JP3758279B2 - Method and apparatus for adjusting objective lens for optical pickup - Google Patents

Description

２群レンズの調整装置１は、このように第４の面２７からの反射光の焦点を遠方に形成して、第２のレンズ２３に対する上記焦点の変位置を増幅させることで、位置検出感度を良好にし、傾きの調整精度を向上させている。
【００５３】
また、第２のレンズ２３の調整について述べたが、２群レンズの調整装置１は、第１のレンズ２２の傾きを調整してから第２のレンズ２３の傾きを調整することもできる。この場合、第１のレンズ２２に対する第２のレンズ２３の傾きの位置決め精度が向上する。
【００５４】
次に第２の実施の形態について説明する。第２の実施の形態は、光学ピックアップの備える２群レンズを調整する光学ピックアップ用対物レンズの調整方法を適用して構成した装置であって、第１のレンズに対する第２のレンズの傾きを調整する２群レンズの調整装置である。
【００５５】
詳しくは、２群レンズの調整装置１は、図４に示すようにレーザ光を第１のレンズ２２及び第２のレンズ２３を透過させ、その透過光の回折パターンの中心位置を遠方で検出することにより第１のレンズ２２に対する第２のレンズ２３の偏芯を調整する。
【００５６】
上記２群レンズは、第１の実施の形態において図２を用いて説明したように、第１のレンズ２２と、光ディスク２９に対向する面である第４の面２７を有する第２のレンズ２３とから構成されている。
【００５７】
上記２群レンズの調整装置は、図４及び図５に示すように、レーザ光を発射するレーザ光源３２と、レーザ光源３２から発射されたレーザ光を広げて出射させるビームエキスパンダ３３と、ビームエキスパンダ３３によって広げられて入射されるレーザ光を平行光にするコリメータレンズ３４と、調整の対象となる２群レンズ２１が載置されるとともに、コリメータレンズ３４からの光が入射されるレンズ載置部３５と、レンズ載置部３５に載置された２群レンズ２１を透過した光が入射されるビームスプリッタ３６と、ビームスプリッタ３６の反射面３６ａで反射された光であって、第１のレンズ２２及び第２のレンズ２３を透過する光の回折パターンを検出するＣＣＤカメラ３７と、ＣＣＤカメラ３７で受光された映像を映すモニター３８と、第１のレンズ２２の光軸に対する垂直面内において第１のレンズ２２の位置を調整する第１の位置調整用ステージ３９と、第２のレンズ２３の光軸に対する垂直面内において第２のレンズ２３の位置を調整する第２の位置調整用ステージ４０とから構成される。
【００５８】
上記２群レンズの調整装置３１において、ビームエキスパンダ３３、コリメータレンズ３４及びビームスプリッタ３６の光軸は、レーザ光源３２の出射するレーザ光の光軸と一致している。さらに、後述するレンズ載置部３に設けられたアパーチャ部４３は、中心が上記レーザ光の光軸と一致している。
【００５９】
上記レーザ光源３２は、ＳＨＧのグリーンレーザであって、波長が５３２ｎｍのレーザ光を発射する。このレーザ光源３２は、レーザ光の光軸がレンズ載置部３５のアパーチャ部４３の中心と一致して、レンズ載置部３５の基準面４１に対し直角になるように位置決めされている。なお、レーザ光源３２の位置決めは、例えばマイケルソン干渉計を用いて、十分な精度に追い込んで行っている。そして、レーザ光源３２から広がりながら発射されたレーザ光は、ビームエキスパンダ３３に入射される。
【００６０】
上記ビームエキスパンダ３３は、レーザ光をさらに広げてコリメータレンズ３４に向けて出射する。
【００６１】
上記コリメータレンズ３４は、広がりながら入射されたビームエキスパンダ４よりのレーザ光を平行光にしてレンズ載置部３５に向けて出射する。
【００６２】
上記レンズ載置部３５は、２群レンズ２１が載置される基準面４１と、２群レンズ２１が載置される部分に位置し、円形に形成された貫通孔である円形孔４２とから構成されている。そして、レンズ載置部３５の円形孔４２には、アパーチャ部４３が設けられている。
【００６３】
上記アパーチャ部４３は、円形孔４２よりやや小とされた径に形成されている。詳しくは、アパーチャ部４３の内径は、２群レンズ２１の第１の面２４の球面部の外径よりやや小とされている。このアパーチャ部４３は、上述したように、軸中心がレーザ光源３２から発せされるレーザ光の光軸と一致している。
【００６４】
よって、レンズ載置部３５は、基準面４１に載置される２群レンズ２１の第１の面２４に入射されるコリメータレンズ３４よりレーザ光をアパーチャ部４３において絞っている。これにより、このアパーチャ部４３を介して２群レンズ２１に入射される光は、回折成分を含んだ光となる。後述するように、２群レンズの調整装置３１は、この回折成分によって形成される回折パターンをもとに、第１のレンズ２２に対する第２のレンズ２３の偏芯を調整している。
【００６５】
アパーチャ部４３を介して２群レンズ２１を透過した光は、ビームスプリッタ３６に入射される。なお、２群レンズ２１を透過した光が第４の面２７から出射直後に焦点を形成するために、ビームスプリッタ３５には、焦点を形成語の広がった光が入射される。
【００６６】
上記ビームスプリッタ３６には、反射面３６ａが形成され、ビームスプリッタ３６は、２群レンズ２１を透過した光を反射面３６ａによって反射し、ＣＣＤカメラ３７に向けて出射する。
【００６７】
このＣＣＤカメラ３７は、受光面３７ａにおいてビームスプリッタ３６の反射面３６ａで反射された光を受光する。なお、ＣＣＤカメラ３７の受光面３７ａは、位置検出分解能が０．５ｍｍ程度の精度を有している。また、ＣＣＤカメラ３７は、位置決めされるために、光軸方向及びこの光軸に対し直角な２軸方向に移動可能に支持されている。
【００６８】
上記ＣＣＤカメラ３７の受光面３７ａにおいて受光された光は、モニター３８に映し出される。ＣＣＤカメラ３７の受光面３７ａに入射された光は、アパーチャ部４３を介したとで回折成分を含んでいることから、モニター３７には、光の回折パターンが映し出される。
【００６９】
なお、ＣＣＤカメラ３７は、図６に示すように、レンズ載置部３５に形成されたアパーチャ部４３よりレーザ光を透過させて予め位置決めされている。
【００７０】
先ず、レーザ光源３２よりのレーザ光がビームエキスパンダ３３，コリメータレンズ３４を介してレンズ載置部３５に形成されたアパーチャ部４３に入射される。アパーチャ部４３に入射され、ここを介して出射されたレーザ光は、回折成分を含む光となる。回折成分を含んだ光は、ビームスプリッタ３６の反射面３６ａを介して、ＣＣＤカメラ３７の受光面３７ａにおいて受光される。そして、モニター３８には、第１のレンズ２２を透過した光の回折パターンが映し出される。
【００７１】
上記ＣＣＤカメラ３７の位置決めは、この回折パターンの中心がＣＣＤカメラ３７の受光面３７ａの中心と一致するようにして行われる。
【００７２】
なお、ＣＣＤカメラ３７は、２群レンズ２１からの光軸上における距離が長くなるように、例えば光軸上における距離が１ｍとされて配設されている。また、この位置において、回折パターンのピッチは、略１ｍｍになる。
【００７３】
このようにＣＣＤカメラ３７が位置決めされた後、図５に示すように、先ず第１のレンズ２２がレンズ載置部３５の円形部５２に嵌合されて基準面４１上に載置され、レンズ載置部３５に対して位置決めされる。
【００７４】
そして、第１のレンズ２２には、レーザ光源３２よりのレーザ光が、ビームエキスパンダ３３、コリメータレンズ３４及びアパーチャ部４３を介して入射される。
【００７５】
上記第１のレンズ２２に入射された光は、アパーチャ部４３によって回折成分を含んだものとなって、ビームスプリッタ３６の反射面３６ａを介してＣＣＤカメラ３７の受光面３７ａにおいて受光される。第１のレンズ２２は、第１の位置調整用ステージ３９によって行い、ＣＣＤカメラ３７の受光面３７ａの中心に回折パターンの中心を一致させて、レンズ載置部３５において位置決めされる。
【００７６】
よって、２群レンズの調整装置３１は、レンズ載置部３５に対する第１のレンズ２２の位置決めを第１のレンズ２２を透過した光の回折パターンに基づいて行っているために、たとえ第１のレンズ２２の外形形状の精度がよくなくても、精度良く調整を行うことができる。
【００７７】
このように第１のレンズ２２がレンズ載置部３５に対して位置決めされた後、第１のレンズ２２上にスペーサを介して第２のレンズ２３が取り付けられ、上述のように、第１のレンズ２２に対する第２のレンズ２３の偏芯の調整が行われる。
【００７８】
例えば、第２のレンズ２３が第１のレンズ２２に対して偏芯している場合、２群レンズ２１の回折パターンの中心は、ＣＣＤカメラ３７の受光面３７ａ中心からずれて受光されることになる。
【００７９】
そして、第２のレンズ２３の偏芯の調整は、モニター３８を見ながら、第２の位置調整用ステージ４０によって行い、ＣＣＤカメラ３７の受光面３７ａの中心に２群レンズ２１を透過してきた光の回折パターンの中心を一致させる。
【００８０】
よって、２群レンズの調整装置３１は、第１のレンズ２２に対する第２のレンズ２３の偏芯の調整を第１のレンズ２２及び第２のレンズ２３を透過した光の回折パターンに基づいて行っているために、たとえ第１のレンズ２２及び第２のレンズ２３の外形形状の精度がよくなくても、精度良く偏芯の調整を行うことができる。したがって、第１のレンズ２２及び第２のレンズ２３を成形するために使用する金型の外形精度が出ていなくても、十分な光学特性をもった２群レンズ２１を提供することができる。
【００８１】
上記２群レンズの調整装置３１は、回折パターンの中心によって光軸中心を割り出しているために、従来の光量分布或いはビームパターンから光軸中心を割り出す手段よりも高い検出感度を得ることができる。
【００８２】
例えば、２群レンズの調整装置３１は、上述したように、２群レンズ２１とＣＣＤカメラ３７との光軸上における距離が略１ｍ（Ｌ）になるように構成されている。そして、ＣＣＤカメラ３７の受光面３７ａの位置検出分解能を０．５ｍｍ（ｄ）程度、２群レンズ２１の焦点距離を略２．５ｍｍ（ｆ）としたとき、第１のレンズ２２に対する第２のレンズ２３の偏芯量の検出感度Δｅは、（２）式で得られるように、１．２５×１０^-3μｍになる。
【００８３】

このように、２群レンズの調整装置３１は、２群レンズ２１から遠方でＣＣＤカメラ３７によって回折パターンの中心を検出することで、偏芯量の検出感度が良好になり、偏芯の調整精度を向上させている。
【００８４】
次に本発明の第３の実施の形態について説明する。第３の実施の形態は、光学ピックアップの備える２群レンズを調整する光学ピックアップ用対物レンズの調整方法を適用して構成した装置であって、第１のレンズと第２のレンズとの距離を調整する２群レンズの調整装置である。
【００８５】
詳しくは、２群レンズの調整装置は、図７に示すように、第１のレンズ２２を介して第２のレンズ２３の第１のレンズ２２に対向する第３の面２６に入射された光の反射光が再び第１のレンズ２２を介して得られる光のビーム径を検出して第１のレンズと第２のレンズとの間隔を調整する。
【００８６】
上記２群レンズ２１は、第１の実施の形態において図２を用いて説明したように、半導体レーザからのレーザ光が入射される第１の面２４と第１の面２４から入射されたレーザ光を第２のレンズ２３に向けて出射する第２の面２５とからなる第１のレンズ２２と、第１のレンズ２２を透過してきた半導体レーザよりのレーザ光が入射される第３の面２６と光ディスク２９に対向する面となる第４の面２７とからなる第２のレンズ２３とから構成されている。
また、２群レンズ２１は、スペーサを介して第１のレンズ２２と第２のレンズ２３とが対向されている。例えば、第１のレンズ２２と第２のレンズ２３との間の距離は、第１のレンズ２２を透過した半導体レーザよりレーザ光が、第２のレンズ２３の第３の面２６に対して垂直に入射されるような最適距離に決定されている。
【００８７】
上記２群レンズの調整装置５１は、図７及び図８に示すように、レーザ光を発射するレーザ光源５２と、レーザ光源５２から発射されたレーザ光の光束径を広げて出射するビームエキスパンダ５３と、ビームエキスパンダ５３によって広がりながら入射されるレーザ光を平行光にするコリメータレンズ５４と、調整の対象となる２群レンズ２１が載置されるとともに、コリメータレンズ５４からの光が入射されるレンズ載置部５５と、コリメータレンズ５４とレンズ載置部５５の間に配設されて、レンズ載置部５５に載置された２群レンズ２１の第３の面２６において反射された光が入射されるビームスプリッタ５６と、第３の面２６で反射された反射光であって、ビームスプリッタ５６の反射面５６ａで反射された光のスポット径を検出するＣＣＤカメラ５７と、ＣＣＤカメラ５７で受光された映像を映すモニター５８と、第１のレンズ２２の光軸に対する垂直面内において第１のレンズ２２の位置を調整する第１の位置調整用ステージ５９と、第２のレンズ２３の光軸方向に第２のレンズ２３を移動調整する第２の位置調整用ステージ６０と、第２の位置調整用ステージ６０の送り量を検出する変位センサー６１とから構成される。
【００８８】
上記２群レンズの調整装置５１において、ビームエキスパンダ５３、コリメータレンズ５４及びビームスプリッタ５６の光軸は、レーザ光源５２が発射するレーザ光の光軸と一致している。さらに、後述するレンズ載置部５５に設けられたアパーチャ６４部は、中心が上記レーザ光の光軸と一致している。
【００８９】
上記レーザ光源５２は、ＳＨＧのグリーンレーザであって、波長が５３２ｎｍのレーザ光を発射する。このレーザ光源５２は、レーザ光の光軸がレンズ載置部５５のアパーチャ部６４の中心と一致して、レンズ載置部５５の基準面６２に対し直角になるように位置決めされている。なお、レーザ光源５２の位置決めは、例えばマイケルソン干渉計を用いて、十分な精度に追い込んで行っている。そして、レーザ光源５２から発射されたレーザ光は、ビームエキスパンダ５３に入射される。
【００９０】
ビームエキスパンダ５３は、光束径が広がりながら入射されたレーザ光をさらに広げてコリメータレンズ５４に向けて出射する。
【００９１】
上記コリメータレンズ５４は、広がりながら入射されたビームエキスパンダ５３よりのレーザ光を、ビームスプリッタ５６に向けて、平行光にして出射する。
【００９２】
上記ビームスプリッタ５６は、コリメータレンズ５４よりのレーザ光を透過する。なお、ビームスプリッタ５６には、反射面５６ａが形成されており、ビームスプリッタ５６は、後述するように、この反射面５６ａによって、第３の面２６よりの反射光をＣＣＤカメラ５７に向けて反射する。したがって、ビームスプリッタ５６は、コリメータレンズ５４よりのレーザ光は透過する。ビームスプリッタ５６を透過したレーザ光は、レンズ載置部５５に載置された２群レンズ２１に入射される。
【００９３】
上記レンズ載置部５５は、２群レンズ２１が載置される基準面６２と、２群レンズ２１が載置される部分に位置して、円形に形成された貫通孔である円形孔６３とから構成されている。そして、レンズ載置部５５の円形孔６３には、アパーチャ部６４が設けられている。
【００９４】
上記アパーチャ部６４は、円形孔６３よりやや小とされた径に形成されている。詳しくは、アパーチャ部６４の内径は、２群レンズ２１の第１の面２４の球面部の外径よりやや小とされている。このアパーチャ部６４は、上述したように、軸中心が上記レーザ光の光軸と一致している。
【００９５】
よって、レンズ載置部５５は、基準面６２に載置される２群レンズ２１の第１の面２４に入射されるレーザ光をアパーチャ部６４において絞っている。
【００９６】
上記２群レンズ２１の第１の面２４に入射された光は、第１のレンズ２２を透過して第２の面２５より出射される。そして、第２の面２５から出射された光は、第２のレンズ２３の第３の面２６に入射される。
【００９７】
第３の面２６は、第２の面２５よりの光の一部を第２の面２５に向けて反射する。２群レンズの調整装置５１は、この第３の面２６で反射された反射光をもとに、第１のレンズ２２と第２のレンズ２３との間の距離を調整する。
【００９８】
上記第２の面２５に入射された第３の面２６よりの反射光は、第１のレンズ２２を透過して、第１の面２４からビームスプリッタ５６に向けて出射される。
【００９９】
ビームスプリッタ５６は、反射面５６ａによって２群レンズ２１の第１の面２４より出射された反射光をＣＣＤカメラ５７に向けて反射する。
【０１００】
上記ＣＣＤカメラ５７は、受光面５７ａにおいてビームスプリッタ５６よりの反射光を受光する。なお、ＣＣＤカメラ５７の受光面５７ａは、位置検出分解能が０．５ｍｍ程度の精度を有している。また、ＣＣＤカメラ３７は、光軸方向及びこの光軸に対し直角な２軸方向に移動可能に支持されている。
【０１０１】
上記ＣＣＤカメラ５７の受光面５７ａにおいて受光された光は、モニター５８に映し出される。第３の面２６において反射された光は、第１のレンズ２２及びビームスプリッタ５６を介しても略平行光のままＣＣＤカメラ５７の受光面５７ａにおいて受光される。よって、モニター５８には、上記反射光がスポットとして映し出される。
【０１０２】
なお、ＣＣＤカメラ５７は、図８に示すように、レンズ載置部５５の基準面６２に載置した、いわゆるオプティカルフラットとされる平板部６５ａを備える平板６５にレーザ光源５２よりレーザ光を照射して予め位置決めされている。
