Optical system thermal distortion testing system and method

Abstract

The application belongs to the technical field of thermal-optical test, and discloses an optical system thermal deformation test system and method, wherein the optical system thermal deformation test system is provided with a temperature test cabinet, the right end of the temperature test cabinet is provided with an infrared target simulator, the bottom side of the temperature test cabinet is provided with a vacuum two-dimensional rotary table, the vacuum two-dimensional rotary table is provided with a scanning pointing mirror and a to-be-tested camera; the scanning pointing mirror is connected with a scanning mirror control system, and the temperature test cabinet is respectively connected with a temperature control and measurement system, a refrigerator control system and a data acquisition system. In the application, the target simulator is used in cooperation in the temperature test process, the performance change caused by the temperature is monitored, the suitable working point of the camera is found, the temperature change performance of the camera is accurately acquired, and the change of the temperature test process is found, which has great benefits. In the application, the infrared target simulator is designed as a vacuum cavity, the temperature test cabinet is directly connected with the infrared target simulator for use, and they are both designed as vacuum cavities.

Description

Technical Field

[0001] This invention belongs to the field of thermo-optical testing technology, and particularly relates to a system and method for testing the thermal deformation of an optical system. Background Technology

[0002] Currently, temperature changes alter the curvature, thickness, and spacing of optical elements, as well as the refractive index of the element's substrate material and the surrounding medium, leading to variations in the imaging quality of the optical system. Therefore, thermal analysis of the optical system is essential, and appropriate anechoic measures must be implemented based on the analysis results. For transmission-type coaxial optical systems, thermal analysis can be performed directly using optical design software (such as Code V and Zemax). This software automatically calculates changes in the curvature, thickness, and refractive index of the optical lenses and uses a cylindrical tube model to calculate the spacing changes between adjacent optical elements based on the thermal expansion coefficients of the structural materials.

[0003] For reflective (hybrid catadioptric) optical systems and complex optical systems with optical elements such as prisms (or mirrors) in the optical path, direct thermal analysis using optical software is inaccurate due to uncertain structural support points and the possibility of multiple structural materials. Therefore, optomechanical-thermal integrated analysis methods are usually adopted. However, this method requires transforming the deformation data of all nodes on all surfaces based on sag or surface normal, followed by polynomial fitting. Sometimes, orthogonalization of the equation system is also required before fitting. This process is computationally intensive, complex, and prone to errors. The accuracy of the thermo-optical analysis and the rationality of the thermal control indicators require further experimental verification.

[0004] Currently, the two most mature vacuum tests are thermal balance testing and thermal vacuum testing. Thermal balance testing primarily aims to verify the correctness of the camera's thermal design and test the functionality of the thermal control subsystem; thermal vacuum testing primarily aims to verify the camera's ability to withstand specified pressure and temperature environments. Neither can verify the camera's optical performance in a working environment. As a means of verifying the optical performance of aerospace optical payloads in a working environment, thermal optical testing is one of the key technologies in the development process of aerospace optical payloads and an important part of the space environment testing of aerospace optical payloads.

[0005] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0006] (1) The optical-mechanical-thermal integrated analysis method involves a large amount of computation, is complex, and is prone to errors.

[0007] (2) Neither thermal vacuum test nor thermal balance test can verify the optical performance of the optical system in the working environment.

[0008] (3) The target simulator of the existing thermo-optical test system is under normal temperature and pressure, and the attitude of the product under test cannot be adjusted, so only the optical performance of a single field of view can be tested.

[0009] The difficulty in solving the above problems and defects lies in the following: To address the error-prone nature of optomechanical-thermal integration analysis, vacuum imaging testing is required. Vacuum imaging testing necessitates simulating the light source, collimator, and the product under test (DUT) within a simulated environment. The DUT must be able to adjust its orientation during testing to ensure accuracy, requiring a complete testing system and methodology. In the simulated environment, the collimator experiences drastic temperature and pressure changes. Due to the difference in expansion coefficients between optical components and mechanical structural materials, stress can easily be generated on the collimator, making it difficult to guarantee its optical performance. This directly affects the accuracy of vacuum imaging of the DUT. Therefore, developing a collimator with stable performance under both ambient temperature and pressure and low-temperature vacuum conditions is not easy.

