A phase-height mapping calibration method and device in a fringe projection method

Abstract

This invention discloses a phase-height mapping calibration method and apparatus in fringe projection, relating to the field of three-dimensional object contour measurement technology. The method includes: controlling a projector to project a set of phase-shifted sinusoidal fringe patterns onto a micromirror array with known height values; simultaneously triggering a camera to acquire fringe image sequences; performing phase shift calculations on the fringe image sequences to obtain a wrap-around phase map; constructing a global optimization model of absolute phase using the known height value of the micromirror array as an absolute constraint; solving for the absolute phase field corresponding to the height of the micromirror array; extracting the center coordinates, absolute phase values, and known height values ​​of each micromirror element; constructing a three-dimensional control point set; fitting the three-dimensional control point set; calculating the continuous model coefficient field; and forming a phase-height lookup table. This invention can significantly improve the real-time calculation efficiency of three-dimensional measurement, meeting the practical needs of high-precision, high-stability industrial three-dimensional shape measurement.

Description

Technical Field

[0001] This invention relates to the field of three-dimensional object contour measurement technology, and in particular to a phase-height mapping calibration method and apparatus in the fringe projection method. Background Technology

[0002] Three-dimensional object contour measurement technology is widely used in industrial inspection, reverse engineering, and robot vision. Among these, phase-shifting profilometry based on sinusoidal grating fringe projection has become mainstream due to its high precision and strong anti-interference capabilities. The core of this technology lies in establishing a precise mapping relationship between the phase information acquired by the camera and the actual height information of the object, i.e., phase-height mapping calibration.

[0003] Existing calibration models are mainly divided into two categories: explicit and implicit. Explicit models require precise calibration of all intrinsic and extrinsic parameters of the camera and projector, a complex process susceptible to error accumulation. Implicit models, on the other hand, do not require knowledge of the system's precise structure and can be solved using only calibration blocks, making them relatively simple to operate and thus widely used. However, current mainstream implicit calibration methods still have significant limitations. For example, one type of method requires multiple movements of a planar calibration plate or specially designed step blocks using a high-precision displacement stage, and obtains discrete height difference data through camera calibration. Its calibration accuracy heavily depends on the mechanical precision of the displacement stage and the accuracy of the camera calibration, and the multiple operations are cumbersome and inefficient. Another type of method avoids camera calibration, but the proposed phase-height model itself is complex, leading to time-consuming parameter fitting calculations, and it also fails to escape dependence on physical displacement operations. The common bottleneck of these methods is that the acquisition of calibration data depends on the physical displacement of the calibration plate, making the calibration process difficult to automate and introducing mechanical errors and operational uncertainties, thus limiting the application of measurement systems in scenarios requiring rapid deployment and high precision. Summary of the Invention

[0004] This invention provides a phase-height mapping calibration method in fringe projection, comprising: Step S1: Control the projector to project a set of phase-shifted sinusoidal fringe patterns onto the micro-reflective array with known height values, and simultaneously trigger the camera to acquire the fringe image sequence. Step S2: Perform phase shift calculation on the stripe image sequence to obtain the wrapping phase map; Step S3: Based on the wrapped phase map, with the known height value of the micro-mirror array as the absolute constraint, construct an absolute phase global optimization model to solve the absolute phase field corresponding to the height of the micro-mirror array. Step S4: Extract the center coordinates, absolute phase value and known height value of each micromirror element from the absolute phase field of the micromirror element array to construct a three-dimensional control point set; Step S5: Fit the three-dimensional control point set, solve the continuous model coefficient field, and form a phase-height lookup table.

[0005] The phase-height mapping calibration method in the fringe projection method described above, wherein controlling the projector to project a set of phase-shifted sinusoidal fringe patterns onto a micromirror array with known height values, and synchronously triggering the camera to acquire the fringe image sequence includes the following sub-steps: Step S11: Control the projector to project N frames of sinusoidal fringe patterns with fixed phase offset onto the micro-reflective mirror array with known height values ​​in sequence. Step S12: After each frame of stripe pattern projection is completed, the camera is synchronously triggered to acquire stripe images and obtain a set of stripe image sequences.

