JP4209023B2 - Image measurement system and image calibration method - Google Patents

Description

【００１４】
このとき、各撮像装置２１，２２，２３に固有の歪みや座標のずれ等が生じていると、計測精度が低下する。そこで、このシステムでは、各撮像装置２１，２２，２３の歪みをソフト的に補正するための画像校正機能を有している。
【００１５】
図３は、このような画像校正機能を有するコンピュータ３０によって実現される画像計測処理システムを示す機能ブロック図である。画像計測処理システムは、画像処理部３１、変換パラメータ算出部３２、変換パラメータ記憶部３３、歪解消変換処理部３４及び表面形状解析処理部３５を備えている。画像処理部３１は、各撮像装置２１，２２，２３で得られた画像データに対してフィルタ処理や特徴抽出処理、図芯算出処理等を施す。変換パラメータ算出部３２は、各撮像装置２１，２２，２３毎に、画像校正用の撮像対象を撮像して得られた校正用の画像データから歪み補正用の変換パラメータを算出する。変換パラメータ記憶部３３は、算出された変換パラメータを記憶する。歪解消変換処理部３４は、変換パラメータ記憶部３３に記憶された変換パラメータに基づいて、計測用の画像データに対して歪解消用の補正処理を施す。表面形状解析処理部３５は、歪解消された計測用の画像データに基づいて表面形状の解析処理を実行する。
【００１６】
次に、このシステムの画像校正処理及び表面形状計測処理の詳細を説明する。
図４（ａ）は画像校正処理、図４（ｂ）は表面形状計測処理をそれぞれ説明するためのフローチャートである。
まず、画像校正処理では、校正用の撮像対象を撮像する（Ｓ１）。校正用の撮像対象としては、例えば図５に示すように、それぞれが分離している所定の面積を持つ複数の図形（この例では円）４１を含むものを使用する。但し、各図形４１の図芯（重心位置）Ｐの座標値は既知である。この図形４１を含む撮像対象４２を、被計測対象６の位置にセットし、各撮像装置２１，２２，２３から得られた画像データを取り込む（Ｓ２）。そして、取り込まれた画像データに対し、フィルタリング処理、特徴抽出処理、図芯検出処理等を適宜施して図芯Ｐの座標を求め、求められた図芯Ｐの座標値と本来の座標値とのずれ量から各撮像装置２１，２２，２３に固有の回転、縮尺、平行移動及び歪を補正するための変換パラメータを以下のように算出する（Ｓ３）。
【００１７】
即ち、図６に示すように、各図形４１の図芯Ｐの理想的な座標位置を（ｘ_i，ｙ_i）（ｉ＝１〜Ｎ）、実際に観測された座標位置を（ｘ_i′，ｙ_i′）とすると、これらの間の回転、縮尺、平行移動、歪みを含めた変換式は、下記数２に示すアフィン変換式を利用することができる。
【００１８】
【数２】

【００１９】
ここで、変換パラメータａ₁，ａ₂，ｂ₁，ｂ₂，ｃ₁，ｃ₂は、下記数３で示す誤差Ｅの最小値を求めることにより算出することができる（最小二乗法）。求められた変換パラメータは、変換パラメータ記憶部３３に格納される。
【００２０】
【数３】

【００２１】
一方、計測時には、図４（ｂ）に示すように、撮像装置２１，２２，２３でそれぞれ計測対象を撮像し（Ｓ１１）、３つの画像データを取り込んだのち（Ｓ１２）、フィルタリング、特徴抽出等の処理を適宜施したのち、歪解消変換処理を実行する（Ｓ１３）。歪解消変換処理は、変換パラメータ記憶部３３に記憶されている変換パラメータを使用して各画像データ毎に実行する。歪みが解消された各画像データを用いて表面形状解析処理を実行する（Ｓ１４）。
【００２２】
なお、以上のシステムにおいて、考えられる変換パラメータとしては、例えば図７（ａ），（ｂ）に示すように、計測光路の光軸Ｃと直交する断面Ａに沿った平行移動量Ｌ１、Ｌ２、同図（ｃ），（ｄ）に示すように、同断面Ａを基準とした法線の傾き量θ１，θ２、同図（ｅ）に示すように、同断面Ａを基準とした光軸回りの回転移動量φ、同図（ｆ）に示すように、光束が非コリメート光束である場合の焦点位置補正量Ｆ等が挙げられる。
【００２３】
このようないわゆるあおりや大きな回転ずれ等があった場合、撮像装置２１，２２，２３の上下左右の方向性を決定づけるために、校正用撮像対象４２の図芯Ｐの間隔を、例えば図８に示すように、非整数倍にしておくことが望ましい。このようにすると、ランドマークプレート等を撮像装置２１，２２，２３で撮像した際の、そのマークの座標系における方向性がチェックし易くなる。但し、校正用撮像対象４２の図芯Ｐの不等ピッチの与え方やマークの付け方（例えばディレクションマークを設ける等）によっては、図芯Ｐのピッチを非整数倍にする必要はない。
【００２４】
