JP3740424B2

JP3740424B2 - Shape measuring method and apparatus using interferometer

Info

Publication number: JP3740424B2
Application number: JP2002060212A
Authority: JP
Inventors: 勝大塚; 仁飯島; 誠一神谷
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2002-03-06
Filing date: 2002-03-06
Publication date: 2006-02-01
Anticipated expiration: 2022-03-06
Also published as: JP2003254730A

Description

【０００１】
【発明の属する技術分野】
本発明は、半導体露光装置用の縮小投影光学レンズやミラー等の球面形状精度を、極めて高い精度で測定する干渉計を用いた形状測定方法及び装置に関するものである。
【０００２】
【従来の技術】
従来より高精度な球面レンズ、ミラーの形状測定方法として、フィゾー干渉計やトワイマン−グリーン干渉計などを用いるのが一般的であるが、いずれも参照する球面や平面が必要であり、絶対精度は基本的にはこれらの参照球面、参照平面の形状精度で規定されてしまう。通常の参照面の製造方法ではＨｅ−Ｎｅレーザ波長をλ（λ＝６３２．８ｎｍ）としてλ／１０〜λ／２０程度を保証するのが限度であると言われている。
【０００３】
一方、半導体露光装置の微細化、高精度化に伴い露光光源波長はＫｒＦエキシマレーザ（λ＝２４８ｎｍ）、ＡｒＦエキシマレーザ（λ＝１９３ｎｍ），Ｆ２レーザ（λ＝１５７ｎｍ）と短波長化し、さらにはＥＵＶ光（ＥｘｔｒｅｍｅＵｌｔｒａＶｉｏｌｅｔ：λ＝１３．６ｎｍ）までも露光光源として使用されるに至っている。これらの露光装置用の投影光学レンズ、ミラーについては１ｎｍ〜０．１ｎｍの形状精度が求められており、このような精度を達成するためにはさらにこれより高い精度の計測装置が必要である。通常このような精度で計測することは単に再現精度を実現することでさえ困難であり、まして絶対精度を保証するということは極めて困難であった。
【０００４】
特開平２−２２８５０５には、光学面の絶対精度を数１０Å以下で保証する技術が記載されている。特開平２−２２８５０５の第１実施例として記載されている第１の従来の技術の構成を図７に示す。図７において光源１から出た光は集光レンズ２により集光されてピンホールミラー３に至り、一部はピンホールを通って被測定物４に当たって再びピンホールミラー３に戻り、今度は反射されて撮像素子７へと到達する。この光を測定光と呼ぶ。それ以外の光はピンホールミラー３で反射され、集光ミラー５で反射され、再びピンホールミラー３に戻り、今度はピンホールを通過して撮像素子７へと到達する。この光を参照光と呼ぶ。これらの測定光と参照光は干渉して干渉縞を形成し撮像素子７で撮像する事で被測定物の表面形状を測定する。
【０００５】
光はピンホールを通過することにより回折理想球面波となる事が知られている。従って測定光はピンホールを通った回折理想球面波となるので被測定物４で反射した光は被測定物４の球面からの形状誤差だけを収差情報として持つ光波が撮像素子７に到達する。参照光は集光ミラー５によって反射集光された後、ピンホールを通過することにより回折理想球面波となるので無収差波面が撮像素子７に到達する。この時集光ミラー５の表面精度は特に高精度でする必要はなく、光を反射する精度があれば充分である。この様にして、測定光と参照光は撮像素子７上で純粋に被測定物４の形状誤差情報だけを有する干渉縞を形成することができ、特別な基準面を設けることなく高い絶対精度で形状測定が出来る。
【０００６】
特開平２−２２８５０５の第２実施例として記載されている第２の従来の技術の構成を図８に示す。図８においては、光源１から出た光を集光レンズ２でピンホールミラー３に設けられたピンホールを通過させて理想球面波としその一部を参照波として撮像素子７に入射させる。また同じ光波の別の一部を被測定物４で反射させた後、ピンホールミラー３で反射させて撮像素子７に入射させて前記参照波と干渉させ、発生する干渉縞像を撮像素子７で撮像する事で被測定物の表面形状を測定する。第２の従来の技術は第１の従来の技術の集光ミラーを省略した構成を取っている。
【０００７】
【発明が解決しようとする課題】
しかしながら、図７に示す特開平２−２２８５０５に第１実施例として記載されている第１の従来の技術では、参照光軸と被測定光軸がほぼ９０度という大きな角度を持って分離されるために、装置が大型化し複雑になってしまう。また、ピンホールと被測定面までの距離を、必ず被測定面の曲率半径分の距離に離す必要があるため、曲率半径の大きな被測定面を測定する場合は光路が長くなり空気揺らぎによる精度低下が避けられない。また、被測定面が凹面であれば測定可能であるが凸面の場合は測定ができないという問題点もある。また、ピンホール部分には必ずミラーが必要なため、ミラーの汚れや微小な凹凸が測定波面に影響する恐れがある。
【０００８】
また、図８に示す特開平２−２２８５０５に第２実施例として記載されている第２の従来の技術では、前記課題の他に、測定光として使えるのはピンホールから出る理想球面波の広がりの一部になってしまうため、光量が少なくなり測定精度が低下する。また、被測定物を配置する領域が限られてしまうため、大きな被測定面を有する被測定物を測定することができない。
【０００９】
【課題を解決するための手段】
本発明においては、光源と、光源からの光を一旦集光させる集光レンズと、該集光した光を理想的な球面波に変換するピンホールとその近傍に設けられた光波面情報を通過させる窓とが形成された光波整形板とを有し、該ピンホールを通過した光の光路中に、お互いの光軸が偏芯した参照面と被測定面とを有する少なくとも１枚のレンズを、該参照面に反射した光が該ピンホールを再度通過し、該測定面に反射した光が該窓を通過する位置に配置し、該参照面で反射し該ピンホールを再度通過した反射光と、該被測定面で反射し該窓を通過した反射光とを干渉させて被測定面の形状を測定する形状測定装置及び形状測定方法を提供している。
【００１０】
また本発明においては、前記レンズは前記ピンホールの近傍で曲率中心が僅かに異なる凹型と凸型の光学面からなる単レンズである干渉計を用いた形状測定装置及び形状測定方法を提供している。
【００１１】
また本発明においては、前記被測定面は，前記レンズの前記ピンホールに最も近い凹型の光学面であり、前記参照面は該凹型の光学面と逆側の凸型の光学面である、干渉計を用いた形状測定装置及び形状測定方法を提供している。
【００１２】
また本発明においては、前記レンズは複数のレンズからなるレンズ群であり、前記参照面と被測定面は、前記ピンホールに最も近いレンズの光学面と、前記ピンホールに最も近いレンズと異なるレンズの光学面のいずれかである干渉計を用いた形状測定装置及び形状測定方法を提供している。
【００１３】
また本発明においては、前記被測定面は、前記ピンホールに最も近いレンズのピンホールに最も近い凹型の光学面であり、前記参照面は、前記ピンホールに最も近いレンズと異なるレンズの光学面である干渉計を用いた形状測定装置及び形状測定方法を提供している。
【００１４】
また本発明においては、光源と、光源からの光を一旦集光させる集光レンズと、該集光した光を理想的な球面波に変換するピンホールとその近傍に設けられた光波面情報を通過させる窓とが形成された光波整形板と、該ピンホールを通過した光を反射する光学反射面を有するミラー部材とを有し、該ピンホールと該ミラー部材の間に、他の光学面と光軸が偏芯した被測定面を有する少なくとも１枚のレンズを該被測定面に反射した光が前記窓を通過する位置に調整し、該ミラー部材を、該光学反射面に光が垂直に入射し、反射した光が該ピンホールを再度通過する位置に配置し、該光学反射面で反射し前記ピンホールを再度通過した反射光と、該被測定面で反射し前記窓を通過した反射光とを干渉させて被測定面の形状を測定する干渉計を用いた形状測定装置及び形状測定方法を提供している。
【００１５】
また本発明においては、前記形状測定方法で前記被測定面を測定した後、前記光波整形板を除去し、該被測定面からの反射光と、該参照面からの反射光とを干渉させて該参照面の形状を測定する干渉計を用いた形状測定方法を提供している。
【００１６】
また本発明においては、前記レンズの前記光源と逆側の光学面は凸型の光学面であり、前記形状測定方法で該凸型の光学面を測定した後、前記光波整形板を除去し、前記レンズの該光源と逆側に第２の被測定面をもつ光学素子を配置し、該第２の被測定面からの反射光と該凸型の光学面からの反射光とを干渉させて該第２の被測定面の形状を測定する干渉計を用いた形状測定方法を提供している。
【００１７】
また本発明においては、前記第２の被測定面は凹型の光学面である干渉計を用いた形状測定方法を提供している。
【００１８】
また本発明においては、前記形状測定方法で前記被測定面を測定した後、前記光波整形板と集光レンズを除去し、前記光源と前記レンズの間に発散型ＴＳレンズを配置し、前記被測定面からの反射光と該発散ＴＳレンズの参照面からの反射光とを干渉させて該発散ＴＳレンズの参照面の形状を測定する干渉計を用いた形状測定方法を提供している。
【００１９】
また本発明においては、前記形状測定方法で前記発散ＴＳレンズの参照面を測定した後、前記レンズを除去し、前記レンズを除去した場所に、第３の被測定面を有するレンズを配置し、前記発散ＴＳレンズの参照面からの反射光と第３の被測定面からの反射光とを干渉させて該第３の被測定面の形状を測定する干渉計を用いた形状測定方法を提供している。
【００２０】
【発明の実施の形態】
次に、本発明の実施の形態を図面を参照して説明する。
【００２１】
（第１の実施の形態）
図１に本発明の第１の実施の形態を示す。図１において、１０１は光源であるところのレーザ、１２１は射出したレーザ光を一旦集光して発散させる集光レンズ、１２２はレーザ光の進行方向をその偏光方位によって変化させる偏光膜付きのビームスプリッタ、１２３は発散するレーザ光を一旦平行光に変換するコリメータレンズ、１０２は平行光をピンホールに集光する集光レンズ、１０３は使用レーザ光の波長程度の直径を有するピンホール１０３ａと、そこから数μｍ〜数１００μｍ離れて隣接して設けられた窓１０３ｂを有する光波整形板、１０４は凹型の光学面１０４ａと、凸型の光学面１０４ｂを持つレンズ、１０６はカメラに干渉縞像を結像させる結像レンズ、１０７は撮像装置であるところのＣＣＤカメラ、１３０は電子化された画像データを処理するコンピュータ、１３１は計測画像または処理画像を映し出すディスプレイ装置である。ここでは光学面１０４ａを被測定面、光学面１０４ｂを参照面とする。また図２は前記光波整形板１０３の詳細図であり、ピンホール１０３ａと窓１０３ｂが隣接して設けられている様子を示した平面図とＡ−Ａ’断面図を示している。
【００２２】
光源１０１から射出したレーザ光は集光レンズ１２１で一旦集光された後、発散し偏光ビームスプリッタ１２２の作用で進行方向を折り曲げられ、コリメータレンズ１２３で平行光に変換された後、集光レンズ１０２で集光され、波形整形板１０３上にあけられたピンホール１０３ａを通過する。このピンホールはその直径φｄが使用光源波長をλ、集光レンズ１０２の開口数をＮＡとすると、
λ／２＜φｄ＜λ／ＮＡ
の範囲にしておけば、回折理論により入射した波面が収差を持っていてもピンホールを透過することにより無収差の理想球面波に変換される。たとえば、使用光源波長λ＝０．６μｍであり集光レンズ１０２の開口数ＮＡ＝０．５である場合、ピンホール１０３ａの直径φｄは
０．３μｍ＜φｄ＜１．２μｍ
にすれば良い。
【００２３】
図１において波線で示された１０４ａ’は光学面１０４ｂと同一の曲率中心をもち、お互いの光軸が一致した仮想の光学面である。図１はやや誇張して描かれているが、レンズ１０４の光学面１０４ａと仮想の光学面１０４ａ’は僅かに偏芯している。従って光学面１０４ａと光学面１０４ｂは、お互いの光軸が僅かに偏芯し、曲率中心はピンホール１０３ａの近傍で僅かに異なっている。
レンズ１０４を、ピンホール１０３ａを通過した光の光路中に配置する。光学面１０４ｂに入射する光は光学面１０４ｂに垂直に入射し、反射した光は正確に同じ経路を辿り、再びピンホール１０３ａを通過する。一方、ピンホール１０３ａを通過した光は、光学面１０４ａにおいても反射するが、光学面１０４ａが光学面１０４ｂと偏芯しているため、ピンホール１０３ａには戻らず、ピンホール１０３ａに隣接して設けられた窓１０３ｂを通過する。ただし、波形整形板１０３は、光学面１０４ａで反射した光が正確に窓１０３ｂを通過するように予めレンズ１０４の形状にあわせてピンホール１０３ａと窓１０３ｂが設計されている。つまり、波形整形板１０３のピンホール１０３ａと窓１０３ｂの位置は、光学面１０４ａの曲率半径と、光学面１０４ａの光軸に対する光学面１０４ｂの光軸の偏芯量により決定されている。
【００２４】
偏芯量は光学面１０４ａと光学面１０４ｂで反射した光が干渉縞を形成する大きさであれば良く、たとえば光学面１０４ａの曲率半径が１００ｍｍで、光学面１０４ａの光軸の光学面１０４ｂの光軸に対する偏芯量が１×１０^‐４ｒａｄであれば、ピンホール１０３ａと窓１０３ｂとの距離は２０μｍにしておけば良い。また、窓１０３ｂの大きさは、光学面１０４ａからの反射光における形状情報等の光波面情報が通過する大きさで有れば良く、通常１０μｍ以上にしておけば問題ない。
【００２５】
窓１０３ｂを通過した反射光と、ピンホール１０３ａを通過した反射光とは干渉し、干渉した両者の光は偏芯分の比較的大きなＴｉｌｔ波面を有する干渉縞として集光レンズ１０２、コリメータレンズ１２３、ビームスプリッタ１２２を今度は直進し、結像レンズ１０６を介して撮像装置であるＣＣＤカメラ１０７で撮像され、電子化された画像データはコンピュータ１３０で縞解析される。
【００２６】
この時得られる干渉縞は、光学面１０４ｂで反射してピンホール１０３ａを通った理想回折球面波を参照光波として、光学面１０４ａの形状誤差情報のみを持つ光波と干渉している。また、ピンホール１０３ａからＣＣＤカメラ１０７に至る光学系の光路は共通光路であるため、光学面１０４ａの絶対形状を高精度に測定する事ができる。尚、前述の通り干渉縞には比較的大きなＴｉｌｔ縞が含まれているが、これは従来から知られている数値処理で容易に除去することが可能である。
【００２７】
以上の様な構成により、参照光軸と被測定光軸がほぼ同一なフィゾー干渉計の構成を取ることができ、装置を小型化する事が可能となる。また、光学面１０４ｂを参照面とする事で通常測定が困難だと言われている凸型の光学面で有っても容易に測定可能である。また、ピンホール部分にミラー部材が不要なため、ミラーの汚れや微小な凹凸が測定に影響を及ぼす事がない。また、ピンホールからの全広がり光束を測定光として使用できるため、光量不足のため測定が不安定になる事がなく確実に精密な形状測定を行う事ができる。また、被測定物を配置する領域に制限がない為、大きな被測定物でも測定が可能である。
【００２８】
尚、光学面１０４ｂと光学面１０４ａは僅かながら偏芯しているため、光学面１０４ｂに入射する光は、光学面１０４ａにおいて僅かに屈折しているが、偏芯量が僅かであれば無視してもかまわない。より高精度に測定する為には、光学面１０４ｂに光が垂直に入射する様に、偏芯量を考慮して光学面１０４ｂを調整しておけば良い。
【００２９】
また、通常高精度な干渉計では干渉縞位相を検出するために参照面をピエゾ素子でλ／２程度動かすことで縞走査するいわゆるフリンジスキャン法が用いられる。しかしながら本実施例では参照面と被測定面が同一部材上にあるためフリンジスキャン法を実施する事はできない。しかしながら、その他の縞走査手段である波長走査法や、Ｔｉｌｔ縞を利用した空間変調法を使用することで容易に干渉縞位相を検出する事ができる。波長走査法を使用する場合は、光源１を半導体レーザなど波長走査可能なものにしておけば良く、また空間変調法の場合は、コンピュータ１３０にその解析機能が搭載されていれば良い。
【００３０】
尚、本実施の形態では、光学面１０４ａを被測定面、光学面１０４ｂを参照面としているが、光学面１０４ａを参照面、光学面１０４ｂを被測定面とする事もできる。その場合には光学面１０４ａに入射する光は光学面１０４ａに垂直に入射し、反射した光は正確に同じ経路を辿り、再びピンホール１０３ａを通過する。一方、光学面１０４ｂにおいて反射した光は、光学面１０４ｂが光学面１０４ａと偏芯しているため、ピンホール１０３ａには戻らず、ピンホール１０３ａに隣接して設けられた窓１０３ｂを通過する。
【００３１】
光学面１０４ｂを被測定面とした場合、光学面１０４ｂで入反射する光は、レンズ１０４の内部を通過しているためレンズの材質による影響を受けてしまう。従って、被測定面はレンズ１０４のピンホール１０３ａに最も近い光学面である事が望ましい。ただし、光学面１０４ｂを被測定面とした場合でも、レンズ１０４の材料の屈折率分布等を考慮しその分の値を補正すれば、高精度に光学面１０４ｂの絶対形状測定する事ができる。
【００３２】
また、本実施の形態における形状方法で絶対精度を測定した光学面１０４ａを使って、光学面１０４ｂの形状を測定することも可能である。前記測定方法で光学面１０４ａを測定した後、波面整形板１０３を取り除く事により、光学面１０４ａを参照面とし光学面１０４ｂを被測定面とする、フィゾー干渉計を構成する事ができる。従って、既に知られている通常のフィゾー干渉計による測定方法で、既に測定済の光学面１０４ａを参照面とし、光学面１０４ｂを測定することができる。このような測定方法を用いれば、通常測定が困難だと言われている凸面を高精度に測定する事ができる。
【００３３】
（第２の実施の形態）
図３は本発明の第２の実施の形態を説明する図である。図３には、レーザ１０１、レンズ１２１、ビームスリッター１２２、コリメータレンズ１２３、結像レンズ１０６、ＣＣＤレンズ１０７、コンピュータ１３０、ディスプレイ装置１３１は第１の実施の形態と同様であるため記載せず、第１の実施の形態と異なる部分のみを示している。第２の実施の形態において、第１の実施の形態と同じ部材には同じ符号を付してある。
【００３４】
図１と同様に１０２は集光レンズであり、１０３は波面整形板である。２０４は複数のレンズ２０５、２０６からなるレンズ群である。２０７はレンズ２０５、２０６を保持する筐体である。レンズ２０５は凹型光学面２０５ａと凸型光学面２０５ｂを有している。またレンズ２０６は凸型光学面２０６ａ、２０６ｂを有している。光学面は集光レンズ１０２側から２０５ａ、２０５ｂ、２０６ａ、２０６ｂの順に並んでいる。本実施形態において光学面２０５ａは被測定面であり、光学面２０６ｂは参照面である。
【００３５】
レンズ群２０４を、ピンホール１０３ａを通過した光の光路中に配置する。レンズ２０５とレンズ２０６は光学面２０５ａと光学面２０６ｂとはお互いの光軸が僅かに偏芯した状態に調整され筐体２０７に固定保持されている。光学面２０６ｂに入射する光は光学面２０６ｂに垂直に入射し、反射した光は正確に同じ経路を辿り、再びピンホール１０３ａを通過する。一方、ピンホール１０３ａを通過した光は、光学面２０５ａにおいても反射するが、光学面２０５ａが光学面２０６ｂと偏芯しているため、ピンホール１０３ａには戻らず、ピンホール１０３ａに隣接して設けられた窓１０３ｂを通過する。ただし、波形整形板１０３は、光学面２０５ａで反射した光が正確に窓１０３ｂを通過するように予めレンズ群２０４の形状にあわせてピンホール１０３ａと窓１０３ｂの位置が設計されている。つまり波形整形板１０３のピンホール１０３ａと窓１０３ｂの位置は、光学面２０５ａの曲率半径と、光学面２０６ｂの光軸に対する光学面２０５ａの光軸の偏芯量により決定されている。このような構成にする事で、第１の実施の形態と同じ手法により、２０５ａの形状の測定を行うことができる。
【００３６】
尚、本実施の形態では、光学面２０５ａを被測定面、光学面２０６ｂを参照面としているが、光学面２０５ａを参照面、光学面２０６ｂを被測定面とする事もできる。その場合には光学面２０５ａに入射する光は光学面２０５ａに垂直に入射し、反射した光は正確に同じ経路を辿り、再びピンホール１０３ａを通過する。一方、光学面２０６ｂにおいて反射した光は、光学面２０６ｂが光学面２０５ａと偏芯しているため、ピンホール１０３ａには戻らず、ピンホール１０３ａに隣接して設けられた窓１０３ｂを通過する。また同様にレンズ群２０４の設計により、光学面２０５ｂ、２０６ａを被測定面にする事も参照面にする事も可能である。
【００３７】
しかしながら、光学面２０５ｂ、２０６ａを被測定面とした場合、光学面２０５ｂ、２０６ａで入反射する光は、レンズ２０５の内部を通過しているためレンズ２０５の材質による影響を受けてしまう。また同様に光学面２０６ｂを被測定面とした場合、光学面２０６ｂで入反射する光は、レンズ２０５、２０６の内部を通過しているためレンズ２０５、２０６の材質による影響を受けてしまう。従って、被測定面はレンズ群２０４のうち、ピンホール１０３ａに最も近いレンズ２０５のピンホール１０３ａに最も近い光学面２０５ａである事が望ましい。ただし、光学面２０５ｂ、２０６ａ、２０６ｂを被測定面とした場合でも、レンズ２０５、２０６の材料の屈折率分布等を考慮しその分の値を補正すれば、高精度に絶対形状測定する事ができる。
