Spliced mirror adjusting method and device based on equal inclination interference

Abstract

The invention relates to a spliced mirror adjusting method and device based on equal inclination interference, belongs to the technical field of large-aperture optical mirror surfaces, and solves the problems of complex system, environment sensitivity, poor real-time performance and the like of the existing spliced mirror co-phase detection method. The method comprises the following steps: installing an adjusting device at a theoretical curvature center position of a primary mirror of the large-aperture optical system; ideal spherical waves emitted by the point light source are divided into two paths through the optical splitter, wherein one path enters the large-aperture optical system reflector and is reflected back to the optical splitter; the other path of light enters the plane mirror through the lens group and is reflected back to the optical splitter; the two paths of reflected light are subjected to equal inclination interference at the optical splitter; and after the number of the equal-inclination interference fringes is extracted through the detection terminal, the position of each splicing mirror in the primary mirror of the large-aperture optical system is adjusted until the number of the equal-inclination interference fringes is minimum. The device is simple in principle, compact in structure and high in environment robustness, and a reliable means is provided for rapid and high-precision real-time co-phase adjustment of the spliced mirror.

Description

Technical Field

[0001] This invention relates to the field of large-aperture optical mirror technology, specifically to a method and apparatus for adjusting splicing mirrors based on equal-inclination interference. Background Technology

[0002] As astronomical research deepens, the exploration of fundamental scientific questions regarding the universe, such as "one dark object, two obscure objects, and three origins," has become a focal point at the international forefront. To meet the demand for high-resolution, high-sensitivity observations of fainter and more distant celestial objects, the next generation of optical survey telescopes is developing towards larger apertures. Limited by materials, manufacturing, launch payloads, and structural stability, using multiple sub-mirrors pieced together to form a large-aperture primary mirror has become the mainstream technological approach, as seen in the James Webb Space Telescope (6.5 meters, 18 sub-mirrors) and numerous ground-based large-aperture telescope projects.

[0003] The key challenge of mosaic mirror technology lies in ensuring that all sub-mirrors are not only coplanar but also in phase, that is, eliminating translational errors (piston errors) between sub-mirrors along the optical axis. Only when a state of in-phase is achieved can the mosaic primary mirror function as a complete diffraction-limited optical system, realizing its theoretical resolving power and imaging quality. Therefore, developing high-precision and high-reliability in-phase detection and adjustment technology is crucial for mosaic telescopes to achieve their scientific goals.

[0004] Currently, the main technical methods used for co-phase detection in splicing mirrors include:

[0005] Dispersion fringe sensing technology: This technology uses dispersive elements to generate wavelength-dependent interference fringes to calculate Piston error, achieving nanometer-level accuracy. It has been successfully applied to space telescopes. However, it typically requires a bright reference source, and the signal-to-noise ratio may be insufficient when observing extremely faint targets. Furthermore, the system is complex, including dispersive optical elements and a spectral analysis module.

[0006] Phase retrieval and curvature sensing technology: Based on acquired focal and defocus images, wavefront phase is inverted using algorithms such as the light intensity transmission equation. This type of method does not require a dedicated reference light source, but it is sensitive to image quality, involves complex computational iterations, has limited real-time performance, and struggles to cope with dynamically changing environmental interference.

[0007] Wavefront slope sensing methods (such as Shaker-Hartmann sensors) reconstruct the phase by measuring the local slope of the wavefront. These methods have low direct sensitivity to pivot errors and require measurement data from multiple sub-apertures to indirectly estimate the co-phase error through complex global fitting. They are susceptible to local wavefront distortion caused by atmospheric turbulence (ground-based) or platform vibration (space-based), and the reliability of the calculations at sub-aperture edges or seams faces challenges.

[0008] Traditional interferometry: extremely high accuracy, but extremely demanding requirements for environmental stability (vibration, airflow). It is difficult to maintain a stable interferometric field in the laboratory environment at the telescope operation site, and is usually limited to offline calibration or assembly stages.

