JPS62282204A - Speckle photograph analyser - Google Patents

Abstract

PURPOSE:To improve S/N ratio and to enable highly accurate and stabilized measurement of deformation of an article, by rotating interference fringe information of a 2-dimensional image developed, obtaining angles and distances of interference fringes from intensity projection information an each rotation angle. CONSTITUTION:A high deflector 23 is so set that a beam of light irradiated a deviation measuring unit of a dry plate 27 and constants (wavelength of laser light, etc.) of optical system are introduced into on arithmetic operation apparatus 35. Next, when a beam of laser light 21 is emitted. Young's interference fringes are regenerated on a semitransparent screen 29 corresponding to direction and magnitude of a deformation on the measuring unit. They are developed as images by a 2-dimensional image-developing apparatus 31 for storing 33. On the apparatus 35, intensity projection in each angle covering 0 deg.-18 deg. is obtained allowing these fringe images to rotate and the angle at the time when, out of the angles, an intensity projection provided with a characteristic different from that of other angle is detected is obtained as an angle of fringe. Next, the fringe image is rotated by the angle of fringe for arithmetic operation of the intensity projection and a decrement is calculated from the result and a frequency analysis is performed using the maximum entropy method for detection of the peak frequency and the fringe distances are obtained from the result by conversion.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Technical Field of the Invention] This invention relates to speckle photo analysis that measures the amount of deformation of an object from interference fringes obtained by imaging speckle patterns of deformation on the surface of the object. Regarding the equipment.

[Technical background of the invention and its problems] A conventional speckle photo analysis device is described in detail in, for example, the magazine "Optics" Vol. 11, No. 6 (December 1982), pages 583 to 588. There is a device that This device irradiates interference fringes using a laser beam, projects the irradiated interference fringes onto a screen via a rotating prism, and converts the projected image into an image using a one-dimensional dynamic image element.

A rotating prism is used to rotate the interference fringes, and the angle of the interference fringes is determined by utilizing the fact that the degree of modulation of the output of the image element changes due to the rotated interference fringes. . Further, the interval between interference fringes is measured by averaging the number of fringes or by using fast Fourier transform. Then, the deformation (2) of the surface of the object is calculated from the angle and interval of the interference fringes obtained in this way.

By the way, the above-mentioned conventional speckle photo analysis device uses a one-dimensional historical imaging element for the movement of interference fringes, uses an averaging method or fast Fourier method to determine the fringe spacing, and uses a Since a rotating prism is used, it is easily susceptible to speckle noise.If the noise is large or the contrast of the stripes is poor, it may be difficult to measure the image. In addition to the difficulty of determining a clear threshold when selecting the use of the fast Fourier method, the fast Fourier method is easily affected by noise and has poor reliability, and it also has the problem of having a large number of optical system components. be. In addition, when the number of fringes is small, methods such as the fast Fourier method have a small amount of data and are affected by noise, so extracting the frequency components of the fringes is a deferred method.
There is also the problem that highly accurate measurements cannot be made.

E. OBJECT OF THE INVENTION] This invention was made in view of the above-mentioned problems, and its purpose is to improve the S/N ratio and provide a highly accurate and stable speckle photo analysis device.

U Overview of the invention j In order to achieve the above object, the present invention provides a speckle photo analysis device for measuring the deformation speed of an object based on interference fringes obtained from a speckle pattern on the surface of the object. As shown, there is an interference fringe image forming means 1 that forms an h1 image of a measurement site of an object irradiated with a laser beam to form interference fringe information of a two-dimensional image, and a rotation unit that rotates the interference fringe image by a predetermined rotation angle. means 3; projection information creation means 5 for creating density projection information at each rotation angle of the interference fringe image rotated by the rotation means 3; The gist of the present invention is to include an interference fringe angle measuring means 7 for determining the angle, and an interference jet distance measuring means 9 for determining the interference fringe interval by analyzing the frequency component of the density projection information.

