JP3604944B2

JP3604944B2 - Three-dimensional shape measuring machine and its measuring method

Info

Publication number: JP3604944B2
Application number: JP07125499A
Authority: JP
Inventors: 誠一神谷
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1999-03-17
Filing date: 1999-03-17
Publication date: 2004-12-22
Anticipated expiration: 2019-03-17
Also published as: JP2000266524A

Description

【０００１】
【発明の属する技術分野】
本発明は、光学部品や金型などの物体表面形状を高精度に測定する３次元形状測定機およびその測定方法に関するものである。
【０００２】
【従来の技術】
光学部品や金型などの物体表面形状を高精度に測定する方法として、３次元形状測定機の利用が広く知られている。一般に３次元形状測定機は接触型もしくは非接触型のプローブを被測定物に近づけ、両者がほぼ一定の距離もしくは一定の力関係になるようプローブ位置を制御させた上で被測定物上をスキャンさせて形状測定を行なうものである。
【０００３】
この種の測定機としては、特開平０９−３１１０２４号公報や特開平０４−２９９２０６号公報等に記載された形状測定機が知られており、従来の形状測定機の一例としては、例えば図９に図示するような構成を備えている。同図において、１０１は図示しない支持台に固定された被測定物、１０３はＸステージであり、その上にＺステージ１０４が搭載され、Ｚステージ１０４上に変位計１０２が配置されている。すなわち、変位計１０２はＸ−Ｚ軸方向への移動が可能となっている。また、Ｚステージ１０４上にはＺ軸用レーザ測長器１０９ｃおよびＸ軸用レーザ測長器１０９ｇが配置されており、位置固定のＺ基準ミラー１０５およびＸ基準ミラー１０６とそれぞれのレーザ測長器１０９ｃ，１０９ｇ間の距離を検出して、変位計１０２のＺ軸座標位置およびＸ軸座標位置を測定している。ここではＸステージ１０３およびＺステージ１０４の移動時に発生するピッチング成分やヨーイング成分の影響によるアッベ誤差を排除するように、それぞれのレーザ測長器の測長光路の中心軸が、変位計１０２の測定点を通り、それぞれのステージの移動軸と平行になるように取り付けられている。被測定物１０１に変位計１０４を近づけ、両者間の距離が０．５μｍ以内になるようサーボをかけた状態でのＸおよびＺ軸座標位置を測定する。これによりＸ軸座標位置Ｘ１でのＺ軸座標位置Ｚ１が求められたことになる。次に、Ｘステージ１０３を動かして変位計１０２をＸ軸方向に移動させ、同様にＸ２，Ｚ２を測定する。このように変位計１０２を被測定物１０１に沿って動かすことによりＸ断面形状が求められる。
【０００４】
また、従来の他の形状測定機としては、図１０に図示するように構成されたものがある。同図において、２０３はＸステージであり、その上にＹステージ２０８、さらにその上にＺステージ２０４が搭載されており、Ｘ−Ｙ−Ｚ軸に対してそれぞれ垂直な平面、すなわち、ＹＺ面、ＸＺ面、ＸＹ面上にそれぞれＸ基準ミラー２０６、Ｙ基準ミラー２０７、Ｚ基準ミラー２０５が配置されている。Ｚステージ２０４上には被測定物２０１とＺステージ２０４上の特定点の距離Ｚ１を検出するプローブ２０２、Ｚステージ２０４上の特定点と位置固定のＺ基準ミラー２０５の距離Ｚ２を検出する測定手段２０９ｃ、Ｚステージ２０４上の特定点と位置固定のＸ基準ミラー２０６の距離Ｘを検出する測定手段２０９ｇ、Ｚステージ２０４上の特定点と位置固定のＹ基準ミラー２０７の距離Ｙを検出する測定手段２０９ｉ（なお、測定手段２０９ｉは図１０には影となるために図示されていない。）が配置されている。したがって、Ｚステージ２０４上に配置したプローブ２０２はＸ−Ｙ−Ｚ軸方向への移動が可能であり、また、その時の３次元座標は、（Ｘ，Ｙ，Ｚ１とＺ２とから算出したＺ）とすることができる。このように、プローブ２０２を被測定物２０１の全面に走査させ、その時の３次元座標を検出することで、被測定物の３次元形状を測定できることになる。
【０００５】
【発明が解決しようとする課題】
ところで、図９に図示するような形状測定機では、被測定物のＸ−Ｚ断面形状についてアッベ誤差を考慮した構成となっており、高精度測定が期待できるけれども、被測定物あるいは光プローブをＹ軸方向に移動させる手段が備えられていないため、被測定物の３次元形状の測定ができないという問題点がある。
【０００６】
図１０に図示するような３次元形状測定機では、次のような問題点があげられる。すなわち、Ｘ−Ｙ−Ｚ軸に対してそれぞれ垂直なＹＺ面、ＸＺ面、ＸＹ面上に基準ミラーを各々配置しているが、これらの基準ミラーは通常２次元上にλ／１０〜λ／２０程度の平面度をもつ基準面が必要となるため、製作方法や製作日数、コスト面などの影響により、大型なものを製作することは困難であった。したがって、被測定物の測定範囲が制約を受けることになる。さらに、プローブはＸもしくはＹ断面上を移動させることにより、例えば軸対象レンズ等はＸ−Ｚ面もしくはＹ−Ｚ面において、Ｘ方向もしくはＹ方向の変化に対してＺ方向の変化が大きい測定物は、プローブの移動速度が上げられず、測定時間が長くなってしまう。また、図９に図示する形状測定機において、Ｙステージを付設し変位計をＸ−Ｙ−Ｚ軸方向に移動可能にするとしても、同様の問題点がある。
【０００７】
そこで、本発明は、上記のような従来技術の有する未解決の課題に鑑みてなされたものであって、被測定物の３次元形状を高精度にかつ短時間で測定することが可能な３次元形状測定機および３次元形状測定方法を提供することを目的とするものである。
【０００８】
【課題を解決するための手段】
上記目的を達成するため、本発明の３次元形状測定機は、被測定物の形状に沿って走査するプローブを用いて被測定物の３次元形状を測定する３次元形状測定機において、
被測定物を支持しかつ該被測定物に垂直方向となるＺ軸方向に対しての回転成分となるθ軸方向に移動可能に設けられたθステージと、前記プローブを前記被測定物に対して水平方向となるＲ軸方向に移動させるＲステージと、前記プローブを前記被測定物に対して垂直方向となるＺ軸方向に移動させるＺステージと、前記Ｒステージおよび前記ＺステージからなるＲ−Ｚステージ上に配設された前記プローブとを備えており、前記プローブの被測定物に対する３次元座標位置におけるＺ軸方向の位置を検出する、前記Ｒ−Ｚステージ上に配設された前記プローブのＺ軸方向の位置を検出するレーザ測長器、およびＲ軸に対して平行でかつＺ軸上を通る位置に配置されたＺ基準ミラーを含む計測系と、前記プローブの被測定物に対する３次元座標位置におけるＲ軸方向の位置を検出する、前記Ｒ−Ｚステージ上に配設された前記プローブのＲ軸方向の位置を検出するレーザ測長器、およびＺ軸に対して平行でかつＲ軸上を通る位置に配置されたＲ基準ミラーを含む計測系と、前記θステージのＺ軸方向の位置を検出する、前記Ｒ−Ｚステージ上とは異なる位置に配置された前記θステージのＺ軸方向の位置を検出するレーザ測長器、および前記Ｚ基準ミラーを含む計測系と、前記θステージのＲ軸方向の位置を検出する、前記Ｒ−Ｚステージ上とは異なる位置に配置された前記θステージのＲ軸方向の位置を検出するレーザ測長器、および前記Ｒ基準ミラーを含む計測系と、前記θステージのθ軸方向の位置を検出する角度検出手段とを有することを特徴とする。
【０００９】
本発明の３次元形状測定機においては、前記プローブを、前記被測定物との距離が常に一定となるようにＺ軸方向に移動させながら前記被測定物の形状に沿って走査することで、前記被測定物に対する前記プローブの３次元座標位置Ｒ，θ，Ｚを同時に検出し、該３次元座標位置Ｒ，θ，Ｚを基にして前記被測定物の形状測定を行うことが好ましい。
【００１０】
本発明の３次元形状測定機においては、前記θステージはエアーベアリングによって構成され、該エアーベアリングのロータ部にはラジアル方向およびスラスト方向にθ基準ミラーを一体化して取り付けられていることが好ましい。
【００１１】
