Optical element multi-dimensional parameter single exposure measurement device and measurement method

Abstract

The present invention discloses a single-exposure measurement device and method for multi-dimensional parameters of an optical element, relating to the technical field of multi-parameter measurement. The device comprises: an illumination system, a polarizer, a sample to be measured, a lens, a modulation plate, a data acquisition system, and a data processing system. The illumination system comprises a coherent light source and a collimation system, providing the system with a beam of coherent illumination light with a diameter of approximately 5 mm. The polarizer is arranged after the illumination system and is used to convert the light beam into illumination light of a specific polarization state. The present invention, through optical path design and data processing algorithms, enables accurate measurement of multi-dimensional parameters of an optical element, such as amplitude, phase, and birefringence, with a single exposure, thereby greatly shortening the measurement time and compressing the measurement process, which may originally take several hours or even longer, to be completed instantly with a single exposure, thereby significantly improving measurement efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-parameter measurement, and in particular to a device and method for measuring multi-dimensional parameters of an optical element in a single exposure. Background Art

[0002] In the field of optics, the performance evaluation of optical components is crucial, and multidimensional parameters such as amplitude, phase, and birefringence are key indicators for measuring the quality of optical components. These parameters can accurately reflect the modulation characteristics of optical components on light and have a profound impact on the design, manufacturing, and performance optimization of optical systems. For example, in many applications such as laser communications, optical imaging, and optical sensing, accurate measurement of the multidimensional parameters of optical components can ensure the stability and reliability of the system, thereby improving overall performance.

[0003] Traditional multidimensional parameter measurement methods for optical components have many limitations and cannot meet the demand for efficient and accurate measurement in the field of modern optics. On the one hand, traditional methods usually require multiple exposures to complete the measurement of different parameters. Each exposure requires precise adjustment of the parameters and state of the measurement system, which undoubtedly greatly increases the measurement time. In actual measurement processes, multiple exposures are also affected by environmental changes such as temperature, humidity, and vibration. These changes may lead to inconsistent measurement conditions for each exposure, thereby introducing large measurement errors. On the other hand, the steps of traditional measurement methods are often complex. The acquisition of amplitude, phase, and birefringence information often relies on step-by-step measurement or a combination of different techniques. For example, interferometry, digital holography, and dot-beam wavefront analysis are used to measure the phase information of the light beam, and multi-wavelength methods, phase shifting methods, and step-by-step loading methods are used to solve the birefringence information. Such schemes not only require complex optical path switching and multi-frame image registration, but also are difficult to apply to high-throughput detection of dynamic living samples or photosensitive materials due to problems such as high cumulative light dose and low temporal resolution. Summary of the Invention

[0004] The purpose of the present invention is to make up for the shortcomings of the existing technology and provide a single-exposure measurement device and method for multi-dimensional parameters of optical elements. It can integrate an illumination system, a polarizer, a sample to be measured, a lens, a modulation plate, a data acquisition system and a data processing system, and use optical path design and data processing algorithms to achieve accurate measurement of multi-dimensional parameters such as amplitude, phase and birefringence of optical elements with a single exposure. In terms of measurement method, single-exposure data acquisition is performed by setting different polarization directions, and the collected data is processed using an iterative algorithm to gradually reconstruct the light field distribution and then solve the birefringence information of the sample.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a device and method for measuring the multi-dimensional parameters of an optical element in a single exposure, the method comprising the following specific steps: an illumination system, a polarizer, a sample to be measured, a lens, a modulation plate, a data acquisition system, and a data processing system;

[0006] The illumination system consists of a coherent light source and a collimation system, which provides the system with a beam of coherent illumination light with a diameter of about 5 mm;

[0007] The polarizer is arranged after the illumination system and is used to convert the light beam into illumination light of a specific polarization state;

[0008] The sample to be tested is placed behind the polarizer;

[0009] The lens is placed behind the sample to be tested, focusing the illumination light and then diverging it;

[0010] The modulation plate is placed behind the focus and is used to modulate the illumination light;

[0011] The data acquisition system is arranged behind the modulation plate and is used to collect diffraction spots;

[0012] The data processing system is connected to the data acquisition system, processes the acquired diffraction spots, and reconstructs the amplitude, phase and birefringence distribution diagram of the sample to be measured through an iterative algorithm.

