JP3453483B2 - Interference fringe phase detection method and interference measurement apparatus using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interference fringe phase detecting method and an interference measuring apparatus using the same, and is particularly suitable for measuring the shape of optical components and the distribution of refractive index using an interferometer. is there.

[0002]

2. Description of the Related Art An interferometer detects the wavefront shape of light as an interference fringe pattern by utilizing the interference phenomenon of light.
You can precisely measure the shape of optical parts such as lenses and mirrors,
It is widely used for industrial purposes as a method for precisely measuring the refractive index distribution of glass.

Particularly, recently, a very precise measurement has become possible by digitizing the pattern of interference fringes as phase information for each pixel.

As one of the methods of digitizing the interference fringe pattern as phase information, there is a phase shift electronic moire method as disclosed in the 1992 Precision Engineering Society Spring Meeting, p.371-372.

FIG. 5 is a configuration diagram of a main part of an interferometric measuring apparatus using a conventional phase shift electronic moire method. In the figure, 10
0 is an interferometer, which is composed of, for example, a Fizeau interferometer,
Interference fringes are generated from the reference surface of the interferometer and the measured surface. 1 is
Two-dimensional image detection means, such as charge coupled device (CCD)
It is composed of a CCD camera, which is a two-dimensional imaging device, and inputs an interference fringe image. 2 is an image input means for extracting a video signal for one screen, 3a, 3b, 3c are reference image memories for storing reference image information for one screen, and 4a, 4b, 4c are multiplications for multiplying two images. , 5a, 5b, 5c are low-pass filters (LPFs) that have the characteristic of removing high spatial frequencies in the image and passing only low spatial frequencies, and 6a, 6b are subtractors that perform subtraction between two images, 7 is a divider that divides two images, and 8 is a non-linear calculator that calculates tan ^-1 .

The interference fringe image generated by the interferometer 100 is intentionally caused to have a large number of fringes by inclining the surface to be measured or the reference surface of the interferometer.
The image is picked up by the three-dimensional image detection means 1 and the image is input by the image input means 2.
Information for the screen is extracted. On the other hand, reference image memories 3a, 3b,
Image information corresponding to a large number of striped reference images is written in advance in 3c. However, each reference image memory 3a, 3b,
The initial phase of the fringes of the reference image recorded in 3c is π
/ 4, 3π / 4, 5π / 4 offset.

The measured image signals picked up by the two-dimensional image detecting means 1 are multiplied by the reference image signals of the reference image memories 3a, 3b and 3c by the multipliers 4a, 4b and 4c, respectively. A kind of moire fringe having a low spatial frequency is generated by this calculation, and the moire fringe represents the degree of fringe bending of the image to be measured. Therefore, the low-pass filter 5
If signals of a large number of fringes, which are carriers, are cut at a, 5b, and 5c, an image equivalent to a state in which interference fringes are roughly produced by accurately performing alignment without tilting the reference surface with an interferometer can be obtained.

At this time, the reference image memories 3a, 3b,
The initial phase of the stripes in the reference image of 3c is π / 4, 3 as described above.
Low-pass filters 5a, 5 due to π / 4, 5π / 4 offset
An image corresponding to a state in which interference fringes are roughly obtained obtained through b and 5c also has an initial phase shift of π / 4, 3π / 4, 5π / 4.

If the phase distribution of the interference fringes to be obtained is φ (x, y), each image is

[0010]

[Equation 1] Therefore, (S ₁ -S ₂ ) / (S ₂ -S ₃ ) = Sin φ (x, y) / Cos φ (x, y) = Tan φ (x, y) ・ ・ ・ (4) φ (x, y) = Tan ^-1 {(S ₁ -S ₂ ) / (S ₂ -S ₃ )} ・ ・ ・ The phase distribution can be calculated by performing the operation of (5). Therefore, the operation of Eq. (4) is performed by subtractors 6a, 6b and divider 7,
If the nonlinear calculator 8 is used to calculate Eq. (5), the desired phase distribution φ (x, y) will be obtained as an output.

Since this method can obtain the phase distribution from one original image of the interference fringes, it has a characteristic that it is strong against mechanical vibration and air fluctuation during measurement.

