A Structured Light System Calibration Method Based on a Color Composite Calibration Plate

Abstract

The present invention discloses a calibration method for a structured light system based on a color composite calibration board, comprising: integrating a checkerboard and circles on the calibration board, and designing a color composite calibration board by using the RGB channel multiplexing principle; respectively projecting the generated horizontal and vertical phase-shifted fringe images onto the surface of the color composite calibration board by a projector and collecting color composite calibration board images in several different poses by a color CCD camera, and processing the collected images by a computer: first, separating the RGB channels and calibrating the internal and external parameters of the color CCD camera based on the feature points of the R and B channels; subsequently, solving the surface phase distribution of the color composite calibration board by using the fringe image of the G channel and calibrating the internal and external parameters of the projector; finally, using the calibration results of the color CCD camera and the projector to complete the polynomial fitting of the per-pixel phase and the world three-dimensional coordinates of the color composite calibration board, and realizing the three-dimensional mapping of the phase and the depth.

Description

Technical Field

[0001] The present invention relates to the technical field of structured light three-dimensional measurement, and particularly relates to a calibration method for a structured light system based on a color composite calibration plate. Background Art

[0002] Benefiting from the characteristics of non-contact, high sensitivity, and high precision, the structured light measurement system has been widely used in technical fields such as three-dimensional detection and three-dimensional reconstruction. System calibration is a key factor affecting the measurement accuracy of structured light. The traditional calibration method is based on the principle of binocular vision calibration, and uses the feature points in a checkerboard or circular calibration plate to establish the relative pose between the camera and the projector, so as to realize the pixel-level mapping relationship between the spatial coordinates and the phase. Although the traditional calibration plate can effectively detect the sub-pixel coordinates of the feature points, for the structured light system, there are still the following two limitations:

[0003] The existing two mainstream calibration plates have their own advantages and disadvantages: The advantage of the checkerboard is that the corner detection is less restricted by the pose, but it is easily affected by image defocus; while the circular calibration plate has a higher tolerance for defocus, but in an extremely tilted pose, it may cause the center detection to fail. The existing calibration plates are designed for camera calibration, and they require high contrast to reduce the difficulty of feature point extraction, so they are all black and white in color. However, this characteristic is not suitable for phase extraction, because the extremely low signal-to-noise ratio and modulation degree in the black part will lead to poor phase quality in this area or even the phase cannot be restored. Moreover, the black and white boundaries will cause phase jumps or phase artifacts, seriously reducing the calibration accuracy.

[0004] In summary, improving the feature point detection accuracy and improving the phase extraction quality are two key links in the calibration of the structured light system. Summary of the Invention

[0005] The purpose of the present invention is to provide a calibration method for a structured light system based on a color composite calibration plate to improve the measurement accuracy of the system.

[0006] To achieve the above task, the present invention adopts the following technical solutions:

[0007] A calibration method for a structured light system based on a color composite calibration plate, the structured light system targeted by the method includes a projector, a color CCD camera, and a computer; the projector and the color CCD camera are respectively connected to the computer through data lines;

[0008] Integrate the checkerboard and circles on the calibration board, and utilize the RGB channel multiplexing principle to construct a color composite calibration board; in the color composite calibration board, the circle area is set to orange, and the checkerboard area alternates between light blue and green; use the projector to project the generated horizontal and vertical phase-shifted fringe images onto the surface of the color composite calibration board in sequence and use a color CCD camera to collect color composite calibration board images in several different poses, and use a computer to process the collected images:

[0009] First, separate the RGB channels of the collected color composite calibration board images and extract the circle centers in the R channel and the corner points in the B channel as feature points respectively, and then use the coordinates of the feature points to complete the calibration of the internal and external parameters of the color CCD camera; subsequently, use the fringe image in the G channel to solve the phase distribution on the surface of the color composite calibration board, then solve the pixel coordinates of the feature points in the color composite calibration board in the projector coordinate system to complete the calibration of the internal and external parameters of the projector; finally, use the calibration results of the color CCD camera and the projector to complete the polynomial fitting of the per-pixel phase and the world three-dimensional coordinates of the color composite calibration board to realize the three-dimensional mapping of the phase and the depth.