そして、本発明の３次元形状測定方法は、被測定物の形状に沿って走査するプローブを前記被測定物の水平方向となるＲ軸方向へ、前記被測定物を前記被測定物の垂直方向となるＺ軸方向に対しての回転成分となるθ軸方向へ、同時にあるいは各々単独で移動させ、該移動時に前記プローブを前記被測定物との距離が常に一定となるように移動させながら前記被測定物の形状に沿って全面を走査し、前記被測定物に対する前記プローブの３次元座標位置Ｒ，Ｚ，θを同時に検出し、前記３次元座標位置Ｒ，Ｚ，θを基に前記被測定物の３次元形状を測定する３次元形状測定方法において、前記被測定物に対する前記プローブの３次元座標位置Ｒは、同一のＲ−Ｚ面内において異なる２か所の位置Ｐ１，Ｐ２においてそれぞれ検出されるＲ座標Ｒ１，Ｒ２と、前記両位置Ｐ１，Ｐ２の中間および前記プローブ先端と前記被測定物との交点におけるＺ方向成分の距離Ｄ１と、前記両位置Ｐ１，Ｐ２の間のＺ方向成分の距離Ｄ２とからアッベ誤差を考慮して算出される前記プローブのＲ軸方向の座標位置を、前記被測定物のＲ軸方向の座標位置から算出される前記被測定物をθ軸方向に回転させる際に発生するラジアル方向の軸ぶれ量により補正することで算出し、前記被測定物に対する前記プローブの３次元座標位置Ｚは、同一のＲ−Ｚ面内において異なる２か所の位置Ｐ３，Ｐ４においてそれぞれ検出されるＺ座標Ｚ１，Ｚ２と、前記両位置Ｐ３，Ｐ４の中間および前記プローブ先端と前記被測定物との交点におけるＲ方向成分の距離Ｄ３と、前記両位置Ｐ３，Ｐ４の間のＲ方向成分の距離Ｄ４とからアッベ誤差を考慮して算出される前記プローブのＺ軸方向の座標位置を、前記被測定物のＺ軸方向の座標位置から算出される前記被測定物をθ軸方向に回転させる際に発生するスラスト方向の面ぶれ量により補正することで算出し、前記被測定物に対する前記プローブの３次元座標位置θは、前記被測定物のθ軸方向の座標位置により算出することを特徴とする。
【００１２】
本発明の３次元形状測定方法においては、前記被測定物に対する前記プローブの３次元座標位置Ｒは、同一のＲ−Ｚ面内において異なる２か所の位置Ｐ１，Ｐ２においてそれぞれ検出されるＲ座標Ｒ１，Ｒ２と、前記両位置Ｐ１，Ｐ２の中間および前記プローブ先端と前記被測定物との交点におけるＺ方向成分の距離Ｄ１と、前記両位置Ｐ１，Ｐ２の間のＺ方向成分の距離Ｄ２とからアッベ誤差を考慮して算出される前記プローブのＲ軸方向の座標位置を、前記被測定物のＲ軸方向の座標位置から算出される前記被測定物をθ軸方向に回転させる際に発生するラジアル方向の軸ぶれ量により補正することで算出し、前記被測定物に対する前記プローブの３次元座標位置Ｚは、同一のＲ−Ｚ面内において異なる２か所の位置Ｐ３，Ｐ４においてそれぞれ検出されるＺ座標Ｚ１，Ｚ２と、前記両位置Ｐ３，Ｐ４の中間および前記プローブ先端と前記被測定物との交点におけるＲ方向成分の距離Ｄ３と、前記両位置Ｐ３，Ｐ４の間のＲ方向成分の距離Ｄ４とからアッベ誤差を考慮して算出される前記プローブのＺ軸方向の座標位置を、前記被測定物のＺ軸方向の座標位置から算出される前記被測定物をθ軸方向に回転させる際に発生するスラスト方向の面ぶれ量により補正することで算出することが好ましい。
【００１４】
本発明の３次元形状測定方法においては、前記被測定物が軸対象形状である場合、前記被測定物の軸と前記θ軸方向の回転軸となるＺ軸とをほぼ一致させるように合わせ込みを行なった後に形状測定を実施することが好ましい。
【００１５】
【作用】
本発明によれば、座標軸をＲ−θ−Ｚ系として、被測定物に対して平行に移動するＲステージ、被測定物の垂直方向に移動するＺステージ、Ｚ方向を回転軸とするすなわち被測定物の垂直方向を回転軸とするθステージとから構成し、被測定物の形状をＲ−Ｚ面内における２次元上で形状測定を行なうことにより、光プローブ位置検出手段となるレーザ測長器に使用されるＲ基準ミラーおよびＺ基準ミラーは、ほぼ１次元上（一直線上）の範囲のみ使用されることになるので、基準ミラーの幅を小さくでき、このため製作が容易になるとともに基準ミラーの平面度の向上が期待できる。
【００１６】
そして、位置検出手段における測定誤差はＲ−Ｚ面内の２次元上についてのみ考慮すればよく、ステージのピッチング成分誤差は測長補正するものの、ヨーイングおよびローリング成分は影響度がかなり小さくなるので補正項目を少なくでき、測定誤差を減少させることができる。また、被測定物の形状が軸対象の場合、被測定物の軸とθステージの回転軸をほぼ一致させて被測定物を回転させると、被測定物の同一半径上の形状はほぼ一定となるので、プローブ等の測定位置検出手段の走査スピードを早くでき、測定時間の短縮を図ることができる。
【００１７】
以上のように、本発明によれば、被測定物の３次元形状を高精度にかつ短時間で測定することが可能となる。
【００１８】
【発明の実施の形態】
本発明の実施の形態を図面に基づいて説明する。
【００１９】
図１は、本発明の３次元形状測定機の要部を概略的に示す斜視図であり、図２は、本発明の３次元形状測定機の要部の概略的な側面図であり、図３は、本発明の３次元測定機におけるＲ−Ｚ面上の光プローブおよびレーザ測長器の配置関係を示す配置構成図である。
【００２０】
図１および図２において、１はθステージ７に載置される軸対象の非球面レンズ等の被測定物であり、２は被測定物１の形状に沿って走査するプローブであり、本実施例ではレンズ等に傷を付けない非接触の光プローブとしているが、接触式のプローブを用いることも可能である。３は被測定物１に対して平行に移動するＲステージ、４は被測定物１の垂直方向に移動するＺステージである。したがって、Ｒステージ３およびＺステージ４上に配設される光プローブ２は、Ｒ−Ｚ方向に移動可能な構成である。５はＲ軸に対して平行でかつＺ軸上を通る位置に配置したＺ基準ミラー、６はＺ軸に対して平行でかつＲ軸上を通る位置に配置したＲ基準ミラーである。７はθステージとなるエアーベアリング部であって、被測定物１をθ軸方向に回転させる手段であり、固定側のハウジング部７Ａと回転側のロータ部７Ｂとから構成される。ロータ部７Ｂ上にはθ基準ミラー１２ａ，１２ｂ（図３および図４も参照）が配置される。９は位置検出手段となるレーザ測長器であり、９ａ，９ｂはＺステージ４上でＺ方向に離間して配置されるＲ測定用のレーザ測長器、９ｃ，９ｄはＺステージ４上でＲ方向に離間して配置されるＺ測定用のレーザ測長器、９ｅ，９ｆ，９ｇ，９ｈはＲ−Ｚステージ３，４外に配置されるθ測定用のレーザ測長器である。１０は後述するスケール１１（図３および図４参照）のスケール検出部（ロータリエンコーダ）で、θステージ７の角度検出手段である。２９はＲステージ３およびＺステージ４を搭載する架台である。
【００２１】
図３にはＲ−Ｚ同一平面上における光プローブとその位置検出手段となるレーザ測長器の配置関係を示す配置構成図を図示し、ＲＤ１はレーザ測長器９ａとＲ基準ミラー６間の距離を示し、ＲＤ２はレーザ測長器９ｂとＲ基準ミラー６間の距離を示し、Ｒステージ３の移動量および移動時に発生する測定誤差補正に使用する。ＺＤ１はレーザ測長器９ｃとＺ基準ミラー５間の距離を示し、ＺＤ２はレーザ測長器９ｄとＺ基準ミラー５間の距離を示し、Ｚステージ４の移動量および移動時に発生する測定誤差補正に使用する。θＤ１，θＤ２はθステージ７のスラスト面に設けてあるθ基準ミラー１２ａとＺ基準ミラー５間の距離を示し、θステージ７のスラスト方向のぶれ量（面ぶれ）の検出に使用し、また、θＤ３，θＤ４はθステージ７のラジアル面に設けてあるθ基準ミラー１２ｂとＲ基準ミラー６ａ間の距離を示し、θステージ７のラジアル方向のぶれ量（軸ぶれ）の検出に使用する。このように、本発明においては、光プローブ２および光プローブ位置検出手段となるレーザ測長器９は全てＲ−Ｚ面の同一平面上に配置している。
【００２２】
なお、図３において、Ｄ１はレーザ測長器９ａ，９ｂの中間と光プローブ２のキャッツアイポイント間のＺ方向成分の距離、Ｄ２はレーザ測長器９ａ，９ｂ間のＺ方向成分の距離、Ｄ３はレーザ測長器９ｃ，９ｄの中間と光プローブ２の中心線までのＲ方向成分の距離、Ｄ４はレーザ測長器９ｃ，９ｄ間のＲ方向成分の距離、Ｄ５はレーザ測長器９ｅ，９ｆ間のＲ方向成分の距離を示す。
【００２３】
