TWI417519B - Interference phase difference measurement method and system - Google Patents

Description

Interferometric phase difference measurement method and system thereof

The present invention relates to an interference phase difference measurement method and system thereof, and more particularly to a differential interference contrast (DIC) measurement using Modified Fourier Phase Integration (MFPI). Method and system.

In the display process, a thin film transistor is fabricated on a transparent substrate, and materials such as a transparent electrode, a glass substrate, or a light guide plate are transparent materials. In the process, internal defects and surface structures are often generated, but such information is not easily obtained by general measurement methods. On the other hand, the soft display, which is currently in the active research stage, will be the trend of development in the future, especially the plastic substrate display, and the development of the flexible display to the roll-to-roll production mode. Therefore, a measurement method that can detect the three-dimensional topography of transparent materials and meet the requirements of high-speed, accurate, and seismic resistance in the roll-to-roll line is an important development issue in the future.

DIC microscopy was originally an image enhancement technique used to enhance the difference between transparent objects and backgrounds, but it can also be used for the measurement of three-dimensional shapes of transparent objects. Figure 1A is a schematic flow chart of the method for measuring the three-dimensional shape of an object by the conventional DIC technology. As shown in FIG. 1A, the method 1 for measuring the three-dimensional shape of an object by using the DIC technology is mainly divided into the following three steps: Step 11: capturing an image with a DIC microscope; Step 12: processing the captured image to obtain a differential phase difference. Information; Step 13: Restore the original phase.

The above three steps are separately described below: In step 11, the image is captured by a DIC microscope. FIG. 1B is a schematic view showing the structure of a conventional DIC microscope. As shown in FIG. 1B, the conventional DIC microscope 100 includes a light source 101, a polarizer 102, a first DIC 103, a focusing lens 104, and a standby lens. The object 105, an objective lens 106, a second DIC port 107, an analyzer 108, and an offset adjusting device 109. Wherein, the offset adjusting device 109 can adjust the bias in the direction indicated by the double arrow, wherein the bias adjusting device 109 can be a position adjusting screw; the double arrow 110 indicates the cutting direction; the first The DIC 稜鏡 103 and the second DIC 稜鏡 104 are here Wollaston prism.

Here, the DIC microscope 100 can be externally connected to a charge-coupled image sensor (not shown in the figure) to capture an image. When capturing an image, first capture a number of images of different biases in the same shear direction in the first selected shear direction (change the offset by the bias adjustment device 109), and then Rotating the object to be tested 105 by 90° to change the shearing direction to obtain a second shearing direction orthogonal to the first shearing direction, and then drawing the same shearing direction in the second shearing direction A number of images are placed (the offset is changed by the offset adjusting means 109). At this point, the complete image data is obtained, and an arithmetic processing unit is input to perform the analysis of the processing operation of the next step 12.

In step 12, the image captured in step 1 is processed to obtain differential phase difference information. For the method of calculating the differential phase difference information, Michael Shribak and Shinya It is described in detail in APPLIED OPTICS Vol. 45, No. 3, 20 January 2006 and US Pat. No. 7,233,434, when 2πσγ/λ<<1:

Where: I : the obtained DIC light intensity; a : a positive integer according to the σ value; I _a : the DIC light intensity obtained at different σ values; : the average value of the incident light source intensity; I _min : the minimum light intensity produced by the background noise λ: the wavelength of the incident light; Γ: the relative optical path difference caused by the adjustment bias; δ: shear distance; σ: shear Azimuth angle; γ: the magnitude of the gradient of the optical path difference caused by the adjustment bias; θ: the azimuth of the gradient of the optical path difference caused by the adjustment bias; π: pi.

Here, taking the four-step image shift method as an example, four images of the shear azimuth angles σ=0°, 90°, 180°, and 270° are taken by the DIC microscope, and brought into the equation (1):

Untie the cubic program (2-1) ~ (2-4), you can find:

y : y coordinate of the spatial position in the reference coordinate system; I ₁ : DIC light intensity obtained at σ = 0°; I ₂ : DIC light intensity obtained at σ = 90°; I ₃ : σ = 180° DIC light intensity obtained at the time; I ₄ : DIC light intensity obtained at σ = 270°.

