JP4100553B2 - Simultaneous measurement apparatus and method for dynamic shape and dynamic position - Google Patents

Description

（１）式において、物体の表面形状測定に不要な項ａ（ｘ，ｙ）、ｂ（ｘ，ｙ）を除去し、物体反射光の位相φ（ｘ，ｙ）を抽出して、それを形状に変換することにより、物体の表面形状が求められる。
【００３０】
本発明では、動いている最中の物体の表面形状を測定するために、時系列的に複数枚の干渉縞画像を収録せず、単一の干渉縞画像を取得する。そのために例えば文献：武田光夫「フーリエ変換と光応用計測」光技術コンタクト、Ｖｏｌ．３６，Ｎｏ．２，（１９９８）に紹介されているフーリエ変換法を用いる。フーリエ変換法では、参照光と物体反射光との間に傾きをあたえた状態で両者を干渉させることにより、（２）式に示されるような空間キャリヤ周波数ｆ_Ｘ０とｆ_Ｙ０をもつ干渉縞を得る。

（２）の干渉縞画像を変数ｘ，ｙについてフーリエ変換すると、（３）式に示すような二次元空間周波数スペクトルが得られる。ここで＊は複素共役、Ａ（ｆ_Ｘ，ｆ_Ｙ）はａ（ｘ，ｙ）のフーリエスペクトルを表し、Ｃ（ｆ_Ｘ，ｆ_Ｙ）は干渉縞の明暗変化の複素振幅である（４）式のフーリエスペクトルを表す。

【００３１】
空間キャリヤ周波数ｆ_Ｘ０とｆ_Ｙ０に対してバックグラウンド強度分布ａ（ｘ，ｙ）や干渉縞の明暗変化の複素振幅分布ｃ（ｘ，ｙ）の変化がゆるやかであれば、各スペクトルがキャリヤ周波数により分離されるため、（３）式における第２項の成分のみを抽出し、フーリエスペクトル座標における原点の位置に移動することにより空間キャリヤ周波数ｆ_Ｘ０とｆ_Ｙ０を取り除き、Ｃ（ｆ_Ｘ，ｆ_Ｙ）を得ることができる。そしてスペクトルＣ（ｆ_Ｘ，ｆ_Ｙ）の逆フーリエ変換により（４）式の複素振幅が得られる。得られた複素振幅の虚部と実部の比のアークタンジェントをとることにより位相φ（ｘ，ｙ）を求めるという一連の処理がフーリエ変換法である。以上のようにフーリエ変換法では物体反射光の位相分布を求めるが、本発明では、それに加えて物体反射光の振幅分布を求める。
参照光の複素振幅Ｕ_Ｒ（ｘ，ｙ）、物体光の複素振幅Ｕ_ｏ（ｘ，ｙ）をそれぞれ（５），（６）式のようにし（Ａは振幅、φは位相を表す）、参照光の位相分布φ_Ｒ（ｘ，ｙ）が０（理想波面）であるとすると、ｂ（ｘ，ｙ）は（７）式のように、参照光の振幅分布Ａ_Ｒ（ｘ，ｙ）と物体光の振幅分布Ａ_ｏ（ｘ，ｙ）によって表現できる。

【００３２】
被測定物を設置しない状態における画像は、参照光のみによる画像となるので、その参照光のみの画像を収録し、ＣＣＤの各々の画素で、その平方根をとることにより、参照光の振幅分布Ａ_Ｒ（ｘ，ｙ）を求めることができる。したがって、そのように取得したＡ_Ｒ（ｘ，ｙ）と、複素振幅ｃ（ｘ，ｙ）の実部Ｒｅ｛ｃ（ｘ，ｙ）｝と虚部Ｉｍ｛ｃ（ｘ，ｙ）｝を用いて、以下の（８）式、（９）式を計算することにより、ＣＣＤの撮像面の位置での物体反射光の位相分布φ_{ｏ 0}（ｘ，ｙ）と振幅分布Ａ_{ｏ 0}（ｘ，ｙ）を求めることができ、（６）式を用いてＣＣＤの撮像面の位置での物体反射光の複素振幅Ｕ_{ｏ 0}（ｘ，ｙ）を表現できる。

（８）式の位相分布にλ／（２π）を乗ずることにより、被測定物の表面形状を求めることができる。
ただし、位相分布による形状は参照面形状に対する相対値であるため、被測定面の位置（物体反射光の略光軸方向への高さ）を求めることはできない。本発明では、そのような位置を（９）式で求めた振幅分布を利用して、合焦法の原理により求める。
【００３３】
合焦法は、例えば文献：石原満宏、佐々木博美「合焦法による高速三次元形状計測」精密工学会誌、ｖｏｌ．６３、Ｎｏ．１、１９９７で報告されているように、被測定物の像を対物レンズにてＣＣＤの撮像面上にほぼ結像させた状態で、対物レンズを光学系光軸方向に移動させながら複数枚の物体画像を収録する。対物レンズを光学系光軸方向に移動させると、その移動量に応じて物体像は焦点ずれをおこすため、それにより像のコントラストが変化する。したがって、焦点が合って、コントラストがピークとなったときの対物レンズ位置を検知することによって、光学系光軸方向における物体の高さを求めることができる。そしてＣＣＤ画像における微小領域毎で、コントラストのピークを検出することにより、その領域での物体の高さを求め、その処理をＣＣＤで観測できる全領域にて実施することにより、その全領域での表面の高さ分布を求めることができる。ただし、その方法によると、対物レンズを時系列的に移動させながら複数枚の画像を収録するため、物体が動いていると測定が困難となってきて、本発明のように動的物体の表面形状測定に適用させることはできない。
【００３４】
本発明では、従来合焦法において対物レンズの移動により生じさせた焦点ずれを、数値演算により与える。焦点ずれを生じさせるために、（８），（９）式で求めた振幅、位相を（６）式に代入して物体反射光の複素振幅Ｕ_ｏ（ｘ，ｙ）を求め、それを（１０）式に代入して、物体反射光のフレネル回折を計算する。

（１０）式において、Ｚは光学系光軸方向におけるＣＣＤ面からの距離を表し、Ｚの値を入力して（１０）式を計算することによりＣＣＤ面からＺだけ離れた位置での物体反射光の複素振幅Ｕ_Zを求めることができる。所定のＺの位置での複素振幅から（９）式を用いて物体反射光の振幅分布Ａ_Z（ｘ，ｙ）を得ることができ、また（９）式で求めた物体反射光の振幅分布は、ＣＣＤで観測した画像における各画素での強度の平方根をとったものと等価である。したがって、Ｚの値を変化させることにより、焦点ずれ量の異なる複数の振幅画像を取得することができる。従来の合焦法では対物レンズを移動させることによって焦点ずれを与えていたが、ここでは仮想的にＣＣＤを光学系光軸方向に移動させることによって焦点ずれを与えるという作業を数値演算処理により行っている。収録するのは単一の干渉縞であり、その後はすべて演算処理にて行うため、物体が動いていても対応可能である。焦点ずれの異なる複数の振幅画像を用い、従来合焦法による処理と同様、微小領域でのコントラストを求め、コントラストがピークとなるときのＺの値がその領域の高さとなる。ここで、焦点ずれに応じたコントラストを検出する場合について、その処理領域内にテクスチャーがある必要がある。従来合焦法では、面の粗い粗面物体を被測定物とすることが多いため、面の粗れをテクスチャーとして扱うことができるが、被測定物がミラー面の場合は、面粗さを光学的に検出するのは困難となる。
【００３５】
本発明では、それへの対応の一例として、被測定物であるミラー面の高さを知るために、ミラーのエッジ部分をテクスチャーとみなし、ミラーエッジの焦点ずれに伴うコントラストピークを検出することによりミラーの略光学系光軸方向における位置（高さ）を求める。その場合、ミラーエッジの像に当たる全てのＣＣＤ画素にて位置測定値が得られるが、ミラーエッジにおける所定の領域を予め基準領域として設定しておき、その領域での測定値をミラーの位置測定値として用いてもよいし、テクスチャーがある微小領域におけるすべての位置測定値を平均して、それをミラーの位置測定値として用いてもよい。ミラーのエッジとエッジ以外のミラー面との位置（高さ）の差は、（８）式の位相分布にて求められるため、位相分布を用いてミラーの表面形状をナノメータオーダーで測定でき、また振幅分布を用いてミラーの位置を測定でき、したがって両者を同時に取得できる。図４（ａ）に焦点ずれを与える数値演算処理のモデルを示し、図４（ｂ）にＺを変化させたときの振幅画像のミラーエッジ位置（●プロット）とミラーエッジ以外の位置（■プロット）におけるコントラスト変化の様子を示す。
【００３６】
図４（ａ）は、被測定物１６の像が、レンズ１７によりＣＣＤ撮像面１８ｂの位置で結像している様子を示している。目視で被測定物１６の像がほぼ結像する位置を原点にして、ＣＣＤの位置を例えば１８ａや１８ｃに仮想的に変化させることによりＺの値を変化させながら（１０）式を計算することによって、振幅像に焦点ずれを与えることができる。図４（ｂ）では横軸のＺの値をとってあり、縦軸にコントラストをとって、Ｚを変化させたときのコントラスト値がプロットしてある。図において●のプロットと■のプロットで示しているように、振幅像において、コントラストを検出する微小領域内にテクスチャーがある場合はコントラスト変化のレベルが大きくなり、テクスチャーがない場合はコントラスト変化のレベルが小さくなる。そのためにコントラスト変化のピーク値にスレッシュをかけることで、コントラストを検出する微小領域内にテクスチャーがあるかないかを判定できる。テクスチャーがある微小領域内でのみＤを求めればよい。
【００３７】
図４（ｂ）におけるＤを次の（１１）式に代入して得られるｄが位置の測定値となる。（１１）式におけるｋは焦点ずれに対する感度、Ｍは光学系倍率である。光学系倍率が大きくなるほど、測定分解能が向上する。