[Embodiments of the invention] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 2 is a block diagram of a speckle photo analysis device according to an embodiment of the present invention. In the figure, a laser source 21
The laser beam outputted from the laser beam is condensed onto the surface α of the dry plate 27 via the optical deflector 23J5 and the collimator lens 25. A semi-transparent screen 29 is arranged at a certain distance H1 from the dry plate 27, and Young's interference fringes are formed on these two semi-transparent screens according to the direction and magnitude of deformation in the area irradiated with the rape light. will be played. This interference fringe image is then displayed on the dry plate 2 through the semi-transparent screen 29.
For example, T is placed at a predetermined distance on the opposite side of
The image is captured by a two-dimensional imager (imaging device 31) consisting of a V-camera, etc., and stored in the image memory 33 as interference fringe information of the two-dimensional image.The interference fringe information stored in the image memory 33 is supplied to the arithmetic unit 35. , the direction and spacing of the stripes are measured from the pictorial image information, and further converted into physical quantities, and the change f
Qffi, the calculation unit 35 as the absolute amount of displacement
is output.

Next, the operation will be explained with reference to the flowchart of FIG.

First, the optical deflector 23 is set so that the laser beam illuminates the site where the displacement is to be measured, that is, the wound site of the displacement meter 1 (Step 110), and then the constants of the optical system are determined by the calculation device 3.
5 (step 120). This constant will be needed later when converting physical quantities.The input items are the wavelength λ of the laser beam, the distance between the dry plate 27 and the two semi-transparent screens, and the fringe magnification ~1 Then, if these three constants and the fringe interval F obtained as described below are measured, the absolute displacement it[)l can be obtained by converting according to the following equation.

+ [)l =λL/MF When the optical deflector 23 is set as described above and the constants of the optical system are input, a laser beam is generated from the laser source 21 and interference fringes are reproduced on the two translucent screens. occurs (step 130)
). These interference fringes are transported by the two-dimensional imaging device 31 and stored in the image memory 33 (step 140).
The resulting interference fringe image information is stored in an image memory 33 such as a VTR or magnetic disk, and later processed in batches by an arithmetic unit 35 to improve efficiency.

Next, the term degree and the fringe interval are measured from the interference fringe information stored in the image memory 33 (steps 150 and 160>
Then, the physical ω is converted, converted into the direction and magnitude of displacement, and outputted from the arithmetic unit 35 (step 17
0,180).

FIGS. 4 and 5 are flowcharts showing detailed procedures for measuring the degree of degree and the distance between fringes, which are carried out in steps 150 and 160.

Q'IJJ, the measurement operation of the degree of term will be explained in detail according to the flowchart of FIG. 4 and with reference to FIG.

First, the striped image input to the image memory 33 is shown in FIG.
), assuming an image as shown by reference numeral 41,
Set the X-Y coordinate system on this image with the origin at the upper left,
Density projection information in the Y-axis direction of the striped image is indicated by reference numeral 43 l1
l-J: Find the sea urchin (step 210).

Next, from the density projection information obtained in this way, Figure 6 (a
) and the variance of this difference shown by the symbol 45 to 1
Cotton (steps 220 and 230).

Then, the dispersion value is calculated (step 240), and if this rotation angle is not 180°, return to step 210, The density projection information is obtained for the rotated striped image in the same manner as in the above process, and the difference J3 and the variance 1 are also calculated (step 250).This processing is performed for each predetermined angle with respect to the striped image. Rotate and repeat until it reaches 180”.

Then, if the rotation angle θ at which the dispersion value at each rotation angle obtained through the above 11 repetitions is maximum is detected, this rotation angle θ is the term α (step 260). More specifically, for example, if the angle, degree, or term, or degree, of the striped image 41 in FIG. When rotated to the angle α, the striped image becomes parallel to the Y1 axis as shown by reference numeral 47. When they become parallel, the concentration is 1
The imaging width of the Ω image information is the maximum, and the dispersion value is also the maximum. Therefore, the angle rotated up to this point becomes the degree. Although FIG. 6(b) is a graph without showing the offset dispersion (direct V(θ)) for each rotation angle of 0, the dispersion value V<θ) is maximum at the term α.