[0013] Furthermore, the polarizer is a linear polarizer with an extinction ratio of not less than 1000:1.

[0014] Furthermore, the modulation plate is a phase-type modulation plate.

[0015] Furthermore, the data acquisition system is a polarization camera that can simultaneously record intensity information in four polarization directions, one of which is the same as the polarizer's light transmission direction and is arranged behind the modulation plate.

[0016] On the other hand, a method for measuring multi-dimensional parameters of an optical element in a single exposure is provided, the method comprising the following components:

[0017] Optical path setup and initial light field preparation: The coherent light emitted by the illumination system passes through the polarizer, forming illumination light with a specific polarization state and irradiating the sample to be tested. The illumination light irradiating the sample to be tested continues to propagate, and is first focused and then diverged by the lens placed behind the sample to be tested. A phase modulator with a known distribution is placed behind the lens focus to modulate the illumination light.

[0018] Single-exposure data acquisition: The data acquisition system records the modulated diffraction spot. The polarization camera's transmission angles are 0°, 45°, 90°, and 135°, respectively, capturing four polarization images.

[0019] Iterative reconstruction of the light field distribution: The four polarization images acquired by a single exposure are transmitted to the data processing system. The amplitude, phase, and birefringence distribution of the sample to be measured are reconstructed using an iterative algorithm. The light field on the camera surface is represented as a complex number. The amplitude portion of the complex number is replaced by the recorded intensity information. The updated light field is then transmitted to the encoding plate surface in the opposite direction of light propagation. The modulation effect of the modulation plate on the illumination light is removed to obtain the incident light distribution on the modulation plate surface. This incident light distribution is then transmitted back to the focal plane. Using the focal plane as a constraint, the updated wavefront distribution of the focal plane is obtained.

[0020] Calculation of birefringence information and determination of parameters: After multiple iterations, the accurate light field distribution at the focus is obtained. This light field distribution is then transmitted back to the lens to remove the phase effect of the lens on the light field. The light field is then transmitted back to the sample to obtain the amplitude and phase distribution of the sample's transmission function in the four polarization directions. The complex amplitude information in the four polarization directions is used to solve the birefringence information of the sample, that is, to determine the angle between the polarizer and the principal axis X of the stress point and the phase difference between the two beams of light. By calculating and analyzing the relevant physical quantities, the principal stress difference is finally obtained.

[0021] Furthermore, in the single exposure data acquisition step, the data acquisition system records the modulated diffraction spot. During the recording process, the linear polarized illumination light after the polarizer is set to , after the sample Then it becomes elliptically polarized light and passes through the lens After focusing, it is irradiated onto the modulation plate The modulator is placed downstream of the focus, and one of the light transmission directions of the polarization camera is parallel to the polarizer. They are 0°, 45°, 90° and 135° respectively, and the collected diffraction spots are recorded as , the transmission process of illumination light from the sample to the polarization camera is expressed as: ,in, represents the light field distribution at the focus, represents the light field distribution on the camera, is the transmission operator related to the focal length of the lens, is the focal length of the lens, is the sample-to-lens transfer operator, represents the distance from the sample to the lens, is the transfer operator from the focus to the modulation plate, is the distance from the focus to the modulation plate, is the transfer operator from the modulation board to the camera, is the distance from the modulator to the camera.

