Three-dimensional reconstruction method and device for double-layer transparent object

Abstract

The invention provides a three-dimensional reconstruction method and device for a double-layer transparent object. The method comprises the following steps: acquiring a double-frequency phase-shift reflection fringe image formed by reflection of a to-be-measured object; preprocessing the dual-frequency phase shift reflection fringe image to obtain a first phase initial value of the front surface of the to-be-measured object and a second phase initial value of the rear surface of the to-be-measured object; based on the first phase initial value, the second phase initial value, a preset first modulation degree initial value and a preset second modulation degree initial value, global optimization is carried out on modulation degrees and phases of the front surface and the rear surface of the to-be-measured object by adopting a mode reconstruction method, and phase resolving results of the front surface and the rear surface of the to-be-measured object are obtained; and performing three-dimensional reconstruction on the to-be-measured object based on the phase resolving result. The method can realize phase decoupling of the front surface and the rear surface of the object to be measured, has the characteristics of high robustness, accuracy and fast decoupling, can be used for a double-layer lens deflection meter system with high precision, high speed and high dynamic range, and has profound significance in the field of precision free-form surface processing and detection.

Description

Technical Field

[0001] The present invention relates to the technical field of precision metrology surface detection, and in particular to a method and device for three-dimensional reconstruction of a double-layer transparent object. Background Art

[0002] Traditional methods face three major challenges in detecting the surface morphology of transparent objects: 1) Sparse textures or features on the surface hinder the effectiveness of texture-based visual inspection methods; 2) The non-diffuse reflective surface of transparent objects is not an ideal Lambertian body model and cannot be detected using the general method for diffuse reflective materials; 3) The complex interaction between incident light and transparent objects, such as reflection, refraction, scattering and absorption, increases the complexity of optical path analysis of transparent objects.

[0003] Currently, phase measurement deflectometry can be used to complete the reconstruction of transparent objects that also have mirror reflection properties.

[0004] However, when using phase measurement deflectometry to reconstruct the three-dimensional of transparent objects, the front and back surfaces of the transparent objects will reflect the light from the display screen, causing the camera to capture aliased stripes. The superposition of the light intensity of the stripes is fatal to pixel matching. Therefore, the above method cannot complete the reconstruction of the front and back surfaces separately. At the same time, the traditional phase demodulation method used in phase measurement deflectometry often faces problems such as front and back surface phase aliasing, phase order jumps, and slow demodulation speed. Summary of the invention

[0005] The present invention provides a method and device for three-dimensional reconstruction of a double-layer transparent object, which are used to solve the defects of front and rear surface fringe aliasing caused by phase measurement deflectometry in the prior art and front and rear surface phase aliasing, phase order jump, slow demodulation speed and the like faced by traditional phase demodulation methods, so as to achieve high-precision three-dimensional reconstruction of a double-layer transparent object.

[0006] The present invention provides a three-dimensional reconstruction method for a double-layer transparent object, which is applied to a transparent object deflectometer system. The system comprises a display screen, an object to be measured, and a camera which are installed in sequence, wherein the object to be measured is a double-layer transparent object; the display screen is used to display a pre-generated dual-frequency phase-shifted initial fringe image, and project the dual-frequency phase-shifted initial fringe image onto the object to be measured; the camera is used to capture a dual-frequency phase-shifted reflected fringe image formed by the dual-frequency phase-shifted initial fringe image being reflected by the front surface and the rear surface of the object to be measured, wherein the front surface and the rear surface respectively represent the surface of the object to be measured that contacts the projected light first and the surface of the object to be measured that contacts the projected light later; The method for three-dimensional reconstruction of a double-layer transparent object comprises the following steps.

[0007] Acquire a dual-frequency phase-shifted reflected fringe image formed by the dual-frequency phase-shifted initial fringe image reflected by the object to be measured; Preprocessing the dual-frequency phase-shifted reflected fringe image to obtain a first initial phase value of the front surface of the object to be measured and a second initial phase value of the rear surface of the object to be measured; Based on the first initial phase value, the second initial phase value, and the preset first initial modulation value of the front surface of the object to be measured and the second initial modulation value of the rear surface of the object to be measured, the modulation degree and phase of the front surface of the object to be measured and the modulation degree and phase of the rear surface are globally optimized based on the pattern reconstruction method to obtain the modulation degree solution result and the phase solution result of the front surface and the rear surface respectively; Based on the modulation degree solution result and the phase solution result, the object to be measured is reconstructed in three dimensions.

[0008] According to a method for three-dimensional reconstruction of a double-layer transparent object provided by the present invention, the dual-frequency phase-shifted initial fringe image is continuously captured by a camera through the reflected fringes reflected by the front surface and the rear surface of the object to be measured, thereby generating the dual-frequency phase-shifted reflected fringe image; The light intensity distribution of the reflected fringes captured by the camera for the nth time I n (x,y) is represented as: , in, is the ambient background light, and are the modulation intensities of the front and rear surfaces, and represent the phase of the front and rear surfaces respectively, , , Indicates the phase shift of the display screen, represents the total phase shift, Represents the frequency ratio in the case of multi-frequency fringes.

[0009] According to a method for three-dimensional reconstruction of a double-layer transparent object provided by the present invention, the step of globally optimizing the modulation degree and phase of the front surface and the modulation degree and phase of the rear surface of the double-layer transparent object to be measured specifically includes: The modulation degree of the front surface of the double-layer transparent object to be tested and Phase , modulation of the rear surface and Phase Set as initial iteration parameters; The initial iteration parameters are reconstructed by using the pattern reconstruction method. , , and Decompose and obtain the decomposition parameter J; set up Residual error, in iWhen 1, 2, 3, and 4 are selected respectively, Use , , and Indicates that the global optimization objective function is set : , in, is the parameter representation of the modulation degree of the front surface of the object to be measured, is the parameter representation of the back surface modulation of the object to be measured, is the parameter representation of the phase of the front surface of the object to be measured, It is the parameter representation of the phase of the rear surface of the object to be measured; Based on the first initial phase value, the second initial phase value, and the preset first modulation index initial value of the front surface of the double-layer transparent object to be measured and the preset second modulation index initial value of the rear surface of the double-layer transparent object to be measured, the global optimization objective function is iteratively solved until a preset number of iterations is reached or a preset step size threshold is reached; Output the calculated front surface modulation , rear surface modulation , front surface phase and rear surface phase .

[0010] According to a method for 3D reconstruction of a double-layer transparent object provided by the present invention, the step of preprocessing the dual-frequency phase-shifted reflection fringe image specifically includes: Performing fast Fourier transform on the dual-frequency phase-shifted reflected fringe image to generate a Fourier transform image; Filtering the Fourier transform image to obtain fringe information on the front and rear surfaces of the object to be measured; Calculating the truncated phases of the front and rear surfaces of the object to be measured based on the fringe information of the front and rear surfaces of the object to be measured; Calculating the phase order and the unwrapped phase of the front and rear surfaces of the object to be measured based on the truncated phases of the front and rear surfaces of the object to be measured; The unwrapped phase of the front surface of the object to be measured is used as a first phase initial value, and the unwrapped phase of the rear surface of the object to be measured is used as a second phase initial value.

