JP2004279075A

JP2004279075A - Lens eccentricity measuring method and measuring device

Info

Publication number: JP2004279075A
Application number: JP2003067673A
Authority: JP
Inventors: Kazuyuki Ogura; 和幸小椋; Masahiro Okitsu; 昌広興津; Hiroshi Hatano; 洋波多野
Original assignee: Minolta Co Ltd
Current assignee: Minolta Co Ltd
Priority date: 2003-03-13
Filing date: 2003-03-13
Publication date: 2004-10-07

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring method and a measuring device which measures the eccentricity quantity of a lens having at least one aspheric surface accurately in a short time. <P>SOLUTION: This measuring method includes processes for: allowing the aspheric axis of a first surface 1a to agree with the rotation axis of an air bearing 11 for holding the lens 1 by observing the first surface 1a whose eccentricity quantity is to be measured of the lens 1 comprising aspheric surfaces wherein the first surface 1a has an aspheric surface and a second surface 1b has a plane part 1c by an interferometer 20, and by adjusting an interference fringe in one color; and measuring runout of the plane part 1c and the second surface 1b by an optical lever 30, and measuring the parallel eccentricity quantity and the tilt eccentricity quantity of the lens 1, in the state where the lens 1 is rotated with the air bearing 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、レンズの偏芯測定方法及び測定装置、特に、少なくとも一方の面が非球面であるレンズの偏芯測定方法及び測定装置に関する。
【０００２】
【従来の技術と課題】
特許文献１：特開平１０−２７１４号公報
特許文献２：特開平１１−１４４９８号公報
特許文献３：特開２００１−１６５８０７号公報
【０００３】
従来、非球面レンズの偏芯の測定方法及び測定装置としては、トワイマン−グリーン干渉計やフィゾー干渉計を使用した位置決め計測による方法及び装置が知られており、特許文献１，２，３に開示されている。これらの測定方法においては、被検レンズの第１面と第２面の両方を干渉計によって観察し、干渉縞をワンカラーに調整することで、それぞれの面の非球面軸を求め、該非球面軸の位置関係から偏芯量を求めていた。
【０００４】
しかしながら、両面とも干渉計を用いる前記測定方法においては、第１面及び第２面を観察する干渉計の光軸を偏芯量の測定精度よりも十分に高い精度で合わせておく必要があった。例えば、平行偏芯量１μｍ以下、傾き偏芯量０．５分以下のような高精度を要求される測定においては、干渉計の光軸の精度は極めて高いものとなる。
【０００５】
このような高精度での測定のためには相当に高度な技術を要する作業となり、調整エラーが残ると偏芯量測定精度の低下を招く。加えて、干渉計での測定において干渉縞をワンカラーに合わせる工程は、ワンカラーの精度を非常に高く調整する必要があるため、被検レンズの両面について測定を行う際には長時間を要し、成形品（被検レンズ）の評価を抜き取り検査のごとくタイムラグを少なく行いたいときなどには不向きであった。
【０００６】
そこで、本発明の目的は、少なくとも一方の面が非球面であるレンズの偏芯量を精度よく、かつ、短時間で測定できる測定方法及び測定装置を提供することにある。
【０００７】
【発明の構成、作用及び効果】
以上の目的を達成するため、第１の発明は、少なくとも一方の面が非球面であるレンズの偏芯量を測定する測定方法であって、前記レンズの一方の面を干渉計で観察して干渉縞をワンカラーに調整する工程と、前記レンズのもう一方の面に設けた有効径部以外の平面部及び／又はもう一方の面にレーザ光を照射し、反射されたレーザ光のレンズ回転時における振れ量を測定する工程とを備えたことを特徴とする。
【０００８】
第１の発明に係る測定方法においては、被検レンズの一方の面を干渉計で観察してワンカラーに調整し、もう一方の面は有効径部以外の平面部及び／又はもう一方の面における光の反射方式（例えば、光てこの方法）により振れ量を測定する。即ち、第１の発明によれば、被検レンズのもう一方の面を光の反射方式で振れ量を高精度に測定でき、かつ、干渉計の光軸と測定回転軸の高精度な芯合わせが不要であり、一方の面のみを干渉計で測定するのであるから二つの干渉計の光軸を合わせるという極めて高精度を要する調軸作業が不要であり、短時間で偏芯量を測定することができる。
【０００９】
