JP2004220702A - Optical information recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To record information efficiently in each recording layer of an optical information recording medium having multi-layer structure and to reproduce recorded information stably. <P>SOLUTION: Optical phase difference of luminous flux in an irradiation optical system 15 irradiating a recording layer with light emitted from light sources 3, 4 in a convergence state is corrected so that wave front aberration in light reflected by an arbitrary recording layer of the optical information recording medium 2 having multi-layer structure in which a plurality of recording layers recording information optically are laminated is reduced. Thereby, a light spot diameter converged at the recording layer can be narrowed to the diffraction limit without causing phase difference for any recording layer in the optical information recording medium 2 can be narrowed to the diffraction limit, information can be recorded efficiently in each recording layer of the optical information recording medium 2 having multi-layer structure, while, recorded information can be reproduced stably. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００８１】
ここで、Ｓ（ξ、η）は瞳内の形状をあらわす関数、Ｗ（ξ、η）は波面収差をあらわす関数である。また、ｋは波数であり、レーザ光の波長をλとすると、ｋ＝２π／λである。
【００８２】
また、像面における振幅分布関数ｈ（ｘ，ｙ）は、上述した瞳関数Ｈ（ξ，η）のフーリエ変換として、以下に示す（２）式によって表わされる。
【００８３】
ｈ（ｘ，ｙ）＝｜ｈ（ｘ，ｙ）｜ｅｘｐ（ｉφ（ｘ，ｙ）） …（２）
【００８４】
一方、像面でのビームスポットは、点像分布関数によって以下に示す（３）式によって表わされる。
【００８５】
ｐ（ｘ，ｙ）＝｜ｈ（ｘ，ｙ）｜^２ …（３）
【００８６】
ところで、光源から光学情報記録媒体２の記録層６までの厚さが異なったり、光記録媒体（記録面）のチルトが発生したりしている場合、光検出器で検出される再生光に波面収差が発生し、像が劣化する。ここで、発生する波面収差をＷＴ（ξ，η）とすると、光検出器１３上にスポットを形成する集光レンズ１２の瞳関数ＨＴ（ξ，η）は、以下に示す（４）式によって表わされる。
【００８７】
ＨＴ（ξ，η）＝Ｓ（ξ，η）ｅｘｐ（ｉｋＷＴ（ξ，η）） …（４）
【００８８】
なお、光学系１５，１６全体の振幅分布関数は、対物レンズ１０に入射したレーザ光束の瞳関数Ｈ（ξ、η）と、光検出器１３上にスポットを形成する集光レンズ１２の瞳関数ＨＴ（ξ，η）とのコンボリューションで表される。
【００８９】
次に、位相差補正素子１７の前面で生じる光学的位相差をＷＭ（ξ，η）とし、位相差補正素子１７によって与えられる光路差をＷＭ（ξ，η）とすると、位相差補正素子１７による光学的位相差の補正後に光検出器１３上にスポットを形成する集光レンズ１２の瞳関数ＨＭ（ξ，η）は、以下に示す（５）式によって表わされる。
【００９０】

【００９１】
（５）式によれば、ＷＴ（ξ，η）−ＷＭ（ξ，η）を０にすることにより、光学情報記録媒体２内で発生した波面収差を打ち消すことが可能であることが判る。
【００９２】
本実施の形態では、位相差補正素子１７により、光学情報記録媒体２厚の変化に応じて、ＷＴ（ξ、η）−ＷＭ（ξ、η）を０もしくは最小にするように、位相差補正素子１７を通過する高速の光路差を調整することにより、位相差を補正する。
【００９３】
具体的に、波面収差をあらわす関数としては、ゼルニケ多項式がよく知られている。この多項式は、ザイデル収差などの光学収差などとよく対応しており、ゼルニケ多項式によれば上述の光記録媒体の球面収差に対応する係数Ｗｃは、以下に示す（６）式によって表わされる。
【００９４】
Ｗｃ＝１−６（ｘ^２＋ｙ^２）＋６（ｘ^２＋ｙ^２）^２ …（６）
【００９５】
ここで、図４は、球面収差が発生した場合の波面収差の一例を示している。図４中横軸は、瞳面半径を１として瞳面座標を規格化した値である。また、図４中縦軸は、波面収差を表わしており、入射波長で規格化した値である。
【００９６】
本実施の形態の光学情報記録再生装置１によれば、図４に示すような球面収差が発生している場合に、液晶パネル制御回路（図示せず）によって、位相差補正素子１７のガラス基板に形成された電極に印加する電圧を電極毎に可変制御することにより、液晶パネルにおける光束の透過状態を調整する。本実施の形態では、図４に示すような球面収差を発生させる光束に対して、図５に示すような位相分布を与えるように、電極に印加する電圧を電極毎に調整する。ここに、位相差補正手段としての機能が実現される。
【００９７】
このように電圧毎に電圧を印加することにより、ガラス基板間における液晶分子の配向を、印加された電圧に応じて発生する電界にしたがって偏倚させることができ、位相差補正素子１７のガラス基板間を透過する光束の進行方向に直交する断面内における屈折率分布を調整することができる。
【００９８】
これによって、球面収差によって発生した波面収差を小さくすることができ、多層構造の光学情報記録媒体２であっても、記録や再生の対象となる記録層６の場所毎の厚みの違いや、記録や再生の対象となる記録層６に到達するまでにレーザ光束が通過する記録層６の数等によって生じる波面収差を補正することができる。
【００９９】
上述したように、光学情報記録媒体２の記録層６の厚さによって生じた球面収差を補正することにより、多層構造を有する光学情報記録媒体２におけるいずれの記録層６に対しても光学的位相差を生じさせることなく、各記録層６に集光される光スポット径を回析限界まで絞ることができ、多層構造を有する光学情報記録媒体２の各記録層６に対して効率よく情報を記録するとともに、記録された情報を安定して再生することができる。
【０１００】
なお、本実施の形態の光学情報記録再生装置１では、対物レンズ１０をフォーカシング方向に移動させて光学情報記録媒体を３次元的に走査することにより、多層構造の光学情報記録媒体２の各記録層６に対して記録マークを３次元的に一点ずつ形成することにより情報を記録する。これによって、大容量の光情報記録再生が実現できる。
【０１０１】
ここで「３次元的に一点ずつ形成する」とは、多層構造の光学情報記録媒体が有する記録層のうち目的とする記録層に対して同心円状またはスパイラル状に配列されるように記録マークを形成すること意味する。
【０１０２】
次に、本発明の第２の実施の形態について図６および図７を参照して説明する。なお、第１の実施の形態と同一部分は同一符号で示し、説明も省略する。以下、同様とする。本実施の形態では、例えば、光学情報記録媒体２が傾いた状態で配置された場合や記録層６の厚みが場所毎に異なる等、照射光学系１５における光束の光軸に直交する面に対して記録層がチルトしている場合等に発生する波面収差を補正する。
【０１０３】
図６は、チルトが発生している状態の波面収差（コマ収差）の一例を示している。本実施の形態では、第１の実施の形態と同様に、このチルトを相殺するような位相分布を光路中に与えることによって、光学情報記録媒体２の記録層６のチルトにより発生する収差成分を小さくすることができる。
【０１０４】
ここで、チルトに対応する係数Ｗｃは、以下に示す（７）式で表わされる。
【０１０５】
Ｗｃ＝−２ｘ＋３ｘ^３＋３ｘｙ^２ …（７）
【０１０６】
公知の技術であるため液晶パネルの図示および説明は省略するが、本実施の形態の光学情報記録再生装置１の液晶パネルにおける一方のガラス基板には、照射光学系１５の光軸方向に直交する方向に対してチルトする方向に沿って複数に分割された透明な電極が形成されている。液晶パネルにおける他方の図示しないガラス基板には、一方のガラス基板の電極に対向する別の透明な電極が形成されている。ガラス基板間における液晶分子は、各ガラス基板に形成された電極間に印加された電圧に応じて発生する電界にしたがって配向状態が偏倚する。
【０１０７】
このような光学情報記録再生装置１では、図６に示すように、チルトによる収差が発生している場合、液晶パネル制御回路（図示せず）によって、位相差補正素子１７のガラス基板に形成された電極に印加する電圧のパターンを可変制御することにより、図６に示すような球面収差を発生させる光束に対して、図７に示すような位相分布を与える。ここに、位相差補正手段が実現される。
【０１０８】
このような電圧印加により、ガラス基板間における液晶分子の配向が、印加された電圧に応じて発生する電界にしたがって偏倚し、位相差補正素子１７のガラス基板間を透過する光束の進行方向に直交する断面内における屈折率分布が記録層６のチルトによる波面収差低減するように調整される。
【０１０９】
これによって、記録層６のチルトによる波面収差を小さくし、多層構造の光学情報記録媒体２であっても、チルトの発生に起因する波面収差を補正することができる。
【０１１０】
上述したように、光学情報記録媒体２の記録層厚によって生じた記録面のチルトによる波面収差を補正することにより、再生対象とする記録層に対して、良好な再生レーザ光スポットを形成することができる。
【０１１１】
次に、本発明の第３の実施の形態について図８を参照して説明する。
【０１１２】
図８は、本実施の形態の光学情報記録再生装置１を示す概略図である。本実施の形態の光学情報記録再生装置１は、図１に示す位相差補正素子１７に代えて、図８に示すように、波面補正ミラー２０が設けられている。
【０１１３】
波面補正ミラー２０は、一面側にミラー面２１ａを有する薄膜状のミラー部材２１と、このミラー部材２１を支持するミラー支持部材としてのミラー支持基板２２と、ミラー部材２１とミラー支持基板２２との間に設けられた図示しない複数の圧電素子（ピエゾ素子）とを有している。公知の技術であるため図示および説明を省略するが、各圧電素子は、電圧を印加するための電極をそれぞれ備えている。ここに、ミラー支持基板２２と圧電素子とによって変形手段が実現されている。
【０１１４】
波面補正ミラー２０のミラー支持基板２２としては、例えば、Ｓｉ単結晶によって構成することが可能である。ミラー支持基板２２の厚さは、例えば、４インチ四方のＳｉ単結晶基板では通常５２５μｍ、６インチ四方のＳｉ単結晶基板では６２５μｍに設定されている。通常の半導体プロセスで用いられて、鏡面研磨された４インチ四方のＳｉ単結晶基板における平面度は、波長６３５ｎｍの光を照射した場合の波面収差のｒｍｓが、０．０２λ程度である。この平面度は、Ｓｉ単結晶基板を波面補正ミラー２０のミラー支持基板２２として用いることに対して、十分実用に耐えうる精度である。
【０１１５】
また、波面補正ミラー２０のミラー支持基板２２としては、例えば、市販されているダイシングソウで数ミリ角程度に切断したＳｉ単結晶であってもよい。特に図示しないが、このようなＳｉ単結晶によって形成したミラー支持基板２２の波面収差のｒｍｓは０．０２λであり、これによりダイシングソウで切断したＳｉ単結晶によりミラー支持基板２２を形成した場合でも、切断時のひずみにより波面収差が劣化する可能性も少ないことが判る。
【０１１６】
特に図示しないが、実際に、元々が４インチ四方のＳｉ単結晶基板を、１％程度の希フッ酸を用いて、軽く表面酸化膜を剥離した後、Ａｌを４０００オングストローム程度に真空蒸着し、ダイシングソウで７ｍｍ×７ｍｍに切断した後、波面収差を測定したところ、０．０２λの波面収差のｒｍｓを有する波面補正ミラー２０を得ることができた。この平面度は、波面補正ミラー２０として用いることに対して、十分実用に耐えうる精度である。
【０１１７】
ミラー支持基板２２上にミラー面２１ａを有するミラー部材２１形成するミラーコーティング材としては、金属、誘電体等が代表的なミラーコーティング材として用いられる。例えば、ミラーコーティング材として金属を用いる場合には、Ａｌ、Ａｕなどが挙げられる。ミラーコーティング材としてＡｌを用いる場合、Ａｌ単体、Ａｌの上にＭｇＦ_２を保護膜としてコーティングしたもの、Ａｌ上にＳｉＯを保護膜としてコーティングしたものなどが用いられる。本実施の形態では、ＭｇＦ_２やＳｉＯ等によって形成される保護膜によって誘電体層が実現されている。また、ミラーコーティング材としてＡｕを用いる場合は、ミラー支持基板２２に対する付着力を強化するため、ミラー支持基板２２上にＣｒを薄くアンダーコーティングした後、Ａｕをコーティングしてもよい。
