Stealth coating damage area three-dimensional reconstruction method based on microwave thermal imaging

Abstract

The invention relates to a microwave thermal imaging-based stealth coating damage area three-dimensional reconstruction method, which belongs to the technical field of measurement, solves the problem of insufficient reconstruction accuracy of stealth coating damage in the prior art, and comprises the following steps: S1, carrying out microwave thermal imaging treatment on a stealth coating with damage to obtain an infrared temperature cloud picture of the surface of the stealth coating; s2, processing to obtain a to-be-reconstructed invisible coating damage area; s3, dividing a to-be-reconstructed invisible coating damage area into triangular surface element grids of a plurality of planes; s4, the center of each triangular surface element grid obtained through division is calculated, the center temperature of each triangular surface element grid is obtained, and the generalized reflectivity of the center of each triangular surface element grid is calculated; s5, calculating the depth of the center of each triangular surface element grid; s6, constructing a triangular body element by combining the depth of the center of each triangular surface element grid; and S7, combining all the triangular voxels to obtain the damage area of the three-dimensional reconstructed stealth coating.

Description

Technical Field

[0001] The present invention relates to the field of measurement technology, and in particular to a three-dimensional reconstruction method of a stealth coating damage area based on microwave thermal imaging. Background Art

[0002] With the continuous development of aerospace technology, the application of stealth technology in aircraft and other equipment is one of the effective ways to improve their functions. Coating radar-absorbing stealth coating (stealth coating for short) is a typical stealth technology. Due to its simple operation and high effectiveness, it has been widely used in targets such as aircraft, ships and ground missile launchers. However, during the service of equipment, due to the long-term exposure of stealth coating to various complex environments, the coating often suffers from scratches, peeling, oxidation and deterioration, such as Figure 2 As shown in the figure, damage types include blistering, cracking, shedding, powdering, rusting, and deterioration; damage shapes mainly include point, line, surface, and irregular shapes. These damages seriously affect the stealth performance of equipment, thereby reducing its safety and functionality. Therefore, detecting, evaluating, and repairing stealth coating damage is of great significance to maintaining the stealth performance of equipment.

[0003] Inspection of stealth coatings is a crucial preparatory step before evaluation and repair, determining whether and how the coating should be repaired. Currently, the main methods for detecting damage to stealth coatings include ultrasonic technology, eddy current technology, radiographic methods, and infrared thermal imaging. Each of these methods has its own advantages and disadvantages. Ultrasonic technology, for example, offers strong penetration and is portable and lightweight, making it easy to carry around. However, it can be challenging to inspect complex workpieces and requires the application of a coupling agent, which can indirectly affect the performance of the stealth coating.

[0004] Damage detection for stealth coatings is a prerequisite for evaluating and repairing them. Whether repairs are warranted depends primarily on the damage's impact on the equipment's stealth performance. Due to the diverse nature of damage, the impacts of different types on stealth performance vary significantly. Detecting damage is a prerequisite, and assessing it is essential. 3D reconstruction of different types of stealth coating damage serves as a bridge between detection and assessment.

[0005] Therefore, there is a need in the art for an improved reconstruction method for damage to the stealth coating of equipment, so as to achieve a rapid and accurate assessment of the impact of the damage on the stealth performance of the equipment. Summary of the Invention

[0006] In view of the above problems, the present invention provides a three-dimensional reconstruction method of stealth coating damage areas based on microwave thermal imaging. This method can realize the three-dimensional reconstruction of stealth coating damage areas of weapons and equipment, effectively solve the impact analysis of coating damage on the stealth performance of equipment, and provide quick and intuitive judgment for equipment damage assessment and maintenance.