At step 13, the original phase is restored. The differential image difference information obtained in step 12 is restored to the original phase, and the most direct use is the use of line integrals, such as Michael Shribak and Shinya. As described in APPLIED OPTICS Vol. 45, No. 3, 20 January 2006 and US Pat. No. 7,233,434, the spatial distribution of the phase is Φ( x , y ), then

Or in pixels (pixel), then equation (4) can be written as

Where m is the row number of a particular pixel, n is the column number of a particular pixel, and Φ _{mn is} the phase value of the (m, n) pixel, that is, the three-dimensional topography The distributed two-dimensional plane is divided into k columns and 1 row, and k and l are both positive integers, and k1 pixels are obtained (the same applies hereinafter).

The line phase is used to restore the original phase. In actual application, since the captured image will generate a lot of noise due to the surrounding environment or electronic interference, the calculation result will have square stripes in the vertical direction of the cut, so only Suitable for an ideal experimental platform.

Instead of using noniterative Fourier phase integration by M. R. ARNISON et al., 2004, The Royal Microscopical Society:

FT: Fourier Transform

IFT: Inverse Fourier Transform

g ( x, y ): any function in the x, y space;

Φ(m,n): a function in m, n space,

m is the number of columns for a particular pixel,

n is the number of rows of a particular pixel;

φ( x,y ): a function in the space of x, y , which differs from g ( x, y ) by the integral constant.

Reducing the original phase with non-aliased Fourier phase integration, although less affected by noise, has the problem of shape distortion and distortion.

When DIC microscopy is used for image enhancement, the accuracy of calculation is not high when using Fourier integral to reduce the differential phase. However, when DIC microscopy is used for 3D topography measurement, how to reduce the noise to Fourier The impact of points becomes very important.

The invention aims at a quantitative reduction original phase algorithm, and proposes a modified Fourier Phase Integration (MFPI) reconstruction algorithm to effectively reduce the influence of noise, and achieve the purpose of high speed, accuracy and earthquake resistance.

In order to achieve the above object, the present invention provides an interference phase difference measurement method, which comprises the steps of: placing an object to be tested in a differential interference contrast microscope; and using the differential interference contrast microscope to mutually orthogonal first shears And respectively cutting a plurality of images of the object to be tested at different offsets in a tangential direction and a second slanting direction; and processing the captured image to obtain differential interference in the two mutually orthogonal shear directions Comparing the differential phase difference information, then calculating the differential phase difference information of the two differential interference contrasts as Fourier integral, and then minimizing the error of the two Fourier integral results.

In order to achieve the above object, an embodiment of the present invention provides an interference phase difference measurement system, which includes: a light source; a differential interference contrast microscope that enables the light source to be orthogonal to each other. The tangential direction and a second shearing direction respectively generate a plurality of images on which one of the objects to be tested is differently biased; an image capturing unit that can extract the light source through the differential interference contrast microscope The generated image; and an operation processing unit electrically connected to the image capturing unit to process the captured image, thereby obtaining a differential phase of the differential interference contrast between the two mutually orthogonal shear directions The difference information is used to perform Fourier integral on the differential phase difference information of the two differential interference contrasts, and then the error of the result obtained by the two Fourier integrals is minimized.

In order to enable the reviewing committee to have a further understanding and understanding of the features, objects and functions of the present invention, the detailed structure of the present invention and the concept of the design are explained in the following, so that the reviewing committee can understand the characteristics of the present invention. The detailed description is as follows: Please refer to FIG. 2A, which is a schematic flow chart showing the method for measuring the interference phase difference of the present invention. As shown in FIG. 2A, the interference phase difference measurement method 2 includes the following steps: Step 21: placing an object to be tested in a DIC microscope; Step 22: using the DIC microscope to cross each other in a first shear The tangential direction and the second slanting direction respectively extract four images of the object to be tested at different offsets; and step 23: processing the captured image by using four image processing methods for the two cutting directions; Step 24: Calculate the DIC differential phase difference information in the two mutually orthogonal shear directions from the results obtained by the four image processing methods; Step 25: Fourier integration of the calculated two DIC differential phase difference information Step 26: Minimize the error of the result obtained by the two Fourier integrals.

The above steps are separately detailed below: First, in step 21, an object to be tested is placed in a DIC microscope.

Then proceeding to step 22, using the DIC microscope to draw four sheets in a first shear direction (here defined as the x direction) and a second shear direction (herein defined as the y direction) which are orthogonal to each other. The object to be tested is in a differently offset image.

