JP2002013919A - Plane shape measuring method for phase-shift interference fringe simultaneous photographing device - Google Patents
Plane shape measuring method for phase-shift interference fringe simultaneous photographing deviceInfo
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- JP2002013919A JP2002013919A JP2000197483A JP2000197483A JP2002013919A JP 2002013919 A JP2002013919 A JP 2002013919A JP 2000197483 A JP2000197483 A JP 2000197483A JP 2000197483 A JP2000197483 A JP 2000197483A JP 2002013919 A JP2002013919 A JP 2002013919A
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- phase difference
- optical
- light
- interference fringe
- optical phase
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- Length Measuring Devices By Optical Means (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、被検面と参照面か
らの反射光が光学的に無干渉状態にある原光束を複数の
分枝原光束に分割し、夫々分枝原光束に異なる固定的光
学位相差を与えて干渉させ、複数の撮像装置で同時撮像
を行う位相シフト干渉縞同時計測装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention divides an original light beam in which light reflected from a test surface and a reference surface is optically free from interference into a plurality of branched original light beams, each of which is different from the branched original light beam. The present invention relates to a phase shift interference fringe simultaneous measurement apparatus that performs simultaneous imaging with a plurality of imaging devices by giving a fixed optical phase difference and causing interference.
【０００２】[0002]
【従来の技術】従来、図１に示すような位相シフト干渉
縞同時計測装置が本出願人による特願平１１−１３６８
３１号出願で提案されている。即ち、同位相シフト干渉
縞同時計測装置においては、レーザ光源１からのレーザ
光束はレンズ２よりビーム径を拡大され、ビームスプリ
ッタ３を透過してコリメートレンズ４にて平行光束とさ
れる。そして、この平行光束は参照面５で反射された参
照光と参照面５，１／４波長板６を透過し被検面７で反
射された試料光を生成するが、この参照光と試料光は直
交する直線偏光で光学的無干渉状態にある。2. Description of the Related Art Conventionally, a phase shift interference fringe simultaneous measuring apparatus as shown in FIG. 1 has been proposed by the present applicant in Japanese Patent Application No. 11-1368.
No. 31 has been proposed. That is, in the simultaneous phase shift interference fringe measuring apparatus, the laser beam from the laser light source 1 is expanded in beam diameter by the lens 2, passes through the beam splitter 3, and is converted into a parallel beam by the collimator lens 4. The parallel light flux transmits the reference light reflected by the reference surface 5 and the sample light transmitted through the reference surface 5 and the quarter-wave plate 6 and reflected by the test surface 7. Is orthogonal linearly polarized light and is optically free from interference.
【０００３】また、ビームスプリッタ３で反射された参
照光と試料光は、１／４波長板８でそれぞれ互いに回転
方向の異なる円偏光状態となり三分光プリズム９で３つ
の分枝光束に分割される。それぞれの分枝光束の光路上
には偏光板１０〜１２が配置され、光軸に対してほぼ直
交する面内における偏光板の透過軸角度が設定され、固
定的光学位相差を与えた分枝位相シフト干渉縞が発生
し、これらの分枝位相シフト干渉縞が撮像装置１３〜１
５により同時に撮像される。Further, the reference light and the sample light reflected by the beam splitter 3 are turned into circularly polarized light states having different rotation directions from each other by a 波長 wavelength plate 8 and are split into three branched light beams by a trispectral prism 9. . Polarizing plates 10 to 12 are arranged on the optical path of each branching light beam, the transmission axis angle of the polarizing plate is set in a plane substantially orthogonal to the optical axis, and a branch having a fixed optical phase difference is provided. Phase shift interference fringes occur, and these branched phase shift interference fringes are captured by the imaging devices 13 to 1.
5 are imaged simultaneously.
【０００４】[0004]
【発明が解決しようとする課題】つまり、この位相シフ
ト干渉縞同時計測装置では、偏光板１０〜１２の透過軸
の正確な角度の設定により、分枝位相シフト干渉縞に固
定的光学位相差が与えられるが、偏光板の透過軸角度を
精度よく設定することは一般に困難であり、また、材質
の不均一性などから偏光板が全領域において光学的に全
く均一に機能することは期待できない。さらに、計画さ
れた固定的光学位相差と実測上での３枚の分枝位相シフ
ト干渉縞間の固定的光学位相差は異なるのが現実であ
り、高精度な位相シフト干渉縞同時撮像装置を製作する
ことは難しい。In other words, in this phase shift interference fringe simultaneous measurement apparatus, a fixed optical phase difference is generated in the branched phase shift interference fringes by setting an accurate angle of the transmission axis of the polarizing plates 10 to 12. However, it is generally difficult to accurately set the transmission axis angle of the polarizing plate, and it is not expected that the polarizing plate functions completely uniformly optically in all regions due to non-uniformity of the material. Further, the fixed optical phase difference between the planned fixed optical phase difference and the actual measured fixed optical phase difference between the three branched phase-shift interference fringes is actually different. It is difficult to make.
【０００５】本発明の目的は、前述したような位相シフ
ト干渉縞同時撮像装置の問題に鑑み、偏光板の透過軸の
設置誤差や偏光板自体の材質の不均一性などにより、分
枝位相シフト干渉縞間の固定的光学位相差に相違があっ
ても、充分に解析できる位相シフト干渉縞画像を得るこ
とができる平面形状計測方法を得るにある。SUMMARY OF THE INVENTION In view of the above-described problems of the phase shift interference fringe simultaneous imaging apparatus, the object of the present invention is to provide a branch phase shift due to a setting error of a transmission axis of a polarizing plate or a non-uniformity of a material of the polarizing plate itself. An object of the present invention is to provide a planar shape measurement method capable of obtaining a phase shift interference fringe image that can be sufficiently analyzed even if there is a difference in a fixed optical phase difference between interference fringes.
【０００６】[0006]
【課題を解決するための手段】この目的を達成するた
め、本発明は、複数の分枝原光束のそれぞれに与えた固
定的光学位相差を撮像装置間の各点ごとに予め計測し、
計測によって得られた固定的光学位相差を被検面起伏形
状算出時に使用することで、位相シフト干渉縞同時撮像
装置の大幅な高精度化を図ることを提案するものであ
る。つまり、本発明においては、レーザ光源からのコヒ
ーレント光束を参照面と被検面に照射し、前記参照面及
び前記被検面のそれぞれからの反射光である参照光と試
料光の偏光面を偏光光学素子を介在させて互いに直交さ
せることにより、光学的無干渉状態となした原光束を生
成する観測光学系と、前記原光束を複数に分光した分枝
原光束に分け、前記分枝原光束のそれぞれに偏光光学素
子を介して異なる固定的光学位相差を与えた複数の分枝
位相シフト干渉縞を発生させ、前記被検面の観測範囲に
ある一つの位置がそれぞれの分枝観測座標系において同
一位置になるよう位置の整合させ、分枝光束ごとに設け
られた撮像装置でこれらの干渉縞に対応する画像データ
を取得し、前記被検面の観測範囲の平面起伏形状を位相
シフト法を用いて数値データとして再現させる位相シフ
ト干渉縞同時撮像装置において、前記参照光と前記試料
光との間に相対的な光学的位相差を別途与えたときに前
記各撮像装置で得られる分枝ごとの位相シフト干渉縞画
像データから位相シフト法を用いて平面起伏形状を分枝
光束ごとに数値データとして算出し、異なる分枝の平面
起伏形状間で位置的に整合された点における前記数値デ
ータの相対的な差から前記固定的光学位相差を各点ごと
に求め、位相シフト法における干渉縞の各点ごとの位相
算出過程にて同固定的光学位相差を使用する位相シフト
干渉縞同時撮像装置における平面形状計測方法が提案さ
れる。In order to achieve this object, the present invention measures in advance a fixed optical phase difference given to each of a plurality of branched original light beams for each point between imaging devices,
The present invention proposes to use the fixed optical phase difference obtained by the measurement at the time of calculating the undulation shape of the surface to be tested, thereby achieving a great improvement in accuracy of the simultaneous phase shift interference fringe imaging apparatus. That is, in the present invention, the reference surface and the test surface are irradiated with the coherent light beam from the laser light source, and the reference light and the sample light, which are the reflected light from the reference surface and the test surface, are polarized. An observation optical system that generates an original light beam in an optically non-interfering state by intersecting the original light beam through an optical element and splitting the original light beam into a plurality of branched original light beams. Generate a plurality of branched phase-shift interference fringes, each of which has a different fixed optical phase difference via a polarizing optical element, and one position in the observation range of the surface to be measured is in each of the branch observation coordinate systems. The positions are aligned so as to be the same position, image data corresponding to these interference fringes is acquired by an imaging device provided for each branch light beam, and the plane undulation shape of the observation range of the surface to be inspected is phase-shifted. Numeric using In the simultaneous phase shift interference fringe imaging apparatus to be reproduced as data, the phase for each branch obtained by each imaging apparatus when a relative optical phase difference is separately provided between the reference light and the sample light. Using a phase shift method from the shifted interference fringe image data, the plane undulation shape is calculated as numerical data for each of the branched light beams, and the relative values of the numerical data at points that are positionally matched between the plane undulation shapes of different branches are calculated. The fixed optical phase difference is obtained for each point from the difference, and the phase shift interference fringe simultaneous imaging apparatus using the same fixed optical phase difference in the phase calculation process for each point of the interference fringe in the phase shift method. A shape measurement method is proposed.
【０００７】後述する本発明の好ましい実施例の説明に
おいては、 1)前記参照光と前記試料光との間に相対的な光学的位相
差を別途与える際、前記レーザ光源の波長をわずかづつ
変化させることにより前記光学的位相差を発生させる方
法、 2)前記参照光と前記試料光との間に相対的な光学的位相
差を別途与える際、前記参照面あるいは前記被検面のど
ちらか一方を光軸に沿ってわずかづつ平行移動させるこ
とにより、前記光学的位相差を発生させる方法、 3)前記参照光と前記試料光との間に相対的な光学的位相
差を別途与える際、前記参照面と前記被検面との間の光
路に１より大きい屈折率をもつ無反射透過体であって、
互いに厚みが異なる少なくとも１枚の平行板を挿入する
ことにより前記光学的位相差を発生させる方法、 4)前記参照光と前記試料光との間に相対的な光学的位相
差を別途与える際、前記参照面と前記被検面との間の光
路に１より大きい屈折率を持つ無反射透過体であって、
参照面及び被検面に向かい合う２面が平行でない光学楔
を挿入し、光軸に対してほぼ略直交する面内において光
学楔を楔方向に移動させ前記光学的位相差を発生させる
方法、 5)前記参照光と前記試料光との間に相対的な光学的位相
差を別途与える際、前記参照面を被検面との間に液晶を
配置し、液晶の電気的な制御により屈折率を可変し、所
定の光学的位相差を発生させる方法、In the following description of a preferred embodiment of the present invention, 1) when a relative optical phase difference is separately provided between the reference light and the sample light, the wavelength of the laser light source is changed little by little. 2) a method of generating a relative optical phase difference between the reference light and the sample light by providing a relative optical phase difference between the reference light and the sample light. The method of generating the optical phase difference by slightly translating the optical axis along the optical axis, 3) When separately providing a relative optical phase difference between the reference light and the sample light, A non-reflective transmissive body having a refractive index greater than 1 in an optical path between a reference surface and the test surface,
A method of generating the optical phase difference by inserting at least one parallel plate having a different thickness from each other, 4) when separately providing a relative optical phase difference between the reference light and the sample light, A non-reflective transmissive body having a refractive index greater than 1 in an optical path between the reference surface and the test surface,
A method in which an optical wedge whose two surfaces facing the reference surface and the test surface are not parallel is inserted, and the optical wedge is moved in the wedge direction in a plane substantially perpendicular to the optical axis to generate the optical phase difference; When separately providing a relative optical phase difference between the reference light and the sample light, a liquid crystal is arranged between the reference surface and the surface to be measured, and the refractive index is controlled by electric control of the liquid crystal. Variable, to generate a predetermined optical phase difference,
【０００８】そして、本発明の実施例の説明において
は、 1)各点ごとに求めた前記固定的光学位相差の他点との差
異が、許容範囲である各点の集合ごとに整理された前記
固定的光学位相差の値であるもの、 2)各点ごとに求めた前記固定的光学位相差の値から得た
単純平均または中央値または２乗平均値が、固定的光学
位相差の代表値として、各点の位置に関係なく全領域に
用いられるもの、 3)前述した各平面形状計測方法を具体化するための、波
長をわずかづつ変化できるレーザ光源、光軸に沿ってわ
ずかづつ平行移動できる前記参照面あるいは前記被検
面、前記参照面と前記被検面との間の光路に位置される
１より大きい屈折率の無反射透過体平行板、前記参照面
と前記被検面との間の光路に位置される１より大きい屈
折率をもちかつ楔方向に移動できる光学楔、前記参照面
と前記被検面との間の光路に位置されかつ電気的制御で
屈折率を変化できる液晶を組み込まれた位相シフト干渉
縞同時撮像装置も説明される。In the description of the embodiments of the present invention, 1) Differences between the fixed optical phase difference and other points obtained for each point are arranged for each set of points within an allowable range. 2) a simple average, a median or a root mean square obtained from the values of the fixed optical phase differences obtained for each point is a representative of the fixed optical phase differences. The values are used for the entire area irrespective of the position of each point.3) A laser light source whose wavelength can be changed little by little, and the light source is slightly parallel along the optical axis to implement each of the above-mentioned planar shape measurement methods. The movable reference surface or the test surface, a non-reflective transmissive parallel plate having a refractive index greater than 1 and located in an optical path between the reference surface and the test surface, the reference surface and the test surface, With a refractive index greater than 1 and located in the optical path between Phase shift interference fringe simultaneous imaging device incorporated a liquid crystal capable of changing the refractive index at the location to and electrically controlling the optical path between the optical wedge, wherein the test surface and the reference surface can move also described.
【０００９】[0009]
【発明の実施の形態】本発明の平面形状計測方法は、図
１に示した位相シフト干渉縞同時撮像装置において、複
数の分枝原光束のそれぞれに与えた固定的光学位相差を
撮像装置間の各点ごとに予め計測し、計測によって得ら
れた光学的位相差を被検面起伏形状算出時に使用するこ
とを特徴とするものである。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The planar shape measuring method according to the present invention uses a fixed optical phase difference given to each of a plurality of branched original luminous fluxes in the phase shift interference fringe simultaneous imaging apparatus shown in FIG. Is measured in advance for each of the points, and the optical phase difference obtained by the measurement is used when calculating the undulating shape of the surface to be measured.
【００１０】本発明の平面形状計測方法を具体的に説明
すると、図１の位相シフト干渉縞同時撮像装置におい
て、被検面７を観測したときに撮像装置１３〜１５で得
られる光学的に位相シフトした分枝位相シフト干渉縞は
次式で表される。The method of measuring a planar shape according to the present invention will be described in detail. In the phase shift interference fringe simultaneous imaging apparatus shown in FIG. 1, the optical phase obtained by the imaging apparatuses 13 to 15 when the surface 7 to be inspected is observed. The shifted branched phase shift interference fringes are expressed by the following equation.
【数１】 (Equation 1)
【００１１】ここで、Ｂ（ｘ，ｙ）、Ａ（ｘ，ｙ）はそ
れぞれ３枚の分枝位相シフト干渉縞のバイアス及び振幅
を、φ（ｘ，ｙ）は参照面に対する被検面の相対起伏形
状を表す干渉縞の位相を、α（ｘ，ｙ）、β（ｘ，ｙ）
は偏光板の透過軸角度などによって発生する固定的光学
位相差をそれぞれ表す。また、（１−１式）〜（１−３
式）のα（ｘ，ｙ）、β（ｘ，ｙ）は、図１に示す光学
系の構成要素の機械的設置誤差、光学的屈折率、反射
率、透過率の不均一性の影響を受け、計画値とは異なっ
た値となるので、このまま干渉縞位相算出にα（ｘ，
ｙ）、β（ｘ，ｙ）の計画値を用いると算出位相に大き
な誤差がでることが解る。この誤差の影響を防ぐために
３枚の分枝位相シフト干渉縞における固定的光学位相差
α（ｘ，ｙ）とβ（ｘ，ｙ）を予め各点（ｘ，ｙ）ごと
に計測し、計画値ではなく計測した固定的光学位相差α
（ｘ，ｙ）、β（ｘ，ｙ）を被検面起伏形状演算時に使
用することで、本発明では、位相シフト干渉縞同時撮像
装置の高精度化を図ることができる。Here, B (x, y) and A (x, y) represent the bias and amplitude of the three branched phase-shift interference fringes, respectively, and φ (x, y) represents the position of the test surface with respect to the reference surface. The phase of the interference fringe representing the relative undulation shape is represented by α (x, y), β (x, y)
Represents a fixed optical phase difference generated by the transmission axis angle of the polarizing plate and the like. Also, (1-1) to (1-3)
Α (x, y) and β (x, y) in the formula) are the effects of the mechanical installation error of the components of the optical system shown in FIG. 1 and the non-uniformity of the optical refractive index, reflectance, and transmittance. As a result, since the value differs from the planned value, α (x,
It is understood that a large error occurs in the calculation phase when the planned values of y) and β (x, y) are used. In order to prevent the influence of this error, fixed optical phase differences α (x, y) and β (x, y) in the three branched phase-shift interference fringes are measured in advance for each point (x, y), and the plan is determined. Fixed optical phase difference α, not value
By using (x, y) and β (x, y) at the time of calculating the undulating shape of the surface to be inspected, the present invention can improve the accuracy of the simultaneous phase shift interference fringe imaging apparatus.
【００１２】一方、参照光と試料光の間に光学的位相差
δi を与えたときに、得られる分枝ごとの位相シフト干
渉縞は次式で表されることになる。On the other hand, when an optical phase difference δ i is given between the reference light and the sample light, the obtained phase shift interference fringe for each branch is expressed by the following equation.
【数２】 (Equation 2)
【００１３】これらの（２−１式）〜（２−３式）にお
いて、δi を任意に変化させて分枝ごとに３枚以上の分
枝位相シフト干渉縞を得れば、分枝原光束ごと独立に被
検面起伏形状を算出できる。例えば、δi を干渉縞位相
１周期２πを等しく分割する値 δi ＝ｉ２π／Ｎ；ｉ＝１，２，３，・・・Ｎ とした場合には、各分枝ごとの被検面起伏形状は次式よ
り得られるわけである。In Equations (2-1) to (2-3), if δ i is arbitrarily changed to obtain three or more branched phase-shifted interference fringes for each branch, the branch original The undulating shape of the test surface can be calculated independently for each light beam. For example, if δ i is a value that equally divides one period 2π of the interference fringe phase, δ i = i2π / N; i = 1, 2, 3,..., N The shape is obtained from the following equation.
【００１４】[0014]
【数３】 式（３−１式）、（３−２式）、（３−３式）の左辺の
関係から、お互いの差をとると、固定的光学位相差α
（ｘ，ｙ）とβ（ｘ，ｙ）が被検面観測領域内の各点に
て算出できる。（３−１式）〜（３−３式）は、別途与
える光学位相差δi を多くとれば、空気揺らぎや振動な
どの偶発的な誤差による計測誤差は軽減され、より高精
度な固定的光学位相差α（ｘ，ｙ）とβ（ｘ，ｙ）の決
定が可能になることを示している。(Equation 3) From the relationship on the left side of Expressions (3-1), (3-2), and (3-3), if the difference between them is taken, the fixed optical phase difference α
(X, y) and β (x, y) can be calculated at each point in the inspection surface observation area. (3-1 type) - (3-3 type) is, taking a lot of optical phase difference [delta] i to provide separately, measurement errors due to accidental errors such as air fluctuation or vibration is reduced, more accurate fixed This shows that the optical phase differences α (x, y) and β (x, y) can be determined.
【００１５】次に、分枝位相シフト干渉縞間の固定的光
学位相差を計測するために、参照光と試料光に光学位相
差を別途与える本発明の方法を原理的に説明する。参照
面に対する被検面の距離がｄ（ｘ，ｙ）のときに、撮像
装置１３で得られる干渉縞は、（１−１式）において、 Next, in order to measure a fixed optical phase difference between the branched phase-shift interference fringes, a method of the present invention for separately giving an optical phase difference to the reference light and the sample light will be described. When the distance of the test surface to the reference surface is d (x, y), the interference fringe obtained by the imaging device 13 is expressed by the following equation (1-1).
【数４】 ここに、Ｉ（ｘ，ｙ）は干渉縞強度、Ｂ（ｘ，ｙ）、Ａ
（ｘ，ｙ）はそれぞれバイアス、振幅、λはレーザ光源
１の波長を表す。(Equation 4) Where I (x, y) is the interference fringe intensity, B (x, y), A
(X, y) represent the bias and amplitude, respectively, and λ represents the wavelength of the laser light source 1.
【００１６】（４式）において、波長λを微少量Δλi
変化させたときの干渉縞は、In equation (4), the wavelength λ is reduced to a small amount Δλ i
The interference fringes when changed
【数５】 として表現できる。(Equation 5) Can be expressed as
【００１７】ここで、Here,
【数６】 である。(Equation 6) It is.
【００１８】したがって、撮像装置１３，撮像装置１
４，撮像装置１５によって得られる干渉縞は、それぞれTherefore, the imaging device 13 and the imaging device 1
4. The interference fringes obtained by the imaging device 15 are respectively
【数７】 で表わされる。(Equation 7) Is represented by
【００１９】よって、δi ＝Ｃ・Δλi に相当する量、
レーザ光源１の波長をΔλi だけ変化させ、参照光と試
料光に光学位相差を別途付加して分枝ごとに被検起伏形
状を計測して数値データを得、分枝ごとの数値データの
差をとることで、固定的光学位相差を被検面計測領域内
の各点にて計測することができる。Therefore, an amount corresponding to δ i = C · Δλ i ,
The wavelength of the laser light source 1 is changed by Δλ i , and an optical phase difference is separately added to the reference light and the sample light to measure the undulation shape of each branch to obtain numerical data. By taking the difference, the fixed optical phase difference can be measured at each point in the measurement surface measurement area.
【００２０】また、参照光と試料光に光学位相差を与え
るには、図２に示すように、被検面７を光軸方向にΔｄ
i 平行移動させるか、または、図３に示すように、参照
面５を光軸方向にΔｄi 平行移動させても、同様に、分
枝位相シフト干渉縞間の固定的光学位相差を計測するこ
とができる。これらの場合の分枝位相シフト干渉縞は次
式で表される。In order to provide an optical phase difference between the reference light and the sample light, as shown in FIG.
Even if the reference plane 5 is moved in parallel by Δd i in the optical axis direction as shown in FIG. 3, the fixed optical phase difference between the branched phase-shift interference fringes is measured in the same manner. be able to. The branch phase shift interference fringes in these cases are expressed by the following equations.
【数８】 つまり、（６−１式）、（６−２式）、（６−３式）か
らは、 に相当する変位量Δｄi を与えたときに、各分枝位相シ
フト干渉縞ごとに（３−１式）、（３−２式）、（３−
３式）と同様の算出を行えば、各分枝ごとに被検面起伏
形状が数値データとして得られ、分枝ごとの数値データ
間の差をとることで固定的光学位相差を計測することが
できることが理解される。(Equation 8) That is, from (Equation 6-1), (Equation 6-2), and (Equation 6-3), (3-1 type) when given the corresponding amount of displacement [Delta] d i, for each branch phase shift interference fringes, (3-2 type), (3-
If the same calculation as in Equation 3) is performed, the undulating shape of the test surface is obtained as numerical data for each branch, and the difference between the numerical data for each branch is taken to measure the fixed optical phase difference. It is understood that can be.
【００２１】また、参照光と試料光に光学位相差を与え
るには、前記参照面５を被検面７との間の光路に１より
大きい屈折率をもつ無反射透過体で厚みの異なる平行板
を挿入しても、分枝位相シフト干渉縞間の固定的光学位
相差を計測することができる。In order to provide an optical phase difference between the reference light and the sample light, the reference surface 5 is provided in an optical path between the reference surface 5 and the surface 7 to be inspected by a non-reflective transmissive member having a refractive index greater than 1 and having different thicknesses. Even if a plate is inserted, the fixed optical phase difference between the branched phase-shift interference fringes can be measured.
【００２２】例えば、図４に示すように屈折率がｎで、
厚みがそれぞれｌ1 、ｌ2 の平行板を用い、 平行板を挿入していない状態を δ1 厚みｌ1 の平行板挿入時を δ2 厚みｌ2 の平行板挿入時を δ3 としても、図５に示すように、屈折率がそれぞれｎ1 、
ｎ2 で、厚みが同じｌの平行板を用いて、 平行板を挿入していない状態を δ1 屈折率ｎ1 の平行板挿入時を δ2 屈折率ｎ2 の平行板挿入時を δ3 としても、参照光と試料光に光学的位相差を別途与える
ことが可能で、分枝位相シフト干渉縞間の固定的光学位
相差を計測することができる。For example, as shown in FIG.
Using parallel plates having a thickness of l 1 and l 2 respectively, δ 1 when the parallel plate is not inserted, δ 2 when the parallel plate with the thickness l 1 is inserted, and δ 3 when the parallel plate with the thickness l 2 is inserted, As shown in FIG. 5, the refractive indices are n 1 ,
n 2 , using a parallel plate having the same thickness l, without inserting the parallel plate, δ 1 when inserting a parallel plate with a refractive index n 1 δ 2 when inserting a parallel plate with a refractive index n 2 δ 3 Also, an optical phase difference can be separately given to the reference light and the sample light, and a fixed optical phase difference between the branched phase-shift interference fringes can be measured.
【００２３】また、参照光と試料光に光学的位相差を別
途与える場合、図６に示すように、前記参照面５を被検
面７との間の光路に１より大きい屈折率を持つ無反射透
過体で、参照面５と被検面７と向かい合う２面が平行で
ない光学楔２０を挿入し、同光学楔２０を光軸と概略直
行する面内において楔方向に移動させ、分枝位相シフト
干渉縞間の固定的光学位相差を計測することも可能であ
る。When an optical phase difference is separately given to the reference light and the sample light, as shown in FIG. 6, the optical path between the reference surface 5 and the surface 7 to be measured has a refractive index larger than 1 in the optical path. An optical wedge 20 whose two surfaces facing the reference surface 5 and the test surface 7 are not parallel to each other is inserted by a reflection / transmission body, and the optical wedge 20 is moved in the wedge direction in a plane substantially perpendicular to the optical axis to obtain a branching phase. It is also possible to measure a fixed optical phase difference between shifted interference fringes.
【００２４】また、図７に示すように、液晶２１を参照
面５と被検面７の間に挿入し、制御装置２２により電圧
などの電気的な制御により同液晶２１の屈折率を可変さ
せることにより、δ1 、δ2 、δ3 に相当する光学的位
相差を発生させても、分枝位相シフト干渉縞間の固定的
光学位相差の計測は可能である。As shown in FIG. 7, a liquid crystal 21 is inserted between the reference surface 5 and the surface 7 to be measured, and the refractive index of the liquid crystal 21 is varied by a control device 22 by means of electrical control such as voltage. Thus, even when the optical phase differences corresponding to δ 1 , δ 2 , and δ 3 are generated, it is possible to measure the fixed optical phase difference between the branched phase shift interference fringes.
【００２５】前述したように、各分枝原光束ごとに得ら
れる被検面起伏形状間の差から算出したα（ｘ，ｙ）、
β（ｘ，ｙ）をそのまま固定的光学位相差として位相シ
フト干渉縞同時撮像装置における位相シフト法に適用す
ることもできるが、データ処理をさらに容易にする本発
明の方法を次に示す。図８はα（ｘ，ｙ）のデータ中の
あるｙ1 における位置ｘと固定的光学位相差の１次元の
データα（ｘ，ｙ1 ）の関係を示し、同図中、グラフは
α（ｘ，ｙ1）が観測領域内の位置ｘに対して値が異な
ることを意味している。本発明の場合、α（ｘ，ｙ1 ）
に対してある許容範囲ｔを設定し、その範囲内にある数
値データ群をひとまとめに整理して代表値で置き換え、
α’（ｘ，ｙ1）で図示したような関係を作成する。こ
の考えを２次元ｘ、ｙのデータ群に応用し、ある許容範
囲ｔ内にある領域のデータ群を代表値で置き換えて、
α’（ｘ，ｙ）を作成する。また、固定的光学位相差β
（ｘ，ｙ）に対しても同様の処理を施してβ’（ｘ，
ｙ）を作成しておけば、α（ｘ，ｙ）、β（ｘ，ｙ）を
用いてｘ、ｙの各点ごとに異なる計算を行なう場合に対
して、α’（ｘ，ｙ）、β’（ｘ，ｙ）を使用すれば、
計算コストを削減することができる。As described above, α (x, y) calculated from the difference between the undulating shapes of the test surface obtained for each of the branched light beams,
Although β (x, y) can be directly applied as a fixed optical phase difference to the phase shift method in the phase shift interference fringe simultaneous imaging apparatus, a method of the present invention that further facilitates data processing will be described below. FIG. 8 shows a relationship between the position x at a certain y 1 in the data of α (x, y) and the one-dimensional data α (x, y 1 ) of the fixed optical phase difference. x, y 1 ) means that the value is different from the position x in the observation area. In the case of the present invention, α (x, y 1 )
, A certain allowable range t is set, numerical data groups within the range are collectively arranged and replaced with representative values,
A relationship as shown in FIG. 1 is created by α ′ (x, y 1 ). Applying this idea to a two-dimensional x, y data group, replacing a data group in an area within a certain allowable range t with a representative value,
Create α ′ (x, y). Also, the fixed optical phase difference β
The same processing is performed on (x, y) to obtain β ′ (x, y).
y), α ′ (x, y), α ′ (x, y) and α (x, y), β (x, y) Using β '(x, y),
Calculation costs can be reduced.
【００２６】本発明においては、図９に示すように、α
（ｘ，ｙ）、β（ｘ，ｙ）を単純平均値や中央値α’、
β’で置き換えるか、あるいは、図１０に示すように、
２乗平均から算出したα’（ｘ，ｙ）、β’（ｘ，ｙ）
を用いれば、位相シフト干渉縞同時撮像装置における被
検面起伏形状算出の際の計算コストをさらに削減でき
る。In the present invention, as shown in FIG.
(X, y) and β (x, y) are calculated as a simple average or median α ',
replace with β ', or as shown in FIG.
Α '(x, y), β' (x, y) calculated from the root mean square
Is used, it is possible to further reduce the calculation cost when calculating the undulating shape of the test surface in the simultaneous phase shift interference fringe imaging apparatus.
【００２７】[0027]
【発明の効果】以上の説明から明らかなように、本発明
によれば、可動部を持たないという特徴から得られる位
相シフト干渉縞同時撮像装置の誤差要素の再現性の良さ
を利用して、光学系固有の固定的光学位相差α（ｘ，
ｙ）、β（ｘ，ｙ）を高精度に算出し、この値を被検面
起伏形状計測時に使用することにより、被検面起伏形状
計測の際の測定精度の大幅な向上を期待できる。As is apparent from the above description, according to the present invention, the good reproducibility of the error element of the phase shift interference fringe simultaneous imaging apparatus obtained from the feature of not having a movable portion is used. The fixed optical phase difference α (x,
By calculating y) and β (x, y) with high accuracy and using these values at the time of measuring the undulating shape of the surface to be inspected, it is possible to expect a significant improvement in the measurement accuracy when measuring the undulating shape of the surface to be inspected.
【図１】本発明による位相シフト干渉縞同時撮像装置の
光学系の概念図である。FIG. 1 is a conceptual diagram of an optical system of a phase shift interference fringe simultaneous imaging apparatus according to the present invention.
【図２】同位相シフト干渉縞同時撮像装置における第１
の光学的位相差付与手段の説明図である。FIG. 2 is a first diagram of the same phase shift interference fringe simultaneous imaging apparatus.
FIG. 4 is an explanatory diagram of an optical phase difference providing means.
【図３】同位相シフト干渉縞同時撮像装置における第２
の光学的位相差付与手段の説明図である。FIG. 3 shows a second example of the phase shift interference fringe simultaneous imaging apparatus.
FIG. 4 is an explanatory diagram of an optical phase difference providing means.
【図４】同位相シフト干渉縞同時撮像装置における第３
の光学的位相差付与手段の説明図である。FIG. 4 is a diagram showing a third example of the simultaneous phase shift interference fringe imaging apparatus.
FIG. 4 is an explanatory diagram of an optical phase difference providing means.
【図５】同位相シフト干渉縞同時撮像装置における第４
の光学的位相差付与手段の説明図である。FIG. 5 shows a fourth example of the same phase shift interference fringe simultaneous imaging apparatus.
FIG. 4 is an explanatory diagram of an optical phase difference providing means.
【図６】同位相シフト干渉縞同時撮像装置における第５
の光学的位相差付与手段の説明図である。FIG. 6 is a diagram showing a fifth example of the simultaneous phase shift interference fringe simultaneous imaging apparatus.
FIG. 4 is an explanatory diagram of an optical phase difference providing means.
【図７】同位相シフト干渉縞同時撮像装置における第６
の光学的位相差付与手段の説明図である。FIG. 7 shows a sixth example of the same phase shift interference fringe simultaneous imaging apparatus.
FIG. 4 is an explanatory diagram of an optical phase difference providing means.
【図８】本発明による固定的光学位相差の算出方法の説
明図である。FIG. 8 is an explanatory diagram of a method for calculating a fixed optical phase difference according to the present invention.
【図９】単純平均あるいは中央値による固定的光学位相
差の算出方法の説明図である。FIG. 9 is an explanatory diagram of a method of calculating a fixed optical phase difference based on a simple average or a median value.
【図１０】２乗平均による固定的光学位相差の算出方法
の説明図である。FIG. 10 is an explanatory diagram of a method of calculating a fixed optical phase difference by means of root mean square.
１ レーザ光源 ２ レンズ ３ ビームスプリッタ ４ コリメータレンズ ５ 参照面 ６ １／４波長板 ７ 被検面 ８ １／４波長板 ９ ３分光プリズム １０〜１２ 偏光板 １３〜１５ 撮像装置 １６〜１９ 平行板 ２０ 光学楔 ２１ 液晶 ２２ 制御装置 DESCRIPTION OF SYMBOLS 1 Laser light source 2 Lens 3 Beam splitter 4 Collimator lens 5 Reference surface 6 1/4 wavelength plate 7 Test surface 8 1/4 wavelength plate 9 3 Dispersion prism 10-12 Polarization plate 13-15 Imaging device 16-19 Parallel plate 20 Optical wedge 21 Liquid crystal 22 Controller
───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 2F064 AA09 BB07 DD08 FF01 FF08 GG22 GG32 GG38 GG53 HH03 JJ01 2F065 AA54 FF01 FF52 GG04 GG25 JJ03 JJ05 LL00 LL32 LL36 LL46 LL47 MM03 QQ31 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F064 AA09 BB07 DD08 FF01 FF08 GG22 GG32 GG38 GG53 HH03 JJ01 2F065 AA54 FF01 FF52 GG04 GG25 JJ03 JJ05 LL00 LL32 LL36 LL46 LL47 MM03 QQ31
Claims (9)
照面と被検面に照射し、前記参照面及び前記被検面のそ
れぞれからの反射光である参照光と試料光の偏光面を偏
光光学素子を介在させて互いに直交させることにより、
光学的無干渉状態となした原光束を生成する観測光学系
と、 前記原光束を複数に分光した分枝原光束に分け、前記分
枝原光束のそれぞれに偏光光学素子を介して異なる固定
的光学位相差を与えた複数の分枝位相シフト干渉縞を発
生させ、前記被検面の観測範囲にある一つの位置がそれ
ぞれの分枝観測座標系において同一位置になるよう位置
の整合させ、分枝光束ごとに設けられた撮像装置でこれ
らの干渉縞に対応する画像データを取得し、前記被検面
の観測範囲の平面起伏形状を位相シフト法を用いて数値
データとして再現させる位相シフト干渉縞同時撮像装置
において、 前記参照光と前記試料光との間に相対的な光学的位相差
を別途与えたときに前記各撮像装置で得られる分枝ごと
の位相シフト干渉縞画像データから位相シフト法を用い
て平面起伏形状を分枝光束ごとに数値データとして算出
し、異なる分枝の平面起伏形状間で位置的に整合された
点における前記数値データの相対的な差から前記固定的
光学位相差を各点ごとに求め、位相シフト干渉縞同時観
測装置における位相シフト法の干渉縞の各点ごとの位相
算出過程にて同固定的光学位相差を使用することを特徴
とする位相シフト干渉縞同時撮像装置における平面形状
計測方法。1. A reference surface and a test surface are irradiated with a coherent light beam from a laser light source, and polarization surfaces of a reference light and a sample light, which are reflected light from the reference surface and the test surface, are polarized by a polarizing optical element. By interposing them at right angles to each other,
An observation optical system that generates an original light beam in an optically non-interfering state; and a divided stationary light beam that is divided into a plurality of branched original light beams by dividing the original light beam into a plurality of divided original light beams via a polarizing optical element. A plurality of branched phase-shifted interference fringes with an optical phase difference are generated, and the positions are matched so that one position in the observation range of the test surface is the same position in each branch observation coordinate system. A phase shift interference fringe that acquires image data corresponding to these interference fringes with an imaging device provided for each branch light beam, and reproduces a plane undulation shape of the observation range of the test surface as numerical data using a phase shift method. In the simultaneous imaging device, a phase shift method is performed from phase-shift interference fringe image data for each branch obtained by each of the imaging devices when a relative optical phase difference is separately provided between the reference light and the sample light. Using The plane undulation shape is calculated as numerical data for each of the branched light beams, and the fixed optical phase difference is calculated for each point from the relative difference between the numerical data at points that are positionally matched between the plane undulation shapes of different branches. In the phase shift interference fringe simultaneous imaging apparatus, the same fixed optical phase difference is used in the phase calculation process for each point of the interference fringe of the phase shift method in the phase shift interference fringe simultaneous observation apparatus. Plane shape measurement method.
な光学的位相差を別途与える際、前記レーザ光源の波長
をわずかづつ変化させることにより前記光学的位相差を
発生させることを特徴とする請求項１記載の位相シフト
干渉縞同時撮像装置における平面形状計測方法。2. The method according to claim 1, wherein when the relative optical phase difference is separately provided between the reference light and the sample light, the optical phase difference is generated by slightly changing the wavelength of the laser light source. The method for measuring a planar shape in a simultaneous phase shift interference fringe imaging apparatus according to claim 1.
な光学的位相差を別途与える際、前記参照面あるいは前
記被検面のどちらか一方を光軸に沿ってわずかづつ平行
移動させることにより、前記光学的位相差を発生させる
ことを特徴とする請求項１記載の位相シフト干渉縞同時
撮像装置における平面形状計測方法。3. When separately giving a relative optical phase difference between the reference light and the sample light, one of the reference surface and the test surface is slightly translated along the optical axis. 2. The method according to claim 1, wherein the optical phase difference is generated.
な光学的位相差を別途与える際、前記参照面と前記被検
面との間の光路に１より大きい屈折率をもつ無反射透過
体であって、互いに厚みが異なる少なくとも１枚の平行
板を挿入することにより前記光学的位相差を発生させる
ことを特徴とする請求項１記載の位相シフト干渉縞同時
撮像装置における平面形状計測方法。4. When separately providing a relative optical phase difference between the reference light and the sample light, the optical path between the reference surface and the test surface has a refractive index greater than 1 in the optical path. The planar shape in the phase shift interference fringe simultaneous imaging apparatus according to claim 1, wherein the optical phase difference is generated by inserting at least one parallel plate having a thickness different from each other in a reflection / transmission body. Measurement method.
な光学的位相差を別途与える際、前記参照面と前記被検
面との間の光路に１より大きい屈折率を持つ無反射透過
体であって、参照面及び被検面に向かい合う２面が平行
でない光学楔を挿入し、光軸に対してほぼ略直交する面
内において光学楔を楔方向に移動させ前記光学的位相差
を発生させることを特徴とする請求項１記載の位相シフ
ト干渉縞同時撮像装置における平面形状計測方法。5. When separately providing a relative optical phase difference between the reference light and the sample light, the optical path between the reference surface and the test surface has a refractive index greater than 1 in the optical path. An optical wedge, which is a reflective / transmissive body and whose two surfaces facing the reference surface and the test surface are not parallel, is inserted, and the optical wedge is moved in a wedge direction in a plane substantially orthogonal to the optical axis to thereby adjust the optical position. 2. The method according to claim 1, wherein a phase difference is generated.
な光学的位相差を与える際、前記参照面と被検面との間
に液晶を配置し、液晶の電気的な制御により屈折率を可
変し、所定の光学的位相差を発生させることを特徴とす
る請求項１記載の位相シフト干渉縞同時撮像装置におけ
る平面形状計測方法。6. When a relative optical phase difference is provided between the reference light and the sample light, a liquid crystal is arranged between the reference surface and the test surface, and the liquid crystal is electrically controlled. 2. The method according to claim 1, wherein the refractive index is varied to generate a predetermined optical phase difference.
の他点との差異が、許容範囲である各点の集合ごとに整
理された前記固定的光学位相差の値であることを特徴と
する請求項１記載の位相シフト干渉縞同時撮像装置にお
ける平面形状計測方法。7. The fixed optical phase difference obtained for each point from another point is a value of the fixed optical phase difference arranged for each set of points within an allowable range. The method for measuring a planar shape in a simultaneous phase shift interference fringe imaging apparatus according to claim 1.
の値から得た単純平均値または中央値または２乗平均値
が、固定的光学位相差の代表値として、各点の位置に関
係なく全領域に用いられることを特徴とする請求項７記
載の位相シフト干渉縞同時撮像装置における平面形状計
測方法。8. A simple average value, a median value, or a root mean square value obtained from the values of the fixed optical phase difference obtained for each point is set as a representative value of the fixed optical phase difference at the position of each point. 8. The method according to claim 7, wherein the method is used for all regions regardless of the plane shape.
載のレーザ光源、光軸に沿ってわずかづつ平行移動でき
る請求項３記載の前記参照面あるいは前記被検面、前記
参照面と前記被検面との間の光路に位置される１より大
きい屈折率をもつ請求項４記載の無反射透過体平行板、
前記参照面と前記被検面との間の光路に位置される１よ
り大きい屈折率をもちかつ楔方向に移動できる請求項５
記載の光学楔、前記参照面と前記被検面との間の光路に
位置されかつ電気的制御で屈折率を変化できる請求項６
記載の液晶の何れかひとつを備える位相シフト干渉縞同
時撮像装置。9. The laser light source according to claim 2, wherein the wavelength can be changed little by little, the reference surface or the test surface, the reference surface and the test object according to claim 3, wherein the laser light source can be moved in parallel little by little along the optical axis. The non-reflective transmissive parallel plate according to claim 4, having a refractive index greater than 1 and located in an optical path between the plane and the surface.
6. A wedge-shaped movable member having a refractive index greater than 1 and located in an optical path between the reference surface and the test surface.
7. The optical wedge according to claim 6, wherein the optical wedge is located in an optical path between the reference surface and the test surface, and the refractive index can be changed by electrical control.
A phase shift interference fringe simultaneous imaging apparatus comprising any one of the liquid crystals described in the above.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010127873A (en) * | 2008-12-01 | 2010-06-10 | Takaoka Electric Mfg Co Ltd | Interferometer |
| WO2013009533A1 (en) * | 2011-07-14 | 2013-01-17 | Faro Technologies, Inc. | Scanner with phase and pitch adjustment |
| US9091529B2 (en) | 2011-07-14 | 2015-07-28 | Faro Technologies, Inc. | Grating-based scanner with phase and pitch adjustment |
| US9170098B2 (en) | 2011-07-13 | 2015-10-27 | Faro Technologies, Inc. | Device and method using a spatial light modulator to find 3D coordinates of an object |
| EP3118571A1 (en) | 2015-07-14 | 2017-01-18 | Mitutoyo Corporation | Instantaneous phase-shift interferometer and measurement method |
-
2000
- 2000-06-30 JP JP2000197483A patent/JP3714853B2/en not_active Expired - Fee Related
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010127873A (en) * | 2008-12-01 | 2010-06-10 | Takaoka Electric Mfg Co Ltd | Interferometer |
| US9170098B2 (en) | 2011-07-13 | 2015-10-27 | Faro Technologies, Inc. | Device and method using a spatial light modulator to find 3D coordinates of an object |
| WO2013009533A1 (en) * | 2011-07-14 | 2013-01-17 | Faro Technologies, Inc. | Scanner with phase and pitch adjustment |
| GB2507021A (en) * | 2011-07-14 | 2014-04-16 | Faro Tech Inc | Scanner with phase and pitch adjustment |
| US9091529B2 (en) | 2011-07-14 | 2015-07-28 | Faro Technologies, Inc. | Grating-based scanner with phase and pitch adjustment |
| EP3118571A1 (en) | 2015-07-14 | 2017-01-18 | Mitutoyo Corporation | Instantaneous phase-shift interferometer and measurement method |
| CN106352789A (en) * | 2015-07-14 | 2017-01-25 | 株式会社三丰 | Instantaneous phase-shift interferometer and measurement method |
| US10088291B2 (en) | 2015-07-14 | 2018-10-02 | Mitutoyo Corporation | Instantaneous phase-shift interferometer |
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