JP3889352B2

JP3889352B2 - Pre-pit detection device and pre-pit detection method

Info

Publication number: JP3889352B2
Application number: JP2002361079A
Authority: JP
Inventors: 富行沼田
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 2002-12-12
Filing date: 2002-12-12
Publication date: 2007-03-07
Anticipated expiration: 2022-12-12
Also published as: JP2004192740A

Description

【０００１】
【発明の属する技術分野】
本発明は、アドレス情報等の情報トラックに関連する情報をプリピットの形態で備えた光学記録媒体に対して、上記プリピットに記録された情報を検出するプリピット検出装置およびプリピット検出方法に関し、特にプリピットの検出感度を高めるものである。
【０００２】
【従来の技術】
従来より、データを追記、または書き換え可能な光記録媒体（記録可能型光記録媒体）が知られている。一般的に、このような記録可能型の光記録媒体では、光記録媒体上での情報の記録を可能にするためのプリピットやプリグルーブなどを、製造時に予め設ける。プリピットやプリグルーブには、情報記録に必要なアドレス情報や、記録再生動作に用いるクロック信号を生成するための基準信号が記録されており、当該プリピット信号に基づいて情報の追記、書き換え、および記録再生が行われている。
【０００３】
図６は、追記可能な高密度光記録媒体である、ＤＶＤ−Ｒ（Digital Versatile Disc ‐ Recordable）の記録面の一部を示す図である。ＤＶＤ−Ｒの記録面には、螺旋状もしくは同心円状に情報トラックであるグルーブ５１が形成され、グルーブ５１領域に画像データやコンピュータデータなどの本来記録すべき情報が記録される。グルーブ５１とグルーブ５１との間の領域は平坦なランド５２となっている。ランド５２には、上述したプリピットとして、その両側のグルーブ５１をつなぐようにランドプリピット（ＬＰＰ）５３が成形されている。
【０００４】
ＬＰＰ５３は、ＬＰＰ５３に隣接するグルーブ５１にレーザビームが照射された時に検出される。すなわち、このとき、レーザビームはＬＰＰ５３を含むグルーブ５１の領域を照射するので、異なるレーザビームの反射光量が検出されるため、ＬＰＰ５３の位置を知ることができる。より詳しくは、レーザビームの反射光は、受光面がトラックの接線と光学的に垂直な方向（ディスク半径方向）に２分割され（以下この分割領域をプリピット検出領域という）、それぞれの領域に照射されたレーザビームは、分割された２つの受光素子に受光されて、それぞれの受光量に応じた電気信号を出力する。この２つの出力信号はＬＰＰ５３を含んでいる場合に非対称となり、ＬＰＰ５３を含んでいない場合と比べ大きく値が異なる。そこでこの出力信号の差分を演算し、この差分信号を所定の閾値と比較し、２値化した２値化信号として出力する。この差分信号はラジアルプッシュプル信号と呼ばれる。
【０００５】
ところが、プリピット検出領域の受光信号の間では、レーザビームの照射域と情報トラックの位置関係により位相差が生じる。このため、レーザビーム照射域にＬＰＰ５３を含んでいる場合の受光信号の差が小さくなってしまう。ＬＰＰ５３に記録される情報は、光ディスクに正しく安定に情報を記録し、あるいは再生するために非常に重要となっているので、ＬＰＰ５３から生成されるラジアルプッシュプル信号の品質を高める必要がある。
【０００６】
そこで、特許文献１には、光ディスクのトラック方向の分割線により２分割された受光面を有し、その受光量に応じた受光信号を出力するプリピット信号検出装置において、個々の受光面からの受光信号のレベルを増幅調整した後に、差分を演算してラジアルプッシュプル信号を検出することで、情報トラックに記録された情報データ信号成分（ＲＦ信号成分）の漏れ込みの影響を回避できることが示されている。
【０００７】
また、特許文献２には、分割されたレーザビーム反射光の受光信号の総和信号を、ラジアルプッシュプル信号に混入するＲＦ信号成分のレベルと等しくなるようにレベル調整し、かつ、位相も合うように遅延時間の調整を行った調節総和信号を、ラジアルプッシュプル信号から差し引くことで、レベル調整、位相調整、ＲＦ信号成分除去を行ってＬＰＰの品質を向上する技術が開示されている。
【０００８】
さらに、非特許文献１には、分割されたレーザビーム反射光の受光信号の、個々の信号の位相を調整するために、遅延している受光信号に位相を合わせた信号をつくり、この信号を利用して受光信号の差分を演算してＬＰＰを検出することで、ＬＰＰ信号振幅を大きくし、品質を向上する技術が開示されている。
【０００９】
一方、光ディスクの情報を記録再生するプリピット検出装置の、小型、薄型化、高信頼性を実現する手段としてホログラムを用いたものが提案されている。例えば、特許文献３に開示されているホログラムは、ディスクのディスク半径方向（ラジアル方向）に対応する方向に延びる分割線により２分割され、その一方がさらにトラック方向に対応する方向に延びる分割線により２分割されている。ディスクのディスク半径方向の分割線に２分割された一方の半分でフォーカスサーボ誤差信号を検出し、他方の半分はさらにトラック方向に２分割され、それぞれの信号の差からラジアルプッシュプル信号を検出し、反射光全体の和信号でＲＦ信号を検出している。半分に分割された反射光が更にディスク半径方向に２分割されるので、ラジアルプッシュプル信号を検出することが可能であり、このラジアルプッシュプル信号はトラックサーボ誤差信号としても用いられる。
【００１０】
【特許文献１】
特開２００１−２３１６８号公報（公開日２００１年１月２６日）
【００１１】
【特許文献２】
特開２００２−７４６７５号公報（公開日２００２年３月１５日）
【００１２】
【特許文献３】
特開平４−２１９２８号公報（公開日１９９２年１月２４日）
【００１３】
【非特許文献１】
加藤正浩、外３名，「DVD-RW version1.0の要素技術」，PIONEER R&D，パイオニア株式会社，2000年，第10巻，第3号，ｐ．４９
【００１４】
【発明が解決しようとする課題】
光ディスクに情報データが記録された領域では、ＬＰＰ検出に用いられるラジアルプッシュプル信号を生成するためのプリピット検出領域の受光信号には、それぞれに、ＬＰＰ信号成分とＲＦ信号成分とが含まれている。このとき、２つの受光信号に含まれるＲＦ信号成分は位相が合致しており、ＬＰＰ信号成分の位相にだけ位相差が存在する場合がある。
【００１５】
特に、特許文献３に示すような、光ディスクからの反射光のうちの半分だけを使って、上記ホログラムを用いた光学系を用いてラジアルプッシュプル信号を検出する場合には顕著である。また、このＬＰＰ信号成分の位相差は、レーザビームが照射される情報トラック上の位置（デトラック量）によって変化する。これは、ＬＰＰ部をレーザビームが通過するときに、ホログラム上の反射光の強度パターンが変化するために生じるものである。
【００１６】
このような場合、従来技術のように、信号レベルを調整したり、ラジアルプッシュプル信号からＲＦ信号成分を減じることでは、ＬＰＰ信号成分の位相差を解消できない。また、特許文献２のような方法ではＬＰＰ信号成分の位相差をあわせることにより、逆にＲＦ信号成分に位相差を発生させてしまうと、ラジアルプッシュプル信号に位相のずれたＲＦ信号成分が漏れ込むこととなり、ＲＦ信号成分を除去できなくなる。さらに、非特許文献１では位相差の調整方法が記されているだけであり、ＲＦ信号除去と位相差調整を両立させてプリピットを良好に検出する方法は開示されていない。
【００１７】
以上のように、従来技術では、ラジアルプッシュプル信号を生成する２つの受光信号に含まれるＲＦ信号成分は位相が合致しており、ＬＰＰ信号成分の位相にだけ位相差が存在するという問題については、何ら示されておらず、このような場合、ＬＰＰの信号品質を向上できないという課題を有している。
【００１８】
本発明は、上記従来の問題に鑑みなされたものであり、その目的は、プリピットの検出性能の優れたプリピット検出装置及びプリピット検出方法を提供することにある。
【００１９】
【課題を解決するための手段】
本発明のプリピット検出装置は、上記の課題を解決するために、情報トラックと情報トラックに関連する情報が記録されたプリピットとを有する光情報記録媒体からのレーザビームの反射光を受光する、複数のプリピット検出領域を含む複数の領域に分割された受光面と、複数のプリピット検出領域それぞれの反射光の光量に応じた複数の受光信号を生成する信号生成手段と、上記複数の受光信号から情報トラックに記録された再生信号を除去する再生信号除去手段と、上記再生信号除去手段により再生信号が除去された複数の受光除去信号の位相差を調整する位相差調整手段と、位相差調整手段により位相差を調整された複数の受光調整信号の差から、プリピット信号を生成するプリピット信号生成手段とを有し、上記位相差調整手段は、光情報記録媒体に照射されるレーザビームの照射領域と、光情報記録媒体の情報トラックとの、ディスク半径方向の相対距離に応じて位相差調整を行うことを特徴としている。
【００２０】
上記構成によれば、光情報記録媒体に照射され、反射されたレーザビームを受光する受光面が複数のプリピット検出領域を含む複数の領域に分割されており、信号生成手段がそのうちの複数のプリピット検出領域に照射されたそれぞれの反射光量に応じて受光信号を生成するため、複数のプリピット検出領域それぞれの反射光量を検出できる。このとき、レーザビーム照射領域にプリピットがあれば、プリピット検出領域における反射光量に大きな差が出るため、このプリピット検出領域の光量を検出することで、プリピットを検出できる。
【００２１】
上記受光面を複数のプリピット検出領域を含む複数の領域に分割する場合、どのような分割をしても構わない。たとえばレーザビーム照射領域の全面を複数の領域に分割してプリピット検出領域としてもよく、複数の領域のうちのいくつかを、あるいはレーザビーム照射領域の一部を複数の領域に分割してプリピット検出領域としてもよい。
【００２２】
また、より正確なプリピット検出には、プリピット検出領域の反射光量からプリピットに影響される反射光量のみを取り出す必要がある。プリピット検出領域の反射光から受光信号を生成した場合、光情報記録媒体に記録されたデータを再生するための再生信号（ＲＦ信号）が含まれているため、まず初めに、再生信号除去手段により、プリピット検出領域の受光信号それぞれから再生信号成分を取り除き、受光除去信号とする。次に、プリピット検出領域の反射光は、トラック方向に回折されているが、レーザビームとプリピットとのトラック方向の位置関係が変化するのにともない、回折の状況が変化するため、プリピット検出の反射光同士に位相差が生じているので、位相差調整手段により上記受光除去信号の位相差を調整する。
【００２３】