第２の発明は、一方の面が非球面、もう一方の面がその有効径部以外に平面部を有する非球面からなるレンズの偏芯量を測定する方法であって、前記一方の面を干渉計で観察して干渉縞をワンカラーに調整することで、一方の面の非球面軸をレンズを保持する軸受け部の回転軸と一致させる工程と、前記軸受け部でレンズを回転させた状態で、振れ量測定器により前記平面部及び前記もう一方の面の振れ量を測定し、該レンズの平行偏芯量及び傾き偏芯量を測定する工程とを備えたことを特徴とする。
【００１０】
第２の発明に係る測定方法においては、被検レンズの一方の面を干渉計で観察してその非球面軸を軸受け部の回転軸と一致するように調整し、もう一方の面は被検レンズを回転させつつ振れ量測定器（例えば、光てこの方法）により有効径以外の平面部及びもう一方の面の振れ量を測定して被検レンズの平行偏芯量及び傾き偏芯量を測定する。即ち、第２の発明によれば、被検レンズのもう一方の面を振れ量測定器により振れ量を高精度に測定でき、かつ、干渉計の光軸と軸受け部の回転軸の高精度な芯合わせが不要であり、一方の面のみを干渉計で測定するのであるから二つの干渉計の光軸を合わせるという極めて高精度を要する調軸作業が不要であり、短時間で偏芯量を測定することができる。
【００１１】
第３の発明は、一方の面が非球面、もう一方の面がその有効径部以外に平面部を有する非球面からなるレンズの偏芯量を測定する方法であって、前記レンズを保持する軸受け部で該レンズを回転させた状態で、振れ量測定器により前記平面部及び前記もう一方の面の振れ量を測定し、もう一方の面の非球面軸を該軸受け部の回転軸と一致させる工程と、前記一方の面を干渉計で観察して前記レンズの平行偏芯量及び傾き偏芯量を測定する工程とを備えたことを特徴とする。
【００１２】
第３の発明に係る測定方法においては、被検レンズを回転させつつ振れ量測定器（例えば、光てこの方法）により有効径以外の平面部及びもう一方の面の振れ量を測定してもう一方の面の非球面軸を軸受け部の回転軸と一致するように調整し、一方の面は干渉計で観察して被検レンズの平行偏芯量及び傾き偏芯量を測定する。即ち、第３の発明によれば、被検レンズのもう一方の面を振れ量測定器により振れ量を高精度に測定でき、かつ、干渉計の光軸と軸受け部の回転軸の高精度な芯合わせが不要であり、一方の面のみを干渉計で測定するのであるから二つの干渉計の光軸を合わせるという極めて高精度を要する調軸作業が不要であり、短時間で偏芯量を測定することができる。
【００１３】
第４の発明は、一方の面が非球面、もう一方の面が平面からなるレンズの偏芯量を測定する方法であって、前記一方の面を干渉計で観察して干渉縞をワンカラーに調整することで、一方の面の非球面軸をレンズを保持する軸受け部の回転軸と一致させる工程と、前記軸受け部でレンズを回転させた状態で、振れ量測定器により前記もう一方の面の振れ量を測定し、該レンズの傾き偏芯量を測定する工程とを備えたことを特徴とする。
【００１４】
第４の発明に係る測定方法においては、被検レンズの一方の面を干渉計で観察してその非球面軸を軸受け部の回転軸と一致するように調整し、もう一方の面は被検レンズを回転させつつ振れ量測定器（例えば、光てこの方法）によりもう一方の面の振れ量を測定して被検レンズの傾き偏芯量を測定する。即ち、第４の発明によれば、被検レンズの平面からなるもう一方の面を振れ量測定器により振れ量を高精度に測定でき、かつ、干渉計の光軸と軸受け部の回転軸の高精度な芯合わせが不要であり、一方の面のみを干渉計で測定するのであるから二つの干渉計の光軸を合わせるという極めて高精度を要する調軸作業が不要であり、短時間で偏芯量を測定することができる。
【００１５】
第５の発明は、少なくとも一方の面が非球面であるレンズの偏芯量を測定する測定装置であって、前記レンズを一方の面の非球面軸を中心に回転させるための軸受け部と、前記軸受け部上に設けた前記レンズを回転軸に対して平行移動及び傾き移動させるステージ部と、前記ステージ部上に設けたレンズホールド部と、前記レンズの一方の面を観察するための干渉計と、前記レンズのもう一方の面に設けた有効径部以外の平面部及び／又はもう一方の面にレーザ光を照射し、反射されたレーザ光のレンズ回転時における振れ量を測定する振れ量測定器とを備えたことを特徴とする。
【００１６】
第５の発明に係る測定装置においては、被検レンズの一方の面を干渉計で測定してその非球面を軸受け部の軸線と一致するように調整し、もう一方の面は有効径以外の平面部及び／又はもう一方の面における光の反射方式（例えば、光てこの方法）により振れ量を測定する。即ち、第５の発明によれば、前記第１〜第４の発明に係る測定方法を効果的に実施することができる。
【００１７】
特に、前記第１〜第５の発明に係る測定方法又は測定装置において、もう一方の面の偏芯量測定に光てこの方法ないし構成を用いることが好ましい。光てこの方法ないし構成は、比較的安価であり、測定精度の向上及び測定時間の短縮化に大きく寄与する。また、光てこの方法ないし構成は、有効径部以外に平面を有する被検レンズに対して、平行偏芯と傾き偏芯とを容易に分離して測定することができる。
【００１８】
【発明の実施の形態】
以下、本発明に係るレンズの偏芯測定方法及び測定装置の実施形態について、添付図面を参照して説明する。
【００１９】
（測定装置、図１参照）
まず、図１を参照して、本発明に係るレンズの偏芯測定装置の一例について説明する。この測定装置は、概略、被検レンズ１の保持機構１０と、干渉計２０と、光てこ部３０とで構成されている。
【００２０】
保持機構１０は、エア軸受け１１上にｘ−ｙ−ｚステージ１２及びチルトステージ１３を介して被検レンズ１を保持するホールド部１４を設けたものである。エア軸受け１１は、被検レンズ１をｚ軸を中心に回転させるものであり、回転ぶれが５０ｎｍ程度で極めて小さく、高精度な振れ量の測定には最適である。
【００２１】
ｘ−ｙ−ｚステージ１２は、ホールド部１４をｘ軸方向、ｙ軸方向及びｚ軸方向に移動可能である。チルトステージ１３は、ホールド部１４をｘ軸及びｙ軸を中心としてその傾きを調整可能である。即ち、保持機構１０は被検レンズ１を５軸に調整することができる。
【００２２】
