A three-dimensional measurement method of arm based on single-axis MEMS fringe projection

Abstract

The present invention discloses a three-dimensional measurement method for an arm based on single-axis MEMS fringe projection, comprising the following steps: constructing a three-dimensional measurement system composed of a single-axis MEMS projector and a camera module thereof for three-dimensional measurement of the arm; acquiring a three-frequency four-step fringe structured light image acquired by the three-dimensional measurement system, performing phase unfolding by a multi-frequency heterodyne method, and acquiring a phase image; calibrating internal and external parameters of the camera module, and acquiring physical position information of the imaging plane; acquiring phase data with height attribute characteristics based on the physical position information and the phase image, and generating a phase-height mapping parameter by an inverse linear theory; acquiring a three-frequency four-step deformed fringe image of the arm, and acquiring a height value of a modulation phase of the three-frequency four-step deformed fringe image according to the phase-height mapping parameter; acquiring a pixel correction offset of the arm based on the height value, and generating three-dimensional point cloud data of the arm; the present invention can meet the needs of a large number of consumer application scenarios.

Description

Technical Field

[0001] The present invention relates to the field of structured light three-dimensional reconstruction, and in particular to a new algorithm system for single-axis MEMS fringe projection technology. Background Art

[0002] Optical 3D measurement technology has been widely used in industrial measurement such as aerospace and biomedicine. In recent years, FPP has been a research hotspot due to its advantages of high speed, high precision and high resolution. The projector uses a digital micromirror device (DMD) and projects a sinusoidal fringe pattern; then, the camera captures the deformed fringe image for phase calculation and 3D reconstruction. Image sensors and digital projection technology have further promoted the development and application of high-speed and real-time in this field.

[0003] Currently, the automatic blood collection robot hopes to be able to automatically complete the blood collection work of the arm veins. However, since the veins in the arm are not obvious, the automatic blood collection robot needs to perform three-dimensional measurement of the arm to obtain accurate physical information of the vein puncture point.

[0004] MEMS fringe projection technology has the advantages of small size, low price, high frame rate, and no need for focusing optics. In particular, a compact projector based on MEMS fringe projection, using a single-axis mirror that scans at thousands of frames, has great application potential for dynamic 3D measurement. The calibration difficulties of the system are mainly limited by the limitations of the MEMS projector's lensless structure and unidirectional stripes; the difficulty in controlling the relative position of the camera and the work platform.

[0005] In the traditional FPP system calibration based on DMD projector, the DMD projector can be regarded as an inverse camera. Therefore, the orthogonal projection stripes can establish the correspondence between DMD and CCD or CMOS camera, and the system calibration is completed using the principle of stereo vision. Due to the structural characteristics of the single-axis MEMS projection, orthogonal stripe patterns cannot be projected, and it cannot be simply used as an inverse camera. Therefore, the system calibration method based on stereo vision theory is not suitable for the FPP system based on MEMS fringe projection. The use of parallel axis phase height model, non-parallel axis phase height model and linear phase height model requires the projector and camera to be arranged according to a strict geometric position relationship. Therefore, it is necessary to establish a theoretical model with a lower degree of restriction to calibrate the three-dimensional arm measurement system based on the single-axis MEMS projector. Summary of the invention

[0006] In order to solve the existing technical problems, the present invention provides a three-dimensional measurement method of an arm based on single-axis MEMS fringe projection, comprising the following steps:

[0007] Construct a 3D measurement system for 3D measurement of the arm, wherein the 3D measurement system is composed of a single-axis MEMS projector and its camera module;

[0008] The three-frequency four-step stripe structured light image collected by the three-dimensional measurement system is obtained, and phase unwrapping is performed by a multi-frequency heterodyne method to obtain a phase image;

[0009] Calibrate the internal and external parameters of the camera module to obtain the physical position information of the imaging plane;

[0010] Based on the physical position information and phase image, phase data with height attribute characteristics are obtained, and phase height mapping parameters are generated through inverse linear theory;

[0011] Collecting a three-frequency four-step deformed fringe image of the arm, and obtaining a height value of a modulation phase of the three-frequency four-step deformed fringe image according to a phase height mapping parameter;

[0012] Based on the height value, the pixel correction offset of different parts of the arm is obtained to generate the three-dimensional point cloud data of the arm.

