Method and apparatus for inspecting large aperture optical systems

Abstract

This invention discloses a method and apparatus for assembling and inspecting a large-aperture optical system. It solves the problem that existing large-aperture optical testing systems cannot provide a safe and reliable environment for personnel to directly enter for assembly, adjustment, and testing. This invention integrates a collimator and the payload to be assembled and inspected into interconnected collimator and payload chambers. Personnel enter the chamber for assembly, adjustment, and testing, maintaining a stable low-pressure environment. This effectively resists sudden airflow interference caused by personnel movement and equipment heat dissipation, while also effectively reducing air density while isolating external airflow disturbances. This ensures system stability and robustness during long-term assembly and inspection, reduces airflow disturbances on the optical system's wavefront, and provides reliable data for precise assembly, adjustment, and final imaging quality. It can meet the requirements for optical index detection and calibration of optical remote sensing payloads in low-vacuum environments, as well as high-precision assembly, adjustment, and integration of optical remote sensing payloads.

Description

Technical Field

[0001] This invention relates to large-aperture optical systems, and more specifically to a method and apparatus for assembling and inspecting large-aperture optical systems. Background Technology

[0002] With the continuous advancement of space optical remote sensing technology, the requirements for system performance indicators are becoming increasingly stringent. In pursuit of higher ground resolution, the aperture and focal length of space optical remote sensors are constantly increasing, which brings new challenges to ground detection and image quality evaluation.

[0003] Space products possess irreversible characteristics; once the launch process begins, on-site adjustments are impossible. Therefore, comprehensive imaging quality testing and verification of optical payloads must be conducted in the laboratory during the development phase and before launch. This is a crucial step in ensuring successful on-orbit mission execution and achieving expected goals. Especially for large-aperture, high-precision optical payloads, the overall satellite design often requires "small size, light weight, and low moment of inertia." This drives the lightweighting of camera structures but also makes their optical performance and imaging quality more susceptible to factors such as gravity, support structures, stability, and temperature. Therefore, conducting comprehensive ground-based testing throughout the entire process is the cornerstone of developing highly reliable, high-performance space optical products.

[0004] As the aperture and focal length of space optical remote sensors increase, the size of the collimator required for detection and image quality evaluation also increases accordingly. This leads to significantly higher requirements for the image quality, focal plane positioning accuracy, and stability of the testing environment of the collimator itself. However, against the backdrop of continuous improvement in the technical specifications of space optical remote sensors, the development of large-size collimators, image quality preservation, focal plane accuracy control, and environmental stability assurance all face increasingly severe technical challenges.

[0005] For space optical remote sensors, ground assembly, testing, and image quality evaluation are fundamental and core aspects of their development process, directly impacting their on-orbit operation and the completion of their intended scientific or military missions. During the ground development of remote sensing cameras, several key stages, such as primary and secondary mirror integration, front-end system and substrate docking, system branch connection, system image quality measurement, and camera internal orientation element testing, require a temperature-stable, vibration-free, and low-airflow-turbulence testing environment. This environment must also allow personnel access for assembly and testing to meet the efficiency requirements of large-aperture optical system assembly and testing.

[0006] During system docking, wavefront distortion and beam jitter caused by airflow can lead to blurring and jitter of target images in the monitoring field of view, resulting in visual misjudgments and alignment deviations, thus reducing the alignment accuracy between optical axes. In image quality measurements, airflow disturbances directly contaminate wavefront information; high-frequency noise from rapid airflow reduces fringe contrast, while slow temperature gradient drift introduces false defocus and astigmatism—low-order aberrations—into the measurement results, leading to poor measurement repeatability. For large-aperture systems, the path integration effect of long optical paths amplifies these effects, and the non-uniform refractive index within the cross-section of a large-aperture beam directly translates into higher-order aberrations, which, combined with mirror surface errors, make it difficult to accurately assess the true performance of the optical system. Therefore, without the aforementioned high-performance, high-stability testing environment, the development of high-resolution space optical remote sensors will face significant challenges.

[0007] To ensure the successful development of the aforementioned space optical remote sensor, an efficient, high-performance, and highly stable testing environment and platform are required to facilitate the assembly and testing of the large-aperture space optical remote sensor and ensure the performance and quality of the remote sensing camera.

[0008] Chinese patent CN107782537A discloses a vacuum optical inspection system, primarily designed to overcome the limitation of interferometers in vacuum environments. This invention provides a solution for testing wavefront aberrations of optical lenses in space optical remote sensors under vacuum conditions, enabling the detection of optical wavefront aberrations in space optical remote sensor lenses within a vacuum environment. However, this invention, which performs optical assembly and inspection of space optical remote sensors in a vacuum environment, prevents assembly and testing personnel from entering and performing real-time assembly and inspection, thus failing to meet the efficiency requirements for the assembly and inspection of large-aperture optical systems.