変換パラメータは、例えば図９に示すように、隣接する３つの図芯Ｐで作られる三角形毎に前述したアフィン変換等を適用して変換パラメータを求めるようにしても良い。このようにして各三角形毎に変換パラメータを算出すると、各三角形内の変換処理は、アフィン変換等の線形変換処理を使用するが、各三角形毎に変換パラメータは異なるので、画像全体として非線形変換処理的な効果を得ることができるという利点がある。
【００２５】
なお、上述した本発明の実施例の干渉計の構造上の利点について述べれば次の通りである。
即ち、特開平２−２８７１０７号では、参照面に対する被検面の形状の差に相当する位相情報を偏光面を直交関係に保ったまま取り出す方法として、透過波面の歪み測定用にはマッハツェンダー干渉計が、また反射光を利用する面形状測定用にはマイケルソン型干渉計が示してある。しかし、面形状測定用の干渉計としてマイケルソン型干渉計を用いると、偏光半透鏡を通過後に参照面側と被検面側に分割された光は、それぞれ独立の光路を経るために測定環境の揺らぎの影響を受けやすいという問題点がある。また、それぞれ独立に介在している光学部品の面精度の影響を受けてしまうために、高精度測定にはあまり向かないという欠点もある。
【００２６】
一方、面形状を高精度に測定するための干渉計として、一般に共通光路型で光学部品点数の少ないフィゾー型干渉計が多く用いられている。この干渉計の特徴は、共通光路型であるために揺らぎの影響を受けにくいことと、参照面以外の光学部品の面精度を受けないことにある。しかし、フィゾー型干渉計は参照光と計測光とを同じ偏光面で発生させて干渉させる光学系であるため、このままでは上記で説明したような偏光板を使用して位相シフト干渉縞を同時に発生させるシステムには適用できない。
【００２７】
これに対し、上述した装置では、図１の１／４波長板５を通過する際に４５度偏光し、検出面６ａで反射後、再び１／４波長板を通過することによって、参照面４からの反射光と９０度直交させ、共通光路をそれぞれ干渉させることなく独立して取り出すことができる。その結果、２次元情報取得装置としてマイケルソン型干渉計で示してある特開平２−２８７１０７号の装置と比べると、空気揺らぎなどの外乱に影響され難く、高精度に位相シフト干渉縞発生が見込めて、且つ少ない光学部品点数でシステムを構築することができる。
【００２８】
【発明の効果】
以上述べたように、この発明によれば、複数の撮像手段のそれぞれ撮像系を機械的な調整機構によって位置調整するのではなく、各撮像手段で得られた画像データから、個々の撮像系の座標のずれや歪みを補正するための変換パラメータを算出し、この変換パラメータによって実際の計測画像を補正するようにしているので、各撮像系の物理的な調整が不要となり、撮像系の座標ずれや歪みによる測定誤差の発生も効果的に防止することができるという効果を奏する。
【図面の簡単な説明】
【図１】 この発明の一実施例に係るフィゾー型干渉計の構成を示す図である。
【図２】 同干渉計で撮像される３つの干渉縞画像を示す図である。
【図３】 同干渉計における画像計測処理システムの機能ブロック図である。
【図４】 同画像計測処理システムの画像校正処理と画像計測処理とを示すフローチャートである。
【図５】 同画像校正処理で使用される校正用撮像対象を示す図である。
【図６】 実際の座標系と歪みを含む撮像座標系とを示す図である。
【図７】 撮像座標系のずれを補正するための変換パラメータの例を示す図である。
【図８】 校正用撮像対象の他の例を示す図である。
【図９】 変換パラメータ算出の他の例を説明するための図である。
【符号の説明】
１…光源、３，７，８…無偏光型ハーフミラー、４…参照面、５，１６…１／４波長板、６…被計測対象、９…全反射ミラー、１０…分割光学系、１１，１２，１３…光学経路、１４…１／２波長板、１５，１７，１８…偏光板、２１，２２，２３…撮像装置、３０…コンピュータ、３１…画像処理部、３２…変換パラメータ算出部、３３…変換パラメータ記憶部、３４…歪み解消変換処理部、３５…表面形状解析処理部。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image measurement system that performs surface shape analysis or the like of a measurement target from image data obtained by measuring the measurement target using a plurality of imaging means, and an image calibration method thereof.