[0013] Preferably, in the process of calibrating the internal and external parameters of the camera module, the focal length of the camera module is fixed, the calibration plate is placed at different spatial positions, no less than 25 images are collected, and the Zhang Zhengyou calibration method is used to obtain the internal parameter matrix, radial distortion and tangential distortion parameters of the camera module, and distortion correction is performed;

[0014] Fix the calibration plate on the work surface, collect no less than 5 images through the camera module, and use Zhang Zhengyou calibration method to obtain the extrinsic rotation matrix and translation matrix of the camera module.

[0015] Preferably, in the process of obtaining the physical position information of the imaging plane, an ideal imaging plane equation is constructed, wherein the distance between the ideal imaging plane and the optical center of the camera is 1 mm, and the equation in the camera coordinate is Zc=1;

[0016] Based on the camera imaging principle, obtain the spatial coordinates of each pixel mapped to the ideal imaging plane;

[0017] According to the external parameter rotation matrix and translation matrix, the plane equation of the worktable in the camera coordinate system is fitted: AX+BY+CZ+D=0, and the optical path equation of the mapping coordinates of each pixel and the ideal imaging plane is constructed:

[0018] Based on the plane equation and the optical path equation, a spatial coordinate information equation is constructed to represent the physical position information of the imaging plane:

[0019]

[0020] Among them, (p ix , p iy , p iz ) and (p rx , pry , p rz ) are the ideal planes p i and the actual imaging plane p r The point above; (p x , p y ) is the pixel coordinate in the pixel coordinate system; f x and f y is the focal length of the camera in two directions; A, B, C, D are the parameters of the space plane equation.

[0021] Preferably, in the process of generating the phase height mapping parameters, the three-frequency four-step phase shift fringe images located at 0 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, and 90 mm are collected by controlling the worktable;

[0022] Phase unwrapping is performed by a multi-frequency heterodyne method, and the unwrapped phase images of 10-90 mm are subtracted from the unwrapped phase images of 0 mm to obtain phase difference images at a height of 10-90 mm;

[0023] The 10-90mm phase difference image corresponds to the known actual physical height, and the phase height mapping parameters at each pixel are fitted using the inverse linear method. The fitting method is:

[0024]

[0025] Where a and b represent the phase height mapping parameters, and H(x, y) is the actual true height of the measured object; is the phase difference caused by height modulation.

[0026] Preferably, in the process of generating the three-dimensional point cloud data of the arm, the actual physical distance between the imaging planes of the camera modules and the coordinate point of the camera optical center projected onto the imaging plane generate the vector relationship between the coordinates of each pixel mapped onto the imaging plane and the coordinate point;

[0027] According to the camera imaging principle, based on the geometric relationship between the phase height mapping parameters, the actual physical distance, and the vector relationship, the actual space coordinates after the pixel imaging coordinate offset correction are obtained;

[0028] Based on the X- and Y-axis coordinate data of the actual space coordinates, and taking the actual physical distance as the Z-axis coordinate value, the three-dimensional point cloud data of the arm is generated.

[0029] Preferably, in the process of generating the vector relationship, the expression of the vector relationship is:

[0030]

[0031] where p a (xc ,y c , z c ) and p b (x cr ,y cr , z cr ) are p e and p d In the real imaging plate P r The projection point on c (x ct ,y ct , z ct ) is the camera optical center O c With real imaging plate P r The vertical point between c O c The distance from the plate Pr; p f (x f ,y f , z f ) is P r A point on the a and p c Not colinear.