図４は、θステージであるエアーベアリング部の拡大図であり、θステージ７は、固定側のハウジング部７Ａと回転側のロータ部７Ｂとから構成され、そのロータ部７Ｂの表面の一部には、精密加工後にアルミ蒸着と研磨によりθ基準ミラーを作製し、スラスト方向のθ基準ミラーを１２ａ、ラジアル方向のθ基準ミラーを１２ｂとする。また、ラジアル方向にはスケール１１が貼り付けられており、スケール検出部１０を用いてθステージ７の角度を検出することができる。
【００２４】
図５には、光プローブの詳細な構成を示し、同図において、１３は偏光方向が互いに直交する２つの光波を作り出すレーザ光源であり、レーザ光源１３から出射した光束は、ビームエキスパンダ１４で光束を拡大された後、偏光ビームスプリッタ１５ａで反射光波と透過光波に分けられる。反射光波はλ／４板１６ａを通ることで直線偏光から円偏光へ変わり、集光レンズ２０ａを介して被測定物１へ入射する。ここでは集光レンズにより光束が焦点に絞られた状態（キャッツアイポイント）で被測定物１に入射し、測定光波となって反射させている。この測定光波は、照射した光束のエリアにおける、被測定物１のＺ方向の面情報を持つことになる。反射した測定光波は元の光路を戻り、再び通るλ／４板１６ａで往きと比べて９０°回転した直線偏光となって、偏光ビームスプリッタ１５ａで今度は透過することになる。もう一方の透過光波は、λ／４板１６ｂを通って直線偏光から円偏光へ変わって参照平面ミラー１７に入射し、参照光波となって反射する。反射した参照光波は、再び通るλ／４板１６ｂで往きと比べて９０°回転した直線偏光となり、偏光ビームスプリッタ１５ａで今度は反射することになる。偏光ビームスプリッタ１５ａで測定光波と参照光波が重なり合い、４５°方位の偏光板１８を通ることで干渉光波となる。この干渉光波はビームスプリッタ１５ｂで２分割され、そのまま透過した干渉光波はラインセンサ１９で検出されることになる。ラインセンサ１９は通常数十〜数千チャンネル数を持つが、ここでは高周波数対応の数十チャンネルのものを使用する。また、複数のラインセンサのチャンネルから１チャンネルを選び出して測定信号とする際の選択条件は、測定点上での被測定物の設計形状から傾斜角を算出し、被測定物に対して法線方向すなわち正反射する光束の光線追跡により、その光束がラインセンサ上のどのチャンネルに取り込まれるかあらかじめ算出して記憶しておき、測定位置によって使用するチャンネルをマルチプレクサによって選択することになる。また、ビームスプリッタ１５ｂで反射した干渉光波は集光レンズ２０ｂを介してフォトディテクタ２１で取り込み、参照信号となる。
【００２５】
図６はＺ軸サーボの構成を示す構成図であり、光プローブ２からの光束がキャッツアイポイントで被測定物１に入射するようにＺステージ４を移動させる。その状態における干渉光波から検出した測定信号および参照信号は、位相計３０に入力されてその位相差を算出し、コンピュータ３１に記憶するとサーボロックが開始状態となる。次に、Ｒステージ３やθステージ７を同時にもしくは単独で移動させ、そのとき得られる位相差と記憶させている位相差を比較し、Ｚサーボコントローラ３２では常にその偏差がゼロとなるようにＺステージ４を移動させる（サーボロック状態）。これにより被測定物１と光プローブ２間の距離を常に一定に保つことが可能となる。
【００２６】
図７の（ａ）および（ｂ）にレーザ測長器の構成を示し、図７の（ａ）はレーザ測長器９ａ，９ｂ，９ｃ，９ｄの構成図であり、レーザ測長器と１つの基準ミラー間の距離を測定する。図７の（ｂ）はレーザ測長器９ｅ，９ｆ，９ｇ，９ｈの構成図であり、２つの基準ミラー間の距離を測定する。ここではともに、測定したい光路を２往復させるダブルパス方式としているため、レーザ測長器の測定分解能は２倍となる。図７の（ａ）において、１３は偏光方向が互いに直交する２つの光波を作り出すレーザ光源である。レーザ光源１３から出射した光束は、偏光ビームスプリッタ１５ｃで反射光波と透過光波に分けられる。透過光波はコーナーキューブ２２ａで２度反射して参照光波となり、再び偏光ビームスプリッタ１５ｃを透過することになる。一方の反射光波は、λ／４板１６ｃを通ることで直線偏光から円偏光へ変わり、基準ミラー５，６（例えばＺ基準ミラー５等）で反射して測定光波となる。測定光波は元の光路を戻り、再び通るλ／４板１６ｃで往きと比べて９０°回転した直線偏光となって、偏光ビームスプリッタ１５ｃで今度は透過し、コーナーキューブ２２ｂで２度反射して再び偏光ビームスプリッタ１５ｃおよびλ／４板１６ｃを通り、基準ミラー５，６に戻ってくる。再度反射した測定光波は、λ／４板１６ｃで往きと比べて９０°回転した直線偏光となって、偏光ビームスプリッタ１５ｃで反射することになる。ここで測定光波と参照光波が重なり、偏光板１８を通過すると干渉光波となり、測長器レシーバ２８で検出される。測定光波と参照光波の位相差の変動は、干渉光波の縞のカウントとして測長器で観測される。参照光波の光路長は常に一定となっているため、ここでは干渉光波の縞のカウントから測定光波の光路長の変動、すなわちここでは各基準ミラーからの各ステージ移動量の２往復分が検出できる。
同様に２つの基準ミラー間の距離を測定するレーザ測長器を図７の（ｂ）で説明する。同図において、レーザ光源１３から出射した直交する２つの光波は、偏光ビームスプリッタ１５ｃで反射光波と透過光波に分けられる。透過光波はコーナーキューブ２２ａで２度反射して参照光波となり、再び偏光ビームスプリッタ１５ｃを透過することになる。一方の反射光波は、λ／４板１６ｃを通ることで直線偏光から円偏光へ変わり、基準ミラー５，６（例えばＺ基準ミラー５等）で反射して測定光波となる。測定光波は元の光路を戻り、再び通るλ／４板１６ｃで往きと比べて９０°回転した直線偏光となって、偏光ビームスプリッタ１５ｃで今度は透過し、λ／４板１６ｄを通って、基準ミラー１２ａ，１２ｂ（例えばθ基準ミラー１２ａ等）で反射し元の光路を戻る。再びλ／４板１６ｃに入射した測定光波は、往きと比べて９０°回転した直線偏光となって、偏光ビームスプリッタ１５ｃで今度は反射してコーナーキューブ２２ａに入射する。測定光波はコーナーキューブ２２ａで２度反射して再び偏光ビームスプリッタ１５ｃに入射し、ここで反射する。この後、測定光波はλ／４板１６ｄを通って再び基準ミラー１２ａ，１２ｂ（例えばθ基準ミラー１２ａ等）で反射し、λ／４板１６ｄおよび偏光ビームスプリッタ１５ｃおよびλ／４板１６ｃを透過して、再度基準ミラー５，６（例えばＺ基準ミラー５等）に入射し、反射する。基準ミラーで反射した測定光波は、再度λ／４板１６ｃを通過することで往きと比べて９０°回転した直線偏光となって、偏光ビームスプリッタ１５ｃで今度は反射する。ここで測定光波と参照光波が重なり、偏光板１８を通過すると干渉光波となり、測長器レシーバ２８で検出される。測定光波と参照光波の位相差の変動は、干渉光波の縞のカウントとして測長器で観測される。参照光波の光路長は常に一定となっているため、ここでは干渉光波の縞のカウントから測定光波の光路長の変動、すなわちここでは２つの基準ミラー間の距離の変動量の２往復分が検出できる。
【００２７】
次に、以上のように構成された３次元形状測定機による具体的な測定方法について説明する。
【００２８】
被測定物である軸対象非球面レンズ１はその軸をθステージ７の回転軸とほぼ一致するようにθステージ７上にセッティングされる。これにより、被測定物側でのθ軸回転および光プローブ側でのＲ−Ｚ軸走査を組み合わせることで、光プローブ２を被測定物１の形状に合わせて全面に走査できることになる。光プローブ２をθ軸の回転中心に移動させ、その後にＺステージ４を下げて被測定物１に近づけていき、光プローブ２の光束が作り出すキャッツアイポイントが被測定物１に入射する状態でサーボロックを開始する。このときのレーザ測長器９ａ〜９ｈおよびロータリエンコーダ１０の出力値を取り込み、それぞれＲＤ１ｏ，ＲＤ２ｏ，ＺＤ１ｏ，ＺＤ２ｏ，θＤ１ｏ，θＤ２ｏ，θＤ３ｏ，θＤ４ｏ，ＲＥｏとしてコンピュータに記憶させておく。次に、サーボロック状態のまま、Ｒステージ３およびθステージ７を単独でもしくは同時に移動させ、測定したい点（ｉ＝１〜ｎ、ｉ：取込順）でレーザ測長器９ａ〜９ｈおよびロータリエンコーダ１０の出力値を同時に取り込み、それぞれＲＤ１ｉ，ＲＤ２ｉ，ＺＤ１ｉ，ＺＤ２ｉ，θＤ１ｉ，θＤ２ｉ，θＤ３ｉ，θＤ４ｉ，ＲＥｉとして記憶させておく。同様にして被測定物１の全面に光プローブ２を走査させてｎ組のデータを取り込み、例えば次に示すような演算処理を行なう。
【００２９】
【数１】