干渉計２０は、被検レンズ１の上方に、透過原器であるゾーンプレート２１を介して設けたもので、トワイマン−グリーン干渉計あるいはフィゾー干渉計として従来知られたものが用いられる。この干渉計２０の光軸とエア軸受け１１の回転軸はｚ軸上で予め一致するように調整されている。
【００２３】
ゾーンプレート２１は、被検レンズ１の第１面１ａである非球面形状に合わせて設計されている回折格子を備えたもので、干渉計２０からの光を被検レンズ１の第１面１ａに照射し、その反射光を干渉計２０に再入射させる。被検レンズ１の第１面１ａからの反射光と参照光との干渉縞をワンカラーに調整することで第１面１ａの非球面軸をエア軸受け１１の回転軸と一致させることができる。
【００２４】
光てこ部３０は、原子間力顕微鏡のカンチレバーの振れ量を観察するために用いられている技術であり、傾きの変化を高精度に測定できる手段である。原理的には、０．０１分の精度で傾きを測定することが可能である。
【００２５】
この光てこ部３０は、レーザ発振器３１、ビームスプリッタ３２、集光レンズ３３、ミラー３４及び４分割フォトディテクタ３５にて構成されている。レーザ発振器３１から放射された光をミラー３４から被検レンズ１の被検面（第２面１ｂ又は該第２面１ｂの有効径部以外の平面部１ｃ）に照射すると、その反射光は、仮に被検面がエア軸受け１１の回転軸に対して傾いていなければ、４分割フォトディテクタ３５上で一点に留まる。しかし、被検面が傾いていれば、四分割フォトディテクタ３５上で傾き量に対応した半径で円周を描く（図２参照）。
【００２６】
なお、図１に示す測定装置では、検出手段として４分割フォトディテクタ３５を用いているが、偏芯量が大きい場合には、それに代えてＣＣＤカメラ等を用いて回転軌跡の半径を目視で実測する構成としてもよい。
【００２７】
以下、前記測定装置を用いて被検レンズ１の偏芯を測定する方法について説明する。
【００２８】
（第１の測定方法）
この第１の測定方法では、被検レンズ１として、第１面１ａ及び第２面１ｂが非球面であり、第２面１ｂに該第２面１ｂの非球面軸に垂直な平面部１ｃを設けたものを測定する。
【００２９】
まず、第１面１ａの非球面軸をエア軸受け１１の回転軸に一致させる調整方法について説明する。干渉計２０で第１面１ａを観察し、エア軸受け１１上のｘ−ｙ−ｚステージ１２及びチルトステージ１３を調整することで、干渉縞をワンカラーに合わせる。このとき、前述のように、干渉計２０の光軸とエア軸受け１１の回転軸とは予めｚ軸に一致するように調整してある。従って、エア軸受け１１により被検レンズ１を回転させたとき、ワンカラーが保たれることになる。このときワンカラーが崩れる状態であると、被検レンズ１の平行、傾きの調整が不完全であり、再調整の必要がある。
【００３０】
勿論、ワンカラーからのずれ量は、偏芯量の測定精度がきつくないときには一定量許容されるものであり、それぞれの測定において基準を設けておいて、その許容ずれ量内に抑えることができるまで調整すればよい。
【００３１】
ここまでの調整で、偏芯量の測定に必要な精度で、被検レンズ１の第１面１ａの非球面軸をエア軸受け１１の回転軸に一致させることができる。次の工程は、被検レンズ１をエア軸受け１１でｚ軸を中心として回転させた状態で、光てこ部３０による偏芯量の測定を行う。
【００３２】
まず、傾き偏芯量を測定する方法を説明する。レーザ発振器３１からの光をビームスプリッタ３２、集光レンズ３３、ミラー３４を介して被検レンズ１の第２面１ｂの平面部１ｃに入射させる。該平面部１ｃからの反射光は前記とは逆の光路を通じてビームスプリッタ３２から４分割フォトディテクタ３５に入射する。
【００３３】
平面部１ｃは、第２面１ｂの非球面軸に対して垂直に設けられたものであり、平面部１ｃを測定することによって第１面１ａ及び第２面１ｂの各非球面軸の平行偏芯に関係なく傾き偏芯量のみを観察できる。
【００３４】
このとき、光の被照射面における集光スポットの直径は約６０μｍとしている。この集光スポット径は、レーザ発振器３１からの光の直径及び集光レンズ３３の焦点距離を調整することで任意に選択することができる。後に説明する非球面である第２面１ｂの測定を考慮すると、反射光の広がりを抑える観点から、被照射面での集光スポット径は小さい方が好ましい。
【００３５】
また、集光レンズ３３から被照射面までの距離は約６００ｍｍとしている。この距離が長いほど被検レンズ１の傾き偏芯量を一定としたときの４分割フォトディテクタ３５上の反射光の回転軌跡の半径が大きくなり、検出感度が高くなる。
【００３６】
光てこ部３０による測定データは次のようになる。４分割フォトディテクタ３５は、図２に示すように、Ａ，Ｂ，Ｃ，Ｄの検出領域が存在し、ここでの測定においては、（Ａ＋Ｂ）−（Ｃ＋Ｄ）及び（Ａ＋Ｃ）−（Ｂ＋Ｄ）の演算値を出力できるようになっている。
【００３７】
図２中、０°、９０°、１８０°は、それぞれ被検レンズ１の基準位置からの回転角度を示している。なお、基準位置の選択は任意であるが、ここでは基準位置方向に被検レンズ１が上側に傾いているときに、４分割フォトディテクタ３５上で図２において最も下側に光スポットが移動する状態としている。
【００３８】
４分割フォトディテクタ３５上の光スポットの軌跡を観察すると、図２に示す例では、０°のときに４分割フォトディテクタ３５上で図２の上側に光スポットが位置しており、被検レンズ１をエア軸受け１１で９０°回転させると、図２の左側に移動している。さらに、被検レンズ１を１８０°回転させると、光スポットは図２の下側に移動している。
【００３９】
前記軌跡を描いた場合の光てこ部３０の出力信号（Ａ＋Ｂ）−（Ｃ＋Ｄ）は、図３に示すとおりであり、正弦波を描く。このときの正弦波の振幅から第２面１ｂの傾き偏芯量が検出でき、位相から傾き偏芯の方向が検出できる。この例では、被検レンズ１が基準位置である０°のときに４分割フォトディテクタ３５上で図２において最も上側に光スポットが位置する状態であることから、１８０°の回転位置の方向に被検レンズ１が上側に傾いている状態である。なお、光てこ部３０の出力信号（Ａ＋Ｃ）−（Ｂ＋Ｄ）は、図３とは９０°位相がずれた正弦波となる。
