Visual measurement method for section parameters of gallium antimonide crystal rod

Abstract

The application discloses a visual measurement method for section parameters of a gallium antimonide crystal rod, and is characterized by the following steps: connecting a camera capable of being adjusted in each dimension through a computer, connecting a fixed-focus lens on the camera for collecting images of the gallium antimonide crystal rod to be measured, and adjusting the position of the camera to ensure that the principal point of the camera is close to the center of the image of the gallium antimonide crystal rod. On this basis, an oblique visual measurement model and a system parameter calibration method are established. After the sampling frequency of the camera is calculated and set, 360 images are continuously collected, effective images are screened according to the detected straight line features after profile extraction, the maximum and minimum sizes in the transverse direction and the longitudinal size of the gallium antimonide crystal rod are calculated, and finally, image fusion is performed to obtain the section shape of the gallium antimonide crystal rod. The above process is repeated to realize online automatic measurement of the growth of the gallium antimonide crystal. The application can not only obtain the size of the section, but also obtain the section shape, and solves the problem that the oblique measurement is blocked and thus a complete image and section parameters cannot be obtained.

Description

Technical Field

[0001] This invention belongs to the field of image measurement method technology, specifically relating to a visual measurement system for the cross-sectional parameters of gallium antimonide crystal rods, and also to a visual measurement method for the cross-sectional parameters of gallium antimonide crystal rods. Background Technology

[0002] In the early 21st century, gallium antimonide (GaSb) gained attention as a promising next-generation semiconductor material, leading to in-depth research into its technology and applications. For GaSb materials, Sb is more prone to dissociation and volatilization during single-crystal growth, resulting in an imbalance in the Ga:Sb stoichiometry ratio within the melt, causing dislocation defects and even distortion into polycrystalline structures. Therefore, the shape of this crystal rod is difficult to control during processing; only controlling its dimensions can ensure constant-diameter growth.

[0003] Currently, the infrared indirect diameter measurement technology used in semi-automatic single crystal furnaces in China cannot obtain the true diameter of the crystal. Therefore, it cannot guarantee that the crystal will achieve constant diameter growth during the growth process, resulting in poor quality crystals with consistent diameter, which falls far short of the current market demand for large-diameter crystals. For irregular crystal rods like gallium antimonide, which have unique cross-sectional parameters, current on-site measurement methods rely solely on visual inspection and experience, leading to significant errors. Visual measurement methods are much more accurate, and no suitable measurement method has yet been proposed in China.

[0004] During crystal pulling, the extremely high temperature in the single crystal furnace makes manual measurement impossible. A camera takes a top-down view through the furnace's observation window. The solid-liquid interface between the molten raw material solution and the formed crystal creates a halo, known as the aperture, which is very bright. Measuring this aperture reflects changes in the single crystal's size. However, due to the angled shooting angle and the obstruction from the single crystal, the captured image is incomplete. Furthermore, the growth environment is demanding, making measurement difficult and achieving high accuracy extremely challenging.

[0005] Therefore, establishing a visual measurement method for the cross-sectional parameters of gallium antimonide crystal rods and achieving automated high-precision measurement is an urgent problem to be solved. Summary of the Invention

[0006] The present invention also aims to provide a visual measurement method for the cross-sectional parameters of gallium antimonide crystal rods, which solves the problem that gallium antimonide crystal rods, which are irregular in shape, are difficult to measure and have low measurement accuracy due to their unique cross-sectional parameters.

[0007] The technical solution adopted in this invention is: a visual measurement method for the cross-sectional parameters of gallium antimonide crystal rods. This method involves establishing an oblique diameter measurement mathematical model to obtain the object-image transformation relationship, then obtaining the camera's intrinsic and extrinsic parameters using the Zhang Zhengyou calibration method and a known size calibration method, and finally calculating and setting the camera sampling frequency. System measurement is then performed, starting with image acquisition using the calculated sampling frequency. The acquired images are then processed to extract the aperture contour, and the images are filtered using the Hough transform line detection method. The cross-sectional parameters of the selected valid images are measured, and finally, the cross-sectional shape is obtained through image stitching.