【００３８】
また光学面２０６ｂが被測定面でも参照面でもない場合、光学面２０６ｂで光が反射しないように反射率を低下させる皮膜を塗布する等処理をしておかなければならない。また、同様に光学面２０６ａ、２０６ｂが共に被測定面でも参照面でもない場合、光学面２０６ａ、２０６ｂで光が反射しないように反射率を低下させる皮膜を塗布する等処理をしておかなければならない。従って参照面はピンホール１０３ａに最も遠いレンズ２０６のピンホール１０３ａに最も遠い光学面２０６ｂである事が望ましい。
【００３９】
本実施の形態によれば、前記第１の実施の形態で得られる効果に加え、レンズ群２０４の光学設計により被測定面２０５ａと参照面２０６ｂが全く異なる曲率中心であっても測定する事ができるため、測定の対象となるレンズのバリエーションが大幅に増え、測定するレンズの形状に左右される事なく曲率半径の大きな光学面や、凹型はもちろん凸型の光学面であても測定が可能である。また、曲率半径の大きな凸面または凹面であってもピンホール２０３ａから短い距離で測定する事が可能であり、装置を小型化できるともに、空気揺らぎによる測定精度低下が防止できる。
【００４０】
また、本実施の形態によれば第１実施の形態と同様に、前記測定方法で光学面２０５ａを測定した後、波面整形板１０３を取り除くことにより、光学面２０５ａを参照面とし、光学面２０６ｂを被測定面とするフィゾー干渉計を構成し、光学面２０６ｂを測定することも可能である。この場合、レンズ群２０４の設計により光学面２０６ｂが曲率半径の大きい凸面や凹面、また平面であっても測定する事が可能である。また同様に２０５ｂ、２０６ａを測定する事も可能である。
【００４１】
（第３の実施の形態）
図４は本発明の第３の実施の形態を説明する図である。図４には、レーザ１０１、レンズ１２１、ビームスリッター１２２、コリメータレンズ１２３、結像レンズ１０６、ＣＣＤレンズ１０７、コンピュータ１３０、ディスプレイ装置１３１は第１の実施の形態と同様であるため記載せず、第１の実施の形態と異なる部分のみを示している。本実施の形態において、第１の実施の形態と同じ部材には同じ符号を付してある。
【００４２】
まず、図４（ａ）は測定するレンズが単レンズの場合を説明する図である。図１と同様に１０２は集光レンズであり、１０３は波面整形板である。本実施の形態では、予め参照面となる凹型の光学反射面３０５ａを有するミラー部材３０５がピンホール１０３ａを通過した光の光路上に配置されている。３０４は凹型の光学面３０４ａ、凸型の光学面３０４ｂを持つレンズであり、光学面３０４ａが被測定面となる。
【００４３】
レンズ３０４を、ピンホール１０３ａを通過した光の光路中に、レンズ３０４の光学面３０４ａとミラー部材３０５の光学反射面３０５ａとはお互いの光軸を僅かに偏芯させて配置する。ピンホール１０３ａを透過した光は、光学面３０４ａで反射するが、光学面３０４ａが光軸と僅かに偏芯しているためピンホール１０３ａには戻らず、ピンホール１０３ａに隣接して設けられた窓１０３ｂを通過する。一方、参照面となる光学反射面３０５ａに入射する光は、光学反射面３０５ａの位置を調整する事により、光学反射面３０５ａに垂直に入射し、反射した光は正確に同じ経路を辿り、再びピンホール１０３ａを通過する。
【００４４】
次に、図４（ｂ）は測定するレンズが複数のレンズからなるレンズ群の場合を説明する図である。本実施の形態におけるレンズ群４０４は凹型の光学面４０５ａ、凸型の光学面４０５ｂを持つレンズ４０５と、凸型の光学面４０６ａ、４０６ｂを持つレンズ４０６とからなる。本実施形態においてはピンホール１０３ａに最も近いレンズ２０５のピンホール１０３ａに最も近い光学面２０６ａが被測定面である。４０７は参照面となる光学反射面４０７ａを有するミラー部材であり、予めピンホールを通過した光の光路上に配置されている。
【００４５】
レンズ４０４を、ピンホール１０３ａを通過した光の光路中に、レンズ４０５の光学面３０５ａとミラー部材４０７の光学反射面４０７ａとはお互いの光軸を僅かに偏芯させて配置する。その状態において、図４（ａ）に示した単レンズの場合と同じ手法により、光学面４０４ａの形状測定を行う。また、図４（ｂ）の場合、レンズ群４０４の設計により、光の屈折率を調整する事が容易にできるため、ミラー部材４０７を光学反射面４０７ａが平面である平板ミラーにする事も可能である。
【００４６】
このような構成にする事で、第１の実施の形態と同じ手法により、光学面３０５ａ、４０５ａの形状測定を行うことができる。本実施の形態によれば、前記第１の実施の形態で得られる効果に加え、予め波形整形板のピンホールと窓の位置を、被測定面の曲率半径と、光光軸に対する偏芯量により調整しておく必要がなく、ミラー部材３０５の位置を調整する事で対応できる。従って被測定物となるレンズもしくはレンズ群の設計が測定可能なある条件を満たしておく必要がなく、測定可能なレンズのバリエーションが増え、測定装置としての汎用性が大幅に向上する。
【００４７】
また、本実施の形態ではレンズ３０４及びレンズ群４０４とミラー部材４０７が別体であるために、第１、第２実施の形態で必要であった被測定面と参照面の２つの面に与える微小な偏芯を、ミラー部材３０５、４０７を少しｔｉｌｔさせるという不図示の機械調整により容易に与えることもできる。
【００４８】
（第４の実施の形態）
図５は本発明の第４の実施の形態を説明する図である。図５には、レーザ１０１、レンズ１２１、ビームスリッター１２２、コリメータレンズ１２３、結像レンズ１０６、ＣＣＤレンズ１０７、コンピュータ１３０、ディスプレイ装置１３１は第１の実施の形態と同様であるため記載せず、第１の実施の形態と異なる部分のみを示している。本実施の形態において、第１の実施の形態と同じ部材には同じ符号を付してある。
【００４９】
本実施の形態では、第１の実施の形態によって形状測定されてレンズ１０４の凸型の光学面１０４ｂを用いて、レンズ１０４の光源であるレーザ１０１（不図示）と逆側に配置されたレンズ５０１の曲率半径の大きい凹型の光学面５０１ａを測定するものである。
【００５０】
図５は第１の実施の形態によりレンズ１０４の凸型の光学面１０４ｂを形状測定した後、そのままレンズ１０４を保持した状態で、凹型の光学面５０１ａをもつレンズ５０１をレンズ１０４の光源であるレーザ１０１と逆側に配置する。このような配置にする事で、光学面１０４ｂを参照面、光学面５０１ａを被測定面とするフィゾー干渉計が構成され、被測定面５０１ａが測定される。この時、波面整形板は既に取り除かれている。この際、光学面１０４ａからの反射光を遮光する必要があるので、遮光板５０２を挿入し光学面１０４ａからの反射光を遮断している。
【００５１】
尚、遮光板５０２の目的は光学面１０４ｂからの反射光を遮断することなので、光学面１０４ｂからの反射光を遮断ができれば、１０４ａ面に反射率を低下させる被膜を塗布する等の別の手段でもかまわない。
【００５２】
本実施の形態では、レンズ１０４の凸型の光学面１０４ｂを参照面としているため、曲率半径の大きい凹型の光学面５０１ａを高精度に測定することができる。また、参照面となる凸型の光学面１０４ｂと被測定面となる凹型の光学面５０１ａとの面間隔を短くすることができるため、空気揺らぎなどの擾乱の影響を受けない高精度な測定ができる。
【００５３】
また、本体の干渉計を動かす事がなく、また参照面となるレンズも参照面の測定後に動かす事ないため、各光学面の物理的な面形状の変動が極めて小さく、また干渉計のカメラと光学素子の位置関係も保持されているので高い信頼性で絶対精度の測定が実施可能である。
【００５４】
（第５の実施の形態）
図６は本発明の第５の実施の形態を説明する図である。図６には、レーザ１０１、レンズ１２１、ビームスリッター１２２、コリメータレンズ１２３、結像レンズ１０６、ＣＣＤレンズ１０７、コンピュータ１３０、ディスプレイ装置１３１は第１の実施の形態と同様であるため記載せず、第１の実施の形態と異なる部分のみを示している。本実施の形態において、第１の実施の形態と同じ部材には同じ符号を付してある。
【００５５】
本実施の形態では、第１の実施の形態によって形状測定されてレンズ１０４の凹型の光学面１０４ａを用いて、ピンホール１０３ａとレンズ１０４の間に配置された、発散型のフィゾー干渉計用ＴＳレンズ面を測定するものである。さらにレンズ１０４を除去し、その場所に凹型の被測定面をもつ別のレンズを配置する事で、既に測定されているＴＳレンズ面を用いて凹型の被測定面を精密に測定するものである。
【００５６】
図６（ａ）は第１の実施の形態で示した方法で１０４ａを測定する図である。第１の実施の形態で示した方法により、被測定面である光学面１０４ａの絶対形状が測定される。次に、図６（ｂ）に示すように、レンズ１０２及び波面整形板１０３を取り除き、代わりに発散型ＴＳレンズ６０１を挿入する。発散型ＴＳレンズ６０１の光学面６０１ａの曲率中心を、光学面１０４ａの曲率中心と一致させることでフィゾー干渉計が構成され、既に絶対形状が求まっている光学面１０４ａを参照面としてＴＳレンズの光学面６０１ａが測定される。
【００５７】
この場合、凸型の光学面６０１ａと凹型の光学面１０４ａとが干渉面配置となるため、面間隔を短くすることができ、空気揺らぎなどの擾乱の影響を受けない高精度な測定も期待できる。
【００５８】
またこの場合、１０４ｂ面からの反射光が不要光となり計測に影響するため、１０４ｂ面に反射率を低下させる皮膜を塗布したり、不図示のピンホールで１０４ｂからの光を遮光するなどの工夫が必要である。
【００５９】
次に、図６（ｃ）に示すようにレンズ１０４を取り除き、その場所に代わりに被測定物となるレンズ６０２を配置する。今度は既に測定されている発散型ＴＳレンズの光学面６０１ａを、今度は参照面として使用し、レンズ６０２の凹型の被測定面６０２ａを測定する。
【００６０】
本実施の形態においては、図６（ｂ）に示した場合と同様に、参照面となる凸型の光学面６０１ａと凹型の光学面６０２ａとは干渉面配置となるため、面間隔を短くすることができ、空気揺らぎなどの擾乱の影響を受けない高精度な測定も期待できる。
【００６１】
また、本実施の形態では、本体の干渉計を動かす事無く、またＴＳレンズを挿入するときに原器として使用するレンズ１０４も動かすことが無い為、測定に使用する物理的な面形状の変動が極めて小さく、また干渉計のカメラと光学素子の位置関係も保持されているので高い信頼性で絶対精度の形状測定が実施可能である。
【００６２】
本実施の形態においては、測定するレンズの形状に曲率や凹凸形状等の制約は全くなく、配置する場合の参照面に対して偏芯を持たせる等の制約もない為、様々なレンズの形状に対して、より汎用的に形状測定を行う事ができる。また、被測定物としての凹面ミラーは必ずしも透明では無く、またレンズの形状としてもよいものばかりではないので、汎用的な使用方法では本実施の形態におけるの使用方法がより現実的となる。
【００６３】
尚、発散型ＴＳレンズとは、参照面が凸面であり射出する光が発散するように設計されたものを指す。
【００６４】
【発明の効果】
以上説明したように本発明においては、光源と、光源からの光を一旦集光させる集光レンズと、該集光した光を理想的な球面波に変換するピンホールとその近傍に設けられた光波面情報を通過させる窓とが形成された光波整形板とを有し、該ピンホールを通過した光の光路中に、お互いの光軸が偏芯した参照面と被測定面とを有する少なくとも１枚のレンズを、該参照面に光が垂直に入射し、反射した光が該ピンホールを再度通過し、該測定面に反射した光が該窓を通過する位置に配置し、該参照面で反射し該ピンホールを再度通過した反射光と、該被測定面で反射し該窓を通過した反射光とを干渉させて被測定面の形状を測定する形状測定装置及び形状測定方法を提供している。
【００６５】
これにより、以上の様な構成により、参照光軸と被測定光軸がほぼ同一なフィゾー干渉計の構成を取ることができ、装置を小型化する事が可能となる。また、光学面１０４ｂを参照面とする事で通常測定が困難だと言われている凸型の光学面で有っても容易に測定可能である。また、ピンホール部分にミラー部材が不要なため、ミラーの汚れや微小な凹凸が測定に影響を及ぼす事がない。また、ピンホールからの全広がり光束を測定光として使用できるため、光量不足のため測定が不安定になる事がなく確実に精密な形状測定を行う事ができる。また、被測定物を配置する領域に制限がない為、大きな被測定物でも測定が可能である。
【００６６】
また、さらに光波整形板を除去し、被測定面からの反射光と、参照面からの反射光とを干渉させて該参照面の形状を測定する形状測定方法により、凸面の形状計測も可能である。
【００６７】
また、さらに被測定面を有するレンズを複数のレンズからなるレンズ群とすることで、被測定面と参照面が同一の曲率中心でなくても測定する事ができるため、測定の対象となるレンズのバリエーションが大幅に増え、測定するレンズの形状に左右される事なく測定が可能である。また、大きな曲率半径の凸面または凹面の計測が集光点から短い距離での測定が可能となり、装置の小型化と空気揺らぎによる精度低下が防止できる。
【００６８】
また、参照面を被測定面を有するレンズもしくはレンズ群とは異なるミラー部材とすることにより、大きな曲率半径の凸面または凹面の計測が集光点から短い距離での測定可能となり、装置の小型化と空気揺らぎによる精度低下が防止できる。また、光学反射面により光を反射するため、光量の損出少なく、より正確な形状測定が可能となる。また、予め波形整形板のピンホールと窓の位置を、被測定面の曲率半径と、光光軸に対する偏芯量により調整しておく必要がなく、ミラー部材３０５の位置を調整する事で対応できるため、被測定物となるレンズもしくはレンズ群の設計を測定可能なものにしておく必要がなく、測定装置としての汎用性が大幅に向上している。
【００６９】
また、前記形状測定方法で前記被測定面を測定した後、前記光波整形板を除去し、該被測定面からの反射光と、該参照面からの反射光とを干渉させて該参照面の形状を測定する事で、通常測定が困難だと言われている凸型の光学面を高精度に測定する事ができる。
【００７０】
また、前記形状測定方法で該凸型の光学面を測定した後、前記光波整形板を除去し、該レンズの該光源と逆側に第２の被測定面をもつ光学素子を配置し、該第２の被測定面からの反射光と該凸型の光学面からの反射光とを干渉させて該第２の被測定面の形状を測定する事で、曲率半径の大きい凹型の光学面を高精度に測定することができる。また、参照面となる凸型の光学面と被測定面となる凹型の光学面との面間隔を短くすることができるため、空気揺らぎなどの擾乱の影響を受けない高精度な測定ができる。また、本体の干渉計を動かす事がなく、また参照面となるレンズを参照面の測定後に動かす事ないため、測定に使用する物理的な面形状の変動が極めて小さく、また干渉計のカメラと光学素子の位置関係も保持されているので高い信頼性で絶対精度の測定が実施可能である。
【００７１】
また、前記形状測定方法で前記被測定面を測定した後、前記光波整形板と集光レンズを除去し、前記光源と前記レンズの間に発散型ＴＳレンズを配置し、前記被測定面からの反射光と該発散ＴＳレンズの参照面からの反射光とを干渉させて該発散ＴＳレンズの参照面の形状を測定するため、発散ＴＳレンズの面精度を高精度に測定する事ができる。
【００７２】
さらに、前記形状測定方法で前記発散ＴＳレンズの参照面を測定した後、前記レンズと除去し、前記レンズを除去した場所に、第３の被測定面を有するレンズを配置し、前記発散ＴＳレンズの参照面からの反射光と第３の被測定面からの反射光とを干渉させて該第３の被測定面の形状を測定するため、装置間の位置の交差や誤差をまったく含まずに測定する事ができるため、非常に高精度に第２のレンズの被測定面の形状を測定する事が可能である。
【図面の簡単な説明】
【図１】第１の実施の形態の説明図
【図２】第１の実施の形態で使用するピンホール部分の詳細説明図
【図３】第２の実施の形態の説明図
【図４】第３の実施の形態の説明図
【図５】第４の実施の形態の説明図
【図６】第５の実施の形態の説明図
【図７】第１の従来の技術の説明図
【図８】第２の従来の技術の説明図
【符号の説明】
１０１レーザ
１０２集光レンズ
１０３波面整形板
１０４レンズ
１０６結像レンズ
１０７ＣＣＤカメラ
１２１集光レンズ
１２２ビームスプリッタ
１２３コリメータレンズ
１３０コンピュータ
１３１ディスプレイ
２０４，２０５，３０４，４０５，４０６，５０１，６０２レンズ
３０５，４０７ミラー部材
６０１発散ＴＳレンズ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shape measuring method and apparatus using an interferometer that measures the spherical shape accuracy of a reduction projection optical lens or a mirror for a semiconductor exposure apparatus with extremely high accuracy.
[0002]
[Prior art]
Generally, Fizeau interferometers and Twiman-Green interferometers are generally used as methods for measuring spherical lenses and mirrors with higher accuracy than before, but both require spherical surfaces and planes to be referenced, and absolute accuracy is Basically, it is defined by the shape accuracy of these reference spherical surfaces and reference planes. It is said that the normal reference surface manufacturing method is limited to guaranteeing about λ / 10 to λ / 20 with the He—Ne laser wavelength being λ (λ = 632.8 nm).
[0003]
On the other hand, with the miniaturization and high precision of the semiconductor exposure apparatus, the exposure light source wavelength is shortened to KrF excimer laser (λ = 248 nm), ArF excimer laser (λ = 193 nm), F2 laser (λ = 157 nm), and Even EUV light (Extreme Ultra Violet: λ = 13.6 nm) has been used as an exposure light source. Projection optical lenses and mirrors for these exposure apparatuses are required to have a shape accuracy of 1 nm to 0.1 nm. To achieve such an accuracy, a measuring device with higher accuracy is required. Usually, it is difficult to measure with such accuracy even by simply realizing reproduction accuracy, and it is extremely difficult to guarantee absolute accuracy.
[0004]
