Partitioned multi-stage confocal method for large aperture segmented telescope

Abstract

The present application relates to the field of confocal modulation of a mosaic telescope, and specifically provides a large-aperture mosaic telescope partition multi-stage confocal method, comprising: performing finite element analysis on a mosaic mirror to obtain a deformation coupling relationship of mosaic sub-mirrors, dividing the mosaic sub-mirrors of the mosaic mirror into multiple structural functional areas, independently confocally adjusting the mosaic sub-mirrors in each structural functional area by using a digital micromirror device, detecting wavefront information of each structural functional area after independent confocal adjustment by using a wavefront sensor, and adjusting all the mosaic sub-mirrors in the structural functional area as a whole according to the wavefront information of each structural functional area, so that the area focal points of all the structural functional areas are collectively converged at a final system focal point of the mosaic mirror. The present application realizes initial misadjustment detection and high-precision confocal correction in a large dynamic range, and reduces confocal adjustment cost and complexity.

Description

Technical Field

[0001] This invention belongs to the field of confocal modulation technology for spliced ​​telescopes, and particularly relates to a multi-level confocal method for large-aperture spliced ​​telescopes. Background Technology

[0002] In pursuit of larger light-gathering areas and higher detection sensitivity, modern ground-based and space-based telescopes are increasingly larger in aperture. However, the fabrication of ultra-large aperture mirrors is limited by manufacturing technology; as the aperture increases, the difficulty and cost of mirror fabrication rise significantly, while mirror accuracy decreases significantly. Therefore, modular telescopes, which use multiple sub-mirrors to construct ultra-large aperture primary mirrors, have become the core technological approach for building the next generation of extremely large aperture telescopes. A key prerequisite for modular telescopes to achieve their scientific goals is to precisely converge the pointing of all sub-mirrors to the same focal point, i.e., to achieve high-precision "confocal" focusing.

[0003] Currently, achieving confocal focusing relies on wavefront sensing and active optical adjustment technologies. For example, the Gaia space telescope uses Hartmann sensors for wavefront sensing, achieving precise stitching and confocal focusing of multiple CCDs. The James Webb Space Telescope (JWST) team proposed a complex method for calculating system aberrations and estimating misalignment to calibrate the 132 degrees of freedom of its 6.5-meter primary mirror. China's large-area multi-object fiber optic spectroscopic telescope utilizes Hartmann wavefront sensors for confocal measurements, ensuring energy overlap across all sub-mirrors. Liu Zhong et al. from the Yunnan Astronomical Observatory, in their research for the Circular Solar Telescope project, used inclinometers to assist in the confocal measurement of the circular telescope.

[0004] However, with the continuous increase in telescope aperture and the significant increase in the number of sub-mirrors, existing confocal technology faces a series of severe challenges in practical applications. Since the mosaic primary mirror consists of hundreds of sub-mirrors, its control system has thousands of degrees of freedom. Globally confocalizing all sub-mirrors as a whole is not only computationally intensive but also results in an extremely complex control system. The coupling effect between the sub-mirrors makes the convergence process slow and unstable. Simultaneously, the deformation of the large-aperture structure under environmental factors such as gravity, wind load, and thermal deformation, and the resulting optical axis jitter, further increase the difficulty of maintaining a long-term confocal state. Furthermore, during telescope observations, atmospheric turbulence causes wavefront distortion, severely reducing the measurement signal-to-noise ratio and accuracy of the wavefront sensor, significantly affecting the confocal alignment accuracy of the mosaic telescope. Summary of the Invention

[0005] In view of this, the present invention aims to provide a multi-level confocal method for large-aperture spliced ​​telescopes, which solves the technical bottlenecks of traditional confocal methods in terms of large dynamic range, atmospheric turbulence suppression and regulation efficiency through structural mechanical partitioning, dynamic photoelectric sensing and hierarchical control strategies.

