Scattering Analysis Method of Ultra-High-Speed Impact on Optical Elements Based on Finite Element Simulation

Abstract

The present invention relates to the field of scattering analysis of optical elements, and particularly to a method for scattering analysis of optical elements under ultra-high-speed impact based on finite element simulation, including: setting the parameters of each impactor and the target plate respectively in finite element simulation software, constructing an impactor model and a target plate model, and the impactor model and the target plate model form an ultra-high-speed impact model; performing ultra-high-speed impact simulation based on the ultra-high-speed impact model to obtain the target plate model after impact, and extracting the three-dimensional topography data of each impact crater from the target plate model after impact; constructing an optical element model, and importing the three-dimensional topography data of each impact crater into the optical element model, and obtaining an optical element model with multiple impact craters through data fitting; calculating the bidirectional scattering distribution function according to each impact crater of the optical element model to obtain the influence of the scattering of the impact crater on the optical system. The present invention can analyze the influence of light scattering caused by impact craters on the imaging quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of scattering analysis of optical elements, and particularly relates to a method for scattering analysis of ultra-high-speed impact on optical elements based on finite element simulation. Background Art

[0002] With the in-depth exploration of the universe by humans, the scale of spacecraft has been continuously expanding, and the space exploration environment has become increasingly crowded. The existence of meteoroids and space debris has begun to affect the execution of space optical detection missions. The dynamic effects of the ultra-fast flight of meteoroids and space debris have had a significant impact on the service life of spacecraft, which is a factor that must be considered in future space flights.

[0003] Micro-meteoroids and space debris with sizes less than 1 mm in the space environment belong to tiny particulate matter in space. Space debris is usually some aluminum alloys and metal oxides such as zinc and titanium, with a density usually at 2.8 g / cm 3 , and the average impact velocity is 10 km / s. The average impact velocity of micro-meteoroids is even higher, up to 20 km / s. Optical devices are important payloads on spacecraft, such as solar spectral radiometers, solar observers, telescopes, optical remote sensors, etc. These optical devices play important roles in aspects such as spacecraft navigation, communication, remote sensing, and scientific experiments. In the space environment, after the optical elements of optical devices are impacted by dust particles, a dust pollution film or impact pits will be formed on their surfaces, which will affect the optical performance of the optical elements. Although these effects will not cause the overall failure of the optical device, the service life of the optical device will inevitably be affected. Therefore, detecting and controlling the surface defects of optical elements is an important means to ensure the quality of optical elements.

[0004] Currently, devices such as dust microparticle accelerators and two-stage light gas guns are usually used to accelerate tiny particles to 1 km / s - 15 km / s to conduct ultra-high-speed impact experiments on optical elements. However, most of the experimental results are about the morphology of the impact pits on the optical elements after ultra-high-speed impact, the spatter around the impact pits, and the film layer changes after impact. The impact of light scattering caused by the impact pits on the imaging quality has not been studied. Summary of the Invention

[0005] In view of this, the present invention aims to provide a method for scattering analysis of ultra-high-speed impact on optical elements based on finite element simulation to analyze the impact of light scattering caused by impact pits on the imaging quality.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows:

[0007] A method for scattering analysis of ultra-high-speed impact on optical elements based on finite element simulation includes the following steps:

[0008] S1: Set the parameters of each projectile and the target plate in the finite element simulation software respectively, construct the projectile model and the target plate model, and the projectile model and the target plate model form a hypervelocity impact model;

[0009] S2: Conduct hypervelocity impact simulation based on the hypervelocity impact model to obtain the target plate model after impact, and extract the three-dimensional topography data of each impact crater from the target plate model after impact;

[0010] S3: Construct an optical element model, import the three-dimensional topography data of each impact crater into the optical element model, and obtain an optical element model with multiple impact craters through data fitting;

[0011] S4: Calculate the bidirectional scattering distribution function according to each impact crater of the optical element model to obtain the scattering characteristics of the optical element surface.

[0012] Furthermore, the parameters of the projectile include shape, density, size, impact velocity and impact angle, and the parameters of the target plate include thickness, size, material, density and Young's modulus.

[0013] Furthermore, the area of the target plate is at least four times the diameter of the projectile, and the thickness of the target plate is at least five times the length of the projectile.

