High-precision edge sensor for spliced mirror surface and working method of high-precision edge sensor

Abstract

The invention discloses a high-precision edge sensor for splicing mirror surfaces and a working method of the high-precision edge sensor in the technical field of mirror surface splicing, the high-precision edge sensor comprises a high-reflection bridging device, the bridging device is arranged in a gap between adjacent spliced sub-mirrors, and a Shack-Hartmann wavefront sensor is arranged behind the bridging device arranged in each sub-mirror. High-reflection bridging devices stretching across adjacent sub-mirrors are installed between splicing seams which are several millimeters wide of a narrow spliced mirror surface, a working light path of an optical system is utilized, the overall tilt error of each sub-mirror is obtained through a Shack-Hartmann wavefront sensor on a system focal plane, and meanwhile the overall tilt error of each sub-mirror is measured through the Shack-Hartmann wavefront sensor, and the overall tilt error of each sub-mirror is measured through the Shack-Hartmann wavefront sensor. And the inclination error at the abutted seam can be obtained (detected on the sub-aperture where the bridging device on the abutted seam is located). The invention has the advantages of extremely low price, stable performance and extremely high precision, is not influenced by environmental factors, and is extremely convenient to install, assemble and debug. The method is suitable for detecting the splicing error between the adjacent sub-mirrors of various optical splicing mirror surfaces.

Description

Technical Field

[0001] The invention relates to a high-precision edge sensor and a working method thereof in the technical field of mirror splicing. Background Art

[0002] High-precision sensor technology is an inevitable choice for the rapid development of science and technology. Currently, there are many kinds of high-precision posture sensors that can be used to detect the height of mirrors when splicing astronomical telescope mirrors. They are mainly divided into contact and non-contact, direct detection and indirect detection, etc.; the contact type mainly includes displacement sensors such as capacitance, inductance, and eddy current installed on the back or side of the mirror, such as the capacitance displacement sensor based on the Keck telescope in the United States, which detects the height of the mirror through pre-calibration; the non-contact type mainly includes fiber optic displacement sensors and other pupil detection and image plane detection methods based on optical systems, such as the use of optical system-level detection methods, judging by changes in light wave transmission performance, and no direct contact in hardware; direct detection refers to directly obtaining the height difference and tilt error expression between the optical reflection surfaces of the mirror, while indirect detection requires other physical quantities to indirectly obtain the height difference and tilt error between the optical reflection surfaces of the mirror through relevant formulas or conversion methods.

[0003] The above methods and the displacement sensors implemented by them all have various disadvantages. Contact measurement installs displacement sensors on the back or side of the mirror, and often requires the use of other instruments to calibrate the sensor at high and low positions, such as the splicing of the main mirror of the Keck, SALT, and LAMOST telescopes, which cannot directly reflect the absolute error state of the mirror splicing; and although the fiber optic displacement sensor can directly reflect the height of the mirror, because it uses optical energy detection, it will bring various factors such as stray light to the optical system (of course, it can be avoided by sealing measures). In addition, the distance between the fiber end face and the mirror will affect the measurement accuracy; the pupil surface detection and image surface detection methods based on the optical detection system will be affected by various environmental factors such as atmospheric turbulence, temperature changes, noise, etc., with limited accuracy and limited detection batches, and limited use occasions.

[0004] The high-precision capacitive displacement sensor (CN201010120779.2) for non-contact direct detection of mirror height difference can directly measure the mirror height difference with high accuracy, but the capacitive sensor is greatly affected by the environment, is expensive, and can only measure the mirror height difference, and cannot simultaneously obtain multiple degrees of freedom errors (dihedral angle error and mirror height difference) of the mirror splicing error. The edge sensor for spliced ​​mirrors based on the interference principle and its working method (CN201911064429.6) can measure the mirror height error and tilt error with high accuracy through the principle of equal thickness interference, and the accuracy is very high, but the system implementation needs to be realized through large-scale Newton ring detection, the hardware such as cameras and cables is expensive, and it is necessary to introduce a visible light source that may cause stray light, and the obtained stripes are semicircular. The software algorithm and large-scale parallel processing are time-consuming and complicated, and the installation and disassembly process on the optical reflective surface seam across the mirror is complicated, so the application scenarios are limited. Summary of the invention

[0005] The purpose of the present invention is to provide a high-precision edge sensor for splicing mirrors and a working method thereof, which has extremely low price, stable performance, extremely high precision, is not affected by environmental factors, and is extremely convenient to install, assemble and debug.

[0006] To achieve the above objectives, the present invention provides a high-precision edge sensor for spliced ​​mirrors, including a high-reflective bridging device, the bridging device is arranged between the gaps of adjacent parallel sub-mirrors, and a Shack-Hartmann wavefront sensor is arranged behind the bridging device inside the sub-mirrors.

