Optical-mechanical-thermal coupling analysis method for discrete error correction of all-aluminum free-form surface camera

Abstract

The present invention provides an optical-mechanical-thermal coupling analysis method for all-aluminum free-form surface camera discrete error correction, which is used to solve the technical problem that the authenticity of optical transfer function analysis of all-aluminum free-form surface camera is low due to the existence of node data discretization error in the optical-mechanical-thermal coupling analysis process of existing all-aluminum free-form surface camera. The method first obtains the temperature field distribution inside the camera through the thermal analysis module of finite element software, and then imports the temperature field data into the mechanical analysis module for static analysis, and obtains the node data of the mirror surface and the focal plane of the all-aluminum free-form surface camera under the temperature field respectively, uses MATLAB programming to perform iterative correction on these node data, and fits to obtain the XY polynomial coefficients of the mirror surface and the focal plane of the all-aluminum free-form surface camera, and imports the polynomial coefficients into the optical design software ZEMAX, and then obtains the optical modulation transfer function of the all-aluminum free-form surface camera under the temperature field through calculation.

Description

Technical Field

[0001] The invention relates to an optomechanical thermal integration analysis method, and in particular to an optomechanical thermal coupling analysis method for discrete error correction of an all-aluminum free-form surface camera. Background Art

[0002] At present, the most commonly used forming method for free-form surface reflectors is to use single-point diamond turning of aluminum alloy. Therefore, the optical elements and structural elements of free-form surface cameras are all made of aluminum alloy. Due to the advantages of low density, low cost, and good machinability, aluminum alloy can effectively reduce the weight of the optomechanical structure and reduce the manufacturing cost of optical cameras. However, compared with commonly used structural materials such as TC4, Invar, and AL-based SIC composite materials, aluminum alloy has poor rigidity and a large thermal expansion coefficient. For the temperature range of drastic changes in the space environment, aluminum alloy materials will undergo large deformation, causing changes in the surface shape, spacing, and position of the optical elements, thereby affecting the imaging quality of the entire machine. However, for cameras with an all-aluminum structure for the optomechanical system, since the expansion coefficients of the lens and the mechanical structure are consistent, they have the characteristics of optomechanical athermalization, and theoretically will not produce thermal defocusing. Therefore, in order to verify the athermalization characteristics of the all-aluminum free-form surface camera, it is necessary to perform optomechanical thermal coupling analysis on the camera.

[0003] The commonly used optomechanical thermal coupling analysis method is to convert the obtained node total deformation data into the coefficients of the Zernike polynomial in the optical design, thereby realizing the conversion and transmission of data during the analysis process. For the optomechanical system of free-form surface, XY polynomial coefficients are often used to characterize the optical design, because the XY polynomial design has a relatively high degree of freedom, strong aberration correction ability, and can correspond to the form of free-form surface CNC machining. However, when it is analyzed by finite element software, it is restricted by the number of units, unit nodes, calculation accuracy, and calculation resources. The analysis results will have discretization errors, and for free-form surface reflectors, this discretization error will cause the error of polynomial coefficient fitting to increase, thereby affecting the authenticity of the subsequent optical transfer function analysis of the all-aluminum free-form surface camera.

[0004] Therefore, for the optomechanical and thermal coupling analysis of the all-aluminum free-form surface camera, how to calculate the XY polynomial coefficients and how to correct the errors in the discretization of node data are problems that researchers need to solve. Summary of the invention

[0005] The purpose of the present invention is to provide an optomechanical-thermal coupling analysis method for all-aluminum free-form surface cameras with discrete error correction, so as to solve the technical problem that the authenticity of optical transfer function analysis of all-aluminum free-form surface cameras is low due to the existence of discretization errors in the optomechanical-thermal coupling analysis process of existing all-aluminum free-form surface cameras.