[0006] The phase-height mapping calibration method in the fringe projection method described above, wherein, based on the wrapped phase map, and with the known height value of the micromirror element array as an absolute constraint, a global optimization model for absolute phase is constructed, and the solution for the absolute phase field corresponding to the height of the micromirror element array includes the following sub-steps: Step S31: Identify the region of each micromirror element in the stripe image and obtain its corresponding center coordinates in the stripe image; Step S32: Based on the wrapped phase map and the center coordinates of each micromirror element, and with the known height value of the micromirror element array as an absolute constraint, construct an absolute phase global optimization model; Step S33: Solve the global optimization model of absolute phase using a continuous alternating iterative algorithm to obtain the absolute phase field corresponding to the height of the micro-mirror array.

[0007] The phase-height mapping calibration method in the fringe projection method described above, wherein extracting the center coordinates, absolute phase values, and known height values ​​of each micromirror element from the absolute phase field of the micromirror element array to construct a three-dimensional control point set includes the following sub-steps: Step S41: Extract the absolute phase value and known height value corresponding to the center coordinates of each micro-mirror element from the absolute phase field of the micro-mirror element array, and construct the three-dimensional control points of each micro-mirror element. Step S42: Verify each three-dimensional control point, remove outliers, and form a set of three-dimensional control points.

[0008] The phase-height mapping calibration method in the fringe projection method described above, wherein fitting the three-dimensional control point set, solving the continuous model coefficient field, and forming the phase-height lookup table includes the following sub-steps: Step S51: Establish a phase-height implicit mapping model with variable coefficients, substitute the three-dimensional control point set into the model for fitting, and obtain the continuous model coefficient field. Step S52: Based on the continuous model coefficient field, calculate the height value corresponding to each pixel under different phase values ​​to form a phase-height lookup table.

[0009] The present invention also provides a phase-height mapping calibration device in the fringe projection method, comprising: The stripe image sequence acquisition module controls the projector to project a set of phase-shifted sinusoidal stripe patterns onto a micro-mirror array with a known height value, and synchronously triggers the camera to acquire the stripe image sequence. The wrapping phase map acquisition module performs phase shift calculations on the stripe image sequence to obtain the wrapping phase map; The absolute phase field generation module, based on the wrapped phase map, uses the known height value of the micro-mirror element array as an absolute constraint to construct a global optimization model of absolute phase and solve for the absolute phase field corresponding to the height of the micro-mirror element array. The 3D control point set construction module extracts the center coordinates, absolute phase values, and known height values ​​of each micromirror element from the absolute phase field of the micromirror element array to construct a 3D control point set. The phase-height lookup table construction module fits the three-dimensional control point set, solves the continuous model coefficient field, and forms a phase-height lookup table.

[0010] As described above, in a phase-height mapping calibration device for a fringe projection method, the fringe image sequence acquisition module specifically includes: The sinusoidal stripe pattern projection submodule controls the projector to sequentially project N frames of sinusoidal stripe patterns with fixed phase offsets onto a micro-reflector array with known height values. The stripe image acquisition submodule synchronously triggers the camera to acquire stripe images after each frame of stripe pattern projection is completed, thus obtaining a set of stripe image sequences.

[0011] As described above, in a phase-height mapping calibration device for a fringe projection method, the absolute phase field generation module specifically includes: The center coordinate acquisition submodule identifies the region of each micromirror element in the stripe image and obtains its corresponding center coordinates in the stripe image; The absolute phase global optimization model construction submodule constructs an absolute phase global optimization model based on the wrapped phase map and the center coordinates of each micromirror element, with the known height value of the micromirror element array as the absolute constraint. The absolute phase solution submodule solves the global optimization model of absolute phase through a continuous alternating iterative algorithm to obtain the absolute phase field corresponding to the height of the micromirror array.