[0011] According to a method for three-dimensional reconstruction of a double-layer transparent object provided by the present invention, the step of filtering the Fourier transform image specifically includes: The logarithmic spectrum of the Fourier transform image is calculated using the following formula: ; in, Respectively represent the pixels in Coordinates of the direction; represents the Fourier transform image, Represents the result of taking the logarithm of the Fourier transform image; Obtaining the position coordinates of the central peak on the frequency spectrum plane formed by the logarithmic spectrum; Based on the position coordinates of the central peak, the stripe information on the front and rear surfaces of the object to be measured is separated.

[0012] According to a method for three-dimensional reconstruction of a double-layer transparent object provided by the present invention, based on the fringe information of the front and rear surfaces of the object to be measured, the truncated phases of the front and rear surfaces of the object to be measured are calculated using a four-step phase shift method.

[0013] According to a method for three-dimensional reconstruction of a double-layer transparent object provided by the present invention, the steps of calculating the phase order and the unfolded phase of the front and rear surfaces of the object to be measured based on the truncated phases of the front and rear surfaces of the object to be measured specifically include: Calculating the phase orders of the front and rear surfaces of the object to be measured based on the truncated phases of the front and rear surfaces of the object to be measured; Based on the truncated phase and phase order of the front and rear surfaces of the object to be measured, the time phase unwrapping technology of the dual-frequency fringes is adopted to calculate the unwrapped phase of the front and rear surfaces of the object to be measured.

[0014] According to a three-dimensional reconstruction method for a double-layer transparent object provided by the present invention, based on the modulation depth solution result and the phase solution result, the front surface of the object to be measured is reconstructed by a method based on predicted surface shape iteration, and the rear surface of the object to be measured is reconstructed by a method based on beam tracing iterative reflection point.

[0015] The present invention also provides a double-layer transparent object three-dimensional reconstruction device, which is applied to a transparent object deflectometer system, wherein the system comprises a display screen, an object to be measured, and a camera which are installed in sequence, wherein the object to be measured is a double-layer transparent object; the display screen is used to display a pre-generated dual-frequency phase-shifted initial fringe image, and project the dual-frequency phase-shifted initial fringe image onto the object to be measured, and the camera is used to capture a dual-frequency phase-shifted reflected fringe image formed by the dual-frequency phase-shifted initial fringe image being reflected by the front surface and the rear surface of the object to be measured, wherein the front surface and the rear surface respectively represent the surface of the object to be measured that contacts the projected light first and the surface of the object to be measured that contacts the projected light later; The double-layer transparent object 3D reconstruction device comprises the following modules: A reflection fringe image acquisition module, used for acquiring a dual-frequency phase-shifted reflection fringe image formed by the dual-frequency phase-shifted initial fringe image being reflected by the object to be measured; A preprocessing module, used for preprocessing the dual-frequency phase-shifted reflected fringe image to obtain a first initial phase value of the front surface of the object to be measured and a second initial phase value of the rear surface of the object to be measured; A global optimization module, for performing global optimization on the modulation and phase of the front surface of the object to be measured and the modulation and phase of the rear surface of the object to be measured based on the first phase initial value, the second phase initial value and the preset first modulation initial value of the front surface of the object to be measured and the second modulation initial value of the rear surface of the object to be measured, based on the pattern reconstruction method, to obtain modulation solution results and phase solution results of the front surface and the rear surface respectively; A reconstruction module is used to perform three-dimensional reconstruction of the object to be measured based on the modulation solution result and the phase solution result.

[0016] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method for three-dimensional reconstruction of a double-layer transparent object as described above is implemented.

[0017] The present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the three-dimensional reconstruction method of a double-layer transparent object as described in any one of the above methods is implemented.

[0018] The present invention also provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the computer program implements any of the above-mentioned methods for three-dimensional reconstruction of a double-layer transparent object.

[0019] The present invention provides a method and device for three-dimensional reconstruction of a double-layer transparent object. The method and device obtain a dual-frequency phase-shifted reflected fringe image formed by reflecting a dual-frequency phase-shifted initial fringe image from an object to be measured; pre-process the dual-frequency phase-shifted reflected fringe image to obtain a first initial phase value of the front surface of the object to be measured and a second initial phase value of the rear surface of the object to be measured; based on the first initial phase value, the second initial phase value and the pre-set first initial modulation value of the front surface of the object to be measured and the second initial modulation value of the rear surface of the object to be measured, the modulation degree and phase of the front surface of the object to be measured and the modulation degree and phase of the rear surface are globally optimized based on a pattern reconstruction method to obtain modulation degree solution results and phase solution results of the front surface and the rear surface respectively; based on the modulation degree solution results and the phase solution results, the object to be measured is reconstructed in three dimensions. The present invention can decouple the mixed stripes of a double-layer transparent object, fully utilizes the physical spatial continuity of the modulation and phase of the front and rear surfaces of the double-layer transparent object, and avoids phase ambiguity, step and low computational efficiency problems; the present invention can reconstruct the double-layer surface profile of any free-form surface lens, and the measurement accuracy can reach the micron level. In addition, the measurement dynamic range of the present invention covers the micron level to the millimeter level, which is more suitable for processing large curvature surfaces. No pre-processing or post-processing is required during the measurement process, and in-situ detection in industrial production is realized. The measurement time of a single element is reduced to a few seconds, which significantly improves the measurement speed; the present invention realizes a high-precision, high-speed and high-dynamic range double-layer lens deflectometer system, which has far-reaching significance for the field of precision free-form surface processing and detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a schematic flow chart of the method for three-dimensional reconstruction of a double-layer transparent object provided by the present invention.

[0022] Figure 2 It is a structural schematic diagram of the transparent object deflectometer system provided by the present invention.

[0023] Figure 3 It is a schematic diagram of the process of preprocessing the dual-frequency phase-shifted reflection fringe image provided by the present invention.

[0024] Figure 4 It is a schematic diagram of a flow chart for globally optimizing modulation index and phase provided by the present invention.

[0025] Figure 5It is the reconstruction result of the plano-convex lens using the double-layer transparent object three-dimensional reconstruction method provided by the present invention.

[0026] Figure 6 This is the reconstruction result of the astigmatism lens using the double-layer transparent object three-dimensional reconstruction method provided by the present invention.

[0027] Figure 7 It is a schematic structural diagram of a double-layer transparent object three-dimensional reconstruction device provided by the present invention.