[0002]
[Prior art]
As an image measurement system using a plurality of imaging devices, for example, a laser interferometer disclosed in JP-A-2-287107 is known. In this system, the light from the light source is divided into two orthogonally polarized light beams and irradiated on the reference surface and the surface to be measured, and the orthogonally polarized light beams respectively reflected from the reference surface and the surface to be measured are wavefront splitting optical systems. Are divided into three luminous fluxes, and three interference fringe images having different phase relations are respectively picked up by three image pickup devices.
[0003]
Thus, in a system that performs measurement using a plurality of imaging devices, the fact that the coordinate systems of the image data obtained by each imaging device match is a major condition for preventing measurement errors. However, since the plurality of imaging devices are actually arranged at different spatial positions, a shift of the coordinate system unique to each imaging device occurs. Therefore, it is necessary to adjust the deviation of each imaging device. Conventionally, the coordinate system of one of the plurality of imaging devices is used as a temporary reference, and each imaging device is arranged in 6-axis directions. The adjustment mechanism that can be adjusted to be adjusted.
[0004]
[Problems to be solved by the invention]
However, in the conventional measurement system described above, the adjustment mechanism in the six-axis direction is large, and the adjustment mechanism is required by the number obtained by multiplying the number of image pickup devices by six. Individual differences caused the error. Furthermore, when there is a distortion or the like inherent in the imaging system of each imaging apparatus, it is practically impossible to adjust this.
[0005]
The present invention has been made in view of such problems, and does not require physical adjustment of each imaging system, and image measurement that can effectively prevent generation of measurement errors due to coordinate deviation or distortion of the imaging system. It is an object of the present invention to provide a system and an image calibration method thereof.
[0006]
[Means for Solving the Problems]
A first image measurement system according to the present invention includes a plurality of imaging means for imaging the same portion of a measurement target, and an image for measuring the measurement target from a plurality of image data obtained by the plurality of imaging means. In the image measurement system having a measurement processing unit, the image measurement processing unit includes an image calibration unit for correcting a shift of a coordinate system of each image data caused by a spatial shift of the plurality of imaging units, The image calibration means includes the coordinate value of the point of interest on image data obtained by imaging the same portion of the calibration imaging target including a plurality of points of interest whose coordinate values are known, Conversion parameter calculation means for calculating a conversion parameter for correcting a deviation of the coordinate system from a known coordinate value, and a conversion parameter for storing the calculated conversion parameter And 憶 means, wherein said is obtained and a correction means for correcting the transformation parameters the image data of the measured object obtained by the image pickup means stored in the conversion parameter storing means.