被測定物が、例えば図１に示したように、ベースに駆動ミラーがとりつけられたもののような場合は、ベースの位置測定値とミラーエッジの位置測定値とのＺの値との差をとれば、それがベースを基準としたときのミラーの位置となる。ベースの焦点ずれを検知する場合、ベースが粗面であれば、面の粗れの像をテクスチャーとして用いる。ベースが鏡面である場合は、ベースにあらかじめ印をつけておき、その印をテクスチャーとして用いてもよいし、ベース面上で結像するようなパターンをベースに投影して、それをテクスチャーとして用いてもよく、また、ベースのエッジが視野内に観測される場合はそれをテクスチャーとして用いてもよい。印をつける方法やパターンを投影する方法は、被測定物であるミラー面にも適用でき、被測定ミラー面上に予め印をつけておいたり、被測定ミラー面上で結像するようにパターンを投影したりして、その印やパターンをテクスチャーとして用いれば、ミラーのエッジをテクスチャーとして用いる必要はない。被測定物が、図２に示したようなミラーアレイの場合も、ミラーのエッジをテクスチャーとしたり、各ミラー面に投影したパターンをテクスチャーとすればよい。
【００３８】
図１に示したような振動ミラーを被測定物としたときの測定手順の例を説明する。図１（ｂ）は振動ミラーの振動の様子を側方から観察し、振動位相とミラーの傾きを説明したものである。
振動ミラーは図の矢印の方向に揺動するかたちで振動し、振動ミラーに照射した光の反射光の向きを変えたり、走査したりするという用途で使用される。振動位相が０度のときにミラー面は水平（図では実線で表した面）となる。そして振動位相が９０度のときにミラー面は左側に最大角度で傾き（図では点線で表した面）、振動位相が１８０度のときにミラー面は再び水平（図では実線で表した面）になり、振動位相が２７０度ときにミラー面は右側に最大角度で傾き（図では一点鎖線で表した面）、振動位相が３６０度のときにミラー面は再度水平（図では実線で表した面）になる。以上の動きを一周期として振動を繰り返し、ミラーの傾きは連続的に変化する。ミラー面の傾きの最大角度は、振動ミラーの振動振幅の仕様値で決定され、振動の周期もまた仕様を設定されている。
【００３９】
測定では振動中のミラーの形状と、ミラー面の略照射光学系光軸方向の位置を本発明による装置及び方法で測定するが、例えば、ミラーが水平になった状態 （振動位相が０度）のときのミラー形状と位置であり、あるいはミラーが最大角度傾いた状態（振動位相が９０度、あるいは２７０度）のときのミラー形状と位置であるといったように、ミラーの傾きが所定の状態であるときのミラーの表面形状と位置を求める。
まず、被測定物を設置しない状態で参照光のみの画像を収録しておき、その後被測定物をセットする。そして被測定物を測定したい傾きで静止させておき、ミラーエッジ等のテクスチャーを目視で確認しながら、ミラー表面にほぼ焦点が合うように、光学系の光軸方向における被測定物の位置を調整する。そして参照ミラーの傾きを調整すると干渉縞が発生する。その後、干渉縞に所定の空間キャリヤ周波数がのるように、参照ミラーの傾きをさらに調整した後、被測定ミラーを振動させる。ＣＣＤカメラの撮像の周期が被測定ミラーの振動周波数に同期していない場合は、発生した干渉縞は動いたり、消えてしまったりする。ＣＣＤカメラの撮像の周期を被測定ミラーの振動周波数に同期させると、干渉縞はみかけ上静止して観測されるため、干渉縞をみかけ上静止させておき、所定のタイミングで干渉縞を収録すると、被測定ミラーの測定したい傾きにおける干渉縞を収録することができる。干渉縞収録後のデータ処理は原理説明で述べたようにすればよい。それにより動いている瞬間における略照射光学系光軸方向における基準となるベース面に対する被測定面の位置と、動いている瞬間における被測定面の表面形状が得られる。測定する際の被測定ミラーの傾きは任意でよいが、干渉縞に所定の空間キャリヤ周波数がのるように、参照ミラーの傾きが調整されていることが必要条件となる。測定したい振動ミラーの傾きによっては、ベース面とミラー面との傾きにより図１（ａ）に示したｓが求められなくなるが、ミラー面の照射光学系光軸方向における位置測定値と、ベース面の照射光学系光軸方向における位置測定値と、ベース面の照射光学系光軸方向における位置を測定した観測面内でのテクスチャー位置と、ミラー面の傾きとの幾何学的関係が求められるため、それを被測定物の性能や加工精度に反映すればよい。
【００４０】
次いで、被測定物が図２のようなミラーアレイを被測定物としたときの測定、処理手順の例を説明する。
ミラーアレイは、ディスプレイにおける空間変調素子として使用される場合は、各ミラー面がいくつか（例えば２つ）の所定の角度に切りかえられることにより、ミラーに照射される光の反射光をＯＮ／ＯＦＦするように作用する。その場合の角度が切りかえられた瞬間でのミラー面の形状と、各ミラー面の略照射光学系光軸方向における相対的な位置を本発明の装置及び方法で測定する。また、ミラーアレイが光通信における光イコライザー用に用いられる場合は、各ミラー面がいくつかの所定の角度に切りかえられることにより、一次元、あるいは二次元に配列された光ファイバーから各ミラーに照射される光の反射光が、一次元的、あるいは二次元的に配列された光ファイバーの所定位置に導光されるように動作する。その場合の角度が切りかえられた瞬間でのミラー面の形状と、各ミラー面の略照射光学系光軸方向における相対的な位置を本発明の装置及び方法で測定する。
【００４１】
測定の際は、まず被測定物を設置しない状態で、参照光のみの画像を収録しておき、その後被測定物をセットする。そしてミラーアレイを測定したいミラー角度において各ミラー面が略平行になるように静止させる。そしてミラーエッジ等のテクスチャーを目視で確認しながら、ミラ−表面にほぼ焦点が合うように、光学系の略光軸方向における被測定物の位置を調整する。そして、参照ミラーの傾きを調整すると、干渉縞が発生する。その後、干渉縞に所定の空間キャリヤ周波数がのるように参照ミラーの傾きをさらに調整した後、各ミラーが略平行になるようにしながらミラーアレイを駆動する。一定の周期で、かつ測定したいミラーの傾きになる状態に１周期内でなるようにミラーアレイを駆動し、ＣＣＤカメラの撮像の周期をミラーアレイの駆動周期に同期させると、干渉縞はみかけ上静止して観測される。逆にＣＣＤカメラの撮像の周期がミラーアレイの駆動周期に同期していないと、発生した干渉縞は動いたり、消えてしまったりする。ＣＣＤカメラの撮像の周期をミラーアレイの駆動周期に同期させて干渉縞をみかけ上静止させておき、所定のタイミングで干渉縞を収録すると、被測定ミラーの測定したい傾きにおける干渉縞を収録することができる。干渉縞収録後のデータ処理は原理説明のところで述べたようにすればよい。それにより動いている瞬間における略照射光学系光軸方向における各ミラー面の相対的位置と、動いている瞬間における各ミラー面の表面形状が得られる。測定する際のミラーの傾きは任意でよいが、干渉縞に所定の空間キャリヤ周波数がのるように、参照ミラーの傾きが調整されていること、また、ミラーアレイを構成する各ミラー面が略平行になるようにミラーアレイを駆動することが必要条件となる。
【００４２】
図５に、被測定面の照射光学系光軸方向における位置の測定と、被測定面の形状測定を行うための測定手順例を示す。図５において、ｉはカウント値、Ｚ０は位置測定を行う場合にＺを変化させる際の初期値、ΔＺはＺを変化させるピッチ、ＮはＺを変化させる回数を表し、他の英文字は実施例記載の英文字と同じ意味である。
【００４３】
２．請求項２に係る発明
請求項１の装置で測定する場合は、参照光のみの画像が必要となる。その場合、被測定物を設置しない状態での画像を収録すればよいが、測定装置の設置環境によっては、装置周りの構造物からの反射光がＣＣＤに入射し、ノイズとなって測定精度を低下させる場合がある。本発明では、測定のプロセスにて、図６に示したように、被測定物からＣＣＤまでの光路中に、手動で遮光板１９を設置し、物体反射光を遮ることにより、ノイズのない参照光のみの画像を取得する。図６における部品番号は、図３におけるものと共通である。それによりノイズの影響を受けない高精度の測定装置を提供することができる。
【００４４】
３．請求項３に係る発明
請求項２における遮光板の設置について、手作業で被測定物からＣＣＤまでの光路中に遮光板を設置してもよいが、被測定物が変わるたびに遮光板を設置する作業がはいった場合、手作業によると作業性、操作性に欠ける。本発明では、図７のように遮光板１９を、光学系光軸とほぼ垂直な方向に進退可能なステージ２０に搭載し、ステージ２０を進退させて遮光板を被測定物からＣＣＤまでの光路中に設置する。ステージ２０の進退を図示しないステッピングモータの回転等により行えば、パルス数の指定により、遮光板が被測定物からＣＣＤまでの光路中の位置に自動的に設置できる。それにより測定の操作性、作業性が向上する。
【００４５】
４．請求項４に係る発明
図８（ａ），（ｂ）を参照して説明する。図８（ａ），（ｂ）において、図３と同じ番号で示された部品は、図３で示した部品と同じである。
符号２１のものは被測定物の像を拡大してＣＣＤの撮像面の位置で結像させる対物レンズである。拡大倍率を上げたい場合は顕微鏡対物レンズを用いればよい。被測定物８とＣＣＤ１０は、対物レンズ２１に関して光学的に共役な関係になるように、光学系光軸方向における位置関係が調整されている。図８（ａ）の構成の場合、物体反射光の光路にのみレンズが設置されているので、参照光と物体反射光とに波面に曲率の差が生じ、それにより発生する干渉縞に図９に示したようなデフォーカス成分が観測される。それにより収録した干渉縞から求めた物体反射光の複素振幅のうち、位相データにデフォーカス成分が生じ、それが表面形状の測定誤差となる。Ｚｅｒｎｉｋｅ多項式等を用いてデフォーカス成分を補正してもよいが、光学系の拡大倍率を大きくしたときなど、デフォーカス成分が大きくなった場合、それに伴い干渉縞間隔が密になるため、ＣＣＤによる干渉縞の検出が不可能になる（干渉縞の間隔がＣＣＤ２画素分のサイズより小さくなる）。
【００４６】
またデフォーカス成分を除去するために、参照光路に対物レンズ２１と同じ焦点距離をもつレンズを設置してもよいが、被測定物８、対物レンズ２１、ＣＣＤ１０の位置関係とほぼ同じになるように、参照面、ＣＣＤ、参照光路に設置するレンズの位置関係を調整しなければならず、光学系も複雑化するうえ、調整誤差に伴う形状測定誤差が生じる。図８（ｂ）は、対物レンズ２３とビームスプリッター２４と参照面２５とを一体化したもので、結像光学系であると同時に干渉光学系として作用する。２２は集光レンズとして作用する。参照光路にも物体反射光路にも同じ対物レンズが設置され、同様に作用するため、干渉縞にデフォーカス成分が生じないし、また、対物レンズの位置調整も容易になる。それにより測定光学系の構成および調整を簡素化でき、形状測定誤差を低減することができる。また光学系の拡大倍率を大きくしたときでも形状測定が可能となる。
【００４７】
５．請求項５に係る発明
被測定物が図１に示したような周期振動をする物体の場合、物体表面の傾きにより、物体反射光と参照光との間の光路差が異なってくるため、干渉縞の縞間隔が異なってくる。したがって、測定する物体表面の傾きにより干渉縞の空間キャリヤ周波数は異なってきて測定条件が変わってくる。
上記のとおりの請求項１に係る発明では、測定する物体表面の傾きにより干渉縞の空間キャリヤ周波数に差異が生じないように、被測定物を測定したい傾きで静止させた状態で、参照ミラー１２の傾きを調整して干渉縞に所定の空間キャリヤ周波数がのるようにしてから干渉縞収録を行う。しかしながらその方法によると、測定しようとする物体表面の傾きを変更する度に上記の作業を行う必要があるので作業性に欠ける。上記の問題を解決する請求項５に係る発明を図１０を参照しながら説明する。なお、図３と同じ符号を付した部品は、図３に示す請求項１に係る発明のそれと同じである。
【００４８】
符号２６は、Ｈｅ−Ｎｅレーザ４と、物体への照射光強度を調整するためのＮＤフィルタ５と、ビームエキスパンダ６と、ビームスプリッタ７と、レンズ９と、ＣＣＤカメラ１０と、ＮＤフィルタ１１と、参照ミラー１２を搭載し、図の矢印まわりに回転するステージである。この回転ステージ２６の回転によって照射光学系の光軸と被測定物８とのなす角度が変化し、物体反射光と参照光との位相差が変化するので、干渉縞の空間キャリヤ周波数が変化する。ただし、被測定面の傾きが変化する方向と、回転ステージ２６の回転方向は同一平面内にある。参照ミラー１２と被測定面のなす角度δと、干渉縞間隔ｇとの関係は、（１２）式のようになる。干渉縞間隔ｇが決まれば空間キャリヤ周波数は決定される。

【００４９】
一方、被測定面の振動の位相が０のとき、照射光学系光軸に対する被測定面の傾きを０度とすると、被測定面の傾きθと被測定面の振動の位相ｐとの関係は、（１３）式のようになる。Ｈは振動ミラーの振動振幅、Ｌは振動ミラーのスパンである。

したがって、はじめに干渉縞間隔ｇを決めておき、（１２）式により参照ミラーと被測定面とのなす角度δを計算して記憶する。振動ミラーの振動位相ｐの変化に合わせて被測定面の傾きθを求め、θ＋δの角度になるように、ステージ２６を回転させる。それにより空間キャリヤ周波数は振動ミラ−面の傾きに一定となり、同じ条件での測定が可能となる。振動位相ｐを入力すると、自動的にステージ２６がθ＋δの角度になるようにプログラムしておけば、効率のよい測定が実現される。
【００５０】
６．請求項６に係る発明
被測定物が図１に示したような周期振動をする物体の場合、物体表面の傾きによって物体反射光と参照光との間の光路差が異なってくるため、干渉縞の縞間隔が異なってくる。したがって、測定する物体表面の傾きにより干渉縞の空間キャリヤ周波数が異なってきて測定条件が変わってくる。図３に示す請求項１に係る発明では、測定する物体表面の傾きにより干渉縞の空間キャリヤ周波数に差異が生じないように、被測定物を測定したい傾きで静止させた状態で、参照ミラーの傾きを調整して干渉縞に所定の空間キャリヤ周波数がのるようにしてから干渉縞収録を行う。しかしこの方法によると、測定しようとする物体表面の傾きを変更する度に上記作業を行う必要があるので作業性に欠ける。この問題を解決する請求項６に係る発明を図１１を参照しながら説明する。図３と同じ符号を付した部品は、図３に示す請求項１に係る発明のそれと同じである。
【００５１】
符号２７を付したものはビームエキスパンダ６のうちのレンズ６ａをその光軸と略垂直な方向に移動させるためのステージである。ただし、被測定面の傾きが変化する方向とステージ２７の移動方向は同一平面内にある。そして、ステージ２７の移動距離ｓと、光学系光軸に対する照射光の角度σとの関係は、（１４）式のようになる。