Japanese Patent Application Laid-Open No. 2-228505 describes a technique for guaranteeing the absolute accuracy of an optical surface to several tens of inches or less. FIG. 7 shows the configuration of the first prior art described as the first embodiment of JP-A-2-228505. In FIG. 7, the light emitted from the light source 1 is collected by the condenser lens 2 and reaches the pinhole mirror 3, and part of the light hits the object to be measured 4 through the pinhole and returns to the pinhole mirror 3. Thus, the image sensor 7 is reached. This light is called measurement light. Other light is reflected by the pinhole mirror 3, reflected by the condenser mirror 5, returns to the pinhole mirror 3 again, passes through the pinhole, and reaches the image sensor 7. This light is called reference light. The measurement light and the reference light interfere to form interference fringes, and the surface shape of the object to be measured is measured by imaging with the image sensor 7.
[0005]
It is known that light becomes a diffractive ideal spherical wave by passing through a pinhole. Accordingly, since the measurement light becomes a diffractive ideal spherical wave that has passed through the pinhole, the light reflected by the measurement object 4 reaches the image pickup device 7 as a light wave having only a shape error from the spherical surface of the measurement object 4 as aberration information. The reference light is reflected and collected by the condenser mirror 5 and then passes through the pinhole to become a diffractive ideal spherical wave, so that the aberration wavefront reaches the image sensor 7. At this time, the surface accuracy of the condensing mirror 5 does not need to be particularly high, and it is sufficient if it has accuracy to reflect light. In this way, the measurement light and the reference light can form interference fringes having only the shape error information of the device under test 4 on the image sensor 7 with high absolute accuracy without providing a special reference plane. Shape measurement is possible.
[0006]
FIG. 8 shows the configuration of the second conventional technique described as the second embodiment of Japanese Patent Laid-Open No. 2-228505. In FIG. 8, the light emitted from the light source 1 is passed through a pinhole provided in the pinhole mirror 3 by the condenser lens 2 to be an ideal spherical wave, and a part thereof is incident on the image sensor 7 as a reference wave. In addition, after another part of the same light wave is reflected by the DUT 4, it is reflected by the pinhole mirror 3 and incident on the image sensor 7 to interfere with the reference wave, and the generated interference fringe image is captured by the image sensor 7. The surface shape of the object to be measured is measured by imaging with The second conventional technique has a configuration in which the condenser mirror of the first conventional technique is omitted.
[0007]
[Problems to be solved by the invention]
However, in the first conventional technique described as the first embodiment in Japanese Patent Laid-Open No. 2-228505 shown in FIG. 7, the reference optical axis and the optical axis to be measured are separated with a large angle of approximately 90 degrees. For this reason, the apparatus becomes large and complicated. In addition, the distance between the pinhole and the surface to be measured must be separated by a distance corresponding to the radius of curvature of the surface to be measured. Therefore, when measuring a surface to be measured with a large radius of curvature, the optical path becomes long and accuracy due to air fluctuations A decline is inevitable. There is also a problem that measurement is possible if the surface to be measured is concave but measurement is not possible if the surface to be measured is convex. In addition, since a mirror is always required for the pinhole portion, dirt and minute unevenness of the mirror may affect the measurement wavefront.
[0008]
In addition, in the second conventional technique described as the second embodiment in Japanese Patent Laid-Open No. 2-228505 shown in FIG. 8, in addition to the above-mentioned problem, it is possible to use the spread of an ideal spherical wave that emerges from a pinhole as the measurement light. Therefore, the amount of light is reduced and the measurement accuracy is lowered. Moreover, since the area | region which arrange | positions a to-be-measured object will be restricted, the to-be-measured object which has a big to-be-measured surface cannot be measured.
[0009]
[Means for Solving the Problems]
In the present invention, a light source, a condensing lens that temporarily collects light from the light source, a pinhole that converts the collected light into an ideal spherical wave, and light wavefront information provided in the vicinity thereof are passed. And at least one lens having a reference surface and a surface to be measured whose optical axes are decentered in the optical path of the light that has passed through the pinhole. The light reflected by the reference surface passes through the pinhole again, and the light reflected by the measurement surface is disposed at a position passing through the window, and is reflected by the reference surface and passes through the pinhole again. And a shape measuring apparatus and a shape measuring method for measuring the shape of the surface to be measured by causing interference between the reflected light reflected by the surface to be measured and the reflected light passing through the window.
[0010]
According to the present invention, there is provided a shape measuring apparatus and a shape measuring method using an interferometer in which the lens is a single lens having a concave and convex optical surface slightly different in the center of curvature in the vicinity of the pinhole. Yes.
[0011]
In the present invention, the measured surface is a concave optical surface closest to the pinhole of the lens, and the reference surface is a convex optical surface opposite to the concave optical surface. A shape measuring apparatus and a shape measuring method using a meter are provided.
[0012]
In the present invention, the lens is a lens group including a plurality of lenses, and the reference surface and the surface to be measured are different from the optical surface of the lens closest to the pinhole and the lens closest to the pinhole. A shape measuring apparatus and a shape measuring method using an interferometer which is any one of the above optical surfaces are provided.
[0013]
In the present invention, the measured surface is a concave optical surface closest to the pinhole of the lens closest to the pinhole, and the reference surface is an optical surface of a lens different from the lens closest to the pinhole. A shape measuring device and a shape measuring method using an interferometer are provided.
[0014]
In the present invention, a light source, a condensing lens that temporarily collects light from the light source, a pinhole that converts the collected light into an ideal spherical wave, and light wavefront information provided in the vicinity thereof A light wave shaping plate formed with a window to pass through, and a mirror member having an optical reflecting surface that reflects light that has passed through the pinhole, and another optical surface between the pinhole and the mirror member And at least one lens having a surface to be measured whose optical axis is decentered is adjusted to a position where light reflected by the surface to be measured passes through the window, and the mirror member is perpendicular to the optical reflecting surface. The reflected light is placed at a position where the reflected light passes through the pinhole again, is reflected by the optical reflecting surface, and passes again through the pinhole, and is reflected by the measured surface and passes through the window. Use an interferometer that measures the shape of the surface to be measured by interfering with the reflected light. It provides a shape measuring apparatus and a shape measuring method.
[0015]
Further, in the present invention, after measuring the measured surface by the shape measuring method, the light wave shaping plate is removed, and the reflected light from the measured surface and the reflected light from the reference surface are caused to interfere with each other. A shape measuring method using an interferometer for measuring the shape of the reference surface is provided.
[0016]
In the present invention, the optical surface opposite to the light source of the lens is a convex optical surface, and after measuring the convex optical surface by the shape measurement method, the light wave shaping plate is removed, An optical element having a second measured surface is arranged on the opposite side of the lens from the light source, and the reflected light from the second measured surface and the reflected light from the convex optical surface are caused to interfere with each other. A shape measuring method using an interferometer for measuring the shape of the second measured surface is provided.
[0017]
In the present invention, there is provided a shape measuring method using an interferometer in which the second surface to be measured is a concave optical surface.
[0018]