プリピット信号生成手段はこのようにして調節された、少なくとも２つの受光調整信号の差を演算することで、プリピットを感度を高く検出することができる。
【００２４】
さらに、本発明のプリピット検出装置は、上記プリピット検出領域の受光信号は、それぞれから再生信号を除去した後に、プリピット検出領域の受光信号位相差を調整して、受光調整信号としている。上述した位相差は、再生信号には生じていないので、位相差調整を再生信号除去の前、あるいは同時に行った場合には、再生信号には逆に位相差が生じてしまい、プリピット信号を生成するときに位相差分の再生信号が除去できずに残ってしまう。したがって、良好にプリピット検出が行えなかった。しかし、本発明のプリピット検出装置によれば、再生信号の位相差を変えずに除去し、プリピット検出領域の受光信号同士の位相差だけを合わせることができる。従って、プリピットの検出感度が高く、かつ再生信号を良好に生成できる。
【００２５】
また、上記信号生成手段が生成した複数の受光信号の位相差は、レーザビーム照射領域と情報トラックとのディスク半径方向の位置関係によって変化するので、位相差の調整量は常に変化する可能性がある。上記構成によれば、デトラック量に応じてプリピット信号成分の位相差調整の量を調整する構成であるので、常に、良好に位相差調整を行うことが出来る。
【００２６】
本発明のプリピット検出装置は、上記の課題を解決するために、上記の構成に加えさらに、上記受光面は、受光面をディスク半径方向の分割線により２分割した一方の第１の受光領域と、他方の領域をさらにトラックの接線方向の分割線により２分割した第２および第３の受光領域とからなるものであり、上記複数のプリピット検出領域が上記第２および第３の受光領域からなることを特徴としている。
【００２７】
ここで、「トラック接線方向」とは、レーザビーム照射領域の中心点における、情報トラックの接線の方向を指し、「ディスク半径方向」とは、トラック接線方向と直交する方向である。上記構成のように、光情報記録媒体からの反射光のうち、反射光受光面をディスク半径方向の分割線により分割した一方の第１の受光領域と、他方の半分の領域をさらにトラック方向の分割線により２分割した第２、第３の受光領域とから受光信号を生成する光ピックアップ装置では、小型、薄型化、高信頼性を実現することができる代わり、この構成によりプリピット検出を行った場合、プリピット検出領域の受光信号間の位相差が顕著になる。
【００２８】
しかし、本発明では、上記信号生成手段により生成した受光信号から再生信号を除去した後に、位相差を調整するので、位相差が大きくても、再生信号除去に影響を与えずにプリピット検出領域の受光信号の位相差を調整できる。よって、小型、薄型化でかつ、高信頼性を有する光ピックアップ装置に適用可能で、高感度でプリピットの検出を行えるプリピット検出装置を提供できる。
【００２９】
本発明のプリピット検出装置は、上記の課題を解決するために、上記の構成に加えさらに、上記再生信号除去手段は、上記受光面の複数に分割された領域に照射されるそれぞれの反射光の光量に応じた受光信号をすべて加算した総和信号を演算する加算手段と、上記総和信号のゲインを調整するゲイン調整手段と、上記信号生成手段が生成した複数の受光信号のそれぞれからゲインを調整された総和信号を減算する少なくとも２つの減算手段とを有することを特徴としている。
【００３０】
上記構成によれば、受光面の複数に分割された領域に照射されるそれぞれの反射光の光量に応じた受光信号をすべて加算した総和信号をゲイン調節した上で、上記信号生成手段が生成した複数の受光信号のそれぞれから減算するので、正確に再生信号が除去される。なお、上記総和信号は、分割する前のレーザビーム全体の受光信号と等しいので、総和信号を用いて再生信号を生成してもよい。
【００３１】
本発明のプリピット検出方法は、上記の課題を解決するために、情報トラックと情報トラックに関連する情報が記録されたプリピットとを有する光情報記録媒体からのレーザビームの反射光を、複数のプリピット検出領域を含む複数の領域に分割された受光面にて受光する受光ステップと、複数のプリピット検出領域それぞれの反射光の光量に応じた複数の受光信号を生成する信号生成ステップと、上記複数の受光信号から情報トラックに記録された再生信号を除去する再生信号除去ステップと、上記再生信号除去ステップにより再生信号が除去された複数の受光除去信号の位相差を調整する位相差調整ステップと、位相差調整ステップにより位相差を調整された複数の受光調整信号の差から、プリピット信号を生成するプリピット信号生成ステップとを有し、上記位相差調整ステップにて、光情報記録媒体に照射されるレーザビームの照射位置と、光情報記録媒体の情報トラックとの、ディスク半径方向の相対距離に応じて位相差を調整することを特徴としている。
【００３２】
上記方法によれば、光情報記録媒体に照射され、反射されたレーザビームを受光する受光面が複数のプリピット検出領域を含む複数の領域に分割されており、信号生成手段がそのうちの複数のプリピット検出領域に照射されたそれぞれの反射光量に応じて受光信号を生成するため、複数のプリピット検出領域それぞれの反射光量を検出できる。このとき、レーザビーム照射領域にプリピットがあれば、プリピット検出領域における反射光量に大きな差が出るため、このプリピット検出領域の光量を検出することで、プリピットを検出できる。
【００３３】
より正確なプリピット検出には、プリピット検出領域の反射光量からプリピットに影響される反射光量のみを取り出す必要がある。そのために、まず初めに、再生信号除去ステップにて、プリピット検出領域の受光信号それぞれから再生信号成分を取り除いて受光除去信号とし、次に位相差調整ステップにてプリピット検出領域の受光信号同士の位相差を調整する。
【００３４】
プリピット信号生成ステップはこのようにして調節された、少なくとも２つの受光調整信号の差を演算することで、プリピットを感度を高く検出することができる。
【００３５】
さらに、本発明のプリピット検出方法は、上記プリピット検出領域の受光信号は、それぞれから再生信号を除去した後に、プリピット検出領域の受光信号位相差を調整して、受光調整信号としている。上記方法によれば、再生信号の位相差を変えずに、プリピット検出領域の受光信号同士の位相差だけを合わせることができる。従って、プリピットの検出感度が高く、かつ再生信号を良好に生成できる。
【００３６】
また、上記信号生成手段が生成した複数の受光信号の位相差は、レーザビーム照射領域と情報トラックとのディスク半径方向の位置関係によって変化するので、位相差の調整量は常に変化する可能性がある。上記構成によれば、デトラック量に応じてプリピット信号成分の位相差調整の量を調整する構成であるので、常に、良好に位相差調整を行うことができる。
【００３７】
本発明のプリピット検出方法は、上記の課題を解決するために、上記の構成に加え、上記再生信号除去ステップは、上記受光面の複数に分割された領域それぞれの反射光の光量に応じた受光信号をすべて加算した総和信号を演算する加算ステップと、上記総和信号のゲインを調整するゲイン調整ステップと、上記信号生成ステップが生成した複数の受光信号のそれぞれからゲインを調整された総和信号を減算する減算ステップとを有することを特徴としている。
【００３８】
上記方法によれば、受光面の複数に分割された領域に照射されるそれぞれの反射光の光量に応じた受光信号をすべて加算した総和信号をゲイン調節した上で、上記信号生成手段が生成した複数の受光信号のそれぞれから減算するので、正確に再生信号が除去される。なお、上記総和信号は、分割する前のレーザビーム全体の受光信号と等しいので、総和信号を用いて再生信号を生成してもよい。
【００３９】
【発明の実施の形態】
本発明の実施の形態に係るプリピット検出装置およびプリピット検出方法について、図１乃至図５を用いて説明する。
【００４０】
本実施の形態のプリピット検出装置は、ホログラム（受光面）５、フォトダイオード（信号生成手段）６・７・８、電流電圧変換回路（Ｉ／Ｖ変換回路）９・１０・１１、再生信号除去手段、位相差調整手段、プリピット信号生成手段からなり、光ディスク（光情報記録媒体）１に記録されたプリピットを検出するものである。
【００４１】
図１は、本発明のプリピット検出装置の、ホログラム（受光面）５、フォトダイオード（信号生成手段）６・７・８、電流電圧（Ｉ／Ｖ）変換回路（信号生成手段）９・１０・１１の部分を示すブロック図である。ホログラム５は、光ディスク１の反射光を受け取るものであり、複数の領域に分割されている。フォトダイオード６・７・８は、上記複数の領域に照射される反射光をそれぞれに応じた電流信号に変換する。電流電圧変換回路（Ｉ／Ｖ変換回路）９・１０・１１は上記電流信号を電圧信号に変換して、受光信号とする。
【００４２】
上記受光信号のうち、プリピット検出に係るプリピット検出領域の反射光の受光信号は、さらに再生信号除去手段により、記録ピットを反映した再生信号を除去して受光除去信号を生成する。その後、位相差調整手段が、上記受光除去信号の位相差を調整して受光調整信号を生成する。プリピット信号生成手段は、受光調整信号の差分からプリピットの検出を示す、プリピット信号を生成する。
【００４３】
また、図２は、本実施の形態のプリピット検出方法を示す図面である。プリピット検出方法は、光ディスク（光情報記録媒体）１にレーザビームを照射した反射光（光ディスクの反射光）を、Ｓ１０の受光ステップにてホログラム（受光面）５で受光し、Ｓ１１の信号生成ステップにて受光した光量を受光信号に変換する。光ディスク１は記録ピットやプリピット等を含むので、受光信号はこれらを反映したものとなる。このうち、プリピット検出に係る受光信号は、Ｓ１２にて再生信号を除去され（受光除去信号）、そのあとＳ１３にて位相差を調整される（受光調整信号）。そして、Ｓ１４にて得られた受光調整信号からプリピット信号を演算する。
【００４４】
以下に本実施の形態のプリピット検出装置の動作について説明する。
【００４５】
まず、スピンドルモータ２により回転駆動されるＤＶＤ−Ｒ等の光ディスク（光情報記録媒体）１の記録面に、半導体レーザ等の発光素子（図示せず）が光を出射する。対物レンズ４は、発光素子からの光を集光してレーザビームとして光ディスク１の任意のポイントを照射させる。対物レンズ４は、さらに光ディスク１の記録面にて反射されたレーザビームを再び通過させ、さらにいくつかの光学素子を通過することでその方向を定められ、信号生成手段のホログラム（受光面）５に導かれる。
【００４６】
ホログラム５は、上記のように導かれたレーザビームをディスク半径方向の分割線ｌにより、領域Ａ（第１の受光領域）、領域Ｂに２分割し、さらに領域Ｂをトラック方向の分割線ｍにより領域Ｂ１（第２の受光領域）と領域Ｂ２（第３の受光領域）とに分割し、領域Ａ，領域Ｂ１，領域Ｂ２に照射された反射光を、それぞれ別のフォトダイオード６，７，８に導く。フォトダイオード６、７、８は光が当たると電流を流す性質を持つものである。ここでは、領域Ａを通過した光束はフォトダイオード６に集光されて光量に応じた電流をＩ／Ｖ変換回路９に出力し、記録再生のための再生信号に利用する。また、領域Ｂ１と領域Ｂ２とを通過した光束は、それぞれフォトダイオード７，８に集光されて光量に応じた電流をそれぞれＩ／Ｖ変換回路１０・１１に出力し、プリピット検出信号およびサーボ誤差演算に利用する。
