A calibration method for structured light 3D scanning system based on MEMS galvanometer

Abstract

The present invention discloses a calibration method for a structured light three-dimensional scanning system based on a MEMS galvanometer. The method comprises: photographing a step surface and synchronously collecting a coded fringe pattern to obtain multiple groups of coded fringe patterns, wherein each group of coded fringe patterns corresponds to a different position on the step surface, and each step on the step surface has multiple marking points; performing noise reduction processing on each group of coded fringe patterns using a two-dimensional Gaussian filter; performing phase unwrapping on the coded fringe patterns and detecting the position of the center of the circle of the marking points in each group of coded fringe patterns in a pixel coordinate system; and performing three-dimensional calibration based on a phase height model, wherein the three-dimensional calibration includes depth calibration and lateral calibration, wherein the depth calibration is used to establish a relationship between absolute phase and depth data, and the lateral calibration is used to establish a relationship between pixel coordinates and the coordinates of the x-axis and y-axis in the world coordinate system. The present invention is simple and easy to operate, takes little calibration time, and can accurately obtain three-dimensional information of an object.

Description

Technical Field

[0001] The present invention relates to the field of computer vision technology, and more specifically, to a calibration method for a structured light three-dimensional scanning system based on a MEMS galvanometer. Background Art

[0002] Structured light 3D scanning systems based on projectors and single cameras are currently the most widely used non-contact 3D measurement methods. Calibration models for these systems are primarily divided into triangular stereo models and phase-height models. Traditional digital light processing (DLP) projectors primarily use triangular stereo models. However, projector systems based on microelectromechanical systems (MEMS) galvanometers, due to the characteristics of the MEMS galvanometers, can only use phase-height models. The most critical step in this model is calibration, as its accuracy directly impacts the accuracy of the final object reconstruction. Traditional calibration methods use a flat plate as a reference plane and a high-precision linear displacement stage. Projections and encoded phase-shift patterns are captured at 5mm intervals within the system's measurement range. Phase is obtained using a phase-decoding algorithm, and the phase-to-height mapping relationship is calibrated using a phase-height model. For a 0.2m2 measurement volume, 41 sets of patterns are required.

[0003] The triangulated stereo model regards the projector as an inverse camera (the projected pattern is regarded as the pattern imaged by the projector), so that the projector can be calibrated like a camera, thereby obtaining the internal and external parameters of the projector and camera. Then, based on the triangulation principle in stereo vision, a triangulation function is established. A specific set of coded patterns is projected by the projector, and each projected pattern is synchronously captured by the camera. The corresponding image decoding algorithm is used to obtain the projected features, thereby establishing a corresponding matching relationship between the projector and the camera to achieve three-dimensional reconstruction.

[0004] In the phase-height model, the height of an object is measured relative to a reference plane. The height is a function of the phase. Generally, the phase-height function depends on the arrangement between the camera and the projector. To increase system flexibility, there are many generalized phase-height models, such as the typical phase-height model, the linear phase-height model, the polynomial phase-height model, and the phase-height model based on the governing equation.

[0005] In the prior art, there are a variety of calibration methods based on the position-height model. For example, patent application CN201911255474.X provides a fast phase-height mapping calibration method. The method includes: establishing a three-dimensional measurement system; using the Harris corner detection algorithm to detect the difference in the pixel coordinate values ​​of specific points on the checkerboard captured by the camera to adjust the CCD camera optical axis to be perpendicular to the reference plane; using a time phase unwrapping method based on periodic correction to obtain high-precision absolute phase values ​​of the standard plane before and after rotation; using the centroid method to perform two-dimensional identification of the marker points on the rotated standard plane to obtain pixel coordinates, and searching for the corresponding marker point absolute phase value in the corresponding standard plane absolute phase value data; using the slope of the standard plane before rotation and the absolute phase value of the marker point to fit several virtual planes, and using the least squares method to optimize the system parameters to complete the phase-height calibration.

[0006] For example, patent application CN201810421266.1 discloses a calibration method for a phase-height mapping system based on piecewise polynomial fitting. This method uses polynomial fitting to perform piecewise calibration of a phase-height mapping system. This method divides the measurement range into intervals and uses polynomial fitting calibration with different fitting orders within different height ranges, thereby minimizing the relative error at each position within the measurement range.

