JP2004037104A

JP2004037104A - Dimension measuring equipment

Info

Publication number: JP2004037104A
Application number: JP2002190620A
Authority: JP
Inventors: Nobuhisa Nishioki; 西沖　暢久; Kazuhiko Hidaka; 日高　和彦
Original assignee: Mitutoyo Corp; Mitsutoyo Kiko Co Ltd
Current assignee: Mitutoyo Corp; Mitsutoyo Kiko Co Ltd
Priority date: 2002-06-28
Filing date: 2002-06-28
Publication date: 2004-02-05
Anticipated expiration: 2022-06-28
Also published as: JP3986903B2

Abstract

<P>PROBLEM TO BE SOLVED: To satisfactorily measure dimensions using a multiple wavelength interference method. <P>SOLUTION: The dimension measuring equipment 110 comprises a first interference length measuring means 112a and a second interference length measuring means 112b each consisting of a multiple wavelength interferometer, and a first mirror 160 and a second mirror 162 arranged while being shifted in parallel such that the optical axis of a first measuring light 122a from the measuring means 112a does not overlap the optical axis of a second measuring light 122b from the measuring means 112b and being spaced apart by a specified distance X<SB>3</SB>. The length measuring means 112a measures differential distance X<SB>1</SB>between distance information L<SB>1</SB>and distance information L<SB>3</SB>, the length measuring means 112b measures differential distance X<SB>2</SB>between distance information L<SB>2</SB>and distance information L<SB>4</SB>, and the dimension between the end faces of an article being measured is determined by the differential distances X<SB>1</SB>and X<SB>2</SB>, and the predetermined distance X<SB>3</SB>between the mirrors. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は寸法測定装置、特に多波長干渉法を用いた寸法測定が良好に行える機構に関する。
【０００２】
【従来の技術】
従来より長さの基準として端度器が用いられている。端度器は両端の平行な二面間の距離で寸法（寸法）を表す標準であり、代表的なものとしてゲージブロックがある。
このゲージブロックは極めて高い寸法精度を持ち、その測定面が他のゲージブロックの測定面に容易に密着する。このため数個のゲージブロックを密着して得た合成寸法は、個々のゲージブロックの寸法の和に等しく、必要な寸法が得られる。その反面、このゲージブロックは、測定面が常に他の測定面と接触するような使い方をするので、傷や磨耗を生じ易く、材料の経年変化もあり、定期的な検査が必要である。
【０００３】
このため、測定手段により個々のゲージブロックの相対向する端面間の寸法を検査する必要がある。
例えば、絶対値が予め定められている基準位置間に、平行な二平面を有する被測定物を挿入する。そして、絶対値測定手段により、被測定物の平面より基準位置までの絶対値を同定し、被測定物の寸法を求めていた。
【０００４】
【発明が解決しようとする課題】
ところで、前記絶対値測定手段としては、光干渉計を用いたものが、非接触である点で注目されている。
光干渉計は、干渉によって光の伝播距離の変化を検出するものであるから、一般的な単一波長干渉計では、光の波長以上の距離の変化量は測定することができない。
【０００５】
そこで、単一波長干渉法では測定することのできない光学波長を越える被測定物の変位量を測定することのできる多波長干渉計を用いることが考えられる。
多波長干渉計を用いた寸法測定装置では、波長の異なる複数種類の測定光を用い、各々の波長での干渉信号に基づき、単一波長での各々の位相を検出し、それらを比較することにより、等価波長における位相を測定する。そして、該等価波長における位相を変位量に換算すると、単一波長干渉法では測定することのできない光学波長を越える被測定物の変位量を求めることができる。
【０００６】
しかしながら、前記寸法測定に多波長干渉計を採用しても、測定することができるのは被測定物の変位量であり、例えばブロック形状の被測定物の寸法を求めるには、平行に対向する二つの端面間の距離として測定する必要がある。しかも、実用性を考慮すると、被測定物を光軸上のどの位置に置いても同じ寸法値が測定できるようでなければならない。
そこで、従来は、例えば図７に示すような寸法測定が考えられる。
すなわち、同図（Ａ）に示す寸法測定装置１０は、例えば多波長干渉計よりなる絶対値（ＡＢＳ）干渉測長計（以下、干渉測長計という）１２と、案内部１４に沿って直線移動するステージ１６と、被測定物１８の右側端面１８ａに設けられたミラー２０を備える。
【０００７】
ここで、同図（Ａ）に示すようにミラー２０の設けられている被測定物１８は、ステージ１６上に載置されている。干渉測長計１２、ステージ１６は、該干渉測長計１２よりの測定光２２の光軸と、案内部１４に沿ったステージ１６の移動方向が直交するように配置されている。
そして、同図（Ａ）に示す状態では、干渉測長計１２よりの測定光２２は、被測定物１８の左側端面１８ｂで反射され、干渉測長計１２に返光される。これににより干渉測長計１２では、被測定物１８の左側端面１８ｂよりの距離情報Ｌ_１が測定される。
【０００８】
また同図（Ｂ）に示すようにステージ１６を案内部１４に沿って測定光２２の光軸と直交方向（図中下方）に移動させ、測定光２２の光軸とミラー２０の反射面を直交させる。すると、干渉測長計１２よりの測定光２２は、ミラー２０で反射され、干渉測長計１２に返光される。これにより干渉測長計１２では、ミラー２０よりの距離、つまり被測定物の右側端面１８ａよりの距離情報Ｌ_２が測定される。
ここで、前記距離情報Ｌ_１，Ｌ_２は、干渉測長計１２での光路長差がゼロとなる位置からの相対的な距離である。つまり前記距離情報Ｌ_１，Ｌ_２は、被検反射面の絶対的な座標位置を示していないが、距離情報Ｌ_１と距離情報Ｌ_２の差（Ｌ_２−Ｌ_１）を求めることにより、被測定物の寸法Ｌを求めることができる。
【０００９】
しかしながら、同図に示す寸法測定装置１０であっても、被測定物１８に予めミラー２０を設ける必要があるので、厳密には非接触測定とは言えない。しかもミラー２０の密着状態によっては、測定の不確かさが増大してしまうことがある。また同図に示す寸法測定装置１０では、被測定物１８を測定光２２の光軸に対し直交方向にシフト移動させる必要があるので、ステージ１６の移動に高い精度を要求する上、測定時間の短縮にはおのずと限界が生じる。
【００１０】
このため、同図に示す寸法測定装置１０は、多波長干渉計を用いた寸法測定装置として採用するには至らなかった。このように多波長干渉計を用いた寸法測定装置は、未だ実用化されていないので、その開発が急務であった。
本発明は前記従来技術の課題に鑑みなされたものであり、その目的は多波長干渉計を用いた寸法測定が良好に行える寸法測定装置を提供することにある。
【００１１】
【課題を解決するための手段】
本発明者らが多波長干渉計を用いた絶対値測定について鋭意検討を行った結果、まず波長の異なる複数種類の可干渉光を出射する光出射手段を用いた多波長干渉計を二系統用いる。そして、被測定物の相対向する平行な二平面に対して、各干渉計よりの測定光をそれぞれ対向させて入射し、各被検反射面の変位情報を測定する。これにより被測定物の相対向する二平面間の寸法測定が、被測定物に対し別部品を付加することなく完全な非接触で行えること、また機械的な移動機構を用いないで済むことを見出した。
【００１２】
前述のような多波長干渉計を用いた絶対値測定について、本発明者らがさらに研究を進めた結果、前記二本の測定光が単に同軸上に配置されただけでは、相手の干渉計に飛込んでしまうことがわかった。これにより多波長干渉計により基準位置間の寸法の絶対値測定を行う際に、干渉計が誤動作してしまい、正確な測定が行えないことがわかった。そして、本発明者らによれば、この問題は、基準位置間での両側よりの投射光と反射光による複雑な干渉により生じているものであり、この干渉を回避することにより、干渉計の誤動作を防止することができることも解明したうえで、本発明を完成するに至った。
【００１３】
すなわち、目的を達成するために本発明にかかる寸法測定装置は、多波長干渉計を用いて被測定物の相対向する第一端面と第二端面間の寸法Ｌを測定する寸法測定装置であって、第一干渉測長手段および第二干渉測長手段と、第一ミラーおよび第二ミラーと、を備える。
そして、前記第一干渉測長手段により、前記ミラー間に被測定物が存在せず第一干渉測長手段よりの第一測定光を第二ミラーで反射させた時の該第二ミラーの距離情報Ｌ_１と、該ミラー間に被測定物が存在し該第一測定光を該被測定物の第一端面で反射させた時の該被測定物第一端面の距離情報Ｌ_３との距離差Ｘ_１を測定する。
【００１４】
前記第二干渉測長手段により、前記ミラー間に被測定物が存在せず第二干渉測長手段よりの第二測定光を第一ミラーで反射させた時の該第一ミラーの距離情報Ｌ_２と、該ミラー間に被測定物が存在し該第二測定光を該被測定物の第二端面で反射させた時の該被測定物第二端面の距離情報Ｌ_４との距離差Ｘ_２を測定する。そして、前記第一干渉測長手段により測定された距離差Ｘ_１、第二干渉測長手段により測定された距離差Ｘ_２、および予め定められた第一ミラーと第二ミラー間の離隔距離Ｘ_３より、前記被測定物の相対向する第一端面と第二端面間の寸法Ｌを数３により求めることを特徴とする。
【００１５】
【数３】
Ｌ＝（Ｘ_１＋Ｘ_２）−Ｘ_３
　ただし、前記距離差Ｘ_１＝前記距離情報Ｌ_１−前記距離情報Ｌ_３
　　　　　前記距離差Ｘ_２＝前記距離情報Ｌ_２−前記距離情報Ｌ_４
　ここで、前記第一干渉測長手段および第二干渉測長手段は、波長の異なる複数種類の可干渉光の一部に基づく参照光と、該可干渉光の残りを測定光として被検反射面に入射させて得られた反射光を合成し干渉光を得、各測定波長での干渉信号に基づいて、個々の測定波長を越える被検反射面の変位を測定する。
【００１６】
また前記第一ミラーおよび第二ミラーは、第一干渉測長手段よりの第一測定光の光軸と第二干渉測長手段よりの第二測定光の光軸が重ならないように平行にずれて配置され、且つ所定の離隔距離Ｘ_３をおいて配置される。
ここにいう被検反射面とは、第一干渉測長手段側では、ミラー間に被測定物が存在しない時は第二ミラーをいい、被測定物が存在する時は被測定物の第一端面をいう。また第二干渉測長手段側では、ミラー間に被測定物が存在しない時は第一ミラーをいい、被測定物が存在する時は被測定物の第二端面をいう。
【００１７】
このため、ここにいう被検反射面の変位とは、ミラー間に被測定物が存在しない時の対応ミラーの位置に対し、被測定物が存在する時の該被測定物の対応端面の位置が変わることをいう。
またここにいう距離情報とは、例えば対応干渉計での光路長差がゼロとなる位置からの距離情報等をいう。
またここにいう干渉測長手段は、測定光の波長を変えて同じ測定を繰り返すことにより、個々の測定波長以上の変位量を測定することができる多波長干渉計ををいう。例えば光出射手段の一例として半導体レーザを用いる際は、駆動条件によってその発振波長を変化させることが特に好ましい。その発振波長を変化させる方法としては、例えば特開平４−２９７８０７号公報、特開平４−２９７８０８号公報、特開２００１−２７５１２号公報等に記載の方法を用いることができる。
【００１８】