【００４７】
なお、フォトダイオード６は、例えば、フォーカスサーボ誤差信号検出に用いられる場合には分割フォトダイオードを用い、領域Ａ内で分割した領域として、それぞれ別の光量を検出してもよいが、ここでは１つのフォトダイオードとして説明し、フォーカスサーボ誤差信号検出についての説明は省略する。
【００４８】
電流電圧（Ｉ／Ｖ）変換回路９，１０，１１は、フォトダイオード６，７，８により出力される検出電流をそれぞれ電圧の信号である受光信号ａ（領域Ａの光量を反映），受光信号ｂ１（領域Ｂ１の光量を反映），受光信号ｂ２（領域Ｂ２の光量を反映）に変換して出力する。
【００４９】
ここで、図３を用いて、プリピット検出領域である領域Ｂ１および領域Ｂ２における光量の受光信号ｂ１，ｂ２について説明する。図３は光ディスク１の記録面と、記録面にレーザビームを照射して得られる受光信号ｂ１、ｂ２の波形を示している。
【００５０】
光ディスク１の記録面には、情報記録のための領域であるグルーブ（情報トラック）３１が形成され、グルーブ３１領域に記録情報が情報ピット３５（斜線部）として記録される。グルーブ３１とグルーブ３１との間は平らなランド３２がある。ランド３２には、プリピットとして、その両側のグルーブ５１をつなぐようにランドプリピット（ＬＰＰ）３３が成形され、情報トラックに関連する情報が記録されている。
【００５１】
レーザビームは、この記録面においてグルーブ３１に沿ってレーザビーム照射域Ｒを移動させる。照射されたレーザビームがグルーブ３１を走査すると、信号ｂ１と信号ｂ２とが、情報信号ピット３５に応じて変調される。このとき、レーザビームは、この情報信号ピット３５列のほぼ中央を走査するように制御されるため、例えば、レーザビーム照射域がＲ１の位置にある場合、情報ピット３５ａがＲ１のグルーブ３１に沿った中心線上にくる。従って、この信号ｂ１と信号ｂ２とに現れる再生信号（ＲＦ信号）は、図３のように、同位相で、かつ、ほぼ同じレベルの信号成分となる。
【００５２】
一方、信号ｂ１と信号ｂ２とは、ＬＰＰ３３によっても変調される。これは、レーザビーム照射域Ｒ２のように照射域にＬＰＰ３３を含む場合は、ＬＰＰ３３によって、グルーブ３１による回折の状態が変化するからである。つまり、ＬＰＰ３３は、グルーブ３１の片側にのみ存在し、両側に同時に現れることはないので、ＬＰＰ３３では、領域Ｂ１および領域Ｂ２の受ける光量（フォトダイオード７とフォトダイオード８の光強度分布）が非対称となり、図３のように、信号ｂ１が増加すると、信号ｂ２が減少し、ＬＰＰ信号成分として表れる。この現象を用いて、信号ｂ１と信号ｂ２の差であるラジアルプッシュプル信号を生成すれば、レーザビーム照射領域がＬＰＰ３３を含む場合に、ｂ１およびｂ２の差が他と比べ非常に大きくなり、ＬＰＰ３３を検出できる。
【００５３】
また、ｂ１とｂ２との信号波形では、位相差φすなわちｂ２に時間的な遅れが生じる。これは、レーザビームがＬＰＰ３３を含む領域を走査するときに、レーザビームがグルーブ３１幅方向だけでなく、トラック方向（トラック接線方向）にも回折され、レーザビームとＬＰＰとのトラック方向の位置関係が変化するのにともない、時間とともに回折の状況が変化するためである。特に、ディスク半径方向の分割線により２分割された反射光の一方（Ｂ領域）のみを使っている場合に、位相差φの発生が顕著である。
【００５４】
以上のように、信号ｂ１および信号ｂ２には、再生信号成分（ＲＦ信号成分）と、ＬＰＰ信号成分が混じっており、さらにＬＰＰ信号成分には位相差φが生じているため、ＬＰＰ信号成分を正確に検出するには、ＲＦ信号成分除去、およびＬＰＰ信号成分の位相差の調整が必要となる。すなわち、図４（ａ）のような信号ｂ１、信号ｂ２から、再生信号除去手段によりＲＦ信号成分の除去を行い、（ｂ）のような信号ｂ１’、信号ｂ２’にする。さらに、信号ｂ１の信号ｂ２との位相差φを調整するために、図４（ｃ）のように位相差調整手段によりｂ１’を位相差φ分遅延させたｂ１”にする。そして、ｂ１”とｂ２’との差を演算して図４（ｄ）のようなプリピット検出信号を出力する。
【００５５】
以下に、図５を用いて、上述したような受光信号からプリピット検出信号を生成する方法について詳しく説明する。本実施の形態においては、ｂ１およびｂ２から、サーボ誤差、プリピット信号を生成しており、さらに信号ａをあわせて再生信号を出力している。
【００５６】
まず、サーボ誤差について説明する。光ディスク１上のグルーブ３１にレーザビームを照射すると、グルーブ３１とレーザビーム照射域Ｒとの相対位置関係によって、グルーブ３１による回折が異なるので、反射光のファーフィールドパターンが変化する。
【００５７】
例えば、グルーブ３１の幅方向の中心にレーザビーム照射域Ｒがある場合は、全面でほぼ均等に光が反射するので、トラック方向の分割線により分割された領域Ｂ１、Ｂ２においてフォトダイオード７とフォトダイオード８に集光する光強度分布は対称となる。しかし、レーザビームがトラック中心からどちらかに偏ると、グルーブ３１による回折により、レーザビーム照射領域内で異なった反射光量が生じるため、領域Ｂ１と領域Ｂ２とにおける反射光量が非対称になり、フォトダイオード７，８の光強度分布も非対称となる。このことを利用して、トラックによる回折光強度分布、いわゆるボールパターンの変化をフォトダイオード７，８で検出し、差信号としてラジアルプッシュプル信号を得る。このラジアルプッシュプル信号はレーザビーム照射域のトラックからのずれを検出するトラックサーボ誤差信号として用いられる。
【００５８】
具体的には、まず、信号ｂ１と信号ｂ２との両者が差動回路１２に入力され、その差が演算されて、トラックサーボ誤差を検出するためのラジアルプッシュプル信号ｓ１を得られる。このラジアルプッシュプル信号ｓ１は、トラックサーボ誤差信号生成回路１３に入力される。トラックサーボ誤差信号生成回路１３では、広帯域ノイズの除去やオフセット調整等が行われ、トラックサーボ誤差信号ｓ２が出力される。トラックサーボ誤差信号ｓ２はサーボ回路１４に入力され、トラックサーボ動作が行われる。
【００５９】
次に、再生信号の生成を説明する。信号ａ，信号ｂ１，信号ｂ２は、加算回路（加算手段）１５で加算され、フォトダイオード６，７，８に入射する光量の総和が演算され、総和信号ｓ３を生成する。この総和信号ｓ３は、光ディスク１に記録された情報を反射光量の増減として検出する再生情報信号（ＲＦ信号）として、再生信号処理回路１６に入力され、ここで総和信号ｓ３を読み取ることで光ディスク１に記録された情報が再生される。
【００６０】
ここで、特許請求の範囲、請求項３に記載の、加算手段は加算回路１５であり、ゲイン調整手段はゲイン調整回路１７であり、減算手段は差動回路１８と差動回路１９である。
【００６１】
最後に、ＬＰＰ信号（プリピット信号）の生成について説明する。ＬＰＰ信号の生成には、上述したように、再生信号除去と位相差調整とが必要になる。再生信号を除去するための再生信号除去手段は、加算回路（加算手段）１５、ゲイン調整回路（ゲイン調整手段）１７、差動回路（減算手段）１８・１９からなる。まず、上述した加算回路１５の総和信号ｓ３を、信号レベルを調整するためのゲイン調整回路（ゲイン調整手段）１７に入力し、ゲイン調節信号ｓ４を得る。ゲイン調整回路１７では、信号ｂ１および信号ｂ２に含まれるＲＦ信号成分のレベルと、同じレベルになるようにＲＦ信号である信号ｓ３が調整される。そして、信号ｂ１とゲイン調節信号ｓ４とが差動回路（減算手段）１８に、信号ｂ２とゲイン調節信号ｓ４とが差動回路（減算手段）１９に入力される。調節信号ｓ４は、信号ｂ１、信号ｂ２、信号ａの総和信号を信号ｂ１、信号ｂ２にあわせてゲインレベル調整をしたものであり、このｓ４と信号ｂ１あるいは信号ｂ２との差を演算することにより、信号ｂ１と信号ｂ２の夫々から、ＲＦ信号成分が除去され、図４（ｂ）の信号ｓ５（受光除去信号、前述のｂ１’）、信号ｓ６（受光除去信号、前述のｂ２’）が出力される。
【００６２】
ここで、ゲイン調整回路を２つ保有し、差動回路１８に入力する信号と、差動回路１９に入力する信号とを、夫々、信号ｂ１に含まれるＲＦ信号成分のレベルと、信号ｂ２に含まれるＲＦ信号成分のレベルとに合うように、個別に調整すれば、よりＲＦ信号成分の除去能力が増す。
【００６３】
信号ｓ５に含まれるＬＰＰ信号成分と、信号ｓ６に含まれるＬＰＰ信号成分とには、上述したように位相差φが生じているので、この位相差φをなくすために、差動回路１８の出力信号ｓ５は、遅延回路（位相差調整手段）２０に入力される。遅延回路２０では、サーボ誤差信号ｓ２に基づいて位相差φが修正されるように遅延量が調整され、信号ｓ５を遅延させて信号ｓ７（受光調整信号、前述のｂ１”）を得る。
【００６４】
なお、信号ｓ５と信号ｓ６とに含まれるＬＰＰ信号成分は、光ディスク上のＬＰＰ３３の位置と、レーザビーム照射域Ｒとの光学的な位置関係で決まるが、ここでは、信号ｓ５に現れるＬＰＰ信号成分が、信号ｓ６のＬＰＰ信号成分よりも先に現れ、信号ｓ５は増加し、信号ｓ６は減少する場合の例を説明する。遅延回路は位相が進む方の信号に設ければよいが、もちろん、この位相関係が逆転するような複数の種類の光ディスクを再生するような装置においては、遅延回路を両方に設けたり、遅延回路を切り替える必要がある。
【００６５】
遅延回路２０を経た信号ｓ７は、差動回路（プリピット信号生成手段）２１の一方の端子に入力され、差動回路２１の他方の入力端子には信号ｓ６が入力される。差動回路２１では、ＬＰＰ信号成分のレベルが増加する信号ｓ７と、レベルが減少するｓ６との差を演算し出力する。この差信号ｓ８によってＬＰＰ信号（プリピット信号）が得られ、この信号を２値化することでＬＰＰが検出される。
【００６６】
ここで、信号ｓ７と信号ｓ８とは、既にそれぞれのＲＦ信号成分が除去されているので、信号ｓ７と信号ｓ８とのゲイン調整を行うための回路を設けなくてもよい。
【００６７】
以上のように、上記プリピット検出領域の受光信号は、それぞれから再生信号を除去した後に、プリピット検出領域の受光信号位相差を調整して、受光調整信号としている。上述した位相差は、再生信号には生じていないので、位相差調整を再生信号除去の前、あるいは同時に行った場合には、再生信号には逆に位相差が生じてしまい、プリピット信号を生成するときに位相差分の再生信号が除去できずに残ってしまう。したがって、良好にプリピット検出が行えなかったが、上記プリピット検出装置によれば、再生信号の位相差を変えずに除去し、プリピット検出領域の受光信号同士の位相差だけを合わせることができる。従って、プリピットの検出感度が高く、かつ再生信号を良好に生成できる。
【００６８】
遅延回路２０の遅延量の調整についてより詳しく説明する。レーザビームがグルーブ３１の中央を走査する場合には、同一の光ディスクであれば、レーザビーム照射位置とＬＰＰとの間の位置関係（ディスク半径方向の位置関係）は変わらないので、信号ｓ５と信号ｓ６とのＬＰＰ成分の位相差φも一定である。しかしながら、情報信号ピットがトラックに対して、どちらかに偏って記録されているような場合には、再生信号品質を最良にするために、レーザビームは、情報信号ピットの中央を走査するようにトラックサーボ制御がなされる。このため、レーザビームは、トラック中央を走査しない場合があり、レーザビームが走査するトラック幅方向の位置（デトラック量）は、刻々と変化することになる。