Next, in step 23, the captured image is processed by four image processing methods for the two cutting directions. That is, the four differential phase difference images captured in the first cutting direction in step 22 and the four differential phase difference images captured in the second cutting direction are respectively brought into the following equation (7-1)~ (7-4):

Here, the formulae (7-1) to (7-4) are the same as the formulae (2-1) to (2-4).

Next, in step 24, the DIC differential phase difference information in the two mutually orthogonal shear directions is calculated from the results obtained by the four image processing methods. That is, the operation result of step 23 is respectively brought into the following equation (8) operation, and two DIC differential phase difference information θ _x and θ _y can be obtained:

x : the x coordinate of the spatial position in the reference coordinate system

(defined here as the first cutting direction);

y : the y coordinate of the spatial position in the reference coordinate system

(defined herein as the second shear direction);

θ _x : θ( x, y ) in the first shear direction (x direction)

(that is, θ( x,y ) in the x direction);

θ _y : the value of θ( x, y ) in the second shear direction (y direction)

(that is, θ( x, y ) in the y direction).

Then, in step 25, the two DIC differential phase difference information θ _x and θ _y calculated in step 24 are Fourier-integrated.

In order to make a general mathematical description, hereby:

θ _x = f ^' (x)..............................(9-1)

as well as

θ _y = f ^' (y)....................................(9-2)

Suppose a continuous phase function fc ( x ), its differential , then the differential Fourier transform can be derived as shown in the following equation (10):

Equation (10) is also called the second theorem of Fourier transform (differential theorem), in which the subscript c indicates that it is a continuous function.

If known , then equation (10) can be rewritten as:

Where: F represents the Fourier Transform; F ^-1 represents the Inverse Fourier Transform.

i represents an imaginary number: i ² =-1; w represents the phase space coordinate after Fourier transform.

Taking a one-dimensional discrete Fourier transform as an example, the discrete Fourier transform F ( u ) of the function f ( x ) can be expressed as:

among them:

u =0,1,2,...,(M-1); j = i represents an imaginary number: j ² =-1.

With the differential phase difference image operation of DIC, the phase difference function f' ( x ) can be Approximation, discrete Fourier transform of this approximation function can be obtained:

When the shear vector is projected on the x-axis with a clipping distance of two pixels (ie h=1), the phase difference function can be written as , the Fourier transform of this approximation function is as follows:

among them:

C ₁ represents a constant term that is affected by unknown boundary conditions.

Then move the items:

among them:

Then perform inverse Fourier transform on the left and right sides of the equal sign:

among them:

Similarly, when the clipping vector is projected to an arbitrary pixel (2h) on the x-axis, the following relationship can be derived:

Where: C represents the integral constant term affected by the unknown boundary conditions.

Finally, step 26 is performed to minimize the error of the results obtained by the two Fourier integrals. Here, since the constant terms C ₁ and C in the equations (14) and (17) are not known from the differential phase difference information obtained from the DIC measurement, the following is proposed as the modified Fourier phase integration method (Modified Fourier). Phase Integration (MFPI) is used as a solution to minimize the error of the result of the integral reconstruction of two different shear directions.

The modified Fourier phase integration method will be described in detail below: Apply the above equation (17) twice, and derive the Fourier integral of the two-dimensional function f ^' (x, y) in the x direction and the y direction, respectively:

Where: x _i represents the number of columns of pixels, and y _j represents the number of rows of pixels.

Next, rewrite the above formula as follows:

f ( i , j )= f _x ( i , j )+C _x ( j ).........result-1............(19-1)

f ( i , j )= f _y ( i , j )+C _y ( i ).........result-2............(19-2)

among them:

f ( i , j )= f ( x _i , y _j ) is the original phase map; a phase map reconstructed in the x direction; The phase map reconstructed in the y direction; C _x ( j ) is the integral constant of the pixel of the jth row; C _y ( i ) is the integral constant of the pixel of the ith row.