[0008] The invention is further characterized in that,

[0009] The visual measurement system for cross-sectional parameters of gallium antimonide crystal rods uses a computer connected to a camera to acquire images of the gallium antimonide crystal rods being measured. The camera is equipped with a fixed-focus lens. The observation window is located diagonally above the single crystal furnace. The camera is fixed to the observation window using a bracket, and the position of the camera is adjusted to ensure that the principal point of the camera is close to the center of the image of the gallium antimonide crystal rod. The bracket needs to ensure that the camera can be adjusted in all dimensions.

[0010] The specific steps for visually measuring the cross-sectional parameters of gallium antimonide crystal rods are as follows:

[0011] Step 1: Establish a mathematical model for oblique diameter measurement: First, establish a mathematical model for oblique diameter measurement based on the system model of visual measurement to obtain the object-image transformation relationship, that is, to obtain the transformation relationship between the coordinates of the object point and the image point;

[0012] Step 2: Calibrate the camera's internal and external parameters;

[0013] Step 3: To improve measurement accuracy, the camera acquires images of the single crystal furnace rotating to multiple angles, capturing images every 1° of furnace rotation, for a total of 360 images; based on the furnace rotation speed of a revolutions per minute (a ≈ 6), the camera sampling frequency μ = 1 / (360 * a / 60) = 1 / 6a; μ ≈ 1 / 36; the acquired images are named according to the sequence number from 1 to 360.

[0014] Step 4: After step 3 is completed, process the 360 ​​images collected using a computer;

[0015] Step 5: Calculate the cross-sectional parameters of the valid images selected in Step 4;

[0016] Step 6: The contours of the 360 ​​images acquired in Step 3 are all obliquely shot. Based on the object-image relationship, inverse projection is performed to obtain a forward object image. The first valid image is used as a reference, and the other images are rotated relative to the reference angle. The images are then fused sequentially to form a complete cross-sectional contour, and finally the cross-sectional shape of the gallium antimonide crystal rod is obtained.

[0017] In the above measurement process, steps 3-6 are completed automatically by the computer. Simply press the start button on the computer to measure the cross-sectional parameters of the gallium antimonide crystal rod. Repeating steps 3 to 6 will complete the measurement process of the entire system.

[0018] Step 1 is as follows:

[0019] Establish a camera coordinate system O-XYZ and a world coordinate system o′-x′y′z′; with the camera optical center O as the origin, the Z-axis coincides with the optical axis; establish an image coordinate system o-xy, with the origin at the intersection of the camera optical axis and the image physical coordinate system;

[0020] In the mathematical model for oblique directional measurement, the world coordinate system o′-x′y′z′ has only a translation along the Z-axis and a rotation relative to the X-axis relative to the camera coordinate system O-XYZ. Therefore, the relationship between the camera coordinate system and the world coordinate system can be described by the rotation matrix and the translation vector:

[0021]

[0022] Where X, Y, Y are the coordinates corresponding to the camera coordinate system, i.e., the image point coordinates;

[0023] x′, y′, z′ are the coordinates corresponding to the world coordinate system, i.e., the coordinates of the object point;

[0024] It is a rotation matrix;

[0025] It is a translation matrix;

[0026] This is the straight-line distance from the camera's optical center to the image.

[0027] α is the angle between the camera's optical center and the image;

[0028] Since the acquired image lies only in the plane o′-x′y′, the z′ coordinate in the world coordinate system is always 0, i.e., z′=0. Therefore:

[0029]

[0030] Then, from the central perspective projection relationship, we obtain:

[0031]

[0032] Where f is the camera focal length.

[0033] This gives us the object-image transformation relationship, i.e., the coordinates of corresponding points in the object plane:

[0034]

[0035] The intrinsic and extrinsic parameters that need to be calibrated in step 2 include:

[0036] (1) Intrinsic parameter focal length f: The intrinsic parameter focal length f was obtained by calibration using the Zhang Zhengyou calibration method when constructing the mathematical model for oblique diameter measurement;

[0037] Because gallium antimonide crystal rods have very high melting points, the crystal pulling process must be carried out in a high-temperature, negative-pressure environment. Diameter measurement must be performed non-contactly outside the crystal pulling furnace through an observation window. Therefore, the angle α and translation parameter T... z Since these parameters are not easily obtained precisely, a method is adopted to calibrate the system parameters based on known dimensions and imaging models to ensure parameter accuracy.