[0006] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0007] This invention provides a method for multi-level confocal partitioning of a large-aperture spliced ​​telescope, comprising:

[0008] Finite element analysis was performed on the spliced ​​mirror to obtain the deformation coupling relationship of the spliced ​​sub-mirrors. Based on the deformation coupling relationship of the spliced ​​sub-mirrors, the spliced ​​mirror was divided into multiple structural functional areas.

[0009] Each structural function is treated as an independent assembly and adjustment target. Confocal adjustment is performed on the splicing sub-mirrors in each structural functional area so that the beams of all splicing sub-mirrors in each structural functional area converge to a regional focal point.

[0010] The confocal adjustment within each structural functional area includes: setting a digital micromirror device (DMD) in front of the telescope's wavefront sensor; controlling each micromirror on the DMD through time-division multiplexing, ensuring that only one micromirror is in a reflective state at any given time, reflecting the incident light towards the wavefront sensor, while the remaining micromirrors are in a non-reflective state; the micromirrors in the reflective state are the dynamic pinholes; controlling the dynamic pinholes to align sequentially with the stitching edges of two adjacent stitching sub-mirrors within the structural functional area along a preset path; detecting the misalignment of the image points formed by the two adjacent stitching sub-mirrors at the stitching edge position through the wavefront sensor; and adjusting the pointing of the two adjacent stitching sub-mirrors iteratively to reduce the misalignment of the image points formed by the adjacent stitching sub-mirrors at the stitching edge position, thus completing the independent confocal adjustment within each structural functional area.

[0011] The overall focusing of each structural functional area is performed. The wavefront sensor is used to detect the wavefront information of each structural functional area that has completed independent confocal adjustment. Based on the wavefront information of each structural functional area, all the stitching sub-mirrors in the structural functional area are adjusted as a whole, so that the regional focus of all structural functional areas converges to the final system focus of the stitching mirror surface.

[0012] Preferably, the spliced ​​mirror is the primary mirror of the telescope.

[0013] Preferably, finite element analysis is performed on the spliced ​​mirror surface to obtain the deformation coupling relationship of the spliced ​​sub-mirrors, including:

[0014] Establish a finite element model of the spliced ​​mirror and supporting structure;

[0015] The structural deformation of each splicing sub-mirror under the conditions of gravity, wind pressure and / or temperature changes was analyzed by simulation.

[0016] Based on the deformation coupling relationship of each splicing sub-mirror, the set of splicing sub-mirrors that deform synchronously is identified, forming a structural functional area.

[0017] Preferably, the aperture of the dynamic pinhole is smaller than the current atmospheric coherence length.

[0018] Preferably, the wavefront sensor is a curvature sensor.

[0019] Preferably, according to the deformation coupling relationship of each segmented mirror, a set of segmented mirrors with synchronous deformation is identified, including:

[0020] Using a clustering algorithm, according to the deformation coupling relationship of each segmented mirror, the segmented mirrors with highly correlated displacements are divided into the same structural and functional area.

[0021] Preferably, the clustering algorithm includes the K-means clustering, hierarchical clustering or spectral clustering algorithm.

[0022] Preferably, the preset path is a serpentine curve path or a "return" character path.

[0023] Preferably, the misalignment amount of the image points formed at the splicing edge between two adjacent segmented mirrors is detected by a wavefront sensor, including:

[0024] The wavefront sensor is used to obtain the image points formed at the splicing edge between two adjacent mirrors. The image points are two separated image points, and the misalignment amount is obtained by measuring the relative position offset and defocus amount between the two separated image points.

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

[0026] By means of the DMD dynamic pinhole scanning technology, the present invention realizes the initial misalignment detection with a large dynamic range and high-precision confocal correction while effectively suppressing atmospheric turbulence, and solves the problems existing in the traditional confocal sensing method.

[0027] Based on the finite element structural mechanics zoning and relay-type iterative adjustment strategy, the present invention decomposes the complex global high-dimensional control problem into multiple low-dimensional local confocal regulation problems, realizes the zonal multi-level confocal adjustment of the large-aperture segmented telescope, and reduces the convergence time of the full-aperture segmented mirrors.