ｆはレンズ６ａの焦点距離である。したがって、（１２）、（１３）式により求めたθ＋δを（１４）式のσに代入するとステージ移動距離ｓが決まるので、被測定面の振動位相ｐの変化に合わせてステージ移動距離ｓを求めてステージ２７を移動させると、空間キャリヤ周波数は振動ミラー面の傾きに一定となり、同じ条件での測定が可能となる。振動位相ｐを入力すると、自動的にステージ２７がｓだけ移動するようにプログラムしておけば、効率のよい測定が行われる。
【００５２】
７．請求項７に係る発明
演算により求めた物体反射光複素振幅データのうちの振幅データ（振幅像）に基づいて物体の位置を求める場合は、物体反射光の略光軸方向における複数の位置での物体反射光の振幅像を求め、画像における像の合焦状態を検出することによって物体位置を測定する。合焦状態を検出するには、像のテクスチャ（模様）のぼけ具合を定量的に検知する必要がある。一方、レーザ光源は時間的、空間的コヒーレンスが高いため、回折の影響によりテクスチャが鮮明に観測できないときがあり、また測定光学系の構成面の反射光によるノイズ干渉縞（物体形状に依存しない干渉縞）が発生しやすいため、それらは測定精度を劣化させる。請求項７に係る発明では、例えば図１２に示すように、Ｈｅ−Ｎｅレーザ４からの出射光を、拡散板２８を用いて拡散させることにより、被測定物への照射光の空間的コヒーレンスを低下させる。拡散板２８をモータ２９を用いて回転させることにより、拡散板での散乱によるスペックルノイズの影響は除去される。空間コヒーレンスの低下により、回折の影響の少ない鮮明なテクスチャの観測が可能になり、またノイズ干渉縞が低減されるので、位置および形状の測定精度を向上させることができる。なお、フィラメント等の発光面積の大きい光源からの光を色フィルターで単色化して、これを用いることもできる。
【００５３】
８．請求項８に係る発明
干渉縞画像を収録して物体表面形状を測定する場合、干渉縞画像を収録している最中に物体が動くと干渉縞が乱れて正確な測定ができなくなる。そのような場合、物体の動作速度に対して十分短い撮像速度で干渉縞を収録するか、物体への光の照射時間を十分短くすればよいが、撮像手段および光源の性能を比較すると、撮像時間を短くするのに比べ、照射時間を短くする方が有利である。本発明では、光源にルビーレーザのような固体パルスレーザを用いたり、半導体レーザをパルス発光駆動することにより、物体への光の照射時間を短くすることにより、物体が高速で動いているような場合でも高精度測定が可能である。
【００５４】
９．請求項９に係る発明
請求項１の動的形状及び動的位置の同時測定装置による測定方法では、参照光のみによる画像が測定の度に必要になるが、被測定物が変わっても光学系のセッティングに変化がなければ同じ参照光のみによる画像が複素振幅Ｕ_oを求めるための計算に使える。請求項９に係る発明は、そのような光学系のセッティングが変わらないような場合に、予め、遮光手段を用いて参照光のみの画像を収録してそれを記憶しておき、記憶した参照光のみの画像を複素振幅Ｕ_oを求めるための計算に用いることによって、測定のたびに参照光のみの画像を収録する手間を省くことができる。
【００５５】
１０．請求項１３に係る発明
請求項１３に係る発明は、請求項１の動的形状及び動的位置の同時測定装置を用い、周期振動する物体の測定を行う場合における干渉縞の収録タイミングの調整方法に関するものであり、ＣＣＤのトリガー入力による画像収録機能を利用するものである。
図１３（ａ）は周期振動する物体としての振動ミラーを駆動するための入力信号の一例であり、図１３（ｂ）はＣＣＤに入力するトリガー信号の一例である。なお、図１３（ａ），（ｂ）において横軸は時間であり、縦軸は入力電圧である。
符号３０は物体の振動周期に相当する。振動ミラーの振動位相とミラー面の傾きとの関係は、上記（１３）式にて示したものであり、したがって、測定したい振動ミラー面の傾きが決まったら、その振動位相にタイミングを調整してＣＣＤにトリガー信号を入力する。トリガー信号を連続して入力して画像収録し、表示すれば、ＣＣＤにて観測される干渉縞画像はみかけ上静止して見えるから、収録した干渉縞のうちの１枚を用いて請求項１に係る発明を実施し、物体の振動速度に合わせてＣＣＤのシャッター速度を短くすれば高速で振動する物体に対応することができる。
【００５６】
１１．請求項１４に係る発明
請求項１４に係る発明は、請求項８の発明の動的形状及び動的位置の同時測定装置を用い、周期振動する物体の測定を行う場合における被測定物へのパルス光の照射タイミング調整方法に関するものであり、図１３においてＣＣＤに入力したトリガー信号をパルスレーザのドライバに入力するものである。そして、パルスレーザに入力するトリガー信号をＣＣＤの画像収録のトリガー信号として併用すれば、みかけ上静止した干渉縞が観測されるので、物体の振動速度に合わせてパルスレーザの発光パルス幅を短くすれば高速で振動する物体にも対応できる。
【００５７】
１２．請求項１５に係る発明
請求項１５に係る発明は、請求項９の動的形状及び動的位置の同時測定方法によって、物体反射光の複素振幅Ｕ_iから求めた物体反射光の振幅データから物体の略照射光学系光軸方向における位置を測定する場合に、物体像の合焦状態を検出するものである。
合焦状態を検出するにはテクスチャー（模様）が必要となり、テクスチャーを観測しながら、その像が最もシャープになるときが合焦点状態であり、ぼけているときが焦点ずれ状態という具合に判定する。合焦点や焦点ずれは、ＣＣＤの微分和等の隣接画素計算によりコントラストのレベルを求めたり、ＣＣＤの単一画素での輝度を抽出したりすることによって定量的に検出される。
この発明では、複数の面から構成された被測定物における所定のある面でのテクスチャーの合焦状態を検出することにより略照射光学系光軸方向における所定のある面の位置を測定し、所定の別の面におけるテクスチャーの合焦状態を検出することにより略照射光学系光軸方向における所定の別の面の位置を測定し、それらの差を求めることにより、略照射光学系光軸方向における面同士の相対的位置を測定する。
【００５８】
１３．請求項１６に係る発明
請求項１６に係る発明は、被測定面が光学的粗面である場合に、被測定面の粗れの像をテクスチャーとする。図１４に、図１の振動ミラーを被測定物としたときの振幅像における面粗れの像の例を示すが、図１４における３１が被測定ミラー面、３２がベース面で、ベース面に符号３３で示す無数の線が粗れテクスチャーを表しており、例えば符号３３の線をテクスチャーとして面の位置測定を実施すればよい。
【００５９】
１４．請求項１７に係る発明
請求項１７に係る発明は、ミラーや光学ガラス等の光学的鏡面をもつ物体では、面の粗れは光の回折限界以下のサイズとなって光学的に観測することができず、そのためテクスチャーが観測できなくなり、テクスチャーがないため合焦状態を検知できないという不具合を生じる。被測定面が光学的鏡面である場合に、予め被測定面に印したマークの像をテクスチャーとする。
図１５に、図１の振動ミラーを被測定物としたときの振幅像を示す（ただし、部品の符号は、図１４と同じ部品のものは同じ符号を用いていている）。ベース面３２に３４のマークを印した様子、ミラー面３１に符号３５のマークの様子を示してあり、符号３４がベース面の略照射光学系光軸方向における位置を測定するためのテクスチャーになり、符号３５が振動ミラー面の略照射光学系光軸方向における位置を測定するためのテクスチャーになる。
【００６０】
１５．請求項１８に係る発明
請求項１８に係る発明は、ミラーや光学ガラス等の光学的鏡面をもつ物体では、面の粗れは光の回折限界以下のサイズとなって光学的に観測することはできず、テクスチャーが観測できなくなり、テクスチャーがないため合焦状態を検知できないという不具合を生じる。被測定面が光学的鏡面である場合に、被測定面のエッジ像をテクスチャーとする。図１６に、図１の振動ミラーを被測定物としたときの振幅像を示す（ただし、部品の符号は、図１４と同じ部品のものは同じ符号を用いている）。符号３６がベース面３２におけるエッジ、３７がミラー面３１におけるエッジの様子を示す。符号３６がベース面の略照射光学系光軸方向における位置を測定するためのテクスチャーになり、符号３７が振動ミラー面の略照射光学系光軸方向における位置を測定するためのテクスチャーになる。
【００６１】
１６．請求項１９に係る発明
請求項１５の方法では、テクスチャー像があるすべての領域で、面の略照射光学系光軸方向における位置の測定値が得られる。被測定面が鏡面である場合、位相データを用いた表面形状の測定値が得られるが、位置の測定値と形状の測定値では分解能が異なるため、両者を関連づけることは困難である（例えば、任意のある部分とある部分の高さの差が、形状測定値をみると数ｎｍしかないのに、位置測定値をみると数μｍもあるという現象が生じる）ので、請求項１９に係る発明は、テクスチャー像がある領域の所定部分を基準と設定しておき、位置測定ではその部分での測定値を被測定面の略照射光学系光軸方向における位置測定値とするものである。
例えば図１６のエッジ３６における位置３８をベース面の基準位置とし、またエッジ３７における位置３９をミラー面の基準位置とし、符号３８，３９における位置測定値を、それぞれベース面、ミラー面の位置測定値とする。
【００６２】
１７．請求項２０に係る発明
請求項１５の方法では、テクスチャー像があるすべての領域で、面の略照射光学系光軸方向における位置の測定値が得られる。被測定面が鏡面である場合、位相データを用いた表面形状の測定値が得られるが、位置の測定値と形状の測定値では分解能が異なるため、両者を関連づけることは困難である（例えば、任意のある領域とある領域の高さの差が、形状測定値をみると数ｎｍしかないのに、位置測定値をみると数μｍもあるという現象が生じる）ので、請求項２０に係る発明は、テクスチャー像における所定領域内での位置測定値の平均値を計算して、それを被測定面の略照射光学系項軸方向における位置測定値とするものである。例えば図１６のエッジ３６を構成する画素すべてにおける位置測定値を求め、その平均値をベース面の位置測定値とし、またエッジ３７を構成する画素すべてにおける位置測定値を求めその平均値をミラー面の位置測定値とする。
【００６３】
【発明の効果】
この発明の効果は、各請求項毎に整理すれば次のとおりである。
１．請求項１に係る発明
物体反射光と参照光との間で発生した干渉縞画像と参照光のみによる画像とから前記撮像手段位置での物体反射光の複素振幅Ｕ_ｏを求め、前記撮像手段位置での物体反射光の複素振幅のフレネル回折を計算することにより物体反射光の光軸方向における複数の位置での物体反射光の複素振幅Ｕ_i（ｉ：整数）を求め、前記Ｕ_iから求めた物体反射光の位相データから物体表面形状を求め、前記Ｕ_iから求めた物体反射光の振幅データから物体の略照射光学系光軸方向における位置を求めることにより、動いている最中の物体の表面形状及び面と略垂直な方向における位置を同時に測定する。それによりＭＥＭＳ等の微細構造の動的物体において、高い面内空間分解能で、物体が動いている最中のナノメータオーダーの表面形状と、略光学系光軸方向における物体の位置を同時に取得可能な測定装置を提供することができる。
【００６４】
２．請求項２に係る発明
被測定物から撮像手段までの光路中に遮光手段を設置し、物体反射光を遮ることにより、ノイズのない参照光のみの画像を取得する。それによりノイズの影響を受けない高精度の測定装置を提供することができる。
【００６５】
３．請求項３に係る発明
遮光手段を、光学系光軸とほぼ垂直な方向に進退可能なステージに搭載し、ステージを駆動させることにより遮光手段の前記光路中への設置を自動化することによって請求項１の装置の操作性を向上させることができる。
【００６６】
４．請求項４に係る発明
物体像を光学的に拡大して撮像手段位置で結像させる場合、物体像を拡大して撮像手段位置で結像するための光学系と干渉光学系とを一体化することにより、物体光を球面波に変換するためのレンズと参照光を球面波にするためのレンズを同一にすることにより、測定光学系の構成および調整を簡素化し、測定誤差を低減することができる。
【００６７】
５．請求項５に係る発明の効果
被測定物が周期振動する物体の場合、前記光源と照射光学系と干渉光学系と撮像手段と結像光学系を一体にしたユニットの傾きを変化させる回転ステージを構成に加え、その回転量を指定することにより干渉縞の縞間隔を設定し、それにより物体表面の傾きに一定条件の安定した測定を効率よく実施することができる。
【００６８】
６．請求項６に係る発明の効果
被測定物が周期振動する物体の場合、前記照射光学系の光軸と前記結像光学系の光軸を相対的にシフトさせる直動ステージを構成に加え、その移動にて被測定面への照射光が被測定面に入射する角度を変化させることにより干渉縞の縞間隔を設定し、それにより物体表面の傾きに一定条件の安定した測定を効率よく実施することができる。
【００６９】
７．請求項７に係る発明の効果
光源に拡散光源を用いることにより、その空間的コヒーレンスを下げ、それにより回折の影響の少ない鮮明なテクスチャを観測可能とし、またノイズ干渉縞を低減することにより、測定精度を向上させることができる。
【００７０】
８．請求項８に係る発明の効果
光源にパルス光源を使用し、物体への光の照射時間を短くすることにより、物体が高速で動いている場合でも、高精度な測定が可能である。
【００７１】
９．請求項９に係る発明
請求項１の装置においては参照光のみによる画像は測定のたびに必要となるが、被測定物が変わっても光学系のセッティングに変化がなければ同じ参照光のみによる画像が複素振幅Ｕ_ｏを求めるための計算に使える。この発明は、そのような光学系のセッティングが変わらないような場合に、予め、遮光手段を用いて参照光のみの画像を収録してそれを記憶しておき、記憶した参照光のみの画像を複素振幅Ｕ_ｏを求めるための計算に用いることによって、測定のたびに参照光のみの画像を収録する手間を省くことができ、測定の操作性、作業性を向上させることができる。
【００７２】
１０．請求項１２に係る発明
請求項５、請求項６の装置により周期振動する物体を測定する場合、物体光と参照光との間で発生する干渉縞の縞間隔を、請求項５のユニットの光学系光軸に対する直交２方向におけるチルトを変化させる回転ステージを用いたり、請求項６の照射光学系と結像光学系の光軸を相対的にシフトさせる直動ステージを用いる等して、任意に設定できるようにしている。収録する干渉縞の間隔が異なると、測定条件がかわり、それにより測定精度が変わってくるため、縞間隔の設定の目的は、被測定面の傾きに表面形状および略光学系光軸方向における位置を同じ測定条件で求めることにある。したがって、物体が振動している最中に、測定したい被測定面の傾き状態に合わせて回転ステージの回転量や直動ステージの移動量を設定する必要がある。しかし、この発明は、被測定物の振動位相データをもとに被測定物の傾きを求め、その傾きから回転ステージの回転量や直動ステージの移動量を設定することにより、物体の傾きに測定条件を一定にして、測定精度を安定させることができる。
【００７３】
１１．請求項１３に係る発明
被測定物が周期振動する場合、物体が評価したい傾きとなった状態にて干渉縞を収録する必要があり、その場合、干渉縞画像の収録タイミングを設定する必要があるが、この発明によれば、上記設定のために被測定物の振動の位相データを用いることにより、物体が所定の傾きとなった状態における干渉縞画像の収録を正確に実施するための方法を実現することができる。
【００７４】
１２．請求項１４に係る発明
被測定物が周期振動する場合、物体が評価したい傾きとなった状態にて干渉縞を収録する必要があり、その場合、光源にパルス光源を用いる場合は、光源のパルス発光のタイミングを設定する必要がある。この発明は、上記設定のために被測定物の振動の位相データを用いることにより、物体が所定の傾きとなった状態における光源のパルス発光を正確に実施するための方法を実現することができる。
【００７５】
１３．請求項１５に係る発明
請求項９の方法においては、前記Ｕ_iから求めた物体反射光の振幅データから物体の略照射光学系光軸方向における位置を測定する場合、物体像の合焦状態を検出する。そして、上記合焦状態を検出するにはテクスチャー（模様）が必要となり、テクスチャーを観測しながら、その像が最もシャープになるときが合焦点状態であり、ぼけているときが焦点ずれ状態であるという具合に判定する。合焦点や焦点ずれは、ＣＣＤの微分和等の隣接画素計算によりコントラストのレベルを求め、あるいはＣＣＤの単一画素での輝度を抽出することによって定量的に検出される。この発明は、複数の面から構成された被測定物における所定のある面でのテクスチャーの合焦状態を検出することにより、略照射光学系光軸方向における所定のある面の位置を測定し、所定の別の面におけるテクスチャーの合焦状態を検出することにより略照射光学系光軸方向における所定の別の面の位置を測定し、それらの差を求めることにより、略照射光学系光軸方向における面同士の相対的位置を測定することにより、請求項９の方法を実現することができる。
【００７６】
１４．請求項１６に係る発明
被測定面が光学的粗面である場合に、被測定面の粗れの像をテクスチャーとすることにより、請求項９の方法を実現することができる。
【００７７】
１５．請求項１７に係る発明
ミラーや光学ガラス等の光学的鏡面をもつ物体では、面の粗れは光の回折限界以下のサイズとなり、光学的に観測することはできず、テクスチャーが観測できなくなり、テクスチャーがないため合焦状態を検知できないという不具合を生じる。被測定面が光学的鏡面である場合に、予め被測定面に印したマークの像をテクスチャーとすることにより、請求項９の方法を実現することができる。
【００７８】
１６．請求項１８に係る発明
ミラーや光学ガラス等の光学的鏡面をもつ物体では、面の粗れは光の回折限界以下のサイズとなり、光学的に観測することはできずに、テクスチャーが観測できなくなり、テクスチャーがないため合焦状態を検知できないという不具合を生じる。被測定面が光学的鏡面である場合に、被測定面のエッジ像をテクスチャーとすることにより、請求項９の方法を実現することができる。
【００７９】
１７．請求項１９に係る発明
請求項１５の方法は、テクスチャー像があるすべての領域で、面の略照射光学系光軸方向における位置の測定値が得られる。被測定面が鏡面である場合、位相データを用いた表面形状の測定値が得られるが、位置の測定値と形状の測定値では分解能が異なるため、両者を関連づけることは困難である（例えば、任意のある部分とある部分の高さの差が、形状測定値をみると数ｎｍしかないのに、位置測定値をみると数μｍもあるという現象が生じる）。そのため、この発明は、テクスチャー像がある領域の所定部分を基準と設定しておき、位置測定ではその部分での測定値を被測定面の略照射光学系光軸方向における位置測定値とすることにより、請求項９の方法を実現することができる。
【００８０】
１８．請求項２０に係る発明
請求項１５の方法では、テクスチャー像があるすべての領域で、面の略照射光学系光軸方向における位置の測定値が得られる。被測定面が鏡面である場合、位相データを用いた表面形状の測定値が得られるが、位置の測定値と形状の測定値では分解能が異なるため、両者を関連づけることは困難である（例えば、任意のある領域とある領域の高さの差が、形状測定値をみると数ｎｍしかないのに、位置測定値をみると数μｍもあるという現象が生じる）。そのため、この発明では、テクスチャー像における所定領域内での位置測定値の平均値を計算して、それを被測定面の略照射光学系項軸方向における位置測定値とすることにより、請求項９の方法を実現することができる。
【図面の簡単な説明】
【図１】は、ベース面に振動ミラーがとり付けられたような構成のＭＥＭＳの概略を説明する図である。
【図２】は、ミラーが複数個配置され、各々独立して駆動するＭＥＭＳの概略を説明する図である。
【図３】は、本発明による測定装置の概略を説明する図である。
【図４】は、焦点ずれを与える数値演算モデルと、検出されるコントラストと位置測定値との関係を説明するための図である。
【図５】は、本発明による測定方法の測定手順を説明するフロー図である。
【図６】は、図３の測定装置の構成に加えて遮光板を設けた測定装置の概略を説明する図である。
【図７】は、図５の測定装置の構成に加えて遮光板を光学系光軸と略垂直な方向に進退させるためのステージを設けた測定装置の概略を説明するための図である。
【図８】は、結像光学系と干渉光学系を一体化した測定装置の概略を説明する図である。
【図９】は、デフォーカス成分が生じた干渉縞の様子の概略を説明する図である。
【図１０】は、図３の測定装置の構成に加えて、光源と照射光学系と干渉光学系と撮像手段と結像光学系を一体にしたユニットの傾きを変化させる回転ステージを設けた測定装置の概略を説明する図である。
【図１１】は、図３の測定装置の構成に加えて、照射光学系の光軸と結像光学系の光軸を相対的にシフトさせるステージを設けた測定装置の概略を説明する図である。
【図１２】は、レーザからの光を拡散させるための構成例の概略を説明する図である。
【図１３】は、被測定振動ミラーの振動とＣＣＤの撮像、あるいはパルス光源の発光のタイミングを説明するための図である。
【図１４】は、被測定物の振幅像における面粗れテクスチャーの様子の概略を説明する図である。
【図１５】は、被測定物の振幅像における被測定面に印したマークテクスチャーの様子の概略を説明するための図である。
【図１６】は、被測定物の振幅像におけるエッジテクスチャーの様子の概略を説明するための図である。
【符号の説明】
１：振動ミラー
２：基準面
３：ミラー面
４：光源
５：ＮＤフィルタ
６：ビームエキスパンダ
６ａ：レンズ
７：ビームスプリッター
８：被測定物
９：レンズ
１０：ＣＣＤカメラ
１１：ＮＤフィルタ
１２：参照ミラー
１３：ホルダー
１４：フレームグラバ
１５：コンピュータ
１６：被測定物
１９：遮光板
２０：ステージ
２１：対物レンズ
２２：集光レンズ
２３：対物レンズ
２４：ビームスプリッター
２５：参照面
２６：回転ステージ
２７：ステージ
２８：拡散板
２９：モータ
３１：被測定ミラー面
３２：ベース面
３４，３５：マーク
３６：ベース面３２におけるエッジ
３７：ミラー面３１におけるエッジ
３８：ベース面の基準位置
３９：ミラー面の基準位置[0001]
[Industrial application fields]
  The present invention relates to a method and an apparatus for performing processing accuracy evaluation and performance evaluation of parts such as MEMS (Micro-Electro-Mechanical-System) having a fine structure and accompanying movement. Nano-order surface shape while the object is moving,OpticalThe position of the object in the system axis direction can be measured at the same time, and can be used for processing accuracy evaluation and operation performance evaluation of a micro-structured dynamic object such as MEMS.
[0002]
[Prior art]
MEMS is a micron-order size device that involves movements such as translational displacement and tilt. Optical equalizers (cross connectors) in wavelength-division multiplexed optical communications, spatial light modulators in projectors and displays, optical deflectors, vibrations, etc. It is used in many applications such as actuators. In the above application, the MEMS plays the role of an optical mirror, and acts to control the angle and position of reflected light by translational displacement and inclination of the mirror surface. In that case, the surface shape of the mirror and the surface shape in motion are required to have high shape accuracy on the order of nanometers.
In the MEMS in which the oscillating mirror 1 is attached to the reference surface 2 as shown in FIG. 1A, the absolute position of the mirror surface with respect to the reference surface deviates from a predetermined position as the mirror is driven (FIG. 1 ( This corresponds to s in a), and the reflected light from the mirror does not reach the predetermined position, which affects the component performance. Therefore, it is important to quantitatively know the position of the mirror surface with respect to the reference surface (substantially the position of the surface in the optical axis direction of the irradiation optical system). Further, when the MEMS is based on a mirror array in which a plurality of mirrors are arranged (reference numeral 3 in FIG. 2 represents each mirror surface) and each moves independently, a direction substantially perpendicular to the mirror surface ( The relative position of each mirror surface (substantially in the optical axis direction of the irradiating optical system) may change depending on the driving of the mirror, and the light reflected by each mirror does not reach each predetermined position. Knowing the relative position of each mirror surface is also important because it affects performance.
[0003]
As a method for measuring the surface shape of an object to be measured on the order of nanometers and measuring the position thereof, Japanese Patent Laid-Open No. 2002-5619 “Interference Measurement Method, Apparatus, and Object Measured by the Method or Apparatus” (known example) 1). In this method, an interference fringe is generated when an object optical path length and a reference optical path length in a low-coherence light source substantially coincide with each other using a lens or a combined lens (group lens) composed of a plurality of lenses as an object to be measured. Is used to change the optical path length of the reference light while moving the reference mirror, and to detect the amount of movement of the reference mirror when the interference fringe is generated, so that the distance between the lens surfaces of the object to be measured, that is, the substantially irradiation optics The surface position in the system optical axis direction is measured. According to this method, it is possible to measure with almost the same resolution as the coherence length of the light source, so it is possible to measure with high resolution if a light source with a short coherence length is used. Since measurement data is recorded in time series while moving mechanically, there is a problem that measurement time is required. Although it is possible to speed up the operation, it is difficult to measure the shape of the moving object when the object moves at high speed due to time series data recording.
[0004]
As a known technique capable of measuring the shape of a moving object, for example, Mitsuo Takeda “Fourier Transform and Applied Optical Measurement”, Optical Technology Contact, Vol. 36, no. 2, (1998), P72-80 (Known Example 2). In this method, the interference fringes generated between the object reflected light and the reference light are spatially modulated (interference fringe spacing is changed), and the object shape is measured on the nanometer order based on a single recorded interference fringe image. It can be measured. Since it is sufficient to record a single image, it is not necessary to perform time-series measurement. Therefore, even if an object is moving, the surface shape during the movement can be measured. However, in this method, the relative shape of the object with respect to the reference surface can be obtained, but the position of the object surface in the direction of the optical axis of the optical system cannot be measured. Therefore, the method is applied to the above-described MEMS position measurement. I can't.
[0005]
As another known technique capable of measuring the shape of a moving object, US Pat. No. 6,262,818B, “A method for the numerical restructuring of digital holograms and examples of a multi-quantitative three-dimensionally-amplified” is shown. In this measurement method, the principle of off-axis digital holography is applied to record a single interference fringe image, from which an amplitude image and a phase image of an object are obtained. Even with this method, since it is sufficient to record a single image, the dynamic shape can be measured even if the object is moving. However, off-axis digital holography adopted in this method can effectively utilize CCD pixels because three images of zero-order light, real image, and virtual image appear in the reproduced image when reproducing the object image. In-plane spatial resolution is low, and in addition, in order to separate the three images, it is necessary to adjust parameters for image reproduction such as the spatial frequency of interference fringes, the object distance, and the reproduction distance.
Also in this method, the relative shape of the object with respect to the reference surface can be obtained, as in the method of the above-described known example 2, but the position of the object surface in the optical system optical axis direction cannot be measured. It cannot be applied to such MEMS position measurement.
[0006]
[Reference 1]
Mitsuo Takeda “Fourier Transform and Applied Optical Measurement”, Optical Technology Contact, Vol. 36, no. 2, (1998), P72-80
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-5619
[Patent Document 2]
US Pat. No. 6,262,818B
[0007]
[Problems to be solved]
[Problem 1]
(Corresponding to claim 1)
Problem 1 of the present invention is to extract only a real image of a finely-structured dynamic object such as a MEMS, and to obtain a surface shape in the order of nanometers while the object is moving, and an object substantially in the optical axis direction of the optical system. It is to be able to acquire the position of at the same time.
[0008]
[Problem 2]
(Corresponding to claim 2)
When the dynamic shape and the dynamic position of claim 1 are measured by the simultaneous measurement apparatus, an image of only the reference light is required. In that case, it is only necessary to record an image without the object to be measured installed, but depending on the installation environment of the measuring device, the reflected light from the structure around the device enters the imaging means and becomes noise, resulting in measurement accuracy. May decrease.
Problem 2 of the present invention is that a light blocking means is installed in the optical path from the object to be measured to the imaging means, and the object reflected light is blocked to obtain an image of only the reference light without noise, thereby reducing the influence of noise. It is to provide a high-accuracy measuring device that does not receive.
[0009]
[Problem 3]
(Corresponding to claim 3)
With regard to the installation of the light shielding means in claim 2, the light shielding means may be manually installed in the optical path from the object to be measured to the imaging means. In this case, it is lacking in workability and operability to perform this manually.
Problem 3 of the present invention is that the light shielding means is mounted on a stage that can advance and retreat in a direction substantially perpendicular to the optical axis of the optical system, and the installation of the light shielding means in the optical path is automated by driving the stage. It is to improve the operability of the simultaneous measurement apparatus for dynamic shape and dynamic position according to claim 1.
[0010]
[Problem 4]
(Corresponding to claim 4)
When the object image is optically enlarged and formed at the position of the image pickup means, a method of making the object reflected light into a spherical wave using a microscope objective lens or the like is effective. In this case, if the reference light is a plane wave, an optical path difference due to the difference in curvature of the wavefront occurs between the reference light and the object reflected light, and a defocus component is placed on the generated interference fringes. To remove the defocus component, the reference light should be a spherical wave with the same curvature as the spherical wave of the object reflected light. However, if a lens is installed in each of the object optical path and the reference optical path, the optical system becomes complicated and adjusted. However, measurement errors are likely to occur.