【００４０】
ここまでで第２面１ｂの傾き偏芯量の測定まで行ったことになる。次に、第１面１ａ及び第２面１ｂの各非球面軸の平行偏芯の測定について説明する。
【００４１】
まず、傾き偏芯量の測定から、第２面１ｂの非球面軸がエア軸受け１１の回転軸に対し、どれだけ傾いているかが測定されたので、その偏芯量分だけ被検レンズ１をエア軸受け１１上のチルトステージ１３により傾け、第２面１ｂの非球面軸とエア軸受け１１の回転軸の傾きを一致させておく。
【００４２】
この状態で、レーザ発振器３１からの光をビームスプリッタ３２、集光レンズ３３、ミラー３４を介して被検レンズ１の第２面１ｂの非球面に入射させる。該非球面からの反射光は前記とは逆の光路を通じてビームスプリッタ３２から４分割フォトディテクタ３５に入射する。
【００４３】
このときの光てこ信号を演算することで第２面の平行偏芯量を測定することができる。このとき光てこ信号及び平行偏芯量の測定は、図２及び図３を参照した前述の傾き偏芯量の測定時とほぼ同様である。
【００４４】
なお、この第１の測定方法では、第２面１ｂの非球面軸とエア軸受け１１の回転軸の傾きを一致させた後に、平行偏芯量の測定を行っている。それ以外に、第２面１ｂの傾き偏芯を残した状態で第２面１ｂの非球面に対して平行偏芯量の測定を行い、得られた光てこ信号から傾き偏芯量の出力電圧を差し引くことで、平行偏芯に関する信号のみを検出することも可能である。
【００４５】
以上説明した第１の測定方法では、干渉計を用いるワンカラーの調整を第１面１ａの１回に減少することができる。また、干渉計での測定に必要であるエア軸受け１１の回転軸との高精度な芯出しを被検レンズ１の第１面１ａ側についてのみ行えばよいことになり、測定精度の向上及び測定時間の短縮化が可能になる。
【００４６】
また、光てこ部３０は、レーザ発振器３１といくつかの光学部品を用いる簡易な構成であり、干渉計を複数用いることに比べて非常に安価な装置で測定することができる。また、傾き偏芯量と平行偏芯量とを容易に分離可能であるという利点も有している。
【００４７】
（第２の測定方法）
この第２の測定方法では、第１の測定方法と同様に、被検レンズ１として、第１面１ａ及び第２面１ｂが非球面であり、第２面１ｂに該第２面１ｂの非球面軸に垂直な平面部１ｃを設けたものを測定する。
【００４８】
まず、第２面１ｂの非球面軸をエア軸受け１１の回転軸に一致させる調整方法について説明する。前記第１の測定方法では、光てこ部３０によって第２面１ｂの傾き偏芯量及び平行偏芯量を測定した。一方、本第２の測定方法では、まず、光てこ部３０によって第２面１ｂの非球面軸をエア軸受け１１の回転軸に一致させる。
【００４９】
その手順は、前記第１の測定方法と同様に、まず、平面部１ｃにて傾き偏芯量を測定することで、第２面１ｂの非球面軸がエア軸受け１１の回転軸に対してどれだけ傾いているかを測定する。そして、測定された偏芯量分だけ被検レンズ１をエア軸受け１１上のチルトステージ１３により傾け、第２面１ｂの非球面軸とエア軸受け１１の回転軸の傾きを一致させる。
【００５０】
次に、前記第１の測定方法と同様に、第２面１ｂの非球面の平行偏芯量を測定することで、第２面１ｂの非球面軸がエア軸受け１１の回転軸に対してどれだけの平行ずれがあるかを測定する。そして、測定された平行偏芯量部だけ被検レンズ１をエア軸受け１１上のｘ−ｙ−ｚステージ１２により平行移動させ、第２面１ｂの非球面軸をエア軸受け１１の回転軸と完全に一致させる。
【００５１】
ここまでの調整で、偏芯量の測定に必要な精度で、被検レンズ１の第２面１ｂの非球面軸をエア軸受け１１の回転軸に完全に一致させることができる。次の工程は、第２面１ｂの非球面軸と第１面１ａの非球面軸との傾き偏芯量及び平行偏芯量を測定する。
【００５２】
まず、干渉計２０で第１面１ａを観察し、フリンジスキャンによる干渉縞の解析を行い、解析の結果から得られたツェルニケ（ｚｅｒｎｉｋｅ）係数から傾き偏芯量及び平行偏芯量を演算する。勿論、この際にも干渉計２０の光軸とエア軸受け１１の回転軸とは予めｚ軸に一致するように調整しておく必要がある。
【００５３】
以上説明した第２の測定方法での利点は、干渉計を用いるワンカラーの調整を第１面１ａの１回に減少することができ、測定精度の向上及び測定時間の短縮化が可能になる等前記第１の測定方法と同様である。
【００５４】
（第３の測定方法）
この第３の測定方法では、被検レンズ１として第１面１ａが非球面、第２面１ｂが平面のものを測定する。
【００５５】
被検レンズ１の第１面１ａの非球面軸をエア軸受け１１の回転軸に一致させる方法は前記第１の測定方法と同様であり、その詳細は省略する。この被検レンズ１にあっては、第２面１ｂは平面であるから、その傾き偏芯量のみを測定すればよい。傾き偏芯量の測定は前記第１の測定方法において説明した平面部１ｃに対する傾き偏芯量の測定と同様であり、その詳細は省略する。
【００５６】
（他の実施形態）
なお、本発明に係るレンズの偏芯測定方法及び測定装置は前記実施形態に限定するものではなく、その要旨の範囲内で種々に変更できることは勿論である。
【図面の簡単な説明】
【図１】本発明に係る測定装置の一例を示す概略構成図。
【図２】前記測定装置における４分割フォトディテクタ上での光スポットの軌跡を示すチャート図。
【図３】前記測定装置における光てこ信号の出力を示すグラフ。
【符号の説明】
１…被検レンズ
１ａ…第１面（一方の面）
１ｂ…第２面（もう一方の面）
１ｃ…平面部
１０…保持機構
１１…エア軸受け
１２…ｘ−ｙ−ｚステージ
１３…チルトステージ
２０…干渉計
３０…光てこ部
３１…レーザ発振器
３５…４分割フォトディテクタ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for measuring eccentricity of a lens, and more particularly to a method and an apparatus for measuring eccentricity of a lens having at least one aspheric surface.