[0028] In addition, the present invention uses DMD dynamic pinhole scanning to obtain the misalignment amount of the image points at the splicing edges of the segmented mirrors. First, regional confocal adjustment is carried out within each structural and functional area, and then overall mirror confocal adjustment is carried out with the structural and functional areas as units. This method does not require the construction of a giant flat mirror or collimator matching the ultra-large aperture primary mirror, greatly reducing the cost and complexity of confocal adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0030] Figure 1 This is a flowchart of a multi-level confocal method for a large-aperture spliced ​​telescope according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the partitioning of a large-aperture spliced ​​telescope mirror provided according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of a large-aperture spliced ​​telescope with zoned focusing provided according to an embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram of image point detection for splicing according to an embodiment of the present invention. Detailed Implementation

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

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

[0039] Please see Figure 1 In one embodiment of the present invention, a multi-level confocal method for a large-aperture mosaic telescope is provided. This method employs a "divide and conquer, step-by-step convergence" design philosophy, dividing the mosaic mirror surface into structural functional zones. After independent confocal adjustment within each zone using a digital micromirror device (DMD), the entire functional zone is then focused based on wavefront information. Specifically, the method includes the following steps:

[0040] S1: Perform finite element analysis on the spliced ​​mirror surface to obtain the deformation coupling relationship of the spliced ​​sub-mirrors, and divide the spliced ​​mirror surface into multiple structural functional areas based on the deformation coupling relationship of the spliced ​​sub-mirrors.

[0041] S2: Treat each of the aforementioned structural functional areas as an independent assembly and adjustment target, and perform confocal adjustment on the splicing sub-mirrors in each structural functional area so that the beams of all splicing sub-mirrors in each structural functional area converge to a regional focal point.

[0042] The confocal adjustment within each structural functional area includes: setting a digital micromirror device in front of the telescope's wavefront sensor; controlling each micromirror on the digital micromirror device through time-division multiplexing, so that only one micromirror is in a reflective state at any given time, reflecting the incident light towards the wavefront sensor, while the remaining micromirrors are in a non-reflective state; the micromirror in the reflective state is the dynamic pinhole; controlling the dynamic pinhole to align sequentially with the stitching edge of two adjacent stitching sub-mirrors within the structural functional area according to a preset path; detecting the misalignment of the image points formed by the two adjacent stitching sub-mirrors at the stitching edge position through the wavefront sensor; adjusting the pointing of the two adjacent stitching sub-mirrors iteratively to reduce the misalignment of the image points formed by the adjacent stitching sub-mirrors at the stitching edge position, thus completing the independent confocal adjustment within each structural functional area;

[0043] S3: Perform overall focusing on each structural functional area, use wavefront sensors to detect the wavefront information of each structural functional area that has completed independent confocal adjustment, and adjust all the stitching sub-mirrors in the structural functional area as a whole based on the wavefront information of each structural functional area, so that the regional focus of all structural functional areas converges to the final system focus of the stitching mirror surface.

[0044] Specifically, in step S1, a three-dimensional model of the large-aperture modular telescope is first established in the finite element analysis software. The three-dimensional model needs to include the modular mirror and the supporting structure. The supporting structure determines the deformation coupling relationship of the modular sub-mirrors on the modular mirror. In the large-aperture modular telescope, the large-aperture modular mirror is mainly the primary mirror; therefore, the modular mirror described here is the primary mirror of the telescope.

