Transparent object stress detection device and method based on full Stokes polarization metasurface

Abstract

The invention discloses a transparent object stress detection device and method based on a full Stokes polarization metasurface, and mainly solves the problems that an existing detection method is easy to introduce system errors, inaccurate in measurement result, poor in dynamic response and the like. The device comprises a light source, a polarizer, a metasurface polarization detecting element, a detector and a processing module, and the polarizer, the metasurface polarization detecting element and the detector are sequentially arranged along an emergent light path of the light source; the polarizer is a linear polarizer, and the included angle between the polarization direction and the optical axis of emergent light of the light source is 0 degree; the metasurface polarization detection element has a periodic structure, and the linearly polarized light is separated into four beams of diffracted light with different polarization states by the metasurface polarization detection element after passing through a transparent object to be detected; the detector is used for receiving the four beams of diffracted light and generating a corresponding light intensity graph; the processing module is connected with the detector and used for receiving the light intensity graph and calculating and outputting the stress distribution condition of the transparent object to be detected, and the device is greatly improved in detection precision, efficiency and integration level.

Description

Technical Field

[0001] This invention relates to a stress detection device and method for transparent objects, and particularly to a stress detection device and method for transparent objects based on a fully Stokes polarized metasurface. Background Technology

[0002] Transparent components are widely used in optical systems. However, due to limitations in manufacturing processes, these components generally suffer from residual stress, which can easily lead to shrinkage, deformation, warping, and even cracking during use. This not only alters the surface morphology and degrades the optical performance of the transparent components but also directly affects the product's lifespan and operational safety. Therefore, conducting stress measurements on transparent components is crucial for ensuring their structural strength and optical performance.

[0003] Currently, stress measurement methods for transparent components are mainly divided into two categories: mechanical methods and optical detection methods. Mechanical methods are indirect measurement techniques and can cause irreversible damage to the component under test. Traditional optical detection methods require rotating analyzers and quarter-wave plates to obtain polarization information, making real-time dynamic monitoring of stress difficult. To overcome this limitation, researchers have proposed using the amplitude-splitting method to simultaneously acquire polarization data in different directions. However, this method requires multiple photoelectric sensors, which can easily lead to asynchronous polarization image acquisition and poor image matching, severely affecting measurement accuracy.

[0004] To effectively address the aforementioned technical challenges, a metasurface-based stress detection solution has emerged. Metasurfaces, composed of subwavelength-scale nanoscale arrays, enable precise local manipulation of the phase, amplitude, and polarization state of incident light. Leveraging their superior light field manipulation capabilities and flexible structural design, metasurfaces can replace traditional optical components such as lenses, gratings, and beam splitters, significantly reducing device size. This aligns perfectly with the current trend towards miniaturization and integration in optical platforms, demonstrating immense application potential in stress detection. Crucially, metasurfaces can planarly integrate the three core functions of "spectral splitting—polarization analysis—imaging" onto a single subwavelength structure. This significantly reduces system size and assembly complexity, and, thanks to their parallel polarization sampling capabilities, achieves a breakthrough in acquiring complete polarization information in a single exposure. This technological innovation represents a leap forward in detection accuracy, speed, and system integration, opening up a completely new technical path for online stress monitoring of transparent components.

[0005] Currently, various methods for stress detection have been proposed in existing patents:

[0006] Chinese invention patent CN111811718A discloses a stress detection device for transparent objects based on a micro-polarizer array. This device includes a light source, a homogenizing plate, a polarizer, a quarter-wave plate, a micro-polarizer array, and a light intensity detector arranged sequentially. The quarter-wave plate is positioned above the sample under test. Linearly polarized light emitted from the polarizer is converted into circularly polarized light after passing through the quarter-wave plate. This circularly polarized light is then decomposed into two beams of polarized light with mutually perpendicular polarization directions after passing through the sample. These beams then pass through the micro-polarizer array and finally reach the photosensitive surface of the light intensity detector. The light intensity detector acquires image information, which is then processed by an image processing element to calculate the stress value of the entire area of ​​the sample under test. However, this detection device requires multiple discrete components such as a polarizer, a quarter-wave plate, and a micro-polarizer array, resulting in significant light energy loss. Alignment errors between the micro-polarizer array pixels and the intensity detector pixels, as well as insufficient polarization extinction ratio of the micro-polarizer array, easily introduce systematic errors. Relying on the fixed polarization direction of the micro-polarizer array makes it difficult to flexibly cover all Stokes-required polarization states, such as horizontal linear polarization, linear polarization at specific angles, and left / right elliptic polarization, thus limiting parameter inversion accuracy. Furthermore, the stacking of multiple discrete components leads to system redundancy and high assembly complexity. Simultaneously, the array manufacturing and calibration costs of this detection device are high, its integration is low, and its miniaturization potential is insufficient.