[0038] (2) External parameter angle α: Given the cross-sectional parameters of a gallium antimonide crystal rod, the parameter can be calibrated using the object-image correspondence at a specific point with the crystal center as the origin.

[0039] Based on the points (x1′, y1′) corresponding to the actual cross section, and according to the object-image transformation formula (4), the upper and lower equations are divided to obtain the result.

[0040]

[0041] Then the angle α can be calculated;

[0042] (3) External parameter translation parameter T z : Through another set of corresponding points (x2′, y2′), according to the object-image transformation formula (4), when y2′=0, y2=0,

[0043]

[0044] We can obtain:

[0045]

[0046] The camera's intrinsic and extrinsic parameters can be obtained using the above calculation methods.

[0047] Step 4 is as follows:

[0048] Step 4.1: Apply median filtering to the 360 ​​images acquired in step 3 to remove noise while protecting the edges of the signal from blurring.

[0049] Step 4.2: Use the Canny operator to extract the edges of the image after processing in step 4.1, and use the area of ​​the contour as a condition to remove redundant contours, thereby filtering out the contour of the aperture.

[0050] Step 4.3: For the 360 ​​images collected in Step 4.1, the Hough transform line detection algorithm is used to detect the straight lines in the contour. As long as the angle between the detected straight line and the horizontal axis is less than 1°, it means that the image is valid and the cross-sectional parameters can be calculated from the image.

[0051] Step 5 is as follows:

[0052] Step 5.1: For the detected straight lines that make an angle of less than 1° with the horizontal axis, the equation of the line is:

[0053] y a =kx+b (8)

[0054] Where k is the slope of the detected line; b is the intercept of the detected line;

[0055] Calculate the pixels where the line intersects the contour and the length of the line. Move the line upwards by 1 pixel each time, that is, decrease the intercept b by 1 each time. Stop moving the line when the current line length is less than the next line length. The equation of the line at this time is:

[0056] y b =kx+(bi) (9)

[0057] Where i is the line y when the line stops moving. b Equivalent to y a The number of pixels that changed;

[0058] At this point, the maximum size of the line can be obtained, which is also the maximum size of the image outline; then calculate the y-axis of the line. b =kx+(bi) is the midpoint of the two pixels that intersect the line y. a The distance = kx + b gives half the minimum dimension of the line; based on the object-image transformation relationship, the cross-sectional dimensions in the object space are as follows:

[0059] Let the line y b =kx+(bi) intersects the contour at the coordinates of the pixels (x2, y2) and (x3, y3). According to the object-image transformation formula (4), the corresponding object points (x2′, y2′) and (x3′, y3′) can be obtained. The distance between the two points is calculated:

[0060]

[0061] D1 is the maximum lateral dimension of the gallium antimonide crystal rod;

[0062] Step 5.2: If two lines are detected whose absolute value of the difference between their angles with the horizontal axis is less than 1°:

[0063]

[0064] Where: k c With k d b is the slope of these two lines; c With b d Let be the intercepts of these two lines;

[0065] Find the relationship between these two lines and y. a =kx+b, the intersection points are (x1, y1) and (x4, y4);

[0066] According to the object-image transformation formula (4), the corresponding object points (x1′, y1′) and (x4′, y4′) can be obtained, and the distance between the two points can be calculated:

[0067]

[0068] D2 is the minimum lateral dimension of the gallium antimonide crystal rod.

[0069] Step 5.3: For the midpoints of (x2, y2) and (x3, y3) Calculate the line that passes through this point and intersects with the line y a The pixel coordinates of the foot of the perpendicular (x5, y5) of =kx+b can be obtained according to the object-image transformation formula (4), which gives the corresponding object point. Given (x5′, y5′), calculate the distance:

[0070]

[0071] D3 is the longitudinal dimension of the gallium antimonide crystal rod.