Then, for any particular pixel, the result-1 of the formula (19-1) and the result-2 of the formula (19-2) are as follows:

Err ( i , j )=[ f _x ( i , j )+ C _x ( j )]-[ f _y ( i , j )+ C _y ( i )]............ (20)

The total error value can be expressed as:

Theoretically, the total error value should be zero, but in fact, due to the existence of an unknown integral constant, an error value is generated. In order to minimize the total error value, that is, when E _{total_err} has a minimum value, find the unknown integral constants C _x ( j ) and C _y ( i ), so the solution is as follows: in order to minimize the total error value, the partial differential can be obtained. The corresponding C _x ( j ) and C _y ( i ) are calculated and brought back into the equation to correct the reconstruction result, thereby accurately reducing the phase difference information. The details are as follows:

make:

D ( i , j )= f _x ( i , j )- f _y ( i , j )

Waiting for (21), you can get:

Where: D ( i,j ) is the phase difference solved by each pixel.

Partial differential (21):

as well as

From equation (22-1):

Available from equation (22-2):

make:

as well as

Substituting into (23-1) and (23-2) respectively, you can get:

as well as

Multiply the equation (24-1) by m and the equation (24-2) by n , and then add the two equations to get:

Available from equation (25) , with back (24-1) can solve C _y ( i ):

Available from equation (25) , with back (24-2) can solve C _x ( j ):

Then, when C _y ( i ) of the formula (26-1) is substituted into the formula (19-2), the result-2 of the formula (19-2) becomes:

Then, when C _x ( j ) of the formula (26-2) is substituted into the formula (19-1), the result-1 of the formula (19-1) becomes:

Finally, define:

As shown in equation (28), let f _MPFI ( i , j ) be the best solution sought, representing the phase of the object to be side reconstructed by "corrected Fourier phase integration (MFPI)".

The error of the result obtained by the Fourier integral is caused by the influence of the unknown boundary condition, which is derived from the noise. Since the present invention minimizes the error by using the modified Fourier phase integral, it can be effectively Reduce the impact of noise.

Please refer to FIG. 2B, which is a schematic diagram showing an interference phase difference measurement system according to an embodiment of the present invention. As shown in FIG. 2B, the interference phase difference measurement system 200 includes: a light source 210; a DIC microscope 220, which can make the light source 210 in a first shear direction and a second cut orthogonal to each other. In the tangential direction, a plurality of images of the transparent object to be tested 225 are respectively offset from each other; and an image capturing unit 230 is configured to capture the image generated by the light source 210 after passing through the DIC microscope 220. And an operation processing unit 240, which is electrically connected to the image capturing unit 230 to process the captured image, thereby obtaining differential phase difference information of the differential interference contrast between the two mutually orthogonal clipping directions. And calculating the differential phase difference information of the two differential interference contrasts as Fourier integral, and then minimizing the error of the result obtained by the two Fourier integrals.

As shown in FIG. 2B, the DIC microscope 220 is a transmissive DIC microscope, which comprises: a polarizer 221, which causes the light wave incident from the light source 210 to become a plane polarized light; a first DIC稜鏡222, which has a spectroscopic effect, can pass plane polarized light through the first DIC 222, and is divided into two ordinary light rays (ordinary ray, hereinafter referred to as o-ray) and extraordinary light (extraordinary). Ray, hereinafter referred to as e-ray); a focusing lens 223, collimating the o-ray and e-ray generated by the first DIC 222; an objective lens 226, collimating o-ray and e -ray focusing; a second DIC 227, synthesizing o-ray and e-ray image information for interference; and a Senarmont compensator 228 for adjusting the bias, wherein A portion of the light wave emitted by the light source 210 passes through the polarizer 221, the first DIC 222, the focus lens 223, the objective lens 226, the second DIC 227, and the Senamont compensator. 228, finally enter the image capturing unit 230.

Here, the first DIC 222 and the second DIC 227 may be a Nomarski prism or a Wollaston 稜鏡, and the Senamont compensator 228 further includes a fixed The quarter wave plate 228a and the rotatable analyzer 228b are such that the combined light of the o-ray and the e-ray synthesized by the second DIC port 227 is first turned into a plane through the quarter wave plate 228a. Polarized or elliptical polarized light, and then passed through the rotatable analyzer 228b, which is used to adjust the bias, as long as the rotatable analyzer 228b is rotated to change its fast axis relative to the quarter The angle of the fast axis of one of the wave plates 228a allows the DIC images to have different offsets. After the rotatable analyzer 228b is rotated by 0°, 90°, 180°, and 270° to obtain four images of different offsets, the object to be tested is rotated by 90° to change the cutting direction 224, and the rotatory inspection is performed. The partial mirror 228b is further rotated by 0°, 90°, 180°, and 270° to obtain four images of different offsets, so that four differently offset images in two mutually orthogonal cutting directions can be obtained.