【００６９】
そこで、遅延回路２０には、デトラック量を示すトラックサーボ誤差信号ｓ２が入力され、信号ｓ２の電圧レベルに応じて、遅延回路２０の遅延量の調整がなされる。これにより、信号ｓ５と信号ｓ６とに含まれるＬＰＰ信号成分の位相を常に合わせることが可能となり、品質の高いＬＰＰ信号ｓ８を得ることが出来る。
【００７０】
ここで、特許請求の範囲、請求項１に記載の、位相差調整手段は、トラックサーボ誤差信号生成回路の出力信号ｓ２により制御される遅延回路２０である。
【００７１】
本実施の形態では、ＤＶＤ−ＲのＬＰＰ信号検出について説明を行ったが、それ以外の光ディスクのプリピット信号検出にも応用できる。
【００７２】
【発明の効果】
本発明のプリピット検出装置は、情報トラックと情報トラックに関連する情報が記録されたプリピットとを有する光情報記録媒体からのレーザビームの反射光を受光する、複数のプリピット検出領域を含む複数の領域に分割された受光面と、複数のプリピット検出領域それぞれの反射光の光量に応じた複数の受光信号を生成する信号生成手段と、上記複数の受光信号から情報トラックに記録された再生信号を除去する再生信号除去手段と、上記再生信号除去手段により再生信号が除去された複数の受光除去信号の位相差を調整する位相差調整手段と、位相差調整手段により位相差を調整された複数の受光調整信号の差から、プリピット信号を生成するプリピット信号生成手段とを有し、上記位相差調整手段は、光情報記録媒体に照射されるレーザビームの照射領域と、光情報記録媒体の情報トラックとの、ディスク半径方向の相対距離に応じて位相差調整を行う構成である。
【００７３】
上記構成によれば、信号生成手段が生成した受光信号に含まれる再生信号の位相差を変えずに除去した後、位相差を合わせるので、適切に再生信号除去および位相差調節された、少なくとも２つの受光調整信号を生成でき、プリピット信号生成手段はこれらの受光調整信号の差を演算することで、プリピットを感度を高く検出することができるという効果を奏する。
【００７４】
さらに、上記構成によれば、光情報記録媒体の情報トラックとの、ディスク半径方向の相対距離（デトラック量）に応じてプリピット信号成分の位相差調整の量を調整する構成であるので、常に、良好に位相調整を行うことができる。
【００７５】
また、本発明のプリピット検出装置は、上記の構成に加えさらに、上記受光面は、受光面をディスク半径方向の分割線により２分割した一方の第１の受光領域と、他方の領域をさらにトラックの接線方向の分割線により２分割した第２および第３の受光領域とからなるものであり、上記複数のプリピット検出領域が上記第２および第３の受光領域からなる構成である。
【００７６】
上記構成によれば、小型、薄型でかつ、高信頼性を有する光ピックアップ装置に適用可能で、高感度でプリピットの検出を行えるプリピット検出装置を提供できるという効果を奏する。
【００７７】
本発明のプリピット検出装置は、上記再生信号除去手段は、上記受光面の複数に分割された領域それぞれに照射される反射光の光量に応じた受光信号をすべて加算した総和信号を演算する加算手段と、上記総和信号のゲインを調整するゲイン調整手段と、上記信号生成手段が生成した複数の受光信号のそれぞれからゲインを調整された総和信号を減算する少なくとも２つの減算手段とを有すること構成である。
【００７８】
上記構成によれば、複数に分割された反射光を加算した総和信号をゲイン調節した上で、上記信号生成手段が生成した複数の受光信号それぞれから減算するので、正確に再生信号が除去されるという効果を奏する。
【００７９】
本発明のプリピット検出方法は、情報トラックと情報トラックに関連する情報が記録されたプリピットとを有する光情報記録媒体からのレーザビームの反射光を、複数のプリピット検出領域を含む複数の領域に分割された受光面にて受光する受光ステップと、複数のプリピット検出領域それぞれの反射光の光量に応じた複数の受光信号を生成する信号生成ステップと、上記複数の受光信号から情報トラックに記録された再生信号を除去する再生信号除去ステップと、上記再生信号除去ステップにより再生信号が除去された複数の受光除去信号の位相差を調整する位相差調整ステップと、位相差調整ステップにより位相差を調整された複数の受光調整信号の差から、プリピット信号を生成するプリピット信号生成ステップとを有し、上記位相差調整ステップにて、光情報記録媒体に照射されるレーザビームの照射位置と、光情報記録媒体の情報トラックとの、ディスク半径方向の相対距離に応じて位相差を調整する方法である。
【００８０】
上記方法によれば、信号生成手段が生成した受光信号に含まれる再生信号の位相差を変えずに除去した後、位相差を合わせるので、適切に再生信号除去および位相差調節された、少なくとも２つの受光調整信号を生成でき、プリピット信号生成手段はこれらの受光調整信号の差を演算することで、プリピットを感度を高く検出することができるという効果を奏する。
【００８１】
さらに、上記方法によれば、光情報記録媒体の情報トラックとの、ディスク半径方向の相対距離（デトラック量）に応じてプリピット信号成分の位相差調整の量を調整できるので、常に、良好に位相調整を行うことができる。
【００８２】
本発明のプリピット検出方法は、上記再生信号除去ステップは、上記再生信号除去ステップは、上記受光面の複数に分割された領域それぞれの反射光の光量に応じた受光信号をすべて加算した総和信号を演算する加算ステップと、上記総和信号のゲインを調整するゲイン調整ステップと、上記信号生成ステップが生成した複数の受光信号のそれぞれからゲインを調整された総和信号を減算する減算ステップとを有する方法である。
【００８３】
上記方法によれば、複数に分割された反射光を加算した総和信号をゲイン調節した上で、プリピット検出領域の受光信号のそれぞれから減算するので、正確に再生信号が除去される。
【図面の簡単な説明】
【図１】本発明の実施の一形態に係るプリピット検出装置の受光面および信号生成手段のブロック図面である。
【図２】本発明の実施の一形態に係るプリピット検出方法を説明する図面である。
【図３】本発明の実施の一形態に係るプリピット検出装置が出力する受光信号と、プリピットが記録された光ディスクの記録面とを示す図面である。
【図４】本発明の実施の一形態に係るプリピット検出装置が出力する受光信号を調整した信号を示す図面であり、（ａ）は受光信号を、（ｂ）は再生信号を除去した受光信号を、（ｃ）は再生信号除去および位相差調整を行った受光信号を、（ｄ）はプリピット信号を示している。
【図５】本発明の実施の一形態に係るプリピット検出装置が出力する受光信号の調整を説明する図面である。
【図６】従来の光ディスクの記録面の表面を示す図面である。
【符号の説明】
１光ディスク（光情報記録媒体）
２スピンドルモータ
４対物レンズ
５ホログラム（受光面）
６，７，８フォトダイオード（信号生成手段）
９，１０，１１電流電圧変換回路（信号生成手段）
１２差動回路
１８，１９差動回路（減算手段）
２１差動回路（プリピット信号生成手段）
１３トラックサーボ誤差信号生成回路
１４サーボ回路
１５加算回路（加算手段）
１６再生信号処理回路（信号生成手段）
１７ゲイン調整回路（ゲイン調整手段）
２０遅延回路（位相差調整手段）
３１，５１グルーブ（情報トラック）
３２，５２ランド
３３，５３ランドプリピット（プリピット）[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a prepit detection apparatus and a prepit detection method for detecting information recorded in the prepit for an optical recording medium having information related to an information track such as address information in the form of a prepit. This increases the detection sensitivity.
[0002]
[Prior art]
  Conventionally, optical recording media (recordable optical recording media) in which data can be additionally written or rewritten are known. Generally, in such a recordable optical recording medium, prepits and pregrooves for enabling information recording on the optical recording medium are provided in advance at the time of manufacture. In the pre-pit and pre-groove, address information necessary for information recording and a reference signal for generating a clock signal used for recording / reproducing operation are recorded, and information is added, rewritten, and recorded based on the pre-pit signal. Playback is taking place.
[0003]
  FIG. 6 is a diagram showing a part of a recording surface of a DVD-R (Digital Versatile Disc-Recordable) which is a recordable high-density optical recording medium. On the recording surface of the DVD-R, a groove 51 as an information track is formed in a spiral shape or concentric shape, and information to be originally recorded such as image data and computer data is recorded in the groove 51 area. A region between the groove 51 and the groove 51 is a flat land 52. Land prepits (LPP) 53 are formed on the land 52 so as to connect the grooves 51 on both sides thereof as the above-described prepits.