[0032] Preferably, in the process of generating the arm three-dimensional point cloud data, the expression of the arm three-dimensional point cloud data is:

[0033]

[0034] Preferably, the arm three-dimensional measurement system for implementing the arm three-dimensional measurement method comprises:

[0035] The first data acquisition and preprocessing module is used to acquire the three-frequency four-step stripe structured light image acquired by the three-dimensional measurement system, perform phase unwrapping through a multi-frequency heterodyne method, and acquire a phase image;

[0036] The first data processing module is used to calibrate the internal and external parameters of the camera module and obtain the physical position information of the imaging plane;

[0037] A second data processing module is used to obtain phase data with height attribute characteristics based on physical position information and phase images, and generate phase height mapping parameters through inverse linear theory;

[0038] The second data acquisition and preprocessing module is used to acquire the three-frequency four-step deformation fringe image of the arm, and obtain the height value of the modulation phase of the three-frequency four-step deformation fringe image according to the phase height mapping parameter;

[0039] The three-dimensional point cloud data generation module is used to obtain the pixel correction offset of different parts of the arm based on the height value and generate the three-dimensional point cloud data of the arm.

[0040] Compared with the existing technology, the present invention has the following advantages:

[0041] 1. Low restrictions: The algorithm system of the present invention has low spatial restrictions on system calibration and does not require strict control of the spatial geometric relationship between the projector, camera and work platform.

[0042] 2. Small size: The hardware platform size of the hardware selected by the present invention is about 1 / 12 of the hardware size of the traditional structured light fringe projection, and can adapt to more complex working environments when combined with equipment such as a robotic arm;

[0043] 3. High precision: The present invention uses a MEMS single-axis fringe projector and a common camera module to build an FPP system, which can ultimately achieve an accuracy of about 0.3mm. This accuracy can meet the needs of many consumer application scenarios.

[0044] 4. Low price: The hardware used in the present invention is relatively low in price. The price of a MEMS projector is about 1 / 5 of that of a traditional DMD projector. The camera module is an ordinary camera integrated module to replace an industrial camera, and its price is about 1 / 14 of that of an ordinary industrial camera. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0046] Figure 1 A flowchart of the steps of the present invention;

[0047] Figure 2 The hardware platform described in the present invention;

[0048] Figure 3 The camera imaging model described in the present invention;

[0049] Figure 4 The height offset correction model described in the present invention;

[0050] Figure 5 Generate effect diagrams for point clouds of arms and the like described in the present invention;

[0051] Figure 6 The present invention is a flow chart of the method described in the present invention. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0053] like Figure 1-6 As shown, the present invention provides a three-dimensional measurement method of an arm based on single-axis MEMS fringe projection, comprising the following steps:

[0054] Construct a 3D measurement system for 3D measurement of the arm, wherein the 3D measurement system is composed of a single-axis MEMS projector and its camera module;

[0055] The three-frequency four-step stripe structured light image collected by the three-dimensional measurement system is obtained, and phase unwrapping is performed by a multi-frequency heterodyne method to obtain a phase image;

[0056] Calibrate the internal and external parameters of the camera module to obtain the physical position information of the imaging plane;

[0057] Based on the physical position information and phase image, phase data with height attribute characteristics are obtained, and phase height mapping parameters are generated through inverse linear theory;

[0058] Collecting a three-frequency four-step deformed fringe image of the arm, and obtaining a height value of a modulation phase of the three-frequency four-step deformed fringe image according to a phase height mapping parameter;

[0059] Based on the height value, the pixel correction offset of different parts of the arm is obtained to generate the three-dimensional point cloud data of the arm.

[0060] Further preferably, in the process of calibrating the internal and external parameters of the camera module, the focal length of the camera module is fixed, the calibration plate is placed in different spatial positions, no less than 25 images are collected, and the Zhang Zhengyou calibration method is used to obtain the internal parameter matrix, radial distortion and tangential distortion parameters of the camera module, and distortion correction is performed;

[0061] Fix the calibration plate on the work surface, collect no less than 5 images through the camera module, and use Zhang Zhengyou calibration method to obtain the extrinsic rotation matrix and translation matrix of the camera module.

[0062] Further preferably, in the process of obtaining the physical position information of the imaging plane, an ideal imaging plane equation is constructed, wherein the distance between the ideal imaging plane and the optical center of the camera is 1 mm, and the equation in the camera coordinate is Zc=1;

[0063] Based on the camera imaging principle, obtain the spatial coordinates of each pixel mapped to the ideal imaging plane;

[0064] According to the external parameter rotation matrix and translation matrix, the plane equation of the worktable in the camera coordinate system is fitted: AX+BY+CZ+D=0, and the optical path equation of the mapping coordinates of each pixel and the ideal imaging plane is constructed:

[0065] Based on the plane equation and the optical path equation, a spatial coordinate information equation is constructed to represent the physical position information of the imaging plane:

[0066]

[0067] Among them, (p ix , p iy , p iz ) and (p rx , p ry , p rz ) are the ideal plane pi and the actual imaging plane p respectively r The point above; (p x , p y ) is the pixel coordinate in the pixel coordinate system; f x and f y is the focal length of the camera in two directions; A, B, C, D are the parameters of the space plane equation.