[0007] For example, Chinese invention patent CN117589348A proposes a photoelastic stress measurement system and method based on a polarization grating. This stress measurement system, along the optical path, includes a light source, a polarizer, the photoelastic sample to be measured, and a polarization grating. The light emitted from the light source is converted into linearly polarized light by the polarizer. The transmitted portion passes through the photoelastic sample, where the light vector is split into two components along the two principal stress directions. The polarization grating causes the diffraction of the incident linearly polarized light to be distributed at the ±1st and 0th orders, thereby achieving the measurement of the stress in the photoelastic sample. However, this stress measurement system uses a photoelastic stress model and a liquid crystal polarization grating to measure the stress of anisotropic materials, making monolithic integration impossible and limiting its miniaturization potential. Furthermore, the diffraction is concentrated only at the ±1st and 0th orders, with residual i-polarized stray light at the 0th order. Although the ±1st order is circularly polarized, the polarization state coverage is incomplete, making it difficult to directly invert the full Stokes parameters. The phase delay is easily coupled with the principal stress direction angle, leading to inaccurate measurement results.

[0008] For example, Chinese invention patent CN118150019A proposes a method for measuring residual stress based on metasurfaces. The steps include: first, calculating the parameters and arrangement of the supercells of the metasurface; then, obtaining the light intensity under four different angles of polarization using an optical system for measuring stress birefringence; next, determining the phase delay and fast axis azimuth of a single point on the sample using a four-step phase-shifting method; then, calculating the residual stress at that point on the sample; and finally, adding a two-dimensional motor to the sample stage to achieve stress measurement across the entire plane of the sample. However, this stress measurement method requires a four-step phase-shifting method combined with two-dimensional motor scanning, which is a time-division point-by-point measurement, making it impossible to obtain complete polarization information in a single exposure, thus failing to meet the requirements of online real-time monitoring and exhibiting poor dynamic response. Furthermore, although this stress measurement method uses a metasurface, it does not achieve parallel sampling of all Stokes polarizations; simultaneously, it relies on two-dimensional motor movement, and mechanical motion easily introduces positioning errors. Summary of the Invention

[0009] The purpose of this invention is to provide a stress detection device and method for transparent objects based on a fully Stokes polarized metasurface, mainly to solve the technical problems of existing stress detection methods such as easy introduction of systematic errors, inaccurate measurement results, and poor dynamic response.

[0010] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0011] A stress detection device for transparent objects based on a fully Stokes polarized metasurface, characterized by:

[0012] It includes a light source, a polarizer, a metasurface polarization analyzer, a detector, and a processing module, wherein the polarizer, the metasurface polarization analyzer, and the detector are arranged sequentially along the outgoing light path of the light source.

[0013] The polarizer is a linear polarizer with a polarization direction that makes a 0-degree angle with the optical axis of the light emitted from the light source, and is used to convert the emitted light into linearly polarized light. The metasurface polarizer has a periodic structure. During detection, the transparent object to be tested is placed coaxially between the polarizer and the metasurface polarizer. After passing through the transparent object to be tested, the linearly polarized light is separated into four diffracted beams with different polarization states by the metasurface polarizer.

[0014] The detector is used to receive the four diffracted beams and generate the corresponding light intensity map.

[0015] The processing module is connected to the detector and is used to receive the light intensity map transmitted by the detector, calculate and output the stress distribution of the transparent object under test.

[0016] Furthermore, the metasurface polarizer is designed based on the principle of matrix Fourier optics, using the Jones matrix as the spatial distribution function. The diffraction behavior of the metasurface polarizer is described by matrix Fourier transform. Each diffraction order of the metasurface polarizer corresponds to a Jones matrix, and multiple diffraction orders operate simultaneously.

[0017] Furthermore, the metasurface polarization analyzer includes a substrate layer and a plurality of nanopillars disposed on the substrate layer and arranged in an array; the plurality of nanopillars are arranged on the side of the substrate layer away from the detector according to the metasurface phase transfer principle, and are used to separate the received linearly polarized light into four diffracted beams with different polarization states.

[0018] Furthermore, the detector is selected as a CMOS image sensor.

[0019] Meanwhile, this invention also provides a method for stress detection of transparent objects based on a fully Stokes polarized metasurface, comprising the following steps:

[0020] Step 1: Assemble the above-mentioned transparent object stress detection device based on the all-Stokes polarization metasurface, and place the transparent object to be tested coaxially between the polarizer and the metasurface polarization analyzer.