【００３０】
このような演算処理により、各測定点での３次元座標を高精度に算出することができる。したがって、ｎ組の３次元座標データを用いて、高精度な被測定物の３次元形状が表現できることになる。
【００３１】
図８には、本発明の３次元測定機によるＲ−θ断面上で見た３パターンのデータ取込み例を図示する。なお、図８における軸については、一般によく使われているＸ−Ｙ座標系に変換して示している。本発明では、Ｒステージおよびθステージを同時に動かしながらデータを等間隔で取り込めば、図８の（ａ）に示すような渦巻きデータとして検出することができ、また、Ｒステージもしくはθステージを単独で動かしながらデータを等間隔で取り込めば、図８の（ｂ）に示すような同心円データとして検出することができる。また、一般に３次元測定機等でよく用いられる格子データ（図８の（ｃ））は、Ｒステージおよびθステージの移動量を格子状に合わせるか、もしくは渦巻きデータや同心円データを座標変換や補間を用いて変換するといった方法により本発明でも対応可能である。
【００３２】
本発明では、被測定物の形状が軸対象の場合、渦巻きデータによってデータ検出を行なうと、θステージや微小なＲステージ移動に対して、サーボロック状態によって移動する光プローブのＺ方向移動量はきわめて小さくなるため、高速な光プローブ走査が可能となる。また、同心円データによってデータ検出を行なう場合は、Ｒステージ移動後にその状態を保持しておき、その後θステージを単独で動かしながらデータを等間隔で取り込むようにすれば、同様にθステージ移動に対してサーボロック状態によって移動する光プローブのＺ方向移動量はきわめて小さくなるため、高速な光プローブ走査が可能となる。
【００３３】
以上のように、本発明による３次元測定機および３次元測定方法において、被測定物をθステージに載置し、光プローブをＲステージおよびＺステージ上に設け、光プローブ位置検出手段はすべてをＲ−Ｚ面内に配置し、被測定物の形状をＲ−Ｚ面内における２次元上で形状測定を行なうことにより、光プローブ位置検出手段となるレーザ測長器に使用されるＲ基準ミラーおよびＺ基準ミラーは、ほぼ１次元上（一直線上）の範囲のみ使用されることになるので、基準ミラーの幅を小さくできる。このため製作が容易になるとともに基準ミラーの平面度の向上が期待できる。そして、位置検出手段における測定誤差はＲ−Ｚ面内の２次元上についてのみ考慮すればよい。すなわち、ステージのピッチング成分誤差は測長補正するものの、ヨーイングおよびローリング成分は影響度がかなり小さくなるので補正項目を少なくでき、測定誤差を減少させることができる。また、被測定物の形状が軸対象の場合、被測定物の軸とθステージの回転軸をほぼ一致させて被測定物を回転させると、被測定物の同一半径上の形状はほぼ一定となるので、プローブ等の測定位置検出手段の走査スピードを早くでき、測定時間の短縮を図ることができる。
【００３４】
【発明の効果】
以上説明したように、本発明によれば、３次元測定機において、被測定物をθステージに載置し、プローブをＲステージおよびＺステージ上に設け、プローブ位置検出手段はすべてをＲ−Ｚ面内に配置し、被測定物の形状をＲ−Ｚ面内における２次元上で形状測定を行なうことにより、以下のような作用効果を得ることができる。
【００３５】
１．光プローブ位置検出手段となるレーザ測長器に使用されるＲ基準ミラーおよびＺ基準ミラーは、ほぼ１次元上（一直線上）の範囲のみ使用されることになるので、基準ミラーの幅を小さくできる。このため製作が容易になるとともに基準ミラーの平面度の向上が期待できる。
【００３６】
２．位置検出手段における測定誤差はＲ−Ｚ面内の２次元上についてのみ考慮すればよい。すなわち、ステージのピッチング成分誤差は測長補正するものの、ヨーイングおよびローリング成分は影響度がかなり小さくなるので補正項目を少なくでき、測定誤差を減少させることができる。
【００３７】
３．被測定物の形状が軸対象の場合、被測定物の軸とθステージの回転軸をほぼ一致させて被測定物を回転させると、被測定物の同一半径上の形状はほぼ一定となるので、プローブ等の測定位置検出手段の走査スピードを早くでき、測定時間の短縮がはかれる。
【００３８】
したがって、本発明の３次元測定機および３次元測定方法によれば、被測定物の３次元形状を高精度にかつ短時間で測定することが可能となる。
【図面の簡単な説明】
【図１】本発明の３次元形状測定機の要部を概略的に示す要部概略図である。
【図２】本発明の３次元形状測定機の要部の概略的な側面図である。
【図３】本発明の３次元測定機におけるＲ−Ｚ面上の光プローブおよびレーザ測長器の配置関係を示す配置構成図である。
【図４】本発明の３次元測定機におけるθステージの一部を拡大して示す構成図である。
【図５】本発明の３次元測定機における光プローブの構成図である。
【図６】本発明の３次元測定機におけるＺ軸サーボの構成を示す構成図である。
【図７】本発明の３次元測定機におけるレーザ測長器の構成を示し、（ａ）はレーザ測長器と１つの基準ミラー間の距離を測定する際に使用するものであり、（ｂ）は２つの基準ミラー間の距離を測定する際に使用するものである。
【図８】本発明の３次元測定機によるデータ取り込み例を示し、（ａ）は渦巻きデータ、（ｂ）は同心円データ、（ｃ）は格子データである。
【図９】従来の形状測定機の一例を示す概略構成図である。
【図１０】従来の形状測定機の他の例を示す概略構成図である。
【符号の説明】
１被測定物（軸対象レンズ）
２光プローブ
３Ｒステージ
４Ｚステージ
５Ｚ基準ミラー
６Ｒ基準ミラー
７ θステージ（エアーベアリング部）
７Ａハウジング部
７Ｂロータ部
９（９ａ〜９ｈ）レーザ測長器
１０角度検出手段（ロータリエンコーダ）
１１スケール
１２ａ，１２ｂ θ基準ミラー
１３レーザ光源
１４ビームエキスパンダ
１５ａ，１５ｂ，１５ｃ偏光ビームスプリッタ
１６ａ，１６ｂ，１６ｃ，１６ｄ λ／４板
１７参照平面ミラー
１８偏光板
１９ラインセンサ
２０ａ，２０ｂ集光レンズ
２１フォトディテクタ
２２ａ，２２ｂコーナーキューブ
３０位相計
３１コンピュータ
３２Ｚサーボコントローラ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a three-dimensional shape measuring instrument for measuring the surface shape of an object such as an optical component or a mold with high accuracy, and a measuring method therefor.
[0002]
[Prior art]
As a method for measuring the surface shape of an object such as an optical component or a mold with high accuracy, use of a three-dimensional shape measuring machine is widely known. In general, a three-dimensional shape measuring machine scans a workpiece by bringing a contact or non-contact probe close to the workpiece and controlling the probe position so that both have a substantially constant distance or a constant force relationship. Then, the shape is measured.
[0003]
As a measuring instrument of this type, a shape measuring instrument described in JP-A-09-311024 and JP-A-04-299206 is known. As an example of a conventional shape measuring instrument, for example, FIG. The configuration shown in FIG. In the figure, reference numeral 101 denotes an object to be measured fixed to a support (not shown), 103 denotes an X stage, on which a Z stage 104 is mounted, and on which a displacement gauge 102 is disposed. That is, the displacement meter 102 can move in the XZ axis direction. Further, a Z-axis laser length measuring device 109c and an X-axis laser length measuring device 109g are arranged on the Z stage 104, and the fixed Z reference mirror 105 and the X reference mirror 106 and the respective laser length measuring devices are arranged. By detecting the distance between 109c and 109g, the Z-axis coordinate position and the X-axis coordinate position of the displacement meter 102 are measured. Here, in order to eliminate Abbe errors caused by the pitching component and the yawing component generated when the X stage 103 and the Z stage 104 move, the central axes of the length measuring optical paths of the respective laser length measuring devices are measured by the displacement meter 102. They are mounted so that they pass through points and are parallel to the movement axis of each stage. The displacement meter 104 is brought closer to the object to be measured 101, and the X and Z axis coordinate positions are measured with the servo applied so that the distance between the two is within 0.5 μm. Thus, the Z-axis coordinate position Z1 at the X-axis coordinate position X1 has been obtained. Next, the X stage 103 is moved to move the displacement meter 102 in the X-axis direction, and X2 and Z2 are measured in the same manner. By moving the displacement meter 102 along the measured object 101 in this manner, the X cross-sectional shape is obtained.
[0004]
As another conventional shape measuring device, there is a device configured as shown in FIG. In the figure, reference numeral 203 denotes an X stage, on which a Y stage 208 and a Z stage 204 are further mounted, and a plane perpendicular to the XYZ axes, that is, a YZ plane, An X reference mirror 206, a Y reference mirror 207, and a Z reference mirror 205 are disposed on the XZ plane and the XY plane, respectively. A probe 202 on the Z stage 204 for detecting a distance Z1 between the object 201 and a specific point on the Z stage 204, and a measuring means for detecting a distance Z2 between a specific point on the Z stage 204 and a fixed position Z reference mirror 205. 209c, measuring means 209g for detecting a distance X between a specific point on the Z stage 204 and the fixed position X reference mirror 206, and measuring means for detecting a distance Y between the specific point on the Z stage 204 and the fixed position Y reference mirror 207. 209i (the measuring means 209i is not shown in FIG. 10 because it is shaded). Therefore, the probe 202 arranged on the Z stage 204 can move in the XYZ axis directions, and the three-dimensional coordinates at that time are (Z calculated from X, Y, Z1 and Z2). It can be. As described above, by scanning the entire surface of the object 201 with the probe 202 and detecting the three-dimensional coordinates at that time, the three-dimensional shape of the object can be measured.
[0005]
[Problems to be solved by the invention]
By the way, in the shape measuring device as shown in FIG. 9, the X-Z cross-sectional shape of the object to be measured is configured in consideration of the Abbe error, and high accuracy measurement can be expected. Since there is no means for moving in the Y-axis direction, there is a problem that the three-dimensional shape of the object to be measured cannot be measured.
[0006]
The three-dimensional shape measuring machine as shown in FIG. 10 has the following problems. That is, the reference mirrors are respectively arranged on the YZ plane, the XZ plane, and the XY plane perpendicular to the XYZ axes, and these reference mirrors usually have two-dimensional λ / 10 to λ / Since a reference surface having a flatness of about 20 is required, it is difficult to manufacture a large-sized device due to the influence of the manufacturing method, the number of days for manufacturing, the cost, and the like. Therefore, the measurement range of the device under test is restricted. Further, by moving the probe on the X or Y section, for example, the axially symmetric lens or the like is measured on the XZ plane or the YZ plane with a large change in the Z direction relative to a change in the X direction or the Y direction. In this case, the moving speed of the probe cannot be increased, and the measuring time becomes longer. Further, in the shape measuring machine shown in FIG. 9, even if a Y stage is attached and the displacement meter can be moved in the XYZ axis directions, there is a similar problem.
[0007]
Therefore, the present invention has been made in view of the above-mentioned unsolved problems of the related art, and is capable of measuring a three-dimensional shape of an object to be measured with high accuracy and in a short time. It is an object to provide a three-dimensional shape measuring device and a three-dimensional shape measuring method.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a three-dimensional shape measuring instrument of the present invention is a three-dimensional shape measuring instrument that measures a three-dimensional shape of an object using a probe that scans along the shape of the object.