Further, in this method, it is possible to perform a null test of an aspherical shape by recording in the reference image memories 3a, 3b, 3c not a simple linear stripe but a curved pattern calculated by a predetermined calculation. have.

[0013]

In the above-mentioned conventional example, in order to obtain the final phase output in real time, it is necessary to perform calculation between images in parallel, and each calculation is a high-speed calculation of about 1/30 second. Need.

Therefore, a plurality of dedicated image processing means must be prepared, and the structure becomes complicated and the system becomes expensive.

According to the present invention, the structure of the apparatus is extremely simple and can be constituted by general-purpose equipment without impairing the measurement accuracy and the characteristics of the phase shift electronic moire method, which is strong against disturbances such as mechanical vibration and air fluctuation during measurement. Therefore, it is an object of the present invention to provide an interference fringe phase detection method capable of significantly reducing cost and space and an interference measuring apparatus using the same.

Others (1-1) Since arithmetic operations with a plurality of reference image data are serially performed by a general-purpose computer, any n-bucket method can be specified by software without changing the hardware configuration, and high precision is achieved. Phase calculation can be realized at low cost. (1-2) It is possible to suppress an increase in the number of bits during calculation and reduce the processing load. (1-3) The amount of data is reduced, and the load on the calculation means can be reduced. (1-4) It is possible to further reduce the processing load. It is an object of the present invention to provide an interference fringe phase detection method having at least one of the above effects, and an interference measurement apparatus using the same.

[0017]

An interference fringe phase detection method according to the present invention comprises: (2-1) a measured interference fringe image in which a large number of interference fringes are generated by an interferometer to generate a spatial carrier wave; A phase shift electronic moire method is used for detecting the phase distribution of the measured interference fringe image by inter-image calculation with a plurality of reference images having interference fringes having a frequency substantially equal to the spatial frequency of the carrier wave and having different initial phases. In the interference fringe phase detection method that was previously used, the inter-image calculation between the interference fringe image from the interferometer and one reference image is performed at the video rate, and the high frequency components of the resulting image signal are cut and output on the monitor screen. Then, an alignment unit for performing alignment of the interferometer and an image for interfering the measured interference fringe image and a plurality of reference images are temporarily stored and held for one screen. Using the unit, by switching these units are characterized by that detects the phase distribution of 該被 measured interference fringe image.

In particular, (2-1-1) causing the arithmetic unit to sequentially call the plurality of reference images to serially execute the arithmetic operation. (2-1-2) In the alignment unit,
The inter-image calculation between the interference fringe image and the reference image is addition or subtraction. (2-1-3) In the alignment unit,
Inter-image operation is performed by AND logic operation or OR logic operation between the binarized interference fringe image and the binarized reference image. It is characterized by such things.

Further, the interference measuring apparatus of the present invention comprises (2-2) an interference fringe image to be measured in which a large number of interference fringes are generated by an interferometer to generate a spatial carrier, and a spatial frequency of the carrier. It has interference fringes of almost equal frequency,
And in the interferometric device using the phase shift electronic moire method for detecting the phase distribution of the measured interference fringe image by inter-image calculation with a plurality of reference images each having a different initial phase,
Two-dimensional image detecting means for detecting an interference fringe image to be measured formed by the interferometer, and image input means for extracting one measured interference fringe image for one screen from a signal output from the two-dimensional image detecting means. , Output destination of the measured interference fringe image for the one screen
Switch means for switching between
At one output destination, a reference image memory for recording one reference image, an arithmetic unit for performing an inter-image calculation between the interference fringe image to be measured for the one screen and the one reference image, and the inter-image calculation A low-pass filter that cuts the high-frequency component of the obtained signal and a monitor that displays an image by the image signal that cuts the high-frequency component are arranged, and the other of the switch means is arranged.
At the output destination, an input image memory for temporarily storing and holding the measured interference fringe image, and a computer for performing inter-image calculation between the measured interference fringe image and a plurality of reference images stored in the data storage means are arranged. It is characterized by being.