[0028] Figure 8 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The present invention is described in detail below in conjunction with the accompanying drawings of the specification. The specific operating method in the method embodiment can also be applied to the device embodiment or the system embodiment. In the description of the present invention, unless otherwise specified, "at least one" includes one or more. "Multiple" refers to two or more. For example, at least one of A, B and C includes: A exists alone, B exists alone, A and B exist at the same time, A and C exist at the same time, B and C exist at the same time, and A, B and C exist at the same time. In the present invention, " / " means or, for example, A / B can mean A or B; "and / or" in this article is only a description of the association relationship of associated objects, indicating that three relationships can exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0031] Transparent objects are widely used in various fields such as optical components, virtual reality devices and glasses, head-up displays (HUDs) and windshields in cars, and screen protectors for 3C devices. The accuracy of their three-dimensional morphology significantly affects the accuracy of the application system, image clarity, durability, and rigidity. Therefore, it is crucial to conduct on-site surface morphology evaluation during the manufacturing process to improve production standards. However, there are three main challenges in detecting the surface morphology of transparent objects: 1) sparse textures or features on the surface hinder the effectiveness of texture-based visual inspection methods, 2) the non-diffuse reflective properties of transparent objects are not ideal Lambertian models and cannot be detected using the general method of diffuse reflective materials, and 3) the complex interactions between the incident light and transparent objects, such as reflection, refraction, scattering, and absorption, exacerbate the complexity of optical path analysis of transparent objects.

[0032] Deflectometry has developed rapidly in recent years. It has the characteristics of simple system, wide dynamic range, fast speed, high precision, etc., and can easily realize in-situ measurement of any free-form surface mirror. The PMD system is based on Snell's reflection law and is usually composed of a screen (usually a liquid crystal display or LCD), a camera and the surface of the object to be measured. The structured light pattern displayed on the LCD is reflected onto the surface of the object to be measured and then captured by the camera. By matching the corresponding pixels on the screen and the camera; then obtaining the gradient of the surface to be measured based on ray tracing; finally, the three-dimensional shape of any free-form surface can be restored through integral reconstruction. The use of phase measurement deflectometry can also complete the reconstruction of transparent objects with mirror reflection characteristics, but it will face the problem of aliasing of the front and back surface stripes: the front and back surfaces will reflect the light from the display screen, resulting in the camera capturing aliased stripes. The superposition of the light intensity of the stripes is fatal to the pixel matching, which will lead to the inability to complete the reconstruction of the front and back surfaces separately. At the same time, traditional phase demodulation methods often face problems such as phase aliasing, phase order jump, and demodulation speed. Phase aliasing refers to the situation where the front and rear surfaces are close to each other and the phase demodulation of the front and rear surfaces is alternating. Phase order jump: Due to the periodic relationship between phase and intensity, it is easy to produce a local optimal solution rather than a global optimal solution during phase demodulation, resulting in phase order jump. Slow demodulation speed: The pixel-by-pixel demodulation method results in a very slow demodulation speed.

[0033] Phase measurement deflectometry (PMD) is a 3D reconstruction technique for mirror objects based on triangulation, which has been widely used in fields such as microelectronics, automotive manufacturing, and aerospace. By simply capturing the deformed grating fringes reflected by the measured mirror, any free-form mirror surface can be restored by integral reconstruction. However, transparent objects such as lenses, screens, and glass pose challenges in phase decoupling due to overlapping fringes caused by reflections from the front and back surfaces. Traditional methods rely on pixel-by-pixel nonlinear equations, which suffer from phase ambiguity, phase steps, and low demodulation efficiency, resulting in poor robustness, high dependence on initial conditions, and low efficiency.

[0034] To solve the above problems, the present invention provides a method and device for three-dimensional reconstruction of a double-layer transparent object, which is applied to a transparent object deflectometer system, fully utilizes the physical spatial continuity of the modulation and phase of the front and back surfaces of the object to be measured, decouples the mixed stripes of the double-layer transparent object through a global optimization iterative algorithm, avoids phase ambiguity, steps and low computational efficiency problems, and provides an effective solution for high-precision three-dimensional reconstruction of transparent objects, which has important industrial application value.

[0035] The present invention will be described in detail below in conjunction with specific implementation modes.

[0036] In some specific embodiments of the present invention, Figure 1 As shown, the present invention provides a method for three-dimensional reconstruction of a double-layer transparent object, which is applied to a transparent object deflectometer system, the system comprising a display screen, an object to be measured, and a camera which are installed in sequence, wherein the object to be measured is a double-layer transparent object; the display screen is used to display a pre-generated dual-frequency phase-shifted initial fringe image, and project the dual-frequency phase-shifted initial fringe image onto the object to be measured, and the camera is used to capture a dual-frequency phase-shifted reflected fringe image formed by the dual-frequency phase-shifted initial fringe image being reflected by the front surface and the rear surface of the object to be measured, wherein the front surface and the rear surface respectively represent the surface of the object to be measured that contacts the projected light first and the surface of the object to be measured that contacts the projected light later; Methods include: Step 100, obtaining a dual-frequency phase-shifted reflected fringe image formed by the dual-frequency phase-shifted initial fringe image reflected by the object to be measured; Step 200, preprocessing the dual-frequency phase-shifted reflection fringe image to obtain a first initial phase value of the front surface of the object to be measured and a second initial phase value of the rear surface of the object to be measured; Step 300: Based on the first phase initial value, the second phase initial value, and the preset first modulation initial value of the front surface of the object to be measured and the preset second modulation initial value of the rear surface of the object to be measured, the modulation and phase of the front surface of the object to be measured and the modulation and phase of the rear surface are globally optimized based on the pattern reconstruction method to obtain the modulation solution results and phase solution results of the front surface and the rear surface respectively; Step 400: Perform three-dimensional reconstruction of the object to be measured based on the modulation depth solution result and the phase solution result.

[0037] It should be noted that the existing 3D reconstruction schemes rely on pixel-by-pixel nonlinear equations, which make it difficult to decouple overlapping fringes and result in problems such as phase ambiguity, phase steps, and low demodulation efficiency.

[0038] Therefore, the present invention pre-processes the dual-frequency phase-shifted reflection fringe image formed by the reflection of the object to be measured, obtains the initial phase value of the front and rear surfaces of the object to be measured, and globally optimizes the phase and modulation of the front and rear surfaces of the object to be measured based on the pattern reconstruction method according to the initial phase value of the front and rear surfaces of the object to be measured and the preset initial modulation value, and performs three-dimensional reconstruction of the object to be measured according to the optimization result. This method is a highly robust, high-precision, and fast phase demodulation method based on a double-layer transparent object, which realizes the phase measurement deflectometry reconstruction of a transparent object, and is of great significance to the field of free-form surface precision machining and detection.

[0039] It is understandable that the existing pixel-by-pixel solution method ignores the continuity of the phase between pixels. In the actual physical world, the front and back surfaces of transparent objects are mostly continuous, so the corresponding phase is also continuous, and the phase of the front and back surfaces can be solved as a whole from a global perspective.