[0002]
[Prior art and problems]
Patent Document 1: Japanese Patent Application Laid-Open No. 10-2714 Patent Document 2: Japanese Patent Application Laid-Open No. 11-14498 Patent Document 3: Japanese Patent Application Laid-Open No. 2001-165807
2. Description of the Related Art Conventionally, as a method and an apparatus for measuring the eccentricity of an aspherical lens, a method and an apparatus based on positioning measurement using a Twyman-Green interferometer or a Fizeau interferometer are known, and are disclosed in Patent Documents 1, 2, and 3. Have been. In these measurement methods, both the first surface and the second surface of the test lens are observed with an interferometer, and the interference fringes are adjusted to one color to determine the aspheric axis of each surface. The amount of eccentricity was determined from the positional relationship of the shaft.
[0004]
However, in the measurement method using the interferometer on both surfaces, it is necessary to align the optical axes of the interferometers observing the first surface and the second surface with sufficiently higher accuracy than the measurement accuracy of the eccentricity. . For example, in a measurement requiring high accuracy such as a parallel eccentricity of 1 μm or less and a tilt eccentricity of 0.5 minute or less, the accuracy of the optical axis of the interferometer becomes extremely high.
[0005]
Such high-precision measurement requires a considerably advanced technique, and if an adjustment error remains, the eccentricity measurement accuracy is reduced. In addition, in the process of adjusting the interference fringes to one color in the measurement with an interferometer, it is necessary to adjust the accuracy of the one color to a very high level. However, it is unsuitable when the evaluation of a molded article (lens to be inspected) is to be performed with a small time lag as in the case of sampling inspection.
[0006]
Therefore, an object of the present invention is to provide a measuring method and a measuring apparatus capable of measuring the amount of eccentricity of a lens having at least one aspherical surface with high accuracy and in a short time.
[0007]
Configuration, operation and effect of the present invention
In order to achieve the above object, a first invention is a measuring method for measuring the amount of eccentricity of a lens having at least one surface an aspherical surface, and observing one surface of the lens with an interferometer. Adjusting the interference fringes to one color, irradiating a laser beam to a plane portion other than the effective diameter portion provided on the other surface of the lens and / or the other surface, and rotating the lens of the reflected laser beam. And measuring the amount of shake at the time.
[0008]
In the measurement method according to the first invention, one surface of the test lens is observed with an interferometer and adjusted to one color, and the other surface is a flat portion other than the effective diameter portion and / or the other surface. The amount of shake is measured by a light reflection method (for example, a light lever method) in the above. That is, according to the first aspect, the amount of shake of the other surface of the lens to be measured can be measured with high accuracy by the light reflection method, and the alignment of the optical axis of the interferometer with the measurement rotation axis can be performed with high accuracy. Is not necessary, and only one surface is measured by an interferometer. Therefore, there is no need for extremely high precision alignment work of aligning the optical axes of the two interferometers, and the eccentricity can be measured in a short time. be able to.
[0009]
The second invention is a method for measuring the amount of eccentricity of a lens in which one surface is formed of an aspheric surface and the other surface is formed of an aspheric surface having a flat surface portion other than its effective diameter portion, wherein Adjusting the interference fringes to one color by observing with an interferometer so that the aspherical axis of one surface coincides with the rotation axis of the bearing unit holding the lens, and a state in which the lens is rotated by the bearing unit Measuring a shake amount of the plane portion and the other surface with a shake amount measuring device, and measuring a parallel eccentric amount and a tilt eccentric amount of the lens.
[0010]
In the measuring method according to the second invention, one surface of the lens to be inspected is observed with an interferometer, the aspherical axis of the lens is adjusted so as to coincide with the rotation axis of the bearing portion, and the other surface of the lens to be inspected is adjusted. While rotating the lens, a shake measuring device (for example, an optical lever method) measures the shake of the plane portion other than the effective diameter and the shake of the other surface to determine the parallel eccentricity and the tilt eccentricity of the lens to be measured. Measure. That is, according to the second aspect, the other surface of the lens to be measured can measure the amount of shake with a shake amount measuring device with high accuracy, and the optical axis of the interferometer and the rotation axis of the bearing unit can be measured with high accuracy. Alignment is not required, and only one surface is measured with an interferometer.Therefore, there is no need for extremely high-precision alignment work of aligning the optical axes of the two interferometers. Can be measured.
[0011]
A third invention is a method for measuring the amount of eccentricity of a lens having one surface formed of an aspherical surface and the other surface formed of an aspherical surface having a plane portion other than its effective diameter portion, and holding the lens. In a state where the lens is rotated by the bearing portion, the shake amount of the flat portion and the other surface is measured by a shake amount measuring device, and the aspherical axis of the other surface coincides with the rotation axis of the bearing portion. And a step of observing the one surface with an interferometer and measuring a parallel eccentric amount and a tilt eccentric amount of the lens.
[0012]
In the measuring method according to the third aspect of the present invention, while the lens to be inspected is being rotated, the shake amount of a plane portion other than the effective diameter and the shake amount of the other surface are measured by a shake amount measuring device (for example, an optical lever method). The aspherical axis of one surface is adjusted to coincide with the rotation axis of the bearing portion, and the other surface is observed with an interferometer to measure the parallel eccentricity and the tilt eccentricity of the lens to be measured. That is, according to the third aspect, the other surface of the lens to be measured can be measured with high accuracy by the shake amount measuring device, and the optical axis of the interferometer and the rotation axis of the bearing unit can be measured with high accuracy. Alignment is not required, and only one surface is measured with an interferometer.Therefore, there is no need for extremely high-precision alignment work of aligning the optical axes of the two interferometers. Can be measured.
[0013]
A fourth invention is a method for measuring the amount of eccentricity of a lens in which one surface is an aspherical surface and the other surface is a flat surface. By adjusting the aspherical axis of one surface to coincide with the rotation axis of the bearing portion holding the lens, and in the state where the lens is rotated in the bearing portion, the other amount by the shake amount measuring device Measuring the amount of surface shake and measuring the amount of tilt and eccentricity of the lens.