[0007] According to an embodiment of the present invention, a method for three-dimensional reconstruction of a stealth coating damage area based on microwave thermal imaging is provided, comprising the following steps:

[0008] Step S1: Microwave thermal imaging of the damaged stealth coating to obtain an infrared temperature cloud map of the stealth coating surface;

[0009] Step S2: Based on the obtained infrared temperature cloud map of the stealth coating surface, the damaged area of ​​the stealth coating to be reconstructed is determined according to the temperature of the damaged area being higher than the temperature of the undamaged area;

[0010] Step S3: performing triangular facet meshing on the damaged area of ​​the stealth coating to be reconstructed, dividing the area into a plurality of triangular facet meshes of a plane;

[0011] Step S4: Calculate the center of each triangular facet mesh obtained by division, obtain the center temperature of each triangular facet mesh, and calculate the generalized reflectivity of the center of each triangular facet mesh;

[0012] Step S5: Calculating the depth of the center of each triangular facet mesh based on the generalized reflectivity of the center of each triangular facet mesh;

[0013] Step S6: Constructing triangular volume elements by combining the depths of the centers of the triangular facet meshes;

[0014] Step S7: Combine all triangular elements to obtain a three-dimensionally reconstructed damaged area of ​​the stealth coating, and provide it to equipment damage assessment and repair processing.

[0015] Optionally, step S1 specifically includes:

[0016] Step S1.1: The test begins by preparing a sample with damaged stealth coating;

[0017] Step S1.2: Setting the heating antenna and aligning the heating antenna with the stealth coating;

[0018] Step S1.3: heating the stealth coating via a heating antenna;

[0019] Step S1.4: The heating antenna heats the stealth coating to a constant temperature and records the temperature of the stealth coating surface;

[0020] Step S1.5: Detecting infrared radiation from the surface of the stealth coating using an infrared detector of the optical system, converting the infrared radiation signal into an electrical signal, and providing it to a computer;

[0021] Step S1.6: The computer processes the obtained electrical signal to obtain an infrared temperature cloud map of the stealth coating surface.

[0022] Optionally, step S2 specifically includes:

[0023] Step S2.1: Preprocessing the infrared temperature cloud image of the stealth coating surface using image noise reduction;

[0024] Step S2.2: performing image enhancement processing on the infrared temperature cloud image of the stealth coating surface after noise reduction;

[0025] Step S2.3: For the infrared temperature cloud image after noise reduction and enhancement, the damaged area of ​​the stealth coating to be reconstructed is determined based on the fact that the temperature of the damaged area is higher than the temperature of the undamaged area.

[0026] Optionally, step S4 specifically includes:

[0027] Step S4.1, calculating the center of each triangular facet mesh obtained by division, and extracting the coordinates and temperature of the mesh nodes of each triangular facet mesh;

[0028] Step S4.2, calculating the center coordinates and temperature of each triangular facet mesh, and calculating the center point temperature of the triangular facet mesh;

[0029] Step S4.3, based on the obtained center point temperature of the triangular surface mesh, calculate the generalized reflectivity of the center of each triangular surface mesh.

[0030] Optionally, step S5 specifically includes:

[0031] The obtained generalized reflectivity of the center of each triangular facet mesh is used as the generalized reflectivity of the triangular facet mesh and substituted into the following formula to calculate the depth of the center of each triangular facet mesh:

[0032]

[0033] Among them, E i represents the generalized reflectivity of the i-th layer of stealth coating, i represents the number of the stealth coating and i=1,2,…,n, n is the total number of stealth coating layers, μ i represents the magnetic permeability of the i-th stealth coating, ε i represents the dielectric constant of the i-th stealth coating, d i represents the thickness of the i-th layer of stealth coating, λ represents the wavelength, e represents the exponent, η i represents the wave impedance of the i-th stealth coating, γ i represents the propagation factor of the i-th layer of stealth coating; where, when i=1, E i-1 is the generalized reflectivity of the metal substrate; when i = n, η i+1 is the wave impedance of air.

[0034] Optionally, step S6 specifically includes:

[0035] Based on the method in step S5, the depth of the center of the triangular surface element grid is obtained. With the triangular surface element grid as the plane and the depth of its center point as the thickness, a triangular prism-shaped triangular element is constructed as the element unit of the stealth coating damage area.