[0007]
In addition, the image calibration method according to the present invention uses the plurality of image data obtained by imaging the same portion of the measurement target with a plurality of imaging units, when the measurement target is measured. An image calibration method for correcting a shift of the coordinate system of each image data caused by a spatial shift of the image pickup means, wherein the same portion of the calibration imaging target including a plurality of points of interest whose coordinate values are known Taking an image with each imaging means, calculating a conversion parameter for correcting a shift of the coordinate system from the coordinate value of the point of interest on the image data obtained thereby and the known coordinate value, The image data of the measurement target obtained by each imaging unit is corrected by the calculated conversion parameter.
[0008]
According to the present invention, instead of adjusting the position of each imaging system of a plurality of imaging means by a mechanical adjustment mechanism, deviations and distortions of coordinates of individual imaging systems are detected from image data obtained by each imaging means. Conversion parameters for correction are calculated, and the actual measurement image is corrected using the conversion parameters. Therefore, physical adjustment of each imaging system is not necessary, and measurement errors caused by coordinate deviation or distortion of the imaging system are eliminated. Occurrence can also be effectively prevented.
[0009]
In the second image measurement system according to the present invention, a reference surface is arranged on a front surface of a test surface to be measured via a quarter-wave plate, and light is irradiated from the reference surface side to the test surface side. Means for generating an optical interference fringe from the measurement light from the test surface of the measurement target and the reference light from the reference surface having polarization planes orthogonal to each other, and the optical interference fringes generated by the means Each of which is shifted by a predetermined amount and simultaneously incident on a plurality of imaging means, and an image measurement processing means for measuring the measurement target from a plurality of image data obtained by the plurality of imaging means. In the image measurement system, the image measurement processing unit includes an image calibration unit for correcting a shift of a coordinate system of each image data caused by a spatial shift of the plurality of imaging units. The calibration unit includes the coordinate value of the target point on the image data obtained by imaging the same portion of the calibration imaging target including a plurality of target points whose coordinate values are known, and the known value. Conversion parameter calculation means for calculating a conversion parameter for correcting the shift of the coordinate system from the coordinate value, conversion parameter storage means for storing the calculated conversion parameter, and the image obtained by each imaging means And correction means for correcting the image data to be measured with the conversion parameter stored in the conversion parameter storage means .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a Fizeau interferometer using a phase shift according to an embodiment of the present invention.
The coherent light beam emitted from the light source 1 is converted into parallel light expanded by the magnifying optical system 2 and is transmitted through the non-polarization type half mirror 3 whose reflectance and transmittance do not depend on the polarization direction. A part of the light is reflected and the rest is transmitted and irradiated to the test surface 6 a of the measurement target 6 through the quarter-wave plate 5. The measurement light reflected from the test surface 6a passes through the quarter wavelength plate 5 again, and its polarization plane is rotated by 90 ° with respect to the polarization plane of the reference light. 3, and is divided into three optical paths 11, 12, and 13 by a three-divided optical system 10 including non-polarization half mirrors 7 and 8 and total reflection mirror 9.
[0011]
The reference light and measurement light traveling through the first optical path 11 are transmitted through the half-wave plate 14 and the polarizing plate 15, and the reference light and measurement light traveling through the second optical path 12 are ¼ wavelength. The reference light and the measurement light that pass through the plate 16 and the polarizing plate 17 and travel through the third optical path 13 pass through only the polarizing plate 18. Thereby, in the imaging devices 21, 22, and 23, three interference fringe images having phases shifted by π / 2 are simultaneously captured via the optical systems 24, 25, and 26, respectively.
[0012]
2A, 2 </ b> B, and 2 </ b> C are diagrams illustrating interference fringe patterns captured by the imaging devices 21, 22, and 23, respectively. Each interference fringe pattern is a pattern whose phase is shifted by α. The image data of these patterns is input to the computer 30 and used for processing for surface shape analysis. That is, assuming that the luminances at the two-dimensional positions (x, y) of the images obtained by the imaging devices 21, 22, 23 are I1, I2, and I3, respectively, the wavefront phase φ (x, y) is given by (Optical Shop Testing, Edit by Malacara: “Three-Step Algorithms”).
[0013]
[Expression 1]

[0014]
At this time, if there is a distortion or a coordinate shift inherent in each of the imaging devices 21, 22, and 23, the measurement accuracy decreases. Therefore, this system has an image calibration function for correcting distortion of each of the imaging devices 21, 22, and 23 in software.