In the present invention, after the surface to be measured is measured by the shape measuring method, the light wave shaping plate and the condenser lens are removed, a divergent TS lens is disposed between the light source and the lens, and the object to be measured is measured. A shape measuring method using an interferometer that measures the shape of the reference surface of the divergent TS lens by causing interference between the reflected light from the measurement surface and the reflected light from the reference surface of the divergent TS lens is provided.
[0019]
Further, in the present invention, after measuring the reference surface of the divergent TS lens by the shape measurement method, the lens is removed, and a lens having a third measured surface is disposed at the place where the lens is removed, A shape measuring method using an interferometer that measures the shape of the third measured surface by causing reflected light from a reference surface of the divergent TS lens to interfere with reflected light from a third measured surface. ing.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0021]
(First embodiment)
FIG. 1 shows a first embodiment of the present invention. In FIG. 1, 101 is a laser as a light source, 121 is a condensing lens that once condenses and diverges emitted laser light, and 122 is a beam with a polarizing film that changes the traveling direction of the laser light according to its polarization direction. The splitter, 123 is a collimator lens that once converts the diverging laser light into parallel light, 102 is a condensing lens that condenses the parallel light into the pinhole, 103 is a pinhole 103a having a diameter of about the wavelength of the used laser light, A light wave shaping plate having a window 103b provided adjacently several μm to several 100 μm away from it, 104 is a lens having a concave optical surface 104a and a convex optical surface 104b, and 106 is an interference fringe image on the camera. An imaging lens for imaging, a CCD camera 107 as an imaging device, a computer 130 for processing digitized image data, Reference numeral 131 denotes a display device that displays a measurement image or a processed image. Here, the optical surface 104a is a measured surface and the optical surface 104b is a reference surface. FIG. 2 is a detailed view of the light wave shaping plate 103, showing a plan view showing a state where the pinhole 103a and the window 103b are provided adjacent to each other, and a sectional view taken along the line AA ′.
[0022]
The laser light emitted from the light source 101 is once condensed by the condenser lens 121, then diverges, the traveling direction is bent by the action of the polarization beam splitter 122, converted into parallel light by the collimator lens 123, and then the condenser lens. The light is condensed at 102 and passes through a pinhole 103 a formed on the waveform shaping plate 103. This pinhole has a diameter φd of λ as the light source wavelength used and NA as the numerical aperture of the condenser lens 102.
λ / 2 <φd <λ / NA
In this range, even if the incident wavefront has an aberration according to the diffraction theory, it is converted into an aspherical ideal spherical wave by passing through the pinhole. For example, when the light source wavelength λ = 0.6 μm and the numerical aperture NA of the condenser lens 102 is 0.5, the diameter φd of the pinhole 103a is
0.3 μm <φd <1.2 μm
You can do it.
[0023]
104a ′ indicated by a wavy line in FIG. 1 is a virtual optical surface having the same center of curvature as the optical surface 104b and having the same optical axis. Although FIG. 1 is drawn slightly exaggerated, the optical surface 104a of the lens 104 and the virtual optical surface 104a ′ are slightly decentered. Therefore, the optical surfaces 104a and 104b are slightly decentered from each other, and the centers of curvature are slightly different in the vicinity of the pinhole 103a.
The lens 104 is disposed in the optical path of the light that has passed through the pinhole 103a. The light incident on the optical surface 104b enters the optical surface 104b perpendicularly, and the reflected light follows the exact same path and passes through the pinhole 103a again. On the other hand, the light that has passed through the pinhole 103a is also reflected by the optical surface 104a, but the optical surface 104a is eccentric to the optical surface 104b, so that it does not return to the pinhole 103a but is adjacent to the pinhole 103a. It passes through the provided window 103b. However, in the waveform shaping plate 103, the pinhole 103a and the window 103b are designed in advance according to the shape of the lens 104 so that the light reflected by the optical surface 104a accurately passes through the window 103b. That is, the positions of the pinhole 103a and the window 103b of the waveform shaping plate 103 are determined by the radius of curvature of the optical surface 104a and the amount of eccentricity of the optical axis of the optical surface 104b with respect to the optical axis of the optical surface 104a.
[0024]
The amount of eccentricity may be any size as long as the light reflected by the optical surfaces 104a and 104b forms an interference fringe. For example, the radius of curvature of the optical surface 104a is 100 mm, and the optical surface 104b of the optical axis of the optical surface 104a Eccentricity with respect to the optical axis is 1 × 10 ^-4 In the case of rad, the distance between the pinhole 103a and the window 103b may be 20 μm. Further, the size of the window 103b may be a size that allows light wavefront information such as shape information in the reflected light from the optical surface 104a to pass, and there is no problem if it is normally set to 10 μm or more.
[0025]
The reflected light that has passed through the window 103b and the reflected light that has passed through the pinhole 103a interfere with each other, and the interfered light is an interference fringe having a relatively large tilt wavefront for eccentricity. Then, the beam splitter 122 goes straight, and is imaged by the CCD camera 107 which is an imaging device via the imaging lens 106, and the digitized image data is subjected to fringe analysis by the computer 130.
[0026]
The interference fringes obtained at this time interfere with a light wave having only the shape error information of the optical surface 104a using the ideal diffraction spherical wave reflected by the optical surface 104b and passing through the pinhole 103a as a reference light wave. Further, since the optical path of the optical system from the pinhole 103a to the CCD camera 107 is a common optical path, the absolute shape of the optical surface 104a can be measured with high accuracy. As described above, the interference fringes include relatively large Tilt fringes, which can be easily removed by conventionally known numerical processing.
[0027]
With the configuration as described above, a configuration of a Fizeau interferometer in which the reference optical axis and the optical axis to be measured are substantially the same can be adopted, and the apparatus can be miniaturized. Further, by using the optical surface 104b as a reference surface, even a convex optical surface that is said to be difficult to measure normally can be easily measured. Further, since no mirror member is required in the pinhole portion, dirt and minute irregularities on the mirror do not affect the measurement. In addition, since the total spread light beam from the pinhole can be used as measurement light, the measurement does not become unstable due to insufficient light quantity, and accurate shape measurement can be performed reliably. Moreover, since there is no restriction | limiting in the area | region which arrange | positions a to-be-measured object, even a big to-be-measured object can be measured.
[0028]
Since the optical surface 104b and the optical surface 104a are slightly decentered, the light incident on the optical surface 104b is slightly refracted on the optical surface 104a, but is ignored if the amount of decentering is small. It doesn't matter. In order to perform measurement with higher accuracy, the optical surface 104b may be adjusted in consideration of the amount of eccentricity so that light enters the optical surface 104b perpendicularly.
[0029]
Further, in general, a highly accurate interferometer uses a so-called fringe scanning method in which fringe scanning is performed by moving a reference surface by about λ / 2 with a piezo element in order to detect an interference fringe phase. However, in this embodiment, since the reference surface and the surface to be measured are on the same member, the fringe scanning method cannot be performed. However, the interference fringe phase can be easily detected by using a wavelength scanning method which is another fringe scanning means or a spatial modulation method using a Tilt fringe. In the case of using the wavelength scanning method, the light source 1 may be configured to be capable of wavelength scanning such as a semiconductor laser, and in the case of the spatial modulation method, the computer 130 may be equipped with the analysis function.
[0030]