【０１１８】
なお、誘電体は、ミラー部材２１を金属を用いて形成する場合に限らず、ミラーコーティング材として用いることが可能であり、誘電体をミラー個ティング材として用いた多層膜構造のミラー部材を有する波面補正ミラーにおいても同様に使用することができる。
【０１１９】
このように、ミラー支持部材２２上にコーティングされた金属層と、この金属層に積層された誘電体層とによってミラー部材２１を構成することにより、ミラー面２１ａでの反射率を高くするとともにミラー面２１ａの機械的な損傷を抑制して機械的強度を強くすることができる。これにより、例えば、ミラー面２１ａをクリーニングすることが可能になり、高い反射率を長期に亘って維持することができる。
【０１２０】
光学情報記録再生装置１は、波面補正ミラー２０における圧電素子（ピエゾ素子）に印加する電圧を、波面補正ミラー２０で反射する光束における収差パターンおよび収差量に応じて調整する波面補正ミラー制御回路を備えている。
【０１２１】
このような光学情報記録再生装置１における情報の記録や再生に際しては、波面補正ミラー制御回路によって、波面補正ミラー２０の各分割部の圧電素子（ピエゾ素子）に印加する電圧を可変制御する。これにより、球面収差あるいはチルトによる波面収差を発生させる光束に対して、この波面収差を相殺するような位相分布を与えることができる。ここに、位相差補正手段としての機能が実現される。
【０１２２】
このような電圧印加により、波面補正ミラー２０におけるミラー面２１が、印加された電圧に応じて変形し、ミラー面によって反射される光束の進行方向に直交する断面内における屈折率分布を調整することができる。
【０１２３】
これによって、球面収差やチルトによる収差に起因して発生した波面収差を小さくして、多層構造の光学情報記録媒体であっても、再生対象となる記録層とレーザ光束が通過する多層構造の光学情報記録媒体２の記録層６の厚みの違いによって生じる波面収差を補正することができる。
【０１２４】
上述したように、光学情報記録媒体２の記録層６の厚さによって生じた球面収差を補正することにより、多層構造を有する光学情報記録媒体２におけるいずれの記録層６に対しても光学的位相差を生じさせることなく、各記録層６に集光される光スポット径を回析限界まで絞ることができ、多層構造を有する光学情報記録媒体２の各記録層６に対して効率よく情報を記録するとともに、記録された情報を安定して再生することができる。
【０１２５】
次に、本発明の第４の実施の形態について説明する。
【０１２６】
特に図示しないが、本実施の形態の光学情報記録再生装置１では、図８に示す波面補正ミラー２０におけるミラー部材２１とミラー支持基板２２との間に、圧電素子に代えて、照射光学系１５における波面収差に応じて（球面収差、チルト等）分割された複数の電極が設けられている。各電極は、ミラー部材２１に対して一定距離離間した状態で対向するようにミラー支持基板２２に設けられている。ここに、ミラー部材２１に対向する電極によって変形手段が実現されている。
【０１２７】
また、光学情報記録再生装置１は、波面補正ミラー２０における各電極に印加する電圧を、波面補正ミラー２０で反射する光束における収差パターンおよび収差量に応じて調整する波面補正ミラー制御回路を備えている。
【０１２８】
このような光学情報記録再生装置１における情報の記録や再生に際しては、波面補正ミラー制御回路によって、波面補正ミラー２０の各分割部の電極に印加する電圧を可変制御する。これにより、ミラー部材２１と電極との間における静電引力を電極毎に可変して、球面収差あるいはチルトによる波面収差を発生させる光束に対して、この波面収差を相殺するような位相分布を与えることができる。ここに、位相差補正手段としての機能が実現される。
【０１２９】
このような電圧印加により、波面補正ミラー２０におけるミラー面２１が、印加された電圧に応じて変形し、ミラー面によって反射される光束の進行方向に直交する断面内における屈折率分布を調整することができる。
【０１３０】
これによって、記録層６のチルトによる波面収差を小さくし、多層構造の光学情報記録媒体２であっても、チルトの発生に起因する波面収差を補正し、多層構造を有する光学情報記録媒体２におけるいずれの記録層６に対しても光学的位相差を生じさせることなく、各記録層６に集光される光スポット径を回析限界まで絞ることができ、多層構造を有する光学情報記録媒体２の各記録層６に対して効率よく情報を記録するとともに、記録された情報を安定して再生することができる。
【０１３１】
なお、対向電極の電極パターンは上述した実施の形態と同様であるため説明を省略する。
【０１３２】
次に、本発明の第５の実施の形態について説明する。
【０１３３】
特に図示しないが、本実施の形態の光学情報記録再生装置１が備える制御部には、光学情報記録媒体２の各記録層６に設けられて、各記録層６を識別するアドレス情報を記憶するアドレス情報記憶部を有している。
【０１３４】
アドレス情報記憶部に記憶されるアドレス情報は、多層構造の光学情報記録媒体２において何番目の記録層６であるかを識別可能な情報を含んでいる。
【０１３５】
また、制御部には、アドレス情報記憶部に記憶される記録層のアドレス情報に応じて、該アドレス情報によって特定される記録層に関する位相差情報が設定される図示しない位相差情報設定部が設けられている。
【０１３６】
なお、各記録層６を区別するアドレス情報は、例えば、各記録層６の内周部側等、各記録層６の一部に事前に作成されている。
【０１３７】
位相差情報設定部に設定される位相差情報は、例えば、再生光が再生対象となる記録層に到達するまでに別の記録層を通過することによって生じる位相差を補正するために、位相差補正素子１７における電極に印加する電圧に関する情報であってもよいし、波面補正ミラー２０において圧電素子（ピエゾ素子）やミラー部材を変形させる電極に印加する電圧に関する情報であってもよい。
【０１３８】
これにより、光学情報記録媒体２に記録された情報の再生に際しては、再生対象となる記録層６のアドレス情報に応じて取得される位相差情報に基づいて、該記録層６によって発生する位相差の補正を簡易化し、位相差補正を光束化することができる。
【０１３９】
【発明の効果】
請求項１記載の発明の光学情報記録再生装置によれば、光を出射する光源と、光を受光する受光素子と、前記光源から出射された光を、光学的に情報を記録する記録層が複数積層された多層構造を有する光学情報記録媒体における任意の一の前記記録層に集光状態で照射させる照射光学系と、前記光学情報記録媒体を経由した光を前記受光素子に受光させる受光光学系と、前記受光素子に受光させた光の波面収差に基づきこの波面収差を低減させるように前記照射光学系における光束の光学的位相差を補正する位相差補正手段と、を具備して、位相差補正手段によって、受光素子に受光させた光の波面収差に基づきこの波面収差を低減させるように、照射光学系における光束の光学的位相差を補正することにより、多層構造を有する光学情報記録媒体におけるいずれの記録層に対しても位相差を生じさせることなく、記録層に集光される光スポット径を回析限界まで絞ることができ、多層構造を有する光学情報記録媒体の各記録層に対して効率よく情報を記録するとともに、記録された情報を安定して再生することができる。
【０１４０】
請求項２記載の発明によれば、請求項１記載の光学情報記録再生装置において、前記位相差補正手段は、前記照射光学系の光路中に設けられて光路方向に対向した状態で液晶を狭持する一対の透明基板と、この透明基板に設けられて複数に分割された透明な電極とを有する液晶パネルを具備し、前記照射光学系における光束の光学的位相差に応じて前記電極に印加する電圧を前記電極毎に調整することにより前記照射光学系における光束の光学的位相差を補正することにより、液晶パネルを用いることにより光利用効率を向上させることができ、各記録面に対して、良好な記録マークを形成し、高いＳ／Ｎ比で再生することができる。
【０１４１】
請求項３記載の発明によれば、請求項１記載の光学情報記録再生装置において、前記位相差補正手段は、前記照射光学系の光路中に設けられて前記照射光学系における光束を反射するミラー面を有するミラー部材と、前記ミラー面を任意形状に変形させる変形手段と、を具備し、前記照射光学系における光束の光学的位相差に応じて前記変形手段によって前記ミラー面を変形させることにより前記照射光学系における光束の光学的位相差を補正することによって、照射光学系における光束をミラー面で反射する際に該光束の光学的位相差を補正することができるので、光学的位相差をより高速に補正することができ、光学情報記録媒体に対する情報の記録や再生を高速化することができる。
【０１４２】
請求項４記載の発明によれば、請求項３記載の光学情報記録再生装置において、前記位相差補正手段は、前記ミラー部材を前記ミラー面とは反対側から支持するミラー支持部材と、このミラー支持部材と前記ミラー部材との間に設けられた複数の圧電素子とを前記変形手段として具備し、前記照射光学系における光束の光学的位相差に応じて前記圧電素子の電極に印加する電圧を前記圧電素子毎に調整することにより前記照射光学系における光束の光学的位相差を補正するので、実用上、圧電素子の電極に印加する電圧を圧電素子毎に調整することで請求項３記載の発明の効果を得ることができる。
【０１４３】
請求項５記載の発明によれば、請求項３記載の光学情報記録再生装置において、前記位相差補正手段は、前記ミラー面とは反対側から前記ミラー部材に対して対向して複数に分割された電極を前記変形手段として具備し、前記照射光学系における光束の光学的位相差に応じて前記電極に印加する電圧を前記電極毎に調整することにより前記照射光学系における光束の光学的位相差を補正するので、実用上、電極に印加する電圧を電極毎に調整して、ミラー面と電極との間における静電引力を電極毎に調整することで請求項３記載の発明の効果を得ることができる。
【０１４４】
請求項６記載の発明によれば、請求項４または５記載の光学情報記録再生装置において、前記ミラー支持部材は、シリコン基板によって構成されているため、ミラー支持部材表面の平面度を良好に維持した状態で、ミラー支持部材の厚さを薄くすることができ、光学情報記録再生装置の小型化を図ることができる。また、ミラー支持部材をシリコン基板によって構成することにより、表面の平面度が良好に維持されたミラー支持部材を大量生産することができるので、光学情報記録再生装置の低コスト化を図ることができる。
【０１４５】
請求項７記載の発明によれば、請求項６記載の光学情報記録再生装置において、前記ミラー部材は、前記ミラー支持部材上にコーティングされた金属層と、この金属層に積層された誘電体層とによって構成されるため、ミラー面での反射率を高くするとともにミラー面の機械的な損傷を抑制して機械的強度を強くすることができ、例えば、ミラー面をクリーニングすることが可能になり、高い反射率を維持することができる。また、高出力な光源を用いることができる。
【０１４６】
請求項８記載の発明によれば、請求項２ないし７のいずれか一に記載の光学情報記録再生装置において、前記電極は、前記照射光学系の光軸を中心として半径方向に沿って分割されている複数の環状パターンを有するため、複数の記録層を通過することによって生じる球面収差に起因する波面収差を電極の形状によって補正することができる。
【０１４７】
請求項９記載の発明によれば、請求項２ないし７のいずれか一に記載の光学情報記録再生装置において、前記電極は、前記照射光学系の光軸方向に直交する方向に対してチルトする方向に沿って複数に分割されているため、例えば、光学情報記録媒体の設置状態等により対象とする記録層が、照射光学系の光軸方向に直交する方向に対してチルトしていることによって生じる収差に起因する波面収差を電極の形状によって補正することができる。
【０１４８】
請求項１０記載の発明によれば、請求項１ないし９のいずれか一に記載の光学情報記録再生装置において、２光子吸収により重合するフォトポリマーによって形成された前記記録層を有する前記光学情報記録媒体を再生対象とし、前記照射光学系は、前記光学情報記録媒体で記録対象となる任意の一の前記記録層で２光子吸収による光重合反応を生じさせるように前記記録用光源から出射された光の焦点を該記録層に合わせて集光させることにより、２光子吸収による光重合反応により情報が記録されるので、回析限界以下のサイズの微細な記録マークを形成し、情報を高密度、高効率に記録することができ、また、記録された情報を安定して再生することができる。
【０１４９】
請求項１１記載の発明によれば、請求項１ないし９のいずれか一に記載の光学情報記録再生装置において、有機フォトクロミック材料によって形成された前記記録層を有する前記光学情報記録媒体を再生対象とし、前記照射光学系は、前記光学情報記録媒体で記録対象となる任意の一の前記記録層における有機フォトクロミック材料をフォトクロミズムさせるように前記記録用光源から出射された光の焦点を該記録層に合わせて集光させることにより、有機フォトクロミック材料のフォトクロミズムにより情報が記録されるので、微細な記録マークを形成し、情報を高密度、高効率に記録することができ、また、記録された情報を安定して再生することができる。
【０１５０】
請求項１２記載の発明によれば、請求項１ないし１１のいずれか一に記載の光学情報記録再生装置において、各記録層に該記録層を識別するアドレス情報が記録された前記光学情報記録媒体を再生対象とし、前記位相差補正手段は、前記光学情報記録媒体から取得した前記アドレス情報に基づいて前記照射光学系における光束の光学的位相差を補正することにより、例えば、各記録層に対する記録や再生時に生じる光学的位相差の補正に関する情報をアドレス情報に応じて予め設定しておくことで、光学的位相差の補正を容易化し、各記録層にして、情報を高密度、高効率に記録することができ、また、記録された情報を安定して再生することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態の光学情報記録再生装置を示す概略図である。
