laser driver 18 performs modulation based on the input recording data WD, generates a laser diode driving voltage combining a required recording level and erasing level, and drives the laser diode 4. Thereby, data recording is executed according to the phase change method. When adopting only the recording / reproducing configuration based on this phase change method, the magnetic head driver 22 and the magnetic head 23 may be omitted.
[0033]
The servo processor 14 generates various servo drive signals for focus, tracking, sled, and spindle from the focus error signal FE, tracking error signal TE, push-pull signal PP, and the like from the RF amplifier 9, and executes the servo operation. That is, the focus drive signal FDR and the tracking drive signal TDR are generated according to the focus error signal FE and the tracking error signal TE and supplied to the biaxial driver 16.
[0034]
The biaxial driver 16 includes, for example, a focus coil driver 16a and a tracking coil driver 16b. The focus coil driver 16a supplies the drive current generated based on the focus drive signal FDR to the focus coil of the biaxial mechanism 3, thereby driving the objective lens 2 in a direction in which the objective lens 2 is in contact with or separated from the disk surface. The tracking coil driver 16b supplies the drive current generated based on the tracking drive signal TDR to the tracking coil of the biaxial mechanism 3, thereby driving the objective lens 2 so as to move along the disk radial direction.
As a result, a tracking servo loop and a focus servo loop are formed by the optical pickup 1, the RF amplifier 9, the servo processor 14, and the biaxial driver 16.
[0035]
The servo processor 14 supplies a spindle drive signal generated from the spindle error signal SPE to a spindle motor driver 17 described later. The spindle motor driver 17 applies, for example, a three-phase drive signal to the spindle motor 6 in accordance with the spindle drive signal, and rotationally drives the spindle motor 6 to have a required rotational speed.
Further, the servo processor 14 generates a spindle drive signal in response to a spindle kick (acceleration) / brake (deceleration) signal from the system controller 10 and also executes operations such as starting or stopping the spindle motor 6 by the spindle motor driver 17. .
[0036]
The servo processor 14 generates a thread drive signal based on, for example, a thread error signal obtained from a low frequency component of the tracking error signal TE, access execution control from the system controller 10, and supplies the thread drive signal to the thread driver 15. The thread driver 15 drives the thread mechanism 8 according to the thread drive signal. The sled mechanism 8 is a mechanism that moves the entire optical pickup 1 in the radial direction of the disk. The sled driver 15 drives a sled motor inside the sled mechanism 8 in accordance with a sled drive signal, so that the optical pickup 1 can be appropriately moved. Is done.
[0037]
Further, the servo processor 14 also executes light emission drive control of the laser diode 4 in the optical pickup 1. The laser diode 4 is driven to emit laser light by a laser driver 18, but the servo processor 14 generates a laser drive signal to execute laser emission at the time of recording / reproduction based on an instruction from the system controller 10, and laser This is supplied to the driver 18. In response to this, the laser driver 18 drives the laser diode 4 to emit light.
[0038]
Various operations such as servo and encoding / decoding as described above are controlled by a system controller 10 including a microcomputer.
For example, operations such as playback start, end, track access, fast forward playback, and fast reverse playback are realized by the system controller 10 controlling the operation of the optical pickup 1 via the servo processor 14.
The table 10a shown in this figure is information stored in a ROM or the like inside the system controller 10, and includes the emboss pits set corresponding to the overwrite area Aov for each disk type. An offset value for the focus bias corresponding to the region Aep is described later.
[0039]
Here, FIG. 5 shows a configuration in which the focus servo system is extracted from the configuration shown in FIG. In this figure, the same parts as those in FIG.
The light reception signal detected by the photodetector of the optical pickup 1 is supplied to the RF amplifier 9 as described above. The RF amplifier 9 generates a focus error signal FE as one of the generated signals and supplies it to the focus servo system in the servo processor 14.
The focus servo system in the servo processor 14 shown in this figure includes a target value control circuit 41, a differential amplifier 42, and a phase compensation circuit 43. The target value control circuit 41 generates and outputs a voltage level as a focus bias to be superimposed on the focus error signal as a target value for the circuit system by the focus servo loop to converge. The value of the focus bias is set based on a bias setting control signal output from the system controller 10.
