Segmented telescope calibration method based on mirror scattering and sphere center imaging

Abstract

The invention relates to the technical field of active optics, in particular to a segmented telescope calibration method based on mirror surface scattering and sphere center imaging, which comprises the following steps: emitting detection laser at an equivalent sphere center of a spliced mirror surface, and arranging a mask plate and a diffraction grating on an emergent light path of the detection laser, so that the detection laser passing through the mask plate is diffracted to form a structured light beam; the structured light beams are copied and deflected in space by utilizing a diffraction grating, so that a two-dimensional periodic light beam array formed by a plurality of structured light beams is generated; scattering light spots are formed around a splicing seam of the spliced mirror surface by utilizing a scattering effect generated by the microscopic roughness of the spliced mirror surface; the distribution image is compared with a preset calibration template, the deviation of scattered light spots on the distribution image relative to theoretical light spots on the calibration template is obtained, and the deviation is inhibited by adjusting the pose of the sub-mirror. According to the invention, the problems of high calibration cost, low energy utilization rate and the like of light spot detection and correction by using a hologram traditionally are solved.

Description

Technical Field

[0001] This invention belongs to the field of active optics technology, and particularly relates to a segmented telescope calibration method based on specular scattering and sphere center imaging. Background Technology

[0002] With the increasing demands for astronomical observation and space exploration, the requirements for the detection accuracy and capabilities of space telescopes are also rising, leading to a continuous increase in the aperture of space telescopes. However, traditional monolithic mirrors are limited by current manufacturing technology, making it difficult to fabricate ultra-large aperture mirrors. Furthermore, large-aperture mirrors face significant challenges in transportation, installation, and gravity unloading. The manufacturing precision of monolithic mirrors is inherently low, making them more susceptible to deformation under external forces during use, further affecting mirror accuracy. Therefore, segmented, modular primary mirrors have become a crucial technological approach for realizing large-aperture telescopes. While segmented, modular mirrors can theoretically meet any aperture requirement, they are composed of numerous sub-mirrors, and deviations in the seam positions are unavoidable. Therefore, seam alignment and co-phase calibration between segmented mirrors have become key technical challenges for their application.

[0003] Traditional seam alignment and co-phase calibration typically require the use of collimators with the same aperture as the segmented mirrors. However, the technology for fabricating ultra-large collimators is still immature and extremely costly. Therefore, there are currently calibration schemes that only target the seam position, such as using computer-generated holograms (CGH) to perform spot detection and correction at the seam position. However, this method has high calibration costs, low energy efficiency, and is difficult to adapt to the real-time adjustment requirements of complex optical systems. Summary of the Invention

[0004] In view of this, the present invention aims to provide a segmented telescope calibration method based on mirror scattering and sphere center imaging. By generating a two-dimensional periodic beam array through a mask-first and grating-lattice method, it solves the problems of high calibration cost and low energy utilization in traditional spot detection and correction using holograms (CGH). Furthermore, it utilizes the scattering effect generated by the micro-roughness of the spliced ​​mirrors to achieve spot capture, avoiding the requirement that the detector must be strictly placed on the reflected light path.

[0005] To achieve the above objectives, the technical solution created by this invention is implemented as follows: This invention provides a segmented telescope calibration method based on specular scattering and spherical center imaging, comprising: A light source is set at the equivalent center of the splicing mirror of the segmented telescope, and the light source is controlled to emit a detection laser from the equivalent center of the splicing mirror. A replaceable mask is set in the output light path of the probe laser. The mask has a light-transmitting area with a specific pattern, so that the probe laser passing through the mask is diffracted to form a structured beam corresponding to the specific pattern on the mask. A diffraction grating is set in the optical path at the rear end of the mask, and the structured beam is copied and deflected in space by the diffraction grating, thereby generating a two-dimensional periodic beam array composed of multiple structured beams. A two-dimensional periodic beam array is irradiated onto the spliced ​​mirror surface. The scattering effect generated by the micro-roughness of the spliced ​​mirror surface is used to form scattered light spots around the seams of the spliced ​​mirror surface. The distribution image of the scattered light spots on the spliced ​​mirror surface is then collected. The distribution image is compared with the preset calibration template to obtain the deviation of the scattered light spots on the distribution image from the theoretical light spots on the calibration template. The deviation is suppressed by adjusting the pose of the sub-mirrors. The calibration template is the light spot distribution pattern of a two-dimensional periodic beam array illuminating an ideal spherical mirror.

[0006] Preferably, a compensator is also provided in the optical path from the light source to the mask to expand the probe laser beam.

[0007] Preferably, the diffraction grating is a transmission grating.

[0008] Preferably, the specific pattern of the light-transmitting area is a cross shape, a ring shape, or a dot shape.

[0009] Preferably, scattered light spots on the distribution image that do not coincide with the light spot distribution of the calibration template are identified and recorded as error light spots. The error light spots are grouped according to their respective sub-mirrors, and the deviation of all error light spots on the same sub-mirror is suppressed by adjusting the pose of the sub-mirrors.

[0010] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention utilizes the imaging analysis of scattered light points generated by the inherent roughness of the mirror surface, combined with the optical path design of emission and reception from the equivalent sphere center, to realize the detection and calibration of the splicing error of the sub-mirrors. It collects scattered light points on the mirror surface based on the micro-roughness of the spliced ​​mirror surface, rather than the traditional reflected light imaging. The error of the sub-mirror is characterized by the deviation between the scattered light point distribution image and the preset calibration template, rather than the traditional defocus analysis, thus avoiding the requirement that the detector must be strictly placed on the reflected light path.

[0011] This invention generates a two-dimensional periodic beam array by first using a mask and then a grating, and uses diffraction elements to generate structured beams, replacing the low-energy-efficiency computer-generated holograms (CGH). This solves the problems of high calibration cost and low energy efficiency in traditional spot detection and correction using holograms (CGH). Attached Figure Description

[0012] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of segmented telescope calibration based on specular scattering and sphere center imaging according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the distribution of scattered light points on the spliced ​​mirror surface according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the distribution image obtained by detection according to an embodiment of the present invention.

[0013] The reference numerals in the figures include: 1. Splicing mirror 2. Light source 3. Mask 4. Diffraction grating 5. Camera 6. Scattered light spot Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and do not constitute a limitation thereof. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0015] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined to form various implementations. Furthermore, the order of the steps or actions in the method description can be changed or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0016] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0017] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0018] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] Please see Figure 1 and Figure 2 In one embodiment of the present invention, a segmented telescope calibration method based on specular scattering and spherical center imaging is provided, comprising: A light source 2 is set at the equivalent center of the splicing mirror 1 of the segmented telescope, and the light source 2 is controlled to emit a detection laser from the equivalent center of the splicing mirror 1. A replaceable mask 3 is set in the output light path of the probe laser. The mask 3 has a light-transmitting area with a specific pattern, so that the probe laser passing through the mask 3 diffracts to form a structured beam corresponding to the specific pattern on the mask 3. A diffraction grating 4 is set in the optical path at the rear end of the mask 3. The structured beam is copied and deflected in space by the diffraction grating 4, thereby generating a two-dimensional periodic beam array composed of multiple structured beams. A two-dimensional periodic beam array is irradiated onto the splicing mirror 1. Utilizing the scattering effect generated by the micro-roughness of the splicing mirror 1, scattered light points 6 are formed around the seams of the splicing mirror 1. The distribution image of the scattered light points 6 on the splicing mirror 1 is collected. The distribution image is compared with the preset calibration template to obtain the deviation of the scattered light point 6 on the distribution image from the theoretical light point on the calibration template. The deviation is suppressed by adjusting the pose of the sub-mirror. The calibration template is the light point distribution pattern of a two-dimensional periodic beam array illuminating an ideal spherical mirror.

[0020] In this invention, the splicing mirror 1 serves as the primary mirror of the segmented telescope, composed of multiple hexagonal reflecting sub-mirrors, with the gaps between adjacent sub-mirrors forming the seams. To correct the splicing error of the splicing mirror 1, this embodiment utilizes the structured beam emitted from the center of the sphere and the microscopic scattering characteristics of the mirror for error correction. Specifically, a light source 2 is first positioned at the equivalent center of the sphere of the splicing mirror 1 of the segmented telescope. This light source 2 uses photon leads to position the light outlet at the equivalent center of the sphere, controlling the direction of the emitted probe laser so that the probe laser shines back along the ideal optical path of the telescope onto the splicing mirror 1. To achieve high-precision calibration of each sub-mirror, a compensator, a replaceable mask 3, and a diffraction grating 4 are sequentially arranged along the optical path from the light source 2 to the splicing mirror 1. The compensator is used to expand the probe laser beam. The mask 3 has a light-transmitting area with a specific pattern etched on it; the specific pattern of the light-transmitting area can be a cross shape, a ring shape, or a dot shape. The probe laser undergoes diffraction after passing through the mask 3, forming a structured beam corresponding to the pattern. For example, when the transparent area is cross-shaped, the probe laser will form a bright cross-shaped structured beam after passing through the mask 3. To facilitate the adjustment of the structured beam, a switching mechanism is designed for the mask 3. The switching mechanism is equipped with multiple different masks 3, and different masks 3 can be placed into or removed from the probe laser optical path by rotation. A diffraction grating 4 is set in the optical path from the mask 3 to the splicing mirror 1. The diffraction grating 4 is a transmission diffraction grating, which is used to replicate and deflect the structured beam in space. The cross-shaped structured beam is replicated by the diffraction grating 4 into multiple identical cross-shaped spots, forming a two-dimensional periodic beam array.

[0021] A two-dimensional periodic beam array illuminates the spliced ​​mirror surface 1. Due to the microscopic roughness of the spliced ​​mirror surface 1, the beam does not undergo perfect mirror reflection. Therefore, the two-dimensional periodic beam array illuminating the spliced ​​mirror surface 1 produces a scattering effect, forming scattered light points 6 on the spliced ​​mirror surface 1. Especially at the seam of adjacent sub-mirrors, some scattered light points 6 will exist on both adjacent sub-mirrors. The neatness of the seam between adjacent sub-mirrors can be judged based on the scattered light points 6 on both sides of the seam. Because of the microscopic roughness of the spliced ​​mirror surface 1, a camera 5 can be used to capture the distribution image of the scattered light points 6 on the spliced ​​mirror surface 1. The specific distribution image obtained is shown in the figure. Figure 3As shown. Camera 5 is a high-resolution imaging camera.

[0022] The distribution image of the collected scattered light point 6 is compared with a pre-calculated and stored calibration template using digital image correlation or feature point matching. This calibration template is the theoretical light point distribution pattern that should be formed when a two-dimensional periodic beam array illuminates a perfect spherical mirror of ideal co-phase.

[0023] Through feature extraction, registration, and difference calculation, the deviation of each scattered light point 6 in the distribution image relative to the corresponding theoretical light point position in the calibration template is quantitatively obtained, including lateral offset and rotation angle. This deviation directly characterizes the pose error of the corresponding sub-mirror. Specifically, based on the deviation of scattered light point 6 in the distribution image relative to the theoretical light point on the calibration template, scattered light points in the distribution image that do not coincide with the light point distribution of the calibration template are identified. These scattered light points are recorded as error light points, and the error light points are grouped according to their respective sub-mirrors. The sub-mirrors with deviations are identified, and the high-precision actuators on the back of each sub-mirror are driven to perform closed-loop adjustment of their pose, thereby gradually suppressing and eventually eliminating the deviation of scattered light point 6 relative to the theoretical light point on the calibration template. That is, the pose suppression of the deviation of all error light points on the same sub-mirror is achieved, so that the actual light spot distribution converges to the ideal template. The calibration template is the theoretical light spot distribution pattern that should be formed when a two-dimensional periodic beam array is irradiated on a perfect spherical mirror in an ideal co-phase state, obtained in advance through optical simulation or theoretical calculation, and serves as the comparison benchmark.

[0024] In summary, the above description is merely a preferred embodiment of this specification and is not intended to limit the scope of protection of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

[0025] The systems, apparatuses, modules, or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, a computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0026] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0027] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

Claims

1. A segmented telescope calibration method based on specular scattering and spherical center imaging, characterized in that, include: A light source is set at the equivalent center of the splicing mirror of the segmented telescope, and the light source is controlled to emit a detection laser from the equivalent center of the splicing mirror. A replaceable mask is set in the output light path of the probe laser. The mask has a light-transmitting area with a specific pattern, so that the probe laser passing through the mask is diffracted to form a structured beam corresponding to the specific pattern on the mask. A diffraction grating is set in the optical path at the rear end of the mask, and the structured beam is copied and deflected in space by the diffraction grating, thereby generating a two-dimensional periodic beam array composed of multiple structured beams. The two-dimensional periodic beam array illuminates the spliced ​​mirror surface, and the scattering effect generated by the micro-roughness of the spliced ​​mirror surface forms scattered light points around the seams of the spliced ​​mirror surface, and the distribution image of the scattered light points on the spliced ​​mirror surface is collected. The distribution image is compared with a preset calibration template to obtain the deviation of the scattered light spots on the distribution image from the theoretical light spots on the calibration template. The deviation is suppressed by adjusting the pose of the sub-mirrors. The calibration template is the light spot distribution pattern of a two-dimensional periodic beam array illuminating an ideal spherical mirror.

2. The segmented telescope calibration method based on specular scattering and spherical center imaging according to claim 1, characterized in that, A compensator is also provided in the optical path from the light source to the mask to expand the probe laser beam.

3. The segmented telescope calibration method based on specular scattering and spherical center imaging according to claim 1, characterized in that, The diffraction grating is a transmission grating.

4. The segmented telescope calibration method based on specular scattering and spherical center imaging according to claim 1, characterized in that, The specific pattern of the light-transmitting area is a cross shape, a ring shape, or a dot shape.

5. The segmented telescope calibration method based on specular scattering and spherical center imaging according to claim 1, characterized in that, Identify the scattered light spots on the distribution image that do not coincide with the light spot distribution of the calibration template, and record them as error light spots. Group the error light spots according to their respective sub-mirrors, and suppress the deviation of all error light spots on the same sub-mirror by adjusting the pose of the sub-mirrors.

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