[0010] Further, the color composite calibration board is a rectangular board, and the pattern on the calibration board consists of a checkerboard grid and circles. One circle is set in each square, and the center of the circle coincides with the centroid of the square. The diameter of the circle is smaller than the side length of the square;

[0011] The color composite calibration board is generally composed of three colors. Among them, the colors of the squares alternate between light blue and green. The RGB channel ratio of the light blue squares is 0:0.5:1, and the RGB channel ratio of the green squares is 0:1:0; the circles are set to orange, and the RGB channel ratio is 1:0.5:0.

[0012] Further, the step of using the projector to project the generated horizontal and vertical phase-shifted fringe images onto the surface of the color composite calibration board in sequence and using a color CCD camera to collect color composite calibration board images in several different poses includes:

[0013] Place the color composite calibration board in the acquisition field of view of the color CCD camera in any pose so that the entire color composite calibration board is within the field of view of the color CCD camera; the projector projects two sets of horizontal and vertical phase-shifted fringe image sequences generated by the computer onto the surface of the color composite calibration board in sequence; among them, the horizontal fringe image and the vertical fringe image need to ensure that the entire color composite calibration board is covered by the fringes; the horizontal and vertical phase-shifted fringe images are respectively expressed as:

[0014]

[0015]

[0016] where Represents a horizontally phase-shifted fringe pattern, Represents a vertically phase-shifted fringe pattern, P is the fringe frequency, i is the serial number of the phase-shift sequence, i = 1, 2, 3; (u c , v c ) are the horizontal and vertical coordinates of the pixels of the image collected by the camera; through the three-step phase-shift method, each time the projector projects a phase-shifted fringe pattern, the camera is triggered to collect an image, and finally a sequence of horizontally phase-shifted fringe patterns and a sequence of vertically phase-shifted fringe patterns

[0017] After finishing the image acquisition under the pose of a color composite calibration board, replace the pose of the color composite calibration board and collect the horizontally phase-shifted fringe pattern and the vertically phase-shifted fringe pattern again in the same way, then two sets of phase-shifted fringe pattern sequences can be obtained under each pose.

[0018] Furthermore, separating the RGB channels of the collected color composite calibration board image and respectively extracting the center of the circle in the R channel and the corner points in the B channel as feature points, and then using the coordinates of the feature points to complete the calibration of the internal and external parameters of the color CCD camera, including:

[0019] Perform the following processing on the sequence of horizontally phase-shifted fringe patterns and the sequence of horizontally phase-shifted fringe patterns collected under each pose:

[0020] Obtain the average intensity image from the sequence of horizontally phase-shifted fringe patterns through the following formula:

[0021]

[0022] Extract the R channel of the average intensity image I avr , and a circle calibration board image with a white circle on a black background can be obtained; use the center detection algorithm to extract the center feature points of this image.

[0023] Extract the B channel of the average intensity image I avr , and a checkerboard calibration board image with black and white alternations can be obtained; use the corner detection algorithm to extract the corner points of this image;

[0024] Take the extracted center and corner points as all the feature points of the color composite calibration board, and use these feature points to obtain the internal and external parameter matrix of the camera through the Zhang Zhengyou camera calibration algorithm, complete the calibration of the color CCD camera, and thus obtain the parameter matrix of the color CCD camera.

[0025] Furthermore, the method for solving the surface phase distribution of the color composite calibration board by using the fringe image of the G channel includes:

[0026] Extract the sequence of horizontally phase-shifted fringe patterns collected and the sequence of vertically phase-shifted fringe patterns For the G channel of each fringe pattern in, as Figure 5 , shown in 6, modulated fringe patterns with a background that is not affected by the circle and square patterns and approximately uniform gray levels can be obtained. These modulated fringe patterns are used to calculate the phase distribution on the calibration plate plane. Among them, the horizontal phase and vertical phase in the phase distribution are solved by the following phase-shifting method respectively:

[0027]

[0028]

[0029] where (u c , v c ) are the horizontal and vertical pixel coordinates of the image collected by the camera, and k hor and k ver represent the horizontal and vertical fringe orders respectively.