[0040] In some possible embodiments of the present invention, Figure 2 As shown, the transparent object deflectometer system 10 comprises a display screen 101, a test mirror 102, and a camera 103 which are sequentially installed, and the test mirror is a double-layer transparent object. The overall idea of ​​the present invention is that the display screen 101 generates a dual-frequency phase-shifted initial fringe image, which enters the front and rear surfaces of the test mirror 102 for reflection, and the camera 103 captures the dual-frequency phase-shifted reflected fringe 104.

[0041] Furthermore, if Figure 3 As shown, in this embodiment, assuming that the camera captures 8 reflection fringe images, a total of 8 dual-frequency phase-shifted reflection fringe images 201 captured by the camera are preprocessed 20, and the preprocessing 20 includes spatial frequency filtering 202, truncated phase extraction 203, and expanded phase acquisition 204 to obtain the initial value of the front and rear surface phases.

[0042] On this basis, the global optimization method based on pattern reconstruction method30 is used, such as Figure 3 As shown in the figure, the modulation degree and phase of the front and rear surfaces are globally optimized; finally, according to the phase solution result, as shown in the figure, Figure 4 As shown, the phase matching between the display screen and the camera is achieved, and the three-dimensional reconstruction of the double-layer surface is achieved by optical path tracing 40.

[0043] Specifically, the transparent object deflectometer system 10 also includes a computer. The two phase-shifted fringes of different frequencies in the dual-frequency phase-shifted initial fringe image are generated by the computer and displayed on a display screen. After being deformed by the mirror to be measured, they are captured by a camera to obtain deformed dual-frequency phase-shifted fringes.

[0044] In a possible embodiment, a standard phase measurement deflectometry system mainly includes a camera (c), a mirror to be measured (m), and a display screen (s). The display screen displays sinusoidally varying grating stripes with phase shifts. The stripe image is deformed after being reflected by the mirror object of the mirror to be measured, and then captured by the camera. The deformed stripe pattern captured by the camera contains the morphological information of the surface of the object to be measured. After phase demodulation and phase order extraction, the unfolded phase is obtained, and then combined with the spatial position relationship between the camera, display screen, and mirror to be measured provided by the system calibration. The surface normal vector of the object is obtained by inverse ray tracing, and then the surface gradient of the object to be measured is calculated, as shown in the formula. Finally, the three-dimensional surface shape of the object to be measured is reconstructed.

[0045] (1) (2) in, They represent the corresponding points of the ray tracing of the test mirror, camera, and display screen respectively. , Respectively M arrive P and M arrive Q distance.

[0046] In some possible implementations of the present invention, the dual-frequency phase-shifted initial fringe image is continuously captured by a camera through the reflected fringes reflected by the front surface and the rear surface of the object to be measured, to generate the dual-frequency phase-shifted reflected fringe image; the light intensity distribution I of the reflected fringes captured by the camera for the nth time n (x,y) is represented as: (3) Among them, A(x, y) is the ambient background light, B f (x,y) and Br(x,y) are the modulation intensities of the front and back surfaces respectively, and represent the phase of the front and rear surfaces respectively, , n=0,1,2…N-1 represents the phase shift of the display screen, N represents the total phase shift, and k represents the frequency ratio in the case of multi-frequency stripes.

[0047] Specifically, this embodiment provides an implementation method for capturing dual-frequency phase-shifted reflection fringe images by a camera, and constructing the light intensity distribution of the reflection fringe captured by the camera each time.

[0048] Specifically, for transparent objects, such as eyeglass lenses, optical lenses, etc., reflection will occur on both the front and back surfaces. The same camera pixel C corresponds to two different display screen pixels S1 and S2. This means that the phases corresponding to the front and back surfaces are different. Simultaneous capture by the camera will result in superposition of fringe intensities. In formula (3), I n (x, y) represents the light intensity distribution captured by the nth phase-shift camera, A(x, y) is the ambient background light, B f (x, y) and Br(x, y) are the modulation intensities of the front and rear surfaces, respectively. and represent the front and rear surface phases respectively, , n=0,1,2…N-1 represents the phase shift of the display screen, N represents the total phase shift, and k represents the frequency ratio in the case of multi-frequency stripes.

[0049] In a specific embodiment, Figure 3 As shown in the figure, if N=4, k=k0, k1, a total of 8 images of 201 4×2 are generated by calculation using formula (3).

[0050] In some possible implementations of the present invention, the step of preprocessing the dual-frequency phase-shifted reflection fringe image specifically includes: Performing fast Fourier transform on the dual-frequency phase-shifted reflected fringe image to generate a Fourier transform image; Filtering the Fourier transform image to obtain fringe information on the front and rear surfaces of the object to be measured; Calculating the truncated phases of the front and rear surfaces of the object to be measured based on the fringe information of the front and rear surfaces of the object to be measured; Calculating the phase order and the unwrapped phase of the front and rear surfaces of the object to be measured based on the truncated phases of the front and rear surfaces of the object to be measured; The unwrapped phase of the front surface of the object to be measured is used as a first phase initial value, and the unwrapped phase of the rear surface of the object to be measured is used as a second phase initial value.

[0051] Specifically, this embodiment provides an implementation method for preprocessing a dual-frequency phase-shifted reflection fringe image, such as Figure 3 As shown, for a double-layer transparent object such as a lens, the image captured by the camera is shown in 201; the image is subjected to fast Fourier transform (FFT) to generate Fourier transform images, as shown in 202; the density and direction of the stripes on the front and back surfaces can be determined according to the shapes of the front and back surfaces of the object to be measured, and the two groups of centrally symmetrical peaks are used as filters to separate the stripe information on the front and back surfaces, as shown in 203; after filtering, the truncated phases of the front and back surfaces can be calculated respectively using the four-step phase shift method; then the time phase unwrapping technology based on dual-frequency stripes is used to calculate the phase order and unwrapping phase of the front and back surfaces, as shown in 204.

[0052] In some possible implementations of the present invention, the step of filtering the Fourier transform image specifically includes: The logarithmic spectrum of the Fourier transform image is calculated using the following formula: (4) in, Respectively represent the coordinates of the pixel in the x and y directions; represents the Fourier transform image, Represents the result of taking the logarithm of the Fourier transform image; Obtaining the position coordinates of the central peak on the frequency spectrum plane formed by the logarithmic spectrum; Based on the position coordinates of the central peak, the stripe information on the front and rear surfaces of the object to be measured is separated.