[0010] The significance of addressing the above problems and shortcomings is as follows: Using the optical system thermal deformation testing system not only allows us to understand the space camera's adaptability to the thermal vacuum environment and verify the rationality of thermal control indicators, but also enables us to derive the temperature-based focusing coefficient and the correction coefficient required for changes in spectral response parameters caused by camera temperature variations. This provides an effective means for focusing and spectral parameter correction in future operating modes. Furthermore, the data obtained from the optical system thermal deformation testing system can also provide a reference for verifying the correctness of the thermo-optical engineering analysis model and for model correction. The corrected model can serve as an effective means for predicting camera imaging quality and analyzing and judging faults under operating conditions. The test data from the optical system thermal deformation testing system can determine whether focusing is necessary and the amount of focusing required. This focusing value and direction are then sent to the focusing control mechanism for focusing in the operating mode. Therefore, the proposed optical system thermal deformation testing system and method have certain engineering practicality. Summary of the Invention

[0011] To address the problems existing in the prior art, the present invention provides an optical system thermal deformation testing system and method.

[0012] This invention is implemented as follows: an optical system thermal deformation testing system includes a temperature test chamber, a vacuum two-dimensional turntable, a scanning pointer, a temperature control and measurement system, a refrigerator control system, a data acquisition system, a vacuum two-dimensional turntable control system, an infrared target simulator, and a scanning control system; characterized in that the infrared target simulator is located on the right side of the temperature test chamber, with its light output port connected to the outlet of the temperature test chamber; the vacuum two-dimensional turntable is located at the bottom of the temperature test chamber; the scanning pointer and the camera under test are placed on the vacuum two-dimensional turntable; the scanning pointer is connected to the scanning pointer control system; and the temperature test chamber is connected to the temperature control and measurement system, the refrigerator control system, and the data acquisition system.

[0013] Furthermore, the temperature test chamber is equipped with a vacuum tank, a heat sink system, a vacuum pumping system, a temperature control system, a refrigeration system, a heating system, and a control system.

[0014] Furthermore, the vacuum pumping system is a rough vacuum system, with a rough vacuum pre-pump, a pneumatic high vacuum baffle valve, and a metal bellows connecting to the vacuum chamber. A dry oil-free pump is used as the back pump of the magnetic levitation molecular pump, and a pneumatic high vacuum baffle valve is used as the high vacuum pumping system.

[0015] Furthermore, the heat sink system is equipped with a heat sink, which adopts a vertical structure and is divided into a cylindrical heat sink and a movable door heat sink.

[0016] Furthermore, the heat sink is cooled with liquid nitrogen, and its inner surface is coated with black paint.

[0017] Furthermore, the vacuum chamber is divided into a main chamber and a secondary chamber, with the main chamber housing a two-dimensional turntable and a camera to be tested;

[0018] The target simulator is placed in the secondary tank, and an optical window is opened on the secondary tank near the focal plane of the target simulator.

[0019] Furthermore, the main tank has a heat sink, the main tank has a top opening, the movable door moves via an automatic control guide rail, and eight pneumatic clamps pre-tighten the movable door's sealing ring to the main tank.

[0020] Furthermore, the auxiliary tank is equipped with a target simulator and a temperature control system, with the optical axis of the target simulator located in the horizontal direction.

[0021] Furthermore, the infrared target simulator is equipped with a collimator, a reticle, a temperature control system, and a high-temperature blackbody, and the optical axis of the infrared target simulator is located in the horizontal direction.

[0022] Another objective of this invention is to provide a method for testing the thermal deformation of an optical system using the aforementioned optical system thermal deformation testing system, the method comprising:

[0023] In a vacuum environment, the on-orbit temperature environment is simulated by the temperature change of the heat sink. This enables the measurement of indicators such as signal-to-noise ratio, spatial resolution, scanning and pointing accuracy of the camera under thermal vacuum conditions and alternating temperature fields, as well as the acquisition of parameters such as optical axis pointing and cooling capacity performance of the cooling mechanism.

[0024] 1) Simulate the on-orbit temperature environment by varying the temperature of the heat sink;

[0025] 2) Select the appropriate reticle according to the performance parameter requirements of the product being tested, and place the reticle precisely at the center of the collimator's foot surface;

[0026] 3) The light source is placed on one side of the focal plane of the collimator to provide illumination for the reticle;

[0027] 4) Adjust the position of the product under test so that the beam emitted from the collimator can cover the aperture of the camera under test within the entire field of view.