【０１０３】
上記平板６５は、断面がほぼ矩形とされ、載置された基準面６２と同一面をなす平面日６５ａを設けている。そして、レーザ光源５２よりのレーザ光は、この平板６５の平面部６５ａに照射される。
【０１０４】
すなわち、平板６５の平面部６５ａには、ビームエキスパンダ、コリメータレンズ５４、ビームスプリッタ５６及びアパーチャ部６４を介したレーザ光源５２よりのレーザ光が照射される。
【０１０５】
そして、平板６５の平面部６５ａは、照射されたレーザ光を反射する。ここで、レーザ光の光軸は、平板６５の平面部６５ａに対する入射と反射において一致している。
【０１０６】
平板６５の平面部６５ａよりの反射光は、ビームスプリッタ５６の反射面５６ａで反射され、ＣＣＤカメラ５７の受光面５７ａにおいて受光される。モニター５８には、ＣＣＤカメラ５７の受光面５７ａに入射された平板６５の平面部６５ａよりの反射光のスポットが映し出される。ＣＣＤカメラ５７の位置決めは、このスポット中心が受光面５７ａの中心と一致するように、モニター５８を見ながらＣＣＤカメラ５７の位置を調整して行う。
【０１０７】
そして、第１のレンズ２２と第２のレンズ２３との間の距離を調整は、平板６５の平面部６５ａよりの反射光によって形成されたスポットの径を基準面として行う。
【０１０８】
なお、ＣＣＤカメラ５７は、２群レンズ２１の第３の面２６からの光軸上における距離が長くなるように、例えば光軸上における距離を０．９ｍとした位置に配設されている。
【０１０９】
上述のようにＣＣＤカメラ５７が位置決めされた２群レンズの調整装置５１によって、レンズ載置部５５に載置された２群レンズ２１の第１のレンズ２２と第２のレンズ２３との間の距離が調整される。
【０１１０】
例えば、通常の２群レンズ２１においては、第１のレンズ２２と第２のレンズ２３の間隔は、上述したように、第２の面２５から出射されて光が、第３の面２６に垂直に入射されるように設定されている。よって、第３の面２６において反射された第２の面２５よりの光も第３の面２６に対して垂直に出射されることになる。
【０１１１】
しかし、第１のレンズ２２と第２のレンズ２３との間の距離が、通常の設定と異なってしまうと、第２の面２５から出射されて光が、第３の面２６に対して垂直に入射されなくなる。すると、第３の面２６において反射された第２の面２５より光も第３の面２６に対して垂直に出射されなくなる。
【０１１２】
したがって、第１のレンズ２２と第２のレンズ２３との間の距離が上記通常の設定と異なっている場合の第３の面２６よりの反射光は、平板６５の平面部６５ａによって得たスポット径よりも小さい又は大きいスポット径をなしてＣＣＤカメラ５７の受光面５７ａにおいて受光される。
【０１１３】
そして、第１のレンズ２２と第２のレンズ２３との間の距離の調整は、モニター５８を見ながら、第２の位置調整用ステージ６０によって行い、第３の面２６よりの反射光のスポット径を平板６５によって得た基準となるスポット径と同径になるようにする。
【０１１４】
よって、２群レンズの調整装置５１は、第１のレンズ２２と第２のレンズ２３との間の距離の調整を第２のレンズ２３の第３の面２６において反射された反射光に基づいて行うため、例え第１のレンズ２２又は第２のレンズ２３の外形形状の精度がよくなくても、精度良く距離の調整をすることができる。したがって、第１のレンズ２２及び第２のレンズ２３を成形するために使用する金型の外形精度がでていなくても、十分な光学特性をもった２群レンズ２１を提供することができる。
【０１１５】
例えば、図２に示すように、光ディスクのガラス基板２９ｂが０．１ｍｍ、ガラス基板２９ｂの表面と第４の面２７との間隔、すなわち作動距離が０．１ｍｍに適用して設計され、第３の面２６の球面半径が１．２５ｍｍ及びこの第３の面２６と第４の面２７との間隔、すなわち第２のレンズ２３のレンズ厚さが１．４ｍｍに設計された２群レンズ２１に関して、第１のレンズ２２と第２のレンズ２３との間の距離が変化した場合のスポット径の変化は以下のようになる。
【０１１６】
なお、光軸上において、ＣＣＤカメラ５７は、第２のレンズ２３の第３の面２６から０．９ｍ離されて配設されている。
【０１１７】
例えば、第１のレンズ２２と第２のレンズ２３との間の距離が上記最適距離よりも０．５４３ｍｍ大きくなった場合、ＣＣＤカメラ５７の受光部５７ａにおけるスポット径は、４．９ｍｍになる。また、第１のレンズ２２と第２のレンズ２３との間の距離が上記最適距離よりも０．５６３ｍｍ大きくなった場合、ＣＣＤカメラ５７の受光部５７ａにおけるスポット径は、８．５ｍｍになる。
【０１１８】
よって、ＣＣＤカメラ５７の受光面５７ａの位置検出分解能が０．５ｍｍであることから、第１のレンズ２２に対する第２のレンズ２３の距離の分解能Ｙは、（３）式で得られるように、２．８μｍになる。
【０１１９】

このように、２群レンズの調整装置５１は、第２のレンズ２３の第３の面２６からの反射光を遠方で検出することで、上記距離の変位量を増幅させて検出感度を良好にし、上記距離の調整精度を向上させている。
【０１２０】
また、２群レンズの調整装置５１は、第１のレンズ２２と第２のレンズ２３との間の距離を任意に設定することができる。例えば、第２の面２５よりの光が第３の面２６に対して任意の角度で入射させるような場合である。
【０１２１】
この場合、先ず第２の面２５よりの光が第３の面２６に対して垂直入射する状態に調整する。そして、第１のレンズ２２と第２のレンズ２３の距離変化と第３の面２６に入射される第２の面２５よりの光の入射角度変化との関係を計算によって求めたうえで、第２のレンズ２３を第２の位置調整用ステージ６０によって適宜移動させる。これにより、第１のレンズ２２と第２のレンズ２３との間の距離を任意に変化させることができる。
【０１２２】
そして、検出精度が１μｍ以下の変位センサー６１によって第２の位置調整用ステージ６０の送り量を制御すれば、第１のレンズ２２と第２のレンズ２３との間の距離を１μｍ以下の精度で変化することもできる。
【０１２３】
次に本発明の第４の実施の形態について説明する。第４の実施の形態は、光学ピックアップの備える２群レンズの第１のレンズに対する第２のレンズの傾き、偏芯及び距離を調整する２群レンズの調整装置である。
【０１２４】
上記２群レンズは、第１の実施の形態において図２を用いて説明したように、半導体レーザからのレーザ光が入射される第１の面２４と第１の面２４から入射されたレーザ光を第２のレンズ２３に向けて出射する第２の面２５とからなる第１のレンズ２２と、第１のレンズ２２を透過した半導体レーザよりのレーザ光が入射される第３の面２６と光ディスク２９に対向する面となる第４の面２７とからなる第２のレンズ２３とから構成されている。
【０１２５】
また、２群レンズ２１は、スペーサによって第１のレンズ２２と第２のレンズ２３とが離間されている。
【０１２６】
上記２群レンズの調整装置は、第１のレンズ２２に対する第２のレンズ２３の傾き及び偏芯を検出するため、図９に示すように、２群レンズ２１が載置されるレンズ載置部７２と、レンズ載置部７２に載置される２群レンズ２１の第４の面２７に向けてレーザ光を発射する第１のレーザ光源７３と、第１のレーザ光源７３とレンズ載置部７２との間に配設されている第１のビームエキスパンダ７４、集光レンズ７５及び第１のビームスプリッタ７６と、第１のビームスプリッタ７６の反射面７６ａを介してレンズ載置部７２に載置される２群レンズ２１の第４の面よりの反射光を検出する第１のＣＣＤカメラ７７と、第１のビームスプリッタ７６と第１のＣＣＤカメラ７７の間に配設され、第１のビームスプリッタ７６の反射面７６ａで反射された光であって第１のレンズ２２及び第２のレンズ２３を透過する後述する第２のレーザ光源７９よりのレーザ光の回折パターンを検出する第２のＣＣＤカメラ７８と、集光レンズ７５と第１のビームスプリッタ７６との間に移動可能に支持されて、レンズ載置部７２に載置された２群レンズ２１に対して第１のレーザ光源７３よりのレーザ光を遮光するメカニカルシャッター９０とを備えている。
【０１２７】
なお、第１のビームエキスパンダ７４，集光レンズ７５及び第１のビームスプリッタ７６は、光軸が第１のレーザ光源７３の発射するレーザ光の光軸と一致している。
【０１２８】
また、２群レンズの調整装置７１は、第１のレンズ２２と第２のレンズ２３との間の距離を検出するため、図９に示すように、レンズ載置部７２に載置される２群レンズ２１であって、第１のレンズ２２を介して第３の面２６にレーザ光を照射する第２のレーザ光源７９と、第２のレーザ光源７９とレンズ載置部７２との間に配設されている第２のビームエキスパンダ８０、コリメータレンズ８１及び第２のビームスプリッタ８２と、第３の面２６で反射された第３の面２６よりの反射光のスポット径を検出する第３のＣＣＤカメラ８３とを備えている。
【０１２９】
さらに、２群レンズの調整装置７１は、レンズ載置部７２に載置された２群レンズ２１の第１のレンズ２２の位置を調整する第２の位置調整用ステージ８４と、第２のレンズ２３の位置を調整する第２の位置調整用ステージ８５と、第２の位置調整用ステージ８５の送り量を検出する変位センサー８６とを備えている。
【０１３０】
また、２群レンズの調整装置７１は、第１のＣＣＤカメラ７７，第２のＣＣＤカメラ７８及び第３のＣＣＤカメラ８３で受光された映像を映し出す第１のモニター８７、第２のモニター８８及び第３のモニター８９とを備えている。
【０１３１】
なお、第２のビームエキスパンダ８０，コリメータレンズ８１及び第２のビームスプリッタ８２は、光軸が第２のレーザ光源７９の発射するレーザ光の光軸と一致している。
【０１３２】
上記２群レンズの調整装置７１において、第１のレーザ光源７３と第２のレーザ光源７９とは、発射するレーザ光について光軸が一致している。また、第１のレーザ光源７３及び第２のレーザ光源７９のレーザ光の光軸は、後述するレンズ載置部７２に設けられたアパーチャ部９３の軸中心と一致している。
【０１３３】
そして、光軸上において、第１のＣＣＤカメラ７７は、レンズ載置部７２に載置された２群レンズ２１の第４の面２７から略５ｍ離された位置に配置され、また、第２のＣＣＤカメラ７７は、レンズ載置部７２に載置された２群レンズ２１から略１ｍ離された位置に配設され、さらに、第３のＣＣＤカメラ８３は、レンズ載置部７２に載置された２群レンズ２１の第３の面２５から略０．９ｍ離された位置に配設されている。
【０１３４】
上記２群レンズ２１は、上述のように構成された２群レンズの調整装置７１のレンズ載置部７２において、第１のレンズ２２に対する第２のレンズ２３の傾き、偏芯及び距離を調整されながら組み立てられる。
【０１３５】
詳しくは、２群レンズ２１の第１のレンズ２２が先ずレンズ載置部７２の基準面９１に載置され、位置決めされる。この位置決めされた第１のレンズ２２上にスペーサを介して第２のレンズ２３が配設される。なお、この時点では、第１のレンズ２２及び第２のレンズ２３は、スペーサに接着されていない。そして、第２のレンズ２３は第１のレンズ２２に対して傾きが調整される。傾きが調整された後、第２のレンズ２３は第１のレンズ２２に対して偏芯が調整される。偏芯が調整された後、第２のレンズ２３は第１のレンズ２２に対して距離が調整される。
【０１３６】
以下に、２群レンズの調整装置７１における第１のレンズ２２に対する第２のレンズ２３の傾き、偏芯及び距離の調整についてさらに詳しく説明する。
【０１３７】
２群レンズの調整装置７１は、第１のレンズ２２に対する第２のレンズ２３の傾きを調整するためのレーザ光を第１のレーザ光源７３より発射させる。
【０１３８】
上記第１のレーザ光源７３は、Ｈｅ−Ｎｅレーザであって、波長が６３２ｎｍのレーザ光を発射する。このレーザ光源７３は、レーザ光の光軸がレンズ載置部７２の開口部９２の中心と一致し、基準面に対して直角になるように位置決めされている。なお、第１のレーザ光源７３の位置決めは、例えばマイケルソン干渉計を用いて、十分な精度に追い込んで行っている。
【０１３９】
上記第１のレーザ光源７３から発射されたレーザ光は、第１のビームエキスパンダ７４及び集光レンズ７５に入射される。第１のビームエキスパンダ７４及び集光レンズ７５は、入射された第１のレーザ光源７３よりのレーザ光を適宜調整して集束させて、第１のビームスプリッタ７６に向けて出射する。
【０１４０】
上記第１のビームスプリッタ７６は、第１のビームエキスパンダ７４及び集光レンズ７５によって集束されたレーザ光を２群レンズ２１が載置されるレンズ載置部７２に向けて透過する。
【０１４１】
上記レンズ載置部７２は、２群レンズ２１が載置される基準面９１と、２群レンズ２１が載置される部分に位置されて円形に形成された貫通孔である円形孔９２とから構成されている。そして、レンズ載置部７２の円形孔９２には、アパーチャ部９３が設けられている。
【０１４２】
上記アパーチャ部９３は、円形孔９２よりやや小とされた径に形成されている。詳しくは、アパーチャ部９３の内径は、２群レンズ２１の第１の面２４の球面部の外径よりやや小とされている。このアパーチャ部９３は、上述したように、軸中心が第１のレーザ光源７３から発せられるレーザ光の光軸と一致している。
【０１４３】
上記レンズ載置部７２は、第１の面２４を円形孔９２によって嵌合し、基準面９１に載置された２群レンズ２１を保持している。
【０１４４】
上記基準面９１に載置された２群レンズ２１は、第４の面２７に対して第１のビームスプリッタ７６を透過されたレーザ光が入射される。第４の面２７は、入射されたレーザ光の一部を第１のビームスプリッタ７６に向けて反射する。
【０１４５】
上記第１のビームスプリッタ７６は、反斜面７６ａによって第４の面２７よりの反射光を第１のＣＣＤカメラ７７に向けて反射する。反射光は、この第１のビームスプリッタ７６の反射面７６ａにおいて反射された後に焦点が形成される。
【０１４６】
上記反射光の焦点は、第１のＣＣＤカメラ７７の受光面７７ａによって受光される。
【０１４７】
この第１のＣＣＤカメラ７７は、上述の第１の実施の形態において図３を用いて説明したように、レンズ載置部７２に平板１４を載置して行われている。すなわち、第１のＣＣＤカメラ７７は、第１のビームスプリッタ７６の反射面７６ａを反射後に形成される平板１４の平面部１４ａよりの反射光の焦点が受光面７７ａ中心に位置するように位置決めされている。
【０１４８】
したがって、２群レンズ２１の第４の面２７において反射された反射光は、上述のように位置決めされた第１のＣＣＤカメラ７７の受光面７７ａにおいて受光されたことになる。
【０１４９】
そして、第２のレンズ２３の傾きの調整は、モニター８７を見ながら、第２の位置調整用ステージ８５によって行い、ＣＣＤカメラ７７の受光面７７ａの中心に第４の面２７よりの反射光の焦点を一致させる。
【０１５０】
よって、２群レンズの調整装置７１は、第１のレンズ２２に対する第２のレンズ２３の傾きの調整を第２のレンズ２３の第４の面２７からの反射光に基づいて行うため、たとえ第２のレンズ２３の外形形状の精度がよくなくても、精度良く傾きの調整をすることができる。
【０１５１】
また、２群レンズの調整装置７１は、第４の面２７よりの反射光の焦点によって、第１のレンズ２２に対する第２のレンズ２３の傾きを調整しているために、たとえＣＣＤカメラ７７の受光面７７ａの位置検出感度が小さくても精度良く傾きの調整をすることができる。
【０１５２】
なお、２群レンズの調整装置７１は、上述したように、第４の面２７と反射光の焦点位置との距離を略５ｍになるように構成されている。これは、第４の面２７と上記焦点の検出位置の距離を長くすることで、位置検出感度を向上させるためである。
【０１５３】
例えば第１のＣＣＤカメラ７７の受光面７７ａの位置検出分解能が０．５ｍｍ程度、光軸上の第４の面２７と第１のＣＣＤカメラ７７との間隔が略５ｍであることから、第２のレンズ２３の傾きの検出分解能Ｘは、上記（１）式で得たように０．０５ｍｒｄになる。
【０１５４】
上記２群レンズの調整装置７１は、このように第４の面２７からの反射光の焦点を遠方に形成して、上記焦点の変位量を増幅させることで、位置検出感度を良好にし、傾きの調整精度を向上させている。
【０１５５】
以上のように第２のレンズ２３の傾きを調整した後、上記２群レンズの調整装置７１は、第１のレンズ２２に対する第２のレンズ２３の偏芯を調整する。
【０１５６】
上記第１のレンズ２２に対する第２のレンズ２３の偏芯の調整は、第１の面２４側から２群レンズ２１に対して第２のレーザ光源７９よりレーザ光を照射して行われる。
【０１５７】
上記第２のレーザ光源７９は、ＳＨＧのグリーンレーザであって、波長が５３２ｎｍのレーザ光を発射する。この第２のレーザ光源７９は、レーザ光の光軸がレンズ載置部７２のアパーチャ部９３の中心と一致し、レンズ載置部７２の基準面９１に対し直角になるように位置決めされている。なお、第２のレーザ光源７９の位置決めは、例えばマイケルソン干渉計を用いて、十分な精度に追い込んで行っている。そして、第２のレーザ光源７９から発射されたレーザ光は、第２のビームエキスパンダ８０及びコリメータレンズ８１に入射される。第２のレーザ光源７９から発射されたレーザ光は、この第２のビームエキスパンダ８０及びコリメータレンズ８１において光束径が広げられた後平行光となって、第２のビームスプリッタ８２に向かって出射される。