[0053] Specifically, this embodiment provides an implementation method for filtering the Fourier transform image obtained by Fourier transform. For a double-layer transparent object, the camera will capture the superimposed fringes 201 after reflection from the front and back surfaces. In order to decouple the phases of the front and back surfaces, a phase initial value preprocessing method is used. Figure 3 , perform fast Fourier transform (FFT) on the image to generate Fourier transform image, and then calculate the logarithmic spectrum of the Fourier transform image , to improve the dynamic range and visualization effect, as shown in 202; due to the different surface shapes of the front and rear surfaces, the spatial modulation of the sinusoidal stripes is also different, so a central peak can be seen on the spectrum surface, representing the part of the ambient light, and two sets of centrally symmetrical peaks, representing the stripes modulated by the front and rear surfaces. The density and direction of the stripes on the front and rear surfaces can be determined according to the shape of the side surface to be examined, and the two sets of centrally symmetrical peaks can be used as filters to separate the stripe information on the front and rear surfaces, as shown in 203.

[0054] In some possible implementations of the present invention, based on the fringe information on the front and rear surfaces of the object to be measured, a four-step phase shift method is used to calculate the truncated phases of the front and rear surfaces of the object to be measured.

[0055] Specifically, this embodiment provides an implementation method for calculating the truncated phases of the front and rear surfaces of the object to be measured. After filtering, the truncated phases of the front and rear surfaces can be calculated respectively using a four-step phase shift method.

[0056] In some possible implementations of the present invention, the step of calculating the phase order and the unwrapped phase of the front and rear surfaces of the object to be measured based on the truncated phases of the front and rear surfaces of the object to be measured specifically includes: Calculating the phase orders of the front and rear surfaces of the object to be measured based on the truncated phases of the front and rear surfaces of the object to be measured; Based on the truncated phase and phase order of the front and rear surfaces of the object to be measured, the time phase unwrapping technology of the dual-frequency fringes is adopted to calculate the unwrapped phase of the front and rear surfaces of the object to be measured.

[0057] Specifically, this embodiment provides an implementation method for calculating the phase order and unfolded phase of the front and rear surfaces of the object to be measured. After obtaining the truncated phases of the front and rear surfaces of the object to be measured, the time phase unfolding technology based on dual-frequency stripes is used to calculate the phase order and unfolded phase of the front and rear surfaces, as shown in 204.

[0058] Specifically, two signals of different frequencies are used to perform initial phase measurement to obtain two corresponding phase diagrams, usually one high-frequency signal and one low-frequency signal; the phase difference between the two frequency signals is calculated, and this setting is used to eliminate the 2π ambiguity problem in phase measurement; based on the calculated phase difference information, the phase of the high-frequency signal is expanded to obtain a high-precision phase value; the phase expansion process of the high-frequency signal is guided by the phase information of the low-frequency signal to improve the measurement accuracy; the expanded high-frequency phase diagram is synthesized into a final high-resolution phase diagram, thereby obtaining a high-precision three-dimensional reconstruction result or phase distribution.

[0059] In a possible embodiment, since the filter is set in the form of a Gaussian function, the standard deviation of the Gaussian filter satisfies the minimum value under specific conditions, that is, the minimum value of the logarithmic spectrum intensity average value (such as less than 0.9 times the peak logarithmic spectrum value) within the range defined by the standard deviation. This dynamic adjustment method ensures that the filter adapts to the data characteristics and sets an appropriate standard deviation for each peak position, thereby achieving effective filtering. However, the actual situation is that the peaks corresponding to the front and rear surfaces are not Gaussian, but are affected by the surface specificity and the off-axis nature of the deflection system, and have directional specificity. This will cause the fringe information after Gaussian filtering to be distorted, which is then reflected in the phase order jump and the error of the unfolded phase. It can be clearly seen from 204 that there is a partial jump phase error.

[0060] In order to further eliminate the error caused by filtering and restore the phase information, a global optimization method based on the pattern reconstruction method is used to accurately reconstruct the front and rear surface phases through continuous iterations.

[0061] In some possible implementations of the present invention, the step of globally optimizing the modulation degree and phase of the front surface and the modulation degree and phase of the rear surface of the double-layer transparent object to be measured specifically includes: The modulation degree of the front surface of the double-layer transparent object to be tested and Phase , modulation of the rear surface and Phase Set as initial iteration parameters; The initial iteration parameters are reconstructed by using the pattern reconstruction method. , , and Decompose and obtain the decomposition parameter J; set up Residual error, in i When 1, 2, 3, and 4 are selected respectively, Use , , and Indicates that the global optimization objective function is set : (5) in, is the parameter representation of the modulation degree of the front surface of the object to be measured, is the parameter representation of the back surface modulation of the object to be measured, is the parameter representation of the phase of the front surface of the object to be measured, It is the parameter representation of the phase of the rear surface of the object to be measured; Based on the first initial phase value, the second initial phase value, and the preset first modulation index initial value of the front surface of the double-layer transparent object to be measured and the preset second modulation index initial value of the rear surface of the double-layer transparent object to be measured, the global optimization objective function is iteratively solved until a preset number of iterations is reached or a preset step size threshold is reached; Output the calculated front surface modulation , rear surface modulation , front surface phase and rear surface phase .

[0062] Specifically, this embodiment provides an implementation method for globally optimizing the modulation and phase of the front and back surfaces of a double-layer transparent object to be tested. In order to further eliminate the error caused by filtering and restore the phase information, a global optimization method based on the pattern reconstruction method is adopted, and the unwrapped phase with error is used as the initial value of the global optimization algorithm based on the pattern reconstruction method. J , the model minimizes the objective function by iterative calculation , ensuring accurate reconstruction of the front and rear surface phases through successive iterations.

[0063] In a possible embodiment, Figure 4 As shown in Figure 2, the specific process of the global optimization method based on the pattern reconstruction method is as follows: First, the initial iteration parameters are selected as the modulation and phase of the front and rear surfaces. , , and ; The four parameters are decomposed by pattern reconstruction method to obtain , converting the surface information into a set of parameters, including modulation and phase parameters related to the front and back surfaces of the object; formulating a global optimization objective function for the iterative parameters Perform nonlinear global optimization; by determining the iteration cutoff condition: k > k max or To decide whether to jump out, if any condition is met, the iteration process is terminated and enters the next step; otherwise, return to the next iteration; finally, the iterative convergence Restore to optimized modulation and phase , , and The final iteration parameters will be used for surface reconstruction of transparent objects, ensuring high accuracy, high speed and high dynamic range of measurement.

[0064] Furthermore, based on the phase information, the light emitted by the same camera pixel can be reflected by the front and rear surfaces to match the two pixels on the display screen. In this way, the shape and position of the front surface can be determined by an iterative method based on the predicted surface shape, and the shape and position of the rear surface need to be corrected for the light refracted into the medium, and the rear surface surface shape iteration converges by optimizing the ray tracing path.

[0065] In a possible embodiment, wavefront reconstruction is performed by pattern reconstruction technology. A set of orthogonal patterns (such as Zernike polynomials or other suitable basis functions) can be used to characterize the wavefront, and the coefficients of each pattern are determined one by one to approximate or reconstruct the complex wavefront. Usually, the least square method or other optimization algorithm is used to fit these patterns based on known measurement data to obtain the coefficients of each pattern. These coefficients can be combined to reconstruct the shape of the original wavefront.

