Mirror surface edge continuous active optical splicing system and working method

Abstract

The invention discloses an active optical splicing system with a continuous mirror surface edge and a working method.The system comprises a plurality of sub-mirrors, sub-mirror supporting mechanisms and sub-mirror adjusting mechanisms, and the sub-mirror supporting mechanisms are installed at the bottoms of the sub-mirrors to support the sub-mirrors; the sub-mirror adjusting mechanism comprises a displacement actuator, a shared supporting plate installed on the displacement actuator and a flexible adjusting device installed on the shared supporting plate, the displacement actuator and the shared supporting plate are arranged on a shared supporting point of the adjacent sub-mirrors, and the flexible adjusting device comprises an adjusting driving device and a flexible supporting rod. The adjusting driving device is connected with one or more flexible supporting rods, each flexible supporting rod is connected with one adjacent sub-mirror, and the height of the sub-mirror perpendicular to the mirror surface direction is adjusted through the sub-mirror adjusting mechanism. The method is suitable for engineering realization of spliced mirror surfaces of various large-aperture astronomical telescopes and large-aperture optical systems.

Description

Technical Field

[0001] The present invention relates to the technical field of mirror splicing optical systems, and in particular to an active optical splicing system for mirror edge continuity and a working method. Background Art

[0002] When building large-aperture astronomical telescopes with an aperture of more than 8 meters and future extremely large-aperture astronomical telescopes, due to the limitations of mirror blank materials, processing and detection, all of them have adopted the active optical technology of spliced ​​mirrors without exception to realize the development of large-aperture optical mirrors and even secondary mirrors. In order to realize the current active optics of spliced ​​mirrors and obtain large-aperture mirrors equivalent to the effect of a whole mirror, in addition to the mirror blanks, processing, detection, support, etc. of large-scale spliced ​​sub-mirrors, it is also inseparable from the core components such as high-precision nano-displacement actuators, nano-edge sensors and optical wavefront sensors, which have rapidly expanded in scale as the aperture increases. Correspondingly, the active optical technology and system of spliced ​​mirrors have become increasingly complex and expensive, and the failure rate remains high. Especially at high altitude, low pressure, and wide temperature range field seeing sites suitable for astronomical telescopes, it has brought great difficulties and pressure to the construction, operation and maintenance. The current spliced ​​mirrors will soon reach the same technical development bottleneck of simply increasing the scale and complexity as adaptive optics. In terms of edge sensor selection, the 10-meter Keck Telescope in the United States, the 30-meter TMT Telescope and the GTC Telescope in Spain all use capacitive sensors as edge sensors, while the SALT Telescope in South Africa and the European Extremely Large Telescope ELT use inductive sensors as edge sensors. These increasingly large-scale electrical edge sensors are expensive and have a high failure rate. They are not yet fully mature in China, which is extremely inconsistent with the rapid development of my country's astronomical optical telescopes at present and in the future. It is urgent to develop a new type of spliced ​​mirror active optical technology and method to surpass the electrical edge displacement sensor to achieve the leapfrog development of my country's astronomical optical technology.

[0003] There are also new methods proposed in China to catch up with international electrical sensors. For example, the invention patent with application number 201010120779.2 proposes a high-precision capacitive displacement sensor that can directly detect the height difference of the mirror without contact. Although it can directly measure the height difference of the mirror with high accuracy, the capacitive sensor is greatly affected by the environment and is expensive. The domestic technology is not mature, and it can only measure the height difference of the mirror, and it is impossible to simultaneously obtain the multiple degrees of freedom errors of the mirror splicing error (dihedral angle error and mirror height difference). The invention patent with application number 201911064429.6 proposes an edge sensor for spliced ​​mirrors based on the interference principle and its working method. Through the principle of equal-thickness interference, it can measure the height error and tilt error of the mirror with high precision. The accuracy is very high, but the system implementation needs to be achieved through large-scale Newton ring detection. Hardware such as cameras and cables are expensive. It is necessary to introduce visible light sources that may cause stray light. The obtained stripes are semicircular. Software algorithms and large-scale parallel processing are time-consuming and complicated. The installation across the optical reflective surface seam of the mirror requires a complicated assembly and disassembly process, so the application scenarios are limited. Summary of the invention

[0004] Purpose of the invention: In view of the above shortcomings, the present invention provides an active optical splicing system and working method for mirror edge continuity.

[0005] Technical solution: To solve the above-mentioned problem, the present invention adopts an active optical splicing system with continuous mirror edge, including a plurality of sub-mirrors, a sub-mirror supporting mechanism, and a sub-mirror adjusting mechanism. The sub-mirror supporting mechanism is installed at the bottom of the sub-mirror to support the sub-mirror. The sub-mirror adjusting mechanism includes a displacement actuator, a common supporting plate installed on the displacement actuator, and a flexible adjusting device installed on the common supporting plate. The displacement actuator and the common supporting plate are arranged on the common supporting point of adjacent sub-mirrors. The flexible adjusting device includes an adjusting driving device and a flexible supporting rod. The adjusting driving device is connected to one or more flexible supporting rods, and each flexible supporting rod is connected to one of the adjacent sub-mirrors. The height of the sub-mirror perpendicular to the mirror surface direction is adjusted by the sub-mirror adjusting mechanism.