【０１５８】
上記第２のビームスプリッタ８２は、コリメータレンズ８１よりのレーザ光をレンズ載置部７２に向かって透過する。そして、第２のビームスプリッタ８２よりのレーザ光は、レンズ載置部７２に形成されたアパーチャ部９３を介して２群レンズ２１の第１のレンズ２２に入射される。ここで、第１のレンズ２２に入射された光は、アパーチャ部９３によって回折成分を含むものとなる。
【０１５９】
第１のレンズ２２に入射した光は、第２のレンズ２３を介して第１のビームスプリッタ７６に向けて出射される。
【０１６０】
なお、２群レンズ２１を透過した光は、第４の面２７から出射直後に焦点を形成するために、光束径が広がった光となる。
【０１６１】
上記第１のビームスプリッタ７６には、上述したように、反射面７６ａが形成されており、第１のビームスプリッタ７６は、反射面７６ａによって、２群レンズ２１よりの光を第２のＣＣＤカメラ７８に向けて出射する。
【０１６２】
上記第２のＣＣＤカメラ７８は、受光面７８ａにおいてビームスプリッタ７６の反射面７６ａで反射された光を受光する。
【０１６３】
なお、第２のＣＣＤカメラ７８は、検出時には、第１のビームスプリッタ７６と第１のＣＣＤカメラ７７との間に位置されているが、非検出時には、第１のＣＣＤカメラ７７の検出の妨げにならないように退避される。
【０１６４】
この第２のＣＣＤカメラ７８は、上述の第２の実施の形態において図６を用いて説明したように、レンズ載置部７２に設けられたアパーチャ部９３を透過されるレーザ光の回折パターンをもとに位置決めされている。なお、第１のレンズ２２も、上記図５を用いて説明したように、回折パターンをもとにレンズ載置部９３に対して位置決めされている。
【０１６５】
よって、２群レンズ２１を透過してきた光は、上述のように位置決めされている第２のＣＣＤカメラ７８の受光面７８ａにおいて受光される。
【０１６６】
そして、第２のレンズ２３の偏芯の調整は、第２のモニター８８を見ながら、第２の位置調整用ステージ８５によって行い、第２のＣＣＤカメラ７８の受光面７８ａの中心に２群レンズ２１を透過してきた光の回折パターンの中心を一致させる。
【０１６７】
よって、２群レンズの調整装置７１は、第１のレンズ２２に対する第２のレンズ２３の偏芯の調整を第１のレンズ２２及び第２のレンズ２３を透過した光の回折パターンに基づいて行っているために、たとえ第１のレンズ２２及び第２のレンズ２３の外形形状の精度がよくなくても、精度良く偏芯の調整を行うことができる。
【０１６８】
上記２群レンズの調整装置７１は、回折パターンの中心によって光軸中心を割り出しているために、従来の光量分布或いはビームパターンから光軸中心を割り出す手段よりも高い検出感度を得ることができる。
【０１６９】
例えば、第２のＣＣＤカメラ７８の受光面７８ａの位置検出分解能が０．５ｍｍ程度、２群レンズ２１の焦点距離が略２．５ｍｍ、光軸上の２群レンズ２１と第２のＣＣＤカメラ７８との距離が１ｍ程度であるから、第１のレンズ２２に対する第２のレンズ２３の偏芯量の検出感度Δｅは、上記（２）式で得たように１．２５×１０^-3μｍになる。
【０１７０】
このように、２群レンズの調整装置７１は、２群レンズ２１から遠方で第２のＣＣＤカメラ７８によって回折パターンの中心を検出することで、偏芯量の検出感度が良好になり、偏芯の調整精度を向上させている。
【０１７１】
以上のように第２のレンズ２３の傾き及び偏芯を調整した後、上記２群レンズの調整装置７１は、第１のレンズ２２と第２のレンズ２３との間の距離を調整する。
【０１７２】
第１のレンズ２２と第２のレンズ２３との間の距離は、第２のレーザ光源７９よりレーザ光を照射して行われる。第２のレーザ光源７９から発射されたレーザ光は、第２のビームエキスパンダ８０、コリメータレンズ８１及び第２のビームスプリッタ８２を介して２群レンズ２１の第１の面２４に入射される。
【０１７３】
第１の面２４に入射されたレーザ光は、第１のレンズ２２内を透過して、第２の面２５から出射される。第２の面２５から出射された光は、第３の面２６に入射される。
【０１７４】
なお、通常の２群レンズ２１は、第２の面２５よりの光が第３の面２６に対して垂直に入射されるように、第１のレンズ２２と第２のレンズ２３との間隔が設定される。
【０１７５】
上記第３の面２６は、第２の面２５よりの光の一部を反射する。第３の面２６において反射された反射光は、第２の面２５に入射され再び第１のレンズ２２内を透過して、第１の面２４より第２のビームスプリッタ８２に向けて出社される。
【０１７６】
上記第２のビームスプリッタ８２には、反射面８２ａが形成されており、第２のビームスプリッタ８２は、反射面８２ａによって、第１の面２４より出射された反射光を第３のＣＣＤカメラ８３に向けて出射する。
【０１７７】
上記第３のＣＣＤカメラ８３は、受光面８３ａにおいて第２のビームスプリッタ８２の反斜面８２ａで反射された反射光を受光する。
【０１７８】
この第３のＣＣＤカメラ８３は、上述の第３の実施の形態において図８を用いて説明したように、レンズ載置部７２に平板６５を載置して位置決めされている。
【０１７９】
すなわち、第３のＣＣＤカメラ８３は、レンズ載置面７２に載置された平板６５の平面部６５ａによって反射された光のスポット中心が受光面８３ａ中心と一致するようにして位置決めされている。
【０１８０】
よって、ビームスプリッタ８２の反射面８２ａで反射された第３の面２６よりの反射光は、上述のように位置決めされた第３のＣＣＤカメラ８３の受光面８３ａに受光されたことになる。
【０１８１】
そして、第１のレンズ２２と第２のレンズ２３との間の距離の調整は、第３のモニター８９を見ながら、第２の位置調整用ステージ８５によって行い、第３の面２６よりの反射光のスポット径を平板６５によって得た基準となるスポット径と同径になるようにする。
【０１８２】
よって、２群レンズの調整装置７１は、第１のレンズ２２と第２のレンズ２３との間の距離の調整を第２のレンズ２３の第３の面２６において反射された反射光に基づいて行うため、例え第１のレンズ２２又は第２のレンズ２３の外形形状の精度がよくなくても、精度良く距離の調整をすることができる。
【０１８３】
また、第３のＣＣＤカメラ８３の受光面８３ａの位置検出分解能が０．５ｍｍであることから、第１のレンズ２２に対する第２のレンズ２３の距離の分解能Ｙは、上記（３）式で得たように２．８μｍになる。
【０１８４】
このように、２群レンズの調整装置７１は、第２のレンズ２３の第３の面２６からの反射光を遠方で検出することで、上記距離の変位量を増幅させて検出感度を良好にし、上記距離の調整精度を向上させている。
【０１８５】
以上のように第１のレンズ２２に対する第２のレンズ２３の傾き、偏芯及び距離が調整された２群レンズ２１は、第１のレンズ２２及び第２のレンズ２３がスペーサに接着されて固定される。
【０１８６】
以上のように、２群レンズの調整装置７１は、２群レンズ２１にレーザ光を照射してその透過光或いは反射光をもとに第１のレンズ２２に対する第２のレンズ２３の傾き、偏芯及び距離を調整しているために、第１のレンズ２２又は第２のレンズ２３の外形形状の精度が良くなくても、精密に上記傾き、偏芯及び距離を調整することができる。
【０１８７】
したがって、第１のレンズ２２及び第２のレンズ２３を成形するために使用する金型の外形精度が出ていなくても、十分な光学特性をもった２群レンズ２１を提供することができる。
【０１８８】
さらに、２群レンズの調整装置７１は、上記傾き、上記偏芯及び上記距離の調整を各光学部品を共有しているので、コストが安くなる。例えば、レーザ光源を第２のレーザ光源７９のみを備えて構成することもできる。この場合、第２のレーザ光源７９よりのレーザ光を、光学レンズを用いて適宜に分岐、反射させるなどして、２群レンズ２１の第４の面２７に対して照射すればよい。
【０１８９】
また、２群レンズの調整装置７１は、第１のレンズ２２と第２のレンズ２３との間の距離を任意に設定することもできる。例えば、第２の面２５よりの光が第３の面２６に対して任意の角度で入射させるような場合である。
【０１９０】
この場合、先ず第２の面２５よりの光が第３の面２６に対して垂直入射する状態に調整する。そして、第１のレンズ２２と第２のレンズ２３の距離変化と第３の面２６に入射される第２の面２５よりの光の入射角度変化との関係を計算によって求めたうえで、第２のレンズ２３を第２の位置調整用ステージ８５によって適宜移動させる。これにより、第１のレンズ２２と第２のレンズ２３との間の距離を任意に変化させることができる。
【０１９１】
そして、検出精度が１μｍ以下の変位センサー８６によって、第２の位置調整用ステージ８５の送り量を制御すれば、第１のレンズ２２と第２のレンズ２３との間の距離を１μｍ以下の精度で変化することもできる。
【０１９２】
【発明の効果】
本発明に係る光ピックアップ用対物レンズの調整方法は、光軸に対する第２のレンズの対向面よりの反射光の垂直面上の位置を対向面から遠方で検出することにより、第１のレンズ及び第２のレンズの外形形状の精度が良くなくても、第１のレンズに対する第２のレンズの傾きを高精度で調整することができる。
【０１９３】
また、本発明に係る光ピックアップ用対物レンズの調整方法は、第１のレンズ及び第２のレンズを透過する光の回折パターンを検出することにより、第１のレンズ及び第２のレンズの外形形状の精度が良くなくても、第１のレンズに対する第２のレンズの偏芯を高精度で調整することができる。
【０１９４】
さらに、本発明に係る光ピックアップ用対物レンズの調整方法は、第１のレンズを介して第２のレンズの第１のレンズに対向する面に入射された光の反射が再び第１のレンズを介して得られる光のビーム径を検出することにより、第１のレンズ及び第２のレンズの外形形状の精度が良くなくても、第１のレンズと第２のレンズとの間の距離を高精度で調整することができる。
【０１９５】
そして、本発明に係る光ピックアップ用対物レンズの調整装置は、基準面に載置される２群レンズの第２のレンズの対向面から遠方に位置されて、光源から照射されて対向面で反射された反射光を検出する検出手段を備えることによって、光軸に対する対向面よりの反射光の垂直面上の位置を対向面から遠方で検出するために、第１のレンズ及び第２のレンズの外形形状の精度が良くなくても、第１のレンズに対する第２のレンズの傾きを高精度で調整することができる。
【０１９６】
また、本発明に係る光ピックアップ用対物レンズの調整装置は、基準面に載置される２群レンズの第２のレンズの対向面から遠方に位置されて光源から照射されて対向面で反射された反射光を検出する第１の検出手段と、第１のレンズ及び第２のレンズを透過する光の回折パターンを検出する第２の検出手段と、第１のレンズを介して第２のレンズの第１のレンズに対向する面に入射された光の反射が再び第１のレンズを介して得られる光のビーム径を検出する第３の検出手段とを備えることによって、２群レンズにレーザ光を照射してその透過光或いは反射光をもとに第１のレンズに対する第２のレンズの傾き、偏芯及び距離を調整しているために、第１のレンズ及び第２のレンズの外形形状の精度が良くなくても、高精度でその傾き、偏芯及び距離を調整することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態となる２群レンズの調整装置であって、２群レンズが載置されたときの構成図である。
【図２】上記２群レンズの調整装置によって調整される２群レンズの正面図である。
【図３】上記第１の実施の形態となる２群レンズの調整装置の備えるＣＣＤカメラの位置決めを行う際の構成図である。
【図４】本発明の第２の実施の形態となる２群レンズの調整装置であって、２群レンズが載置されたときの構成図である。
【図５】上記第２の実施の形態となる２群レンズの調整装置であって、第１のレンズが載置されたときの構成図である。
【図６】上記第２の実施の形態となる２群レンズの調整装置の備えるＣＣＤカメラの位置決めを行う際の構成図である。
【図７】本発明の第３の実施の形態となる２群レンズの調整装置であって、２群レンズが載置されたときの構成図である。
【図８】上記第３の実施の形態となる２群レンズの調整装置の備えるＣＣＤカメラの位置決めを行う際の構成図である。
【図９】本発明の第４の実施の形態となる２群レンズの調整装置であって、２群レンズが載置されたときの構成図である。
【図１０】従来の第１のレンズに対する第２のレンズの傾き、偏芯及び距離の調整の説明に用いた２群レンズの正面図である。
【符号の説明】
１ ２群レンズの調整装置、２ レーザ光源、３ レンズ載置部、７ ＣＣＤカメラ、１２ 基準面、２１ ２群レンズ、２２ 第１のレンズ、２３ 第２のレンズ、２４ 第１の面、２５ 第２の面、２６ 第３の面、２７ 第４の面、２９ 光ディスク、３１ ２群レンズの調整装置、３２ レーザ光源、３５ レンズ載置部、３７ ＣＣＤカメラ、４１ 基準面、５１ ２群レンズの調整装置、５２ レーザ光源、５５ レンズ載置部、５７ ＣＣＤカメラ、５９ 第１の位置調整用ステージ、６０ 第２の位置調整用ステージ、６２ 基準面、７１ ２群レンズの調整装置、７２ レンズ載置部、７３ 第１のレーザ光源、７７ 第１のＣＣＤカメラ、７８ 第２のＣＣＤカメラ、７９ 第２のレーザ光源、８３ 第３のＣＣＤカメラ、８４ 第１の位置調整用ステージ、８５ 第２の位置調整用ステージ、９１ 基準面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an adjustment apparatus for an objective lens for an optical pickup that adjusts the position of a second lens with respect to the first lens of a two-group lens including a first lens and a second lens provided in the optical pickup.
[0002]
[Prior art]
Conventionally, various optical recording media such as so-called optical disks, magneto-optical disks, or optical cards have been proposed as information signal recording media. An optical pickup has been proposed in which light from a light source is irradiated onto the optical recording medium to write and read information signals on the optical recording medium.
[0003]
In the optical pickup described above, the objective lens can reduce the beam diameter of the light condensed on the optical recording medium by increasing the numerical aperture (NA), thereby improving the signal recording density of the optical recording medium. be able to.
[0004]
However, with a so-called single lens, when a high numerical aperture is to be obtained, a refractive power is required. When the refractive power is increased, the curvature of the objective lens is reduced, and the positioning accuracy between the refractive surfaces becomes severe. Therefore, with a single lens, it was the limit to make the numerical aperture about 0.6.
[0005]