なお、本発明においては、前記第一測定光の光軸上に位置する前記第一ミラーの部位に、前記第一測定光を通過させる第一光通過用穴を設ける。前記ミラー間に被測定物が存在しない時に、前記第一ミラーの第一光通過穴を通過した第一干渉測長手段よりの第一測定光を反射し、該第一光通過用穴に返光するように、第一測定光の光軸上に前記第二ミラーの鏡面が位置する。前記第二測定光の光軸上に位置する前記第二ミラーの部位に、前記第二測定光を通過させる第二光通過用穴を設ける。前記ミラー間に被測定物が存在しない時に、前記第二ミラーの第二光通過穴を通過した第二干渉測長手段よりの第二測定光を反射し、該第二光通過用穴に返光するように、第二測定光の光軸上に前記第一ミラーの鏡面が位置することが好適である。
【００１９】
また前記目的を達成するために本発明にかかる寸法測定は、第一干渉測長手段および第二干渉測長手段と、第一の非干渉手段及び第二の非干渉手段と、を備える。
そして、前記第一干渉測長手段により、前記非干渉手段間に寸法が既知Ｌ_Ｓの標準サンプルが存在し、該第一干渉測長手段よりの第一測定光を標準サンプルの第一端面で反射させた時の該標準サンプル第一端面の距離情報Ｌ_１と、該非干渉手段間に被測定物が存在し、該第一測定光を該被測定物の第一端面で反射させた時の該被測定物第一端面の距離情報Ｌ_３との距離差Ｘ_１を測定する。
【００２０】
前記第二干渉測長手段により、前記非干渉手段間に前記標準サンプルが存在し、該第二干渉測長手段よりの第二測定光を標準サンプルの第二端面で反射させた時の該標準サンプル第二端面の距離情報Ｌ_２と、該非干渉手段間に被測定物が存在し、該第二測定光を該被測定物の第二端面で反射させた時の該被測定物第二端面の距離情報Ｌ_４との距離差Ｘ_２を測定する。
そして、前記第一干渉測長手段により測定された距離差Ｘ_１、第二干渉測長手段により測定された距離差Ｘ_２、および予め値付けされた標準サンプルの寸法Ｌ_Ｓより、前記被測定物の相対向する第一端面と第二端面間の寸法Ｌを数４により求めることを特徴とする。
【００２１】
【数４】
Ｌ＝Ｌ_Ｓ−（Ｘ_１＋Ｘ_２）
ただし、前記距離差Ｘ_１＝前記距離情報Ｌ_３−前記距離情報Ｌ_１
　　　　　前記距離差Ｘ_２＝前記距離情報Ｌ_４−前記距離情報Ｌ_２
【００２２】
ここで、前記第一干渉測長手段および第二干渉測長手段は、波長の異なる複数種類の可干渉光の一部に基づく参照光と、該可干渉光の残りを測定光として被検反射面に入射させて得られた反射光を合成し干渉光を得、各測定波長での干渉信号に基づいて、該個々の測定波長を越える被検反射面の変位を測定する。
また前記第一非干渉手段及び第二非干渉手段は、前記被測定物の測長軸と一致した光軸を有し、かつ所定の離隔距離をおいて配置される。該第一非干渉手段は、測定光の通過と測定光の遮蔽を交互に行う。該第二非干渉手段は、第一非干渉手段で測定光の通過時は測定光の遮蔽かつ該第一非干渉手段で測定光の遮蔽時は測定光の通過を、前記第一非干渉手段での測定光の通過と遮蔽の切替と同期させて交互に行う。
【００２３】
ここにいう被検反射面とは、第一干渉測長手段側では、非干渉手段間に標準サンプルが存在する時は、該標準サンプルの第一端面をいい、被測定物が存在する時は、被測定物の第一端面をいう。また第二干渉測長手段側では、非干渉手段間に標準サンプルが存在する時は、該標準サンプルの第二端面をいい、被測定物が存在する時は被測定物の第二端面をいう。
このため被検反射面の変位とは、非干渉手段間に標準サンプルが存在する時の対応端面の位置に対し、被測定物が存在する時の対応端面の位置が変わることをいう。
【００２４】
またここにいう距離情報とは、例えば対応干渉計での光路長差がゼロとなる位置からの距離情報等をいう。
なお、本発明において、前記非干渉手段はシャッタであり、前記シャッタの開閉を行う駆動手段を備える。そして、前記駆動手段による前記シャッタの開閉により、前記測定光の通過と遮蔽の切替えを行うことが好適である。本発明のシャッタは、例えば液晶シャッタ等を一例として用いることができる。
【００２５】
また本発明において、前記非干渉手段は音響光学素子であり、前記音響光学素子の変調、非変調を行う駆動手段を備える。そして、前記駆動手段による前記音響光学素子の変調、非変調により、前記測定光の通過と遮蔽の切替えを行うことも好適である。
また本発明において、前記非干渉手段は鏡面のチルトにより光路を変更するミラーであり、前記駆動手段による前記ミラーのチルトにより測定光の光路を変更することにより、前記測定光の通過と遮蔽の切替えを行うことも好適である。本発明のミラーは、例えばガルバノミラー等を一例として用いることができる。
【００２６】
さらに本発明においては、測定光の光軸方向に平行な、被測定物の並進移動による測定量への影響を排除するために、前記第一干渉測長手段による距離差Ｘ_１の測定と、前記第二干渉測長手段による距離差Ｘ_２の測定を同時に行うことが好適である。
本発明者らは、被測定物の相対向する平行な二平面の寸法測定に、光学波長を越える変位量の測定が行える多波長干渉法を採用している。
この多波長干渉法の原理を図８に従って説明する。
【００２７】
同図に示す寸法測定装置１０は、干渉測長計１２を備える。
ここで、前記干渉測長計１２は、例えば多波長干渉計等よりなり、一の光出射手段を構成する光源２４，２６と、ビームスプリッタ２８と、ビームスプリッタ３０と、参照ミラー３２と、ビームスプリッタ３４と、光フィルタ３６，３８と、受光素子４０，４２と、位相比較器４４を備える。
【００２８】
ここで、前記光源２４，２６は、例えば半導体レーザ（ＬＤ）等よりなり、ドライバ４６，４８を備える。該ドライバ４６，４８は、例えば互いに反転した鋸歯波状変調電流で光源２４，２６を駆動しており、光源２４はレーザ光（λ_１）を出射し、光源２６はレーザ光（λ_２）を出射する。
そして、光源２４よりのレーザ光（λ_１）と光源２６よりのレーザ光（λ_２）は、直交偏光状態に置かれており、ビームスプリッタ２８で重ね合わされ、ビームスプリッタ３０に入射される。該ビームスプリッタ３０では、ビームスプリッタ２８よりの光が第一分割光５０と第二分割光（測定光）２２に分割される。
【００２９】
前記参照ミラー３２は、光路変調用圧電素子５２により光軸方向に変位されることにより、第一分割光５０に位相シフト、或いは周波数シフトを与えて反射する。また前記ビームスプリッタ３０よりの測定光２２の光軸上には、被測定物１８が配置されており、該被測定物１８で測定光２２を反射する。
そして、参照ミラー３２よりの反射光と被測定物１８よりの反射光は、ビームスプリッタ３０で合成され、干渉光が生起される。該２つの波長での干渉光は、偏光状態の違いを利用してビームスプリッタ３４で分離され、２つの干渉ビート信号のクロストークを除くための光フィルタ３６，３８を介して、それぞれの干渉ビート信号が２つの受光素子４０，４２で検出される。
【００３０】
前記受光素子４０，４２よりの出力信号は、位相比較器４４に入力され、位相比較器４４では、光源２４，２６への変調電流のいずれか一方を参照信号として、等価位相がヘテロダイン検出される。
このように本実施形態は、各々の波長での干渉信号に基づき、単一波長での各々の位相を検出し、各位相を比較することにより、等価波長における位相を測定することができる。等価波長はＡ＝（λ_１・λ_２）／（｜λ_１−λ_２｜）となるので、絶対値測長範囲も、レーザ光の個々の波長λ_１，λ_２を超える（λ_１・λ_２）／（｜λ_１−λ_２｜）となる。
【００３１】
このような多波長干渉計を用いることにより、単一波長干渉法では測定することができない光学波長を越える被測定物の変位量を測定することができるので、該等価波長における位相、つまり等価位相から被検反射面の変位量に換算することができる。
なお、本発明では、測定光の波長を変える方法としては、種々のものを用いることができるが、例えば光源に半導体レーザ（ＬＤ）光源を用いて、該レーザへの注入電流等の駆動条件を変える方法等が、発振波長を容易に変化させることができるので、特に好ましい。
【００３２】
【発明の実施の形態】
以下、図面に基づいて本発明の好適な一実施形態について説明する。
【００３３】
第一実施形態
　図１には本発明の第一実施形態にかかる寸法測定装置の概略構成が示されている。本実施形態では、高速で厚さまたは被検反射位置が変動する被測定物を想定しており、前記図８に示した干渉測長計１２を２系統備え、該基準位置間に二本の測定光の光軸をオフセット配置し、二の干渉測長計を同時に動作させる例について説明する。前記図７，８と対応する部分には符号１００を加えて示し説明を省略する。
同図に示す寸法測定装置１１０は、第一の干渉測長計（第一干渉測長手段）１１２ａ及び第二の干渉測長計（第二干渉測長手段）１１２ｂと、ミラー（第一ミラー，基準位置）１６０及びミラー（第二ミラー，基準位置）１６２と、コンピュータ１６４を備える。
【００３４】
また本実施形態は、干渉測長計１１２ａとミラー１６０間にミラー１６５，１６６を備え、干渉測長計１１２ｂとミラー１６２間にミラー１６８，１６９を備える。
ここで、ミラー１６０，１６２は、所定の離隔距離Ｘ_３をおいて対向配置されており、基準位置として用いられる。
【００３５】
またミラー１６０，１６２間での干渉測長計１１２ａよりの第一測定光１２２ａの光軸と、干渉測長計１１２ｂよりの第二測定光１２２ｂの光軸は、互いに重ならないようにオフセット配置されている。
ミラー１６０，１６２間に被測定物が存在しない時に、オフセット配置の第一測定光１２２ａの光軸はミラー１６２と直交し、第二測定光１２２ｂの光軸は、ミラー１６０と直交している。
このために本実施形態では、ミラー１６０に第一光通過用穴１７２が設けられ、ミラー１６２に第二光通過用穴１７４が設けられている。
【００３６】
ここで、前記第一光通過用穴１７２は、第一測定光１２２ａの光軸上に位置するミラー１６０の部位に設けられているので、第一測定光１２２ａを通過させる。　前記ミラー１６０，１６２間に被測定物が存在しない時に、ミラー１６０の第一光通過穴１７２を通過した干渉測長計１１２ａよりの第一測定光１２２ａを反射し、該第一光通過用穴１７２に返光するように、第一測定光１２２ａの光軸上にミラー１６２の鏡面が位置している。該ミラー１６２で反射され、第一光通過用穴１７２に返光された測定光１２２ａは、ミラー１６６，１６５を介して干渉測長計１１２ａに入射される。
【００３７】
また前記第二光通過用穴１７４は、測定光１２２ｂの光軸上に位置するミラー１６２の部位に設けられ、干渉測長計１１２ｂよりの測定光１２２ｂを通過させる。前記ミラー１６０，１６２間に被測定物が存在しない時に、ミラー１６２の第二光通過穴１７４を通過した干渉測長計１１２ｂよりの測定光１２２ｂを反射し、該第二光通過用穴１７４に返光するように、第二測定光１２２ｂの光軸上にミラー１６０の鏡面が位置している。該ミラー１６０で反射され、第二光通過用穴１７４に返光された測定光１２２ｂは、ミラー１６９，１６８を介して干渉測長計１１２ｂに入射される。
該干渉測長計１１２ａでは、被測定物が存在しない時と被測定物が存在する時の右側被検反射面の距離差Ｘ_１を測定する。
【００３８】
すなわち、干渉測長計１１２ａは、ミラー１６０，１６２間に被測定物が存在せず、干渉測長計１１２ａよりの測定光１２２ａをミラー（被検反射面）１６２で反射させた時の、該ミラー１６２よりの距離情報Ｌ_１と、ミラー１６０，１６２間に被測定物が存在し、干渉測長計１１２ａよりの測定光１２２ａを該被測定物の右側端面（被検反射面，第一端面）で反射させた時の、該被測定物右側端面よりの距離情報Ｌ_３との距離差Ｘ_１を測定する。
また干渉測長計１１２ｂでは、被測定物が存在しない時と被測定物が存在する時の左側被検反射面の距離差Ｘ_２を測定する。
【００３９】
すなわち、干渉測長計１１２ｂは、ミラー１６０，１６２間に被測定物が存在せず、干渉測長計１１２ｂよりの第二測定光１２２ｂを第一ミラー（被検反射面）１６０で反射させた時の、該第一ミラー１６０よりの距離情報Ｌ_２と、ミラー１６０，１６２間に被測定物が存在し、干渉測長計１１２ｂよりの第二測定光１２２ｂを該被測定物の左側端面（被検反射面，第二端面）で反射させた時の、該被測定物左側端面よりの距離情報Ｌ_４との距離差Ｘ_２を測定する。
そして、前記コンピュータ１６４は、前述のようにして干渉測長計１１２ａにより測定された右側被検反射面の距離差Ｘ_１と、干渉測長計１１２ｂにより測定された左側被検反射面の距離差Ｘ_２と、予め定められたミラー１６０，１６２間の離隔距離Ｘ_３より、被測定物の相対向する平行な二面間の寸法（厚さ）Ｌを数５により求める。
【００４０】
【数５】
Ｌ＝（Ｘ_１＋Ｘ_２）−Ｘ_３
　ただし、前記距離差Ｘ_１＝前記距離情報Ｌ_１−前記距離情報Ｌ_３
　　　　　前記距離差Ｘ_２＝前記距離情報Ｌ_２−前記距離情報Ｌ_４
　本実施形態にかかる寸法測定装置１１０は概略以上のように構成され、以下にその作用について説明する。
【００４１】
まず同図に示すようにミラー１６０，１６２間に被測定物が存在しない時に、距離情報Ｌ_１，Ｌ_２を得ておく。
すなわち、多波長干渉計を用いた寸法測定装置では、基準位置間の絶対値寸法を測定する必要があるが、この測定の際は、ミラー１６０，１６２間に被測定物が存在しない。ここで、第一測定光と第二測定光を単に同軸上に配置したのでは、測定光が相手側の干渉測長計に飛び込んで、受光素子や光源等に悪影響を及ぼすことがある。
【００４２】
そこで、本実施形態では、基準位置間の絶対値測定の際の、両側の投射光と反射光による複雑な干渉を回避するために、基準位置間で第一測定光と第二測定光の光軸が重ならないようにオフセット配置している。つまり本実施形態では、測定光による測定位置（反射位置）をずらし、かつオフセットによる誤差を打ち消す二の光出射手段による同時投射を行っている。