[0004]
  The LPP 53 is detected when the groove 51 adjacent to the LPP 53 is irradiated with a laser beam. That is, at this time, since the laser beam irradiates the region of the groove 51 including the LPP 53, the amount of reflected light of the different laser beam is detected, so that the position of the LPP 53 can be known. More specifically, the reflected light of the laser beam is divided into two in the direction optically perpendicular to the track tangent (disk radial direction) (hereinafter this divided area is referred to as a pre-pit detection area), and each area is irradiated. The laser beam thus received is received by the two divided light receiving elements, and an electric signal corresponding to each received light amount is output. These two output signals are asymmetric when LPP 53 is included, and are greatly different from those when LPP 53 is not included. Therefore, the difference between the output signals is calculated, the difference signal is compared with a predetermined threshold value, and output as a binarized binary signal. This difference signal is called a radial push-pull signal.
[0005]
  However, there is a phase difference between the light reception signals in the prepit detection area due to the positional relationship between the laser beam irradiation area and the information track. For this reason, the difference in the received light signal when the LPP 53 is included in the laser beam irradiation area becomes small. Information recorded on the LPP 53 is very important for recording or reproducing information on the optical disc correctly and stably. Therefore, it is necessary to improve the quality of the radial push-pull signal generated from the LPP 53.
[0006]
  Therefore, in Patent Document 1, a pre-pit signal detection device that has a light receiving surface divided into two by a dividing line in the track direction of an optical disk and outputs a light reception signal corresponding to the amount of light received, receives light from each light receiving surface. It is shown that the influence of leakage of the information data signal component (RF signal component) recorded on the information track can be avoided by calculating the difference and detecting the radial push-pull signal after the signal level is amplified and adjusted. ing.
[0007]
  In Patent Document 2, the total signal of the light reception signals of the divided laser beam reflected light is adjusted so as to be equal to the level of the RF signal component mixed in the radial push-pull signal, and the phase is matched. A technique for improving the quality of the LPP by performing level adjustment, phase adjustment, and RF signal component removal by subtracting the adjusted sum signal after delay time adjustment from the radial push-pull signal is disclosed.
[0008]
  Further, in Non-Patent Document 1, in order to adjust the phase of each signal of the divided received light signal of the laser beam reflected light, a signal that is in phase with the delayed received light signal is created. A technique for increasing the amplitude of the LPP signal and improving the quality by detecting the LPP by calculating the difference between the received light signals by using it is disclosed.
[0009]
  On the other hand, a pre-pit detection device that records and reproduces information on an optical disc has been proposed that uses a hologram as a means for realizing a reduction in size, thickness, and high reliability. For example, the hologram disclosed in Patent Document 3 is divided into two by a dividing line extending in a direction corresponding to the disk radial direction (radial direction) of the disk, and one of the holograms is further divided by a dividing line extending in a direction corresponding to the track direction. It is divided into two. The focus servo error signal is detected by one half of the disk divided into two in the radial direction of the disk, and the other half is further divided by two in the track direction, and a radial push-pull signal is detected from the difference between the signals. The RF signal is detected by the sum signal of the entire reflected light. Since the reflected light divided in half is further divided into two in the radial direction of the disk, it is possible to detect a radial push-pull signal, and this radial push-pull signal is also used as a track servo error signal.
[0010]
[Patent Document 1]
        Japanese Patent Laying-Open No. 2001-23168 (Publication date: January 26, 2001)
[0011]
[Patent Document 2]
        JP 2002-74675 A (publication date March 15, 2002)
[0012]
[Patent Document 3]
        JP-A-4-21928 (Publication date: January 24, 1992)
[0013]
[Non-Patent Document 1]
        Masahiro Kato, 3 others, “Elemental technology of DVD-RW version 1.0”, PIONEER R & D, Pioneer Corporation, 2000, Vol. 10, No. 3, p. 49
[0014]
[Problems to be solved by the invention]
  In the area where the information data is recorded on the optical disc, the light reception signal in the pre-pit detection area for generating the radial push-pull signal used for LPP detection includes an LPP signal component and an RF signal component, respectively. . At this time, the RF signal components included in the two received light signals are in phase, and there may be a phase difference only in the phase of the LPP signal component.
[0015]
  This is particularly noticeable when a radial push-pull signal is detected using an optical system using the hologram by using only half of the reflected light from the optical disk as shown in Patent Document 3. Further, the phase difference of the LPP signal component varies depending on the position (detrack amount) on the information track irradiated with the laser beam. This occurs because the intensity pattern of the reflected light on the hologram changes when the laser beam passes through the LPP portion.
[0016]
  In such a case, the phase difference of the LPP signal component cannot be eliminated by adjusting the signal level or subtracting the RF signal component from the radial push-pull signal as in the prior art. Further, in the method as disclosed in Patent Document 2, if the phase difference of the RF signal component is generated by adjusting the phase difference of the LPP signal component, the RF signal component having a phase shift leaks to the radial push-pull signal. Therefore, the RF signal component cannot be removed. Furthermore, Non-Patent Document 1 only describes a method for adjusting a phase difference, and does not disclose a method for detecting a pre-pit well by combining both RF signal removal and phase difference adjustment.
[0017]
  As described above, in the related art, the RF signal components included in the two light receiving signals that generate the radial push-pull signal have the same phase, and there is a problem that the phase difference exists only in the phase of the LPP signal component. In such a case, there is a problem that the signal quality of LPP cannot be improved.
[0018]
  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a prepit detection apparatus and a prepit detection method having excellent prepit detection performance.
[0019]
[Means for Solving the Problems]
  In order to solve the above-described problem, the prepit detection apparatus of the present invention receives a reflected light of a laser beam from an optical information recording medium having an information track and a prepit on which information related to the information track is recorded. A light receiving surface divided into a plurality of areas including a prepit detection area, a signal generating means for generating a plurality of light reception signals according to the amount of reflected light of each of the plurality of prepit detection areas, and information from the plurality of light reception signals A reproduction signal removing means for removing the reproduction signal recorded on the track, a phase difference adjusting means for adjusting the phase difference of the plurality of light receiving removal signals from which the reproduction signal has been removed by the reproduction signal removing means, and a phase difference adjusting means. Prepit signal generation means for generating a prepit signal from the difference between a plurality of light receiving adjustment signals adjusted in phase difference.The phase difference adjusting means adjusts the phase difference in accordance with the relative distance in the disc radial direction between the irradiation region of the laser beam irradiated on the optical information recording medium and the information track of the optical information recording medium.It is characterized by that.
[0020]
  According to the above configuration, the light receiving surface that receives the reflected laser beam irradiated to the optical information recording medium is divided into a plurality of regions including a plurality of prepit detection regions, and the signal generating means includes a plurality of prepits. Since the light reception signal is generated in accordance with each reflected light amount irradiated to the detection region, the reflected light amount of each of the plurality of prepit detection regions can be detected. At this time, if there is a pre-pit in the laser beam irradiation area, a large difference appears in the amount of reflected light in the pre-pit detection area. Therefore, the pre-pit can be detected by detecting the light quantity in this pre-pit detection area.
[0021]
  When the light receiving surface is divided into a plurality of areas including a plurality of prepit detection areas, any division may be performed. For example, the entire area of the laser beam irradiation area may be divided into a plurality of areas to be used as a prepit detection area, or some of the plurality of areas or a part of the laser beam irradiation area may be divided into a plurality of areas for prepit detection. It may be an area.
[0022]
  For more accurate pre-pit detection, it is necessary to extract only the reflected light amount affected by the pre-pits from the reflected light amount in the pre-pit detection area. When the light reception signal is generated from the reflected light in the pre-pit detection area, a reproduction signal (RF signal) for reproducing the data recorded on the optical information recording medium is included. The reproduction signal component is removed from each light reception signal in the pre-pit detection area to obtain a light reception removal signal. Next, the reflected light from the pre-pit detection area is diffracted in the track direction. However, as the positional relationship between the laser beam and the pre-pit in the track direction changes, the diffraction situation changes. Since there is a phase difference between the lights, the phase difference of the received light removal signal is adjusted by the phase difference adjusting means.
[0023]
  The pre-pit signal generation means can detect the pre-pit with high sensitivity by calculating the difference between at least two light receiving adjustment signals adjusted in this way.
[0024]
  Furthermore, in the prepit detection apparatus of the present invention, the light reception signal in the prepit detection area is used as a light reception adjustment signal by adjusting the light reception signal phase difference in the prepit detection area after removing the reproduction signal from each. Since the phase difference described above does not occur in the playback signal, if the phase difference adjustment is performed before or at the same time as the playback signal removal, a phase difference will occur in the playback signal and a pre-pit signal is generated. In this case, the phase difference reproduction signal cannot be removed and remains. Therefore, pre-pit detection cannot be performed satisfactorily. However, according to the pre-pit detection apparatus of the present invention, it is possible to remove the reproduction signal without changing the phase difference, and to match only the phase difference between the received light signals in the pre-pit detection area. Therefore, the detection sensitivity of the prepit is high and the reproduction signal can be generated satisfactorily.
[0025]
  In addition, since the phase difference between the plurality of received light signals generated by the signal generation unit changes depending on the positional relationship in the disk radial direction between the laser beam irradiation area and the information track, the adjustment amount of the phase difference may always change. is there. According to the above configuration, the phase difference adjustment amount of the pre-pit signal component is adjusted according to the detrack amount, so that the phase difference adjustment can always be performed satisfactorily. I can do it.
[0026]
  In order to solve the above-described problem, the pre-pit detection device according to the present invention further includes, in addition to the above-described configuration, the light-receiving surface and one first light-receiving region obtained by dividing the light-receiving surface into two by a dividing line in the disk radial direction , And the other region is further divided into second and third light receiving regions which are divided into two by dividing lines in the tangential direction of the track, and the plurality of pre-pit detection regions are composed of the second and third light receiving regions. It is characterized by that.
[0027]
  Here, the “track tangential direction” refers to the direction of the tangent of the information track at the center point of the laser beam irradiation region, and the “disk radial direction” is the direction orthogonal to the track tangential direction. As in the above configuration, of the reflected light from the optical information recording medium, one first light receiving area obtained by dividing the reflected light receiving surface by a dividing line in the disk radial direction and the other half area in the track direction are further divided. In the optical pickup device that generates the light reception signal from the second and third light receiving regions divided into two by the dividing line, prepit detection is performed by this configuration, instead of realizing a small size, a thin shape, and high reliability. In this case, the phase difference between the received light signals in the pre-pit detection area becomes significant.
[0028]
  However, in the present invention, the phase difference is adjusted after removing the reproduction signal from the light reception signal generated by the signal generation means, so even if the phase difference is large, the pre-pit detection area is not affected without affecting the reproduction signal removal. The phase difference of the received light signal can be adjusted. Therefore, it is possible to provide a prepit detection device that can be applied to an optical pickup device that is small and thin and has high reliability, and that can detect prepits with high sensitivity.