[0007] Compared with the prior art, the beneficial effect of the present invention is that, by installing a high-reflection bridge device across adjacent sub-mirrors between the narrow seams of a few millimeters wide of the spliced ​​mirror, the working optical path of the optical system itself is used to obtain the overall tilt error of each sub-mirror (tested on the sub-aperture inside the sub-mirror) through the Shack-Hartmann wavefront sensor on the focal plane of the system, and at the same time, the tilt error at the seam (tested on the sub-aperture where the bridge device on the seam is located) can be obtained. Through the geometric relationship between the tilt error (angle) of the sub-aperture inside the sub-mirror, the tilt error (angle) at the seam, the seam width and the high and low position difference Piston, the splicing error of adjacent sub-mirrors in the spliced ​​mirror surface can be obtained at the same time, including the high and low position difference (Piston error) and the dihedral angle error (Tip / Tilt error). The present invention is extremely low in price, stable in performance, extremely high in precision, not affected by environmental factors, and extremely convenient to install, assemble and debug. The present invention is suitable for the detection of splicing errors between adjacent sub-mirrors of various optical spliced ​​mirror surfaces.

[0008] As a further improvement of the present invention, the bridging device is an elastic film, the elastic film has a uniform thickness as a whole, and a surface is coated with an anti-transmission high-reflection film.

[0009] In this way, the height difference of the joints between adjacent sub-mirrors can be reflected by an elastic film of equal thickness, and a sub-aperture on the joint is formed. Together with the sub-aperture inside the surface of the sub-mirror, when the entire large spliced ​​optical system is working, the light beam is irradiated on the two sub-apertures respectively.

[0010] As a further improvement of the present invention, the bridging device is a parallel plate, the parallel plates are of uniform thickness as a whole, and are coated with an anti-transmission high-reflection film on the surface.

[0011] In this way, the height difference of the adjacent sub-mirrors can be reflected by parallel plates of equal thickness, and sub-apertures on the seams are formed. Together with the sub-apertures inside the sub-mirrors' surfaces, when the entire large spliced ​​optical system is working, the light beams are respectively irradiated on the two sub-apertures.

[0012] As a further improvement of the present invention, the bridging device is a flat crystal, the flat crystal has a uniform thickness as a whole, and is coated with an anti-transmission high-reflection film on the surface.

[0013] In this way, the height difference of the adjacent sub-mirrors can be reflected by the flat crystal of equal thickness, and the sub-aperture on the splicing seam is formed. Together with the sub-aperture inside the sub-mirror surface, when the entire large splicing optical system is working, the light beam is irradiated on the two sub-apertures respectively. As a further improvement of the present invention, the Shack-Hartmann wavefront sensor comprises a collimator, a small lens array is arranged directly behind the collimator, and an imaging surface detector is arranged directly behind the small lens array.

[0014] In this way, the detection or imaging light beams of the spliced ​​optical system are reflected together into the subsequent Shack-Hartmann wavefront sensor after being irradiated by the spliced ​​mirror, and are converged into a light spot on the back-focus imaging surface of the lens array through the collimator and discrete spatial sampling of the small lens array, and are finally recorded by the detector 9 on the imaging surface.

[0015] In order to achieve the above object, the present invention also provides a working method of a high-precision edge sensor for splicing mirrors, comprising the following steps: S1, device installation; S2, optical imaging; S3, data processing.

[0016] Compared with the prior art, the invention has the advantages that it can realize high-precision measurement of spliced ​​mirror surface errors, has the characteristics of clear principle, simple and compact structure, simple process, etc., shares the optical path and the necessary Shack-Hartmann wavefront sensor with the optical system, avoids the use of artificial light sources and the influence of stray light that may be introduced, and avoids the high complexity and time-consuming various algorithms of splicing error calibration based on complex multi-wavelength and physical optics in the current large-scale sub-mirror splicing. Compared with the international cutting-edge solutions of edge displacement sensors (for confocal maintenance and common phase maintenance) and upgraded complex versions of physical optics Shack-Hartmann wavefront sensors (for common phase calibration) in conventional spliced ​​optical telescopes, the invention is extremely cheap, has stable performance, extremely high precision, is not affected by environmental factors, and is extremely convenient to install, assemble and debug. The invention is suitable for splicing error detection between adjacent sub-mirrors of various optical splicing mirrors.

[0017] As a further improvement of the present invention, the specific contents of S1 include the following situations: S1.1, placing an elastic film of equal thickness on the joints between adjacent sub-mirrors of a concave spherical or concave aspherical spliced ​​mirror system, the elastic film spanning over the surfaces of the adjacent sub-mirrors and flattening the surfaces; S1.2, an elastic film is placed on the joints between adjacent sub-mirrors of a concave spherical or concave aspherical spliced ​​mirror system, and the upper reflective surface of the elastic film is at the same height as the reflective surfaces of the sub-mirrors on both sides; S1.3, placing a parallel plate or a flat crystal on the joints between adjacent sub-mirrors of a concave spherical or concave aspherical spliced ​​mirror system, the parallel plate or the flat crystal spanning the joints between adjacent sub-mirrors; S1.4, when the sub-mirror of the spliced ​​mirror to be measured is a flat sub-mirror, an auxiliary detection mirror is arranged between the Shack-Hartmann wavefront sensor and the bridging device.