[0006] Furthermore, the adjustment drive device is a motor, the output end of the motor is connected to a guide rail, and the flexible support rod is installed on the guide rail.

[0007] Furthermore, the sub-mirror adjustment mechanism also includes a force sensor, which is installed in series with the adjustment drive device and the flexible support rod, and is used to measure the force perpendicular to the mirror surface.

[0008] Furthermore, the flexible support rod is made of low expansion material.

[0009] Furthermore, it also includes a height detection sensor, which is arranged above the mirror surface of the sub-mirror and is used to detect the height difference between adjacent sub-mirrors.

[0010] Furthermore, the sub-mirror supporting mechanism includes a center hole supporting device and a mirror surface supporting device, the center hole supporting device is installed at the center of the sub-mirror, and the mirror surface supporting device is evenly arranged at the bottom of the sub-mirror surface.

[0011] Furthermore, the center hole support device includes a center hole support bracket and a support member installed on the center hole support bracket, and the support member is a center hole diaphragm or a center hole linear bearing.

[0012] Furthermore, the mirror support device is one of an axial lever counterweight floating support, an axial Whiffletree support, a pneumatic floating support or a hydraulic floating support.

[0013] Furthermore, the sub-mirror is in the shape of a regular hexagon or a fan.

[0014] The present invention also provides a working method of the active optical splicing system, and provides a Hartmann-Shack wavefront sensor, which specifically includes the following steps:

[0015] S1, installing the sub-mirror support mechanism;

[0016] S2, installing the sub-mirror adjustment mechanism;

[0017] S3, perform optical imaging and data processing through the Hartmann-Shack wavefront sensor; place the Hartmann-Shack wavefront sensor behind the sub-mirror, so that the light beam of the sub-mirror enters the Hartmann-Shack wavefront sensor to form a spot signal, and measure the stitching error of the stitching system according to the following formula:

[0018] θx=(dx / f)*(D / d), θy=(dy / f)*(D / d)

[0019] Where, (θx, θy) is the sub-mirror attitude error, (dx, dy) is the center of mass position difference of the light spot of the wavefront sensor, f is the focal length of the small lens array in the Hartmann-Shack wavefront sensor, D is the sub-aperture on the pupil plane, and d is the diameter of the small lens in the Hartmann-Shack wavefront sensor;

[0020] S4. Feedback the stitching error to the displacement actuator and adjust the sub-mirrors to make the stitching system achieve confocality and common phase.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) by setting a sub-mirror adjustment mechanism to adjust the height difference of the sub-mirrors, the displacement actuator is set at a common support point to achieve common adjustment of adjacent sub-mirrors, reduce the number of displacement actuators, and make the adjustment of adjacent sub-mirrors completely synchronized; (2) by using a wavefront sensor to measure the posture error (Tip / Tilt error) of the spliced ​​sub-mirrors with high precision, and feed it back to the displacement actuator in real time for closed-loop correction, so that the splicing system can achieve the final confocal and common phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the splicing structure of sub-mirrors in Example 1;

[0023] Figure 2 This is a schematic diagram of a shared support point for sub-mirrors in Example 1;

[0024] Figure 3 This is a schematic diagram of a sub-mirror support mechanism of Example 1;

[0025] Figure 4 This is a schematic diagram of a sub-mirror support mechanism and a sub-mirror adjustment mechanism in Example 1;

[0026] Figure 5 This is a schematic structural diagram of a flexible adjustment device according to Embodiment 1;

[0027] Figure 6 This is a schematic diagram of the installation of a height detection sensor in Example 1;

[0028] Figure 7 It is a schematic diagram of the working principle of the Hartmann-Shack wavefront sensor;

[0029] Figure 8 Schematic diagram of the correspondence between the pupil plane and the imaging plane of the Hartmann-Shack wavefront sensor;

[0030] Fig. 9 This is a schematic diagram of a sub-mirror support mechanism of Example 2;

[0031] Fig.10 This is a schematic diagram of a sub-mirror support mechanism and a sub-mirror adjustment mechanism of Example 2;

[0032] Fig.11 This is a schematic diagram of a sub-mirror support mechanism of Example 3;

[0033] Fig.12 This is a schematic diagram of a sub-mirror support mechanism and a sub-mirror adjustment mechanism of Example 3;

[0034] Fig.13 This is a schematic diagram of the splicing structure of sub-mirrors in Example 4;

[0035] Fig.14 Schematic diagram of the shared support point of the sub-mirrors in the fourth embodiment. DETAILED DESCRIPTION

[0036] Embodiment 1

[0037] like Figure 1 As shown in FIG. 1 , an active optical splicing system with continuous mirror edges in this embodiment includes seven sub-mirrors, a sub-mirror support mechanism, and a sub-mirror adjustment mechanism. The sub-mirrors are all regular hexagons, one of which is located in the center, and the other six sub-mirrors are arranged around the six edges of the central sub-mirror. Figure 2 As shown, the joints of adjacent sub-mirrors (1, 2) have corresponding common support points 3'. One end of the sub-mirror support mechanism is mounted on the mirror room truss 7, and the other end is mounted on the bottom of the sub-mirror. Each sub-mirror is supported by a sub-mirror support mechanism.