[0014]
In the measurement method according to the fourth invention, one surface of the lens to be inspected is observed with an interferometer, and the aspherical axis thereof is adjusted so as to coincide with the rotation axis of the bearing portion, and the other surface is inspected. While rotating the lens, the shake amount of the other surface is measured by a shake amount measuring device (for example, an optical lever method) to measure the tilt eccentric amount of the test lens. That is, according to the fourth aspect, the other surface consisting of the flat surface of the test lens can be measured with high accuracy by the shake amount measuring device, and the optical axis of the interferometer and the rotation axis of the bearing portion can be measured. Since high-precision alignment is not required and only one surface is measured with an interferometer, there is no need for extremely high-precision alignment work of aligning the optical axes of the two interferometers. The core amount can be measured.
[0015]
A fifth invention is a measuring device for measuring the amount of eccentricity of a lens having at least one surface aspherical, and a bearing unit for rotating the lens around an aspherical axis of one surface, A stage unit provided on the bearing unit for moving the lens in parallel and tilting with respect to a rotation axis, a lens holding unit provided on the stage unit, and an interferometer for observing one surface of the lens And a shake amount for irradiating a laser beam to a plane portion other than the effective diameter portion provided on the other surface of the lens and / or the other surface, and measuring a shake amount of the reflected laser light during rotation of the lens. And a measuring device.
[0016]
In the measuring device according to the fifth invention, one surface of the test lens is measured with an interferometer, and the aspheric surface is adjusted so as to coincide with the axis of the bearing portion, and the other surface has a diameter other than the effective diameter. The amount of shake is measured by a light reflection method (for example, an optical lever method) on the flat portion and / or the other surface. That is, according to the fifth aspect, the measuring methods according to the first to fourth aspects can be effectively implemented.
[0017]
In particular, in the measuring method or the measuring apparatus according to the first to fifth aspects, it is preferable to use the optical lever or the method for measuring the eccentricity of the other surface. The optical lever method or configuration is relatively inexpensive and greatly contributes to improvement of measurement accuracy and reduction of measurement time. In addition, the optical lever method or configuration can easily separate and measure parallel eccentricity and tilt eccentricity of a test lens having a plane other than the effective diameter portion.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a lens eccentricity measuring method and a measuring apparatus according to the present invention will be described with reference to the accompanying drawings.
[0019]
(Measuring device, see Fig. 1)
First, an example of a lens eccentricity measuring apparatus according to the present invention will be described with reference to FIG. This measuring device generally includes a holding mechanism 10 for the lens 1 to be measured, an interferometer 20, and an optical lever 30.
[0020]
The holding mechanism 10 is provided with a holding unit 14 that holds the test lens 1 on an air bearing 11 via an xyz stage 12 and a tilt stage 13. The air bearing 11 rotates the test lens 1 about the z-axis, and has extremely small rotational shake of about 50 nm, which is optimal for highly accurate measurement of the shake amount.
[0021]
The xyz stage 12 is capable of moving the hold unit 14 in the x-axis direction, the y-axis direction, and the z-axis direction. The tilt stage 13 is capable of adjusting the tilt of the hold unit 14 about the x-axis and the y-axis. That is, the holding mechanism 10 can adjust the test lens 1 in five axes.
[0022]
The interferometer 20 is provided above the test lens 1 via a zone plate 21 which is a transmission standard, and a conventionally known Twyman-Green interferometer or Fizeau interferometer is used. The optical axis of the interferometer 20 and the rotation axis of the air bearing 11 are adjusted in advance on the z-axis.
[0023]
The zone plate 21 includes a diffraction grating designed in accordance with the aspherical shape that is the first surface 1a of the lens 1 to be inspected, and transmits light from the interferometer 20 to the first surface 1a of the lens 1 to be inspected. And the reflected light is re-incident on the interferometer 20. By adjusting the interference fringes between the reflected light from the first surface 1a of the test lens 1 and the reference light in one color, the aspherical axis of the first surface 1a can be made to coincide with the rotation axis of the air bearing 11.
[0024]
The optical lever 30 is a technique used for observing the amount of deflection of the cantilever of an atomic force microscope, and is a means for measuring a change in inclination with high accuracy. In principle, it is possible to measure the tilt with an accuracy of 0.01 minutes.
[0025]
The optical lever unit 30 includes a laser oscillator 31, a beam splitter 32, a condenser lens 33, a mirror 34, and a four-divided photodetector 35. When the light emitted from the laser oscillator 31 is irradiated from the mirror 34 onto the surface to be measured (the second surface 1b or the plane portion 1c other than the effective diameter portion of the second surface 1b), the reflected light is If the test surface is not inclined with respect to the rotation axis of the air bearing 11, the test surface remains at one point on the four-divided photodetector 35. However, if the surface to be inspected is inclined, a circumference is drawn on the four-division photodetector 35 with a radius corresponding to the amount of inclination (see FIG. 2).
[0026]
In the measuring device shown in FIG. 1, a four-divided photodetector 35 is used as the detecting means. However, when the eccentricity is large, the radius of the rotation locus is actually measured visually using a CCD camera or the like instead. It may be configured.
[0027]
Hereinafter, a method for measuring the eccentricity of the lens 1 to be measured using the measuring device will be described.
[0028]
(First measurement method)
In the first measurement method, the lens 1 to be measured has a first surface 1a and a second surface 1b having an aspheric surface, and a second surface 1b having a flat portion 1c perpendicular to the aspheric axis of the second surface 1b. Measure the provided one.
[0029]
First, an adjustment method for making the aspherical axis of the first surface 1a coincide with the rotation axis of the air bearing 11 will be described. By observing the first surface 1 a with the interferometer 20 and adjusting the xyz stage 12 and the tilt stage 13 on the air bearing 11, the interference fringes are adjusted to one color. At this time, as described above, the optical axis of the interferometer 20 and the rotation axis of the air bearing 11 are adjusted in advance so as to coincide with the z-axis. Therefore, when the test lens 1 is rotated by the air bearing 11, one-color is maintained. At this time, if the one color is in a collapsed state, the adjustment of the parallelism and the inclination of the lens 1 to be inspected is incomplete, and it is necessary to readjust.