[0015]
FIG. 3 is a functional block diagram showing an image measurement processing system realized by the computer 30 having such an image calibration function. The image measurement processing system includes an image processing unit 31, a conversion parameter calculation unit 32, a conversion parameter storage unit 33, a distortion elimination conversion processing unit 34, and a surface shape analysis processing unit 35. The image processing unit 31 performs filter processing, feature extraction processing, centroid calculation processing, and the like on the image data obtained by the imaging devices 21, 22, and 23. The conversion parameter calculation unit 32 calculates a distortion correction conversion parameter from calibration image data obtained by imaging an imaging target for image calibration for each of the imaging devices 21, 22, and 23. The conversion parameter storage unit 33 stores the calculated conversion parameter. The distortion elimination conversion processing unit 34 performs a distortion elimination correction process on the measurement image data based on the conversion parameters stored in the conversion parameter storage unit 33. The surface shape analysis processing unit 35 executes surface shape analysis processing based on the measurement-use image data whose distortion has been eliminated.
[0016]
Next, details of image calibration processing and surface shape measurement processing of this system will be described.
FIG. 4A is a flowchart for explaining image calibration processing, and FIG. 4B is a flowchart for explaining surface shape measurement processing.
First, in the image calibration processing, an imaging target for calibration is imaged (S1). As an object to be calibrated, for example, as shown in FIG. 5, an object including a plurality of figures (circles in this example) 41 having a predetermined area separated from each other is used. However, the coordinate value of the centroid (center of gravity position) P of each figure 41 is known. The imaging target 42 including the figure 41 is set at the position of the measurement target 6, and the image data obtained from each imaging device 21, 22, 23 is captured (S2). Then, the captured image data is appropriately subjected to filtering processing, feature extraction processing, centroid detection processing, and the like to obtain the coordinates of the centroid P, and the obtained coordinate values of the centroid P and the original coordinate values are obtained. Conversion parameters for correcting the rotation, scale, translation, and distortion inherent to each of the imaging devices 21, 22, and 23 are calculated from the deviation amount as follows (S3).
[0017]
That is, as shown in FIG. 6, the ideal coordinate position of the centroid P of each figure 41 is (x _i , y _i ) (i = 1 to N), and the actually observed coordinate position is (x _i ′). , Y _i ′), the transformation formula including rotation, scale, translation, and distortion between them can use the affine transformation formula shown in the following equation (2).
[0018]
[Expression 2]

[0019]
Here, the conversion parameters a ₁ , a ₂ , b ₁ , b ₂ , c ₁ , and c ₂ can be calculated by obtaining the minimum value of the error E expressed by the following equation (3) (least square method). The obtained conversion parameter is stored in the conversion parameter storage unit 33.
[0020]
[Equation 3]

[0021]
On the other hand, at the time of measurement, as shown in FIG. 4B, each of the measurement objects is imaged by the imaging devices 21, 22, 23 (S11), and after three image data are captured (S12), filtering, feature extraction, etc. After performing the above process as appropriate, the distortion elimination conversion process is executed (S13). The distortion elimination conversion process is executed for each image data using the conversion parameter stored in the conversion parameter storage unit 33. Surface shape analysis processing is executed using each image data from which distortion has been eliminated (S14).
[0022]
In the above system, possible conversion parameters include, for example, parallel movement amounts L1 and L2 along a cross section A orthogonal to the optical axis C of the measurement optical path, as shown in FIGS. 7 (a) and 7 (b). As shown in FIGS. 7C and 7D, normal inclinations θ1 and θ2 with respect to the section A, and around the optical axis with the section A as a reference, as shown in FIG. , And a focal position correction amount F when the light beam is a non-collimated light beam, as shown in FIG.