[0072] The beneficial effects of this invention are:

[0073] (1) The system model of visual measurement of the present invention simplifies the system model, reduces unknown parameters, and improves measurement accuracy by adding an adjustment step to adjust the principal point of the camera to be consistent with the center of the crystal rod image.

[0074] (2) The external parameter calibration method of the present invention obtains the camera external parameters by establishing a calibration method based on the known size and imaging model, thus overcoming the problem that the parameters are not easy to obtain accurately in the field measurement.

[0075] (3) The method for measuring the cross-sectional parameters of gallium antimonide crystal rods of the present invention can not only obtain the size of the cross-section, but also the shape of the cross-section, which makes up for the fact that the oblique measurement is blocked and therefore cannot obtain a complete image, and that the cross-sectional parameters of gallium antimonide rods cannot be obtained in the industrial field.

[0076] (4) In the system structure of this invention, the single crystal furnace is used to provide measurement parameters, the camera is used to provide measurement reference, and the computer is used to provide measurement algorithms. Through organic integration, these components can automatically and with high precision measure the cross-sectional parameters of gallium antimonide crystal rods. Attached Figure Description

[0077] Figure 1 This is a schematic diagram of the cross-sectional shape and dimensions of the gallium antimonide crystal rod of the present invention;

[0078] Figure 2 This is a schematic diagram of the oblique diameter measurement mathematical model of the present invention;

[0079] Figure 3 This is a schematic diagram of the system model for visual measurement according to the present invention;

[0080] Figure 4(a) is an image of gallium antimonide crystal rod material collected in Example 3;

[0081] Figure 4(b) is another image of the gallium antimonide crystal rod from Example 3;

[0082] Figure 4(c) shows the solid-liquid interface extraction effect during the gallium antimonide crystal rod processing;

[0083] Figure 4(d) shows the effective images selected based on the straight line characteristics during the gallium antimonide crystal rod processing;

[0084] Figure 4(e) shows the process of finding the maximum lateral dimension during the processing of gallium antimonide crystal rods;

[0085] Figure 4(f) shows the cross-sectional shape obtained by image fusion during the processing of gallium antimonide crystal rods.

[0086] In the figure, 1. Gallium antimonide crystal rod under test, 2. Single crystal furnace, 3. Support, 4. Camera, 5. Fixed-focus lens, 6. Computer, 7. Camera data cable. Detailed Implementation

[0087] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0088] Example 1

[0089] The structure of the visual measurement system for the cross-sectional parameters of gallium antimonide crystal rods of the present invention is as follows: Figure 3As shown, the computer 6 is connected to the camera 4 via a camera data cable 7 to acquire images of the gallium antimonide crystal rod 1 under test. A fixed-focus lens 5 is connected to the camera 4. The observation window is located diagonally above the single crystal furnace 2 at a certain angle. The camera 4 needs to be fixed to the observation window using a bracket 3. At the same time, the position of the camera 4 can be adjusted to ensure that the principal point of the camera 4 is close to the center of the image of the gallium antimonide crystal rod. The bracket 3 needs to ensure that the camera 4 can be adjusted in all dimensions.

[0090] In the above structure, the single crystal furnace 2 provides measurement parameters, the camera 4 provides a measurement reference, and the computer 6 provides the measurement algorithm. Through the organic integration of these components, the cross-sectional parameters of gallium antimonide crystal rods can be measured completely and with high precision.

[0091] Example 2

[0092] The present invention discloses a visual measurement method for the cross-sectional parameters of gallium antimonide crystal rods. The system's working principle is as follows: Before using this method, preparation work for the operating environment is required. An oblique diameter measurement mathematical model is established to obtain the object-image transformation relationship. Then, the camera's intrinsic and extrinsic parameters are obtained using the Zhang Zhengyou calibration method and a calibration method based on known dimensions. Finally, the camera sampling frequency is calculated and set using system parameters. Then, the system measurement is performed. Images are acquired using the calculated sampling frequency. The acquired images are then processed to extract the aperture contour. Images are filtered using Hough transform line detection. The cross-sectional parameters of the selected valid images are measured. Finally, the cross-sectional shape is obtained by image stitching.