【図２】光学情報記録媒体の構造を示す断面図である。
【図３】位相差補正素子を用いた光学的位相差の補正について説明する説明図である。
【図４】球面収差が発生した場合の波面収差の一例を示す説明図である。
【図５】球面収差を発生させる光束に対して与える位相分布を示す説明図である。
【図６】チルトが発生している状態の波面収差の一例を示す説明図である。
【図７】チルトによる収差を発生させる光束に対して与える位相分布を示す説明図である。
【図８】本発明の第３の実施の形態の光学情報記録再生装置を示す概略図である。
【符号の説明】
１ 光学情報記録再生装置
３，４ 光源
１５ 照射光学系
１６ 受光光学系
２０ 収差補正ミラー
２１ ミラー部材
２１ａ ミラー面
２２ ミラー支持部材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical information recording / reproducing device.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the development of technology related to multimedia that records (stores) various types of information such as audio and video moving image files, text files, and the like, a large amount of information can be optically recorded. An optical information recording medium (optical disk) and an optical information recording / reproducing apparatus capable of rapidly recording and reproducing a large amount of information have become essential.
[0003]
The optical information recording / reproducing apparatus and the optical information recording medium relating to such large-capacity information processing are expected to be further spread in the future. In particular, when bi-directional image communication such as high-definition (High-Definition) moving images and VOD (Video-On-Demand) is realized, the recording capacity required for the optical information recording medium further increases. Will be.
[0004]
However, in conventional optical information recording media and optical information recording / reproducing devices that use light for recording or reproducing information, as long as light is used for recording or reproducing information, the recording density per unit area is equal to the diffraction of the wavelength used. It is limited by the spot diameter determined by the limit. Therefore, in order to record a larger capacity using a conventional optical information recording medium and an optical information recording / reproducing apparatus that use light for writing and reading data, the area of the optical information recording medium must be increased. Must.
[0005]
By the way, an optical information recording medium having a three-dimensional structure capable of recording data not only in a two-dimensional plane but also in a depth direction (optical axis direction) (for example, see Patent Document 1), and information on the optical information recording medium By realizing an optical information recording / reproducing apparatus that enables recording and reproduction in three-dimensional directions, it is possible to realize a larger recording capacity.
[0006]
Such a method of recording and reproducing information in a three-dimensional direction can be realized by utilizing the fact that two-photon absorption occurs in proportion to the square of light intensity (for example, Non-Patent Document 1). reference).
[0007]
That is, since two-photon absorption occurs in proportion to the square of the light intensity, for example, when recording information on an optical information recording medium having a recording layer formed of a photopolymer, a laser beam is applied to the optical information recording medium. The light is condensed to cause two-photon absorption only in the vicinity of the focal point where the laser light intensity is large, and changes the bonding state of the photopolymer in the portion where the two-photon absorption occurs. Since the refractive index of the photopolymer whose bonding state has changed changes, the refractive index only near the laser focus can be changed by using two-photon absorption. When recording information on an optical information recording medium having a multilayer structure in which a plurality of recording layers are stacked, it is possible to record information in a three-dimensional direction by scanning the focal position of a laser beam three-dimensionally one point at a time. it can. Thereby, a large-capacity optical information recording medium and an optical information recording / reproducing apparatus can be realized. Conventionally, there is a technology that enables a sharp image recording by forming a cured portion by causing a photopolymerization reaction by a two-photon absorption phenomenon in a laser beam irradiation portion of a photosensitive plate-making material (for example, Patent Document 2). As a method for reproducing data recorded three-dimensionally in an optical information recording medium, a method using a confocal optical system has been proposed.
[0008]
By the way, when performing recording or reproduction on an optical information recording medium having a multilayer structure, a phase difference occurs due to the thickness of the recording layer and the protective layer between the recording layers, and the originally desired condensed spot cannot be formed, There is a problem that a good recording / reproducing operation cannot be performed.
[0009]
Further, in the optical information recording / reproducing apparatus as described above, since the laser beam is designed so as to focus on the transparent substrate having a predetermined thickness so as not to cause aberration, spherical aberration is caused by a thickness error of the transparent substrate. There is a problem that occurs. Spherical aberration due to a thickness error of the transparent substrate is more likely to occur when an objective lens having a large numerical aperture is used than when an objective lens having a small numerical aperture is used, and an objective lens having a large numerical aperture is used. In this case, even a small thickness error causes a large spherical aberration.
[0010]
In particular, when reproducing an optical information recording medium having a multilayer structure, there is a problem that a spherical aberration occurs due to a difference in the thickness of the light transmitting substrate depending on a recording layer to be reproduced, and it becomes difficult to reproduce a good signal.