[0045] On the established model, various real physical loads are applied to simulate the environment faced by the telescope in actual operation, in order to obtain comprehensive structural response data, such as gravity, wind pressure, and / or temperature changes. Simulation data under various conditions are obtained, and the rigid displacement of each sub-mirror is extracted as its feature vector from the simulation results for each condition. Typically, the translation perpendicular to the optical axis and the tilt angle around the X and Y axes of the sub-mirror's center point or actuation point are chosen as feature vectors to reflect the deformation of the entire sub-mirror. The displacement data of all sub-mirrors under all conditions are combined into a feature matrix, and the displacement correlation coefficient between any two adjacent sub-mirrors is calculated to construct the correlation matrix of the sub-mirrors in the entire mosaic surface. Based on the calculated correlation matrix, a clustering algorithm is used for automatic clustering and grouping. Sub-mirrors with highly correlated displacements and synchronous deformation are automatically identified and grouped into the same set. The sub-mirrors in each set constitute a structural functional area. Each sub-mirror is generally equipped with three actuators for pose control and adjustment to achieve confocal adjustment. Because the movement of sub-mirrors within the same functional area is highly synchronized, they can be controlled collaboratively as a whole. This significantly reduces the dimensionality of the control system, transforming a complex global problem into a hierarchical issue where coordination within a region is addressed first, followed by coordination between regions. Commonly, splicing mirrors without special structural support designs can be divided into... Figure 2 The six structural functional zones shown all have direct or indirect coupling with the supporting structure for all the splicing sub-mirrors in each zone. Therefore, the splicing sub-mirrors in each zone have highly correlated deformation coupling relationships, while the correlation of deformation coupling relationships between different splicing sub-mirrors in different zones is relatively weak.

[0046] As an optional implementation, the clustering algorithm can be K-means clustering, hierarchical clustering, or spectral clustering.

[0047] In step S2, as Figure 3 and Figure 4 As shown, after dividing the structural functional areas, each structural functional area is first treated as an independent assembly and adjustment target, and then assembled and adjusted independently within each area. All the splicing sub-mirrors in the same structural functional area are adjusted for confocal focus within the area. The ultimate optical goal of each structural functional area is to converge the sub-beams reflected by all the splicing sub-mirrors within it to a single focal point on the telescope target surface by adjusting all the splicing sub-mirrors within it.

[0048] For confocal adjustment within each structural functional area, the embodiments of the present invention employ the following method:

[0049] A digital micromirror device (DMM) is placed in front of the telescope's wavefront sensor. The reflected light path of the DMM points towards the telescope's inherent wavefront sensor, specifically a curvature sensor. The DMM has numerous micromirrors, which are controlled via time-division multiplexing through high-speed programming. This ensures that at any given time, the control signal guarantees that only one micromirror at a specific location is in a reflecting state, reflecting the incident light to the wavefront sensor, while the micromirrors at other locations are in a non-reflecting state. The micromirrors in the reflecting state are the dynamic pinholes. In this case, only a small beam of incident light reflected from the mosaic mirrors is reflected to the wavefront sensor by the dynamic pinholes. Traditional confocal modulation methods typically perform a full-aperture scan of the entire mirror surface. This not only makes mirror decoupling calculations for each mosaic sub-mirror extremely complex, but the detection results are also affected by atmospheric turbulence. Wavefront distortion caused by atmospheric turbulence severely impacts confocal modulation. In this embodiment of the invention, a digital micromirror device is designed to form a dynamic pinhole. The size of a single micromirror in the digital micromirror device is fixed, and its corresponding field of view is extremely small. The entrance pupil diameter corresponding to the dynamic pinhole is smaller than the current atmospheric coherence length. Light passing through this small aperture can be regarded as passing through a window unaffected by atmospheric turbulence, and the light wave passing through can be regarded as an ideal plane wave. Because there is almost no atmospheric turbulence interference in each measurement, the sensor can operate at a high signal-to-noise ratio, thereby achieving nanometer-level final correction accuracy. Traditional methods are almost unable to achieve high-precision confocalization under poor seeing conditions, while this invention can almost avoid the interference of atmospheric turbulence.

[0050] Unlike traditional methods that measure the wavefront of the entire sub-mirror, couple the wavefront information of all sub-mirrors for calculation, and then optimize based on the wavefront information until the entire stitched mirror surface converges to confocal focus, this invention precisely aligns a programmed, selected dynamic pinhole with and scans the physical stitching edge of two adjacent stitched sub-mirrors. The image formed on the focal plane by a small beam of light reflected from the dynamic pinhole to the wavefront sensor is affected by the orientation of the mirrors on both sides of the stitching seam. When there is a stitching error between two sub-mirrors, the wavefront sensor detects an imbalance in the image points formed by the two adjacent stitched sub-mirrors at the stitching edge, thus obtaining separate image points. These two separate image points originate from two adjacent stitched sub-mirrors, and the relative positional offset and defocusing amount between these two image points represent the imbalance of these two sub-mirrors at that stitching edge position.