[0093] Example 3

[0094] This invention relates to a visual measurement method for the cross-sectional parameters of gallium antimonide crystal rods, specifically implemented according to the following steps:

[0095] I. Preparation of the Operating Environment

[0096] 1. Establish a mathematical model for oblique diameter measurement: First, establish a mathematical model for oblique diameter measurement based on the system model of visual measurement to obtain the object-image conversion relationship, that is, the conversion relationship between the coordinates of the object point and the image point.

[0097] Mathematical models for oblique diameter measurement, such as Figure 2 As shown, a camera coordinate system O-XYZ is established with the camera's optical center O as the origin, the Z-axis coinciding with the optical axis and perpendicular to the image coordinate system plane and passing through the origin of the image coordinate system, and the X and Y axes parallel to the x and y axes of the image. Simultaneously, o′-x′y′z′ is established as the world coordinate system. o-xy is the image coordinate system, with its origin at the intersection of the camera's optical axis and the image's physical coordinate system.

[0098] In this model, the world coordinate system o′-x′y′z′ has only a translation along the Z-axis and a rotation relative to the X-axis with respect to the camera coordinate system O-XYZ. Therefore, the relationship between the camera coordinate system and the world coordinate system can be described by the rotation matrix and the translation vector:

[0099]

[0100] Where (X, Y, Y) are the coordinates corresponding to the camera coordinate system, i.e., the image point coordinates;

[0101] (x′, y′, z′) are the coordinates corresponding to the world coordinate system, i.e., the coordinates of the object point;

[0102] It is a rotation matrix;

[0103] It is a translation matrix;

[0104] This is the straight-line distance from the camera's optical center to the image.

[0105] α is the angle between the camera's optical center and the image.

[0106] Since the acquired image lies only in the plane o′-x′y′, the z′ coordinate in the world coordinate system is always 0, i.e., z′=0. Therefore, we can obtain:

[0107]

[0108] Then, from the central perspective projection relationship, we obtain:

[0109]

[0110] Where f is the camera focal length.

[0111] This gives us the object-image transformation relationship, i.e., the coordinates of corresponding points in the object plane:

[0112]

[0113] 2. Intrinsic and Extrinsic Parameter Calibration: After the system is built, the intrinsic and extrinsic parameters of the camera need to be calibrated. The unknown parameters include: (1) intrinsic parameter focal length f; (2) extrinsic parameter angle α; (3) extrinsic parameter translation parameter T. z The internal focal length f was calibrated using Zhang Zhengyou's calibration method during system construction. Because gallium antimonide crystal rods have very high melting points, the crystal pulling process is always conducted in a high-temperature, negative-pressure environment. Therefore, diameter measurement must be performed non-contactly outside the crystal pulling furnace through an observation window. Thus, the angle α and translation parameter T... z Since these parameters are not easily obtained precisely, a method is adopted to calibrate the system parameters based on known dimensions and imaging models to ensure parameter accuracy.

[0114] Given the cross-sectional parameters of a gallium antimonide crystal rod, the parameters can be calibrated using the object-image correspondence at specific points, with the crystal center as the origin. Figure 1 As shown:

[0115] Based on the points (x1′, y1′) corresponding to the actual cross section, and according to the object-image transformation formula (4), the upper and lower equations are divided to obtain the result.

[0116]

[0117] Then the angle α can be calculated.

[0118] Then, using another set of corresponding points (x2′, y2′), according to the object-image transformation formula (4), when y2′=0, y2=0.

[0119]

[0120] We can obtain:

[0121]

[0122] The camera's intrinsic and extrinsic parameters can be obtained using the above calculation methods.

[0123] 3. Calculate the camera sampling frequency: To improve measurement accuracy, the camera acquires images of the single crystal furnace rotating at multiple angles, with images acquired every 1° of furnace rotation. Therefore, based on the furnace rotation speed of a revolutions per minute (a≈6), the camera sampling frequency μ = 1 / (360*a / 60) = 1 / 6a (μ≈1 / 36).