[0028] 5) Adjust the angle of the camera under test using a two-dimensional turntable so that the reticle on the focal plane of the collimator is imaged onto the focal plane detector of the product under test.

[0029] 6) Based on the collected data, analyze and calculate the measured values ​​of each performance parameter.

[0030] A plane wave generated by a collimating beam amplification via a dynamic interferometer is introduced into the camera. The camera's thermal deformation in a vacuum environment causes an image change in this standard plane wave. This image change is used to verify the effectiveness of thermal deformation control, evaluate the impact of thermal deformation on the camera's detection performance, and further optimize the camera's thermal deformation control design. During the test, the optical performance of the full-field-of-view camera is tested by changing the attitude of the product under test and the position of the dynamic interferometer.

[0031] Combining all the above technical solutions, the advantages and positive effects of this invention are as follows: During the construction process, infrared cameras present new demands for water vapor contamination, heat leakage control, and real-time dynamic measurement of the line-of-sight during testing. In this invention, a target simulator is required during temperature testing to monitor performance changes caused by temperature, helping to identify the camera's suitable operating point and accurately obtain its temperature change performance. This also significantly benefits the detection of changes during the temperature testing process. In this invention, the infrared target simulator is designed as a vacuum chamber, which is connected to the temperature testing cabinet. This connection can be made via a window or directly, making it feasible and cost-effective. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of the optical system thermal deformation testing system provided in an embodiment of the present invention.

[0034] Figure 2 This is a top view of the optical system thermal deformation testing system provided in an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of the temperature test cabinet structure provided in an embodiment of the present invention.

[0036] Figure 4 This is a schematic diagram of the vacuum tank structure provided in an embodiment of the present invention.

[0037] Figure 5 This is a schematic diagram of the flange structure provided in an embodiment of the present invention.

[0038] Figure 6 This is a schematic diagram of the vacuum pumping system provided in an embodiment of the present invention.

[0039] Figure 7 This is a schematic diagram of the control cabinet structure provided in an embodiment of the present invention.

[0040] Figure 8 This is a diagram showing the distribution of the cooling area of ​​the top cover provided in an embodiment of the present invention.

[0041] Figure 9 This is a diagram showing the distribution of the heating area of ​​the top cover provided in an embodiment of the present invention.

[0042] Figure 10 This is an overall block diagram provided in the embodiments of the present invention.

[0043] Figure 11 This is a top view of the optical path diagram of the collimator provided in an embodiment of the present invention.

[0044] In the diagram: 1. Temperature test chamber; 2. Vacuum two-dimensional turntable; 3. Scanning pointer mirror; 4. Temperature control and measurement system; 5. Refrigeration control system; 6. Data acquisition system; 7. Vacuum two-dimensional turntable control system; 8. Infrared target simulator; 9. Scanning mirror control system; 10. Heat sink system; 11. Vacuum pumping system; 12. Temperature control system; 13. Heating system; 14. Control system; 15. Vacuum chamber; 16. Cylinder; 17. Main vacuum tank; 18. Secondary vacuum tank; 19. Connector mounting hole; 20. Flange; 21. Infrared simulator optical window; 22. Camera under test; Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] To address the problems existing in the prior art, the present invention provides an optical system thermal deformation testing system and method, which will be described in detail below with reference to the accompanying drawings.

[0047] like Figure 1As shown, in the optical system thermal deformation testing system provided in this embodiment of the invention, an infrared target simulator 8 is provided on the right end of the temperature test cabinet 1, and a vacuum two-dimensional turntable 2 is provided on the bottom side of the temperature test cabinet 1. A scanning pointing mirror 3 and a camera under test are provided on the vacuum two-dimensional turntable 2. The scanning pointing mirror 3 is connected to the scanning mirror control system 9, and the temperature test cabinet 1 is connected to the temperature control and measurement system 4, the refrigeration control system 5, and the data acquisition system 6.

[0048] Temperature test chamber 1 is equipped with a vacuum tank, heat sink system, vacuum pumping system, temperature control system, refrigeration system, heating system, and control system.

[0049] The vacuum pumping system is a rough vacuum system, with a rough vacuum pre-pump, equipped with a pneumatic high vacuum baffle valve and a metal bellows connecting to the vacuum chamber. A dry oil-free pump is used as the back pump of the magnetic levitation molecular pump, and a pneumatic high vacuum baffle valve is used as the high vacuum pumping system.

