A method for assembling a long focal length catadioptric optical system
By using CGH compensators and interference alignment methods, the positions of the mirrors in the long focal length total internal reflection optical system are gradually adjusted, solving the problem of the difficulty in assembling and adjusting multi-mirror systems and achieving efficient and high-precision assembly and adjustment results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGGUANG SATELLITE TECH CO LTD
- Filing Date
- 2025-05-28
- Publication Date
- 2026-07-07
AI Technical Summary
The large number of mirrors in the optical system of a long focal length, total internal reflection space camera makes assembly and adjustment difficult. Current technology can only adjust some mirrors, leaving many degrees of freedom and making it difficult to achieve efficient and precise assembly and adjustment.
The detection area is divided using a CGH compensator. Combined with an interferometer and a theodolite, the positions of the primary mirror, secondary mirrors and other reflectors are gradually adjusted through interferometric alignment and autocollimation methods, reducing the degrees of freedom to five dimensions to achieve high-precision assembly and adjustment.
It achieves high-efficiency and high-precision assembly and adjustment of a large-aperture, long-focal-length total internal reflection optical system, reduces the degree of freedom in adjusting the mirror, and improves assembly and adjustment efficiency and accuracy.
Smart Images
Figure CN120469090B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of precision optomechanical assembly and testing technology. Background Technology
[0002] With the development of science and technology, aerospace remote sensing technology has been widely applied in agriculture, surveying and mapping, marine exploration, and military reconnaissance, becoming one of the important means for people to obtain space information. Space cameras have also developed towards higher resolution, with focal lengths continuously increasing. Total internal reflection optical systems can meet the requirements of long focal lengths and large fields of view, improving image quality. However, long focal length, total internal reflection space camera optical systems contain five mirrors: primary mirror, secondary mirror, third mirror, folding mirror, and focusing mirror. The large number of mirrors leads to an increase in adjustable variables. During the assembly and adjustment of the optical system, it is difficult to accurately adjust the spatial relative positions of each mirror, resulting in low adjustment efficiency and increased assembly and inspection difficulty, which restricts the development of total internal reflection space cameras.
[0003] The Computer-generated hologram (CGH) compensator is a binary diffractive optical element based on the wavefront recording and reconstruction principles of traditional optical holography. The CGH modulates the incident wavefront by creating a diffraction pattern on a substrate, ensuring the test wavefront propagates to the measured surface and ideally matches it. Due to its unique wavefront transformation capability and simple structure, the CGH compensator is widely used in aspherical interferometric testing. Existing technologies utilizing the multi-mirror detection capabilities of the CGH compensator for off-axis reflection systems only allow for positioning of the primary mirror and two of the three mirrors, leaving a considerable number of degrees of freedom for adjusting the mirrors. Summary of the Invention
[0004] To further improve the assembly and adjustment efficiency and accuracy of large-aperture, long-focal-length total internal reflection optical systems, this invention proposes an assembly and adjustment method suitable for large-aperture, long-focal-length total internal reflection optical systems, such as... Figure 1 As shown, it includes the following steps:
[0005] Step 1, as follows Figure 2 As shown, the CGH compensator 1 substrate is divided according to the reflector to be installed and adjusted as follows:
[0006] A circular detection area 101, which coincides with the center of the substrate, is used to detect the shape of the secondary mirror and determine the spatial position of the secondary mirror.
[0007] The concentric circular detection area 102, located on the outer ring of detection area 101, is used to detect the shape of the primary mirror and determine the spatial position of the primary mirror.
[0008] The square reflective area 103 located above the detection area 2 102 uses the normal of the reflective area 103 as the reference optical axis during the assembly and adjustment process.
[0009] The remaining area after removing detection area 101, detection area 2 102 and reflection area 103 is the alignment area 104, which is used for interference alignment with interferometer 4;
[0010] Step 2: Adjust the position of interferometer 4 to align with the alignment area 104;
[0011] Step 3, Determine the position of primary mirror 2: (e.g.) Figure 3 As shown, the wavefront emitted by the interferometer passes through detection area 2 102 and the primary mirror and returns to the interferometer. The attitude of the primary mirror is adjusted so that the light reflected back to the interferometer 4 interferes on the interferometer to form zero-order fringes and the wave aberration meets the requirements. The surface shape accuracy of the primary mirror 2 is completed, the actual optical axis is established with the reference optical axis, and the position of the primary mirror is determined.