[0051] Based on the misalignment, the pointing of adjacent stitching sub-mirrors is adjusted iteratively to reduce the misalignment of the image points formed by adjacent stitching sub-mirrors at the stitching edge, thus completing independent confocal adjustment within each structural functional area. The specific confocal process is a closed-loop iterative process based on the misalignment: a scanning path is planned for the current structural functional area; this scanning path is the preset path. The preset path can typically be a serpentine curve path or a "U"-shaped path. The serpentine curve path facilitates the determination of the continuity of adjacent stitching sub-mirrors, while the "U"-shaped path facilitates the determination of overall confocality of the stitching sub-mirrors within the area. Dynamic pinholes are controlled to align sequentially with the stitching edges of adjacent stitching sub-mirrors within the structural functional area along the preset path, ensuring that the stitching edges of all adjacent sub-mirrors within the area can be traversed sequentially along the preset path. During the scanning process along the preset path, the dynamic pinhole is controlled to move to the measurement point of the stitching edge of the current two stitching sub-mirrors. This measurement point is usually selected as the key point of the stitching edge of the two stitching sub-mirrors. The wavefront sensor detects the misalignment of the two stitching sub-mirrors at this measurement point. Based on the misalignment, the pointing and position of the two stitching sub-mirrors, or one of the stitching sub-mirrors, are adjusted to reduce or even eliminate the misalignment until the misalignment meets the design requirements, achieving convergence. Then, the above method is used to adjust every two adjacent stitching sub-mirrors sequentially. The above process is repeated iteratively. When the scanning and adjustment of all stitching edges along the preset path are completed, and the image point misalignment at all measurement points is less than the preset threshold, it is determined that the structural functional area has achieved regional confocalization.

[0052] After confocal adjustment is complete, the digital micromirror device can be re-encoded, and a new scanning path can be designed so that the measurement point falls on the focal point of the stitching edge of the three adjacent stitched sub-mirrors. At this point, the wavefront sensor obtains the image points of the three stitched sub-mirrors. If the image points coincide, or the coincidence degree meets the preset requirements, the verification considers the confocal adjustment of this structural functional area to be correct. This method can be used to further verify the confocality within the region.

[0053] As an optional embodiment, a reduction control strategy is used for confocal adjustment of the stitching sub-mirrors in each structural functional area, including:

[0054] In a single control iteration, at least three stitching sub-mirrors are selected from all stitching sub-mirrors in the current structural functional area as a fixed reference group. Taking three stitching sub-mirrors as an example, first, these three stitching sub-mirrors are adjusted to a confocal state. Then, the drive state of the drivers for the stitching sub-mirrors in this fixed reference group remains unchanged. Based on the misalignment of the stitching edges between the adjacent stitching sub-mirrors detected by the wavefront sensor, the spatial position and orientation of the stitching sub-mirrors adjacent to the fixed reference group are adjusted. The adjusted stitching sub-mirrors are then combined to form a fixed reference group, and the adjustment of the stitching sub-mirrors adjacent to the new fixed reference group continues until all stitching sub-mirrors have completed confocal adjustment.

[0055] After completing one control iteration, at least three stitched sub-mirrors are reselected as new fixed reference groups, and the above control iteration steps are repeated until the overall norm of the image point misalignment of all stitched edges is less than the preset threshold, or the decrease in the norm is less than the preset tolerance in multiple consecutive iterations.

[0056] Furthermore, when an actuator in a stitching sub-lens is damaged or its precision is reduced, during the adjustment of the stitching sub-lens, the other two actuators can be adjusted based on the damaged or low-precision actuator to achieve confocal adjustment.