[0036] Compared with the existing technology, the present invention has at least the following beneficial effects: the present invention uses microwave thermal imaging technology to perform heating / cooling imaging on damaged stealth coating samples, analyzes the thermal infrared cloud map of the sample and extracts the areas with higher temperatures, and finely divides the areas with higher temperatures into "triangular surface element grids". By applying the multi-physics field relationship of heat transfer and electromagnetics, the depth information of the "triangular surface element grid" is obtained, and then the "triangular body elements" are obtained. All the "triangular body elements" are combined to realize three-dimensional reconstruction of the damaged area of ​​the stealth coating, which can improve the efficiency of stealth coating damage assessment and maintenance and reduce the maintenance cost of equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order 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. By referring to the drawings, the features and advantages of the present invention can be more clearly understood. The drawings are schematic and should not be understood as limiting the present invention in any way. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0038] Figure 1 It is a flow chart of a method for three-dimensional reconstruction of a stealth coating damage area based on microwave thermal imaging provided according to an embodiment of the present invention.

[0039] Figure 2 It is a logic diagram for stealth coating damage behavior analysis.

[0040] Figure 3 This is a flow chart of microwave thermal imaging of stealth coating samples in a three-dimensional reconstruction method of a stealth coating damage area based on microwave thermal imaging provided according to an embodiment of the present invention.

[0041] Figure 4 It is a schematic diagram of the "triangular facet mesh" of the damaged area of ​​the stealth coating sample obtained by applying the example of the three-dimensional reconstruction method of the damaged area of ​​the stealth coating based on microwave thermal imaging provided according to the embodiment of the present invention.

[0042] Figure 5 It is a schematic diagram of the three-dimensional reconstruction of the damaged area of ​​the stealth coating sample obtained by applying an example of the three-dimensional reconstruction method of the damaged area of ​​the stealth coating based on microwave thermal imaging provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features therein can be combined with each other without conflict.

[0044] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0045] The following describes in detail a method for three-dimensional reconstruction of a stealth coating damage area based on microwave thermal imaging according to an embodiment of the present invention with reference to the accompanying drawings.

[0046] like Figure 1 As shown, a three-dimensional reconstruction method of a stealth coating damage area based on microwave thermal imaging provided in accordance with an embodiment of the present invention includes the following steps.

[0047] Step S1: Microwave thermal imaging of the damaged stealth coating to obtain an infrared temperature cloud map of the surface of the stealth coating. The damage to the stealth coating to be detected causes heat transfer obstruction, resulting in differences in the surface temperature of the stealth coating. The surface temperature of the stealth coating is transmitted to the optical system through the atmosphere in the form of infrared radiation. The infrared detector in the optical system obtains the infrared radiation on the surface of the stealth coating and converts the infrared radiation signal into an electrical signal, which is provided to the computer for processing. The computer processes the electrical signal to obtain an infrared temperature cloud map of the surface of the stealth coating. The infrared detector can use an infrared thermal imager. Optionally, the stealth coating is a radar absorbing coating. The detection process is as follows: Figure 3 The step S1 specifically includes the following steps.

[0048] Step S1.1: The test begins by preparing a sample with damaged stealth coating.

[0049] Step S1.2: Set up the heating antenna and align the heating antenna with the stealth coating.

[0050] Step S1.3: heating the stealth coating via the heating antenna.

[0051] Step S1.4: The heating antenna heats the stealth coating to a constant temperature and records the temperature value of the stealth coating surface.

[0052] Step S1.5: Detect infrared radiation from the surface of the stealth coating through the infrared detector of the optical system, convert the infrared radiation signal into an electrical signal, and provide it to the computer.

[0053] Step S1.6: The computer processes the obtained electrical signal to obtain an infrared temperature cloud map of the stealth coating surface.

[0054] Step S2: Based on the obtained infrared temperature cloud map of the stealth coating surface, the damaged stealth coating region to be reconstructed is determined, as the damaged region is higher in temperature than the undamaged region. The region with a higher temperature than other regions on the stealth coating surface is processed and extracted as the damaged region to be reconstructed. The computer extracts the higher temperature regions on the stealth coating surface based on the temperature cloud map. Step S2 specifically includes the following steps.