すなわち、干渉測長計１１２ａよりの第一測定光１２２ａは、第一ミラー１６０の第一光通過用穴１７２に入射される。該第一光通過用穴１７２を通過した第一測定光１２２ａは、被測定物が存在しない時の被検反射面としての第二ミラー１６２の鏡面に入射され、反射される。該第二ミラー１６２よりの反射光は、再度、第一ミラー１６０の第一光通過用穴１７２を通過して干渉測長計１１２ａに入射される。該干渉測長計１１２ａでは、被測定物が存在しない時の被検反射面としての第二ミラー１６２よりの距離情報Ｌ_１が求められる。
【００４３】
本実施形態では、前記干渉測長計１１２ａによる測定と同時に、干渉測長計１１２ｂによる測定を行っている。
すなわち、干渉測長計１１２ｂよりの第二測定光１２２ｂは、第二ミラー１６２の第二光通過用穴１７４に入射される。第二光通過用穴１７４を通過した第二測定光１２２ｂは、被測定物が存在しない時の被検反射面としての第一ミラー１６０の鏡面に入射され、反射される。該第一ミラー１６０よりの反射光は、再度、第二ミラー１６２の第二光通過用穴１７４を通過して干渉測長計１１２ｂに入射される。該干渉測長計１１２ｂでは、被測定物が存在しない時の被検反射面としての第一ミラー１６０よりの距離情報Ｌ_２が測定される。
【００４４】
このように本実施形態は、干渉測長計１１２ａによる、第一測定光１２２ａが第二ミラー１６２で反射された時の距離情報Ｌ１と、干渉測長計１１２ｂによる、第二測定光１２２ｂが第一ミラー１６０で反射された時の距離情報Ｌ_２を同時に測定している。
ここで、本実施形態は、２系統の干渉測長計１１２ａ，１１２ｂが、第一測定光１２２ａと第二測定光１２２ｂをそれぞれ対向させて出射している。ミラー１６０，１６２間では、該二本の測定光１２２ａ，１２２ｂが互いに平行であるが、測定光同士が重なってしまわないように、測定光のビーム径以上の距離を持たせて並べている。光通過用穴１７２の開いたミラー１６０と光通過用穴１７４の開いたミラー１６２を測定光と垂直に配置している。このため、本実施形態では、該ミラー１６０，１６２間に被測定物の存在しない時には、対向する測定光をそれぞれ反射して、各干渉測長計に戻すようにしている。
【００４５】
このため、本実施形態では、被測定物が存在しない時に、対向する測定光が相手側の干渉測長計に飛び込んで、受光素子や光源に悪影響を及ぼすことを防いでいる。
また図２に示すようにミラー１６０，１６２間に被測定物１１８が存在する状態で、干渉測長計１１２ａ，１１２ｂによる同時測定を行う。
【００４６】
すなわち、同図に示すように干渉測長計１１２ａよりの第一測定光１２２ａは、第一ミラー１６０の光通過用穴１７２に入射される。該光通過用穴１７２を通過した第一測定光１２２ａは、被測定物１１８が存在する時の被検反射面としての被測定物１１８の右側端面１１８ａに入射され、反射される。該被測定物１１８の右側端面１１８ａよりの反射光は、第一ミラー１６０の第一光通過用穴１７２を通過して干渉測長計１１２ａに入射される。該干渉測長計１１２ａでは、被測定物１１８が存在する時の被検反射面としての被測定物の右側端面１１８ａよりの距離情報Ｌ３が測定される。
【００４７】
本実施形態では、前記干渉測長計１１２ａによる測定と同時に、干渉測長計１１２ｂによる測定を行う。
すなわち、干渉測長計１１２ｂよりの第二測定光１２２ｂは、第二ミラー１６２の光通過用穴１７４に入射される。該光通過用穴１７４を通過した第二測定光１２２ｂは、被測定物１１８が存在する時の被検反射面としての被測定物の左側端面１１８ｂに入射され、反射される。該被測定物の左側端面１１８ｂよりの反射光は、第二ミラー１６２の光通過用穴１７４を通過して干渉測長計１１２ｂに入射される。該干渉測長計１１２ｂでは、被測定物１１８が存在する時の被検反射面としての被測定物の左側端面１１８ｂよりの距離情報Ｌ４が測定される。
【００４８】
このようにして本実施形態は、干渉測長計１１２ａによる、第一測定光１２２ａが被測定物の右側端面１１８ａで反射された時の距離情報Ｌ_３と、干渉測長計１１２ｂによる、第二測定光１２２ｂが被測定物の左側端面１１８ｂで反射された時の距離情報Ｌ_４が、同時に測定される。
ここで、本実施形態では、個々の距離情報は、対応干渉測長計での光路長差が零となる点からの相対的な距離であり、反射面の絶対的な座標位置を示していないが、これらの距離情報より距離差Ｘ_１、距離差Ｘ_２を求めることにより、光出射手段から遠くにいても近くにいても同じ値が測定できる。
【００４９】
したがって、本実施形態は、被測定物が存在していない時と被測定物が存在している時の被検反射面の変位を同時測定することにより、平行な二平面間の距離（絶対値）として測定することができる。
ここで、本実施形態は、干渉測長計として多波長干渉計を用いることにより、個々の測定波長以上の変位を測定することができる。このような干渉測長計により、被検反射面の変位測定として、被測定物が存在しない時のミラーの鏡面と被測定物が存在する時のその端面の距離差を測定するので、個々の測定波長以上の変位を測定することのできる多波長干渉計を用いて、光学波長を越える寸法を求めることができる。
【００５０】
また本実施形態は、所定の離隔距離Ｘ_３をおいて配置された第一のミラー１６０と第二のミラー１６２間に被測定物１１８を配置し、第一測定光１２２ａと第二測定光１２２ｂを被測定物１１８の両側より同時に対向させて入射して、測定を行っている。
このために被測定物１１８をミラー１６０，１６２間の光軸上のどの位置に置いても、光軸方向の相対的な変位が距離差Ｘ_１と距離差Ｘ_２の和をとった時点でキャンセルされるため、同じ値を測定することができる。
【００５１】
このようにすれば、本実施形態は、寸法測定を完全に非接触で行うことができる。また本実施形態は、機械的な可動要素を必要としないので、高速で高精度な寸法測定が行える。
特に本実施形態では、被測定物が高速で出入りするようなものであっても、ミラー間での測定光の光軸のオフセット配置、測定光の被測定物両側よりの同時投射により、高精度な寸法測定が行える。
【００５２】
このように本実施形態では、二系統の干渉測長計で得られる測定値は、被測定物１１８の右側端面１１８ａと第二ミラー１６２の反射面との距離差Ｘ_１、および被測定物１１８の左側端面１１８ｂと第一ミラー１６０の反射面との距離差Ｘ_２である。このミラー１６０の反射面とミラー１６２の反射面との離隔距離をＸ_３とすれば、寸法Ｌとの間には、数６で表せる関係がある。
【００５３】
【数６】
Ｘ_３＋Ｌ＝Ｘ_１＋Ｘ_２
　このため、本実施形態では、ミラー１６０，１６２間の離隔距離Ｘ_３を予め求めておけば、寸法Ｌは、前記数式６を変形した前記数式５により算出することができる。なお、前記離隔距離Ｘ_３の同定は、例えば寸法の正確に値付けされた標準サンプルを用いて逆算すれば、簡単に行える。
【００５４】
以上のように本実施形態にかかる寸法測定装置によれば、光学波長を越える変位を測定することのできる多波長干渉計を用いて、基準位置間の被測定物の相対向する平面に対し両方向より測定光を対向入射させることとした。
この結果、本実施形態は、被測定物の相対向する平行な二平面間の寸法を完全な非接触で、被測定物に対し別部品の付加することなく、良好に測定することができる。
しかも、本実施形態は、被測定物を光軸上のどの位置に置いても、被測定物の位置や光軸方向の並進振動に影響を受けずに正確な寸法測定が行える。
【００５５】
また本実施形態は、被測定物端面と基準位置としてのミラーの距離差を被検反射面の変位として考えているので、変位を測定する多波長干渉計を用いても、その距離差を、測定することができる。
しかも、本実施形態は、前記測定光のオフセット配置、二の光出射手段により測定光を対向させての同時投射を採用することにより、光学式干渉系を用いた寸法の絶対値測定において、高速で出入りする被測定物の高速測定であっても、高精度化が図られる。
【００５６】
特に本実施形態は、前記基準位置にミラーを配置し、該ミラー間で測定光の光軸をオフセットすることとしたので、前記基準位置間の絶対値を多波長干渉計で測定をする際の、両側の投射光と反射光による複雑な干渉を確実に回避することができる。これにより本実施形態は、多波長干渉計の誤動作を防止することができるので、前記寸法測定がより正確に行える。
【００５７】
また本実施形態では、例えば人手や、被測定物保持手段等の機械的な機構により、被測定物の出入れを高速に行っても、前記第一干渉測長計による距離差Ｘ_１の測定と、第二干渉測長計による距離差Ｘ_２の測定を同時に行っているため、前記被測定物の前記測定光の光軸方向に平行な並進移動による測定量への影響を大幅に排除することができる。そして、本実施形態は、被測定物と測定装置との相対的な並進振動に対して非常に安定した寸法測定が行えるため、ノギスやマイクロメータ等のハンドツール形態の非接触化に非常に有効となる。
【００５８】
第二実施形態
　図３には本発明の第二実施形態にかかる寸法測定装置の概略構成が示されている。本実施形態では基準位置間に二本の測定光をゼロオフセット配置し、二の干渉測長計を時分割に動作させる例について説明する。前記第一実施形態と対応する部分には符号１００を加えて示し説明を省略する。
同図に示す寸法測定装置２１０では、多波長干渉計により基準位置間の寸法を絶対値測定する際の、両側の投射光と反射光による複雑な干渉を回避するために時分割で動作させる、例えば液晶シャッタ等を含む第一非干渉装置（第一非干渉手段，基準位置）２７６ａ及び第二非干渉装置（第二非干渉手段，基準位置）２７６ｂと、ドライバ（駆動手段）２７８ａ，２７８ｂと、コンピュータ２６４を備える。
【００５９】
ここで、前記非干渉装置２７６ａ，２７６ｂは、測定光２２２ａ，２２２ｂの光軸と一致する光軸を有し、且つ所定の離隔距離をおいて配置されており、基準位置として用いられる。
そして、本実施形態は、コンピュータ２６４がドライバ２７８ａ，２７８ｂにより、前記液晶シャッタ等の非干渉装置２７６ａ，２７６ｂの動作を交互（時分割）に行わせ、測定が図中、右側経路と左側経路とで交互に行われる。つまり、測定光２２２ａの干渉測長計２１２ａへの入射及び干渉測長計２１２ｂへの非入射と、測定光２２２ｂの干渉測長計２１２ａへの非入射及び干渉測長計２１２ｂへの入射を交互に切替えている。
【００６０】
このように本実施形態では、常に非干渉装置２７６ａ，２７６ｂを交互に動作させているので、非干渉装置２７６ａ，２７６ｂ間にたとえワークが存在していないときであっても、同軸で対向するビームが飛込んで誤動作しないようにしている。
また本実施形態では、干渉測長計２１２ａ，２１２ｂは、共通の光出射手段を用いており、つまり一の光出射手段を用いて、該干渉測長計２１２ａによる測定光の投射とその反射光の測定と、該干渉測長計２１２ｂによる測定光の投射とその反射光の測定を行っている。
【００６１】
すなわち、干渉測長計２１２ａは、非干渉装置２７６ａ，２７６ｂ間に予め値付けされた標準サンプル２８０が存在し、干渉測長計２１２ａよりの第一測定光２２２ａを該標準サンプル右側端面２８０ａで反射させた時の、該標準サンプル右側端面２８０ａよりの距離情報Ｌ_１と、非干渉装置２７６ａ，２７６ｂ間に寸法を求めたい被測定物が存在し、干渉測長計２１２ａよりの第一測定光２２２ａを該被測定物右側端面で反射させた時の、該被測定物右側端面よりの距離情報Ｌ_３との距離差Ｘ_１を測定する。
【００６２】
また干渉測長計２１２ｂは、非干渉装置２７６ａ，２７６ｂ間に前記予め値付けされた標準サンプル２８０が存在し、干渉測長計２１２ｂよりの第二測定光２２２ｂを該標準サンプル左側端面２８０ｂで反射させた時の、該標準サンプル左側端面２８０ｂよりの距離情報Ｌ_２と、非干渉装置２７６ａ，２７６ｂ間に前記寸法を求めたい被測定物が存在し、干渉測長計２１２ｂよりの第二測定光２２２ｂを該被測定物左側端面で反射させた時の、該被測定物左側端面よりの距離情報Ｌ_４との距離差Ｘ_２を測定する。
【００６３】
このようにして干渉測長計２１２ａと干渉測長計２１２ｂの時分割測定により、非干渉装置２７６ａ，２７６ｂ間に、寸法が既知Ｌ_Ｓと予め値付けされた標準サンプル２８０が存在する時と、寸法を求めたい被測定物が存在する時の、左右の被検反射面の変位を測定する。
コンピュータ２６４は、前述のようにして干渉測長計２１２ａにより測定された距離差Ｘ_１、干渉測長計２１２ｂにより測定された距離差Ｘ_２、および予め値付けされた標準サンプル２８０の寸法Ｌ_Ｓより、被測定物の対向する平行な二平面間の寸法（厚さ）Ｌを数７により求める。
【００６４】
【数７】
Ｌ＝Ｌ_Ｓ−（Ｘ_１＋Ｘ_２）
ただし、前記距離差Ｘ_１＝前記距離情報Ｌ_３−前記距離情報Ｌ_１
　　　　　前記距離差Ｘ_２＝前記距離情報Ｌ_４−前記距離情報Ｌ_２
　本実施形態にかかる寸法測定装置２１０は概略以上のように構成され、以下にその作用について説明する。
【００６５】
まず図３に示すように寸法がＬ_Ｓと正確に値付けされた標準サンプル２８０を用い、前記２系統の干渉測長計２１２ａ，２１２ｂにより、距離情報Ｌ_１，Ｌ_２を得ておく。この作業は初期段階で最低１回行っておけばよい。
本実施形態においては、同図に示すように非干渉装置２７６ａ，２７６ｂは、ワークの有る無しに関らず、つまり標準サンプルの有る無し及び被測定物の有る無しに関らず、交互に動作している。
このために非干渉装置２７６ａが開の状態でかつ非干渉装置２７６ｂが閉の状態のときに実質的に干渉測長計２１２ａのみが動作していることとなり、干渉測長計２１２ａによる測定を行っている。
【００６６】