Problem 4 of the present invention is that a lens for converting object light into a spherical wave and reference light are integrated by integrating an optical system and an interference optical system for enlarging an object image to form an image at the position of the imaging means. Is the same lens for making spherical waves, thereby simplifying the configuration and adjustment of the measurement optical system and reducing measurement errors.
[0011]
[Problem 5]
(Corresponding to claim 5)
When the object to be measured is an object that vibrates periodically, the optical path difference between the object reflected light and the reference light varies depending on the tilt of the vibrating object surface. The spacing will be different.
When spatial modulation is applied to the interference fringes, the fringe spacing of the interference fringes must be set to a predetermined amount. If the measurement conditions change because the spatial carrier frequency of the interference fringes varies depending on the tilt of the object surface being measured, Sex is reduced. The procedure of adjusting the angle between the object surface and the reference mirror while the object is stationary so that the spatial carrier frequency of the interference fringe is constant may be followed by the procedure of recording the interference fringe. However, if the work is performed every time measurement is performed, workability and operability are poor, and measurement efficiency is lowered.
Problem 5 of the present invention is to add a rotation stage that changes the inclination of a unit in which the light source, the irradiation optical system, the interference optical system, the imaging unit, and the imaging optical system are integrated, and to specify the amount of rotation. It is to set the fringe spacing of the interference fringes so that stable measurement under a certain condition can be efficiently performed regardless of the inclination of the object surface.
[0012]
[Problem 6]
(Corresponding to claim 6)
When the object to be measured is an object that vibrates periodically, the optical path difference between the object reflected light and the reference light varies depending on the tilt of the vibrating object surface. The spacing will be different.
When spatial modulation is applied to the interference fringes, the fringe spacing of the interference fringes must be set to a predetermined amount. If the measurement conditions change because the spatial carrier frequency of the interference fringes varies depending on the tilt of the object surface being measured, Sex is reduced. The procedure of adjusting the angle between the object surface and the reference mirror in a state where the object is stationary so that the spatial carrier frequency of the interference fringe is constant, and then recording the interference fringe may be included. However, if the work is performed every time measurement is performed, workability and operability are poor, and measurement efficiency is lowered.
Problem 6 of the present invention is that a linear motion stage that relatively shifts the optical axis of the irradiation optical system and the optical axis of the imaging optical system is added to the configuration, and the movement of the irradiation light onto the surface to be measured is performed. By changing the angle of incidence on the measurement surface, the fringe spacing of the interference fringes is set, so that stable measurement under certain conditions can be performed efficiently regardless of the inclination of the object surface.
[0013]
[Problem 7]
(Corresponding to claim 7)
When obtaining the position of an object based on the amplitude data (amplitude image) of the object reflected light complex amplitude data obtained by calculation, amplitude images of the object reflected light at a plurality of positions in the substantially optical axis direction of the object reflected light are obtained. The object position is measured by obtaining and detecting the focused state of the image in the image. In order to detect the in-focus state, it is necessary to quantitatively detect the degree of blurring of the texture (pattern) of the image. On the other hand, because laser light sources have high temporal and spatial coherence, textures may not be clearly observable due to diffraction effects, and noise interference fringes (interferences that do not depend on the object shape) due to the reflected light from the constituent surfaces of the measurement optical system Since stripes are likely to occur, they degrade measurement accuracy.
Problem 7 of the present invention is that a diffused light source is used as a light source to reduce its spatial coherence, thereby enabling a clear texture with little influence of diffraction to be observed, and reducing noise interference fringes, thereby improving measurement accuracy. It is to improve.
[0014]
[Problem 8]
(Corresponding to claim 8)
When measuring an object surface shape by recording an interference fringe image, if the object moves during the recording of the interference fringe image, the interference fringe is disturbed and accurate measurement cannot be performed. In such a case, it is sufficient to record interference fringes at an imaging speed that is sufficiently short relative to the operation speed of the object, or to sufficiently shorten the irradiation time of light on the object, but when comparing the performance and price of the imaging means and the light source, It is more advantageous to shorten the irradiation time than to shorten the imaging time.
Problem 8 of the present invention is to use a pulsed light source as a light source and shorten the irradiation time of light on an object so that the object can be measured with high accuracy even when the object is moving at high speed. .
[0015]
[Problem 9]
(Corresponding to claim 9)
Problem 9 is to provide a method for realizing the dynamic shape and dynamic position simultaneous measurement apparatus of claim 1.
[0016]
[Problem 10]
(Corresponding to claim 9)
  The apparatus for simultaneously measuring dynamic shape and dynamic position according to claim 1 is to provide a method for acquiring an image using only reference light.
[0017]
[Problem 11]
(Corresponding to claim 11)
In the apparatus for simultaneously measuring a dynamic shape and a dynamic position according to claim 1, an image using only the reference light is necessary for each measurement. Image with light only is complex amplitude U_oIt can be used for calculation to find
Problem 11 of the present invention is that when such an optical system setting does not change, an image of only the reference light is recorded and stored in advance using a light shielding means, and only the stored reference light is stored. Image of complex amplitude U_oBy using it for the calculation for obtaining the above, it is possible to save the trouble of recording an image of only the reference light every measurement and improve the operability and workability of the measurement.
[0018]
[Problem 12]
(Corresponding to claim 12)
When measuring an object that is periodically oscillated by the apparatus for simultaneously measuring dynamic shape and dynamic position according to claim 5 and claim 6, the fringe spacing of the interference fringes generated between the object light and the reference light is determined. A rotating stage that changes the tilt in two directions orthogonal to the optical axis of the optical system of the unit 5; or a linear stage that relatively shifts the optical axes of the irradiation optical system and the imaging optical system according to claim 6; It can be set arbitrarily. If the interference fringe interval recorded differs, the measurement conditions will change, and the measurement accuracy will change accordingly.The purpose of setting the fringe interval is to determine the surface shape and position in the optical axis direction of the optical system in relation to the inclination of the surface to be measured. Is obtained under the same measurement conditions. Therefore, while the object is vibrating, it is necessary to set the rotation amount of the rotary stage and the movement amount of the linear motion stage in accordance with the tilt state of the measurement target surface to be measured.
Problem 12 of the present invention is that the inclination of the object to be measured is obtained based on the vibration phase data of the object to be measured, and the rotation amount of the rotary stage and the movement amount of the linear motion stage are set based on the inclination to thereby determine the inclination of the object. In other words, the measurement conditions are fixed and the measurement accuracy is stabilized.
[0019]
[Problem 13]
(Corresponding to claim 13)
When the object to be measured vibrates periodically, it is necessary to record interference fringes in a state where the object has an inclination to be evaluated. In that case, it is necessary to set the recording timing of the interference fringe image.
Problem 13 of the present invention is to accurately record the interference fringe image in a state where the object has a predetermined inclination by using the phase data of the vibration of the measured object to set the recording timing of the interference fringe image. Is to provide a way to do that.
[0020]
[Problem 14]
(Corresponding to claim 14)
When the object to be measured vibrates periodically, it is necessary to record interference fringes in a state where the object has an inclination to be evaluated. In that case, when a pulse light source is used as the light source, it is necessary to set the timing of pulse light emission of the light source.
Problem 14 of the present invention is to accurately perform pulse light emission of a light source in a state where an object has a predetermined inclination by using phase data of vibration of an object to be measured in order to set timing of pulse light emission of the light source. Is to provide a method for
[0021]
[Problem 15]
(Corresponding to claim 15)
According to the simultaneous measurement method of the dynamic shape and the dynamic position of claim 9, the complex amplitude (U_iWhen measuring the position of the object in the direction of the optical axis of the substantially irradiating optical system from the amplitude data of the object reflected light obtained from (1), the in-focus state of the object image is detected. In order to detect the in-focus state, a texture (pattern) is required. While observing the texture, it is determined that the image becomes sharpest when the image is sharpest, and the defocused state when the image is blurred. In-focus and defocus are quantitatively detected by obtaining the level of contrast by calculating adjacent pixels such as the differential sum of the CCD, or extracting the luminance at a single pixel of the CCD.
Problem 15 of the present invention is to measure the position of a predetermined surface substantially in the optical axis direction of the irradiation optical system by detecting the in-focus state of the texture on the predetermined surface in the measurement object composed of a plurality of surfaces. The position of the predetermined other surface in the optical axis direction of the substantially irradiating optical system is measured by detecting the in-focus state of the texture on the predetermined other surface, and the difference between them is obtained to obtain the substantially irradiating optical system light. The relative position of the surfaces in the axial direction is measured, thereby realizing the simultaneous measurement method of claim 9.
[0022]
[Problem 16]
(Corresponding to Claim 16)
Problem 16 is to realize the simultaneous measurement method of claim 9 by using a rough image of the measurement surface as a texture when the measurement surface is an optical rough surface.
[0023]
[Problem 17]
(Corresponding to Claim 17)
In an object having an optical mirror surface such as a mirror or optical glass, the roughness of the surface becomes a size equal to or smaller than the diffraction limit of light, and cannot be observed optically, and texture cannot be observed. There is a problem that the in-focus state cannot be detected because there is no texture.
Problem 17 of the present invention is to realize the simultaneous measurement method of claim 9 by using, as a texture, an image of a mark previously marked on the measurement surface when the measurement surface is an optical mirror surface.
[0024]
[Problem 18]
(Corresponding to Claim 18)
For an object with an optical mirror such as a mirror or optical glass, the roughness of the surface is below the diffraction limit of light and cannot be observed optically, and texture cannot be observed, and therefore there is no texture. For this reason, there arises a problem that the in-focus state cannot be detected.
Problem 18 of the present invention is to realize the simultaneous measurement method according to claim 9 by using the edge image of the measurement surface as a texture when the measurement surface is an optical mirror surface.
[0025]
[Problem 19]
(Corresponding to Claim 19)
In the measurement method according to the fifteenth aspect, a measurement value of the position of the surface in the direction of the optical axis of the substantially irradiating optical system can be obtained in all regions where the texture image exists. When the surface to be measured is a mirror surface, a surface shape measurement value using phase data can be obtained. However, since the resolution is different between the position measurement value and the shape measurement value, it is difficult to relate the two (for example, The difference in height between an arbitrary certain part and a certain part is only a few nm when looking at the shape measurement value, but there is a phenomenon that there are several μm when looking at the position measurement value).
Problem 19 of the present invention is to set a predetermined portion of a region having a texture image as a reference, and in the position measurement, the measurement value at that portion is set as the position measurement value in the optical axis direction of the substantially irradiated optical system, Thus, the simultaneous measurement method of claim 9 is realized.
[0026]
[Problem 20]
(Corresponding to Claim 20)
In the measurement method according to the fifteenth aspect, a measurement value of the position of the surface in the direction of the optical axis of the substantially irradiating optical system can be obtained in all regions where the texture image exists. When the surface to be measured is a mirror surface, a surface shape measurement value using phase data can be obtained. However, since the resolution is different between the position measurement value and the shape measurement value, it is difficult to relate the two (for example, The difference between the height of an arbitrary region and a certain region is only a few nanometers when looking at the shape measurement value, but there is a phenomenon where there are several μm when looking at the position measurement value).
Problem 20 of the present invention is to calculate an average value of position measurement values in a predetermined region in a texture image, and to set the average value as a position measurement value in a direction of a substantially irradiated optical system term of the surface to be measured. 9 simultaneous measurement methods are realized.
[0027]
Configuration and operation of the invention
  Next, the structure and operation of the present invention will be described sequentially for each main claim with reference to the drawings.
  1. Invention according to claim 1
  FIG. 3 shows an example of an apparatus configuration according to the present invention.Depending on the device configurationThe principle of the measurement method and the calculation formula will be described.
  In FIG. 3, 4 is a He—Ne laser as a light source, 5 is an ND filter for adjusting the intensity of light irradiated to an object, and 6 is a beam expander for expanding light from the laser. The parallel light that is enlarged by the beam expander 6 and transmitted through the beam splitter 7 is irradiated to the object 8 to be measured. The light reflected by the measurement object 8 is reflected by the beam splitter 7 and reaches the CCD camera 10 via the lens 9. The relative positions of the object 8 to be measured, the lens 9 and the CCD camera 10 are adjusted so that the object 8 to be measured and the CCD camera 10 have a substantially conjugate relationship (imaging relationship). On the other hand, the light expanded by the beam expander 6 and reflected by the beam splitter 7 passes through the ND filter 11 and is reflected by the reference mirror 12. The reference mirror is held by a holder 13 having a mechanism for changing the tilt of the mirror surface with respect to the optical axis of light incident on the reference mirror, and the tilt of the mirror surface can be adjusted.
[0028]
The light reflected by the reference mirror 12 passes through the ND filter 11 in the direction opposite to that of the ND filter 11, passes through the beam splitter 7, and reaches the CCD camera 10 through the lens 9. The light reflected by the object to be measured 8 becomes object light, the light reflected by the reference mirror 12 becomes reference light, both interfere to generate an interference fringe, and the interference fringe is imaged by the CCD camera 10. The captured interference fringe image is transferred to the computer 15 via the frame grabber 14 and recorded in the memory of the computer. The lengths of the reference optical path and the object optical path after being branched by the beam splitter 7 are set to be equal to or shorter than the coherence length of the He—Ne laser of the light source. In addition, the ND filter 5 adjusts the irradiation light intensity to the object to be measured so that the reflected light from the object to be measured has an intensity suitable for imaging with the CCD camera, and the reflected light from the object to be measured. The reference light intensity is adjusted by the ND filter 11 so that the contrast of the interference fringes generated by the interference with the reference light becomes high. The fringe spacing of the interference fringes is adjusted by changing the inclination of the reference mirror surface by the holder 13.
[0029]
Interference fringes generated by the interference between the object beam and the reference beam are expressed by the following equation (1). In equation (1), x and y represent coordinates on the imaging surface of the CCD, I (x, y) is an interference fringe intensity distribution, a (x, y) is an interference fringe background intensity distribution, and b ( x, y) represents the amplitude distribution of the change in brightness of the interference fringes, and φ (x, y) represents the phase distribution of the object reflected light corresponding to the shape of the object to be measured.