[0009] Chinese patent CN114076575A discloses a vacuum interferometer device and its optical inspection method. By separating the interferometer body from the phase shifter and standard mirror, and placing the interferometer body in a normal temperature and pressure environment while placing the phase shifter, standard mirror, and the component under test in a vacuum or low-pressure environment, the random and systematic errors introduced by the parallel flat window into the interferometric detection optical path can be eliminated. Furthermore, it enables optical inspection of the component under test without atmospheric disturbance. This invention is an improvement on the interferometer, but it still cannot solve the problem of optical system assembly and inspection, nor can it enable real-time assembly and inspection by assembly and testing personnel, thus failing to meet the assembly and inspection requirements of large-aperture optical systems.

[0010] Chinese patent CN108132142A discloses a testing device and method for large-aperture reflective optical systems. It primarily replaces expensive plane mirrors with arrayed corner reflectors, still employing a self-collimating interferometry method. Furthermore, by utilizing the backlighting characteristics of the corner reflectors, wavefront aberrations of the optical system can be measured under different fields of view without requiring further adjustment of the corner reflectors. However, this invention fails to address the problem that large-aperture optical system testing is highly susceptible to environmental factors such as airflow and vibration, and therefore cannot meet the assembly and testing requirements of large-aperture optical systems.

[0011] Chinese patent CN112556997A discloses a method, apparatus, and equipment for testing large-aperture optical systems. It mainly involves designing a rectangular aperture collimator with a rectangular primary mirror, controlling the calibrated collimator to rotate at multiple angles to test the full field-of-view imaging performance of the optical system under test in different directions. However, this invention also fails to address the problem that large-aperture optical system testing is highly susceptible to environmental factors such as airflow and vibration, and therefore cannot meet the assembly and testing requirements of large-aperture optical systems.

[0012] Chinese patents CN114185144A and CN115016116A both disclose a method for assembling and adjusting a large-aperture optical system based on a small-aperture plane mirror. This method primarily uses a small-aperture plane mirror instead of a large-aperture one, reducing equipment costs and enabling the assembly and adjustment of the large-aperture optical system using a small-aperture plane mirror. However, this invention still cannot solve the problem that the testing of large-aperture optical systems is highly susceptible to environmental factors such as airflow and vibration, and therefore cannot meet the assembly and inspection requirements of large-aperture optical systems.

[0013] Chinese patent CN115016116A provides a method and apparatus for assembling and adjusting a large-aperture optical system. The method primarily involves aligning the large-aperture port of the beam expander system with a standard mirror and the small-aperture port with an interferometer during the assembly and adjustment process. The attitude of the beam expander system is adjusted and fixed according to the optical path between the standard mirror and the interferometer. This reduces the hardware and space requirements for assembling and adjusting large-aperture optical systems, minimizes assembly and adjustment errors, and simplifies the assembly and adjustment process. However, this invention mainly focuses on testing the image quality of beam expander systems, not on measuring the image quality of large-aperture imaging and detection optical systems. It cannot address the problem that testing large-aperture optical systems is highly susceptible to environmental factors such as airflow and vibration, and therefore cannot meet the efficiency requirements for assembling and inspecting large-aperture optical systems.

[0014] As can be seen, the aforementioned patents address some issues in image quality measurement of large-aperture optical systems from different perspectives. Some patents resolve the impact of airflow disturbances on image quality measurement, but they cannot meet the requirements for real-time assembly and inspection of large-aperture optical systems. Some patents provide different assembly and inspection methods for large-aperture optical systems, but they do not solve the problem that the testing of large-aperture optical systems is highly susceptible to environmental factors such as airflow and vibration. Some patents are not specifically designed for the assembly and inspection of imaging and detection optical systems, and therefore cannot meet the real-time assembly and inspection requirements of large-aperture optical systems. Therefore, none of them can meet the demand for efficient integrated assembly and inspection of large-aperture optical systems.

[0015] For the reasons mentioned above, there is an urgent need for a low-pressure integrated assembly and inspection platform for large-aperture optical systems to meet the requirements of efficient integrated assembly and inspection of large-aperture optical systems. Summary of the Invention

[0016] To address the technical problem that existing large-aperture optical testing systems cannot provide a safe and reliable testing environment that can be directly accessed by testing personnel, or are highly susceptible to environmental factors such as airflow and vibration, this invention provides a testing method and apparatus for large-aperture optical systems.