[0040]
The focus error signal FE is input to the non-inverting input of the differential amplifier 42, and the voltage level as the focus bias output from the target value control circuit 41 is supplied to the inverting input. As a result, the differential amplifier 42 outputs a focus error signal FE on which the focus bias set by the target value control circuit 41 is superimposed.
[0041]
The output of the differential amplifier 42 is phase compensated by the phase compensation circuit 43 and supplied to the focus coil driver 16a as the focus coil drive signal FDR. From the focus coil driver 16a, the focus coil of the biaxial mechanism 3 is driven in accordance with the input focus coil drive signal FDR, and the objective lens 2 is moved in the direction of contacting / separating the disk.
[0042]
In the configuration shown in FIG. 5, if the focus offset value to be output in the target value control circuit 41 is “0”, the focus servo loop circuit system operates so that the focus error signal level becomes zero. It will be. If the focus bias value as the value “x” is set, the operation is performed so that the focus error signal is converged to the level shifted by the focus bias value “x” with respect to the 0 level of the focus error signal. .
[0043]
As described above in the conventional example, due to various factors, a state where the focus state is not the best imaging state when the focus error signal is 0 level occurs. By setting the focus bias for FE, it is possible to always obtain an appropriate imaging state as focus servo control by closed loop.
In the present embodiment, a configuration for determining a focus bias to be set for the target value control circuit 41 will be described next.
[0044]
2. Focus bias setting (first example)
In the present embodiment, the focus bias as the optimum value is set as follows.
First, in the present embodiment, when the disk D is loaded, test recording (trial recording) is performed on a predetermined area (for example, a preset test recording area) of the disk D.
At this time, as the focus bias, the focus bias is sequentially changed at a predetermined timing within an appropriately set range.
In general, a predetermined laser power (normal recording laser power) stronger than that in reproduction suitable for data recording is set during normal recording. In the present embodiment, this test recording is performed. In some cases, a predetermined laser power (test recording laser power) is set which is lower than the normal recording laser power but allows data recording.
That is, in the present embodiment, test recording is performed while changing the focus bias with a test recording laser power lower than the normal recording laser power.
[0045]
Originally, in order to record data properly, it is necessary that the laser beam irradiated on the signal recording surface of the disc is in an optimal imaging state, but recording is performed while varying the focus bias. Is nothing but recording while forcibly defocusing the laser beam in a focused state (a state in which it is out of just focus). As a result, the quality of the pits formed as recording data on the disc can change depending on the degree of the defocus state that is compulsorily created.
However, when recording is performed with the normal recording laser power, there is a case where the pit quality to be formed is not significantly changed even in a certain defocus state. On the other hand, when recording is performed at a level lower than the normal recording laser power, such as the above test recording laser power, on the contrary, the pit shape formed by even a slight defocus appears greatly. It is. That is, the quality of the recording data can be greatly changed according to the degree of defocus.
[0046]
In this embodiment, the data recorded by the test recording is reproduced, the predetermined signal characteristic of the reproduced data is measured, and the measured signal characteristic is set to the focus set at the time of the test recording. The sample is held in association with the bias.
Here, as described above, the pits recorded in the test on the disc were recorded with a test recording laser power level lower than that of the normal recording laser power, so that the change in the quality according to the defocus is remarkable. It has become a thing. Therefore, a significant change in signal characteristics corresponding to the defocus state at the time of recording is also obtained as the reproduced signal.
[0047]
Here, as a first example of the configuration for setting the focus bias according to the present embodiment, the signal modulation degree is used as a signal characteristic that becomes a determination material for obtaining the optimum focus bias. The signal modulation degree is determined by the spot diameter and pit shape of the laser light irradiated on the disk signal surface, but it is known that the signal modulation degree is greatly influenced by defocusing.
[0048]
FIG. 6 shows the relationship between the degree of modulation of the reproduction signal and the focus bias set at the time of test recording as a result of sampling the reproduction signal. In this figure, the horizontal axis is the focus bias, and the vertical axis is the degree of modulation.
Moreover, the x mark shown in the coordinates of the figure indicates a sample point (measurement point). In this case, the modulation degree is measured for six sample points (six points of focus bias, -4, -3, -2, -1, 0, 1).
Also, the sample points marked with ◯ shown in the coordinates of the figure show the relationship between the focus bias and the modulation factor during recording when recording is performed with the normal recording laser power. As can be seen by comparing the state of the sample points of the X mark and the ○ mark, the change in the modulation degree of the reproduction signal in accordance with the defocus is small when recording with the normal recording laser power. This is remarkable when recording is performed with a test recording laser power lower than this.