In contrast to this single lens, the second group lens can increase the numerical aperture. As shown in FIG. 10, the second group lens includes a first lens 101 including a first surface 103 on which laser light from a semiconductor laser is incident and a second surface 104 facing the second lens 102. From the second lens 102 composed of the third surface 105 on which the laser beam from the semiconductor laser that has passed through the first lens 101 is incident and the fourth surface 106 that faces the optical recording medium. It is configured. The thus configured second group lens 100 can disperse the refractive power. Further, the first lens 101 and the second lens 102 are easy to manufacture.
[0006]
Specifically, in the second group lens 100, the distance between the first lens 101 and the second lens 102 is constant, and the posture of the second lens 102 with respect to the first lens 101 is also precisely positioned. For example, conventionally, the first lens 101 and the second lens 102 are molded using a mold. Positioning regarding the distance between the first lens 101 and the second lens 102 and the posture of the second lens 102 with respect to the first lens 101 is performed based on the outer shape of each lens. Therefore, it is required to mold the lens outer shape with high accuracy.
[0007]
[Problems to be solved by the invention]
However, in the above mold, the first lens 101 and the second lens 102 can be molded only with a certain degree of accuracy. Therefore, the first lens 101 and the second lens 102 cannot be accurately positioned based on the outer shape having an error.
[0008]
If the positioning cannot be performed accurately, the second lens 102 may be at a different distance from the design with respect to the first lens 101, or may be inclined or decentered.
[0009]
As described above, when the distance of the second lens 102 is changed with respect to the first lens 101 or an inclination or decentration occurs, the second group lens 100 has an allowable range required as a single lens, for example, 0. Aberrations exceeding 04 rms are generated.
[0010]
Therefore, the present invention has been made in view of the above-described circumstances, and it is possible to accurately position the second lens with respect to the first lens of the second group lens even if there is an error in the outer shape of the lens. An object of the present invention is to provide an adjustment device for an objective lens for an optical pickup.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problem, the optical pickup objective lens adjusting apparatus according to the present invention has a two-group lens including a first lens and a second lens, a predetermined resolution, and the first lens. Detecting means for detecting a beam diameter of light obtained again through the first lens by reflection of light incident on the surface of the second lens facing the first lens through the first lens; Displacement means for displacing the distance between the first lens and the second lens, and driving the displacement means to cause the beam diameter to be the same as the reference beam diameter. An optical pickup objective lens adjusting device that adjusts the distance from the second lens, wherein the distance between the detection means and the second group lens is determined by the displacement of the beam diameter relative to the feed amount of the displacement means and the detection. Depending on the resolution of the means And wherein the determined.
[0012]
Moreover, in order to solve the above-described problem, the optical pickup objective lens adjusting device according to the present invention includes a first lens and a second lens group having a second lens having a facing surface facing the optical recording medium. An optical pickup objective lens adjusting device that adjusts the inclination, decentering, and distance of the second lens with respect to the first lens has a light source, a reference surface on which the second group lens is placed, and a predetermined resolution. And a first detection unit that is positioned far from the facing surface of the second group lens placed on the reference surface, detects reflected light that is irradiated from the light source and reflected by the facing surface; Second detection means for detecting each diffraction pattern of light transmitted through the first lens and the second lens, and the first lens of the second lens facing the first lens through the first lens Incident on the surface The third detection means for detecting the beam diameter of the light obtained through the first lens again, and the results detected by the first detection means to the third detection means, Adjusting means for adjusting the inclination, decentering, and distance of the second lens with respect to one lens, and the distance between the detecting means and the opposing surface is the accuracy required for detecting the inclination of the lens and the first. It depends on the resolution of the detection means.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings.
The first embodiment is an apparatus configured by applying an adjustment method of an objective lens for an optical pickup that adjusts a second group lens included in the optical pickup, and adjusts the inclination of the second lens with respect to the first lens. This is an adjusting device for the second group lens.
[0017]
Specifically, as shown in FIG. 1, the adjusting device for the second group lens irradiates the fourth surface 27 of the second group lens 21 with laser light and detects the reflected light at a distance, thereby providing the first lens. The inclination of the second lens 23 with respect to 22 is adjusted.
[0018]
The second group lens is an objective lens that is provided in the optical pickup and focuses the laser light emitted from the semiconductor laser on the signal recording surface of the optical disk.
[0019]
As shown in FIG. 2, the second group lens includes a first surface 24 on which a laser beam 28 incident from a semiconductor laser is incident, and a laser beam 28 incident on the first surface 24 as a second lens. A first lens 22 composed of a second surface 25 that emits light to 23, a third surface 26 on which laser light from a semiconductor laser that has passed through the first lens 22 is incident, and the third surface 26. The second lens 23 is composed of a fourth surface 27 that emits laser light incident from the surface 26 to an optical disk 29 disposed so as to face the laser beam. That is, the second group lens 21 receives laser light from the semiconductor laser in the order of the first surface 24, the second surface 25, the third surface 26, and the fourth surface 27. The light beam converged with respect to 29 is emitted.
[0020]
In the first lens 22, the first surface 24 is formed as an aspheric surface so as to be convex toward the semiconductor laser, and its outer peripheral portion 24a is formed as a flat surface. The second surface 25 is formed as an aspheric surface so as to be convex toward the second lens 23.
[0021]
In the second lens 23, the third surface 26 is formed into a spherical surface so as to be convex toward the opposing first lens 22 side. Moreover, the 4th surface 27 is formed in the plane.
[0022]
The second group lens 21 keeps the distance between the first lens 22 and the second lens 23 constant. The thus configured second group lens 21 can focus the laser beam on the signal recording surface 29 a of the optical disk 29. For example, the second group lens 21 has a numerical aperture of 0.7 to 0.95.
[0023]
In the second group lens 21, the first lens 22 and the second lens 23 are actually separated by a spacer (not shown). The first lens 22 and the second lens 23 are bonded to the spacer after adjusting the inclination of the second lens 21 with respect to the first lens 22.
