A method for analyzing optomechanical thermal integration of a space cryogenic infrared camera

Abstract

This invention discloses a method for integrated optomechanical-thermal analysis of a space cryogenic infrared camera, belonging to the field of space optical remote sensing technology. The method includes: firstly, structural modeling of the parameters of the cryogenic infrared optical system under normal temperature conditions during the design of the system; secondly, establishing corresponding structural and thermal control analysis finite element models based on the structural model; thirdly, using the temperature field analyzed by thermal control analysis as the input for structural finite element analysis, and performing structural simulation analysis on changes in the mirror accuracy and position of the optical system; fourthly, processing these accuracy and position change data into a format recognizable by cryogenic optical system design software before importing them into the optical design software; and finally, evaluating the optical performance and internal orientation element stability of the cryogenic optical system at low temperatures using the optical design software, thereby improving the reliability of the cryogenic optical system. This method provides guidance from room temperature assembly and testing to cryogenic use, and solves the problem of difficulty in predicting and evaluating the system performance of cryogenic infrared optical systems under large thermal deformation.

Description

Technical Field

[0001] This invention relates to the field of space optical remote sensing technology, and in particular to a method for integrated optomechanical and thermal analysis of a space cryogenic infrared camera. Background Technology

[0002] With the widespread application of infrared optical remote sensing technology in agricultural and forestry monitoring, meteorological observation, astronomical observation, and space military target detection, the requirements for the detection sensitivity of infrared optical systems are becoming increasingly stringent. Low-temperature optics are needed to reduce system background. In low-temperature environments, camera structures undergo significant deformation. Inadequate optomechanical structural design can lead to decreased optical surface accuracy and changes in the relative positions of mirrors, resulting in degraded camera optical performance. The low-temperature infrared optical optomechanical thermal integration analysis method can evaluate the optical performance and internal orientation element stability of low-temperature optical systems at low temperatures, improving their reliability. It provides guidance for the transition from room-temperature assembly and testing to low-temperature use of low-temperature optical systems. It solves the problem of difficulty in predicting and evaluating the performance of low-temperature infrared optical systems under large thermal deformation.

[0003] Currently, Chinese invention patent application publication (CN110245367B) discloses a method for processing surface shape errors in optomechanical integrated analysis. This involves a method for extracting rigid body displacement, spherical aberration, and flexible surface errors from the finite element analysis results of a mirror. When calculating the surface shape error, the rigid body displacement and spherical aberration of the mirror are subtracted. The rigid body displacement is compensated for during assembly, and the spherical aberration is compensated for by focusing. This patent only extracts and processes rigid body displacement and spherical aberration from the finite element analysis results of the mirror, without omitting any deformation. Chinese invention patent application publication (CN101114309A) discloses an optomechanical integrated analysis method based on int files. This includes coordinate transformation processing of finite element analysis results for optical mirrors of arbitrary shapes, and an optomechanical data interface based on int files. This patent's optomechanical integrated analysis method, based on an int file data interface for processing finite element analysis results of optical mirrors of arbitrary shapes, improves surface shape adaptability and reduces the data fitting process. Chinese invention patent application publication (CN106649922B) discloses a preprocessing interface program for optomechanical integrated analysis and a mirror surface optimization method. This solves the problems of high computational load and fitting failure caused by large amounts of fitted data in post-processing methods of optomechanical programs. However, it is only a preprocessing method for optomechanical integrated analysis. Chinese invention patent application publication (CN101504685A) discloses an optomechanical-thermal integrated analysis method based on Fringe-Zernike polynomials. This patent allows for arbitrary setting of the number of Fringe-Zernike polynomial terms and can calculate their expressions. It also uses .dat files to transfer the Zernike fitting coefficients to the optomechanical analysis software. This only discloses an application method of Fringe-Zernike polynomials in integrated analysis.