[0006] In order to solve the above technical problems, the present invention provides an optical-mechanical-thermal coupling analysis method for discrete error correction of an all-aluminum free-form surface camera, which is special in that it includes the following steps:

[0007] Step 1, obtaining the temperature field distribution data of different areas inside the all-aluminum free-form surface camera through the thermal analysis module in the finite element software; the different areas include each mirror surface and focal plane of the all-aluminum free-form surface camera; each mirror surface is an optical surface of each reflector; the focal plane refers to a virtual surface of the final imaging of the all-aluminum free-form surface camera;

[0008] Step 2, importing the temperature field distribution data obtained in step 1 into the static analysis module of the finite element software, and obtaining the node data of each mirror surface and focal plane of the all-aluminum free-form surface camera in the global coordinate system of the corresponding temperature field;

[0009] Step 3: Define the coordinate values ​​of each node of one of the mirrors in the global coordinate system as The deformation value is B i (x di ,y di ,z di ), where i represents the node number and i≥1; x ci is the coordinate value of each node in the X direction, x di is the deformation value of the same node in the X direction; y ci is the coordinate value of each node in the Y direction, y di is the deformation value of the same node in the Y direction; z ci is the coordinate value of each node in the Z direction, z di is the deformation value of the same node in the Z direction;

[0010] Step 4: calculate the coordinate value A of each node in the global coordinate system described in step 3 i (x ci ,y ci ,z ci ) to perform iterative correction and obtain the coordinate value of each node after iterative correction or Where M and N are the number of iterative corrections, and N>M; A 3rd Represents the coordinate value obtained after each correction; the iterative correction is to cyclically transform and calculate the coordinate value of each node in the global coordinate system and the local coordinate system; the global coordinate system refers to the same coordinate system where each mirror surface and focal plane of the all-aluminum free-form surface camera are located; the local coordinate system refers to the coordinate system where each mirror surface or focal plane of the all-aluminum free-form surface camera takes the center of the circle where the optical surface is located as the coordinate origin, and the direction perpendicular to the optical surface is the +Z direction;

[0011] Step 5: The corrected coordinate values ​​obtained in step 4 or Add the deformation value B described in step 3 i (x di ,y di ,z di ) and then perform coordinate transformation to obtain the total deformation data C of each node in the local coordinate system i (x i ,y i ,z i );

[0012] Step 6: The total deformation data C obtained in step 5 i (x i ,y i ,z i ) is substituted into the XY polynomial for reverse fitting to obtain the XY polynomial coefficient C of one of the mirrors. (m,n) , where m≥0, n≥0, m+n≥1;

[0013] Step 7, according to steps 3 to 6, obtain the XY polynomial coefficients of the remaining mirror surfaces and focal planes of the all-aluminum free-form surface camera under the temperature field;

[0014] Step 8, import the XY polynomial coefficients of each mirror surface and focal plane of the all-aluminum free-form surface camera into the optical design software ZEMAX, and obtain the optical modulation transfer function of the all-aluminum free-form surface camera under the temperature field.

[0015] Furthermore, in step 1, the number of the reflectors is 2 or 3 or 4.

[0016] Furthermore, step 4 specifically includes the following steps:

[0017] Step 4.1: Use MATLAB programming to calculate the coordinate values ​​of each node of one of the mirror surfaces in the global coordinate system described in step 3. Perform a coordinate transformation to obtain the coordinate values ​​of each node in the local coordinate system Among them, A 1st Indicates that each node has completed a transformation from the global coordinate system to the local coordinate system;

[0018] Step 4.2: Extract the coordinates of each node in the local coordinate system in step 4.1 and Use XY polynomial to calculate and get the new coordinate value of each node in the local coordinate system Among them, A 2nd Indicates the new coordinate values ​​of each node after completing a calculation in the local coordinate system. The calculation formula is:

[0019]

[0020] In the formula, is the arrow height of each node obtained after completing a calculation; is the coordinate of each node after completing a coordinate transformation from the global coordinate system to the local coordinate system; c is the curvature of the base quadratic surface; k is the cone constant of the base quadratic surface; p is the highest degree of the XY polynomial; C (m,n) are the coefficients of the XY polynomial, where m ≥ 0, n ≥ 0, m + n ≥ 1;

[0021] Step 4.3: The new coordinate values ​​obtained in step 4.2 Use MATLAB programming to perform coordinate transformation and obtain the new coordinate values ​​of each node in the global coordinate system This coordinate value is the coordinate value obtained after completing one correction;