This is because in obtaining the optimum focus bias as described below, a more accurate result is obtained when the change in the modulation degree according to defocus is significant as in the present embodiment. It means that it can be done.
[0049]
When the sample result shown in FIG. 6 is obtained, the focus bias as the optimum value can be obtained as follows.
One is a method of setting the focus bias as the optimum value when the largest modulation degree (best value) is obtained among the sample points. In the case of FIG. 6, the coordinates (−1, 5) are extreme values. Accordingly, in this case, focus bias = −1 is set as the optimum value.
One is to find a sample area where the rate of change of the modulation factor is the lowest and to set a focus bias corresponding to this area. In the case of FIG. 6, the rate of change of the modulation degree is the lowest near the coordinates (−1, 5). Accordingly, also in this case, the focus bias = −1 is set as the optimum value.
[0050]
One is that the modulation degree of the coordinates is close to a predetermined value that is set in advance, and the average value or arithmetic average value of two sample points sandwiching the extreme value as the modulation degree is set as the optimum value of the focus bias. It is a method of setting.
Here, in the case of FIG. 6, if the predetermined modulation degree set in advance is “2”, two sample points that are close to the jitter value 2 and sandwich the extreme coordinates (−1, 5). As coordinates (−3, 2) (1, 2.5). And when calculating the average value using the focus bias value of these two sample points,
(−3 + 1) / 2 = −1
Thus, focus bias = −1 is obtained.
In addition, in the case of FIG. 6, if the arithmetic average value is obtained, as in the case where the average value is obtained, if the preset jitter value is “2”, the coordinates of the extreme value (−1, Coordinates (−3, 2) (1, 2.5) are obtained as two sample points sandwiching 5) and close to the jitter value 2. Then, based on the values of these two coordinates, the arithmetic mean is obtained using the weighting parameter as the modulation degree.
{(−3 × 2) + (1 × 2.5)} / (| −3 + 1 |) ≈−1.8
Thus, the focus bias = −1.8 is obtained. Note that other arithmetic expressions for obtaining the arithmetic mean are conceivable.
[0051]
Further, the measurement of each sample point is performed by utilizing a certain degree of correlation between the focus bias and the modulation degree (for example, the result shown in FIG. 6 has a quadratic function relationship). By executing the required numerical calculation processing using all or a part of the result, a value that is assumed that the jitter value is an extreme value is calculated, and the focus bias that is estimated to correspond to this extreme value Calculate the value. Then, the calculated focus bias value is set as an optimum value.
In the case of FIG. 6, numerical calculation processing is performed by using all or part of sample information (focus bias and modulation degree measured corresponding thereto) obtained at six sample points. , And a focus bias assumed to correspond to the jitter value calculated as an extreme value at this time is calculated, and this is set as an optimum value.
[0052]
The focus bias as the optimum value set as described above is held in, for example, an internal RAM (not shown) of the system controller 10. In actual recording or reproduction, the focus servo loop control may be executed by superimposing the focus bias held in the internal RAM on the focus error signal FE. For this purpose, as described above, the system controller 10 outputs the bias setting control signal S1 to set the first focus bias obtained by the detection operation so far for the target value control circuit 41. It is sufficient to execute the control.
[0053]
3. Focus bias setting (second example)
In the first example, the signal modulation degree is used as a reproduction signal characteristic to be sampled in order to obtain an optimum focus bias, but it is also possible to use jitter of the reproduction signal. The amount of jitter that appears in the playback signal also depends on the quality (shape) of the recording pits according to the defocus at the time of recording, and defocusing occurs when recording with a test recording laser power lower than the normal recording laser power. The corresponding changes are significant.
Therefore, hereinafter, as a second example of the present embodiment, a configuration in which the focus bias is set based on the jitter of the reproduction signal will be described.
[0054]
First, a configuration example for obtaining a jitter value in the disk drive device of the present embodiment will be described.
In the present embodiment, jitter is detected by the jitter detection circuit 21 shown in FIG.
[0055]
FIG. 7 is a block diagram illustrating a configuration example of the jitter detection circuit 21.
The jitter detection circuit 21 shown in this figure includes a multiplier 30, a ΔT detection circuit 31, and a jitter value calculation circuit 32.