[0009] In summary, existing co-phase detection methods still face the following challenges when applied to next-generation telescope systems with larger apertures, more sub-mirrors, and the need to operate in real-time under complex observation environments:

[0010] System complexity and reliability: High-precision methods (such as dispersive fringes) often introduce additional dedicated optical paths and components, increasing system complexity, assembly and adjustment difficulty, and failure risk;

[0011] Environmental robustness: Many sophisticated methods (such as conventional interferometry and fine phase retrieval) are extremely sensitive to environmental perturbations and are difficult to operate stably at the actual operating points of telescopes where residual vibrations or turbulence exist.

[0012] Real-time performance and simplicity: Closed-loop active control requires high-frequency error feedback, while methods based on complex image processing and iterative calculations are difficult to meet the requirements for fast and simple judgment in the millihertz to hertz range.

[0013] Interference with observation: Independent sensing optical paths may occupy scientific exploration time or optical channel resources.

[0014] Therefore, there is an urgent need to develop a novel detection method and device that is simple in principle, compact in optical path, highly robust to environmental conditions, and capable of providing rapid, intuitive, and high-precision criteria for determining the co-phase state of mosaic mirrors. This would support the efficient and reliable real-time co-phase maintenance and adjustment of mosaic mirror telescopes. This is not only crucial for improving the performance of existing telescopes but also an essential technological reserve for future large-scale mosaic mirror systems. Summary of the Invention

[0015] To address the problems existing in the prior art, the present invention provides a method and apparatus for adjusting splicing mirrors based on equal tilt interference.

[0016] The technical solution adopted in this invention is as follows:

[0017] A splicing mirror adjustment device based on equal inclination interference includes a beam splitter, a point light source, a lens group, a plane mirror, a substrate, and a detection terminal, wherein the plane mirror is disposed on the substrate;

[0018] The point light source is used to emit ideal spherical waves;

[0019] The beam splitter is used to split the ideal spherical wave emitted by the point light source;

[0020] The lens group is used to converge one of the beams after the beam splitter has split the light, while the other beam is incident on the large-aperture optical system mirror and reflected back into the beam splitter by the large-aperture optical system mirror along the original path.

[0021] The plane mirror is used to reflect the converged light rays from the lens group;

[0022] The detection terminal is used to extract the equal-inclination interference fringes formed by the reflected light from the large-aperture optical system mirror and the plane mirror.

[0023] Adjust the positions of each splicing mirror in the primary mirror of the large-aperture optical system according to the number of equal-inclination interference fringes until they are in phase.

[0024] The splicing mirror adjustment method based on equal inclination interference includes the following steps:

[0025] Step 1: Install a splicing mirror adjustment device based on equal inclination interference at the theoretical curvature center of the primary mirror of the large-aperture optical system;

[0026] Step 2: A point light source emits an ideal spherical wave, which is split into two paths by a beam splitter. One path of light enters the large-aperture optical system mirror and is reflected back into the beam splitter along the original path. The other path of light enters the lens group, and after passing through the lens group, enters the plane mirror set on the substrate and is reflected back into the beam splitter. The light reflected back by the plane mirror and the light reflected back by the large-aperture optical system mirror undergo equal-inclination interference at the beam splitter.

[0027] Step 3: After extracting the number of equal-inclination interference fringes through the detection terminal, adjust the position of each splicing mirror in the primary mirror of the large-aperture optical system until the number of equal-inclination interference fringes is minimized.

[0028] The present invention has the following beneficial effects:

[0029] (1) Simple principle and simplified structure: By using the principle of equal inclination interference, the adjustment of the splicing mirror is guided by directly observing the change in the number of interference fringes. Compared with traditional methods that require complex wavefront reconstruction algorithms (such as Shaker-Hartmann sensing) or multiple image processing (such as phase difference imaging), the optical path structure of this invention is intuitive, with fewer core device components, which reduces the optical and mechanical complexity of the system.

[0030] (2) Direct operation and strong real-time performance: No complex offline calculation or iterative optimization process is required. It can realize fast and real-time judgment and adjustment of the common phase state of the splicing mirror, which helps to improve the correction frequency and response speed of the active optical system.