[0017] To achieve the above objectives, the present invention adopts the following technical solution: A method for assembling and inspecting a large-aperture optical system, characterized by the following steps: Step 1: Construct a testing and assembly device for a large-aperture optical system. The testing and assembly device includes an air-bearing vibration isolation platform, a load chamber and a light tube chamber that are connected to each other and set on the air-bearing vibration isolation platform, and a collimator set in the light tube chamber. A semi-transparent and semi-reflective sealed light window is provided on the side wall of the light tube chamber. The incident end of the collimator corresponds to the sealed light window, and its exit end corresponds to the load chamber. A target wheel and an interferometer are provided outside the sealed light window. The transmittance-to-reflectance ratio of the sealed light window is in the range of 6:4 to 9:1. Step 2: The interferometer emits a spherical wave. Adjust the target wheel so that the spherical wave can pass through the empty target position on the target wheel and reach the sealed optical window, and be reflected back to the interferometer by the sealed optical window. Move the interferometer until interference fringes appear on the screen of the interferometer. Then the optical axis of the spherical wave emitted by the interferometer is parallel to the normal direction of the sealed optical window. Step 3: Set up a plane mirror in the load chamber and adjust the azimuth and / or elevation angle of the plane mirror until interference fringes appear on the interferometer. The interference fringes become sparse or dense as the azimuth and / or elevation angle of the plane mirror changes. At this point, adjust the azimuth and / or elevation angle of the plane mirror again until the interference fringes are sparsest. Then the plane mirror is perpendicular to the parallel light emitted from the collimator. Step 4: Move the interferometer gradually along the Y-axis and observe the defocus term or wavefront RMS value corresponding to each position. When the interferometer is at the zero point of the defocus term or the local minimum value of the RMS value, stop moving. At this time, the convergence point of the spherical waves emitted by the interferometer is the focal plane position of the collimator. The Y-axis direction is the direction away from or towards the target wheel. Step 5: Move the plane mirror out of the load chamber and switch the target wheel so that the pre-selected target plate on the target wheel is opposite to the interferometer; move the target wheel along the Y-axis until the defocus term of the interferometer is zero, then stop moving. The position of the target plate is the focal plane position of the collimator. Step 6: Replace the interferometer with a light source. The light source illuminates the target plate. Set the load to be inspected in the load chamber and adjust the load to make the target on the target plate imaged at the center of the detector field of view of the load to be inspected, thereby providing an infinite distance target for the load to be inspected. Step 7: Adjust the air pressure in the load chamber to 76000Pa~81000Pa or below 50000Pa, and complete the installation, adjustment and testing of the load to be installed and tested based on the infinity target.

[0018] Furthermore, in step 1, the target wheel is mounted on a two-dimensional displacement stage; the interferometer is mounted on a single-axis translation stage; the single-axis direction of the single-axis translation stage is the Y-axis; the load chamber is equipped with a track; and a cargo vehicle is mounted on the track. In step 3, the step of setting up a plane reflector in the load chamber specifically involves setting up a plane reflector on a cargo vehicle, moving the cargo vehicle along the track, and thus pushing the plane reflector to the center of the load chamber.

[0019] Furthermore, step 6 specifically includes: The interferometer and single-axis translation stage are replaced with a light source that illuminates the target plate. A vacuum turntable is set on the cargo vehicle, and the load to be inspected is placed on the vacuum turntable. The cargo vehicle is moved along the track to push the vacuum turntable and the load to be inspected to the center of the load chamber. The vacuum turntable is rotated to adjust the orientation of the load to be inspected so that the target on the target plate is imaged at the center of the detector field of view of the load to be inspected, thus providing an infinite distance target for the load to be inspected.

[0020] Furthermore, in step 1, the load chamber is connected to a vacuum system; Step 7 specifically involves evacuating the load chamber using a vacuum system until the air pressure inside the load chamber drops to below 76000Pa~81000Pa or 50000Pa, and then completing the installation, adjustment, and testing of the load to be installed and tested based on the infinity target.

[0021] Furthermore, in step 7, the load chamber is evacuated using a vacuum system until the air pressure inside the load chamber drops below 80,000 Pa or 50,000 Pa.

[0022] An assembly and inspection device for a large-aperture optical system, used in the aforementioned assembly and inspection method for the large-aperture optical system, is characterized by: It includes an air-floating vibration isolation platform, a load chamber and a light tube chamber that are installed on the air-floating vibration isolation platform and are interconnected, a parallel light tube installed in the light tube chamber, as well as a plane mirror and a light source; The load chamber is used to house a plane mirror or a load to be installed or inspected. The side wall of the light tube chamber is provided with a semi-transparent and semi-reflective sealed light window; the transmission-to-reflection ratio of the sealed light window is in the range of 6:4 to 9:1. The incident end of the parallel light tube corresponds to the sealed light window, and its exit end corresponds to the load chamber. A target wheel and an interferometer are provided outside the sealed optical window, with the target wheel positioned between the sealed optical window and the interferometer; the target wheel has multiple target positions for setting the target plate and one empty target position; The light source is used to illuminate the target plate.

[0023] Furthermore, a two-dimensional displacement stage and a single-axis translation stage are provided outside the sealed light window, with the two-dimensional displacement stage positioned between the sealed light window and the single-axis translation stage; The target wheel is mounted on a two-dimensional displacement stage; The single-axis translation stage is used to set up the interferometer, and its single-axis direction is the Y-axis. The load chamber is equipped with a track; The track is equipped with a cargo vehicle for carrying plane mirrors or loads to be inspected.