すなわち、同図に示すように非干渉装置２７６ａ，２７６ｂ間に、予め値付けされた標準サンプル２８０が存在している。そして、干渉測長計２１２ａよりの第一測定光２２２ａは、非干渉装置２７６ａを通過し、被検反射面としての前記標準サンプル右側端面２８０ａに入射されて反射される。該標準サンプル右側端面２８０ａよりの反射光は、非干渉装置２７６ａを通過して干渉測長計２１２ａに入射される。該干渉測長計２１２ａでは、被検反射面としての前記標準サンプル右側端面２８０ａよりの距離情報Ｌ_１が測定される。
【００６７】
一方、非干渉装置２７６ａが閉の状態でかつ非干渉装置２７６ｂが開の状態のときに実質的に干渉測長計２１２ｂのみが動作していることとなり、干渉測長計２１２ｂによる測定を行っている。
すなわち、干渉測長計２１２ｂよりの第二測定光２２２ｂは、非干渉装置２７６ｂを通過し、被検反射面としての前記標準サンプル左側端面２８０ｂに入射され、反射される。該標準サンプル左側端面２８０ｂよりの反射光は、非干渉装置２７６ｂを通過して干渉測長計２１２ｂに入射される。該干渉測長計２１２ｂでは、被検反射面としての前記標準サンプル左側端面２８０ｂよりの距離情報Ｌ_２が求められる。
【００６８】
このように本実施形態では、同図のように２系統の干渉測長計を用いて、二本の測定光２２２ａ，２２２ｂをそれぞれ対向させて出射し時分割に入射している。　なお、図では便宜上、わざとずらして描かれているが、対向する二本の測定光２２２ａ，２２２ｂは互いに平行でしかも同一軸上にある。
そして、本実施形態では、前述のような干渉測長計２１２ａによる距離情報Ｌ_１の測定と前記干渉測長計２１２ｂによる距離情報Ｌ_２の測定が交互に、つまり時分割に行われる。
【００６９】
次いて前記予め値付けされた標準サンプル２８０に代えて、寸法を求めたい被測定物が光軸上に挿入される。このように前記標準サンプル２８０と寸法を求めたい被測定物の出入れを行うと、基準位置間にワーク（標準サンプル２８０或いは寸法を求めたい被測定物）が存在しない時がある。本実施形態のように基準位置間にて測定光の光軸が同軸上に位置すると、被測定物が存在しない時に、対向する測定光がそれぞれ相手側の干渉測長計に飛び込んで受光素子や光源に悪影響を及ぼすことがある。
そこで、本実施形態は、これを防ぐために、基準位置に液晶シャッタ等よりなる非干渉装置２７６ａ，２７６ｂを配置している。
【００７０】
そして、本実施形態は、コンピュータ２６４がドライバ２７８ａ，２７８ｂにより、前記液晶シャッタ等の非干渉装置２７６ａ，２７６ｂの動作を交互に行わせている。このような非干渉装置２７６ａ，２７６ｂの時分割の動作は、非干渉装置２７６ａ，２７６ｂ間にワークの有る無しに関らず行われている。
この結果、本実施形態は、前記液晶シャッタ等の非干渉装置２７６ａ，２７６ｂの動作を交互に行わせているので、たとえワークが存在しない時であっても、対向するビームが相手側の干渉測長計に飛び込んで受光素子や光源に悪影響を及ぼすことを防いでいる。
また非干渉装置２７６ａ，２７６ｂ間にワークが存在するときであれば、測定が図中、右側経路と左側経路とで交互に行われる。
【００７１】
次いて図４に示すように寸法を求めたい被測定物２１８を光軸上に挿入して該被測定物２１８の対向する二平面間の寸法Ｌを求める。
この場合も、前記予め値付けされた標準サンプル２８０の場合と同様に、前記二系統の干渉測長計２１２ａ，２１２ｂによる時分割測定で距離情報Ｌ_３，Ｌ_４を得ている。
すなわち、干渉測長計２１２ａよりの第一測定光２２２ａは、非干渉装置２７６ａに入射する。
【００７２】
ここで、非干渉装置２７６ａが開の状態、かつ非干渉装置２７６ｂが閉の状態のとき、第一測定光２２２ａは非干渉装置２７６ａを通過し、被検反射面としての被測定物右側端面２１８ａに入射される。該被測定物右側端面２１８ａよりの反射光は、非干渉装置２７６ａを通過して干渉測長計２１２ａに入射される。該干渉測長計２１２ａでは、被検反射面としての被測定物右側端面２１８ａよりの距離情報Ｌ_３が測定される。
【００７３】
一方、非干渉装置２７６ａが閉の状態、かつ非干渉装置２７６ｂが開の状態のとき、干渉測長計２１２ｂよりの第二測定光２２２ｂは、非干渉装置２７６ｂに入射すると、この第二測定光２２２ｂは、非干渉装置２７６ｂを通過し、被検反射面としての被測定物左側端面２１８ｂに入射され、反射される。該被測定物左側端面２１８ｂよりの反射光は、非干渉装置２７６ｂを通過し、干渉測長計２１２ｂに入射される。該干渉測長計２１２ｂでは、被検反射面としての被測定物左側端面２１８ｂよりの距離情報Ｌ_４が求められる。
【００７４】
このように本実施形態は、前記第一実施形態と同様、波長の異なる複数種類の可干渉光を出射する光出射手段を用い、また個々の測定波長以上の距離の変位測定が行える多波長干渉測長計を二系統備えている。そして、被測定物の対向する平行な二つの端面に対して、二本の測定光をそれぞれ対向させて時分割に入射している。
ここで、本実施形態は、多波長干渉計により測定することのできる各被検反射面の変位情報として、右側経路では予め値付けされた標準サンプルの右側端面と、寸法Ｌを求めたい被測定物の右側端面との距離差を用いている。左側経路では予め値付けされた標準サンプルの左側端面と寸法Ｌを求めたい被測定物の左側端面との距離差を用いている。
【００７５】
この結果、本実施形態は、前記第一実施形態と同様、変位量を測定することのできる多波長干渉計よりなる干渉測長計を用いて、非接触で、光学波長を越える距離差の測定が行える。
また本実施形態は、前記第一実施形態と同様、被測定物に対し対向方向より測定を行うことにより、寸法測定を完全に非接触で行うことができ、また機械的な可動要素を必要としないので、高速で高精度な寸法測定が行える。
【００７６】
なお、本実施形態は、シャッタ（非干渉装置）での表面反射光（戻り光）があっても、空間一杯にワークがあるのと等価で、オフセット誤差発生要因くらいにはなるが、これは固定値なので容易に補正することができる。このため本実施形態では、シャッタ（非干渉装置）での表面反射光は測定には影響しない。
そして、本実施形態は、前述のようにして干渉測長計２１２ａにより測定された距離差Ｘ_１、干渉測長計２１２ｂにより測定された距離差Ｘ_２、および予め値付けされた被測定物（標準サンプル）２８０の寸法Ｌ_Ｓより、被測定物２１８の右側端面２１８ａと左側端面２１８ｂ間の寸法Ｌが前記数７により求める。
【００７７】
以上のように本実施形態は、基準位置間での測定光のゼロオフセット配置、一の光出射手段、液晶シャッタ等の非干渉装置による測定光の時分割投射を採用している。
この結果、本実施形態は、二つの非干渉装置を交互に動作させることにより、前記第一実施形態と同様、多波長干渉計により基準位置間の絶対値測定を行う際に、両側の投射光と反射光による複雑な干渉を回避することができる。
また本実施形態では、前記第一実施形態と同様、被測定物を光軸上のどの位置に置いても、光軸方向の相対的な変位が距離差Ｘ_１と距離差Ｘ_２の和をとった時点でキャンセルされるため、同じ値が測定できる。
【００７８】
このように本実施形態においても、被測定物と測定装置との相対的な並進振動に対して非常に安定した寸法測定が行えるため、ノギスやマイクロメータ等のハンドツール形態の非接触化に非常に有効となる。
なお、本実施形態では、各干渉測長計にそれぞれ一の光出射手段を設けること、つまり装置全体で二の光出射手段を用いることもできるが、コストの大幅な低減を図るためには、二の干渉測長計で共通の光出射手段を用いること、つまり装置全体で一の光出射手段を用いることも好ましい。
【００７９】
また本実施形態では、被測定物２１８の測定毎に、寸法を求めたい被測定物２１８、予め値付けされた標準サンプル２８０の測定を順に行うこともできるが、測定回数の低減、効率化のためには、例えば予め値付けされた標準サンプル２８０の測定を行った後に、寸法を求めたい複数の被測定物２１８の測定を行うようにしても良い。
また本実施形態においても、被測定物の測定光の光軸方向に平行な並進移動による測定量への影響を大幅に排除するために、該距離差Ｘ_１の測定と距離差Ｘ_２の測定を高速で切換えて行うことが好ましい。
【００８０】
また本実施形態では、非干渉装置として液晶シャッタを用いた例について説明したが、液晶シャッタに代えて音響光学素子（ＡＯＭ）或いはガルバノミラーを用いることも、液晶シャッタと同様、本発明の寸法測定装置の非干渉装置として特に好適である。
図５には非干渉装置として音響光学素子を用いた寸法測定装置の概略構成が示されている。なお、前記第二実施形態と対応する部分には符号１００を加えて示し説明を省略する。
同図に示す非干渉装置（非干渉手段）３７６ａ，３７６ｂは、音響光学素子を含む。
【００８１】
ここで、前記音響光学素子は、発生する０次光を音響光学素子の出力側で遮蔽もしくは吸収させている。同図では、測定光を遮蔽したい時に動作しないようにしておけば、なにも出力されないが、通過させたい時はドライバ２７８ａ，２７８ｂにより音響光学素子２７６ａ，２７６ｂへ高周波電圧を供給すると、１次光を出力するので、この１次光を寸法測定に用いればよい。
すなわち、非干渉装置３７６ａが干渉測長計３１２ａよりの測定光３２２ａを被検反射面に出力し、かつ該測定光の該被検反射面よりの反射光を干渉測長計３１２ａに出力しているとき、非干渉装置３７６ｂは光を遮蔽、つまり何も出力しない状態とし、干渉測長計３１２ａによる該被検反射面の測定を行う。
【００８２】
一方、非干渉装置３７６ａが光を遮蔽、つまり何も出力していないとき、非干渉装置３７６ｂは干渉測長計３１２ｂよりの測定光３２２ｂを被検反射面に出力し、かつ該測定光の該被検反射面よりの反射光を干渉測長計３１２ｂに出力している状態とし、干渉測長計３１２ｂによる被検反射面の測定を行う。
このように本実施形態では、非干渉装置３７６ａ，３７６ｂでの変調、非変調を交互（時分割）に行うことにより、干渉測長計３１２ａによる測定と干渉測長計３１２ｂによる測定を交互（時分割）に行えるので、前記液晶シャッタと同様の効果を得ることができる。
【００８３】
図６には非干渉装置としてガルバノミラーを用いた寸法測定装置の概略構成が示されている。なお、前記第二実施形態と対応する部分には符号２００を加えて示し説明を省略する。
同図に示す非干渉装置（非干渉手段）４７６ａ，４７６ｂは、測定光の光路を機械的に変更するガルバノミラーで構成されている。
【００８４】
ここで、前記ガルバノミラーは、そのチルトにより測定光の光路を変化させるものである。そして、測定光を遮蔽したい時には一方の測定光が他方の干渉測長計に入射しないような光路となる角度にガルバノミラーをチルトしておけば、測定光は相手の干渉測長計に入射しない。被測定物を通過したい時は、測定光が干渉測長計に入射するような光路となる角度にガルバノミラーをチルトしておけば、寸法測定が行える。
このように測定光の通過と遮蔽の切替を、ガルバノミラーのチルトにより行っても、前記液晶シャッタ、音響光学素子と同様の効果を得ることができる。
【００８５】
【発明の効果】
以上説明したように本発明にかかる寸法測定装置によれば、前記多波長干渉計よりなる第一干渉測長手段及び第二干渉測長手段と、所定の離隔距離をおいて配置され、被測定物が出入りされる第一ミラー及び第二ミラーを備え、該ミラー間での前記第一干渉測長手段よりの第一測定光の光軸及び第二干渉測長手段よりの第二測定光の光軸をオフセット配置し、同時測定を行うこととした。
この結果、本発明は、被測定物が存在しない時に、干渉測長手段の誤動作を防ぐことができるので、多波長干渉計を用いた寸法測定が良好に行える。
また本発明にかかる寸法測定装置によれば、前記多波長干渉計よりなる第一干渉測長手段及び第二干渉測長手段と、前記被測定物の測長軸と一致した光軸を有し、かつ所定の離隔距離をおいて配置された第一非干渉手段及び第二非干渉手段を備え、該非干渉手段を交互に動作させることとした。
この結果、本発明は、被測定物が存在しない時に、干渉測長手段の誤動作を防ぐことができるので、多波長干渉計を用いた寸法測定が良好に行える。
また本発明においては、前記非干渉手段としてシャッタ、音響光学素子あるいはミラーを採用することにより、前記多波長干渉計を用いた寸法測定がより良好に行える。
【図面の簡単な説明】
【図１】本発明の第一実施形態にかかる寸法測定装置の概略構成の説明図である。
【図２】図１に示した寸法測定装置の作用の説明図である。
【図３】本発明の第二実施形態にかかる寸法測定装置の概略構成の説明図である。
【図４】図３に示した寸法測定装置の作用の説明図である。
【図５】
【図６】図３に示した寸法測定装置の非干渉装置の変形例である。
【図７】一般的な寸法測定装置による一般的な寸法測定方法の説明図である
【図８】本実施形態の寸法測定装置に用いられる多波長干渉計の一例である。
【符号の説明】
１１０，２１０　寸法測定装置
１１２ａ，２１２ａ　干渉測長計（第一干渉測長手段）
１１２ｂ，２１２ｂ　干渉測長計（第二干渉測長手段）
１１８，２１８　被測定物
１６０　ミラー（第一ミラー）
１６２　ミラー（第二ミラー）
２７６ａ　非干渉装置（第一非干渉手段）
２７６ｂ　非干渉装置（第二非干渉手段）
２８０　値付けされた標準サンプル[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a dimension measuring device, and particularly to a mechanism capable of favorably measuring a dimension using a multi-wavelength interferometry.