[0031] (3) High adjustment accuracy: Interferometry itself has high sensitivity on the order of wavelength, and theoretically it can detect changes in optical path difference at the subwavelength level, thereby providing high-precision feedback information for adjusting the piston error of the splicing mirror;

[0032] (4) High optical path efficiency and minimal interference to scientific observation: The device is compact and easy to integrate into specific locations such as the curvature center of the telescope. Furthermore, the detection optical path shares part of the path with the main optical path, which may eliminate the need to introduce a large number of additional dedicated sensing components. This helps to reduce the occupation of backend scientific observation resources and potential optical interference. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the splicing mirror adjustment device based on equal inclination interference according to the present invention;

[0034] Figure 2 This is the overall optical path diagram of the system;

[0035] Figure 3 This is a flowchart of the splicing mirror adjustment method based on equal inclination interference described in this invention;

[0036] Figure 4 The image shows the interference fringe pattern during the equal inclination adjustment process.

[0037] Explanation of reference numerals in the attached diagram: 1. Primary mirror of the large-aperture optical system; 2. Reflector of the large-aperture optical system; 3. Beam splitter; 4. Point light source; 5. Lens group; 6. Plane mirror; 7. Substrate; A. Theoretical center of curvature; B. Adjustment device; C. Ideal spherical wave. Detailed Implementation

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

[0039] First, the structural composition of existing large-aperture optical systems is clarified. Existing large-aperture optical systems mainly include: a large-aperture optical system primary mirror 1 and a large-aperture optical system reflecting mirror 2. In this invention, the large-aperture optical system primary mirror 1 is a large-aperture optical system splicing mirror.

[0040] In a first aspect, the present invention provides a splicing mirror adjustment device based on equal-inclination interference, see [link to previous document]. Figure 1 As described above, the adjusting device B of the present invention specifically includes the following components:

[0041] The components include a beam splitter 3, a point light source 4, a lens group 5, a plane mirror 6, a substrate 7, and a detection terminal; the plane mirror 6 is mounted on the substrate 7.

[0042] Point light source 4 is used to emit an ideal spherical wave C.

[0043] Beam splitter 3 is used to split the ideal spherical wave C emitted by point source 4.

[0044] Lens group 5 is used to converge one of the beams after it has been split by beam splitter 3.

[0045] The plane mirror 6 is used to reflect one of the light rays after the beam splitter 3 splits the beam. The other light ray after the beam splitter 3 splits the beam is incident on the large-aperture optical system mirror 2 and is reflected back into the beam splitter 3 along the original path by the large-aperture optical system mirror 2.

[0046] The base 7 is used to provide support for the plane mirror 6.

[0047] The detection terminal is used to extract the equal-inclination interference fringes formed by the reflected light from the large-aperture optical system's mirror 2 and plane mirror 6.

[0048] Based on the number of equal-inclination interference fringes, adjust the positions of each splicing mirror in the primary mirror 1 of the large-aperture optical system until the number of equal-inclination interference fringes is minimized, so that the ideal spherical wave C is in phase with the primary mirror 1 of the large-aperture optical system.

[0049] Figure 1 In this context, "k" represents the curvature difference between the primary mirror 1 of the large-aperture optical system and the ideal spherical wave.

[0050] As a specific implementation, the adjustment device B is equipped with an adjustment system consisting of two lenses to ensure that the interference of the entire adjustment device system is at the optimal focal plane position.

[0051] Figure 2 The mid-space filtering module is used to filter out high-frequency optical signals.

[0052] The adjustment device described in this embodiment utilizes the principle of equal inclination interference to guide the adjustment of the mosaic mirror by directly observing changes in the number of interference fringes. Compared to traditional methods that require complex wavefront reconstruction algorithms (such as Shaker-Hartmann sensing) or multiple image processing (such as phase difference imaging), this adjustment device has a more intuitive optical path structure, fewer core components, and reduces the optical and mechanical complexity of the system. At the same time, the device has a compact structure, making it easy to integrate into specific locations such as the curvature center of the telescope. Furthermore, since the detection optical path shares part of the path with the main optical path, it may not require the introduction of a large number of additional dedicated sensing components, which helps to reduce the occupation of backend scientific observation resources and potential optical interference.