[0011]
Further, in the technique described in Patent Literature 1, at the time of recording, a laser light passes through another recording layer between a laser light source that emits recording light and a recording layer to be recorded, thereby making the recording target. The data is also recorded on another recording layer different from the recording layer, or cross writing occurs.
[0012]
On the other hand, in the technique described in Patent Document 2, cross-light can be prevented because the two-photon absorption phenomenon is used.
[0013]
However, in any of the techniques described in Patent Literature 1 and Patent Literature 2, when trying to focus on a recording layer to be recorded on an optical information recording medium having a multilayer structure, an upper recording layer and a lower recording layer are required. Since the number of recording layers that pass through differs, an optical path difference occurs. As a result, aberrations occur on the focal plane, making it difficult to narrow the laser spot to the diffraction limit, and failing to improve the recording density in the plane direction.
[0014]
As a countermeasure, a liquid crystal element having a plurality of concentrically divided electrodes is used to adjust the voltage applied to the electrodes to change the refractive index of a light beam passing through the liquid crystal element, thereby forming a multilayer structure. There is a technique for correcting spherical aberration with respect to an optical information recording medium having the same (for example, see Patent Document 3).
[0015]
Further, there is a technique in which aberration correction is performed using a reflection mirror having a divided pupil plane (see Patent Document 4). According to this technique, it is possible to correct a spherical aberration of an optical disk having a multilayer structure and a wavefront aberration due to tilt.
[0016]
[Patent Document 1]
JP-A-11-195243
[Patent Document 2]
JP 2001-166467 A
[Patent Document 3]
JP-A-10-269611
[Patent Document 4]
JP-A-13-209961
[Non-patent document 1]
D. A. Parthenopoulos and P.S. M. Rentzepis: Science Vol. 245, 843-844, 1989; Hunter, F.S. Kiamilev, S.M. Esener, D.A. A. Parthenopoulos, andP. M. Rentzepis: Appl. Opt. Vol. 29, 2058-2066, 1990; H. Srickler and W.C. W. Webb: Opt. Lett. Vol. 16, 1780-1782, 1991
[0017]
[Problems to be solved by the invention]
However, in the techniques described in Patent Document 3 and Patent Document 4 described above, good characteristics can be obtained by correcting optical aberrations generated when recording or reproducing information on an optical information recording medium having a multilayer structure. However, depending on the optical system used for recording, it is not possible to form a recording mark having a size equal to or less than the diffraction limit, and it is not possible to sufficiently improve the recording density.
[0018]
Further, in the techniques described in Patent Document 3 and Patent Document 4 described above, the recordable area in the depth of focus direction cannot be limited, and a recording mark is formed by two-photon absorption. Since recording is performed with a threshold value lower than the threshold value, cross-writing occurs between recording layers during recording.
[0019]
An object of the present invention is to efficiently record information on each recording layer of an optical information recording medium having a multilayer structure and to stably reproduce the recorded information.
[0020]
[Means for Solving the Problems]
The optical information recording / reproducing apparatus according to the first aspect of the present invention includes a light source for emitting light, a light receiving element for receiving light, and a plurality of recording layers for optically recording information on the light emitted from the light source. An irradiation optical system for irradiating any one of the recording layers of the optical information recording medium having a multilayered structure in a condensed state, and a light receiving optical system for receiving the light passing through the optical information recording medium to the light receiving element. A phase difference corrector that corrects an optical phase difference of a light beam in the irradiation optical system so as to reduce the wavefront aberration based on the wavefront aberration of the light received by the light receiving element.
[0021]
Therefore, the phase difference correcting means corrects the optical phase difference of the light beam in the irradiation optical system so as to reduce the wavefront aberration based on the wavefront aberration of the light received by the light receiving element.
[0022]
According to a second aspect of the present invention, in the optical information recording / reproducing apparatus according to the first aspect, the phase difference correction means is provided in an optical path of the irradiation optical system and holds the liquid crystal in a state of facing the optical path direction. A liquid crystal panel having a pair of transparent substrates and a plurality of divided transparent electrodes provided on the transparent substrate, and a voltage applied to the electrodes according to an optical phase difference of a light beam in the irradiation optical system. Is adjusted for each of the electrodes to correct the optical phase difference of the light beam in the irradiation optical system.
[0023]
Therefore, light use efficiency can be improved by using a liquid crystal panel.
[0024]
According to a third aspect of the present invention, in the optical information recording / reproducing apparatus according to the first aspect, the phase difference correcting means includes a mirror surface provided in an optical path of the irradiation optical system and reflecting a light beam in the irradiation optical system. And a deforming means for deforming the mirror surface into an arbitrary shape, wherein the irradiation is performed by deforming the mirror surface by the deforming means according to an optical phase difference of a light beam in the irradiation optical system. The optical phase difference of the light beam in the optical system is corrected.
[0025]
Therefore, when the light beam in the irradiation optical system is reflected by the mirror surface, the optical phase difference of the light beam can be corrected.
[0026]
According to a fourth aspect of the present invention, in the optical information recording / reproducing apparatus according to the third aspect, the phase difference correction means includes a mirror supporting member that supports the mirror member from a side opposite to the mirror surface, and a mirror supporting member. And a plurality of piezoelectric elements provided between the mirror member and the mirror member, as the deforming means, and applying a voltage applied to an electrode of the piezoelectric element in accordance with an optical phase difference of a light beam in the irradiation optical system to the piezoelectric element. The adjustment of each element corrects the optical phase difference of the light beam in the irradiation optical system.
[0027]
Therefore, in practice, the effect of the invention described in claim 3 can be obtained by adjusting the voltage applied to the electrodes of the piezoelectric element for each piezoelectric element.
[0028]
According to a fifth aspect of the present invention, in the optical information recording / reproducing apparatus according to the third aspect, the phase difference correction means is divided into a plurality of electrodes facing the mirror member from a side opposite to the mirror surface. Is provided as the deforming means, and the voltage applied to the electrodes is adjusted for each electrode in accordance with the optical phase difference of the light beam in the irradiation optical system, thereby correcting the optical phase difference of the light beam in the irradiation optical system. I do.
[0029]
Therefore, in practice, the effect of the invention described in claim 3 can be obtained by adjusting the voltage applied to the electrode for each electrode and adjusting the electrostatic attraction between the mirror surface and the electrode for each electrode. .
[0030]
According to a sixth aspect of the present invention, in the optical information recording / reproducing apparatus according to the fourth or fifth aspect, the mirror support member is formed of a silicon substrate.
[0031]
Therefore, the thickness of the mirror support member can be reduced while maintaining the flatness of the surface of the mirror support member satisfactorily. In addition, it is possible to mass-produce a mirror supporting member whose surface flatness is well maintained.
[0032]
According to a seventh aspect of the present invention, in the optical information recording / reproducing apparatus according to the sixth aspect, the mirror member includes a metal layer coated on the mirror support member and a dielectric layer laminated on the metal layer. Be composed.
[0033]
Therefore, it is possible to increase the reflectivity on the mirror surface and suppress mechanical damage to the mirror surface to increase the mechanical strength.
[0034]
According to an eighth aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the second to seventh aspects, the electrode is divided along a radial direction around an optical axis of the irradiation optical system. It has a plurality of annular patterns.
[0035]
Therefore, the wavefront aberration caused by the spherical aberration caused by passing through a plurality of recording layers can be corrected by the shape of the electrode.
[0036]
According to a ninth aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the second to seventh aspects, the electrode is tilted in a direction tilted with respect to a direction orthogonal to an optical axis direction of the irradiation optical system. It is divided into multiple along.
[0037]
Therefore, for example, the wavefront aberration of the electrode caused by aberration caused by tilting the target recording layer in the direction orthogonal to the optical axis direction of the irradiation optical system due to the installation state of the optical information recording medium or the like is described. It can be corrected by the shape.
[0038]
According to a tenth aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the first to ninth aspects, the optical information recording medium having the recording layer formed of a photopolymer polymerized by two-photon absorption is provided. As a reproduction target, the irradiating optical system is configured to control the light emitted from the recording light source so as to cause a photopolymerization reaction by two-photon absorption in any one of the recording layers to be recorded in the optical information recording medium. The light is focused on the recording layer.
[0039]
Therefore, since information is recorded by a photopolymerization reaction by two-photon absorption, a fine recording mark having a size equal to or less than the diffraction limit can be formed, and information can be recorded with high density and high efficiency. Information can be reproduced stably.
[0040]
According to an eleventh aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the first to ninth aspects, the optical information recording medium having the recording layer formed of an organic photochromic material is to be reproduced, and The irradiation optical system focuses light emitted from the recording light source so as to cause the organic photochromic material in any one of the recording layers to be recorded on the optical information recording medium to perform photochromism, and focuses the light on the recording layer. Light up.
[0041]
Therefore, since information is recorded by the photochromism of the organic photochromic material, fine recording marks can be formed, information can be recorded with high density and high efficiency, and the recorded information can be reproduced stably. Can be.
[0042]
According to a twelfth aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the first to eleventh aspects, the optical information recording medium in which address information for identifying the recording layer is recorded on each recording layer is reproduced. As the target, the phase difference correction means corrects the optical phase difference of the light beam in the irradiation optical system based on the address information obtained from the optical information recording medium.
[0043]
Therefore, for example, by preliminarily setting information relating to the correction of the optical phase difference occurring at the time of recording or reproduction for each recording layer according to the address information, the correction of the optical phase difference is facilitated, and The information can be recorded with high density and high efficiency, and the recorded information can be reproduced stably.
[0044]
BEST MODE FOR CARRYING OUT THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. This embodiment shows an example of application to an optical information recording / reproducing device.
[0045]
FIG. 1 is a schematic diagram showing an optical information recording / reproducing apparatus according to the present embodiment. As shown in FIG. 1, an optical information recording / reproducing apparatus 1 according to the present embodiment includes a first light source that emits recording light to be applied to the optical information recording medium 2 when information is recorded on the optical information recording medium 2. 3 is provided. In the present embodiment, a high-power femtosecond laser for recording is used as the first light source 3.