A θ stage provided to support an object to be measured and movable in a θ-axis direction as a rotation component with respect to a Z-axis direction perpendicular to the object to be measured, and the probe is moved relative to the object to be measured. An R-stage that moves the probe in the R-axis direction, which is a horizontal direction, a Z-stage that moves the probe in the Z-axis direction, which is a direction perpendicular to the device under test, and an R-stage including the R stage and the Z stage. With the probe arranged on the Z stage Laser measurement for detecting a position in the Z-axis direction of the probe in a three-dimensional coordinate position with respect to the object to be measured, and detecting a position in the Z-axis direction of the probe disposed on the R-Z stage. A measuring system including a long device and a Z reference mirror arranged at a position parallel to the R axis and passing on the Z axis, and detecting the position of the probe in the R axis direction at a three-dimensional coordinate position with respect to the measured object A laser length measuring device for detecting a position in the R-axis direction of the probe disposed on the R-Z stage, and an R reference disposed at a position parallel to the Z-axis and passing on the R-axis. A measurement system including a mirror, and a laser length measuring device for detecting the position of the θ stage in the Z-axis direction, for detecting the position of the θ stage in the Z-axis direction, and detecting the position of the θ stage in a different position from the R-Z stage. , And the Z reference mirror And a laser measuring device for detecting the position of the θ stage in the R-axis direction, detecting the position of the θ stage in the R-axis direction, and detecting the position of the θ stage in the R-axis direction, which is arranged at a position different from the position on the RZ stage. And a measurement system including the R reference mirror, Of the θ stage Detect the position in the θ-axis direction And an angle detecting means.
[0009]
In the three-dimensional shape measuring machine of the present invention, Record By moving the probe along the shape of the object to be measured while moving the probe in the Z-axis direction so that the distance to the object to be measured is always constant, the three-dimensional coordinate position of the probe with respect to the object to be measured R, θ, and Z are simultaneously detected, and the shape of the object is measured based on the three-dimensional coordinate positions R, θ, and Z. U Is preferred.
[0010]
In the three-dimensional shape measuring apparatus of the present invention, it is preferable that the θ stage is constituted by an air bearing, and a θ reference mirror is integrally attached to a rotor portion of the air bearing in a radial direction and a thrust direction.
[0011]
In the three-dimensional shape measuring method according to the present invention, the probe that scans along the shape of the measured object is moved in the R-axis direction, which is the horizontal direction of the measured object, and the probe is moved in the vertical direction of the measured object. In the θ-axis direction, which is a rotation component with respect to the Z-axis direction, is simultaneously or independently moved, and during the movement, the probe is moved so that the distance from the object to be measured is always constant. Scan the entire surface along the shape of the DUT, For the measured object 3D coordinate position of the probe R, Z, θ At the same time, Previous 3D coordinates Position R, Z, θ A three-dimensional shape measuring method for measuring a three-dimensional shape of the object to be measured based on Previous The three-dimensional coordinate position R of the probe with respect to the object to be measured Are the R coordinates R1 and R2 detected at two different positions P1 and P2 in the same RZ plane, respectively, the middle of the two positions P1 and P2, the tip of the probe and the object to be measured. The R-axis coordinate position of the probe, which is calculated from the distance D1 of the Z-direction component at the intersection and the distance D2 of the Z-direction component between the two positions P1 and P2 in consideration of the Abbe error, is measured. The probe is calculated by compensating for the amount of axial deviation in the radial direction that occurs when rotating the object to be measured in the θ-axis direction, which is calculated from the coordinate position of the object in the R-axis direction. The dimensional coordinate position Z is defined by Z coordinates Z1 and Z2 detected at two different positions P3 and P4 in the same RZ plane, an intermediate point between the two positions P3 and P4, and the tip of the probe. The coordinates in the Z-axis direction of the probe calculated from the distance D3 of the R-direction component at the intersection with the object to be measured and the distance D4 of the R-direction component between the positions P3 and P4 in consideration of the Abbe error. The position is calculated by correcting the position of the object to be measured based on the Z-axis coordinate position of the object to be measured based on a surface shake amount in a thrust direction generated when the object to be measured is rotated in the θ-axis direction. The three-dimensional coordinate position θ of the probe with respect to the object is calculated from the coordinate position of the measured object in the θ-axis direction. It is characterized by doing.
[0012]
In the three-dimensional shape measuring method of the present invention, For the measured object 3D coordinates of the probe position R Is , R coordinates R1 and R2 detected at two different positions P1 and P2 in the same RZ plane, an intersection between the two positions P1 and P2, and an intersection between the probe tip and the object to be measured. Abbe error is considered from the distance D1 of the Z-direction component at and the distance D2 of the Z-direction component between the two positions P1 and P2. The radial position of the probe calculated from the coordinate position of the probe in the R-axis direction is calculated from the coordinate position of the probe in the R-axis direction. The three-dimensional coordinate position Z of the probe with respect to the measured object is Z coordinate Z1, which is detected at two different positions P3 and P4 in the same RZ plane. Z2, the distance D3 of the R direction component between the two positions P3 and P4 and the intersection of the probe tip and the object to be measured, and the distance D4 of the R direction component between the two positions P3 and P4. The thrust generated when rotating the object to be measured in the θ-axis direction, which is calculated from the coordinate position in the Z-axis direction of the object to be measured, from the coordinate position in the Z-axis direction of the probe, which is calculated in consideration of the error, Directional Calculate by correcting by the amount of runout Is preferred.
[0014]
In the three-dimensional shape measuring method according to the present invention, when the object to be measured has an axially symmetric shape, the axis of the object to be measured and the Z axis that is the rotation axis in the θ-axis direction are aligned so as to substantially coincide with each other. It is preferable to carry out shape measurement after performing the above.
[0015]
[Action]
According to the present invention, an R-stage that moves in parallel to an object to be measured, a Z stage that moves in a direction perpendicular to the object to be measured, and a rotation axis in the Z direction, A θ stage whose rotation axis is the vertical direction of the object, Suffered By measuring the shape of the object to be measured two-dimensionally in the RZ plane, the R reference mirror and the Z reference mirror used in the laser length measuring device serving as the optical probe position detecting means are almost one-dimensional. Since only the range (on a straight line) is used, the width of the reference mirror can be reduced, which facilitates the manufacture and improves the flatness of the reference mirror.
[0016]
The measurement error in the position detecting means only needs to be considered on two dimensions in the RZ plane, and the pitching component error of the stage is length-measured, but the yawing and rolling components are corrected because the degree of influence is considerably small. Items can be reduced, and measurement errors can be reduced. In addition, when the shape of the DUT is axially symmetric and the DUT is rotated with the axis of the DUT and the rotation axis of the θ stage substantially coincident, the shape of the DUT on the same radius is substantially constant. Therefore, the scanning speed of the measurement position detecting means such as a probe can be increased, and the measurement time can be reduced.
[0017]
As described above, according to the present invention, it is possible to measure a three-dimensional shape of an object to be measured with high accuracy and in a short time.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a perspective view schematically showing a main part of the three-dimensional shape measuring machine of the present invention, and FIG. 2 is a schematic side view of a main part of the three-dimensional shape measuring machine of the present invention. FIG. 3 is an arrangement configuration diagram showing an arrangement relationship between an optical probe and a laser length measuring device on the RZ plane in the three-dimensional measuring device of the present invention.
[0020]
In FIGS. 1 and 2, reference numeral 1 denotes an object to be measured such as an asymmetrical aspheric lens which is mounted on the