[0012] As described above, in a phase-height mapping calibration device for fringe projection, the three-dimensional control point set construction module specifically includes: The 3D control point construction submodule extracts the absolute phase value and known height value corresponding to the center coordinates of each micromirror element from the absolute phase field of the micromirror element array, and constructs the 3D control points of each micromirror element. The 3D control point set formation submodule verifies each 3D control point, removes outliers, and forms a 3D control point set.

[0013] As described above, in a phase-height mapping calibration device for a fringe projection method, the phase-height lookup table construction module specifically includes: The continuous model coefficient field acquisition submodule establishes a phase-height implicit mapping model with variable coefficients, substitutes the three-dimensional control point set into the model for fitting, and obtains the continuous model coefficient field. The phase-height lookup table submodule calculates the height value of each pixel at different phase values ​​based on the continuous model coefficient field, thus forming the phase-height lookup table.

[0014] The beneficial effects achieved by this invention are as follows: This invention can effectively solve the problems of low accuracy of traditional fringe projection phase-height calibration, phase unfolding error propagation, and difficulty in compensating for system nonlinear distortion. It avoids various error interferences in the traditional calibration process from the root, significantly improves the global consistency and data reliability of phase calculation, greatly enhances the adaptability to non-ideal system factors, effectively improves the calibration accuracy and stability of phase-height mapping, and significantly improves the real-time calculation efficiency of three-dimensional measurement. It can fully meet the actual application needs of high-precision and high-stability industrial three-dimensional topography measurement. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0016] Figure 1 This is a flowchart of a phase-height mapping calibration method in a fringe projection method provided in Embodiment 1 of this application; Figure 2 This is a schematic diagram of a phase-height mapping calibration device in a fringe projection method provided in Embodiment 2 of this application. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 like Figure 1 As shown, Embodiment 1 of this application provides a phase-height mapping calibration method in the fringe projection method, which includes the following steps: Step S1: Control the projector to project a set of phase-shifted sinusoidal fringe patterns onto the micro-reflective array with known height values, and simultaneously trigger the camera to acquire the fringe image sequence. Furthermore, the projector projects a set of phase-shifted sinusoidal fringe patterns onto a micromirror array with known height values, and the camera is simultaneously triggered to acquire the fringe image sequence, including the following sub-steps: Step S11: Control the projector to project N frames of sinusoidal fringe patterns with fixed phase offset onto the micro-reflective mirror array with known height values ​​in sequence. Specifically, a micro-mirror array with known height values ​​is placed in a measurement field of view where its surface can be completely covered by the projected pattern and the reflected light can be completely captured by the camera. The projector is controlled to project N frames of sinusoidal fringe patterns sequentially according to a preset fixed phase offset. The micro-mirror array consists of M×N independent micro-mirror units arranged in a grid according to a preset number of rows and columns and spacing rules. Each micro-mirror unit has a unique and known tiny height value relative to the macroscopic reference plane, and each identifiable mirror unit center point corresponds to a precise physical coordinate value.

[0019] Step S12: After the stripe pattern is projected in each frame, the camera is synchronously triggered to acquire stripe images and obtain a set of stripe image sequences. Specifically, after the projector completes the loading of a frame of stripe pattern, it sends a trigger pulse signal to the camera. After receiving the signal, the camera performs an exposure and image acquisition, and sequentially captures the stripe images corresponding to the projected pattern. After the image acquisition is completed, a set of N frames of stripe images that are continuous in time and shifted equally in phase are obtained.

[0020] Step S2: Perform phase shift calculation on the stripe image sequence to obtain the wrapping phase map; Specifically, based on the phase shift step N of the striped image sequence, the corresponding N-step phase shift calculation formula is selected. The coordinates of each pixel in the striped image sequence are traversed. The light intensity value sequence of the pixel in the N frames of striped images is substituted into the selected N-step phase shift calculation formula to calculate the wrapping phase value of the corresponding pixel. The wrapping phase values ​​of all pixels are integrated to obtain the wrapping phase map.