In equation (1), the terms a (x, y) and b (x, y) unnecessary for measuring the surface shape of the object are removed, the phase φ (x, y) of the object reflected light is extracted, and By converting into a shape, the surface shape of the object is obtained.
[0030]
In the present invention, in order to measure the surface shape of the moving object, a single interference fringe image is acquired without recording a plurality of interference fringe images in time series. For this purpose, for example, literature: Mitsuo Takeda “Fourier Transform and Applied Optical Measurement”, Optical Technology Contact, Vol. 36, no. 2, the Fourier transform method introduced in (1998) is used. In the Fourier transform method, a spatial carrier frequency f as shown in the equation (2) is obtained by causing interference between the reference light and the object reflected light in an inclined state._X0And f_Y0Interference fringes with

When the interference fringe image of (2) is Fourier transformed with respect to the variables x and y, a two-dimensional spatial frequency spectrum as shown in equation (3) is obtained. Where * is a complex conjugate and A (f_X,f_Y) Represents the Fourier spectrum of a (x, y) and C (f_X,f_Y) Represents the Fourier spectrum of equation (4), which is the complex amplitude of the change in brightness of the interference fringes.

[0031]
Spatial carrier frequency f_X0And f_Y0If the change in the background intensity distribution a (x, y) or the complex amplitude distribution c (x, y) of the change in the interference fringes is gentle, each spectrum is separated by the carrier frequency. Only the component of the second term in the equation is extracted and moved to the position of the origin in the Fourier spectrum coordinates to obtain the spatial carrier frequency f_X0And f_Y0And remove C (f_X, F_Y) Can be obtained. And spectrum C (f_X, F_Y) To obtain the complex amplitude of equation (4). A series of processes for obtaining the phase φ (x, y) by taking the arc tangent of the ratio between the imaginary part and the real part of the obtained complex amplitude is the Fourier transform method. As described above, in the Fourier transform method, the phase distribution of the object reflected light is obtained. In the present invention, in addition to this, the amplitude distribution of the object reflected light is obtained.
Complex amplitude U of reference light_R(X, y), complex amplitude U of object light_o(X, y) are respectively expressed by equations (5) and (6) (A represents amplitude and φ represents phase), and the phase distribution φ of the reference light_RAssuming that (x, y) is 0 (ideal wavefront), b (x, y) is an amplitude distribution A of the reference light as shown in equation (7)._R(X, y) and object light amplitude distribution A_oIt can be expressed by (x, y).

[0032]
Since the image in the state in which the object to be measured is not installed is an image based only on the reference light, the image of only the reference light is recorded, and the square root of each pixel of the CCD is taken to obtain the amplitude distribution A of the reference light._R(X, y) can be obtained. Therefore, A acquired in that way_R(X, y), real part Re {c (x, y)} and imaginary part Im {c (x, y)} of complex amplitude c (x, y), By calculating equation (9), the phase distribution φ of the object reflected light at the position of the imaging surface of the CCD_{o 0}(X, y) and amplitude distribution A_{o 0}(X, y) can be obtained, and the complex amplitude U of the object reflected light at the position of the imaging surface of the CCD is obtained using the equation (6)._{o 0}(X, y) can be expressed.

By multiplying the phase distribution of equation (8) by λ / (2π), the surface shape of the object to be measured can be obtained.
However, since the shape by the phase distribution is a relative value with respect to the reference surface shape, the position of the surface to be measured (the height of the object reflected light in the substantially optical axis direction) cannot be obtained. In the present invention, such a position is obtained by the principle of the focusing method using the amplitude distribution obtained by the equation (9).
[0033]
Focusing methods are described in, for example, documents: Mitsuhiro Ishihara and Hiromi Sasaki, “High-speed three-dimensional shape measurement by focusing method”, Journal of Precision Engineering, vol. 63, no. 1, as reported in 1997, a plurality of sheets are measured while moving the objective lens in the direction of the optical axis of the optical system in a state where the image of the object to be measured is substantially imaged on the imaging surface of the CCD by the objective lens. Record object images. When the objective lens is moved in the direction of the optical axis of the optical system, the object image is defocused in accordance with the amount of movement, thereby changing the contrast of the image. Therefore, the height of the object in the optical axis direction of the optical system can be obtained by detecting the position of the objective lens when the focus is achieved and the contrast reaches a peak. Then, by detecting the peak of contrast in each minute area in the CCD image, the height of the object in that area is obtained, and the processing is carried out in all areas that can be observed by the CCD. The height distribution of the surface can be obtained. However, according to the method, since a plurality of images are recorded while moving the objective lens in time series, it is difficult to measure if the object is moving, and the surface of the dynamic object as in the present invention. It cannot be applied to shape measurement.
[0034]
In the present invention, the defocus caused by the movement of the objective lens in the conventional focusing method is given by numerical calculation. In order to cause defocusing, the amplitude and phase obtained by the equations (8) and (9) are substituted into the equation (6), and the complex amplitude U of the object reflected light U_o(X, y) is obtained and substituted into equation (10) to calculate the Fresnel diffraction of the object reflected light.