[0014] Furthermore, the bidirectional scattering distribution function The calculation formula is:

[0015]

[0016] In the formula, is the differential scattered radiance, is the differential incident irradiance, and are the elevation angle and azimuth angle of the incident light of the optical element respectively, and are the elevation angle and azimuth angle of the scattered light of the optical element respectively, is the differential incident optical flux, is the azimuth angle, is the incident optical flux.

[0017] Furthermore, the bidirectional scattering distribution function includes the bidirectional reflectance distribution function The bidirectional reflectance distribution function The calculation formula is:

[0018]

[0019] Where, is the maximum elevation angle of the scattered light of the optical element, is the minimum elevation angle at which the optical element scatters light, is the Harvey model scattering parameter in the maximum scattering direction, is the maximum difference between the projections of the unit vectors of the scattering direction and the specular reflection direction on the surface of the optical element, is the minimum difference between the projections of the unit vectors of the scattering direction and the specular reflection direction on the surface of the optical element, and s is the spatial distribution characteristic of the scattered light.

[0020] Furthermore, the influence on the point spread function PSF is evaluated according to the scattering characteristics of the optical element surface. The calculation formula of the point spread function PSF is:

[0021]

[0022] Wherein, is the radiance; γ is a constant; is the luminous flux reflected by the optical element surface.

[0023] Furthermore, the influence on the modulation transfer function MTF is evaluated according to the scattering characteristics of the optical element surface. The calculation formula of the modulation transfer function MTF is:

[0024]

[0025] Wherein, and are the maximum and minimum gray values of the image stripes respectively.

[0026] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0027] The present invention can use finite element simulation software to simulate the ultra-high-speed impact of tiny particulate matter on the optical element, and analyze the influence of the light scattering caused by the impact crater on the imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0029] Figure 1 is a flowchart of the scattering analysis method of the ultra-high-speed impact on the optical element based on finite element simulation according to the embodiment of the present invention;

[0030] Figure 2 is a structural diagram of the ultra-high-speed impact model according to the embodiment of the present invention;

[0031] Figure 3It is the structural diagram after the impact of the target plate model according to the embodiments of the present invention;

[0032] Figure 4 It is the cloud map of hypervelocity impact after SPH algorithm operation according to the embodiments of the present invention;

[0033] Figure 5 It is the export drawing of the target plate model according to the embodiments of the present invention;

[0034] Figure 6 It is the three-dimensional morphology map of the impact crater extracted from the target plate model according to the embodiments of the present invention;

[0035] Figure 7 It is the fitting diagram of the three-dimensional morphology of the impact crater and the optical element according to the embodiments of the present invention;

[0036] Figure 8 It is the bidirectional scattering distribution function diagram according to the embodiments of the present invention. Detailed implementation manners

[0037] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention.

[0038] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0040] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments.

[0042] As Figures 1-8 shown, an embodiment of the present invention provides a method for scattering analysis of ultra-high-speed impact on optical elements based on finite element simulation, including the following steps:

[0043] S1: Set the parameters of each impactor and the target plate in the finite element simulation software respectively, construct an impactor model and a target plate model, and the impactor model and the target plate model constitute an ultra-high-speed impact model.

[0044] The finite element simulation software is ANSYS-LSDYNA. The ultra-high-speed impact model includes two parts: an impactor model and a target plate model. The impactor model is constructed by setting the shape, density, size, impact velocity, and impact angle of the impactor in the finite element simulation software, and the target plate model is constructed by setting the thickness, size, material, density, and Young's modulus of the target plate in the finite element simulation software. To prevent the impactor from penetrating the target plate and affecting the export of the impact results, the thickness of the target plate is at least set to five times the length of the impactor.

[0045] First, establish a coordinate system to facilitate setting the position parameters. Then, construct an impactor through the FEM (finite element) module, set the state equation of the impactor, and then construct a single-layer target plate model and set the state equation of the single-layer target plate model.

[0046] S2: Perform ultra-high-speed impact simulation based on the ultra-high-speed impact model to obtain the target plate model after impact, and extract the three-dimensional topography data of each impact crater from the target plate model after impact.

[0047] The hypervelocity impact model is connected to the equation of state of the impactor model and the equation of state of the single-layer target plate model, and then the initial conditions are set, and then the hypervelocity impact simulation is performed. The size and impact velocity of the impactor are optimized, and the impact angle is changed at the same time. By changing the target plate material (using SiC and other materials) and the impactor material parameters (changing to ice and other material density parameters), the sensitivity of the hypervelocity impact model is analyzed using the control variable method. For example, the target plate is set to SiC material, and the physical parameters of the impactor are set to be consistent. First, the speed of the impactor is changed to a speed range of 3-10km / s, and the target plate damage morphology is observed; then the speed of the impactor is fixed, the geometric parameters of the impactor are modified, and the target plate damage morphology is observed; then the geometric parameters and speed of the impactor are fixed, and the impactor material is modified, and the target plate damage morphology is observed. Replace the target plate material and perform the above operations again to study the degree of damage to the target plate caused by the hypervelocity impact, so as to find suitable materials to extend the service life of optical components and reduce the impact effect.

[0048] After the target plate model is hit by a hypervelocity impact, sputtering will be formed around the impact crater. During the impact process, micro-explosion will occur due to the high speed, leaving parameters such as the impact stress on the target plate. A dynamic physical model is constructed by combining key parameters such as different impact angles, different impact speeds, different impact object sizes, and different target plate materials. The dynamic physical model is used to extract the deformation parameters of different impact results. The target plate data is processed and extracted using the post-processing algorithm of the finite element simulation software, and the three-dimensional morphology of the impact crater after the impact is extracted using the morphology extraction algorithm. The post-processing algorithm is an algorithm that comes with the finite element simulation software and is exportable data, such as stress and other parameters. The basic process of the morphology extraction algorithm is to import the deformation parameters of the impact result, filter the deformation data with abnormal values, and finally re-fit the filtered data to facilitate the subsequent combination of the impact result with the optical element model.

[0049] S3: Construct an optical element model and import the three-dimensional morphology data of each impact crater into the optical element model, and obtain an optical element model with multiple impact craters through data fitting.

[0050] The optical component model of the curved surface structure was constructed using ANSYS-ZEMAX software. The deformation data extracted by the morphology extraction algorithm was imported into the optical component model, and the three-dimensional morphology of the impact crater after the impact was extracted. It was precisely coupled with the constructed optical component model, and the impact crater formed by the impact was fitted on the surface, thus successfully constructing the optical component model after the hypervelocity impact. Subsequently, the precise setting of the material and grid of the curved surface was completed, and the model after the three-dimensional morphology of the impact crater and the optical component model were successfully constructed, such as Figure 7 shown.

[0051] Based on the model obtained by fitting the three-dimensional topography of the impact crater and the optical element model constructed above, different illumination light sources are set according to different impact craters. For example, for tiny impact craters, a light source with high light intensity is required to irradiate and analyze the scattered light. For the overall scattered light, parallel light is used for analysis. The analysis of the position of the impact crater needs to be carried out by means of ray tracing. Add a geometric optics interface, and analyze the shape and position of the impact crater according to ray tracing. This ray tracing method can intuitively observe the scattering effect brought by the impact crater, analyze the position where the impact crater is located, and facilitate the search for stray light at the image plane position. A detector is set at the image plane to facilitate the observation of the change of the physical field and the observation of the scattering effect brought by the impact crater.

[0052] S4: Calculate the bidirectional scattering distribution function according to each impact crater of the optical element model to obtain the scattering characteristics of the optical element surface.

[0053] For the scattered light analyzed by the above optical software, analyze the stray light data on the image plane, normalize the irradiance to obtain the influence of the impact crater on the optical system, so as to facilitate the evaluation of the influence of the scattering caused by the impact crater on the image contrast, PSF, and MTF. With the physical field map generated by the detector, observe the scattered light spot brought by the impact crater and observe the changes in the mirror focal length and field of view caused by the impact crater.

[0054] PSF describes the response of the optical system to a point light source and determines the resolution and clarity of the imaging system. In a scattering medium, the scattering of light will cause the expansion and deformation of PSF, thus affecting the imaging quality. The narrower the PSF, the stronger the resolution ability of the imaging system to the point light source close to it, and the higher the imaging quality.

[0055] Image contrast refers to the measurement of the different brightness levels between the brightest white area and the darkest black area in the bright and dark areas of an image, that is, the size of the gray contrast of an image. The larger the difference range, the greater the contrast, and the smaller the difference range, the smaller the contrast.

[0056] Example 1

[0057] For micrometeoroids in space, their density is uncertain. The density of micrometeoroids is not calculated by a fixed statistical method, but obtained by observations using scientific technologies such as radar. From radar observations, we know that the density range of micrometeoroids is approximately between 0.16 g / cm 3 and 4 g / cm 3 However, there are great differences in the average mass density values from different literatures. Generally, 0.5 g / cm 3 is selected as the benchmark value for estimation, and the mass density relationship is

[0058] (1);

[0059] Among them, m represents the mass of the micrometeoroid, with the unit of g. In the studies on the impacts of small debris on the EURECA and HST solar panels, the diameter of the conchoidal fracture zone of the impact crater ( ), the target density ( ), the particle density ( ), the particle diameter ( ), as well as the particle velocity ( ) and the particle impact angle (θ) and a series of characteristic parameters are defined.

[0060] (2);

[0061] The uniformity and standardization of these characteristic parameters make them an important basis and reference for subsequent ground simulation studies on the characteristics of impact craters. As Figure 2 shown, it is a model diagram of hypervelocity impact. The geometric parameters of the model are constructed based on the input parameters. The impactor is a cylinder with a diameter of 100 μm, a length of 50 μm, and a density of 2.8 g / cm 3 . The geometric parameters of the target plate are 800 μm × 800 μm × 400 μm. After correction, the empirical formula with the impact angle is:

[0062] (3);

[0063] Among them, is the diameter of the central impact crater.

[0064] The expression for deriving the ballistic limit in the space data is:

[0065] (4).

[0066] The ballistic limit is used for the calculation of the impact process, mainly affecting the diameter of the impact crater. is the yield strength of the target plate, is the density of the target plate. Combining formula (1) and formula (4), the relational expression between the ballistic limit and the diameter of the conchoidal fracture zone of the impact crater can be obtained, and then the proportionality factor is given by experience, as shown in the following formula:

[0067] (5);

[0068] (6).

[0069] Among them, It represents the volume of the impact particle. The scaling factor is related to the diameter of the fragmentation zone and is an empirical value summarized from a large amount of experimental data. Excluding the influence of the defects of the impact crater itself, factors such as cracks around the crater will also affect the scattering. Therefore, the scaling factor belongs to the maximum range of calculation and mainly has an impact during the impact process.

[0070] This is a method for damage assessment, which reveals the influence of relevant parameters related to impact on the impact crater. As Figure 3 shown, the maximum diameter of the defect crater on the target plate after impact is about 4 times that of the impact object. For the multi-particle swarm in the space environment, a flux model is usually used for description. Flux is a physical quantity representing the number of objects hitting a unit area of the spacecraft surface per unit time in a certain space. The micrometeoroid environment flux model is a commonly used model at present. Its advantages are simple calculation and wide application range. The expression of the micrometeoroid environment flux model gives the total average meteoroid flux in integral form, that is, the number of impact particles per square meter per year with a mass greater than or equal to the given mass m.

[0071] Without considering the influence of the Earth's shielding and gravity effects, the flux of the micrometeoroid environment flux model is omnidirectional, that is, regardless of the position and direction of the spacecraft, it will be impacted by meteoroids from all directions. The micrometeoroid environment flux model is applicable to meteoroids with a mass of 10 -18 g to 100 g. For meteoroids with a larger or smaller mass, other models need to be used for calculation. As Figure 4 shown is the cloud map of hypervelocity impact after SPH algorithm operation. According to the micrometeoroid environment flux model, the flux of meteoroids can be expressed as:

[0072] (7);

[0073] Among them, refers to the particle flux with a mass greater than 10 -9 g, refers to the particle flux with a mass greater than 10 -14 g and less than 10 -9 g, refers to the particle flux with a mass less than 10 -14 g;

[0074]

[0075] (8).

[0076]

[0077] The micrometeoroid environmental flux model is widely used for the risk assessment of spacecraft in the Earth-Moon orbit space. Currently, the maximum impact crater diameter in the simulation results being 4 times the diameter of the impacting object is in line with theoretical research. As Figure 5 shown, it is the derived geometric model of the target plate after impact, Figure 6 and it is the curve surface topography map extracted through the algorithm. By fitting the extracted three-dimensional topography with the mirror surface, the defect and mirror surface fitting map as shown in Figure 7 can be obtained.

[0078] The bidirectional scattering distribution function (BSDF) uses geometric calculation methods to characterize the surface spatial scattering characteristics. This definition indicates that the ratio of the scattering radiance to the incident irradiance at a certain point on the surface is an important parameter for measuring the surface spatial scattering characteristics at that point. The theoretical calculation of BSDF stems from the geometric optical model. The significance of this model lies in that it can not only be measured and fitted through experiments, but also the BSDF value can be calculated and analyzed theoretically to understand and quantify the scattering characteristics of the optical surface.

[0079] (9);

[0080] Among them, is the differential scattering radiance, is the differential incident irradiance, and are respectively the elevation angle and azimuth angle of the incident light of the optical element, and are respectively the elevation angle and azimuth angle of the scattered light of the optical element.

[0081] is the differential incident optical flux, written as the result of the differential scattered optical flux within each differential projected solid angle ( , representing stray light) being normalized by the differential incident optical flux ( ):

[0082] (10).

[0083] For an optical element being a mirror, more attention is paid to the bidirectional reflectance distribution function (BRDF). As Figure 8 shown, both BRDF and BTDF (bidirectional transmittance distribution function, BTDF is used to illustrate that the BSDF studied in the present invention is composed of BRDF and BTDF. In this embodiment, the impacted optical element is a mirror, so BSDF mainly includes reflected light and does not include transmitted light. Therefore, there is no need to calculate BTDF) are important components of BSDF. The BRDF expression in the modified ABg model is:

[0084] (11);

[0085] Among them, is the maximum elevation angle at which the optical element scatters light, is the minimum elevation angle at which the optical element scatters light, is the Harvey model scattering parameter in the maximum scattering direction, is the difference between the projections of the unit vectors in the scattering direction and the specular reflection direction on the surface of the optical element, is the maximum value of this difference, is the minimum value of this difference, and s is the spatial distribution characteristic of the scattered light.

[0086] When the incident angle is fixed, the optical flux is redistributed based on the BRDF distribution (scattering component). Therefore, when the incident angle and other conditions remain unchanged, the equation can be simplified to:

[0087] (12);

[0088] Among them, C is the simplified constant term coefficient, is the azimuth angle of the projection of the scattered light on the XOY plane, is the incident wavelength, and are two micro-surfaces, representing tiny area units.

[0089] For a linear invariant optical system, the optical transfer function OTF can be expressed as:

[0090] (13);

[0091] Among them, is the exit pupil coordinate of the optical system, is the pupil function of the optical system, is the complex conjugate of the pupil function at the position on the pupil plane, represents displacement, is the displacement vector on the pupil plane.

[0092] The purpose of calculating the optical transfer function OTF is to solve the PSF. The Fourier transform of the PSF intensity is the optical transfer function OTF.

[0093] According to the Huygens superposition principle, the light field distribution on the reflection hemisphere can be expressed as:

[0094] (14);

[0095] Among them, are all direction cosines, j is the imaginary number, is the exit pupil coordinate of the optical system, γ is a constant used to normalize or adjust the amplitude of the function, is the initial pupil function of the optical system, and F is the Fourier transform flag.

[0096] When the optical element is a mirror, the light flux reflected from the mirror surface can be expressed in integral form as:

[0097] (15);

[0098] According to the radiation propagation law in optics:

[0099] (16);

[0100] Where, is the radiance, is the solid angle.

[0101] Combining formulas (15) and (16), we can obtain:

[0102] (17);

[0103] For the hemispherical receiving surface, the PSF can be calculated by the following formula:

[0104] (18).

[0105] When light passes through a scattering medium (such as biological tissue, haze, etc.), the information of the original object will be disrupted, and the shape and width of the PSF will be affected by the scattering characteristics. This effect makes it challenging for the imaging system to restore the target image. Especially in a high-scattering environment, the change of the PSF will significantly reduce the clarity and contrast of the image. Therefore, the PSF itself can represent the impact of scattering on the imaging quality.

[0106] For the MTF, its calculation formula is as follows:

[0107] (19);

[0108] Where, and are the maximum and minimum gray values of the image fringes respectively.

[0109] In this way, the scattering effect caused by the damage of optical elements due to the hypervelocity impact of micrometeoroids can be evaluated. The complexity of the space environment has a huge impact on aerospace missions. If it can be verified in ground experiments and solutions are proposed, or the influence of stray light caused by impacts such as micrometeoroids is excluded, the processed results will be more accurate. In traditional research, there have been many studies on hypervelocity impacts, but there is no research on the influence of the light scattering caused by impact craters on the imaging quality of optical systems. This method is based on finite element simulation of hypervelocity impacts, extracts the three-dimensional morphology of the impact crater from the impact target surface, fits the three-dimensional morphology of the impact crater with the optical element and conducts multi-physics field coupling simulation, and finally obtains the influence of hypervelocity impacts on the scattering of optical elements.

[0110] In summary, this method can be used to evaluate the damage of optical elements caused by the hypervelocity impacts of micrometeoroids and space debris in the space environment. For example, it can evaluate the influence of physical damage caused by hypervelocity impacts on the service life of optical elements, and evaluate the influence of scattered light caused by the defects generated on the mirror surface due to the occurrence of impact events on the imaging quality of optical systems. It can also be used for the detection of the surface roughness of optical elements. These simulations are for the protection of space telescopes, the evaluation of imaging quality, and the in-depth understanding of the optical and mechanical properties of materials, providing guidance for the development of new materials and the improvement of existing materials. It should be understood that various forms of the processes shown above can be used, reordering, adding or deleting steps. For example, the steps described in the disclosure of the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is made herein.

[0111] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A scattering analysis method for optical elements caused by hypervelocity impact based on finite element simulation, characterized in that: The steps include: S1: setting the parameters of each impactor and target plate in the finite element simulation software, constructing the impactor model and the target plate model, which constitute the hypervelocity impact model; wherein the parameters of the impactor include shape, density, size, impact velocity and impact angle, and the parameters of the target plate include thickness, size, material, density and Young's modulus; S2: Perform hypervelocity impact simulation based on the hypervelocity impact model to obtain a target plate model after impact, and extract the three-dimensional morphology data of each impact crater from the target plate model after impact; The size and impact speed of the impactor are optimized, and the impact angle is changed at the same time. By changing the target plate material and the parameters of the impactor material, the sensitivity of the hypervelocity impact model is analyzed using the control variable method to study the degree of damage to the target plate caused by the hypervelocity impact; a dynamic physical model is constructed by combining different impact angles, different impact speeds, different impactor sizes, and different target plate materials to extract the morphological parameters of different impact results; the target plate data is processed and extracted using the post-processing algorithm of the finite element simulation software, and the three-dimensional morphology of the impact crater after the impact is extracted using the morphology extraction algorithm; S3: construct an optical element model, and import the three-dimensional morphology data of each impact crater into the optical element model, and obtain an optical element model with multiple impact craters through data fitting; S4: Calculate the bidirectional scattering distribution function according to each impact crater of the optical element model to obtain the scattering characteristics of the optical element surface.

2. The method for analyzing the scattering of an optical element by a hypervelocity impact based on finite element simulation according to claim 1, characterized in that: The area of ​​the target plate is at least four times the diameter of the impactor, and the thickness of the target plate is at least five times the length of the impactor.

3. The method for analyzing the scattering of optical elements by hypervelocity impact based on finite element simulation according to claim 1, characterized in that: Bidirectional scattering distribution function The calculation formula is: In the formula, is the diffuse differential radiance, is the incident differential irradiance, and are the elevation angle and azimuth angle of the incident light of the optical element, and are the elevation and azimuth angles of the scattered light from the optical element, is the differential scattered light flux, is the scattered light flux, is the azimuth, is the differential azimuth, is the incident luminous flux.

4. The method for analyzing the scattering of optical elements by hypervelocity impact based on finite element simulation according to claim 3, characterized in that: Bidirectional scattering distribution function Including Bidirectional Reflectance Distribution Function , bidirectional reflectance distribution function The calculation formula is: in, is the maximum elevation angle of light scattered by the optical element, is the minimum elevation angle of light scattered by the optical element, is the Harvey model scattering parameter in the maximum scattering direction, is the scattering parameter of the Harvey model in the minimum scattering direction, is the maximum difference between the projections of the unit vectors of the scattering direction and the specular reflection direction on the surface of the optical element, is the minimum difference between the projections of the unit vectors of the scattering direction and the mirror reflection direction on the surface of the optical element, and s is the spatial distribution characteristic of the scattered light.

5. The method for analyzing the scattering of optical elements by hypervelocity impact based on finite element simulation according to claim 1, characterized in that: The influence on the point spread function PSF is evaluated based on the scattering characteristics of the optical element surface. The calculation formula of the point spread function PSF is: in, is the radiance; γ is a constant; is the luminous flux reflected by the surface of the optical element.

6. The method for analyzing the scattering of optical elements by hypervelocity impact based on finite element simulation according to claim 1, characterized in that: The influence of the scattering characteristics of the optical element surface on the modulation transfer function MTF is evaluated. The calculation formula of the modulation transfer function MTF is: in, and are the maximum and minimum grayscale values ​​of the image stripes, respectively.

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