[0050] The heat sink system is equipped with a heat sink, which adopts a vertical structure and is divided into a cylindrical heat sink and a sliding door heat sink. The heat sink is cooled by liquid nitrogen and the inner surface of the heat sink is coated with black paint.

[0051] The vacuum chamber consists of a main chamber and a secondary chamber. The main chamber houses a two-dimensional turntable and the camera under test; the secondary chamber houses the target simulator, with an optical window on the secondary chamber near the focal plane of the target simulator. The main chamber has a heat sink and a top opening. The moving door moves via an automatically controlled guide rail, and eight pneumatic clamps pre-tighten the door's sealing ring to the main chamber. The secondary chamber houses the target simulator and temperature control system; the target simulator's optical axis is horizontal.

[0052] The infrared target simulator 8 is equipped with a collimator, a reticle, a temperature control system, and a high-temperature blackbody. The optical axis of the infrared target simulator 8 is located in the horizontal direction.

[0053] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0054] The thermo-optical testing equipment in this embodiment of the invention mainly consists of a temperature testing chamber, a vacuum chamber, a vacuum two-dimensional turntable, an infrared target simulator, and auxiliary structures.

[0055] 1. Temperature test chamber

[0056] The temperature test chamber is the electrical control part of the thermo-optical test equipment. It can be operated manually or automatically by setting parameters through software to realize the operation of the vacuum pump, liquid nitrogen temperature control, etc. in the equipment.

[0057] During the construction process, the infrared camera raised new requirements for water vapor pollution control, heat leakage control, and real-time dynamic measurement of line-of-sight during the test. In addition, the target simulator needs to be used in conjunction with the temperature test to monitor the performance changes caused by temperature. This is of great benefit for finding the camera's suitable operating point, accurately obtaining the camera's performance under temperature changes, and detecting changes in the temperature test process. In this way, the test plan is in line with the most advanced international test plan (the camera development process conditions meet the requirements of ground test).

[0058] Since the infrared target simulation in this invention is designed as a vacuum chamber, the temperature test cabinet can be directly connected to it, either through a window or by direct connection.

[0059] Based on the camera parameters and line-of-sight pointing test requirements, the core technical specifications of the temperature test chamber equipment are as follows: internal effective dimensions not less than 2.4m × 1.7m × 2.6m; temperature cycling range greater than -40℃ to +60℃; vacuum degree better than 1×10⁻⁶. -3 Pa; directly connected to an infrared target simulator with a 1m aperture. The hardware scheme for the camera's overall thermal deformation test, detector calibration under quasi-operational conditions, and line-of-sight pointing test is consistent, and the layout is shown in the following two figures.

[0060] like Figures 2-3 As shown, the temperature test chamber of this invention consists of seven parts: a cylindrical body, a heat sink system, a vacuum pumping system, a temperature control system, a refrigeration system, a heating system, and a control system.

[0061] like Figures 4-5 Vacuum tank section.

[0062] like Figure 6 As shown, the rough vacuum system uses an SP-630 dry vacuum pump as the rough vacuum pre-pump, equipped with a GDQ-100 pneumatic high-vacuum baffle valve and a metal bellows connecting to the vacuum chamber. A TS600 dry oil-free pump serves as the backing pump for the magnetic levitation molecular pump, equipped with a GDQ-J250 BP pneumatic high-vacuum baffle valve for the high-vacuum pumping system. A ULVAC CRYO-22P cryogenic pump from Japan Vacuum is used as the main pump, equipped with a CCQ-550 pneumatic high-vacuum gate valve to form the main pumping system. This reduces the pressure inside the vacuum chamber to 3*10... - 5 The ultimate pressure in Pa.

[0063] like Figure 7 As shown, the electrical control system has circuit overload protection and main power protection devices, a main power switch status display, fault alarm prompts, warning signs, etc. It features power outage and water outage alarms; digital displays for temperature and vacuum levels; a flowchart of equipment operation status; necessary interlocks on the circuit (executed by PLC); and a function to prevent misoperation.

[0064] The system is equipped with four electrical control cabinets: a high-voltage control cabinet, a low-voltage instrument control cabinet, and a temperature control cabinet. The dimensions of each control cabinet are 2000×900×600mm (height×width×depth).