In the equation (10), Z represents the distance from the CCD surface in the optical axis direction of the optical system, and the object reflection at a position away from the CCD surface by Z by inputting the value of Z and calculating the equation (10). Complex amplitude U of light_ZCan be requested. The amplitude distribution A of the object reflected light from the complex amplitude at a predetermined Z position using equation (9)_Z(X, y) can be obtained, and the amplitude distribution of the object reflected light obtained by the equation (9) is equivalent to a value obtained by taking the square root of the intensity at each pixel in the image observed by the CCD. Therefore, by changing the value of Z, a plurality of amplitude images having different defocus amounts can be acquired. In the conventional focusing method, the defocus was given by moving the objective lens, but here the operation of giving the defocus by virtually moving the CCD in the optical axis direction of the optical system is performed by numerical calculation processing. ing. Since a single interference fringe is recorded, and all subsequent processing is performed by calculation processing, it is possible to handle even if an object is moving. Using a plurality of amplitude images having different defocuss, the contrast in a very small area is obtained as in the conventional focusing method, and the value of Z when the contrast reaches a peak is the height of the area. Here, in the case of detecting the contrast according to the defocus, it is necessary to have a texture in the processing region. In the conventional focusing method, since a rough object with a rough surface is often used as the object to be measured, the roughness of the surface can be treated as a texture, but when the object to be measured is a mirror surface, the surface roughness is reduced. It becomes difficult to detect optically.
[0035]
  In the present invention, as an example of dealing with this, in order to know the height of the mirror surface that is the object to be measured, the edge portion of the mirror is regarded as a texture, and the contrast peak accompanying the defocusing of the mirror edge is detected. The position (height) of the mirror in the optical system optical axis direction is obtained. In this case, position measurement values are obtained for all CCD pixels that correspond to the image of the mirror edge, but a predetermined area at the mirror edge is set in advance as a reference area, and the measurement value in that area is used as the position measurement value of the mirror. It may be used as an average, or all the position measurement values in a minute area where the texture is present may be averaged and used as the mirror position measurement value. Since the difference in position (height) between the mirror edge and the mirror surface other than the edge is obtained by the phase distribution of equation (8), the surface shape of the mirror can be measured in nanometer order using the phase distribution, and The amplitude distribution can be used to measure the position of the mirror and thus both can be acquired simultaneously. FIG. 4A shows a numerical calculation processing model that gives a defocus, and FIG. 4B shows the mirror edge position (● plot) and the mirror edge of the amplitude image when Z is changed.Other thanThe state of the contrast change at the position (■ plot) is shown.
[0036]
FIG. 4A shows a state in which an image of the DUT 16 is formed by the lens 17 at the position of the CCD imaging surface 18b. Calculate the expression (10) while changing the value of Z by virtually changing the position of the CCD to 18a or 18c, for example, with the position where the image of the object 16 to be measured is substantially formed by visual observation. Can give a defocus to the amplitude image. In FIG. 4B, the value of Z on the horizontal axis is taken, the contrast is plotted on the vertical axis, and the contrast value when Z is changed is plotted. As shown by the ● and ■ plots in the figure, in the amplitude image, the level of contrast change increases when there is a texture in a small area where contrast is detected, and the level of contrast change when there is no texture. Becomes smaller. Therefore, by applying a threshold to the peak value of the contrast change, it is possible to determine whether or not there is a texture in a minute region where the contrast is detected. It is only necessary to obtain D within a minute region where the texture exists.
[0037]
The value d obtained by substituting D in the following equation (11) in FIG. In equation (11), k is the sensitivity to defocus, and M is the optical system magnification. The measurement resolution improves as the optical system magnification increases.

When the object to be measured is, for example, as shown in FIG. 1 where a drive mirror is attached to the base, the difference between the Z value of the base position measurement value and the mirror edge position measurement value can be obtained. For example, this is the position of the mirror when the base is used as a reference. When detecting the defocus of the base, if the base is a rough surface, an image having a rough surface is used as the texture. If the base is a mirror surface, the base may be pre-marked and the mark may be used as a texture, or a pattern that forms an image on the base surface is projected onto the base and used as a texture. If the edge of the base is observed in the field of view, it may be used as a texture. The method of marking and the method of projecting the pattern can be applied to the mirror surface, which is the object to be measured, and the pattern can be formed in advance on the mirror surface to be measured or imaged on the surface of the mirror to be measured. If the mark or pattern is used as a texture, the edge of the mirror does not need to be used as a texture. In the case where the object to be measured is a mirror array as shown in FIG. 2, the mirror edge may be textured, or the pattern projected on each mirror surface may be textured.
[0038]
An example of a measurement procedure when the vibration mirror as shown in FIG. FIG. 1B illustrates the vibration phase and the tilt of the mirror by observing the vibration state of the vibration mirror from the side.
The oscillating mirror oscillates in the direction of the arrow in the figure, and is used for changing the direction of reflected light of the light irradiated on the oscillating mirror or for scanning. When the vibration phase is 0 degree, the mirror surface is horizontal (the surface represented by a solid line in the figure). When the vibration phase is 90 degrees, the mirror surface tilts to the left at the maximum angle (the surface represented by the dotted line in the figure), and when the vibration phase is 180 degrees, the mirror surface is horizontal again (the surface represented by the solid line). When the vibration phase is 270 degrees, the mirror surface is tilted to the right at the maximum angle (the surface represented by the alternate long and short dash line in the figure), and when the vibration phase is 360 degrees, the mirror surface is again horizontal (the solid line is represented in the figure) Surface). The vibration is repeated with the above movement as one cycle, and the tilt of the mirror continuously changes. The maximum inclination angle of the mirror surface is determined by the specification value of the vibration amplitude of the vibration mirror, and the specification of the vibration period is also set.
[0039]
In the measurement, the shape of the mirror in vibration and the position of the mirror surface in the direction of the optical axis of the substantially irradiated optical system are measured by the apparatus and method according to the present invention. For example, the mirror is horizontal (the vibration phase is 0 degree). The mirror shape and position at the time of the mirror or the mirror shape and position when the mirror is tilted at the maximum angle (the vibration phase is 90 degrees or 270 degrees). The surface shape and position of the mirror at a certain time are obtained.
First, an image of only the reference light is recorded in a state where the object to be measured is not installed, and then the object to be measured is set. Adjust the position of the object in the optical axis direction of the optical system so that the mirror surface is in focus, while visually checking the texture of the mirror edge, etc. To do. When the tilt of the reference mirror is adjusted, interference fringes are generated. Thereafter, the tilt of the reference mirror is further adjusted so that a predetermined spatial carrier frequency is placed on the interference fringes, and then the mirror to be measured is vibrated. When the imaging period of the CCD camera is not synchronized with the vibration frequency of the mirror to be measured, the generated interference fringes move or disappear. When the imaging cycle of the CCD camera is synchronized with the vibration frequency of the mirror to be measured, the interference fringes are observed to stand still, so if the interference fringes are apparently stopped and the interference fringes are recorded at a predetermined timing, The interference fringes at the inclination to be measured of the mirror under measurement can be recorded. Data processing after interference fringe recording may be as described in the explanation of the principle. Thereby, the position of the surface to be measured with respect to the base surface serving as a reference in the optical axis direction of the substantially irradiating optical system at the moment of movement and the surface shape of the surface to be measured at the moment of movement are obtained. The tilt of the mirror under measurement at the time of measurement may be arbitrary, but it is a necessary condition that the tilt of the reference mirror is adjusted so that a predetermined spatial carrier frequency is placed on the interference fringes. Depending on the tilt of the vibrating mirror to be measured, s shown in FIG. 1A cannot be obtained due to the tilt between the base surface and the mirror surface. However, the position measurement value of the mirror surface in the optical axis direction of the irradiation optical system and the base surface The geometrical relationship between the measured position in the optical axis direction of the irradiation optical system, the texture position in the observation plane where the position in the optical axis direction of the irradiation optical system of the base surface is measured, and the tilt of the mirror surface is required. This may be reflected in the performance and processing accuracy of the object to be measured.
[0040]
Next, an example of measurement and processing procedures when the object to be measured is a mirror array as shown in FIG. 2 will be described.
When the mirror array is used as a spatial modulation element in a display, each mirror surface is switched to several (for example, two) predetermined angles to turn on / off the reflected light of the light irradiated on the mirror. Acts like In this case, the shape of the mirror surface at the moment when the angle is switched and the relative position of each mirror surface in the optical axis direction of the substantially irradiating optical system are measured by the apparatus and method of the present invention. In addition, when the mirror array is used for an optical equalizer in optical communication, each mirror surface is switched to several predetermined angles, so that each mirror is irradiated from an optical fiber arranged in one or two dimensions. The reflected light is guided to a predetermined position of the optical fiber arranged one-dimensionally or two-dimensionally. In this case, the shape of the mirror surface at the moment when the angle is switched and the relative position of each mirror surface in the optical axis direction of the substantially irradiating optical system are measured by the apparatus and method of the present invention.
[0041]
At the time of measurement, first, an image of only the reference light is recorded without setting the object to be measured, and then the object to be measured is set. Then, the mirror array is stopped so that the mirror surfaces are substantially parallel at the mirror angle to be measured. Then, while visually confirming the texture such as the mirror edge, the position of the object to be measured in the direction of the optical axis of the optical system is adjusted so that the mirror surface is substantially focused. When the tilt of the reference mirror is adjusted, interference fringes are generated. Thereafter, the tilt of the reference mirror is further adjusted so that a predetermined spatial carrier frequency is placed on the interference fringes, and then the mirror array is driven while making each mirror substantially parallel. When the mirror array is driven so that the mirror to be measured is tilted at a certain period and within one period, and the CCD camera imaging period is synchronized with the mirror array driving period, the interference fringes appear to be apparent. Observed stationary. Conversely, if the imaging cycle of the CCD camera is not synchronized with the drive cycle of the mirror array, the generated interference fringes move or disappear. Synchronize the CCD camera imaging period with the mirror array drive period, make the interference fringes appear and stop, and record the interference fringes at the predetermined timing when recording the interference fringes. Can do. Data processing after interference fringe recording may be as described in the explanation of the principle. Thereby, the relative position of each mirror surface in the direction of the optical axis of the substantially irradiating optical system at the moment of movement and the surface shape of each mirror surface at the moment of movement are obtained. The tilt of the mirror at the time of measurement may be arbitrary, but the tilt of the reference mirror is adjusted so that a predetermined spatial carrier frequency is placed on the interference fringes, and each mirror surface constituting the mirror array is substantially omitted. It is a necessary condition to drive the mirror array to be parallel.
[0042]
FIG. 5 shows an example of a measurement procedure for measuring the position of the surface to be measured in the direction of the optical axis of the irradiation optical system and measuring the shape of the surface to be measured. In FIG. 5, i is a count value, Z0 is an initial value for changing Z when position measurement is performed, ΔZ is a pitch for changing Z, N is a number of times of changing Z, and other English letters are implemented It has the same meaning as the English letters in the examples.
[0043]
2. Invention according to claim 2
When measuring with the apparatus of claim 1, an image of only the reference light is required. In that case, it is only necessary to record an image without the object to be measured. However, depending on the installation environment of the measurement device, the reflected light from the structure around the device may enter the CCD, resulting in noise and improving the measurement accuracy. May decrease. In the present invention, as shown in FIG. 6, in the measurement process, a light-shielding plate 19 is manually installed in the optical path from the object to be measured to the CCD to block the object reflected light, thereby making noise-free reference. Get a light-only image. The part numbers in FIG. 6 are the same as those in FIG. Thereby, it is possible to provide a highly accurate measuring apparatus that is not affected by noise.
[0044]
3. Invention according to claim 3
Regarding the installation of the light shielding plate according to claim 2, the light shielding plate may be manually installed in the optical path from the object to be measured to the CCD, but when the work to install the light shielding plate occurs every time the object to be measured changes. According to manual work, workability and operability are lacking. In the present invention, as shown in FIG. 7, the light shielding plate 19 is mounted on a stage 20 that can be advanced and retracted in a direction substantially perpendicular to the optical axis of the optical system, and the stage 20 is advanced and retracted to move the light shielding plate from the object to be measured to the CCD. Install inside. If the stage 20 is moved back and forth by rotating a stepping motor (not shown) or the like, the light shielding plate can be automatically installed at a position in the optical path from the object to be measured to the CCD by specifying the number of pulses. Thereby, the operability and workability of measurement are improved.
[0045]
4). Invention according to claim 4
This will be described with reference to FIGS. 8 (a) and 8 (b). 8A and 8B, the parts indicated by the same numbers as those in FIG. 3 are the same as the parts shown in FIG.
Reference numeral 21 denotes an objective lens that enlarges the image of the object to be measured and forms an image at the position of the imaging surface of the CCD. In order to increase the magnification, a microscope objective lens may be used. The positional relationship in the optical axis direction of the optical system is adjusted so that the DUT 8 and the CCD 10 have an optically conjugate relationship with respect to the objective lens 21. In the case of the configuration of FIG. 8A, since the lens is installed only in the optical path of the object reflected light, a difference in curvature occurs in the wave front between the reference light and the object reflected light, and the interference fringes generated thereby are shown in FIG. A defocused component as shown in FIG. As a result, among the complex amplitudes of the object reflected light obtained from the recorded interference fringes, a defocus component is generated in the phase data, which becomes a measurement error of the surface shape. The defocus component may be corrected by using a Zernike polynomial or the like. However, when the defocus component becomes large, such as when the enlargement magnification of the optical system is increased, the interference fringe interval becomes small accordingly. Detection of interference fringes becomes impossible (interference fringe spacing is smaller than the size of two CCD pixels).
[0046]
In order to remove the defocus component, a lens having the same focal length as that of the objective lens 21 may be provided in the reference optical path. However, the positional relationship between the measured object 8, the objective lens 21, and the CCD 10 is substantially the same. In addition, the positional relationship between the reference surface, the CCD, and the lens installed in the reference optical path must be adjusted, the optical system becomes complicated, and a shape measurement error accompanying an adjustment error occurs. In FIG. 8B, the objective lens 23, the beam splitter 24, and the reference surface 25 are integrated, and it functions as an interference optical system as well as an imaging optical system. 22 acts as a condenser lens. Since the same objective lens is installed in both the reference optical path and the object reflection optical path and operates in the same manner, a defocus component does not occur in the interference fringes, and the position adjustment of the objective lens is facilitated. Thereby, the configuration and adjustment of the measurement optical system can be simplified, and the shape measurement error can be reduced. Further, the shape can be measured even when the magnification of the optical system is increased.
[0047]
5. Invention according to claim 5
When the object to be measured is an object that vibrates periodically as shown in FIG. 1, the optical path difference between the object reflected light and the reference light varies depending on the inclination of the object surface, so the fringe spacing of the interference fringes differs. Come. Therefore, the spatial carrier frequency of the interference fringes varies depending on the inclination of the object surface to be measured, and the measurement conditions change.
In the invention according to claim 1 as described above, the reference mirror 12 is set in a state where the object to be measured is stationary at the inclination to be measured so that the spatial carrier frequency of the interference fringes does not differ due to the inclination of the object surface to be measured. The interference fringe recording is performed after adjusting the inclination of the interference fringe so that a predetermined spatial carrier frequency is placed on the interference fringe. However, according to this method, it is necessary to perform the above work every time the inclination of the object surface to be measured is changed, so that workability is lacking. The invention according to claim 5 for solving the above problem will be described with reference to FIG. The parts denoted by the same reference numerals as those in FIG. 3 are the same as those in the invention according to claim 1 shown in FIG.
[0048]
Reference numeral 26 denotes a He-Ne laser 4, an ND filter 5 for adjusting the intensity of light irradiated to an object, a beam expander 6, a beam splitter 7, a lens 9, a CCD camera 10, and an ND filter 11. And a stage mounted with a reference mirror 12 and rotated around an arrow in the figure. The rotation stage 26 changes the angle between the optical axis of the irradiation optical system and the object 8 to be measured, and the phase difference between the object reflected light and the reference light changes, so that the spatial carrier frequency of the interference fringes changes. . However, the direction in which the inclination of the measurement surface changes and the rotation direction of the rotary stage 26 are in the same plane. The relationship between the angle δ formed by the reference mirror 12 and the surface to be measured and the interference fringe spacing g is expressed by equation (12). If the interference fringe spacing g is determined, the spatial carrier frequency is determined.