[0004] None of the above invention patents propose specific technical methods for low-temperature infrared optics. Summary of the Invention

[0005] The present invention aims to provide a method for integrated optomechanical and thermal analysis of a space cryogenic infrared camera to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for integrated optomechanical-thermal analysis of a space cryogenic infrared camera includes the following steps:

[0008] S1. Establish a common coordinate system for the model: The coordinate system at which the light from the low-temperature optical system enters the first mirror vertex is used as the coordinate system for the optical, mechanical, and thermal disciplines. This coordinate system also serves as the common coordinate system for data transfer between the optical, mechanical, and thermal disciplines.

[0009] S2. Exporting the required files for the finite element model using optical design software: Use optical design software to export the room temperature optical system corresponding to the low temperature infrared optical system into STEP or igs format files; export the model containing mirror information of the mirrors, lenses, and optical elements in the optical system, light rays of each field of view and wavelength, and mirror vertex coordinate information;

[0010] S3. Create a 3D model of the camera: Import the STEP or igs format file exported from the optical design software into the structural design software; based on the coordinate system position of the low-temperature optical system, create a model of the mirror or lens, as well as a 3D model of the lens or camera;

[0011] S4. Establish static and thermal analysis finite element models: Based on the three-dimensional model of the lens or camera established in the previous step, import it into the mechanical finite element analysis software and thermal analysis finite element software through the corresponding software interfaces to establish the mechanical analysis model and thermal analysis model of the lens or camera respectively.

[0012] S5. Establish nodal temperature field based on temperature data: According to the input parameters of the lens or camera, which are not limited to track, external heat flow, temperature control requirements, etc., conduct thermal analysis of the camera and export the analysis temperature field distribution results in tabular form;

[0013] S6: Map the temperature field onto the finite element model: The temperature field derived in the previous step is mapped and input as a load into the mechanical analysis model. The temperature field distribution of the mechanical analysis model is then compared with that of the thermal analysis model to determine if they are consistent. Mechanical simulation analysis is performed under the influence of the temperature field to obtain the mirror deformation in the lens or camera.

[0014] S7. Extract mirror displacement data and import it into SigmaIT software to calculate mirror surface shape: Use data processing and analysis software or professional optomechanical-thermal interface data processing software to parse and process the mirror deformation data output by mechanical analysis; obtain the deformation values ​​and rigid body displacement values ​​of each mirror in the low-temperature optical system, and form the data into an interface file that can be input into the optical design software;

[0015] S8. Importing optical zpl files into Zemax software for optical performance evaluation: The files generated from data processing and analysis are integrated with the low-temperature optical design files through the optical design software interface; the changes in optical performance such as lens or lens transfer function, energy concentration, and blur spot under the influence of temperature field are evaluated using optical analysis software.

[0016] S9. Simulate the change in the line of sight of a lens under the influence of temperature: Based on the previous step, further use optical software to analyze data and calculate the change in the line of sight of the lens or camera under the influence of temperature field.

[0017] Preferably, the low-temperature optical system is any one of three types: total internal reflection optical system, total projection system, and mirror + transmission system;

[0018] The low-temperature optical system may or may not include any one of the following: a compensating mirror for room-temperature optical calibration and testing.

[0019] Preferably, the coordinate system of the cryogenic optical system is located at the vertex of the first mirror into which the light enters the cryogenic optical system.

[0020] Preferably, the mirror surface model of the lens or camera is directly imported from the optical model, and the lens model is directly imported from the optical model; the structural finite element model of the lens or camera is small in size, numerous, and focuses on key stress and high-precision parts, reflecting the details of the structural parts; the thermal analysis finite element model has large unit size, few units, and reflects the shape of the parts.

[0021] Preferably, the thermal analysis of the lens or camera is a temperature field exported in tabular form, which includes finite element node coordinates and node temperature information; in the thermal analysis finite element model, low-temperature components are grouped separately according to the temperature requirements of each component, and large temperature difference parts may exist in the group; the parts contained in the mechanical analysis model component and the thermal analysis model component are consistent.