In the embodiment, the DIC microscope 220 is a transmissive DIC microscope, and is applied to the object to be tested as a transparent object to be tested 225, and the transparent object to be tested 225 is placed on the focusing lens 223 and the There are many details about the principle and operation mode of the objective lens 226, and details are not described herein. In addition, the image capturing unit 230 of the present invention can use a charge-coupled device (CCD).

However, the DIC microscope 220 used in the interference phase difference measuring system 200 of the present invention is not limited thereto, and may be any DIC microscope. FIG. 2C is a schematic diagram of an interference phase difference measurement system according to another embodiment of the present invention. As shown in FIG. 2C, the interference phase difference measurement system 200' differs from the interference phase difference measurement system 200 of FIG. 2B in that a transmissive DIC microscope 220 is replaced by a reflective DIC microscope 220'. The DIC microscope 220' is applied when the object to be tested is an opaque object 2205 to be tested. As shown in FIG. 2C, the interference phase difference measuring system 200' includes: a polarizer 2201 for causing a light wave incident from the light source 210 to become a plane polarized light; and a beam splitter 2202 having a light splitting effect; a DIC 稜鏡 2203; an objective lens 2204 for focusing light; and a Senarmont compensator 2206 for adjusting the offset when an opaque object to be tested 2205 is placed in the reflection When the DIC microscope 220' is used, a part of the light wave emitted by the light source 210 passes through the polarizer 2201, the beam splitter 2202, the DIC 稜鏡 2203, the objective lens 2204, the opaque object to be tested 2205, and the plug. The monster compensator 2206 is finally entered into the image capturing unit 230.

Wherein, the DIC 稜鏡 2203 may be a Normaski 稜鏡 or a Wollaston 稜鏡, and the Senamon compensator 2206 further includes a fixed quarter wave plate 2206a and a rotatable analyzer 2206b. The function and operation of the Senamont compensator 2206 is the same as that of the Senamont compensator 228 described above, and will not be described again. In addition, the principle and operation mode of the reflective DIC microscope are well described in detail, and will not be described herein.

However, the above is only an embodiment of the present invention, and the scope of the present invention is not limited thereto. It is to be understood that the scope of the present invention is not limited by the spirit and scope of the present invention, and should be considered as a further embodiment of the present invention.

1. . . DIC technology measurement object three-dimensional shape method

11~13. . . step

100. . . DIC microscope

101. . . light source

102. . . Polarizer

103. . . First DIC稜鏡

104. . . Focusing lens

105. . . Analyte

106. . . Objective lens

107. . . Second DIC稜鏡

108. . . Detector

109. . . Offset adjustment device

110. . . Cutting direction

2. . . Interferometric phase difference measurement method

21~26. . . step

200, 200’. . . Interferometric phase difference measurement system

210. . . light source

220. . . DIC microscope

221. . . Polarizer

222. . . First DIC稜鏡

223. . . Focusing lens

224. . . Cutting direction

225. . . Transparent object to be tested

226. . . Objective lens

227. . . Second DIC稜鏡

228. . . Senamon compensator

228a. . . Quarter wave plate

228b. . . Rotatable analyzer

220’. . . Reflective DIC microscope

2201. . . Polarizer

2202. . . Beam splitter

2203. . . DIC稜鏡

2204. . . Objective lens

2205. . . Opaque object to be tested

2206. . . Senamon compensator

2206a. . . Quarter wave plate

2206b. . . Rotatable analyzer

230. . . Image capture unit

240. . . Operation processing unit

Figure 1A is a schematic flow chart of the method for measuring the three-dimensional shape of an object by the conventional DIC technology.

Figure 1B is a schematic diagram of a conventional DIC microscope structure.

Figure 2A is a schematic flow chart of the method for measuring the interference phase difference of the present invention.

FIG. 2B is a schematic diagram of an interference phase difference measurement system according to an embodiment of the present invention.

FIG. 2C is a schematic diagram of an interference phase difference measurement system according to another embodiment of the present invention.