[0029]
  In order to solve the above-described problem, the pre-pit detection device according to the present invention, in addition to the above-described configuration, further includes the reproduction signal removal means for each of the reflected lights applied to a plurality of divided areas of the light receiving surface. The gain is adjusted from each of a plurality of light reception signals generated by the addition means for calculating the sum signal obtained by adding all the light reception signals corresponding to the amount of light, the gain adjustment means for adjusting the gain of the sum signal, and the signal generation means. And at least two subtracting means for subtracting the sum signal.
[0030]
  According to the above configuration, the signal generation unit generates the signal after adjusting the gain of the sum signal obtained by adding all the received light signals corresponding to the amounts of the reflected lights irradiated to the plurality of divided areas of the light receiving surface. Since the subtraction is performed from each of the plurality of light reception signals, the reproduction signal is accurately removed. Since the total signal is equal to the light reception signal of the entire laser beam before the division, the reproduction signal may be generated using the total signal.
[0031]
  In order to solve the above-described problem, the prepit detection method of the present invention uses a plurality of prepits to reflect reflected light of a laser beam from an optical information recording medium having an information track and a prepit on which information related to the information track is recorded. A light receiving step for receiving light at a light receiving surface divided into a plurality of regions including a detection region, a signal generating step for generating a plurality of light reception signals according to the amount of reflected light of each of the plurality of prepit detection regions, A reproduction signal removal step for removing the reproduction signal recorded on the information track from the light reception signal, a phase difference adjustment step for adjusting the phase difference of the plurality of light reception removal signals from which the reproduction signal has been removed by the reproduction signal removal step, Pre-pit signal generation that generates a pre-pit signal from the difference between multiple light reception adjustment signals whose phase difference has been adjusted by the phase difference adjustment step Yes and stepIn the phase difference adjusting step, the phase difference is adjusted according to the relative distance in the radial direction of the disc between the irradiation position of the laser beam applied to the optical information recording medium and the information track of the optical information recording medium.It is characterized by doing.
[0032]
  According to the above method, the light receiving surface that receives the reflected laser beam irradiated to the optical information recording medium is divided into a plurality of regions including a plurality of prepit detection regions, and the signal generating means includes a plurality of prepits. Since the light reception signal is generated in accordance with each reflected light amount irradiated to the detection region, the reflected light amount of each of the plurality of prepit detection regions can be detected. At this time, if there is a pre-pit in the laser beam irradiation area, a large difference appears in the amount of reflected light in the pre-pit detection area. Therefore, the pre-pit can be detected by detecting the light quantity in this pre-pit detection area.
[0033]
  For more accurate pre-pit detection, it is necessary to extract only the reflected light amount affected by the pre-pits from the reflected light amount in the pre-pit detection area. For this purpose, first, in the reproduction signal removal step, the reproduction signal component is removed from each light reception signal in the prepit detection area to obtain a light reception removal signal, and then in the phase difference adjustment step, the positions of the light reception signals in the prepit detection area are compared. Adjust the phase difference.
[0034]
  The pre-pit signal generation step can detect the pre-pit with high sensitivity by calculating the difference between at least two light receiving adjustment signals adjusted in this way.
[0035]
  Furthermore, in the prepit detection method of the present invention, the light reception signal in the prepit detection area is used as a light reception adjustment signal by adjusting the light reception signal phase difference in the prepit detection area after removing the reproduction signal from each. According to the above method, only the phase difference between the received light signals in the pre-pit detection area can be matched without changing the phase difference of the reproduction signal. Therefore, the detection sensitivity of the prepit is high and the reproduction signal can be generated satisfactorily.
[0036]
  In addition, since the phase difference between the plurality of received light signals generated by the signal generation unit changes depending on the positional relationship in the disk radial direction between the laser beam irradiation area and the information track, the adjustment amount of the phase difference may always change. is there. According to the above configuration, the phase difference adjustment amount of the prepit signal component is adjusted according to the detrack amount, so that the phase difference adjustment can always be performed satisfactorily.
[0037]
  In order to solve the above-described problem, the pre-pit detection method of the present invention, in addition to the above-described configuration, includes the step of removing the reproduction signal in accordance with the amount of reflected light in each of the divided areas of the light-receiving surface. An addition step for calculating a sum signal obtained by adding all signals, a gain adjustment step for adjusting the gain of the sum signal, and a subtraction of the sum signal whose gain is adjusted from each of a plurality of received light signals generated by the signal generation step. And a subtracting step.
[0038]
  According to the above method, the signal generation unit generates the signal after adjusting the gain of the sum signal obtained by adding all the received light signals corresponding to the amounts of the reflected lights irradiated to the plurality of divided areas of the light receiving surface. Since the subtraction is performed from each of the plurality of light reception signals, the reproduction signal is accurately removed. Since the total signal is equal to the light reception signal of the entire laser beam before the division, the reproduction signal may be generated using the total signal.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
  A prepit detection apparatus and a prepit detection method according to an embodiment of the present invention will be described with reference to FIGS.
[0040]
  The pre-pit detection apparatus according to the present embodiment includes a hologram (light receiving surface) 5, photodiodes (signal generation means) 6, 7 and 8, current-voltage conversion circuits (I / V conversion circuits) 9, 10, and 11, and reproduction signal removal. Means, a phase difference adjusting means, and a pre-pit signal generating means for detecting pre-pits recorded on the optical disc (optical information recording medium) 1.
[0041]
  1 shows a hologram (light-receiving surface) 5, photodiodes (signal generation means) 6, 7, 8 and current / voltage (I / V) conversion circuit (signal generation means) 9, 10, FIG. 11 is a block diagram showing a portion 11. The hologram 5 receives the reflected light of the optical disc 1 and is divided into a plurality of regions. The photodiodes 6, 7, 8 convert the reflected light applied to the plurality of regions into current signals corresponding to the respective regions. Current / voltage conversion circuits (I / V conversion circuits) 9, 10, and 11 convert the current signal into a voltage signal to obtain a light reception signal.
[0042]
  Among the light reception signals, the light reception signal of the reflected light in the prepit detection area related to the prepit detection is further generated by the reproduction signal removal means to remove the reproduction signal reflecting the recording pits to generate a light reception removal signal. Thereafter, the phase difference adjusting means adjusts the phase difference of the light reception removal signal to generate a light reception adjustment signal. The pre-pit signal generation means generates a pre-pit signal indicating detection of the pre-pit from the difference between the light reception adjustment signals.
[0043]
  FIG. 2 is a diagram showing a pre-pit detection method according to the present embodiment. In the prepit detection method, reflected light (reflected light of the optical disk) irradiated with a laser beam on the optical disk (optical information recording medium) 1 is received by the hologram (light receiving surface) 5 in the light receiving step of S10, and a signal generation step of S11 is performed. The amount of light received at is converted into a received light signal. Since the optical disc 1 includes recording pits, pre-pits, etc., the received light signal reflects these. Among these, the light reception signal related to the pre-pit detection is subjected to removal of the reproduction signal in S12 (light reception removal signal), and then the phase difference is adjusted in S13 (light reception adjustment signal). Then, a pre-pit signal is calculated from the light reception adjustment signal obtained in S14.
[0044]
  The operation of the pre-pit detection device according to the present embodiment will be described below.
[0045]
  First, a light emitting element (not shown) such as a semiconductor laser emits light to a recording surface of an optical disc (optical information recording medium) 1 such as a DVD-R that is rotationally driven by a spindle motor 2. The objective lens 4 collects light from the light emitting element and irradiates an arbitrary point of the optical disc 1 as a laser beam. The objective lens 4 further allows the laser beam reflected by the recording surface of the optical disc 1 to pass again, and further passes through several optical elements to determine the direction thereof, and a hologram (light receiving surface) 5 of the signal generating means. Led to.
[0046]
  The hologram 5 divides the laser beam guided as described above into a region A (first light receiving region) and a region B by a dividing line l in the disk radial direction, and further divides the region B into a dividing line m in the track direction. Are divided into a region B1 (second light receiving region) and a region B2 (third light receiving region), and the reflected light applied to the region A, the region B1, and the region B2 is divided into separate photodiodes 6, 7, Lead to 8. The photodiodes 6, 7, and 8 have a property of flowing current when exposed to light. Here, the light beam that has passed through the region A is condensed on the photodiode 6 and a current corresponding to the light amount is output to the I / V conversion circuit 9 and used as a reproduction signal for recording and reproduction. Further, the light beams that have passed through the region B1 and the region B2 are collected by the photodiodes 7 and 8, respectively, and currents corresponding to the light amounts are output to the I / V conversion circuits 10 and 11, respectively, and the prepit detection signal and the servo error are output. Used for calculation.
[0047]
  For example, when the photodiode 6 is used for focus servo error signal detection, a divided photodiode may be used to detect different amounts of light as areas divided in the area A. The description will be made with reference to two photodiodes, and a description of focus servo error signal detection will be omitted.
[0048]
  The current-voltage (I / V) conversion circuits 9, 10, and 11 receive the detection currents output from the photodiodes 6, 7, and 8, respectively, the light reception signal a (reflecting the amount of light in the region A) and the light reception signal. b1 (reflects the amount of light in the region B1) and light reception signal b2 (reflects the amount of light in the region B2) for output.
[0049]
  Here, the light receiving signals b1 and b2 of the light amounts in the areas B1 and B2 which are the prepit detection areas will be described with reference to FIG. FIG. 3 shows the recording surface of the optical disc 1 and the waveforms of the received light signals b1 and b2 obtained by irradiating the recording surface with a laser beam.
[0050]
  A groove (information track) 31 that is an area for information recording is formed on the recording surface of the optical disc 1, and recorded information is recorded as information pits 35 (shaded portions) in the groove 31 area. There is a flat land 32 between the groove 31 and the groove 31. Land prepits (LPP) 33 are formed on the land 32 so as to connect the grooves 51 on both sides as prepits, and information related to the information track is recorded.
[0051]
  The laser beam moves the laser beam irradiation area R along the groove 31 on the recording surface. When the irradiated laser beam scans the groove 31, the signal b 1 and the signal b 2 are modulated according to the information signal pit 35. At this time, since the laser beam is controlled so as to scan substantially the center of the information signal pit 35 row, for example, when the laser beam irradiation area is at the position R1, the information pit 35a is along the groove 31 of R1. Come on the centerline. Therefore, the reproduction signals (RF signals) appearing in the signals b1 and b2 are signal components having the same phase and substantially the same level as shown in FIG.