[0022] Preferably, the integrated analysis of the low-temperature optical system includes performance analysis of the low-temperature optical system under low-temperature loads and optical performance analysis under other loads directly applied in structural finite element analysis software.

[0023] Preferably, the analysis of the reflective mirror surface deformation data is performed by solving the Zernike polynomial coefficients to refit the optical mirror surface after deformation.

[0024] Preferably, the simulation of the change in the pointing of the visual axis involves inserting two virtual surfaces with a known spacing at the front end of the low-temperature optical system, and calculating the change in the visual axis by calculating the coordinate deviation of the center points of the light spots through the two virtual surfaces before and after the application of the external load.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Low-temperature infrared optical systems operate in low-temperature environments, resulting in significant temperature differences and thermal deformation among the various components of the optomechanical structure. Unifying the modeling coordinate systems for optics, structure, and thermal control in the modeling of low-temperature optical systems improves model consistency and allows for full utilization of software interfaces.

[0027] 2. The model exported from optical software is used for modeling, which improves the modeling accuracy of the mirror surface, especially for aspherical mirror surfaces;

[0028] 3. When performing thermal analysis modeling, ensuring the shape and form of each part can improve the accuracy of the transition from the thermal analysis model to the structural analysis model from the temperature field.

[0029] 5. By adopting a mapping method, the temperature is transferred from the thermal analysis model to the structural analysis model, which solves the problem of differences in element size, number of elements, and element node position between the thermal analysis and mechanical analysis finite element models.

[0030] 6. Grouping parts in the thermal analysis model and mechanical analysis model based on the temperature distribution of the lens or camera can reduce the error of the temperature field from the thermal analysis model to the structural analysis model caused by the camera temperature difference.

[0031] 7. This method can not only obtain changes in the low-temperature infrared optical properties, but also changes in the optical axis orientation. Attached Figure Description

[0032] Figure 1 A flowchart of an optomechanical-thermal integrated analysis method for a low-temperature infrared optical system;

[0033] Figure 2 Convert optical files into 3D model images;

[0034] Figure 3 A schematic diagram of the temperature field results table for each node.

[0035] Figure 4 Mapping the temperature field to the mechanical analysis model diagram;

[0036] Figure 5 Diagram showing the field of view settings during line-of-sight calculations;

[0037] Figure 6 This is a diagram showing the coordinates of the center point of the area covered by the central field of view spot during the calculation of the visual axis. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0039] The specific implementation process is as follows:

[0040] like Figure 1 As shown, a method for optomechanical-thermal integrated analysis of a low-temperature infrared optical system, a lens, and a camera are disclosed. The method includes the following steps:

[0041] Step 1: Use the coordinate system of the point where light enters the first mirror vertex in the low-temperature optical system as the unified coordinate system for the entire simulation process. This coordinate system will be shared among the optical, mechanical, and thermal disciplines to ensure seamless data transfer between different software and disciplines. Set a global coordinate system in the Zemax optical design software, with this vertex as the origin, to ensure that subsequent exported and imported models are based on the same coordinate reference.

[0042] Step Two: After completing the design of the low-temperature infrared optical system in the Zemax optical design software, export the optical system file in STEP format using the software's export function. The exported file should include information on all key optical components, such as the mirror and lens surface shapes, light data for each field of view and wavelength, and the coordinate information of the mirror vertices. Pay special attention to ensuring that the exported model coordinate system uses the first mirror vertex as its origin to maintain consistency with subsequent structural and thermal analyses.

[0043] Step 3: Import the STEP file exported from Zemax into the UG structural design software. During the import process, ensure that the positions and dimensions of the optical components remain consistent, and use the unified coordinate system of the optical system as a reference. Establish a complete 3D structural model of the mirror, lens, and other key components for mechanical and thermal analysis in subsequent steps. Figure 2 As shown, a few lenses and lens structures are briefly listed;

[0044] Step 4: Based on the 3D model created using UG structural design software, establish mechanical and thermal analysis models. For the thermal analysis model, boundary conditions need to be set, such as external heat flow, radiative heat transfer, and temperature control parameters. Fine meshing of the optical components ensures the accuracy of the thermal analysis results. Simultaneously, a mechanical analysis model is established, applying appropriate constraints, considering the mirror's support method and actual load conditions, including the effects of gravity and temperature fields.