[0021] Step 2: The emitted light from the light source is converted into linearly polarized light after passing through the polarizer, and then passes through the transparent object to be tested to reach the metasurface polarization analyzer. The metasurface polarization analyzer then separates the light into four diffracted beams with different polarization states and transmits them to the detector.

[0022] Step 3: The detector generates corresponding intensity maps from the four diffracted beams and transmits them to the processing module.

[0023] Step 4: Based on the corresponding light intensity map, the processing module uses the phase-shifting method to obtain the stress distribution of the transparent object under test, thereby realizing stress detection of transparent objects based on the all-Stokes polarized metasurface.

[0024] Furthermore, in step 2, the four diffracted beams with different polarization states are horizontally linearly polarized light, 57-degree linearly polarized light, elliptically polarized light with a left-handed 60-degree rotation, and elliptically polarized light with a right-handed 60-degree rotation.

[0025] Furthermore, step 4 specifically involves:

[0026] 4.1 The processing module converts the polarization state of the diffracted light corresponding to the intensity map into the Mueller matrix of the metasurface polarization analyzer based on the corresponding intensity map.

[0027] 4.2 By combining the Mueller matrix of the metasurface analyzer, the Mueller matrix M1 of the polarizer, the Mueller matrix M2 of the transparent object under test, and the light intensity of the four diffracted beams, the phase retardation distribution and stress direction angle distribution of the transparent object under test can be obtained.

[0028] 4.3 Based on the phase delay distribution of the transparent object under test, the stress distribution of the transparent object under test is further calculated, thereby realizing stress detection of transparent objects based on a fully Stokes polarized metasurface.

[0029] Furthermore, in step 4.1, the Mueller matrix of the metasurface polarizer includes the Mueller matrix of horizontally polarized light. Mueller matrix of 57-degree linearly polarized light Muller matrix of ellipticized light with a left-handed 60-degree rotation And the Mueller matrix of right-handed 60-degree elliptically polarized light Their expressions are as follows:

[0030] ;

[0031] ;

[0032] ;

[0033] ;

[0034] In step 4.2, the Mueller matrix M1 of the polarizer is:

[0035] ;

[0036] The Mueller matrix M2 of the transparent object to be tested is:

[0037] ;

[0038] in, The phase delay of the transparent object under test is given by [the value of the measurement]. The stress direction angle of the transparent object to be tested is denoted as .

[0039] Further, in step 4.2, the phase delay of the transparent object under test is calculated by the following formula;

[0040] ;

[0041] In the formula, I A I is the intensity of horizontally linearly polarized light. B The intensity of linearly polarized light at 57 degrees; I C The intensity of elliptically polarized light with a left-handed rotation of 60 degrees; I D The intensity of right-handed elliptically polarized light (60 degrees right-handed);

[0042] The stress direction angle of the transparent object 3 to be tested is calculated by the following formula:

[0043] .

[0044] Further, in step 4.3, the stress of the transparent object to be tested is calculated using the following formula:

[0045] ;

[0046] In the formula, Δ represents the stress of the transparent object to be measured, d represents the thickness of the transparent object to be measured, and λ represents the wavelength of the light emitted from the light source.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] 1. The stress detection device for transparent objects based on a fully Stokes polarized metasurface provided by this invention includes a light source, a polarizer, a metasurface polarization analyzer, a detector, and a processing module. The metasurface polarization analyzer and the detector are combined to integrate the three major functions of beam splitting, polarization analysis, and imaging. Compared with existing stress detection devices, there is no need for mechanical adjustment components such as rotating the polarizer, which avoids the systematic errors caused by angle adjustment from the root and ensures the accuracy of phase delay inversion and stress conversion.

[0049] 2. The transparent object stress detection device based on the all-Stokes polarization metasurface provided by this invention has no complex discrete components (such as 1 / 4 wave plates, polarization gratings, micro polarizer arrays, etc.). Compared with existing stress detection devices, its size and weight are greatly reduced. It can be directly integrated into the front end of the detector, significantly reducing the complexity of assembly and adjustment, and adapting to the trend of miniaturization and integration of optical platforms.

[0050] 3. In the transparent object stress detection device based on a fully Stokes polarized metasurface provided by the present invention, the metasurface polarization analyzer is designed based on the matrix Fourier optics principle. Each diffraction order of the metasurface polarization analyzer corresponds to a Jones matrix, and multiple diffraction orders work simultaneously. Complete polarization information can be obtained in a single shot, achieving a simultaneous leap in detection accuracy, speed and integration, and providing a brand-new technical path for online stress detection of transparent elements.

[0051] 4. The stress detection method for transparent objects based on a fully Stokes polarized metasurface provided by this invention can capture four light intensity images in a single exposure. Combined with the phase-shifting method, the stress distribution of the transparent object under test can be quickly inverted. The dynamic response capability is significantly better than the point-by-point time-division scheme, meeting the requirements of online real-time monitoring.

[0052] 5. The stress detection method for transparent objects based on a fully Stokes polarized metasurface provided by this invention realizes full-field, real-time, and visualized imaging of the stress distribution of transparent objects. It solves the pain point that existing stress detection methods are difficult to balance in terms of accuracy, efficiency, and integration, and promotes the leap from static laboratory measurement to dynamic monitoring in industrial field for polarized optical stress detection. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of an embodiment of the transparent object stress detection device based on a fully Stokes polarized metasurface according to the present invention (processing module not shown).

[0054] Figure 2 This is a partial structural schematic diagram of the metasurface polarization analyzer element in an embodiment of the stress detection device for transparent objects based on a fully Stokes polarized metasurface of the present invention.

[0055] Figure 3 This is a schematic diagram of the nanopillar arrangement structure of the metasurface polarization analyzer element and a polarization distribution diagram of four diffracted beams in an embodiment of the stress detection device for transparent objects based on a fully Stokes polarized metasurface of the present invention. (a) is a schematic diagram of the nanopillar arrangement structure in the metasurface polarization analyzer element, and (b) is a polarization distribution diagram of four diffracted beams with different polarization states.

[0056] Figure 4 These are four light intensity maps generated by the detector in step 3 of the embodiment of the stress detection method for transparent objects based on a fully Stokes polarized metasurface of the present invention. Among them, (a) is the light intensity map of horizontally linearly polarized light, (b) is the light intensity map of 57-degree linearly polarized light, (c) is the light intensity map of 60-degree left-handed elliptically polarized light, and (d) is the light intensity map of 60-degree right-handed elliptically polarized light.

[0057] Figure 5 This is a phase delay distribution map of the transparent object under test obtained in step 4.2 of the embodiment of the stress detection method for transparent objects based on a fully Stokes polarized metasurface of the present invention;

[0058] Figure 6 This is a stress direction angle distribution diagram of the transparent object under test obtained in step 4.2 of the embodiment of the stress detection method for transparent objects based on a fully Stokes polarized metasurface of the present invention;

[0059] Figure 7 This is the stress distribution map of the transparent object to be tested obtained in step 4.3 of the embodiment of the stress detection method for transparent objects based on a fully Stokes polarized metasurface of the present invention.

[0060] The annotations in the attached figures are explained as follows:

[0061] 1-Light source, 2-Polarizer, 3-Transparent object to be measured, 4-Metasurface polarization analyzer, 41-Substrate, 42-Nanopillar, 5-Detector. Detailed Implementation

[0062] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0063] like Figure 1 As shown, a stress detection device for transparent objects based on a fully Stokes-polarized metasurface includes a light source 1, a polarizer 2, a metasurface polarization analyzer 4, a detector 5, and a processing module (not shown in the figure). The polarizer 2, metasurface polarization analyzer 4, and detector 5 are sequentially arranged along the outgoing optical path of the light source 1. During detection, the transparent object 3 to be tested is coaxially placed between the polarizer 2 and the metasurface polarization analyzer 4. In this embodiment, the light source 1 uses a 940nm laser light source. The transparent object 3 to be tested is transparent in the 940nm wavelength band and exhibits good stress-optical response.

[0064] The polarizer 2 is a linear polarizer, and the angle between its polarization direction and the optical axis of the light emitted from the light source 1 is 0 degrees. It is used to convert the emitted light into linearly polarized light. The linearly polarized light passes through the transparent object 3 to be tested and then reaches the metasurface polarization analyzer 4.

[0065] The metasurface polarization analyzer 4 has a periodic structure and is designed based on the principle of matrix Fourier optics, using the Jones matrix as the spatial distribution function. The diffraction behavior of the metasurface polarization analyzer 4 is described by matrix Fourier transform, where each diffraction order of the metasurface polarization analyzer 4 corresponds to a Jones matrix, and multiple diffraction orders work simultaneously, performing polarization analysis in parallel. This allows for the acquisition of complete polarization information in a single operation, achieving a simultaneous leap in detection accuracy, speed, and integration, and providing a novel technical path for online stress detection of transparent components.

[0066] like Figure 2 As shown, in this embodiment, the metasurface polarization analyzer 4 operates at a wavelength of 940 nm. It includes a substrate layer 41 and several nanopillars 42 arranged in an array on the substrate layer 41. The substrate layer 41 is a square plate structure made of transparent silicon dioxide (SiO2) with a thickness of H2. Each nanopillar 42 is a columnar structure with a height (in the same direction as the thickness of the substrate layer 41) of H1 and a lattice period of P. The cross-section of the nanopillar 42 is rectangular, with a length of L and a width of W. Each nanopillar 42 is made of silicon nitride. The several nanopillars 42 are arranged on the side of the substrate layer 41 away from the detector 5 according to the metasurface phase transfer principle, and are used to separate the received linearly polarized light into four spatially separated diffracted beams with different polarization states.

[0067] During the design phase, the length L, width W, height H1, and rotation angle of the nanopillar 42 on the substrate layer 41 are all adjustable. The length L and width W determine the degree of phase delay in light polarization, the rotation angle determines the direction of the polarized light, and the height H1 ensures efficient light transmission without loss. Once the position and orientation of all nanopillars 42 are determined, their polarization control effect on the optical path can be determined. The nanopillars 42 are arranged by tiling small array units (e.g., 11×11). The position and orientation of the nanopillars 42 within each small unit are obtained through multiple optimization designs. The purpose is to couple the four polarization components to be detected in the incident light into four fixed diffraction channels, thereby transforming the local polarization control of a single nanopillar 42 into directional delivery to four fixed diffraction channels, ultimately forming four fixed diffracted beams with different polarization states.

[0068] In this embodiment, the metasurface polarization analyzer 4 is modeled and simulated using the finite-difference time-domain (FDTD) method based on the transmission phase principle and geometric phase principle of metasurfaces. The target phase is calculated, and then nanoantennas matching the target phase in both polarization states are selected from the basic unit structure phase library. In this embodiment, the incident light wavelength λ is set to 940 nm, the height H1 of the nanopillars 42 is fixed at 700 nm, and the lattice period P is 450 nm. The bottom surface of the nanopillars 42 is scanned within the range of 0.2 P to 0.8 P at 1 nm intervals. This establishes the relationship between the phase delay and the length, width, and rotation angle of the nanopillars 42 point by point, thereby obtaining the optimal arrangement of the nanopillars 42. Figure 3 As shown in Figure (a).

[0069] In this embodiment, detector 5 is a CMOS image sensor, which is used to receive the four diffracted beams and generate corresponding light intensity maps in their respective four quadrants.

[0070] The processing module is connected to the detector 5 and is used to receive the light intensity map transmitted by the detector 5, calculate and output the stress distribution of the transparent object 3 under test.

[0071] This embodiment also provides a method for stress detection of transparent objects based on a fully Stokes polarized metasurface, including the following steps:

[0072] Step 1: Assemble the aforementioned transparent object stress detection device based on a fully Stokes polarized metasurface, and place the transparent object 3 to be tested coaxially between the polarizer 2 and the metasurface polarization analyzer 4.

[0073] When placing the transparent object 3 to be tested, the polarizer 2, the transparent object 3, and the metasurface analyzer 4 must be placed coaxially in sequence and coaxial with the optical axis of the emitted light. The transparent object 3 must be placed perpendicular to the optical axis of the linearly polarized light emitted from the polarizer 2 to ensure that the linearly polarized light is incident perpendicularly on the transparent object 3, avoiding additional polarization distortion caused by oblique incidence. This also ensures that the stress birefringence effect of the transparent object 3 is determined only by its own residual stress, rather than the additional phase difference introduced by the incident angle. In this embodiment, the transparent sample 3 to be tested inherently has stress, and the target of the test is its own stress. The linearly polarized light emitted from the transparent object 3 must be incident perpendicularly on the metasurface analyzer 4 and kept parallel to the optical axis of the metasurface analyzer 4 to avoid oblique incidence causing an effective angular shift in the analysis direction, thus preventing systematic errors in the calculation of phase delay and stress direction angle. The transparent object 3 under test has no rotation angle requirement, but its stress direction angle can be calculated by formula. Therefore, during the test, it is only necessary to ensure that the transparent object 3 under test is placed stably and that the light path direction does not deflect.

[0074] Step 2: A light source 1 with a wavelength of 940nm is used. Its emitted light is converted into linearly polarized light by a polarizer 2, and then passes through the transparent object 3 to be tested before reaching the metasurface analyzer 4. The metasurface analyzer 4 then separates the light into four diffracted beams with different polarization states, which are then transmitted to the detector 5. In this embodiment, the four diffracted beams with different polarization states are horizontally linearly polarized light, 57-degree linearly polarized light, elliptically polarized light with a left-handed 60-degree rotation, and elliptically polarized light with a right-handed 60-degree rotation. Figure 3 As shown in (b), the double arrow on the left ( The symbol ) represents horizontally linearly polarized light. The double arrow tilted to the right represents 57-degree linearly polarized light. The upper ellipse represents elliptically polarized light with a leftward rotation of 60 degrees, and the lower ellipse represents elliptically polarized light with a rightward rotation of 60 degrees.

[0075] Step 3: Detector 5 generates corresponding intensity maps of the four diffracted beams and transmits them to the processing module.

[0076] Figure 4 The image shows four light intensity diagrams obtained by detector 5 under four polarization states, where (a) is the light intensity diagram of horizontally linearly polarized light, (b) is the light intensity diagram of 57-degree linearly polarized light, (c) is the light intensity diagram of left-handed 60-degree elliptically polarized light, and (d) is the light intensity diagram of right-handed 60-degree elliptically polarized light.

[0077] Step 4: Based on the corresponding light intensity map, the processing module uses the phase shift method to obtain the stress distribution of the transparent object 3 under test, thereby realizing the stress detection of transparent objects based on the all-Stokes polarized metasurface.

[0078] In a polarization system, the Stokes vector S of the incident light in After passing through the optical element, the Stokes vector S of the emitted lightout satisfy: , where M is the Mueller matrix of the optical element.

[0079] In the field of stress measurement, the optical path difference generated by stress birefringence per unit thickness of the sample under test is typically used. This indicates the magnitude of its stress, i.e.: In the formula, Let λ represent the phase retardation of the sample under test (i.e., the phase retardation caused by stress birefringence), d represent the thickness of the sample under test, and λ represent the wavelength of the light emitted from the light source. Therefore, in actual measurements, for a sample with a known thickness, the stress magnitude can be calculated simply by measuring the corresponding phase retardation.

[0080] In the field of polarization optics, a 4×4 Mueller matrix (M) is typically used to characterize the polarization characteristics of optical elements, and a 4×1 Stokes vector (S) is used to represent the polarization state of light. The polarization result of the incident light passing through several polarization elements (M1, M2, ..., M...) can be obtained by matrix multiplication. n The polarization state of the incident light is known. Therefore, if the polarization state of the incident light and the Mueller matrix of each polarization element are known, and the polarization information of the outgoing light is collected, the phase delay of the sample under test can be calculated.

[0081] Based on the above principles, step 4 of this embodiment is specifically as follows:

[0082] 4.1 The processing module converts the polarization state of the diffracted light corresponding to the intensity diagram into the Mueller matrix of the metasurface polarimetric analyzer 4 based on the corresponding intensity diagram.

[0083] First, taking the propagation direction of the emitted light from light source 1 as the z-axis, the Stokes vector of monochromatic light with intensity I0 is expressed as: .

[0084] Secondly, polarizer 2 is a linear polarizer with an angle θ=0 between it and the optical axis of the emitted light. Therefore, the Mueller matrix of polarizer 2 is... for: .

[0085] Furthermore, the Mueller matrix M2 of the transparent object 3 to be tested is expressed as:

[0086] ;

[0087] in, In this context, it refers to the phase delay of the transparent object 3 under test. This is the stress direction angle of the transparent object 3 to be tested.

[0088] Based on this, the Mueller matrix of the metasurface polarizer 4 includes the Mueller matrix of horizontally polarized light. Mueller matrix of 57-degree linearly polarized light Muller matrix of ellipticized light with a left-handed 60-degree rotation And the Mueller matrix of right-handed 60-degree elliptically polarized light .

[0089] Among them, (1) the polarization state of horizontally linearly polarized light ;

[0090] Stokes vector of horizontally linearly polarized light ;

[0091] The Mueller matrix of horizontally linearly polarized light Represented as:

[0092] .

[0093] (2) Polarization state of 57-degree linearly polarized light ;

[0094] Stokes vector of 57-degree linearly polarized light ;

[0095] The Mueller matrix of linearly polarized light at 57 degrees. Represented as:

[0096] .

[0097] (3) Polarization state of elliptically polarized light with a left-handed 60-degree rotation , i represents a complex number;

[0098] Stokes vector of elliptically polarized light with a left-handed 60-degree rotation ;

[0099] The Mueller matrix of left-handed 60-degree elliptically polarized light Represented as:

[0100] .

[0101] (4) Polarization state of right-handed elliptically polarized light with a polarization degree of 60 degrees ;

[0102] Stokes vector of right-handed 60-degree elliptically polarized light ;

[0103] The Mueller matrix of right-handed 60-degree elliptically polarized light Represented as:

[0104] .

[0105] 4.2 By combining the Mueller matrix of the metasurface analyzer 4, the Mueller matrix M1 of the polarizer 2, the Mueller matrix M2 of the transparent object 3 under test, and the light intensity of the four diffracted beams, the phase delay distribution and stress direction angle distribution of the transparent object 3 under test are obtained.

[0106] In this embodiment, the light intensity map obtained by detector 5 ( Figure 4 As shown in the figure, the light intensity I corresponding to the four diffracted beams can be directly obtained. A I B I C I D ,Right now: , among which, I A I is the intensity of horizontally linearly polarized light. B The intensity of linearly polarized light at 57 degrees; I C The intensity of elliptically polarized light with a left-handed rotation of 60 degrees; I D Let I be the intensity of right-handed elliptically polarized light with a polarization of 60 degrees. Then, the corresponding intensities I of the four diffracted beams are... A I B I C I D They can be represented as:

[0107] ;

[0108] ;

[0109] ;

[0110] ;

[0111] Solving the above equation, we can obtain:

[0112] ;

[0113] ;

[0114] in, The phase delay distribution of the transparent object 3 under test is shown in the figure below. Figure 5 As shown, the horizontal axis represents the horizontal pixel position, the vertical axis represents the vertical pixel position, and the color bar on the right side of the figure represents the stress delay.

[0115] The stress direction angle distribution of the transparent object 3 under test is shown in the figure below. Figure 6 As shown, the horizontal axis represents the horizontal pixel position, the vertical axis represents the vertical pixel position, and the color bar on the right side of the figure represents the stress direction angle.

[0116] 4.3 Based on the phase delay distribution of the transparent object 3 under test, the stress distribution of the transparent object 3 under test is further calculated, thereby realizing the stress detection of transparent objects based on the all-Stokes polarization metasurface.

[0117] The stress of the transparent object 3 to be tested is calculated using the following formula:

[0118] ;

[0119] In the formula, Δ represents the stress of the transparent object 3 to be tested, d represents the thickness of the transparent object 3 to be tested, and λ represents the wavelength of the light emitted from the light source 1 in this embodiment, i.e., 940nm. Figure 7 This is a stress distribution diagram of the transparent object 3 to be tested obtained in this embodiment. The horizontal axis represents the horizontal pixel position, the vertical axis represents the vertical pixel position, and the color bar on the right side of the diagram represents the stress direction angle.

[0120] This invention reconstructs the system architecture for polarization stress detection using metasurface technology. Through the technical advantages of "no mechanical adjustment, high integration, and parallel detection," it achieves full-field, real-time, and visualized imaging of stress distribution in transparent objects, and achieves a leapfrog improvement in detection accuracy, speed, and integration. It provides a new technical path for online stress monitoring of transparent components, solves the pain point of traditional methods that make it difficult to balance accuracy, efficiency, and integration, and promotes the leap of polarization optical stress detection from static laboratory measurement to dynamic monitoring in industrial settings.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A stress detection device for transparent objects based on a fully Stokes-polarized metasurface, characterized in that: It includes a light source (1), a polarizer (2), a metasurface polarization analyzer (4), a detector (5), and a processing module. The polarizer (2), the metasurface polarization analyzer (4), and the detector (5) are arranged sequentially along the outgoing light path of the light source (1). The polarizer (2) is a linear polarizer, and the angle between the polarization direction and the optical axis of the light emitted from the light source (1) is 0 degrees, which is used to convert the emitted light into linearly polarized light; the metasurface polarizer (4) has a periodic structure; during detection, the transparent object (3) to be tested is placed coaxially between the polarizer (2) and the metasurface polarizer (4), and the linearly polarized light is separated into four diffracted beams with different polarization states by the metasurface polarizer (4) after passing through the transparent object (3); The detector (5) is used to receive the four diffracted beams and generate the corresponding light intensity map; The processing module is connected to the detector (5) and is used to receive the light intensity map transmitted by the detector (5), calculate and output the stress distribution of the transparent object (3) to be tested.

2. The transparent object stress detection device based on a fully Stokes polarized metasurface according to claim 1, characterized in that: The metasurface polarizer (4) is designed based on the matrix Fourier optics principle and uses the Jones matrix as the spatial distribution function. The diffraction behavior of the metasurface polarizer (4) is described by matrix Fourier transform. Each diffraction order of the metasurface polarizer (4) corresponds to a Jones matrix, and multiple diffraction orders work simultaneously.