[0052]
  On the other hand, the signal b1 and the signal b2 are also modulated by the LPP 33. This is because when the irradiation region includes the LPP 33 as in the laser beam irradiation region R2, the state of diffraction by the groove 31 is changed by the LPP 33. That is, the LPP 33 exists only on one side of the groove 31 and does not appear simultaneously on both sides. Therefore, in the LPP 33, the amount of light received by the region B1 and the region B2 (light intensity distribution of the photodiode 7 and the photodiode 8) becomes asymmetric. As shown in FIG. 3, when the signal b1 increases, the signal b2 decreases and appears as an LPP signal component. If a radial push-pull signal that is the difference between the signal b1 and the signal b2 is generated using this phenomenon, when the laser beam irradiation region includes the LPP 33, the difference between b1 and b2 becomes very large compared to the other, and the LPP 33 Can be detected.
[0053]
  Further, in the signal waveforms of b1 and b2, there is a time delay in the phase difference φ, that is, b2. This is because the laser beam is diffracted not only in the groove 31 width direction but also in the track direction (track tangential direction) when scanning the region including the LPP 33, and the positional relationship between the laser beam and the LPP in the track direction. This is because the state of diffraction changes with time as the value changes. In particular, the occurrence of the phase difference φ is remarkable when only one of the reflected lights (B region) divided into two by the dividing line in the disk radial direction is used.
[0054]
  As described above, the reproduction signal component (RF signal component) and the LPP signal component are mixed in the signal b1 and the signal b2, and the phase difference φ is generated in the LPP signal component. To detect accurately, it is necessary to remove the RF signal component and adjust the phase difference of the LPP signal component. That is, the RF signal component is removed from the signals b1 and b2 as shown in FIG. 4A by the reproduction signal removing means to obtain the signals b1 'and b2' as shown in (b). Further, in order to adjust the phase difference φ between the signal b1 and the signal b2, as shown in FIG. 4C, b1 ′ is delayed by the phase difference φ by the phase difference adjusting means to be b1 ″. And the difference between b2 ′ and the pre-pit detection signal as shown in FIG.
[0055]
  Hereinafter, a method for generating the pre-pit detection signal from the light reception signal as described above will be described in detail with reference to FIG. In the present embodiment, a servo error and a pre-pit signal are generated from b1 and b2, and a reproduction signal is output together with the signal a.
[0056]
  First, the servo error will be described. When the groove 31 on the optical disk 1 is irradiated with a laser beam, the diffraction by the groove 31 varies depending on the relative positional relationship between the groove 31 and the laser beam irradiation region R, and the far field pattern of the reflected light changes.
[0057]
  For example, when the laser beam irradiation region R is at the center of the groove 31 in the width direction, the light is reflected almost evenly on the entire surface. Therefore, in the regions B1 and B2 divided by the dividing line in the track direction, the photodiode 7 and the photo diode The light intensity distribution focused on the diode 8 is symmetric. However, if the laser beam is deviated from the center of the track, different amounts of reflected light are generated in the laser beam irradiation region due to diffraction by the groove 31, so that the amount of reflected light in the region B1 and the region B2 becomes asymmetric. The light intensity distributions 7 and 8 are also asymmetric. By utilizing this fact, a diffracted light intensity distribution by a track, that is, a so-called ball pattern change is detected by the photodiodes 7 and 8, and a radial push-pull signal is obtained as a difference signal. This radial push-pull signal is used as a track servo error signal for detecting the deviation of the laser beam irradiation area from the track.
[0058]
  Specifically, first, both the signal b1 and the signal b2 are input to the differential circuit 12, and a difference between them is calculated to obtain a radial push-pull signal s1 for detecting a track servo error. The radial push-pull signal s1 is input to the track servo error signal generation circuit 13. The track servo error signal generation circuit 13 performs broadband noise removal, offset adjustment, etc., and outputs a track servo error signal s2. The track servo error signal s2 is input to the servo circuit 14, and a track servo operation is performed.
[0059]
  Next, generation of a reproduction signal will be described. The signal a, signal b1, and signal b2 are added by an adder circuit (adding means) 15, and the sum of the amounts of light incident on the photodiodes 6, 7, and 8 is calculated to generate a sum signal s3. The sum signal s3 is input to the reproduction signal processing circuit 16 as a reproduction information signal (RF signal) for detecting information recorded on the optical disc 1 as an increase / decrease in the amount of reflected light. By reading the sum signal s3, the optical disc 1 is read. The information recorded in is reproduced.
[0060]
  In this case, the adding means is the adding circuit 15, the gain adjusting means is the gain adjusting circuit 17, and the subtracting means is the differential circuit 18 and the differential circuit 19.
[0061]
  Finally, generation of an LPP signal (pre-pit signal) will be described. As described above, the generation of the LPP signal requires the reproduction signal removal and the phase difference adjustment. The reproduction signal removal means for removing the reproduction signal includes an addition circuit (addition means) 15, a gain adjustment circuit (gain adjustment means) 17, and differential circuits (subtraction means) 18 and 19. First, the sum signal s3 of the addition circuit 15 described above is input to a gain adjustment circuit (gain adjustment means) 17 for adjusting the signal level to obtain a gain adjustment signal s4. In the gain adjustment circuit 17, the signal s3, which is an RF signal, is adjusted so as to be the same level as the level of the RF signal component included in the signal b1 and the signal b2. The signal b1 and the gain adjustment signal s4 are input to the differential circuit (subtraction means) 18, and the signal b2 and the gain adjustment signal s4 are input to the differential circuit (subtraction means) 19. The adjustment signal s4 is obtained by adjusting the gain level of the sum signal of the signal b1, the signal b2, and the signal a according to the signal b1 and the signal b2, and calculating the difference between the signal s4 and the signal b1 or the signal b2. , The RF signal component is removed from each of the signals b1 and b2, and the signal s5 (light reception removal signal, b1 ′ described above) and the signal s6 (light reception removal signal, b2 ′ described above) of FIG. 4B are output. Is done.
[0062]
  Here, two gain adjusting circuits are provided, and the signal input to the differential circuit 18 and the signal input to the differential circuit 19 are respectively set to the level of the RF signal component included in the signal b1 and the signal b2. If the adjustment is performed individually so as to match the level of the RF signal component included, the ability to remove the RF signal component is further increased.
[0063]
  Since the phase difference φ is generated between the LPP signal component included in the signal s5 and the LPP signal component included in the signal s6 as described above, the output of the differential circuit 18 is used to eliminate the phase difference φ. The signal s5 is input to the delay circuit (phase difference adjusting means) 20. The delay circuit 20 adjusts the delay amount so that the phase difference φ is corrected based on the servo error signal s2, and delays the signal s5 to obtain the signal s7 (light reception adjustment signal, b1 ″ described above).
[0064]
  Note that the LPP signal component included in the signal s5 and the signal s6 is determined by the optical positional relationship between the position of the LPP 33 on the optical disc and the laser beam irradiation area R, but here, the LPP signal component that appears in the signal s5. Will be described before the LPP signal component of the signal s6, the signal s5 increases, and the signal s6 decreases. The delay circuit may be provided for the signal whose phase is advanced. Of course, in an apparatus for reproducing a plurality of types of optical disks whose phase relationship is reversed, the delay circuit may be provided for both. It is necessary to switch.
[0065]
  The signal s7 that has passed through the delay circuit 20 is input to one terminal of a differential circuit (prepit signal generating means) 21, and the signal s6 is input to the other input terminal of the differential circuit 21. The differential circuit 21 calculates and outputs the difference between the signal s7 in which the level of the LPP signal component increases and the signal s6 in which the level decreases. An LPP signal (pre-pit signal) is obtained from the difference signal s8, and LPP is detected by binarizing this signal.
[0066]
  Here, since the RF signal components of the signal s7 and the signal s8 have already been removed, it is not necessary to provide a circuit for adjusting the gain of the signal s7 and the signal s8.
[0067]
  As described above, the light reception signal in the prepit detection area is used as a light reception adjustment signal by adjusting the light reception signal phase difference in the prepit detection area after removing the reproduction signal from each. Since the phase difference described above does not occur in the playback signal, if the phase difference adjustment is performed before or at the same time as the playback signal removal, a phase difference will occur in the playback signal and a pre-pit signal is generated. In this case, the phase difference reproduction signal cannot be removed and remains. Therefore, although the prepit detection could not be performed satisfactorily, according to the prepit detection device, it is possible to remove the reproduction signal without changing the phase difference, and to adjust only the phase difference between the received light signals in the prepit detection area. Therefore, the detection sensitivity of the prepit is high and the reproduction signal can be generated satisfactorily.
[0068]
  The adjustment of the delay amount of the delay circuit 20 will be described in more detail. When the laser beam scans the center of the groove 31, the positional relationship (positional relationship in the radial direction of the disk) between the laser beam irradiation position and the LPP does not change if the same optical disk is used. The phase difference φ of the LPP component from s6 is also constant. However, in the case where the information signal pits are recorded on either side of the track, the laser beam should be scanned in the center of the information signal pits in order to optimize the reproduction signal quality. Track servo control is performed. For this reason, the laser beam may not scan the center of the track, and the position (detrack amount) in the track width direction scanned by the laser beam changes every moment.
[0069]
  Therefore, the track servo error signal s2 indicating the detrack amount is input to the delay circuit 20, and the delay amount of the delay circuit 20 is adjusted according to the voltage level of the signal s2. As a result, the phases of the LPP signal components included in the signal s5 and the signal s6 can always be matched, and a high-quality LPP signal s8 can be obtained.
[0070]
  Where:Claim 1The phase difference adjusting means is a delay circuit 20 controlled by the output signal s2 of the track servo error signal generation circuit.
[0071]
  In the present embodiment, the DVD-R LPP signal detection has been described. However, the present invention can also be applied to detection of pre-pit signals of other optical disks.
[0072]
【The invention's effect】
  The prepit detection apparatus of the present invention receives a reflected light of a laser beam from an optical information recording medium having an information track and a prepit on which information related to the information track is recorded, and includes a plurality of areas including a plurality of prepit detection areas And a signal generating means for generating a plurality of received light signals according to the amount of reflected light from each of the plurality of prepit detection areas, and a reproduction signal recorded on the information track is removed from the plurality of received light signals. A reproduction signal removing means for adjusting the phase difference of the plurality of light receiving removal signals from which the reproduction signal has been removed by the reproduction signal removing means, and a plurality of light receiving signals having the phase difference adjusted by the phase difference adjusting means. Pre-pit signal generation means for generating a pre-pit signal based on the difference between the adjustment signals.The phase difference adjusting means adjusts the phase difference in accordance with the relative distance in the disc radial direction between the irradiation region of the laser beam irradiated on the optical information recording medium and the information track of the optical information recording medium.It is a configuration.
[0073]
  According to the above configuration, since the phase difference is adjusted after removing the reproduction signal included in the light reception signal generated by the signal generation unit without changing the phase difference, the reproduction signal is appropriately removed and the phase difference is adjusted. One light receiving adjustment signal can be generated, and the pre-pit signal generating means calculates the difference between these light receiving adjustment signals, thereby producing an effect that the pre-pit can be detected with high sensitivity.