[0007] After analysis, the existing methods mainly have the following problems:

[0008] 1) There are many issues that need to be considered during the calibration process, such as the selection of the calibration plate and the accuracy of the translation platform during the calibration process. For example, a high-precision linear displacement platform (accuracy of 0.1 μm) is required, which is expensive and not suitable for widespread use.

[0009] 2) The calibration process requires collecting a large number of pattern groups, is time-consuming, and can only map from phase to height, that is, only a depth map can be obtained, and the three-dimensional information of the object cannot be obtained.

[0010] 3) For projectors based on MEMS galvanometers, the noise caused by the speckle effect is not processed, resulting in excessive errors. In addition, there are also human operational errors in the calibration and operation processes, which increases the uncertainty of the results. Summary of the Invention

[0011] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a calibration method for a structured light 3D scanning system based on a MEMS galvanometer. The method comprises the following steps:

[0012] A structured light 3D scanning system based on a MEMS galvanometer is used to photograph the step surface and simultaneously collect the coded fringe patterns to obtain multiple groups of coded fringe patterns. Each group of coded fringe patterns corresponds to a different position on the step surface, and each step on the step surface has multiple marking points.

[0013] Two-dimensional Gaussian filtering is used to perform noise reduction on each group of coded stripe patterns;

[0014] Performing phase unwrapping on the coded fringe pattern and detecting the position of the center of the circle of the marking point in each group of coded fringe patterns in the pixel coordinate system;

[0015] Three-dimensional calibration is performed based on the phase height model, and the three-dimensional calibration includes depth calibration and lateral calibration. The depth calibration is used to establish the relationship between the absolute phase and depth data, and the lateral calibration is used to establish the relationship between the pixel coordinates and the coordinates of the x-axis and y-axis in the world coordinate system.

[0016] Compared with the existing technology, the advantage of the present invention is that the step surface is photographed multiple times by a structured light three-dimensional scanning system based on a MEMS galvanometer, each image is denoised using a two-dimensional Gaussian filter, the position of the center of the circle of the marked points in each group of images in the pixel coordinate system is detected using a circle detection algorithm, and then three-dimensional calibration is completed based on a polynomial phase height model. The whole process is simple and easy to operate, the calibration takes less time, and the three-dimensional information of the object can be accurately obtained.

[0017] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0019] Figure 1 This is a flow chart of a calibration method for a structured light 3D scanning system based on a MEMS galvanometer according to an embodiment of the present invention;

[0020] Figure 2 is a schematic diagram of a step surface used for calibration according to one embodiment of the present invention;

[0021] Figure 3 is an example of a square grid marking point pattern according to one embodiment of the present invention. DETAILED DESCRIPTION

[0022] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0023] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0024] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0025] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0026] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0027] See also Figure 1 As shown, the provided calibration method of the structured light 3D scanning system based on MEMS galvanometer includes the following steps:

[0028] Step S110 , calibrating the camera to obtain the intrinsic and extrinsic parameters of the camera.

[0029] A structured light 3D scanning system based on a MEMS galvanometer typically consists of a MEMS scanner and a camera. The goal of structured light system calibration is to calculate the intrinsic parameter matrices, distortion coefficients, and extrinsic parameter matrices of the camera and projector, as well as their relative positions. Calculating the 3D coordinates of an object relies on this calibration.

[0030] In one embodiment, the Zhang calibration method is used to calibrate the intrinsic and extrinsic parameters of the camera, which specifically includes the following steps: preparing a checkerboard plane; taking a set of pictures with the camera by rotating and moving the reference plane; extracting corner points from the pictures; estimating the intrinsic and extrinsic parameters in the absence of distortion; and calculating radial distortion using a least squares algorithm.

[0031] Step S120 , placing the step surface in the field of view to be reconstructed, using a camera to synchronously capture the coded fringe pattern, and obtaining multiple sets of coded fringe patterns by translating the step surface.

[0032] In one embodiment, the step surface used is as follows Figure 2As shown, the height and width of the step surface are known, and the step surface can be customized through factory processing. There are multiple marking points on each step. For example, there are 3*3 square grid marking points on each step, such as Figure 3 shown.

[0033] It should be understood that Figure 3 The calibration image used is a dot matrix image with dots as markers. Other types of markers can also be selected as long as the distance between the markers is accurately known.