[0024] Furthermore, multiple column supports are respectively installed at the bottom of the optical tube chamber and the load chamber; The lower end of the column support is fixedly connected to the air-float vibration isolation platform, and the upper end passes through the light tube chamber or load chamber and is fixedly connected to the parallel light tube or track accordingly. The column support is fitted with a sealed corrugated pipe. The lower end of the sealed bellows is fixedly connected to the column support, and the upper end is correspondingly connected to the flange on the outer wall of the tube chamber or load chamber.

[0025] Furthermore, it also includes a vacuum turntable; the vacuum turntable is used to support and adjust the orientation of the load to be inspected; The load chamber is connected to a vacuum system; the inner wall of the load chamber is equipped with a lighting unit, a camera unit, and an environmental monitoring unit.

[0026] Furthermore, the collimator includes a folding plane mirror, a secondary mirror, and a primary mirror arranged sequentially along the optical path from the incident end to the exit end; The folding plane mirror corresponds to the sealed light window, and the primary mirror corresponds to the load chamber.

[0027] The beneficial effects of this invention are: 1. This invention integrates a collimator and a large-aperture payload into interconnected optical tube and payload chambers. Personnel can enter the chamber for assembly, adjustment, and testing, maintaining a stable low-pressure environment within the chamber. This ingenious design effectively resists sudden airflow interference caused by changes in the external environment, such as personnel movement and equipment heat dissipation. It also effectively reduces air density while isolating external airflow disturbances, ensuring system stability and robustness during long-term assembly and testing. This significantly reduces the interference of airflow disturbances on the wavefront of the optical system, providing reliable data for the precise assembly, adjustment, and final imaging quality testing of the large-aperture optical system. Thus, it effectively suppresses the impact of external airflow disturbances on the high-precision assembly and testing process of the optical system, and meets the requirements for optical index testing and calibration, as well as high-precision assembly, adjustment, and integration of space optical remote sensors in low-vacuum environments.

[0028] 2. This invention precisely controls the indoor air pressure to a low of 80,000 Pa, similar to an environment at an altitude of 2,000 m. The indoor air pressure ensures that loading and inspection personnel can safely enter and work continuously for 4 hours. At the same time, the indoor space is equipped with an environmental monitoring unit, a lighting unit, and a camera unit. Under the premise of fully ensuring the safety of personnel, loading and inspection personnel can enter the indoor space to work, and ensure that large-diameter loads are always in a stable environment with airflow isolation and vibration control, thereby significantly improving loading and inspection efficiency and having strong engineering practicality and application value.

[0029] 3. In this invention, each component of the parallel optical tube is installed on an independent through-chamber type column support. The column support passes through the optical tube chamber and is fixedly connected to the external ground air-floating vibration isolation platform. The cargo vehicle and track are also fixedly connected to the vibration isolation platform and isolated from the load chamber. This achieves physical decoupling of the vibration transmission path, ensuring that the vibration of the optical tube chamber and the load chamber during operation will not affect the optical path accuracy and effectively reducing the impact of vibration transmission on the assembly and inspection.

[0030] 4. The collimator of this invention adopts an off-axis two-mirror optical structure, which has the advantages of no central obstruction, full aperture utilization, and no chromatic aberration. It can effectively avoid diffraction stray light caused by the secondary mirror support structure of the coaxial system, thereby improving the system signal-to-noise ratio and target contrast. The overall optical path layout is flexible, and the combination of long focal length and large aperture can be achieved in a limited space through optical path folding, thereby outputting a parallel beam with extremely high collimation, providing high-quality simulation of infinity targets for large-aperture payloads.

[0031] 5. The target wheel of the present invention is equipped with multiple target positions, which can be set with target plates with different functions. With the help of the light source, it can provide target information with different wavelengths, color temperatures and patterns. This design can fully support the entire process of load assembly and adjustment, including benchmark establishment, multi-branch and multi-spectral band docking, system performance testing, detection capability evaluation and final high-precision assembly and integration, optical index detection and calibration.

[0032] 6. This invention is equipped with a vacuum turntable, which can measure the imaging quality of large-aperture loads under different fields of view without frequent attitude adjustments, thereby improving the loading and inspection efficiency of large-aperture loads. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the mounting and testing device structure for the large-aperture optical system corresponding to step 1 in this embodiment of the invention. Figure 2 This is a schematic diagram of the mounting and testing device structure for the large-aperture optical system corresponding to step 6 in this embodiment of the invention. Figure 3 This is a schematic diagram of the connection structure between the optical tube chamber and the air-floating vibration isolation platform in an embodiment of the present invention, wherein (b) is the AA cross-sectional view of (a).