In particular, (2-2-1) the arithmetic unit is a multiplier that multiplies between images. (2-2-2) The arithmetic unit is an adder that performs addition between images or a subtractor that performs subtraction. (2-2-3) The arithmetic unit is an AND logical arithmetic unit or an OR logical arithmetic unit, the binarized reference image is recorded in the reference image memory, and the interference fringes are generated by the binarizing unit. The image is binarized, and the inter-image calculation is performed by the binarized reference image and the AND logical operation unit or the OR logical operation unit. (2-2-4) The computer sequentially calls the plurality of reference images from the data storage unit to serially execute the operation. It is characterized by such things.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The interference fringe phase detection method of the present invention comprises:
The feature is that the phase is detected by switching the three steps and detecting the phase.

That is, the interference fringe phase detection method of the present invention comprises: (1) Interference fringe image data input from the image input means and one reference image data prepared in advance in order to perform alignment of the interferometer. Alignment step in which the difference or product is calculated and filtered only at a video rate (approximately 1/30 second) and the alignment result is displayed on the monitor screen. (2) Input from image input means
An image storage step of temporarily storing one screen of the measured interference fringe image in the input image memory, (3) Data of the measured interference fringe image stored in the input image memory, and prepared in advance and stored in the data storage means. It is characterized in that it has an operation step of serially processing an operation with a plurality of reference image data existing therein using a general-purpose computer to obtain a phase distribution.

An embodiment of the interference measuring device will be described below. FIG. 1 is a schematic view of the essential portions of Embodiment 1 of the interference measuring apparatus of the present invention. In the figure, reference numeral 100 denotes an interferometer, which is composed of, for example, a Fizeau interferometer, and generates an interference fringe from the reference surface and the measured surface of the interferometer. Reference numeral 1 is a two-dimensional image detecting means, which is composed of, for example, a CCD camera having a charge-coupled device (CCD) as a two-dimensional image pickup device and inputs an interference fringe image. 2
Is an image input means for extracting a video signal for one screen, 11 is a preprocessing means for performing preprocessing such as temporal averaging, spatial averaging, background noise removal, and camera sensitivity unevenness correction, and 12 is a step at the time of measurement. Is a changeover switch for changing over.
301 is a reference image memory means, which stores one reference image with fine stripes calculated or imaged in advance,
This reference image can be read out at an appropriate video rate. 13 is an input image memory means for temporarily storing the interference fringe image to be measured for which the input and preprocessed phase distribution is to be measured, and 14 is a place where a plurality (n) of reference image data are stored in advance. Data storage means, 401 is a multiplier (calculator) that performs high-speed multiplication between the interference fringe image input from the image input means and the reference image in the reference image memory, and 5 is the low frequency component in the image. Is a low-pass filter (LPF) that passes only the stripes, 9 is a monitor that displays processed images, and 10 is a general-purpose computer that serially processes calculations between images.

Of the above elements, the reference image memory 301
, The multiplier 401, the LPF 5, the monitor 9 and the like constitute one element of the alignment unit, and the input image memory 13, the data storage means 14, the computer 10 and the like constitute one element of the arithmetic unit.

The operation of this embodiment will be described. Interferometer 100
The interference fringe image containing a large number of fringes is detected by the two-dimensional image detection means 1, converted into digital data for one screen by the image input means 2, and then the preprocessing means 11 outputs the time as necessary. Preprocessing such as dynamic averaging, spatial averaging, background noise removal, camera sensitivity unevenness correction, and unnecessary area masking is performed.

The subsequent data flow differs depending on the measurement step, and therefore each step will be described.

First, since the reference surface and the surface to be measured must be aligned in the interferometer 100, the device is set in the alignment step by connecting the changeover switch 12 to the a side to perform the alignment.

In the normal alignment of the interferometer, the purpose is to roughly produce interference fringes, whereas in the phase shift electronic moire method, a large number of fringes corresponding to a predetermined spatial frequency must be produced. , Special treatment is needed.

After inputting by connecting the changeover switch 12 to the side a, the pre-processed interference fringe image is sequentially multiplied in the multiplier 401 for each pixel corresponding to the reference image data in the reference image memory 301 at the video rate. To do.