[0030] Furthermore, solving for the pixel coordinates of the feature points in the color composite calibration plate in the projector coordinate system to complete the calibration of the internal and external parameters of the projector includes:

[0031] The phase value corresponding to the feature point with the horizontal and vertical pixel coordinates (u c , v c ) of the image collected by the camera is denoted as Φ(u c , v c ). The pixel coordinates (u p , v p ) of the feature point in the projector image can be solved through the phase value of the feature point, that is:

[0032] v p = Φ hor (u c , v c ) × P / (2π)

[0033] u p = Φ ver (u c , v c ) × P / (2π)

[0034] where Φ hor (u c , v c ) and Φ ver (u c , v c ) represent the horizontal phase and vertical phase of the feature point, and P represents the fringe frequency;

[0035] Using the pixel coordinates (u p , v p ) of the feature point in the projector image to calculate the internal and external parameter matrices of the projector to complete the calibration of the projector.

[0036] Furthermore, using the calibration results of the color CCD camera and the projector, a polynomial fitting of the per-pixel phase and the world three-dimensional coordinates is performed on the color composite calibration board to achieve a three-dimensional mapping of the phase and the depth, including:

[0037] Calculating the world coordinates corresponding to each pixel on the color composite calibration board in each pose using the calibration results of the color CCD camera and the projector, as shown in the following formula:

[0038]

[0039] where (u c , v c ) are the camera pixel coordinates, (u p , v p ) are the pixel coordinates in the projector image, and (X, Y, Z) are the coordinates in the world coordinate system; is the element in the first row and first column of the parameter matrix of the color CCD camera, is the element in the first row and first column of the parameter matrix of the projector;

[0040] Finally, perform an N-order polynomial fitting on the world three-dimensional coordinates and the corresponding phase values of each pixel in the color calibration board images collected in all poses.

[0041] Compared with the prior art, the present invention has the following technical features:

[0042] While the present invention combines the checkerboard and the circle calibration board to achieve complementary defects, it increases the number of feature points in the limited calibration space, effectively reducing the statistical error of camera calibration. In addition, the image processing mechanism of color channel separation can simultaneously achieve high-precision feature point detection and high-quality phase extraction, thereby improving the calibration accuracy. Description of the Drawings

[0043] Figure 1 is a schematic diagram of the calibration process based on the color composite calibration board;

[0044] Figure 2 is a schematic diagram of the structured light calibration system based on the color composite calibration board;

[0045] Figure 3 is the R-channel image of the average light intensity map;

[0046] Figure 4 is the B-channel image of the average light intensity map;

[0047] Figure 5 is one of the G-channel images in the horizontal phase-shifted fringe pattern sequence;

[0048] Figure 6It is one of the G-channel images in the sequence of vertically phase-shifted fringe patterns. Detailed implementation mode

[0049] Referring to the attached drawings, the present invention provides a calibration method for a structured light system based on a color composite calibration plate. The system used in this method is as Figure 2 shown, including a projector 2, a color CCD camera 3, and a computer 4; the projector 2 and the color CCD camera 3 are respectively connected to the computer 4 through data lines;