[0018] In this way, when different sub-mirrors are spliced ​​together, suitable devices and suitable positions are selected for installation, which can reflect the height differences on the seams of adjacent sub-mirrors and form sub-apertures on the seams. The sub-apertures on the seams and the sub-apertures inside the sub-mirrors are reflected together after the detection or imaging beams of the spliced ​​optical system are irradiated on the spliced ​​mirror surface and enter the subsequent Shack-Hartmann wavefront sensor.

[0019] As a further improvement of the present invention, S2 includes the following contents: The detection or imaging light beam of the entire optical system is reflected on the spliced ​​sub-mirrors, and also on the highly reflective bridging device, that is, the elastic film or parallel plate or flat crystal. For the subsequent Shack-Hartmann wavefront sensor, two sub-apertures are formed through collimation by a collimator: the sub-aperture inside the sub-mirror and the sub-aperture on the seam of adjacent sub-mirrors. Discrete spatial sampling is performed through a small lens array matching the sub-aperture distribution. The small lens array also forms two small lenses accordingly: the small lens inside the sub-mirror and the small lens on the seam of adjacent sub-mirrors. After passing through the small lenses, different sub-apertures and small lens groups converge into light spots on the post-focus imaging surface of the lens array, and are finally recorded by the detector on the imaging surface.

[0020] In this way, the light beam from the system light source is respectively irradiated on the sub-mirror (sub-aperture inside the sub-mirror) and the elastic film or parallel plate or flat crystal (sub-aperture on the seam of the sub-mirror). Through the rear high-precision Shack-Hartmann wavefront sensor, the wavefront slope error (Tip / Tilt error) on different sub-apertures on the spliced ​​mirror can be measured.

[0021] As a further improvement of the present invention, S3 includes the following contents: By processing the digital image of the detector on the imaging surface and using the Shack-Hartmann wavefront sensing principle, the wavefront slope error of various sub-apertures on the stitched mirror can be obtained. Combined with the formula, the stitching error can be derived and calculated.

[0022] In this way, through the geometric relationship between the tilt error (angle) of the sub-aperture inside the sub-mirror, the tilt error (angle) at the seam, the seam width and the height difference Piston, the stitching error of adjacent sub-mirrors in the stitched mirror can be obtained at the same time, including the height difference (Piston error) and the dihedral angle error (Tip / Tilt error).

[0023] As a further improvement of the present invention, S3 also includes the following content: By measuring the tilt error θ‌2 on the sub-aperture inside the spliced ​​sub-mirrors, assuming that sub-mirror No. 1 is the reference mirror and does not move, if sub-mirror No. 2 only has the height difference Piston, the height difference Piston on the splicing seam can be directly obtained by the splicing seam width L and measuring the tilt error θ‌1 on the splicing seam sub-aperture of the adjacent sub-mirrors; P=L*θ‌1 If sub-mirror No. 2 has both zero high and low position difference Piston and tilt error Tip / tilt, the high and low position difference Piston on the seam can be directly obtained by the seam width L, the tilt error θ‌2 on the sub-aperture inside the sub-mirror, the sub-mirror diameter D and the tilt error θ‌1 on the sub-aperture of the seam between adjacent sub-mirrors; P=L*θ‌1- D / 2*θ‌2.

[0024] In this way, the measurement accuracy of the wavefront tilt error can reach one hundredth of an arc second. On a 3 mm wide seam, the adjacent high and low position difference can reach 3mm*0.01" / 206265=0.15nm. Even on a 5 mm wide seam, a wavefront tilt error of 1 arc second corresponds to an adjacent high and low position difference of only 25nm, which is better than the requirements for the stitching error of the stitching telescope: wavefront tilt error 0.01" (RMS), adjacent high and low position difference 25nm (RMS). BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a Shack-Hartmann wavefront detection sensor for a concave spherical or concave aspherical spliced ​​mirror surface mainly includes two subapertures on the pupil plane.

[0026] Figure 2 A schematic diagram of a Shack-Hartmann wavefront detection sensor for a plane mirror splicing mirror, mainly including two subapertures on the pupil plane.

[0027] Figure 3 Traditional plane, spherical or aspherical mirrors are made of hexagonal sub-mirrors.

[0028] Figure 4 The corresponding diagram of the pupil plane and imaging plane of the Shack-Hartmann wavefront sensor. The sub-aperture in a single sub-mirror and the sub-aperture on a single seam are used for detection to obtain the imaging spots of the two sub-apertures respectively.