The horizontal direction of the CCD of the two-dimensional image detecting means 1
In the reference image memory 301, where x is the vertical direction and y is
If a reference image with a high spatial frequency V in the x direction is prepared, the reference image luminance signal I _R and the input interference fringe image luminance signal I _S are I _R = A ・ sin (Vx + P ) + R ・ ・ ・ (6) I _S = B ・ sin (Wx + Q) + S ・ ・ ・ (7) Where A and B are the reference image and the brightness amplitude of the input interference fringe image, V and W are the reference image and the spatial frequency in the x direction of the interference fringe image, and P and Q are the reference image and the initial fringe image, respectively. Phase, R and S are reference images,
It is the bias component of the interference fringe image.

When the multiplication of the equations (6) and (7) is performed by the multiplier 401, I = I _R × I _S = ABsin (Vx + P) sin (Wx + Q) + ASsin (Vx + P) + BRsin (Wx + Q) + RS = (AB / 2) [cos {(VW) x + PQ} -cos {(V + W) x + P + Q}] + ASsin (Vx + P) + BRsin (Wx + Q) + RS ・ ・ ・ (8) is calculated, and it becomes an image containing four spatial frequencies of VW, V + W, V, W. However, if the cutoff frequency of the low-pass filter 5 is set to, for example, about 50 stripes, only the signal of the difference frequency (VW) will pass by the action of this filter, and the image observed on the monitor 9 will be _m = (AB / 2) [cos {(VW) x + PQ}] + RS becomes (9), and if the interferometer is adjusted so that the fringes appear most coarsely on the monitor 9, the input interference fringes Since the spatial frequency V of the image matches the spatial frequency W of the reference image, the purpose of alignment in the phase shift electronic moire method is achieved. As long as the image on the monitor 9 is being viewed, this operation is almost the same as the operation of aligning the interference fringes with a normal interferometer so that the operator can perform the operation without any discomfort.

Further, when the difference frequency VW becomes close to 0 in the equation (9), the phase difference PQ between the input image and the reference image appears as stripes, so that the approximate wavefront error and refractive index distribution are visually recognized from the stripe pattern. Can be recognized. With the above, the alignment by the alignment step is completed.

When the alignment is completed, the changeover switch 12 is changed over to the b side to enter the image storing step.
In the image storing step, the interference fringe image to be measured for which the preprocessing is completed is to be measured and is stored in the input image memory 13 for one screen. 1 Screen shutter speed is normal
The CCD camera takes 1/30 to 1/1000 seconds, and if a special camera or pulsed laser light source is used, it is possible to freeze and detect interference fringes in a short time of 1/1000000 seconds or less. The above is the image storing step.

In this way, if only the image to be measured is instantaneously captured in the image storing step, the subsequent arithmetic processing is performed.
(Calculation step) can be done slowly without any problem.

In the calculation step, the calculation processing of the data of the interference fringe image to be measured for one screen stored in the input image memory 13 and the plurality of reference image data i previously prepared and stored in the data storage means 14 is performed. This is a step for serial processing by the general-purpose computer 10. FIG. 2 shows a flow of arithmetic processing.

First, the data of the interference fringe image to be measured stored in the input image memory 13 is loaded (s21), and then the reference image data 1 is loaded from the data storage means 14 (s22).
. At this time, the striped reference image having the same spatial frequency V as the reference image recorded in the reference image memory 301 used in the alignment step is recorded in the reference image data 1.

The luminance signals of the reference image data 1 and the data of the input image memory 13 are I _R1 = Asin (Vx + P ₁ ) + R (10) I _S , respectively, as in equations (1) and (2). = Bsin (Wx + Q) + S ・ ・ ・ (11), then if the multiplication between images (s23) and the low-pass filter processing (s24) are performed, the equations (6) to (9) are obtained. Since the same calculation holds, the brightness distribution image I _m1 : I _m1 = (AB / 2) [cos {(VW) x + P ₁ -Q}] + RS (12) is obtained.

Since the spatial frequency (VW) in the x direction is adjusted to 0 or a sufficiently small state by the alignment step described above, I _m1 = (AB / 2) [cos (P ₁ -Q)] + RS after all.・ A brightness distribution image of (13) is obtained. The data of this brightness distribution image I _m1 is temporarily stored in the computer 10 (s25).
.

A plurality of reference image data are prepared in advance in the data storage means 14, and each data is a stripe pattern having the same spatial frequency distribution, but the initial phase is slightly shifted. That is, as the reference image data i, I _R1 = Asin (Vx + P ₁ ) + RI _R2 = Asin (Vx + P ₂ ) + R ・ ・ I _Rn = Asin (Vx + P _n ) + R ・ ・ ・ (14 ) Is recorded.