[0034] The attached figures are labeled as follows: 111. Primary mirror; 112. Secondary mirror; 113. Folding plane mirror; 12. Air-bearing vibration isolation platform; 13. Column support; 21. Load chamber; 211. Camera unit; 212. Environmental monitoring unit; 22. Light tube chamber; 221. Sealed light window; 23. Track; 31. Target wheel; 32. Light source; 33. Two-dimensional displacement stage; 4. Plane mirror; 5. Vacuum turntable; 6. Load to be loaded and inspected; 7. Single-axis translation stage; 8. Interferometer; 9. Sealed bellows. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention provides an assembly and inspection device for a large-aperture optical system, such as... Figure 1 , Figure 2 As shown, the loading and testing device includes an air-floating vibration isolation platform 12, a load chamber 21 and a light tube chamber 22 that are installed on the air-floating vibration isolation platform 12 and are interconnected, a parallel light tube installed in the light tube chamber 22, a plane mirror 4, a vacuum turntable 5, a light source 32, a two-dimensional displacement stage 33, a single-axis translation stage 7, and an integrated control and management subsystem.

[0037] The load chamber 21 and the light tube chamber 22 are connected by a flange to form a low-pressure tank. The dimensions of the load chamber 21 are 6m (W) × 6m (H) × 8m (L), and the dimensions of the light tube chamber 22 are Φ4.5m × 8m (L). The inner walls are matte treated. The ultimate vacuum degree is less than 30000Pa. The evacuation time from 1 atmosphere to the working low pressure of 80000Pa is 20 minutes. The pressure change rate and the low pressure state of 80000Pa ensure personnel safety. The oxygen content in the low-pressure tank can supply two people for 40 hours.

[0038] The load chamber 21 is equipped with a track 23; a trolley is mounted on the track 23 to carry the plane reflector 4 or the load 6 to be inspected. The trolley measures 4m × 5m and has a total load capacity of not less than 15t. The track 23 is at the same height as the track laid on the laboratory floor, facilitating the entry and exit of the trolley from the tank. The trolley adopts an interlocking structure that works with the track 23, forming a single-degree-of-freedom linear sliding pair. Only the trolley is allowed to translate along the direction of the track 23, while all other degrees of freedom are constrained, thus preventing overturning and locking it to the track 23 inside the low-pressure tank.

[0039] The load chamber 21 is connected to a vacuum system. The inner wall of the load chamber 21 is equipped with a lighting unit, a camera unit 211 (pan-tilt camera), and an environmental monitoring unit 212. The camera unit 211 facilitates observation of the test specimens and personnel inside the low-pressure tank. The environmental monitoring unit 212 monitors the oxygen concentration and atmospheric pressure in the environment in real time. When abnormal indicators are detected, an audible alarm is triggered, prompting personnel to evacuate immediately. The environmental monitoring unit also provides supporting terminal software that can remotely display environmental parameters inside the low-pressure tank in real time. When personnel enter, they wear a vital signs monitoring system. This system combines high-speed photoelectric blood oxygenation detection with volumetric pulse scanning technology to monitor blood oxygen saturation and pulse rate in real time. An external comfort blood oxygen probe is connected to improve the comfort of personnel undergoing long-term continuous monitoring. The vital signs monitoring system also provides supporting terminal software that can remotely display the vital signs data of personnel inside the low-pressure tank in real time.

[0040] The side wall of the light tube chamber 22 is provided with a semi-transparent, semi-reflective sealed light window 221. The sealed light window 221 is made of quartz glass and has a parallelism of less than [missing information]. Its transmittance-to-reflectance ratio ranges from 6:4 to 9:1, and in this embodiment, 9:1 is preferred; such as Figure 3As shown, a column support 13 is installed at the bottom of the light tube chamber 22; the lower end of the column support 13 is fixed to the air-floating vibration isolation platform 12 by expansion bolts, and the upper end is fixed to the parallel light tube; a sealed bellows pipe 9 is installed on the outer sleeve of the column support 13; the lower end of the sealed bellows pipe 9 is fixed to the column support 13, and the upper end is connected to the flange on the outer wall of the light tube chamber 22 to ensure the sealed isolation between the tank body of the light tube chamber 22 and the through-wall column support 13, and to avoid stress between the tank body and other external support structures. Similarly, the track 23 in the load chamber 21 is also fixed to the air-floating vibration isolation platform 12 through the column support 13 and the sealed bellows pipe 9, and is elastically connected to the load chamber 21.

[0041] The collimator is an off-axis dual-reflector structure with an effective aperture ≥ Φ2m, a focal length of 50m, and a focal length error better than ±0.5%. The center field-of-view aberration is ≤ λ / 20@632.8nm, where λ is the wavelength; the full field-of-view aberration is ≤ λ / 15@632.8nm; and the beam parallelism of the full-aperture collimator is less than [value missing]. The change in the optical axis of the optical tube from normal pressure to low pressure is less than The collimator's incident end corresponds to the sealed optical window 221, and its exit end corresponds to the load chamber 21. Specifically, the collimator includes a folding plane mirror 113, a secondary mirror 112, and a primary mirror 111 arranged sequentially along the optical path from the incident end to the exit end. The folding plane mirror 113 corresponds to the sealed optical window 221, and the primary mirror 111 corresponds to the load chamber 21. The surface profiles of the folding plane mirror 113, the secondary mirror 112, and the primary mirror 111 are all ≤λ / 60@632.8nm. The primary mirror 111 and the secondary mirror 112 are both coated with an aluminum film and a protective film, with the protective film located on the outer side. In the spectral range of 0.35μm to 14μm, the average reflectivity is greater than or equal to 90%.

