A polarization measurement method for three-dimensional distribution of window deformation and stress

Abstract

The application discloses a polarization measurement method for three-dimensional distribution of window deformation and stress, comprising the following steps: S1, projecting a polarized light beam with geometric texture to the window, and collecting polarization information and geometric texture information of the transmitted light beam before and after the window is pressurized; S2, respectively reconstructing the three-dimensional shape of the window containing deformation according to the polarization information and the geometric texture information; S3, fusing the window three-dimensional shape result information obtained according to the polarization information and the geometric texture information to obtain the fused three-dimensional distribution of the window deformation. The application simultaneously analyzes from two angles of the polarization information and the geometric texture information, can improve the robustness and the measurement accuracy of the data, realizes the measurement of the three-dimensional distribution of the window deformation, and can non-contact, non-damage and real-time measure the three-dimensional distribution of the window deformation. When the method is applied to a submarine, it has important significance for normal use and safety guarantee of the submarine.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical measurement, in particular to a polarization measurement method for three-dimensional distribution of window deformation and stress. BACKGROUND

[0002] Deep-sea equipment is a national interest weapon for deep-sea resource development and scientific exploration, and the full-sea depth (about 11000 meters) challenges the technical limit. The submersible relies on the sealed cabin composed of metal pressure-resistant shell and large-thickness transparent optical window to resist hydrostatic pressure, and the window is also the main way for the deep-sea manned submersible to perceive the outside world. With the increase of water depth, the water pressure on the window increases, which will cause the window to deform, such as distortion, expansion, and change the space between the window and the window seat, affecting the optical and sealing performance of the submersible. The window under pressure may have stress concentration, and may break at some weak or defective structures, affecting the strength and stability of the submersible structure. In summary, detecting the deformation and stress distribution of the window can ensure the safety and reliability of the submersible.

[0003] In the current stress detection method: when the simulation conditions set by the finite element method are different from the real situation, there is a difference between the results and the real situation; the strain gauge must be attached to the object to be measured, and only single-direction and small-area strain measurement can be achieved; the speckle method needs to spray materials on the window surface; the digital holography method has high requirements for ambient light and narrow measurement range. In summary, there is currently a lack of simple, reliable and high-precision measurement method for three-dimensional distribution of deformation and stress of the window under pressure.

[0004] The disclosure of the above background art content is only used to assist in understanding the inventive concept and technical solutions of the present application, and it does not necessarily belong to the prior art of the present application. In the absence of explicit evidence that the above-mentioned content has been disclosed in the prior art of the present application, the above background technology should not be used to evaluate the novelty and inventiveness of the present application. SUMMARY

[0005] The purpose of the present application is to provide a polarization measurement method for three-dimensional distribution of window deformation and stress, which can non-contact, non-destructive and real-time measure the three-dimensional distribution of window deformation and stress, and has good simplicity, robustness and high measurement accuracy.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] The application discloses a polarization measurement method for three-dimensional distribution of window deformation and stress, which comprises the following steps: S1, projecting a polarized light beam with geometric texture to the window, and collecting polarization information and geometric texture information of the transmitted light beam before and after the window is pressurized; S2, reconstructing the three-dimensional shape of the window containing deformation according to the polarization information and the geometric texture information; and S3, fusing the three-dimensional shape information of the window obtained according to the polarization information and the geometric texture information to obtain the fused three-dimensional distribution of the window deformation.

[0008] In some embodiments of the application, the step S2 of reconstructing the three-dimensional shape of the window according to the polarization information comprises the following steps: calculating the degree of polarization by the Stokes formula according to the polarization information, calculating the zenith angle according to the Fresnel refraction law by using the degree of polarization and the refractive index of the window, and calculating the polarization azimuth angle to obtain the surface azimuth angle; determining the normal vector of the window surface according to the zenith angle and the surface azimuth angle; and obtaining the three-dimensional shape of the window by global curved surface integration according to the gradient data in the normal vector.