In S26, it is determined whether or not the calculation with all the reference image data has been completed. If not completed, the next reference image data I _Ri is input (s27), s23
When processed by the loop of ~ s26, the same result as Eq. (13) is obtained, and I _m1 = (AB / 2) [cos (P ₁ -Q)] + RS I _m2 = (AB / 2) [cos (P ₂ -Q)) + RS ··· I _mn = (AB / 2) [cos (P _n -Q)] + RS (15) A plurality of brightness distribution images are stored in the computer 10.

The bucket method is widely known as a method for calculating the initial phase distribution of interference fringes. The bucket method is a method of calculating the initial phase of a signal that changes in a sinusoidal shape from three or more representative point data, and the initial phase can be obtained by simple four arithmetic operations by appropriately selecting the phase difference of the representative point data. it can.

The data of each representative point is now represented as follows.

I ₁ = Kcos (θ + φ ₁ ) + L I ₂ = Kcos (θ + φ ₂ ) + L I _n = Kcos (θ + φ _n ) + L (16) where K is Signal amplitude, L is signal offset, φ _n
Is a phase difference, and θ is an initial phase to be obtained. For example n = 3
, Φ ₁ = π / 4, φ ₂ = 3π / 4, φ ₃ = 5π / 4,

[0044]

[Equation 2] Therefore, θ = Tan ^-1 (sin θ / cos θ) = Tan ^-1 {(I ₃ -I ₂ ) / (I ₁ -I ₂ )} ・ ・ ・ (19), and the effect of amplitude K and offset L is good. Is deleted to obtain the initial phase θ.

In addition to this, by giving an appropriate phase difference φ _n corresponding to n = 4, 5, ...
It is known that the initial phase θ can be calculated by the operation of ^-1 , and generally, the larger n is, the higher the measurement accuracy becomes.

Therefore, the phase distribution Q is calculated by applying the above-mentioned bucket method to the intermediate data (luminance distribution image) of this embodiment represented by the equation (15) (s28).

The phase distribution Q calculated by the calculation of Tan ⁻¹ is ±
Since only the range of π / 2 can be expressed, if there is a phase distribution that exceeds this range, originally smooth data can be obtained as discontinuous data. Therefore, in s29, the discontinuity elimination process called the phase connection process is performed to convert to smooth data.

Furthermore, if necessary, a three-dimensional drawing, a contour map,
The information is displayed on the screen of the computer 10 as information that can be understood by the measurer by performing visualization processing such as arbitrary cross-section display and data reduction processing such as orthogonal polynomial fitting (s31).

The above is the description of the first embodiment, but the two-dimensional image detecting means 1 of the present embodiment is not only a CCD camera but also a photoelectric imaging tube such as a vidicon, a means for scanning a one-dimensional CCD, and the like. I don't mind.

In the image storing step after the alignment is completed, the interference fringe image to be measured may be input from a video device which records the interference fringe image picked up by these photoelectric conversion means, or a silver halide camera. The interference fringe image to be measured may be input from an image obtained by reading the interference fringe image captured by the scanner device with a scanner device and converting it into an electric signal.

The image input means 2 may include an interface function for matching signals with various image pickup means.

The changeover switch 12 does not necessarily need to switch the signal circuit, and may be a distributor that distributes the input image to both the alignment side and the detection side.

The reference image memory means 301 may be a storage device having a reading speed slower than the video rate.

The multiplier (calculator) 401 can be used even if it is replaced with an adder or a subtractor as long as it observes moire fringes.

As the data storage means 14 storing the reference image data, a semiconductor memory device, a hard disk device, a magneto-optical storage device, a magnetic tape recording device or the like can be used.

As the low-pass filter 5, an analog filter including a condenser, a resistor, an OP amplifier, a digital filter by a high speed computer, etc. can be used, and the cutoff frequency may be fixed or variable.