[0002]
[Prior art]
Conventionally, an edger has been used as a length reference. A terminator is a standard that represents a dimension (dimension) by a distance between two parallel surfaces at both ends, and a typical example is a gauge block.
This gauge block has extremely high dimensional accuracy, and its measuring surface easily comes into close contact with the measuring surface of another gauge block. Therefore, the composite dimension obtained by closely contacting several gauge blocks is equal to the sum of the dimensions of the individual gauge blocks, and the required dimensions are obtained. On the other hand, since the gauge block is used in such a manner that the measurement surface always comes into contact with another measurement surface, the gauge block is liable to be scratched or worn, and the material is aged, so that periodic inspection is required.
[0003]
For this reason, it is necessary to inspect the dimension between the opposing end faces of the individual gauge blocks by the measuring means.
For example, an object to be measured having two parallel planes is inserted between reference positions whose absolute values are predetermined. Then, the absolute value from the plane of the measured object to the reference position is identified by the absolute value measuring means, and the dimensions of the measured object are obtained.
[0004]
[Problems to be solved by the invention]
By the way, attention has been paid to an absolute value measuring means using an optical interferometer because it is non-contact.
Since the optical interferometer detects a change in the propagation distance of light due to interference, a general single-wavelength interferometer cannot measure a change in distance over the wavelength of light.
[0005]
Therefore, it is conceivable to use a multi-wavelength interferometer capable of measuring the displacement of an object exceeding an optical wavelength that cannot be measured by the single-wavelength interferometry.
A dimension measuring device using a multi-wavelength interferometer uses multiple types of measurement light with different wavelengths, detects each phase at a single wavelength based on the interference signal at each wavelength, and compares them. To measure the phase at the equivalent wavelength. Then, when the phase at the equivalent wavelength is converted into a displacement amount, the displacement amount of the measured object exceeding the optical wavelength that cannot be measured by the single wavelength interferometry can be obtained.
[0006]
However, even if a multi-wavelength interferometer is adopted for the dimension measurement, it is possible to measure the displacement of the object to be measured. It must be measured as the distance between the two end faces. In addition, in consideration of practicality, it is necessary that the same dimensional value can be measured regardless of where the object to be measured is placed on the optical axis.
Therefore, conventionally, for example, dimensional measurement as shown in FIG. 7 has been considered.
That is, the dimension measuring apparatus 10 shown in FIG. 1A linearly moves along an absolute value (ABS) interferometer (hereinafter referred to as an interferometer) 12 composed of, for example, a multi-wavelength interferometer, and a guide unit 14. The apparatus includes a stage 16 and a mirror 20 provided on a right end face 18 a of the device under test 18.
[0007]
Here, the DUT 18 provided with the mirror 20 is mounted on the stage 16 as shown in FIG. The interferometer 12 and the stage 16 are arranged so that the optical axis of the measuring light 22 from the interferometer 12 and the moving direction of the stage 16 along the guide 14 are orthogonal to each other.
Then, in the state shown in FIG. 2A, the measurement light 22 from the interferometer 12 is reflected by the left end face 18b of the DUT 18 and returned to the interferometer 12. Accordingly, in the interferometer 12, the distance information L from the left end face 18 b of the DUT 18 is obtained.₁Is measured.
[0008]
Also, as shown in FIG. 4B, the stage 16 is moved along the guide portion 14 in a direction orthogonal to the optical axis of the measurement light 22 (downward in the figure), and the optical axis of the measurement light 22 and the reflection surface of the mirror 20 are moved. Make them orthogonal. Then, the measurement light 22 from the interferometer 12 is reflected by the mirror 20 and returned to the interferometer 12. Accordingly, in the interferometer 12, the distance information L from the mirror 20, that is, the distance information L from the right end face 18 a of the measured object is obtained.₂Is measured.
Here, the distance information L₁, L₂Is a relative distance from a position where the optical path length difference in the interferometer 12 becomes zero. That is, the distance information L₁, L₂Does not show the absolute coordinate position of the reflection surface to be measured, but the distance information L₁And distance information L₂Difference (L₂-L₁), The dimension L of the measured object can be obtained.
[0009]
However, even with the dimension measuring apparatus 10 shown in the figure, since it is necessary to provide the mirror 20 on the DUT 18 in advance, it cannot be said that the measurement is strictly non-contact. In addition, the uncertainty of measurement may increase depending on the state of close contact of the mirror 20. Further, in the dimension measuring device 10 shown in the figure, since the object to be measured 18 needs to be shifted in the direction orthogonal to the optical axis of the measuring light 22, high accuracy is required for the movement of the stage 16 and the measuring time is reduced. There is naturally a limit to shortening.
[0010]
For this reason, the dimension measuring apparatus 10 shown in the figure has not been adopted as a dimension measuring apparatus using a multi-wavelength interferometer. Since the dimension measuring device using the multi-wavelength interferometer has not been put to practical use yet, its development has been urgently required.
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and an object of the present invention is to provide a dimension measuring apparatus capable of performing excellent dimension measurement using a multiwavelength interferometer.
[0011]
[Means for Solving the Problems]
The present inventors have conducted intensive studies on absolute value measurement using a multi-wavelength interferometer. As a result, first, two systems of multi-wavelength interferometers using light emitting means for emitting a plurality of types of coherent light having different wavelengths are used. . Then, the measurement light from each interferometer is incident on two opposing parallel planes of the object to be measured, and the displacement information of each reflection surface to be measured is measured. As a result, the dimension measurement between two opposing planes of the device under test can be performed without contacting the device under test without additional components, and the need for a mechanical moving mechanism is eliminated. I found it.
[0012]
As for the absolute value measurement using the multi-wavelength interferometer as described above, as a result of further research by the present inventors, the two measurement lights were simply arranged coaxially, and the other I knew I would jump. As a result, it has been found that when the absolute value of the dimension between the reference positions is measured by the multi-wavelength interferometer, the interferometer malfunctions and accurate measurement cannot be performed. According to the present inventors, this problem is caused by complicated interference between projected light and reflected light from both sides between reference positions, and by avoiding this interference, the interferometer After clarifying that a malfunction can be prevented, the present invention has been completed.
[0013]
That is, in order to achieve the object, a dimension measuring apparatus according to the present invention is a dimension measuring apparatus that measures a dimension L between opposed first and second end faces of a device under test using a multi-wavelength interferometer. A first interferometer and a second interferometer, a first mirror and a second mirror.
The distance between the first mirror and the second mirror when the object to be measured does not exist between the mirrors and the first measurement light from the first interference length measuring means is reflected by the second mirror. Information L₁And distance information L on the first end face of the DUT when the DUT exists between the mirrors and the first measurement light is reflected by the first end face of the DUT.₃Distance difference X from₁Is measured.
[0014]
The distance information L of the first mirror when the object to be measured does not exist between the mirrors and the second measurement light from the second interference length measuring means is reflected by the first mirror by the second interference measuring means.₂And distance information L on the second end face of the DUT when the DUT exists between the mirrors and the second measurement light is reflected by the second end face of the DUT.₄Distance difference X from₂Is measured. And the distance difference X measured by the first interferometer.₁, The distance difference X measured by the second interferometer₂And a predetermined separation distance X between the first mirror and the second mirror₃Further, a dimension L between the opposed first end face and the second end face of the object to be measured is obtained by Expression 3.
[0015]
(Equation 3)
L = (X₁+ X₂) -X₃
However, the distance difference X₁= The distance information L₁-The distance information L₃
The distance difference X₂= The distance information L₂-The distance information L₄
Here, the first and second interferometers include a reference light based on a part of a plurality of types of coherent lights having different wavelengths, and a test light reflected by the remaining coherent light as measurement light. The reflected light obtained by being incident on the surface is synthesized to obtain interference light, and the displacement of the reflection surface to be measured exceeding each measurement wavelength is measured based on the interference signal at each measurement wavelength.
[0016]
The first mirror and the second mirror are displaced in parallel so that the optical axis of the first measurement light from the first interferometer and the optical axis of the second measurement light from the second interferometer do not overlap. And a predetermined separation distance X₃It is arranged at.
The reflection surface to be measured here means the second mirror when the object to be measured does not exist between the mirrors on the first interferometer, and when the object to be measured exists, the first mirror of the object to be measured. Refers to the end face. On the side of the second interferometer, it refers to the first mirror when the object to be measured does not exist between the mirrors, and refers to the second end face of the object to be measured when the object to be measured exists.
[0017]
For this reason, the displacement of the reflection surface to be measured here refers to the position of the corresponding end face of the object to be measured when the object to be measured exists relative to the position of the corresponding mirror when the object to be measured does not exist between the mirrors. Changes.
Further, the distance information referred to here means, for example, distance information from a position where the optical path length difference in the corresponding interferometer becomes zero.
Further, the interferometer means a multi-wavelength interferometer capable of measuring the displacement amount of each measurement wavelength or more by repeating the same measurement while changing the wavelength of the measurement light. For example, when using a semiconductor laser as an example of the light emitting means, it is particularly preferable to change the oscillation wavelength according to the driving conditions. As a method of changing the oscillation wavelength, for example, the methods described in JP-A-4-297807, JP-A-4-297808, JP-A-2001-27512 and the like can be used.
[0018]
In the present invention, a first light passage hole for passing the first measurement light is provided at a portion of the first mirror located on the optical axis of the first measurement light. When the object to be measured does not exist between the mirrors, the first measurement light from the first interferometer having passed through the first light passage hole of the first mirror is reflected and returned to the first light passage hole. The mirror surface of the second mirror is positioned on the optical axis of the first measurement light so as to emit light. A second light passage hole for passing the second measurement light is provided at a portion of the second mirror located on an optical axis of the second measurement light. When the object to be measured does not exist between the mirrors, the second measurement light from the second interferometer having passed through the second light passage hole of the second mirror is reflected and returned to the second light passage hole. It is preferable that the mirror surface of the first mirror be located on the optical axis of the second measurement light so as to emit light.
[0019]
In order to achieve the above object, the dimensional measurement according to the present invention includes a first interferometer and a second interferometer, a first non-interferer and a second non-interferer.
Then, the first interferometer has a known dimension L between the non-interferers._SAnd the distance information L of the first end face of the standard sample when the first measurement light from the first interferometer is reflected by the first end face of the standard sample.₁And the distance information L on the first end surface of the DUT when the DUT exists between the non-interfering means and the first measurement light is reflected by the first end surface of the DUT.₃Distance difference X from₁Is measured.
[0020]
By the second interferometer, the standard sample is present between the non-interferometers, and the standard when the second measurement light from the second interferometer is reflected by the second end face of the standard sample Distance information L of sample second end face₂And the distance information L of the object second end face when the object to be measured exists between the non-interfering means and the second measurement light is reflected by the second end face of the object to be measured.₄Distance difference X from₂Is measured.
And the distance difference X measured by the first interferometer.₁, The distance difference X measured by the second interferometer₂, And the dimension L of the pre-valued standard sample_SFurther, a dimension L between the opposed first end face and the second end face of the object to be measured is obtained by Equation 4.
[0021]
(Equation 4)
L = L_S− (X₁+ X₂)
However, the distance difference X₁= The distance information L₃-The distance information L₁
The distance difference X₂= The distance information L₄-The distance information L₂
[0022]
Here, the first and second interferometers include a reference light based on a part of a plurality of types of coherent lights having different wavelengths, and a test light reflected by the remaining coherent light as measurement light. The reflected light obtained by being incident on the surface is synthesized to obtain interference light, and based on the interference signal at each measurement wavelength, the displacement of the reflection surface to be measured exceeding the individual measurement wavelength is measured.
Further, the first non-interfering means and the second non-interfering means have an optical axis coinciding with the length measurement axis of the object to be measured, and are arranged at a predetermined separation distance. The first non-interfering means alternately passes the measurement light and blocks the measurement light. The second non-interfering means shields the measuring light when the measuring light passes through the first non-interfering means and blocks the measuring light when the measuring light is shielded by the first non-interfering means. Are performed alternately in synchronization with the passage of the measuring light and the switching of the shielding in the step (1).
[0023]
The reflection surface to be referred to here means, on the first interferometer, the side of the first sample of the standard sample when the standard sample exists between the non-interfering means, and when the object to be measured exists. , The first end surface of the device under test. On the second interferometer side, when the standard sample exists between the non-interfering means, it refers to the second end face of the standard sample, and when the DUT exists, it refers to the second end face of the DUT. .
Therefore, the displacement of the reflection surface to be inspected means that the position of the corresponding end face when the object to be measured is present changes from the position of the corresponding end face when the standard sample exists between the non-interfering means.
[0024]
Further, the distance information referred to here means, for example, distance information from a position where the optical path length difference in the corresponding interferometer becomes zero.