[0029] Figure 5 The corresponding diagram of the pupil plane and imaging plane of the Shack-Hartmann wavefront sensor. Multiple sub-apertures within the sub-mirrors and multiple sub-apertures on the seams are used for detection to obtain imaging spots of the two sub-apertures respectively.

[0030] Figure 6 The error principle of sub-mirror splicing is derived by measuring the height difference between sub-mirrors through a strictly equal-thickness reflector or elastic film on the reflecting surface across the splicing seam.

[0031] Figure 7 Schematic diagram of the error principle of sub-mirror splicing. The height difference between sub-mirrors is measured by a strictly equal-thickness elastic film on the reflecting surface across the splicing seam.

[0032] Figure 8 Schematic diagram of the error principle of sub-mirror splicing. The height difference between sub-mirrors is measured by parallel plates or flat crystals of strictly equal thickness on the reflecting surface across the splicing seam.

[0033] Fig. 9 The error principle of sub-mirror splicing is derived, and the height difference between sub-mirrors is measured by connecting an elastic film between the seams that is strictly at the same height as the reflecting surface.

[0034] Fig.10Schematic diagram of the error principle of sub-mirror splicing. The height difference between sub-mirrors is measured by connecting an elastic film between the seams that is strictly at the same height as the reflective surface.

[0035] Fig.11 Illustration of spherical aberration or loss of focus introduced by using flat reflections instead of stitching spherical surfaces.

[0036] Fig.12 After replacing the spliced ​​spherical surfaces with plane reflections, similar operations need to be performed on the sub-apertures on the seams to form a consistent image on the imaging surface.

[0037] Fig.13 After replacing the spliced ​​spherical surface with a plane reflection, the sub-aperture on the spliced ​​seam is not subjected to a similar focusing operation, and the image on the imaging surface has a diffuse spot caused by defocus.

[0038] in, Figure 1 Among them, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 3. sub-apertures inside sub-mirrors, 4. sub-apertures inside sub-mirrors forming light spots on the imaging surface, 5. sub-apertures between the seams of sub-mirrors, 6. sub-apertures between the seams of sub-mirrors forming light spots on the imaging surface, 7. collimating mirrors, 8. small lens arrays, 9. imaging surface detectors.

[0039] Figure 2 Among them, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 3. sub-apertures inside sub-mirrors, 4. sub-apertures inside sub-mirrors forming light spots on the imaging surface, 5. sub-apertures between the seams of sub-mirrors, 6. sub-apertures between the seams of sub-mirrors forming light spots on the imaging surface, 7. collimating mirror, 8. small lens array, 9. imaging surface detector, 10. auxiliary detection mirror.

[0040] Figure 3 In the figure, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors.

[0041] Figure 4 Among them, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 3. single sub-aperture in a sub-mirror, 4. single sub-aperture in a sub-mirror forms a light spot on the imaging surface, 5. single sub-aperture between the seams of sub-mirrors, 6. single sub-aperture between the seams of sub-mirrors forms a light spot on the detector on the imaging surface.

[0042] Figure 5 Among them, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 3. multiple sub-apertures in a sub-mirror, 4. multiple sub-apertures in a sub-mirror form light spots on the imaging surface, 5. multiple sub-apertures between the seams of sub-mirrors, 6. multiple sub-apertures between the seams of sub-mirrors form light spots on the detector on the imaging surface.

[0043] Figure 6 Among them, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 11. reflective mirrors or elastic films of equal thickness on the reflective surface across the joint.

[0044] Figure 7In the invention, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 11. elastic films of equal thickness on the reflecting surfaces across the joints, and 12. fixing fixtures.

[0045] Figure 8 Among them, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 13. reflectors or flat crystals of equal thickness on the reflective surface across the seam.

[0046] Fig. 9 In the embodiment, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 14. elastic films having the same height as the reflecting surface as the connecting seams.

[0047] Fig.10 In the invention, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 12. fixing fixtures, and 15. elastic films having the same height as the reflecting surface as those between the connecting seams.

[0048] Fig.11 In the invention, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 11. a reflector or elastic film of equal thickness on the reflecting surface across the joints, 13. a reflector or flat crystal of equal thickness on the reflecting surface across the joints, 15. an elastic film of equal height with the reflecting surface connecting the joints, 16. a device and method for focusing function.

[0049] Fig.12 Among them, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 4. a single sub-aperture in a sub-mirror forms a light spot on the imaging surface detector, 6. a single sub-aperture between the sub-mirrors forms a light spot on the imaging surface, 11. an equally thick reflector or elastic film on the reflecting surface across the seam, 13. an equally thick reflector or flat crystal on the reflecting surface across the seam, 15. an elastic film with the same height as the reflecting surface connecting the seams, 16. a device and method for focusing function.