[0042] A target wheel 31 and an interferometer 8 are provided outside the sealed light window 221, with the target wheel 31 positioned between the sealed light window 221 and the interferometer 8. The target wheel 31 has multiple target positions for setting the target plate and one empty target position. The target wheel 31 is mounted on a high-precision two-dimensional displacement stage 33. In this embodiment, the two-dimensional displacement stage 33 can be adjusted along the X and Y axes, with an adjustment range of 200mm (-100mm to +100mm), and has both manual and electric adjustment functions; the adjustment accuracy is ≤ ±0.005mm; the target movement sway is ≤0.01mm; the target wheel 31 has ≥12 target positions with a positioning accuracy ≤0.03mm; the target wheel 31 has a temperature measurement function and is electrically adjustable; the adjustment speed is ≥3. mm / s; The target wheel 31 is equipped with a visible-near infrared target plate and a mid-to-long-wave infrared target plate. The visible-near infrared target plate is made of fused silica material with an effective aperture of Φ60mm. The visible-near infrared target plate includes a set of resolution plates (5 pieces), star-shaped holes (Φ0.005, Φ0.01, Φ0.02, Φ0.03, Φ0.05, Φ0.1, Φ0.2, Φ0.5, Φ1), a glass plate, and four stripe plates. The mid-to-long-wave infrared target plate has an effective aperture of Φ60mm. There are a total of 14 mid-to-long-wave infrared target plates, including a set of four-bar target plates (5 pieces), a set of round hole plates (5 pieces), a knife-edge target, a cross plate, a square hole target, and a strip target.

[0043] The plane mirror 4 is installed inside the load chamber 21.

[0044] The vacuum turntable 5 can be moved into or out of the low-pressure tank along the track 23 as a whole.

[0045] Light source 32 is used to illuminate the target board. In this embodiment, light source 32 includes a large dynamic range visible light uniform light source and a surface source differential blackbody; the large dynamic range visible light uniform light source has a spectral range of 300nm to 2500nm, an outlet diameter of 100mm, a brightness surface uniformity of ≥99%, and has a conventional brightness mode and a weak light mode, and can continuously change from the weak light mode to the conventional brightness mode, with continuously adjustable brightness in each mode; the surface source differential blackbody has an emission area of ​​100mm×100mm, and at an ambient temperature of 20ºC, its absolute temperature range is -15ºC to +150ºC; the differential temperature range is -35ºC to +130ºC.

[0046] An interferometer 8 is set on a single-axis translation stage 7, with its single-axis direction being the Y-axis.

[0047] The integrated control and management subsystem is located outside the load room 21 and the light tube room 22.

[0048] The assembly and inspection process using the aforementioned assembly and inspection device includes the following steps: Step 1: Construct the mounting and testing equipment for the large-aperture optical system described above; Step 2: The interferometer 8 emits a spherical wave. The target wheel 31 is adjusted so that the spherical wave can pass through the empty target position on the target wheel 31 and reach the sealed optical window 221, and be reflected back to the interferometer 8 by the sealed optical window 221. The interferometer 8 is moved until interference fringes appear on the screen of the interferometer 8. Then the optical axis of the spherical wave emitted by the interferometer is parallel to the normal direction of the sealed optical window 221.

[0049] Step 3: Set up the plane mirror 4 on the cargo vehicle, move the cargo vehicle along the track 23 to push the plane mirror 4 to the middle of the load chamber 21, adjust the azimuth and / or elevation angle of the plane mirror 4 until interference fringes appear on the interferometer 8, and the interference fringes become sparse or dense as the azimuth and / or elevation angle of the plane mirror 4 changes. At this time, adjust the azimuth and / or elevation angle of the plane mirror 4 again until the interference fringes are the sparsest, then the plane mirror 4 is perpendicular to the parallel light emitted from the collimator.

[0050] Step 4: Move the interferometer 8 gradually along the Y-axis and observe the defocus term or wavefront RMS value corresponding to each position. When the interferometer 8 is at the zero point of the defocus term or the local minimum value of the RMS value, stop moving. At this time, the convergence point of the spherical wave emitted by the interferometer 8 is the focal plane position of the collimator. The Y-axis direction is the direction away from or close to the target wheel 31.

[0051] Step 5: Move the plane mirror 4 out of the load chamber 21 and switch the target wheel 31 so that the target plate with reflectivity on the target wheel 31 is opposite to the interferometer 8; move the target wheel 31 along the Y-axis until the defocus term of the interferometer 8 is zero and then stop moving. The position of the target plate is the focal plane position of the collimator.