FIG. 3 shows a second embodiment of the interferometer according to the present invention.
FIG. In the second embodiment, the multiplier 401 of the first embodiment is replaced with an AND logical operation unit 403, the reference image memory 301 is replaced with a binarized reference image memory 302, and the preprocessing in the alignment step is performed. All are the same as the first embodiment except that a binarizing means 15 for binarizing the completed interference fringe image is added.
Therefore, only the difference in operation in the alignment step will be described.

In the present embodiment, the binarizing means 15, 2
Quantized reference image memory 302, AND logical operation unit 403, LPF5
The monitor 9 and the like form one element of the alignment unit. The arithmetic unit is the same as that of the first embodiment.

The alignment step of this embodiment is shown in FIG.
This is executed by connecting the changeover switch 12 of the above to the a side. In the alignment step, after the input, the interference fringe image that has been preprocessed is converted into a binarized interference fringe image by comparing a constant slice level and luminance level for each pixel in the binarizing means 15.

On the other hand, in the binarized reference image memory 302, data obtained by binarizing the reference image with fine stripes calculated or imaged is prepared in advance, and the binary data is binarized by the AND logic operation unit 403. Import reference image data and one screen
The AND logic operation is performed on the binarized interference fringe image data for each corresponding pixel at the video rate.

In the horizontal direction of the CCD of the two-dimensional image detecting means 1,
If x and the vertical direction are y, and if binarized reference image data with high spatial frequency V in the x direction is prepared, the luminance signal I _R of the reference image, the input interference fringe image The luminance signal I _S of each is expressed as I _R = A · sin (Vx + P) + R (20) I _S = B · sin (Wx + Q) + S (21). Where A and B are the reference image and the brightness amplitude of the input interference fringe image, V and W are the reference image and the spatial frequency in the x direction of the interference fringe image, and P and Q are the reference image and the initial fringe image, respectively. Phase, R and S are reference images,
It is the bias component of the interference fringe image.

When both luminance signals are binarized with the median value of the sine wave as the slice level, I _R2 = 1 [Asin (Vx + P) ≧ 0], = 0 [Asin (Vx + P) <0 ] ・ ・ ・ (22) I _S2 = 1 [Bsin (Wx + Q) ≧ 0], = 0 [Bsin (Wx + Q) <0] ・ ・ ・ (23) When white and 0 correspond to black, the binarized reference signal I _R2 and binarized interference fringe signal I _S2 are shown in Figs. 4 (A) and (B).
When the AND operation of both signals is performed, only the white parts of both stripes are white, and the other parts are black, so that the overlapping parts appear white as shown in Fig. 4 (C).

Therefore, this is also a kind of moire fringe, and since the fringe pattern represents the phase difference distribution between the reference image and the input interference fringe image, the interferometer is arranged so that the fringe becomes the coarsest on the monitor 9 while observing the fringe pattern. If is adjusted, the spatial frequency V of the input interference fringe image is made to match the spatial frequency W of the reference image, and the purpose of alignment in the phase shift electronic moire method is achieved.

The AND logic operation unit 403 of this embodiment is
Even if it is replaced with an OR logical operation unit, substantially the same result is obtained as shown in FIG.

[0065]

According to the present invention, the phase shift electronic moire method which is strong against external disturbances such as mechanical vibrations and air fluctuations at the time of measurement by switching the two units and detecting the phase distribution of the interference fringes has the above-mentioned configuration. Achieves an interference fringe phase detection method and an interferometric measurement device using the method, which allows the device configuration to be extremely simple and to be configured with general-purpose equipment without sacrificing features or measurement accuracy, resulting in significant cost reduction and space saving. To do.

Others (3-1) Since arithmetic operations with a plurality of reference image data are serially performed by a general-purpose computer, any n-bucket method can be specified by software without changing the hardware configuration, and high precision is achieved. Phase calculation can be realized at low cost. (3-2) By replacing multiplication with addition or subtraction, it is possible to suppress an increase in the number of bits during calculation and reduce the processing load. (3-3) As shown in the second embodiment, the amount of data is reduced to 1/8 by processing the part that has to perform the inter-image calculation at high speed with the binarized data, and the load on the calculation means is reduced. can do. (3-4) By replacing the multiplier with an AND logical operation unit or an OR logical operation unit, the processing load can be further reduced. (EN) An interference fringe phase detection method having at least one effect and an interferometer using the same.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of Embodiment 1 of an interferometer according to the present invention.