[0056]
For the ΔT detection circuit 31, the binarized signal from the binarization circuit 11, the reproduction clock PLCK, and the multiplication clock MCK (= n × PLCK) obtained by multiplying the reproduction clock PLCK by a predetermined multiple n by the multiplier 30. ) Is entered. Here, it is assumed that the multiple n = 10 and the multiplied clock MCK is a frequency signal obtained by multiplying the reproduction clock PLCK to about 10 times. It should be noted that the actual multiple n may be arbitrarily set to a value that can accurately count the period of ΔT described later.
[0057]
FIG. 8 is a timing chart showing signals input to the ΔT detection circuit 31, and FIGS. 8A, 8B, and 8C show the input binary signal, the reproduction clock PLCK, and MCK, respectively. Is shown.
Here, as the binarized signal shown in FIG. 8A, the inversion interval by the H level of 3T is shown.
Further, as described above, the reproduction clock PLCK shown in FIG. 8B is a signal having the channel bit frequency of the binarized signal and synchronized with the binarized signal. Further, since the multiplied clock MCK shown in FIG. 8C is a frequency signal obtained by multiplying the reproduction clock PLCK, the frequency signal is synchronized with the reproduction clock PLCK.
[0058]
By the way, ideally, the edge timing of the binarized signal and the edge timing of the reproduction clock PLCK should coincide with each other in terms of time axis. ˜t1 and subsequent periods t2 to t3 may cause a phase error indicated by ΔT.
[0059]
The jitter amount here refers to the fluctuation range of the phase error ΔT. That is, for example, if ΔT, ΔT, ΔT... Sampled each time the binarized signal is inverted, the jitter is set to 0 if it is constant. On the other hand, if ΔT, ΔT, ΔT,... Are not constant and change is observed, there will be jitter, and the greater the change amount, the greater the jitter amount.
Although several factors can be considered for the occurrence of such jitter, there are mainly variations in the recording pit length itself formed as data on the disk D. Moreover, it occurs depending on the operating performance of the reproduction system including the optical system, including the defocusing of the laser beam irradiated during reproduction. That is, the jitter amount can indicate the formation state of the recording pit length and can also be handled as information indicating the good reproduction characteristics.
[0060]
The ΔT detection circuit 31 detects the phase error amount as ΔT every time the binarized signal waveform is inverted and the edge position is obtained. The detection can be performed, for example, as follows. .
[0061]
FIG. 9 shows the vicinity of the period t0 to t1 in FIG. 8 in an enlarged manner.
When the jitter detection circuit 21 detects the rising (or falling) edge position of the input binarized signal waveform (FIG. 9A) at time t0, for example, from this time t0. A period between time points t1 when the leading edge of the first PLCK (FIG. 9B) is obtained (that is, a period in which the phase error ΔT is generated), a cycle of the multiplied clock MCK shown in FIG. Count). The multiplied clock MCK is a signal synchronized with the reproduction clock PLCK.
[0062]
FIG. 9 shows a state in which exactly three cycles of the multiplied clock MCK are obtained in the period t0 to t1, and “6” is obtained as the number of inversions. In the ΔT detection circuit 31, for example, the counted inversion The number of times is output to the jitter value calculation circuit 32 as the value of the phase error ΔT. Here, the value of the phase error ΔT is used as the number of inversions. However, the number of inversions is not particularly limited as long as an accurate value can be obtained. For example, the number of H-level pulses may be used. is there.
[0063]
The jitter value calculation circuit 32 obtains information on the value of the phase error ΔT every time the binarized signal is inverted.
Therefore, the jitter value calculation circuit 32 obtains the jitter value JT by taking a predetermined number of m samples and sequentially performing the following calculation for the phase error ΔT obtained sequentially every time the binarized signal is inverted. To be. Here, m phase errors ΔT to be sampled are represented as ΔTi (1 ≦ i ≦ m) according to the sampled time axis.
First,
[Expression 1]

Is obtained, an average value of m sampled ΔTi, ΔTi, ΔTi... Is obtained. And using this average value,
[Expression 2]

The jitter value JT is obtained by executing the calculation indicated by. The jitter value JT indicated by this (Equation 2) indicates the fluctuation range between the sampled m ΔTi, ΔTi.
The jitter value JT calculated in this way is input to the system controller 10.