[0021] Step S3: Based on the wrapped phase map, with the known height value of the micro-mirror array as the absolute constraint, construct an absolute phase global optimization model to solve the absolute phase field corresponding to the height of the micro-mirror array. Furthermore, based on the wrapped phase map, and with the known height of the micromirror element array as an absolute constraint, a global optimization model for absolute phase is constructed. Solving for the absolute phase field corresponding to the height of the micromirror element array includes the following sub-steps: Step S31: Identify the region of each micromirror element in the stripe image and obtain its corresponding center coordinates in the stripe image; Specifically, the first frame of the striped image sequence is selected as the reference image. Through adaptive threshold segmentation, morphological operations, and connected component analysis, the independent regions corresponding to each micromirror element in the reference image are identified. Based on the number of rows and columns and the spacing of the micromirror element array, the projection grid model of the micromirror element array is fitted to obtain the center coordinates of each micromirror element in the reference image.

[0022] Step S32: Based on the wrapped phase map and the center coordinates of each micromirror element, and with the known height value of the micromirror element array as an absolute constraint, construct an absolute phase global optimization model; Specifically, based on the center coordinates of each micromirror element region in the fringe image, the wrapping phase value of each micromirror element is extracted from the wrapping phase map. Simultaneously, the known height values ​​of each micromirror element are read to construct a set of absolute height constraints, and a phase-height relaxation constraint model is established. ,in, For micro-reflective mirror elements The absolute phase value, For micro-reflective mirror elements The wrapping phase value, For micro-reflective mirror elements Integer offset, For phase prediction model functions, To control the order of the height expansion of the model complexity, The range of values ​​is , To control the order of the positional expansion for model complexity, The range of values ​​is , Let be the continuity coefficients to be determined. For micro-reflective mirror elements The known height value, For micro-reflective mirror elements The center coordinates corresponding to the stripe image The coordinate power adjustment factor is used; and an adaptive spatial smoothness constraint model is established. ,in, For adaptive spatial smoothing constraints, This represents the row number of the micromirror element array. The range of values ​​is , The number of columns in the micromirror array. The range of values ​​is , For the neighborhood micromirror meta-index, For micro-reflective mirror elements The set of neighborhood micromirrors For micro-reflective mirror elements The center coordinates corresponding to the stripe image For neighborhood micromirror element set Medium micro-reflective mirror element The center coordinates corresponding to the stripe image For distance attenuation factor, For micro-reflective mirror elements The wrapping phase gradient, For neighborhood micromirror element set Medium micro-reflective mirror element The wrapping phase gradient, For micro-reflective mirror elements Integer offset, For neighborhood micromirror element set Medium micro-reflective mirror element Integer offsets; a global optimization objective function is constructed based on the phase-height relaxation constraint model and the adaptive spatial smoothness constraint model. ,in, To globally optimize the objective function value, Let be the set of integer offsets for the micromirror elements. For a set of continuous coefficients, This represents the row number of the micromirror element array. The range of values ​​is , The number of columns in the micromirror array. The range of values ​​is , For micro-reflective mirror elements The wrapping phase value, For micro-reflective mirror elements Integer offset, For phase prediction model functions, , For the regularization weights of the integer approximation terms, Integer offset Continuous estimates, , Indicates continuous estimates Round to the nearest integer. For the regularization weights of the space smoothing term, This is the spatial smoothing term.