In the present embodiment, the optical surface 104a is the measurement surface and the optical surface 104b is the reference surface. However, the optical surface 104a can be the reference surface and the optical surface 104b can be the measurement surface. In that case, the light incident on the optical surface 104a enters the optical surface 104a perpendicularly, and the reflected light follows the exact same path and passes through the pinhole 103a again. On the other hand, the light reflected by the optical surface 104b does not return to the pinhole 103a but passes through the window 103b provided adjacent to the pinhole 103a because the optical surface 104b is eccentric with the optical surface 104a.
[0031]
When the optical surface 104b is a measurement target surface, the light incident and reflected by the optical surface 104b passes through the inside of the lens 104 and is affected by the lens material. Therefore, it is desirable that the surface to be measured is an optical surface closest to the pinhole 103a of the lens 104. However, even when the optical surface 104b is a surface to be measured, the absolute shape of the optical surface 104b can be measured with high accuracy by correcting the corresponding value in consideration of the refractive index distribution of the material of the lens 104.
[0032]
Further, it is possible to measure the shape of the optical surface 104b by using the optical surface 104a whose absolute accuracy is measured by the shape method in this embodiment. After measuring the optical surface 104a by the measurement method, the Fizeau interferometer can be configured with the optical surface 104a as a reference surface and the optical surface 104b as a measured surface by removing the wavefront shaping plate 103. Therefore, the optical surface 104b can be measured by using the already known normal Fizeau interferometer as a reference surface with the optical surface 104a already measured. By using such a measurement method, it is possible to measure a convex surface, which is usually said to be difficult to measure, with high accuracy.
[0033]
(Second Embodiment)
FIG. 3 is a diagram for explaining a second embodiment of the present invention. In FIG. 3, the laser 101, the lens 121, the beam slitter 122, the collimator lens 123, the imaging lens 106, the CCD lens 107, the computer 130, and the display device 131 are not described because they are the same as those in the first embodiment. Only the parts different from the first embodiment are shown. In the second embodiment, the same members as those in the first embodiment are denoted by the same reference numerals.
[0034]
As in FIG. 1, reference numeral 102 denotes a condenser lens, and reference numeral 103 denotes a wavefront shaping plate. A lens group 204 includes a plurality of lenses 205 and 206. A housing 207 holds the lenses 205 and 206. The lens 205 has a concave optical surface 205a and a convex optical surface 205b. The lens 206 has convex optical surfaces 206a and 206b. The optical surfaces are arranged in the order of 205a, 205b, 206a, and 206b from the condenser lens 102 side. In the present embodiment, the optical surface 205a is a surface to be measured, and the optical surface 206b is a reference surface.
[0035]
The lens group 204 is disposed in the optical path of the light that has passed through the pinhole 103a. The lens 205 and the lens 206 are adjusted and held in a state where the optical axes of the optical surface 205a and the optical surface 206b are slightly decentered from each other. The light incident on the optical surface 206b enters the optical surface 206b perpendicularly, and the reflected light follows the exact same path and passes through the pinhole 103a again. On the other hand, the light that has passed through the pinhole 103a is also reflected by the optical surface 205a, but the optical surface 205a is eccentric to the optical surface 206b, so that it does not return to the pinhole 103a but is adjacent to the pinhole 103a. It passes through the provided window 103b. However, in the waveform shaping plate 103, the positions of the pinhole 103a and the window 103b are designed in advance according to the shape of the lens group 204 so that the light reflected by the optical surface 205a accurately passes through the window 103b. That is, the positions of the pinhole 103a and the window 103b of the waveform shaping plate 103 are determined by the radius of curvature of the optical surface 205a and the amount of eccentricity of the optical axis of the optical surface 205a with respect to the optical axis of the optical surface 206b. With such a configuration, the shape of 205a can be measured by the same method as in the first embodiment.
[0036]
In this embodiment, the optical surface 205a is the measurement target surface and the optical surface 206b is the reference surface. However, the optical surface 205a may be the reference surface and the optical surface 206b may be the measurement surface. In that case, the light incident on the optical surface 205a is incident on the optical surface 205a perpendicularly, and the reflected light follows the exact same path and again passes through the pinhole 103a. On the other hand, the light reflected by the optical surface 206b does not return to the pinhole 103a but passes through the window 103b provided adjacent to the pinhole 103a because the optical surface 206b is eccentric with the optical surface 205a. Similarly, depending on the design of the lens group 204, the optical surfaces 205b and 206a can be used as measurement surfaces or reference surfaces.
[0037]
However, when the optical surfaces 205b and 206a are measured surfaces, the light incident and reflected by the optical surfaces 205b and 206a is affected by the material of the lens 205 because it passes through the lens 205. Similarly, when the optical surface 206b is a surface to be measured, the light incident / reflected by the optical surface 206b passes through the inside of the lenses 205 and 206, and thus is affected by the material of the lenses 205 and 206. Therefore, it is desirable that the surface to be measured is the optical surface 205a closest to the pinhole 103a of the lens 205 closest to the pinhole 103a in the lens group 204. However, even when the optical surfaces 205b, 206a, and 206b are measured surfaces, if the refractive index distribution of the material of the lenses 205 and 206 is taken into consideration and the corresponding value is corrected, the absolute shape can be measured with high accuracy. it can.
[0038]
Further, when the optical surface 206b is neither a surface to be measured nor a reference surface, it is necessary to perform a process such as applying a film that reduces the reflectance so that the optical surface 206b does not reflect light. Similarly, if both the optical surfaces 206a and 206b are neither the surface to be measured nor the reference surface, the optical surfaces 206a and 206b must be treated such as applying a film that reduces the reflectance so that the light is not reflected. Don't be. Therefore, the reference surface is preferably the optical surface 206b farthest from the pinhole 103a of the lens 206 farthest from the pinhole 103a.
[0039]
According to the present embodiment, in addition to the effects obtained in the first embodiment, it is possible to measure even if the measured surface 205a and the reference surface 206b have completely different curvature centers due to the optical design of the lens group 204. As a result, the number of lens variations to be measured is greatly increased, and measurement is possible on optical surfaces with large curvature radii, convex optical surfaces as well as concave ones, regardless of the shape of the lens being measured. is there. Further, even a convex surface or a concave surface having a large curvature radius can be measured at a short distance from the pinhole 203a, and the apparatus can be miniaturized and measurement accuracy can be prevented from being lowered due to air fluctuation.
[0040]
Further, according to the present embodiment, as in the first embodiment, after the optical surface 205a is measured by the measurement method, the wavefront shaping plate 103 is removed, so that the optical surface 205a becomes the reference surface and the optical surface 206b. It is also possible to configure a Fizeau interferometer with the surface to be measured and measure the optical surface 206b. In this case, measurement is possible even if the optical surface 206b is a convex surface, a concave surface, or a flat surface having a large radius of curvature by the design of the lens group 204. Similarly, 205b and 206a can be measured.
[0041]
(Third embodiment)
FIG. 4 is a diagram for explaining a third embodiment of the present invention. In FIG. 4, the laser 101, the lens 121, the beam slitter 122, the collimator lens 123, the imaging lens 106, the CCD lens 107, the computer 130, and the display device 131 are not described because they are the same as those in the first embodiment. Only the parts different from the first embodiment are shown. In the present embodiment, the same members as those in the first embodiment are denoted by the same reference numerals.
[0042]