[0046]
In addition, the optical information recording / reproducing apparatus 1 includes a second light source 4 that emits reproduction light that irradiates the optical information recording medium 2 when reproducing information from the optical information recording medium 2.
[0047]
In the present embodiment, a light source is realized by the first and second light sources 3 and 4.
[0048]
In the present embodiment, as shown in FIG. 2, a support substrate 5, a plurality of recording layers 6 sequentially stacked on one surface side of the support substrate 5, and a plurality of buffer layers 7 separating the respective recording layers 6 are provided. The optical information recording medium 2 having a multi-layer structure and having the above-mentioned structure is an object to be recorded / reproduced. As the support substrate 5 in the optical information recording medium 2, polycarbonate is used. Each recording layer 6 in the optical information recording medium 2 of the present embodiment is formed of a material such as a photopolymer that changes its coupling state by two-photon absorption.
[0049]
By the way, in normal light absorption, one photon is absorbed by one electron in a substance, but there is a process of absorbing two or more photons by increasing the light intensity temporally and spatially. It has been known. The phenomenon of absorbing two or more photons is called two-photon absorption, and it is known that such two-photon absorption occurs in proportion to the square of the intensity of the excitation light.
[0050]
In the optical information recording / reproducing apparatus 1 of the present embodiment, when a laser beam is focused to the diffraction limit, two-photon absorption that occurs only in a portion where the light intensity is higher than normal absorption is actually used. It is possible to limit the area where two-photon absorption occurs to an area smaller than the converging spot and make the diameter of the actually formed recording spot equal to or smaller than the diffraction limit.
[0051]
The photopolymer used for the recording layer 6 of the optical information recording medium 2 having a multilayer structure is a polymer compound that changes from a monomer to a polymer when irradiated with light, and is usually a polymer compound. , Photopolymerizable monomers, prepolymers (ie, dimers, trimers and oligomers), or mixtures thereof, and copolymers thereof (hereinafter, these are collectively referred to as photopolymerizable compounds) And a sensitizer and a polymerization initiator. Particularly preferred photopolymerizable compounds include esters of unsaturated carboxylic acids and aliphatic polyhydric alcohol compounds, and amides of unsaturated carboxylic acids and aliphatic polyamine compounds.
[0052]
In the present embodiment, a material in which such a photopolymer layer is provided on a supporting substrate 5 formed of polycarbonate or the like is used as a photopolymer photosensitive material.
[0053]
Further, a system containing a π-conjugated compound having high sensitivity for two-photon absorption as a photoinitiator, for example, a polymer binder, a polymerizable acrylate monomer, and a D-π-D compound (D is a π-conjugated bridge (π-conjugated bridge) ) May be applied to the support substrate 5 formed of a material such as polycarbonate as the recording layer 6.
[0054]
In the present embodiment, each recording layer 6 in the optical information recording medium 2 is formed of a material whose coupling state changes by two-photon absorption, such as a photopolymer, but is not limited to this. Alternatively, the recording layer may be formed of an organic photochromic material that causes photochromism by irradiating light. For example, a thin film in which diarylethene molecules, which are organic photochromic materials, are dispersed in a polymer may be provided as a recording layer on a support substrate.
[0055]
The optical information recording / reproducing apparatus 1 includes a beam splitter 8 for mixing laser beams emitted from the light sources 3 and 4, a collimator lens 9 for converting a beam passing through the beam splitter 8 into a parallel beam, and an optical information recording medium. 2 is provided with an objective lens 10 for condensing light at a recording position of a recording layer 6 to be recorded or reproduced. The light collected by the objective lens 10 is reflected by the recording layer 6 of the optical information recording medium 2.
[0056]
The objective lens 10 is provided so as to be movable in the focusing direction and the tracking direction with respect to the optical information recording medium 2, and is driven by a focusing unit and a tracking unit (not shown) to perform the recording direction and the tracking direction during recording and reproduction, which will be described later. Move in the direction.
[0057]
The optical information recording / reproducing apparatus 1 further includes a beam splitter 11 for separating a light beam reflected by the recording layer 6 of the optical information recording medium 2 from a light beam condensed by the objective lens 10 and bending the traveling direction. And a photodetector 13 having a light receiving element to which the reflected light that has been separated in the optical path by the splitter 11 and condensed by the condenser lens 12 is incident. The reflected light incident on the photodetector 13 is detected as a reflected signal.
[0058]
Immediately before the photodetector 13, a pinhole plate 14 having a pinhole 14a is arranged. The size of the pinhole 14a of the pinhole plate 14 is preferably about one to two times the size of the Airy disk of the spot formed on the photodetector 13.
[0059]
In the present embodiment, the pinhole plate 14 having the pinhole 14a is provided immediately before the photodetector 13. However, the present invention is not limited to this. Instead of the pinhole 14a, the size of the pinhole 14a is reduced. Even if a photodetector (not shown) having a light receiving range of the same size as the above is used, the same effect as when the pinhole plate 14 having the pinhole 14a is arranged can be obtained.
[0060]
In the present embodiment, the irradiation optical system 15 is realized by the beam splitter 8, the collimator lens 9, the beam splitter 11, and the objective lens 10, and the objective lens 10, the beam splitter 11, the condenser lens 12, the photodetector 13, the pinhole The plate 14 implements a light receiving optical system 16.
[0061]
Incidentally, the optical information recording medium 2 to be recorded / reproduced by the optical information recording / reproducing apparatus 1 of the present embodiment has a multilayer structure in which a plurality of recording layers 6 are stacked. An optical phase difference occurs for each recording layer 6 to be recorded / reproduced. When such an optical phase difference occurs, the light beam focused on the recording layer 6 to be recorded / reproduced is defocused.
[0062]
For this reason, the optical information recording / reproducing apparatus 1 according to the present embodiment has a position for correcting the optical phase difference caused by the optical information recording medium 2 between the collimator lens 9 and the beam splitter 11 in the irradiation optical system 15. A phase difference correction element 17 is provided.
[0063]
The phase difference correction element 17 can be realized by a liquid crystal panel (both not shown) including a glass substrate pair in which liquid crystal molecules having refractive index anisotropy are oriented in a predetermined direction. Although illustration and explanation of the liquid crystal panel are omitted because it is a known technique, a plurality of transparent electrodes are formed on one glass substrate of the liquid crystal panel in an annular pattern having different diameters. The plurality of electrodes formed in an annular pattern are arranged on concentric circles. On the other glass substrate (not shown) of the liquid crystal panel, another transparent electrode facing the electrode of one glass substrate is formed. The alignment state of the liquid crystal molecules between the glass substrates is deviated according to the electric field generated according to the voltage applied between the electrodes formed on each glass substrate.
[0064]
The optical information recording / reproducing device 1 includes a liquid crystal panel control circuit (not shown) that variably adjusts the electrodes of the phase difference correction element 17 for each electrode pattern and applies a voltage.
[0065]
In addition, although not particularly shown, the optical information recording / reproducing apparatus 1 performs optical information recording / reproducing such as driving of a liquid crystal panel control circuit, ON / OFF of the first and second light sources 3 and 4, focusing / tracking of the objective lens 10, and the like. A control unit for driving and controlling each unit included in the device 1 is provided.
[0066]
When recording in such an optical information recording / reproducing apparatus 1, the recording layer 6 to be recorded on the optical information recording medium 2 is irradiated with the laser light emitted from the first light source 3 via the irradiation optical system 15.
[0067]
As a result, two-photon absorption occurs at the position where the laser beam having the square of the light intensity is irradiated on the recording layer 6 to be recorded, and the bonding state of the photopolymer at the position where the two-photon absorption occurs changes. The structure of the photopolymer changes.
[0068]
At this time, as described above, since the two-photon absorption occurs only in the vicinity of the focal point where the laser light intensity is large in proportion to the square of the light intensity, the bonding state of the photopolymer in the recording layers other than the recording layer to be recorded is It is possible to change only the optical characteristics (refractive index) of the recording layer to be recorded near the focal point of the laser beam without changing.
[0069]
That is, by using two-photon absorption, a minute recording mark having a size equal to or smaller than the diffraction limit can be formed.
[0070]
Further, by using two-photon absorption, the region in which the bonding state of the photopolymer forming the recording mark is changed can be limited in the depth of focus direction of the light applied to the optical information recording medium 2.
[0071]
Therefore, in the case where a recording mark is formed on a recording layer far from the light source by utilizing one-photon absorption in an optical information recording medium having a multilayer structure, a portion where a light beam passes through a recording layer which is not a recording target is used. It is possible to suppress a problem that absorption occurs and the optical characteristics (refractive index) of another recording layer that is not a recording target are changed, and it is possible to prevent cross-write between the recording layers 6 during recording.
[0072]
That is, by utilizing two-photon absorption in which the distribution of the square of the laser beam spot intensity is substantially localized within the focal spot, the recording layer to be recorded can be recorded without recording other than the recording layer 6 to be recorded. No. 6 can be recorded.
[0073]
When reproducing information recorded on such an optical information recording medium, a laser beam from the second light source 4 is applied to the optical information recording medium 2 to reflect light from the recording layer 6 of the optical information recording medium 2. Is detected by the photodetector 13 via the light receiving optical system 16.
[0074]
The photodetector 13 outputs a reflection signal corresponding to the intensity of the received reflected light to a control unit (not shown). The control unit generates a reproduction signal according to the reflection signal.
[0075]
Here, in the optical information recording / reproducing apparatus 1 of the present embodiment, since the pinhole plate 14 having the pinhole 14a is provided immediately before the photodetector 13, only the light from the focal plane of the objective lens 10 is emitted. Light that reaches the photodetector 13 and is reflected from the optical information recording medium 2 other than the focal plane is blurred on the photodetector 13 and is not detected.
[0076]
When recording or reproducing information recorded on the optical information recording medium 2, the information is reproduced by converging a laser beam onto the recording layer 6 to be recorded or reproduced by the irradiation optical system 15. When reproducing the recording layer 6 located on the side farther away from the lens 10, the condensed laser beam passes through the recording layer 6 other than the recording layer 6 to be recorded or reproduced and the buffer layer 7. .