[0049]
On the other hand, when the phase of the vibration of the surface to be measured is 0 and the inclination of the surface to be measured with respect to the optical axis of the irradiation optical system is 0 degree, the relationship between the inclination θ of the surface to be measured and the phase p of the vibration of the surface to be measured is (13). H is the vibration amplitude of the vibrating mirror, and L is the span of the vibrating mirror.

Therefore, the interference fringe interval g is first determined, and the angle δ formed by the reference mirror and the surface to be measured is calculated and stored by the equation (12). In accordance with the change in the vibration phase p of the vibration mirror, the inclination θ of the surface to be measured is obtained, and the stage 26 is rotated so as to have an angle of θ + δ. As a result, the spatial carrier frequency becomes constant to the inclination of the vibration mirror surface, and measurement under the same conditions becomes possible. When the vibration phase p is input, if the stage 26 is automatically programmed to have an angle of θ + δ, efficient measurement can be realized.
[0050]
6). Invention concerning Claim 6
In the case where the object to be measured is an object that periodically vibrates as shown in FIG. 1, the optical path difference between the object reflected light and the reference light varies depending on the inclination of the object surface. come. Accordingly, the spatial carrier frequency of the interference fringes varies depending on the inclination of the object surface to be measured, and the measurement conditions change. In the invention according to claim 1 shown in FIG. 3, the object to be measured is kept stationary at the inclination to be measured so that the spatial carrier frequency of the interference fringes does not vary due to the inclination of the object surface to be measured. Interference fringe recording is performed after adjusting the inclination so that a predetermined spatial carrier frequency is placed on the interference fringe. However, according to this method, it is necessary to perform the above work every time the inclination of the object surface to be measured is changed, so that workability is lacking. The invention according to claim 6 for solving this problem will be described with reference to FIG. Parts denoted by the same reference numerals as those in FIG. 3 are the same as those in the invention according to claim 1 shown in FIG.
[0051]
What is denoted by reference numeral 27 is a stage for moving the lens 6a of the beam expander 6 in a direction substantially perpendicular to its optical axis. However, the direction in which the inclination of the surface to be measured changes and the moving direction of the stage 27 are in the same plane. Then, the relationship between the moving distance s of the stage 27 and the angle σ of the irradiation light with respect to the optical axis of the optical system is expressed by equation (14).