[0023] Step S33: Solve the global optimization model of absolute phase using a continuous alternating iterative algorithm to obtain the absolute phase field corresponding to the height of the micro-mirror array; Specifically, set the initial integer offset for all micromirror elements. Initialize the set of continuous coefficients using robust linear regression. , ,in, This represents the row number of the micromirror element array. The range of values ​​is , The number of columns in the micromirror array. The range of values ​​is , Here is the Huber loss function. For micro-reflective mirror elements The wrapping phase value, For phase prediction model functions, For micro-reflective mirror elements The known height value, For micro-reflective mirror elements The center coordinates corresponding to the stripe image Given the set of continuous coefficients to be determined; update the integer offset and continuous coefficients using a continuous alternating iterative algorithm. Specifically, in the t-th iteration, fix the set of continuous coefficients obtained in the (t-1)-th iteration. Update the formula using integer variables Update the integer offset, where, The micro-reflective mirror element obtained in the t-th iteration Integer offset, Let be the integer variable to be solved. express Belongs to the set of integers. For micro-reflective mirror elements The wrapping phase value, For phase prediction model functions, For micro-reflective mirror elements The known height value, For micro-reflective mirror elements The center coordinates corresponding to the stripe image Let be the set of continuous coefficients obtained in the (t-1)th iteration. Adjust the weights to approximate integers. For the (t-1)th iteration, the micromirror element integer offset Continuous estimates, Adjusting weights for spatial smoothing For the neighborhood micromirror meta-index, For micro-reflective mirror elements The set of neighborhood micromirrors For adaptive weights, , For micro-reflective mirror elements The center coordinates corresponding to the stripe image For neighborhood micromirror element set Medium micro-reflective mirror element The center coordinates corresponding to the stripe image For distance attenuation factor, For micro-reflective mirror elements The wrapping phase gradient, For neighborhood micromirror element set Medium micro-reflective mirror element The wrapping phase gradient, For neighborhood micromirror elements The integer offset obtained in the (t-1)th iteration; after updating the integer offset, the integer offset of the tth iteration is fixed. Update formula through continuous coefficients Update the continuous coefficients, where, Let be the set of continuous coefficients obtained in the t-th iteration. Let the continuous coefficient variables be the ones to be solved. The micro-reflective mirror element obtained in the t-th iteration Integer offset, For micro-reflective mirror elements The wrapping phase value, For phase prediction model functions, For micro-reflective mirror elements The known height value, For micro-reflective mirror elements The center coordinates corresponding to the stripe image For regularization weights, Continuity coefficients The gradient is calculated; the average change in integer offsets between adjacent iterations is calculated, and iteration is stopped when the average change is less than a preset threshold or the maximum number of iterations is reached, and the final set of integer offsets is output. ,pass Calculate the absolute phase value of each micromirror element, where, For micro-reflective mirror elements The absolute phase value, For micro-reflective mirror elements The wrapping phase value, For micro-reflective mirror elements The final integer offset represents the absolute phase value at the center point of each micromirror element. The components are integrated to form an absolute phase field corresponding to the known height value of the micromirror array.

[0024] Step S4: Extract the center coordinates, absolute phase value and known height value of each micromirror element from the absolute phase field of the micromirror element array to construct a three-dimensional control point set; Furthermore, from the absolute phase field of the micromirror array, the center coordinates, absolute phase values, and known height values ​​of each micromirror element are extracted to construct a three-dimensional control point set, including the following sub-steps: Step S41: Extract the absolute phase value and known height value corresponding to the center coordinates of each micro-mirror element from the absolute phase field of the micro-mirror element array, and construct the three-dimensional control points of each micro-mirror element. Specifically, based on the center coordinates of each micromirror element in the fringe image, the absolute phase value corresponding to each center coordinate is queried in the absolute phase field. At the same time, the known height value corresponding to each micromirror element is read. The center coordinates, absolute phase values ​​and known height values ​​are associated to form a three-dimensional control point representing the phase and height of the micromirror element corresponding to each center coordinate.

[0025] Step S42: Verify each 3D control point, remove outliers, and form a 3D control point set; Specifically, based on the center coordinates and absolute phase values ​​of all micromirror elements, a reference phase distribution is generated using a surface fitting method. This reference phase distribution represents the phase distribution when the height is zero. Based on the reference phase distribution, the phase difference of all three-dimensional control points is calculated. Based on the phase difference of all three-dimensional control points and the known height value, a robust statistical method is used to calculate its principal distribution model and set a confidence interval. Three-dimensional control points whose residuals exceed the confidence interval are identified as outliers and removed. All remaining three-dimensional control points are then integrated to form a three-dimensional control point set.