[0022] Step 4.4, the coordinate values ​​obtained in step 4.3 According to the same method from step 4.1 to step 4.3, the coordinate transformation and calculation are repeated. After M cycles, the coordinate values ​​of each node in the local coordinate system are obtained. And the coordinate values ​​of each node in the global coordinate system Where M≥5;

[0023] Step 4.5, calculate the coordinate values ​​obtained in step 4.4 middle With coordinate values middle If the error between the two is less than or equal to 1×10 -3 nm, the loop is terminated and step 4.7 is executed;

[0024] If the error between the two is greater than 1×10 -3 nm, then execute step 4.6;

[0025] Step 4.6: Perform another cycle of calculations using the same method as steps 4.1 to 4.3 to obtain the coordinate values ​​of each node under local coordinates. And the coordinate values ​​of each node in the global coordinate system Among them, N>M, if and The error between them is less than or equal to 1×10 -3 nm, the loop terminates and executes step 4.7; if and The error between them is greater than 1×10 -3 nm, then continue to repeat the calculation in the same way as steps 4.1 to 4.3 until the error between the two is less than or equal to 1×10 -3 nm, execute step 4.7;

[0026] Step 4.7, change the coordinate value under the global coordinate or As the iteratively corrected coordinate value of each node.

[0027] Furthermore, in step 4.2, p=7.

[0028] Furthermore, in step 4.4, M=15.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The optical-mechanical-thermal coupling analysis method for discrete error correction of an all-aluminum free-form surface camera of the present invention comprises the following steps: firstly, the temperature field distribution inside the camera is obtained by a thermal analysis module of a finite element software, and then the temperature field data is imported into a mechanical analysis module for static analysis, and the node data of the free-form surface mirror and the focal plane of the camera under the temperature field are obtained respectively. The node data are iteratively corrected using MATLAB programming, and the XY polynomial coefficients of the mirror and focal plane of the all-aluminum free-form surface camera are obtained by fitting, and the polynomial coefficients are imported into an optical design software ZEMAX, and the optical modulation transfer function (MTF) of the all-aluminum free-form surface camera under the temperature field is obtained by calculation. The optical modulation transfer function obtained by the method has a high degree of authenticity, and the optical modulation transfer function can determine the applicable ambient temperature range of the camera, thereby clarifying the ambient temperature range of the camera, and providing a theoretical basis for efficient imaging of the camera.

[0031] 2. The optical-mechanical-thermal coupling analysis method for discrete error correction of the all-aluminum free-form surface camera of the present invention iteratively corrects the data of each node by cyclically performing coordinate transformation and calculation in the global coordinate system and the local coordinate system, and converts the coordinate data and deformation data of the node obtained by finite element analysis into XY polynomial coefficients. The node data discrete error correction method has a wide range of application, not only for free-form surface shapes, but also for spherical and aspherical surface shapes, and the method is simple and can be popularized.

[0032] 3. The optical-mechanical-thermal coupling analysis method for discrete error correction of the all-aluminum free-form surface camera of the present invention has a maximum order of 7 for the XY polynomial, which can accurately calculate the optical modulation transfer function of the all-aluminum free-form surface camera and provide a theoretical basis for actual optical and structural design. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flowchart of an embodiment of the optomechanical thermal coupling analysis method for discrete error correction of an all-aluminum free-form surface camera.

[0034] Figure 2It is the coordinate value of a certain node of the mirror surface in the global coordinate system in the embodiment of the optomechanical thermal coupling analysis method for discrete error correction of the all-aluminum free-form surface camera of the present invention.

[0035] Figure 3 It is the coordinate value of a certain node of the mirror surface in the local coordinate system in the embodiment of the optomechanical thermal coupling analysis method for discrete error correction of the all-aluminum free-form surface camera of the present invention.

[0036] Figure 4 The first correction in the embodiment of the optical-mechanical-thermal coupling analysis method for the discrete error correction of the all-aluminum free-form surface camera of the present invention and The node data error value.

[0037] Figure 5 The optical-mechanical-thermal coupling analysis method for the discrete error correction of the all-aluminum free-form surface camera of the present invention is corrected after the 15th correction and The node data error value.