[0066] It can be understood that the four unknown quantities, such as the modulation degree and phase of the front and rear surfaces of the object to be measured, are continuous in the x and y directions, and it is feasible to use modal wavefront reconstruction. Therefore, this embodiment proposes a global optimization method based on modal wavefront reconstruction, which uses a series of mutually orthogonal polynomials to simulate the modulation intensity and phase of the front and rear surfaces. Generally, the choice of polynomials (such as Legendre polynomials, Chebyshev polynomials, or Zernike polynomials) depends on the specific surface shape analyzed. Zernike polynomials are usually used for circular areas, while Legendre polynomials are used for rectangular areas. Modal wavefront reconstruction uses fewer parameters to represent the entire surface. This allows the phase and modulation of the entire surface to be optimized in the nonlinear programming (NLP) process, significantly reducing the need to calculate the modulation intensity and phase pixel by pixel. Phase decoupling of the entire front and rear surfaces can be achieved through a single iteration, ensuring phase continuity and improving the robustness of phase reconstruction, while avoiding phase ambiguity and phase order jumps.

[0067] For example, when using Zernike polynomials, the four unknowns , , and Expressed as Zernike polynomial terms A linear combination of n from 0 to l, m from -n in steps of 2. The coefficients represents the fitting parameters of these polynomials. The appropriate polynomial order can be selected according to the complexity of the front and back surface profiles l If you set l is 5, covering The first 21 items of , and the operations of other parameters are similar, as shown in formula (6) or (7). , , and It can also be expressed as a linear combination of the product of Legendre polynomials D(x) and D(y) in the x and y directions, where k represents the order of the Legendre polynomials, as shown in formula (6) or (7).

[0068] (6) (7) In the subsequent calculation process, this embodiment uses Zernike fitting as an example to illustrate the modeling process, and the process of selecting other polynomials for modeling can be analogous to this method.

[0069] On this basis, based on the global optimization method of modal wavefront reconstruction, the objective function can be set as shown in formula (8): (8) Taking the dual-frequency phase shift method as an example, its objective function is defined as the residual , , and The square sum of the optimization parameters J represents the Zernike fitting parameters , by applying nonlinear least squares optimization, a set of optimal parameters can be determined .

[0070] The above-mentioned setting of this embodiment effectively minimizes the difference between the predicted model and the actual measurement by treating the entire surface as a whole. This holistic perspective not only improves the accuracy of the model, but also solves basic problems such as local phase ambiguity and order jump. In addition, this method significantly improves the efficiency of the measurement process and provides a more simplified and reliable means of phase acquisition.

[0071] In a specific embodiment, Figure 5 As shown, Figure 5 It is the reconstruction result of the plano-convex lens using the double-layer transparent object 3D reconstruction method provided by the present invention, wherein (a) and (b) are the reconstruction results of the front and back surfaces respectively; (c) and (d) are the residuals after comparison with the standard model respectively. In order to verify the effectiveness of the above method, a K9 plano-convex lens commonly used in optical experiments is reconstructed, with a focal length of 1000mm, a front surface of which is a spherical surface with a radius of curvature of 516.82mm, a refractive index of the material of 1.5163, and a reconstruction range of the front surface of 20mm×20mm; while the reconstruction range of the back surface is limited by ray tracing and is therefore slightly smaller than the front surface. Figure 5 In the figure, (a) and (b) are the front and back surface reconstruction results. The measured results are compared with the surface profile provided by the manufacturer, such as Figure 5 As shown in (c) and (d).

[0072] In another specific embodiment, Figure 6 As shown, Figure 6 This is the reconstruction result of the astigmatism lens using the double-layer transparent object 3D reconstruction method provided by the present invention. Among them, (a) and (b) are the actual picture of the progressive eyeglass and the measured scatter diagram using a 3D profilometer, respectively; (c) and (d) are the reconstruction results of the front and back surfaces, respectively; (e) and (f) are the residuals after comparison with the standard model, respectively. The measurement result of another astigmatism eyeglass lens proves the universal applicability of this method. This lens has different curvature radii and thicknesses in different directions, such as Figure 6 The shape of the lens surface can be expressed as an elliptical parabola. Description, where x and y are along the two main axes respectively. The rear surface is a spherical surface with a radius of R. Since the curvature of the lens varies greatly, the dynamic range of the white light interferometer cannot meet the measurement requirements. The surface is sprayed with a powder with diffuse reflection characteristics, and then the ATOS capsule 12M is used to perform blue light 3D scanning on the object to obtain the three-dimensional morphology of the surface, such as Figure 6 (b) shows that the measured data is used as the standard value. The phase reconstruction result obtained by the method of the present invention and the deviation from the standard value are shown in Figure 6 As shown in (c)-(f).

[0073] The above verification results prove that the global optimization iterative algorithm based on the pattern reconstruction method can realize the decoupling of the aliasing fringes of double-layer transparent objects. This method makes full use of the physical spatial continuity of the modulation and phase of the front and back surfaces to avoid the phase ambiguity, order jump, and low solution efficiency caused by the pixel-by-pixel phase solution. On this basis, a phase deflectometry system based on this method was built to realize the reconstruction of the double-layer profile of any free-form surface lens. The measurement accuracy can reach the micron level, which is comparable to the three-dimensional measurement profiler. In addition, its measurement dynamic range can be from microns to millimeters, far exceeding the white light interferometer, and is better at processing large curvature surfaces. There is no need for any pre-treatment (powder spraying) and post-treatment process (cleaning) during measurement, and in-situ detection can be realized during industrial production and processing. At the same time, the measurement speed is greatly improved, and the measurement time of a single component can be completed within a few seconds. This method is of great significance in the field of free-form surface precision machining and manufacturing.

[0074] In some possible embodiments of the present invention, based on the modulation depth solution results and the phase solution results, the front surface of the object to be measured is reconstructed using a method based on predicted surface shape iteration, and the back surface of the object to be measured is reconstructed using a method based on beam tracing iterative reflection points.

[0075] Specifically, this embodiment provides an implementation method for reconstructing the front and back surfaces of the object to be measured. When selecting a reconstruction method, the shapes and characteristics of the front and back surfaces of the object to be measured are considered, and different reconstruction methods are used for reconstruction.

[0076] The three-dimensional reconstruction method of a double-layer transparent object proposed in the present invention is essentially a global iterative method based on free-form surface phase modeling. The phase and modulation of the front and rear surfaces are constructed by adopting a pattern reconstruction method, and the fitting parameters are used as optimization parameters to perform global nonlinear optimization iterations for the entire surface. The problems of phase confusion, order jump, and low demodulation efficiency can be solved at the same time. By designing an optimization method based on global free-form surface phase modeling, the phase decoupling of the front and rear surfaces can be achieved, and it has the characteristics of high robustness, accuracy, and rapid decoupling. The application of the present invention in phase deflectometry can realize the three-dimensional reconstruction of double-layer transparent objects. The high-precision, high-speed, and high-dynamic range double-layer lens deflectometer system has far-reaching significance in the field of precision free-form surface processing and detection.