[0057] In step S3, after the intra-regional adjustment of each structural functional area in step S2, the stitching sub-mirrors in each structural functional area can be regarded as a whole, that is, the stitching sub-mirrors in the structural functional area are regarded as an ideal whole mirror. At this time, the stitching mirror can be regarded as 6 ideal sub-mirrors. The further goal is to accurately converge the regional focus of all the independent confocal structural functional areas to a unified, shared final system focus, thereby ultimately achieving confocality of the entire large-aperture stitched primary mirror. The adjustment object in step S2 is a single sub-mirror or adjacent sub-mirror pairs. At this stage, the basic unit of adjustment is the entire structural functional area. Since the number of structural functional areas that need to be focused is relatively small at this time, the focus of the wavefront sensor is shifted from the stitching edge between the stitching sub-mirrors to the overall deviation between the regional focus of each structural functional area and the ideal system focus. Wavefront sensors are used to detect the wavefront information of each structural functional area that has completed independent confocal adjustment. The wavefront sensors will detect multiple light spots, each of which corresponds to the regional focal point of a structural functional area. Based on the wavefront information of each structural functional area, the misalignment between adjacent structural functional areas can be determined, namely the relative position deviation and the defocus amount. The relative position deviation is the X and Y direction offset of the focal point of each area on the focal plane, and the defocus amount is the Z direction position difference of the focal point of each area along the optical axis.

[0058] Based on the regional wavefront information provided by the wavefront sensor, the structural functional area is used as the adjustment unit to adjust all the stitching sub-mirrors in the structural functional area as a whole, correct the overall tilt and defocus error of each structural functional area, so that the regional focus of all structural functional areas converges to the final system focus of the stitching mirror surface, and all stitching sub-mirrors of the entire stitching mirror surface achieve confocal adjustment in real time.

[0059] As an alternative approach, before performing confocal adjustment, the position of each stitching sub-mirror can be initialized. The axial spacing between adjacent stitching sub-mirrors is adjusted to ensure the optical path difference between adjacent sub-mirrors is greater than the coherence length of the incident light, thus suppressing interference from coherence fringes on confocal adjustment. Based on this, the pointing of each stitching sub-mirror is adjusted so that the edge of the beam from each sub-aperture is aligned with the predetermined stitching position of the composite aperture. Independent confocal adjustment and overall focusing are then performed. After the pointing of the stitching sub-mirrors is determined, since the axial distance between the different stitching sub-mirrors is initially increased, the stitching sub-mirrors are controlled to move and scan along their respective axes. By optimizing the light intensity signal, the position where the light intensity correlation function reaches its maximum value is determined, thus resolving the axial distance adjustment.

[0060] As an optional embodiment, after the regional focal points of all structural functional areas converge to the final system focal point of the spliced ​​mirror surface, electrical sensors can be used to provide feedback on the position and orientation of each sub-mirror, forming a feedback control loop to actively maintain the stability of the calibration state. Under closed-loop maintenance, the incident light can be further controlled to traverse each detection position within the field of view, and the optical aberration corresponding to each position can be calculated. By comparing the aberration values, the actual point of the beam passing through the target surface corresponding to the global minimum aberration is determined, and this point is ultimately defined as the optical axis reference of the system, which can further realize the system optical axis calibration.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. 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 method for multi-level confocal partitioning in a large-aperture spliced ​​telescope, characterized in that, Comprising: Performing finite element analysis on the segmented mirror to obtain the deformation coupling relationship of the segmented sub - mirrors, and dividing the segmented sub - mirrors of the segmented mirror into multiple structural functional regions according to the deformation coupling relationship of the segmented sub - mirrors; Taking each of the said structural functional regions as an independent alignment target, and respectively performing confocal adjustment on the segmented sub - mirrors in each structural functional region to make the light beams of all the segmented sub - mirrors in each structural functional region converge at one regional focus; Among them, the confocal adjustment in each structural functional region includes: setting a digital micromirror device in front of the wavefront sensor of the telescope, controlling each micromirror on the digital micromirror device through time - division multiplexing, so that only one micromirror is in the reflection state at each moment, reflecting the incident light towards the wavefront sensor, and the remaining micromirrors are in the non - reflection state. The micromirror in the reflection state is the dynamic pinhole; controlling the dynamic pinhole to sequentially align with the splicing edges of two adjacent segmented sub - mirrors in the structural functional region according to a preset path, detecting the misalignment amount of the image points formed at the splicing edge position of two adjacent segmented sub - mirrors through the wavefront sensor, and adjusting the directions of two adjacent segmented sub - mirrors in an iterative manner to reduce the misalignment amount of the image points formed at the splicing edge position of adjacent segmented sub - mirrors, and completing the independent confocal adjustment within each structural functional region; Performing overall focusing on each structural functional region, detecting the wavefront information of each structural functional region that has completed independent confocal adjustment by using the wavefront sensor, and globally adjusting all the segmented sub - mirrors within the structural functional region according to the wavefront information of each structural functional region, so that the regional foci of all structural functional regions jointly converge at the final system focus of the segmented mirror.