[0068] Further preferably, in the process of generating the phase height mapping parameters, by controlling the worktable, three-frequency four-step phase shift fringe images located at 0 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, and 90 mm are collected;

[0069] Phase unwrapping is performed by a multi-frequency heterodyne method, and the unwrapped phase images of 10-90 mm are subtracted from the unwrapped phase images of 0 mm to obtain phase difference images at a height of 10-90 mm;

[0070] The 10-90mm phase difference image corresponds to the known actual physical height, and the phase height mapping parameters at each pixel are fitted using the inverse linear method. The fitting method is:

[0071]

[0072] Where a and b represent the phase height mapping parameters, and H(x, y) is the actual true height of the measured object; is the phase difference caused by height modulation.

[0073] Further preferably, in the process of generating the three-dimensional point cloud data of the arm, the actual physical distance between the imaging planes of the camera modules and the coordinate point where the optical center of the camera is projected onto the imaging plane generate a vector relationship between the coordinates of each pixel mapped onto the imaging plane and the coordinate point;

[0074] According to the camera imaging principle, based on the geometric relationship between the phase height mapping parameters, the actual physical distance, and the vector relationship, the actual space coordinates after the pixel imaging coordinate offset correction are obtained;

[0075] Based on the X- and Y-axis coordinate data of the actual space coordinates, and taking the actual physical distance as the Z-axis coordinate value, the three-dimensional point cloud data of the arm is generated.

[0076] Further preferably, in the process of generating the vector relationship, the expression of the vector relationship is:

[0077]

[0078] where p a (x c ,y c , z c ) and p b (x cr ,y cr , z cr ) are p e and p d In the real imaging plate P r The projection point on c (x ct ,y ct , z ct ) is the camera optical center O c With real imaging plate P r The vertical point between c O c With Tablet P r The distance between f (x f ,y f , z f ) is P r A point on the a and p c Not colinear.

[0079] Preferably, in the process of generating the arm three-dimensional point cloud data, the expression of the arm three-dimensional point cloud data is:

[0080]

[0081] The present invention also discloses an arm three-dimensional measurement system for implementing the arm three-dimensional measurement method, comprising:

[0082] The first data acquisition and preprocessing module is used to acquire the three-frequency four-step stripe structured light image acquired by the three-dimensional measurement system, perform phase unwrapping through a multi-frequency heterodyne method, and acquire a phase image;

[0083] The first data processing module is used to calibrate the internal and external parameters of the camera module and obtain the physical position information of the imaging plane;

[0084] A second data processing module is used to obtain phase data with height attribute characteristics based on physical position information and phase images, and generate phase height mapping parameters through inverse linear theory;

[0085] The second data acquisition and preprocessing module is used to acquire the three-frequency four-step deformation fringe image of the arm, and obtain the height value of the modulation phase of the three-frequency four-step deformation fringe image according to the phase height mapping parameter;

[0086] The three-dimensional point cloud data generation module is used to obtain the pixel correction offset of different parts of the arm based on the height value and generate the three-dimensional point cloud data of the arm.

[0087] The invention also discloses a computer program for realizing the arm three-dimensional measurement system, and the computer program realizes the logical relationship of the arm three-dimensional measurement method.

[0088] The invention also discloses a storable medium for carrying the computer program and realizing logical control of the three-dimensional measurement system according to the computer program.

[0089] Embodiment 1: This embodiment provides an arm three-dimensional measurement algorithm system based on single-axis MEMS fringe projection, and its implementation process is as follows: Figure 1 As shown, the following steps are included:

[0090] Step S1: Control the projector and camera to collect fringe images. Specifically:

[0091] Step S11: Select the Zhongke Fusion BN6MF5851 single-axis MEMS projector with a near-infrared laser light source of 854nm wavelength and the Vision WSD-2830-v1.0 near-infrared narrow-band camera module to build the hardware platform of the FPP system, such as Figure 2 shown.