[0124] II. System Measurement Work

[0125] Once the operating environment preparation is complete, the system's model formulas, camera intrinsic and extrinsic parameters, and camera sampling frequency are obtained. Measurement work can then commence, and the specific procedures are as follows:

[0126] Step 1: Use a computer-controlled camera to acquire images of gallium antimonide crystal rods. Specifically, follow these steps: Based on the sampling frequency calculated during the preparation of the operating environment, the camera acquires one image every 1 / 6a second, i.e., one image every 1°. Name the acquired images according to numbers from 1 to 360. See Figures 4(a) and 4(b) for the two images.

[0127] Step 2: After Step 1 is completed, process the acquired images using a computer. The size of the aperture in the image of the gallium antimonide crystal rod can reflect the change in single crystal size; therefore, it is necessary to extract the aperture feature information. Image processing algorithms are used to improve image quality, enhance image positioning accuracy, and reduce image information storage capacity, thereby extracting the aperture image. Specifically, the following method is implemented:

[0128] Step 2.1: Apply median filtering to the 360 ​​images acquired in Step 1 to remove noise, while protecting the edges of the signal so as not to blur them.

[0129] Step 2.2: Use the Canny operator to extract the edges of the image after processing in step 2.1. Use the area of ​​the contour as a condition to remove redundant contours, thereby filtering out the contour of the aperture, as shown in Figure 4(c).

[0130] Step 2.3: For the 360 ​​images collected in Step 2.1, since they are all incomplete images, the most accurate cross-sectional parameters can only be obtained when the direction of the maximum dimension of the contour is parallel to the coordinate axis. Therefore, the Hough transform line detection algorithm is used to detect the straight lines in the contour. As long as the angle between the detected straight line and the horizontal coordinate axis is less than 1°, it means that the image is valid and the cross-sectional parameters can be calculated from the image. Figure 4(d) shows all the detected straight lines. The thick black lines are the straight lines with an angle of less than 1° with the horizontal coordinate axis, and the thick gray dashed lines are the straight lines with an absolute value of the difference between the angles of the two horizontal coordinate axes that is less than 1°.

[0131] Step 3: Calculate the cross-sectional parameters of the valid images selected in Step 2, specifically according to the following method:

[0132] Step a: For the detected straight lines that make an angle of less than 1° with the horizontal axis, the equation is:

[0133] y a =kx+b (8)

[0134] Where k is the slope of the detected line; b is the intercept of the detected line.

[0135] Calculate the pixels where the line intersects the contour and the length of the line. Move the line upwards by 1 pixel each time, that is, decrease the intercept b by 1 each time. When the length of the line in this step is less than the length of the line in the next step, stop moving the line, as shown by the long black line in Figure 4(e). The equation of the line at this point is:

[0136] y b =kx+(bi) (9)

[0137] Where i is the line y when the line stops moving. b Equivalent to ya The number of pixels that changed.

[0138] At this point, the maximum size of the line can be obtained, which is also the maximum size of the image outline; then calculate the y-axis of the line. b =kx+(bi) is the midpoint of the two pixels that intersect the line y. a The distance = kx + b gives half the minimum dimension of the line. Based on the object-image transformation relationship, the cross-sectional dimensions in object space are as follows:

[0139] Assume the line y b =kx+(bi) intersects the contour at the coordinates of the pixels (x2, y2) and (x3, y3). According to the object-image transformation formula (4), the corresponding object points (x2′, y2′) and (x3′, y3′) can be obtained. The distance between the two points is calculated:

[0140]

[0141] D1 is the maximum lateral dimension of the gallium antimonide crystal rod.

[0142] Step b: Two straight lines whose absolute value of the angle difference with the horizontal axis is less than 1° are detected.

[0143]

[0144] Where: k c With k d b is the slope of these two lines; c With b d Let be the intercepts of these two lines.

[0145] Find the relationship between these two lines and y. a =kx+b, the intersection points are (x1, y1) and (x4, y4).

[0146] Based on the object-image transformation relationship (4), the corresponding object points (x1′, y1′) and (x4′, y4′) can be obtained, and the distance between the two points can be calculated:

[0147]

[0148] D2 is the minimum lateral dimension of the gallium antimonide crystal rod.