[0024]
As shown in FIG. 1, the adjusting device 1 for the second group lens includes a laser light source 2 that emits laser light, a lens placement unit 3 on which a second group lens 21 is disposed, a laser light source 2 and a lens placement. Positioned far from the fourth surface 27 of the second group lens 21 disposed on the lens mounting unit 3 and the beam expander 4, the condenser lens 5 and the beam splitter 6 disposed between the unit 3 and the lens 3. The positions of the CCD camera 7 that detects the reflected light emitted from the laser light source 2 and reflected by the fourth surface 27, the monitor 8 that displays the image received by the CCD camera 7, and the position of the first lens 22 are detected. The first position adjustment stage 9 to be adjusted and the second position adjustment stage 10 to adjust the second lens 23 in parallel or tilt with respect to the first lens 22 are configured.
[0025]
In the second group lens adjusting apparatus 1, the optical axes of the beam expander 4, the condenser lens 5, and the beam splitter 6 coincide with the optical axis of the laser light emitted from the laser light source 2. Furthermore, the center of an opening 13 of the lens mounting portion 3 described later coincides with the optical axis of the laser beam.
[0026]
In the second group lens adjusting device 1, the beam expander 4 and the condenser lens 5 are configured such that the reflected light from the fourth surface 27 of the second group lens 21 placed on the lens placement unit 3 is reflected by the beam splitter 6. It is positioned so as to form a focal point after being reflected by the reflecting surface 6a. The beam expander 4 and the condenser lens 5 are positioned so that the distance from the fourth surface 27 of the second group lens 21 to the position where the focal point is formed becomes longer, for example, 5 m.
[0027]
Further, the second group lens adjusting device 1 includes a mechanical shutter 11 supported so as to be movable between the condenser lens 5 and the beam splitter 6. The mechanical shutter 11 is used to shield the laser light from the laser light source 2 from the lens mounting unit 3.
[0028]
The laser light source 2 is a He—Ne laser and emits laser light having a wavelength of 632 nm. The laser light source 2 is positioned so that the optical axis of the laser light coincides with the center of the opening 13 of the lens mounting portion 3 and is perpendicular to the reference surface 12. The positioning of the laser light source 2 is performed with sufficient accuracy using, for example, a Michelson interferometer.
[0029]
Laser light emitted while spreading from the laser light source 2 is incident on the beam expander 4. The beam expander 4 further spreads the incident laser light and emits it toward the condenser lens 5.
[0030]
In the condensing lens 5, the laser beam from the beam expander 4 that has been spread and incident is focused toward the beam splitter 6 and emitted.
[0031]
The beam splitter 6 transmits the laser beam from the condenser lens 5 and emits the laser beam toward the lens mounting portion 3 on which the second group lens 21 is mounted. The beam splitter 6 has a reflecting surface 6a. The beam splitter 6 reflects the reflected light from the fourth surface 27 of the second lens 23 on the reflecting surface 6a, as will be described later. have.
[0032]
The lens placing portion 3 is composed of a reference surface 12 on which the second group lens 21 is placed and an opening 13 formed in a circular shape, located on a portion on which the second group lens 21 is placed. . The opening 13 has substantially the same diameter as the outer diameter of the spherical portion of the first surface 24 of the second group lens 21.
[0033]
The lens mounting unit 3 holds the second group lens 21 mounted on the reference surface 12 by fitting the first surface 24 with the opening 13.
[0034]
Laser light from the beam splitter 6 is incident on the fourth surface 27 of the second group lens 21 placed on the reference surface 12. The fourth surface 27 reflects a part of the incident laser light toward the beam splitter 6.
[0035]
The beam splitter 6 reflects the reflected light from the fourth surface 27 toward the CCD camera 7 on the reflecting surface 6a. The reflected light forms a focal point after being reflected by the reflecting surface 6 a of the beam splitter 6. The CCD camera 7 is positioned in the vicinity of the focal point of the reflected light, and receives the focal point of the reflected light by the light receiving surface 7a. The light receiving surface 7a of the CCD camera 7 has a position detection resolution of about 0.5 mm.
[0036]
As shown in FIG. 3, the CCD camera 7 is preliminarily positioned by placing a flat plate 14 having a flat surface portion 14 a as a so-called optical flat on a reference surface 12 of the lens placement portion 3.
[0037]
The flat plate 14 includes a parallel surface 14 a having a substantially rectangular cross section and formed in parallel with the reference surface 12. Here, the cross-sectional thickness of the flat plate 14 is determined such that when the flat plate 14 is placed on the reference surface 12, the position of the flat surface portion 14 a is substantially the same as the height of the fourth surface 27 of the second group lens 21. Has been.
[0038]
The positioning of the CCD camera 7 is performed by the same procedure as irradiating the fourth surface 27 of the second group lens 21 with the laser beam, and irradiating the plane portion 14a of the flat plate 14 with the laser beam. .
[0039]
In other words, the laser light from the laser light source 2 is applied to the flat portion 14 a of the flat plate 14 via the beam expander 4, the condenser lens 5 and the beam splitter 6.
[0040]
The laser light incident on the flat surface portion 14 a of the flat plate 14 is reflected toward the beam splitter 4. Here, since the flat surface portion 14a of the flat plate 14 is positioned parallel to the reference surface 12, the optical axis of the laser light coincides with the incidence and reflection on the flat surface portion 14a.
[0041]
The reflected light from the flat surface portion 14a of the flat plate 14 is reflected by the reflecting surface 6a of the beam splitter 6, and then a focal point is formed. The CCD camera 7 is previously positioned near the focal point of the reflected light. The CCD camera 7 is supported so as to be movable in the optical axis direction of the reflected light and in two axial directions perpendicular to the optical axis.
[0042]
The CCD camera 7 is positioned by moving the CCD camera 7 while looking at the monitor 8 so that the center of the light receiving surface 7a coincides with the center of the optical axis of the reflected light, that is, the focal point of the reflected light.
[0043]
Then, after the center position of the light receiving surface 7a is determined, the light receiving surface 7a is adjusted to be perpendicular to the optical axis of the reflected light.
[0044]
The CCD camera 7 is positioned as described above.
[0045]
Therefore, the light receiving surface 7 a of the CCD camera 7 is disposed at a position where the focal point of the reflected light from the fourth surface 27 of the second lens 22 can be received.
[0046]
For example, when the second lens 22 is inclined, the focal point of the reflected light from the fourth surface 27 of the second group lens 21 placed on the reference surface 12 is a deviation in the direction perpendicular to the optical axis. Thus, the light is deviated from the center of the light receiving surface 7a.
[0047]
Then, the tilt of the second lens 23 is adjusted by the second position adjusting stage 10 while looking at the monitor 8, and the reflected light from the fourth surface 27 is centered on the light receiving surface 7 a of the CCD camera 7. Match the focus.
[0048]
Accordingly, the second group lens adjustment device 1 adjusts the inclination of the second lens 23 with respect to the first lens 22 based on the reflected light from the fourth surface 27 of the second lens 23. Even if the accuracy of the outer shape of the second lens 23 is not good, the tilt can be adjusted with high accuracy. Therefore, even if the outer diameter accuracy of the mold used to mold the first lens 22 and the second lens 23 is not obtained, the two-group lens 21 having sufficient optical characteristics can be provided. .
[0049]
The second group lens adjustment device 1 adjusts the inclination of the second lens 23 relative to the first lens 22 by the focus of the reflected light from the fourth surface 27, so Even if the position detection sensitivity of the light receiving surface 7a is small, the tilt can be adjusted with high accuracy.
[0050]
As described above, the second-group lens adjustment device 1 is configured such that the distance between the fourth surface 27 and the focal position of the reflected light is 5 m. This is because the position detection sensitivity is improved by increasing the distance between the fourth surface 27 and the focus detection position.
[0051]
For example, since the position detection resolution of the light receiving surface 7a of the CCD camera 7 is about 0.5 mm, the detection resolution X of the inclination of the second lens 23 is 0.05 mrad as obtained by the equation (1). Become.
[0052]

The second-group lens adjustment device 1 thus forms the focal point of the reflected light from the fourth surface 27 in the distance, and amplifies the inflection position of the focal point with respect to the second lens 23, thereby detecting the position detection sensitivity. To improve the tilt adjustment accuracy.
[0053]
Although the adjustment of the second lens 23 has been described, the second-group lens adjustment device 1 can also adjust the inclination of the second lens 23 after adjusting the inclination of the first lens 22. In this case, the positioning accuracy of the inclination of the second lens 23 with respect to the first lens 22 is improved.
[0054]
Next, a second embodiment will be described. The second embodiment is an apparatus configured by applying an adjustment method of an objective lens for an optical pickup that adjusts a second group lens included in the optical pickup, and adjusts the inclination of the second lens with respect to the first lens. This is an adjusting device for the second group lens.
[0055]
Specifically, as shown in FIG. 4, the second group lens adjustment device 1 transmits the laser light through the first lens 22 and the second lens 23 and detects the center position of the diffraction pattern of the transmitted light at a distance. Thus, the eccentricity of the second lens 23 with respect to the first lens 22 is adjusted.
[0056]
As described with reference to FIG. 2 in the first embodiment, the second group lens includes the first lens 22 and the second lens 23 having the fourth surface 27 that is a surface facing the optical disk 29. It is composed of.
[0057]
As shown in FIGS. 4 and 5, the adjusting device for the second group lens includes a laser light source 32 that emits laser light, a beam expander 33 that spreads and emits the laser light emitted from the laser light source 32, and a beam A collimator lens 34 that collimates the laser light that is spread and incident by the expander 33 and a second group lens 21 to be adjusted are mounted, and a lens mount on which light from the collimator lens 34 is incident. A first light beam reflected by a reflecting surface 36a of the beam splitter 36, a beam splitter 36 on which the light transmitted through the mounting portion 35, the second lens group 21 placed on the lens placing portion 35 is incident; CCD camera 37 for detecting a diffraction pattern of light transmitted through the lens 22 and the second lens 23, and a monitor 3 for displaying an image received by the CCD camera 37 A first position adjusting stage 39 that adjusts the position of the first lens 22 in a plane perpendicular to the optical axis of the first lens 22, and a second in a plane perpendicular to the optical axis of the second lens 23. And a second position adjustment stage 40 for adjusting the position of the lens 23.
[0058]
In the second group lens adjustment device 31, the optical axes of the beam expander 33, the collimator lens 34, and the beam splitter 36 coincide with the optical axis of the laser light emitted from the laser light source 32. Further, an aperture 43 provided in the lens mounting portion 3 described later has a center that coincides with the optical axis of the laser beam.
[0059]
The laser light source 32 is an SHG green laser and emits laser light having a wavelength of 532 nm. The laser light source 32 is positioned so that the optical axis of the laser light coincides with the center of the aperture 43 of the lens mounting portion 35 and is perpendicular to the reference surface 41 of the lens mounting portion 35. The laser light source 32 is positioned with sufficient accuracy using, for example, a Michelson interferometer. The laser light emitted while spreading from the laser light source 32 is incident on the beam expander 33.
[0060]
The beam expander 33 further expands the laser beam and emits it toward the collimator lens 34.
[0061]
The collimator lens 34 radiates the laser beam from the beam expander 4 that is incident while spreading, and emits the collimated lens 34 toward the lens mounting portion 35.
[0062]
The lens placement portion 35 includes a reference surface 41 on which the second group lens 21 is placed, and a circular hole 42 that is located in a portion on which the second group lens 21 is placed and is a circular through hole. It is configured. An aperture portion 43 is provided in the circular hole 42 of the lens placement portion 35.
[0063]
The aperture portion 43 is formed to have a diameter slightly smaller than the circular hole 42. Specifically, the inner diameter of the aperture portion 43 is slightly smaller than the outer diameter of the spherical portion of the first surface 24 of the second group lens 21. As described above, the aperture unit 43 has an axial center that coincides with the optical axis of the laser light emitted from the laser light source 32.
[0064]
Therefore, the lens mounting unit 35 narrows the laser beam in the aperture unit 43 from the collimator lens 34 incident on the first surface 24 of the second group lens 21 mounted on the reference surface 41. As a result, the light incident on the second group lens 21 via the aperture 43 becomes light including a diffraction component. As will be described later, the adjusting device 31 for the second group lens adjusts the eccentricity of the second lens 23 with respect to the first lens 22 based on the diffraction pattern formed by this diffraction component.
[0065]
The light transmitted through the second group lens 21 through the aperture unit 43 is incident on the beam splitter 36. In addition, since the light transmitted through the second group lens 21 forms a focal point immediately after exiting from the fourth surface 27, light having a focal point forming word is incident on the beam splitter 35.
[0066]
The beam splitter 36 is formed with a reflecting surface 36 a, and the beam splitter 36 reflects the light transmitted through the second group lens 21 by the reflecting surface 36 a and emits it toward the CCD camera 37.
[0067]
The CCD camera 37 receives light reflected by the reflecting surface 36a of the beam splitter 36 on the light receiving surface 37a. The light receiving surface 37a of the CCD camera 37 has a position detection resolution with an accuracy of about 0.5 mm. Further, since the CCD camera 37 is positioned, the CCD camera 37 is supported so as to be movable in the optical axis direction and in two axial directions perpendicular to the optical axis.
[0068]
The light received on the light receiving surface 37 a of the CCD camera 37 is displayed on the monitor 38. Since the light incident on the light receiving surface 37 a of the CCD camera 37 includes a diffraction component through the aperture 43, a light diffraction pattern is displayed on the monitor 37.
[0069]
As shown in FIG. 6, the CCD camera 37 is positioned in advance by transmitting laser light from an aperture portion 43 formed in the lens placement portion 35.
[0070]
First, the laser light from the laser light source 32 is incident on the aperture unit 43 formed on the lens mounting unit 35 via the beam expander 33 and the collimator lens 34. The laser light incident on the aperture portion 43 and emitted through the aperture portion 43 becomes light including a diffraction component. The light containing the diffraction component is received by the light receiving surface 37 a of the CCD camera 37 through the reflecting surface 36 a of the beam splitter 36. A diffraction pattern of light transmitted through the first lens 22 is displayed on the monitor 38.