[0050] Integrate the checkerboard and circles on the calibration plate, and at the same time utilize the RGB channel multiplexing principle to construct a color composite calibration plate 1; the circle area in the color composite calibration plate 1 is set to orange, and the checkerboard area is alternately light blue and green; use the projector 2 to project the generated horizontal and vertical phase-shifted fringe images onto the surface of the color composite calibration plate 1 in sequence and use the color CCD camera 3 to collect images of the color composite calibration plate 1 in several different poses, and use the computer 4 to process the collected images: First, separate the RGB channels of the collected color composite calibration plate 1 images and extract the circle centers in the R channel and the corner points in the B channel as feature points respectively, and then use the coordinates of the feature points to complete the internal and external parameter calibration of the color CCD camera 3; Subsequently, use the fringe image of the G channel to solve the phase distribution on the surface of the color composite calibration plate 1, then solve the pixel coordinates of the feature points in the color composite calibration plate 1 in the coordinate system of the projector 2 to complete the internal and external parameter calibration of the projector 2; Finally, use the calibration results of the color CCD camera 3 and the projector 2 to complete the polynomial fitting of the per-pixel phase and the world three-dimensional coordinates of the color composite calibration plate 1 to realize the three-dimensional mapping of the phase and the depth.

[0051] 1. Color composite calibration plate

[0052] The color composite calibration plate is a rectangular plate, and the pattern on the calibration plate is composed of a checkerboard grid and circles. One circle is set in each grid, and the center of the circle coincides with the centroid of the grid. The diameter of the circle is smaller than the side length of the grid; the number of grids is set to 9*12, and it can also be other sizes, but it should not be too small. Figure 1 It is only a schematic diagram, so only the local 3*3 area is used for illustration.

[0053] The color composite calibration plate is generally composed of three colors. Among them, the colors of the grids are alternately light blue and green. The RGB channel ratio of the light blue grid is 0:0.5:1, and the RGB channel ratio of the green grid is 0:1:0; the circles are set to orange, and the RGB channel ratio is 1:0.5:0.

[0054] 2. Calibration process

[0055] S1. Place the color composite calibration board in the acquisition field of view of the color CCD camera in an arbitrary pose. This arbitrary pose does not need to limit the vertical optical axis and specific angles, as long as the entire color composite calibration board is clearly imaged within the field of view of the color CCD camera. The projector projects two sets of phase-shifted fringe pattern sequences, horizontal and vertical, generated by the computer, onto the surface of the color composite calibration board in sequence. Among them, the horizontal fringe pattern and the vertical fringe pattern need to ensure that they completely cover the color composite calibration board. The horizontal and vertical phase-shifted fringe patterns are respectively expressed as:

[0056]

[0057]

[0058] Among them represents the horizontal phase-shifted fringe pattern, represents the vertical phase-shifted fringe pattern, P is the fringe frequency, indicating that there are P pixels in one period; i is the phase-shift sequence number. In this scheme, the three-step phase-shift method is used, so i = 1, 2, 3; (u c , v c ) are the horizontal and vertical coordinates of the pixels of the image acquired by the camera. Through the three-step phase-shift method, there are 3 horizontal phase-shifted fringe patterns and 3 vertical phase-shifted fringe patterns, a total of 6 fringe patterns are projected onto the color composite calibration board in sequence. Each time the projector projects a phase-shifted fringe pattern, the camera is triggered to acquire an image. Finally, a sequence of horizontal phase-shifted fringe patterns and a sequence of vertical phase-shifted fringe patterns

[0059] S2. After finishing the image acquisition in a pose of the color composite calibration board, change the pose of the color composite calibration board and acquire the horizontal and vertical phase-shifted fringe patterns again in the same way. Without limiting the rotation angle and translation distance of the pose change on the premise that the calibration board is completely present in the field of view of the color CCD camera and is clearly imaged. Dozens or even dozens of different poses need to be changed during the calibration process, and two sets of phase-shifted fringe pattern sequences can be obtained for each pose.

[0060] S3. Perform RGB channel separation and feature point extraction on the acquired phase-shifted fringe pattern sequences

[0061] For the sequence of horizontal phase-shifted fringe patterns and the sequence of horizontal phase-shifted fringe patterns acquired in each pose, the following processing is performed:

[0062] S3-1. Obtain the average intensity image of the sequence of horizontal phase-shifted fringe patterns through the following formula:

[0063]

[0064] Among them, the average intensity image I avr is a color three-channel image.