[0050] Fig.13 Among them, 1. adjacent sub-mirrors, 2. adjacent sub-mirrors, 4. a single sub-aperture in a sub-mirror forms a light spot on the imaging surface detector, 6. a single sub-aperture between the sub-mirrors forms a light spot on the imaging surface, 11. an equally thick reflector or elastic film on the reflecting surface across the seam, 13. an equally thick reflector or flat crystal on the reflecting surface across the seam, 15. an elastic film with the same height as the reflecting surface connecting the seams, 16. a device and method for focusing function. DETAILED DESCRIPTION

[0051] The present invention is further described below in conjunction with the accompanying drawings: like Figure 1-13 A high-precision edge sensor for a spliced ​​mirror is shown, characterized in that it includes a highly reflective bridging device, which is arranged between the gaps of adjacent parallel sub-mirrors, and a Shack-Hartmann wavefront sensor is arranged behind the bridging device inside the sub-mirror.

[0052] The bridge device is an elastic film, which has the same thickness as a whole and is coated with a high-reflection film for anti-transmission on the surface. The bridge device is a parallel plate, which has the same thickness as a whole and is coated with a high-reflection film for anti-transmission on the surface. The bridge device is a flat crystal, which has the same thickness as a whole and is coated with a high-reflection film for anti-transmission on the surface. The Shack-Hartmann wavefront sensor includes a collimator, a small lens array is arranged directly behind the collimator, and an imaging surface detector is arranged directly behind the small lens array.

[0053] like Figure 1-13 A working method of a high-precision edge sensor for a spliced ​​mirror is shown, including the following contents: S1, device installation.

[0054] S1.1, placing an elastic film of equal thickness on the joints between adjacent sub-mirrors of a concave spherical or concave aspherical spliced ​​mirror system, the elastic film spanning over the surfaces of the adjacent sub-mirrors and flattening the surfaces; S1.2, an elastic film is placed on the joints between adjacent sub-mirrors of a concave spherical or concave aspherical spliced ​​mirror system, and the upper reflective surface of the elastic film is at the same height as the reflective surfaces of the sub-mirrors on both sides; S1.3, placing a parallel plate or a flat crystal on the joints between adjacent sub-mirrors of a concave spherical or concave aspherical spliced ​​mirror system, the parallel plate or the flat crystal spanning the joints between adjacent sub-mirrors; S1.4, when the sub-mirror of the spliced ​​mirror to be measured is a flat sub-mirror, an auxiliary detection mirror is arranged between the Shack-Hartmann wavefront sensor and the bridging device.

[0055] S2, optical imaging.

[0056] The detection or imaging light beam of the entire optical system is reflected on the spliced ​​sub-mirrors, and also on the highly reflective bridging device, that is, the elastic film or parallel plate or flat crystal. For the subsequent Shack-Hartmann wavefront sensor, two sub-apertures are formed through collimation by a collimator: the sub-aperture inside the sub-mirror and the sub-aperture on the seam of adjacent sub-mirrors. Discrete spatial sampling is performed through a small lens array matching the sub-aperture distribution. The small lens array also forms two small lenses accordingly: the small lens inside the sub-mirror and the small lens on the seam of adjacent sub-mirrors. After passing through the small lenses, different sub-apertures and small lens groups converge into light spots on the post-focus imaging surface of the lens array, and are finally recorded by the detector on the imaging surface.

[0057] S3, data processing.

[0058] By processing the digital image of the detector on the imaging surface and using the Shack-Hartmann wavefront sensing principle, the wavefront slope error of various sub-apertures on the stitched mirror can be obtained. Combined with the formula, the stitching error can be derived and calculated.

[0059] By measuring the tilt error θ‌2 on the sub-aperture inside the spliced ​​sub-mirrors, assuming that sub-mirror No. 1 is the reference mirror and does not move, if sub-mirror No. 2 only has the height difference Piston, the height difference Piston on the splicing seam can be directly obtained by the splicing seam width L and measuring the tilt error θ‌1 on the splicing seam sub-aperture of the adjacent sub-mirrors; P=L*θ‌1 If sub-mirror No. 2 has both zero high and low position difference Piston and tilt error Tip / tilt, the high and low position difference Piston on the seam can be directly obtained by the seam width L, the tilt error θ‌2 on the sub-aperture inside the sub-mirror, the sub-mirror diameter D and the tilt error θ‌1 on the sub-aperture of the seam between adjacent sub-mirrors; P=L*θ‌1- D / 2*θ‌2.

[0060] The present invention installs a connecting elastic reflective optical film or a flat crystal or a parallel flat plate across adjacent sub-mirrors between the narrow joints of a few millimeters wide of the jointed mirror surface, and the elastic reflective film is adjusted to the same height as the optical mirror surface. The working optical path of the optical system itself is used to obtain the overall tilt error of each sub-mirror (tested on the sub-aperture inside the sub-mirror) through the standard Shack-Hartmann wavefront sensor on the focal plane of the system, and the tilt error at the joint (tested on the sub-aperture where the elastic reflective film is located on the joint). Through the geometric relationship between the tilt error (angle) of the sub-aperture inside the sub-mirror, the tilt error (angle) at the joint, the joint width and the high and low position difference Piston, the splicing errors of adjacent sub-mirrors in the spliced ​​mirror surface can be obtained at the same time, including the high and low position difference (Piston error) and the dihedral angle error (Tip / Tilt error).