In the present invention, the non-interfering means is a shutter, and includes a driving means for opening and closing the shutter. It is preferable that switching between passage and blocking of the measurement light is performed by opening and closing the shutter by the driving unit. As the shutter of the present invention, for example, a liquid crystal shutter or the like can be used as an example.
[0025]
Further, in the present invention, the non-interference means is an acousto-optic element, and includes a driving means for performing modulation and non-modulation of the acousto-optic element. Further, it is also preferable that switching between the passage of the measurement light and the shielding is performed by modulation and non-modulation of the acousto-optic element by the driving unit.
In the present invention, the non-interference means is a mirror that changes an optical path by tilting a mirror surface, and the driving means changes an optical path of measurement light by tilting the mirror, thereby switching between passing and blocking of the measurement light. Is also suitable. As the mirror of the present invention, for example, a galvanometer mirror or the like can be used as an example.
[0026]
Further, in the present invention, in order to eliminate the influence on the measurement amount due to the translation of the object to be measured, which is parallel to the optical axis direction of the measurement light, the distance difference X by the first interferometer is used.₁And the distance difference X by the second interferometer.₂It is preferable to perform the measurement at the same time.
The present inventors employ a multi-wavelength interferometry capable of measuring a displacement amount exceeding an optical wavelength for measuring the dimensions of two opposing parallel planes of an object to be measured.
The principle of this multi-wavelength interferometry will be described with reference to FIG.
[0027]
The dimension measuring device 10 shown in FIG. 1 includes an interferometer 12.
Here, the interferometer 12 comprises, for example, a multi-wavelength interferometer and the like, and constitutes one light emitting means, light sources 24 and 26, a beam splitter 28, a beam splitter 30, a reference mirror 32, and a beam splitter. 34, optical filters 36 and 38, light receiving elements 40 and 42, and a phase comparator 44.
[0028]
Here, the light sources 24 and 26 are made of, for example, a semiconductor laser (LD) and include drivers 46 and 48. The drivers 46 and 48 drive the light sources 24 and 26 with, for example, inverted sawtooth modulation currents.₁), And the light source 26 emits laser light (λ₂).
Then, the laser light (λ₁) And the laser light (λ₂) Are placed in the orthogonal polarization state, are superimposed by the beam splitter 28, and are incident on the beam splitter 30. In the beam splitter 30, the light from the beam splitter 28 is split into a first split light 50 and a second split light (measurement light) 22.
[0029]
The reference mirror 32 is displaced in the optical axis direction by the optical path modulating piezoelectric element 52, and reflects the first split light 50 with a phase shift or a frequency shift. On the optical axis of the measurement light 22 from the beam splitter 30, an object to be measured 18 is arranged, and the object to be measured 18 reflects the measurement light 22.
The reflected light from the reference mirror 32 and the reflected light from the device under test 18 are combined by the beam splitter 30 to generate interference light. The interference lights at the two wavelengths are separated by the beam splitter 34 using the difference in the polarization state, and are passed through optical filters 36 and 38 for eliminating crosstalk between the two interference beat signals. The signal is detected by the two light receiving elements 40 and 42.
[0030]
Output signals from the light receiving elements 40 and 42 are input to a phase comparator 44. The phase comparator 44 heterodyne-detects an equivalent phase using one of the modulation currents to the light sources 24 and 26 as a reference signal. .
As described above, in the present embodiment, the phase at the equivalent wavelength can be measured by detecting each phase at a single wavelength based on the interference signal at each wavelength and comparing each phase. The equivalent wavelength is A = (λ₁・ Λ₂) / (| Λ₁−λ₂|), The absolute value measurement range is also the individual wavelength λ of the laser light.₁, Λ₂Exceeds (λ₁・ Λ₂) / (| Λ₁−λ₂|).
[0031]
By using such a multi-wavelength interferometer, it is possible to measure the amount of displacement of an object exceeding an optical wavelength that cannot be measured by single-wavelength interferometry. Can be converted into the displacement of the reflection surface to be measured.
In the present invention, various methods can be used to change the wavelength of the measurement light. For example, a semiconductor laser (LD) light source is used as a light source, and driving conditions such as an injection current to the laser are adjusted. The changing method is particularly preferable because the oscillation wavelength can be easily changed.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
[0033]
First embodiment
FIG. 1 shows a schematic configuration of a dimension measuring apparatus according to the first embodiment of the present invention. In the present embodiment, it is assumed that an object to be measured has a thickness or a reflection position to be measured which fluctuates at a high speed, and two interferometers 12 shown in FIG. 8 are provided, and two measurement units are provided between the reference positions. An example in which the optical axes of light are offset and two interferometers are operated simultaneously will be described. Parts corresponding to those in FIGS. 7 and 8 are denoted by reference numeral 100, and description thereof is omitted.
The dimension measuring device 110 shown in the figure includes a first interferometer (first interferometer) 112a and a second interferometer (second interferometer) 112b, and a mirror (first mirror, reference mirror). Position) 160, a mirror (second mirror, reference position) 162, and a computer 164.
[0034]
In this embodiment, mirrors 165 and 166 are provided between the interferometer 112a and the mirror 160, and mirrors 168 and 169 are provided between the interferometer 112b and the mirror 162.
Here, the mirrors 160 and 162 are separated by a predetermined separation distance X.₃And is used as a reference position.
[0035]
The optical axis of the first measurement light 122a from the interferometer 112a between the mirrors 160 and 162 and the optical axis of the second measurement light 122b from the interferometer 112b are offset so as not to overlap with each other. .
When an object to be measured does not exist between the mirrors 160 and 162, the optical axis of the first measurement light 122a in the offset arrangement is orthogonal to the mirror 162, and the optical axis of the second measurement light 122b is orthogonal to the mirror 160.
For this reason, in the present embodiment, the mirror 160 is provided with the first light passage hole 172, and the mirror 162 is provided with the second light passage hole 174.
[0036]
Here, since the first light passage hole 172 is provided at a portion of the mirror 160 located on the optical axis of the first measurement light 122a, the first measurement light 122a passes therethrough. When an object to be measured does not exist between the mirrors 160 and 162, the first measurement light 122a from the interferometer 112a that has passed through the first light passage hole 172 of the mirror 160 is reflected, and the first light passage hole 172 is reflected. Is mirrored on the optical axis of the first measurement light 122a. The measurement light 122a reflected by the mirror 162 and returned to the first light passage hole 172 enters the interferometer 112a via the mirrors 166 and 165.
[0037]
The second light passage hole 174 is provided at a portion of the mirror 162 located on the optical axis of the measurement light 122b, and allows the measurement light 122b from the interferometer 112b to pass therethrough. When an object to be measured does not exist between the mirrors 160 and 162, the measuring light 122b from the interferometer 112b passing through the second light passage hole 174 of the mirror 162 is reflected and returned to the second light passage hole 174. The mirror surface of the mirror 160 is positioned on the optical axis of the second measurement light 122b so as to emit light. The measurement light 122b reflected by the mirror 160 and returned to the second light passage hole 174 is incident on the interferometer 112b via the mirrors 169 and 168.
In the interferometer 112a, the distance difference X between the right side reflection surface when the object does not exist and when the object exists exists.₁Is measured.
[0038]
That is, the interferometer 112a is configured such that when the object to be measured does not exist between the mirrors 160 and 162, and the measurement light 122a from the interferometer 112a is reflected by the mirror (measurement reflection surface) 162, the mirror 162 is used. Distance information L₁And an object to be measured is present between the mirrors 160 and 162, and the measurement light 122a from the interferometer 112a is reflected by the right end face (the test reflection face, the first end face) of the measurement object. Distance information L from right end face of DUT₃Distance difference X from₁Is measured.
Also, in the interferometer 112b, the distance difference X between the left subject reflection surface when the subject does not exist and when the subject exists.₂Is measured.
[0039]
That is, the interferometer 112b is used when the object to be measured does not exist between the mirrors 160 and 162, and the second measurement light 122b from the interferometer 112b is reflected by the first mirror (reflection surface to be measured) 160. , Distance information L from the first mirror 160₂And the object to be measured is present between the mirrors 160 and 162, and the second measurement light 122b from the interferometer 112b is reflected by the left end face (the reflection surface to be measured, the second end face) of the object to be measured. , Distance information L from the left end face of the measured object₄Distance difference X from₂Is measured.
Then, the computer 164 calculates the distance difference X of the right-side target reflection surface measured by the interferometer 112a as described above.₁And the distance difference X between the left reflective surface to be measured measured by the interferometer 112b.₂And a predetermined separation distance X between the mirrors 160 and 162₃Thus, the dimension (thickness) L between the two opposing parallel surfaces of the object to be measured is calculated by Expression 5.
[0040]
(Equation 5)
L = (X₁+ X₂) -X₃
However, the distance difference X₁= The distance information L₁-The distance information L₃
The distance difference X₂= The distance information L₂-The distance information L₄
寸法 The dimension measuring apparatus 110 according to the present embodiment is configured as described above, and its operation will be described below.
[0041]
First, as shown in the figure, when there is no measured object between the mirrors 160 and 162, the distance information L₁, L₂Get it.
That is, in the dimension measuring device using the multi-wavelength interferometer, it is necessary to measure the absolute value dimension between the reference positions. In this measurement, there is no measurement object between the mirrors 160 and 162. Here, if the first measurement light and the second measurement light are simply arranged coaxially, the measurement light may jump into the interferometer of the other party and adversely affect the light receiving element and the light source.
[0042]
Therefore, in the present embodiment, when measuring the absolute value between the reference positions, in order to avoid complicated interference due to the projected light and reflected light on both sides, the light of the first measurement light and the second measurement light They are offset so that the axes do not overlap. That is, in the present embodiment, simultaneous projection is performed by two light emitting units that shift the measurement position (reflection position) by the measurement light and cancel the error due to the offset.
That is, the first measurement light 122a from the interferometer 112a enters the first light passage hole 172 of the first mirror 160. The first measurement light 122a that has passed through the first light passage hole 172 is incident on a mirror surface of the second mirror 162 as a test reflection surface when no test object exists, and is reflected. The reflected light from the second mirror 162 passes through the first light passage hole 172 of the first mirror 160 again to be incident on the interferometer 112a. In the interferometer 112a, the distance information L from the second mirror 162 as the reflection surface to be measured when the object to be measured does not exist.₁Is required.
[0043]
In the present embodiment, the measurement by the interferometer 112b is performed simultaneously with the measurement by the interferometer 112a.
That is, the second measurement light 122b from the interferometer 112b enters the second light passage hole 174 of the second mirror 162. The second measurement light 122b that has passed through the second light passage hole 174 is incident on and reflected by the mirror surface of the first mirror 160 as a reflection surface to be measured when there is no measurement object. The reflected light from the first mirror 160 passes through the second light passage hole 174 of the second mirror 162 again and is incident on the interferometer 112b. In the interferometer 112b, distance information L from the first mirror 160 as a reflection surface to be measured when no object to be measured exists.₂Is measured.
[0044]
As described above, in the present embodiment, the distance information L1 when the first measurement light 122a is reflected by the second mirror 162 by the interferometer 112a and the second measurement light 122b by the interferometer 112b are converted to the first mirror. Distance information L when reflected at 160₂Are measured simultaneously.
Here, in the present embodiment, two systems of the interferometers 112a and 112b emit the first measurement light 122a and the second measurement light 122b so as to face each other. Between the mirrors 160 and 162, the two measurement lights 122a and 122b are parallel to each other, but are arranged with a distance equal to or greater than the beam diameter of the measurement light so that the measurement lights do not overlap. A mirror 160 having a light passing hole 172 and a mirror 162 having a light passing hole 174 are arranged perpendicular to the measurement light. For this reason, in the present embodiment, when there is no object to be measured between the mirrors 160 and 162, the measurement light facing each is reflected and returned to each interferometer.
[0045]
For this reason, in the present embodiment, when the object to be measured does not exist, the opposed measuring light is prevented from jumping into the interferometer of the other party and adversely affecting the light receiving element and the light source.
Simultaneous measurement by the interferometers 112a and 112b is performed in a state where the object to be measured 118 exists between the mirrors 160 and 162 as shown in FIG.
[0046]
That is, as shown in the figure, the first measurement light 122a from the interferometer 112a enters the light passage hole 172 of the first mirror 160. The first measurement light 122a that has passed through the light passage hole 172 is incident on the right end surface 118a of the test object 118 as the test reflection surface when the test object 118 is present, and is reflected. The reflected light from the right end surface 118a of the device under test 118 passes through the first light passage hole 172 of the first mirror 160 and is incident on the interferometer 112a. The interferometer 112a measures distance information L3 from the right end surface 118a of the object as the reflection surface to be measured when the object 118 is present.
[0047]
In the present embodiment, the measurement by the interferometer 112b is performed simultaneously with the measurement by the interferometer 112a.
That is, the second measurement light 122b from the interferometer 112b enters the light passage hole 174 of the second mirror 162. The second measurement light 122b that has passed through the light passage hole 174 is incident on the left end surface 118b of the object to be measured when the object 118 is present and is reflected. The light reflected from the left end face 118b of the object to be measured passes through the light passage hole 174 of the second mirror 162 and is incident on the interferometer 112b. The interferometer 112b measures distance information L4 from the left end surface 118b of the measured object as a reflection surface to be measured when the measured object 118 is present.
[0048]
Thus, in the present embodiment, the distance information L when the first measurement light 122a is reflected by the right end face 118a of the measured object by the interferometer 112a.₃And distance information L when the second measurement light 122b is reflected by the left end face 118b of the measured object by the interferometer 112b.₄Are measured simultaneously.
Here, in the present embodiment, each distance information is a relative distance from a point at which the optical path length difference in the corresponding interferometer becomes zero, and does not indicate the absolute coordinate position of the reflecting surface. , The distance difference X from these distance information₁, Distance difference X₂By obtaining the above, the same value can be measured regardless of whether the distance is far from or near the light emitting means.