[0045] Step 5: Based on the temperature field distribution of the lens components, group and name the component distributions. According to input parameters such as lens trajectory, external heat flow, and temperature control requirements (not limited to), perform thermal analysis on the camera and export the temperature field distribution analysis results in tabular form, such as... Figure 3 As shown;

[0046] Step Six: In the mechanical analysis model, first, group the structural model according to the grouping method of the thermal analysis model to ensure consistency between the two in the common optomechanical-thermal coordinate system. When importing temperature field data, input the node information through a table file, where the dependent variable is selected as the temperature value, the independent variable is set to the node coordinates in the Cartesian coordinate system, and the established temperature field dataset is named using the group name. Next, in the UG software, select the component to which the temperature field needs to be applied, and use the "Select Existing Field" function to map the corresponding temperature field onto the specified component, such as... Figure 4 As shown. Finally, a mechanical simulation under the action of a temperature field is run to simulate the structural response of the lens under temperature load, thereby obtaining the deformation and displacement data file of the lens surface, providing accurate input for subsequent optical performance analysis.

[0047] Step 7: Utilize the professional optomechanical-thermal interface data processing software SigFit to parse the mirror deformation displacement file output from the mechanical analysis. First, define the geometric characteristics of the optical mirror in SigFit and clarify the relationship between the mirror and the displacement file. Transform the deformation data of the finite element nodes into the optical coordinate system and project the displacement field onto the mirror surface. Subsequently, perform surface shape fitting on the mirror deformation data, typically using the standard Zernike polynomial fitting method to accurately describe the mirror surface shape error. The fitting results can calculate key parameters such as RMS (root mean square) error and PV (peak-valley) error. These data are further used to evaluate the impact of mirror surface shape changes on the optical system performance, generating analysis results for optical performance parameters such as wavefront error, point spread function (PSF), and modulation transfer function (MTF). Finally, output the processed data as a ZPL macro file recognizable by the Zemax optical design software for further performance evaluation and optimization within the software.

[0048] Step 8: During the optical performance evaluation, the ZPL macro file generated after data processing and analysis is imported into the Zemax optical design software and integrated with the previously established low-temperature optical design file. The Zemax software will apply the mirror deformation information in the ZPL macro file to the optical system model, thereby simulating the performance changes of the optical system under the influence of the temperature field.

[0049] The optical analysis function is used to evaluate the changes in the system's optical performance under temperature loads, particularly the changes in the lens's transfer function (MTF), energy concentration, and speckle distance (PSF). Zemax outputs corresponding graphical results, including transfer function plots, energy concentration plots, and speckle distance plots, to further verify and optimize the performance of the optical design.

[0050] Step Nine: Building upon the previous step, we can further simulate the change in the lens or camera's axial pointing under the influence of a temperature field. In the Zemax optical design software, open the field of view settings, select "True Image Height," and set the image height to 0, 0, as shown below. Figure 5 As shown (to calculate the change in the field of view, only the central field of view needs to be set); insert two virtual surfaces (tentatively named S2 and S3) at the front of the optical system, with an interval of d=100mm (the interval can be set as needed). Open the light trace diagram and view the X and Y coordinates of the center points of the areas covered by the light spots in the central field of view of the two surfaces S2 and S3 respectively; click "Text" at the top of the light trace diagram window to directly view the results in the opened window, such as... Figure 6 As shown; assuming the center coordinates of the light spot on surface S2 are (X2, Y2) and the center coordinates of the light spot on surface S3 are (X3, Y3), the method for calculating the line-of-sight deviation is as follows:

[0051]