[0061] Since the commonly used spliced ​​mirrors in the world are concave or flat, if the spliced ​​mirror system to be tested is concave, use Figure 1 The principle of Shack-Hartmann wavefront measurement is used; if the spliced ​​mirror system to be measured is a plane, the Figure 2 The principle of the realization of Shack-Hartmann wavefront measurement; traditional plane, spherical or aspherical splicing mirror, usually using Figure 3 Hexagonal mirrors are spliced ​​together; Figure 4 Single or Figure 5 The pupil plane and imaging plane of the Shack-Hartmann wavefront sensor, in which multiple subapertures improve measurement accuracy and spatial resolution, have a similar correspondence. Figure 6 and Fig. 9 An elastic film or parallel plate or flat crystal is installed on the neutron mirror joints. Figure 7 It is a reflector or elastic film of strict uniform thickness on the reflecting surface across the joint. Figure 8 It is a parallel plate or flat crystal with strict equal thickness on the reflecting surface across the joint. Fig.10It is an elastic film that is connected between the seams and has a strictly equal height to the reflecting surface. Fig.11 This elastic film or parallel plate or flat crystal on the seam is flat, and there is a discrepancy between the sub-mirrors being spliced, resulting in spherical aberration or defocus, which needs to be corrected by a slight zoom / focus adjustment operation. This can be achieved by changing the focal length of the small lens corresponding to the sub-aperture on the seam, thereby obtaining a consistent and clear image on the Shack-Hartmann wavefront sensor detector ( Fig.12 As shown), otherwise the imaging diagram ( Fig.13 The spot position measurement on each sub-aperture is converted into the tilt error (wavefront slope) measurement, which can be reversed to the measurement of the two stitching errors. The current conventional wavefront tilt error measurement accuracy can reach one hundredth of an arc second. On a 3 mm wide stitching seam, the adjacent high and low position difference can reach 3mm*0.01" / 206265=0.15nm. Even on a 5 mm wide stitching seam, the adjacent high and low position difference corresponding to a wavefront tilt error of 1 arc second is only 25nm, which is better than the stitching error requirements of the stitching telescope: wavefront tilt error 0.01" (RMS), adjacent high and low position difference 25nm (RMS).

[0062] The spliced ​​mirror system to be tested is installed on a supporting back frame, and an elastic film or parallel plate or flat crystal is installed on the sub-mirror seams of the spliced ​​mirror to be tested. The elastic film or parallel plate or flat crystal has strictly equal thickness and is coated with a high-reflection film for anti-transmission on the surface. It is fixedly or elastically connected to the adjacent spliced ​​sub-mirrors, and can reflect the height difference on the seams of adjacent sub-mirrors and form sub-apertures on the seams; the light beam from the system light source is respectively irradiated on the sub-mirrors (sub-apertures inside the sub-mirrors) and the elastic film or parallel plate or flat crystal (sub-apertures on the sub-mirror seams), passes through a traditional Shack-Hartmann wavefront sensor, is collimated by a beam collimator, and is subjected to discrete segmentation sampling of the sub-apertures by a specially customized small lens array (customized to match the spatial distribution of the sub-apertures and scaled in accordance with the ratio), and finally forms light spots of different sub-apertures on the imaging detector. With the help of image processing methods, by comparing the centroid position of the direct imaging spot with the standard / reference calibration beam of the Shack-Hartmann wavefront sensor, the measurement of the corresponding wavefront tilt error Tip / Tilt on the two sub-apertures can be achieved, and then the height difference Piston between adjacent sub-mirrors in another dimension can be derived through the geometric relationship formula, and finally the stitching error information of the stitched sub-mirrors can be reconstructed.

[0063] Below Figure 1 ( Figure 2 Similar) Based on the working principle of Shack-Hartmann wavefront sensor, it can be used to measure the wavefront slope error (Tip / tilt) of the sub-aperture on the pupil to be measured, and then reconstruct the wavefront information on the entire pupil surface. Figure 6 and Fig. 9As shown, by measuring the tilt error θ‌2 on the sub-aperture inside the sub-mirror, assuming that the reference mirror of sub-mirror No. 1 does not move, if sub-mirror No. 2 only has the high and low position difference Piston (the tilt error Tip / tilt is zero), the high and low position difference Piston on the seam can be directly obtained by measuring the seam width L and the tilt error θ‌1 on the sub-aperture of the seam of adjacent sub-mirrors.

