TW389832B - Digital speckle deformation measurement system - Google Patents

Abstract

Digital speckle deformation measurement system comprises a Michelson shearing mechanism, a digital image processing system, and an illumination system. The Michelson shearing mechanism comprises two reflective mirrors, two lenses and a stereo spectroscope, fixed on a base to cooperate with a lens for capturing images. The digital image processing system includes a digital camera and an image processing system. And the illumination system includes a laser and beam amplifier. When the illumination system lights up the object to be measured, the speckle image shearing can be done by the Michelson shearing mechanism and the accurate strain value can be calculated based on the interference principle of digital shearing speckles, thus a convenient and accurate measurement system is provided.

Description

V. Description of the invention (I) The present invention relates to a digital measurement system with four spots. ^ ^, Especially a measurement system consisting of a Kersen shearing mechanism, a digital image processing system, and an illumination mechanism. This measurement system can measure the strain field information, and further understand the deformation, damage and defects of the structure, and provide a convenient and accurate measurement system-the general structure of the structure has a direct relationship with the magnitude of the stress, which may be caused by the stress and Stress analysis is performed on the relationship between strains. If the structure has defects or is damaged, the defects of the product can be directly observed through the stripe image of the strain. If the magnitude of the strain can be measured quickly and accurately, it can be further evaluated. The size of the defect or the degree of damage; traditional strain gauging techniques, such as strain gauges, can only be measured point by point. As for the moire method or holographic interferometry, although “%” is used as a full meaning analysis, The obtained result is only a displacement field instead of a strain field, and often requires re-differentiation to obtain the strain, which is easy to cause errors and is time-consuming and inconvenient in application. After the introduction of laser technology from the measurement technology, the measurement technology has been further improved. "Because the laser has the characteristics of high directivity, high brightness, high monochromaticity and high coherence," the laser is more widely used in various projects. On the other hand, if high-coherence light is used to irradiate the surface of a rough object, the light scattered from each point on the surface of the object to the observation point will interfere with the light scattered from other points, resulting in irregularly distributed spots. If you can find the regularity of these irregular patterns, you can measure the roughness. In addition, you can apply this laser technology to various measurements, such as displacement, deformation, vibration, Measurement of speed, etc. Only in the application process of the laser technology, its measurement is still only the paper two coffees > p Guan Jia Standard (CNS) A4 Regulation G χ 297 public love) S ' --- V. Description of the invention) Shift: It also needs to be subjected to re-differentiation to obtain the strain, so in order to reduce the measurement change to a low level, the inventor devised a kind of "digital spot deformation, 'system "Dhai measurement system The Maxson shearing mechanism, digital imaging system and lighting mechanism are composed of non-contact, non-destructive and Wang Changsheng optical measurement methods, which can measure the strain field information, and further understand Destruction and destruction of structures provide a convenient and accurate measurement system. The main purpose of the invention design is to provide _ a variety of "digital spot deformation measurement system," "J" This measurement system consists of Maxson shearing mechanism, digital image processing system and lighting mechanism, Maxson shearing mechanism consists of two 'Reflectors' two lenses and a stereo spectroscope _ set on _ the bottom plate, and with a lens for image acquisition procedures '' and the digital image processing line is composed of digital cameras and image processing seasons '' with laser and The illumination mechanism composed of the beam amplifier 'when the illumination mechanism is irradiated on the object to be measured, the spot image can be cut by the Maxson shearing mechanism', which is added and subtracted in real time to two different force states II You can obtain interference fringe artifacts by cutting the artifacts below, and then calculate the correct strain according to the principle of digital shear spot interferometry to provide a convenient and accurate measurement system. In order to make your reviewing committee better understand the measuring system of the present invention, it is explained with the drawings: (A) Schematic part: The first figure is a plan view of the digital spot deformation measuring system of the present invention. The second picture is a test circle image obtained by using laser light as a light source according to the present invention. The fifth and the description of the invention (2) Gray scale arrow-direction test circle image diagram. The fourth picture is a test circle obtained by using white light as a light source according to the present invention. The cut shadows and pentagrams of the present invention use white light as a light source to