[0092] Step S12: Design a drive control program for the projector and camera module, whose main control logic is: first send a string of data to drive the MEMS projector to regularly project stripe structured light with a set phase and frequency, and at the same time control the camera module to collect stripe structured light images at a certain time interval.

[0093] Step S2: A three-frequency four-step multi-frequency heterodyne method is used, the three frequencies are 70, 64, and 59, and the image size is 1280*960. The 12 fringe images collected in step S1 are phase-unwrapped to obtain an unambiguous phase-unwrapped image.

[0094] Step S31: fix the focal length of the camera, place the calibration plate at different spatial positions, and collect no less than 25 images. Use Zhang Zhengyou calibration method to obtain the camera's intrinsic parameter matrix, radial distortion and tangential distortion parameters, and perform distortion correction.

[0095] Step S32: Fix the calibration plate on the work surface, and use the camera to collect no less than 5 images. Calculate the camera extrinsic rotation matrix and translation matrix using Zhang Zhengyou calibration method.

[0096] Step S41: construct an ideal imaging plane equation, whose position is 1 mm away from the optical center of the camera, and whose equation in the camera coordinates is Zc = 1. The camera imaging principle is used to calculate the spatial coordinates of each pixel mapped to the ideal imaging plane.

[0097] Step S42: Using the camera's external parameter rotation matrix and translation matrix, fit the plane equation AX+BY+CZ+D=0 of the work surface with higher flatness in the camera coordinate system. Construct the optical path equation of each pixel and the mapping coordinate on the ideal imaging plane

[0098] Step S43: According to the equation of the work surface and the pixel optical path equation in the fitted camera coordinate system, the spatial coordinate information of the actual imaging plane can be obtained. Its theoretical model is Figure 3 shown.

[0099] Step S51: Use a high-precision mobile platform to control a work surface with a high flatness, and collect three-frequency four-step phase-shift fringe images when the high-precision mobile platform is located at 0mm, 10mm, 20mm, 30mm, 40m, 50mm, 60mm, 70mm, 80mm, and 90mm respectively.

[0100] Step S52: Calculate the unwrapped phase at each height using the method in step S2, and subtract the unwrapped phase image of 10-90 mm from the unwrapped phase image of 0 mm to obtain a phase difference image at a height of 10-90 mm.

[0101] Step S53: Correspond the 10-90mm phase difference image to the known actual physical height, and use the inverse linear method to fit the phase height mapping parameters a and b at each pixel.

[0102] Step S6: Collect the stripe image of the arm, use the method in step S2 to calculate the unfolded phase of the arm, and then use the phase height mapping parameters in step S5 to calculate the actual physical height information of the arm.

[0103] Step S71: Calculate the actual physical distance Lc between the camera and the imaging plane, the coordinate point Pc of the camera optical center projected onto the imaging plane; calculate the vector relationship between the coordinate of each pixel mapped onto the imaging plane and Pc:

[0104]

[0105] Step S72: According to the camera imaging principle, the actual spatial coordinates after the pixel imaging coordinate offset correction can be calculated by using the geometric relationship between the height of each pixel obtained in step S6, the actual physical distance Lc between the camera and the imaging plane, and the vector relationship between the coordinates mapped to the imaging plane and Pc. The theoretical model is as follows: Figure 4 shown.

[0106] Step S8: Extract the X and Y values ​​of the spatial coordinates of each pixel obtained in step S7 after offset correction as the X and Y axis coordinate values ​​of the imaging coordinates of the pixel point, and extract the actual height value attached to each pixel in step S6 as the Z axis coordinate value of the imaging coordinates of the pixel, so as to determine the three-dimensional point cloud data of the arm:

[0107]

[0108] Arm and other measurement effects such as Figure 5 shown.