First, FIG. 4A is a diagram illustrating a case where a lens to be measured is a single lens. As in FIG. 1, reference numeral 102 denotes a condenser lens, and reference numeral 103 denotes a wavefront shaping plate. In this embodiment, a mirror member 305 having a concave optical reflection surface 305a serving as a reference surface is disposed on the optical path of light that has passed through the pinhole 103a. Reference numeral 304 denotes a lens having a concave optical surface 304a and a convex optical surface 304b, and the optical surface 304a is a surface to be measured.
[0043]
The lens 304 is arranged in the optical path of the light that has passed through the pinhole 103a, with the optical surface 304a of the lens 304 and the optical reflection surface 305a of the mirror member 305 slightly decentered from each other. The light transmitted through the pinhole 103a is reflected by the optical surface 304a, but is not returned to the pinhole 103a because the optical surface 304a is slightly decentered from the optical axis, and is provided adjacent to the pinhole 103a. It passes through the window 103b. On the other hand, the light incident on the optical reflecting surface 305a serving as the reference surface is incident on the optical reflecting surface 305a perpendicularly by adjusting the position of the optical reflecting surface 305a, and the reflected light follows the same path exactly, Passes through the pinhole 103a.
[0044]
Next, FIG. 4B is a diagram illustrating a case where the lens to be measured is a lens group including a plurality of lenses. The lens group 404 in this embodiment includes a lens 405 having a concave optical surface 405a and a convex optical surface 405b, and a lens 406 having convex optical surfaces 406a and 406b. In the present embodiment, the optical surface 206a closest to the pinhole 103a of the lens 205 closest to the pinhole 103a is the surface to be measured. Reference numeral 407 denotes a mirror member having an optical reflection surface 407a serving as a reference surface, and is disposed on the optical path of light that has passed through a pinhole in advance.
[0045]
The lens 404 is disposed in the optical path of the light that has passed through the pinhole 103a, with the optical surface 305a of the lens 405 and the optical reflection surface 407a of the mirror member 407 slightly decentered from each other. In this state, the shape of the optical surface 404a is measured by the same method as that for the single lens shown in FIG. In the case of FIG. 4B, the refractive index of light can be easily adjusted by the design of the lens group 404, so that the mirror member 407 can be a flat mirror whose optical reflection surface 407a is a flat surface. It is.
[0046]
With such a configuration, the shape of the optical surfaces 305a and 405a can be measured by the same method as in the first embodiment. According to the present embodiment, in addition to the effects obtained in the first embodiment, the pinholes and window positions of the waveform shaping plate are previously set, the radius of curvature of the surface to be measured, and the amount of eccentricity with respect to the optical axis. It is not necessary to adjust the position of the mirror member 305 by adjusting the position of the mirror member 305. Therefore, it is not necessary to satisfy certain conditions that allow the design of the lens or lens group to be measured to be measured, the number of measurable lens variations increases, and the versatility of the measuring apparatus is greatly improved.
[0047]
In this embodiment, since the lens 304 and the lens group 404 and the mirror member 407 are separate bodies, the measurement surface and the reference surface that are necessary in the first and second embodiments are given to the two surfaces. A minute eccentricity can be easily given by mechanical adjustment (not shown) in which the mirror members 305 and 407 are slightly tilted.
[0048]
(Fourth embodiment)
FIG. 5 is a diagram for explaining a fourth embodiment of the present invention. In FIG. 5, the laser 101, the lens 121, the beam slitter 122, the collimator lens 123, the imaging lens 106, the CCD lens 107, the computer 130, and the display device 131 are not described because they are the same as those in the first embodiment. Only the parts different from the first embodiment are shown. In the present embodiment, the same members as those in the first embodiment are denoted by the same reference numerals.
[0049]
In the present embodiment, the lens whose shape is measured according to the first embodiment and is disposed on the opposite side to the laser 101 (not shown) that is the light source of the lens 104 using the convex optical surface 104b of the lens 104. A concave optical surface 501a having a large curvature radius of 501 is measured.
[0050]
FIG. 5 shows a lens 501 having a concave optical surface 501a as a light source of the lens 104 while the lens 104 is held as it is after measuring the shape of the convex optical surface 104b of the lens 104 according to the first embodiment. The laser 101 is disposed on the opposite side. With this arrangement, a Fizeau interferometer having the optical surface 104b as a reference surface and the optical surface 501a as a measured surface is configured, and the measured surface 501a is measured. At this time, the wavefront shaping plate has already been removed. At this time, since it is necessary to block the reflected light from the optical surface 104a, the light blocking plate 502 is inserted to block the reflected light from the optical surface 104a.
[0051]
Since the purpose of the light shielding plate 502 is to block the reflected light from the optical surface 104b, if the reflected light from the optical surface 104b can be blocked, another means such as applying a coating for reducing the reflectance on the 104a surface. But it doesn't matter.
[0052]
In the present embodiment, since the convex optical surface 104b of the lens 104 is used as a reference surface, the concave optical surface 501a having a large curvature radius can be measured with high accuracy. In addition, since the distance between the convex optical surface 104b serving as the reference surface and the concave optical surface 501a serving as the measurement surface can be shortened, highly accurate measurement that is not affected by disturbance such as air fluctuations can be performed. it can.
[0053]
In addition, since the interferometer of the main body is not moved, and the lens serving as the reference surface is not moved after the measurement of the reference surface, the variation of the physical surface shape of each optical surface is extremely small. Since the positional relationship of the optical elements is also maintained, it is possible to perform absolute measurement with high reliability.
[0054]
(Fifth embodiment)
FIG. 6 is a diagram for explaining a fifth embodiment of the present invention. In FIG. 6, the laser 101, the lens 121, the beam slitter 122, the collimator lens 123, the imaging lens 106, the CCD lens 107, the computer 130, and the display device 131 are not described because they are the same as those in the first embodiment. Only the parts different from the first embodiment are shown. In the present embodiment, the same members as those in the first embodiment are denoted by the same reference numerals.
[0055]
In the present embodiment, a divergent Fizeau interferometer TS, which is disposed between the pinhole 103a and the lens 104 by using the concave optical surface 104a of the lens 104 whose shape is measured by the first embodiment. The lens surface is measured. Further, the lens 104 is removed, and another lens having a concave measurement surface is disposed at that location, thereby accurately measuring the concave measurement surface using the already measured TS lens surface. .
[0056]
FIG. 6A is a diagram in which 104a is measured by the method described in the first embodiment. By the method shown in the first embodiment, the absolute shape of the optical surface 104a, which is the surface to be measured, is measured. Next, as shown in FIG. 6B, the lens 102 and the wavefront shaping plate 103 are removed, and a divergent TS lens 601 is inserted instead. The Fizeau interferometer is constructed by matching the center of curvature of the optical surface 601a of the divergent TS lens 601 with the center of curvature of the optical surface 104a, and the optical surface of the TS lens is configured using the optical surface 104a whose absolute shape has already been obtained as a reference surface. Surface 601a is measured.
[0057]
In this case, since the convex optical surface 601a and the concave optical surface 104a form an interference surface arrangement, the distance between the surfaces can be shortened, and high-precision measurement that is not affected by disturbance such as air fluctuation can be expected. .
[0058]
In this case, since the reflected light from the 104b surface becomes unnecessary light and affects the measurement, a coating for reducing the reflectance is applied to the 104b surface, or light from the 104b is blocked by a pinhole (not shown). is required.
[0059]
Next, as shown in FIG. 6C, the lens 104 is removed, and a lens 602 serving as an object to be measured is disposed instead of the lens 104. The optical surface 601a of the divergent TS lens that has already been measured is now used as a reference surface, and the concave measured surface 602a of the lens 602 is measured.