[0009] In some embodiments of the application, the step S2 of reconstructing the three-dimensional shape of the window according to the geometric texture comprises the following steps: analyzing the geometric information in the grid pattern, extracting the intersection points and bending points of the grid by image processing of edge detection and corner detection, calculating the displacement and curvature information of the window surface at the intersection points and bending points, constructing the three-dimensional point cloud by using the geometric relationship between the camera and the window and the feature point matching relationship, and obtaining the three-dimensional shape of the window by Poisson reconstruction.

[0010] In some embodiments of the application, the step S3 of performing weighted average on the relatively rough three-dimensional shape reconstructed according to the geometric texture information and the three-dimensional shape with pixel-level precision reconstructed according to the polarization information.

[0011] In some embodiments of the application, the method further comprises the following step: S4, determining the Stokes vector information of the incident light beam and the transmitted light beam according to the polarization information, further obtaining the Mueller matrix image of the window, taking the fused three-dimensional distribution of the window deformation as a condition, obtaining the one-dimensional equivalent stress distribution of the window from the physical information contained in the Mueller matrix by characteristic decoupling, analyzing the stress distribution of the window layer by layer based on the one-dimensional equivalent stress distribution by using the layer-by-layer analysis mode, obtaining the two-dimensional stress distribution image corresponding to each layer, and combining a plurality of two-dimensional stress distribution images to realize the measurement of the three-dimensional stress distribution of the window.

[0012] In some embodiments of the present application, in step S4, the polarization parameter feature representing the phase delay property of the window is extracted from the Mueller matrix image by a polarization feature parameter extraction algorithm, and the fused window deformation three-dimensional distribution and the phase delay are taken as known data according to the relationship that the phase delay is the product of the window axial length and the refractive index, and the refractive index distribution information is separated out, and according to the birefringence effect generated by the window under the action of the unidirectional force and the linear relationship between the change of the refractive index and the stress size, the one-dimensional equivalent stress distribution of the window is calculated.

[0013] In some embodiments of the present application, a tomographic model of the optical polarization properties of the window is established, the polarization effect of the window with a large thickness is equivalent to the superposition effect of a plurality of small-thickness phase delay devices, the corresponding refractive index and stress distribution are calculated according to the relationship between the Mueller matrix M and the equivalent multi-layer phase delay device, and then the obtained multiple two-dimensional stress distribution images are sequentially inserted into a three-dimensional space along the vertical direction, so as to obtain the three-dimensional stress distribution of the window.

[0014] In some embodiments of the present application, the polarization illumination system for projecting the polarized light beam comprises a parallel light source, a linear polarizer and a rotatable first quarter-wave plate, the parallel light source emits a parallel light beam and sequentially passes through the linear polarizer and the rotatable quarter-wave plate to obtain incident light with different polarization states, and the light beam is perpendicularly incident on the window and is emitted after penetrating the window.

[0015] In some embodiments of the present application, the polarization imaging system for collecting the transmitted light beam comprises a non-polarizing beam splitter prism, a rotatable second quarter-wave plate and two split focal plane polarization cameras, the non-polarizing beam splitter prism splits the light into two beams at a ratio of 50:50, the transmitted light of the non-polarizing beam splitter prism passes through the second quarter-wave plate and is collected by one split focal plane polarization camera, and the reflected light is directly collected by the other split focal plane polarization camera.

[0016] In some embodiments of the present application, the geometric texture is formed by a transparent grid film arranged between the window and the projection light source, and the transparent grid film is located in front of the polarization device.

[0017] The present application has the following beneficial effects:

[0018] The present application projects the polarized light beam with geometric texture to the window by means of active illumination, polarization imaging and geometric texture, simultaneously analyzes from two angles of polarization information and geometric texture information, can improve the robustness and measurement accuracy of data, realizes the measurement of the three-dimensional distribution of the window deformation, and can non-contact, non-destructively and in real time measure the three-dimensional distribution of the window deformation. Compared with the existing method, the method of the present application has good reliability, high measurement accuracy and low requirement on the measurement conditions. When the method is applied to a submarine, it has important significance for the normal use and safety guarantee of the submarine.