[0023]
When such a so-called tilt, a large rotation deviation, or the like occurs, the interval between the centroids P of the calibration imaging object 42 is determined, for example, in FIG. As shown, non-integer multiples are desirable. This makes it easy to check the directionality of the mark in the coordinate system when the landmark plate or the like is imaged by the imaging devices 21, 22, and 23. However, it is not necessary to make the pitch of the figure core P non-integer multiples depending on how to give the unequal pitch of the figure core P of the calibration imaging object 42 and how to mark (for example, providing a direction mark).
[0024]
For example, as shown in FIG. 9, the conversion parameter may be obtained by applying the above-described affine transformation or the like for each triangle formed by three adjacent graphic cores P. When the conversion parameters are calculated for each triangle in this way, the conversion processing in each triangle uses linear conversion processing such as affine conversion, but since the conversion parameters differ for each triangle, the nonlinear conversion processing is performed for the entire image. There is an advantage that a special effect can be obtained.
[0025]
The structural advantages of the interferometer of the embodiment of the present invention described above will be described as follows.
That is, in Japanese Patent Laid-Open No. 2-287107, Mach-Zehnder interference is used for measuring distortion of a transmitted wavefront as a method of extracting phase information corresponding to the difference in shape of the test surface with respect to the reference surface while maintaining the polarization plane in an orthogonal relationship. A Michelson interferometer is shown for measuring the surface shape using reflected light. However, when a Michelson interferometer is used as an interferometer for measuring the surface shape, the light that has been split into the reference surface side and the test surface side after passing through the polarizing semi-transparent mirror passes through an independent optical path. There is a problem that it is easily affected by fluctuations in In addition, since it is affected by the surface accuracy of the optical components that are interposed independently, there is a drawback that it is not suitable for high-accuracy measurement.
[0026]
On the other hand, as an interferometer for measuring a surface shape with high accuracy, a Fizeau interferometer with a common optical path type and a small number of optical parts is generally used. The features of this interferometer are that it is not affected by fluctuations because it is a common optical path type, and that it is not subject to surface accuracy of optical components other than the reference surface. However, since the Fizeau interferometer is an optical system that causes the reference light and measurement light to be generated and interfere with each other on the same polarization plane, the phase shift interference fringes are generated simultaneously using the polarizing plate as described above. It is not applicable to the system
[0027]
On the other hand, in the above-described apparatus, the reference surface 4 is polarized by 45 degrees when passing through the quarter-wave plate 5 of FIG. 1, reflected by the detection surface 6a, and then again through the quarter-wave plate. And 90 degrees orthogonal to the reflected light from the light, and the common optical paths can be extracted independently without causing interference. As a result, compared to the device disclosed in Japanese Patent Laid-Open No. 2-287107, which is shown as a Michelson interferometer as a two-dimensional information acquisition device, it is less susceptible to disturbances such as air fluctuations, and phase shift interference fringes can be generated with high accuracy. In addition, a system can be constructed with a small number of optical components.
[0028]
【The invention's effect】
As described above, according to the present invention, the position of each image pickup system of the plurality of image pickup means is not adjusted by a mechanical adjustment mechanism, but the individual image pickup system is obtained from the image data obtained by each image pickup means. Conversion parameters for correcting coordinate deviations and distortions are calculated, and actual measurement images are corrected using these conversion parameters. This eliminates the need for physical adjustment of each imaging system, resulting in coordinate deviations in the imaging system. It is possible to effectively prevent the occurrence of measurement errors due to distortion and distortion.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a Fizeau interferometer according to an embodiment of the present invention.
FIG. 2 is a diagram showing three interference fringe images captured by the interferometer.
FIG. 3 is a functional block diagram of an image measurement processing system in the interferometer.
FIG. 4 is a flowchart showing an image calibration process and an image measurement process of the image measurement processing system.
FIG. 5 is a diagram illustrating a calibration imaging target used in the image calibration processing.
FIG. 6 is a diagram illustrating an actual coordinate system and an imaging coordinate system including distortion.
FIG. 7 is a diagram illustrating an example of conversion parameters for correcting a shift in the imaging coordinate system.
FIG. 8 is a diagram illustrating another example of a calibration imaging target.