[0064] P=L*θ‌1 If sub-mirror No. 2 has both a height position difference Piston and a tilt error Tip / tilt of zero, the height position difference Piston on the seam can be directly obtained through the seam width L, the tilt error θ‌2 on the sub-aperture inside the sub-mirror, the sub-mirror diameter D and measuring the tilt error θ‌1 on the sub-aperture of the seam between adjacent sub-mirrors.

[0065] P=L*θ‌1- D / 2*θ‌2 The above formula is mainly derived and explained for the simple case of vertical joints, such as Figure 4 The actual tilt error Tip / Tilt is in two dimensions (X, Y). It is necessary to arrange at least two sub-apertures on the seam to measure the height difference Piston, such as Figure 5 It can not only improve the accuracy, eliminate measurement errors and sub-mirror processing errors, but also provide splicing error measurement accuracy.

[0066] The following four embodiments are used for specific description. Embodiment 1

[0067] Reference Figure 1 and Figure 7 : An elastic film is placed on the joint of sub-mirror 1 and sub-mirror 2 on a concave spherical or concave aspherical spliced ​​mirror system. The elastic film 11 of strict equal thickness is installed across the surface of adjacent sub-mirrors through a fixing fixture 12. The surface is flattened and has a high reflectivity, forming a sub-aperture 5 on the joint. The sub-aperture on the joint and the sub-aperture 3 inside the sub-mirror are reflected together into the subsequent Shack-Hartmann wavefront sensor after the detection or imaging beam of the spliced ​​optical system is irradiated to the spliced ​​mirror surface. After being collimated by a collimator 7 and discrete spatial sampling of a small lens array 8, they converge into a light spot on the back-focus imaging surface of the lens array 8, and are finally recorded by a detector 9 on the imaging surface. Finally, the spliced ​​mirror surface error (wavefront tilt error and high and low position difference) is obtained by computer image processing and formula solution.

[0068] The sub-aperture size on the seam here can be enlarged by adjusting the film size, and matched with the small lens on the conjugate seam of the small lens array of the subsequent Shack-Hartmann wavefront sensor (collimator 7, small lens array 8, imaging surface detector 9), so that the sensitivity and detection accuracy of the Shack-Hartmann sensor can be adjusted. Embodiment 2

[0069] Reference Figure 1 and Fig.10 , which is different from the first embodiment, is that an elastic film is placed between the joints of sub-mirrors 1 and 2 on the concave spherical or concave aspherical spliced ​​mirror system, and the elastic film 15 of strict equal thickness is installed across the joints between adjacent sub-mirrors through a fixing fixture 12, and the upper reflection surface of the elastic film 15 is kept at the same height as the reflection surfaces of the sub-mirrors on both sides by adjustment. The subsequent Shack-Hartmann wavefront sensor structure and data processing method are the same as those of the first embodiment, and both solve the spliced ​​mirror error (wavefront slope error and high and low position difference). Embodiment 3

[0070] Reference Figure 1 and Figure 8 The difference from the first embodiment is that a parallel plate or a flat crystal is placed between the joints of the sub-mirror 1 and the sub-mirror 2 on the concave spherical or concave aspherical spliced ​​mirror system, and the parallel plate or flat crystal 13 of strict equal thickness is installed across the joints between the adjacent sub-mirrors through a fixing fixture. The subsequent Shack-Hartmann wavefront sensor structure and data processing method are the same as those in the first embodiment, and both solve the spliced ​​mirror error (wavefront slope error and high and low position difference). Embodiment 4

[0071] Reference Figure 2 Since the spliced ​​mirror is composed of plane sub-mirrors, an auxiliary detection mirror 10 (plane mirror) is added, and the image is also formed by the Shack-Hartmann wavefront sensor (collimator 7, small lens array 8, detector 9), and the splicing error is also obtained by computer image processing and formula calculation. The system architecture of this embodiment mainly adds an auxiliary detection mirror 10, which can be a combination of various mirrors or lenses that help convergence.

[0072] In embodiments 1 to 3, since a flat reflective surface is used instead of a concave spherical surface, the introduced system error (spherical aberration or defocus) needs to be compensated on the lenslet array. The focal length of the lenslets on the seam can be corrected so that a consistent and clear image is finally obtained on the imaging surface detector.

[0073] In embodiments 1 to 4, the measurement accuracy and sensitivity can be further improved by optimizing the sub-aperture size, the focal length of the lens array, etc.

[0074] The invention has the characteristics of clear principle, simple and compact structure, simple process, etc. It shares the optical path and the necessary Shack-Hartmann wavefront sensor with the optical system, avoids the use of artificial light sources and the influence of stray light that may be introduced, and avoids the high complexity and time-consuming various algorithms of stitching error calibration based on complex multi-wavelength and physical optics in the current large-scale sub-mirror stitching. Compared with the international cutting-edge solutions of edge displacement sensors (for confocal maintenance and common phase maintenance) and upgraded complex versions of physical optics Shack-Hartmann wavefront sensors (for common phase calibration) in conventional splicing optical telescopes, the invention is extremely cheap, stable in performance, extremely high in precision, not affected by environmental factors, and extremely convenient to install, assemble and debug. The invention is suitable for stitching error detection between adjacent sub-mirrors of various optical splicing mirrors.