[0030]
Of course, the deviation amount from one color is allowed to be a fixed amount when the measurement accuracy of the eccentricity amount is not tight, and a standard is provided for each measurement, and the deviation amount can be suppressed within the allowable deviation amount. Adjust it up to.
[0031]
With the adjustments so far, the aspherical axis of the first surface 1a of the test lens 1 can be made to coincide with the rotation axis of the air bearing 11 with the accuracy required for measuring the amount of eccentricity. In the next step, the amount of eccentricity measured by the optical lever 30 is measured while the test lens 1 is rotated about the z-axis by the air bearing 11.
[0032]
First, a method for measuring the amount of tilt eccentricity will be described. Light from the laser oscillator 31 is incident on the plane portion 1c of the second surface 1b of the lens 1 to be measured via the beam splitter 32, the condenser lens 33, and the mirror. The reflected light from the plane portion 1c enters the four-divided photodetector 35 from the beam splitter 32 through an optical path opposite to that described above.
[0033]
The plane portion 1c is provided perpendicular to the aspherical axis of the second surface 1b. By measuring the plane portion 1c, the parallel deviation of each aspherical axis of the first surface 1a and the second surface 1b is measured. Only the amount of tilt eccentricity can be observed regardless of the center.
[0034]
At this time, the diameter of the condensed spot on the light irradiation surface is about 60 μm. The diameter of the converging spot can be arbitrarily selected by adjusting the diameter of the light from the laser oscillator 31 and the focal length of the converging lens 33. Considering the measurement of the second surface 1b, which is an aspheric surface, which will be described later, it is preferable that the diameter of the condensed spot on the irradiated surface be small from the viewpoint of suppressing the spread of reflected light.
[0035]
The distance from the condenser lens 33 to the surface to be irradiated is about 600 mm. The longer this distance is, the larger the radius of the rotation trajectory of the reflected light on the four-divided photodetector 35 when the amount of tilt and eccentricity of the lens 1 to be measured is constant, and the higher the detection sensitivity.
[0036]
The data measured by the optical lever 30 is as follows. As shown in FIG. 2, the four-segment photodetector 35 has detection areas A, B, C, and D. In this measurement, (A + B)-(C + D) and (A + C)-(B + D) Calculation values can be output.
[0037]
In FIG. 2, 0 °, 90 °, and 180 ° indicate the rotation angles of the test lens 1 from the reference position. Note that the selection of the reference position is arbitrary, but here, the state where the light spot moves to the lowermost position in FIG. And
[0038]
When observing the trajectory of the light spot on the four-segment photodetector 35, in the example shown in FIG. 2, at 0 °, the light spot is located on the upper part of the four-segment photodetector 35 in FIG. When rotated 90 ° by the air bearing 11, it has moved to the left side in FIG. When the test lens 1 is further rotated by 180 °, the light spot moves to the lower side in FIG.
[0039]
The output signal (A + B)-(C + D) of the optical lever 30 when the locus is drawn is as shown in FIG. 3, and draws a sine wave. The inclination eccentric amount of the second surface 1b can be detected from the amplitude of the sine wave at this time, and the direction of the inclination eccentric can be detected from the phase. In this example, when the test lens 1 is at the reference position of 0 °, the light spot is located at the uppermost position in FIG. This is a state where the inspection lens 1 is inclined upward. The output signal (A + C)-(B + D) of the optical lever 30 is a sine wave whose phase is shifted by 90 ° from that of FIG.
[0040]
Up to this point, the measurement of the amount of tilt and eccentricity of the second surface 1b has been performed. Next, measurement of parallel eccentricity of each aspheric axis of the first surface 1a and the second surface 1b will be described.
[0041]
First, from the measurement of the amount of tilt and eccentricity, how much the aspherical axis of the second surface 1b is tilted with respect to the rotation axis of the air bearing 11 was measured. The air bearing 11 is tilted by the tilt stage 13 so that the aspherical axis of the second surface 1b and the rotation axis of the air bearing 11 are matched.
[0042]
In this state, light from the laser oscillator 31 is made incident on the aspheric surface of the second surface 1b of the lens 1 to be measured via the beam splitter 32, the condenser lens 33, and the mirror. The reflected light from the aspheric surface enters the four-divided photodetector 35 from the beam splitter 32 through an optical path opposite to that described above.
[0043]
By calculating the optical lever signal at this time, the amount of parallel eccentricity of the second surface can be measured. At this time, the measurement of the optical lever signal and the amount of parallel eccentricity is almost the same as the measurement of the amount of tilt eccentricity described above with reference to FIGS.
[0044]
In the first measurement method, the parallel eccentricity is measured after the inclination of the aspheric axis of the second surface 1b and the inclination of the rotation axis of the air bearing 11 are matched. In addition, the parallel eccentricity is measured with respect to the aspheric surface of the second surface 1b while the tilt eccentricity of the second surface 1b is left, and the output voltage of the tilt eccentricity is obtained from the obtained optical lever signal. Is subtracted, it is also possible to detect only a signal related to parallel eccentricity.
[0045]
In the first measuring method described above, the one-color adjustment using the interferometer can be reduced to one time for the first surface 1a. In addition, it is only necessary to perform high-precision centering with the rotation axis of the air bearing 11 necessary for measurement by the interferometer only on the first surface 1a side of the test lens 1, thereby improving measurement accuracy and measuring. Time can be reduced.
[0046]
Further, the optical lever unit 30 has a simple configuration using the laser oscillator 31 and some optical components, and can perform measurement with a very inexpensive device as compared with using a plurality of interferometers. Also, there is an advantage that the amount of tilt eccentricity and the amount of parallel eccentricity can be easily separated.
[0047]
(Second measurement method)
In the second measuring method, as in the first measuring method, the first surface 1a and the second surface 1b of the lens 1 to be inspected are aspherical surfaces, and the second surface 1b has a non-spherical surface. One having a plane portion 1c perpendicular to the spherical axis is measured.
[0048]
First, an adjustment method for making the aspherical axis of the second surface 1b coincide with the rotation axis of the air bearing 11 will be described. In the first measurement method, the tilt eccentricity and the parallel eccentricity of the second surface 1b were measured by the optical lever 30. On the other hand, in the second measuring method, first, the aspherical axis of the second surface 1 b is made to coincide with the rotation axis of the air bearing 11 by the optical lever 30.