[0019] In some embodiments of the present invention, the embodiments of the present invention utilize the physical information contained in the Mueller matrix through feature decoupling, and use the deformation of the window as a condition to separate the one-dimensional equivalent stress distribution, and then use the tomography method to analyze the stress distribution of the window layer by layer, and merge multiple two-dimensional images to achieve the measurement of the three-dimensional distribution of window stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the background technology, the drawings required for use in the embodiments of the present invention or the background technology will be described below.

[0021] Figure 1 Flowchart of the steps for measuring the three-dimensional distribution of window deformation in an embodiment of the present invention;

[0022] Figure 2 Flowchart of the steps for measuring window deformation and three-dimensional stress distribution in an embodiment of the present invention;

[0023] Figure 3 Schematic diagram of the optical path structure of an embodiment of the present invention;

[0024] Figure 4 Schematic diagram of the three-dimensional distribution of deformation of the measurement window in an embodiment of the present invention;

[0025] Figure 5 Schematic diagram of the three-dimensional stress distribution of the measurement window in an embodiment of the present invention;

[0026] The reference numerals are as follows:

[0027] 101-parallel light source, 102-linear polarizer, 103-first quarter wave plate;

[0028] 201-window seat;

[0029] 301 - non-polarizing beam splitting prism, 302 - second quarter-wave plate, 303 - first focal plane polarization camera, 304 - second focal plane polarization camera, 305 - telecentric lens. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following Figures 1 to 5 The present invention is described in further detail.

[0031] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0032] The terms "first" and "second" and the like in the specification, claims and drawings of the present application are used to distinguish different objects, and are not used to describe a particular order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or units inherent to the process, method, product or device.

[0033] The embodiment of the present application provides a polarization measurement method for window deformation and stress three-dimensional distribution. When applied to a submersible, the method can obtain a Mueller matrix image of the window of the submersible in a water pressure environment in real time, non-contact and non-destructive, and realize measurement of the three-dimensional distribution of the deformation and stress of the window under pressure.

[0034] The method in the embodiment of the present application belongs to an optical measurement method, and the optical measurement method has the characteristics of non-contact, low damage and high resolution. The polarization state of light is very sensitive to microstructures of subwavelength level, and the expression is simple, can be compatible with other non-polarized optical instruments, and has application potential for in-situ detection underwater. The Mueller matrix of the sample obtained by polarization measurement further contains rich microstructure information of the measured window. The application advantages of the polarization light technology lay a theoretical foundation for integrating the measurement sensor based on the polarization method into a field underwater device for window stress and strain measurement, and the development of the polarization measurement method is an important way to solve the window deformation and stress measurement problem.

[0035] As shown in Figure 1 and Figure 4 Based on the principles of polarization transmission imaging and geometric texture (geometric clues), the polarization measurement method for window deformation and stress three-dimensional distribution provided by the embodiment of the present application includes the following steps:

[0036] S1, projecting a polarization light beam with geometric texture to the window, and collecting polarization information and geometric texture information of the transmission light beam before and after the window is pressurized.

[0037] The principle of the polarization transmission imaging mode is as shown in Figure 4As shown in part (a), the modulated incident polarized light enters the window perpendicularly. Before the window is pressurized, it exhibits relatively uniform optical properties, and the direction of the transmitted polarized light is consistent. After the window is pressurized, it deforms, the propagation path of the light changes, and the state of the transmitted polarized light also changes accordingly.