[0055] Step S2.1: Preprocess the infrared temperature cloud map of the stealth coating surface using image noise reduction. The infrared cloud map detected by the infrared thermal imager contains a certain amount of noise, requiring some preprocessing of the original infrared cloud map. Image noise reduction and image enhancement are used to preprocess the infrared cloud map. The noise sources of infrared images mainly include system noise and environmental noise. System noise is generated by the system itself and can be reduced by improving the system and components. Environmental noise mainly includes background noise caused by the object's own radiation and interference noise from impurities in the air. It can be addressed by using filtering noise reduction methods such as mean, median, and Gaussian.

[0056] Step S2.2: Perform image enhancement on the de-noised infrared temperature cloud image of the stealth coating surface. After de-noising the original infrared cloud image, it needs to be enhanced to improve the distinction of damaged areas and to make the details of the damaged areas clearer. Image enhancement can be performed using grayscale transformation, which can include linear, piecewise linear, and nonlinear transformations, depending on the transformation method.

[0057] Step S2.3: For the infrared temperature cloud map after noise reduction and enhancement, where the temperature of the damaged area is higher than that of the undamaged area, determine the damaged area of ​​the stealth coating to be reconstructed. After the above image preprocessing, the infrared temperature cloud map obtained by the original detection obtains a clearer infrared cloud map, where the temperature of the damaged area is significantly higher than that of the undamaged area. The area with a temperature significantly higher than that of other areas is extracted as the damaged area of ​​the stealth coating to be reconstructed. The temperature of the undamaged area is close to the ambient temperature. For example, when the ambient temperature is 20°C, the area with a surface temperature of 22 to 25°C can be extracted from the infrared temperature cloud map of the stealth coating surface, that is, the area 2 to 5°C higher than other areas as the damaged area of ​​the stealth coating to be reconstructed.

[0058] Step S3: Perform triangular binning on the damaged area of ​​the stealth coating to be reconstructed. CAD software is used to perform fine triangular binning on the damaged area of ​​the stealth coating to be reconstructed, evenly dividing the surface of the damaged area of ​​the stealth coating to be reconstructed into a planar triangular mesh, i.e., a triangular bin mesh. Alternatively, CATIA software can be used for triangular binning. The number of triangular bin meshes can be set to cover the damaged area of ​​the stealth coating to be reconstructed, and the size of the triangular bin mesh can be set to no larger than 1 mm.

[0059] Step S4: Calculate the center of each triangular facet mesh obtained by division, obtain the center temperature of each triangular facet mesh, and use the center temperature of the triangular facet mesh to calculate the generalized reflectivity of the center of the triangular facet mesh. Optionally, this step obtains and calculates the center temperature and generalized reflectivity of the triangular facet mesh of a single layer of stealth coating. Step S4 specifically includes the following steps.

[0060] Step S4.1, calculate the center of each triangular facet mesh obtained by division, and extract the temperature of the mesh node of each triangular facet mesh. The mesh node coordinates and temperatures of the triangular facet mesh are:

[0061] {(x s ,y s ,z s ),T s}、{(x j ,y j ,z j ),T j} and {(x k ,y k ,z k ),T k}

[0062] Among them, (x s ,y s ,z s ) represents the coordinates of the sth grid node, T s represents the temperature corresponding to the sth grid node, s, j, and k represent the numbers of the grid nodes of the triangular surface grid, respectively, where the three grid nodes are the nodes of the three sides of the triangular surface grid.

[0063] The grid node coordinates of the triangular surface element grid can be exported from the grid file created when dividing the grid in step S3, and the grid node temperatures of the triangular surface element grid can be obtained from the infrared temperature cloud map of the stealth coating surface obtained in step S1.