[0026] Step S5: Fit the three-dimensional control point set, solve the continuous model coefficient field, and form a phase-height lookup table; Furthermore, fitting the three-dimensional control point set, solving the continuous model coefficient field, and forming a phase-height lookup table includes the following sub-steps: Step S51: Establish a phase-height implicit mapping model with variable coefficients, substitute the three-dimensional control point set into the model for fitting, and obtain the continuous model coefficient field. Specifically, a phase-height implicit mapping model is established. ,in, This is the physical height value. and To follow the pixel position of the camera image plane The changing field of unknown coefficients, The phase difference relative to the reference phase distribution. , The absolute phase value. As a reference phase distribution, each 3D control point in the 3D control point set is substituted into the phase-height implicit mapping model to construct an overdetermined set of equations for the coefficient field. The coefficient field is parameterized using a representation method based on the expansion of 2D tensor product spline basis functions. The coefficients of the basis functions are solved using the regularized least squares method to obtain the model coefficient field that continuously varies on the camera image plane. and .

[0027] Step S52: Based on the continuous model coefficient field, calculate the height value corresponding to each pixel under different phase values ​​to form a phase-height lookup table; Specifically, the process iterates through the pixel coordinates of the striped image. For each pixel, its reference phase distribution is determined. For any absolute phase value, its phase difference based on the reference phase distribution is calculated. Within the phase difference measurement range, discrete sampling is performed at fixed intervals to obtain a set of phase difference sequences. For each phase difference value in the sequence, a coefficient corresponding to the pixel coordinate is used. and The corresponding physical height value is calculated based on the phase-height implicit mapping model; the phase difference value and physical height value of each pixel are stored in a predefined format to generate a phase-height lookup table.

[0028] Example 2 like Figure 2 As shown, Embodiment 2 of this application provides a phase-height mapping calibration device in the fringe projection method, comprising: The stripe image sequence acquisition module 21 controls the projector to project a set of phase-shifted sinusoidal stripe patterns onto a micro-reflector array with a known height value, and synchronously triggers the camera to acquire the stripe image sequence. Furthermore, the stripe image sequence acquisition module 21 includes the following sub-modules: The sinusoidal stripe pattern projection submodule controls the projector to sequentially project N frames of sinusoidal stripe patterns with fixed phase offsets onto a micro-reflector array with known height values. The stripe image acquisition submodule synchronously triggers the camera to acquire stripe images after each frame of stripe pattern projection is completed, thereby obtaining a set of stripe image sequences; The package phase map acquisition module 22 performs phase shift calculations on the stripe image sequence to obtain the package phase map; The absolute phase field generation module 23, based on the wrapped phase map, uses the known height value of the micro-mirror element array as an absolute constraint to construct an absolute phase global optimization model and solve the absolute phase field corresponding to the height of the micro-mirror element array. Furthermore, the absolute phase field generation module 23 includes the following sub-modules: The center coordinate acquisition submodule identifies the region of each micromirror element in the stripe image and obtains its corresponding center coordinates in the stripe image; The absolute phase global optimization model construction submodule constructs an absolute phase global optimization model based on the wrapped phase map and the center coordinates of each micromirror element, with the known height value of the micromirror element array as the absolute constraint. The absolute phase solution submodule solves the global optimization model of absolute phase through a continuous alternating iterative algorithm to obtain the absolute phase field corresponding to the height of the micro-mirror array; The three-dimensional control point set construction module 24 extracts the center coordinates, absolute phase values ​​and known height values ​​of each micro-mirror element from the absolute phase field of the micro-mirror element array to construct a three-dimensional control point set; Furthermore, the 3D control point set construction module 24 includes the following sub-modules: The 3D control point construction submodule extracts the absolute phase value and known height value corresponding to the center coordinates of each micromirror element from the absolute phase field of the micromirror element array, and constructs the 3D control points of each micromirror element. The 3D control point set formation submodule verifies each 3D control point, removes outliers, and forms a 3D control point set. Phase-height lookup table construction module 25 fits the three-dimensional control point set, solves the continuous model coefficient field, and forms a phase-height lookup table; Furthermore, the phase-height lookup table construction module 25 includes the following sub-modules: The continuous model coefficient field acquisition submodule establishes a phase-height implicit mapping model with variable coefficients, substitutes the three-dimensional control point set into the model for fitting, and obtains the continuous model coefficient field. The phase-height lookup table formation submodule calculates the height value of each pixel at different phase values ​​based on the continuous model coefficient field, thus forming a phase-height lookup table. Corresponding to the above embodiments, the present invention provides a computer storage medium, including: at least one memory and at least one processor; The memory is used to store one or more program instructions; A processor for running one or more program instructions to perform a phase-height mapping calibration method in a fringe projection method.