[0065] like Figures 8-9 As shown, in the heat sink system: the heat sink adopts a vertical structure and is divided into a cylindrical heat sink and a sliding door heat sink. The heat sink is cooled by liquid nitrogen, and the temperature of the heat sink does not exceed 100K. The inner surface of the heat sink is coated with black paint, and the surface absorptivity of sunlight αs ≥ 0.95 and the hemispherical emissivity εH ≥ 0.90 ± 0.02 are all within the heat sink.

[0066] Heat sink specifications: Under liquid nitrogen refrigeration, temperature distribution uniformity ≤ ±5K; average cooling rate ≥ 2.0℃ / min (heat sink wall); the heat sink surface is coated with black paint, the infrared absorption coefficient of the black paint is > 0.93; and it will not peel off during long-term use in the temperature range of 100K to 373K; a local 15K cold plate is provided, with an effective radiation area of ​​not less than 2m×2m.

[0067] Refrigeration distribution: The cylinder is divided into 8 zones, and the top cover is divided into 4 zones;

[0068] A5 A6 A7 A8

[0069] Heating distribution: The cylinder is divided into 16 zones, and the top cover is divided into 7 zones;

[0070] B9 B10 B11 B12 B13 B14 B15 B16

[0071] 2. Vacuum container

[0072] The main function of the vacuum tank is to provide a sealed vacuum temperature-controlled environment, while also providing mechanical support for the two-dimensional turntable, heat sink, and target simulator. It mainly consists of three parts: the tank body, the heat sink, and the vacuum system.

[0073] This vacuum chamber is shared with the "Composite Structure Stability Monitoring System".

[0074] 2.1 The vacuum chamber consists of a main chamber and an auxiliary chamber. The main chamber houses the two-dimensional turntable and the camera under test. Due to the large size of the camera, with a longest diagonal length of 3.1m, additional lifting fixtures are provided, and an operating space of 0.7m on each side is reserved for the operator. The required effective working space for vacuum testing is [missing information - likely a measurement in the original text]. Additionally, the camera needs to be placed on a two-dimensional turntable, with a sideways height of 1.5m. Including the tooling and turntable, the required effective vacuum working space is 4m high vertically. The auxiliary container is used to house the target simulator, which uses a parallel light tube opening. A collimator with a focal length of 13m, equipped with mechanical support and a temperature control system, and an auxiliary tank. An optical window is opened near the focal plane of the target simulator.

[0075] 2.2 Vacuum Tank System

[0076] like Figure 10 As shown, the vacuum tank is composed of Main tank and vice The tank consists of a main tank with a heat sink, and a secondary tank housing the target simulator and temperature control system, but without a heat sink. The optical axis of the target simulator is horizontal.

[0077] Tank sliding door: The main tank has a top opening, and the sliding door moves via an automatic control guide rail. Eight pneumatic clamps are used to pre-tighten the sliding door's sealing ring to the main tank.

[0078] Flange interfaces: The tank body is provided with flange openings for vacuum systems, heat sinks, target simulators, measurement and control systems, etc., as required.

[0079] Window Interface: Based on the focal plane position of the collimator in the target simulator and the requirements of the product testing plan, the sub-tank is equipped with a collimator near the focal plane position in the target simulator. Optical windows are opened in multiple locations on the side wall of the main tank. Optical window.

[0080] Interface sealing: Fluororubber rings are used for sealing doors, windows and flanges.

[0081] Tank coating: The inner surface is polished to Ra=0.8, and the outer surface is painted.

[0082] System leakage rate: 1x10⁻⁵ Pa m³ / s.

[0083] Ground-based transfer vehicles with a load capacity of 2T, guide rails, and gantry cranes facilitate docking.

[0084] Air flotation platform: The vacuum tank is built on an air flotation platform, with a vibration isolation frequency better than 2Hz.

[0085] Vacuum systems: roughing system and high vacuum system.

[0086] For the coarse pumping system, three sets of RuvacWAC2001 Roots vacuum pumps and ScrewlineSP630 dry Roots pumps were selected as the pre-pumping units.

[0087] The high vacuum system uses a cryogenic pump from a refrigeration unit as the main high vacuum pump, and a two-way gate valve is installed between the pump and the container.

[0088] The nitrogen system is an important subsystem in the environmental simulator, consisting of a liquid nitrogen system and a gaseous nitrogen system. Its first function is to provide liquid nitrogen to the heat sink in the simulation chamber, keeping its temperature below 100K to simulate the cold, dark environment of the space. Its second function is to bake the heat sink after the experimental conditions are completed, raising its temperature above room temperature.

