JP3816583B2 - Recording method of optical information recording medium - Google Patents

Description

【００４３】
表１からわかるように、従来例では書き換え回数の増加に伴ってジッタ値が著しく増加しているが、本実施例ではジッタ値の増加はわずかである。つまり、本実施例では繰り返し記録による再生信号品質の劣化が抑制されていることがわかる。
【００４４】
なお、特開平２−９４１１３号公報に開示されているようなセクタにおける記録開始点をランダムに変化させる方法と本発明の上記実施形態による方法とを併用すれば、多数回の溶融／固化を繰り返す部分と全く溶融しない部分との境界が形成される確率が記録領域のいずれの位置においてもほぼ均一になるので、記録薄膜の劣化がさらに抑制される。具体的な回路構成としては、図１中の合成回路８の出力路に遅延量を段階的に変更し得る遅延回路を設け、セクタの書き換えごとに遅延量をランダムに変更すればよい。このようにして繰り返し記録を行ったときのジッタ値σ／Ｔｗの測定結果が表１に示した「他の実施例」の欄である。遅延量は８段階に変更し、その間隔はディスク上で最短マーク長に相当する間隔とした。表１から、ジッタ値の増加が上記第１の実施例と比べてさらに抑制されていることがわかる。
【００４５】
また、本実施形態では変調方式として、記録マークのエッジ間隔に信号を対応させるパルス幅変調を用いており、記録データの符号を反転させても記録マークのエッジ間隔は変化しない。そのため符号の反転した記録データの復調も、符号の反転していない記録データと同じ方法で可能であり、復調回路の構成が容易である。記録マークの中心間隔に信号を対応させるパルス間変調方式等においても、パルス幅変調方式と同様に本発明を適用することにより、記録薄膜の劣化を抑制することができる。
【００４６】
次に、本発明の別の実施形態について説明する。
図４に、第２の実施形態に係る記録再生装置の構成をブロック図で示す。また、この装置が、あるセクタの記録情報を書き換えるために行う動作を図５のフローチャートに示す。まず、ステップ５０１において、書き換えるセクタのＩＤ情報（アドレス情報）１６を検出した後、上位計算機と接続されたシステム制御回路４が記録すべき記録情報５を２値化信号として出力する（ステップ５０２）。この記録情報５は、変調回路７ａによりエラー訂正情報を付加され（５０３）、変調される（５０４）。そして合成回路８において、各セクタに記録するデータ長ごとに同期信号発生回路２からの同期信号（ＶＦＯ）等が付加されて記録データ１１ａとなる（ステップ５０５）。
。
【００４７】
次に、ダミーデータ発生回路２１にて、記録データ１１ａの前に付加するダミーデータ２６が生成され、第２の合成回路２２にて記録データ１１ａとダミーデータ２６とが合成される（５０６）。これがレーザパワー制御回路１２に入力されてレーザ光の強度が変調され（５０７）、光ディスク１に照射されることによりデータが記録される（５０８）。なお、ここでいうダミーデータ２６は、同期信号等を含む本来の記録データに付加されるデータである。図６にダミーデータ発生回路２１の構成の一例を示す。また、この回路の各部の信号波形を図７に示す。
【００４８】
システム制御回路４からダミーデータ発生用の信号２７がダミーデータ発生回路２１に与えられる。ダミーデータ発生用信号２７は、記録時の最短パルス幅に対応したクロック２４とアドレス情報検出信号３０とからなる。クロック２４は分周回路２８、分周比設定回路３３、および信号反転検出回路２９に入力され、アドレス情報検出信号３０は遅延回路３２に入力される。この遅延回路３２の遅延時間として、記録データの前にダミーデータを付加するために必要な所定の時間が設定される。遅延回路３２から分周回路２８と分周比設定回路３３とに信号３１が入力されるとクロック２４の分周がスタートする。
【００４９】
分周比設定回路３３は、分周回路２８の分周比を漸減させるような分周比設定信号を分周回路２８に与える。これにより、分周回路２８は、図７に示すように周期が漸減するパルス信号２５を出力する。この信号２５が入力される信号反転検出回路２９は、信号２５の反転時に所定クロック数分のパルス幅を有するパルス信号を発生させる。このパルス信号がダミーデータ２６となる。
【００５０】
図８に、本記録再生装置による記録データ、レーザ光の強度変調、光ディスクへの記録状態の一例を示す。図８からわかるように、このダミーデータの記録マークを形成するパルス間隔とパルス幅（レーザ光のパワーがPpの期間）との比、したがって、光ディスクに形成される記録マーク間隔Ｓwと記録マーク長Ｍwとの比はダミーデータの始端に近いほど大きくなっている。
【００５１】
上記のような記録方法によれば、記録薄膜への熱的負担はダミーデータの始端に近づくに従って漸減し、記録薄膜の物質移動量もダミーデータの始端に近づくに従って漸減する。その結果、記録薄膜における記録開始点へのダメージの集中を防止でき、多数回の書き換えによる記録データの始端における記録薄膜の劣化を防ぐことができる。
【００５２】
以下に、具体的な実施例について説明する。
使用した光ディスク、変調方式、記録再生パワーは第１の実施例と同様のものである。記録情報にはランダム信号を使用し、記録データの前に図８に示したようなダミーデータを付加して、３万回、５万回、７万回、１０万回の４通りで繰り返し記録を行なった。そしてダミーデータを含む記録データの始端部分で再生信号波形が歪んだ領域を再生信号劣化領域とし、始端からの劣化領域の長さを測定した。なお、ダミーデータの長さはディスク上で５０μｍである。図８に示したように、ダミーデータの記録マーク間隔Ｓwと記録マーク長Ｍwとの比をダミーデータの始端に近いほど大きくした。
【００５３】
表２に、本実施例（第２の実施例）及び後述する他の実施例における再生信号劣化領域の長さの測定結果を従来例の記録方式による再生信号劣化領域の長さと比較して示す。
【００５４】
【表２】

【００５５】
表２からわかるように、本実施例における始端部分の再生信号劣化領域の長さは、従来例と比較して短くなっている。つまり、本実施例では繰り返し記録による記録薄膜の劣化が抑制されていることがわかる。
【００５６】
なお、本実施例では記録薄膜の繰り返し劣化がセクタの前方で顕著に生じる場合を想定してダミーデータを記録データの前に付加したが、光学情報記録媒体の膜構造によっては、記録薄膜の繰り返し劣化がセクタの後方で顕著に生じる場合もある。この場合は図９に示すように、記録データの後にダミーデータを付加し、ダミーデータの終端に近いほど記録マーク間隔と記録マーク長との比を大きくすれば、記録データの終端における記録薄膜の劣化を防ぐ効果が得られる。
【００５７】
また本実施例のダミーデータは、記録マーク長Ｍwを一定にして記録マーク間隔Ｓwを変化させているが、記録マーク間隔を一定にして記録マーク長を変化させてもよい。記録開始・終了点における記録薄膜への熱的負担の急変を緩和するものであれば、ランダム信号パターンやＤＣ信号パターンのような他のパターンを用いてもよい。
【００５８】
図４に示した第２の実施形態に係る記録再生装置の構成において、ダミーデータ発生回路２１および第２の合成回路２２の代わりに、図１０に示すように、レーザ光の強度を段階的に増加または減少させるパターン発生回路３４と第２のレーザパワー制御回路３５、そしてレーザパワー制御回路を第１と第２とで切り換えるためのセレクタ３６を設けてもよい。そして、図１１又は図１２に示すように、記録データの前又は後のダミー領域において、レーザ光の強度を漸増または漸減させ、セレクタ３６を切り換えることによって、ダミー領域と記録データ領域とが連結したレーザ光強度変調波形３６ａを得る。これを記録用の光ビームとして光ディスクに照射すれば上記実施例と同様の効果が得られる。
【００５９】
また、前述のセクタにおける記録開始点をランダムに変化させる方法と、本実施形態で示した方法とを併用すれば、ダミーデータ始端での熱的負担の減少がより滑らかになり、表２の「他の実施例」の欄に示すように、記録データ始端での記録薄膜の劣化防止が一層効果的になる。
【００６０】
また、必要に応じてダミーデータの長さを書き換えごとにランダムに変更してもよく、これにより記録開始点をランダムに変化させる方法と同様の効果を得ることができる。
【００６１】
また、本実施例では、記録データの前に付加したダミーデータの終端の記録マーク長及び記録マーク間隔を同期信号部の記録マーク長及び記録マーク間隔に等しくした。これはダミーデータと同期信号部との境界で熱的負担が急変するのを防止し、同期信号部の始端から記録薄膜の劣化が生ずることを抑制するためである。
【００６２】
さらに、本実施形態のように記録データの前にダミーデータを付加する方法と、第１の実施形態のように記録データの符号をランダムに反転する方法とを併用して、図１３に示す構成の装置を用いれば、記録データの始端・終端での記録薄膜の劣化と記録データ中の局所的な記録薄膜の劣化の両方が抑制されるので、繰り返し寿命を高めるのに一層効果的である。
【００６３】
次に本発明の第３の実施形態について説明する。
図１６に、第３の実施形態に係る光学情報記録再生装置の構成をブロック図で示す。また、図１７に、本発明に係る光ディスクのセクタ記録フォーマットの構造を示す。図１７において、４１はセクタのアドレス情報が記録されているＩＤ、４２はＰＬＬの同期引き込みのための同期信号（ＶＦＯ）、４３は記録したデータの先頭を識別するためのデータ先頭識別マークＤＭ、４４は本来のデータを誤り検出符号化したデータブロック、４５はデータブロック４４に引き続いて記録されるダミーブロックＤＭＹである。データの記録・再生・消去が行なわれるデータの記録領域４６とＩＤ４１の間には光ディスクの回転変動等に対処するためのＧＡＰ４７、４８が設けられている。繰り返し記録に対する要求が低い場合については、ＤＭＹ４５を省略することができる。なお、第１および第２の実施形態では、データ先頭識別マークＤＭを、本来の記録データに含めている。
【００６４】
図１６において、２００１は光ディスク、２００２は光ディスク２００１の案内トラックに追従して記録面に半導体レーザの出力光を照射し、データの記録・再生・消去を行なう光ピックアップ、２００３は光ディスク上の所望の位置にレーザ光が集光するように光ピックアップの位置を制御するサーボ制御回路、２００４は符号化データを記録に適した形にデジタル変調するデータ変調回路、２００５はＰＬＬの同期引き込みのための同期信号（ＶＦＯ）を発生する同期信号発生回路、２００６はデータ先頭識別信号ＤＭを発生させるＤＭ発生回路、２００７はダミーデータを発生させるダミーデータ発生回路、２００８はデータを誤り検出訂正符号化する符号化回路、２００９は記録のタイミングを制御する記録タイミング制御回路、２０１０はセクタのＩＤ２１から目的アドレスを検出するアドレス検出回路、２０１１はマイクロプロセッサー等で構成され全体を制御するシステム制御回路である。
【００６５】
以上のように構成された光ディスク装置の動作を説明する。データの記録時、システム制御回路２０１１は記録すべき目的セクタのアドレスをサーボ制御回路２００３に与える。サーボ制御回路２００３はアドレス検出回路からのアドレスと目的アドレスとを比較して光ピックアップ２００２のサーボ制御を行なう。システム制御回路２０１１は符号化回路２００８に符号化命令２０１３を出し、記録タイミング制御回路２００９に記録命令を出す。
【００６６】
符号化回路２００８は符号化命令２０１３に従ってデータ２０１２を誤り検出訂正符号化し、符号化したデータ２０１４をデータ変調回路２００４に渡す。データ変調回路２００４は符号化データ２０１４をデジタル変調する。
【００６７】
記録タイミング制御回路２００９はシステム制御回路２０１１からの記録命令によって起動され、アドレス検出回路２０１０が目的セクタを検出するのをまって同期信号発生回路２００５、ＤＭ発生回路２００６、データ変調回路２００４、ダミーデータ発生回路２００７に順次起動命令を与え、これによってセクタの記録領域４６にデータが記録される。この際、同期信号発生回路２００５は同期信号を発生し、ＤＭ発生回路２００６はデータ先頭識別信号ＤＭを発生する。ダミーデータ発生回路２００７は所定のダミーデータを発生する。繰り返し記録に対する要求が低い場合については、ダミーデータ発生回路２００７を省略することができる。
【００６８】
次に、記録タイミング制御回路２００９のうち、同期信号発生回路２００５に起動命令を与える部分の構成例を図１８に示し、タイミングチャートを示す図１９を参照しながら本装置の動作を説明する。
【００６９】
アドレス検出回路２０１０が再生したアドレス信号からセクタ区間を示すセクタパルス２２０１が取り出され、これは遅延回路２２０２に送られ所定の遅延時間ｄ１を与えられてスタートパルス２２０３になる。スタートパルス２２０３は同期信号発生回路２００５に送られ、ここで同期信号が発生する。この際、同一セクタに情報を記録する場合は、同じ遅延時間が与えられる。すなわち、光ディスク上の同じ場所から同期信号の記録が始まる。一方、セクタパルス２２０１はもう１つの遅延回路２２０４にも送られ、所定の遅延時間ｄ２を与えられてスタートパルス２２０５になる。ｄ２はｄ１より大きな値である。
【００７０】
カウンタ２２０９は、ある周期のクロック入力２２１０を分周して、データ入力パルス２２０５と非同期の適当な周期のクロック２２０８を作り、このクロック２２０８をＤタイプ−フリップフロップ（以下Ｄ−ＦＦと呼ぶ）２２０６に与える。Ｄ−ＦＦ２２０６はデータ入力としての遅延回路２２０４からのパルス２２０５をラッチし、出力２２０７をストップパルスとして同期信号発生回路２００５に与える。この際、データ入力パルス２２０５と非同期のクロック入力２２０８の周期によって、ランダムな遅延時間がストップパルス２２０７に生じる。従って同期信号発生回路２００５は、同期信号の停止点をランダムに変化させる。記録タイミング制御回路２００９は同期信号発生回路２００６に起動命令を与えた後、ストップパルス２２０７に同期してＤＭ発生回路２００６に起動命令を送りデータ先頭識別マークを記録させる。
【００７１】
以上のように本実施形態によれば、同期信号発生回路２００５の前にＤ−ＦＦ２２０６を設けることにより、同一セクタに繰り返し記録する場合、光ディスク上での同期信号の記録開始位置は変えずに、同期信号の長さをランダムに変えることができる。
【００７２】
ここで、従来の記録方法と本実施形態に係る記録方法とについて、同一セクタに繰り返し記録を行なう場合の再生波形の劣化抑制効果を比較する。図２０に、同一セクタに記録する際の同期信号の記録場所を示す模式図を示す。図２０の方法（１）は従来の記録方法で同期信号の記録開始位置をランダムに変化させる場合を示し、図２０の方法（２）は本発明の記録方法で同期信号記録開始位置は変えずに同期信号の長さをランダムに変化させる場合を示している。それぞれの場合において、同期信号４２の終了点の位置が記録開始点に近いものから遠くのものへ順に並べているが、実際にはランダムにこれらのパターンが記録される。同期信号４２の終了点の最大位置ずれ量２４０１は、従来の記録方法と本記録方法とで同じ値をとることになる。
【００７３】
図２０の方法（２）に示した本記録方法の模式図において、同期信号の最短長さ２４０２は次のように設定する。繰り返し記録を行なった場合に、同期信号の記録開始点から再生波形劣化が生じ、繰り返し回数の増加に伴ってレーザビームの進行方向へ波形劣化が伝播・進行する。従って、同期信号の最短長さ２４０２は使用にあたって想定した最大繰り返し記録後にも同期信号の少なくとも後端が再生可能で、ＰＬＬの同期引き込みに支障が生じないように設定される。
【００７４】
ここで、図２０の方法（１）に示す従来の記録方法において同期信号の最短長さ２４０３を図２０の方法（２）に示す本記録方法のＶＦＯ最短長さ２４０２と同じにすれば、同期信号４２の終了点がランダムに変化する範囲については、図２０をみるかぎり、従来の記録方法と本記録方法とで差異はない。しかしながら、同期信号の長さ２４０３が固定の従来の記録方法に比べて、同期信号の長さが上記２４０３の長さに等しい最短長さ２４０２からこれに最大位置ずれ量２４０１を加えた最長長さとの間でランダムに変化する本記録方法は、以下の理由により有利である。つまり、本記録方法における同期信号の平均長さは、従来の記録方法における同期信号の固定長さ２４０３より最大位置ずれ量の半分に相当する長さだけ長くなる。一方、繰り返し記録に伴う劣化は記録開始点、即ち同期信号の開始点を起点にして進行する。従って、本記録方法によれば、同期信号の平均長さが従来の記録方法の固定長さより長い分だけ、繰り返し記録による劣化が記録データの先頭のＤＭに達するまでの時間が長くなる。つまり、繰り返し記録可能な回数が多くなる（繰り返し記録の寿命が長くなる）。
【００７５】
逆に、同程度の繰り返し寿命を得るためには、本実施形態の光ディスク装置は従来の装置に比べて、同期信号に割り当てる長さを短くすることができるので、同一光ディスクにおける実質上の記録容量を従来の装置より増加することができる。なお、記録領域の開始点に、同期信号に先行する何らかの記録すべきデータがある場合であっても本発明を適用することができる。例えば、同期信号の記録に先だってダミーデ−タを記録する場合等があてはまる。この場合には、ダミーデータの記録開始位置を揃え、かつ、同期信号の終了位置をランダムに変えて記録することで、本発明による効果が得られる。
【００７６】