[0071]
The CCD camera 37 is positioned such that the center of the diffraction pattern coincides with the center of the light receiving surface 37 a of the CCD camera 37.
[0072]
Note that the CCD camera 37 is disposed at a distance of 1 m on the optical axis, for example, so that the distance on the optical axis from the second group lens 21 becomes longer. At this position, the pitch of the diffraction pattern is approximately 1 mm.
[0073]
After the CCD camera 37 is positioned in this manner, as shown in FIG. 5, the first lens 22 is first fitted into the circular portion 52 of the lens mounting portion 35 and placed on the reference surface 41, and the lens It is positioned with respect to the mounting portion 35.
[0074]
Then, the laser light from the laser light source 32 is incident on the first lens 22 via the beam expander 33, the collimator lens 34, and the aperture unit 43.
[0075]
The light incident on the first lens 22 includes a diffraction component by the aperture 43 and is received by the light receiving surface 37a of the CCD camera 37 via the reflecting surface 36a of the beam splitter 36. The first lens 22 is performed by the first position adjustment stage 39, and is positioned by the lens mounting portion 35 so that the center of the diffraction pattern coincides with the center of the light receiving surface 37 a of the CCD camera 37.
[0076]
Therefore, since the second group lens adjustment device 31 positions the first lens 22 with respect to the lens mounting portion 35 based on the diffraction pattern of the light transmitted through the first lens 22, even if the first lens 22 is positioned. Even if the accuracy of the outer shape of the lens 22 is not good, the adjustment can be made with high precision.
[0077]
After the first lens 22 is positioned with respect to the lens mounting portion 35 in this way, the second lens 23 is attached on the first lens 22 via the spacer, and as described above, The eccentricity of the second lens 23 with respect to the lens 22 is adjusted.
[0078]
For example, when the second lens 23 is eccentric with respect to the first lens 22, the center of the diffraction pattern of the second group lens 21 is received with a deviation from the center of the light receiving surface 37 a of the CCD camera 37. Become.
[0079]
The eccentricity of the second lens 23 is adjusted by the second position adjustment stage 40 while looking at the monitor 38, and the light transmitted through the second group lens 21 at the center of the light receiving surface 37 a of the CCD camera 37. The centers of the diffraction patterns are matched.
[0080]
Therefore, the second group lens adjusting device 31 adjusts the eccentricity of the second lens 23 with respect to the first lens 22 based on the diffraction pattern of the light transmitted through the first lens 22 and the second lens 23. Therefore, even if the accuracy of the outer shape of the first lens 22 and the second lens 23 is not good, the eccentricity can be adjusted with high accuracy. Therefore, the second group lens 21 having sufficient optical characteristics can be provided even if the outer shape accuracy of the mold used to mold the first lens 22 and the second lens 23 is not obtained.
[0081]
Since the second group lens adjusting device 31 determines the center of the optical axis based on the center of the diffraction pattern, it can obtain higher detection sensitivity than the conventional means for determining the center of the optical axis from the light amount distribution or the beam pattern.
[0082]
For example, as described above, the second group lens adjusting device 31 is configured such that the distance on the optical axis between the second group lens 21 and the CCD camera 37 is approximately 1 m (L). Then, when the position detection resolution of the light receiving surface 37a of the CCD camera 37 is about 0.5 mm (d), and the focal length of the second lens group 21 is about 2.5 mm (f), the second relative to the first lens 22 is obtained. The detection sensitivity Δe of the amount of eccentricity of the lens 23 is 1.25 × 10 as obtained by the equation (2). ^-3 μm.
[0083]

As described above, the adjusting device 31 of the second lens group detects the center of the diffraction pattern by the CCD camera 37 far from the second lens group 21, thereby improving the detection sensitivity of the eccentricity amount and adjusting the eccentricity. Has improved.
[0084]
Next, a third embodiment of the present invention will be described. The third embodiment is an apparatus configured by applying an adjustment method of an objective lens for an optical pickup that adjusts a second group lens included in the optical pickup, and the distance between the first lens and the second lens is set. This is an adjusting device for the second group lens to be adjusted.
[0085]
Specifically, as shown in FIG. 7, the adjusting device for the second group lens has light incident on the third surface 26 of the second lens 23 facing the first lens 22 via the first lens 22. The distance between the first lens and the second lens is adjusted by detecting the beam diameter of the light obtained by the reflected light again through the first lens 22.
[0086]
As described with reference to FIG. 2 in the first embodiment, the second group lens 21 includes the first surface 24 on which the laser light from the semiconductor laser is incident and the laser incident from the first surface 24. A first lens 22 composed of a second surface 25 that emits light toward the second lens 23, and a third surface on which laser light from the semiconductor laser that has passed through the first lens 22 is incident 26 and a second lens 23 composed of a fourth surface 27 which is a surface facing the optical disk 29.
In the second group lens 21, the first lens 22 and the second lens 23 are opposed to each other through a spacer. For example, the distance between the first lens 22 and the second lens 23 is such that the laser beam from the semiconductor laser transmitted through the first lens 22 is perpendicular to the third surface 26 of the second lens 23. Is determined to be an optimum distance so as to be incident on the beam.
[0087]
As shown in FIGS. 7 and 8, the adjusting device 51 for the second group lens includes a laser light source 52 that emits laser light, and a beam expander that emits the laser beam emitted from the laser light source 52 with an expanded beam diameter. 53, a collimator lens 54 that collimates the incident laser light while being spread by the beam expander 53, and a second group lens 21 to be adjusted are mounted, and light from the collimator lens 54 is incident thereon. And the light reflected on the third surface 26 of the second lens group 21 placed between the lens placement portion 55 and the collimator lens 54 and the lens placement portion 55 and placed on the lens placement portion 55. Is detected, and the spot diameter of the light reflected by the third surface 26 and reflected by the reflecting surface 56a of the beam splitter 56 is detected. A CCD camera 57, a monitor 58 that displays an image received by the CCD camera 57, and a first position adjustment stage 59 that adjusts the position of the first lens 22 in a plane perpendicular to the optical axis of the first lens 22. And a second position adjustment stage 60 that moves and adjusts the second lens 23 in the optical axis direction of the second lens 23, and a displacement sensor 61 that detects the feed amount of the second position adjustment stage 60. Composed.
[0088]
In the second group lens adjusting device 51, the optical axes of the beam expander 53, the collimator lens 54, and the beam splitter 56 coincide with the optical axis of the laser light emitted from the laser light source 52. Further, an aperture 64 portion provided in a lens mounting portion 55 described later has a center coincident with the optical axis of the laser beam.
[0089]
The laser light source 52 is an SHG green laser and emits laser light having a wavelength of 532 nm. The laser light source 52 is positioned so that the optical axis of the laser light coincides with the center of the aperture portion 64 of the lens placement portion 55 and is perpendicular to the reference surface 62 of the lens placement portion 55. The positioning of the laser light source 52 is performed with sufficient accuracy using, for example, a Michelson interferometer. Then, the laser light emitted from the laser light source 52 enters the beam expander 53.
[0090]
The beam expander 53 further spreads the incident laser beam while expanding the beam diameter, and emits it toward the collimator lens 54.
[0091]
The collimator lens 54 emits the laser beam from the beam expander 53 that is incident while spreading toward the beam splitter 56 as parallel light.
[0092]
The beam splitter 56 transmits the laser light from the collimator lens 54. The beam splitter 56 has a reflecting surface 56a. The beam splitter 56 reflects the reflected light from the third surface 26 toward the CCD camera 57 by the reflecting surface 56a, as will be described later. To do. Therefore, the beam splitter 56 transmits the laser light from the collimator lens 54. The laser light that has passed through the beam splitter 56 is incident on the second group lens 21 placed on the lens placement portion 55.
[0093]
The lens placing portion 55 includes a reference surface 62 on which the second group lens 21 is placed, and a circular hole 63 that is a through hole formed in a circular shape and located on a portion on which the second group lens 21 is placed. It is composed of An aperture portion 64 is provided in the circular hole 63 of the lens placement portion 55.
[0094]
The aperture portion 64 is formed to have a diameter slightly smaller than the circular hole 63. Specifically, the inner diameter of the aperture portion 64 is slightly smaller than the outer diameter of the spherical surface portion of the first surface 24 of the second group lens 21. As described above, the axial center of the aperture portion 64 coincides with the optical axis of the laser beam.
[0095]
Therefore, the lens placing portion 55 narrows the laser light incident on the first surface 24 of the second group lens 21 placed on the reference surface 62 at the aperture portion 64.
[0096]
The light incident on the first surface 24 of the second group lens 21 passes through the first lens 22 and is emitted from the second surface 25. The light emitted from the second surface 25 is incident on the third surface 26 of the second lens 23.
[0097]
The third surface 26 reflects part of the light from the second surface 25 toward the second surface 25. The second group lens adjustment device 51 adjusts the distance between the first lens 22 and the second lens 23 based on the reflected light reflected by the third surface 26.
[0098]
The reflected light from the third surface 26 incident on the second surface 25 is transmitted through the first lens 22 and emitted from the first surface 24 toward the beam splitter 56.
[0099]
The beam splitter 56 reflects the reflected light emitted from the first surface 24 of the second lens group 21 toward the CCD camera 57 by the reflecting surface 56a.
[0100]
The CCD camera 57 receives the reflected light from the beam splitter 56 on the light receiving surface 57a. The light receiving surface 57a of the CCD camera 57 has a position detection resolution with an accuracy of about 0.5 mm. The CCD camera 37 is supported so as to be movable in the optical axis direction and in two axial directions perpendicular to the optical axis.
[0101]
The light received on the light receiving surface 57 a of the CCD camera 57 is displayed on the monitor 58. The light reflected by the third surface 26 is received by the light receiving surface 57 a of the CCD camera 57 as substantially parallel light through the first lens 22 and the beam splitter 56. Therefore, the reflected light is projected as a spot on the monitor 58.
[0102]
As shown in FIG. 8, the CCD camera 57 irradiates a laser beam from a laser light source 52 onto a flat plate 65 having a flat plate portion 65a placed on the reference surface 62 of the lens mounting portion 55 and having a so-called optical flat. Thus, the positioning is performed in advance.
[0103]
The flat plate 65 has a substantially rectangular cross section and is provided with a flat surface 65a that is flush with the mounted reference surface 62. The laser light from the laser light source 52 is applied to the flat portion 65 a of the flat plate 65.
[0104]
That is, the flat surface portion 65 a of the flat plate 65 is irradiated with laser light from the laser light source 52 via the beam expander, the collimator lens 54, the beam splitter 56, and the aperture portion 64.
[0105]
The flat portion 65a of the flat plate 65 reflects the irradiated laser light. Here, the optical axis of the laser beam coincides with the incidence and reflection with respect to the flat portion 65 a of the flat plate 65.
[0106]
The reflected light from the flat portion 65 a of the flat plate 65 is reflected by the reflecting surface 56 a of the beam splitter 56 and received by the light receiving surface 57 a of the CCD camera 57. On the monitor 58, a spot of reflected light from the flat surface portion 65a of the flat plate 65 incident on the light receiving surface 57a of the CCD camera 57 is displayed. The CCD camera 57 is positioned by adjusting the position of the CCD camera 57 while looking at the monitor 58 so that the spot center coincides with the center of the light receiving surface 57a.
[0107]
The distance between the first lens 22 and the second lens 23 is adjusted using the diameter of the spot formed by the reflected light from the flat portion 65a of the flat plate 65 as a reference plane.
[0108]
The CCD camera 57 is disposed at a position where the distance on the optical axis is 0.9 m, for example, so that the distance on the optical axis from the third surface 26 of the second group lens 21 becomes longer.
[0109]
As described above, the adjustment device 51 for the second group lens in which the CCD camera 57 is positioned is provided between the first lens 22 and the second lens 23 of the second group lens 21 placed on the lens placement portion 55. The distance is adjusted.
[0110]
For example, in the normal second group lens 21, the distance between the first lens 22 and the second lens 23 is such that the light emitted from the second surface 25 is perpendicular to the third surface 26 as described above. It is set to enter. Therefore, the light from the second surface 25 reflected by the third surface 26 is also emitted perpendicular to the third surface 26.
[0111]
However, if the distance between the first lens 22 and the second lens 23 is different from the normal setting, the light emitted from the second surface 25 is perpendicular to the third surface 26. Is not incident on. Then, no light is emitted perpendicularly to the third surface 26 from the second surface 25 reflected by the third surface 26.
[0112]
Therefore, the reflected light from the third surface 26 when the distance between the first lens 22 and the second lens 23 is different from the normal setting is a spot obtained by the flat portion 65 a of the flat plate 65. The light is received by the light receiving surface 57a of the CCD camera 57 with a spot diameter smaller or larger than the diameter.
[0113]
The adjustment of the distance between the first lens 22 and the second lens 23 is performed by the second position adjustment stage 60 while looking at the monitor 58, and the spot of the reflected light from the third surface 26. The diameter is made equal to the reference spot diameter obtained by the flat plate 65.
[0114]
Therefore, the adjusting device 51 for the second group lens adjusts the distance between the first lens 22 and the second lens 23 based on the reflected light reflected on the third surface 26 of the second lens 23. Therefore, even if the accuracy of the outer shape of the first lens 22 or the second lens 23 is not good, the distance can be adjusted with high accuracy. Therefore, the second group lens 21 having sufficient optical characteristics can be provided even if the outer shape accuracy of the mold used to mold the first lens 22 and the second lens 23 is not achieved.
[0115]
For example, as shown in FIG. 2, the glass substrate 29b of the optical disk is designed to be 0.1 mm, and the distance between the surface of the glass substrate 29b and the fourth surface 27, that is, the working distance is 0.1 mm. The second group lens 21 is designed so that the spherical radius of the surface 26 is 1.25 mm and the distance between the third surface 26 and the fourth surface 27, that is, the lens thickness of the second lens 23 is 1.4 mm. The change in the spot diameter when the distance between the first lens 22 and the second lens 23 changes is as follows.
[0116]
On the optical axis, the CCD camera 57 is disposed 0.9 m away from the third surface 26 of the second lens 23.