[0049]
Therefore, the present embodiment measures the distance between the two parallel planes (absolute value) by simultaneously measuring the displacement of the test reflection surface when the test object is not present and when the test object is present. ) Can be measured.
Here, in the present embodiment, a displacement of each measurement wavelength or more can be measured by using a multi-wavelength interferometer as an interferometer. With such an interferometer, the distance difference between the mirror surface of the mirror when the object is not present and the end surface when the object is present is measured as the displacement of the reflection surface to be measured. By using a multi-wavelength interferometer capable of measuring a displacement exceeding a wavelength, a dimension exceeding an optical wavelength can be obtained.
[0050]
In this embodiment, the predetermined separation distance X₃The device under test 118 is arranged between the first mirror 160 and the second mirror 162 arranged at a distance, and the first measuring light 122a and the second measuring light 122b are simultaneously opposed from both sides of the device under test 118. It is incident and measuring.
For this reason, no matter where the device under test 118 is placed on the optical axis between the mirrors 160 and 162, the relative displacement in the optical axis direction is equal to the distance difference X.₁And distance difference X₂Is canceled when the sum of is obtained, the same value can be measured.
[0051]
According to this embodiment, the dimension measurement can be performed completely without contact. Further, in this embodiment, since no mechanical movable element is required, high-speed and high-accuracy dimension measurement can be performed.
In particular, in the present embodiment, even if the object to be measured enters and exits at high speed, the offset arrangement of the optical axis of the measurement light between the mirrors, and the simultaneous projection of the measurement light from both sides of the object to be measured provide high precision Dimension measurement can be performed.
[0052]
As described above, in the present embodiment, the measurement value obtained by the two systems of the interferometers is based on the distance difference X between the right end surface 118a of the DUT 118 and the reflection surface of the second mirror 162.₁And the distance difference X between the left end surface 118b of the device under test 118 and the reflection surface of the first mirror 160.₂It is. The separation distance between the reflecting surface of the mirror 160 and the reflecting surface of the mirror 162 is X₃Then, there is a relationship expressed by Equation 6 with the dimension L.
[0053]
(Equation 6)
X₃+ L = X₁+ X₂
Therefore, in the present embodiment, the separation distance X between the mirrors 160 and 162₃Is obtained in advance, the dimension L can be calculated by the above-described equation (5) obtained by modifying the equation (6). The separation distance X₃Can be easily determined, for example, by performing a back calculation using a standard sample whose dimensions are accurately valued.
[0054]
As described above, according to the dimension measuring apparatus according to the present embodiment, a multi-wavelength interferometer capable of measuring a displacement exceeding the optical wavelength is used, and a bi-directional measurement is performed in both directions with respect to an opposing plane of the DUT between reference positions. It was decided that the measuring light was made to be incident oppositely.
As a result, in the present embodiment, it is possible to measure the dimension between two opposing parallel planes of the device under test completely without contact and without adding another component to the device under test.
In addition, in the present embodiment, accurate dimension measurement can be performed regardless of the position of the object to be measured at any position on the optical axis without being affected by the position of the object to be measured or translational vibration in the optical axis direction.
[0055]
In addition, in the present embodiment, since the distance difference between the end surface of the object to be measured and the mirror as the reference position is considered as the displacement of the reflection surface to be measured, even if a multi-wavelength interferometer for measuring the displacement is used, the distance difference is Can be measured.
In addition, the present embodiment employs the offset arrangement of the measurement light and the simultaneous projection of the measurement light facing each other by the two light emitting means, thereby achieving high-speed measurement of the absolute value of the dimension using the optical interference system. High accuracy can be achieved even in the case of high-speed measurement of an object to be measured which enters and exits at.
[0056]
Particularly, in the present embodiment, a mirror is arranged at the reference position, and the optical axis of the measurement light is offset between the mirrors. Therefore, when measuring the absolute value between the reference positions with a multi-wavelength interferometer. Thus, complicated interference between the projected light and the reflected light on both sides can be reliably avoided. Thus, in the present embodiment, the malfunction of the multi-wavelength interferometer can be prevented, so that the dimension measurement can be performed more accurately.
[0057]
Further, in the present embodiment, even if the object to be measured is moved in and out at a high speed by, for example, a manual mechanism or a mechanical mechanism such as an object to be measured holding means, the distance difference X by the first interferometer can be obtained.₁Measurement and the distance difference X by the second interferometer₂, The influence of the translation of the measurement object parallel to the optical axis direction of the measurement light on the measurement amount can be largely eliminated. In addition, the present embodiment can perform very stable dimension measurement with respect to relative translational vibration between the object to be measured and the measuring device, and thus is very effective for non-contact of hand tools such as calipers and micrometers. It becomes.
[0058]
Second embodiment
FIG. 3 shows a schematic configuration of a dimension measuring apparatus according to the second embodiment of the present invention. In the present embodiment, an example will be described in which two measurement beams are arranged with a zero offset between reference positions, and two interferometers are operated in a time-division manner. Parts corresponding to those in the first embodiment are denoted by reference numeral 100, and description thereof is omitted.
In the dimension measuring device 210 shown in FIG. 5, when measuring the absolute value of the dimension between the reference positions by the multi-wavelength interferometer, the dimension measuring apparatus 210 is operated in a time-division manner to avoid complicated interference by the projected light and the reflected light on both sides. For example, a first non-interfering device (first non-interfering means, reference position) 276a and a second non-interfering device (second non-interfering means, reference position) 276b including a liquid crystal shutter and the like, and drivers (driving means) 278a, 278b , A computer 264.
[0059]
Here, the non-interfering devices 276a and 276b have optical axes coinciding with the optical axes of the measuring beams 222a and 222b and are arranged at a predetermined separation distance, and are used as reference positions.
In the present embodiment, the computer 264 causes the drivers 278a and 278b to alternately (time-divisionally) operate the non-interfering devices 276a and 276b such as the liquid crystal shutter, and performs measurement on the right path and the left path in the figure. Are performed alternately. That is, the incidence of the measuring light 222a on the interferometer 212a and the non-incidence of the interferometer 212b, and the non-incident of the measuring light 222b on the interferometer 212a and the incidence on the interferometer 212b are alternately switched. .
[0060]
As described above, in this embodiment, since the non-interfering devices 276a and 276b are always operated alternately, even when there is no work between the non-interfering devices 276a and 276b, the beams coaxially opposed to each other. To prevent malfunction.
Further, in the present embodiment, the interferometers 212a and 212b use a common light emitting unit. That is, using one light emitting unit, the measurement light is projected by the interferometer 212a and the reflected light is measured. And the measurement light is projected by the interferometer 212b and the reflected light is measured.
[0061]
That is, in the interferometer 212a, the standard sample 280 pre-valued exists between the non-interferometers 276a and 276b, and the first measurement light 222a from the interferometer 212a is reflected by the right end face 280a of the standard sample. At the time, the distance information L from the right end face 280a of the standard sample.₁The object to be measured is present between the non-interfering devices 276a and 276b, and the object to be measured when the first measurement light 222a from the interferometer 212a is reflected by the right end face of the object to be measured. Distance information L from right end face₃Distance difference X from₁Is measured.
[0062]
Also, the interferometer 212b has the standard sample 280 pre-valued between the non-interferometers 276a and 276b, and reflects the second measurement light 222b from the interferometer 212b on the left end face 280b of the standard sample. Information L from the left end surface 280b of the standard sample at the time.₂The object to be measured is present between the non-interference devices 276a and 276b, and the second measurement light 222b from the interferometer 212b is reflected by the left end face of the object to be measured. Distance information L from the left side of the object₄Distance difference X from₂Is measured.
[0063]
In this way, by the time-division measurement of the interferometer 212a and the interferometer 212b, the dimension between the non-interfering devices 276a and 276b is known._SThe displacement of the left and right reflection surfaces to be measured is measured when there is a standard sample 280 pre-valued and when there is an object to be measured whose dimensions are to be obtained.
The computer 264 calculates the distance difference X measured by the interferometer 212a as described above.₁, The distance difference X measured by the interferometer 212b₂, And the dimension L of the pre-valued standard sample 280_SThus, the dimension (thickness) L between two opposing parallel planes of the object to be measured is calculated by Expression 7.
[0064]
(Equation 7)
L = L_S− (X₁+ X₂)
However, the distance difference X₁= The distance information L₃-The distance information L₁
The distance difference X₂= The distance information L₄-The distance information L₂
寸法 The dimension measuring apparatus 210 according to the present embodiment is configured as described above, and its operation will be described below.
[0065]
First, as shown in FIG._SThe distance information L is obtained by the two interferometers 212a and 212b using the standard sample 280 accurately priced.₁, L₂Get it. This operation may be performed at least once at the initial stage.
In the present embodiment, as shown in the figure, the non-interfering devices 276a and 276b operate alternately with or without a work, that is, with or without a standard sample and with or without an object to be measured. are doing.
Therefore, when the non-interfering device 276a is in the open state and the non-interfering device 276b is in the closed state, substantially only the interferometer 212a is operating, and the measurement by the interferometer 212a is performed. .
[0066]
That is, as shown in the figure, a standard sample 280 that has been priced in advance exists between the non-interfering devices 276a and 276b. Then, the first measurement light 222a from the interferometer 212a passes through the non-interferometer 276a, is incident on the standard sample right end surface 280a as a test reflection surface, and is reflected. The reflected light from the right end face 280a of the standard sample passes through the non-interfering device 276a and enters the interferometer 212a. In the interferometer 212a, distance information L from the standard sample right end surface 280a as a reflection surface to be inspected is obtained.₁Is measured.
[0067]
On the other hand, when the non-interfering device 276a is in the closed state and the non-interfering device 276b is in the open state, substantially only the interferometer 212b is operating, and the measurement by the interferometer 212b is performed.
That is, the second measurement light 222b from the interferometer 212b passes through the non-interferometer 276b, enters the standard sample left end surface 280b as a reflection surface to be detected, and is reflected. The reflected light from the standard sample left end surface 280b passes through the non-interfering device 276b and is incident on the interferometer 212b. In the interferometer 212b, the distance information L from the standard sample left end surface 280b as a test reflection surface is obtained.₂Is required.
[0068]
As described above, in the present embodiment, two measurement beams 222a and 222b are emitted to face each other and input in a time-division manner using two systems of interferometers as shown in FIG. In the figure, the two measurement beams 222a and 222b facing each other are parallel and coaxial with each other, although they are intentionally shifted for convenience.
In the present embodiment, the distance information L by the interferometer 212a as described above is used.₁Measurement and distance information L by the interferometer 212b₂Are alternately performed, that is, time-divisionally.
[0069]
Next, an object to be measured whose dimensions are to be obtained is inserted on the optical axis in place of the standard sample 280 which has been previously priced. As described above, when the object to be measured and the standard sample 280 are moved in and out, the workpiece (the standard sample 280 or the object to be measured) does not exist between the reference positions. When the optical axis of the measurement light is located coaxially between the reference positions as in the present embodiment, when the object to be measured does not exist, the opposing measurement lights each jump into the interferometer of the other party, and the light receiving element or the light source May have adverse effects.
Therefore, in the present embodiment, in order to prevent this, non-interfering devices 276a and 276b including a liquid crystal shutter and the like are arranged at the reference position.
[0070]
In this embodiment, the computer 264 causes the drivers 278a and 278b to alternately operate the non-interference devices 276a and 276b such as the liquid crystal shutter. Such time-sharing operation of the non-interfering devices 276a and 276b is performed regardless of whether or not there is a work between the non-interfering devices 276a and 276b.
As a result, in the present embodiment, the operations of the non-interference devices 276a and 276b such as the liquid crystal shutter are alternately performed. This prevents the light receiving element and light source from being adversely affected by jumping into the length gauge.
If a workpiece exists between the non-interfering devices 276a and 276b, the measurement is performed alternately on the right path and the left path in the figure.
[0071]
Next, as shown in FIG. 4, the measured object 218 whose dimension is to be determined is inserted on the optical axis, and the dimension L between two opposing planes of the measured object 218 is determined.
In this case as well, similarly to the case of the standard sample 280 that has been priced in advance, the distance information L is obtained by time-division measurement using the two systems of interferometers 212a and 212b.₃, L₄Have gained.
That is, the first measurement light 222a from the interferometer 212a enters the non-interferometer 276a.
[0072]
Here, when the non-interfering device 276a is in the open state and the non-interfering device 276b is in the closed state, the first measurement light 222a passes through the non-interfering device 276a, and the right end face 218a of the object as the reflection surface to be measured. Is incident on. The reflected light from the right end face 218a of the measured object passes through the non-interfering device 276a and enters the interferometer 212a. In the interferometer 212a, distance information L from the right end face 218a of the object as the reflection surface to be measured is obtained.₃Is measured.
[0073]
On the other hand, when the non-interference device 276a is in the closed state and the non-interference device 276b is in the open state, when the second measurement light 222b from the interferometer 212b enters the non-interference device 276b, the second measurement light 222b Passes through the non-interfering device 276b, is incident on the left end surface 218b of the DUT as a reflection surface to be measured, and is reflected. The reflected light from the left end face 218b of the measured object passes through the non-interfering device 276b and is incident on the interferometer 212b. In the interferometer 212b, distance information L from the left end face 218b of the object as the reflection surface to be measured is provided.₄Is required.
[0074]
As described above, the present embodiment uses the light emitting unit that emits a plurality of types of coherent light beams having different wavelengths, similarly to the first embodiment, and performs multi-wavelength interference that can perform displacement measurement at a distance equal to or longer than each measurement wavelength. It has two length measuring systems. Then, two measurement lights are time-divisionally incident on two opposing parallel end faces of the object to be measured, respectively.