[0077]
For this reason, in a conventional optical information recording / reproducing apparatus using one-photon absorption, an optical phase difference generated when a laser beam passes through a recording layer 6 other than the recording layer 6 to be recorded or reproduced is affected by an optical phase difference, Spherical aberration occurs. The spherical aberration causes a wavefront aberration, and the focused spot of the laser beam on the recording layer 6 to be recorded or reproduced cannot be narrowed down to the diffraction limit. Recording marks could not be formed, and it was difficult to reproduce each recording mark.
[0078]
On the other hand, in the optical information recording / reproducing apparatus 1 of the present invention, this problem can be improved by correcting the optical phase difference by the phase difference correcting element 17.
[0079]
Hereinafter, the correction of the optical phase difference using the phase difference correction element 17 will be described with reference to FIG. In FIG. 3, when the ξ-η plane is the exit pupil of the objective lens 10 and the xy plane is the image plane (the recording layer 6 to be recorded or reproduced on the optical recording medium 1), the laser beam incident on the objective lens 10 The pupil function H (ξ, η) of the light flux is represented by the following equation (1).
[0080]

[0081]
Here, S (ξ, η) is a function representing the shape in the pupil, and W (ξ, η) is a function representing the wavefront aberration. Further, k is a wave number, and assuming that the wavelength of the laser beam is λ, k = 2π / λ.
[0082]
The amplitude distribution function h (x, y) on the image plane is expressed by the following equation (2) as the Fourier transform of the above-described pupil function H (ξ, η).
[0083]
h (x, y) = | h (x, y) | exp (iφ (x, y)) (2)
[0084]
On the other hand, the beam spot on the image plane is represented by the following equation (3) using a point spread function.
[0085]
p (x, y) = | h (x, y) | ² … (3)
[0086]
By the way, if the thickness from the light source to the recording layer 6 of the optical information recording medium 2 is different or if the optical recording medium (recording surface) is tilted, the reproduction light detected by the photodetector has a wavefront. Aberration occurs and the image deteriorates. Here, assuming that the generated wavefront aberration is WT (ξ, η), the pupil function HT (ξ, η) of the condenser lens 12 that forms a spot on the photodetector 13 is expressed by the following equation (4). Is represented.
[0087]
HT (ξ, η) = S (ξ, η) exp (ikWT (ξ, η)) (4)
[0088]
Note that the amplitude distribution functions of the entire optical systems 15 and 16 are the pupil function H (ξ, η) of the laser beam incident on the objective lens 10 and the pupil function of the condenser lens 12 that forms a spot on the photodetector 13. It is expressed by convolution with HT (ξ, η).
[0089]
Next, assuming that the optical phase difference generated on the front surface of the phase difference correction element 17 is WM (η, η) and the optical path difference given by the phase difference correction element 17 is WM (ξ, η), the phase difference correction element 17 The pupil function HM (ξ, η) of the condenser lens 12 that forms a spot on the photodetector 13 after the correction of the optical phase difference is represented by the following equation (5).
[0090]

[0091]
According to equation (5), it can be seen that by setting WT (ξ, η) −WM (ξ, η) to 0, it is possible to cancel the wavefront aberration generated in the optical information recording medium 2.
[0092]
In the present embodiment, the phase difference correction element 17 corrects the phase difference so that WT (ξ, η) −WM (ξ, η) becomes 0 or minimum according to the change in the thickness of the optical information recording medium 2. The phase difference is corrected by adjusting the high-speed optical path difference passing through the element 17.
[0093]
Specifically, a Zernike polynomial is well known as a function representing the wavefront aberration. This polynomial corresponds well to optical aberrations such as Seidel aberration, and according to the Zernike polynomial, the coefficient Wc corresponding to the above-mentioned spherical aberration of the optical recording medium is represented by the following equation (6).
[0094]
Wc = 1-6 (x ² + Y ² ) +6 (x ² + Y ² ) ² … (6)
[0095]
Here, FIG. 4 shows an example of wavefront aberration when spherical aberration occurs. The horizontal axis in FIG. 4 is a value obtained by standardizing the pupil plane coordinates with the pupil plane radius being 1. The vertical axis in FIG. 4 represents the wavefront aberration, which is a value normalized by the incident wavelength.
[0096]
According to the optical information recording / reproducing apparatus 1 of the present embodiment, when a spherical aberration as shown in FIG. 4 is generated, the glass substrate of the phase difference correction element 17 is controlled by a liquid crystal panel control circuit (not shown). By variably controlling the voltage applied to the electrodes formed in each of the electrodes, the transmission state of the luminous flux in the liquid crystal panel is adjusted. In the present embodiment, the voltage applied to the electrodes is adjusted for each electrode so that a phase distribution as shown in FIG. 5 is given to a light beam that causes spherical aberration as shown in FIG. Here, a function as a phase difference correction unit is realized.
[0097]
By applying a voltage for each voltage in this manner, the orientation of the liquid crystal molecules between the glass substrates can be deviated according to the electric field generated according to the applied voltage. The refractive index distribution in a cross section orthogonal to the traveling direction of the light beam passing through can be adjusted.
[0098]
As a result, the wavefront aberration generated by the spherical aberration can be reduced, and even if the optical information recording medium 2 has a multilayer structure, the difference in the thickness of the recording layer 6 to be recorded or reproduced at each location, the recording Wavefront aberration caused by the number of recording layers 6 through which a laser beam passes before reaching the recording layer 6 to be read or reproduced can be corrected.
[0099]
As described above, by correcting the spherical aberration caused by the thickness of the recording layer 6 of the optical information recording medium 2, the optical position of any recording layer 6 in the optical information recording medium 2 having a multilayer structure is corrected. The diameter of the light spot focused on each recording layer 6 can be reduced to the diffraction limit without causing a phase difference, and information can be efficiently transmitted to each recording layer 6 of the optical information recording medium 2 having a multilayer structure. In addition to recording, the recorded information can be reproduced stably.
[0100]
In the optical information recording / reproducing apparatus 1 according to the present embodiment, the objective lens 10 is moved in the focusing direction and the optical information recording medium is three-dimensionally scanned, so that each recording on the optical information recording medium 2 having a multilayer structure is performed. Information is recorded by forming recording marks three-dimensionally on the layer 6 one by one. Thereby, large-capacity optical information recording / reproduction can be realized.
[0101]
Here, “forming three-dimensionally one point at a time” means that recording marks are arranged concentrically or spirally with respect to a target recording layer among the recording layers of an optical information recording medium having a multilayer structure. Means to form.
[0102]
Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The same applies hereinafter. In the present embodiment, for example, when the optical information recording medium 2 is arranged in an inclined state, or when the thickness of the recording layer 6 varies from place to place, the plane perpendicular to the optical axis of the light beam in the irradiation optical system 15 is used. To correct the wavefront aberration generated when the recording layer is tilted.
[0103]
FIG. 6 shows an example of a wavefront aberration (coma aberration) in a state where a tilt has occurred. In the present embodiment, as in the first embodiment, by providing a phase distribution in the optical path that cancels the tilt, the aberration component generated by the tilt of the recording layer 6 of the optical information recording medium 2 can be reduced. Can be smaller.
[0104]
Here, the coefficient Wc corresponding to the tilt is expressed by the following equation (7).
[0105]
Wc = -2x + 3x ³ + 3xy ² … (7)
[0106]
Although illustration and description of the liquid crystal panel are omitted because it is a known technique, one glass substrate of the liquid crystal panel of the optical information recording / reproducing apparatus 1 of the present embodiment is orthogonal to the optical axis direction of the irradiation optical system 15. A transparent electrode divided into a plurality of parts along a direction tilting with respect to the direction is formed. On the other glass substrate (not shown) of the liquid crystal panel, another transparent electrode facing the electrode of one glass substrate is formed. The alignment state of the liquid crystal molecules between the glass substrates is deviated according to the electric field generated according to the voltage applied between the electrodes formed on each glass substrate.
[0107]
In such an optical information recording / reproducing apparatus 1, as shown in FIG. 6, when an aberration due to tilt occurs, the optical information recording / reproducing apparatus 1 is formed on a glass substrate of the phase difference correction element 17 by a liquid crystal panel control circuit (not shown). By variably controlling the pattern of the voltage applied to the applied electrodes, a phase distribution as shown in FIG. 7 is given to a light beam that generates spherical aberration as shown in FIG. Here, a phase difference correction unit is realized.
[0108]
With such a voltage application, the orientation of the liquid crystal molecules between the glass substrates is deviated according to the electric field generated according to the applied voltage, and is orthogonal to the traveling direction of the light beam transmitted between the glass substrates of the phase difference correction element 17. The refractive index distribution in the cross section is adjusted so as to reduce the wavefront aberration due to the tilt of the recording layer 6.
[0109]
Thus, the wavefront aberration due to the tilt of the recording layer 6 can be reduced, and the wavefront aberration due to the tilt can be corrected even in the optical information recording medium 2 having a multilayer structure.
[0110]
As described above, by correcting the wavefront aberration caused by the tilt of the recording surface caused by the recording layer thickness of the optical information recording medium 2, a good reproduction laser beam spot is formed on the recording layer to be reproduced. Can be.
[0111]
Next, a third embodiment of the present invention will be described with reference to FIG.
[0112]
FIG. 8 is a schematic diagram showing the optical information recording / reproducing apparatus 1 of the present embodiment. The optical information recording / reproducing apparatus 1 of the present embodiment is provided with a wavefront correction mirror 20 as shown in FIG. 8, instead of the phase difference correction element 17 shown in FIG.
[0113]
The wavefront correction mirror 20 includes a thin-film mirror member 21 having a mirror surface 21a on one surface side, a mirror support substrate 22 serving as a mirror support member for supporting the mirror member 21, and a mirror member 21 and a mirror support substrate 22. And a plurality of piezoelectric elements (piezo elements) (not shown) provided therebetween. Although not shown and described because it is a known technique, each piezoelectric element is provided with an electrode for applying a voltage. Here, a deformation means is realized by the mirror support substrate 22 and the piezoelectric element.