distribute along the arrow steps. The sixth figure is a schematic diagram of a cut image of a test circle of the present invention. The seventh image is a test circle image after the median filtering according to the present invention. The eighth figure is the median filtering of the present invention: the gray-scale distribution 圏. "The ninth picture of the test circle in the arrow direction is the image of the edge detection image of the test circle of the present invention. The tenth picture is the test circle gray image of the gray level distribution of the edge detection image of the invention in the direction of the arrow. Uneven test surface cut-off image. The twelfth figure is the distribution chart of the test circle gray scale of the present invention. The thirteenth direction is the light path diagram of the present invention for measurement. The fourteenth figure This is the fifteenth figure of the digital cut image obtained by using the image addition of the present invention. The second figure of the digital cut image obtained by using the image subtraction of the present invention is the second part. (1 0) mirror (1 2) Lens A7 V. Description of the invention (B7 (14) Beamsplitter (15) Lens (20) Digital camera (30). Image processing system The digital spot deformation measurement system of the present invention is a Maxson shearing mechanism The digital image processing system and the lighting mechanism are composed of which the Maxson shearing mechanism is the most important part of the entire measurement system. When the laser generated by the lighting mechanism is shot on the item to be measured, that is, Clipping image can be generated by Maxson shearing mechanism Then, the digital image system is used to capture the image and perform image pre-processing and image calculation functions. The Maxson shearing mechanism, as shown in the first figure, is composed of two mirrors (1 0) (1 1 ), Two lenses (i 2) (2 3), a stereo spectroscope (1 4), and a lens (1 5), the lens (1 3) is placed on a telescopic sleeve (2 1), To connect with the digital camera ccD 〇), the digital camera CCD (20) and the image processing system (30) 'The telescopic sleeve (2 丄) can change the distance between the camera and the transparent brother (1 3), so that the image Appropriate imaging on the camera's sensor, and through the proper positioning of the sleeve 'make the camera easy to disassemble, easy to carry and use' to make the camera's scope of application. Increase. 'Another lighting mechanism is laser and beam amplifier In the combination, the laser is selected from He ~ Ne or other lasers, and the beam amplifier can be composed of a 10-fold microscope objective lens. = When the illumination of the present invention is irradiated on the object to be measured, Spot-shearing The principle of the speckle interferometry adds and subtracts the shear image and calculates the positive strain variable 1. I did measure the strain on the surface of the object ', so the correct amount must be measured first (please read the precautions on the back before filling this page). ------ Order ---------- Line Γ The paper ruler is thin 6 χ 297 mm y -III. A7 V. Description of the invention The magnification of the imaging system and the incident angle of the object light are accurate. The correct distance between the surface of the object to be measured and the clipping system is not directly or accurately measured. Therefore, image processing technology is used to quickly and accurately Measure the amount of shear. In general, the displacement field derivative in any direction, and the relationship between the amount of shear and the phase difference can be expressed as the form shown in Formula A: Another one C2 ¥ + Ci) (Formula A) If the amount of shear j > (and 〇 In the X and Y directions, respectively, the meaning is the form shown by formula B: [(知) 2 + (< 5 /) 2] 2 (Form B) Therefore, to obtain the correct amount of shear, First measure 彡 X and multi / correctly. For the measurement of the shear amount, a black test circle with a white background and a known diameter (D) is placed on the object to be measured. Due to the speckles generated by the laser light, The nuclear test that affects the edge, in order to avoid the speckle effect caused by the laser light, the white light is used in the measurement of the shear amount. The second picture shows the test circle image obtained by using the laser light as the light source. As shown in the figure, it is a grayscale distribution chart along the direction of the arrow. Due to the effect of spots, the grayscale value also shows discontinuity at non-boundaries, and edge detection will be difficult; and as shown in the fourth figure, In order to obtain a test circle image obtained by using white light as a light source, the fifth figure shows the grayscale distribution chart in the direction of the arrow, and the grayscale is compared with the third figure The values are relatively flat except that there is a large gradient on the boundary. You can first filter the image by median value and then calculate and detect the boundary of the test circle. If you place the test circle on the part to be tested and capture it The cut wheat image is shown in the fourth picture, and the schematic diagram is shown in the sixth picture. The two circles are round: The size of the paper is applicable to the Chinese National Standard (CNS) A4 specification (210 X 297 male ir. Please read the back V) Please fill in this page again for attention} Install ------------------ rr (> < i, / z) (X3, y3), test circle top, bottom