θ stage

7, and 2 denotes a probe which scans along the shape of the object 1. In the example, a non-contact optical probe that does not damage a lens or the like is used. However, a contact-type probe can be used. Reference numeral 3 denotes an R stage that moves in parallel with the

DUT

1, and 4 denotes a Z stage that moves in the vertical direction of the DUT 1. Therefore, the optical probe 2 disposed on the R stage 3 and the Z stage 4 is configured to be movable in the RZ direction. Reference numeral 5 denotes a Z reference mirror arranged at a position parallel to the R axis and passing on the Z axis, and reference numeral 6 denotes an R reference mirror arranged at a position parallel to the Z axis and passing on the R axis. Reference numeral 7 denotes an air bearing unit serving as a θ stage, which is a means for rotating the DUT 1 in the θ axis direction, and includes a fixed housing unit 7A and a rotating rotor unit 7B. The θ reference mirrors 12a and 12b (see also FIGS. 3 and 4) are arranged on the rotor section 7B. Reference numeral 9 denotes a laser length measuring device serving as a position detecting means, 9a and 9b denote laser measuring devices for R measurement arranged on the Z stage 4 so as to be separated from each other in the Z direction, and 9c and 9d denote laser length measuring devices on the Z stage 4. Laser measuring instruments 9e, 9f, 9g, and 9h arranged apart from each other in the R direction are laser measuring instruments for θ measurement arranged outside the R-Z stages 3 and 4. Reference numeral 10 denotes a scale detection unit (rotary encoder) of a later-described scale 11 (see FIGS. 3 and 4), which is an angle detection unit of the θ stage 7. Reference numeral 29 denotes a mount on which the R stage 3 and the Z stage 4 are mounted.
[0021]
FIG. 3 is a view showing the arrangement of the optical probe and the laser length measuring device serving as its position detecting means on the same plane of the RZ. The RD 1 is located between the laser length measuring device 9 a and the R reference mirror 6. RD2 indicates the distance between the laser length measuring device 9b and the R reference mirror 6, and is used for correcting the amount of movement of the R stage 3 and the measurement error generated during the movement. ZD1 indicates the distance between the laser length measuring device 9c and the Z reference mirror 5, ZD2 indicates the distance between the laser length measuring device 9d and the Z reference mirror 5, and the amount of movement of the Z stage 4 and the measurement error correction that occurs during the movement. Used for θD1 and θD2 indicate the distance between the θ reference mirror 12a and the Z reference mirror 5 provided on the thrust surface of the θ stage 7, and are used for detecting the amount of shake (surface shake) of the θ stage 7 in the thrust direction. θD3 and θD4 indicate the distance between the θ reference mirror 12b and the R reference mirror 6a provided on the radial surface of the θ stage 7, and are used to detect the amount of shake (axis shake) of the θ stage 7 in the radial direction. As described above, in the present invention, the optical probe 2 and the laser length measuring device 9 serving as the optical probe position detecting means are all arranged on the same plane of the RZ plane.
[0022]
In FIG. 3, D1 is the distance of the Z-direction component between the center of the laser

length measuring devices

9a and 9b and the cat's eye point of the optical probe 2, D2 is the distance of the Z-direction component between the laser

length measuring devices

9a and 9b, D3 is the distance of the R direction component between the center of the laser length measuring devices 9c and 9d and the center line of the optical probe 2, D4 is the distance of the R direction component between the laser length measuring devices 9c and 9d, and D5 is the laser length measuring device 9e. , 9f.
[0023]
FIG. 4 is an enlarged view of an air bearing portion serving as a θ stage. The θ stage 7 includes a fixed housing portion 7A and a rotating rotor portion 7B, and a part of the surface of the rotor portion 7B is provided. Is a method in which a θ reference mirror is manufactured by aluminum evaporation and polishing after precision processing, and a θ reference mirror in the thrust direction is 12a and a θ reference mirror in the radial direction is 12b. A scale 11 is attached in the radial direction, and the angle of the θ stage 7 can be detected using the scale detection unit 10.
[0024]
FIG. 5 shows a detailed configuration of the optical probe. In FIG. 5, reference numeral 13 denotes a laser light source that generates two light waves whose polarization directions are orthogonal to each other, and a light beam emitted from the laser light source 13 is transmitted by a beam expander 14. After the light beam is expanded, the light beam is split into a reflected light wave and a transmitted light wave by the polarization beam splitter 15a. The reflected light wave changes from linearly polarized light to circularly polarized light by passing through the λ / 4 plate 16a, and is incident on the DUT 1 via the condenser lens 20a. Here, the light beam is incident on the DUT 1 in a state where the light beam is focused to the focal point (cat's eye point) by the condenser lens, and is reflected as a measurement light wave. The measurement light wave has surface information of the DUT 1 in the Z direction in the area of the irradiated light beam. The reflected measurement light wave returns to the original optical path, becomes linearly polarized light rotated by 90 ° as compared with the outgoing light at the λ / 4 plate 16a that passes again, and is transmitted by the polarization beam splitter 15a this time. The other transmitted light wave changes from linearly polarized light to circularly polarized light through the λ / 4 plate 16b, enters the reference plane mirror 17, and is reflected as a reference light wave. The reflected reference light wave becomes linearly polarized light rotated by 90 ° as compared with the outgoing light at the λ / 4 plate 16b which passes again, and is then reflected by the polarization beam splitter 15a. The measurement lightwave and the reference lightwave overlap each other in the polarization beam splitter 15a, and pass through the polarizing plate 18 in the 45 ° azimuth to become an interference lightwave. The interference light wave is split into two by the beam splitter 15b, and the transmitted interference light wave is detected by the line sensor 19. The line sensor 19 usually has several tens to thousands of channels, but here, one having several tens of channels corresponding to a high frequency is used. The selection condition when one channel is selected from a plurality of line sensor channels and used as a measurement signal is as follows: the inclination angle is calculated from the design shape of the DUT at the measurement point, and the normal to the DUT is obtained. According to the ray tracing of the light beam that is reflected in the direction, that is, the specularly reflected light beam, which channel on the line sensor is taken in advance is calculated and stored, and the channel to be used is selected by the multiplexer according to the measurement position. The interference light wave reflected by the beam splitter 15b is captured by the photodetector 21 via the condenser lens 20b and becomes a reference signal.
[0025]
FIG. 6 is a configuration diagram showing the configuration of the Z-axis servo. The Z stage 4 is moved so that the light beam from the optical probe 2 enters the DUT 1 at the cat's eye point. The measurement signal and the reference signal detected from the interference lightwave in that state are input to the phase meter 30 to calculate the phase difference, and when stored in the computer 31, the servo lock is started. Next, the R stage 3 and the θ stage 7 are moved simultaneously or independently, and the phase difference obtained at that time is compared with the stored phase difference. The Z servo controller 32 sets the Z difference so that the deviation always becomes zero. The stage 4 is moved (servo lock state). This makes it possible to always keep the distance between the DUT 1 and the optical probe 2 constant.
[0026]
FIGS. 7A and 7B show the configuration of a laser length measuring device, and FIG. 7A is a configuration diagram of laser