[0114]
The mirror support substrate 22 of the wavefront correction mirror 20 can be made of, for example, a Si single crystal. The thickness of the mirror support substrate 22 is set to, for example, usually 525 μm for a 4-inch square Si single crystal substrate and 625 μm for a 6-inch square Si single crystal substrate. The flatness of a mirror-polished 4-inch square Si single crystal substrate used in a normal semiconductor process has a wavefront aberration rms of about 0.02λ when irradiated with light having a wavelength of 635 nm. This flatness is an accuracy enough to withstand practical use for using the Si single crystal substrate as the mirror support substrate 22 of the wavefront correction mirror 20.
[0115]
The mirror support substrate 22 of the wavefront correction mirror 20 may be, for example, a Si single crystal cut to a size of several millimeters with a commercially available dicing saw. Although not particularly shown, the rms of the wavefront aberration of the mirror support substrate 22 formed of such a Si single crystal is 0.02λ, so that even when the mirror support substrate 22 is formed of a Si single crystal cut by a dicing saw, It can be seen that there is little possibility that the wavefront aberration is deteriorated due to the distortion at the time of cutting.
[0116]
Although not particularly shown, actually, a 4-inch square Si single crystal substrate was lightly peeled off from the surface oxide film using about 1% of dilute hydrofluoric acid, and then Al was vacuum-deposited to about 4000 angstroms, After cutting to 7 mm × 7 mm with a dicing saw, the wavefront aberration was measured. As a result, a wavefront correction mirror 20 having a wavefront aberration rms of 0.02λ was obtained. This flatness is sufficiently accurate to be practically used for the wavefront correction mirror 20.
[0117]
As a mirror coating material for forming the mirror member 21 having the mirror surface 21a on the mirror supporting substrate 22, a metal, a dielectric, or the like is used as a typical mirror coating material. For example, when using a metal as a mirror coating material, Al, Au, etc. are mentioned. When Al is used as a mirror coating material, it is preferable to use Al alone, MgF ₂ Is used as a protective film, or Al is coated with SiO as a protective film. In the present embodiment, MgF ₂ The dielectric layer is realized by a protective film formed of, for example, SiO. When Au is used as the mirror coating material, the mirror supporting substrate 22 may be coated with Au after a thin undercoat of Cr on the mirror supporting substrate 22 in order to strengthen the adhesion to the mirror supporting substrate 22.
[0118]
Note that the dielectric is not limited to the case where the mirror member 21 is formed using metal, but can be used as a mirror coating material, and has a multi-layer structure mirror member using the dielectric as a mirror individual material. The same can be used for a wavefront correction mirror.
[0119]
As described above, by configuring the mirror member 21 with the metal layer coated on the mirror support member 22 and the dielectric layer laminated on the metal layer, the reflectance on the mirror surface 21a can be increased and the mirror can be improved. The mechanical strength of the surface 21a can be suppressed and mechanical strength can be increased. Thereby, for example, the mirror surface 21a can be cleaned, and a high reflectance can be maintained for a long time.
[0120]
The optical information recording / reproducing apparatus 1 includes a wavefront correction mirror control circuit that adjusts a voltage applied to a piezoelectric element (piezo element) in the wavefront correction mirror 20 according to an aberration pattern and an aberration amount of a light beam reflected by the wavefront correction mirror 20. Have.
[0121]
When recording or reproducing information in such an optical information recording / reproducing apparatus 1, the voltage applied to the piezoelectric element (piezo element) of each division of the wavefront correction mirror 20 is variably controlled by the wavefront correction mirror control circuit. Thereby, a phase distribution that cancels out the wavefront aberration can be given to the light beam that generates the wavefront aberration due to the spherical aberration or the tilt. Here, a function as a phase difference correction unit is realized.
[0122]
By applying such a voltage, the mirror surface 21 of the wavefront correction mirror 20 is deformed according to the applied voltage, and the refractive index distribution in a cross section orthogonal to the traveling direction of the light beam reflected by the mirror surface is adjusted. Can be.
[0123]
As a result, wavefront aberrations caused by spherical aberration and aberrations due to tilt are reduced, and even in the case of an optical information recording medium having a multilayer structure, the recording layer to be reproduced and the optical layer having a multilayer structure through which a laser beam passes. Wavefront aberration caused by a difference in thickness of the recording layer 6 of the information recording medium 2 can be corrected.
[0124]
As described above, by correcting the spherical aberration caused by the thickness of the recording layer 6 of the optical information recording medium 2, the optical position of any recording layer 6 in the optical information recording medium 2 having a multilayer structure is corrected. The diameter of the light spot focused on each recording layer 6 can be reduced to the diffraction limit without causing a phase difference, and information can be efficiently transmitted to each recording layer 6 of the optical information recording medium 2 having a multilayer structure. In addition to recording, the recorded information can be reproduced stably.
[0125]
Next, a fourth embodiment of the present invention will be described.
[0126]
Although not particularly shown, in the optical information recording / reproducing apparatus 1 of the present embodiment, the irradiation optical system 15 is provided between the mirror member 21 and the mirror support substrate 22 of the wavefront correction mirror 20 shown in FIG. There are provided a plurality of electrodes divided according to the wavefront aberration (spherical aberration, tilt, etc.). Each electrode is provided on the mirror support substrate 22 so as to face the mirror member 21 at a predetermined distance. Here, a deforming unit is realized by the electrode facing the mirror member 21.
[0127]
Further, the optical information recording / reproducing apparatus 1 includes a wavefront correction mirror control circuit that adjusts a voltage applied to each electrode of the wavefront correction mirror 20 according to an aberration pattern and an aberration amount of a light beam reflected by the wavefront correction mirror 20. I have.
[0128]
When recording or reproducing information in such an optical information recording / reproducing apparatus 1, the voltage applied to the electrodes of the respective divided portions of the wavefront correction mirror 20 is variably controlled by the wavefront correction mirror control circuit. Thereby, the electrostatic attraction between the mirror member 21 and the electrode is varied for each electrode, and a phase distribution that cancels the wavefront aberration is given to a light beam that generates a wavefront aberration due to spherical aberration or tilt. be able to. Here, a function as a phase difference correction unit is realized.
[0129]
By applying such a voltage, the mirror surface 21 of the wavefront correction mirror 20 is deformed according to the applied voltage, and the refractive index distribution in a cross section orthogonal to the traveling direction of the light beam reflected by the mirror surface is adjusted. Can be.
[0130]
Thereby, the wavefront aberration due to the tilt of the recording layer 6 is reduced, and even in the optical information recording medium 2 having a multilayer structure, the wavefront aberration due to the occurrence of the tilt is corrected, and the optical information recording medium 2 having a multilayer structure is obtained. The optical spot diameter focused on each recording layer 6 can be reduced to the diffraction limit without causing an optical phase difference to any of the recording layers 6, and the optical information recording medium 2 having a multilayer structure Information can be efficiently recorded on each recording layer 6, and the recorded information can be reproduced stably.
[0131]
Note that the electrode pattern of the counter electrode is the same as in the above-described embodiment, and a description thereof will be omitted.
[0132]
Next, a fifth embodiment of the present invention will be described.
[0133]
Although not particularly shown, a control unit provided in the optical information recording / reproducing apparatus 1 of the present embodiment is provided in each recording layer 6 of the optical information recording medium 2 and stores address information for identifying each recording layer 6. It has an address information storage unit.
[0134]
The address information stored in the address information storage unit includes information capable of identifying the order of the recording layer 6 in the optical information recording medium 2 having a multilayer structure.
[0135]
The control unit further includes a phase difference information setting unit (not shown) for setting phase difference information on the recording layer specified by the address information according to the address information of the recording layer stored in the address information storage unit. Have been.
[0136]
The address information for distinguishing each recording layer 6 is created in advance in a part of each recording layer 6, for example, on the inner peripheral side of each recording layer 6.
[0137]
The phase difference information set in the phase difference information setting unit is, for example, a phase difference for correcting a phase difference caused by the reproduction light passing through another recording layer before reaching the recording layer to be reproduced. The information may be information on a voltage applied to an electrode of the correction element 17 or information on a voltage applied to an electrode that deforms a piezoelectric element (piezo element) or a mirror member in the wavefront correction mirror 20.
[0138]
Accordingly, when information recorded on the optical information recording medium 2 is reproduced, the phase difference generated by the recording layer 6 is determined based on the phase difference information obtained according to the address information of the recording layer 6 to be reproduced. Can be simplified, and the phase difference correction can be made into a luminous flux.
[0139]
【The invention's effect】
According to the optical information recording / reproducing device of the first aspect of the present invention, a light source for emitting light, a light receiving element for receiving light, and a recording layer for optically recording information on the light emitted from the light source are provided. An irradiation optical system for irradiating any one of the recording layers in an optical information recording medium having a multilayer structure with a plurality of layers in a condensed state, and a light receiving optical for receiving the light passing through the optical information recording medium to the light receiving element And a phase difference correction means for correcting an optical phase difference of a light beam in the irradiation optical system so as to reduce the wavefront aberration based on the wavefront aberration of light received by the light receiving element. Optical information having a multilayer structure is corrected by correcting an optical phase difference of a light beam in an irradiation optical system so as to reduce the wavefront aberration based on the wavefront aberration of light received by the light receiving element by a phase difference correction unit. The optical spot diameter focused on the recording layer can be reduced to the diffraction limit without causing a phase difference to any recording layer in the recording medium, and each recording of the optical information recording medium having a multilayer structure can be performed. The information can be efficiently recorded on the layer, and the recorded information can be reproduced stably.
[0140]
According to the second aspect of the present invention, in the optical information recording / reproducing apparatus according to the first aspect, the phase difference correction means is provided in an optical path of the irradiation optical system and narrows the liquid crystal in a state of facing the optical path direction. A liquid crystal panel having a pair of transparent substrates and a plurality of divided transparent electrodes provided on the transparent substrate, and applying a voltage to the electrodes according to an optical phase difference of a light beam in the irradiation optical system. By adjusting the voltage to be applied to each of the electrodes to correct the optical phase difference of the luminous flux in the irradiation optical system, it is possible to improve the light use efficiency by using a liquid crystal panel. A good recording mark can be formed and reproduced at a high S / N ratio.