[0012] Step 4, determine the position of secondary mirror 3: such as Figure 3 As shown, the wavefront emitted by the interferometer returns to the secondary mirror and interferometer after passing through the detection area 101. The attitude of the secondary mirror is adjusted so that the light reflected back to the interferometer 4 interferes on the interferometer to form zero-order fringes and the wave aberration meets the requirements. The surface shape accuracy of the secondary mirror 3 is completed, the actual optical axis is established with the reference optical axis, and the position of the secondary mirror is determined.
[0013] Step 5, Determine the position of folding mirror 5: (e.g.) Figure 4 As shown, the interferometer is removed, the theodolite 1 601 is auto-aligned with the reflection area 103, the optical axis is rotated 90° and then transferred to the theodolite 2 602 to achieve auto-alignment of the two theodolites, the attitude of the folding mirror 5 is adjusted so that the folding mirror rotates the optical axis by 45°, and the position of the folding mirror is determined.
[0014] Step 6, Determine the position of the focusing lens 7: (e.g.) Figure 5 As shown, after the optical axis is rotated 90°, it is transmitted to the theodolite 3 603 on the opposite side of the theodolite 2 602 to achieve self-alignment of the two theodolites. The theodolite 3 is self-aligned with the reference on the back of the focusing lens. The attitude of the focusing lens is adjusted so that the pitch and yaw directions of the focusing lens satisfy the optical axis rotation of 90°, and the position of the focusing lens 7 is determined.
[0015] Step 7, as follows Figure 6 As shown, the CGH compensator is removed, a plane mirror 9 is provided on the left side of the secondary mirror 3, and a dynamic interferometer 10 is provided at the focal plane of the optical system. The wavelet aberration of the optical system is tested using the self-collimating interferometry method. Combining the wavelet aberration values measured in each field of view and the Zernike coefficient, the attitude of the three mirrors 8 is adjusted iteratively with computer assistance until the wavelet aberration of each field of view of the optical system meets the requirements. The positions of the three mirrors are then determined, and the long focal length total internal reflection optical system is assembled and adjusted.
[0016] Technical effects:
[0017] This invention provides a method for assembling and adjusting a large-aperture, long-focal-length total internal reflection optical system. By using a CGH compensator to detect the surface shape accuracy of the primary and secondary mirrors and determine their spatial positions, and by combining the coating area on the CGH compensator that characterizes the optical axis, the positions of the folding mirror and the focusing mirror are precisely located. Ultimately, the 30 degrees of freedom of the five mirrors in the optical system are reduced to 5 degrees of freedom for the three mirrors: pitch, deflection, up / down, front / back, and left / right. This achieves high-precision and high-efficiency assembly and adjustment of the large-aperture, long-focal-length total internal reflection optical system. Attached Figure Description
[0018] Figure 1 This is a flowchart illustrating the overall process of this invention.
[0019] Figure 2 This is a schematic diagram of the CGH compensator substrate in this invention.
[0020] Figure 3 A schematic diagram of the main and secondary mirror positioning system.
[0021] Figure 4 A schematic diagram of the fashion adjustment system for positioning a folding mirror.
[0022] Figure 5 A schematic diagram of the focusing system for positioning the focusing lens.
[0023] Figure 6 A schematic diagram of the overall test optical path when assembling and adjusting three mirrors for the self-collimating interferometry method.
[0024] Among them, 1. CGH compensator, 101. Detection area one, 102. Detection area two, 103. Reflection area, 104. Alignment area, 2. Primary mirror, 3. Secondary mirror, 4. Interferometer, 5. Folding mirror, 601. Theodolite one, 602. Theodolite two, 603. Theodolite three, 7. Focusing mirror, 8. Three mirrors, 9. Plane reflecting mirror, 10. Dynamic interferometer. Detailed Implementation
[0025] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0026] After the CGH compensator 1 substrate is divided, it is mounted on the adjustment frame. The interferometer 4 is mounted on the interferometer adjustment frame. When the wavefront emitted by the interferometer 4 passes through the interferometer standard lens and is aligned with the alignment area 104 and returns to the interferometer 4, interference fringes are generated. The attitude of the interferometer 4 is adjusted by adjusting the interferometer adjustment frame. When the interference fringes become zero-order fringes, the interference alignment between the interferometer 4 and the alignment area 104 is completed.
[0027] After the positions of the primary and secondary mirrors are determined, remove interferometer 4, such as... Figure 4As shown, the theodolite 601 and the reflection zone 103 are self-aligned, and the reference optical axis is transferred to the theodolite 601. The mechanical reference transfer method enables the theodolite 601 and the theodolite 602 to be mutually aligned. After the optical axis is folded by 90°, the reference optical axis is transferred to the theodolite 602, realizing the self-alignment of the two theodolites. The light emitted from the theodolite 602 passes through the folding mirror 5 and enters the CGH compensator 1. The light light passes through the CGH compensator 1 and is reflected back to the folding mirror 5 and enters the theodolite 602. The spatial attitude of the folding mirror 5 is adjusted so that the incident light coincides with the crosshairs in the theodolite 602. The folding mirror 5 folds the optical axis by 45°, and the position adjustment of the folding mirror 5 is completed.