次に、本発明の第４の実施形態について説明する。同一セクタに繰り返し記録する場合には、前述のように、同期信号の記録終了点がランダムに変化するように記録することにより、データブロックに同じパターンを記録しても確実にデータが再生できる。この場合、同じ容量のデータを記録してもデータの記録終了位置は光ディスク上でランダムに変化する。光ディスクの回転数の変動が充分に小さい場合には、記録毎のデータ記録終了位置は、同期信号の記録終了位置、即ちデータ先頭識別マークＤＭの記録位置から等距離離れた位置となるので、光ディスク上のデータの記録終了位置はデータ先頭識別マークＤＭの位置に連動してランダムに変化する。データの後に従来のように一定長のダミーデータを書き加えると、ダミーデータの記録終了位置もデータ先頭識別マークＤＭの位置に連動してランダムに変化する。そこで、同一セクタに繰り返し記録する場合、データ先頭識別マークの位置が後ろにずれているほどダミーデータの長さを短く、逆にデータ先頭識別マークの位置が前にずれているほどダミーデータの長さを長く記録するというように、ダミーデータの長さをデータ先頭識別マークの位置に連動させる手段を光ディスク装置に設ける。理想的には、同一セクタに繰り返し記録する場合に、光ディスク上でダミーデータの記録終了位置が常に同じ位置になるようにする。以下、第４の実施形態を具体的に説明する。
【００７７】
図１６に示した光ディスク装置の記録タイミング制御回路２００９のうち、ダミーデータの記録制御部の構成例を図２１に示すとともに、その動作のタイミングチャートを図２２に示す。
【００７８】
図１６に示すように、記録タイミング制御回路２００９はアドレス検出回路２０１０によって目的セクタが検出されると、同期信号発生回路２００５、ＤＭ発生回路２００６、データ変調回路２００４、ダミーデータ発生回路２００７に順次起動命令を与える。この際、同期信号発生回路２００５に与えるスタートパルス２２０３かストップパルス２２０７のどちらかにランダムな遅延時間を与える。図２２は、ストップパルス２２０７にランダムな遅延時間を与えた場合を示している。一方、図２１の記録タイミング制御回路２００９に設けた遅延回路２５０１は、セクタ区間を示すセクタパルス２２０１をアドレス検出回路２０１０から受け取ってから、所定の遅延時間ｄ３後にストップパルス２５０２をダミーデータ発生回路２００７に出力する。ストップパルス２５０２を受け取ったダミーデータ発生回路２００７はダミーデータの発生を停止する。遅延回路２５０１によって与えられる遅延時間ｄ３は、ある想定した繰り返し回数を記録した後に生じる記録終端部での再生波形劣化をダミーデータで吸収して、データブロック４４の再生に影響を与えないような長さのダミーデータが記録できる時間に設定すればよい。以上のように本実施形態によれば、遅延回路２５０１を設けることにより、光ディスク上でのダミーデータの記録終了位置を同じにすることができる。ただし、実際には光ディスクを回転させるモータにある程度の回転むらが生じるので、記録終了位置を完全に同じ位置にできるとは限らない。
【００７９】
ここで、従来の記録方法と本実施形態による記録方法とについて、同一セクタに繰り返し記録を行なう場合の記録領域終端部での再生波形の劣化抑制効果を比較する。図２３に、同一セクタに記録する際のダミーデータの記録場所を示す模式図を示す。図２３の方法（１）は従来の記録方法であって、ダミーデータ４５の長さが一定である場合を示し、図２３の方法（２）は本実施形態による記録方法であって、ダミーデータ４５の記録終了位置をディスク上の同じ場所とする場合を示している。それぞれの場合において、データ先頭識別マークの位置が記録開始点から遠いものから近くなる順に並べているが、実際にはランダムにこれらのパターンが記録される。
【００８０】
図２３の方法（２）に示す本実施形態による記録方法でのダミーデータ４５の最短長さを図２３の方法（１）に示す従来方法でのダミーデータ４５の一定の長さと等しく設定した場合、本記録方法のダミーデータ４５の平均長さは従来方法でのダミーデータ４５の一定長さより長くなるので、その分だけ本記録方法は有利になる。つまり、この場合の繰り返し記録に伴う劣化は記録終了点を起点にして進行するので、その劣化がデータブロック４４の終端に達するまでの時間、つまり繰り返し記録寿命は、本記録方法の方が長くなる。
【００８１】
逆に、同程度の繰り返し寿命を得るためには、本実施形態の光ディスク装置は従来の装置に比べて、ダミーデータに割り当てる長さを短くすることができるので、同一光ディスクにおける実質上の記録容量を従来の装置より増加することができる。
【００８２】
次に、本発明の第５の実施形態について説明する。本実施形態は、光ディスク上で異なる半径のセクタに記録する場合に、レーザ光の照射位置における光ディスクの移動速度（以下線速度と呼ぶ）を記録半径に連動して変化させる光ディスク装置に適用される。例えば、記録するセクタの半径によらず光ディスクを一定回転数で回転させて記録する場合はこれに該当する。
【００８３】
まず、記録時の線速度によって繰り返し記録に伴う劣化がどのように生じるかを実験で調べた。その結果、ディスク構造、すなわち各層の膜厚、材料組成、或は記録時の線速度、レーザ光照射パワー、記録密度等をわずかに変化させると、繰り返し記録に伴う種々の劣化現象が大きく変化することがわかった。このことは、以下の点を考慮すれば定性的に理解できる。
【００８４】
（１）記録のためのレーザ光照射部分における温度プロファイル（例えば到達温度、昇温後の冷却速度等）は記録線速度の影響を強く受ける。
（２）記録の繰り返しに伴う再生波形劣化は、レーザ光照射部分の温度プロファイルの非対称性を１つの駆動力として生じる。
【００８５】
記録時の線速度に応じて記録パワーやレーザ光照射時間を変えたり、ディスク構造をディスク半径に応じて変化させる等の手段を用いても、繰り返し記録に伴う種々の劣化現象の記録線速度依存性を解消することはできなかった。
【００８６】
光ディスクシステムでは、記録容量の確保の観点から、同一セクタに情報を繰り返し多数回記録した場合の一連の記録領域の始端部（記録開始部）と終端部（記録終了部）における再生信号の劣化長の和が、記録時の使用想定線速度いずれに対してもできるだけ短くなるように、レーザ光照射プロファイル、またはディスク構造が調整されていることが望ましい。このような観点で実験を行なった結果、ある程度の成果が得られ、かつ記録領域の始端部における繰り返し記録に伴う再生波形劣化長と終端部における再生波形劣化長の比が、通常、記録線速度に応じて変化することがわかった。また、両劣化長の比と記録線速度との関係は１次関数で表わすことができなかった。繰り返し記録に伴って生じる再生波形劣化がデータブロックの再生に影響を与えないような同期信号の長さ、及びダミーデータの長さは、各光ディスクシステムに固有の、記録線速度に応じた最適値を有することがわかった。
【００８７】
また、同一セクタ内に同じパターンの信号が多数回記録されても再生波形劣化が生じないようにデータ先頭識別マークの記録位置をランダムに変化させる記録方法を実施する場合、記録開始位置の最大位置ずれ量（ＩＤに最も近く記録されたデータ先頭識別マークと、最も遠く記録されたデータ先頭識別マークとの距離）にも、記録線速度に応じた最適の長さがあることがわかった。データ先頭識別マークの最適の最大位置ずれ量と記録線速度との関係も１次関数で表わすことができなかった。データ先頭識別マークの位置をランダムに変化させるには、前述のように、同期信号の記録開始点を一定にしてその長さをランダムに変化させたり、或は同期信号の長さを一定にして同期信号の記録開始点をランダムに変化させる方法等が考えられる。
【００８８】
以上の実験結果から、繰り返し記録可能な相変化型光ディスク装置において、繰り返し記録に伴う再生波形劣化を抑制するには以下の３つの記録方法が有効であることがわかる。
【００８９】
（１）記録領域に同期信号（ＶＦＯ）、データ先頭識別マーク（ＤＭ）、変調データ、必要ならばダミーデータの順に続けて記録し、かつデータ先頭識別マークの位置をランダムに変化させる。
【００９０】
（２）同一セクタにおけるデータ先頭識別マークの最大位置ずれ量、及び／または同期信号の平均長さを記録時の線速度に応じた最適な値に選んで記録する。（３）同一セクタにおけるダミーデータの平均長さを記録時の線速度に応じた最適な値に選んで記録する。
【００９１】
実際の光ディスク装置では通常、記録時の線速度と記録半径が１：１に対応するので、上述の（２）または（３）の方法を実施するには、光ディスク装置が、記録半径毎に最適のデータ先頭識別マークの最大位置ずれ量、及び／または同期信号の平均長さ、ダミーデータの平均長さの換算表を備え、その換算表に従って所望の記録領域に記録するように構成すればよい。以下、具体的に実施形態を説明する。
【００９２】
図２４に、第５の実施形態に係る光ディスク装置の構成を示すブロック図を示す。この光ディスク装置も図１７に示した記録フォーマットでデータを記録することができる。図２４に示す光ディスク装置は図１６に示した光ディスク装置に対して、アドレス−（同期信号，ダミーデータ記録方法）変換メモリ（以下、単に変換メモリという）２８０１が付加されている。変換メモリ２８０１には、記録アドレス毎に最適のデータ先頭識別マークの最大位置ずれ量、同期信号の長さ、ダミーデータの長さ、またはダミーデータ記録終了位置等のデータが記憶されている。
【００９３】
以上のように構成された光ディスク装置について、以下その動作を説明する。データの記録時、システム制御回路２０１１は記録すべき目的セクタのアドレスをサーボ制御回路２００３と変換メモリ２８０１に与える。サーボ制御回路２００３はアドレス検出回路からのアドレスと目的アドレスとを比較して光ピックアップ２００２のサーボ制御を行なう。変換メモリ２８０１は、記録すべき目的セクタのアドレスに対応する記録フォーマットデータを記録タイミング制御回路２００９に与える。システム制御回路２０１１は符号化回路２００８に符号化命令２０１３を出すと共に、記録タイミング制御回路２００９に記録命令を出す。符号化回路２００８はデータ２０１２を誤り検出訂正符号化し、データ変調回路２００４に出力する。データ変調回路２００４は符号化されたデータ２０１４をデジタル変調する。繰り返し記録に対する要求が低い場合については、ダミーデータ発生回路２００７を省略することができる。
【００９４】
記録タイミング制御回路２００９はアドレス検出回路２０１０によって目的セクタが検出されると、変換メモリ２８０１から送られるデータに従って同期信号発生回路２００５、ＤＭ発生回路２００６、データ変調回路２００４、ダミーデータ発生回路２００７に順次起動命令を与え、セクタの記録領域４６に最適のデータ先頭識別マークの最大位置ずれ量を与える同期信号，データ先頭識別マーク，変調データ，適当の長さのダミーデータを順次記録する。また、変換メモリ２８０１に記録すべきアドレスを与えるのがはシステム制御回路２０１１である必要はなく、記録直前にアドレス検出回路２０１０が、検出したアドレス信号を変換メモリ２８０１に送ってもよい。また、変換メモリ２８０１を光ディスク装置内に持つ変わりに、光ディスク２００１に予めアドレス−（同期信号，ダミーデータ記録方法）を記録しておき、その情報に従って記録を行なうようにしてもよい。
【００９５】
以上のように本実施形態によれば、アドレス−（同期信号，ダミーデータ記録方法）変換メモリを設けることによって、記録半径に応じて最適のデータ先頭識別マークの最大位置ずれ量、及び／または同期信号の平均長さ、ダミーデータの平均長さを選択して記録することができる。この結果、記録線速度によらずに、繰り返し記録に伴って生じる記録再生波形劣化の影響を受けないようにしながら、従来に比べて光ディスクの実質上の記録容量を向上させることができる。
【００９６】
次に本発明の第６の実施形態について説明する。
図２５に、第６の実施形態に係る記録再生装置の構成をブロック図で示す。この記録再生装置が、あるセクタの記録情報を書き換えるために行なう動作を図２６のフローチャートに示す。また、記録動作のタイミングチャートを図２７に示す。図２６のステップ３００１において、書き換えるセクタのＩＤ情報４１（アドレス情報）を検出した後、上記計算機と接続されたシステム制御回路４が記録情報５を２値化した信号として出力する（３００２）。この記録情報は変調回路７ａにてエラー訂正情報を付加され（３００３）、変調される（３００４）。そして、合成回路８において、各セクタに記録するデータ長ごとに、同期信号発生回路２からの同期信号４２やダミーデータ発生回路２１からのダミーデータ４５等が付加されて記録データ１１ｃとなり（３００５）、このデータに従ってレーザ制御回路１２が光ヘッド３内のレーザを駆動してレーザ光の強度変調を行なう（３００６）。これによって光ディスク１の該当セクタにデータが記録される（３００７）。以上の動作は従来の構成と同様であるが、次に説明する動作が従来と異なっている。
【００９７】
上記の記録を行いながら、記録のために照射した光ビームが光ディスク１から反射してくる再生信号をストップパルス検出回路４９で検出する（３００８）。ストップパルス検出回路４９が、ダミーゲート発生回路５０で発生したダミーゲートで定めた検出時間内に光ディスク１の局部的な反射率変化として検知されるストップパルス５３を検出すれば、遅延回路５１で定めた所定の遅延時間ｄ４後に（３００９）ダミーデータの記録を停止する（３０１１）。一方、ストップパルス検出回路４９がダミーゲート発生回路５０で発生したダミーゲート５４で定めた検出時間内にストップパルスを検出しなければ、別の遅延回路５２で定めた所定遅延時間ｄ５後に（３０１０）ダミーデータの記録を停止する（３０１１）。上記ストップパルスは、光ディスク１上の各セクタの記録領域の終端近くで、ガイド溝の溝幅変化や溝深さを変化させたり、或はプリピットを設けて発生させる。
【００９８】
本発明によると、光ディスクを回転させるモータに回転ジッタが生じても、各セクタにおける記録終了位置を正確に揃えることができる。これは、ストップパルスが記録セクタの終了位置近くにあるため、ストップパルスを検出してから目的の記録終了位置に達するまでの時間が、セクタの記録開始点から記録終了点に達するまでの時間に比べて短くなることによる。すなわち、従来の記録方法だと、記録開始から所定の時間後に記録動作を停止するが、実際にはモータの回転むら等の影響があって、記録毎に記録終了位置は変化し得る。一方、本発明のようにストップパルスを検出してから、所定時間後に記録を終了する方法だと、従来例よりも、はるかに記録終了位置が揃う。別の言い方をすると、本記録方法を採用すると、モータの回転ジッタ等の影響を考慮せずに、使用できる記録領域の最後まで使いきることができる。すなわち、例えば、ダミーデータの領域を従来の記録方法よりも長くとることができる。
【００９９】
何等かの理由でストップパルスの検出に失敗した場合には、後続のＩＤ領域に入る前に記録を停止しなければならない。そこで、ストップパルスが検出されるべき時間を過ぎてもストップパルスが検出されなければ、モータの回転ジッタを考慮して、記録を停止する必要がある。また、ストップパルスの検出動作をはやい段階から開始すると、ストップパルスでない信号変化をストップパルスと誤って検出した場合に、本来の記録の途中で記録動作を停止することになる。このような理由で、ストップパルスの検出動作は、ストップパルス検出予定時間にモータの回転ジッタ等、考えられる時間ずれをつけ加えた時間範囲で内で行なえばよい。ダミーゲート発生回路５０が生成するダミーゲートは、ストップパルスを検出すべき時間内でストップパルスの検出を行なうようにするものである。
【０１００】
図２７のタイミングチャートに示されるように、光ディスク上の案内溝１７が途切れた部分でストップパルスを検出する場合、ストップパルスを検出してから遅延時間ｄ４後にダミーデータの記録が停止される。所定の検出時間内にストップパルスが検出されなかった場合は、その後、遅延時間ｄ５が経過するに伴ってダミーデータの記録が停止される。ストップパルスの検出に失敗した場合に遅延回路５２によって与えられる遅延時間ｄ５は、モータの回転ジッタ等を考慮に入れた記録終了位置が記録ストップパルスの検出に成功した場合の記録終了位置よりも後にならにように設定される。
【０１０１】
次に具体的な実施例を示す。実施例１に示した構成の光ディスク及び、記録条件で信号を繰り返し記録し、１回記録する毎に、記録終了位置（次のＩＤまでの距離）を測定した。ストップパルスの発生位置は、各セクタを２０：１に内分する位置（セクタの後部）とした。図２８，３３に、本実施例による、光ディスクの一例を示す。図２８は、案内溝がある場合で、ストップパルスは、案内溝がとぎれた部分で反射率が高くなって検出される。図２８のような光ディスクを用いた場合、記録動作中にストップパルスを検出することができ、従来の記録方法と比べて、同一セクタにおける記録終端位置のばらつきが２０分の１となることを確認した。
【０１０２】
案内溝を有する光ディスクでは、溝幅を局所的に細くしたり、或は溝深さを浅くしたりすることによっても、ストップパルスの検出が可能である。
また、図２９に示したように、いわゆるサンプルサーボ方式の光ディスクでは、プリピットの大きさが他のプリピットよりも大きなプリピットを記録領域の終端近くに設け、この大きなプリピットからの信号をストップパルスとして検出することも可能である。
【０１０３】
次に、本発明の第７の実施形態について説明する。先に述べた第３の実施形態では、セクター内に情報を記録する際に、同期信号であるＶＦＯ信号の記録を一定の位置から開始し、かつ、記録の度にＶＦＯ信号の長さをランダムに変化させることにより、記録始端の劣化を補償しながらデータ部の波形歪みを解消することを実現する。しかし、この場合、ＶＦＯ信号が光ディスクに対して常に一定のタイミングで記録されるので、回転精度および信号の時間精度が高い記録装置で記録した場合に、ＶＦＯ領域で固定パターン特有の波形歪みが生じる場合がある。