[0034] The step surface with marking points is placed in the field of view that needs to be reconstructed, and the coded stripe pattern is synchronously captured using a camera. During the capture process, multiple groups of coded stripe patterns can be obtained by translating the step surface, that is, each group of coded stripe patterns corresponds to a position on the step surface.

[0035] Step S130 , performing two-dimensional Gaussian filtering noise reduction processing on each group of coded stripe patterns.

[0036] After obtaining multiple sets of coded fringe patterns at different step positions, a two-dimensional Gaussian filter can be used to reduce noise on each image. Before phase unwrapping, using a two-dimensional Gaussian filter to reduce noise on each image can effectively restore the sinusoidal nature of the projected pattern. The two-dimensional Gaussian function is as follows:

[0037]

[0038] Here, σ is the standard deviation of the Gaussian distribution.

[0039] It should be understood that in addition to Gaussian filtering, other filtering methods may also be used.

[0040] Step S140 : performing phase unwrapping on the coded fringe pattern to extract phase information.

[0041] In one embodiment, a time phase unwrapping algorithm such as a negative exponential fitting method is used as the phase unwrapping algorithm.

[0042] The negative exponential fitting method selects the maximum number of projected fringes as t = s, s-1, s-2, s-4, ..., s / 2. The number of fringes decreases exponentially. The phase difference between two adjacent sets of projected fringes can be calculated using equations (2) and (3). To facilitate the expression of the unwrapped phase Φ(x, y) and wrapped phase φ(x, y) of fringe patterns of different frequencies, the position coordinates (x, y) are omitted in the equations.

[0043] ΔΦ(st′,s-2t′)=U{Δφ(st′,s-2t′),ΔΦ(s,st′)} (2)

[0044] ΔΦ(s,s-2t′)=ΔΦ(st′,s-2t′)+ΔΦ(s,st′) (3)

[0045] Where: t′=1,2,4,...,2 v ,...,s / 2;v=0,1,2,...,log2 (s / 2) U{} represents the unpacking operation, and its expression is: s represents the number of the highest frequency fringes projected, ΔΦ(t1, t2) represents the phase difference between two adjacent sets of fringes, t1 and t2 represent two adjacent sets of fringes, v represents the index of 2 corresponding to each frequency fringe projected, φ1 and φ2 represent the frequencies of two adjacent sets of fringes, and represents the unwrapped phase of the two sets of fringes t1 and t2.

[0046] Directly through Solving for Δφ(t1, t2) will result in a large jitter error. To avoid this error affecting the unwrapping process, when extracting the wrapped phase using the four-step phase shift method, the wrapped phase difference Δφ(t1, t2) between two adjacent sets of fringes is directly extracted. This approach limits Δφ(t1, t2) to the range (-π, π). The expression for Δφ(t1, t2) is:

[0047]

[0048] Where: I represents the light intensity of the stripe, ΔI kl =I k -I l The starting conditions for iterative dephasing using formulas (2) and (3) are:

[0049] ΔΦ(s,s-1)=Δφ(s,s-1) (5)

[0050] The final iteration result is:

[0051] ΔΦ(s,0)=Φ(s) (6)

[0052] Where Φ(s) is the final unwrapped phase of the iteration, and ΔΦ(s, 0) represents the unwrapped phase from the maximum frequency to the minimum frequency.

[0053] In order to improve the accuracy of the final unwrapped phase, the results obtained from the intermediate unwrapping can be used to obtain the slope r (which is the slope of the unwrapped phase value) through least squares fitting. The final unwrapped phase obtained after fitting is Φ. The expressions of r and Φ are:

[0054]

[0055] Φ=s·r (8)

[0056] Step S150 : performing three-dimensional calibration based on the phase height model.

[0057] The acquired phase information can be used for 3D calibration. This involves two conversions: from phase to depth and from pixels to coordinates, referred to as depth calibration and lateral calibration, respectively. Depth calibration establishes the relationship between absolute phase and depth data, while lateral calibration establishes the relationship between pixel position and its x- and y-axis coordinates in the world coordinate system. Prior to 3D calibration, the camera's intrinsic and extrinsic parameters were obtained using the Zhang Zhengyou calibration method.