[0065] S3-2, extract the average intensity image I avr of the R channel, as Figure 3 shown, a circular calibration plate image with a white circle on a black background can be obtained; use the center detection algorithm to extract the center feature points of this image.

[0066] S3-3, extract the average intensity image I avr of the B channel, as Figure 4 shown, a checkerboard calibration plate image with black and white alternations can be obtained; use the corner detection algorithm to extract the corners of this image.

[0067] S4, Take the centers and corners extracted in step S3 as all the feature points of the color composite calibration plate, and use these feature points to obtain the internal and external parameter matrices of the camera through the Zhang Zhengyou camera calibration algorithm, complete the calibration of the color CCD camera, and thus obtain the parameter matrix of the color CCD camera:

[0068]

[0069] Among them, A c is the internal parameter matrix of the camera, M c is the external parameter matrix of the camera, that is:

[0070]

[0071]

[0072] Among them, and are the focal lengths along the u c and v c directions respectively, is the coordinate of the camera principal point, is the rotation matrix, is the translation vector; in the parameter matrix, is the element in the first row and first column of the parameter matrix, and the meanings of other parameters are similar.

[0073] S5, Extract the G channels of each fringe pattern in the collected horizontal phase-shifted fringe pattern sequence and the vertical phase-shifted fringe pattern sequence , as Figure 5 , shown in Figure 6, a modulated fringe pattern with a background not affected by the circle and square patterns and approximately uniform gray levels can be obtained, and these modulated fringe patterns are used to calculate the phase distribution on the calibration plate plane; among them, the horizontal phase and vertical phase in the phase distribution are solved by the following phase-shift methods respectively:

[0074]

[0075]

[0076] where k hor and k ver represent the horizontal and vertical stripe orders respectively.

[0077] S6. Solve for the pixel coordinates of the feature points in the color composite calibration board in the projector coordinate system, and then obtain the internal and external parameters of the projector to complete the projector calibration.

[0078] The pixel coordinates of the image captured by the camera for the feature point (u c , v c ) are represented by the phase value Φ(u c , v c ). The pixel coordinates (u p , v p ) of the feature point in the projector image can be solved through the phase value of the feature point, that is:

[0079] v p = Φ hor (u c , v c ) × P / (2π)

[0080] u p = Φ ver (u c , v c ) × P / (2π)

[0081] S7. Use the pixel coordinates (u p , v p ) of the feature point in the projector image to calculate the internal and external parameter matrices of the projector to complete the projector calibration, as shown in the following formula:

[0082]

[0083] Among them, A p is the internal parameter matrix of the projector, and M p is the external parameter matrix of the projector, that is:

[0084]

[0085]

[0086] Among them, and are the focal lengths along the u p and v p directions respectively, is the coordinate of the principal point of the projector, is the rotation matrix, is the translation vector; in the parameter matrix, is the element in the first row and first column of the parameter matrix, and the meanings of other parameters are similar.

[0087] For S8, perform polynomial fitting of the phase and world coordinates pixel by pixel on the color composite calibration board to achieve three-dimensional mapping of the phase and depth.

[0088] Calculate the world coordinates corresponding to each pixel on the color composite calibration board at each pose using the calibration results of the color CCD camera and the projector, as shown in the following formula:

[0089]

[0090] where (u c , v c ) are the camera pixel coordinates, and (X, Y, Z) are the coordinates in the world coordinate system.