【０１０４】
そこで本実施形態では、この波形歪みを抑制するために、上記の方法に加えて、繰り返し記録の度に信号極性を反転し、または記録始端をシフトする方法を組み合わせることにより、繰り返し記録の性能をさらに向上させる。この記録方法について、図３０のブロック図と図３１のタイミングチャートを用いて説明する。
【０１０５】
光ディスク１からの再生信号１４が、再生信号処理回路１３、アドレス検出回路２０１０を経て復調され、ＩＤ信号６０がシステム制御回路４に入力される。上位計算機からの指示に従ってシステム制御回路４は、記録すべきセクターの範囲を示すセクター信号６１を記録タイミング制御回路２００９に出力する。記録タイミング制御回路２００９は、はじめに、再生信号からデータ信号を復調する際の同期信号であるＶＦ０信号を出力するためのゲート信号６２を、セクター信号６１から一定の時間Ｌｇだけ遅れたタイミングで同期信号発生回路２００５に出力する。なおゲート信号６２の区間は、必要とするＶＦＯ信号の区間Ｌｖよりも十分長い値に設定される。同期信号発生回路２００５は、ゲート信号区間に対応したＶＦＯ信号６５を合成回路８に出力する。
【０１０６】
また、記録タイミング制御回路２００９は、データの終端部の劣化を補償するためのダミー信号を得るためのダミーゲート信号６３をダミーデータ発生回路に出力する。ダミーゲート信号６３は、最終的に必要とするダミーデータ長よりも長い区間出力される。また、その終端位置がセクター信号６１の後端よりも前になるように、セクター開始点から一定時間Ｌｄｓ経過後に停止される。ダミーデータ発生回路２００７は、ダミーゲート信号６３に従って、ダミーデータ信号６７を合成回路１７に出力する。
【０１０７】
一方、システム制御回路４は、記録する情報信号に基づいて２値化された情報信号５を変調回路７ａに出力する。変調回路７ａは、記録信号５にエラー訂正符号を付加し、さらに光ディスクの記録に適した変調コード、例えばＥＦＭコード、（１，７）コード、または（８，１６）コードに従って変調を行う。変調された信号はデータ信号１９ｂとなり、この信号にはデータマーク、データ中の同期信号、パリティ等が含まれる。
【０１０８】
データ信号１９ｂの出力開始タイミングは、記録タイミング制御回路２００９からのＶＦＯゲート信号６２の立ち上がりからＬｖだけ遅れた記録開始パルス６４によって決まる。データ信号１９ｂは、第１のランダム遅延回路７０によって時間幅Ｍだけ遅延されて遅延データ信号７１となり、これが合成回路８に入力される。第１のランダム遅延回路７０は、入力された信号をＭ＝０〜Ｍｍａｘの範囲内のいずれかの遅延時間で遅延させる。
【０１０９】
第１の合成回路８は、遅延データ信号７１とＶＦＯ信号６５とを合成し、続く第２の合成回路１７がさらにダミーデータ信号６７を合成し、合成データ信号７２が生成される。このとき、データ信号７１とダミーデータ信号６７との重なり部分ではデータ信号７１が優先され、その後にダミーデータ信号６７が続くように合成される。ＶＦＯ、データ信号、およびダミー信号からなる合成データ信号７２は、第２のランダム遅延回路７３によって全体が遅延時間Ｎだけ遅れた遅延合成信号７４となる。なお、第２のランダム遅延回路７３は、入力された信号を、Ｎ＝０〜Ｎｍａｘの範囲内のいずれかの遅延時間で遅延させる。
【０１１０】
ランダム反転回路７５は、遅延合成信号７４の極性をランダムに反転して記録データ信号７６を生成する。この記録データ信号７６に従って、レーザパワー制御回路１２が光ヘッド３内のレーザを駆動し、レーザ光の強度を変調することにより光ディスク１上に信号の記録が行われる。なお、ランダム反転回路７５は、図１で示したように反転回路１０と選択回路９とを用い、記録データ信号または極性反転した記録データ信号をランダムに選択するように構成することができる。
【０１１１】
図３２に、記録するセクター内で信号の記録位置をランダムに変化させるために用いるランダム遅延回路７０の一例を示す。このランダム遅延回路７０は、シフトレジスタ８０、選択器８１、およびカウンタ８２から構成される。記録データ１９ｂとデータの基準クロック信号８３がシフトレジスタ８０に入力されると、シフトレジスタ８０はクロックの周期に対応する時間遅れをもつ８種類の信号（ｃ）〜（ｊ）を選択回路８１に出力する。カウンタ８２は、一連のデータ信号列、例えば１つのセクター内に記録するデータ列が入力される度にカウントアップし、その結果を選択回路８１に出力する。選択回路８１は、カウンタ８２の２進カウント信号（ｋ）〜（ｍ）の出力を、シフトレジスタ８０からの出力信号を選択するための信号として用い、選択した遅延データ信号７１を得る。
【０１１２】
以上の構成により、データ信号にランダムな遅延時間を与えることができる。また、遅延時間をさらに大きくとる場合は、シフトレジスタ８０のビット数を増やし、またはクロック８３を分周したものをシフトレジスタ８０に入力すればよい。また、第２の遅延回路７３についても同様の構成とすることができる。
【０１１３】
図３３は上記の方法により得られる光記録媒体の記録フォーマットを示す。記録媒体のセクター上には、ＩＤ信号４１に続いて、第１のギャップ領域４７、ＶＦＯ領域４２、データブロック４４、ダミーデータ４２、および第２のギャップ領域４８が配置される。
【０１１４】
第１および第２のギャップ領域４７、４８は、光ディスクの回転変動、記録ゲートのタイミングの変動等による誤記録が生じないようにするために設けられる。また、第１のギャップ領域４７の長さは、記録に先立って半導体レーザ等の光源のパワー設定を行うのに必要な時間を含むように設定することが望ましい。第２のギャップ領域４８は、主に回転変動によるＩＤ信号上への誤記録を防止するためのものであり、スピンドルモータおよびサーボ回路の性能に応じてその長さが決定される。
【０１１５】
ＶＦＯ信号４２については、繰り返し記録を行った後の記録始端での信号の劣化を考慮に入れた長さＬｖを設定する。記録媒体の補償する繰り返し記録回数、あるいは記録媒体を構成する材料に応じて、信号劣化を吸収できるような長さとする。即ち、ＶＦＯ信号４２は復調回路７ｂがデータ信号を復調する際に同期クロックのタイミングを得るための信号であるので、記録始端劣化が生じた後においても復調回路のＰＬＬ引き込みに必要な長さを越えるＶＦＯ信号の長さが確保されるようにする必要がある。
【０１１６】
データブロック４４に続くダミーデータ４５は、繰り返し記録を行った場合の記録終端部の劣化がデータブロックに及ばないように、この最大劣化長さを越える長さに設定する必要がある。
【０１１７】
次に、二つのランダム遅延回路７０、７３により、繰り返し記録の度に設定されるセクターフォーマットのパターンについて説明する。図３３の（ａ−１）は第１のランダム遅延回路７０による遅延量Ｍ、および、第２のランダム遅延回路７３による遅延量Ｎが共に０である場合であり、データブロックが最も前方、即ちＩＤ信号４１ａに最も近い位置にある。（ａ−２）はＮ＝Ｎ１の場合であり、遅延量Ｎ１分だけセクターの後方へＶＦＯ、データブロック、およびダミーデータの全体が移動する。（ａ−３）は、遅延量Ｎが最大値Ｎｍａｘの場合であり、ＶＦＯの先頭部が最も遅れた状態となる。このとき、ダミーデータ４５の後端部も（ａ−１）に比べて遅延量Ｎｍａｘだけ遅れ、その分、第２のギャップ領域が短くなる。
【０１１８】
図３３の（ｂ−１）は第１のランダム遅延回路７０による遅延量がＭ＝Ｍ１の場合であり、遅延量Ｍ１だけＶＦＯ領域の長さが伸びてＬｖ＋Ｍ１となる。従って、データブロックは（ａ−１）に比べてＭ１だけ遅れた位置から開始する。データブロックの後端部、即ちダミーデータ４５の始端部もＭ１だけ遅れるが、ダミーデータ４５の後端部は（ａ−１）と同位置である。つまり、ダミーデータの長さがＬｄ−Ｍ１に短縮される。以下、同様にして、ＶＦＯの長さと始端位置とが変化する。
【０１１９】
図３３の（ｃ−３）は、Ｍ＝Ｍｍａｘ、Ｎ＝Ｎｍａｘの場合であり、データブロックの遅延量が最も大きくなる（Ｍｍａｘ＋Ｎｍａｘ）。実際の記録動作においては、これらの遅延状態がランダムに選択される。したがってデータブロック４４の位置は、遅延量がゼロからＭｍａｘ＋Ｎｍａｘの範囲内でランダムに変化する。また、記録の始端は遅延量がゼロからＮｍａｘの範囲内でランダムに変化する。
【０１２０】
次に、本実施形態の効果を確かめるために行なった比較実験（実施例）について説明する。第１の実施例と同様に、光ディスク１のディスク基板には、直径１３０ｍｍ、厚さ０.６ ｍｍのポリカーボネート樹脂を用いた。この樹脂基板には、凸凹形状の位相ピットをあらかじめアドレス情報としてプリフォーマットし、セクタ領域には記録用ガイド溝を形成した。ガイド溝のピッチは１．６μｍである。基板上に保護膜、光感応性記録膜、保護膜、反射膜をスパッタリング法により４層成膜し、その上に保護基板を接着した。
【０１２１】
保護膜としてＺnＳ-ＳiＯ₂、光感応性記録薄膜としてＴe-Ｓb-Ｇe、反射膜としてＡlを用いた。そして、スピンドルモーター１５によりこのディスクを線速度６ｍ／ｓで回転させ、波長６８０ｎｍのレーザ光を開口数（ＮＡ）０．６の対物レンズで集束させて記録を行なった。
【０１２２】
記録再生時のレーザ光のパワーは、Pp=１１ｍＷ、Pb=４ｍＷ、Pr=１ｍＷとした。記録情報の変調方式は（８，１６）コードを用い、パルス幅変調で記録を行った。クロックの周期Ｔは３４ｎｓ、ビット長０．４μｍ、最短マーク長は０．６μｍとした。変調方式は、１個のマークに対して複数のパルス列からなる光照射を行うマルチパルス変調を適用した。セクター上に記録するデータのフォーマットとして、最短のギャップ長Ｌｇが３２バイト、ＶＦＯ長Ｌｖが６５バイト、データブロック長が２４１８バイト、ダミーデータ長Ｌｄが８２バイトのフォーマットを用い、ＶＦＯの変化量（遅延量）Ｍとギャップ長の変化量（遅延量）Ｎを変えながら記録実験を行った。なお、ＶＦＯ信号とダミー信号のパターンは、共に連続した４Ｔ信号を用いた。また、それぞれの変化量に対して、ランダム反転回路７５を用いた信号反転の有無による再生信号の劣化比較をも行った。
【０１２３】
図３４（ａ）および（ｂ）に実験結果を示す。これらのグラフにおいて、縦軸のジッターσ／Ｔｗ（％）は、再生信号のジッター値をウィンドウ幅に対する標準偏差の総和で表したものである。上記の光ディスクのセクター上に、同一のデータ信号を１０万回繰り返し記録した後のジッター値である。なお、復調の際のエラー発生確率が１万分の１程度以下である条件を目安として、ジッター値が１３％以下である条件をデータ再生の基準とした。
【０１２４】
図３４（ａ）はギャップ長を固定し、ＶＦＯ長の最大変化量Ｍｍａｘを段階的に変化させながら、その範囲内でＶＦＯ長をクロック周期Ｔ単位でランダムに変化させて記録動作を行った場合のジッターを測定したものである。曲線８４は信号極性のランダム反転をしなかった場合であり、曲線８５はランダム反転をした場合である。ＶＦＯ長の最大変化量Ｍｍａｘの増大に伴ってジッターの改善がみられる。曲線８４では８０Ｔ（５バイト）程度以上でジッターが１３％以下になり、曲線８５では４０Ｔ（２．５バイト）程度以上でジッターが１３％以下になっている。ランダム反転記録を加えることにより、ジッターが大きく改善されデータのシフト量を小さく設定できることがわかる。
【０１２５】
図３４（ｂ）はＶＦＯ長を固定し、ギャップ長の最大変化量Ｎｍａｘを段階的に変化させながら、記録動作を行った場合のジッターを測定したものである。ジッターの測定は、ＶＦＯ信号のＰＬＬに必要な長さが確保されるか否かチェックする観点からデータブロック側の３５バイトの領域で測定した。曲線８６は信号極性のランダム反転をしなかった場合であり、曲線８７はランダム反転をした場合である。図３４（ａ）と同様に、ギャップ長の最大変化量Ｎｍａｘの増大に伴ってジッターの改善がみられる。曲線８６では６Ｔ程度以上でジッターが１３％以下になり、曲線８７では２Ｔ程度以上でジッターが１３％以下になっている。この場合も、ランダム反転記録を加えることにより、ジッターが大きく改善されることがわかる。
【０１２６】
また、図３４の（ａ）と（ｂ）とを比較してわかるように、ジッター値が１３％以下である条件を満足するために必要なギャップ長の最大変化量Ｎｍａｘは、同じく必要なＶＦＯ長の最大変化量Ｍｍａｘに比べて小さい値でよい。セクター上に記録するフォーマット信号のパターンとして、ＶＦＯ長の最大変化量Ｍｍａｘに対して、ギャップ長の最大変化量Ｎｍａｘを小さく設定することにより、セクター中のデータブロックの容量をほとんど低下することなく波形劣化を効果的に抑制することができる。
【０１２７】
記録フォーマットの一例として、図３４（ａ），（ｂ）の結果に基づいて、２つの変化量の実用的な値を見積もる。これらの値は、上記の実験結果に加えて記録装置の特性変動、装置間の誤差、記録媒体の特性ばらつき等によるジッターの悪化要素を補償できるように設定しなければならない。ここでは、これらの要素を考慮して、ジッターが１３％以下となる量の３倍を実用上必要な変化量と見積もってみる。
【０１２８】
この結果、ランダム反転を行う場合はギャップ長の最大変化量Ｎｍａｘは６Ｔとなる。バイト数で表すと０．３８バイト、端数を切り上げて１バイトとなる。同じく、ＶＦＯ長の最大変化量Ｍｍａｘは７．５バイト、端数を切り上げて８バイトとなる。
【０１２９】
これに対してランダム反転しない場合は、ギャップ長の最大変化量Ｎｍａｘは１８Ｔとなる。バイト数で表すと１．１３バイト、端数を切り上げて２バイトとなる。同じく、ＶＦＯ長の最大変化量Ｍｍａｘは１５バイトとなる。これらの値を用いた記録フォーマットを適用することにより、１０万回の繰り返し後において、ＶＦＯ部、データブロック部を含めて再生信号に波形歪みが無く、始端劣化および終端劣化が補償された記録を行うことができる。
【０１３０】
記録再生装置の構成を簡素化する観点からは、ランダム反転回路７５を省略することも可能である。この場合は、ランダム反転記録を併用する場合に比べて繰り返し記録時のジッターが大きくなるが、これを補償するためにＶＦＯ長の最大変化量Ｍｍａｘを増大させ、その分、データ容量を削減することで対応することができる。
【０１３１】
なお、本実施形態ではダミーデータ長がＬｄ−Ｍであり、Ｍのランダム変化に応じてダミーデータ長が変化するが、終端劣化の小さい媒体を用いる場合には、データブロック４４の終端に固定長のダミーデータを付加するようにしてもよい。
【０１３２】
以上のように、フォーマット記録の際のギャップ長とＶＦＯ長をランダムに変化させることにより、同じデータを繰り返し記録した場合において、セクター上のトラックの同じ位置への記録を回避し、かつ、始端終端の劣化量を補償した記録を行うことができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態に係る記録再生装置の構成を示すブロック図
【図２】図１の記録再生装置が、あるセクタの記録情報を書き換えるために行う動作を示すフローチャート
【図３】図１の記録再生装置における記録データ、反転記録データ、レーザ光の強度変調、及び光ディスクへの記録状態を示すタイミングチャート
【図４】本発明の第２の実施形態に係る記録再生装置の構成を示すブロック図
【図５】図４の記録再生装置においてセクタの記録情報を書き換えるためにシステム制御回路が行う処理を示すフローチャート
【図６】図４の記録再生装置におけるダミーデータ発生回路の構成を示すブロック図
【図７】図４の記録再生装置におけるダミーデータ発生回路の各部の信号を示すタイミングチャート
【図８】図４の記録再生装置における記録データ、レーザ光の強度変調、及び光ディスクへの記録状態を示すタイミングチャート
【図９】図４の記録再生装置の変形例における記録データ、レーザ光の強度変調、及び光ディスクへの記録状態を示すタイミングチャート
【図１０】図４の記録再生装置の変形例の構成を示すブロック図
【図１１】図１０の記録再生装置における記録データ及びレーザ光の強度変調を示すタイミングチャート
【図１２】図１０の記録再生装置における記録データ及びレーザ光の強度変調の変形例を示すタイミングチャート
【図１３】図４の記録再生装置の他の変形例の構成を示すブロック図
【図１４】従来の記録再生装置の構成を示すブロック図
【図１５】図１４の記録再生装置による記録データ、レーザ光の強度変調、及び光ディスクへの記録状態を示すタイミングチャート
【図１６】本発明の第３の実施形態に係る記録再生装置の構成を示すブロック図
【図１７】光ディスクにおけるセクタの記録フォーマットの構成を示す図
【図１８】図１６の記録再生装置における記録タイミンング制御回路の構成を示すブロック図
【図１９】図１８の回路部分の動作を示すタイミングチャート
【図２０】図１６の記録再生装置によって記録される同期信号のパターン例を示す図
【図２１】本発明の第４の実施形態に係る記録再生装置の記録タイミング制御回路の構成を示すブロック図
【図２２】図２１の記録再生装置の構成部分の動作を示すタイミングチャート
【図２３】図２１の構成部分を備える記録再生装置によって記録されるダミーデータのパターン例を示す図
【図２４】本発明の第５の実施形態に係る記録再生装置の構成を示すブロック図
【図２５】本発明の第６の実施形態に係る記録再生装置の構成を示すブロック図
【図２６】図２５の記録再生装置が、あるセクタの記録情報を書き換えるために行う動作を示すフローチャート
【図２７】図２５の記録再生装置におけるストップパルス位置、及び記録状態を示すタイミングチャート
【図２８】本発明の第６の実施形態に係る光学情報記録媒体のガイド溝の形状の一例を示す平面図
【図２９】本発明の第６の実施形態に係る光学情報記録媒体のプリピットの形状の一例を示す平面図
【図３０】本発明の第７の実施形態に係る記録再生装置の構成を示すブロック図