[0038] Figure 6 It is the optical transfer function at -20°C in the embodiment of the opto-mechanical thermal coupling analysis method for discrete error correction of the all-aluminum free-form surface camera of the present invention. DETAILED DESCRIPTION

[0039] The optomechanical thermal coupling analysis method for discrete error correction of the all-aluminum free-form surface camera of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0040] Combination Figures 1 to 6 As shown, the present invention provides an optical-mechanical-thermal coupling analysis method for discrete error correction of an all-aluminum free-form surface camera, comprising the following steps:

[0041] Step 1, obtaining the temperature field distribution data of different areas inside the all-aluminum free-form surface camera model through the thermal analysis module in the finite element software; the different areas include the various mirror surfaces and focal planes of the all-aluminum free-form surface camera, wherein the various mirror surfaces of the all-aluminum free-form surface camera are optical surfaces of each reflector, and the number of the reflectors can be 2 or 3 or 4. In this embodiment, the number of reflectors is 3; the focal plane of the all-aluminum free-form surface camera refers to a virtual surface of the last imaging of the all-aluminum free-form surface camera.

[0042] Specifically, the Steady-StateThermal module is opened in the finite element software workbench, the 3D model of the all-aluminum free-form surface camera is imported, the material properties of all the camera components are loaded according to the initial design values, and then the all-aluminum free-form surface camera is meshed to obtain discretized nodes. Then the boundary conditions are input (i.e., an external temperature value of -20°C is loaded at the camera light entrance), and then the data distribution of the node temperature field of the all-aluminum free-form surface camera from the light entrance to the focal plane position is solved.

[0043] Step 2: Import the temperature field distribution data obtained in step 1 into the static analysis module of the finite element software to obtain the node data of each mirror surface and focal plane of the all-aluminum free-form surface camera in the global coordinate system of the corresponding temperature field.

[0044] Specifically, the temperature field distribution data in step 1 is imported into the static structure static analysis module as the boundary condition, and then a fixed constraint is imposed on the fixed hole position of the all-aluminum free-form surface camera to obtain the coordinate data and deformation data of each node of the three reflector surfaces and the camera focal plane of the all-aluminum free-form surface camera in the X, Y, and Z directions under the temperature field.

[0045] Step 3: Define the coordinate value of each node on the mirror surface of one of the three reflectors in the global coordinate system as A i (x ci ,y ci ,z ci ) and the deformation value is B i (x di ,y di ,z di ), where i represents the node number and i≥1; x ci is the coordinate value of each node in the X direction, x di is the deformation value of the same node in the X direction; y ci is the coordinate value of each node in the Y direction, y di is the deformation value of the same node in the Y direction; z ci is the coordinate value of each node in the Z direction, z di is the deformation value of the same node in the Z direction.

[0046] Step 4: The coordinate values ​​of each node in step 3 Perform iterative correction to obtain the iteratively corrected coordinate values ​​of each node Where M≥5. The iterative correction in this embodiment refers to cyclically transforming and calculating the coordinates of each node in the global coordinate system and the local coordinate system, wherein the global coordinate system refers to the same coordinate system where the mirrors and focal planes of the all-aluminum free-form surface camera are located; the local coordinate system refers to the coordinate system where the center of the circle where the optical surface of each mirror or focal plane of the all-aluminum free-form surface camera is located as the coordinate origin, and the direction perpendicular to the optical surface is the +Z direction. The number of corrections in this embodiment is 15 times, that is, M=15, and the corrected coordinate value is finally obtained. The specific correction process is as follows:

[0047] Step 4.1: Use MATLAB programming to calculate the coordinate values ​​in step 3. Perform a coordinate transformation (such as Figure 2 As shown), the coordinate values ​​of each node in the local coordinate system are obtained.

[0048]

[0049] Since the node data obtained in step 3 are all in the global coordinate system, it is necessary to transform the node data into the local coordinate system of each reflector or focal plane. The coordinate transformation includes translation in three directions and rotation in three directions. The matrix formula of coordinate transformation is as follows:

[0050]

[0051]

[0052] In formula (1) and formula (2), x ci平 ,y ci平 , z ci平 are the coordinate values ​​obtained after translation in three directions, x' ci , y' ci , z' ci is the coordinate value after coordinate transformation (such as Figure 3 dx, dy, dz represent the distances between the origin of the global coordinate system and the origin of the local coordinate system in the X, Y, and Z directions, respectively; θ represents the angle between the X axis in the global coordinate system and the X′ axis in the local coordinate system; α represents the angle between the Y axis in the global coordinate system and the Y′ axis in the local coordinate system; β represents the angle between the Z axis in the global coordinate system and the Z′ axis in the local coordinate system; θ, α, and β are all acute angles.