[0038] S2. Reconstruct the three-dimensional shape of the deformed window according to the polarization information and the geometric texture information. Schematically, the three-dimensional shape of the window is reconstructed according to the polarization information, as follows:

[0039] The Stokes vector can be used to describe the state of any polarized light, including the degree of polarization. The Stokes vector S is a column vector containing 4 elements, notated as:

[0040]

[0041] Among them, S0, S1, S2, S3 are the four elements in the Stokes vector S, I p , I s , I 45° and I -45° Represents the intensity of the x component, y component, 45° direction and -45° direction linear polarization light, I L and I R Indicates the intensity of left-handed and right-handed circularly polarized light. When light passes through a device or system, the Stokes vector S of the incident light in and the Stokes vector S of the outgoing light out It can be related to a 4×4 matrix M that describes the polarization properties of the medium. The relationship is as follows:

[0042] S out =M·S in (2)

[0043] The expansion of formula (2) is as follows:

[0044]

[0045] The matrix M is called the Mueller matrix. It is an inherent property of the sample medium and depends solely on the properties of the medium itself, independent of the polarization state of the incident and outgoing light. By analyzing the physical information contained in the Mueller matrix, we can deduce the microstructural changes occurring within the material.

[0046] The above method obtains the Mueller matrix image. According to formula (3), more than 4 sets of S are required. in and the corresponding S outAs a natural extension of this method, if light of a certain polarization state is sensitive to the deformation and stress of the window, we can also use light (beam) of a specific polarization to illuminate the window and measure the Stokes vector after it passes through the window. That is, only the Stokes vector S of the incident light of a specific polarization state is needed. in The Stokes vector S of the emitted light corresponding to the measurement out , without calculating the Mueller matrix, the polarization information of the window used to measure the three-dimensional distribution of window deformation and stress can be obtained, thereby simplifying the test process and shortening the sampling time.

[0047] In a preferred embodiment, reconstructing the three-dimensional shape of the window based on polarization information includes: analyzing the polarization information of the parallel light beam before and after passing through the pressurized window, calculating the degree of polarization DoP according to the above Stokes formula, the refractive index n is known, and the zenith angle θ is derived according to the Fresnel refraction law, and the polarization azimuth AoP is calculated to obtain the surface azimuth Ψ. The calculation steps are shown in formulas (4)-(6):

[0048]

[0049]

[0050]

[0051] The normal vector of the window surface can be expressed by the zenith angle θ and the surface azimuth angle Ψ as: n = (tanθcosΨ, tanθsinΨ, 1); then, based on the gradient data in the normal vector, the three-dimensional shape of the window can be obtained through global surface integral.

[0052] In a preferred embodiment, the geometric texture includes a grid pattern, and the principle of the geometric texture information method is as follows: Figure 4 As shown in part (b) of the figure, a transparent grid is placed between a parallel light source and a linear polarizer. Since the transparent grid is located before the polarizer (linear polarizer and quarter-wave plate), it does not affect the modulation of the polarization state during the aforementioned polarization imaging process. After the parallel light beam passes through the grid, it carries the grid texture, passes through the polarizer, and is projected onto the lower end face of the window and emitted from the upper end face of the window. The compressive deformation of the window changes the propagation path of the light, and the emitted grid texture has a specific distribution depending on the degree of deformation of the window.

[0053] Illustratively, after the distorted grid pattern is captured by the camera, the three-dimensional shape of the window is reconstructed according to the geometric texture, including: analyzing the geometric information in the pattern, extracting the intersection and bending points of the grid by edge detection and corner detection image processing techniques, calculating the displacement and curvature information of the window surface at these points, constructing a three-dimensional point cloud using the geometric relationship between the camera and the window and the feature point matching relationship, and obtaining the three-dimensional shape of the window by Poisson reconstruction.

[0054] S3, fusing the window three-dimensional shape result information obtained according to the polarization information and the geometric texture information to obtain a fused window three-dimensional distribution.