【図３１】図３０の記録再生装置における各部信号のタイミングチャート
【図３２】図３０の記録再生装置におけるランダム遅延回路を例示する回路図
【図３３】図３０の記録再生装置による光記録媒体の記録フォーマットを示す図
【図３４】図３０の記録再生装置による繰り返し記録後の再生信号のジッター値を比較して示すグラフ
【符号の説明】
１ 光ディスク
２ 同期信号発生回路
３ 光ヘッド
４ システム制御回路
５ 記録情報
６ 再生情報
７ａ 変調回路
７ｂ 復調回路
８ 合成回路
９ 選択回路
１０ 反転回路
１１ａ 記録データ
１１ｂ 反転記録データ
１２ レーザパワー制御回路
１３ 再生信号処理回路
１４ ＲＦ信号
１５ スピンドルモーター[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk device you record the data in sector units with respect to a rewritable optical disk (optical information recording medium).
[0002]
[Prior art]
As an optical information recording medium capable of recording / reproducing and erasing a signal, a phase change type optical disk using a chalcogenide as a recording thin film material is known. In the case of a phase change optical disk, the recording thin film is a light sensitive thin film that causes a phase transition between crystals or amorphous when irradiated with a light beam such as a laser beam. In the case of a rewritable phase change optical disc, generally, a signal is obtained by setting a recording thin film in a crystalline state to an unrecorded state, irradiating a laser beam, and melting and quenching the recording thin film into an amorphous state. Record. On the other hand, when erasing the signal, the recording thin film is heated to a crystalline state by irradiating a laser beam having a power lower than that during recording.
[0003]
One of the merits of phase change recording is that an information signal can be overwritten using only a single laser beam as a recording means. In other words, if the laser output is modulated between two levels of the recording level and the erasing level according to the information signal and irradiated onto the recorded information track, a new signal can be recorded while erasing the existing information signal. (Japanese Patent Laid-Open No. 56-145530). Taking advantage of this feature, phase change optical discs are used as document files, image files, and data files.
[0004]
In rewritable optical discs, it is common to provide optically detectable guide tracks in a concentric or spiral manner on the substrate because of the need for higher recording tracks and discrete partial writing / erasing. Is. An optical disc apparatus records or reproduces information by irradiating a recording thin film formed on a guide track of an optical disc with a laser beam with a diameter of 1 μm or less.
[0005]
Also, digital information with variable data length is often handled by dividing a track into a plurality of sectors in order to increase recording efficiency, and in a fixed information unit, for example, 512 bytes or 1 Kbyte. Each sector includes a sector ID portion including a track address and sector address information and a recording area for recording and reproducing data. The address portion represents the physical address of the sector and is preformatted when the disc is manufactured.
[0006]
Usually, the recording format of data to be recorded in the recording area is a synchronization signal portion VFO for PLL (Phase Locked Loop) synchronization pull-in, data that is a synchronization signal added before the recording data and for identifying the head of the data A head identification mark DM (data mark), a modulated modulation data portion, a resynchronization signal portion that synchronizes the data with words, and the like. When recording data, the address information of the target sector ID portion is read, and a data group to be recorded in the sector at the timing of address detection is recorded in the recording area of the target sector.
[0007]
Recording methods can be roughly divided into an inter-pulse modulation method and a pulse width modulation method. In the inter-pulse modulation, the signal is detected by detecting the position of the mark during reproduction, whereas in the pulse width modulation, the signal is detected by detecting both ends of the mark. Pulse width modulation can increase the recording density compared to pulse-to-pulse modulation.
[0008]
A conventional recording / reproducing method for a phase change optical disc will be described below with reference to FIGS. FIG. 14 shows an example of the configuration of a conventional recording / reproducing apparatus. FIG. 15 is an explanatory diagram of a recording / reproducing operation with respect to an optical disc (optical information recording medium), and shows recording data, intensity modulation of laser light, and a recording state on the optical disc.
[0009]
As shown in FIG. 14, the record information 5 to be recorded is output as a binarized signal from the system control circuit 4 connected to the host computer. After the error correction information is added to the recorded information 5, the modulation / demodulation circuit 7a performs, for example, (1,7) RLL modulation method modulation. In the synthesizing circuit 8, a synchronizing signal (VFO) from the synchronizing signal generating circuit 2 is added for each data length to be recorded in each sector, and the recording data 11a is obtained. Corresponding to the recording data 11a, the laser power control circuit 12 drives and controls the laser in the optical head 3 to modulate the intensity of the laser light. Further, the system control circuit 4 drives the spindle motor 15 to rotate the optical disc 1.
[0010]
When the modulated laser light (laser light power Pp) from the optical head 3 is irradiated onto the recording thin film of the optical disc 1 and the temperature of the recording thin film rises above the melting point, the portion irradiated with the laser light is melted, The recording mark 20 is rapidly cooled to be in an amorphous state (see FIG. 15). Further, when a laser beam (laser beam power Pb) that raises the temperature of the recording thin film to a temperature equal to or higher than the crystallization temperature and lower than the melting point is focused and irradiated, the recording thin film in the irradiated portion enters a crystalline state. Information is stored by utilizing the difference between the crystalline state and the amorphous state.
[0011]
Next, reproduction from the optical disk is performed by utilizing the fact that the optical characteristics of the recording thin film are different between an amorphous state and a crystalline state. A weak laser beam (laser beam power Pr) is focused and irradiated onto the optical disc, and a change in reflected light is detected to obtain a reproduction RF signal 14 of recorded data. Then, the reproduction signal processing circuit 13 performs signal processing such as binarization, performs demodulation and error correction, and obtains necessary reproduction information 6.
[0012]
Even during recording, when scanning the ID section 16 which is the address information portion between the sectors 18 of the optical disk, the intensity of the laser light is reduced to a weak power similar to that during reproduction to irradiate the optical disk with address information. Reproduce.
[0013]
However, it is known that when a large number of information is repeatedly recorded in the same sector of an optical disk in an optical disk apparatus using a phase change optical disk, a deterioration phenomenon inherent to the phase change optical disk occurs, and the recorded information cannot be reproduced accurately. . In many cases, this type of degradation phenomenon spreads with the number of repetitions. There are three main deterioration patterns.
[0014]
(1) At the start end (record start portion) of a series of recording areas, a defect is gradually generated in the recording thin film as the recording is repeated, and the defect is rearward from the start end (relative laser traveling direction on the optical disk). ).