[0117]
For example, when the distance between the first lens 22 and the second lens 23 is 0.543 mm larger than the optimum distance, the spot diameter at the light receiving portion 57a of the CCD camera 57 is 4.9 mm. When the distance between the first lens 22 and the second lens 23 is 0.563 mm larger than the optimum distance, the spot diameter at the light receiving portion 57a of the CCD camera 57 is 8.5 mm.
[0118]
Therefore, since the position detection resolution of the light receiving surface 57a of the CCD camera 57 is 0.5 mm, the resolution Y of the distance of the second lens 23 with respect to the first lens 22 can be obtained by equation (3). 2.8 μm.
[0119]

As described above, the adjusting device 51 for the second lens group detects the reflected light from the third surface 26 of the second lens 23 at a distance, thereby amplifying the displacement amount of the distance and improving the detection sensitivity. The accuracy of adjusting the distance is improved.
[0120]
Further, the second group lens adjusting device 51 can arbitrarily set the distance between the first lens 22 and the second lens 23. For example, the light from the second surface 25 is incident on the third surface 26 at an arbitrary angle.
[0121]
In this case, first, the light from the second surface 25 is adjusted so as to be perpendicularly incident on the third surface 26. And after calculating | requiring the relationship between the distance change of the 1st lens 22 and the 2nd lens 23, and the incident angle change of the light from the 2nd surface 25 which injects into the 3rd surface 26 by calculation, The second lens 23 is appropriately moved by the second position adjustment stage 60. Thereby, the distance between the 1st lens 22 and the 2nd lens 23 can be changed arbitrarily.
[0122]
If the feed amount of the second position adjustment stage 60 is controlled by the displacement sensor 61 having a detection accuracy of 1 μm or less, the distance between the first lens 22 and the second lens 23 is accurate to 1 μm or less. It can also change.
[0123]
Next, a fourth embodiment of the present invention will be described. The fourth embodiment is an apparatus for adjusting a second group lens that adjusts the tilt, decentering, and distance of the second lens with respect to the first lens of the second group lens provided in the optical pickup.
[0124]
As described with reference to FIG. 2 in the first embodiment, the second group lens includes the first surface 24 on which the laser beam from the semiconductor laser is incident and the laser beam incident from the first surface 24. A first lens 22 composed of a second surface 25 that emits light toward the second lens 23, and a third surface 26 on which laser light from a semiconductor laser that has passed through the first lens 22 is incident. The second lens 23 includes a fourth surface 27 that is a surface facing the optical disk 29.
[0125]
In the second lens group 21, the first lens 22 and the second lens 23 are separated by a spacer.
[0126]
The second group lens adjusting device detects the inclination and eccentricity of the second lens 23 with respect to the first lens 22, and as shown in FIG. 9, a lens placement portion on which the second group lens 21 is placed. 72, a first laser light source 73 that emits laser light toward the fourth surface 27 of the second group lens 21 placed on the lens placement portion 72, a first laser light source 73, and the lens placement portion. 72, the first beam expander 74, the condensing lens 75, the first beam splitter 76, and the lens mounting portion 72 via the reflection surface 76a of the first beam splitter 76. The first CCD camera 77 for detecting the reflected light from the fourth surface of the second group lens 21 to be placed, and disposed between the first beam splitter 76 and the first CCD camera 77. Reflected by the reflecting surface 76a of the beam splitter 76 A second CCD camera 78 for detecting a diffraction pattern of laser light from a second laser light source 79 (described later) that is transmitted light and passes through the first lens 22 and the second lens 23, and a condenser lens 75. And a first beam splitter 76 that are movably supported and mechanical shutters that shield the laser light from the first laser light source 73 from the second group lens 21 placed on the lens placement portion 72. 90.
[0127]
The first beam expander 74, the condensing lens 75, and the first beam splitter 76 have optical axes that coincide with the optical axis of the laser light emitted by the first laser light source 73.
[0128]
Further, the second group lens adjusting device 71 detects the distance between the first lens 22 and the second lens 23, and is mounted on the lens mounting portion 72 as shown in FIG. A second laser light source 79 that irradiates the third surface 26 with laser light via the first lens 22, and between the second laser light source 79 and the lens mounting portion 72. The second beam expander 80, the collimator lens 81, the second beam splitter 82, and the spot diameter of the reflected light from the third surface 26 reflected by the third surface 26 are detected. 3 CCD cameras 83.
[0129]
Further, the second group lens adjustment device 71 includes a second position adjustment stage 84 that adjusts the position of the first lens 22 of the second group lens 21 placed on the lens placement portion 72, and a second lens. The second position adjusting stage 85 for adjusting the position 23 and a displacement sensor 86 for detecting the feed amount of the second position adjusting stage 85 are provided.
[0130]
The second group lens adjusting device 71 includes a first monitor 87, a second monitor 88, and a second monitor 88 that project images received by the first CCD camera 77, the second CCD camera 78, and the third CCD camera 83. And a third monitor 89.
[0131]
The second beam expander 80, the collimator lens 81, and the second beam splitter 82 have optical axes that coincide with the optical axis of the laser light emitted by the second laser light source 79.
[0132]
In the second group lens adjusting device 71, the first laser light source 73 and the second laser light source 79 have the same optical axis for the emitted laser light. Further, the optical axes of the laser beams of the first laser light source 73 and the second laser light source 79 coincide with the axial center of the aperture section 93 provided in the lens mounting section 72 described later.
[0133]
On the optical axis, the first CCD camera 77 is arranged at a position approximately 5 m away from the fourth surface 27 of the second group lens 21 placed on the lens placement section 72, and the second The CCD camera 77 is disposed at a position approximately 1 m away from the second group lens 21 placed on the lens placement portion 72, and the third CCD camera 83 is placed on the lens placement portion 72. The second group lens 21 is disposed at a position approximately 0.9 m away from the third surface 25.
[0134]
The second lens group 21 is adjusted in the inclination, eccentricity, and distance of the second lens 23 with respect to the first lens 22 in the lens mounting portion 72 of the adjusting device 71 of the second lens group configured as described above. It is assembled while.
[0135]
Specifically, the first lens 22 of the second group lens 21 is first placed on the reference surface 91 of the lens placement portion 72 and positioned. A second lens 23 is disposed on the positioned first lens 22 via a spacer. At this time, the first lens 22 and the second lens 23 are not bonded to the spacer. The tilt of the second lens 23 is adjusted with respect to the first lens 22. After the inclination is adjusted, the eccentricity of the second lens 23 with respect to the first lens 22 is adjusted. After the eccentricity is adjusted, the distance between the second lens 23 and the first lens 22 is adjusted.
[0136]
Hereinafter, the adjustment of the inclination, eccentricity, and distance of the second lens 23 with respect to the first lens 22 in the adjusting device 71 for the second group lens will be described in more detail.
[0137]
The second group lens adjustment device 71 causes the first laser light source 73 to emit laser light for adjusting the inclination of the second lens 23 with respect to the first lens 22.
[0138]
The first laser light source 73 is a He—Ne laser and emits laser light having a wavelength of 632 nm. The laser light source 73 is positioned so that the optical axis of the laser light coincides with the center of the opening 92 of the lens mounting portion 72 and is perpendicular to the reference plane. Note that the positioning of the first laser light source 73 is performed with sufficient accuracy using, for example, a Michelson interferometer.
[0139]
The laser light emitted from the first laser light source 73 is incident on the first beam expander 74 and the condenser lens 75. The first beam expander 74 and the condensing lens 75 appropriately adjust and focus the incident laser light from the first laser light source 73 and emit it toward the first beam splitter 76.
[0140]
The first beam splitter 76 transmits the laser light focused by the first beam expander 74 and the condenser lens 75 toward the lens mounting portion 72 on which the second group lens 21 is mounted.
[0141]
The lens mounting portion 72 includes a reference surface 91 on which the second group lens 21 is mounted, and a circular hole 92 that is a circular through hole that is positioned on the portion on which the second group lens 21 is mounted. It is configured. An aperture portion 93 is provided in the circular hole 92 of the lens placement portion 72.
[0142]
The aperture portion 93 is formed to have a diameter slightly smaller than the circular hole 92. Specifically, the inner diameter of the aperture portion 93 is slightly smaller than the outer diameter of the spherical surface portion of the first surface 24 of the second group lens 21. As described above, the axial center of the aperture portion 93 coincides with the optical axis of the laser beam emitted from the first laser light source 73.
[0143]
The lens mounting portion 72 holds the second group lens 21 mounted on the reference surface 91 by fitting the first surface 24 with the circular hole 92.
[0144]
The second group lens 21 placed on the reference surface 91 is incident on the fourth surface 27 with the laser light transmitted through the first beam splitter 76. The fourth surface 27 reflects a part of the incident laser light toward the first beam splitter 76.
[0145]
The first beam splitter 76 reflects the reflected light from the fourth surface 27 toward the first CCD camera 77 by the anti-slope 76 a. The reflected light is reflected by the reflecting surface 76a of the first beam splitter 76, and then a focal point is formed.
[0146]
The focal point of the reflected light is received by the light receiving surface 77 a of the first CCD camera 77.
[0147]
The first CCD camera 77 is performed by placing the flat plate 14 on the lens placing portion 72 as described with reference to FIG. 3 in the first embodiment. That is, the first CCD camera 77 is positioned so that the focal point of the reflected light from the flat surface portion 14a of the flat plate 14 formed after reflecting the reflecting surface 76a of the first beam splitter 76 is located at the center of the light receiving surface 77a. ing.
[0148]
Therefore, the reflected light reflected by the fourth surface 27 of the second group lens 21 is received by the light receiving surface 77a of the first CCD camera 77 positioned as described above.
[0149]
Then, the inclination of the second lens 23 is adjusted by the second position adjustment stage 85 while looking at the monitor 87, and the reflected light from the fourth surface 27 is centered on the light receiving surface 77 a of the CCD camera 77. Match the focus.
[0150]
Therefore, since the second group lens adjustment device 71 adjusts the inclination of the second lens 23 with respect to the first lens 22 based on the reflected light from the fourth surface 27 of the second lens 23, Even if the accuracy of the outer shape of the second lens 23 is not good, the tilt can be adjusted with high accuracy.
[0151]
The second group lens adjusting device 71 adjusts the inclination of the second lens 23 relative to the first lens 22 by the focus of the reflected light from the fourth surface 27, so Even if the position detection sensitivity of the light receiving surface 77a is small, the tilt can be adjusted with high accuracy.
[0152]
As described above, the second group lens adjusting device 71 is configured such that the distance between the fourth surface 27 and the focal position of the reflected light is approximately 5 m. This is because the position detection sensitivity is improved by increasing the distance between the fourth surface 27 and the focus detection position.
[0153]
For example, the position detection resolution of the light receiving surface 77a of the first CCD camera 77 is about 0.5 mm, and the distance between the fourth surface 27 on the optical axis and the first CCD camera 77 is about 5 m. The detection resolution X of the inclination of the lens 23 is 0.05 mrd as obtained by the above equation (1).
[0154]
The second group lens adjusting device 71 thus forms the focal point of the reflected light from the fourth surface 27 in the distance and amplifies the displacement amount of the focal point, thereby improving the position detection sensitivity and tilting. The adjustment accuracy is improved.
[0155]
After adjusting the inclination of the second lens 23 as described above, the second group lens adjusting device 71 adjusts the eccentricity of the second lens 23 with respect to the first lens 22.
[0156]
Adjustment of the eccentricity of the second lens 23 with respect to the first lens 22 is performed by irradiating the second group lens 21 with laser light from the second laser light source 79 from the first surface 24 side.
[0157]
The second laser light source 79 is an SHG green laser and emits laser light having a wavelength of 532 nm. The second laser light source 79 is positioned so that the optical axis of the laser beam coincides with the center of the aperture 93 of the lens mounting portion 72 and is perpendicular to the reference surface 91 of the lens mounting portion 72. . The positioning of the second laser light source 79 is performed with sufficient accuracy using, for example, a Michelson interferometer. Then, the laser light emitted from the second laser light source 79 is incident on the second beam expander 80 and the collimator lens 81. The laser light emitted from the second laser light source 79 becomes parallel light after the beam diameter is expanded by the second beam expander 80 and the collimator lens 81, and is emitted toward the second beam splitter 82. Is done.
[0158]
The second beam splitter 82 transmits the laser light from the collimator lens 81 toward the lens mounting portion 72. Then, the laser beam from the second beam splitter 82 is incident on the first lens 22 of the second group lens 21 through the aperture section 93 formed in the lens mounting section 72. Here, the light incident on the first lens 22 includes a diffraction component by the aperture section 93.
[0159]
The light incident on the first lens 22 is emitted toward the first beam splitter 76 via the second lens 23.
[0160]
The light transmitted through the second group lens 21 is light having a widened beam diameter in order to form a focal point immediately after emission from the fourth surface 27.
[0161]
As described above, the reflection surface 76a is formed on the first beam splitter 76, and the first beam splitter 76 transmits light from the second group lens 21 to the second CCD camera by the reflection surface 76a. It emits toward 78.
[0162]
The second CCD camera 78 receives light reflected by the reflecting surface 76a of the beam splitter 76 on the light receiving surface 78a.
[0163]
Note that the second CCD camera 78 is positioned between the first beam splitter 76 and the first CCD camera 77 at the time of detection, but prevents detection of the first CCD camera 77 at the time of non-detection. It is evacuated so as not to become.
[0164]
As described with reference to FIG. 6 in the second embodiment, the second CCD camera 78 has a diffraction pattern of laser light transmitted through the aperture section 93 provided in the lens mounting section 72. Originally positioned. The first lens 22 is also positioned with respect to the lens mounting portion 93 based on the diffraction pattern, as described with reference to FIG.
[0165]
Accordingly, the light transmitted through the second group lens 21 is received by the light receiving surface 78a of the second CCD camera 78 positioned as described above.
[0166]
The eccentricity of the second lens 23 is adjusted by the second position adjusting stage 85 while looking at the second monitor 88, and the second group lens is formed at the center of the light receiving surface 78a of the second CCD camera 78. The center of the diffraction pattern of the light transmitted through 21 is matched.
[0167]
Therefore, the second group lens adjustment device 71 adjusts the eccentricity of the second lens 23 relative to the first lens 22 based on the diffraction pattern of the light transmitted through the first lens 22 and the second lens 23. Therefore, even if the accuracy of the outer shape of the first lens 22 and the second lens 23 is not good, the eccentricity can be adjusted with high accuracy.