In the above process, the density (the difference in the density and the variance (1α) are calculated to obtain the term degree. In other words, while rotating the striped image by a predetermined angle,
The density IQ shadow at each angle up to 80° is determined, and the angle at which a density projection having features different from those of the back of the density IQ shadow at each angle is detected is the term α.

Next, the operation of measuring the fringe interval will be described in detail according to flowchart 1 to FIG. 5.

First, as explained in FIG.
) as shown by the symbol 47, set it parallel to the Y axis (
step 310). Then, the density projection of this image, that is, the density projection indicated by reference numeral 19 in FIG. 6(a), is calculated, and the difference indicated by reference numeral 51 in FIG. 6(a) is calculated from this density projection (step 320). .330). Next, frequency analysis is performed using the maximum entropy method (MEM) (step 340), the frequency components of the fringes are extracted, the peak frequency is detected, and the fringe spacing is calculated from this (step 350). .360). In addition, the 6th
Figure (C) is a graph showing the MEM spectrum versus fringe frequency.

[Effects of the Invention] As explained above, according to the present invention, the interference fringe information of a simulated two-dimensional image is rotated, the interference fringe angle is determined from the characteristics of the density projection information at each rotation angle, and the density projection Since the interference fringe spacing is determined by analyzing the frequency components of the information, the signal-to-noise ratio of the art dealer is improved by using the multiplier of the JH degree projection information, and the optical noise and fringes peculiar to speckle images are improved. Stable results can be obtained even under conditions such as poor contrast.Furthermore, since the maximum entropy method is used to analyze the frequency components of the density projection information, the spectral resolution is high and the manuscript is Highly accurate measurement is possible regardless of the number of tubes.

[Brief explanation of drawings]

FIG. 1 is a diagram corresponding to claims of the present invention, FIG. 2 is a block diagram of a speckle photo analysis device according to an embodiment of the present invention, and FIGS. 3 to 5 are flowcharts showing the operation of the device in FIG. 2. , FIG. 6 is a diagram for explaining the operation of the apparatus shown in FIG. 2. 1...Interference fringe image forming means 3...Rotating means 5...Projection information creating means 7...Interference fringe angle measuring means 9...Interference fringe interval measuring means Particularly Applicant 1 Nissan Motor Co., Ltd. Agent Patent Attorney Yasuo MiyoshiFigure 1Figure 3Figure 2

Claims (5)

[Claims] (1) In a speckle photo analysis device that measures the amount of deformation of an object based on interference fringes obtained from a speckle pattern on the surface of the object, the measurement area of the object irradiated with laser light is imaged and two-dimensional An interference fringe image forming means for forming interference fringe information of an image, a rotating means for rotating the interference fringe image by a predetermined rotation angle, and density projection information at each rotation angle of the interference fringe image rotated by the rotating means. projection information creation means for creating a projection information; interference fringe angle measurement means for determining an interference fringe angle based on the characteristics of each density projection information at each rotation angle; and interference fringe angle measuring means for determining an interference fringe interval by analyzing frequency components of the density projection information. 1. A speckle photo analysis device comprising: interference fringe interval measuring means. (2) The speckle photo analysis apparatus according to claim 1, wherein the interference fringe image forming means images the measurement site using an imaging means having a two-dimensional imaging area. (3) The specification according to claim 1 or 2, wherein the interference fringe angle measuring means obtains a first-order difference of the projection information, and measures the interference fringe angle from the variance of the difference. photo analysis device. (4) The speckle photo analysis apparatus according to claim 2 or 3, wherein the interference fringe interval measuring means analyzes frequency components using a maximum entropy method. (5) The speckle photo analysis apparatus according to claim 2 or 3, wherein the interference fringe interval measuring means includes means for measuring the interference fringe interval from the interval between extreme values of projection information. .