2. The method for multi-level confocal partitioning of a large-aperture spliced ​​telescope according to claim 1, characterized in that, The segmented mirror is the primary mirror of the telescope.

3. The method for multi-level confocal partitioning of a large-aperture spliced ​​telescope according to claim 1, characterized in that, The performing finite element analysis on the segmented mirror to obtain the deformation coupling relationship of the segmented sub - mirrors includes: Establishing a finite element model of the segmented mirror and the support structure; Analyzing the structural deformation of each segmented sub - mirror under the working conditions of gravity, wind pressure and / or temperature change through simulation; According to the deformation coupling relationship of each segmented sub - mirror, identifying the set of segmented sub - mirrors with synchronous deformation and forming a structural functional region.

4. The method for multi-level confocal partitioning of a large-aperture spliced ​​telescope according to claim 1, characterized in that, The aperture of the dynamic pinhole is smaller than the current atmospheric coherence length.

5. The method for multi-level confocal partitioning of a large-aperture spliced ​​telescope according to claim 1, characterized in that, The wavefront sensor is a curvature sensor.

6. The method for multi-level confocal partitioning of a large-aperture spliced ​​telescope according to claim 3, characterized in that, The identifying the set of segmented sub - mirrors with synchronous deformation according to the deformation coupling relationship of each segmented sub - mirror includes: Using a clustering algorithm to divide the segmented sub - mirrors with relevant displacement height into the same structural functional region according to the deformation coupling relationship of each segmented sub - mirror.

7. The method for multi-level confocal partitioning of a large-aperture spliced ​​telescope according to claim 6, characterized in that, The clustering algorithm includes K - means clustering, hierarchical clustering or spectral clustering algorithm.

8. The method for multi-level confocal partitioning of a large-aperture spliced ​​telescope according to claim 1, characterized in that, The preset path is a serpentine curve path or a "return" character path.

9. The method for multi-level confocal partitioning of a large-aperture spliced ​​telescope according to claim 1, characterized in that, The detecting the misalignment amount of the image points formed at the splicing edge position of two adjacent segmented sub - mirrors through the wavefront sensor includes: Obtaining the image points formed at the splicing edge position of two adjacent sub - mirrors through the wavefront sensor. The image points are two separated image points, and obtaining the misalignment amount by measuring the relative position offset and defocus amount between the two separated image points.

10. The method for multi-level confocal partitioning of a large-aperture spliced ​​telescope according to claim 1, characterized in that, Before taking each of the said structural functional regions as an independent alignment target and respectively performing confocal adjustment on the segmented sub - mirrors in each structural functional region, initializing the segmented sub - mirrors is also included: Adjust the spacing between adjacent splicing sub-mirrors along the mirror axis so that the optical path difference between adjacent splicing sub-mirrors is greater than the coherence length of the incident light, in order to suppress the interference of coherence fringes on confocal adjustment.

Images