[0052] Step 6: Replace the interferometer 8 and the single-axis translation stage 7 with the light source 32. The light source 32 illuminates the target plate. Set up a vacuum turntable 5 on the cargo cart and place the load to be inspected 6 on the vacuum turntable 5. Move the cargo cart along the track 23 to push the vacuum turntable 5 and the load to be inspected 6 to the middle of the load chamber 21. Rotate the vacuum turntable 5 to adjust the orientation of the load to be inspected 6 so that the target on the target plate is imaged at the center of the detector field of view of the load to be inspected 6, thereby providing an infinite distance target for the load to be inspected 6.

[0053] Step 7: Evacuate the low-pressure tank using a vacuum system until the pressure inside the low-pressure tank reaches 76000Pa~81000Pa or below 50000Pa. Then, based on the infinite distance target, complete the assembly, adjustment, and testing of the load 6 to be inspected. In this embodiment, the pressure inside the load chamber 21 is evacuated to below 80000Pa or 50000Pa.

[0054] When assembling and testing the load 6 to be inspected based on the infinity target, the personnel enter the low-pressure tank to maintain the internal pressure between 76,000 Pa and 81,000 Pa (approximately at an altitude of 2,000 to 2,400 meters, personnel are well adapted to an air pressure of 80,000 Pa). At this pressure, real-time assembly, adjustment, and testing of the load 6 can be performed. A star-hole plate can be used to perform focal plane alignment and imaging geometric aberration detection of the load 6; a lenticular plate can be used to perform focal length detection of the load 6; and a resolution plate can be used to perform resolution testing of the load 6, etc. After the load 6 is assembled and adjusted, the low-pressure tank is restored to normal pressure. After the personnel leave the low-pressure tank, the pressure inside is reduced to below 50,000 Pa to allow for testing of the assembled load 6 under low-pressure conditions. By using a combination of a four-bar target plate and a surface-source differential blackbody, the minimum resolvable contrast ratio (MRC) and minimum resolvable temperature difference (MRTD) of the load to be tested can be detected; by using a stripe plate, the modulation transfer function (MTF) and other indicators of the load to be tested can be detected.

[0055] 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 changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for assembling and inspecting a large-aperture optical system, characterized in that, Includes the following steps: Step 1: Construct a testing and inspection device for a large-aperture optical system; the testing and inspection device includes an air-bearing vibration isolation platform (12), a load chamber (21) and a light tube chamber (22) set on the air-bearing vibration isolation platform (12) and connected to each other, and a collimator set in the light tube chamber (22); a semi-transparent and semi-reflective sealed light window (221) is provided on the side wall of the light tube chamber (22); the incident end of the collimator corresponds to the sealed light window (221), and its exit end corresponds to the load chamber (21); a target wheel (31) and an interferometer (8) are provided outside the sealed light window (221); the transmission-to-reflection ratio of the sealed light window (221) is 6:4 to 9:1; Step 2: The interferometer (8) emits a spherical wave. The target wheel (31) is adjusted so that the spherical wave can pass through the empty target position on the target wheel (31) and reach the sealed optical window (221), and be reflected back to the interferometer (8) by the sealed optical window (221). The interferometer (8) is moved until interference fringes appear on the screen of the interferometer (8). Then the optical axis of the spherical wave emitted by the interferometer (8) is parallel to the normal direction of the sealed optical window (221). Step 3: Set up a plane mirror (4) in the load chamber (21), and adjust the azimuth and / or elevation angle of the plane mirror (4) until interference fringes appear on the interferometer (8), and the interference fringes become sparse or dense as the azimuth and / or elevation angle of the plane mirror (4) changes. At this time, adjust the azimuth and / or elevation angle of the plane mirror (4) again until the interference fringes are sparsest, then the plane mirror (4) is perpendicular to the parallel light emitted from the collimator. Step 4: Move the interferometer (8) gradually along the Y-axis and observe the defocus term or wavefront RMS value corresponding to each position. When the interferometer (8) is at the zero point of the defocus term or the local minimum value of the RMS value, stop moving. At this time, the convergence point of the spherical wave emitted by the interferometer (8) is the focal plane position of the collimator. The Y-axis direction is the direction away from or close to the target wheel (31). Step 5: Move the plane mirror (4) out of the load chamber (21) and switch the target wheel (31) so that the pre-selected target plate on the target wheel (31) is opposite to the interferometer (8); move the target wheel (31) along the Y-axis until the defocus term of the interferometer (8) is zero and then stop moving. The position of the target plate is the focal plane position of the collimator. Step 6: Replace the interferometer (8) with a light source (32). The light source (32) illuminates the target plate. Set up the load to be inspected (6) in the load chamber (21). Adjust the load to be inspected (6) so that the target on the target plate is imaged at the center of the detector field of view of the load to be inspected (6), thereby providing an infinite distance target for the load to be inspected (6). Step 7: Adjust the air pressure in the load chamber (21) to 76000Pa~81000Pa or below 50000Pa, and complete the installation, adjustment and testing of the load (6) to be installed and tested based on the infinity target.