[0064]
The number m of samples may be arbitrarily set in consideration of obtaining the jitter value JT with as high accuracy as possible and preventing the time required for calculating the jitter value JT from becoming longer than necessary. .
Further, since various internal configurations of each part forming the jitter detection circuit 21 can be considered, detailed illustration is omitted here. For example, the ΔT detection circuit 31, the jitter value calculation circuit 32, and the like can be easily realized by combining various digital circuits and logic circuits.
Further, the calculation method of the jitter value JT shown by the above (Equation 1) and (Equation 2) is merely an example, and may be performed using other arithmetic expressions.
[0065]
In the case of the second example, the test recording is performed in the same manner as in the case of the first example. However, when the data recorded by the test recording is reproduced and the signal characteristics are measured, as described above. The jitter value JT obtained as described above is taken as a sample value, and is stored in, for example, the RAM inside the system controller 10 in association with the focus bias set at the time of test recording.
[0066]
Here, FIG. 10 shows the relationship between the jitter value of the reproduction signal and the focus bias set at the time of test recording as a result of performing the sampling as described above. In this figure, the horizontal axis is the focus bias, and the vertical axis is the jitter value. In the coordinates of the figure, six sample points A to F are indicated by x marks. The better the jitter value is, the smaller the value is. Therefore, the tendency tends to be opposite to the relationship between the modulation degree and the focus bias shown in FIG.
[0067]
For example, as shown in FIG. 10, as long as the relationship between the jitter value of the reproduction signal and the focus bias set at the time of test recording is obtained as sample information, the optimum focus bias can be obtained in the first example. It can be obtained in the same manner as described above.
In other words, the focus bias when the smallest jitter value (best value) is obtained among the sample points can be set as the optimum value.
Further, it is possible to find a sample area where the change rate of the jitter value is the lowest, and to set a focus bias corresponding to this area as an optimum focus bias.
Further, an average value or an arithmetic average value of two sample points with a jitter value close to a predetermined value set in advance and sandwiching an extreme value as the jitter value can be set as the optimum value of the focus bias.
Further, based on the sample result, the extreme value of the signal characteristic is calculated, and further, a numerical calculation process for calculating the estimated focus bias corresponding to this extreme value is executed, thereby setting the focus bias as the optimum value. can do.
[0068]
4). Processing action
Next, the processing operation for realizing the operation for setting the focus bias as the optimum value described so far will be described with reference to the flowcharts of FIGS. This processing operation is executed by the system controller 10. In the following description of the processing operation, a case where the modulation factor is adopted as the reproduction signal characteristic to be measured according to the first example will be described as an example.
[0069]
As the processing operation for setting the focus bias as the optimum value, as shown in FIG. 11, first, in step S101, the process waits for the disk to be loaded. When it is determined that the disc is loaded, the process proceeds to step S102, and the test recording laser power is set. That is, the laser power is set at a level lower than the laser power set during normal recording.
[0070]
In the subsequent step S103, seek is performed on the test recording area, that is, the recording area on the disc that is set in advance for test recording, for example. When the seek is completed, the test recording described above in step S104 and the data recorded by the test recording are reproduced to obtain sample information (modulation level of the reproduction signal corresponding to each changed focus bias). Process.
[0071]
However, in this embodiment, two methods can be considered as the test recording operation.
One is a method of performing data recording on the same recording area in the test recording area with the focus bias changed and set (hereinafter, also referred to as first test recording), and the other is a method for adjusting the focus bias. This is a method of performing data recording on the same recording area in the test recording area (hereinafter also referred to as second test recording).
For example, the normal test recording may be the second test recording, but for example, depending on the disc, the sensitivity may vary depending on the recording area. In the case where the first test recording is adopted, it is possible to obtain a highly reliable result that is not affected by variations in sensitivity depending on the recording area even as a reproduction signal characteristic.
[0072]
Therefore, as a control process for test recording and sample acquisition as step S104, a process for acquiring sample information by the first test record and a process for acquiring sample information by the second test record are shown in FIG. 12 and the flowchart of FIG.
[0073]
First, the processing for obtaining a sample by the first test recording shown in FIG. 12 will be described.
In the routine shown in this figure, first, in step S201, control for accessing a predetermined address in the test recording area is executed, and in the subsequent first step as step S202, the test recording is handled in advance. Among the plurality of focus biases corresponding to the predetermined number of samples set in this way, a required focus bias to be set first is set.