[0053] Step 4.2: Extract the coordinates of each node in the local coordinate system in step 4.1 and Use XY polynomial to calculate and get the new coordinate value of each node in the local coordinate system Then calculate and The error of the two Among them, the coordinates The calculation formula is:

[0054]

[0055] In formula (3), is the arrow height of each node obtained after completing a calculation; is the coordinate of each node after completing a coordinate transformation from the global coordinate system to the local coordinate system; c is the curvature of the base quadratic surface; k is the cone constant of the base quadratic surface; p is the highest degree of the polynomial, and in this embodiment, p is 7; C (m,n) are the weight coefficients of the XY subpolynomial, where m ≥ 0, n ≥ 0, 7 ≥ m + n ≥ 1, c, k, C (m,n) These are the initial design values, which are the ideal parameters when the optical design of the all-aluminum free-form surface camera begins.

[0056] like Figure 4 As shown, after completing a coordinate transformation and calculation, and The error between z is 60nm. In this embodiment, the error value is set to be less than or equal to 1×10 -3 nm (that is, the error requirement must be less than or equal to 1×10 -3 nm), and the error value D z The error is greater than the required value, so further correction is required. In general, the order of magnitude of the extracted coordinate values ​​is 10 -3 m, the deformation value is on the order of 10 -6 Therefore, in the process of fitting coefficients, the error of the coordinate value has a greater impact on it, so the iterative correction method described in this embodiment is mainly to correct the coordinate value of the node.

[0057] Step 4.3: The new coordinate values ​​obtained in step 4.2 Use MATLAB programming to perform coordinate transformation. The coordinate transformation method is the same as step 4.1. Get the new coordinate value of each node after correction in the global coordinate system. In this embodiment, because and The error between z The required error value is not met, so it is necessary to continue to correct the coordinate values ​​of each node.

[0058] Step 4.4, the coordinate values ​​obtained in step 4.3 According to the same method as step 4.1 and step 4.3, the coordinate transformation and calculation are repeated 15 times, and the coordinate values ​​of each node under the local coordinates are obtained respectively. And the coordinate values ​​of each node in the global coordinate system

[0059] Step 4.5, calculate the coordinate values ​​obtained in step 4.4 middle With coordinate values middle The error, caused by Figure 5 It can be seen that and The error between -9 nm, which is less than the required error value (1×10 -3 nm), the loop is terminated at this time, and the coordinate values ​​of each node in the global coordinate system are As the iteratively corrected coordinate value of each node.

[0060] In the actual design and analysis process, if the error of each node is still greater than 1×10 -3 nm, then the calculation can be continued in the same way as in steps 4.1 to 4.3 until the error is less than or equal to 1×10 -3 nm, when the error meets the requirements, the coordinate values ​​of each node after iterative correction can be obtained.

[0061] Step 5: Combine the iteratively corrected coordinate values ​​of each node obtained in step 4 and the deformation value B of each node in step 3 i (x di ,y di ,z di ),because and B i (x di ,y di ,z di ) are all in the global coordinate system. and B i (x di ,y di ,z di ) The added data is transformed into the local coordinate system, and then the total deformation data C of each node in the local coordinate system is obtained. i (x i ,y i ,z i ).

[0062] Step 6: The total deformation data C of each node on one of the mirror surfaces i (x i ,y i ,z i) into the XY polynomial for reverse fitting, and the XY polynomial coefficient C of one of the mirrors is obtained. i , where the calculation formula for the polynomial coefficients is:

[0063]

[0064] In formula (4), x, y, and z are C i (x i ,y i ,z i ) in the graph; c is the curvature of the base quadratic surface; k is the conic constant of the base quadratic surface; R m is the normalized radius; C i is the weight coefficient of the i-th XY polynomial, i ≥ 1; N is the number of terms in the polynomial, N ≥ 1; m ≥ 0, n ≥ 0, 1 ≤ m + n ≤ 7; c, k, R m These are the initial design values ​​for optical design.