Here, in the present embodiment, as the displacement information of each of the reflection surfaces to be measured, which can be measured by the multi-wavelength interferometer, on the right side path, the right end face of the standard sample that is pre-valued and the measurement target The difference in distance from the right end surface of the object is used. The left path uses the difference in distance between the left end face of the standard sample and the left end face of the measured object for which the dimension L is to be obtained, which is determined in advance.
[0075]
As a result, in the present embodiment, similarly to the first embodiment, the distance difference exceeding the optical wavelength can be measured in a non-contact manner using an interferometer including a multi-wavelength interferometer capable of measuring a displacement amount. I can do it.
Also, in the present embodiment, as in the first embodiment, by measuring from the facing direction to the object to be measured, dimension measurement can be performed completely without contact, and a mechanical movable element is required. Therefore, high-speed and high-precision dimension measurement can be performed.
[0076]
In the present embodiment, even if there is surface reflected light (return light) at the shutter (non-interfering device), it is equivalent to having a work in a full space, which is a factor of causing an offset error. Since it is a fixed value, it can be easily corrected. Therefore, in the present embodiment, the surface reflected light from the shutter (non-interfering device) does not affect the measurement.
In the present embodiment, the distance difference X measured by the interferometer 212a as described above is used.₁, The distance difference X measured by the interferometer 212b₂, And the dimension L of the DUT (standard sample) 280 that has been pre-valued_SAccordingly, the dimension L between the right end surface 218a and the left end surface 218b of the device under test 218 is obtained by the above equation (7).
[0077]
As described above, the present embodiment employs the zero offset arrangement of the measurement light between the reference positions, the time-division projection of the measurement light by a non-interference device such as one light emitting unit, and a liquid crystal shutter.
As a result, the present embodiment operates the two non-interfering devices alternately, so that when measuring the absolute value between the reference positions using the multi-wavelength interferometer as in the first embodiment, the projection light on both sides is used. And complicated interference by reflected light can be avoided.
Further, in this embodiment, as in the first embodiment, the relative displacement in the optical axis direction is equal to the distance difference X regardless of the position of the object to be measured on the optical axis.₁And distance difference X₂Since the sum is canceled, the same value can be measured.
[0078]
As described above, also in this embodiment, very stable dimension measurement can be performed with respect to relative translational vibration between the object to be measured and the measuring device. It is effective for
In this embodiment, it is possible to provide one light emitting means for each interferometer, that is, to use two light emitting means for the entire apparatus. However, in order to greatly reduce the cost, two light emitting means are required. It is also preferable to use a common light emitting means in the interferometer of the above, that is, to use one light emitting means in the entire apparatus.
[0079]
In the present embodiment, the measurement of the object 218 whose dimensions are to be obtained and the standard sample 280 pre-valued can be performed in order for each measurement of the object 218. For this purpose, for example, after measuring the standard sample 280 that has been priced in advance, the measurement of a plurality of objects 218 whose dimensions are to be obtained may be performed.
Also in the present embodiment, in order to largely eliminate the influence on the measurement amount due to the translational movement of the measuring light parallel to the optical axis direction of the measuring object, the distance difference X₁Measurement and distance difference X₂It is preferable to perform the measurement at high speed by switching.
[0080]
In the present embodiment, the example in which the liquid crystal shutter is used as the non-interfering device has been described. However, an acousto-optic device (AOM) or a galvanometer mirror may be used instead of the liquid crystal shutter. It is particularly suitable as a non-interfering device for the device.
FIG. 5 shows a schematic configuration of a dimension measuring device using an acousto-optical element as a non-interfering device. The portions corresponding to those in the second embodiment are denoted by reference numeral 100, and description thereof is omitted.
The non-interfering devices (non-interfering means) 376a and 376b shown in FIG.
[0081]
Here, the acousto-optic element shields or absorbs the generated zero-order light on the output side of the acousto-optic element. In the figure, if no operation is performed when it is desired to block the measurement light, nothing is output. However, when the measurement light is to be passed, a high-frequency voltage is supplied to the acousto-optic elements 276a and 276b by the drivers 278a and 278b, and the primary Since light is output, the primary light may be used for dimension measurement.
That is, when the non-interfering device 376a outputs the measurement light 322a from the interferometer 312a to the reflection surface to be measured, and outputs the reflected light of the measurement light from the reflection surface to be measured to the interferometer 312a. The non-interference device 376b blocks light, that is, outputs no light, and measures the reflection surface to be measured by the interferometer 312a.
[0082]
On the other hand, when the non-interfering device 376a blocks light, that is, outputs no light, the non-interfering device 376b outputs the measuring light 322b from the interferometer 312b to the reflection surface to be measured, and outputs the measuring light 322b. The reflected light from the inspection and reflection surface is output to the interferometer 312b, and the measurement of the reflection surface to be measured is performed by the interferometer 312b.
As described above, in the present embodiment, the modulation and non-modulation by the non-interference devices 376a and 376b are performed alternately (time division), so that the measurement by the interference length meter 312a and the measurement by the interference length meter 312b are alternately (time division). Therefore, the same effect as that of the liquid crystal shutter can be obtained.
[0083]
FIG. 6 shows a schematic configuration of a dimension measuring device using a galvanometer mirror as a non-interfering device. The portions corresponding to those in the second embodiment are denoted by reference numeral 200, and description thereof is omitted.
The non-interfering devices (non-interfering means) 476a and 476b shown in the figure are constituted by galvanomirrors that mechanically change the optical path of the measurement light.
[0084]
Here, the galvanomirror changes the optical path of the measurement light by its tilt. When the galvanomirror is tilted at an angle such that an optical path does not allow one of the measurement lights to enter the other interferometer when it is desired to block the measurement light, the measurement light does not enter the other interferometer. When it is desired to pass through the object to be measured, the dimension can be measured by tilting the galvanomirror at an angle that forms an optical path such that the measuring light enters the interferometer.
Thus, even if the switching between the passage of the measuring light and the shielding is performed by tilting the galvanomirror, the same effects as those of the liquid crystal shutter and the acousto-optic device can be obtained.
[0085]
【The invention's effect】
As described above, according to the dimension measuring apparatus of the present invention, the first interferometer and the second interferometer comprising the multi-wavelength interferometer are arranged at a predetermined distance from each other, and An optical axis of the first measurement light from the first interferometer and an optical axis of the second measurement light from the second interferometer between the mirrors; The optical axis was offset and the simultaneous measurement was performed.
As a result, the present invention can prevent erroneous operation of the interferometer when no object is present, so that dimensional measurement using a multi-wavelength interferometer can be performed satisfactorily.
Further, according to the dimension measuring apparatus according to the present invention, the first and second interferometers comprising the multi-wavelength interferometer and the optical axis coincident with the length measurement axis of the object to be measured. And a first non-interfering means and a second non-interfering means arranged at a predetermined separation distance, and the non-interfering means are operated alternately.
As a result, the present invention can prevent erroneous operation of the interferometer when no object is present, so that dimensional measurement using a multi-wavelength interferometer can be performed satisfactorily.
Further, in the present invention, by using a shutter, an acousto-optic device or a mirror as the non-interfering means, the dimensional measurement using the multi-wavelength interferometer can be performed more favorably.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a schematic configuration of a dimension measuring device according to a first embodiment of the present invention.
FIG. 2 is an explanatory view of the operation of the dimension measuring device shown in FIG.
FIG. 3 is an explanatory diagram of a schematic configuration of a dimension measuring device according to a second embodiment of the present invention.
FIG. 4 is an explanatory view of the operation of the dimension measuring device shown in FIG.
FIG. 5
FIG. 6 is a modification of the non-interfering device of the dimension measuring device shown in FIG.
FIG. 7 is an explanatory diagram of a general dimension measuring method using a general dimension measuring device.
FIG. 8 is an example of a multi-wavelength interferometer used for the dimension measuring device of the present embodiment.
[Explanation of symbols]
110,210 mm dimension measuring device
112a, 212a interferometer (first interferometer)
112b, 212b Interferometer (second interferometer)
118,218 DUT
160 mirror (first mirror)
162 mirror (second mirror)
276a Non-interference device (first non-interference means)
276b non-interference device (second non-interference means)
280 ° standard sample

Claims

A dimension measuring apparatus that measures a dimension L between opposed first end faces and a second end face of an object to be measured using a multi-wavelength interferometer,
A reference light based on a part of a plurality of types of coherent lights having different wavelengths and a reflected light obtained by allowing the rest of the coherent light to be incident on a reflection surface to be measured as measurement light to obtain an interference light, Based on the interference signal at the measurement wavelength, the first interferometer and the second interferometer that measure the displacement of the test reflection surface exceeding the individual measurement wavelength,
The optical axis of the first measurement light from the first interferometer and the optical axis of the second measurement light from the second interferometer are displaced in parallel so that they do not overlap, and have a predetermined separation distance X. _A first mirror and a second mirror arranged at ₃
The first interference measurement means, the object to be measured does not exist between the mirrors, the first measurement light from the first interference measurement means reflected by the second mirror of the second mirror a distance information L _1, the distance information L ₃ of該被measured first end surface when the object to be measured between the mirror is existent said first measurement light is reflected by the first end surface of the該被measured the distance difference _{X 1} is measured,
The distance information L of the first mirror when the object to be measured does not exist between the mirrors and the second measurement light from the second interference length measuring means is reflected by the first mirror by the second interference measuring means. _2, the distance difference X between the distance information L ₄ of該被measured second end surface when the object to be measured and the presence and said second measured light is reflected by the second end surface of the該被measured between the mirror Measure ₂ and
Than distance X ₃ between said first interferometer unit distance difference X ₁ measured by the _first mirror and a second mirror which is defined by the distance difference X _2, and previously measured by the second interferometer unit A dimension measuring device for determining a dimension L between the first and second end faces of the object to be measured, which is opposite to each other, by Equation 1.

The dimension measuring device according to claim 1,
At the portion of the first mirror located on the optical axis of the first measurement light, a first light passage hole for passing the first measurement light is provided,
When the object to be measured does not exist between the mirrors, the first measurement light from the first interferometer having passed through the first light passage hole of the first mirror is reflected and returned to the first light passage hole. So that the mirror surface of the second mirror is located on the optical axis of the first measurement light,
At the portion of the second mirror located on the optical axis of the second measurement light, a second light passage hole for passing the second measurement light is provided,
When the object to be measured does not exist between the mirrors, the second measurement light from the second interferometer having passed through the second light passage hole of the second mirror is reflected and returned to the second light passage hole. A dimension measuring device, wherein the mirror surface of the first mirror is positioned on the optical axis of the second measurement light so as to emit light.

A dimension measuring apparatus that measures a dimension L between opposed first end faces and a second end face of an object to be measured using a multi-wavelength interferometer,
A reference light based on a part of a plurality of types of coherent lights having different wavelengths and a reflected light obtained by allowing the rest of the coherent light to be incident on a reflection surface to be measured as measurement light to obtain an interference light, Based on the interference signal at the measurement wavelength, the first interferometer and the second interferometer that measure the displacement of the test reflection surface exceeding the individual measurement wavelength,
A first non-interfering means having an optical axis coinciding with the length measuring axis of the object to be measured, and arranged at a predetermined distance, alternately passing measurement light and blocking measurement light; and When the measurement light passes through the non-interference means, the measurement light is shielded and when the measurement light is shielded by the first non-interference means, the measurement light passes when the measurement light passes through the first non-interference means. A second non-interfering means alternately performed in synchronization with the switching,
Wherein the first interferometer has a standard sample having a known size L _S between the non-interferers, and the first measurement light from the first interferometer measures the first end face of the standard sample. The distance information L1 of the _first end face of the standard sample at the time of reflection and the object to be measured are present between the non-interfering means, and the first measurement light is reflected at the first end face of the object to be measured. the distance difference X ₁ between the distance information L ₃ of該被measured first end surface and measurements,
By the second interferometer, the standard sample is present between the non-interferometers, and the standard when the second measurement light from the second interferometer is reflected by the second end face of the standard sample a distance information L ₂ samples the second end surface, the measurement object is present between the non-interference unit,該被measured second end surface when said second measuring beam was reflected by the second end surface of the該被measured the distance difference _{X 2} between the distance information _{L 4} of measure,
From the distance difference X ₁ measured by the first interferometer, the distance difference X ₂ measured by the second interferometer, and the dimension L _{S of the} standard sample previously determined, A dimension measuring device, wherein a dimension L between a first end face and a second end face facing each other is obtained by Expression 2.

The dimension measuring device according to claim 3,
The non-interfering means is a shutter,
Driving means for opening and closing the shutter,
A dimension measuring device, wherein switching between passing and blocking of the measurement light is performed by opening and closing the shutter by the driving unit.

The dimension measuring device according to claim 3,
The non-interfering means is an acousto-optic element,
Modulation of the acousto-optic element, comprising a driving means for non-modulation,
A dimension measuring apparatus characterized in that switching between passing and blocking of the measurement light is performed by modulation and non-modulation of the acousto-optic element by the driving unit.

The dimension measuring device according to claim 3,
The non-interfering means is a mirror that changes an optical path by tilting a mirror surface,
A dimension measuring apparatus characterized in that the path of the measurement light is switched or shielded by changing the optical path of the measurement light by tilting the mirror by the driving unit.

The dimension measuring device according to any one of claims 1 to 6,
Dimension measuring apparatus and carrying out the measurement of the distance difference X ₁ by the first interferometer unit, the measurement of the distance difference X ₂ by the second interferometer unit simultaneously.