length measuring devices

9a, 9b, 9c and 9d. Measure the distance between two reference mirrors. FIG. 7B is a configuration diagram of the laser length measuring devices 9e, 9f, 9g, and 9h, and measures the distance between two reference mirrors. In this case, the measurement resolution of the laser length measuring device is doubled because the double-path method is used in which the optical path to be measured is reciprocated twice. In FIG. 7A, reference numeral 13 denotes a laser light source that generates two light waves whose polarization directions are orthogonal to each other. The light beam emitted from the laser light source 13 is divided into a reflected light wave and a transmitted light wave by the polarization beam splitter 15c. The transmitted light wave is reflected twice by the corner cube 22a to become a reference light wave, and passes through the polarization beam splitter 15c again. One reflected light wave changes from linearly polarized light to circularly polarized light by passing through the λ / 4 plate 16c, and is reflected by the reference mirrors 5 and 6 (for example, the Z reference mirror 5) to become a measurement light wave. The measurement light wave returns to the original optical path, becomes linearly polarized light rotated by 90 ° as compared with the outgoing light at the λ / 4 plate 16c passing again, transmitted through the polarization beam splitter 15c, and reflected twice by the corner cube 22b. The light again returns to the reference mirrors 5 and 6 through the polarization beam splitter 15c and the λ / 4 plate 16c. The measurement light wave reflected again becomes linearly polarized light rotated by 90 ° as compared with the outgoing light on the λ / 4 plate 16c, and is reflected on the polarization beam splitter 15c. Here, the measurement lightwave and the reference lightwave overlap, and when passing through the polarizing plate 18, become an interference lightwave, which is detected by the length measuring device receiver 28. The fluctuation of the phase difference between the measurement lightwave and the reference lightwave is observed by the length measuring device as the count of the fringe of the interference lightwave. Since the optical path length of the reference light wave is always constant, a change in the optical path length of the measurement light wave, that is, two round trips of each stage movement amount from each reference mirror can be detected here from the count of the interference light wave fringes. .
Similarly, a laser length measuring device for measuring the distance between two reference mirrors will be described with reference to FIG. In the figure, two orthogonal light waves emitted from the laser light source 13 are divided into a reflected light wave and a transmitted light wave by the polarization beam splitter 15c. The transmitted light wave is reflected twice by the corner cube 22a to become a reference light wave, and passes through the polarization beam splitter 15c again. One reflected light wave changes from linearly polarized light to circularly polarized light by passing through the λ / 4 plate 16c, and is reflected by the reference mirrors 5 and 6 (for example, the Z reference mirror 5) to become a measurement light wave. The measuring light wave returns to the original optical path, becomes linearly polarized light rotated by 90 ° as compared with the outgoing light at the λ / 4 plate 16c passing again, transmits through the polarizing beam splitter 15c, passes through the λ / 4 plate 16d, The light is reflected by the reference mirrors 12a and 12b (for example, the θ reference mirror 12a) and returns to the original optical path. The measurement light wave again incident on the λ / 4 plate 16c becomes linearly polarized light rotated by 90 ° as compared with the outgoing light, and is then reflected by the polarization beam splitter 15c and incident on the corner cube 22a. The measurement light wave is reflected twice by the corner cube 22a, reenters the polarization beam splitter 15c, and is reflected there. Thereafter, the measurement light wave passes through the λ / 4 plate 16d, is reflected again by the reference mirrors 12a and 12b (for example, the θ reference mirror 12a), and transmits through the λ / 4 plate 16d, the polarization beam splitter 15c, and the λ / 4 plate 16c. Then, the light again enters the reference mirrors 5 and 6 (for example, the Z reference mirror 5 and the like) and is reflected. The measurement lightwave reflected by the reference mirror passes through the λ / 4 plate 16c again, becomes linearly polarized light rotated by 90 ° as compared with the outgoing light, and is reflected by the polarization beam splitter 15c this time. Here, the measurement lightwave and the reference lightwave overlap, and when passing through the polarizing plate 18, become an interference lightwave, which is detected by the length measuring device receiver 28. The fluctuation of the phase difference between the measurement lightwave and the reference lightwave is observed by the length measuring device as the count of the fringe of the interference lightwave. Since the optical path length of the reference light wave is always constant, the variation of the optical path length of the measured light wave, that is, the two round trips of the amount of change in the distance between the two reference mirrors is detected here from the count of the interference light wave fringes. it can.
[0027]
Next, a specific measuring method using the three-dimensional shape measuring machine configured as described above will be described.
[0028]
The axisymmetric aspheric lens 1 as an object to be measured is set on the θ stage 7 so that its axis substantially coincides with the rotation axis of the θ stage 7. Thus, the optical probe 2 can be scanned over the entire surface in accordance with the shape of the DUT 1 by combining the θ-axis rotation on the DUT side and the RZ-axis scanning on the optical probe side. The optical probe 2 is moved to the center of rotation of the θ axis, and then the Z stage 4 is lowered to approach the DUT 1, and the cat's eye point generated by the light flux of the optical probe 2 is incident on the DUT 1. Start servo lock. The output values of the laser length measuring devices 9a to 9h and the rotary encoder 10 at this time are fetched and stored in the computer as RD1o, RD2o, ZD1o, ZD2o, θD1o, θD2o, θD3o, θD4o, and REo, respectively. Next, in the servo locked state, the R stage 3 and the θ stage 7 are moved independently or simultaneously, and at the points to be measured (i = 1 to n, i: order of capture), the laser length measuring devices 9a to 9h and the rotary The output values of the encoder 10 are simultaneously captured and stored as RD1i, RD2i, ZD1i, ZD2i, θD1i, θD2i, θD3i, θD4i, and REi, respectively. Similarly, the entire surface of the DUT 1 is scanned by the optical probe 2 to acquire n sets of data, and for example, the following arithmetic processing is performed.
[0029]
(Equation 1)

[0030]
Through such arithmetic processing, three-dimensional coordinates at each measurement point can be calculated with high accuracy. Therefore, a highly accurate three-dimensional shape of the device under test can be expressed using n sets of three-dimensional coordinate data.
[0031]
FIG. 8 shows an example of data acquisition of three patterns viewed on the R-θ cross section by the three-dimensional measuring device of the present invention. It should be noted that the axes in FIG. 8 are shown after being converted to an XY coordinate system that is generally used. In the present invention, if data is captured at regular intervals while simultaneously moving the R stage and the θ stage, the data can be detected as spiral data as shown in FIG. 8A, and the R stage or the θ stage can be used alone. If data is captured at regular intervals while moving, it can be detected as concentric circle data as shown in FIG. In general, grid data (FIG. 8 (c)) often used in a three-dimensional measuring device is obtained by adjusting the movement amounts of the R stage and the θ stage in a grid pattern, or by converting spiral data or concentric data into coordinate transformation or interpolation. The present invention can also cope with a method such as conversion using.
[0032]
In the present invention, when the shape of the object to be measured is axially symmetric, if data is detected based on the spiral data, the amount of movement of the optical probe in the Z direction by the servo lock state with respect to the θ stage or minute R stage movement is Since it is extremely small, high-speed optical probe scanning becomes possible. When data detection is performed using concentric circle data, the state is maintained after the R stage is moved, and then the data is taken in at regular intervals while the θ stage is moved independently. As a result, the amount of movement of the optical probe in the Z direction that moves in the servo locked state is extremely small, so that high-speed optical probe scanning becomes possible.
[0033]
As described above, in the three-dimensional measuring machine and the three-dimensional measuring method according to the present invention, the object to be measured is mounted on the θ stage, the optical probe is provided on the R stage and the Z stage, and all the optical probe position detecting means are provided. An R reference mirror used for a laser length measuring device serving as an optical probe position detecting means by being arranged in the RZ plane and measuring the shape of the object to be measured in two dimensions in the RZ plane. Since the reference mirror and the Z reference mirror are used only in a substantially one-dimensional (on a straight line) range, the width of the reference mirror can be reduced. For this reason, the manufacture is facilitated and the flatness of the reference mirror can be improved. Then, the measurement error in the position detection means only needs to be considered on two dimensions in the RZ plane. That is, while the pitching component error of the stage is length-measured, the yaw and rolling components have a considerably small degree of influence, so that the number of correction items can be reduced, and the measurement error can be reduced. In addition, when the shape of the DUT is axially symmetric and the DUT is rotated with the axis of the DUT and the rotation axis of the θ stage substantially coincident, the shape of the DUT on the same radius is substantially constant. Therefore, the scanning speed of the measurement position detecting means such as a probe can be increased, and the measurement time can be reduced.
[0034]
【The invention's effect】
As described above, according to the present invention, in the three-dimensional measuring machine, the object to be measured is mounted on the θ stage, the probes are provided on the R stage and the Z stage, and all of the probe position detecting means are R-Z. The following operational effects can be obtained by arranging the object in the plane and measuring the shape of the object to be measured in two dimensions in the RZ plane.
[0035]
1. Since the R reference mirror and the Z reference mirror used in the laser length measuring device serving as the optical probe position detecting means are used only in a substantially one-dimensional (on a straight line) range, the width of the reference mirror can be reduced. . For this reason, the manufacture is facilitated and the flatness of the reference mirror can be improved.
[0036]
2. The measurement error in the position detection means only needs to be considered on two dimensions in the RZ plane. That is, while the pitching component error of the stage is length-measured, the yaw and rolling components have a considerably small degree of influence, so that the number of correction items can be reduced, and the measurement error can be reduced.
[0037]
3. When the shape of the DUT is axially symmetric, when the DUT is rotated with the axis of the DUT and the rotation axis of the θ stage substantially coincident, the shape of the DUT on the same radius is substantially constant. The scanning speed of the measurement position detecting means such as a probe can be increased, and the measurement time can be reduced.
[0038]
Therefore, according to the three-dimensional measuring device and the three-dimensional measuring method of the present invention, it is possible to measure the three-dimensional shape of the measured object with high accuracy and in a short time.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a main part of a three-dimensional shape measuring instrument according to the present invention.
FIG. 2 is a schematic side view of a main part of the three-dimensional shape measuring instrument of the present invention.
FIG. 3 is an arrangement configuration diagram showing an arrangement relationship between an optical probe and a laser length measuring device on the RZ plane in the three-dimensional measuring device of the present invention.
FIG. 4 is a configuration diagram showing an enlarged part of a θ stage in the three-dimensional measuring machine of the present invention.
FIG. 5 is a configuration diagram of an optical probe in the three-dimensional measuring device of the present invention.
FIG. 6 is a configuration diagram showing a configuration of a Z-axis servo in the three-dimensional measuring machine of the present invention.
7A and 7B show the configuration of a laser length measuring device in the three-dimensional measuring device of the present invention, wherein FIG. 7A is used for measuring the distance between the laser length measuring device and one reference mirror, and FIG. ) Is used to measure the distance between two reference mirrors.
8A and 8B show examples of data acquisition by the three-dimensional measuring device of the present invention, wherein FIG. 8A shows spiral data, FIG. 8B shows concentric circle data, and FIG. 8C shows grid data.
FIG. 9 is a schematic configuration diagram showing an example of a conventional shape measuring device.
FIG. 10 is a schematic configuration diagram showing another example of a conventional shape measuring instrument.
[Explanation of symbols]
1 DUT (axial lens)
2 Optical probe
3 R stage
4 Z stage
5 Z reference mirror
6 R reference mirror
7 θ stage (air bearing part)
7A Housing part
7B Rotor part
9 (9a-9h) Laser length measuring instrument
10 Angle detection means (rotary encoder)
11 scale
12a, 12b θ reference mirror
13 Laser light source
14 Beam expander
15a, 15b, 15c Polarizing beam splitter
16a, 16b, 16c, 16d λ / 4 plate
17 Reference plane mirror
18 Polarizing plate
19 Line sensor
20a, 20b condenser lens
21 Photo Detector
22a, 22b corner cube
30 phase meter
31 Computer
32 Z servo controller