[0168]
Since the second group lens adjusting device 71 determines the center of the optical axis based on the center of the diffraction pattern, it can obtain a higher detection sensitivity than the conventional means for determining the center of the optical axis from the light amount distribution or the beam pattern.
[0169]
For example, the position detection resolution of the light receiving surface 78a of the second CCD camera 78 is about 0.5 mm, the focal length of the second group lens 21 is about 2.5 mm, the second group lens 21 on the optical axis and the second CCD camera 78. Since the distance to the first lens 22 is about 1 m, the detection sensitivity Δe of the eccentric amount of the second lens 23 relative to the first lens 22 is 1.25 × 10 as obtained from the above equation (2). ^-3 μm.
[0170]
In this way, the second group lens adjustment device 71 detects the center of the diffraction pattern far away from the second group lens 21 by the second CCD camera 78, so that the sensitivity of detecting the eccentricity is improved and the eccentricity is improved. The adjustment accuracy is improved.
[0171]
After adjusting the inclination and eccentricity of the second lens 23 as described above, the second group lens adjusting device 71 adjusts the distance between the first lens 22 and the second lens 23.
[0172]
The distance between the first lens 22 and the second lens 23 is determined by irradiating a laser beam from the second laser light source 79. The laser light emitted from the second laser light source 79 is incident on the first surface 24 of the second group lens 21 via the second beam expander 80, the collimator lens 81, and the second beam splitter 82.
[0173]
The laser light incident on the first surface 24 passes through the first lens 22 and is emitted from the second surface 25. The light emitted from the second surface 25 is incident on the third surface 26.
[0174]
The normal second group lens 21 has a distance between the first lens 22 and the second lens 23 so that the light from the second surface 25 is incident on the third surface 26 perpendicularly. Is set.
[0175]
The third surface 26 reflects part of the light from the second surface 25. The reflected light reflected by the third surface 26 is incident on the second surface 25, passes through the first lens 22 again, and comes to the office from the first surface 24 toward the second beam splitter 82. The
[0176]
The second beam splitter 82 has a reflecting surface 82a. The second beam splitter 82 reflects the reflected light emitted from the first surface 24 by the third CCD camera 83 by the reflecting surface 82a. Exit toward
[0177]
The third CCD camera 83 receives the reflected light reflected by the anti-inclined surface 82a of the second beam splitter 82 on the light receiving surface 83a.
[0178]
As described with reference to FIG. 8 in the third embodiment, the third CCD camera 83 is positioned by mounting the flat plate 65 on the lens mounting portion 72.
[0179]
That is, the third CCD camera 83 is positioned so that the spot center of the light reflected by the flat portion 65a of the flat plate 65 placed on the lens placement surface 72 coincides with the center of the light receiving surface 83a.
[0180]
Therefore, the reflected light from the third surface 26 reflected by the reflecting surface 82a of the beam splitter 82 is received by the light receiving surface 83a of the third CCD camera 83 positioned as described above.
[0181]
Then, the adjustment of the distance between the first lens 22 and the second lens 23 is performed by the second position adjustment stage 85 while looking at the third monitor 89, and the reflection from the third surface 26. The spot diameter of light is made the same as the reference spot diameter obtained by the flat plate 65.
[0182]
Therefore, the second group lens adjusting device 71 adjusts the distance between the first lens 22 and the second lens 23 based on the reflected light reflected by the third surface 26 of the second lens 23. Therefore, even if the accuracy of the outer shape of the first lens 22 or the second lens 23 is not good, the distance can be adjusted with high accuracy.
[0183]
Further, since the position detection resolution of the light receiving surface 83a of the third CCD camera 83 is 0.5 mm, the resolution Y of the distance of the second lens 23 relative to the first lens 22 is obtained by the above equation (3). As shown, it becomes 2.8 μm.
[0184]
Thus, the second group lens adjusting device 71 detects the reflected light from the third surface 26 of the second lens 23 at a distance, thereby amplifying the displacement amount of the distance and improving the detection sensitivity. The accuracy of adjusting the distance is improved.
[0185]
As described above, the second lens group 21 in which the tilt, eccentricity, and distance of the second lens 23 with respect to the first lens 22 are adjusted is fixed by bonding the first lens 22 and the second lens 23 to the spacer. Is done.
[0186]
As described above, the second group lens adjusting device 71 irradiates the second group lens 21 with laser light, and tilts or deviates the second lens 23 relative to the first lens 22 based on the transmitted light or reflected light. Since the core and distance are adjusted, the tilt, eccentricity, and distance can be adjusted precisely even if the accuracy of the outer shape of the first lens 22 or the second lens 23 is not good.
[0187]
Therefore, the second group lens 21 having sufficient optical characteristics can be provided even if the outer shape accuracy of the mold used to mold the first lens 22 and the second lens 23 is not obtained.
[0188]
Furthermore, since the second group lens adjusting device 71 shares the optical components for adjusting the tilt, the eccentricity, and the distance, the cost is reduced. For example, the laser light source can be configured to include only the second laser light source 79. In this case, the laser light from the second laser light source 79 may be irradiated to the fourth surface 27 of the second group lens 21 by appropriately branching and reflecting the light using an optical lens.
[0189]
The second group lens adjustment device 71 can also arbitrarily set the distance between the first lens 22 and the second lens 23. For example, the light from the second surface 25 is incident on the third surface 26 at an arbitrary angle.
[0190]
In this case, first, the light from the second surface 25 is adjusted so as to be perpendicularly incident on the third surface 26. And after calculating | requiring the relationship between the distance change of the 1st lens 22 and the 2nd lens 23, and the incident angle change of the light from the 2nd surface 25 which injects into the 3rd surface 26 by calculation, The second lens 23 is appropriately moved by the second position adjustment stage 85. Thereby, the distance between the 1st lens 22 and the 2nd lens 23 can be changed arbitrarily.
[0191]
If the feed amount of the second position adjustment stage 85 is controlled by the displacement sensor 86 with a detection accuracy of 1 μm or less, the distance between the first lens 22 and the second lens 23 is an accuracy of 1 μm or less. Can also change.
[0192]
【The invention's effect】
The method for adjusting an objective lens for an optical pickup according to the present invention detects the position on the vertical surface of the reflected light from the facing surface of the second lens with respect to the optical axis at a distance from the facing surface, and the first lens and Even if the accuracy of the outer shape of the second lens is not good, the inclination of the second lens with respect to the first lens can be adjusted with high accuracy.
[0193]
In the method for adjusting an objective lens for an optical pickup according to the present invention, the outer shapes of the first lens and the second lens are detected by detecting a diffraction pattern of light transmitted through the first lens and the second lens. Even if the accuracy of the second lens is not good, the eccentricity of the second lens with respect to the first lens can be adjusted with high accuracy.
[0194]
Furthermore, in the method for adjusting an objective lens for an optical pickup according to the present invention, the reflection of light incident on the surface of the second lens facing the first lens through the first lens again causes the first lens to be reflected. The distance between the first lens and the second lens can be increased even if the accuracy of the outer shape of the first lens and the second lens is not good. It can be adjusted with accuracy.
[0195]
The optical pickup objective lens adjusting device according to the present invention is located far from the facing surface of the second lens of the second group lens placed on the reference surface, irradiated from the light source, and reflected by the facing surface. By detecting the reflected light, the first lens and the second lens can detect the position on the vertical surface of the reflected light from the facing surface with respect to the optical axis at a distance from the facing surface. Even if the accuracy of the outer shape is not good, the inclination of the second lens with respect to the first lens can be adjusted with high accuracy.
[0196]
In addition, the optical pickup objective lens adjusting device according to the present invention is positioned far from the facing surface of the second lens of the second group lens placed on the reference surface, irradiated from the light source, and reflected by the facing surface. First detection means for detecting the reflected light, second detection means for detecting the diffraction pattern of the light transmitted through the first lens and the second lens, and the second lens via the first lens. And a third detection means for detecting the beam diameter of the light obtained by the reflection of the light incident on the surface facing the first lens again through the first lens. Since the light is irradiated and the inclination, decentering, and distance of the second lens with respect to the first lens are adjusted based on the transmitted or reflected light, the outer shape of the first lens and the second lens Even if the accuracy of the shape is not good, its inclination and deviation are highly accurate. And the distance can be adjusted.
[Brief description of the drawings]
FIG. 1 is a second group lens adjusting apparatus according to a first embodiment of the present invention, and is a configuration diagram when a second group lens is placed.
FIG. 2 is a front view of a second group lens adjusted by the second group lens adjustment apparatus;
FIG. 3 is a configuration diagram when positioning a CCD camera included in the second group lens adjusting device according to the first embodiment;
FIG. 4 is a second group lens adjusting apparatus according to a second embodiment of the present invention, and is a configuration diagram when the second group lens is mounted;
FIG. 5 is a configuration diagram of the second group lens adjusting apparatus according to the second embodiment when the first lens is mounted;
FIG. 6 is a configuration diagram when positioning a CCD camera included in the second group lens adjusting apparatus according to the second embodiment;
FIG. 7 is an adjustment device for a second group lens according to a third embodiment of the present invention, and is a configuration diagram when the second group lens is placed.
FIG. 8 is a configuration diagram when positioning a CCD camera included in the second group lens adjusting apparatus according to the third embodiment;
FIG. 9 is a second group lens adjusting apparatus according to a fourth embodiment of the present invention, and is a configuration diagram when the second group lens is mounted;
FIG. 10 is a front view of a second group lens used for explaining the tilt, decentering, and distance adjustment of the second lens with respect to the conventional first lens.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Adjustment apparatus of 2 group lens, 2 Laser light source, 3 Lens mounting part, 7 CCD camera, 12 Reference surface, 21 2nd group lens, 22 1st lens, 23 2nd lens, 24 1st surface, 25 2nd surface, 26 3rd surface, 27 4th surface, 29 Optical disk, 31 2nd group lens adjustment apparatus, 32 Laser light source, 35 Lens mounting part, 37 CCD camera, 41 Reference surface, 51 2nd group lens Adjusting device, 52 laser light source, 55 lens mounting portion, 57 CCD camera, 59 first position adjusting stage, 60 second position adjusting stage, 62 reference surface, 71 second lens group adjusting device, 72 lens Placement part, 73 1st laser light source, 77 1st CCD camera, 78 2nd CCD camera, 79 2nd laser light source, 83 3rd CCD camera, 84 1st position adjustment stage, 85 1st 2 Position adjustment stage, 91 reference plane

Claims (10)

A two-group lens composed of a first lens and a second lens;
Reflection of light having a predetermined resolution and incident on the surface of the second lens facing the first lens through the first lens is obtained again through the first lens. Detection means for detecting the beam diameter;
Displacement means for displacing the distance between the first lens and the second lens;
An apparatus for adjusting an objective lens for an optical pickup that drives the displacement means to adjust the distance between the first lens and the second lens so that the beam diameter is the same as a reference beam diameter,
An apparatus for adjusting an objective lens for an optical pickup, characterized in that a distance between the detection means and the second group lens is determined by a displacement amount of the beam diameter with respect to a feed amount of the displacement means and a resolution of the detection means.   The reference beam diameter is a beam diameter formed on the detection means by light reflected on a plane perpendicular to the optical axis of the first lens for light incident on the first lens. The adjusting device for an objective lens for an optical pickup according to claim 1.   Reflection of light perpendicularly incident on the surface of the second lens facing the first lens from the first lens again has a reference beam diameter of the light detected through the first lens. 2. The adjusting device for an objective lens for an optical pickup according to claim 1, wherein a distance between the first lens and the second lens is set to an arbitrary value. An objective for an optical pickup that adjusts the inclination, decentering, and distance of the second lens with respect to the first lens of the second lens group consisting of a first lens and a second lens having a facing surface facing the optical recording medium In the lens adjustment device,
A light source;
A reference surface on which the second group lens is placed;
A first detection unit that has a predetermined resolution and that is positioned far from the facing surface of the second group lens placed on the reference surface, detects reflected light that is irradiated from the light source and reflected by the facing surface. Detection means;
Second detection means for detecting each diffraction pattern of light transmitted through the first lens and the second lens;
Reflection of light incident on the surface of the second lens facing the first lens through the first lens detects again the beam diameter of the light obtained through the first lens. 3 detection means;
Adjusting means for adjusting the inclination, decentering, and distance of the second lens with respect to the first lens based on the results detected by the first detection means to the third detection means;
An apparatus for adjusting an objective lens for an optical pickup, characterized in that the distance between the detection means and the facing surface is determined by the accuracy required for detecting the tilt of the lens and the resolution of the first detection means.   The first detection means detects a focal point of the reflected light formed by irradiating the light from the light source focused by a condenser lens onto the facing surface of the second lens. The adjustment apparatus of the objective lens for optical pick-ups of Claim 4. The second detection means is a distance determined by the focal length of the first lens and the second lens, the resolution of the second detection means, and the accuracy required to adjust the eccentricity. 5. The apparatus for adjusting an objective lens for an optical pickup according to claim 4, wherein the center position of the diffraction pattern is detected at a position distant from the group lens.   The distance between the third detection means and the second lens group depends on the displacement of the beam diameter with respect to the displacement of the distance between the first lens and the second lens and the resolution of the third detection means. 5. The adjusting device for an objective lens for an optical pickup according to claim 4, wherein the adjusting device is determined.   Instead of the first lens, a plane perpendicular to the optical axis of the first lens is arranged, and the beam diameter formed on the third detection means by the light reflected by the plane is defined as a reference beam diameter, and the reference The apparatus for adjusting an objective lens for an optical pickup according to claim 4, wherein a distance between the first lens and the second lens is adjusted so that a beam diameter matches.   Reflection of light perpendicularly incident on the surface of the second lens facing the first lens from the first lens was again detected by the third detection means via the first lens. The apparatus for adjusting an objective lens for an optical pickup according to claim 4, wherein a distance between the first lens and the second lens is set to an arbitrary value based on a reference beam diameter of light.   5. The objective lens adjustment device for an optical pickup according to claim 4, wherein the first detection means to the third detection means are imaging devices.

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