[0064] Step S4.2, based on the obtained grid node coordinates of the triangular panel mesh, calculate the center coordinates of each triangular panel mesh:

[0065]

[0066] Based on the obtained temperature of the grid nodes of the triangular surface element grid, the temperature of the center point of the triangular surface element grid is calculated as:

[0067]

[0068] In step S4.3, based on the obtained center point temperature of the triangular surface grid, the generalized reflectivity of the center of each triangular surface grid is calculated as follows:

[0069]

[0070] in, is the generalized reflection coefficient of the stealth coating, represents the inverse of the energy density of the electromagnetic wave, ε is the solid surface emissivity and is dimensionless, and σ is the Boltzmann constant, which can be set to 5.67×10 -8 W·(m 2 ·K 4 ) -1 , T amb represents the test environment temperature, η0 represents the intrinsic impedance (or wave impedance) of free space, E i0 Represents the incident electromagnetic intensity.

[0071] Step S5: using the obtained generalized reflectivity of the center of each triangular surface mesh as the generalized reflectivity of the triangular surface mesh, the depth of the center of the triangular surface mesh is calculated to obtain the depth of each triangular surface mesh.

[0072] According to the transmission line theory, for an n-layer structure lined with a metal backplane (the metal substrate is the 0th layer, the outermost layer is the nth layer, and the air is the n+1th layer), the relationship between the generalized reflectivity of the flat absorbing material and the thickness of the stealth coating is:

[0073]

[0074] Among them, E i represents the generalized reflectivity of the i-th layer of stealth coating, i represents the number of the stealth coating and i=1,2,…,n, μ i represents the magnetic permeability of the i-th stealth coating, ε i represents the dielectric constant of the i-th stealth coating, d i represents the thickness of the i-th layer of stealth coating, λ represents the wavelength, e represents the exponent, η i represents the wave impedance of the i-th stealth coating, γ i represents the propagation factor of the i-th layer of stealth coating. When i=1, E i-1 is the generalized reflectivity of the metal substrate; when i = n, η i+1is the wave impedance of air.

[0075] The generalized reflectivity of the center of each triangular facet mesh obtained in step S4 is Substitute the above formula as the generalized reflectivity E of the i-th layer of stealth coating i , get the depth d of the center of each triangular facet grid of each layer of stealth coating i .

[0076] Here, a single-layer stealth coating is taken as an example, where i=1 represents the stealth coating, i-1=0 represents the metal substrate, and i+1=2 represents the air layer. The formula for calculating the depth of the center of the triangular surface element grid using the generalized reflectivity of the triangular surface element is:

[0077]

[0078] in, μ1 represents the magnetic permeability of the single-layer stealth coating, ε1 represents the dielectric constant of the single-layer stealth coating, d1 represents the thickness of the single-layer stealth coating, and η2 is the wave impedance of the air layer. i-1 is 1.

[0079] Step S6: Construct triangular volume elements based on the depth of the center of the obtained triangular surface element mesh.

[0080] Based on the method in step S5, the depth of the center of the triangular surface element grid is obtained. The triangular surface element grid is used as a plane and the depth of its center point is used as the thickness to construct a triangular prism triangular element, which is the element unit of the stealth coating damage area.

[0081] Step S7: Combine all triangular elements to three-dimensionally reconstruct the damaged area of ​​the stealth coating.

[0082] In step S7, all triangular elements obtained in step S6 are combined to obtain a 3D reconstruction of the stealth coating damage area, thereby achieving 3D reconstruction of the stealth coating damage area. The obtained 3D reconstruction of the stealth coating damage area can be provided for subsequent equipment damage assessment and repair processing.

[0083] Example 1

[0084] This embodiment 1 is an example of a three-dimensional reconstruction method of a stealth coating damage area based on microwave thermal imaging provided by the above-mentioned embodiment, wherein a single-layer stealth coating sample is tested, and the stealth coating sample is heated by microwaves to increase the surface temperature, and a temperature cloud map of the sample surface is obtained. The higher temperature area is extracted, and the higher temperature area is divided into a "triangular surface element grid" using CAD software. The center point depth of each triangular surface element grid is calculated by combining heat transfer and electromagnetics to obtain a "triangular element". After combining all the triangular elements, the three-dimensional reconstruction of the stealth coating damage area is achieved. The process is as follows: Figure 1 As shown, the specific steps include the following steps.