[0058] For example, in depth calibration, a polynomial phase height model is used to establish the relationship between absolute phase and depth. During the calibration process, the step surface is placed at several different positions in the measurement volume for calibration. At each position, a sinusoidal fringe pattern is projected onto the step surface, and the absolute phase information of each pixel is obtained by phase calculation. The center position [u, v] of each marker point in the pixel coordinate system is obtained by a circle detection algorithm. After obtaining the center position of each marker point, the coordinates of all markers at different positions in the pixel coordinate system can be determined. The external parameters R and T of each surface on the step surface relative to the camera are calculated by the following formula:

[0059] λ[uv 1] T =A[RT][x w y w z w 1] T (9)

[0060] Where R is the rotation matrix representing the three rotation angles, T = [T x ,T y ,T z ] is a vector representing linear translation in three directions, [x w ,y w ,z w ] is the coordinate vector of the marker point P on the step surface, [u,v] is the coordinate vector of P in the pixel coordinate system, A is the internal parameter matrix of the camera, λ is an arbitrary scale factor and [] T Indicates transpose.

[0061] The world coordinates of each pixel on the step surface are obtained using the external parameters R and T, thereby obtaining the relative depth of each pixel relative to the reference plane. Therefore, the relationship between the absolute phase and depth data at each pixel can be established through a polynomial phase height model for accurate depth calibration.

[0062] Lateral calibration determines the relationship between pixel coordinates and x and y coordinates. In practical imaging systems, this relationship is nonlinear due to optical imaging and projection lens distortion. Lateral calibration utilizes depth information obtained from the projected fringe pattern. Therefore, at each pixel location, the following two polynomials are used to provide a high-precision relationship between pixel coordinates and x and y coordinates:

[0063]

[0064] Among them, a0, b0, c0, a1, b1, c1 are the coefficient sets of system parameters, [u, v] is the coordinate vector of a point in the pixel coordinate system, x r ,y r , z r It is the coordinate of the same point on the step surface in the world coordinate system.

[0065] The present invention uses a stepped surface with markers to laterally calibrate the relationship between pixel positions and x, y coordinates. Using the known intervals between adjacent discrete markers and the obtained depth, the positions x of all pixels in the world coordinate system are r ,y r , z r It can be obtained during the depth calibration process. The polynomial coefficients of each pixel can be obtained by the x r ,y r , z r And the pixel coordinates (u, v) of all points on the step surface are determined.

[0066] In summary, the present invention uses a step surface as an experimental target for calibration of a structured light system based on a MEMS galvanometer. It is simple to implement and the results are reliable. Reliable results can be obtained without the need for a high-precision and expensive displacement platform. Compared with existing methods, the present invention can not only obtain a depth map of an object, but also obtain three-dimensional information of the object. In addition, noise reduction processing is performed on the noise caused by the speckle effect of the MEMS galvanometer, and the calibration process is less time-consuming and does not require consideration of steps such as the adjustment of the polynomial fitting order. It has been verified that the present invention can simplify the calibration process, reduce the calibration time, and obtain more accurate three-dimensional information of the scanned object.

[0067] The present invention may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present invention.

[0068] Computer-readable storage medium can be a tangible device that can keep and store the instructions used by the instruction execution device.Computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device or any suitable combination thereof.More specific examples (non-exhaustive list) of computer-readable storage medium include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, for example, a punch card or a convex structure in a groove having instructions stored thereon, and any suitable combination thereof.Computer-readable storage medium used herein is not interpreted as a transient signal itself, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagated by waveguides or other transmission media (for example, light pulses by fiber optic cables), or electrical signals transmitted by wires.

[0069] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions to be stored in the computer-readable storage medium in each computing / processing device.

[0070] The computer program instructions for performing the operation of the present invention can be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, Python, and conventional procedural programming languages ​​such as "C" language or similar programming languages. The computer readable program instructions can be executed entirely on the user's computer, partially on the user's computer, as an independent software package, partially on the user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), is personalized by utilizing the state information of the computer readable program instructions, and the electronic circuit can execute the computer readable program instructions, thereby realizing various aspects of the present invention.

[0071] Various aspects of the present invention are described herein with reference to flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It should be understood that each block of the flowcharts and / or block diagrams, and combinations of blocks in the flowcharts and / or block diagrams, can be implemented by computer-readable program instructions.