[0015]
(2) At the end portion (recording end portion) of a series of recording areas, as the recording is repeated, defects gradually occur in the recording thin film, and the defects are forward from the end portion (relative laser traveling direction on the optical disk). In the opposite direction).
[0016]
(3) When a mark row having the same pattern is repeatedly recorded at the same position in the sector, a defect occurs in the recording thin film at the place where the same pattern is recorded as the recording is repeated, and the defect spreads forward and backward. To go. Generally, when rewriting recorded data on an optical disc, rewriting is performed in units of sectors. Therefore, even when information on a part of the sector is changed, the entire sector is rewritten. In a TOC (Table of Contents) area or directory area where information corresponding to the table of contents of recorded information on the disk is recorded, particularly similar data is often repeatedly recorded, and rewriting frequency is high. In such a region, the pattern (3) is deteriorated.
[0017]
It has been found that all of these three types of deterioration are due to the fact that the material constituting the recording thin film gradually moves in the laser traveling direction or the opposite direction with repeated recording. However, it is not yet well understood what the driving force that the recording thin film material moves at the time of laser irradiation. Possible driving forces include surface tension accompanying a temperature gradient in the recording layer at the time of laser irradiation, or deformation of the optical disk constituting thin film due to a thermal load. In any case, when the recording thin film deteriorates, a predetermined light reflectance cannot be obtained in an unrecorded state and a recorded state. That is, the reproduction waveform is deteriorated, and this portion of information cannot be optically reproduced. Various proposals have been made on recording methods for solving these problems and improving the information rewriting performance. For example, there is an optical disc apparatus that reduces the degradation by changing the recording start position of the synchronization signal on the optical disc each time the degradation pattern (3) is rewritten (Japanese Patent Laid-Open No. 63-229625). Further, for the deterioration pattern (2), after recording the data block, the dummy data having a certain length is recorded and then propagated forward (direction toward the recording start point) from the recording end portion. An optical disc apparatus that eliminates the influence of waveform deterioration on information reproduction has been proposed (Japanese Patent Laid-Open No. Hei 2-297724).
[0018]
[Problems to be solved by the invention]
However, in the conventional recording method as described above, the recording start position of the synchronization signal is changed every time the recording start position is rewritten in order to suppress the reproduction waveform deterioration due to the repeated recording of the phase change optical disk and improve the repeated recording characteristics. Since a certain length of dummy data is added after the data block has been recorded, a dummy data area or the like is required in addition to the data block recording area. Therefore, the recording capacity is substantially reduced as compared with a case where these methods for improving the recording characteristics are not adopted.
[0019]
The present invention has been made in view of the above circumstances, and its purpose is to efficiently suppress deterioration due to repeated recording and improve the number of rewritable times in a rewritable phase change optical disc. it is to provide a recording how that can be.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, a recording method of an optical information recording medium according to the present invention includes a step of inverting a sign of recording data having a predetermined block length including recording information, and whether to invert the sign of the recording data. The recording data or the inverted recording data obtained by inverting the sign of the recording data is recorded on the photosensitive recording thin film according to the determination of the step of randomly determining whether to invert or not. And a step of performing.
An optical information recording apparatus according to the present invention includes a modulation circuit that generates recording data from recording information having a predetermined block length, an inversion circuit that inverts the sign of the recording data to generate inverted recording data, and the recording data Alternatively, a selection circuit that randomly selects one of the inverted recording data and a control circuit that controls the irradiation power of the light beam in accordance with an output of the selection circuit.
[0021]
As a result, the sign of the recording data is randomly inverted, so that even when similar recording data such as the TOC area is repeatedly overwritten at the same position on the disk, the concentration of damage to a specific position of the recording thin film is reduced. It is avoided and deterioration of the recording thin film due to rewriting many times can be suppressed.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of a recording / reproducing apparatus according to the first embodiment of the present invention. The operation performed by the recording / reproducing apparatus for rewriting the recording information of a certain sector is shown in the flowchart of FIG. First, in step 201, after detecting ID information (address information) of a sector to be rewritten, the system control circuit 4 connected to the host computer outputs the recording information 5 as a binarized signal (step 202). The recording information 5 is added with error correction information by the modulation circuit 7a (203) and modulated (204). Then, the synthesizing circuit 8 adds the sync signal (VFO) from the sync signal generating circuit 2 for each data length to be recorded in each sector to form the record data 11a (205). The above operation is the same as that of the conventional configuration, but the operation described below is different from the conventional operation.
[0033]
As shown in FIG. 1, the recording data 11a is branched into two and one is directly input to the selection circuit 9, while the other is converted to the inverted recording data 11b via the inverting circuit 10 (FIG. 2). Step 207), and this becomes the other input of the selection circuit 9. The selection circuit 9 is composed of a selector that triggers detection of address information of a sector that needs to be rewritten, and randomly selects one of the two inputs, and the selected position until recording in the sector is completed. Hold. That is, it is determined by this selection circuit 9 whether or not to reverse the sign of the recording data recorded in the corresponding sector (step 206 in FIG. 2).
[0034]
In a recording / reproducing apparatus used for the purpose of randomly accessing each sector of an optical disk, if the selection circuit 9 alternately selects one of the two inputs for each rewriting operation, it is substantially random. It will be the same as that selected. Therefore, the selection circuit 9 does not necessarily include a random number generation circuit for random selection. The output from the selection circuit 9, that is, the recording data 11a or the inverted recording data 11b is input to the laser power control circuit 12, and the laser power control circuit 12 drives the laser in the optical head 3 according to this data, and the intensity of the laser light. Modulation is performed (step 208). As a result, data is recorded in the corresponding sector of the optical disc 1 (209).
[0035]
FIG. 3 shows an example of the recording data, the intensity modulation of the laser beam, and the recording state on the optical disc by the recording / reproducing apparatus. When the same information is recorded, the waveform is the same up to the output of the synthesis circuit 8 regardless of inversion. However, the laser light intensity (laser power) when the inverted recording data 11b is selected by the selection circuit 9 is opposite to the relationship between Pp and Pb with respect to the laser power when the recording data 11a is selected. It has become. As a result, the recording mark 20 in the amorphous state is formed on the sector 18 of the optical disc with the opposite positional relationship despite the fact that the same information is recorded.
[0036]
Therefore, even if the same information is repeatedly recorded in the same sector, the probability that a recording mark is formed is almost uniform at any position in the recording area in the sector. In this way, local damage that can occur in the recording area due to many rewrites is eliminated.
[0037]
Specific examples will be described below.
As a disk substrate of the optical disk 1, a polycarbonate resin having a diameter of 130 mm was used. Uneven phase pits were preformatted as address information on the resin substrate, and recording guide grooves were formed in the sector area. A protective film, a photosensitive recording thin film, and a reflective film were formed on the substrate by a sputtering method, and a protective substrate was bonded thereon.
[0038]
In this example, ZnS—SiO ₂ was used as the protective film, Te—Sb—Ge as the photosensitive recording thin film, and Al as the reflective film. The disk was rotated by a spindle motor 15 (see FIG. 1) at a linear velocity of 5 m / s, and laser light having a wavelength of 680 nm was focused by an objective lens having a numerical aperture (NA) of 0.6 to perform recording.
[0039]
The power of the laser beam during recording / reproduction was Pp = 11 mW, Pb = 4 mW, and Pr = 1 mW. As a modulation method of recording information, 1-7 RLL PWM (pulse width modulation) was used. The shortest mark length and the shortest mark interval were each 0.6 μm.
[0040]
Using the above conditions, as the most extreme example of similar recorded information, the same recorded information was repeatedly overwritten and recorded in the same sector, and the jitter value of the reproduced signal was measured. The number of repetitions was 1, 10, 100, 1000, and 10,000. The information recorded in one sector is 2970 bytes.
[0041]
Table 1 shows the measurement result of the jitter value σ / Tw of the present embodiment (first embodiment) and other embodiments described later in comparison with the jitter value σ / Tw by the recording method of the conventional example. Here, σ is the standard deviation of the jitter value at the zero cross point of the reproduction signal, and Tw is the window width of the detection system.
[0042]
[Table 1]

[0043]
As can be seen from Table 1, in the conventional example, the jitter value increases remarkably with the increase in the number of rewrites, but in this embodiment, the increase in the jitter value is slight. That is, in this embodiment, it can be seen that the degradation of the reproduction signal quality due to repetitive recording is suppressed.
[0044]
If the method for randomly changing the recording start point in the sector as disclosed in Japanese Patent Laid-Open No. 2-94113 and the method according to the above embodiment of the present invention are used in combination, the melting / solidification is repeated many times. Since the probability that a boundary between a portion and a portion that does not melt at all is formed is almost uniform at any position in the recording area, the deterioration of the recording thin film is further suppressed. As a specific circuit configuration, a delay circuit capable of changing the delay amount in a stepwise manner is provided in the output path of the synthesis circuit 8 in FIG. 1, and the delay amount may be changed randomly every time the sector is rewritten. The measurement result of the jitter value σ / Tw when repeated recording is performed in this way is the column of “Other Examples” shown in Table 1. The delay amount was changed to 8 stages, and the interval was set to an interval corresponding to the shortest mark length on the disk. From Table 1, it can be seen that the increase in the jitter value is further suppressed as compared with the first embodiment.
[0045]
Further, in the present embodiment, as the modulation method, pulse width modulation is used in which a signal corresponds to the edge interval of the recording mark, and the edge interval of the recording mark does not change even if the sign of the recording data is inverted. Therefore, the demodulated recording data whose code is inverted can be demodulated by the same method as the recording data whose code is not inverted, and the configuration of the demodulation circuit is easy. Even in the inter-pulse modulation method that associates the signal with the center interval of the recording marks, the deterioration of the recording thin film can be suppressed by applying the present invention in the same manner as the pulse width modulation method.
[0046]
Next, another embodiment of the present invention will be described.
FIG. 4 is a block diagram showing the configuration of the recording / reproducing apparatus according to the second embodiment. FIG. 5 is a flowchart showing an operation performed by this apparatus to rewrite recording information of a certain sector. First, in step 501, after detecting ID information (address information) 16 of a sector to be rewritten, the recording information 5 to be recorded by the system control circuit 4 connected to the host computer is output as a binarized signal (step 502). . The record information 5 is added with error correction information by the modulation circuit 7a (503) and modulated (504). Then, the synthesizing circuit 8 adds the sync signal (VFO) from the sync signal generating circuit 2 for each data length to be recorded in each sector to form the recording data 11a (step 505).
.
[0047]
Next, the dummy data generating circuit 21 generates dummy data 26 to be added before the recording data 11a, and the second combining circuit 22 combines the recording data 11a and the dummy data 26 (506). This is input to the laser power control circuit 12, the intensity of the laser beam is modulated (507), and the optical disk 1 is irradiated to record data (508). The dummy data 26 here is data added to the original recording data including the synchronization signal and the like. FIG. 6 shows an example of the configuration of the dummy data generation circuit 21. FIG. 7 shows signal waveforms at various parts of the circuit.
[0048]
A dummy data generation signal 27 is supplied from the system control circuit 4 to the dummy data generation circuit 21. The dummy data generation signal 27 includes a clock 24 corresponding to the shortest pulse width during recording and an address information detection signal 30. The clock 24 is input to the frequency divider 28, the frequency division ratio setting circuit 33, and the signal inversion detection circuit 29, and the address information detection signal 30 is input to the delay circuit 32. As a delay time of the delay circuit 32, a predetermined time required for adding dummy data before the recording data is set. When the signal 31 is input from the delay circuit 32 to the frequency dividing circuit 28 and the frequency dividing ratio setting circuit 33, the frequency division of the clock 24 starts.
[0049]
The frequency division ratio setting circuit 33 gives a frequency division ratio setting signal that gradually decreases the frequency division ratio of the frequency division circuit 28 to the frequency division circuit 28. As a result, the frequency dividing circuit 28 outputs a pulse signal 25 whose period gradually decreases as shown in FIG. The signal inversion detection circuit 29 to which the signal 25 is input generates a pulse signal having a pulse width corresponding to a predetermined number of clocks when the signal 25 is inverted. This pulse signal becomes dummy data 26.
[0050]
FIG. 8 shows an example of the recording data, the intensity modulation of the laser beam, and the recording state on the optical disc by the recording / reproducing apparatus. As can be seen from FIG. 8, the ratio of the pulse interval and pulse width (period in which the laser beam power is Pp) for forming the dummy data recording mark, and therefore the recording mark interval Sw and recording mark length formed on the optical disc. The ratio with Mw increases as it approaches the beginning of the dummy data.
[0051]
According to the above recording method, the thermal burden on the recording thin film gradually decreases as it approaches the starting end of the dummy data, and the mass transfer amount of the recording thin film also decreases gradually as it approaches the starting end of the dummy data. As a result, it is possible to prevent the concentration of damage to the recording start point in the recording thin film, and it is possible to prevent the recording thin film from deteriorating at the beginning of the recording data due to rewriting many times.
[0052]
Specific examples will be described below.
The optical disk, modulation method, and recording / reproducing power used are the same as those in the first embodiment. Random signals are used for recording information, and dummy data as shown in FIG. 8 is added in front of the recording data, and recording is repeated in four ways: 30,000 times, 50,000 times, 70,000 times, and 100,000 times. Was done. Then, the region where the reproduction signal waveform was distorted at the beginning of the recording data including the dummy data was defined as the reproduction signal degradation region, and the length of the degradation region from the beginning was measured. The length of the dummy data is 50 μm on the disk. As shown in FIG. 8, the ratio between the recording mark interval Sw of the dummy data and the recording mark length Mw is increased as it is closer to the starting end of the dummy data.
[0053]
Table 2 shows the measurement results of the length of the reproduction signal deterioration area in the present embodiment (second embodiment) and other embodiments described later in comparison with the length of the reproduction signal deterioration area by the recording method of the conventional example. .
[0054]
[Table 2]

[0055]
As can be seen from Table 2, the length of the reproduction signal degradation region at the start end in this example is shorter than that in the conventional example. That is, in this example, it can be seen that deterioration of the recording thin film due to repeated recording is suppressed.
[0056]
In this embodiment, the dummy data is added before the recording data on the assumption that the repeated deterioration of the recording thin film occurs remarkably in front of the sector. However, depending on the film structure of the optical information recording medium, the recording thin film may be repeated. Degradation may occur significantly behind the sector. In this case, as shown in FIG. 9, if dummy data is added after the recording data and the ratio between the recording mark interval and the recording mark length is increased as the distance from the end of the dummy data increases, the recording thin film at the end of the recording data is increased. The effect of preventing deterioration is obtained.
[0057]
In the dummy data of this embodiment, the recording mark interval Sw is changed with the recording mark length Mw constant, but the recording mark length may be changed with the recording mark interval fixed. Other patterns such as a random signal pattern or a DC signal pattern may be used as long as they can alleviate a sudden change in the thermal burden on the recording thin film at the recording start / end points.