[0085] Step S1: Microwave thermal imaging of the damaged stealth coating. Specific test process, such as Figure 3 As shown in the figure, in a small microwave anechoic chamber, a damaged stealth coating sample is heated using a heating antenna, and the sample temperature is monitored using an infrared thermal imager. The antenna is first moved over the sample to heat it until it reaches a constant temperature and the temperature is recorded. The antenna is then removed and the sample is inspected using an infrared imager. To ensure effective inspection, the antenna must move as quickly as possible. In this embodiment, a motorized slide supports the antenna, and a microcontroller controls the motor drive to control the antenna's movement.

[0086] Step S2: Extract the area with higher temperature on the surface of the stealth coating.

[0087] Step S3: Divide the area with higher surface temperature of the stealth coating into a "triangular surface element grid".

[0088] The damaged area with higher temperature in the infrared cloud image is meshed and the triangular surface element mesh of the area is finely divided using CAD software CATIA. The mesh is divided as follows: Figure 4 As shown, in this embodiment, in order to better fit the contour information of the damaged area, the number of grids is set to about 20,000, so as to fit a more accurate contour of the damaged area.

[0089] Step S4: Calculate the coordinates of the center of the triangular facet mesh and obtain the center temperature information, and calculate the facet generalized reflectivity using the center temperature of the triangular facet mesh.

[0090] Extract the center temperature information of each triangular facet mesh. The coordinates and temperatures of the mesh nodes of the triangular facet mesh are {(x s ,y s ,z s ),T s}、{(x j ,y j ,z j ),T j} and {(x k ,y k ,z k ),T k}, then the coordinates and temperature of the center of the triangular face grid are

[0091] The generalized reflectivity at the center of the triangular facet grid is calculated using the following formula:

[0092]

[0093] in, is the generalized reflection coefficient of the stealth coating, represents the energy density of electromagnetic waves, ε is the solid surface emissivity, dimensionless, and σ is the Boltzmann constant, which is 5.67×10 -8 W·(m 2 ·K 4 ) -1 , T obj is the temperature of the center point of the triangular surface element grid, that is T amb Indicates the test environment temperature, which is set to 20 degrees in this embodiment.

[0094] Step S5: Use the generalized reflectivity of the triangular surface grid to infer the depth of the triangular surface grid, that is, the depth information of the triangular surface grid. In this embodiment, a single-layer stealth coating sample is tested. For each triangular surface grid, the relationship between the generalized reflectivity and thickness of the triangular surface grid is:

[0095]

[0096] Where η2 is the wave impedance of the air layer, and the generalized reflectivity of the metal substrate is 1.

[0097] The generalized reflectivity of the center of the triangular facet mesh obtained in step S4 Substituting the above formula as the generalized reflectivity E of the triangular surface mesh, the thickness d1 is calculated, which is the depth of the center point of the triangular surface mesh.

[0098] Step S6: combining the depth information of the triangular surface element mesh to obtain triangular volume elements;

[0099] Using the method in step S5, the depth at the center point of all triangular facet meshes is calculated. Using the triangular facet mesh as a plane and the depth of its center point as the thickness, a triangular prism-shaped triangular volume element is constructed, which is the volume element unit of the stealth coating damage area.

[0100] Step S7: Combine all triangular elements to reconstruct the damaged area of ​​the stealth coating.

[0101] like Figure 5 As shown, based on the arrangement of triangular face elements, all triangular elements are combined to obtain a three-dimensional reconstruction of the damaged area of ​​the stealth coating.

[0102] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

[0103] All of the above optional technical solutions can be combined in any way to form optional embodiments of the present application, and will not be described in detail here.