[0055] The geometric texture method has strong environmental interference resistance, and thus a preliminary overall three-dimensional shape is calculated; the polarization transmission imaging method has pixel-level precision; preferably, the three-dimensional shape calculated according to the geometric texture information is weighted and averaged with the three-dimensional shape calculated according to the polarization information, which has pixel-level precision, to enrich the local texture details of the shape. Further, the window three-dimensional distribution of the stress is obtained as shown in part (c) of the method. Figure 4

[0056] As shown in Figure 2 and Figure 5 In some preferred embodiments, a polarization measurement method for the three-dimensional distribution of the stress of the window is also proposed based on polarization decoupling and tomography, which further includes step S4: determining the Stokes vector information of the incident light beam and the transmitted light beam according to the polarization information, further obtaining the Mueller matrix image of the window, using the fused window three-dimensional distribution as a condition, obtaining the one-dimensional equivalent stress distribution of the window from the physical information contained in the Mueller matrix by characteristic decoupling, and then using a layer-by-layer analysis method to analyze the stress distribution of the window based on the one-dimensional equivalent stress distribution, to obtain a two-dimensional stress distribution image corresponding to each layer, and then combining multiple two-dimensional stress distribution images to realize the measurement of the three-dimensional distribution of the stress of the window.

[0057] Illustratively, the principle of the measurement method of the three-dimensional distribution of the stress of the window is shown in Figure 5 Using the known incident Stokes vector information and the measured exit Stokes vector information by the polarization camera, the 4x4 Mueller matrix image of the window can be calculated according to the above Mueller matrix calculation formula. The deformation changes the propagation distance of the light, and the stress changes the refractive index of the medium in the sample, and the physical information exhibited by the Mueller matrix is the combined effect of the phase delay, depolarization, dichroism, optical rotation, symmetry, etc. caused by the window under pressure, and the deformation and stress information are also contained therein.

[0058] ​Preferably, the polarized parameter feature representing the phase delay property of the window can be extracted from the Mueller matrix image by a polarized parameter feature extraction algorithm, the polarized parameter feature extraction algorithm includes a Mueller matrix transformation (MMT) algorithm and a Mueller matrix polar decomposition (MMPD) algorithm, and the polarized parameter feature includes a delta parameter and an anisotropy b parameter, etc.; the phase delay is the product of the axial length of the window and the refractive index, and the phase delay and the fused three-dimensional deformation result of the window in mode (1) are taken as known data to separate the refractive index distribution information; according to the photoelasticity theory, the window generates a birefringence effect under the action of a single force, and the change of the refractive index is linearly related to the stress size, so the one-dimensional equivalent stress distribution of the window can be calculated.

[0059] Subsequently, the measurement of the three-dimensional distribution of the stress is realized by layer-by-layer analysis: the window is pressed on one side, and the stress is distributed in layers in the window with a large thickness; a tomographic model of the optical polarization property of the window is established, the polarization effect of the window with a large thickness is equivalent to the superposition of a plurality of small-thickness phase delay devices (the more the layers d are, the higher the spatial resolution is), and the relationship between the sample Mueller matrix M and the equivalent multi-layer phase delay device M LR is shown in formula (7), and the corresponding refractive index and stress distribution are calculated from the thickness and the phase delay of each layer, the obtained plurality of two-dimensional stress distribution images are sequentially inserted into a three-dimensional space along the vertical direction, and thus the three-dimensional distribution of the stress of the window is obtained.

[0060] M=M LRd ·...M LR4 ·M LR3 ·M LR2 ·M LR1 (7)