[0022] Furthermore, in the step of iteratively reconstructing the light field distribution, an iterative algorithm is used to reconstruct the amplitude, phase and birefringence distribution diagrams of the sample to be tested. Specifically, in the first In the iteration, the light field on the camera surface is written in complex form, that is, ,in, It is Iteration, The complex form of the camera light field in the polarization direction, is the amplitude of the light field, is the phase of the light field, and the amplitude is replaced by the intensity information recorded by the camera ,in, The camera recorded the Iteration, The light intensity information of each polarization direction is transmitted back to the encoding plate. ,in, It is the light field distribution transmitted in reverse to the encoding plate surface. is the distance from the modulator to the camera The related inverse transmission operator removes the modulation of the modulation plate and obtains the incident light distribution on the modulation plate surface ,in, is the incident light distribution on the modulation plate surface, is the complex conjugate of the modulation plate phase function, is the maximum value of the square of the modulator phase function, It is The focal plane light field distribution of the iteration is Back to the focal plane, ,in, is the focal length of the lens The related inverse transport operator uses the focal plane as a constraint to obtain the updated wavefront distribution at the focal plane. ,in, It is The focal plane wavefront distribution of the iteration, R is the aperture function that changes with the number of iterations, and the relaxation factor , repeat the iteration to obtain the light field distribution at the focus, reverse it back to the lens, remove the phase of the lens, and then reverse it back to the sample to obtain the transmission function of the sample Amplitudes in four polarization directions and phase distribution, i.e. .

[0023] Furthermore, in the birefringence information calculation and parameter determination step, the complex amplitudes of the four polarization directions are used to solve the birefringence information of the sample, that is, to solve the principal axis of the polarizer and the stress point. The angle between , and the phase difference between the two beams , and its calculation formula is: ,in, is the amplitude under different polarization directions, is an amplitude parameter related to the birefringence of the sample, representing the initial amplitude component not affected by birefringence, The polarizer light transmission direction and the principal axis of the sample stress point The angle between them is used to characterize the directional characteristics of birefringence. is the phase difference between the two orthogonal polarized lights in the sample, reflecting the intensity of birefringence. Solving the equations yields , bring in , get irrelevant Expression , and further obtain the principal stress difference ,in, and are the principal stresses in two perpendicular directions at the stress point, is the wavelength of the illumination light, is the reduced Planck constant, is the stress-strain coefficient of the sample, which is used to characterize the conversion relationship between stress and birefringence.

[0024] Compared with the prior art, this optical element multi-dimensional parameter single exposure measurement device and measurement method has the following beneficial effects:

[0025] 1. Through optical path design and data processing algorithms, the present invention achieves accurate measurement of multi-dimensional parameters such as amplitude, phase, and birefringence of optical components with a single exposure, greatly shortening the measurement time. The measurement process, which may originally take several hours or even longer, is compressed into a single exposure, greatly improving measurement efficiency. At the same time, since the measurement process is completed within a single exposure, the measurement error caused by environmental factors such as temperature fluctuations and air disturbances is effectively reduced, significantly improving the accuracy and stability of the measurement, and meeting the needs of the modern optical field for efficient and precise measurement.

[0026] 2. The present invention, through the design of the device structure and measurement method, can accurately reconstruct the amplitude, phase and birefringence distribution diagram of the sample to be measured, and uses an iterative algorithm to process the four polarization images collected by a single exposure, fully considering the various physical effects of light during the propagation process, so that the measurement results have high accuracy.

[0027] Other advantages, objects and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art based on an examination of the following or may be learned from the practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To more clearly illustrate the embodiments of the present invention or the technical solutions in 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 only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0029] Figure 1 Schematic diagram of a device for measuring multi-dimensional parameters of an optical element in a single exposure;

[0030] Figure 2 The present invention is a flowchart of a method for measuring multi-dimensional parameters of an optical element in a single exposure;

[0031] In the figure: 1. Illumination system; 2. Polarizer; 3. Sample to be tested; 4. Lens; 5. Modulation board; 6. Data acquisition system. DETAILED DESCRIPTION

[0032] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0033] Example 1

[0034] The measuring device is composed of an illumination system 1, a polarizer 2, a sample to be measured 3, a lens 4, a modulation plate 5, a data acquisition system 6 and a data processing system. Figure 1 As shown, the various components are arranged in sequence along the light propagation direction in the optical path. The illumination system 1 provides a beam of coherent illumination light with a diameter of about 5 mm for the entire measurement system. The coherent light it emits is directly incident on the polarizer 2. The two are in a front-to-back order in the optical path to ensure that the light can pass through the polarizer 2 smoothly.

[0035] Polarizer 2 converts the light provided by illumination system 1 into linearly polarized light of a specific polarization state. Its light transmission direction is vertically upward, and its extinction ratio is 10000:1. The polarizer only allows light vibrating in a specific direction to pass through. When coherent light is incident on polarizer 2, only light vibrating in the same direction as the light transmission direction of polarizer 2 can pass through. Light vibrating in other directions is greatly attenuated, thereby obtaining high-quality linearly polarized light. The emitted linearly polarized light is irradiated onto the sample to be tested 3.

[0036] The sample 3 to be measured is located behind the polarizer 2. As the object being measured, its optical properties will modulate the amplitude, phase, and polarization state of the illuminating light. When linearly polarized light passes through the sample 3 to be measured, due to the anisotropy of the sample, the propagation speed and attenuation degree of the light in different directions of the sample are different, resulting in attenuation of the amplitude of the light, phase delay, and change of the polarization state from linearly polarized light to elliptically polarized light. These changes contain information about the amplitude, phase, and birefringence of the sample.

[0037] The light modulated by the sample to be tested 3 is emitted to the lens 4. The lens 4 is located behind the sample to be tested 3 and focuses and diverges the light. According to the imaging principle of the lens 4, after the light is emitted from the sample to be tested 3, it will be refracted when passing through the lens 4. When the light enters the lens 4, it will be converged to the focus by the lens 4 to form a focal point. Then, the light begins to diverge again after the focus. Through this focusing and diverging process, the propagation path of the light is constrained, so that the spatial distribution of the light meets the requirements of subsequent modulation and data acquisition.

[0038] The light emitted from lens 4 reaches the modulation plate 5, which is set at the downstream position of the focus of lens 4 and is used to further modulate the light. The modulation plate 5 itself does not change the amplitude of the light, but modulates the phase of the light to be measured through its specific phase distribution. When the light emitted from lens 4 is irradiated on the modulation plate 5, the light will obtain different phase delays when passing through different positions of the modulation plate 5, thereby realizing phase encoding of the light field. This modulation allows the information of the light field to be encoded into the modulated light field distribution, providing the necessary conditions for the subsequent inversion of the optical parameters of the sample through an iterative algorithm.

[0039] The modulated light eventually enters the data acquisition system 6, which is a polarization camera that can simultaneously record intensity information in four polarization directions: 0°, 45°, 90°, and 135°. The 0° direction is the same as the light transmission direction of the polarizer 2. The polarization camera integrates multiple polarization direction detection units. When the modulated light is incident on the camera, light in different polarization directions will be received by the corresponding detection units and converted into corresponding electrical signals, thereby recording the diffraction spot intensity information in the four polarization directions. These intensity information contains comprehensive information about the light field after modulation by the sample and the modulation plate 5, and is the original data for subsequent data processing and parameter reconstruction.

[0040] The data processing system is connected to the data acquisition system 6 via a data line, and processes the four polarization images collected by the data acquisition system 6. The amplitude, phase and birefringence distribution diagrams of the sample to be tested 3 are reconstructed through an iterative algorithm. First, the intensity data of the four polarization directions from the data acquisition system 6 are received, and then the polarization coherence modulation imaging algorithm is used for iterative calculation. During the iteration process, the light field distribution is gradually updated by continuously reversely transmitting the light field of the camera surface to the modulation plate 5 surface, removing the modulation of the modulation plate 5, and reversely transmitting it to the focal plane. Finally, the light field distribution at the focus is obtained, and then reversely transmitted back to the sample, thereby obtaining the amplitude and phase distribution of the sample in the four polarization directions. Finally, according to the four-step phase shift theory, the complex amplitude information of the four polarization directions is used to solve the birefringence information of the sample, including the angle between the polarizer 2 and the main axis of the stress point and the phase difference between the two beams of light, and then the principal stress difference and other related parameters are obtained.

[0041] Example 2

[0042] In the field of laser processing and optical material research, damage points generated in fused quartz after laser irradiation can cause complex changes in the optical properties of the material, including amplitude attenuation, phase delay, and coupling of birefringence effects. The device and method of the present invention are used to achieve single-exposure synchronous measurement of damage point parameters.

[0043] The measuring device includes an illumination system 1, a polarizer 2, a sample to be measured 3, a lens 4, a modulation plate 5 and a data acquisition system 6. The illumination system 1 adopts a helium-neon laser with a wavelength of 633nm (output power 5mW, coherence length>20cm), and is matched with a collimating lens 4 with a diameter of 50.8mm and a focal length of 400mm to intercept the light beam into parallel coherent light with a diameter of 5mm. The polarizer 2 uses a linear polarizer with a diameter of 50.8mm and an extinction ratio of 10000:1. The light transmission direction is set to the vertical direction to ensure the purity of the linearly polarized light. The sample to be measured 3 is fused quartz glass (size 20mm×20mm×3mm). The surface is irradiated with carbon dioxide laser and nanosecond pulse laser to form a damage point. The diameter of the damaged area is about 100μm. The lens 4 is selected with a diameter of 25.4m The achromatic lens of size 100 mm, with a focal length of f=400 mm and an antireflection coating on the surface (transmittance at 633 nm wavelength >99%), is used to focus and diverge the light beam. The modulation plate 5 uses a slice of the stem of the money tree as a phase-type modulation plate (size 10 mm×10 mm). Its phase distribution is known and has random phase characteristics, which is used to spatially modulate the illumination light. The data acquisition system 6 uses a four-channel polarization camera (resolution 1280×1024, pixel size 5.5μm×5.5μm), with light transmission directions of 0° (parallel to the polarizer 2), 45°, 90°, and 135°, respectively. It is placed 200 mm behind the modulation plate 5. The data processing system processes the collected diffraction spots and reconstructs the amplitude, phase, and birefringence distribution maps of the sample 3 to be tested through an iterative algorithm.

[0044] Turn on the HeNe laser and preheat for 30 minutes until the power is stable (fluctuation <±0.1%). Adjust the optical path through the aperture and reflector to ensure that the coaxiality deviation of the light beam and the system optical axis is <0.05mm. Use the power meter to rotate the polarizer 2 and fix the position when the transmitted light intensity reaches the minimum value. At this time, the light transmission direction of the polarizer 2 is defined as 0°. Place the fused quartz sample on the three-dimensional fine-tuning stand and adjust it so that the light beam is perpendicular to the center of the damage point. Place the lens 4 400mm behind the sample. Confirm the focal position of the lens 4 by the focused spot method with an error of <0.5mm. Fix the modulation plate 5 50mm behind the focus of the lens 4 to ensure that the plane of the modulation plate 5 is perpendicular to the optical axis. Install the polarization camera 200mm behind the modulation plate 5 and use the leveling bracket to ensure that the camera target surface is perpendicular to the optical axis with an inclination of <0.5°.

[0045] Set the exposure time to 100ms, the gain to 10dB, and the trigger mode to single synchronous exposure to ensure that the four polarization channels are collected simultaneously. First, block the light path to collect the dark noise image, and then use uniform diffuse light to collect the flat field image for subsequent data preprocessing. Open the light path and the camera will synchronously record the diffraction spot images in the four directions of 0°, 45°, 90°, and 135°. Figure 2 As shown, during the recording process, the linear polarized illumination light after the polarizer 2 is , after the sample Then it becomes elliptically polarized light and passes through lens 4 After focusing, the light is irradiated onto the modulator plate 5M(x, y) surface. The modulator plate 5 is placed downstream of the focus. One of the light transmission directions of the polarization camera is parallel to the polarizer 2, and the angle is They are 0°, 45°, 90° and 135° respectively, and the collected diffraction spots are recorded as , the transmission process of illumination light from the sample to the polarization camera is expressed as: ,in, represents the light field distribution at the focus, represents the light field distribution on the camera, is the transmission operator related to the focal length of lens 4, is the focal length of lens 4, is the transfer operator from the sample to lens 4, represents the distance from the sample to the lens 4, is the transfer operator from the focus to the modulation plate 5, is the distance from the focus to the modulation plate 5, is the transfer operator from modulation board 5 to the camera, is the distance from the modulation board 5 to the camera. After acquisition, check the symmetry of the light spot in real time to ensure that there is no obvious deviation in the optical path.

[0046] Dark noise subtraction, flat field correction and Gaussian filtering were performed on the four images to eliminate speckle noise and background interference. The maximum number of iterations was set to 500 times and the relaxation factor was set to =0.7, the initial value of the aperture function R is 0.3 (increases linearly to 1 with the number of iterations), the initial phase is set to 0, and the camera surface light field is expressed as ,in, It is Iteration, The complex form of the camera light field in the polarization direction, is the amplitude of the light field, is the phase of the light field, and the amplitude is replaced by the intensity information recorded by the camera ,in, The camera recorded the Iteration, The light intensity information of each polarization direction is transmitted back to the encoding plate. ,in, It is the light field distribution transmitted in reverse to the encoding plate surface. is the distance from the modulation board 5 to the camera The relevant inverse transmission operator removes the modulation of the modulation plate 5 and obtains the incident light distribution on the surface of the modulation plate 5 ,in, is the incident light distribution on the 5th surface of the modulation plate, is the complex conjugate of the phase function of modulation plate 5, is the maximum value of the square of the modulus of the phase function of modulation plate 5, It is The focal plane light field distribution of the iteration is Back to the focal plane, ,in, Is the focal length of the lens 4 The related inverse transport operator uses the focal plane as a constraint to obtain the updated wavefront distribution at the focal plane. , the iteration is terminated when the root mean square error of the light field between adjacent iterations is < 0.01, and it actually converges at the 320th iteration.

[0047] The converged focal plane light field is transmitted back to the sample plane, and after removing the lens 4 and the propagation phase, the complex amplitude of the transmission function of the sample in the four polarization directions is obtained. ,in is the amplitude, For phase.

[0048] Extract the squared amplitude values ​​of the four polarization directions 、 、 、 , substitute into the birefringence equations: , solve for the angle between polarizer 2 and the stress principal axis =22.5°±0.3°, phase difference =1.2rad±0.05rad, according to the formula , where the stress-strain coefficient of fused quartz is =3.1×10⁻¹²Pa⁻¹, wavelength =633nm, the principal stress difference is calculated =19.8MPa±0.8MPa.

[0049] The test results were used to generate a three-dimensional amplitude distribution map, a phase contour map, and a birefringence direction vector map. The amplitude attenuation in the central area of ​​the damage point reached 30%, the maximum phase delay was 1.8π, and the angle between the birefringence main axis and the laser incident direction was 23°, which was consistent with theoretical expectations.

[0050] In summary, the multi-dimensional parameter single-exposure measurement device for optical elements described in the present invention records the diffraction spots in four polarization directions through a single exposure with a polarization camera, and uses the polarization coherent coded imaging algorithm for calculation. The amplitude, phase, and birefringence distribution of the damage points produced by carbon dioxide laser and nanosecond pulse laser in fused silica can be obtained.

[0051] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for measuring multi-dimensional parameters of an optical element in a single exposure, characterized in that: The method comprises the following components: Optical path setting and initial light field preparation: After the coherent light emitted by the illumination system (1) passes through the polarizer (2), it forms illumination light of a specific polarization state and irradiates the sample to be tested (3). The illumination light irradiated on the sample to be tested (3) continues to propagate, and is first focused and then diverged by the lens (4) placed behind the sample to be tested (3). A phase-type modulator (5) with a known distribution is placed behind the focus of the lens (4) to modulate the illumination light. Single exposure data acquisition: The data acquisition system (6) records the modulated diffraction spot, where the light transmission angles of the polarization camera are 0°, 45°, 90°, and 135°, respectively, and four polarization images are collected; Iterative reconstruction of light field distribution: four polarization images collected by a single exposure are transmitted to a data processing system, and an iterative algorithm is used to reconstruct the amplitude, phase and birefringence distribution diagram of the sample to be tested (3). The light field on the camera surface is represented as a complex form, and the amplitude part in the complex form is replaced by the recorded intensity information. The updated light field is transmitted to the encoding plate surface in the opposite direction to the light propagation, and the modulation effect of the modulation plate (5) on the illumination light is removed to obtain the incident light distribution on the modulation plate (5) surface. The incident light distribution is transmitted back to the focal plane in reverse, and the focal plane is used as a constraint condition to obtain the updated wavefront distribution of the focal plane. Calculation of birefringence information and determination of parameters: After multiple iterations, the accurate light field distribution at the focus is obtained, and the light field distribution is reversely transmitted to the lens (4), and the phase effect of the lens (4) on the light field is removed. The light field distribution is then reversely transmitted to the sample to obtain the amplitude and phase distribution of the sample's transmission function in the four polarization directions. The complex amplitude information in the four polarization directions is used to solve the birefringence information of the sample, that is, to solve the angle φ between the polarizer (2) and the main axis X of the stress point, and the phase difference δ between the two beams of light. The calculation formula is: Among them, Am γ is the amplitude under different polarization directions. OE is the amplitude parameter related to the birefringence of the sample, representing the initial amplitude component not affected by birefringence. φ is the angle between the light direction of the polarizer (2) and the principal axis X of the stress point of the sample, which is used to characterize the directional characteristics of birefringence. δ is the phase difference between the two orthogonal polarized beams in the sample, reflecting the intensity of birefringence. Solving the equations, we can get φ = Bring in sin 2 φ+cos 2 φ=1, we get the expression of δ which is independent of φ. We can further obtain the principal stress difference σ1- Among them, σ1 and σ2 are the principal stresses in two perpendicular directions at the stress point, λ is the wavelength of the illumination light, is the reduced Planck constant, and C is the stress strain coefficient of the sample, which is used to characterize the conversion relationship between stress and birefringence, and ultimately obtain the principal stress difference.

2. The method for measuring multi-dimensional parameters of an optical element in a single exposure according to claim 1, wherein: In the single exposure data acquisition step, the data acquisition system (6) records the modulated diffraction spot. During the recording process, the linear polarized illumination light after the polarizer (2) is set as P (x, y). l (x, y) is converted into elliptically polarized light, and then focused by lens (4) L (x, y) and irradiated onto the modulator (5) M (x, y) surface. The modulator (5) is placed downstream of the focus. One of the light transmission directions of the polarization camera is parallel to the polarizer (2), and the angle x is l The angles of the diffraction spots are 0°, 45°, 90° and 135° respectively, and the collected diffraction spots are recorded as I l , the transmission process of illumination light from the sample to the polarization camera is expressed as: Among them, φ l (x,y) represents the light field distribution of the focus, E l (x,y) represents the light field distribution on the camera, is the transmission operator related to the focal length of lens (4), f is the focal length of lens (4), is the transmission operator from the sample to the lens (4), d0 represents the distance from the sample to the lens (4), is the transmission operator from the focus to the modulation plate (5), d1 is the distance from the focus to the modulation plate (5), is the transmission operator from the modulation plate (5) to the camera, and d2 is the distance from the modulation plate (5) to the camera.