[0104] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0105] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A three-dimensional reconstruction method for stealth coating damage areas based on microwave thermal imaging, characterized in that: The following steps are involved: Step S1: Microwave thermal imaging of the damaged stealth coating to obtain an infrared temperature cloud map of the stealth coating surface; Step S2: Based on the obtained infrared temperature cloud map of the stealth coating surface, the damaged area of ​​the stealth coating to be reconstructed is determined according to the temperature of the damaged area being higher than the temperature of the undamaged area; Step S3: performing triangular facet meshing on the damaged area of ​​the stealth coating to be reconstructed, dividing the area into a plurality of triangular facet meshes of a plane; Step S4: Calculate the center of each triangular facet mesh obtained by division, obtain the center temperature of each triangular facet mesh, and calculate the generalized reflectivity of the center of each triangular facet mesh; Step S5: Calculating the depth of the center of each triangular facet mesh based on the generalized reflectivity of the center of each triangular facet mesh; Step S6: Constructing triangular volume elements by combining the depths of the centers of the triangular facet meshes; Step S7: Combine all triangular elements to obtain a three-dimensionally reconstructed damaged area of ​​the stealth coating, and provide it to equipment damage assessment and repair processing.

2. The method for three-dimensional reconstruction of stealth coating damage area based on microwave thermal imaging according to claim 1, characterized in that: Step S1 specifically includes: Step S1.1: The test begins by preparing a sample with damaged stealth coating; Step S1.2: Setting the heating antenna and aligning the heating antenna with the stealth coating; Step S1.3: heating the stealth coating via a heating antenna; Step S1.4: The heating antenna heats the stealth coating to a constant temperature and records the temperature of the stealth coating surface; Step S1.5: Detecting infrared radiation from the surface of the stealth coating using an infrared detector of the optical system, converting the infrared radiation signal into an electrical signal, and providing it to a computer; Step S1.6: The computer processes the obtained electrical signal to obtain an infrared temperature cloud map of the stealth coating surface.

3. The method for three-dimensional reconstruction of stealth coating damage area based on microwave thermal imaging according to claim 1, characterized in that: Step S2 specifically includes: Step S2.1: Preprocessing the infrared temperature cloud image of the stealth coating surface using image noise reduction; Step S2.2: performing image enhancement processing on the infrared temperature cloud image of the stealth coating surface after noise reduction; Step S2.3: For the infrared temperature cloud image after noise reduction and enhancement, the damaged area of ​​the stealth coating to be reconstructed is determined based on the fact that the temperature of the damaged area is higher than the temperature of the undamaged area.

4. The method for three-dimensional reconstruction of stealth coating damage area based on microwave thermal imaging according to claim 1, characterized in that: Step S4 specifically includes: Step S4.1, calculating the center of each triangular facet mesh obtained by division, and extracting the coordinates and temperature of the mesh nodes of each triangular facet mesh; Step S4.2, calculating the center coordinates and temperature of each triangular facet mesh, and calculating the center point temperature of the triangular facet mesh; Step S4.3, based on the obtained center point temperature of the triangular surface mesh, calculate the generalized reflectivity of the center of each triangular surface mesh.

5. The method for three-dimensional reconstruction of stealth coating damage area based on microwave thermal imaging according to claim 1, characterized in that: Step S5 specifically includes: The obtained generalized reflectivity of the center of each triangular facet mesh is used as the generalized reflectivity of the triangular facet mesh and substituted into the following formula to calculate the depth of the center of each triangular facet mesh: Among them, E i represents the generalized reflectivity of the i-th layer of stealth coating, i represents the number of the stealth coating and i=1,2,…,n, n is the total number of stealth coating layers, μ i represents the magnetic permeability of the i-th stealth coating, ε i represents the dielectric constant of the i-th stealth coating, d i represents the thickness of the i-th layer of stealth coating, λ represents the wavelength, e represents the exponent, η i represents the wave impedance of the i-th stealth coating, γ i represents the propagation factor of the i-th layer of stealth coating; where, when i=1, E i-1 is the generalized reflectivity of the metal substrate; when i = n, η i+1 is the wave impedance of air.

6. The method for three-dimensional reconstruction of stealth coating damage area based on microwave thermal imaging according to claim 1, characterized in that: Step S6 specifically includes: Based on the method in step S5, the depth of the center of the triangular surface element grid is obtained. With the triangular surface element grid as the plane and the depth of its center point as the thickness, a triangular prism-shaped triangular element is constructed as the element unit of the stealth coating damage area.

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