[0029] Corresponding to the above embodiments, the present invention provides a computer-readable storage medium containing one or more program instructions, which are used by a processor to perform a phase-height mapping calibration method in a fringe projection method.

[0030] The embodiments disclosed in this invention provide a computer-readable storage medium storing computer program instructions that, when executed on a computer, cause the computer to perform the phase-height mapping calibration method in the above-described fringe projection method.

[0031] In this embodiment of the invention, the processor can be an integrated circuit chip with signal processing capabilities. The processor can be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0032] The various methods, steps, and logic diagrams disclosed in the embodiments of this invention can be implemented or executed. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this invention can be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software modules can reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. The processor reads information from the storage medium and, in conjunction with its hardware, completes the steps of the above methods.

[0033] The storage medium can be memory, such as volatile memory or non-volatile memory, or may include both volatile and non-volatile memory.

[0034] Among them, non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory.

[0035] Volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (Synchlink DRAM, SLDRAM), and direct memory bus RAM (DRRAM).

[0036] The storage media described in the embodiments of the present invention are intended to include, but are not limited to, these and any other suitable types of memory.

[0037] Those skilled in the art will recognize that, in one or more of the examples above, the functions described in this invention can be implemented using a combination of hardware and software. When applied as software, the corresponding functions can be stored in a computer-readable medium or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media include computer storage media and communication media, wherein communication media include any medium that facilitates the transmission of computer programs from one place to another. Storage media can be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0038] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of the present invention should be included within the scope of protection of the present invention.

Claims

1. A phase-height mapping calibration method in fringe projection, characterized in that, include: Step S1: Control the projector to project a set of phase-shifted sinusoidal fringe patterns onto the micro-reflective array with known height values, and simultaneously trigger the camera to acquire the fringe image sequence. Step S2: Perform phase shift calculation on the stripe image sequence to obtain the wrapping phase map; Step S3: Based on the wrapped phase map, with the known height value of the micro-mirror array as the absolute constraint, construct an absolute phase global optimization model to solve the absolute phase field corresponding to the height of the micro-mirror array. Step S4: Extract the center coordinates, absolute phase value and known height value of each micromirror element from the absolute phase field of the micromirror element array to construct a three-dimensional control point set; Step S5: Fit the three-dimensional control point set, solve the continuous model coefficient field, and form a phase-height lookup table.

2. The phase-height mapping calibration method in the fringe projection method as described in claim 1, characterized in that, The projector projects a set of phase-shifted sinusoidal fringe patterns onto a micromirror array with a known height value, and the camera is simultaneously triggered to acquire the fringe image sequence, which includes the following sub-steps: Step S11: Control the projector to project N frames of sinusoidal fringe patterns with fixed phase offset onto the micro-reflective mirror array with known height values ​​in sequence. Step S12: After each frame of stripe pattern projection is completed, the camera is synchronously triggered to acquire stripe images and obtain a set of stripe image sequences.

3. The phase-height mapping calibration method in the fringe projection method as described in claim 1, characterized in that, Based on the wrapped phase map, and with the known height of the micromirror element array as an absolute constraint, a global optimization model for absolute phase is constructed. Solving for the absolute phase field of the micromirror element array corresponding to its height includes the following sub-steps: Step S31: Identify the region of each micromirror element in the stripe image and obtain its corresponding center coordinates in the stripe image; Step S32: Based on the wrapped phase map and the center coordinates of each micromirror element, and with the known height value of the micromirror element array as an absolute constraint, construct an absolute phase global optimization model; Step S33: Solve the global optimization model of absolute phase using a continuous alternating iterative algorithm to obtain the absolute phase field corresponding to the height of the micro-mirror array.

4. The phase-height mapping calibration method in the fringe projection method as described in claim 1, characterized in that, The process of extracting the center coordinates, absolute phase value, and known height value of each micromirror element from the absolute phase field of the micromirror element array to construct a three-dimensional control point set includes the following sub-steps: Step S41: Extract the absolute phase value and known height value corresponding to the center coordinates of each micro-mirror element from the absolute phase field of the micro-mirror element array, and construct the three-dimensional control points of each micro-mirror element. Step S42: Verify each three-dimensional control point, remove outliers, and form a set of three-dimensional control points.

5. The phase-height mapping calibration method in the fringe projection method as described in claim 1, characterized in that, Fitting the 3D control point set, solving the continuous model coefficient field, and forming the phase-height lookup table includes the following sub-steps: Step S51: Establish a phase-height implicit mapping model with variable coefficients, substitute the three-dimensional control point set into the model for fitting, and obtain the continuous model coefficient field. Step S52: Based on the continuous model coefficient field, calculate the height value corresponding to each pixel under different phase values ​​to form a phase-height lookup table.

6. A phase-height mapping calibration device in a fringe projection method, characterized in that, include: The stripe image sequence acquisition module controls the projector to project a set of phase-shifted sinusoidal stripe patterns onto a micro-mirror array with a known height value, and synchronously triggers the camera to acquire the stripe image sequence. The wrapping phase map acquisition module performs phase shift calculations on the stripe image sequence to obtain the wrapping phase map; The absolute phase field generation module, based on the wrapped phase map, uses the known height value of the micro-mirror element array as an absolute constraint to construct a global optimization model of absolute phase and solve for the absolute phase field corresponding to the height of the micro-mirror element array. The 3D control point set construction module extracts the center coordinates, absolute phase values, and known height values ​​of each micromirror element from the absolute phase field of the micromirror element array to construct a 3D control point set. The phase-height lookup table construction module fits the three-dimensional control point set, solves the continuous model coefficient field, and forms a phase-height lookup table.

7. The phase-height mapping calibration device in the fringe projection method as described in claim 6, characterized in that, The stripe image sequence acquisition module specifically includes: The sinusoidal stripe pattern projection submodule controls the projector to sequentially project N frames of sinusoidal stripe patterns with fixed phase offsets onto a micro-reflector array with known height values. The stripe image acquisition submodule synchronously triggers the camera to acquire stripe images after each frame of stripe pattern projection is completed, thus obtaining a set of stripe image sequences.

8. The phase-height mapping calibration device in the fringe projection method as described in claim 6, characterized in that, The absolute phase field generation module specifically includes: The center coordinate acquisition submodule identifies the region of each micromirror element in the stripe image and obtains its corresponding center coordinates in the stripe image; The absolute phase global optimization model construction submodule constructs an absolute phase global optimization model based on the wrapped phase map and the center coordinates of each micromirror element, with the known height value of the micromirror element array as the absolute constraint. The absolute phase solution submodule solves the global optimization model of absolute phase through a continuous alternating iterative algorithm to obtain the absolute phase field corresponding to the height of the micromirror array.

9. The phase-height mapping calibration device in the fringe projection method as described in claim 6, characterized in that, The 3D control point set construction module specifically includes: The 3D control point construction submodule extracts the absolute phase value and known height value corresponding to the center coordinates of each micromirror element from the absolute phase field of the micromirror element array, and constructs the 3D control points of each micromirror element. The 3D control point set formation submodule verifies each 3D control point, removes outliers, and forms a 3D control point set.

10. The phase-height mapping calibration device in the fringe projection method as described in claim 6, characterized in that, The phase-height lookup table construction module includes: The continuous model coefficient field acquisition submodule establishes a phase-height implicit mapping model with variable coefficients, substitutes the three-dimensional control point set into the model for fitting, and obtains the continuous model coefficient field. The phase-height lookup table submodule calculates the height value of each pixel at different phase values ​​based on the continuous model coefficient field, thus forming the phase-height lookup table.

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