[0072] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, thereby producing a machine, so that when these instructions are executed by the processor of the computer or other programmable data processing device, a device is generated that implements the functions / actions specified in one or more blocks in the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium, where these instructions cause the computer, programmable data processing device, and / or other device to operate in a specific manner. Thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing various aspects of the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0073] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device so that a series of operational steps are performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to implement the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0074] The flowcharts and block diagrams in the accompanying drawings show the possible implementation architecture, functions and operations of the systems, methods and computer program products according to multiple embodiments of the present invention. In this regard, each box in the flowchart or block diagram can represent a module, program segment or part of an instruction, and the module, program segment or part of the instruction contains one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system that performs the specified function or action, or can be implemented by a combination of dedicated hardware and computer instructions. It is well known to those skilled in the art that implementation by hardware, implementation by software, and implementation by a combination of software and hardware are all equivalent.

[0075] While various embodiments of the present invention have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein. The scope of the present invention is defined by the appended claims.

Claims

1. A calibration method for a structured light 3D scanning system based on a MEMS galvanometer, comprising the following steps: A structured light 3D scanning system based on a MEMS galvanometer is used to photograph the step surface and simultaneously collect the coded fringe patterns to obtain multiple groups of coded fringe patterns. Each group of coded fringe patterns corresponds to a different position on the step surface, and each step on the step surface has multiple marking points. Two-dimensional Gaussian filtering is used to perform noise reduction on each group of coded stripe patterns; Performing phase unwrapping on the coded fringe pattern and detecting the position of the center of the circle of the marking point in each group of coded fringe patterns in the pixel coordinate system; Three-dimensional calibration is performed based on the phase height model, and the three-dimensional calibration includes depth calibration and lateral calibration. The depth calibration is used to establish the relationship between the absolute phase and depth data, and the lateral calibration is used to establish the relationship between the pixel coordinates and the coordinates of the x-axis and y-axis in the world coordinate system.

2. The method according to claim 1, characterized in that Each step of the step surface has a 3*3 square grid of marking points.

3. The method according to claim 1, characterized in that The coded stripe pattern is photographed by a camera, and the camera is calibrated using Zhang's calibration method to obtain intrinsic parameters and extrinsic parameters.

4. The method according to claim 1, wherein The three-dimensional calibration based on the phase height model includes: Performing phase unwrapping operation on each group of coded fringe patterns; Depth calibration is performed using a depth calibration polynomial phase height model to establish the relationship between absolute phase information and depth information; The obtained depth information is used to perform lateral calibration to determine the relationship between pixel coordinates and the coordinates of the x-axis and y-axis in the world coordinate system.

5. The method according to claim 4, characterized in that During the depth calibration process, the following formula is used to determine the coordinates of the marker points at different positions in the pixel coordinate system: λ[u v 1] T =A[R T][x w y w z w 1] T Among them, R and T are the external parameters of the camera, R represents the rotation matrix of the three rotation angles, T = [T x ,T y ,T z ] represents the vector of linear translation in three directions, [x w ,y w ,z w ] is the coordinate vector of the marker point P, [u,v] is the coordinate vector of P in the pixel coordinate system, A is the intrinsic parameter matrix of the camera, λ is an arbitrary scale factor, [] T Indicates transpose.

6. The method according to claim 4, characterized in that During the horizontal calibration process, at each pixel position, the mapping relationship is calculated using the following formula: Among them, a0, b0, c0, a1, b1, c1 are coefficient sets, [u, v] is the coordinate vector of a point in the pixel coordinate system, x r ,y r , z r It is the coordinate of the same point on the step surface in the world coordinate system.

7. The method according to claim 1, characterized in that The negative exponential fitting method is used to perform phase unwrapping on the coded fringe pattern.

8. The method according to claim 7, characterized in that The result of phase unwrapping for the coded fringe pattern is expressed as: Φ=s·r Where v represents the index of 2 corresponding to each frequency stripe of the projection, v = 0, 1, 2, ..., log2 (s / 2) , s represents the number of the highest frequency fringes projected, r is the slope of the unwrapped phase value, and Φ is the final unwrapped phase.

9. A computer-readable storage medium having a computer program stored thereon, wherein: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

10. A computer device comprising a memory and a processor, wherein a computer program capable of being run on the processor is stored in the memory, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

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