Claims

In a three-dimensional shape measuring machine that measures a three-dimensional shape of a measured object using a probe that scans along a shape of the measured object,
A θ stage provided to support an object to be measured and movable in a θ-axis direction as a rotation component with respect to a Z-axis direction perpendicular to the object to be measured, and the probe is moved relative to the object to be measured. An R-stage that moves the probe in the R-axis direction, which is a horizontal direction, a Z-stage that moves the probe in the Z-axis direction, which is a direction perpendicular to the device under test, and an R-stage that includes the R stage and the Z stage. And the probe arranged on a Z stage ,
A laser length measuring device for detecting a position in the Z-axis direction of the probe disposed on the R-Z stage, for detecting a position of the probe in a three-dimensional coordinate position with respect to an object to be measured; A measurement system including a Z reference mirror disposed at a position parallel to the axis and passing on the Z axis;
A laser length measuring device for detecting a position in the R-axis direction of the probe disposed on the R-Z stage, for detecting a position in the R-axis direction in a three-dimensional coordinate position of the probe with respect to the measured object; A measurement system including an R reference mirror arranged at a position parallel to the axis and passing on the R axis;
A laser length measuring device for detecting the position of the θ stage in the Z-axis direction, which is disposed at a position different from the position on the R-Z stage, for detecting the position of the θ stage in the Z-axis direction, and the Z reference mirror. Measurement system including
A laser length measuring device for detecting the position of the θ stage in the R-axis direction, which is disposed at a position different from the position on the R-Z stage, for detecting the position of the θ stage in the R-axis direction, and the R reference mirror. Measurement system including
A three-dimensional shape measuring device comprising: an angle detecting means for detecting a position of the θ stage in a θ axis direction .

The pre-Symbol probe, said that the distance between the object to be measured is always scanned along the shape of the object to be measured while moving in the Z axis direction to be constant, the three-dimensional of the probe relative to the object to be measured coordinate position R, theta, and detects Z simultaneously, the three-dimensional coordinate position R, theta, a three-dimensional shape measurement according to claim 1, wherein the intends line measurement of the shape of the object to be measured based on Z Machine.

A laser measuring device for detecting the position of the probe in the Z-axis direction and a laser measuring device for detecting the position of the θ stage in the Z-axis direction are arranged in the R-axis direction in the R-Z plane in which the probe is movable. by arranging side by side by two, respectively, to detect the Z in the three-dimensional coordinate positions,
A laser measuring device for detecting the position of the probe in the R-axis direction and a laser measuring device for detecting the position of the θ stage in the R-axis direction are arranged in the Z-axis direction in the R-Z plane in which the probe can move. by arranging side by side by two, respectively, to detect the R in the 3-dimensional coordinate positions,
The angle detecting means for detecting the position of the θ stage in the θ axis direction is a scale arranged in a radial direction of a rotor unit of a rotating mechanism constituting the θ stage and a scale detecting unit fixed outside the θ stage. 3. The three-dimensional shape measuring machine according to claim 2, wherein:

A laser length measuring device that detects the position of the probe in the Z-axis direction, a laser length measuring device that detects the position of the probe in the R-axis direction, a laser length measuring device that detects the position of the θ stage in the Z-axis direction, The three-dimensional laser apparatus according to any one of claims 1 to 3, wherein the laser length measuring devices for detecting the position of the θ stage in the R-axis direction are all arranged on the same RZ plane. Shape measuring instruments.

The said (theta) stage is comprised by the air bearing, The (theta) reference mirror is integrally attached to the rotor part of this air bearing in the radial direction and the thrust direction, The Claim 1 characterized by the above-mentioned. 3D shape measuring machine.

6. The device according to claim 1, wherein the object to be measured has an axially symmetric shape, and is supported so that an axis of the object to be measured and a θ axis of the θ stage substantially coincide with each other. 3D shape measuring machine.

A probe that scans along the shape of the measured object in the R-axis direction, which is the horizontal direction of the measured object, and rotates the measured object with respect to the Z-axis direction, which is the vertical direction of the measured object. In the θ-axis direction, simultaneously or independently, scanning the entire surface along the shape of the measured object while moving the probe so that the distance from the measured object is always constant during the movement. , 3-dimensional coordinate position R of the probe relative to the object to be measured, Z, detect θ simultaneously, before Symbol 3-dimensional coordinate position R, Z, three-dimensional measuring the three-dimensional shape of the object to be measured based on θ In the shape measurement method,
3-dimensional coordinate position of the probe relative to prior Symbol DUT R is the same R-Z plane two positions P1, P2 that are different in the R coordinate R1, R2 which are detected, the two positions P1, The distance is calculated from the distance D1 of the Z-direction component at the middle of P2 and the intersection of the probe tip and the object to be measured and the distance D2 of the Z-direction component between the two positions P1 and P2 in consideration of the Abbe error. The coordinate position of the probe in the R-axis direction is corrected based on a radial axis shift amount generated when the device to be measured is rotated in the θ-axis direction, calculated from the coordinate position of the device to be measured in the R-axis direction. Calculated by
The three-dimensional coordinate position Z of the probe with respect to the object to be measured includes Z coordinates Z1, Z2 respectively detected at two different positions P3, P4 in the same RZ plane, and the two positions P3, P4. And the distance D3 of the R-direction component at the middle of and the intersection of the probe tip and the object to be measured, and the distance D4 of the R-direction component between the two positions P3 and P4 in consideration of Abbe error. Correcting the coordinate position of the probe in the Z-axis direction by the amount of surface displacement in the thrust direction generated when the device to be measured is rotated in the θ-axis direction calculated from the coordinate position of the device to be measured in the Z-axis direction. Calculated by
A three-dimensional shape measuring method , wherein the three-dimensional coordinate position θ of the probe with respect to the measured object is calculated based on the coordinate position of the measured object in the θ-axis direction .

Said object to be measured Ri axisymmetric shape der performs a shape measurement the after performing the narrowing combined so as to substantially coincide with the Z axis as the rotation axis of the shaft and the θ-axis direction of the object The method of measuring a three-dimensional shape according to claim 7, wherein: