JPH0652162B2 - Interferometry method - Google Patents
Interferometry methodInfo
- Publication number
- JPH0652162B2 JPH0652162B2 JP60070637A JP7063785A JPH0652162B2 JP H0652162 B2 JPH0652162 B2 JP H0652162B2 JP 60070637 A JP60070637 A JP 60070637A JP 7063785 A JP7063785 A JP 7063785A JP H0652162 B2 JPH0652162 B2 JP H0652162B2
- Authority
- JP
- Japan
- Prior art keywords
- spectrum
- area sensor
- light
- measurement
- wavefront
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000000034 method Methods 0.000 title claims description 13
- 238000005305 interferometry Methods 0.000 title 1
- 238000005259 measurement Methods 0.000 claims description 23
- 238000001228 spectrum Methods 0.000 claims description 21
- 238000005070 sampling Methods 0.000 claims description 13
- 238000012545 processing Methods 0.000 claims description 10
- 238000000691 measurement method Methods 0.000 claims description 7
- 230000004907 flux Effects 0.000 claims 1
- 238000009826 distribution Methods 0.000 description 6
- 238000004364 calculation method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000004088 simulation Methods 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000005094 computer simulation Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02083—Interferometers characterised by particular signal processing and presentation
- G01B9/02084—Processing in the Fourier or frequency domain when not imaged in the frequency domain
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
- G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
- G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
- G01J9/0215—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods by shearing interferometric methods
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Mathematical Physics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Instruments For Measurement Of Length By Optical Means (AREA)
- Length Measuring Devices By Optical Means (AREA)
Description
【発明の詳細な説明】 （技術分野） 本発明は、干渉測定方法に関する。TECHNICAL FIELD The present invention relates to an interference measurement method.
（従来技術） 干渉測定方法は、基準面からの反射光である参照光と、
測定面からの反射光である測定光とを干渉せしめ、その
干渉縞の解析により測定波面と参照波面との差異を知
り、測定面の形状を高精度に測定する方法である。(Prior Art) The interferometric measurement method uses a reference light that is reflected light from a reference surface,
This is a method in which the measurement light, which is the reflected light from the measurement surface, is caused to interfere with each other, the difference between the measurement wavefront and the reference wavefront is known by analyzing the interference fringes, and the shape of the measurement surface is measured with high accuracy.
このような干渉測定方法のうちに、フーリエ変換を利用
する方法がある。すなわち、測定光と参照光とを所定面
内で互いに微小角θ傾けてエリアセンサーに入射せし
め、両者の干渉縞をエリアセンサーによりウィンドウ処
理をして読取り、その結果をフーリエ変換することによ
り、傾き角θによる分離された３群の空間周波数のスペ
クトル群を得、これらスペクトル群からひとつの単側波
帯のみを選択し、これを周波数軸上で傾き角θに対応す
る量だけスペクトル移動し、これによって傾き成分を除
去し、得られるスペクトルに対し逆フーリエ変換と逆ウ
ィンドウ処理とを行ない、その結果から位相部分を算出
することにより、エリアセンサー上の測定波面の、参照
波面からの偏差を算出する測定方法である。Among such interference measurement methods, there is a method using Fourier transform. That is, the measurement light and the reference light are made to enter the area sensor with a small angle θ with respect to each other within a predetermined plane, the interference fringes of both are subjected to window processing by the area sensor and read, and the result is Fourier transformed to obtain the tilt. Obtaining spectrum groups of three spatial frequencies separated by the angle θ, selecting only one single sideband from these spectrum groups, and moving the spectrum by an amount corresponding to the tilt angle θ on the frequency axis, By this, the slope component is removed, the obtained spectrum is subjected to inverse Fourier transform and inverse window processing, and the phase portion is calculated from the result, thereby calculating the deviation of the measured wavefront on the area sensor from the reference wavefront. It is a measuring method.
（目的） 本発明は、上記の如きフーリエ変換を利用する干渉測定
方法を改良し、演算が容易で測定精度の高い干渉測定方
法の提供を目的としている。(Object) The object of the present invention is to provide an interference measurement method that improves the interference measurement method using the Fourier transform as described above and is easy to calculate and has high measurement accuracy.
（構成） 以下、本発明を説明する。(Structure) Hereinafter, the present invention will be described.
本発明の特徴は、以下にのべる点にある。The features of the present invention are as follows.
フーリエ変換や、その逆変換の演算は離散的に行なわれ
るのであるが、傾き角θに対応する空間周波数ｏとサ
ンプリング区間Ｄとの間に、ｎを整数として、ｏ＝ｎ
／Ｄが成立つように、θとＤの関係を定める。上記空間
周波数ｏは、λを波長として、 で与えられる。The Fourier transform and its inverse transform are discretely performed. However, between the spatial frequency o corresponding to the tilt angle θ and the sampling interval D, n is an integer, and o = n
The relationship between θ and D is determined so that / D holds. The spatial frequency o is the wavelength of λ, Given in.
また、フーリエ変換に先立つウィンドウ処理において
は、読取りの各ラインごとに、ウインドウ両端部を、入
力光束の境界部と一致させるように、スレッシュホール
ドレベルを設ける。In addition, in the window processing prior to the Fourier transform, a threshold level is set for each line of reading so that both ends of the window coincide with the boundary of the input light beam.
さらに、スペクトル移動の際に、１周期の出力周波数領
域を越える成分については、移動方向と反対方向に1/d
だけ移動させる。ここにｄはサンプリングピッチであ
る。Furthermore, when the spectrum is moved, the component that exceeds the output frequency region of one cycle is 1 / d in the direction opposite to the moving direction.
Just move. Here, d is a sampling pitch.
以下、図面を参照しながら、説明する。Hereinafter, description will be given with reference to the drawings.
第１図において、符号10はビームスプリッター符号12は
測定対象物、符号14は平面鏡、符号16はレンズ、符号18
はエリアセンサーをそれぞれ示している。測定対象物12
は測定面を有する。平面鏡14の鏡面は基準面である。ま
たｘ方向、ｚ方向を図の如く定め、ｙ方向は、図面に直
交する方向とする。平面鏡14は、その鏡面に法線が、所
定のｘｚ面内でｘ方向に対して微小角傾いている。In FIG. 1, reference numeral 10 is a beam splitter, reference numeral 12 is an object to be measured, reference numeral 14 is a plane mirror, reference numeral 16 is a lens, and reference numeral 18 is provided.
Indicate area sensors. Object to be measured 12
Has a measurement surface. The mirror surface of the plane mirror 14 is a reference surface. Further, the x direction and the z direction are defined as shown in the drawing, and the y direction is a direction orthogonal to the drawing. The plane of the plane mirror 14 has a normal to the mirror surface inclined at a slight angle with respect to the x direction within a predetermined xz plane.
今、ビームスピリッター10に対し、平面波が左方からＺ
方向に入射すると、この平面波はビームスプリッター10
により２分割され、一方は、測定対象物12に、他方は平
面鏡14に入射する。測定対象物12に入射した平面波は、
測定面により反射され、測定光となりビームスプリッタ
ー10に入射し、ｘ方向へ反射され、レンズ16を介してエ
リアセンサー18に入射し、エリアセンサー18の受光面上
に測定面形状に応じた位相形状を形成する。この位相形
状をWA(x)とする。この位相形状は、本来はｘ、ｙの関
数としてWA(x、y)と書くべきものである。一方平面鏡14
に入射した平面波は、反射されて参照波となり、ビーム
スプリッター10、レンズ16を介してエリアセンサー18に
入射する。この参照波の波面は平面である。参照光は、
平面鏡14の傾きのため、測定光に対して微小角θだけ傾
いてエリアセンサー18に入射する。従って参照波面はｘ
方向に対して傾いたものとなる。この参照波面（参照波
の位相形状）をWB(x)とする。測定光と参照光とは干渉
しエリアセンサー上に干渉縞を生ずる。Now, for the beam spirit 10, the plane wave is Z from the left.
Upon incidence in this direction, this plane wave is reflected by the beam splitter 10.
It is divided into two by one, and one is incident on the measuring object 12 and the other is incident on the plane mirror 14. The plane wave incident on the measurement target 12 is
It is reflected by the measurement surface, becomes measurement light, enters the beam splitter 10, is reflected in the x direction, enters the area sensor 18 via the lens 16, and has a phase shape corresponding to the shape of the measurement surface on the light receiving surface of the area sensor 18. To form. Let this phase shape be WA (x). This phase shape should be originally written as WA (x, y) as a function of x and y. Meanwhile, plane mirror 14
The plane wave incident on is reflected and becomes a reference wave, and is incident on the area sensor 18 via the beam splitter 10 and the lens 16. The wavefront of this reference wave is a plane. The reference light is
Due to the inclination of the plane mirror 14, the light enters the area sensor 18 with a small angle θ with respect to the measurement light. Therefore the reference wavefront is x
It will be inclined to the direction. This reference wavefront (phase shape of the reference wave) is WB (x). The measurement light and the reference light interfere with each other to generate interference fringes on the area sensor.
測定波面WA(x)と参照波面WB(x)の相対的な位置関係を第
１図（II）に示す。The relative positional relationship between the measured wavefront WA (x) and the reference wavefront WB (x) is shown in Fig. 1 (II).
これらWA(x)，WB(x)の複素振幅分布を、それぞれ、α
(ｘ)ｅj(WA(x)+2 π ox)，β(x)とすると、干渉縞の強
度分布g(x)は、 となる。ただし、ｏは、λを波長として であり、ａ(ｘ)＝α2(ｘ)，ｂ(ｘ)＝２α(ｘ)β(ｘ)， である。これから分るように、測定波面WA(x)の情報
は、(1)式の２項と３項に入っている。The complex amplitude distributions of WA (x) and WB (x) are
(x) e j (WA (x) +2 π ox) and β (x), the intensity distribution g (x) of the interference fringes is Becomes Where o is the wavelength And a (x) = α 2 (x), b (x) = 2α (x) β (x), Is. As can be seen, the information on the measured wavefront WA (x) is contained in the second and third terms of equation (1).
この強度分布ｇ(ｘ)をサンプリング区間についてウィン
ドウ処理を行ない、これをｘに関してフーリエ変換する
と、 Ｇ()＝Ａ()＋Ｃ（−o）＋Ｃ＊（＋o）
(3) というスペクトルが得られる。このスペクトル(3)式
は、傾き角θに応じた空間周波数ｏにより３群Ａ
()，Ｃ（−ｏ），Ｃ＊（＋o）に分離してい
る。もとめるべき測定波面WA(x)に関する情報は、単側
波帯Ｃ（−o）とＣ＊（＋o）に含まれている。
そこで、このうち、ひとつの単側波帯Ｃ（−ｏ）を
選択する。This intensity distribution g (x) is subjected to window processing for sampling intervals, and Fourier transform is performed for this as x. G () = A () + C (−o) + C * (+ o)
The spectrum (3) is obtained. This spectrum (3) is obtained by the third group A by the spatial frequency o according to the tilt angle θ.
(), C (-o), C * (+ o). The information on the measured wavefront WA (x) to be obtained is contained in the single sidebands C (−o) and C * (+ o).
Therefore, of these, one single sideband C (−o) is selected.
そのためには、(3)式の右辺のスペクトル群Ａ()，Ｃ
＊（−ｏ）をフィルターで除去すればよい。このよ
うにして得られるＣ（−ｏ）を、周波数軸上で、
ｏだけ原点にむけて、スペクトル移動すると、Ｃ()な
るスペクトルが得られるが、このスペクトルＣ()で
は、傾き角θにもとづく傾き成分が除去されている。そ
こで、Ｃ()を逆フーリエ変換し、逆ウィンドウ処理す
ると が求められる。測定波面WA(x)は の位相部分であるから、WA(x)は、 として与えられる。For that purpose, the spectrum groups A (), C on the right side of the equation (3) are used.
* (-O) may be removed by a filter. C (-o) obtained in this way is
When the spectrum is moved toward the origin by o, a spectrum C () is obtained. In this spectrum C (), the tilt component based on the tilt angle θ is removed. Therefore, if we perform inverse Fourier transform of C () and perform inverse window processing, Is required. The measured wavefront WA (x) is WA (x) is the phase part of Given as.
測定波面WA(x)は、本来WA(x、y)と記するべきものであ
る旨先に述べたが、エリアセンサー18による読取は、ｙ
方向については、１ラインずつ行なうので各ラインの読
取結果についての演算プロセスでは、これをｘのみの関
数WA(x)としてあつかってよい。As mentioned earlier, the measured wavefront WA (x) should be written as WA (x, y), but the reading by the area sensor 18 is y
Regarding the direction, since it is performed line by line, this may be treated as a function WA (x) of only x in the calculation process for the read result of each line.
さて、周知の如く、離散的なフーリエ変換においては、
サンプリングピッチｄでＮ個の値についてフーリエ変換
すると、周波数領域でのスペクトルは、ピッチが1/D
で、周期が1/dとなる。ここにＤはサンプリング区間で
あってＤ＝ｄ・（Ｎ＋１）で与えられる。As is well known, in the discrete Fourier transform,
When Fourier transform is performed on N values at the sampling pitch d, the spectrum in the frequency domain has a pitch of 1 / D.
And the cycle becomes 1 / d. Here, D is a sampling interval and is given by D = d · (N + 1).
例えば、第１図（III）において、フーリエ変換される
べき強度分布ｇ(ｘ)が、破線の如きものとするとき、サ
ンプリングピッチｄで、サンプリング区間Ｄ内のＮ点に
ついてフーリエ変換を行なうと、その結果は第１図（I
V）に示す如くなる。スペクトルＧ()は、ピッチが１
／Ｄで、周期１／ｄの周期関数である。For example, in FIG. 1 (III), when the intensity distribution g (x) to be Fourier transformed is as shown by a broken line, Fourier transform is performed for N points in the sampling section D at the sampling pitch d, The results are shown in Fig. 1 (I
V). The pitch of spectrum G () is 1
/ D is a periodic function having a period of 1 / d.
従って、空間周波数ｏに対して、ｎを整数として、 とすると、スイペクトルにおけるｏ成分は１区間にの
み表われることになり、(3)式におけるＣ（−
ｏ），Ｃ＊（＋ｏ）の広がりが抑制され、フィルタ
ー操作，スペクトル移動操作を正確に行うことができ、
演算も簡単化される。ｏは であるから、 を実現するには、予め定められたＤに対して を満足するように、傾き角θを定める方法（第１の方
法）と、他の測定器で傾き角θを正確に測定し、 を満足するようにサンプリング区間を調整する方法（第
２の方法）とがある。Therefore, for spatial frequency o, n is an integer, Then, the o component in the swipe vector will appear only in one section, and C (-
The spread of o) and C * (+ o) is suppressed, and the filter operation and the spectrum transfer operation can be performed accurately,
The calculation is also simplified. o is Therefore, In order to realize To satisfy the above condition (first method) and another measuring device to accurately measure the tilt angle θ, There is a method (second method) of adjusting the sampling interval so that
第１の方法は、エリアセンサー18として、出力がサンプ
ルホールドされ、サンプリングピッチｄが固定されるも
のを用いる場合に有効である。第２の方法は、出力が連
続的で、サンプリングピッチｄを可変にできるようなエ
リアセンサーを用いる場合に、角θの許容誤差が厳しい
ときに有効である。The first method is effective when an area sensor 18 whose output is sampled and held and whose sampling pitch d is fixed is used. The second method is effective when the area sensor having a continuous output and capable of varying the sampling pitch d is used and the allowable error of the angle θ is severe.
また、エリアセンサー18による読取りは、ｙ方向につい
てはｘ方向の複数ラインとして読みとられるのである
が、この場合に、各ラインについてＤの値を共通にし、
信号強度方向にスレッシュホールドレベルを設けて、ウ
ィンドウの広さを可変とし、各ラインごとに、ウィンド
ウ両端部を入力光束の境界部と一致させることにより、
測定精度を高めることができる。Further, the reading by the area sensor 18 is performed as a plurality of lines in the x direction in the y direction. In this case, the value of D is made common to each line,
By providing a threshold level in the signal strength direction, the width of the window is made variable, and for each line, both ends of the window are aligned with the boundaries of the input light beam,
The measurement accuracy can be improved.
さらに、スペクトル移動を行うとき、ＦＦＴプロセッサ
ーでは、通常、第１図（IV）の０〜1/dの周波数領域で
の結果が出力される。従って、側波帯Ｃ（−ｏ）を
周波数軸の原点側へｏだけ移動させる際、負領域へ入
る部分は1/dだけ正方向へ移動させることにより、正確
かつ容易に逆変換を実行できる。Further, when performing spectrum shifting, the FFT processor normally outputs the result in the frequency region of 0/1 / d in FIG. 1 (IV). Therefore, when the sideband C (-o) is moved to the origin side of the frequency axis by o, the portion entering the negative region is moved by 1 / d in the positive direction, whereby the inverse conversion can be accurately and easily performed. .
２次元の波面形状WA（ｘ、ｙ）を知るには、平面鏡14の
法線をｘｙ面に平行な面内でｘ方向に対して微小角傾
け、ｙ方向について、前記と同様の方法で１ライン分の
みの形状をもとめ、求められたｙ方向１ライン分の形状
に、先に求められたｘ方向の各ライン（ｙ方向へ並列し
ている）の形状をのせてやればよい。In order to know the two-dimensional wavefront shape WA (x, y), the normal line of the plane mirror 14 is tilted by a slight angle with respect to the x direction within a plane parallel to the xy plane, and the 1 It suffices to obtain the shape of only the lines and add the shape of each line in the x direction (which is parallel to the y direction) previously obtained to the shape of the obtained one line in the y direction.
以下、コンピューターによるシミュレーション例を示
す。The following is an example of computer simulation.
第２図において（Ｉ）は、エリアセンサー上の測定波面
WA(x)を示す。（II）は、測定光と参照光とのおりなす
干渉縞の光強度分布、（III）は、（II）に示す光強度
分布に、ウィンドウ処理を行った状態を示す。ウィンド
ウ関数Ｗは である。また、ウィンドウ両端部は入射光束端部と一致
させている。（IV）は、（III）の結果をフーリエ変換
した状態、（Ｖ）は、単側波帯Ｃ（−ｏ）をスペク
トル移動して傾き成分を除去した状態，(IV)は（Ｖ）の
スペクトルに対し、逆フーリエ変換と逆ウィンドウ処理
を施して得られるＣ(ｘ)につき、その絶対値｜Ｃ(ｘ)｜
と、その位相部分arg（Ｃ(ｘ)）すなわちWA(x)を示す
図、第２図(VII)は、第２図（Ｉ）に示すWA(x)と、上記
の如く算出されたWA(x)（第２図（VI））との差異、す
なわち、測定誤差を示す。この図から明らかなように両
端部をのぞけば、WA(x)は、極めて良好に測定さてい
る。In Fig. 2, (I) is the measured wavefront on the area sensor.
Indicates WA (x). (II) shows the light intensity distribution of the interference fringes formed by the measurement light and the reference light, and (III) shows the light intensity distribution shown in (II) after windowing. Window function W Is. Further, both ends of the window are made to coincide with the ends of the incident light beam. (IV) is a state in which the result of (III) is Fourier-transformed, (V) is a state in which the tilt component is removed by spectrally moving the single sideband C (-o), and (IV) is in (V). Absolute value | C (x) | of C (x) obtained by applying inverse Fourier transform and inverse window processing to the spectrum
And the phase portion arg (C (x)), that is, WA (x), FIG. 2 (VII) shows WA (x) shown in FIG. 2 (I) and the WA calculated as described above. The difference from (x) (Fig. 2 (VI)), that is, the measurement error is shown. As is clear from this figure, WA (x) is measured extremely well except for both ends.
第３図は、従来法による測定のシミュレーションを示
す。（Ｉ）〜（VII）の各図は、第２図における（Ｉ）
〜（VII）にそれぞれ対応している。第３図（III）は、
干渉縞ｇ（ｘ）（同図（II））にウィンドウ処理を施し
た状態を示す。ウィンドウ関数Ｗは、 であって、ウィンドウ両端部は、入力光束の端部を合致
していない。FIG. 3 shows a simulation of measurement by the conventional method. Each of (I) to (VII) corresponds to (I) in FIG.
~ (VII) are supported respectively. Figure 3 (III) shows
The interference fringes g (x) ((II) in the figure) are shown in a state where the window processing is performed. The window function W is However, the both ends of the window do not match the ends of the input light beam.
このため、第３図（VII）に示すように全体にわたって
誤差が生じている。Therefore, as shown in FIG. 3 (VII), an error has occurred throughout.
（効果） 以上、本発明によれば、新規な干渉測定方法を提供でき
る。本発明は上記の如くに構成されているので、従来法
に比し演算が簡単化され、測定精度も向上する。(Effect) As described above, according to the present invention, a novel interference measurement method can be provided. Since the present invention is configured as described above, the calculation is simplified and the measurement accuracy is improved as compared with the conventional method.
第１図は、本発明を説明するための図、第２図は、本発
明の測定方法のシミュレーションの１例を示す図、第３
図は従来の測定方法のシミュレーションの１例を示す図
である。 10……ビームスプリッター、12……測定対象物、14……
平面鏡、16……レンズ、18……エリアセンサー、WA(x)
……測定波面、WB(x)……参照波面FIG. 1 is a diagram for explaining the present invention, FIG. 2 is a diagram showing an example of simulation of the measuring method of the present invention, and FIG.
The figure is a diagram showing an example of a simulation of a conventional measuring method. 10 …… Beam splitter, 12 …… Measurement target, 14 ……
Plane mirror, 16 …… Lens, 18 …… Area sensor, WA (x)
…… Measurement wavefront, WB (x) …… Reference wavefront
Claims (1)
角θ傾けてエリアセンサーに入射せしめ、測定光と参照
光との干渉縞を、エリアセンサーにより、ウィンドウ処
理して上記所定面に平行な方向へ読取り、読取結果をフ
ーリエ変換することにより、上記傾き角θにより分離さ
れた３群の空間周波数のスペクトル群を得、これらスペ
クトル群からひとつの単側波帯のみを選択し、これを周
波数軸上で、上記傾き角θに対応する量だけずらすスペ
クトル移動を行うことによって、傾き成分を除去し、得
られるスペクトルに対し逆フーリエ変換と逆ウィンドウ
処理とを行ない、その結果から位相部分を算出すること
により、エリアセンサー上における測定光の波面の、参
照波面からの偏差を算出する干渉測定方式において、 空間周波数ｏ が、ｎを整数、Ｄをサンプリング区間として、ｏ＝ｎ
／Ｄを満足するように、傾き角θとサンプリング区間Ｄ
との関係を定め、 フーリエ変換に先立つウィンドウ処理において、各ライ
ンごとにウィンドウ両端部を、入力光束の境界部と一致
させるように、スレッシュホールドレベルを設け、 かつ、上記スペクトル移動する際、１周期の出力周波数
領域をこえる成分については、移動方向と反対方向に1/
d（ｄ；サンプリングピッチ）だけ、移動させることを
特徴とする、干渉測定方法。1. The measurement light and the reference light are incident on an area sensor at a small angle θ with respect to each other within a predetermined surface, and the interference fringes of the measurement light and the reference light are windowed by the area sensor to perform the window processing. By reading in the direction parallel to, and Fourier-transforming the read result to obtain three groups of spatial frequency spectrums separated by the inclination angle θ, and selecting only one single sideband from these spectrum groups, The spectrum component is shifted on the frequency axis by an amount corresponding to the tilt angle θ to remove the tilt component, and the obtained spectrum is subjected to inverse Fourier transform and inverse window processing, and the phase is calculated from the result. In the interferometric method for calculating the deviation of the wavefront of the measurement light on the area sensor from the reference wavefront by calculating the portion, the spatial frequency o Where n is an integer and D is a sampling interval, and o = n
Slope angle θ and sampling interval D so as to satisfy / D
In the window processing prior to the Fourier transform, a threshold level is set so that both ends of the window are aligned with the boundary of the input light flux for each line, and one cycle is required when moving the spectrum. For components that exceed the output frequency range of, 1 /
An interference measurement method characterized by moving by d (d; sampling pitch).
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60070637A JPH0652162B2 (en) | 1985-04-03 | 1985-04-03 | Interferometry method |
| US06/840,442 US4744659A (en) | 1985-03-20 | 1986-03-17 | Method of and apparatus for measuring the shape of a wavefront |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60070637A JPH0652162B2 (en) | 1985-04-03 | 1985-04-03 | Interferometry method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61230002A JPS61230002A (en) | 1986-10-14 |
| JPH0652162B2 true JPH0652162B2 (en) | 1994-07-06 |
Family
ID=13437356
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60070637A Expired - Lifetime JPH0652162B2 (en) | 1985-03-20 | 1985-04-03 | Interferometry method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0652162B2 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4583619B2 (en) * | 2000-09-13 | 2010-11-17 | 富士フイルム株式会社 | Method for detecting fringe image analysis error and method for correcting fringe image analysis error |
| JP2002202112A (en) * | 2000-11-06 | 2002-07-19 | Fujitsu Ltd | Shape measuring apparatus |
| JP4610117B2 (en) * | 2001-03-29 | 2011-01-12 | 富士フイルム株式会社 | Fourier transform fringe analysis method and apparatus |
| WO2006030482A1 (en) * | 2004-09-13 | 2006-03-23 | Mitsubishi Denki Kabushiki Kaisha | Laser beam path length difference detector, laser phase controller and coherent optical coupler |
| WO2007088789A1 (en) * | 2006-02-01 | 2007-08-09 | Tokyo Institute Of Technology | Surface shape measuring method and device using the same |
| EP2327956B1 (en) * | 2009-11-20 | 2014-01-22 | Mitutoyo Corporation | Method and apparatus for determining the height of a number of spatial positions on a sample |
| JP6180909B2 (en) * | 2013-12-06 | 2017-08-16 | 東京エレクトロン株式会社 | Method for obtaining distance, method for neutralizing electrostatic chuck, and processing apparatus |
-
1985
- 1985-04-03 JP JP60070637A patent/JPH0652162B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61230002A (en) | 1986-10-14 |
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