[0149] Step c: For the midpoints of (x2, y2) and (x3, y3) Calculate the line that passes through this point and intersects with the line y a The pixel coordinates of the foot of the perpendicular (x5, y5) of =kx+b can be obtained according to the object-image transformation relationship (4), which gives the corresponding object point. Given (x5′, y5′), calculate the distance:

[0150]

[0151] D3 is the longitudinal dimension of the gallium antimonide crystal rod.

[0152] Step 4: Obtain the cross-sectional shape from the contours of the 360 ​​images processed in Step 2. This is implemented as follows: All 360 acquired image contours are obliquely photographed. Based on the object-image relationship, inverse projection is performed to obtain a forward-facing object image. Using the first valid image as a reference, the other images are rotated relative to the reference angle, and then sequentially fused to form a complete cross-sectional contour, ultimately obtaining the cross-sectional shape of the gallium antimonide crystal rod. The stitching result is shown in Figure 4(f).

[0153] In the above measurement process, all steps are automatically completed by computer 6. Simply press the start button on the computer to measure the cross-sectional parameters of the gallium antimonide crystal rod. Repeat steps 1 to 4 to complete the measurement process of the entire system.

[0154] The system model for visual measurement and the visual measurement method for gallium antimonide crystal rod cross-sectional parameters of this invention can overcome the limitations of current on-site measurement, achieve high measurement accuracy, and provide gallium antimonide crystal rod cross-sections.

Claims

1. A visual measurement method for cross-sectional parameters of gallium antimonide crystal rods, characterized in that, A visual measurement system for the cross-sectional parameters of gallium antimonide crystal rods was used. A mathematical model for oblique diameter measurement was established to obtain the object-image transformation relationship. Then, the camera's intrinsic and extrinsic parameters were obtained using the Zhang Zhengyou calibration method and a known-size calibration method, respectively. Finally, the camera sampling frequency was calculated and set. System measurements were then performed. Images were acquired using the calculated sampling frequency, and the acquired images were processed to extract the aperture contour. Images were then filtered using the Hough transform line detection method. The cross-sectional parameters of the selected valid images were measured, and finally, the cross-sectional shape was obtained by image stitching. The specific operation steps are as follows: Step 1: Establish a mathematical model for oblique diameter measurement: First, establish a mathematical model for oblique diameter measurement based on the system model of visual measurement to obtain the object-image transformation relationship, that is, to obtain the transformation relationship between the coordinates of the object point and the image point; Step 2: Calibrate the camera's internal and external parameters; Step 3: The camera captures images of the single crystal furnace rotating at multiple angles, acquiring images every 1° of furnace rotation, for a total of 360 images; based on the furnace's rotation speed... Transfers / minutes 6. Calculate and set the camera's sampling frequency. =1 / (360* / 60)=1 / 6 ; 1 / 36; The acquired images are named according to the sequence number from 1 to 360; Step 4: After step 3 is completed, process the 360 ​​images collected using a computer; Step 5: Calculate the cross-sectional parameters of the valid images selected in Step 4; Step 6: The contours of the 360 ​​images acquired in Step 3 are all obliquely shot. Based on the object-image relationship, the inverse projection transformation is performed to obtain the forward object image. The first valid image is used as the reference, and the other images are rotated relative to the reference angle. The images are then fused sequentially to form a complete cross-sectional contour, and finally the cross-sectional shape of the gallium antimonide crystal rod is obtained. By repeating steps 3 to 6, the entire system can be automated for measurement. The visual measurement system for the cross-sectional parameters of gallium antimonide crystal rods includes a computer (6) connected to a camera (4) to acquire images of the gallium antimonide crystal rod (1) under test. A fixed-focus lens (5) is connected to the camera (4). The observation window is located diagonally above the single crystal furnace (2). The camera (4) is fixed to the observation window using a bracket (3). At the same time, the position of the camera (4) is adjusted to ensure that the principal point of the camera is close to the center of the image of the gallium antimonide crystal rod. The bracket (3) needs to ensure that the camera (4) can be adjusted in all dimensions. Step 4 is as follows: Step 4.1: Apply median filtering to the 360 ​​images acquired in step 3 to remove noise while protecting the edges of the signal from blurring. Step 4.2: Use the Canny operator to extract the edges of the image after processing in step 4.1, and use the area of ​​the contour as a condition to remove redundant contours, thereby filtering out the contour of the aperture. Step 4.3: For the 360 ​​images collected in Step 4.1, the Hough transform line detection algorithm is used to detect the straight lines in the contour. As long as the angle between the detected straight line and the horizontal axis is less than 1°, it means that the image is valid and the cross-sectional parameters can be calculated from the image. Step 5 is as follows: Step 5.1: For the detected straight lines that make an angle of less than 1° with the horizontal axis, the equation of the line is: （8） in, To detect the slope of the straight line; To detect the intercept of the line; Calculate the pixels where the line intersects the contour and the length of the line. Move the line upwards by 1 pixel each time, that is, decrease the intercept b by 1 each time. When the length of the line in this step is greater than the length of the line in the next step, stop moving the line. The equation of the line at this point is: （9） in, When the line stops moving, the line Equivalent to The number of pixels that changed; At this point, the maximum dimension of the straight line, which is also the maximum dimension of the image outline, can be obtained. Based on the object-image transformation relationship, the cross-sectional dimensions in object space are as follows: Let the straight line The coordinates of the pixels intersecting the contour are According to the object-image transformation formula, the corresponding object point is obtained. and Calculate the distance between two points: （10） This refers to the maximum lateral dimension of the gallium antimonide crystal rod. Step 5.2: If two lines are detected whose absolute value of the difference between their angles with the horizontal axis is less than 1°: （11） in: and Let be the slope of these two lines; and Let be the intercepts of these two lines; Find the intersection of these two lines and... intersection and ; Based on the object-image transformation formula, the corresponding object point is obtained. and Calculate the distance between two points: （12） It refers to the minimum lateral dimension of gallium antimonide crystal rods; Step 5.3: For midpoint of ) ), calculate the line that passes through this point and intersects with the line foot drop The pixel coordinates are used to obtain the corresponding object point based on the object-image transformation formula. and Calculate the distance: （13） It refers to the longitudinal dimension of the gallium antimonide crystal rod.