[0053] Secondly, the present invention provides a method for adjusting a splicing mirror based on equal-inclination interference, see [link to relevant documentation]. Figure 3 The measurement method of the present invention specifically includes the following steps:

[0054] Step 1: Install the adjustment device B provided by the first aspect of the present invention at position A, the theoretical curvature center of the large-aperture optical system; emit an ideal spherical wave C using a point light source 4, project the ideal spherical wave C onto the primary mirror 1 of the large-aperture optical system, and collect the light at position A, the theoretical curvature center, through a detection terminal.

[0055] Step 2: An ideal spherical wave C is emitted from the point light source 4 and split into two paths by the beam splitter 3. One path of light is incident on the large-aperture optical system mirror 2 and reflected back to the beam splitter 3 along the original path. The other path of light is incident on the lens group 5 and, after passing through the lens group 5, is incident on the plane mirror 6 set on the substrate 7 and reflected back to the beam splitter 3. The light reflected back by the plane mirror 6 and the light reflected back by the large-aperture optical system mirror 2 undergo equal inclination interference at the beam splitter 3.

[0056] Step 3: After extracting the number of equal-inclination interference fringes through the detection terminal, adjust the position of each splicing mirror in the primary mirror 1 of the large-aperture optical system until the number of equal-inclination interference fringes is minimized.

[0057] like Figure 4 As shown, step 3 specifically includes the following steps:

[0058] Step 1: First, by adjusting the position of the splicing mirror, a confocal test is performed on the dense interference fringes to connect them and form interference fringes of equal thickness.

[0059] Step 2: Continue to adjust the position of the splicing mirrors, and adjust the equal thickness interference fringes on each splicing mirror to equal inclination interference fringes, and turn them into ring fringes;

[0060] Step 3: Continue to adjust the position of the splicing mirrors so that all the splicing mirrors form an equally inclined ring stripe.

[0061] Furthermore, the following process is also included between the first and second steps:

[0062] Keep the signal light constant and adjust the reference light to reduce the density of the interference fringes.

[0063] During the adjustment process towards the center, two stripes may merge into one at the edge. In this case, the middle part needs to be removed to avoid the two stripes from merging together and to eliminate the overlapping of reflective stripes at the boundary, so as to better judge the difference in the density of the stripes.

[0064] This invention includes two scenarios. The first scenario involves the formation of equal-inclination interference. Due to the excellent symmetry of equal-inclination interference, symmetrical fringes can be counted. In this case, the reciprocal of the fringe value is taken, and an average filter is first applied using a series transformation. Then, the fringe is enhanced, and its maximum value is found. The spacing is then directly calculated based on the maximum value.

[0065] The second case is non-equidistant interference. In this case, 3 to 4 standard sine waves are used for fitting. In actual use, the fringes will shake and drift back and forth due to airflow. Therefore, the optimal position is equivalent to the average of the peak positions, or the position with the highest probability of occurrence is statistically analyzed, or the segment with the highest probability of occurrence is identified. Then, the position with the highest probability of occurrence is taken as the position of the fringe.

[0066] During the adjustment process, since the primary mirror 1 of the large-aperture optical system involved in this invention is a large-aperture optical system splicing mirror, it is necessary to adjust the position of the plane mirror 6 in real time so that the light always covers the seam of the splicing mirror and the area of ​​the sub-mirrors themselves, thereby ensuring that the splicing mirror as a whole maintains a near-ideal continuous mirror surface and that the radius of curvature remains consistent.