[0058]
In the configuration of the recording / reproducing apparatus according to the second embodiment shown in FIG. 4, instead of the dummy data generating circuit 21 and the second synthesizing circuit 22, as shown in FIG. A pattern generating circuit 34 and a second laser power control circuit 35 for increasing or decreasing, and a selector 36 for switching the laser power control circuit between the first and second may be provided. Then, as shown in FIG. 11 or FIG. 12, in the dummy area before or after the recording data, the intensity of the laser beam is gradually increased or decreased, and the selector 36 is switched to connect the dummy area and the recording data area. A laser light intensity modulation waveform 36a is obtained. If this is irradiated onto the optical disk as a recording light beam, the same effect as in the above embodiment can be obtained.
[0059]
Further, if the method of randomly changing the recording start point in the sector described above and the method shown in the present embodiment are used in combination, the reduction of the thermal burden at the beginning of the dummy data becomes smoother. As shown in the column “Other Embodiments”, the deterioration of the recording thin film at the beginning of the recording data becomes more effective.
[0060]
In addition, the length of the dummy data may be randomly changed for each rewriting as necessary, whereby the same effect as the method of randomly changing the recording start point can be obtained.
[0061]
In this embodiment, the recording mark length and the recording mark interval at the end of the dummy data added before the recording data are made equal to the recording mark length and the recording mark interval of the synchronization signal portion. This is to prevent the thermal burden from suddenly changing at the boundary between the dummy data and the sync signal portion, and to suppress the deterioration of the recording thin film from the start end of the sync signal portion.
[0062]
Further, the configuration shown in FIG. 13 is used in combination with the method of adding dummy data before recording data as in the present embodiment and the method of randomly inverting the sign of recording data as in the first embodiment. If this apparatus is used, both deterioration of the recording thin film at the start and end of the recording data and local deterioration of the recording thin film in the recording data are suppressed, so that it is more effective in increasing the repeated life.
[0063]
Next, a third embodiment of the present invention will be described.
FIG. 16 is a block diagram showing the configuration of the optical information recording / reproducing apparatus according to the third embodiment. FIG. 17 shows the structure of the sector recording format of the optical disc according to the present invention. In FIG. 17, 41 is an ID in which sector address information is recorded, 42 is a synchronization signal (VFO) for pulling in PLL, 43 is a data head identification mark DM for identifying the head of recorded data, Reference numeral 44 denotes a data block obtained by error-detecting and encoding original data, and reference numeral 45 denotes a dummy block DMY recorded following the data block 44. GAPs 47 and 48 are provided between the data recording area 46 where data is recorded / reproduced / erased and the ID 41 to cope with rotational fluctuations of the optical disk. When the requirement for repeated recording is low, DMY 45 can be omitted. In the first and second embodiments, the data head identification mark DM is included in the original recording data.
[0064]
In FIG. 16, reference numeral 2001 denotes an optical disc, 2002 denotes an optical pickup for irradiating the recording surface with the output light of the semiconductor laser following the guide track of the optical disc 2001, and 2003 denotes a desired optical disc on the optical disc. A servo control circuit that controls the position of the optical pickup so that the laser beam is focused on the position, 2004 is a data modulation circuit that digitally modulates the encoded data into a form suitable for recording, and 2005 is a synchronization for pulling in the PLL. A synchronization signal generation circuit that generates a signal (VFO), 2006 a DM generation circuit that generates a data head identification signal DM, 2007 a dummy data generation circuit that generates dummy data, and 2008 an encoding that performs error detection and correction encoding of the data Circuit 2009, a recording timing control circuit for controlling the recording timing, 2 10 address detection circuit for detecting a target address from ID21 sector, 2011 is a system control circuit for controlling the whole is constituted by a microprocessor or the like.
[0065]
The operation of the optical disk apparatus configured as described above will be described. At the time of data recording, the system control circuit 2011 gives the address of the target sector to be recorded to the servo control circuit 2003. The servo control circuit 2003 compares the address from the address detection circuit with the target address and performs servo control of the optical pickup 2002. The system control circuit 2011 issues an encoding command 2013 to the encoding circuit 2008 and issues a recording command to the recording timing control circuit 2009.
[0066]
The encoding circuit 2008 performs error detection / correction encoding on the data 2012 in accordance with the encoding instruction 2013, and passes the encoded data 2014 to the data modulation circuit 2004. The data modulation circuit 2004 digitally modulates the encoded data 2014.
[0067]
The recording timing control circuit 2009 is activated by a recording command from the system control circuit 2011, and the address detection circuit 2010 detects the target sector and stops synchronizing signal generation circuit 2005, DM generation circuit 2006, data modulation circuit 2004, dummy data. A start command is sequentially given to the generation circuit 2007, whereby data is recorded in the recording area 46 of the sector. At this time, the synchronization signal generation circuit 2005 generates a synchronization signal, and the DM generation circuit 2006 generates a data head identification signal DM. The dummy data generation circuit 2007 generates predetermined dummy data. When the demand for repeated recording is low, the dummy data generation circuit 2007 can be omitted.
[0068]
Next, FIG. 18 shows a configuration example of a portion of the recording timing control circuit 2009 that gives a start command to the synchronization signal generation circuit 2005, and the operation of this apparatus will be described with reference to FIG. 19 showing a timing chart.
[0069]
A sector pulse 2201 indicating a sector section is extracted from the address signal reproduced by the address detection circuit 2010, and is sent to the delay circuit 2202 to give a predetermined delay time d1 to become a start pulse 2203. The start pulse 2203 is sent to the synchronization signal generation circuit 2005, where a synchronization signal is generated. At this time, when recording information in the same sector, the same delay time is given. That is, recording of the synchronization signal starts from the same location on the optical disc. On the other hand, the sector pulse 2201 is also sent to another delay circuit 2204, and given a predetermined delay time d2, becomes a start pulse 2205. d2 is a value larger than d1.
[0070]
The counter 2209 divides the clock input 2210 having a certain period to generate a clock 2208 having an appropriate period asynchronous with the data input pulse 2205, and this clock 2208 is a D-type flip-flop (hereinafter referred to as D-FF) 2206. To give. The D-FF 2206 latches the pulse 2205 from the delay circuit 2204 as a data input, and supplies the output 2207 to the synchronization signal generation circuit 2005 as a stop pulse. At this time, a random delay time is generated in the stop pulse 2207 according to the period of the clock input 2208 that is asynchronous with the data input pulse 2205. Therefore, the synchronization signal generation circuit 2005 randomly changes the stop point of the synchronization signal. The recording timing control circuit 2009 gives an activation command to the synchronization signal generation circuit 2006 and then sends the activation command to the DM generation circuit 2006 in synchronization with the stop pulse 2207 to record the data head identification mark.
[0071]
As described above, according to the present embodiment, by providing the D-FF 2206 in front of the synchronization signal generation circuit 2005, when recording is repeatedly performed on the same sector, the recording start position of the synchronization signal on the optical disc is not changed. The length of the synchronization signal can be changed randomly.
[0072]
Here, the conventional recording method and the recording method according to the present embodiment are compared with respect to the effect of suppressing the deterioration of the reproduction waveform when the recording is repeatedly performed in the same sector. FIG. 20 is a schematic diagram showing the recording location of the synchronization signal when recording in the same sector. Method (1) in FIG. 20 shows a case in which the recording start position of the synchronization signal is randomly changed in the conventional recording method, and method (2) in FIG. 20 is the recording method of the present invention without changing the synchronization signal recording start position. Fig. 5 shows a case where the length of the synchronization signal is changed randomly. In each case, the positions of the end points of the synchronization signal 42 are arranged in order from the one near the recording start point to the one far from the recording start point, but actually these patterns are recorded at random. The maximum positional deviation amount 2401 at the end point of the synchronization signal 42 takes the same value between the conventional recording method and the present recording method.
[0073]
In the schematic diagram of the recording method shown in the method (2) in FIG. 20, the minimum length 2402 of the synchronization signal is set as follows. When repetitive recording is performed, the reproduction waveform deteriorates from the recording start point of the synchronization signal, and the waveform deterioration propagates and proceeds in the traveling direction of the laser beam as the number of repetitions increases. Therefore, the minimum length 2402 of the synchronization signal is set so that at least the rear end of the synchronization signal can be reproduced even after the maximum number of repetitive recordings assumed for use, and no trouble occurs in the PLL synchronization pull-in.
[0074]
Here, in the conventional recording method shown in the method (1) of FIG. 20, if the minimum length 2403 of the synchronization signal is made the same as the VFO minimum length 2402 of the present recording method shown in the method (2) of FIG. As far as FIG. 20 is concerned, there is no difference between the conventional recording method and the present recording method regarding the range in which the end point of the signal 42 changes randomly. However, compared with the conventional recording method in which the length 2403 of the synchronization signal is fixed, the length of the synchronization signal is the shortest length 2402 equal to the length of 2403 and the maximum length obtained by adding the maximum positional deviation amount 2401 to the maximum length. This recording method, which randomly changes between the two, is advantageous for the following reason. That is, the average length of the synchronization signal in this recording method is longer than the fixed length 2403 of the synchronization signal in the conventional recording method by a length corresponding to half of the maximum positional deviation amount. On the other hand, deterioration due to repetitive recording proceeds from the recording start point, that is, the start point of the synchronization signal. Therefore, according to the present recording method, the time until the deterioration due to repetitive recording reaches the first DM of the recording data becomes longer by the amount that the average length of the synchronization signal is longer than the fixed length of the conventional recording method. That is, the number of times that repetitive recording is possible increases (the life of repeated recording becomes longer).
[0075]
On the other hand, in order to obtain the same repetitive life, the optical disk apparatus of the present embodiment can reduce the length allocated to the synchronization signal as compared with the conventional apparatus. Can be increased over conventional devices. Note that the present invention can be applied even when there is some data to be recorded preceding the synchronization signal at the start point of the recording area. For example, this is the case when dummy data is recorded prior to the recording of the synchronization signal. In this case, the effect of the present invention can be obtained by recording the dummy data at the same recording start position and by randomly changing the synchronization signal end position.
[0076]
Next, a fourth embodiment of the present invention will be described. When recording repeatedly in the same sector, as described above, by recording so that the recording end point of the synchronization signal changes at random, data can be reliably reproduced even if the same pattern is recorded in the data block. In this case, even when data of the same capacity is recorded, the data recording end position changes randomly on the optical disc. When the fluctuation of the rotation speed of the optical disk is sufficiently small, the data recording end position for each recording is a position that is equidistant from the recording end position of the synchronization signal, that is, the recording position of the data head identification mark DM. The recording end position of the upper data changes randomly in conjunction with the position of the data head identification mark DM. When dummy data having a certain length is written after the data as in the prior art, the recording end position of the dummy data also randomly changes in conjunction with the position of the data head identification mark DM. Therefore, when recording repeatedly in the same sector, the length of the dummy data becomes shorter as the position of the data head identification mark is shifted backward, and conversely, the length of the dummy data is shifted as the position of the data head identification mark is shifted forward. The optical disk device is provided with means for interlocking the length of the dummy data with the position of the data head identification mark so that the length is recorded longer. Ideally, when recording is repeatedly performed in the same sector, the recording end position of the dummy data is always set to the same position on the optical disc. The fourth embodiment will be specifically described below.
[0077]
A configuration example of a recording control unit for dummy data in the recording timing control circuit 2009 of the optical disc apparatus shown in FIG. 16 is shown in FIG. 21, and a timing chart of its operation is shown in FIG.
[0078]
As shown in FIG. 16, when the target sector is detected by the address detection circuit 2010, the recording timing control circuit 2009 is sequentially activated by the synchronization signal generation circuit 2005, the DM generation circuit 2006, the data modulation circuit 2004, and the dummy data generation circuit 2007. Give instructions. At this time, a random delay time is given to either the start pulse 2203 or the stop pulse 2207 given to the synchronization signal generation circuit 2005. FIG. 22 shows a case where a random delay time is given to the stop pulse 2207. On the other hand, the delay circuit 2501 provided in the recording timing control circuit 2009 in FIG. 21 receives the sector pulse 2201 indicating the sector section from the address detection circuit 2010 and then supplies the stop pulse 2502 to the dummy data generation circuit 2007 after a predetermined delay time d3. Output to. Upon receiving the stop pulse 2502, the dummy data generation circuit 2007 stops generating dummy data. The delay time d3 given by the delay circuit 2501 is such a length that does not affect the reproduction of the data block 44 by absorbing the reproduction waveform deterioration at the recording end portion that occurs after recording a certain assumed number of repetitions with the dummy data. This time may be set to a time when the dummy data can be recorded. As described above, according to this embodiment, by providing the delay circuit 2501, the recording end position of dummy data on the optical disc can be made the same. However, in practice, the motor for rotating the optical disc has some degree of rotation unevenness, so the recording end position cannot always be made exactly the same position.
[0079]
Here, the conventional recording method and the recording method according to the present embodiment are compared with respect to the effect of suppressing the deterioration of the reproduction waveform at the end of the recording area when recording is repeatedly performed in the same sector. FIG. 23 is a schematic diagram showing a recording location of dummy data when recording in the same sector. The method (1) in FIG. 23 is a conventional recording method and shows the case where the length of the dummy data 45 is constant, and the method (2) in FIG. 23 is the recording method according to the present embodiment and is a dummy data. A case where the recording end position of 45 is set to the same place on the disc is shown. In each case, the positions of the data head identification marks are arranged in order from the farthest from the recording start point, but in actuality, these patterns are recorded at random.
[0080]
When the minimum length of the dummy data 45 in the recording method according to the present embodiment shown in the method (2) of FIG. 23 is set equal to a certain length of the dummy data 45 in the conventional method shown in the method (1) of FIG. Since the average length of the dummy data 45 in the present recording method is longer than the predetermined length of the dummy data 45 in the conventional method, the present recording method is advantageous to that extent. That is, since the deterioration accompanying the repeated recording in this case proceeds from the recording end point, the time until the deterioration reaches the end of the data block 44, that is, the repeated recording life is longer in the present recording method. .
[0081]
On the contrary, in order to obtain the same repetitive life, the optical disk apparatus of the present embodiment can reduce the length allocated to dummy data as compared with the conventional apparatus. Can be increased over conventional devices.
[0082]
Next, a fifth embodiment of the present invention will be described. The present embodiment is applied to an optical disc apparatus that changes the moving speed (hereinafter referred to as linear velocity) of an optical disc at a laser beam irradiation position in conjunction with the recording radius when recording in sectors of different radii on the optical disc. . For example, this applies to the case where recording is performed by rotating the optical disk at a constant rotational speed regardless of the radius of the recording sector.
[0083]
First, it was experimentally examined how deterioration caused by repeated recording occurs depending on the linear velocity during recording. As a result, if the disk structure, that is, the film thickness of each layer, the material composition, or the linear velocity during recording, the laser beam irradiation power, the recording density, etc. are slightly changed, various deterioration phenomena due to repeated recording will change greatly. I understood it. This can be qualitatively understood by considering the following points.
[0084]
(1) The temperature profile (for example, the reached temperature, the cooling rate after the temperature rise, etc.) in the laser beam irradiated portion for recording is strongly influenced by the recording linear velocity.
(2) The reproduction waveform deterioration due to the repetition of recording is caused by the asymmetry of the temperature profile of the laser light irradiated portion as one driving force.