3. The method for measuring multi-dimensional parameters of an optical element in a single exposure according to claim 1, wherein: In the step of iteratively reconstructing the light field distribution, an iterative algorithm is used to reconstruct the amplitude, phase and birefringence distribution diagram of the sample to be tested (3). Specifically, in the kth iteration, the light field on the camera surface is written into a complex form, that is, ψ k,l (x,y)=|E k,l (x,y)|exp[iθ k,l (x,y)], where ψ k,l (x,y) is the complex form of the camera light field at the kth iteration and the lth polarization direction, |E k,l (x,y)| is the amplitude of the light field, θ k,l (x,y) is the phase of the light field, and the amplitude is replaced by the intensity information recorded by the camera Among them, I k,l It is the light intensity information of the kth iteration and the lth polarization direction recorded by the camera, and the updated light field is transmitted back to the encoding plate surface Among them, T′ k,l (x,y) is the light field distribution transmitted to the encoding plate in reverse direction, is the inverse transmission operator related to the distance d2 from the modulation plate (5) to the camera. By removing the modulation of the modulation plate (5), the incident light distribution on the surface of the modulation plate (5) is obtained. Among them, φ′ k,l (x, y) is the incident light distribution on the modulator (5), M * (x,y) is the complex conjugate of the phase function of the modulation plate (5), is the maximum value of the square of the phase function modulator (5), φ k (x,y) is the focal plane light field distribution of the kth iteration, Back to the focal plane, in, is the inverse transport operator related to the focal length f of lens (4), using the focal plane as a constraint to obtain the updated wavefront distribution at the focal plane Among them, φ k+1,l (x, y) is the focal plane wavefront distribution of the k+1th iteration, R is the aperture function that changes with the number of iterations, the relaxation factor β∈(0,1], repeat the iteration to obtain the light field distribution at the focus, reversely transmit it back to the lens (4), remove the phase of the lens (4), and then reversely transmit it back to the sample, that is, the transmission function S of the sample is obtained. l The amplitude Am of (x,y) in the four polarization directions l (x,y) and phase P l (x,y) distribution, that is, S l (x,y)=Am l (x,y)·P l (x,y)。 4. A device for measuring a multi-dimensional parameter single exposure of an optical element, the device being applicable to a method for measuring a multi-dimensional parameter single exposure of an optical element according to any one of claims 1 to 3, characterized in that: The device comprises the following components: an illumination system (1), a polarizer (2), a sample to be measured (3), a lens (4), a modulation plate (5), a data acquisition system (6) and a data processing system; The illumination system (1) consists of a coherent light source and a collimation system, which provides the system with a beam of coherent illumination light with a diameter of about 5 mm; The polarizer (2) is arranged after the illumination system (1) and is used to convert the light beam into illumination light of a specific polarization state; The sample to be tested (3) is placed behind the polarizer (2); The lens (4) is placed behind the sample to be tested (3) to focus the illumination light and then diverge it; The modulation plate (5) is placed behind the focus and is used to modulate the illumination light; The data acquisition system (6) is arranged behind the modulation plate (5) and is used to collect diffraction spots. The data acquisition system (6) is a polarization camera that can simultaneously record intensity information in four polarization directions, one of which has a light transmission direction that is the same as the light transmission direction of the polarizer (2) and is arranged behind the modulation plate (5); The data processing system is connected to the data acquisition system (6), processes the acquired diffraction spots, and reconstructs the amplitude, phase and birefringence distribution diagram of the sample to be measured (3) through an iterative algorithm.

5. The optical element multi-dimensional parameter single exposure measurement device according to claim 4, characterized in that: The polarizer (2) is a linear polarizer with an extinction ratio of not less than 1000:

1.

6. The optical element multi-dimensional parameter single exposure measurement device according to claim 4, characterized in that: The modulation plate (5) is a phase-type modulation plate.

Images