[0077] In some specific embodiments of the present invention, Figure 7 As shown, the present invention provides a double-layer transparent object three-dimensional reconstruction device, which is applied to a transparent object deflectometer system, wherein the system comprises a display screen, an object to be measured, and a camera which are installed in sequence, wherein the object to be measured is a double-layer transparent object; the display screen is used to display a pre-generated dual-frequency phase-shifted initial fringe image, and project the dual-frequency phase-shifted initial fringe image onto the object to be measured, and the camera is used to capture a dual-frequency phase-shifted reflected fringe image formed by the dual-frequency phase-shifted initial fringe image being reflected by the front surface and the rear surface of the object to be measured, wherein the front surface and the rear surface respectively represent the surface of the object to be measured that contacts the projected light first and the surface of the object to be measured that contacts the projected light later; The device includes: A reflection fringe image acquisition module 71 is used to acquire a dual-frequency phase-shifted reflection fringe image formed by the dual-frequency phase-shifted initial fringe image being reflected by the object to be measured; A preprocessing module 72, used for preprocessing the dual-frequency phase-shifted reflected fringe image to obtain a first initial phase value of the front surface of the object to be measured and a second initial phase value of the rear surface of the object to be measured; A global optimization module 73 is used to perform global optimization on the modulation and phase of the front surface of the object to be measured and the modulation and phase of the rear surface of the object to be measured based on the first phase initial value, the second phase initial value and the preset first modulation initial value of the front surface of the object to be measured and the second modulation initial value of the rear surface of the object to be measured based on the pattern reconstruction method, so as to obtain the modulation solution result of the front surface and the phase solution result of the rear surface respectively; The reconstruction module 74 is used to perform three-dimensional reconstruction of the object to be measured based on the modulation degree solution result and the phase solution result.

[0078] The implementation principle and beneficial effects of the double-layer transparent object three-dimensional reconstruction device provided in the embodiment of the present invention are similar to the implementation principle and beneficial effects of the double-layer transparent object three-dimensional reconstruction method shown in the above embodiment. Please refer to the implementation principle and beneficial effects of the double-layer transparent object three-dimensional reconstruction method shown in the above embodiment, and no further details will be given here.

[0079] Figure 8 An example of a physical structure diagram of an electronic device is shown in FIG. Figure 8 As shown, the electronic device may include: a processor (processor) 810, a communication interface (Communications Interface) 820, a memory (memory) 830 and a communication bus 840, wherein the processor 810, the communication interface 820, and the memory 830 communicate with each other through the communication bus 840. The processor 810 can call the logic instructions in the memory 830 to execute a three-dimensional reconstruction method for a double-layer transparent object, which includes: obtaining a dual-frequency phase-shifted reflected fringe image formed by reflecting the dual-frequency phase-shifted initial fringe image from the object to be measured; preprocessing the dual-frequency phase-shifted reflected fringe image to obtain a first initial phase value of the front surface of the object to be measured and a second initial phase value of the rear surface of the object to be measured; based on the first initial phase value, the second initial phase value and the pre-set first initial modulation value of the front surface of the object to be measured and the second initial modulation value of the rear surface of the object to be measured, globally optimizing the modulation degree and phase of the front surface of the object to be measured and the modulation degree and phase of the rear surface based on the pattern reconstruction method, and obtaining the modulation degree solution results and phase solution results of the front surface and the rear surface respectively; based on the modulation degree solution result and the phase solution result, reconstructing the object to be measured in three dimensions.

[0080] In addition, the logic instructions in the above-mentioned memory 830 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0081] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the double-layer transparent object three-dimensional reconstruction method provided by the above-mentioned methods, the method including: obtaining a dual-frequency phase-shifted reflected fringe image formed by reflecting the dual-frequency phase-shifted initial fringe image from the object to be measured; preprocessing the dual-frequency phase-shifted reflected fringe image to obtain a first initial phase value of the front surface of the object to be measured and a second initial phase value of the rear surface of the object to be measured, respectively; based on the first initial phase value, the second initial phase value and the pre-set first initial modulation value of the front surface of the object to be measured and the second initial modulation value of the rear surface of the object to be measured, based on the pattern reconstruction method, globally optimize the modulation degree and phase of the front surface of the object to be measured and the modulation degree and phase of the rear surface, respectively obtain the modulation degree solution results and phase solution results of the front surface and the rear surface; based on the modulation degree solution result and the phase solution result, perform three-dimensional reconstruction of the object to be measured.

[0082] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the three-dimensional reconstruction method of a double-layer transparent object provided by the above-mentioned methods, the method comprising: obtaining a dual-frequency phase-shifted reflected fringe image formed by reflecting a dual-frequency phase-shifted initial fringe image from an object to be measured; preprocessing the dual-frequency phase-shifted reflected fringe image to obtain a first initial phase value of the front surface of the object to be measured and a second initial phase value of the rear surface of the object to be measured, respectively; based on the first initial phase value, the second initial phase value and the pre-set first initial modulation value of the front surface of the object to be measured and the second initial modulation value of the rear surface of the object to be measured, globally optimizing the modulation degree and phase of the front surface of the object to be measured and the modulation degree and phase of the rear surface based on a pattern reconstruction method, obtaining modulation degree solution results and phase solution results of the front surface and the rear surface, respectively; and reconstructing the object to be measured in three dimensions based on the modulation degree solution result and the phase solution result.

[0083] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0084] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for three-dimensional reconstruction of a double-layer transparent object, applied to a transparent object deflectometer system, characterized in that: The system comprises a display screen, an object to be tested, and a camera which are installed in sequence, wherein the object to be tested is a double-layer transparent object; the display screen is used to display a pre-generated dual-frequency phase-shifted initial fringe image, and project the dual-frequency phase-shifted initial fringe image onto the object to be tested, and the camera is used to capture a dual-frequency phase-shifted reflected fringe image formed by the dual-frequency phase-shifted initial fringe image being reflected by the front surface and the rear surface of the object to be tested, wherein the front surface and the rear surface respectively represent the surface of the object to be tested that contacts the projected light first and the surface of the object to be tested that contacts the projected light later; The double-layer transparent object three-dimensional reconstruction method comprises: Acquire a dual-frequency phase-shifted reflected fringe image formed by the dual-frequency phase-shifted initial fringe image reflected by the object to be measured; Preprocessing the dual-frequency phase-shifted reflected fringe image to obtain a first initial phase value of the front surface of the object to be measured and a second initial phase value of the rear surface of the object to be measured; Based on the first initial phase value, the second initial phase value, and the preset first initial modulation value of the front surface of the object to be measured and the second initial modulation value of the rear surface of the object to be measured, the modulation degree and phase of the front surface of the object to be measured and the modulation degree and phase of the rear surface of the object to be measured are globally optimized based on the pattern reconstruction method to obtain the modulation degree solution result and the phase solution result of the front surface and the rear surface of the object to be measured respectively; Based on the modulation degree solution result and the phase solution result, the object to be measured is reconstructed in three dimensions.