~ y ^ + (y2-^) And the relationship between the digital camera cc D and the 0 pixels change, the expression can be represented-the actual size of the object and the amount of clipping on the shadow (C type) (D type) Let's do nothing = 夂 and every pixel in the direction ... 丄 Γ, the above C formula and D formula can be defined in the X and / direction (E formula) < 5y β J »^ (/ 3-y2) *- -~ ^ 3 (^ -y ^ + (r2 ~ yl) (F type) The size of the shear amount can be obtained by image processing technology, which is obtained from E type and f type: 'Only the center position and radius of two circles are required. Shearing seedlings can be obtained by their size. The factors that affect the measurement results of the shearing amount can be summarized into two major factors of the image system analysis process = image processing process. The system's magnification, lens ball and astigmatism will affect The resolution of the imaging system; the lighting when taking images: the noise of the system and the outside world will affect the results of image processing. If the measurement in the knife is directly scanned to determine the edge capture of the test circle There is a high requirement on the quality of the measured circle image, otherwise a greater error will occur A7

5. Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs, and the description of the invention is poor. In order to reduce the W of the heart, the method of heart and radius is carried out. First cut the test image of the test circle to median wave to eliminate the noise in the image. As shown in Figure 7, the test circle image after filtering by the median value is not shown in Figure 8 Gray scale distribution. Then use the edge detection technology to detect the boundary of the image. As shown in the ninth figure, the image obtained by the edge detection technology can be observed to show a larger gray level value on the test circle boundary. The grayscale distribution along the arrow direction can clearly distinguish the boundary of the test circle from the maximum grayscale value on the figure; the principle of the center and radius of the circle can be determined by using three different points on the circle boundary. In the image of the edge detection result, The center and radius of the circle are determined by taking three points on each of the two circle boundaries. You can determine the approximate center and radius of the circle by taking three points on each of the two circle boundaries, and then use this as the center and radius to approach the surrounding area. The points and neighboring radii are searched to find the center and radius. The search of the center is to search from the center to the range of 24 points. The radius is searched by increasing or decreasing the range of two pixels. The steps for determining the center and radius are as follows. : 1 · Use the edge detection technology to obtain the border image. 2 · Determine the approximate circle center mark and its radius from any three points on the boundary. 3 · Take the approximate circle center as the center, select the range of 24 points adjacent to the circle, and add and subtract two pixels to this possible radius. The radius. 4 · Calculate the grayscale value and N of each point on the circumference of the circle with various points within the range of the selected center of the circle. This paper size is applicable to Chinese National Standard (CNS) A, 4 (210 X 297 cm)

^ Install —, — order — ------ line "(Please read the precautions on the back before filling this page)

5. Compare the sum of gray scale values N 'on the circumference of various circle centers and radius combinations, taking the circle center and radius with the largest N value as the circle center and radius of the test circle. In order to eliminate the influence of noise, the time-averaged chirp wave is first processed when the image is read, and to avoid the edge detection of the test circle is often affected by the uneven illumination, as shown in Figure 11 and Figure 12, At this time, the lighting compensation method can be used to improve it. Therefore, using the symmetry of the circle, the center and radius of the test circle can be quickly and reliably determined by the search method, and the shear amount can be determined. The principle of measurement. Please refer to Figure 13. When the laser light is irradiated on the object to be measured, the laser light emitted by the object to be measured is passed through a Maxson shearing mechanism placed in front of the camera lens to divide the light into The two light beams, transmitted and reflected, are directed to the mirror (丄 〇) (in), and the light is reflected by the mirror (10) (11) to form interference in the beam splitter and is imaged on the sensor of the digital camera. The mirror (10) will form a shearing effect after a small angle, so that the object j will interfere with the spectroscope to form an image on the sensor of the pure eyepiece. ~ Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs

-% '装 -------- Order · ίI ----- 线 ---- ΙΜ (Please read the notes on the back before filling this page) (nnnn For digital cut-outs, you can First, a digital camera records the speckle image before and after the force of the object to be measured, converts the light intensity signal into a voltage signal, and the image processing system converts the voltage signal into a grayscale image, and then subtracts or subtracts the subsequent grayscale image. The process of adding = Cut ™ 'such as ... ㈣ Digital color cutout using color image addition 3: to, and the fifteenth is a digital cutout image using square poems subtracted from the image.

Paper ruler x 297 mm)

Therefore, with the cooperation of the Maxson shearing mechanism, digital image processing system, and lighting mechanism, the internal measurement method of this month can measure strain using non-contact, non-destructive and full-field optical measurement methods. Field information, advance — Y understand, structure damage and defects, because the design of the present invention is not subject to micro-J vibration ~% is suitable for field measurement, so it has more industrial applicability and should meet the requirements of invention patents, The application is made in accordance with the law. f Please read the notes on the back before filling out this page.) ---- I I I I Order --- Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs

This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) I ----- line

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Claims (1)

A8 B8 C8 D8 Patent Application Scope 1: A "Digital Spot Deformation Measurement System" This measurement system is composed of Maxson shearing mechanism, digital image system and lighting mechanism. Maxson's cutting mechanism is composed of two mirrors, Two lenses and a three-dimensional beam splitter are fixed on a base plate and cooperate with a lens that performs the image acquisition process. The digital imaging system consists of a digital camera and a processing system. And constitute a measurement system. 2 · According to the “Digital Light Spot Deformation Measurement and Measurement System” described in Item 1 of the scope of the patent application, the shear measurement method of the Maxson shearing mechanism can be preceded by a test circle on the flat plate, and the white light source projected by the light source is another The circle image must be tested, and then the center of a circle and its radius can be used to measure the amount of shear. 3. The "digital spot deformation measurement system" as described in item 范围 of the scope of patent application, wherein the light source may be a laser light source. 、 (Please read the notes on the back before filling this page} '1T · Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economy 12 This paper size is applicable to the national standard (CNS) A4 (210X297 mm) 1