[0074]
  Furthermore, according to the above configuration, the amount of phase difference adjustment of the pre-pit signal component is adjusted according to the relative distance (detrack amount) in the disc radial direction from the information track of the optical information recording medium. The phase adjustment can be performed satisfactorily.
[0075]
  In addition to the above-described configuration, the pre-pit detection device according to the present invention further includes a first light-receiving area obtained by dividing the light-receiving surface into two by a dividing line in the radial direction of the disk, and further tracking the other area. The second and third light receiving regions are divided into two by a dividing line in the tangential direction, and the plurality of prepit detection regions are composed of the second and third light receiving regions.
[0076]
  According to the above configuration, it is possible to provide a prepit detection device that can be applied to an optical pickup device that is small, thin, and highly reliable, and that can detect prepits with high sensitivity.
[0077]
  In the pre-pit detection apparatus of the present invention, the reproduction signal removing means is an adding means for calculating a sum signal obtained by adding all received light signals according to the amount of reflected light applied to each of the divided areas of the light receiving surface. And a gain adjusting means for adjusting the gain of the sum signal, and at least two subtracting means for subtracting the sum signal whose gain has been adjusted from each of the plurality of light receiving signals generated by the signal generating means. is there.
[0078]
  According to the above-described configuration, the sum signal obtained by adding the reflected light divided into a plurality of parts is subjected to gain adjustment, and then subtracted from each of the plurality of received light signals generated by the signal generation unit, so that the reproduction signal is accurately removed. There is an effect.
[0079]
  The pre-pit detection method of the present invention divides reflected light of a laser beam from an optical information recording medium having an information track and a pre-pit on which information related to the information track is recorded into a plurality of areas including a plurality of pre-pit detection areas. A light receiving step for receiving light on the received light receiving surface, a signal generating step for generating a plurality of light receiving signals according to the amount of reflected light of each of the plurality of prepit detection areas, and the information track recorded from the plurality of light receiving signals. The reproduction signal removal step for removing the reproduction signal, the phase difference adjustment step for adjusting the phase difference of the plurality of received light removal signals from which the reproduction signal has been removed by the reproduction signal removal step, and the phase difference are adjusted by the phase difference adjustment step. A pre-pit signal generation step for generating a pre-pit signal from the difference between a plurality of received light adjustment signals.In the phase difference adjusting step, the phase difference is adjusted according to the relative distance in the radial direction of the disc between the irradiation position of the laser beam applied to the optical information recording medium and the information track of the optical information recording medium.It is a method to do.
[0080]
  According to the above method, since the phase difference is adjusted after removing the reproduction signal included in the received light signal generated by the signal generation means without changing the phase difference, the reproduction signal is appropriately removed and the phase difference is adjusted. One light receiving adjustment signal can be generated, and the pre-pit signal generating means calculates the difference between these light receiving adjustment signals, thereby producing an effect that the pre-pit can be detected with high sensitivity.
[0081]
  Furthermore, according to the above method, the amount of phase difference adjustment of the pre-pit signal component can be adjusted according to the relative distance (detrack amount) in the disc radial direction with respect to the information track of the optical information recording medium. Phase adjustment can be performed.
[0082]
  In the pre-pit detection method of the present invention, the reproduction signal removal step includes a sum signal obtained by adding all the received light signals according to the amount of reflected light of each of the divided areas of the light receiving surface. An addition step for calculating, a gain adjustment step for adjusting the gain of the sum signal, and a subtraction step for subtracting the sum signal whose gain has been adjusted from each of the plurality of received light signals generated by the signal generation step. is there.
[0083]
  According to the above method, the sum signal obtained by adding the reflected light divided into a plurality of parts is gain-adjusted and then subtracted from each of the light reception signals in the pre-pit detection area, so that the reproduction signal is accurately removed.
[Brief description of the drawings]
FIG. 1 is a block diagram of a light receiving surface and signal generation means of a prepit detection apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a pre-pit detection method according to an embodiment of the present invention.
FIG. 3 is a diagram showing a light reception signal output from a pre-pit detection device according to an embodiment of the present invention and a recording surface of an optical disc on which pre-pits are recorded.
FIGS. 4A and 4B are diagrams illustrating a signal obtained by adjusting a light reception signal output from a prepit detection apparatus according to an embodiment of the present invention, where FIG. 4A is a light reception signal, and FIG. 4B is a light reception signal from which a reproduction signal is removed; (C) shows the received light signal after reproduction signal removal and phase difference adjustment, and (d) shows the pre-pit signal.
FIG. 5 is a diagram for explaining adjustment of a received light signal output from a pre-pit detection apparatus according to an embodiment of the present invention.
FIG. 6 is a drawing showing the surface of a recording surface of a conventional optical disc.
[Explanation of symbols]
    1 Optical disc (optical information recording medium)
    2 Spindle motor
    4 Objective lens
    5 Hologram (light receiving surface)
    6,7,8 Photodiode (Signal generation means)
    9, 10, 11 Current-voltage conversion circuit (signal generating means)
    12 Differential circuit
    18, 19 Differential circuit (subtraction means)
    21 Differential circuit (Prepit signal generation means)
    13 Track servo error signal generation circuit
    14 Servo circuit
    15 Adder circuit (addition means)
    16 Reproduction signal processing circuit (signal generation means)
    17 Gain adjustment circuit (gain adjustment means)
    20 delay circuit (phase difference adjusting means)
    31, 51 groove (information track)
    32,52 rand
    33,53 Land pre-pit (pre-pit)

Claims

A light-receiving surface divided into a plurality of regions including a plurality of pre-pit detection regions, which receives reflected light of a laser beam from an optical information recording medium having an information track and a pre-pit on which information related to the information track is recorded;
Signal generating means for generating a plurality of light receiving signals according to the amount of reflected light of each of the plurality of prepit detection areas;
Reproduction signal removing means for removing the reproduction signal recorded on the information track from the plurality of received light signals;
A phase difference adjusting means for adjusting a phase difference of a plurality of light receiving removal signals from which the reproduction signal has been removed by the reproduction signal removing means;
From the difference between the plurality of light receiving adjustment signal adjusted the phase difference by the phase difference adjusting means, have a pre-pit signal generating means for generating a pre-pit signal,
The phase difference adjusting means adjusts the phase difference according to the relative distance in the radial direction of the disc between the irradiation area of the laser beam irradiated on the optical information recording medium and the information track of the optical information recording medium. Pre-pit detection device.

The light receiving surface includes one first light receiving region obtained by dividing the light receiving surface into two by a dividing line in the disc radial direction, and second and third light receiving portions obtained by further dividing the other region into two by a dividing line in the tangential direction of the track. 2. The prepit signal detection device according to claim 1, wherein the plurality of prepit detection areas include the second and third light receiving areas.

The reproduction signal removing means includes an adding means for calculating a sum signal obtained by adding all received light signals according to the amount of reflected light applied to each of the plurality of divided areas of the light receiving surface,
Gain adjusting means for adjusting the gain of the sum signal,
3. The pre-pit detection apparatus according to claim 1, further comprising at least two subtracting means for subtracting a sum signal whose gain is adjusted from each of the plurality of light receiving signals generated by the signal generating means.

The reflected light of the laser beam from the optical information recording medium having the information track and the pre-pit on which the information related to the information track is recorded is received by the light receiving surface divided into a plurality of areas including a plurality of pre-pit detection areas. A light receiving step;
A signal generation step for generating a plurality of received light signals according to the amount of reflected light of each of the plurality of prepit detection areas;
A reproduction signal removing step for removing the reproduction signal recorded on the information track from the plurality of received light signals;
A phase difference adjustment step for adjusting the phase difference of the plurality of light reception removal signals from which the reproduction signal has been removed by the reproduction signal removal step;
A pre-pit signal generation step for generating a pre-pit signal from a difference between a plurality of light receiving adjustment signals whose phase differences have been adjusted by the phase difference adjustment step ;
In the phase difference adjusting step, the phase difference is adjusted according to the relative distance in the disc radial direction between the irradiation position of the laser beam irradiated on the optical information recording medium and the information track of the optical information recording medium. A pre-pit signal detection method.

The reproduction signal removal step includes an addition step of calculating a sum signal obtained by adding all the received light signals according to the amount of reflected light of each of the divided areas of the light receiving surface,
A gain adjustment step for adjusting the gain of the sum signal,
5. The pre-pit detection method according to claim 4 , further comprising: a subtracting step of subtracting a sum signal whose gain is adjusted from each of the plurality of light receiving signals generated in the signal generating step.

A light-receiving surface divided into a plurality of regions including a plurality of pre-pit detection regions, which receives reflected light of a laser beam from an optical information recording medium having an information track and a pre-pit on which information related to the information track is recorded;
Signal generating means for generating a plurality of light receiving signals according to the amount of reflected light of each of the plurality of prepit detection areas;
Reproduction signal removing means for removing the reproduction signal recorded on the information track from the plurality of received light signals;
A phase difference adjusting means for adjusting a phase difference of a plurality of light receiving removal signals from which the reproduction signal has been removed by the reproduction signal removing means;
From the difference between the plurality of light receiving adjustment signal adjusted the phase difference by the phase difference adjusting means, have a pre-pit signal generating means for generating a pre-pit signal,
The light receiving surface includes one first light receiving region obtained by dividing the light receiving surface into two by a dividing line in the disc radial direction, and second and third light receiving portions obtained by further dividing the other region into two by a dividing line in the tangential direction of the track. And a plurality of pre-pit detection areas including the second and third light-receiving areas .

A light-receiving surface divided into a plurality of regions including a plurality of pre-pit detection regions, which receives reflected light of a laser beam from an optical information recording medium having an information track and a pre-pit on which information related to the information track is recorded;
Signal generating means for generating a plurality of light receiving signals according to the amount of reflected light of each of the plurality of prepit detection areas;
Reproduction signal removing means for removing the reproduction signal recorded on the information track from the plurality of received light signals;
A phase difference adjusting means for adjusting a phase difference of a plurality of light receiving removal signals from which the reproduction signal has been removed by the reproduction signal removing means;
From the difference between the plurality of light receiving adjustment signal adjusted the phase difference by the phase difference adjusting means, have a pre-pit signal generating means for generating a pre-pit signal,
The reproduction signal removing means includes an adding means for calculating a sum signal obtained by adding all received light signals according to the amount of reflected light applied to each of the plurality of divided areas of the light receiving surface,
Gain adjusting means for adjusting the gain of the sum signal,
A pre-pit detecting apparatus comprising: at least two subtracting means for subtracting a sum signal whose gain is adjusted from each of a plurality of light receiving signals generated by the signal generating means .