2. The method for three-dimensional reconstruction of a double-layer transparent object according to claim 1, characterized in that: Continuously capturing, by a camera, the reflected fringes of the dual-frequency phase-shifted initial fringe image reflected by the front surface and the rear surface of the object to be measured, to generate the dual-frequency phase-shifted reflected fringe image; The light intensity distribution of the reflected fringes captured by the camera for the nth time I n (x,y) is represented as: ， in, is the ambient background light, and are the modulation intensities of the front and rear surfaces, and represent the phase of the front and rear surfaces respectively, , n=0,1,2…N-1, n represents the phase shift of the display screen, N represents the total phase shift, and k represents the frequency ratio in the case of multi-frequency stripes.

3. The method for three-dimensional reconstruction of a double-layer transparent object according to claim 2, characterized in that: The step of globally optimizing the modulation degree and phase of the front surface and the modulation degree and phase of the rear surface of the double-layer transparent object to be measured specifically includes: The modulation degree of the front surface of the double-layer transparent object to be tested B f ( x,y ) and phase , modulation of the rear surface B r ( x,y ) and phase Set as initial iteration parameters; The initial iteration parameters are reconstructed by using the pattern reconstruction method. , , and Decompose and obtain the decomposition parameter J; set up Residual error, in i When 1, 2, 3, and 4 are taken respectively, Use , , and Indicates that the global optimization objective function is set : ， in, is the parameter representation of the modulation degree of the front surface of the object to be measured, is the parameter representation of the back surface modulation of the object to be measured, is the parameter representation of the phase of the front surface of the object to be measured, It is the parameter representation of the phase of the rear surface of the object to be measured; Based on the first initial phase value, the second initial phase value, and the preset first modulation index initial value of the front surface of the double-layer transparent object to be measured and the preset second modulation index initial value of the rear surface of the double-layer transparent object to be measured, the global optimization objective function is iteratively solved until a preset number of iterations is reached or a preset step size threshold is reached; Output the calculated front surface modulation , rear surface modulation , front surface phase and rear surface phase .

4. The method for three-dimensional reconstruction of a double-layer transparent object according to any one of claims 1 to 3, characterized in that: The step of preprocessing the dual-frequency phase-shifted reflection fringe image specifically includes: Performing fast Fourier transform on the dual-frequency phase-shifted reflected fringe image to generate a Fourier transform image; Filtering the Fourier transform image to obtain fringe information on the front and rear surfaces of the object to be measured; Calculating the truncated phases of the front and rear surfaces of the object to be measured based on the fringe information of the front and rear surfaces of the object to be measured; Calculating the phase order and the unwrapped phase of the front and rear surfaces of the object to be measured based on the truncated phases of the front and rear surfaces of the object to be measured; The unwrapped phase of the front surface of the object to be measured is used as a first phase initial value, and the unwrapped phase of the rear surface of the object to be measured is used as a second phase initial value.

5. The method for three-dimensional reconstruction of a double-layer transparent object according to claim 4, characterized in that: The step of filtering the Fourier transform image specifically includes: The logarithmic spectrum of the Fourier transform image is calculated using the following formula: ； in, Respectively represent the pixels in The coordinates of the direction; represents the Fourier transform image, Represents the result of taking the logarithm of the Fourier transform image; Obtaining the position coordinates of the central peak on the frequency spectrum plane formed by the logarithmic spectrum; Based on the position coordinates of the central peak, the stripe information on the front and rear surfaces of the object to be measured is separated.

6. The method for three-dimensional reconstruction of a double-layer transparent object according to claim 4, characterized in that: Based on the fringe information of the front and rear surfaces of the object to be measured, the truncated phases of the front and rear surfaces of the object to be measured are calculated using a four-step phase shift method.

7. The method for three-dimensional reconstruction of a double-layer transparent object according to claim 4, characterized in that: The step of calculating the phase order and the unfolded phase of the front and rear surfaces of the object to be measured based on the truncated phase of the front and rear surfaces of the object to be measured specifically includes: Calculating the phase orders of the front and rear surfaces of the object to be measured based on the truncated phases of the front and rear surfaces of the object to be measured; Based on the truncated phase and phase order of the front and rear surfaces of the object to be measured, the time phase unwrapping technology of the dual-frequency fringes is adopted to calculate the unwrapped phase of the front and rear surfaces of the object to be measured.

8. The method for 3D reconstruction of a double-layer transparent object according to claim 1, characterized in that: Based on the modulation degree solution results and the phase solution results, the front surface of the object to be measured is reconstructed using a method based on predicted surface iteration, and the back surface of the object to be measured is reconstructed using a method based on beam tracing iterative reflection points.

9. A double-layer transparent object 3D reconstruction device, applied to a transparent object deflectometer system, characterized in that: The system comprises a display screen, an object to be tested, and a camera which are installed in sequence, wherein the object to be tested is a double-layer transparent object; the display screen is used to display a pre-generated dual-frequency phase-shifted initial fringe image, and project the dual-frequency phase-shifted initial fringe image onto the object to be tested, and the camera is used to capture a dual-frequency phase-shifted reflected fringe image formed by the dual-frequency phase-shifted initial fringe image being reflected by the front surface and the rear surface of the object to be tested, wherein the front surface and the rear surface respectively represent the surface of the object to be tested that contacts the projected light first and the surface of the object to be tested that contacts the projected light later; The double-layer transparent object three-dimensional reconstruction device comprises: A reflection fringe image acquisition module, used for acquiring a dual-frequency phase-shifted reflection fringe image formed by the dual-frequency phase-shifted initial fringe image being reflected by the object to be measured; A preprocessing module, used for preprocessing the dual-frequency phase-shifted reflected fringe image to obtain a first initial phase value of the front surface of the object to be measured and a second initial phase value of the rear surface of the object to be measured; A global optimization module, for performing global optimization on the modulation and phase of the front surface of the object to be measured and the modulation and phase of the rear surface of the object to be measured based on the first phase initial value, the second phase initial value and the preset first modulation initial value of the front surface of the object to be measured and the second modulation initial value of the rear surface of the object to be measured, based on the pattern reconstruction method, to obtain modulation solution results and phase solution results of the front surface and the rear surface respectively; A reconstruction module is used to perform three-dimensional reconstruction of the object to be measured based on the modulation solution result and the phase solution result.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the method for three-dimensional reconstruction of a double-layer transparent object as described in any one of claims 1 to 8 is implemented.

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