[0085]
Depending on the linear velocity at the time of recording, the recording power and laser light irradiation time are changed, and even if means such as changing the disc structure according to the radius of the disc are used, various deterioration phenomena due to repeated recording depend on the recording linear velocity. It was not possible to eliminate the sex.
[0086]
In the optical disc system, from the viewpoint of securing the recording capacity, the degradation length of the reproduction signal at the start end (record start portion) and end end (record end portion) of a series of recording areas when information is repeatedly recorded in the same sector many times. It is desirable that the laser light irradiation profile or the disk structure is adjusted so that the sum of the values becomes as short as possible with respect to any expected linear velocity at the time of recording. As a result of experiments from this point of view, a certain level of results was obtained, and the ratio of the reproduction waveform deterioration length due to repeated recording at the beginning of the recording area and the reproduction waveform deterioration length at the end is usually the recording linear velocity. It turned out to change according to. Further, the relationship between the ratio between the two degradation lengths and the recording linear velocity could not be expressed by a linear function. The length of the sync signal and the length of the dummy data so that the reproduction waveform deterioration caused by repeated recording does not affect the reproduction of the data block and the length of the dummy data are optimum values according to the recording linear velocity, which are unique to each optical disc system. It was found to have
[0087]
In addition, when performing a recording method in which the recording position of the data head identification mark is randomly changed so that reproduction waveform deterioration does not occur even if the same pattern signal is recorded many times in the same sector, the maximum position of the recording start position It was found that the amount of deviation (the distance between the data head identification mark recorded closest to the ID and the data head identification mark recorded farthest) also has an optimum length according to the recording linear velocity. The relationship between the optimum maximum positional deviation amount of the data head identification mark and the recording linear velocity could not be expressed by a linear function. In order to change the position of the data head identification mark randomly, as described above, the recording start point of the synchronization signal is made constant and the length thereof is changed randomly, or the length of the synchronization signal is made constant. A method of changing the recording start point of the synchronization signal at random can be considered.
[0088]
From the above experimental results, it can be seen that the following three recording methods are effective in suppressing the deterioration of the reproduction waveform due to the repeated recording in the phase change type optical disk apparatus capable of repeated recording.
[0089]
(1) A synchronization signal (VFO), a data head identification mark (DM), modulated data, and, if necessary, dummy data are sequentially recorded in the recording area, and the position of the data head identification mark is randomly changed.
[0090]
(2) The maximum positional deviation amount of the data head identification mark and / or the average length of the synchronization signal in the same sector is selected and recorded to an optimum value according to the linear velocity at the time of recording. (3) The average length of dummy data in the same sector is selected and recorded to an optimum value corresponding to the linear velocity at the time of recording.
[0091]
In an actual optical disc apparatus, the linear velocity and the recording radius at the time of recording usually correspond to 1: 1, so that the optical disc apparatus is optimal for each recording radius in order to carry out the above method (2) or (3). A conversion table of the maximum positional deviation amount of the data head identification mark and / or the average length of the synchronization signal and the average length of the dummy data may be provided and recorded in a desired recording area according to the conversion table. . The embodiment will be specifically described below.
[0092]
FIG. 24 is a block diagram showing the configuration of the optical disc apparatus according to the fifth embodiment. This optical disc apparatus can also record data in the recording format shown in FIG. The optical disk apparatus shown in FIG. 24 has an address- (synchronization signal, dummy data recording method) conversion memory (hereinafter simply referred to as a conversion memory) 2801 added to the optical disk apparatus shown in FIG. The conversion memory 2801 stores data such as the maximum displacement amount of the optimum data head identification mark, the length of the synchronization signal, the length of the dummy data, or the dummy data recording end position for each recording address.
[0093]
The operation of the optical disk apparatus configured as described above will be described below. At the time of data recording, the system control circuit 2011 gives the address of the target sector to be recorded to the servo control circuit 2003 and the conversion memory 2801. The servo control circuit 2003 compares the address from the address detection circuit with the target address and performs servo control of the optical pickup 2002. The conversion memory 2801 gives the recording format data corresponding to the address of the target sector to be recorded to the recording timing control circuit 2009. The system control circuit 2011 issues an encoding command 2013 to the encoding circuit 2008 and issues a recording command to the recording timing control circuit 2009. The encoding circuit 2008 performs error detection / correction encoding on the data 2012 and outputs it to the data modulation circuit 2004. The data modulation circuit 2004 digitally modulates the encoded data 2014. When the demand for repeated recording is low, the dummy data generation circuit 2007 can be omitted.
[0094]
When the address detection circuit 2010 detects the target sector, the recording timing control circuit 2009 sequentially applies to the synchronization signal generation circuit 2005, DM generation circuit 2006, data modulation circuit 2004, and dummy data generation circuit 2007 according to the data sent from the conversion memory 2801. A start command is given, and a synchronization signal, a data head identification mark, modulation data, and dummy data of an appropriate length are sequentially recorded in the recording area 46 of the sector, which gives the maximum amount of positional deviation of the optimum data head identification mark. It is not necessary for the system control circuit 2011 to give an address to be recorded in the conversion memory 2801. The address detection circuit 2010 may send the detected address signal to the conversion memory 2801 immediately before recording. Further, instead of having the conversion memory 2801 in the optical disk apparatus, an address- (synchronization signal, dummy data recording method) may be recorded in advance on the optical disk 2001, and recording may be performed according to the information.
[0095]
As described above, according to the present embodiment, by providing an address- (synchronization signal, dummy data recording method) conversion memory, the optimum maximum positional deviation amount of the data head identification mark and / or synchronization is provided according to the recording radius. The average length of the signal and the average length of the dummy data can be selected and recorded. As a result, the actual recording capacity of the optical disc can be improved as compared with the conventional one while being not affected by the recording / reproducing waveform deterioration caused by repeated recording regardless of the recording linear velocity.
[0096]
Next, a sixth embodiment of the present invention will be described.
FIG. 25 is a block diagram showing the configuration of the recording / reproducing apparatus according to the sixth embodiment. An operation performed by the recording / reproducing apparatus for rewriting the recording information of a certain sector is shown in the flowchart of FIG. A timing chart of the recording operation is shown in FIG. In step 3001 of FIG. 26, after the ID information 41 (address information) of the sector to be rewritten is detected, the system control circuit 4 connected to the computer outputs the recorded information 5 as a binary signal (3002). The recording information is added with error correction information by the modulation circuit 7a (3003) and modulated (3004). Then, the synthesizing circuit 8 adds the synchronizing signal 42 from the synchronizing signal generating circuit 2, the dummy data 45 from the dummy data generating circuit 21 and the like to the recording data 11c for each data length to be recorded in each sector (3005). In accordance with this data, the laser control circuit 12 drives the laser in the optical head 3 to modulate the intensity of the laser light (3006). As a result, data is recorded in the corresponding sector of the optical disc 1 (3007). The above operation is the same as the conventional configuration, but the operation described below is different from the conventional one.
[0097]
While performing the above recording, the reproduction signal reflected from the optical disk 1 by the light beam irradiated for recording is detected by the stop pulse detection circuit 49 (3008). If the stop pulse detection circuit 49 detects the stop pulse 53 detected as a local reflectance change of the optical disc 1 within the detection time determined by the dummy gate generated by the dummy gate generation circuit 50, the delay circuit 51 determines the stop pulse 53. After a predetermined delay time d4 (3009), recording of dummy data is stopped (3011). On the other hand, if the stop pulse detection circuit 49 does not detect a stop pulse within the detection time determined by the dummy gate 54 generated by the dummy gate generation circuit 50, after a predetermined delay time d5 determined by another delay circuit 52 (3010). Recording of dummy data is stopped (3011). The stop pulse is generated near the end of the recording area of each sector on the optical disc 1 by changing the groove width or groove depth of the guide groove or by providing prepits.
[0098]
According to the present invention, even if rotational jitter occurs in the motor that rotates the optical disk, the recording end position in each sector can be accurately aligned. This is because the stop pulse is near the end position of the recording sector, so the time from when the stop pulse is detected until the target recording end position is reached is the time from the sector recording start point to the recording end point. Because it is shorter than that. That is, according to the conventional recording method, the recording operation is stopped after a predetermined time from the start of recording. However, in practice, the recording end position may change for each recording due to the influence of uneven rotation of the motor. On the other hand, when the method of ending the recording after a predetermined time after detecting the stop pulse as in the present invention, the recording end positions are aligned much more than in the conventional example. In other words, when the present recording method is adopted, it is possible to use up to the end of the usable recording area without considering the influence of the rotational jitter of the motor. That is, for example, the dummy data area can be made longer than the conventional recording method.
[0099]
If the detection of the stop pulse fails for some reason, the recording must be stopped before entering the subsequent ID area. Therefore, if the stop pulse is not detected even after the time for which the stop pulse is to be detected, it is necessary to stop the recording in consideration of the rotation jitter of the motor. When the stop pulse detection operation is started from a very early stage, the recording operation is stopped in the middle of the original recording when a signal change other than the stop pulse is erroneously detected as a stop pulse. For this reason, the stop pulse detection operation may be performed within a time range in which a possible time shift such as motor rotation jitter is added to the stop pulse detection scheduled time. The dummy gate generated by the dummy gate generation circuit 50 detects the stop pulse within the time when the stop pulse should be detected.
[0100]
As shown in the timing chart of FIG. 27, when a stop pulse is detected at a portion where the guide groove 17 on the optical disc is interrupted, recording of dummy data is stopped after a delay time d4 after the stop pulse is detected. If no stop pulse is detected within a predetermined detection time, then recording of dummy data is stopped as the delay time d5 elapses. The delay time d5 given by the delay circuit 52 when the detection of the stop pulse has failed is after the recording end position when the recording stop pulse is successfully detected in consideration of the rotational jitter of the motor. If so set.
[0101]
Next, specific examples will be described. The signal was repeatedly recorded under the optical disk having the configuration shown in Example 1 and the recording conditions, and the recording end position (distance to the next ID) was measured each time recording was performed. The stop pulse was generated at a position (the rear part of the sector) that internally divides each sector into 20: 1. 28 and 33 show an example of an optical disk according to the present embodiment. FIG. 28 shows a case where there is a guide groove, and a stop pulse is detected at a portion where the guide groove is broken and the reflectance becomes high. When using the optical disk as shown in FIG. 28, it is possible to detect a stop pulse during the recording operation, and confirm that the variation in the recording end position in the same sector is 1/20 compared to the conventional recording method. did.
[0102]
In an optical disk having a guide groove, it is possible to detect a stop pulse by locally narrowing the groove width or by reducing the groove depth.
In addition, as shown in FIG. 29, in the so-called sample servo type optical disc, a prepit larger in size than other prepits is provided near the end of the recording area, and a signal from this large prepit is detected as a stop pulse. It is also possible to do.
[0103]
Next, a seventh embodiment of the present invention will be described. In the third embodiment described above, when recording information in a sector, recording of a VFO signal as a synchronization signal is started from a certain position, and the length of the VFO signal is randomly set for each recording. By changing to, it is possible to eliminate the waveform distortion of the data portion while compensating for the deterioration of the recording start end. However, in this case, since the VFO signal is always recorded on the optical disc at a constant timing, when recording is performed with a recording apparatus having high rotational accuracy and signal time accuracy, a waveform distortion peculiar to the fixed pattern occurs in the VFO region. There is a case.
[0104]
Therefore, in this embodiment, in order to suppress this waveform distortion, in addition to the above method, the method of repetitive recording is improved by combining the method of inverting the signal polarity every time repetitive recording or shifting the recording start end. Further improve. This recording method will be described with reference to the block diagram of FIG. 30 and the timing chart of FIG.
[0105]
The reproduction signal 14 from the optical disc 1 is demodulated through the reproduction signal processing circuit 13 and the address detection circuit 2010, and the ID signal 60 is input to the system control circuit 4. The system control circuit 4 outputs a sector signal 61 indicating the sector range to be recorded to the recording timing control circuit 2009 in accordance with an instruction from the host computer. The recording timing control circuit 2009 first synchronizes the gate signal 62 for outputting the VF0 signal, which is a synchronization signal when demodulating the data signal from the reproduction signal, at a timing delayed from the sector signal 61 by a certain time Lg. This is output to the generation circuit 2005. Note that the interval of the gate signal 62 is set to a value sufficiently longer than the interval Lv of the required VFO signal. The synchronization signal generation circuit 2005 outputs the VFO signal 65 corresponding to the gate signal interval to the synthesis circuit 8.
[0106]
In addition, the recording timing control circuit 2009 outputs a dummy gate signal 63 for obtaining a dummy signal for compensating for the deterioration of the terminal portion of the data to the dummy data generating circuit. The dummy gate signal 63 is output for a period longer than the dummy data length that is finally required. Further, the signal is stopped after a lapse of a certain time Lds from the sector start point so that the end position is before the rear end of the sector signal 61. The dummy data generation circuit 2007 outputs a dummy data signal 67 to the synthesis circuit 17 in accordance with the dummy gate signal 63.
[0107]
On the other hand, the system control circuit 4 outputs the information signal 5 binarized based on the information signal to be recorded to the modulation circuit 7a. The modulation circuit 7a adds an error correction code to the recording signal 5, and further performs modulation according to a modulation code suitable for recording on the optical disc, for example, an EFM code, a (1, 7) code, or a (8, 16) code. The modulated signal becomes a data signal 19b, which includes a data mark, a synchronization signal in data, a parity, and the like.
[0108]
The output start timing of the data signal 19b is determined by the recording start pulse 64 delayed by Lv from the rising edge of the VFO gate signal 62 from the recording timing control circuit 2009. The data signal 19 b is delayed by the time width M by the first random delay circuit 70 to become a delayed data signal 71, which is input to the synthesis circuit 8. The first random delay circuit 70 delays the input signal by any delay time within the range of M = 0 to Mmax.
[0109]
The first synthesizing circuit 8 synthesizes the delayed data signal 71 and the VFO signal 65, and the subsequent second synthesizing circuit 17 further synthesizes the dummy data signal 67 to generate a synthesized data signal 72. At this time, the data signal 71 is synthesized in the overlapping portion of the data signal 71 and the dummy data signal 67, and then the dummy data signal 67 is followed. The synthesized data signal 72 composed of the VFO, the data signal, and the dummy signal becomes a delayed synthesized signal 74 that is delayed by a delay time N as a whole by the second random delay circuit 73. The second random delay circuit 73 delays the input signal by any delay time within a range of N = 0 to Nmax.
[0110]
The random inversion circuit 75 generates the recording data signal 76 by inverting the polarity of the delay composite signal 74 at random. In accordance with the recording data signal 76, the laser power control circuit 12 drives the laser in the optical head 3 and modulates the intensity of the laser light to record a signal on the optical disc 1. Note that the random inversion circuit 75 can be configured to use the inversion circuit 10 and the selection circuit 9 as shown in FIG. 1 to randomly select a recording data signal or a recording data signal whose polarity is inverted.
[0111]
FIG. 32 shows an example of a random delay circuit 70 used for randomly changing the recording position of a signal within a recording sector. The random delay circuit 70 includes a shift register 80, a selector 81, and a counter 82. When the recording data 19b and the data reference clock signal 83 are input to the shift register 80, the shift register 80 supplies eight types of signals (c) to (j) having a time delay corresponding to the clock cycle to the selection circuit 81. Output. The counter 82 counts up each time a series of data signal strings, for example, a data string to be recorded in one sector is input, and outputs the result to the selection circuit 81. The selection circuit 81 uses the output of the binary count signals (k) to (m) of the counter 82 as a signal for selecting the output signal from the shift register 80, and obtains the selected delayed data signal 71.