2. The visual measurement method for cross-sectional parameters of gallium antimonide crystal rods according to claim 1, characterized in that, Step 1 is as follows: Establish camera coordinate system and world coordinate system ; With the camera's optical center O as the origin, and the Z-axis coinciding with the optical axis, establish an image coordinate system. The origin of the coordinate system is the intersection of the camera's optical axis and the physical coordinate system of the image. The relationship between the camera coordinate system and the world coordinate system in the oblique azimuth measurement mathematical model is described as follows: （2） in: , Z represents the coordinates in the camera coordinate system, i.e., the image point coordinates; , , These are the coordinates corresponding to the world coordinate system, i.e., the coordinates of the object point; since the acquired image is only located in a plane... In the world coordinate system, therefore The coordinates are always 0, that is =0; , is the straight-line distance from the camera's optical center to the image; The angle between the camera's optical center and the image; Then, from the central perspective projection relationship, we obtain: （3） This gives us the object-image transformation relationship, i.e., the coordinates of corresponding points in the object plane: （4）。 3. The visual measurement method for cross-sectional parameters of gallium antimonide crystal rods according to claim 2, characterized in that, The intrinsic and extrinsic parameters to be calibrated in step 2 include: (1) Intrinsic parameter focal length Internal reference focal length The mathematical model for oblique diameter measurement was obtained through calibration using the Zhang Zhengyou calibration method during its construction. (2) External parameter angle Given the cross-sectional parameters of a gallium antimonide crystal rod, the parameters can be calibrated using the object-image correspondence at specific points, with the crystal center as the origin. Based on the points corresponding to the actual cross section According to the object-image transformation formula (4), dividing the upper and lower equations yields the result. （5） Then calculate the angle. ; (3) External parameters translation parameters : Through another set of corresponding points According to the object-image transformation relationship formula (4), when hour, , （6） get: （7） The camera's intrinsic and extrinsic parameters can be obtained using the above calculation methods.

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