3. The transparent object stress detection device based on a fully Stokes polarized metasurface according to claim 2, characterized in that: The metasurface polarization analyzer (4) includes a substrate layer (41) and a plurality of nanopillars (42) arranged in an array on the substrate layer (41). The plurality of nanopillars (42) are arranged on the side of the substrate layer (41) away from the detector (5) according to the metasurface phase transfer principle, and are used to separate the received linearly polarized light into four diffracted beams with different polarization states.

4. The transparent object stress detection device based on a fully Stokes polarized metasurface according to claim 1, 2, or 3, characterized in that: The detector (5) is selected as a CMOS image sensor.

5. A method for stress detection of transparent objects based on a fully Stokes-polarized metasurface, characterized in that, Includes the following steps: Step 1: Assemble the transparent object stress detection device based on the all-Stokes polarization metasurface as described in any of claims 1 to 4, and place the transparent object (3) to be tested coaxially between the polarizer (2) and the metasurface polarization analyzer (4); Step 2: The emitted light from the light source (1) is converted into linearly polarized light after passing through the polarizer (2), and then passes through the transparent object to be tested (3) to reach the metasurface polarization analyzer (4). After being separated into four diffracted beams with different polarization states by the metasurface polarization analyzer (4), the beams are transmitted to the detector (5). Step 3: The detector (5) generates corresponding intensity maps of the four diffracted beams and transmits them to the processing module; Step 4: Based on the corresponding light intensity map, the processing module uses the phase shift method to obtain the stress distribution of the transparent object (3) to be tested, thereby realizing the stress detection of transparent objects based on the all-Stokes polarized metasurface.

6. The method for stress detection of transparent objects based on a fully Stokes polarized metasurface according to claim 5, characterized in that: In step 2, the four diffracted beams with different polarization states are horizontally linearly polarized light, 57-degree linearly polarized light, elliptically polarized light with a left-handed 60-degree rotation, and elliptically polarized light with a right-handed 60-degree rotation.

7. The method for stress detection of transparent objects based on a fully Stokes-polarized metasurface according to claim 6, characterized in that, Step 4 is as follows: Step 4.1, the processing module converts the polarization state of the diffracted light corresponding to the intensity diagram into the Mueller matrix of the metasurface polarization analyzer (4) based on the corresponding intensity diagram; Step 4.2: By combining the Mueller matrix of the metasurface analyzer (4), the Mueller matrix M1 of the polarizer (2), the Mueller matrix M2 of the transparent object (3) under test, and the light intensity of the four diffracted beams, the phase delay distribution and stress direction angle distribution of the transparent object (3) under test are obtained. Step 4.3: Based on the phase delay distribution of the transparent object (3) under test, the stress distribution of the transparent object (3) under test is further calculated, thereby realizing the stress detection of transparent objects based on the all-Stokes polarization metasurface.

8. The method for stress detection of transparent objects based on a fully Stokes polarized metasurface according to claim 7, characterized in that: In step 4.1, the Mueller matrix of the metasurface polarizer (4) includes the Mueller matrix of horizontally polarized light. Mueller matrix of 57-degree linearly polarized light Muller matrix of ellipticized light with a left-handed 60-degree rotation And the Mueller matrix of right-handed 60-degree elliptically polarized light Their expressions are as follows: ； ； ； ； In step 4.2, the Mueller matrix M1 of the polarizer (2) is: ； The Mueller matrix M2 of the transparent object (3) to be tested is: ； in, The phase delay of the transparent object (3) under test is given. The stress direction angle of the transparent object (3) to be tested.

9. The method for stress detection of transparent objects based on a fully Stokes polarized metasurface according to claim 8, characterized in that: In step 4.2, the phase delay of the transparent object (3) to be tested is calculated by the following formula; ； In the formula, I A I is the intensity of horizontally linearly polarized light. B The intensity of linearly polarized light at 57 degrees; I C The intensity of elliptically polarized light with a left-handed rotation of 60 degrees; I D The intensity of right-handed elliptically polarized light (60 degrees right-handed); The stress direction angle of the transparent object (3) to be tested is calculated by the following formula: 。 10. The method for stress detection of transparent objects based on a fully Stokes polarized metasurface according to claim 9, characterized in that: In step 4.3, the stress of the transparent object (3) to be tested is calculated by the following formula: ； In the formula, Δ represents the stress of the transparent object (3) to be tested, d represents the thickness of the transparent object (3) to be tested, and λ represents the wavelength of the light emitted from the light source (1).

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