[0112]
With the above configuration, a random delay time can be given to the data signal. In order to further increase the delay time, the number of bits of the shift register 80 may be increased, or the clock 83 divided may be input to the shift register 80. The second delay circuit 73 can also have a similar configuration.
[0113]
FIG. 33 shows a recording format of the optical recording medium obtained by the above method. Following the ID signal 41, a first gap area 47, a VFO area 42, a data block 44, dummy data 42, and a second gap area 48 are arranged on the sector of the recording medium.
[0114]
The first and second gap regions 47 and 48 are provided to prevent erroneous recording due to fluctuations in the rotation of the optical disc, fluctuations in timing of the recording gate, and the like. Further, it is desirable that the length of the first gap region 47 is set so as to include a time necessary for setting the power of a light source such as a semiconductor laser prior to recording. The second gap region 48 is mainly for preventing erroneous recording on the ID signal due to rotational fluctuations, and its length is determined according to the performance of the spindle motor and servo circuit.
[0115]
For the VFO signal 42, a length Lv is set in consideration of signal degradation at the recording start end after repeated recording. The length is set such that signal deterioration can be absorbed in accordance with the number of repeated recordings to be compensated for by the recording medium or the material constituting the recording medium. That is, since the VFO signal 42 is a signal for obtaining the timing of the synchronous clock when the demodulating circuit 7b demodulates the data signal, the length required for pulling in the PLL of the demodulating circuit even after the recording start end deterioration occurs. It is necessary to ensure the length of the VFO signal that exceeds the maximum.
[0116]
The dummy data 45 following the data block 44 needs to be set to a length exceeding the maximum degradation length so that the degradation of the recording end portion when repeated recording does not reach the data block.
[0117]
Next, a sector format pattern set by the two random delay circuits 70 and 73 for each repeated recording will be described. (A-1) in FIG. 33 shows a case where the delay amount M by the first random delay circuit 70 and the delay amount N by the second random delay circuit 73 are both 0, that is, the data block is at the forefront, that is, It is located closest to the ID signal 41a. (A-2) is a case where N = N1, and the entire VFO, data block, and dummy data move to the rear of the sector by the delay amount N1. (A-3) is a case where the delay amount N is the maximum value Nmax, and the leading portion of the VFO is in the most delayed state. At this time, the rear end portion of the dummy data 45 is also delayed by the delay amount Nmax compared to (a-1), and the second gap region is shortened accordingly.
[0118]
(B-1) of FIG. 33 is a case where the delay amount by the first random delay circuit 70 is M = M1, and the length of the VFO region is increased by L1 + M1 by the delay amount M1. Therefore, the data block starts from a position delayed by M1 compared to (a-1). The rear end of the data block, that is, the start end of the dummy data 45 is also delayed by M1, but the rear end of the dummy data 45 is at the same position as (a-1). That is, the length of the dummy data is shortened to Ld−M1. In the same manner, the length of the VFO and the start position change in the same manner.
[0119]
(C-3) of FIG. 33 is a case where M = Mmax and N = Nmax, and the delay amount of the data block becomes the largest (Mmax + Nmax). In an actual recording operation, these delay states are selected at random. Therefore, the position of the data block 44 changes randomly within a range of the delay amount from zero to Mmax + Nmax. Further, the start of recording changes randomly within a range of delay amount from zero to Nmax.
[0120]
Next, a comparative experiment (Example) conducted to confirm the effect of this embodiment will be described. As in the first embodiment, a polycarbonate resin having a diameter of 130 mm and a thickness of 0.6 mm was used for the disk substrate of the optical disk 1. This resin substrate was preformatted with uneven phase pits as address information in advance, and a recording guide groove was formed in the sector area. The pitch of the guide grooves is 1.6 μm. Four layers of a protective film, a photosensitive recording film, a protective film, and a reflective film were formed on the substrate by a sputtering method, and a protective substrate was adhered thereon.
[0121]
ZnS—SiO ₂ was used as the protective film, Te—Sb—Ge was used as the photosensitive recording thin film, and Al was used as the reflective film. The disk was rotated by a spindle motor 15 at a linear velocity of 6 m / s, and recording was performed by focusing laser light having a wavelength of 680 nm with an objective lens having a numerical aperture (NA) of 0.6.
[0122]
The power of the laser beam during recording / reproduction was Pp = 11 mW, Pb = 4 mW, and Pr = 1 mW. The recording information was modulated by pulse width modulation using (8, 16) code. The clock cycle T was 34 ns, the bit length was 0.4 μm, and the shortest mark length was 0.6 μm. As a modulation method, multi-pulse modulation in which light irradiation consisting of a plurality of pulse trains is applied to one mark is applied. As a format of data to be recorded on the sector, a format in which the shortest gap length Lg is 32 bytes, the VFO length Lv is 65 bytes, the data block length is 2418 bytes, and the dummy data length Ld is 82 bytes is used. Recording experiments were performed while changing the amount of delay (M) and the amount of change (delay amount) N of the gap length. Note that a continuous 4T signal was used as the pattern of the VFO signal and the dummy signal. In addition, the deterioration of the reproduced signal was also compared for each change amount depending on the presence or absence of signal inversion using the random inversion circuit 75.
[0123]
34 (a) and 34 (b) show the experimental results. In these graphs, the vertical axis jitter σ / Tw (%) represents the jitter value of the reproduction signal as the sum of the standard deviations with respect to the window width. This is a jitter value after the same data signal is repeatedly recorded 100,000 times on the sector of the optical disk. Note that the condition that the error occurrence probability during demodulation is about 1 / 10,000 or less is used as a guide, and the condition that the jitter value is 13% or less is used as a reference for data reproduction.
[0124]
FIG. 34A shows a case where the recording operation is performed with the gap length fixed and the maximum change amount Mmax of the VFO length being changed stepwise while the VFO length is randomly changed within the range in units of the clock period T. The jitter was measured. A curve 84 is a case where random inversion of the signal polarity is not performed, and a curve 85 is a case where random inversion is performed. As the maximum change amount Mmax of the VFO length increases, the jitter is improved. In the curve 84, the jitter is 13% or less at about 80T (5 bytes) or more, and in the curve 85, the jitter is 13% or less at about 40T (2.5 bytes) or more. It can be seen that by adding random inversion recording, the jitter is greatly improved and the data shift amount can be set small.
[0125]
FIG. 34B shows the jitter measured when the recording operation is performed while the VFO length is fixed and the maximum change amount Nmax of the gap length is changed stepwise. The jitter was measured in a 35-byte area on the data block side from the viewpoint of checking whether or not the length required for the PLL of the VFO signal is secured. A curve 86 is a case where random inversion of the signal polarity is not performed, and a curve 87 is a case where random inversion is performed. Similar to FIG. 34 (a), an improvement in jitter is observed with an increase in the maximum change amount Nmax of the gap length. In the curve 86, the jitter is 13% or less at about 6T or more, and in the curve 87, the jitter is 13% or less at about 2T or more. Also in this case, it can be seen that jitter is greatly improved by adding random inversion recording.
[0126]
Further, as can be seen by comparing (a) and (b) of FIG. 34, the maximum change amount Nmax of the gap length necessary for satisfying the condition that the jitter value is 13% or less is also the required VFO. The value may be smaller than the maximum change amount Mmax in length. As a pattern of the format signal to be recorded on the sector, by setting the gap length maximum change amount Nmax to be smaller than the VFO length maximum change amount Mmax, the waveform hardly decreases in capacity of the data block in the sector. Deterioration can be effectively suppressed.
[0127]
As an example of the recording format, practical values of the two variations are estimated based on the results of FIGS. These values must be set so as to compensate for deterioration factors of jitter due to characteristics variation of the recording apparatus, errors between apparatuses, characteristic variations of the recording medium, etc. in addition to the above experimental results. Here, in consideration of these factors, the amount of change required for practical use is estimated to be three times the amount at which the jitter is 13% or less.
[0128]
As a result, when random inversion is performed, the maximum change amount Nmax of the gap length is 6T. Expressed in bytes, it is 0.38 bytes, rounded up to 1 byte. Similarly, the maximum change amount Mmax of the VFO length is 7.5 bytes, rounded up to 8 bytes.
[0129]
On the other hand, when the random inversion is not performed, the maximum change amount Nmax of the gap length is 18T. Expressed in bytes, it is 1.13 bytes, rounded up to 2 bytes. Similarly, the maximum change amount Mmax of the VFO length is 15 bytes. By applying a recording format using these values, after 100,000 iterations, the recorded signal including the VFO part and the data block part has no waveform distortion and the start and end deteriorations are compensated. It can be carried out.
[0130]
From the viewpoint of simplifying the configuration of the recording / reproducing apparatus, the random inverting circuit 75 can be omitted. In this case, the jitter at the time of repeated recording becomes larger than when random reversal recording is used together. To compensate for this, the maximum change amount Mmax of the VFO length is increased, and the data capacity is reduced accordingly. Can respond.
[0131]
In this embodiment, the dummy data length is Ld-M, and the dummy data length changes according to a random change of M. However, when a medium with small termination deterioration is used, a fixed length is provided at the end of the data block 44. The dummy data may be added.
[0132]
As described above, when the same data is repeatedly recorded by changing the gap length and the VFO length at the time of format recording, recording at the same position of the track on the sector is avoided, and the start end Recording that compensates for the amount of deterioration of the image can be performed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a recording / reproducing apparatus according to a first embodiment of the present invention. FIG. 2 is a flowchart showing an operation performed by the recording / reproducing apparatus of FIG. 1 to rewrite recording information in a certain sector. 3 is a timing chart showing recording data, inverted recording data, intensity modulation of laser light, and a recording state on an optical disc in the recording / reproducing apparatus of FIG. 1. FIG. 4 is a recording / reproducing apparatus according to a second embodiment of the invention. FIG. 5 is a flowchart showing processing performed by the system control circuit to rewrite the recording information of the sector in the recording / reproducing apparatus of FIG. 4. FIG. 6 is a diagram of the dummy data generating circuit in the recording / reproducing apparatus of FIG. FIG. 7 is a block diagram showing the configuration. FIG. 7 is a timing chart showing signals at various parts of the dummy data generating circuit in the recording / reproducing apparatus of FIG. FIG. 9 is a timing chart showing recording data, laser beam intensity modulation, and recording state on an optical disc in a live device. FIG. 9 shows recording data, laser beam intensity modulation, and optical disc recording in a modification of the recording / reproducing apparatus in FIG. FIG. 10 is a block diagram showing a configuration of a modification of the recording / reproducing apparatus of FIG. 4. FIG. 11 is a timing chart showing intensity modulation of recording data and laser light in the recording / reproducing apparatus of FIG. 10 is a timing chart showing a modified example of intensity modulation of recording data and laser light in the recording / reproducing apparatus of FIG. 10. FIG. 13 is a block diagram showing a configuration of another modified example of the recording / reproducing apparatus of FIG. FIG. 15 is a block diagram showing the configuration of a recording / reproducing apparatus. FIG. 15 shows recording data, intensity modulation of laser light, and optical decoding by the recording / reproducing apparatus in FIG. FIG. 16 is a block diagram showing a configuration of a recording / reproducing apparatus according to a third embodiment of the present invention. FIG. 17 is a diagram showing a configuration of a recording format of a sector on an optical disc. 16 is a block diagram showing the configuration of a recording timing control circuit in the recording / reproducing apparatus of FIG. 16. FIG. 19 is a timing chart showing the operation of the circuit portion of FIG. 18. FIG. FIG. 21 is a block diagram showing a configuration of a recording timing control circuit of a recording / reproducing apparatus according to a fourth embodiment of the present invention. FIG. 22 shows operations of components of the recording / reproducing apparatus of FIG. FIG. 23 is a timing chart showing a pattern example of dummy data recorded by a recording / reproducing apparatus having the components shown in FIG. FIG. 25 is a block diagram showing a configuration of a recording / reproducing apparatus according to a fifth embodiment of the present invention. FIG. 25 is a block diagram showing a configuration of a recording / reproducing apparatus according to the sixth embodiment of the present invention. FIG. 27 is a flowchart showing an operation performed by the apparatus to rewrite recording information in a certain sector. FIG. 27 is a timing chart showing stop pulse positions and recording states in the recording / reproducing apparatus of FIG. 25. FIG. FIG. 29 is a plan view showing an example of the shape of the guide groove of the optical information recording medium according to the embodiment. FIG. 29 is a plan view showing an example of the shape of the prepit of the optical information recording medium according to the sixth embodiment of the invention. FIG. 31 is a block diagram showing the configuration of a recording / reproducing apparatus according to a seventh embodiment of the present invention. FIG. 31 is a timing chart of signals at various parts in the recording / reproducing apparatus of FIG. FIG. 33 is a circuit diagram illustrating a recording format of an optical recording medium by the recording / reproducing apparatus in FIG. 30. FIG. 34 is a jitter value of a reproduction signal after repeated recording by the recording / reproducing apparatus in FIG. Graph showing comparison of [Description of symbols]
DESCRIPTION OF SYMBOLS 1 Optical disk 2 Synchronous signal generation circuit 3 Optical head 4 System control circuit 5 Recording information 6 Reproduction information 7a Modulation circuit 7b Demodulation circuit 8 Synthesis circuit 9 Selection circuit 10 Inversion circuit 11a Recording data 11b Inversion recording data 12 Laser power control circuit 13 Reproduction signal Processing circuit 14 RF signal 15 Spindle motor

Claims (6)

A recording method of an optical information recording medium for recording binarized information by changing the state of a light-sensitive recording thin film by irradiation with a light beam, the step of inverting the sign of recording data having a predetermined block length including the recording information And inverting the sign of the recording data or the recording data according to the determination of deciding whether to invert the sign of the recording data and determining the step of randomly determining whether to invert the recording data. And recording any one of the recorded data on a light-sensitive recording thin film.   2. The recording method for an optical information recording medium according to claim 1, wherein the binarized information is binarized by pulse width modulation.   The optical information recording medium divided into a plurality of sectors, the recording data of the predetermined block length is recorded in a recording area in each sector, and the recording start point in the sector is randomly changed. Recording method for a static information recording medium. An optical information recording medium recording apparatus for recording binarized information by changing the state of a photosensitive recording thin film by irradiation with a light beam, a modulation circuit for generating recording data from recording information of a predetermined block length; An inverting circuit that inverts the sign of the recording data to obtain inverted recording data, a selection circuit that randomly selects either the recording data or the inverted recording data, and irradiation of the light beam according to an output of the selection circuit An optical information recording apparatus comprising a control circuit for controlling power. 5. The optical information recording apparatus according to claim 4, wherein the binarized information is binarized by pulse width modulation. 5. The optical information recording apparatus according to claim 4, wherein the optical information recording medium divided into a plurality of sectors is used, the recording data is recorded in a recording area in each sector, and a recording start point in the sector is randomly changed. .

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