[0091] For S9, finally, perform N-order polynomial fitting on the three-dimensional world coordinates and the corresponding phase values of each pixel in the calibrated color board images collected at all poses:

[0092]

[0093]

[0094]

[0095] where N represents the order of the polynomial; Φ(u c , v c ) represents the phase value of the calibration board plane at a certain pose where the pixel coordinates are (u c , v c ); X, Y, and Z are the corresponding three-dimensional world coordinates at the pixel coordinates (u c , v c ); a i , b i , c i represent the polynomial fitting coefficients to be solved. Once a i , b i , c i are solved, the mapping relationship between the three-dimensional coordinates (X, Y, Z) of any point in space and its phase in the image coordinates Φ(u c , v c ) is established, and the system calibration is completed; in the subsequent actual measurement process, when the phase information Φ of the measured object is extracted, its three-dimensional coordinates (X, Y, Z) can be obtained through the above formula.

[0096] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A calibration method for a structured light system based on a color composite calibration board, characterized in that The structured light system to which the method is applied includes a projector (2), a color CCD camera (3), and a computer (4); the projector (2) and the color CCD camera (3) are respectively connected to the computer (4) through data lines; Integrate a checkerboard and circles on the calibration board, and at the same time utilize the RGB channel multiplexing principle to construct a color composite calibration board (1); the circle area in the color composite calibration board (1) is set to orange, and the checkerboard area is alternately light blue and green; use the projector (2) to project the generated horizontal and vertical phase-shifted fringe images onto the surface of the color composite calibration board (1) in sequence and use the color CCD camera (3) to collect images of the color composite calibration board (1) in several different poses, and use the computer (4) to process the collected images: First, separate the RGB channels of the collected color composite calibration board (1) images and extract the center of the circle in the R channel and the corner points in the B channel as feature points respectively, and then use the coordinates of the feature points to complete the internal and external parameter calibration of the color CCD camera (3); subsequently, use the fringe image in the G channel to solve the phase distribution on the surface of the color composite calibration board (1), then solve the pixel coordinates of the feature points in the color composite calibration board (1) in the coordinate system of the projector (2) to complete the internal and external parameter calibration of the projector (2); finally, use the calibration results of the color CCD camera (3) and the projector (2) to complete the polynomial fitting of the per-pixel phase and the world three-dimensional coordinates of the color composite calibration board (1) to realize the three-dimensional mapping of phase and depth; The step of using the projector (2) to project the generated horizontal and vertical phase-shifted fringe images onto the surface of the color composite calibration board (1) in sequence and using the color CCD camera (3) to collect images of the color composite calibration board (1) in several different poses includes: Place the color composite calibration board in an arbitrary pose in the acquisition field of view of the color CCD camera so that the entire color composite calibration board is within the field of view of the color CCD camera; the projector projects two groups of horizontal and vertical phase-shifted fringe image sequences generated by the computer onto the surface of the color composite calibration board in sequence; among them, the horizontal fringe image and the vertical fringe image need to ensure that the entire color composite calibration board is covered; the horizontal and vertical phase-shifted fringe images are respectively expressed as: Among them represents the horizontal phase-shifted fringe pattern, represents the vertical phase-shifted fringe pattern, P is the fringe frequency, i is the phase-shift sequence number, i = 1, 2, 3; (uc, vc) are the horizontal and vertical coordinates of the pixels of the image captured by the camera; through the three-step phase-shift method, each time the projector projects a phase-shifted fringe pattern, the camera is triggered to capture an image, and finally a sequence of horizontal phase-shifted fringe patterns and a sequence of vertical phase-shifted fringe patterns After finishing the image acquisition in one pose of the color composite calibration board, change the pose of the color composite calibration board and collect the horizontal phase-shifted fringe image and the vertical phase-shifted fringe image again in the same way, then two groups of phase-shifted fringe image sequences can be obtained in each pose; The step of using the fringe image in the G channel to solve the phase distribution on the surface of the color composite calibration board (1) includes: Extract the sequence of horizontally phase-shifted fringe patterns collected and the sequence of vertically phase-shifted fringe patterns For each fringe pattern in the sequence, the G channel can be extracted to obtain modulated fringe patterns with a background that is not affected by the circle and square patterns and has approximately uniform gray levels. These modulated fringe patterns are used to calculate the phase distribution on the calibration plate plane. Among them, the horizontal phase and vertical phase in the phase distribution are solved by the following phase-shifting methods respectively: Among them, (uc, vc) are the horizontal and vertical pixel coordinates of the image collected by the camera, and k hor and k ver represent the horizontal and vertical fringe orders respectively.