[0049]
As in the first measuring method, first, the amount of inclination and eccentricity is measured at the flat surface portion 1c, so that the aspherical axis of the second surface 1b is shifted with respect to the rotation axis of the air bearing 11. Just measure what is tilted. Then, the test lens 1 is tilted by the tilt stage 13 on the air bearing 11 by the measured eccentric amount, and the tilt of the aspherical axis of the second surface 1b and the tilt of the rotation axis of the air bearing 11 are matched.
[0050]
Next, similarly to the first measuring method, the amount of parallel eccentricity of the aspherical surface of the second surface 1b is measured so that the aspherical axis of the second surface 1b can be determined with respect to the rotation axis of the air bearing 11. Measure whether there is only a parallel shift. Then, the test lens 1 is translated by the xyz stage 12 on the air bearing 11 by the measured parallel eccentric amount, and the aspherical axis of the second surface 1 b is completely aligned with the rotation axis of the air bearing 11. To match.
[0051]
With the adjustments so far, the aspherical axis of the second surface 1b of the lens 1 to be inspected can be completely matched with the rotation axis of the air bearing 11 with the accuracy required for measuring the amount of eccentricity. In the next step, the amounts of inclination and parallel eccentricity between the aspherical axis of the second surface 1b and the aspherical axis of the first surface 1a are measured.
[0052]
First, the first surface 1a is observed with the interferometer 20, an interference fringe is analyzed by fringe scanning, and a tilt eccentricity and a parallel eccentricity are calculated from Zernike coefficients obtained from the analysis result. Of course, also at this time, the optical axis of the interferometer 20 and the rotation axis of the air bearing 11 need to be adjusted in advance so as to coincide with the z-axis.
[0053]
The advantage of the second measurement method described above is that the one-color adjustment using the interferometer can be reduced to one time on the first surface 1a, and the measurement accuracy can be improved and the measurement time can be shortened. The same is the same as in the first measurement method.
[0054]
(Third measurement method)
In the third measurement method, the lens 1 to be measured has an aspheric first surface 1a and a flat second surface 1b.
[0055]
The method for matching the aspherical axis of the first surface 1a of the lens 1 to be measured with the rotation axis of the air bearing 11 is the same as the first measuring method, and the details are omitted. In the test lens 1, the second surface 1b is a flat surface, so that only the amount of tilt and eccentricity needs to be measured. The measurement of the tilt eccentricity is the same as the measurement of the tilt eccentricity with respect to the plane portion 1c described in the first measuring method, and the details are omitted.
[0056]
(Other embodiments)
Note that the method and apparatus for measuring the eccentricity of the lens according to the present invention are not limited to the above-described embodiment, but can be variously changed within the scope of the gist.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a measuring device according to the present invention.
FIG. 2 is a chart showing the trajectory of a light spot on a four-segment photodetector in the measuring device.
FIG. 3 is a graph showing an output of an optical lever signal in the measuring device.
[Explanation of symbols]
1 .... lens 1a to be tested ... 1st surface (one surface)
1b 2nd surface (the other surface)
1c Planar part 10 Holding mechanism 11 Air bearing 12 Xyz stage 13 Tilt stage 20 Interferometer 30 Optical lever 31 Laser oscillator 35 Four-split photodetector

Claims

A measurement method for measuring the amount of eccentricity of a lens in which at least one surface is an aspheric surface,
Observing one surface of the lens with an interferometer and adjusting the interference fringes to one color,
A step of irradiating a laser beam to a plane portion other than the effective diameter portion provided on the other surface of the lens and / or the other surface, and measuring a shake amount of the reflected laser light during rotation of the lens,
A method for measuring eccentricity of a lens, comprising:

A method for measuring the amount of eccentricity of a lens having one surface an aspheric surface and the other surface having an aspheric surface having a plane portion other than its effective diameter portion,
By adjusting the interference fringes to one color by observing the one surface with an interferometer, a step of matching the aspheric axis of the one surface with the rotation axis of the bearing unit holding the lens,
A step of measuring the shake amount of the flat portion and the other surface with a shake amount measuring device while rotating the lens in the bearing portion, and measuring the tilt eccentric amount and the parallel eccentric amount of the lens; ,
A method for measuring eccentricity of a lens, comprising:

A method for measuring the amount of eccentricity of a lens composed of an aspheric surface having one flat surface portion in addition to the effective diameter portion, the other surface being an aspheric surface,
In a state where the lens is rotated by the bearing portion holding the lens, the shake amount of the flat portion and the other surface is measured by a shake amount measuring device, and the aspherical axis of the other surface is set to the bearing portion. A step of matching with the rotation axis;
Observing the one surface with an interferometer and measuring the amount of tilt eccentricity and the amount of parallel eccentricity of the lens,
A method for measuring eccentricity of a lens, comprising:

A method for measuring the amount of eccentricity of a lens in which one surface is an aspheric surface and the other surface is a flat surface,
By adjusting the interference fringes to one color by observing the one surface with an interferometer, a step of matching the aspheric axis of the one surface with the rotation axis of the bearing unit holding the lens,
In the state where the lens is rotated in the bearing portion, the shake amount of the other surface is measured by a shake amount measuring device, and a step of measuring the tilt eccentric amount of the lens,
A method for measuring eccentricity of a lens, comprising:

A measuring device for measuring the amount of eccentricity of a lens at least one surface of which is an aspheric surface,
A bearing part for rotating the lens about an aspherical axis of one surface,
A stage unit that translates and tilts the lens provided on the bearing unit with respect to a rotation axis,
A lens hold unit provided on the stage unit,
An interferometer for observing one surface of the lens,
A shake amount measuring device that irradiates a laser beam onto a plane portion other than the effective diameter portion provided on the other surface of the lens and / or the other surface, and measures the shake amount of the reflected laser light during rotation of the lens. When,
An eccentricity measuring device for a lens, comprising: