Aerodynamic optical transmission effects simulation system

Abstract

This invention relates to the field of aero-optics technology, specifically providing an aero-optical transmission effect simulation system, comprising: a light source, a target simulator, a collimation subsystem, an anisotropic structural element, and an imaging subsystem. The anisotropic structural element is the core component of this system, employing a trapezoidal columnar structure with a convex curved surface as the incident surface and a standard plane as the exit surface, capable of effectively simulating the anisotropic aero-optical transmission effect generated by the aero-optical flow field. This invention can accurately simulate the non-uniform characteristics of aero-optical transmission effects under laboratory conditions, generating corresponding degraded images, and providing an experimental device for designing aberration correction systems and degraded image restoration algorithms.

Description

Technical Field

[0001] This invention belongs to the field of aero-optics technology, and in particular relates to an aero-optics transmission effect simulation system. Background Technology

[0002] When an aircraft flies at high speed within the atmosphere, complex flow field structures such as shock waves and boundary layers exist outside the optical window. Dramatic changes in gas density within these structures lead to non-uniform refractive indices, causing light deflection, wavefront distortion, and image blurring—a phenomenon known as aero-optical transmission effect. This directly impacts the performance of tasks such as infrared guidance, laser communication, and imaging detection. Accurately understanding and simulating this aero-optical transmission effect is crucial for evaluating optical system performance, designing aberration correction systems, and developing image correction algorithms, directly affecting the target detection and recognition capabilities of high-speed aircraft.

[0003] Currently, simulation methods for aero-optical transmission effects are mainly divided into two categories: numerical simulation and physical phase modulation. Numerical simulation typically obtains the flow field density distribution through computational fluid dynamics, then converts it into a refractive index field according to the Gladstone-Dale relation, and uses ray tracing to calculate optical distortion. Physical phase modulation, on the other hand, mainly relies on programmable optical modulation devices, such as deformable mirrors and digital micromirrors (DMMs), to reproduce aero-optical transmission effects through controlled phase modulation. Among them, deformable mirrors can generate continuous mirror deformation to simulate smooth phase changes caused by shock waves, while DMMs achieve amplitude-type or phase-type distortion simulation through high-speed refresh of the micromirror array. Both can reproduce the main characteristics of aero-optical transmission effects to a certain extent. However, existing methods have significant shortcomings in simulating non-isohalous characteristics: whether it is numerical simulation based on flow field data or laboratory simulation based on modulation devices, they can essentially only generate wavefront aberrations corresponding to fixed or discrete field angles, while the real non-isohalous characteristics of aero-optical transmission effects require light rays from different field angles to experience continuously changing flow field structures. This continuous dependence of "each field of view corresponds to a specific shock wave shape" is fundamentally contradictory to "a modulation device can only generate a fixed wavefront shape", which means that existing methods cannot truly reproduce the continuous angle dependence characteristics caused by the strong discontinuous structure of shock waves.

[0004] Although a mature multi-phase screen method exists for simulating non-uniform halo characteristics in atmospheric turbulence—that is, by setting up a phase screen conforming to Kolmogorov statistics to simulate the decrease in wavefront correlation caused by light rays traveling along different paths at different field of view—this method has significant limitations when applied to simulating non-uniform halo characteristics of aero-optical transmission effects. The flow field causing aero-optical transmission effects exhibits extremely strong anisotropy and localized characteristics, making it impossible to describe using the statistical theory of atmospheric turbulence or to achieve the same effect using a simple multi-phase screen model. Therefore, an effective method for simulating non-uniform halo characteristics of aero-optical transmission effects is currently lacking in the laboratory. Summary of the Invention

[0005] In view of this, the present invention aims to provide a simulation system for aero-optical transmission effects. By setting an anisotropic structural element as the core distortion generating component of the system, with its incident surface being an outwardly convex curved surface and its exit surface being a standard plane, light rays from different field angles undergo continuously varying cumulative optical paths within the anisotropic structural element, generating wavefront aberrations that continuously vary with the field of view. Under laboratory conditions, the non-isotropic characteristics of aero-optical transmission effects are realistically reproduced, providing an effective experimental verification platform for aberration correction systems and image restoration algorithms.

[0006] To achieve the above objectives, the technical solution created by this invention is implemented as follows: This invention provides a system for simulating aero-optical transmission effects, comprising: a light source, a target simulator, a collimation subsystem, an anisotropic structural element, and an imaging subsystem; The light source is used to emit light, which passes through the target simulator to form a light beam carrying the test image. The target simulator is positioned at the object-side focal plane of the collimation subsystem, which is used to convert light rays carrying the test image into parallel light rays carrying the test image. The anisotropic structural element includes an incident surface and an exit surface. The incident surface is a convex curved surface, and the exit surface is a standard plane. Parallel light carrying the test image passes through the anisotropic structural element. The light emitted from the anisotropic structural element contains aero-optical transmission aberrations that vary continuously with the line of sight angle. The imaging subsystem is used to receive light emitted from anisotropic structural elements and to form an image.

[0007] Preferably, the target simulator uses a transmissive film or a resolution test target as the carrier for each point in the test image.

[0008] Preferably, the collimation subsystem is implemented using a transmission optical structure, a reflection optical structure, or a catadioptric optical structure; The aperture and focal length of the collimation subsystem are determined based on the size of the test image and the required field of view range to be simulated.

[0009] Preferably, the perimeter of the anisotropic structural element includes: an upper surface, a lower surface, a front surface, and a rear surface; The upper surface includes: a curved segment and a straight segment, wherein the curved segment is symmetrical about the perpendicular bisector of the straight segment. The lower surface includes: a curved segment and a straight segment, wherein the curved segment is symmetrical about the perpendicular bisector of the straight segment. The rear surface includes: a straight line segment on the upper surface, a straight line segment on the lower surface, and a line connecting the two endpoints of the straight line segment on the upper surface and the two endpoints of the straight line segment on the lower surface; the lines connecting the endpoints of the straight line segment on the upper surface and the endpoints of the straight line segment on the lower surface do not intersect, the upper surface and the lower surface are both perpendicular to the rear surface, and the upper surface and the lower surface are both located on the same side of the rear surface. The front surface is obtained by lofting the upper surface curve segment and the lower surface curve segment; The front surface, upper surface, lower surface and rear surface form a closed structure.

[0010] Preferably, the shape of the anisotropic structural element is set as follows: The initial design value of the upper surface curve segment is the boundary of the compressed flow field region to be simulated, which is close to the nose of the aircraft and in contact with the uncompressed flow field region. The initial design value of the lower surface curve segment is the boundary of the compressed flow field region to be simulated, which is close to the tail of the aircraft and in contact with the uncompressed flow field region. The initial design value of the straight segment on the upper surface is the boundary where the optical window is close to the nose of the aircraft and in contact with the region of the compressed flow field to be simulated; The initial design value of the straight segment on the lower surface is the boundary where the optical window is close to the tail of the aircraft and in contact with the region of the compressed flow field to be simulated.

[0011] Preferably, the anisotropic structural element is a solid structure, and the material of the anisotropic structural element is a uniform light-transmitting solid material, the refractive index of which is higher than that of air.

[0012] Preferably, the geometric parameters and refractive index of the anisotropic structural element are obtained by parameter optimization starting from the initial design values ​​of the anisotropic structural element. The geometric parameters include: the shape of the upper surface curve segment, the length of the upper surface straight segment, the shape of the lower surface curve segment, the length of the lower surface straight segment, the distance between the upper and lower surfaces, and the shortest distance between the front and rear surfaces. The initial design value of the distance between the upper and lower surfaces is determined by the field of view range along the flight direction of the aircraft to be simulated. The initial design value of the shortest distance between the front and rear surfaces is determined by the minimum thickness of the compressed flow field region to be simulated. The initial design value of the refractive index of the anisotropic structural element is determined by the equivalent refractive index of the compressed flow field region to be simulated.

[0013] Preferably, obtaining the refractive index of the compressed flow field region to be simulated includes: performing numerical simulation of the compressed flow field region outside the optical window using fluid dynamics methods; establishing a three-dimensional flow field grid covering different viewing angle regions using the numerically simulated compressed flow field region outside the optical window; obtaining the temperature field, pressure field, and density field distribution on each grid node in the three-dimensional flow field grid based on the three-dimensional flow field grid; and converting the density field into a refractive index field of the corresponding wavelength based on the Gladstone-Dale formula to obtain the refractive index.

[0014] Preferably, the calculation of aero-optical transmission aberrations includes: solving the ray equation using the fourth-order Runge-Kutta method, calculating the deviation between the wavefront phase distribution of light rays after passing through the refractive index at different viewing angles and the ideal reference wavefront phase distribution at the same viewing angle without a flow field, and obtaining the aero-optical transmission aberrations corresponding to different viewing angles.

[0015] Preferably, the parameter optimization adopts an iterative optimization algorithm, with the optimization criterion being minimizing the deviation between the aberration distribution of anisotropic structural elements and aero-optical transmission aberration.

[0016] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention combines the convex curved surface of an anisotropic structural element as the incident surface with a standard plane as the exit surface, so that light rays from different field angles undergo continuously varying cumulative optical paths within the anisotropic structural element, naturally generating a wavefront aberration distribution that varies continuously with the field of view.

[0017] The anisotropic structural element of this invention employs a physical structure, requiring no power supply, no servo control, and no moving parts, greatly reducing system complexity and manufacturing costs. Simultaneously, the solid optical glass possesses long-term stability, is unaffected by electromagnetic interference, and is suitable for deployment in various laboratory environments.

[0018] By changing the shape and size of the upper surface curved segment, the upper surface straight segment, the lower surface curved segment, the lower surface straight segment, the distance between the upper and lower surfaces, the shortest distance between the front and rear surfaces, and the refractive index of the material, the aero-optical transmission effects at different flight Mach numbers and flight altitudes can be simulated. The solid structure can be adapted to different wavebands by changing different materials, greatly expanding the system's application scenarios.

[0019] This invention can directly generate physically degraded images with non-isohalous distortion, providing a real and reliable source of experimental data for the performance evaluation of subsequent aero-optical aberration correction systems and the training and verification of image restoration algorithms, and strongly supporting the improvement of target detection and recognition capabilities of high-speed aircraft. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a composition diagram of the aero-optical transmission effect simulation system provided according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the compressed flow field region to be simulated according to an embodiment of the present invention; Figure 3 This is a structural diagram of an anisotropic structural element provided according to an embodiment of the present invention; Figure 4 The ±5° is obtained by ray tracing calculation of the compressed flow field region to be simulated, as provided in the embodiments of the present invention. Distribution of aero-optical transmission aberrations at different line-of-sight angles within a ±5° field of view; Figure 5 The ±5° is obtained by ray tracing calculation of the compressed flow field region to be simulated, as provided in the embodiments of the present invention. Deviation distribution of aero-optical transmission aberrations at different line-of-sight angles and aero-optical transmission aberrations at the center of the field of view within a ±5° field of view; Figure 6 The anisotropic structural element provided according to the embodiments of the present invention is within ±5° ±5° field of view line-of-sight aberration distribution map of aero-optical transmission aberrations; Figure 7 The anisotropic structural element provided according to the embodiments of the present invention is within ±5° Deviation distribution diagram of aero-optical transmission aberrations at the line-of-sight angle within ±5° field of view and aero-optical transmission aberrations at the center of the field of view.

[0021] The reference numerals in the figures include: Light source 1; Target Simulator 2; Collimation subsystem 3; Anisotropic structural element 4, upper surface 41, rear surface 42, front surface 43, lower surface 44, upper surface curved segment 411, upper surface straight segment 412, upper surface perpendicular bisector 413, lower surface curved segment 441, lower surface straight segment 442, lower surface perpendicular bisector 443 Imaging subsystem 5. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and do not constitute a limitation thereof. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; the relevant operations can be fully understood based on the description in the specification and general technical knowledge in the art.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined to form various implementations. Furthermore, the order of the steps or actions in the method description can be changed or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] Please see Figure 1 In one embodiment of the present invention, a pneumatic optical transmission effect simulation system is provided, comprising: a light source 1, a target simulator 2, a collimation subsystem 3, an anisotropic structural element 4, and an imaging subsystem 5; Among them, light source 1 is used to emit light, and the light passes through target simulator 2 to form a light ray carrying the test image; The target simulator 2 is positioned at the object-side focal plane of the collimation subsystem 3, which is used to convert the light carrying the test image into parallel light carrying the test image. The anisotropic structural element 4 includes an incident surface and an exit surface. The incident surface is a convex curved surface, and the exit surface is a standard plane. Parallel light carrying the test image passes through the anisotropic structural element 4. The light emitted from the anisotropic structural element 4 contains aero-optical transmission aberrations that change continuously with the line of sight angle. The imaging subsystem 5 is used to receive the light emitted from the anisotropic structural element 4 and to form an image.

[0028] Please refer to Figure 2 The aero-optical transmission effect to be simulated is caused by the anisotropic compressible flow field region A2 generated by the high-speed motion of the aircraft A1 relative to the incoming flow. The anisotropic compressible flow field region A2 has different density distributions in different viewing angle directions, causing light rays at different viewing angles to experience a continuously changing flow field structure, thereby producing the non-uniform corona characteristics of the aero-optical transmission effect.

[0029] The aero-optical transmission effect simulation system includes: a light source 1, a target simulator 2, a collimation subsystem 3, an anisotropic structural element 4, and an imaging subsystem 5 arranged sequentially along the optical path.

[0030] Light source 1 provides uniform illumination for the aero-optical transmission effect simulation system. The light emitted by light source 1 passes through target simulator 2, forming a ray carrying the test image. Light source 1 uses an incoherent light source to avoid interference fringes and speckle noise generated by coherent light in the system, ensuring that the image acquired by imaging subsystem 5 only reflects the influence of aero-optical transmission effect.

[0031] The target simulator 2 is used to provide test images for the aero-optical transmission effect simulation system. The target simulator 2 is positioned at the object-side focal plane of the collimation subsystem 3, and uses a transmissive film or a resolution test target as the carrier for the test image. Light emitted from the light source 1 passes through the transmissive film or resolution test target, and light rays are emitted from each point in the test image, forming a light beam carrying the test image. The target simulator 2 can be a striped target or a grid target.

[0032] Light carrying the test image enters the collimation subsystem 3, which converts the light carrying the test image into a parallel light carrying the test image, simulating a light carrying the test image at an infinite distance as a light carrying the test image at an infinite distance. The collimation subsystem 3 can be implemented using a transmission optical structure, a reflection optical structure, or a catadioptric optical structure. When a transmission structure is adopted, the collimation subsystem 3 includes one or more lenses arranged sequentially from the object side to the image side along the optical path. By combining the optical power of each lens, the object-side focal plane of the collimation subsystem 3 is located at the position of the target simulator 2, so that the light emitted from each object point of the test image of the target simulator 2 is emitted as parallel light after passing through the collimation subsystem 3. When a reflection structure is adopted, the collimation subsystem 3 uses an off-axis parabolic mirror or a coaxial parabolic mirror. The target simulator 2 is placed at the focal plane of the parabolic mirror. The light carrying the test image is reflected by the parabolic mirror and emitted as parallel light. When a catadioptric structure is adopted, the collimation subsystem 3 includes a combination of a reflective element and a transmission element. The target simulator 2 is placed at the focal plane of the parabolic mirror. The reflective element and the transmission element together collimate the light carrying the test image into parallel light for emission. The aperture and focal length of the collimation subsystem 3 are determined based on the size of the target simulator 2 and the required field of view range to ensure that the light carrying the test image at different viewing angles can fill the aperture of the collimation subsystem 3 and exit as parallel light rays. In this embodiment, the collimation subsystem 3 is implemented using a transmission optical structure.

[0033] Please see Figure 3 The anisotropic structural element 4 is the core component of this system. It adopts a trapezoidal columnar structure and includes an incident surface and an exit surface. The incident surface is a convex curved surface, and the exit surface is a standard plane. After the parallel light carrying the test image passes through the anisotropic structural element 4, it forms aero-optical transmission aberrations that change continuously with the line of sight angle.

[0034] The anisotropic structural element 4 includes an upper surface 41, a lower surface 44, a front surface 43, and a rear surface 42.

[0035] The upper surface 41 is composed of an upper surface curved segment 411 and an upper surface straight segment 412. The upper surface curved segment 411 is symmetrical about the upper surface perpendicular line 413 of the upper surface straight segment 412.

[0036] The lower surface 44 is composed of a lower surface curved segment 441 and a lower surface straight segment 442. The lower surface curved segment 441 is symmetrical about the lower surface perpendicular line 443 of the lower surface straight segment 442.

[0037] The rear surface 42 is bounded by the upper surface straight line segment 412, the lower surface straight line segment 442, and the lines connecting the two endpoints of the upper surface straight line segment 412 and the two endpoints of the lower surface straight line segment 442. The lines connecting the endpoints of the upper surface straight line segment 412 and the endpoints of the lower surface straight line segment 442 do not intersect.

[0038] The upper surface 41 and the lower surface 44 are both perpendicular to the rear surface 42 and are located on the same side of the rear surface 42.

[0039] The front surface 43 is obtained by lofting the upper surface curve segment 411 and the lower surface curve segment 441. Using the upper surface curve segment 411 and the lower surface curve segment 441 as guide lines, it is stretched and lofted in a direction perpendicular to the rear surface 42 to form an outwardly convex curved surface structure, which serves as the incident surface of the anisotropic structural element 4. The front surface 43, together with the upper surface 41, the lower surface 44, and the rear surface 42, forms a closed structure.

[0040] In this embodiment, the anisotropic structural element 4 adopts a solid structure, and its material is a uniform, light-transmitting solid material. The refractive index of the light-transmitting solid material is higher than that of air, in order to simulate the compressed flow field region where the refractive index is higher than that of the uncompressed region after compression. The light-transmitting solid material is optical glass, and its surface accuracy meets the requirements of optical imaging.

[0041] The imaging subsystem 5 includes a camera and an imaging lens, used to receive and image the light emitted from the anisotropic structural element 4, generating a degraded image with non-isotropic aero-optical transmission effects. The degraded image is used to evaluate the impact of aero-optical transmission effects on the performance of the optical system, or to support the design of aberration correction systems and the development of image restoration algorithms. The camera can be a CCD camera, and the parameters of the imaging lens are determined based on the required field of view and image plane size to be simulated.

[0042] The shape of the anisotropic structural element 4 matches the shape of the compressed flow field region to be simulated. Specifically: The upper surface 41 represents the cross-section of the compressed flow field region to be simulated near the nose of the aircraft. The initial design value of the upper surface curve segment 411 is close to the boundary of the compressed flow field region to be simulated near the nose of the aircraft, where it contacts the uncompressed flow field region. The nose of the aircraft refers to the foremost point of the aircraft along the flight direction.

[0043] The lower surface 44 represents the cross-section of the compressed flow field region to be simulated near the tail of the aircraft. The initial design value of the lower surface curve segment 441 is close to the boundary of the compressed flow field region to be simulated near the tail of the aircraft, where it contacts the uncompressed flow field region. The tail of the aircraft refers to the very end of the aircraft along the flight direction.

[0044] The front surface 43 represents the curved surface at the intersection of the compressed flow field region to be simulated and the uncompressed flow field region. The initial design value of the straight line segment 412 on the upper surface is close to the optical window near the boundary where the nose of the aircraft contacts the compressed flow field region to be simulated; the initial design value of the straight line segment 442 on the lower surface is close to the optical window near the boundary where the tail of the aircraft contacts the compressed flow field region to be simulated.

[0045] The rear surface 42 represents the plane where the optical window is located, that is, the plane at the intersection of the compressed flow field region to be simulated and the optical window.

[0046] The geometry of the anisotropic structural element 4 is consistent with the spatial morphology of the actual flow field during the initial design stage.

[0047] The design geometric parameters of the anisotropic structural element 4 include: the shape of the upper surface curved segment 411, the length of the upper surface straight segment 412, the shape of the lower surface curved segment 441, the length of the lower surface straight segment 442, the distance between the upper surface 41 and the lower surface 44, the shortest distance between the front surface 43 and the rear surface 42, and the refractive index of the material of the anisotropic structural element 4. The initial values ​​of each parameter are determined according to the following principles: The initial design value of the distance between the upper surface 41 and the lower surface 44 (i.e. the height of the trapezoidal column structure) is determined by the field of view range along the flight direction of the aircraft that needs to be simulated. This ensures that when light is transmitted within the field of view range, it passes through the anisotropic structural element 4 completely through the front surface 43 and the rear surface 42. In other words, it ensures that light from different field of view angles can enter from the front surface 43 and exit from the rear surface 42.

[0048] The initial design value of the shortest distance between the front surface 43 and the rear surface 42 (i.e., the minimum thickness of the trapezoidal columnar structure) is determined by the minimum thickness of the compressed flow field region to be simulated. This minimum thickness typically occurs at the thinnest point of the compressed flow field region near the nose of the aircraft.

[0049] The initial design value of the refractive index of the anisotropic structural element 4 is determined by the equivalent refractive index of the compressed flow field region to be simulated. The equivalent refractive index refers to the average value of the refractive index of the compressed flow field to be simulated outside the optical window of the aircraft under the simulated flight conditions. For solid structures, this refractive index is achieved by selecting a light-transmitting solid material with a corresponding refractive index.

[0050] Please see Figure 4 and Figure 5 Based on the actual aero-optical transmission effect to be simulated, the specific geometric parameters and refractive index of the anisotropic structural element 4 are determined so that the aberration distribution generated by the anisotropic structural element 4 accurately matches the aero-optical transmission aberration generated by the actual flow field.

[0051] To obtain the refractive index of the compressed flow field region to be simulated, the following steps are taken: numerically simulating the compressed flow field outside the optical window of the aircraft using hydrodynamic methods; establishing a three-dimensional flow field mesh covering different viewing angle regions using the numerically simulated compressed flow field outside the optical window; obtaining the temperature field, pressure field, and density field distribution at each mesh node in the three-dimensional flow field mesh based on the three-dimensional flow field mesh; and then converting the solved density field into a refractive index field corresponding to the wavelength based on the Gladstone-Dale formula (GD formula) to obtain the refractive index that varies with spatial position.

[0052] Ray tracing is performed on the propagation path of light carrying the test image through the refractive index to calculate aero-optical transmission aberrations. The light rays are incident at different angles into the refractive index field, and the ray equations are numerically solved using the fourth-order Runge-Kutta method. During the solution process, the propagation path and cumulative optical path of each ray in the flow field are recorded. When a ray reaches the receiving aperture, its corresponding wavefront phase is extracted. The wavefront phase distribution of the light rays at different viewing angles after passing through the flow field and reaching the receiving aperture is compared with the ideal reference wavefront phase distribution at the same viewing angle without a flow field to obtain the wavefront aberrations corresponding to each viewing angle. This yields the aero-optical transmission aberrations that continuously vary with the viewing angle. Simultaneously, the deviation distribution between the aero-optical transmission aberrations at each viewing angle and the aero-optical transmission aberration at the center of the field of view is calculated. This deviation distribution quantitatively characterizes the strength of the non-uniform halo characteristic.

[0053] Starting from the initial values ​​of the determined parameters, the geometric and material parameters of the anisotropic structural element 4 are iteratively optimized using a parameter optimization method. This is achieved by adjusting the following parameters: the shape of the upper surface curve segment 411, the length of the upper surface straight segment 412, the shape of the lower surface curve segment 441, the length of the lower surface straight segment 442, the distance between the upper surface 41 and the lower surface 44, the shortest distance between the front surface 43 and the rear surface 42, and the refractive index of the material of the anisotropic structural element 4.

[0054] The parameter optimization employs an iterative optimization algorithm, with the optimization criterion being minimizing the deviation between the aberration distribution of the anisotropic structural element 4 and the aero-optical transmission aberration. The parameter optimization includes: an initialization step, which uses the initial values ​​of each design parameter of the anisotropic structural element 4 as the current parameter set, i.e., initializing the optimization process; an evaluation step, which calculates the aero-optical transmission aberration corresponding to the current parameter set and determines the fitness of the current parameter set relative to the optimization criterion; an update step, which perturbs the parameters of the current parameter set based on the fitness to generate the next generation parameter set; and an iteration step, which repeats the evaluation and update steps until a preset termination condition is met, and the parameter set with the smallest fitness deviation when the termination condition is met is taken as the optimization result.

[0055] Please see Figure 4 , Figure 5 , Figure 6 and Figure 7 . Figure 4 ±5° is obtained through ray tracing calculations of the compressed flow field region to be simulated. Distribution of aero-optical transmission aberrations at different line-of-sight angles within a ±5° field of view; Figure 5 ±5° is obtained through ray tracing calculations of the compressed flow field region to be simulated. Deviation distribution of aero-optical transmission aberrations at different line-of-sight angles and aero-optical transmission aberrations at the center of the field of view within a ±5° field of view; Figure 6 For anisotropic structural element 4 at ±5° ±5° field of view line-of-sight aberration distribution map of aero-optical transmission aberrations; Figure 7 For anisotropic structural element 4 at ±5° Deviation distribution diagram of aero-optical transmission aberrations at the line-of-sight angle within a ±5° field of view versus aero-optical transmission aberrations at the center of the field of view. (Comparison) Figure 4 and Figure 6 , Figure 5 and Figure 7 It can be seen that the deviation distribution of the aero-optical transmission aberration generated by the anisotropic structural element 4 from the aero-optical transmission aberration at the center of the field of view is highly consistent with the corresponding distribution generated by the compressed flow field region to be simulated, proving that the anisotropic structural element 4 of the present invention can accurately reproduce the non-uniform characteristics of the real aero-optical transmission effect.

[0056] In summary, the above description is merely a preferred embodiment of this specification and is not intended to limit the scope of protection of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

[0057] The systems, apparatuses, modules, or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, a computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0058] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0059] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

Claims

1. A system for simulating aero-optical transmission effects, characterized in that, include: Light source, target simulator, collimation subsystem, anisotropic structural elements, and imaging subsystem; The light source is used to emit light, which passes through the target simulator to form a light beam carrying the test image; The target simulator is positioned at the object-side focal plane of the collimation subsystem, which is used to convert the light carrying the test image into parallel light carrying the test image. The anisotropic structural element includes an incident surface and an exit surface. The incident surface is a convex curved surface, and the exit surface is a standard plane. The parallel light carrying the test image passes through the anisotropic structural element, and the light emitted from the anisotropic structural element contains aero-optical transmission aberrations that vary continuously with the line of sight angle. The imaging subsystem is used to receive the light emitted from the anisotropic structural element and to form an image.

2. The aero-optical transmission effect simulation system according to claim 1, characterized in that, The target simulator uses a transmissive film or a resolution test target as the carrier for each point in the test image.

3. The aero-optical transmission effect simulation system according to claim 1, characterized in that, The collimation subsystem is implemented using a transmission optical structure, a reflection optical structure, or a catadioptric optical structure. The aperture and focal length of the collimation subsystem are determined based on the size of the test image and the required simulated field of view.