2. The calibration method of the structured light system based on the color composite calibration plate according to claim 1, wherein The color composite calibration board is a rectangular board, and the pattern on the calibration board consists of a checkerboard grid and circles. One circle is set in each grid, the center of the circle coincides with the centroid of the grid, and the diameter of the circle is smaller than the side length of the grid; The color composite calibration board is generally composed of three colors. Among them, the color of the grid is alternately light blue and green. The RGB channel ratio of the light blue grid is 0:0.5:1, and the RGB channel ratio of the green grid is 0:1:0; the circles are set to orange, and the RGB channel ratio is 1:0.5:

0.

3. The calibration method of the structured light system based on the color composite calibration plate according to claim 2, characterized in that Separating the RGB channels of the collected color composite calibration board (1) image, respectively extracting the center of the circle in the R channel and the corner points in the B channel as feature points, and then using the coordinates of the feature points to complete the internal and external parameter calibration of the color CCD camera (3), including: Performing the following processing on the horizontally phase-shifted fringe pattern sequence and the horizontally phase-shifted fringe pattern sequence collected in each pose: Obtaining the average intensity image of the horizontally phase-shifted fringe pattern sequence through the following formula: Extract the average light intensity map I avr For the R channel, a calibration plate image with white circles on a black background can be obtained; the center detection algorithm is used to extract the center feature points of this image; Extract the average light intensity map I avr For the B channel, a checkerboard calibration plate image with black and white intervals can be obtained; use the corner detection algorithm to extract the corners of this image; Taking the extracted center of the circle and corner points as all the feature points of the color composite calibration board, and using these feature points to obtain the internal and external parameter matrices of the camera through the Zhang Zhengyou camera calibration algorithm, completing the calibration of the color CCD camera, and thus obtaining the parameter matrix of the color CCD camera.

4. The calibration method of the structured light system based on the color composite calibration plate according to claim 1, characterized in that, Solving the pixel coordinates of the feature points in the color composite calibration board (1) in the coordinate system of the projector (2), and completing the internal and external parameter calibration of the projector (2), including: The horizontal and vertical coordinates of the image pixels collected by the camera are (u c , v c ), and the phase value corresponding to the feature point is represented as Φ(u c , v c ); the pixel coordinates (u p , v p ) of the feature point in the projector image can be solved through the phase value of the feature point, that is: v p = Φ hor (u c , v c ) × P / (2π) u p = Φ ver (u c , v c ) × P / (2π) Among them, Φ hor (u c , v c ) and Φ ver (u c , v c ) represent the horizontal phase and vertical phase of the feature points, and P represents the fringe frequency; Using the pixel coordinates (u p , v p ) of the feature points in the projector image to calculate the internal and external parameter matrices of the projector and complete the calibration of the projector.

5. The calibration method of the structured light system based on the color composite calibration plate according to claim 1, characterized in that, Using the calibration results of the color CCD camera (3) and the projector (2) to complete the polynomial fitting of the per-pixel phase and the world three-dimensional coordinates of the color composite calibration board (1), and realizing the three-dimensional mapping of the phase and the depth, including: Calculating the world coordinates corresponding to each pixel point on the color composite calibration board in each pose by using the calibration results of the color CCD camera and the projector, as shown in the following formula: Among them, (u c , v c ) are the camera pixel coordinates, (u p , v p ) are the pixel coordinates in the projector image, and (X, Y, Z) are the world coordinate system coordinates; is the element in the first row and first column of the parameter matrix of the color CCD camera, is the element in the first row and first column of the parameter matrix of the projector; Finally, performing N-order polynomial fitting on the world three-dimensional coordinates and the corresponding phase values of each pixel in the calibrated color board images collected in all poses.

Images