2. . . Interferometric phase difference measurement method

21~26. . . step

Claims (14)

An interference phase difference measurement method includes the steps of: placing an object to be tested in a differential interference contrast microscope; using the differential interference contrast microscope to mutually orthogonal a first shear direction and a second shear Extracting a plurality of images of the object to be tested at different offsets in the tangential direction; and processing the captured image to obtain differential phase difference information of the differential interference contrast between the two mutually orthogonal shear directions, Then, the differential phase difference information of the two differential interferences calculated is Fourier integral, and the error of the result obtained by the two Fourier integrals is minimized. The interference phase difference measurement method according to claim 1, wherein the step 2 uses four image processing methods to process the captured image. The interference phase difference measurement method according to claim 1, wherein the error of the result obtained by the two Fourier integrals is minimized by using the modified Fourier phase integral. An interference phase difference measuring system includes: a light source; a differential interference contrast microscope, wherein the light source can generate a complex number in a first shear direction and a second shear direction orthogonal to each other An image on which one of the objects to be tested is differently biased; an image capturing unit that captures an image produced by the light source through the differential interference contrast microscope; and an arithmetic processing unit And the image capturing unit is electrically connected to process the captured image, thereby obtaining differential phase difference information of the difference interference between the two mutually orthogonal shear directions, and calculating the two differential interferences The compared differential phase difference information is Fourier integral, and then the error of the result obtained by the two Fourier integrals is minimized. The interference phase difference measuring system according to claim 4, wherein the differential interference contrast microscope is a penetrating differential interference contrast microscope, which is capable of penetrating light waves through a transparent object to be measured for measurement. The three-dimensional shape of the transparent object to be tested. The interference phase contrast measuring system of claim 5, wherein the differential interference contrast microscope further comprises: a polarizer for causing a light wave incident from the light source to become a plane polarized light; a first differential interference Comparing 稜鏡, the system has a spectroscopic effect, and the plane polarized light can be divided into two normal light and abnormal light whose polarization directions are perpendicular to each other through the first differential interference contrast; a focusing lens, the first The differential interference contrast 稜鏡 produces normal light and anomalous light collimation; an objective lens that focuses the collimated normal light and the extraordinary light; a second differential interference contrast 稜鏡 combines the ordinary light with the abnormal light and produces interference Image information; and a serrano compensator for adjusting the bias, wherein a portion of the light wave emitted by the light source sequentially passes through the polarizer, the first differential interference contrast 稜鏡, the focusing lens The objective lens, the second differential interference contrast 稜鏡 and the Senamont compensator, and finally enter the image capturing unit. The interference phase difference measurement system according to claim 6, wherein the first differential interference contrast 稜鏡 and the second differential interference contrast are Normaski or Wollaston. The interference phase difference measuring system according to claim 6, wherein the Senamon compensator further comprises: a fixed quarter wave plate; and a rotatable analyzer for adjusting Offset, such that the combined light of the ordinary light and the extraordinary light synthesized by the second differential interference contrast 先 is first converted into plane polarized light or elliptical polarized light by the fixed quarter wave plate, and then rotated through the rotation An analyzer. The interference phase contrast measurement system of claim 4, wherein the differential interference contrast microscope is a reflective differential interference contrast microscope that reflects light waves from an opaque object to be measured to measure the The three-dimensional shape of the opaque object to be tested. The interference phase contrast measuring system according to claim 9, wherein the differential interference contrast microscope further comprises: a polarizer for causing a light wave incident from the light source to become a plane polarized light; and a beam splitter; The system has a spectroscopic effect; a differential interference contrast; an objective lens for focusing the light; and a serrano compensator for adjusting the bias so that when an opaque object to be tested is placed in the reflection In a differential interference contrast microscope, a portion of the light wave emitted by the light source passes through the polarizer, the beam splitter, the differential interference contrast 稜鏡, the objective lens, the opaque object to be tested, and the Senamon compensator. Finally, enter the image capture unit. The interference phase difference measuring system according to claim 10, wherein the differential interference contrast system is Normaski or Wollaston. The interference phase difference measuring system according to claim 10, wherein the Senamont compensator further comprises: a fixed quarter wave plate; and a rotatable analyzer for adjusting Offset, such that the combined light of the ordinary light and the extraordinary light synthesized by the second differential interference contrast 先 is first converted into plane polarized light or elliptical polarized light by the fixed quarter wave plate, and then rotated through the rotation An analyzer. The interference phase difference measuring system according to claim 4, wherein the image capturing unit is a charge coupled device. The interference phase difference measuring system according to claim 4, wherein the arithmetic processing unit performs a modified Fourier phase integral to minimize the error of the result obtained by the two Fourier integrals.