[0075] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed herein, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A high-precision edge sensor for splicing mirrors, characterized in that: The invention comprises a high-reflective bridging device, wherein the bridging device is arranged between gaps of adjacent parallel sub-mirrors, and a Shack-Hartmann wavefront sensor is arranged behind the bridging device arranged inside the sub-mirrors.

2. A high-precision edge sensor for splicing mirrors according to claim 1, characterized in that: The bridging device is an elastic film, the elastic film has uniform thickness as a whole, and the surface is coated with an anti-transmission high-reflection film.

3. A high-precision edge sensor for splicing mirrors according to claim 1, characterized in that: The bridging device is a parallel plate, the parallel plates have the same thickness as a whole, and are coated with a high-reflection film for anti-transmission on the surface.

4. A high-precision edge sensor for splicing mirrors according to claim 1, characterized in that: The bridging device is a flat crystal, which has uniform thickness as a whole and is coated with a high-reflection film for anti-transmission.

5. A high-precision edge sensor for splicing mirrors according to any one of claims 1 to 4, characterized in that: The Shack-Hartmann wavefront sensor comprises a collimator, a small lens array is arranged directly behind the collimator, and an imaging surface detector is arranged directly behind the small lens array.

6. A working method of a high-precision edge sensor for splicing mirrors, characterized in that: Include the following: S1, device installation; S2, optical imaging; S3, data processing.

7. A working method of a high-precision edge sensor for splicing mirrors according to claim 6, characterized in that: The specific contents of S1 include the following situations: S1.1, placing an elastic film of equal thickness on the joints between adjacent sub-mirrors of a concave spherical or concave aspherical spliced ​​mirror system, the elastic film spanning over the surfaces of the adjacent sub-mirrors and flattening the surfaces; S1.2, an elastic film is placed on the joints between adjacent sub-mirrors of a concave spherical or concave aspherical spliced ​​mirror system, and the upper reflective surface of the elastic film is at the same height as the reflective surfaces of the sub-mirrors on both sides; S1.3, placing a parallel plate or a flat crystal on the joints between adjacent sub-mirrors of a concave spherical or concave aspherical spliced ​​mirror system, the parallel plate or the flat crystal spanning the joints between adjacent sub-mirrors; S1.4, when the sub-mirror of the spliced ​​mirror to be measured is a flat sub-mirror, an auxiliary detection mirror is arranged between the Shack-Hartmann wavefront sensor and the bridging device.

8. A working method of a high-precision edge sensor for splicing mirrors according to claim 7, characterized in that: S2 includes the following: The detection or imaging light beam of the entire optical system is reflected on the spliced ​​sub-mirrors, and also on the highly reflective bridging device, that is, the elastic film or parallel plate or flat crystal. For the subsequent Shack-Hartmann wavefront sensor, two sub-apertures are formed through collimation by a collimator: the sub-aperture inside the sub-mirror and the sub-aperture on the seam of adjacent sub-mirrors. Discrete spatial sampling is performed through a small lens array matching the sub-aperture distribution. The small lens array also forms two small lenses accordingly: the small lens inside the sub-mirror and the small lens on the seam of adjacent sub-mirrors. After passing through the small lenses, different sub-apertures and small lens groups converge into light spots on the post-focus imaging surface of the lens array, and are finally recorded by the detector on the imaging surface.

9. A working method of a high-precision edge sensor for splicing mirrors according to claim 8, characterized in that: S3 includes the following: By processing the digital image of the detector on the imaging surface and using the Shack-Hartmann wavefront sensing principle, the wavefront slope error of various sub-apertures on the stitched mirror can be obtained. Combined with the formula, the stitching error can be derived and calculated.

10. A working method of a high-precision edge sensor for splicing mirrors according to claim 9, characterized in that: S3 also includes the following: By measuring the tilt error θ‌2 on the sub-aperture inside the spliced ​​sub-mirrors, assuming that sub-mirror No. 1 is the reference mirror and does not move, if sub-mirror No. 2 only has the height difference Piston, the height difference Piston on the splicing seam can be directly obtained by the splicing seam width L and measuring the tilt error θ‌1 on the splicing seam sub-aperture of the adjacent sub-mirrors; P=L*θ‌1 If sub-mirror No. 2 has both zero high and low position difference Piston and tilt error Tip / tilt, the high and low position difference Piston on the seam can be directly obtained by the seam width L, the tilt error θ‌2 on the sub-aperture inside the sub-mirror, the sub-mirror diameter D and the tilt error θ‌1 on the sub-aperture of the seam between adjacent sub-mirrors; P=L*θ‌1- D / 2*θ‌2.

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