FIG. 9 is a diagram for explaining another example of conversion parameter calculation;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light source, 3, 7, 8 ... Non-polarization type half mirror, 4 ... Reference surface, 5, 16 ... 1/4 wavelength plate, 6 ... Measuring object, 9 ... Total reflection mirror, 10 ... Divided optical system, 11 , 12, 13 ... optical path, 14 ... 1/2 wavelength plate, 15, 17, 18 ... polarizing plate, 21, 22, 23 ... imaging device, 30 ... computer, 31 ... image processing unit, 32 ... conversion parameter calculation unit 33 ... Conversion parameter storage unit, 34 ... Distortion elimination conversion processing unit, 35 ... Surface shape analysis processing unit.

Claims (7)

A plurality of imaging means for imaging the same portion of the measurement target;
In an image measurement system comprising: an image measurement processing unit that performs measurement processing on the measurement target from a plurality of image data obtained by the plurality of imaging units.
The image measurement processing means includes
Image correction means for correcting a shift of the coordinate system of each image data caused by a spatial shift of the plurality of imaging means,
The image proofing means includes
From the coordinate value of the point of interest on the image data obtained by imaging the same portion of the calibration imaging target including a plurality of points of interest whose coordinate values are known, and the known coordinate value Conversion parameter calculation means for calculating a conversion parameter for correcting the shift of the coordinate system;
Conversion parameter storage means for storing the calculated conversion parameter;
An image measurement system comprising: a correction unit that corrects the image data of the measurement target obtained by each of the imaging units using a conversion parameter stored in the conversion parameter storage unit. The measurement surface having polarization planes orthogonal to each other by irradiating light from the reference surface side to the test surface side through a ¼ wavelength plate on the front surface of the test surface to be measured. It means for generating an optical interference fringes by the reference light from the reference surface and the measurement light from the test surface of the target,
Means for shifting the phases of the optical interference fringes generated by this means by a predetermined amount and making them simultaneously enter a plurality of imaging means respectively;
Image measurement processing means for measuring the measurement target from a plurality of image data obtained by the plurality of imaging means;
In an image measurement system having
The image measurement processing means includes
Image correction means for correcting a shift of the coordinate system of each image data caused by a spatial shift of the plurality of imaging means,
The image proofing means includes
From the coordinate value of the point of interest on the image data obtained by imaging the same portion of the calibration imaging target including a plurality of points of interest whose coordinate values are known, and the known coordinate value Conversion parameter calculation means for calculating a conversion parameter for correcting the shift of the coordinate system;
Conversion parameter storage means for storing the calculated conversion parameter;
Correction means for correcting the image data of the measurement target obtained by each of the imaging means with the conversion parameter stored in the conversion parameter storage means;
Images measuring system that comprising the. When measuring the measurement target using a plurality of image data obtained by imaging the same portion of the measurement target with a plurality of imaging means, the plurality of imaging means are caused by a spatial shift of the plurality of imaging means. An image calibration method for correcting a shift in the coordinate system of each image data,
The same part of the calibration imaging target including a plurality of points of interest whose coordinate values are known is imaged by each imaging means,
A conversion parameter for correcting a shift of the coordinate system is calculated from the coordinate value of the point of interest on the image data obtained in this way and the known coordinate value, and obtained by each imaging unit. An image calibration method for an image measurement system, wherein the image data to be measured is corrected by the calculated conversion parameter.   4. The image measurement according to claim 3, wherein the calibration imaging target includes a plurality of figures that are separated from each other and have a predetermined area and whose coordinate values of the centroid are known. System image calibration method.   5. The image calibration method for an image measurement system according to claim 4, wherein the interval between the centroids is a non-integer multiple.   The conversion parameter includes the amount of parallel movement along a cross section orthogonal to the optical axis of the measurement optical path, the amount of inclination of a normal line based on the cross section, the amount of rotational movement around the optical axis based on the cross section, and the luminous flux. The image calibration method for an image measurement system according to claim 3, wherein the image calibration system is at least one focus position correction amount in the case of a non-collimated light beam.   6. The image calibration method for an image measurement system according to claim 4, wherein the conversion parameter is calculated for each triangle formed by three adjacent graphic cores.

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