[0074]
In the next step S203, data recording is performed from a predetermined address in the test recording area accessed in step S201. As data to be recorded at this time, a predetermined pattern determined in advance for test recording may be recorded.
[0075]
When the data recording in step S203 is completed, the address where recording was started in step S204 is accessed again, and in step S205, control processing for reproducing data from the accessed address is executed. As a result, the data recorded in the test with a certain focus bias set is reproduced.
The signal reproduced in this way is sent to the decoder unit of the encoder / decoder 12 via the RF amplifier 9 and the binarization circuit 11, and the system controller 10 reproduces the signal input to this decoder unit in step S206. The data is sampled and the degree of modulation is measured, and the measurement result is stored in the internal RAM as sample information in association with the currently set focus bias.
[0076]
In the subsequent step S207, it is determined whether or not all sample information has been acquired. If it is determined that not all sample information has been acquired, in step S208, the recording start address ( In this case, access is made to the same address as that accessed in steps S201 and S204, and the process returns to step S202.
In the second and subsequent steps S202, a predetermined focus bias different from the previously set focus bias is set, and the processing from step S203 is executed. By executing such processing, the data recorded with the changed focus bias is reproduced and the modulation degree is measured until all sample information is acquired, and the measurement result is obtained at this time. The operation of associating and holding in the internal RAM is obtained. Further, since the data recording is performed after returning to the same recording start address by the processing in step S208, the data recording while changing the focus bias is always performed on the same recording area. .
[0077]
When it is determined in step S207 that all sample information has been acquired, the process proceeds to step S105 shown in FIG.
[0078]
Next, a process for acquiring sample information by the second test record shown in FIG. 13 will be described.
In the routine shown in this figure, the process from step S302 to S307 started from step S301 and executed for the first time is the same as the process from step S201 to S207 shown in FIG. However, if a negative result is obtained in step S307 and it is necessary to acquire the next sample, in step S308, for example, an address that is not included in the area in which data was recorded in the previous step S303 is It is set as a recording start address. Then, the process proceeds to step S302, where a required focus bias different from the previous focus bias is set, and the process proceeds to step S303 and subsequent steps. As described above, through the processing of step S308, the processing of the second and subsequent steps S302 to S307 is executed, so that data recording is performed on different recording areas each time the focus bias is variably set. .
Also in this case, if it is determined in step S307 that all sample information has been acquired, the process proceeds to step S105 shown in FIG.
[0079]
In step S105 shown in FIG. 11, the focus bias as the optimum value is obtained by using any of the various calculation methods described with reference to FIG. 6 using the sample information obtained by the process of step S104. The Then, the focus bias as the calculated optimum value is held in the internal RAM of the system controller 10.
In this way, the focus bias as the optimum value calculated in step S105 and held in the internal RAM is read according to the area to be reproduced at the time of subsequent disk reproduction, as described above. Thus, the setting is made for the target value control circuit 41 (see FIG. 5). As a result, during actual reproduction, focus servo control by closed loop is executed under a state where a focus bias set in conformity with each loaded disc is applied. That is, an appropriate focus servo control operation can be obtained.
[0080]
When the jitter value is handled as a signal characteristic as in the second example, control is performed so as to capture the jitter value instead of the modulation degree in the processing operations shown in FIGS. 11, 12, and 13. If the processing is executed, the focus bias can be set by the same processing procedure.
Further, for example, depending on disc variations and various conditions, the test recording laser power set in step S102 is too weak to obtain a required modulation degree necessary for focus bias setting for any sample, Alternatively, there may be a case where the test recording laser power is too strong and the modulation degree for each sample does not change much. Therefore, when it is determined during the processing operation shown in FIG. 11 (and FIGS. 12 and 13) that such a state exists, the process returns to step S102 again to increase or decrease the test recording laser power. It is conceivable to configure the setting again.
[0081]
Further, the present invention is not limited to the configuration described so far. For example, the disk drive device of FIG. 1 shows only a general-purpose configuration to some extent, and each part is appropriately changed, such as addition or deletion of a necessary functional circuit unit according to the actually corresponding disk type. It is what is done.
Also, the degree of modulation or the jitter value is adopted as the signal characteristic for obtaining the focus bias, but if it is a reproduction signal characteristic that changes depending on the quality of the recording pit according to the defocus state at the time of recording For example, other signal characteristics may be employed.