[0067] In addition to the interference step, this invention provides an important method for extracting the edges of equal-inclination interference fringes. This method involves extending the light intensity exposure time to create overexposure, thereby determining clearer edges of the equal-inclination interference fringes. Reference light, measurement light, and their combined light images, as well as the corresponding reference light image, measurement light image, and interferogram, are obtained separately. Essentially, this equal-thickness interference mode is first used to create an inclination angle. After creating the inclination angle, the fringes become very fine. Using these fine fringes for confocal adjustment, the reference light and measurement light are aligned to essentially the same angle. Ultimately, this achieves co-phase adjustment using the equal-inclination interference fringes.

[0068] Because interferometry itself has high sensitivity on the order of wavelength, it can theoretically detect changes in optical path difference at the subwavelength level. Therefore, it provides high-precision feedback information for adjusting the phase error of the splicing mirror, making the adjustment device described in this embodiment more accurate using the equal-inclination interferometry method. At the same time, this adjustment method does not require complex offline calculation or iterative optimization process, and can realize fast and real-time judgment and adjustment of the phase state of the splicing mirror, which helps to improve the correction frequency and response speed of the active optical system.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A splicing mirror adjustment device based on equal-inclination interference, characterized in that, It includes a beam splitter (3), a point light source (4), a lens group (5), a plane mirror (6), a substrate (7), and a detection terminal, wherein the plane mirror (6) is disposed on the substrate (7); The point light source (4) is used to emit an ideal spherical wave (C); The beam splitter (3) is used to perform beam splitting on the ideal spherical wave (C) emitted by the point light source (4); The lens group (5) is used to converge one of the beams after the beam splitter (3) splits the light, and the other beam is incident on the large aperture optical system mirror (2) and reflected back into the beam splitter (3) along the original path by the large aperture optical system mirror (2); The plane mirror (6) is used to reflect the light rays converged by the lens group (5); The detection terminal is used to extract the equal-inclination interference fringes formed by the reflected light from the large-aperture optical system mirror (2) and the plane mirror (6); Adjust the position of each splicing mirror in the primary mirror (1) of the large-aperture optical system according to the number of equal-inclination interference fringes until they are in phase.

2. The splicing mirror adjustment device based on equal-inclination interference according to claim 1, characterized in that, It also includes an adjustment system consisting of two lenses to ensure that the interference of the adjustment device is at the optimal focal plane position.

3. A method for adjusting splicing mirrors based on equal-inclination interference, characterized in that, Includes the following steps: Step 1: Install a splicing mirror adjustment device (B) based on equal inclination interference at the theoretical curvature center position (A) of the primary mirror (1) of the large aperture optical system; Step 2: The point light source (4) emits an ideal spherical wave (C), which is split into two paths by the beam splitter (3). One path of light is incident on the large-aperture optical system mirror (2) and reflected back to the beam splitter (3) along the original path. The other path of light is incident on the lens group (5), and after passing through the lens group (5), it is incident on the plane mirror (6) set on the substrate (7) and reflected back to the beam splitter (3). The light reflected back by the plane mirror (6) and the light reflected back by the large-aperture optical system mirror (2) undergo equal inclination interference at the beam splitter (3). Step 3: After extracting the number of equal-inclination interference fringes through the detection terminal, adjust the position of each splicing mirror in the primary mirror (1) of the large-aperture optical system until the number of equal-inclination interference fringes is minimized, thus achieving co-phase.

4. The splicing mirror adjustment method based on equal-inclination interference according to claim 3, characterized in that, Step 3 includes the following steps: Step 1: By adjusting the position of the splicing mirror, the dense interference fringes are confocalized so that they connect with each other to form interference fringes of equal thickness. Step 2: Continue to adjust the position of the splicing mirrors, and adjust the equal thickness interference fringes on each splicing mirror to equal inclination interference fringes, and turn them into ring fringes; Step 3: Continue to adjust the position of the splicing mirrors so that all the splicing mirrors form an equally inclined ring stripe.

5. The splicing mirror adjustment method based on equal-inclination interference according to claim 4, characterized in that, Between the first and second steps, there is also Includes the following processes: Keep the signal light constant and adjust the reference light to reduce the density of the interference fringes.

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