[0060]
In the present embodiment, similarly to the case shown in FIG. 6B, the convex optical surface 601a and the concave optical surface 602a serving as the reference surface are arranged in an interference surface, so that the surface interval is shortened. High-precision measurement that is not affected by disturbances such as air fluctuations can be expected.
[0061]
In this embodiment, since the interferometer of the main body is not moved, and the lens 104 used as a master is not moved when the TS lens is inserted, the physical surface shape used for measurement varies. Is extremely small, and the positional relationship between the interferometer camera and the optical element is maintained, so that highly accurate shape measurement can be performed with high reliability.
[0062]
In this embodiment, there are no restrictions on the shape of the lens to be measured, such as curvature and uneven shape, and there are no restrictions such as providing eccentricity with respect to the reference surface in the case of arrangement, so various lens shapes can be used. On the other hand, shape measurement can be performed more generally. Further, since the concave mirror as the object to be measured is not necessarily transparent and is not limited to a lens shape, the usage method in the present embodiment is more realistic in a general usage method.
[0063]
The divergent TS lens refers to a lens whose reference surface is convex and designed so that emitted light diverges.
[0064]
【The invention's effect】
As described above, in the present invention, the light source, the condensing lens that once condenses the light from the light source, the pinhole that converts the condensed light into an ideal spherical wave, and the vicinity thereof are provided. A light wave shaping plate formed with a window through which the light wavefront information is passed, and at least a reference surface and a surface to be measured whose optical axes are decentered in the optical path of the light that has passed through the pinhole. One lens is arranged at a position where light is incident on the reference surface perpendicularly, reflected light passes through the pinhole again, and light reflected on the measurement surface passes through the window, and the reference surface Provide a shape measuring apparatus and a shape measuring method for measuring the shape of the surface to be measured by causing the reflected light reflected by the light beam to pass through the pinhole again and the reflected light reflected by the surface to be measured and passed through the window to interfere with each other is doing.
[0065]
Thus, with the configuration as described above, it is possible to adopt a Fizeau interferometer configuration in which the reference optical axis and the measured optical axis are substantially the same, and the apparatus can be miniaturized. Further, by using the optical surface 104b as a reference surface, even a convex optical surface that is said to be difficult to measure normally can be easily measured. Further, since no mirror member is required in the pinhole portion, dirt and minute irregularities on the mirror do not affect the measurement. In addition, since the total spread light beam from the pinhole can be used as measurement light, the measurement does not become unstable due to insufficient light quantity, and accurate shape measurement can be performed reliably. Moreover, since there is no restriction | limiting in the area | region which arrange | positions a to-be-measured object, even a big to-be-measured object can be measured.
[0066]
Furthermore, the shape of the convex surface can be measured by removing the light wave shaping plate and measuring the shape of the reference surface by making the reflected light from the surface to be measured interfere with the reflected light from the reference surface. is there.
[0067]
In addition, the lens to be measured can be measured even if the measured surface and the reference surface are not at the same center of curvature by making the lens having a measured surface into a lens group consisting of a plurality of lenses. The variation of the is greatly increased, and measurement is possible regardless of the shape of the lens to be measured. In addition, the convex or concave surface having a large radius of curvature can be measured at a short distance from the focal point, and the apparatus can be reduced in size and accuracy can be prevented from being lowered due to air fluctuations.
[0068]
In addition, by making the reference surface a mirror member that is different from the lens or lens group having the surface to be measured, it is possible to measure a convex or concave surface with a large curvature radius at a short distance from the focal point, and downsizing the device And accuracy degradation due to air fluctuation can be prevented. In addition, since the light is reflected by the optical reflecting surface, the amount of light is not lost and more accurate shape measurement is possible. In addition, it is not necessary to adjust the position of the pinhole and window of the waveform shaping plate in advance by the curvature radius of the surface to be measured and the amount of eccentricity with respect to the optical axis, and this can be done by adjusting the position of the mirror member 305. Therefore, it is not necessary to make the design of the lens or lens group that is the object to be measured measurable, and the versatility as a measuring apparatus is greatly improved.
[0069]
Further, after measuring the surface to be measured by the shape measuring method, the light wave shaping plate is removed, and reflected light from the surface to be measured and reflected light from the reference surface are caused to interfere with each other. By measuring the shape, it is possible to measure a convex optical surface, which is usually difficult to measure, with high accuracy.
[0070]
Further, after measuring the convex optical surface by the shape measuring method, the light wave shaping plate is removed, and an optical element having a second measured surface is disposed on the opposite side of the lens from the light source, By measuring the shape of the second measured surface by causing interference between the reflected light from the second measured surface and the reflected light from the convex optical surface, a concave optical surface having a large curvature radius is obtained. It can be measured with high accuracy. In addition, since the distance between the convex optical surface serving as the reference surface and the concave optical surface serving as the measurement surface can be shortened, high-accuracy measurement can be performed without being affected by disturbance such as air fluctuation. In addition, the interferometer of the main body is not moved, and the lens that becomes the reference surface is not moved after the measurement of the reference surface. Since the positional relationship of the optical elements is also maintained, it is possible to perform absolute measurement with high reliability.
[0071]
Further, after measuring the surface to be measured by the shape measuring method, the light wave shaping plate and the condenser lens are removed, a divergent TS lens is disposed between the light source and the lens, and from the surface to be measured Since the reflected light and the reflected light from the reference surface of the divergent TS lens interfere with each other to measure the shape of the reference surface of the divergent TS lens, the surface accuracy of the divergent TS lens can be measured with high accuracy.
[0072]
Furthermore, after measuring the reference surface of the divergent TS lens by the shape measuring method, the lens having the third surface to be measured is disposed at the place where the lens is removed and the lens is removed, and the divergent TS lens Since the reflected light from the reference surface and the reflected light from the third measured surface are caused to interfere with each other to measure the shape of the third measured surface, it does not include any position crossing or error between the devices. Since it can be measured, the shape of the surface to be measured of the second lens can be measured with very high accuracy.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a first embodiment.
FIG. 2 is a detailed explanatory diagram of a pinhole portion used in the first embodiment.
FIG. 3 is an explanatory diagram of the second embodiment.
FIG. 4 is an explanatory diagram of the third embodiment.
FIG. 5 is an explanatory diagram of the fourth embodiment.
FIG. 6 is an explanatory diagram of the fifth embodiment.
FIG. 7 is an explanatory diagram of the first conventional technique.
FIG. 8 is an explanatory diagram of a second conventional technique.
[Explanation of symbols]
101 laser
102 Condensing lens
103 Wavefront shaping plate
104 lenses
106 Imaging lens
107 CCD camera
121 condenser lens
122 Beam splitter
123 Collimator lens
130 computers
131 display
204, 205, 304, 405, 406, 501, 602 Lens
305,407 Mirror member
601 Divergent TS lens