2. The assembly and inspection method for a large-aperture optical system according to claim 1, characterized in that: In step 1, the target wheel (31) is set on a two-dimensional displacement stage (33); the interferometer (8) is set on a single-axis translation stage (7); the single-axis direction of the single-axis translation stage (7) is the Y-axis; the load chamber (21) is equipped with a track (23); a cargo vehicle is set on the track (23); In step 3, the installation of the plane mirror (4) in the load chamber (21) specifically involves installing the plane mirror (4) on the cargo vehicle and moving the cargo vehicle along the track (23) to push the plane mirror (4) to the middle of the load chamber (21).

3. The assembly and inspection method for a large-aperture optical system according to claim 2, characterized in that, Step 6 specifically involves: Replace the interferometer (8) and the single-axis translation stage (7) with a light source (32). The light source (32) illuminates the target plate. Set up a vacuum turntable (5) on the cargo vehicle and place the load to be inspected (6) on the vacuum turntable (5). Move the cargo vehicle along the track (23) to push the vacuum turntable (5) and the load to be inspected (6) to the middle of the load chamber (21). Rotate the vacuum turntable (5) to adjust the orientation of the load to be inspected (6) so that the target on the target plate is imaged at the center of the detector field of view of the load to be inspected (6), thereby providing an infinite distance target for the load to be inspected (6).

4. The assembly and inspection method for a large-aperture optical system according to claim 1, 2, or 3, characterized in that: In step 1, the load chamber (21) is connected to a vacuum system; Step 7 specifically involves evacuating the load chamber (21) using a vacuum system until the air pressure inside the load chamber (21) drops to below 76000Pa~81000Pa or 50000Pa, and then completing the installation, adjustment and testing of the load (6) to be installed and tested based on the infinity target.

5. The assembly and inspection method for a large-aperture optical system according to claim 4, characterized in that: In step 7, the load chamber (21) is evacuated by a vacuum system until the air pressure inside the load chamber (21) reaches 80000Pa.

6. A mounting and inspection apparatus for a large-aperture optical system, used in the mounting and inspection method for the large-aperture optical system according to any one of claims 1-5, characterized in that: It includes an air-floating vibration isolation platform (12), a load chamber (21) and a light tube chamber (22) that are installed on the air-floating vibration isolation platform (12) and are interconnected, a parallel light tube installed in the light tube chamber (22), a plane mirror (4) and a light source (32). The load chamber (21) is used to set up the plane mirror (4) or the load to be installed (6). The side wall of the light tube chamber (22) is provided with a semi-transparent and semi-reflective sealed light window (221); the transmission-to-reflection ratio of the sealed light window (221) is in the range of 6:4 to 9:1; The incident end of the parallel light tube corresponds to the sealed light window (221), and its exit end corresponds to the load chamber (21); The sealed light window (221) is provided with a target wheel (31) and an interferometer (8) outside the sealed light window (221). The target wheel (31) is located between the sealed light window (221) and the interferometer (8). The target wheel (31) is provided with multiple target positions for setting the target plate and an empty target position. The light source (32) is used to illuminate the target plate.

7. The mounting and testing device for a large-aperture optical system according to claim 6, characterized in that: A two-dimensional displacement stage (33) and a single-axis translation stage (7) are provided outside the sealed light window (221), and the two-dimensional displacement stage (33) is located between the sealed light window (221) and the single-axis translation stage (7); The target wheel (31) is mounted on a two-dimensional displacement stage (33); The single-axis translation stage (7) is used to set up the interferometer (8), and its single-axis direction is the Y-axis; The load chamber (21) is equipped with a track (23); The track (23) is equipped with a cargo vehicle for carrying the plane mirror (4) or the load to be inspected (6).

8. The mounting and testing device for a large-aperture optical system according to claim 7, characterized in that: Multiple column supports (13) are respectively installed at the bottom of the light tube chamber (22) and the load chamber (21); The lower end of the column support (13) is fixedly connected to the air-floating vibration isolation platform (12), and the upper end passes through the light tube chamber (22) or the load chamber (21) and is fixedly connected to the parallel light tube or the track (23). The column support (13) is fitted with a sealed corrugated pipe (9). The lower end of the sealed corrugated pipe (9) is fixedly connected to the column support (13), and the upper end is correspondingly connected to the outer flange of the light tube chamber (22) or the load chamber (21).

9. The mounting and inspection device for a large-aperture optical system according to claim 8, characterized in that: It also includes a vacuum turntable (5); the vacuum turntable (5) is used to carry and adjust the orientation of the load (6) to be inspected; The load chamber (21) is connected to a vacuum system; the inner wall of the load chamber (21) is provided with a lighting unit, a camera unit (211) and an environmental detection unit (212).

10. The mounting and inspection device for a large-aperture optical system according to claim 9, characterized in that: The collimator includes a folding plane mirror (113), a secondary mirror (112), and a primary mirror (111) arranged sequentially along the optical path from the incident end to the exit end. The folding plane mirror (113) corresponds to the sealed light window (221), and the main mirror (111) corresponds to the load chamber (21).

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