[0061] Illustratively, the optical path for measuring the three-dimensional distribution of the deformation and the stress of the window of the present application is as shown in Figure 3As shown, the polarized illumination system for projecting the polarized light beam is composed of a parallel light source 101, a linear polarizer 102 and a first quarter-wave plate 103, the parallel light source 101 emits a parallel light beam and sequentially passes through the linear polarizer 102 and the rotatable first quarter-wave plate 103 to obtain incident light with different polarization states. Subsequently, the light beam is perpendicularly incident on the sample, i.e., the window, and is emitted after penetrating the window. The window is fixed on the window seat 201, and the bottom of the window is pressurized by the pressurizing device. The incident light with the same polarization state passes through the window to obtain the outgoing light with the polarization state changing with the physical properties inside the window. The polarized imaging system for collecting the projected light beam includes a non-polarized beam-splitting prism 301, a rotatable second quarter-wave plate 302 and two focal-plane polarized cameras (including a first focal-plane polarized camera 303 and a second focal-plane polarized camera 304), the non-polarized beam-splitting prism 302 splits the light into two beams at a ratio of 50:50, the transmitted light passes through the second quarter-wave plate 302 and is collected by one focal-plane polarized camera, and the reflected light is directly collected by the other focal-plane polarized camera 2; illustratively, the transmitted light is collected by the first focal-plane polarized camera 303, and the reflected light is collected by the second focal-plane polarized camera 304; the polarized images captured by the cameras are recorded, and the measurement of the three-dimensional distribution of the window deformation and stress can be realized through image processing and analysis, feature parameter extraction, statistical analysis and the like. Preferably, the polarized imaging system further includes a telecentric lens 305 for receiving the outgoing parallel light; in the application examples, the first quarter-wave plate 103 and the second quarter-wave plate 302 can use zero-order quarter-wave plates.

[0062] Preferably, the geometric texture is formed by a transparent grid film arranged between the window and the projection light source, and the transparent grid film is located before the polarized device.

[0063] Since there are various methods for measuring the Mueller matrix of a sample, the above merely describes a typical Mueller matrix measurement method, and the present application is not limited to the above method.

[0064] In summary, the embodiments of the present application have the following characteristics:

[0065] (1) For the measurement of the three-dimensional distribution of the window deformation. Since the window is made of transparent materials such as organic glass, the surface lacks contrast, it is difficult to accurately identify the edge and surface features in the imaging process, and the internal information is difficult to directly capture or observe, and the reflection of the surface and the surrounding environment will also interfere with the measurement results of the three-dimensional structure. In view of the above problems, the embodiments of the present application project the polarized light beam with geometric texture to the window by combining polarized transmission imaging and geometric texture, and simultaneously analyze from the two angles of polarization information and geometric information, which can improve the robustness and measurement accuracy of the data and realize the measurement of the three-dimensional distribution of the window deformation.

[0066] (2) For the measurement of the three-dimensional distribution of window stress. After the window is stressed, a series of complex changes occur in the internal microstructure, and the polarization information is the result of the joint action of many physical effects. The internal stress of a large-thickness window is no longer a simple linear relationship with its macroscopic deformation, and the stress presents a three-dimensional distribution in space. In view of the above problems, the embodiment of the application separates out a one-dimensional equivalent stress distribution by using the physical information contained in the Mueller matrix and taking the deformation of the window as a condition in a feature decoupling manner, and then analyzes the stress distribution of the window layer by layer using a tomographic method, combines multiple two-dimensional images, and realizes the measurement of the three-dimensional distribution of the window stress.

[0067] The embodiment of the application measures the three-dimensional distribution of the deformation and stress of the window after being stressed in a non-contact, non-destructive and real-time manner by active illumination and polarization imaging, has good robustness and high measurement accuracy. When applied to a submarine, it has important significance for the normal use and safety protection of the submarine.

[0068] The above is a further detailed description of the application in combination with specific / preferred embodiments, and the specific implementation of the application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the application belongs, some alternatives or modifications can be made to the described embodiments without departing from the concept of the application, and these alternatives or modifications should be regarded as falling within the protection scope of the application.