[0141]
According to a third aspect of the present invention, in the optical information recording / reproducing apparatus according to the first aspect, the phase difference correction means is provided in an optical path of the irradiation optical system and reflects a light beam in the irradiation optical system. A mirror member having a surface, and a deforming means for deforming the mirror surface into an arbitrary shape, by deforming the mirror surface by the deforming means according to an optical phase difference of a light beam in the irradiation optical system. By correcting the optical phase difference of the light beam in the irradiation optical system, it is possible to correct the optical phase difference of the light beam when the light beam in the irradiation optical system is reflected on the mirror surface. The correction can be performed at higher speed, and the speed of recording and reproducing information on the optical information recording medium can be increased.
[0142]
According to a fourth aspect of the present invention, in the optical information recording / reproducing apparatus according to the third aspect, the phase difference correction means includes: a mirror support member that supports the mirror member from a side opposite to the mirror surface; A plurality of piezoelectric elements provided between a support member and the mirror member are provided as the deforming means, and a voltage applied to an electrode of the piezoelectric element according to an optical phase difference of a light beam in the irradiation optical system is provided. 4. The voltage applied to the electrodes of the piezoelectric element is adjusted for each piezoelectric element in practical use, since the optical phase difference of the light beam in the irradiation optical system is corrected by adjusting the piezoelectric element. The effects of the invention can be obtained.
[0143]
According to the fifth aspect of the present invention, in the optical information recording / reproducing apparatus according to the third aspect, the phase difference correction unit is divided into a plurality of parts facing the mirror member from a side opposite to the mirror surface. Electrodes as the deforming means, and adjusting the voltage applied to the electrodes for each of the electrodes in accordance with the optical phase difference of the light beam in the irradiation optical system to thereby adjust the optical phase difference of the light beam in the irradiation optical system. In practice, the voltage applied to the electrodes is adjusted for each electrode, and the electrostatic attraction between the mirror surface and the electrode is adjusted for each electrode, so that the effect of the third aspect is obtained. be able to.
[0144]
According to the sixth aspect of the present invention, in the optical information recording / reproducing apparatus according to the fourth or fifth aspect, since the mirror supporting member is made of a silicon substrate, the flatness of the surface of the mirror supporting member is maintained well. In this state, the thickness of the mirror supporting member can be reduced, and the size of the optical information recording / reproducing apparatus can be reduced. In addition, since the mirror supporting member is made of a silicon substrate, it is possible to mass-produce the mirror supporting member whose surface flatness is well maintained, so that the cost of the optical information recording / reproducing apparatus can be reduced. .
[0145]
According to the seventh aspect of the present invention, in the optical information recording / reproducing apparatus according to the sixth aspect, the mirror member includes a metal layer coated on the mirror support member, and a dielectric layer laminated on the metal layer. Therefore, it is possible to increase the reflectivity on the mirror surface, suppress mechanical damage to the mirror surface, and increase the mechanical strength.For example, it is possible to clean the mirror surface. , High reflectivity can be maintained. Further, a high-output light source can be used.
[0146]
According to an eighth aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the second to seventh aspects, the electrode is divided along a radial direction around an optical axis of the irradiation optical system. Since there are a plurality of annular patterns, the wavefront aberration caused by the spherical aberration caused by passing through the plurality of recording layers can be corrected by the shape of the electrode.
[0147]
According to a ninth aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the second to seventh aspects, the electrode is tilted with respect to a direction orthogonal to an optical axis direction of the irradiation optical system. Since the recording layer is divided into a plurality along the direction, for example, the target recording layer is tilted with respect to the direction orthogonal to the optical axis direction of the irradiation optical system due to the installation state of the optical information recording medium and the like. The wavefront aberration caused by the generated aberration can be corrected by the shape of the electrode.
[0148]
According to a tenth aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the first to ninth aspects, the optical information recording device having the recording layer formed of a photopolymer polymerized by two-photon absorption. With the medium as a reproduction target, the irradiation optical system was emitted from the recording light source so as to cause a photopolymerization reaction by two-photon absorption in any one of the recording layers to be recorded in the optical information recording medium. By focusing the light on the recording layer and condensing the information, information is recorded by a photopolymerization reaction by two-photon absorption. Thus, recording can be performed with high efficiency, and the recorded information can be reproduced stably.
[0149]
According to an eleventh aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the first to ninth aspects, the optical information recording medium having the recording layer formed of an organic photochromic material is to be reproduced. The irradiating optical system focuses light emitted from the recording light source on the recording layer so as to cause the organic photochromic material in any one of the recording layers to be recorded on the optical information recording medium to perform photochromism. By collecting light, the information is recorded by the photochromism of the organic photochromic material, so that fine recording marks can be formed, and information can be recorded with high density and high efficiency. And can be played.
[0150]
According to the twelfth aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the first to eleventh aspects, the optical information recording medium in which address information for identifying the recording layer is recorded on each recording layer. And the phase difference correction means corrects the optical phase difference of the light beam in the irradiation optical system based on the address information obtained from the optical information recording medium, for example, recording on each recording layer. Information about the correction of the optical phase difference that occurs at the time of reproduction or playback is set in advance in accordance with the address information, thereby facilitating the correction of the optical phase difference, and allowing each recording layer to store information with high density and high efficiency. Recording can be performed, and recorded information can be reproduced stably.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an optical information recording / reproducing apparatus according to a first embodiment of the present invention.
FIG. 2 is a sectional view showing a structure of an optical information recording medium.
FIG. 3 is an explanatory diagram illustrating correction of an optical phase difference using a phase difference correction element.
FIG. 4 is an explanatory diagram showing an example of wavefront aberration when spherical aberration occurs.
FIG. 5 is an explanatory diagram showing a phase distribution given to a light beam that generates spherical aberration.
FIG. 6 is an explanatory diagram illustrating an example of a wavefront aberration in a state where a tilt has occurred.
FIG. 7 is an explanatory diagram showing a phase distribution given to a light beam that causes aberration due to tilt.
FIG. 8 is a schematic diagram showing an optical information recording / reproducing apparatus according to a third embodiment of the present invention.
[Explanation of symbols]
1 Optical information recording / reproducing device
3,4 light source
15 Irradiation optical system
16 Receiving optical system
20 Aberration correction mirror
21 Mirror member
21a Mirror surface
22 Mirror support member

Claims (12)

A light source for emitting light,
A light receiving element for receiving light,
An irradiation optical system for irradiating the light emitted from the light source in a condensed state to any one of the recording layers in an optical information recording medium having a multilayer structure in which a plurality of recording layers for optically recording information are stacked. ,
A light receiving optical system that causes the light receiving element to receive light that has passed through the optical information recording medium,
Phase difference correction means for correcting the optical phase difference of the light beam in the irradiation optical system so as to reduce the wavefront aberration based on the wavefront aberration of the light received by the light receiving element,
An optical information recording / reproducing device comprising: The phase difference correction unit is provided in the optical path of the irradiation optical system, a pair of transparent substrates that sandwich the liquid crystal in a state facing the optical path direction, a transparent substrate provided on the transparent substrate and divided into a plurality of And a liquid crystal panel having electrodes, and by adjusting a voltage applied to the electrodes for each of the electrodes in accordance with the optical phase difference of the light beam in the irradiation optical system, the optical phase difference of the light beam in the irradiation optical system. 2. The optical information recording / reproducing apparatus according to claim 1, wherein the optical information recording / reproducing apparatus corrects. The phase difference correction unit includes a mirror member provided in an optical path of the irradiation optical system and having a mirror surface that reflects a light beam in the irradiation optical system, and a deformation unit that deforms the mirror surface into an arbitrary shape. 2. The optical information recording according to claim 1, wherein the optical phase difference of the light beam in the irradiation optical system is corrected by deforming the mirror surface by the deforming means in accordance with the optical phase difference of the light beam in the irradiation optical system. Playback device. The phase difference correction unit includes: a mirror support member that supports the mirror member from a side opposite to the mirror surface; and a plurality of piezoelectric elements provided between the mirror support member and the mirror member. And correcting the optical phase difference of the light beam in the irradiation optical system by adjusting the voltage applied to the electrode of the piezoelectric element for each of the piezoelectric elements according to the optical phase difference of the light beam in the irradiation optical system. The optical information recording / reproducing device according to claim 3. The phase difference correction unit includes, as the deformation unit, an electrode that is divided into a plurality of portions facing the mirror member from a side opposite to the mirror surface, and adjusts an optical phase difference of a light beam in the irradiation optical system. 4. The optical information recording / reproducing apparatus according to claim 3, wherein a voltage applied to the electrodes is adjusted for each of the electrodes in accordance with the correction so as to correct an optical phase difference of a light beam in the irradiation optical system. 6. The optical information recording / reproducing device according to claim 4, wherein the mirror support member is formed of a silicon substrate. 7. The optical information recording / reproducing apparatus according to claim 6, wherein the mirror member includes a metal layer coated on the mirror support member, and a dielectric layer laminated on the metal layer. The optical information recording / reproducing apparatus according to any one of claims 2 to 7, wherein the electrode has a plurality of annular patterns divided along a radial direction around an optical axis of the irradiation optical system. The optical information recording / reproducing apparatus according to claim 2, wherein the electrode is divided into a plurality of parts along a direction tilted with respect to a direction orthogonal to an optical axis direction of the irradiation optical system. The optical information recording medium having the recording layer formed of a photopolymer that polymerizes by two-photon absorption is to be reproduced,
The irradiation optical system focuses the light emitted from the recording light source so as to cause a photopolymerization reaction by two-photon absorption in any one of the recording layers to be recorded on the optical information recording medium. The optical information recording / reproducing apparatus according to claim 1, wherein light is condensed according to a layer. The optical information recording medium having the recording layer formed of an organic photochromic material to be reproduced,
The irradiation optical system focuses light emitted from the recording light source so as to cause the organic photochromic material in any one of the recording layers to be recorded on the optical information recording medium to perform photochromism on the recording layer. The optical information recording / reproducing apparatus according to claim 1, wherein the optical information is focused. The optical information recording medium in which the address information for identifying the recording layer is recorded in each recording layer is to be reproduced,
The optical information recording device according to any one of claims 1 to 11, wherein the phase difference correction unit corrects an optical phase difference of a light beam in the irradiation optical system based on the address information obtained from the optical information recording medium. Playback device.

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