[0082]
【The invention's effect】
As described above, the present invention performs trial recording while changing the focus bias with a laser power for trial recording lower than the laser power during normal recording, and reproduces the data recorded in this way. An optimum focus bias is set based on predetermined signal characteristics.
According to this configuration, first, the focus bias is set in conformity with each loaded disc. In other words, it is possible to obtain an optimum focus bias for each loaded disc regardless of variations in conditions due to changes in the optical system over time and variations from disk to disk. Therefore, an appropriate focus servo control can be executed no matter what disk is loaded.
In addition, by using a reproduction signal, it becomes possible to obtain a focus bias value with high accuracy, for example, even in a system in which a defocus margin is small by dealing with a high recording density medium. High reliability is obtained. Furthermore, by using a reproduction signal, it is not necessary to add a functional circuit unit for obtaining a focus bias in particular, and can be realized with a relatively simple configuration.
Further, even if no data is recorded in the rewritable disc area, the present invention includes a procedure for performing data recording by performing trial recording, so that the focus bias can be obtained appropriately. Is.
[0083]
Also, when obtaining the focus bias based on the signal characteristics, the focus bias that was set when the predetermined signal characteristics were the best or when the rate of change was minimized was set as the optimum focus bias. Then, the focus bias can be obtained by a relatively simple process.
Further, an arithmetic average or an average value of the focus bias that is set corresponding to two or more samples sandwiching the extreme value and having a predetermined characteristic close to the best extreme value is set as an optimum focus bias. Furthermore, if the focus bias as the optimum value is obtained by executing a numerical calculation process for obtaining a focus bias that is supposed to correspond to the extreme value of the signal characteristic based on the sample value, the necessary minimum value can be obtained. A focus bias can be obtained with high accuracy even with a small number of samples.
[0084]
When the reproduction signal characteristic used for obtaining the optimum focus bias is configured to detect the change amount of the signal modulation degree or jitter, for example, as a function of the original disk drive device, the modulation degree and jitter If a configuration for detecting the amount of change is provided, this may be used, and it is not necessary to add a functional circuit unit, so that the cost can be reduced. Even if such a function is added in accordance with the present invention, the increase in circuit scale and cost increase can be reduced.
[0085]
Also, during test recording, if data recording is performed on the same predetermined area of the optical recording medium while variably setting the focus bias, defocusing is possible without being affected by variations in sensitivity depending on the recording area. Pit quality can be obtained according to Therefore, a measurement result that does not depend on the sensitivity variation due to the recording area can be obtained as the reproduction signal characteristic, and a highly reliable result can be obtained as the focus bias obtained based on this measurement result.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a disk drive device according to an embodiment of the present invention.
FIG. 2 is a structural diagram conceptually showing a structural example of an optical system of an optical pickup.
FIG. 3 is an explanatory diagram showing a detection operation by a photodetector of the optical pickup.
FIG. 4 is an explanatory diagram showing the shape of a beam spot received by a photodetector according to a focus state.
FIG. 5 is a block diagram showing a focus servo system of the present embodiment.
FIG. 6 is an explanatory diagram showing an example of a relationship between a focus bias at the time of test recording and a modulation degree of a reproduction signal.
FIG. 7 is a block diagram illustrating a configuration example of a jitter detection circuit according to the present embodiment;
FIG. 8 is a timing chart for explaining an operation of detecting a phase difference between a binarized signal and a reproduction clock, which is necessary for jitter detection according to the present embodiment.
FIG. 9 is a timing chart for explaining an operation of detecting a phase difference between a binarized signal and a reproduction clock, which is necessary for jitter detection according to the present embodiment.
FIG. 10 is an explanatory diagram showing an example of the relationship between a focus bias at the time of test recording and a jitter value of a reproduction signal.
FIG. 11 is a flowchart showing a processing operation for obtaining a focus bias as an optimum value.
FIG. 12 is a flowchart showing a processing operation for obtaining a sample by the first test recording.
FIG. 13 is a flowchart showing a processing operation for obtaining a sample by the second test recording.
FIG. 14 is an explanatory diagram conceptually showing a state of laser light irradiated on a disk signal surface.