[0065] Step 7, according to steps 3 to 6, obtain the XY polynomial coefficients of the remaining mirror surfaces and focal plane of the all-aluminum free-form surface camera under the temperature field.

[0066] According to the above steps, the XY polynomial coefficients of the three free-form surface reflectors of the all-aluminum free-form surface camera of this example are obtained. In this embodiment, the number of XY polynomial terms of the camera is 19, as shown in Table 1, where M1 represents reflector surface one, M2 represents reflector surface two, and M3 represents reflector surface three.

[0067] Table 1: XY polynomial coefficients of the three mirrors of the free-form surface camera

[0068]

[0069]

[0070] Step 8: Import the XY polynomial coefficients of all mirrors and focal planes into the optical design software ZEMAX to obtain the MTF (optical modulation transfer function) of the all-aluminum free-form surface camera under the temperature field, as shown in Figure 6 As shown, the imaging quality of the all-aluminum free-form surface camera in this embodiment is still close to the diffraction limit when the ambient temperature is -20°C.

[0071] The whole method of the present invention is to evaluate the designed camera. According to the MTF finally obtained, the applicable ambient temperature range of the camera can be determined. In this example, the ambient temperature of the all-aluminum free-form surface camera is -50℃~+70℃.

[0072] The existing optomechanical thermal coupling analysis is mainly aimed at spherical and aspherical optical systems. The coefficients finally obtained during the coupling analysis are Zernike polynomial coefficients. Although the optomechanical thermal coupling analysis of the all-aluminum free-form surface can also be performed using Zernike polynomial coefficients, it is relatively cumbersome for designers. The present invention performs discretization error correction of nodes based on multiple iterative compensation (i.e., multiple coordinate conversions and XY polynomial calculations) algorithms, and converts the coordinate data and deformation data of the nodes obtained by finite element analysis into XY polynomial coefficients. The node data discrete error correction method has a wide range of application, not only for free-form surface types, but also for spherical and aspherical surface types. Moreover, the method is simple and can be promoted for use.

[0073] Although the embodiments of the present invention have been shown and described above, it will be apparent to those skilled in the art that any changes or modifications to the above embodiments should be considered to be within the protection scope of the present invention as long as they are within the spirit and scope of the present invention.

Claims

1. An optomechanical thermal coupling analysis method for discrete error correction of an all-aluminum free-form surface camera, characterized in that: The following steps are involved: Step 1, obtaining the temperature field distribution data of different areas inside the all-aluminum free-form surface camera through the thermal analysis module in the finite element software; the different areas include each mirror surface and focal plane of the all-aluminum free-form surface camera; each mirror surface is an optical surface of each reflector; the focal plane refers to a virtual surface of the final imaging of the all-aluminum free-form surface camera; Step 2, importing the temperature field distribution data obtained in step 1 into the static analysis module of the finite element software, and obtaining the node data of each mirror surface and focal plane of the all-aluminum free-form surface camera in the global coordinate system of the corresponding temperature field; Step 3: Define the coordinate value of each node of one of the mirrors in the global coordinate system as A i (x ci ,y ci ,z ci ), deformation value is B i (x di ,y di ,z di ), where i represents the node number and i≥1; x ci is the coordinate value of each node in the X direction, x di is the deformation value of the same node in the X direction; y ci is the coordinate value of each node in the Y direction, y di is the deformation value of the same node in the Y direction; z ci is the coordinate value of each node in the Z direction, z di is the deformation value of the same node in the Z direction; Step 4: calculate the coordinate value A of each node in the global coordinate system described in step 3 i (x ci ,y ci ,z ci ) to perform iterative correction and obtain the coordinate value of each node after iterative correction or Where M and N are the number of iterative corrections, and N>M; A 3rd Represents the coordinate value obtained after each correction; the iterative correction is to cyclically transform and calculate the coordinate value of each node in the global coordinate system and the local coordinate system; the global coordinate system refers to the same coordinate system where each mirror surface and focal plane of the all-aluminum free-form surface camera are located; the local coordinate system refers to the coordinate system where each mirror surface or focal plane of the all-aluminum free-form surface camera takes the center of the circle where the optical surface is located as the coordinate origin, and the direction perpendicular to the optical surface is the +Z direction; Step 5: Iterate and correct the coordinate values ​​of each node obtained in step 4 or Add the deformation value B described in step 3 i (x di ,y di ,z di ) and then perform coordinate transformation to obtain the total deformation data C of each node in the local coordinate system i (x i ,y i ,z i ); Step 6: The total deformation data C obtained in step 5 i (x i ,y i ,z i ) is substituted into the XY polynomial for reverse fitting to obtain the XY polynomial coefficient C of one of the mirrors. (m,n) , where m≥0, n≥0, m+n≥1; Step 7, according to steps 3 to 6, obtain the XY polynomial coefficients of the remaining mirror surfaces and focal planes of the all-aluminum free-form surface camera under the temperature field; Step 8, import the XY polynomial coefficients of each mirror surface and focal plane of the all-aluminum free-form surface camera into the optical design software ZEMAX, and obtain the optical modulation transfer function of the all-aluminum free-form surface camera under the temperature field.