[0089] The measurement and control system includes subsystems such as vacuum system measurement and control, cryogenic system measurement and control, temperature measurement system, cooling system, and gate operation control system, employing a local controller based on a PLC. The PLC is installed inside the control cabinet, with each system's control cabinet placed near the equipment. Data exchange is achieved via industrial Ethernet with the central control room computer. The central control room houses control computers for each subsystem, allowing users to control the equipment via computer or through touch-screen industrial tablets on their local control cabinets. On-site inching and remote measurement and control serve as backups for each other. At least four camera systems should be installed inside the container to meet the testing's video recording requirements. All camera system operations can be controlled locally or remotely.

[0090] The power supply for valves, instruments, and other low-voltage devices in the field control cabinet should be centralized to a single incoming line point for easy connection to a UPS.

[0091] It is equipped with a UPS that takes into account the power consumption of each system device to connect to the low-voltage part;

[0092] The container is equipped with four lights, with a voltage of 36V.

[0093] 2.3 The vacuum chamber mainly provides the environmental background for the experiment, and its main parameters are as follows:

[0094] 1) Vertical structure, dimensions Φ3600×2430mm (straight section), net internal dimensions of heat sink are Φ3300×2120mm (total height);

[0095] 2) Temperature cycling range: The heat sink temperature is -60℃ to +100℃, the heating rate of the heat sink is 1℃ / min, the cooling rate is 0.6℃ / min, and the temperature uniformity of the heat sink is ±1.5℃.

[0096] 3) Vacuum degree: The equipment is evacuated at room temperature, and reaches 3×10⁻⁶ vacuum level in 16 hours. -5 Pa; vacuum level was restored, reaching 3 × 10⁻⁶ Pa in 5 hours. -4 Pa, working pressure better than 1×10 -3 Pa;

[0097] 4) Cool black background: Liquid nitrogen temperature control -173℃, temperature uniformity ±21℃;

[0098] 5) Test equipment interfaces: 5 flanges with 55-pin interfaces (CX2-55C), totaling 44 interfaces. The flange diameter is 335mm, and the 9 55-pin interfaces are distributed as follows: 1 in the center, and the other 8 are evenly distributed on a Φ180mm circle centered on the flange center.

[0099] 3. Vacuum two-dimensional rotary table

[0100] A two-dimensional turntable is used for the mechanical support of the camera and for adjusting the relative position of the camera's optical axis and the collimator's optical axis. It operates in a vacuum environment, allowing for two-dimensional adjustment of azimuth and pitch. Flatness: better than 0.1mm, load capacity not less than 2T. In order to achieve full field of view and full aperture working performance testing of the camera, it is necessary to use a two-dimensional turntable for adjustment.

[0101] The specific parameters are as follows:

[0102] (1) Pitch rotation range: ±11°, azimuth axis rotation range: ±180°;

[0103] (2) At ambient temperatures of -10℃ to +30℃, the control accuracy of the two-axis (pitch and azimuth) angles is ≤2″ (peak-to-peak), and the angular position measurement accuracy is ≤2″ (peak-to-peak). At ambient temperatures of -60℃ to -10℃ and +30℃ to +40℃, the control accuracy of the two-axis (pitch and azimuth) angles is ≤4″ (peak-to-peak), and the angular position measurement accuracy is ≤2″ (peak-to-peak).

[0104] (3) The minimum displacement of the two axes (pitch and azimuth) is ≤1″;

[0105] (4) The turntable's load-bearing capacity shall not be less than 1.65T;

[0106] (5) Turntable surface The table surface has 10 rings of 12 M12 universal threaded holes, with adjacent threaded hole rings spaced 100mm apart;

[0107] (6) The distance from the turntable to the center axis of the target simulator is 897mm.

[0108] 4. Infrared target simulator

[0109] The target simulator consists of a collimator, a reticle, a temperature control system, and a high-temperature blackbody. The optical axis of the target simulator is located in the horizontal direction. The optical path of the collimator is as follows: Figure 11 As shown, the optical path diagram of the collimator is viewed from above.

[0110] The primary function of the target simulator is to provide a target source for infrared camera performance testing. To complete a full-aperture test of the camera's performance, the camera needs to be adjusted for azimuth and pitch using an adjustment platform. The camera inlet is located at the edge of the turntable, away from the axis of rotation. When the turntable is adjusted for azimuth and pitch, the camera opening position correspondingly undergoes spatial displacement in the horizontal and vertical directions, particularly a translation of approximately ±220mm in the vertical direction. Additional position adjustment margins are provided. The effective aperture of the target simulator is approximately... (≈550+220×2).