[Explanation of symbols]
1 optical pickup, 2 objective lens, 3 biaxial mechanism, 4 laser diode, 5 photo detector, 5a split detector, 5b differential amplifier, 6 spindle motor, 7 turntable, 8 thread mechanism, 9 RF amplifier, 10 system controller, 11 Binary circuit, 12 decoder, 13 interface unit, 14 servo processor, 15 thread driver, 16 biaxial driver, 16a focus coil driver, 16b tracking coil driver, 17 spindle motor driver, 18 laser driver, 20 PLL circuit, 21 jitter Detection circuit, 22 magnetic head driver, 23 magnetic head, 30 multiplier, 31 ΔT detection circuit, 32 jitter value calculation circuit, 51 collimator lens, 52 beam splitter, 3 a condenser lens, 36 a cylindrical lens, 41 a target value control circuit, 42 differential amplifier, 43 a phase compensation circuit, D disk,

Claims (10)

An optical recording / reproducing apparatus configured to perform recording / reproduction by irradiating an optical recording medium with a converged laser beam, and to set a focus bias for giving an offset with respect to the focal position of the converged laser beam. Te, a trial recording means sets the laser power lower than the laser power, and performing a trial recording for recording data the focus bias on the optical recording medium with variable settings that are set during normal recording,
Data reading means for reading the recording data recorded by the trial recording from the optical recording medium;
Measuring a predetermined signal characteristic of the recording data read by the data reading means, and obtaining a sample result as sample information in association with the focus bias set at the time of the trial recording;
A focus bias setting means for setting a focus bias to be optimized based on the sample information obtained by the sample means;
An optical recording / reproducing apparatus comprising: The focus bias setting means includes
Based on the sample information, an optimum focus bias is set by specifying the focus bias set at the time of the trial recording corresponding to the recording data for which the predetermined signal characteristic is best. The optical recording / reproducing apparatus according to claim 1, configured as described above. The focus bias setting means includes
Based on the sample information, an optimum focus bias is determined by specifying the focus bias set at the time of the trial recording corresponding to the recording data for which the change rate of the predetermined signal characteristic is the minimum The optical recording / reproducing apparatus according to claim 1, wherein the optical recording / reproducing apparatus is configured to set the value. The focus bias setting means includes
Based on the sample information, the predetermined signal characteristic is obtained at two measurement points that are close to a predetermined value set in advance and sandwich the measurement point that is the extreme value of the measured predetermined signal characteristic. 2. The optical recording / reproducing apparatus according to claim 1, wherein an average value is calculated using a focus bias as sample information, and the calculated average value is set as an optimum focus bias. The focus bias setting means includes
Based on the sample information, the predetermined signal characteristic is obtained at two measurement points that are close to a predetermined value set in advance and sandwich the measurement point that is the extreme value of the measured predetermined signal characteristic. 2. The optical recording / reproducing according to claim 1, wherein an arithmetic average value for the focus bias is calculated using sample information, and the calculated arithmetic average value is set as an optimum focus bias. Equipment . The focus bias setting means includes
Based on the sample information, a required numerical calculation process for obtaining a focus bias that corresponds to an extreme value as a signal characteristic is performed, and a value obtained from the calculation result is set as an optimum focus bias. The optical recording / reproducing apparatus according to claim 1. The focus bias setting means includes
2. The optical recording / reproducing apparatus according to claim 1, wherein a signal modulation degree is measured as the predetermined signal characteristic. The focus bias setting means includes
2. The optical recording / reproducing apparatus according to claim 1, wherein a change amount of jitter is measured as the predetermined signal characteristic. The trial recording means includes:
The data recording is performed on the same predetermined area of the optical recording medium when data recording is performed on the optical recording medium while variably setting a focus bias. Optical recording / reproducing apparatus . This is performed in a recording / reproducing apparatus that can perform recording / reproduction by irradiating the converged laser beam onto an optical recording medium, and a focus bias for providing an offset with respect to the focal position of the converged laser beam. A focus bias setting method for setting,
Trial recording procedure for performing trial recording for recording data on the optical recording medium while setting the laser power lower than the laser power set during normal recording and variably setting the focus bias;
A data reading procedure for reading the recording data recorded by the trial recording from the optical recording medium;
Measuring a predetermined signal characteristic of the recording data read by the data reading procedure, and obtaining a sample result corresponding to the focus bias set at the time of the trial recording as a sample procedure;
A focus bias setting procedure for setting an optimum focus bias based on the sample information obtained by the sample procedure;
A focus bias setting method characterized in that

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