[0028] like Figure 5 As shown, theodolite 2 602 is removed, and theodolite 3 603 is provided. A mechanical reference transfer method enables theodolite 1 601 and theodolite 3 603 to align with each other. After the optical axis is rotated 90°, the reference optical axis is transferred to theodolite 3 603, achieving self-collimation of the two theodolites. The light emitted from theodolite 3 603 self-collides with the back of focusing lens 7. The spatial attitude of focusing lens 7 is adjusted so that the self-collimating ray coincides with the crosshairs in theodolite 3 603. The pitch and yaw directions of focusing lens 7 satisfy the 90° optical axis rotation, and the position adjustment of focusing lens 7 is completed.
[0029] like Figure 6 As shown, a self-collimating test optical path for the optical system is constructed using a plane mirror 9 and a dynamic interferometer 10. The plane mirror 9 is located to the left of the secondary mirror 3, and the dynamic interferometer 10 is positioned at the focal plane of the optical system. Light emitted from the dynamic interferometer 10 passes through the focusing mirror 7, the three mirrors 8, the folding mirror 5, the secondary mirror 3, and the primary mirror 2 before illuminating the plane mirror 9. The light then returns along its original path and enters the dynamic interferometer 10, producing interference fringes. The self-collimating interferometry method is used to measure the wavefront aberrations and Zernike coefficients of the optical system at ±1, ±0.5, and 0 corresponding fields of view. Computer-aided adjustment methods are used to calculate wavefront aberration data, guiding the precise adjustment of the attitude of the three mirrors 8. The adjustment dimensions are deflection, pitch, vertical, horizontal, and forward / backward. Simultaneously, the angle of the plane mirror 9 and the position of the dynamic interferometer 10 are adjusted to ensure that the wavefront aberrations of each field of view meet the system requirements. Once the three mirrors 8 are adjusted, the long-focal-length total internal reflection optical system is assembled and adjusted.
[0030] All content not described in detail in this specification belongs to the prior art known to those skilled in the art. Furthermore, for those skilled in the art, there will be changes in specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.
Claims
1. A method for assembling and adjusting a large-aperture, long-focal-length total internal reflection optical system, characterized in that, Includes the following steps: Step 1: Divide the CGH compensator (1) substrate according to the reflector to be installed as follows: A circular detection area (101) that coincides with the center of the substrate is used to detect the shape of the secondary mirror and determine the spatial position of the secondary mirror. The concentric circular detection area 2 (102) located on the outer ring of detection area 1 (101) is used to detect the surface shape of the primary mirror and determine the spatial position of the primary mirror; The square reflective area (103) located above the detection area 2 (102) uses the normal of the reflective area (103) as the reference optical axis during the assembly process; The remaining area after removing detection area 1 (101), detection area 2 (102) and reflection area (103) is the alignment area (104), which is used for interference alignment with the interferometer (4); Step 2: Adjust the position of the interferometer (4) and align it with the alignment area (104) for interference alignment; Step 3, Determine the position of the primary mirror (2): The wavefront emitted by the interferometer (4) passes through the detection area 2 (102) and the primary mirror (2) and returns to the interferometer (4). Adjust the attitude of the primary mirror so that the light reflected back to the interferometer (4) interferes on the interferometer to form zero-order fringes and the wave aberration meets the requirements. The surface accuracy of the primary mirror (2) is completed, and the actual optical axis is connected with the reference optical axis. The position of the primary mirror (2) is determined. Step 4, Determining the position of the secondary mirror (3): After the wavefront emitted by the interferometer (4) passes through the detection area 1 (101), it returns to the secondary mirror (3) and the interferometer (4). Adjust the attitude of the secondary mirror so that the light reflected back to the interferometer (4) interferes on the interferometer to form zero-order fringes and the wave aberration meets the requirements. The surface shape accuracy of the secondary mirror (3) is completed, and the actual optical axis is established in relation to the reference optical axis. The position of the secondary mirror (3) is determined. Step 5, Determine the position of the folding mirror (5): Remove the interferometer, auto-align the theodolite one (601) with the reflection area (103), fold the optical axis 90° and transfer it to the theodolite two (602) to achieve auto-alignment of the two theodolites, adjust the attitude of the folding mirror (5) so that the folding mirror folds the optical axis 45°, and the position of the folding mirror (5) is determined; Step 6, Determine the position of the focusing lens (7): After the optical axis is rotated 90°, it is transferred to the theodolite 3 (603) on the opposite side of the theodolite 2 (602) to achieve self-alignment of the two theodolites. The theodolite 3 (603) is self-aligned with the back reference of the focusing lens (7). Adjust the attitude of the focusing lens so that the pitch direction and yaw direction of the focusing lens (7) meet the 90° rotation of the optical axis. The position of the focusing lens (7) is determined. Step 7: Remove the CGH compensator, provide a plane mirror (9) on the left side of the secondary mirror (3), and provide a dynamic interferometer (10) at the focal plane of the optical system. Use the self-collimating interferometry method to test the wave aberration of the optical system. Combine the wave aberration values and Zernike coefficients measured in each field of view, and use computer-aided iterative adjustment of the attitude of the three mirrors (8) until the wave aberrations of each field of view of the optical system meet the requirements. The positions of the three mirrors (8) are determined, and the long focal length total internal reflection optical system is assembled and adjusted.
2. The assembly and adjustment method for a large-aperture, long-focal-length total internal reflection optical system according to claim 1, characterized in that, When the wavefront emitted by the interferometer (4) passes through the standard lens of the interferometer and aligns with the alignment area (104) and returns to the interferometer (4), interference fringes are generated. When the interference fringes are adjusted to zero-order fringes by the interferometer (4), the interference alignment between the interferometer (4) and the alignment area (104) is completed.
3. The assembly and adjustment method for a large-aperture, long-focal-length total internal reflection optical system according to claim 1, characterized in that, The theodolite 1 (601) and the reflection zone (103) are self-aligned, and the reference optical axis is transferred to the theodolite 1 (601). The mechanical reference transfer method makes the theodolite 1 (601) and the theodolite 2 (602) mutually aligned. After the optical axis is folded by 90°, the reference optical axis is transferred to the theodolite 2 (602) to achieve self-alignment of the two theodolites. The light emitted by the theodolite 2 (602) passes through the folding mirror (5) and is incident on the CGH compensator (1). The light passes through the CGH compensator (1) and is reflected back to the folding mirror (5) and incident on the theodolite 2 (602). The spatial attitude of the folding mirror (5) is adjusted so that the incident light coincides with the crosshairs in the theodolite 2 (602). The folding mirror (5) folds the optical axis by 45°, and the position adjustment of the folding mirror (5) is completed.
4. The assembly and adjustment method for a large-aperture, long-focal-length total internal reflection optical system according to claim 1, characterized in that, Remove the second theodolite (602) and provide the third theodolite (603). The mechanical reference transfer method enables the first theodolite (601) and the third theodolite (603) to align with each other. After the optical axis is rotated 90°, the reference optical axis is transferred to the third theodolite (603) to achieve self-collimation of the two theodolites. The light emitted by the third theodolite (603) is self-collimated with the back of the focusing lens (7). The spatial attitude of the focusing lens (7) is adjusted so that the self-collimating light coincides with the crosshairs in the third theodolite (603). The pitch direction and yaw direction of the focusing lens (7) satisfy the optical axis rotation of 90°. The position adjustment of the focusing lens (7) is completed.
5. The assembly and adjustment method for a large-aperture, long-focal-length total internal reflection optical system according to claim 1, characterized in that, An optical system self-collimation test optical path is constructed using a plane mirror (9) and a dynamic interferometer (10). The plane mirror (9) is provided on the left side of the secondary mirror (3), and the dynamic interferometer (10) is provided at the focal plane of the optical system. The light emitted from the dynamic interferometer (10) passes through the focusing mirror (7), the three mirrors (8), the folding mirror (5), the secondary mirror (3), and the primary mirror (2) before illuminating the plane mirror (9). The light then returns along the original path and is incident on the dynamic interferometer (10) to produce interference fringes. The self-collimation test optical path is constructed using a plane mirror (9). The wavefront aberrations and Zernike coefficients of the optical system at ±1, ±0.5, and 0 corresponding fields of view are measured by the method. The wavefront aberration data are calculated by the computer-aided assembly and adjustment method to guide the precise adjustment of the attitude of the three mirrors (8). The adjustment dimensions are five dimensions: yaw, pitch, up and down, left and right, and front and back. At the same time, the angle of the plane mirror (9) and the position of the dynamic interferometer (10) are adjusted so that the wavefront aberrations of each field of view meet the system requirements. The adjustment of the three mirrors (8) is completed, and the assembly and adjustment of the long focal length total internal reflection optical system is completed.