[0111] During infrared camera performance testing, a reticle and a high-temperature blackbody are placed on the focal plane of the collimator of the target simulator. The product under test is placed on the working platform, and the camera aperture is aligned with the collimator aperture. Adjustments are made using a two-dimensional turntable to ensure the optical axis of the collimator beam is parallel to the optical axis of the product, allowing the camera to image the reticle and the high-temperature blackbody, thus completing the camera performance test. During the testing process, a vacuum chamber simulates the on-orbit operating temperature field.

[0112] Specific structural form: off-axis RC, vacuum type; effective aperture: ≥Φ1000mm; focal length: 13000mm; working band: 0.4um-1um; eccentricity: 500mm; back cutoff (distance from focal surface to flange surface): 180.246mm.

[0113] Equipment Name and Quantity

[0114] a) Name: Ground-based testing equipment for infrared camera thermo-optical testing; Quantity: 1 unit

[0115] b) Main technical parameters and indicators

[0116] Test space: Test mass range: 0—; Test optical aperture range: 0—600mm;

[0117] Test accuracy: better than 10%; Applicable scope: measurement of parameters such as focal length and resolution of cameras under on-orbit operating temperature conditions.

[0118] c) Main uses and necessity of newly added non-standard special equipment

[0119] Test conditions requirements

[0120] Vacuum testing environment requirements

[0121] Infrared camera performance testing requires a vacuum environment, primarily for the following two reasons:

[0122] The camera operates in the shortwave and midwave atmospheric absorption bands. The atmospheric transmittance curve is shown in the figure below. If two cameras are placed in an atmospheric environment for optical calibration, the signal light will be severely attenuated by the atmosphere, affecting the testing of camera performance and the judgment of calibration results. This, in turn, affects the testing and judgment of camera performance parameters such as MTF, SNR, on-orbit effective working time, and target acquisition capability. Therefore, the performance testing of infrared cameras needs to be carried out under vacuum conditions.

[0123] The camera is calibrated under normal atmospheric pressure and used in a vacuum environment. The camera uses a transmission element, and the refractive index of the environment around the transmission element changes from the atmospheric refractive index to the vacuum refractive index, which affects the light transmission path and thus the position of the camera's optimal focal plane. Therefore, it is necessary to determine the optimal focal plane position of the camera under vacuum conditions.

[0124] Requirements for variable temperature environments:

[0125] Because the camera is located on a satellite platform and revolves around the sun while rotating with the Earth, it experiences drastic temperature field changes, with a large cycle every year and a small cycle every day, especially the scanning pointing mirror assembly exposed on the outside of the camera.

[0126] The experiment requires the camera payload to be placed in a simulated on-orbit temperature field. For example, the scanning mirror assembly of the scanning camera needs to be placed at a temperature of -11.3°C. If an optical single-mirror assembly is placed at -11.3°C under normal atmospheric pressure, the optical mirror surface will freeze, making testing impossible. Therefore, performance testing of the camera under on-orbit operating temperature conditions needs to be conducted in a vacuum environment.

[0127] 5. Auxiliary Structures

[0128] A. Used in experiments requiring vacuum and low temperature in focal plane testing equipment, it connects to an infrared target simulator through the focal plane window. The main parameters are as follows:

[0129] B. Horizontal structure, vacuum chamber size: Φ800×780mm (straight section), heat sink internal net size not less than Φ600×750mm;

[0130] C. Automatic heat sink control with liquid nitrogen cooling, temperature below -173℃, temperature control accuracy ±5℃;

[0131] D. Eight 55-pin connectors (CX2-55C) are available;

[0132] E. The flange aperture for docking with the target simulator shall be no less than 160mm.

[0133] The working principle of this invention is as follows: The thermal deformation test simulates the on-orbit temperature environment by varying the heat sink temperature in a vacuum setting. This allows for the measurement of camera parameters such as signal-to-noise ratio, spatial resolution, scanning and pointing accuracy under thermal vacuum conditions and alternating temperature fields, as well as obtaining parameters such as optical axis pointing and cooling capacity performance of the cooling mechanism. The test scheme involves introducing a plane wave generated by a dynamic interferometer and collimated by a collimating optical tube into the camera. The thermal deformation of the camera in the vacuum environment will produce an image change on this standard plane wave. This image change is used to verify the effectiveness of thermal deformation control, evaluate the impact of thermal deformation on camera detection performance, and provide important data for further optimization of camera thermal deformation control design.