4. The aero-optical transmission effect simulation system according to claim 1, characterized in that, The perimeter of the anisotropic structural element includes: the upper surface, the lower surface, the front surface, and the rear surface; The upper surface includes: an upper surface curved segment and an upper surface straight segment, wherein the upper surface curved segment is symmetrical about the perpendicular bisector of the upper surface straight segment; The lower surface includes: a lower surface curved segment and a lower surface straight segment, wherein the lower surface curved segment is symmetrical about the perpendicular bisector of the lower surface straight segment; The rear surface includes: a straight line segment of the upper surface, a straight line segment of the lower surface, and a line connecting the two endpoints of the straight line segment of the upper surface and the two endpoints of the straight line segment of the lower surface; the line connecting the endpoints of the straight line segment of the upper surface and the endpoints of the straight line segment of the lower surface does not intersect; the upper surface and the lower surface are both perpendicular to the rear surface; the upper surface and the lower surface are both located on the same side of the rear surface. The front surface is obtained by lofting the upper surface curve segment and the lower surface curve segment; The front surface, the upper surface, the lower surface, and the rear surface form a closed structure.

5. The aero-optical transmission effect simulation system according to claim 4, characterized in that, The shape of the anisotropic structural element is defined as follows: The initial design value of the upper surface curve segment is the boundary of the compressed flow field region to be simulated, which is close to the nose of the aircraft and in contact with the uncompressed flow field region. The initial design value of the lower surface curve segment is the boundary of the compressed flow field region to be simulated, which is close to the tail of the aircraft and in contact with the uncompressed flow field region. The initial design value of the straight segment on the upper surface is the boundary where the optical window is close to the nose of the aircraft and in contact with the region of the compressed flow field to be simulated. The initial design value of the straight segment on the lower surface is the boundary where the optical window is close to the tail of the aircraft and in contact with the region of the compressed flow field to be simulated.

6. The aero-optical transmission effect simulation system according to claim 1, characterized in that, The anisotropic structural element is a solid structure, and the material of the anisotropic structural element is a uniform light-transmitting solid material, the refractive index of which is higher than that of air.

7. The aero-optical transmission effect simulation system according to claim 5, characterized in that, The geometric parameters and refractive index of the anisotropic structural element are obtained by parameter optimization starting from the initial design value of the anisotropic structural element. The geometric parameters include: the shape of the upper surface curve segment, the length of the upper surface straight segment, the shape of the lower surface curve segment, the length of the lower surface straight segment, the distance between the upper and lower surfaces, and the shortest distance between the front and rear surfaces. The initial design value of the distance between the upper and lower surfaces is determined by the field of view range along the flight direction of the aircraft to be simulated. The initial design value of the shortest distance between the front and rear surfaces is determined by the minimum thickness of the compressed flow field region to be simulated. The initial design value of the refractive index of the anisotropic structural element is determined by the equivalent refractive index of the compressed flow field region to be simulated.

8. The aero-optical transmission effect simulation system according to claim 7, characterized in that, Obtaining the refractive index of the compressed flow field region to be simulated includes: performing numerical simulation of the compressed flow field region outside the optical window using hydrodynamic methods; establishing a three-dimensional flow field grid covering different viewing angle regions using the numerically simulated compressed flow field region outside the optical window; obtaining the temperature field, pressure field, and density field distribution on each grid node in the three-dimensional flow field grid based on the three-dimensional flow field grid; and converting the density field into a refractive index field of the corresponding wavelength based on the Gladstone-Dale formula to obtain the refractive index.

9. The aero-optical transmission effect simulation system according to claim 8, characterized in that, The calculation of the aero-optical transmission aberration includes: solving the ray equation using the fourth-order Runge-Kutta method; calculating the deviation between the wavefront phase distribution of light rays after passing through the refractive index at different viewing angles and the ideal reference wavefront phase distribution at the same viewing angle without a flow field; and obtaining the aero-optical transmission aberration corresponding to different viewing angles.

10. The aero-optical transmission effect simulation system according to claim 9, characterized in that, The parameter optimization employs an iterative optimization algorithm, with the optimization criterion being minimizing the deviation between the aberration distribution of the anisotropic structural element and the aero-optical transmission aberration.

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