2. The optical-mechanical-thermal coupling analysis method for discrete error correction of an all-aluminum free-form surface camera according to claim 1, characterized in that: In step 1, the number of the reflectors is 2, 3 or 4.

3. The optical-mechanical-thermal coupling analysis method for discrete error correction of an all-aluminum free-form surface camera according to claim 2, characterized in that: Step 4 specifically includes the following steps: Step 4.1, use MATLAB programming to calculate the coordinate value A of each node of one of the mirrors in the global coordinate system described in step 3 i (x ci ,y ci ,z ci ) performs a coordinate transformation to obtain the coordinate values ​​of each node in the local coordinate system Among them, A 1st Indicates that each node has completed a transformation from the global coordinate system to the local coordinate system; Step 4.2: Extract the coordinates of each node in the local coordinate system in step 4.1 and Use XY polynomial to calculate and get the new coordinate value of each node in the local coordinate system Among them, A 2nd Indicates the new coordinate values ​​of each node after completing a calculation in the local coordinate system. The calculation formula is: In the formula, is the arrow height of each node obtained after completing a calculation; is the coordinate of each node after completing a coordinate transformation from the global coordinate system to the local coordinate system; c is the curvature of the base quadratic surface; k is the cone constant of the base quadratic surface; p is the highest degree of the XY polynomial; C (m,n) are the coefficients of the XY polynomial, where m ≥ 0, n ≥ 0, m + n ≥ 1; Step 4.3: The new coordinate values ​​obtained in step 4.2 Use MATLAB programming to perform coordinate transformation and obtain the new coordinate values ​​of each node in the global coordinate system This coordinate value is the coordinate value obtained after completing one correction; Step 4.4, the coordinate values ​​obtained in step 4.3 According to the same method from step 4.1 to step 4.3, the coordinate transformation and calculation are repeated. After M cycles, the coordinate values ​​of each node in the local coordinate system are obtained. And the coordinate values ​​of each node in the global coordinate system Where M≥5; Step 4.5, calculate the coordinate values ​​obtained in step 4.4 middle With coordinate values middle If the error between the two is less than or equal to 1×10 -3 nm, the loop is terminated and step 4.7 is executed; If the error between the two is greater than 1×10 -3 nm, then execute step 4.6; Step 4.6: Perform another cycle of calculations using the same method as steps 4.1 to 4.3 to obtain the coordinate values ​​of each node under local coordinates. And the coordinate values ​​of each node in the global coordinate system Among them, N>M, if and The error between them is less than or equal to 1×10 -3 nm, the loop terminates and executes step 4.7; if and The error between them is greater than 1×10 -3 nm, then continue to repeat the calculation in the same way as steps 4.1 to 4.3 until the error between the two is less than or equal to 1×10 -3 nm, execute step 4.7; Step 4.7, change the coordinate value under the global coordinate or As the iteratively corrected coordinate value of each node.

4. The optical-mechanical-thermal coupling analysis method for discrete error correction of an all-aluminum free-form surface camera according to claim 3 is characterized in that: In step 4.2, p=7.

5. The optical-mechanical-thermal coupling analysis method for discrete error correction of an all-aluminum free-form surface camera according to claim 4, characterized in that: In step 4.4, M=15.

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