[0134] It should be noted that embodiments of the present invention can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the above-described devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuitry such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above-described hardware circuitry and software, such as firmware.

[0135] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A thermal deformation testing system for an optical system, characterized in that, The optical system thermal deformation testing system includes a temperature test chamber, a vacuum two-dimensional turntable, a scanning pointing mirror, a temperature control and measurement system, a refrigerator control system, a data acquisition system, a vacuum two-dimensional turntable control system, an infrared target simulator, and a scanning control system. The infrared target simulator is set on the right side of the temperature test chamber, and the light output port of the target simulator is connected to the outlet of the temperature test chamber. The vacuum two-dimensional turntable is set at the bottom of the temperature test chamber. The scanning pointer and the camera under test are placed on the vacuum two-dimensional turntable. The scanning pointer is connected to the scanning mirror control system. The temperature test chamber is connected to the temperature control and measurement system, the refrigeration control system and the data acquisition system respectively. The infrared target simulator is equipped with a collimator, a reticle, a temperature control system, and a high-temperature blackbody. The optical axis of the infrared target simulator is located in the horizontal direction. The temperature test chamber is equipped with a vacuum chamber, which is divided into a main chamber and a secondary chamber. The main chamber contains a two-dimensional turntable and a camera under test; the secondary chamber contains a target simulator, and an optical window is opened on the secondary chamber near the focal plane of the target simulator. The vacuum two-dimensional turntable can be adjusted in both azimuth and pitch. The optical system thermal deformation test method for implementing the optical system thermal deformation test system includes: simulating the on-orbit temperature environment by changing the temperature of the heat sink in a vacuum environment, and realizing the measurement of the signal-to-noise ratio, spatial resolution, scanning and pointing accuracy of the camera under thermal vacuum conditions and alternating temperature fields, as well as obtaining the optical axis pointing and cooling capacity performance parameters of the cooling mechanism. The plane wave generated by the dynamic interferometer through collimation tube amplification is introduced into the camera. The thermal deformation of the camera in a vacuum environment will produce an imaging change on the standard plane wave. The effectiveness of thermal deformation control is verified by the imaging change, the impact of thermal deformation on the camera's detection performance is evaluated, and the camera's thermal deformation control design is further optimized. 1) Simulate the on-orbit temperature environment by varying the temperature of the heat sink; 2) Select the appropriate reticle according to the performance parameter requirements of the product being tested, and place the reticle precisely at the center of the collimator's foot surface; 3) The light source is placed on one side of the focal plane of the collimator to provide illumination for the reticle; 4) Adjust the position of the product under test so that the beam emitted from the collimator can cover the aperture of the camera under test within the entire field of view. 5) Adjust the angle of the camera under test using a two-dimensional turntable so that the reticle on the focal plane of the collimator is imaged onto the focal plane detector of the product under test. 6) Based on the collected data, analyze and calculate the measured values ​​of each performance parameter.

2. The optical system thermal deformation testing system as described in claim 1, characterized in that, The temperature test chamber is also equipped with a heat sink system, a vacuum pumping system, a temperature control system, a refrigeration system, a heating system, and a control system.

3. The optical system thermal deformation testing system as described in claim 2, characterized in that, The vacuum pumping system is a rough vacuum system, with a rough vacuum pre-pump, a pneumatic high vacuum baffle valve, and a metal bellows connecting to the vacuum chamber. It uses a dry oil-free pump as the back pump of the magnetic levitation molecular pump and a pneumatic high vacuum baffle valve as the high vacuum pumping system.

4. The optical system thermal deformation testing system as described in claim 2, characterized in that, The heat sink system is equipped with a heat sink, which adopts a vertical structure and is divided into a cylindrical heat sink and a movable door heat sink.

5. The optical system thermal deformation testing system as described in claim 4, characterized in that, The heat sink is cooled by liquid nitrogen and its inner surface is coated with black paint.

6. The optical system thermal deformation testing system as described in claim 2, characterized in that, The main tank has a heat sink and a top opening. The movable door moves via an automatic control guide rail, and eight pneumatic clamps are used to pre-tighten the sealing ring of the movable door to the main tank.

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