f is the focal length of the lens 6a. Therefore, if θ + δ obtained by the equations (12) and (13) is substituted for σ in the equation (14), the stage moving distance s is determined. Therefore, the stage moving distance s is obtained in accordance with the change of the vibration phase p of the surface to be measured. When the stage 27 is moved, the spatial carrier frequency becomes constant with the tilt of the vibrating mirror surface, and measurement under the same conditions is possible. If the stage 27 is programmed to automatically move by s when the vibration phase p is input, efficient measurement can be performed.
[0052]
7. Invention according to claim 7
When obtaining the position of the object based on the amplitude data (amplitude image) of the complex amplitude data of the object reflection light obtained by calculation, the amplitude image of the object reflection light at a plurality of positions in the substantially optical axis direction of the object reflection light. And the object position is measured by detecting the in-focus state of the image in the image. In order to detect the in-focus state, it is necessary to quantitatively detect the degree of blurring of the texture (pattern) of the image. On the other hand, because laser light sources have high temporal and spatial coherence, textures may not be clearly observable due to diffraction effects, and noise interference fringes (interferences that do not depend on the object shape) due to the reflected light from the constituent surfaces of the measurement optical system Since stripes are likely to occur, they degrade measurement accuracy. In the invention according to claim 7, for example, as shown in FIG. 12, the light emitted from the He—Ne laser 4 is diffused by using the diffusion plate 28, so that the spatial coherence of the irradiation light to the measurement object is increased. Reduce. By rotating the diffusion plate 28 using the motor 29, the influence of speckle noise due to scattering on the diffusion plate is removed. Due to the reduction in spatial coherence, it becomes possible to observe a clear texture with little influence of diffraction, and noise interference fringes are reduced, so that the position and shape measurement accuracy can be improved. Note that light from a light source having a large light emitting area, such as a filament, can be monochromatic with a color filter and used.
[0053]
8). Invention concerning Claim 8
When measuring an object surface shape by recording an interference fringe image, if the object moves during the recording of the interference fringe image, the interference fringe is disturbed and accurate measurement cannot be performed. In such a case, it is sufficient to record interference fringes at a sufficiently short imaging speed relative to the operation speed of the object, or to sufficiently shorten the irradiation time of light on the object. It is more advantageous to shorten the irradiation time than to shorten the time. In the present invention, a solid pulse laser such as a ruby laser is used as a light source, or a semiconductor laser is driven to emit light, thereby shortening the light irradiation time on the object, so that the object is moving at high speed. Even in this case, high-precision measurement is possible.
[0054]
  9. Invention concerning Claim 9
  In the measuring method using the dynamic shape and dynamic position measuring apparatus according to claim 1, an image using only the reference light is required for each measurement, but the setting of the optical system does not change even if the object to be measured changes. For example, an image with only the same reference beam is a complex amplitude U_oCan be used in calculations to find According to the ninth aspect of the present invention, when such an optical system setting does not change, an image of only the reference light is recorded and stored in advance using the light shielding means, and the stored reference light is stored. Only the complex amplitude U_oBy using it for the calculation for obtaining the value, it is possible to save the trouble of recording an image of only the reference light every time measurement is performed.
[0055]
10. Invention concerning Claim 13
A thirteenth aspect of the present invention relates to a method for adjusting the recording timing of interference fringes in the case of measuring a periodically vibrating object using the dynamic shape and dynamic position simultaneous measurement apparatus of the first aspect. The image recording function by trigger input is used.
FIG. 13A is an example of an input signal for driving a vibrating mirror as a periodically vibrating object, and FIG. 13B is an example of a trigger signal input to the CCD. In FIGS. 13A and 13B, the horizontal axis represents time, and the vertical axis represents input voltage.
Reference numeral 30 corresponds to the vibration period of the object. The relationship between the vibration phase of the vibration mirror and the inclination of the mirror surface is shown by the above equation (13). Therefore, once the inclination of the vibration mirror surface to be measured is determined, the timing is adjusted to the vibration phase. A trigger signal is input to the CCD. If the trigger signal is continuously input and the image is recorded and displayed, the interference fringe image observed by the CCD appears to be stationary, so one of the recorded interference fringes is used. If the invention according to the above is implemented and the shutter speed of the CCD is shortened in accordance with the vibration speed of the object, it is possible to deal with an object that vibrates at high speed.
[0056]
11. Invention according to claim 14
According to a fourteenth aspect of the present invention, there is provided a method for adjusting the irradiation timing of pulsed light on an object to be measured when measuring an object that vibrates periodically using the dynamic shape and dynamic position simultaneous measurement apparatus according to the eighth aspect of the present invention. In FIG. 13, the trigger signal input to the CCD in FIG. 13 is input to the pulse laser driver. If the trigger signal input to the pulse laser is also used as a trigger signal for CCD image recording, an apparently stationary interference fringe is observed. Therefore, the emission pulse width of the pulse laser should be shortened according to the vibration speed of the object. It can handle objects that vibrate at high speed.
[0057]
12 The invention according to claim 15
According to the fifteenth aspect of the present invention, the complex amplitude U of the object reflected light is obtained by the simultaneous measurement method of the dynamic shape and the dynamic position of the ninth aspect._iWhen the position of the object in the direction of the optical axis of the substantially irradiating optical system is measured from the amplitude data of the object reflected light obtained from the above, the in-focus state of the object image is detected.
In order to detect the in-focus state, a texture (pattern) is required. While observing the texture, when the image is sharpest, the in-focus state is determined, and when the image is blurred, the defocus state is determined. . In-focus and defocus are quantitatively detected by obtaining the level of contrast by calculating adjacent pixels such as the differential sum of the CCD, or extracting the luminance at a single pixel of the CCD.
In this invention, the position of a predetermined surface in the optical axis direction of the irradiation optical system is measured by detecting the focus state of the texture on the predetermined surface in the measurement object composed of a plurality of surfaces. Measure the position of a predetermined other surface in the optical axis direction of the illumination optical system by detecting the focus state of the texture on the other surface, and determine the difference between them in the optical axis direction of the illumination optical system. Measure the relative position of the faces.
[0058]
13. Invention according to claim 16
According to the sixteenth aspect of the present invention, when the surface to be measured is an optical rough surface, a rough image of the surface to be measured is used as a texture. FIG. 14 shows an example of a rough surface image in the amplitude image when the vibration mirror of FIG. 1 is used as an object to be measured. In FIG. 14, 31 is a mirror surface to be measured, 32 is a base surface, and 32 is a base surface. The innumerable line indicated by reference numeral 33 represents a rough texture. For example, the surface position may be measured using the reference numeral 33 as a texture.
[0059]
14 The invention according to claim 17
In the invention according to claim 17, in an object having an optical mirror surface such as a mirror or optical glass, the roughness of the surface cannot be optically observed because the size is equal to or smaller than the diffraction limit of light. It becomes impossible to observe and there is a problem that the in-focus state cannot be detected because there is no texture. When the surface to be measured is an optical mirror surface, an image of a mark marked in advance on the surface to be measured is used as a texture.
FIG. 15 shows an amplitude image when the oscillating mirror of FIG. 1 is used as an object to be measured (however, the same reference numerals are used for the same components as in FIG. 14). The mark 34 is marked on the base surface 32, the mark 35 is marked on the mirror surface 31, and the sign 34 is a texture for measuring the position of the base surface in the direction of the optical axis of the substantially irradiating optical system. , 35 is a texture for measuring the position of the vibrating mirror surface in the optical axis direction of the substantially irradiating optical system.
[0060]
15. The invention according to claim 18
In the invention according to claim 18, in the case of an object having an optical mirror surface such as a mirror or optical glass, the roughness of the surface cannot be optically observed because the size is less than the diffraction limit of light, and the texture is observed. It becomes impossible, and there is a problem that the in-focus state cannot be detected because there is no texture. When the surface to be measured is an optical mirror surface, an edge image of the surface to be measured is used as a texture. FIG. 16 shows an amplitude image when the oscillating mirror of FIG. 1 is used as an object to be measured (however, the same reference numerals are used for the same components as in FIG. 14). Reference numeral 36 denotes an edge on the base surface 32, and 37 denotes an edge state on the mirror surface 31. Reference numeral 36 is a texture for measuring the position of the base surface in the optical axis direction of the substantially irradiating optical system, and reference numeral 37 is a texture for measuring the position of the vibrating mirror surface in the optical axis direction of the irradiating optical system.
[0061]
16. Invention according to claim 19
According to the method of the fifteenth aspect, the measurement value of the position of the surface in the direction of the optical axis of the substantially irradiating optical system is obtained in all the areas where the texture image exists. When the surface to be measured is a mirror surface, a surface shape measurement value using phase data can be obtained. However, since the resolution is different between the position measurement value and the shape measurement value, it is difficult to relate the two (for example, The difference in height between an arbitrary certain part and a certain part is only a few nanometers when looking at the shape measurement value, but there is a phenomenon that there are several μm when looking at the position measurement value), so the invention according to claim 19 In this case, a predetermined portion of a region having a texture image is set as a reference, and in the position measurement, a measurement value at that portion is set as a position measurement value in the direction of the optical axis of the substantially irradiated optical system.
For example, the position 38 at the edge 36 in FIG. 16 is set as the reference position of the base surface, the position 39 at the edge 37 is set as the reference position of the mirror surface, and the position measurement values at reference numerals 38 and 39 are respectively the position measurement of the base surface and the mirror surface. Value.
[0062]
17. Invention according to claim 20
According to the method of the fifteenth aspect, the measurement value of the position of the surface in the direction of the optical axis of the substantially irradiating optical system is obtained in all the areas where the texture image exists. When the surface to be measured is a mirror surface, a surface shape measurement value using phase data can be obtained. However, since the resolution is different between the position measurement value and the shape measurement value, it is difficult to relate the two (for example, The height difference between an arbitrary region and a certain region is only a few nanometers when looking at the shape measurement value, but there is a phenomenon that there are several μm when looking at the position measurement value), so the invention according to claim 20 Is to calculate the average value of the position measurement values in a predetermined area in the texture image, and to use it as the position measurement value of the surface to be measured in the direction of the approximate illumination optical system term. For example, the position measurement values for all the pixels constituting the edge 36 in FIG. 16 are obtained, and the average value is used as the position measurement value for the base surface, and the position measurement values for all the pixels constituting the edge 37 are obtained and the average value is used as the mirror surface. The position measurement value of
[0063]
【The invention's effect】
The effects of the present invention are summarized as follows for each claim.
1. Invention according to claim 1
The complex amplitude U of the object reflected light at the position of the imaging means from the interference fringe image generated between the object reflected light and the reference light and the image by only the reference light._oAnd the complex amplitude U of the object reflected light at a plurality of positions in the optical axis direction of the object reflected light by calculating the complex amplitude Fresnel diffraction of the object reflected light at the position of the imaging means._i(I: integer)_iThe object surface shape is obtained from the phase data of the object reflected light obtained from_iBy determining the position of the object in the direction of the optical axis of the substantially irradiating optical system from the amplitude data of the object reflected light obtained from the above, the surface shape of the moving object and the position in the direction substantially perpendicular to the surface are simultaneously measured. This makes it possible to simultaneously acquire the surface shape of the nanometer order while the object is moving and the position of the object in the direction of the optical axis of the optical system with a high in-plane spatial resolution. A measuring device can be provided.
[0064]
2. Invention according to claim 2
A light shielding unit is installed in the optical path from the object to be measured to the imaging unit, and the object reflected light is blocked to obtain an image of only the reference light without noise. Thereby, it is possible to provide a highly accurate measuring apparatus that is not affected by noise.
[0065]
3. Invention according to claim 3
2. The operability of the apparatus according to claim 1, wherein the light shielding means is mounted on a stage that can be moved back and forth in a direction substantially perpendicular to the optical axis of the optical system, and the installation of the light shielding means in the optical path is automated by driving the stage. Can be improved.
[0066]
4). Invention according to claim 4
When an object image is optically enlarged and imaged at the position of the imaging means, the object light is integrated by integrating an optical system and an interference optical system for enlarging the object image and forming an image at the position of the imaging means. By using the same lens for converting to a spherical wave and a lens for converting the reference light into a spherical wave, the configuration and adjustment of the measurement optical system can be simplified and measurement errors can be reduced.
[0067]
5. Effects of the invention according to claim 5
When the object to be measured is an object that vibrates periodically, a rotation stage that changes the tilt of a unit that integrates the light source, irradiation optical system, interference optical system, imaging means, and imaging optical system is added to the configuration, and the amount of rotation is By specifying, the fringe spacing of the interference fringes can be set, and thereby stable measurement with a constant condition can be efficiently performed on the inclination of the object surface.
[0068]
6). Effect of the Invention of Claim 6
When the object to be measured is an object that vibrates periodically, a linear motion stage that relatively shifts the optical axis of the irradiation optical system and the optical axis of the imaging optical system is added to the configuration, and the movement causes By changing the angle at which the irradiated light is incident on the surface to be measured, the fringe spacing of the interference fringes can be set, thereby making it possible to efficiently carry out stable measurement with a constant condition on the inclination of the object surface.
[0069]
7. Effect of the Invention of Claim 7
By using a diffused light source as the light source, the spatial coherence can be lowered, thereby making it possible to observe a clear texture with little influence of diffraction, and reducing noise interference fringes can improve measurement accuracy.
[0070]
8). Effect of the Invention of Claim 8
By using a pulsed light source as the light source and shortening the irradiation time of light to the object, high-precision measurement is possible even when the object is moving at high speed.
[0071]
9. Invention concerning Claim 9
  In the apparatus of claim 1, an image using only the reference light is required for each measurement. However, if the setting of the optical system does not change even if the object to be measured changes, an image using only the same reference light is converted to the complex amplitude U._oCan be used in calculations to find In the case where the setting of such an optical system does not change, the present invention records in advance an image of only reference light using a light shielding means and stores it, and stores the image of only stored reference light. Complex amplitude U_oBy using it for the calculation for obtaining the value, it is possible to save the trouble of recording an image of only the reference light every measurement, and to improve the operability and workability of the measurement.
[0072]
10. Invention which concerns on Claim 12
When measuring the object which vibrates periodically by the apparatus of Claim 5 and Claim 6, the fringe interval of the interference fringe generated between the object light and the reference light is set to 2 orthogonal to the optical system optical axis of the unit of Claim 5. It can be arbitrarily set by using a rotary stage that changes the tilt in the direction, or by using a linear motion stage that relatively shifts the optical axes of the irradiation optical system and the imaging optical system. . If the interference fringe spacing recorded is different, the measurement conditions will change and the measurement accuracy will change accordingly.Therefore, the purpose of setting the fringe spacing is to determine the surface shape and position in the optical axis direction of the optical system. Is obtained under the same measurement conditions. Therefore, while the object is vibrating, it is necessary to set the rotation amount of the rotary stage and the movement amount of the linear motion stage in accordance with the tilt state of the measurement target surface to be measured. However, according to the present invention, the inclination of the object to be measured is obtained by determining the inclination of the object to be measured based on the vibration phase data of the object to be measured, and setting the rotation amount of the rotary stage and the movement amount of the linear motion stage from the inclination. The measurement accuracy can be stabilized by keeping the measurement conditions constant.
[0073]
11. Invention concerning Claim 13
When the object to be measured vibrates periodically, it is necessary to record the interference fringes in the state where the object has the inclination to be evaluated. In this case, it is necessary to set the recording timing of the interference fringe image. For example, by using the phase data of the vibration of the object to be measured for the above setting, it is possible to realize a method for accurately recording the interference fringe image in a state where the object has a predetermined inclination.
[0074]
12 Invention according to claim 14
When the object to be measured vibrates periodically, it is necessary to record the interference fringes in the state where the object has the inclination to be evaluated. In this case, when using a pulsed light source as the light source, set the pulse emission timing of the light source. There is a need. According to the present invention, by using the phase data of the vibration of the object to be measured for the above setting, it is possible to realize a method for accurately performing pulsed light emission of the light source in a state where the object has a predetermined inclination. .
[0075]
13. The invention according to claim 15
10. The method of claim 9, wherein the U_iWhen measuring the position of the object in the optical axis direction of the substantially irradiating optical system from the amplitude data of the object reflected light obtained from the above, the in-focus state of the object image is detected. In order to detect the in-focus state, a texture (pattern) is required. While observing the texture, the image is sharpest when it is in focus, and when it is blurred, it is out of focus. Judge the condition. In-focus and defocus are quantitatively detected by obtaining the level of contrast by calculating adjacent pixels such as the differential sum of the CCD or by extracting the luminance at a single pixel of the CCD. This invention measures the position of a predetermined surface substantially in the optical axis direction of the irradiation optical system by detecting the in-focus state of the texture on the predetermined surface in the object to be measured configured from a plurality of surfaces, By measuring the position of the predetermined other surface in the optical axis direction of the substantially irradiated optical system by detecting the in-focus state of the texture on the predetermined other surface, and calculating the difference between them, the optical axis direction of the substantially irradiated optical system The method of claim 9 can be realized by measuring the relative positions of the surfaces at.
[0076]
14 Invention according to claim 16
When the surface to be measured is an optical rough surface, the method of claim 9 can be realized by using a rough image of the surface to be measured as a texture.
[0077]
15. The invention according to claim 17
In an object with an optical mirror such as a mirror or optical glass, the roughness of the surface is smaller than the diffraction limit of light, and cannot be observed optically, texture cannot be observed, and there is no texture. This causes a problem that the state cannot be detected. In the case where the surface to be measured is an optical mirror surface, the method of claim 9 can be realized by using an image of a mark previously marked on the surface to be measured as a texture.
[0078]
16. The invention according to claim 18
For an object with an optical mirror surface such as a mirror or optical glass, the roughness of the surface is below the diffraction limit of light, and it cannot be observed optically, texture cannot be observed, and there is no texture. This causes a problem that the focus state cannot be detected. When the surface to be measured is an optical mirror surface, the method of claim 9 can be realized by using the edge image of the surface to be measured as a texture.
[0079]
17. Invention according to claim 19
According to the method of the fifteenth aspect, the measurement value of the position of the surface in the direction of the optical axis of the substantially irradiating optical system can be obtained in all the regions where the texture image exists. When the surface to be measured is a mirror surface, a surface shape measurement value using phase data can be obtained. However, since the resolution is different between the position measurement value and the shape measurement value, it is difficult to relate the two (for example, The difference in height between an arbitrary certain part and a certain part is only a few nm when looking at the shape measurement value, but there is a phenomenon that there are several μm when looking at the position measurement value). Therefore, in the present invention, a predetermined portion of a region having a texture image is set as a reference, and in the position measurement, the measurement value at that portion is set as the position measurement value in the optical axis direction of the substantially irradiated optical system. Thus, the method of claim 9 can be realized.
[0080]
18. Invention according to claim 20
According to the method of the fifteenth aspect, the measurement value of the position of the surface in the direction of the optical axis of the substantially irradiating optical system is obtained in all the areas where the texture image exists. When the surface to be measured is a mirror surface, a surface shape measurement value using phase data can be obtained. However, since the resolution is different between the position measurement value and the shape measurement value, it is difficult to relate the two (for example, The difference between the height of an arbitrary region and a certain region is only a few nanometers when looking at the shape measurement value, but there is a phenomenon where there are several μm when looking at the position measurement value). Therefore, in the present invention, the average value of the position measurement values in the predetermined region in the texture image is calculated, and is used as the position measurement value in the approximate illumination optical system term axis direction of the measured surface. This method can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an outline of a MEMS having a configuration in which a vibrating mirror is attached to a base surface.
FIG. 2 is a diagram for explaining the outline of a MEMS in which a plurality of mirrors are arranged and driven independently.
FIG. 3 is a diagram for explaining the outline of a measuring apparatus according to the present invention.
FIG. 4 is a diagram for explaining a relationship between a numerical calculation model that gives a defocus, a detected contrast, and a position measurement value;
FIG. 5 is a flowchart illustrating a measurement procedure of the measurement method according to the present invention.
6 is a diagram for explaining the outline of a measuring apparatus provided with a light shielding plate in addition to the configuration of the measuring apparatus of FIG.
7 is a view for explaining an outline of a measuring apparatus provided with a stage for moving a light shielding plate in a direction substantially perpendicular to the optical axis of the optical system in addition to the configuration of the measuring apparatus of FIG.
FIG. 8 is a diagram for explaining an outline of a measuring apparatus in which an imaging optical system and an interference optical system are integrated.
FIG. 9 is a diagram for explaining an outline of a state of an interference fringe in which a defocus component is generated.
10 is a measurement provided with a rotating stage for changing the inclination of a unit in which a light source, an irradiation optical system, an interference optical system, an imaging means, and an imaging optical system are integrated in addition to the configuration of the measurement apparatus of FIG. It is a figure explaining the outline of an apparatus.
FIG. 11 is a diagram for explaining the outline of a measuring apparatus provided with a stage for relatively shifting the optical axis of the irradiation optical system and the optical axis of the imaging optical system in addition to the configuration of the measuring apparatus of FIG. 3; is there.
FIG. 12 is a diagram illustrating an outline of a configuration example for diffusing light from a laser.
FIG. 13 is a diagram for explaining the vibration of the vibration mirror to be measured and the image pickup of the CCD or the light emission timing of the pulse light source.
FIG. 14 is a diagram for explaining an outline of a state of a rough texture in an amplitude image of an object to be measured.
FIG. 15 is a diagram for explaining an outline of a state of a mark texture marked on a measurement surface in an amplitude image of the measurement object.
FIG. 16 is a diagram for explaining the outline of the state of the edge texture in the amplitude image of the object to be measured;
[Explanation of symbols]
1: Vibration mirror
2: Reference plane
3: Mirror surface
4: Light source
5: ND filter
6: Beam expander
6a: Lens
7: Beam splitter
8: Object to be measured
9: Lens
10: CCD camera
11: ND filter
12: Reference mirror
13: Holder
14: Frame grabber
15: Computer
16: Object to be measured
19: Shading plate
20: Stage
21: Objective lens
22: Condensing lens
23: Objective lens
24: Beam splitter
25: Reference plane
26: Rotating stage
27: Stage
28: Diffuser
29: Motor
31: Mirror surface to be measured
32: Base surface
34, 35: Mark
36: Edge on the base surface 32
37: Edge on the mirror surface 31
38: Base surface reference position
39: Reference position of the mirror surface

Claims (9)

A light source that generates light having a substantially single wavelength, an irradiation optical system for irradiating an object with light from the light source, an interference optical system for causing object reflected light and reference light to interfere with each other, and the interference optical system. Imaging means from imaging means for imaging generated interference fringes, an imaging optical system for imaging an object image at the position of the imaging means, and a single interference fringe image by the imaging means and an image by only reference light an arithmetic unit 1 for obtaining the complex amplitude Uo object light reflected at the position, at a plurality of positions in the optical axis direction of the object reflected light by calculating the Fresnel diffraction of the complex amplitude Uo object light reflected by the imaging means position an arithmetic unit 2 for obtaining the complex amplitude U _Z of the object reflected light, composed from the arithmetic unit 3 which for determining the position in substantially the irradiation optical system in the optical axis direction of the surface shape and the object of the object from said complex amplitude U _Z Same dynamic shape and dynamic position Measuring device.   The simultaneous measurement of the dynamic shape and the dynamic position according to claim 1, further comprising a light shielding unit for shielding the object reflected light placed in the optical path between the object and the imaging unit in order to obtain an image of only the reference light. apparatus.   3. The apparatus for simultaneously measuring a dynamic shape and a dynamic position according to claim 2, further comprising a linear motion stage for moving the light shielding means back and forth in a direction substantially perpendicular to the optical axis of the optical system.   The apparatus for simultaneously measuring a dynamic shape and a dynamic position according to claim 1, wherein the interference optical system and the imaging optical system are integrated.   The apparatus for simultaneously measuring a dynamic shape and a dynamic position according to claim 1, further comprising a rotation stage that changes a tilt of a unit in which the light source, the irradiation optical system, the interference optical system, the imaging unit, and the imaging optical system are integrated.   The apparatus for simultaneously measuring a dynamic shape and a dynamic position according to claim 1, further comprising a linear motion stage that relatively shifts the optical axis of the irradiation optical system and the optical axis of the imaging optical system.   The apparatus for simultaneously measuring a dynamic shape and a dynamic position according to claim 1, wherein the light source is a diffused light source that generates diffused light.   The apparatus for simultaneously measuring a dynamic shape and a dynamic position according to claim 1, wherein the light source is a pulsed light source that generates pulsed light. In the dynamic shape and dynamic position simultaneous measurement method by the dynamic shape and dynamic position simultaneous measurement device of claim 1,
A complex amplitude Uo of the object reflected light at the position of the imaging unit is obtained from an interference fringe image generated between the object reflected light and the reference light and an image using only the reference light, and the complex of the object reflected light at the position of the imaging unit is obtained. By calculating the Fresnel diffraction of the amplitude Uo , the complex amplitude Uz of the object reflected light at a plurality of positions in the optical axis direction of the object reflected light is obtained, and the object surface shape is obtained from the phase data of the object reflected light obtained from the complex amplitude Uz. Is obtained from the amplitude data of the object reflected light obtained from the complex amplitude Uz, and the position of the object in the direction of the optical axis of the substantially irradiating optical system is obtained. A simultaneous measurement method of a dynamic shape and a dynamic position for simultaneously measuring positions in
By installing a light blocking means in the optical path between the object and the image pickup means, an image based only on the reference light is recorded,
A reference light image recorded by installing the light shielding means in the optical path between the object and the imaging means is stored, and the stored reference light image is used for calculation for obtaining the complex amplitude Uo. And simultaneous measurement method of dynamic position.

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