Claims

A light source, a condensing lens that once collects light from the light source, a pinhole that converts the collected light into an ideal spherical wave, and a window that passes light wavefront information provided in the vicinity of the pinhole are formed An optical wave shaping plate, and at least one lens having a reference surface in which the optical axes of each other are decentered and a surface to be measured in the optical path of the light passing through the pinhole. The reflected light passes through the pinhole again, the light reflected by the measurement surface is disposed at a position passing through the window, the reflected light reflected by the reference surface and passed through the pinhole again, and the measured object A shape measuring apparatus using an interferometer, characterized in that the shape of a surface to be measured is measured by causing interference with reflected light that has been reflected by a surface and passed through the window.

2. The shape measuring apparatus using an interferometer according to claim 1, wherein the lens is a single lens composed of concave and convex optical surfaces having slightly different curvature centers in the vicinity of the pinhole.

The lens is a lens group including a plurality of lenses, and the reference surface and the surface to be measured are any one of an optical surface of a lens closest to the pinhole and an optical surface of a lens different from the lens closest to the pinhole. The shape measuring apparatus using the interferometer according to claim 1, wherein:

A light source, a condensing lens that once collects light from the light source, a pinhole that converts the collected light into an ideal spherical wave, and a window that passes light wavefront information provided in the vicinity of the pinhole are formed And a mirror member having an optical reflection surface that reflects light that has passed through the pinhole, and the other optical surface and the optical axis are decentered between the pinhole and the mirror member. At least one lens having the measured surface is disposed at a position where the light reflected by the measured surface passes through the window, and the mirror member is reflected by the light incident on the optical reflecting surface perpendicularly. The light is adjusted to a position where it passes through the pinhole again, and the reflected light reflected by the optical reflecting surface and passed through the pinhole again interferes with the reflected light reflected by the measured surface and passed through the window. A shape using an interferometer characterized by measuring the shape of the surface to be measured Constant apparatus.

A light source, a condensing lens that temporarily collects light from the light source, a pinhole that converts the collected light into an ideal spherical wave, and a window that passes light wavefront information provided in the vicinity of the pinhole are formed. An optical wave shaping plate, and at least one lens having a reference surface in which the optical axes of each other are decentered and a surface to be measured in the optical path of the light passing through the pinhole. The reflected light passes through the pinhole again, the light reflected by the measurement surface is disposed at a position passing through the window, the reflected light reflected by the reference surface and passed through the pinhole again, and the measured object A shape measuring method using an interferometer, characterized in that the shape of a surface to be measured is measured by causing interference with reflected light reflected by a surface and passing through the window.

6. The shape measuring method using an interferometer according to claim 5, wherein the lens is a single lens composed of a concave and a convex optical surface having slightly different curvature centers in the vicinity of the pinhole.

The lens is a lens group including a plurality of lenses, and the reference surface and the surface to be measured are any one of an optical surface of a lens closest to the pinhole and an optical surface of a lens different from the lens closest to the pinhole. The shape measuring method using the interferometer according to claim 5 , wherein:

A light source, a condensing lens that temporarily collects light from the light source, a pinhole that converts the collected light into an ideal spherical wave, and a window that passes light wavefront information provided in the vicinity of the pinhole are formed. And a mirror member having an optical reflection surface that reflects light that has passed through the pinhole, and the other optical surface and the optical axis are decentered between the pinhole and the mirror member. At least one lens having the measured surface is disposed at a position where the light reflected by the measured surface passes through the window, the mirror member is positioned at a position where the light is perpendicularly incident on the optical reflecting surface, The reflected light is adjusted to a position where it passes through the pinhole again, and the reflected light that is reflected by the optical reflecting surface and then passes again through the pinhole, and the reflected light that is reflected by the measured surface and passes through the window Using an interferometer characterized by measuring the shape of the surface to be measured by interfering Shape measuring method.

After measuring the surface to be measured by the shape measuring method, the light wave shaping plate is removed, and the reflected light from the surface to be measured and the reflected light from the reference surface are made to interfere with each other to change the shape of the reference surface. The shape measurement method using the interferometer according to claim 5 , wherein measurement is performed.

The optical surface opposite to the pinhole of the lens is a convex optical surface, and after measuring the convex optical surface by the shape measuring method, the light wave shaping plate is removed, and the light source of the lens An optical element having a second measured surface is disposed on the opposite side of the second measured surface, and the reflected light from the second measured surface and the reflected light from the convex optical surface are caused to interfere with each other. The shape measuring method using the interferometer according to any one of claims 5 and 9, wherein the shape of the measurement surface is measured.

After measuring the surface to be measured by the shape measuring method, the light wave shaping plate and the condenser lens are removed, a divergent TS lens is disposed between the light source and the lens, and reflected light from the surface to be measured 6. The shape measuring method using an interferometer according to claim 5, wherein the shape of the reference surface of the divergent TS lens is measured by causing interference between the reflected light from the reference surface of the divergent TS lens and the reflected light from the reference surface of the divergent TS lens.

After measuring the reference surface of the divergent TS lens by the shape measurement method, the lens is removed, and a lens having a third surface to be measured is disposed at the place where the lens is removed, and the diverging TS lens is referenced. The interferometer according to claim 11, wherein the shape of the third measured surface is measured by causing the reflected light from the surface to interfere with the reflected light from the third measured surface. Shape measurement method.