Claims

1. A polarization measurement method for window deformation and three-dimensional stress distribution, characterized in that: The steps include: S1, projecting a polarized light beam with a geometric texture onto the window, and collecting polarization information and geometric texture information of the transmitted light beam before and after the window is pressurized; S2. Reconstructing the three-dimensional shape of the deformed window according to the polarization information and the geometric texture information; wherein, reconstructing the three-dimensional shape of the window according to the polarization information comprises: calculating the degree of polarization according to the Stokes formula according to the polarization information, calculating the zenith angle according to the Fresnel refraction law using the degree of polarization and the refractive index of the window, and calculating the polarization azimuth to obtain the surface azimuth; determining the normal vector of the window surface according to the zenith angle and the surface azimuth; obtaining the three-dimensional shape of the window by global surface integral based on the gradient data in the normal vector; the geometric texture comprises a grid pattern, and reconstructing the three-dimensional shape of the window according to the geometric texture comprises: parsing the geometric information in the grid pattern, extracting the intersection points and bending points of the grid through edge detection and corner detection image processing, calculating the displacement and curvature information of the window surface at the intersection points and bending points, constructing a three-dimensional point cloud by using the geometric relationship between the camera and the window and the feature point matching relationship, and obtaining the three-dimensional shape of the window by Poisson reconstruction; S3. Fusing the three-dimensional shape result information of the window reconstructed according to the polarization information and the geometric texture information to obtain a fused three-dimensional distribution of window deformation.

2. The method according to claim 1, wherein In step S3, a weighted average is performed on the coarser three-dimensional shape reconstructed based on the geometric texture information and the three-dimensional shape with pixel-level accuracy reconstructed based on the polarization information.

3. The method according to claim 1, wherein The following steps are also included: S4. Determine the Stokes vector information of the incident light beam and the transmitted light beam based on the polarization information, and further obtain the Mueller matrix image of the window. Using the fused three-dimensional distribution of the window deformation as a condition, obtain the one-dimensional equivalent stress distribution of the window from the physical information contained in the Mueller matrix through feature decoupling. Then, use a layer-by-layer analysis method to analyze the stress distribution of the window layer by layer based on the one-dimensional equivalent stress distribution to obtain the two-dimensional stress distribution image of each layer. Then, merge multiple two-dimensional stress distribution images to achieve the measurement of the three-dimensional stress distribution of the window.

4. The method according to claim 3, wherein In step S4, polarization parameter features characterizing the phase delay properties of the window are extracted from the Mueller matrix image through a polarization feature parameter extraction algorithm. According to the relationship that the phase delay is the product of the axial length of the window and the refractive index, the fused three-dimensional distribution of the window deformation and the phase delay are used as known data to separate the refractive index distribution information. According to the birefringence effect generated by the unidirectional force on the window and the linear relationship between the change in the refractive index and the stress magnitude, the one-dimensional equivalent stress distribution of the window is calculated.

5. The method according to claim 3, wherein In step S4, a tomographic model of the optical polarization properties of the window is established, and the polarization effect of the thick window is equivalent to the superposition of multiple thin phase delay devices. M The relationship between the window and the equivalent multi-layer phase delay device is calculated, and the corresponding refractive index and stress distribution are calculated according to the thickness and phase delay of each layer. Then, the multiple two-dimensional stress distribution images obtained are inserted into the three-dimensional space in sequence along the vertical direction to obtain the three-dimensional stress distribution of the window.

6. The method according to any one of claims 1 to 5, characterized in that The polarization illumination system for projecting a polarized light beam includes a parallel light source, a linear polarizer, and a rotatable first quarter-wave plate. The parallel light source emits a parallel light beam and passes through the linear polarizer and the rotatable quarter-wave plate in sequence to obtain incident light with different polarization states. The light beam is vertically incident on the window and is emitted after passing through the window.

7. The method according to any one of claims 1 to 5, characterized in that The polarization imaging system for collecting transmitted light beams includes a non-polarizing beam splitting prism, a rotatable second quarter-wave plate, and two focal plane polarization cameras. The non-polarizing beam splitting prism splits light into two beams in a 50:50 ratio. The transmitted light of the non-polarizing beam splitting prism passes through the second quarter-wave plate and is directly collected by one focal plane polarization camera, while the reflected light is directly collected by the other focal plane polarization camera.

8. The method according to any one of claims 1 to 5, characterized in that The geometric texture is formed by a transparent grid film arranged between the window and the projection light source, and the transparent grid film is located in front of the polarizing device.

Images