FIG. 2 is an explanatory diagram of a procedure of computer processing according to the first embodiment.

FIG. 3 is a schematic view of a main part of Embodiment 2 of the interferometer according to the present invention.

FIG. 4 is an explanatory diagram of binarized data processing according to the second embodiment.

FIG. 5 is a configuration diagram of a main part of a conventional interferometer using an electronic moire method.

[Explanation of symbols]

1 2D image detection means 2 Image input method 3a, 3b, 3c image memory 4a, 4b, 4c multiplier 5a, 5b, 5c low pass filter 6a, 6b subtractor 7 divider 8 Non-linear calculator 9 monitor 10 computers 11 Pretreatment means 12 Changeover switch 13 Input image memory 14 Data storage means 15 Binarization means

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01B 9/02 G01B 11/25 G01M 11/00

Claims (9)

(57) [Claims] 1. An interference fringe image to be measured, in which a large number of interference fringes are generated by an interferometer to generate a spatial carrier wave,
A phase shift electronic moire method is used for detecting the phase distribution of the measured interference fringe image by inter-image calculation with a plurality of reference images having interference fringes having a frequency substantially equal to the spatial frequency of the carrier wave and having different initial phases. In the conventional interference fringe phase detection method, the inter-image calculation between the interference fringe image from the interferometer and one reference image is performed at a video rate, and the high frequency component of the image signal obtained therefrom is cut and output on the monitor screen. And an alignment unit for aligning the interferometer and 1
An arithmetic unit that temporarily stores and holds the measured interference fringe image for the screen and performs inter-image calculation between the measured interference fringe image and a plurality of reference images is used, and these units are switched to change the measured interference fringe. An interference fringe phase detection method characterized by detecting a phase distribution of a fringe image. 2. The interference fringe phase detection method according to claim 1, wherein the arithmetic unit sequentially calls the plurality of reference images and serially executes the arithmetic operation. 3. The interference fringe phase detection method according to claim 1, wherein in the alignment unit, the inter-image calculation between the interference fringe image and the reference image is addition or subtraction. 4. In the alignment unit, 2
2. The interference fringe phase detecting method according to claim 1, wherein the inter-image operation is performed by AND logic operation or OR logic operation between the binarized interference fringe image and the binarized reference image. 5. An interference fringe image to be measured, in which a large number of interference fringes are generated by an interferometer to generate a spatial carrier wave,
A phase shift electronic moire method is used for detecting the phase distribution of the measured interference fringe image by inter-image calculation with a plurality of reference images having interference fringes having a frequency substantially equal to the spatial frequency of the carrier wave and having different initial phases. In the interferometer, the two-dimensional image detecting means for detecting the measured interference fringe image formed by the interferometer, and the measured interference fringe image for one screen based on the signal output from the two-dimensional image detection means. Image input means for extraction and output destination of the measured interference fringe image for the one screen
The switches and a switch means, of said switching means
At one output destination, a reference image memory for recording one reference image, an arithmetic unit for performing an inter-image calculation between the interference fringe image to be measured for the one screen and the one reference image, and the inter-image calculation A low-pass filter that cuts the high-frequency component of the obtained signal and a monitor that displays an image by the image signal that cuts the high-frequency component are arranged, and the other of the switch means is arranged.
At the output destination, an input image memory for temporarily storing and holding the measured interference fringe image, and a computer for performing inter-image calculation between the measured interference fringe image and a plurality of reference images stored in the data storage means are arranged. interference measuring apparatus characterized by being. 6. The interference measuring apparatus according to claim 5, wherein the arithmetic unit is a multiplier that multiplies between images. 7. The arithmetic unit is an adder for performing addition between images or a subtractor for performing subtraction between images.
Interference measurement device. 8. The operator is an AND logic operator or O.
It is an R logic operation unit, the reference image which is binarized is recorded in the reference image memory, and the interference fringe image is binarized by a binarizing means, and the binarized reference image and the AND. The interferometer according to claim 5, wherein the inter-image operation is performed by a logical operation unit or the OR logical operation unit. 9. The interference measuring apparatus according to claim 5, wherein the computer sequentially calls the plurality of reference images from the data storage unit and serially executes an operation.