[0109] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0110] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0111] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0112] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A three-dimensional measurement method for an arm based on single-axis MEMS fringe projection, characterized in that: The following steps are involved: Constructing a three-dimensional measurement system for three-dimensional measurement of an arm, wherein the three-dimensional measurement system is composed of a single-axis MEMS projector and its camera module; Acquire a three-frequency four-step stripe structured light image collected by the three-dimensional measurement system, perform phase unwrapping by a multi-frequency heterodyne method, and acquire a phase image; Calibrate the internal and external parameters of the camera module to obtain the physical position information of the imaging plane; Based on the physical position information and the phase image, phase data with height attribute characteristics is acquired, and phase height mapping parameters are generated through inverse linear theory; Collecting a three-frequency four-step deformed fringe image of the arm, and obtaining a height value of a modulation phase of the three-frequency four-step deformed fringe image according to the phase height mapping parameter; Based on the height value, obtaining pixel correction offsets of different parts of the arm to generate three-dimensional point cloud data of the arm; In the process of calibrating the internal and external parameters of the camera module, the focal length of the camera module is fixed, the calibration plate is placed in different spatial positions, no less than 25 images are collected, and the Zhang Zhengyou calibration method is used to obtain the internal parameter matrix, radial distortion and tangential distortion parameters of the camera module, and distortion correction is performed; Fix the calibration plate on the work surface, collect no less than 5 images through the camera module, and use the Zhang Zhengyou calibration method to obtain the external parameter rotation matrix and translation matrix of the camera module; In the process of obtaining the physical position information of the imaging plane, the ideal imaging plane equation is constructed, wherein the distance between the ideal imaging plane and the optical center of the camera is 1 mm, and the equation in the camera coordinate is Zc=1; Based on the camera imaging principle, obtaining the spatial coordinates of each pixel mapped to the ideal imaging plane; According to the external parameter rotation matrix and the translation matrix, the plane equation of the worktable in the camera coordinate system is fitted: AX+BY+CZ+D=0, and the optical path equation of the mapping coordinates of each pixel and the ideal imaging plane is constructed: Based on the plane equation and the optical path equation, a spatial coordinate information equation for representing the physical position information of the imaging plane is constructed: Among them, (p ix , p iy , p iz ) and (p rx , p ry , p rz ) are the ideal planes p i and the actual imaging plane p r The point above; (p x , p y ) is the pixel coordinate in the pixel coordinate system; f x and f y is the focal length of the camera in two directions; A, B, C, D are the parameters of the space plane equation; In the process of generating the phase height mapping parameters, by controlling the worktable, three-frequency four-step phase shift fringe images located at 0 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, and 90 mm are collected; Phase unwrapping is performed by a multi-frequency heterodyne method, and the unwrapped phase images of 10-90 mm are subtracted from the unwrapped phase images of 0 mm to obtain a phase difference image at a height of 10-90 mm; The 10-90mm phase difference image corresponds to the known actual physical height, and the phase height mapping parameters at each pixel are fitted using the inverse linear method, wherein the fitting method is: Where a and b represent phase height mapping parameters, and H(x, y) is the actual true height of the measured object; The phase difference produced by height modulation; In the process of generating the three-dimensional point cloud data of the arm, the actual physical distance between the imaging planes of the camera module and the coordinate point where the optical center of the camera is projected onto the imaging plane generate the vector relationship between the coordinate of each pixel mapped onto the imaging plane and the coordinate point; According to the camera imaging principle, based on the phase height mapping parameter, the actual physical distance, and the geometric relationship between the vector relationship, the actual space coordinates after the pixel imaging coordinate offset correction are obtained; Based on the X-axis and Y-axis coordinate data of the actual space coordinates, and taking the actual physical distance as the Z-axis coordinate value, generating the three-dimensional point cloud data of the arm; In the process of generating the vector relationship, the expression of the vector relationship is: Among them, p a (x c ,y c , z c ) and p b (x cr ,y cr , z cr ) are p e and p d In the real imaging plate P r The projection point on c (x ct ,y ct , z ct ) is the camera optical center O c With real imaging plate P r The vertical point between c O c With Tablet P r The distance between f (x f ,y f , z f ) is a point on Pr, a and p c Not collinear; In the process of generating the three-dimensional point cloud data of the arm, the expression of the three-dimensional point cloud data of the arm is:

Images