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[0054] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for integrated optomechanical-thermal analysis of a space cryogenic infrared camera, characterized in that, Includes the following steps: S1. Establish a common coordinate system for the model: The coordinate system at which the light from the low-temperature optical system enters the first mirror vertex is used as the common coordinate system for establishing the model in the fields of optics, mechanics, and thermodynamics; this coordinate system also serves as the common coordinate system for data transfer between the fields of optics, mechanics, and thermodynamics. S2. Export the room-temperature optical system corresponding to the low-temperature infrared optical system into a STEP or igs format file using optical design software; export the model containing mirror information of the mirrors, lenses, and optical elements in the optical system, light rays of each field of view and wavelength, and mirror vertex coordinate information; S3. Create a 3D model of the camera: Import the STEP or igs format file exported from the optical design software into the structural design software; based on the coordinate system position of the low-temperature optical system, create a model of the mirror or lens, as well as a 3D model of the lens or camera; S4. Establish mechanical and thermal analysis models: Based on the three-dimensional model of the lens or camera established in the previous step, import it into the mechanical finite element analysis software and the thermal finite element analysis software through the corresponding software interfaces; establish the mechanical analysis model and the thermal analysis model of the lens or camera respectively. S5. Establish nodal temperature field based on temperature data: Group the component distribution based on the component temperature field distribution of the lens or camera; input parameters according to the lens or camera track, external heat flow, and temperature control requirements, perform thermal analysis on the camera, and export the analysis temperature field distribution results in tabular form; S6. Map the temperature field onto the finite element model: In the mechanical analysis model, group the components using the same method as the thermal analysis model; input the temperature field derived in the previous step as a load into the mechanical analysis model through mapping, and compare whether the temperature field distribution of the mechanical analysis model and the thermal analysis model are consistent; perform mechanical simulation analysis under the action of the temperature field to obtain the mirror deformation in the lens or camera; S7. Extract mirror displacement data and import it into SigFit software to calculate mirror surface shape: Use data processing and analysis software or optomechanical-thermal interface data processing software to analyze and process the mirror deformation data output by mechanical analysis; obtain the deformation values ​​and rigid body displacement values ​​of each mirror in the low-temperature optical system, and form the data into an interface file that can be input into the optical design software; S8. Importing optical ZPL files into optical design software for optical performance evaluation: The files generated from data processing and analysis are integrated with the low-temperature optical design files through the optical design software interface; S9. Simulation of the change in the line-of-view pointing of a lens under the influence of temperature: Further use optical software to analyze data and calculate the change in the line-of-view pointing of a lens or camera under the influence of temperature field.

2. The method for integrated optomechanical-thermal analysis of a space cryogenic infrared camera according to claim 1, characterized in that: The low-temperature optical system can be any one of a total internal reflection optical system, a total projection system, or a mirror + transmission system.

3. The method for integrated optomechanical-thermal analysis of a space cryogenic infrared camera according to claim 1, characterized in that: The coordinate system of the cryogenic optical system is located at the vertex of the first mirror into which the light enters.

4. The method for integrated optomechanical-thermal analysis of a space cryogenic infrared camera according to claim 1, characterized in that: The mirror surface model is directly built on the optical import model, and the lens directly adopts the optical import model.

5. The method for integrated optomechanical-thermal analysis of a space cryogenic infrared camera according to claim 1, characterized in that: The temperature field includes finite element node coordinates and node temperature information.

6. The method for integrated optomechanical-thermal analysis of a space cryogenic infrared camera according to claim 1, characterized in that: The aforementioned integrated analysis of the low-temperature optical system includes performance analysis of the low-temperature optical system under low-temperature loads and optical performance analysis under other loads directly applied in structural finite element analysis software.

7. The method for integrated optomechanical-thermal analysis of a space cryogenic infrared camera according to claim 1, characterized in that: The change in the line of sight direction mentioned in step S9 involves inserting two virtual surfaces with a known spacing at the front end of the low-temperature optical system, and calculating the coordinate deviation of the center point of the light spot through the two virtual surfaces before and after the application of the external load to calculate the change in the line of sight.

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