[0038] like Figure 3 As shown, the sub-mirror support mechanism includes a central hole support device and a mirror surface support device. The central hole support device is installed at the center of the sub-mirror, and the mirror surface support device is evenly arranged at the bottom of the sub-mirror surface for side support of the mirror surface. The central hole support device includes a central hole support bracket 6 and a central hole diaphragm 5 installed on the central hole support bracket 6. A groove is opened at the center of the bottom surface of the sub-mirror, and the central hole diaphragm 5 is installed in the groove. The central hole diaphragm 5 can achieve a certain range of free movement in the direction perpendicular to the mirror surface (axial direction). The mirror surface support device is an axial lever counterweight floating support 4. During the pitch and roll process of the mirror surface, the axial component of gravity, together with the lever counterweight mechanism, can always maintain the floating motion balance of the sub-mirror axial direction with full unloading, thereby realizing the axial lever counterweight floating support and maintaining the excellent surface shape.

[0039] like Figure 4 As shown, the sub-mirror adjustment mechanism includes a displacement actuator 8 mounted on the mirror chamber truss 7, a common support plate 3 mounted on the displacement actuator 8, a flexible adjustment device 9 and a force sensor mounted on the common support plate 3, and the common support plate 3 is arranged on the common support point of adjacent sub-mirrors. Figure 5 As shown, the flexible adjustment device 9 includes an adjustment drive device 91 and a flexible support rod 92. The adjustment drive device 91 and the flexible support rod 92 have two setting modes: one adjustment drive device is set, the adjustment drive device is connected to multiple flexible support rods, each flexible support rod is connected to a sub-mirror, and each flexible support rod is driven together by one adjustment drive device; multiple adjustment drive devices are set, each adjustment drive device is connected to a flexible support rod, each flexible support rod is connected to a sub-mirror, and each flexible support rod is independently driven by its own adjustment drive device; both setting modes can realize the adjustment of the height of the sub-mirror perpendicular to the mirror surface.

[0040] The adjustment drive device 91 is a precision motor, and the output end of the precision motor is connected to a precision guide rail 93, and a flexible support rod 92 is installed on the guide rail 93. The flexible support rod 92 is made of low expansion material, such as indium steel. When the mirror height is adjusted, the flexible support rod will only produce an axial displacement perpendicular to the mirror, and will not produce lateral bending moment or stress deformation. The force sensor 94 is installed in series with the adjustment drive device 91 and the flexible support rod 92 to measure the force perpendicular to the mirror direction. The sub-mirror adjustment mechanism executes the displacement adjustment command through the displacement actuator 8, and cooperates with the flexible adjustment device 9 to support the sub-mirror common support point to achieve the adjustment of the sub-mirror height. The sub-mirror adjustment mechanism needs to release the lateral degree of freedom (lateral translation error, Tip / Tilt error and sub-mirror spin error) to ensure that the flexible adjustment device and the displacement actuator are not stuck or constrained during the adjustment process.

[0041] like Figure 6 As shown, a height detection sensor 10 is also provided above the sub-mirror surface for detecting the height difference between adjacent sub-mirrors. The height detection sensor 10 cooperates with the sub-mirror adjustment mechanism to adjust the height difference between adjacent sub-mirrors so that the mirror surface reaches a leveling state.

[0042] The working method of the active optical splicing system of the present invention is as follows:

[0043] S1. Install the sub-mirror support mechanism.

[0044] S2. Install the sub-mirror adjustment mechanism.

[0045] S3, optical imaging and data processing through Hartmann-Shack wavefront sensor. Figure 7 As shown, the light beam of the sub-mirror is collimated by the collimator 16, and then converged by the small lens array 17, and finally forms a light spot signal 19 on the imaging surface 18. Figure 8 As shown, 15 is the sub-aperture of the wavefront sensor corresponding to the sub-mirror, and 19 is the imaging light spot after passing through the wavefront sensor. The digital image signal is measured for the centroid position of the light spot, and the data is processed with the help of the Shack-Hartmann wavefront sensor principle. The stitching error of the stitching system is measured according to the following formula:

[0046] θx=(dx / f)*(D / d), θy=(dy / f)*(D / d)

[0047] Among them, (θx, θy) is the sub-mirror posture error, (dx, dy) is the position difference of the center of mass of the light spot of the wavefront sensor, f is the focal length of the small lens array in the Hartmann-Shack wavefront sensor, D is the sub-aperture on the pupil plane, and d is the diameter of the small lens in the Hartmann-Shack wavefront sensor.

[0048] S4. Feedback the stitching error to the displacement actuator and adjust the sub-mirrors to make the stitching system achieve confocality and common phase.

[0049] Embodiment 2

[0050] like Fig. 9 and Fig.10 As shown, the center hole support device of this embodiment adopts a center hole support bracket 6 and a center hole linear bearing 13 installed on the center hole support bracket 6, and other structures are the same as those in the first embodiment.

[0051] Embodiment 3

[0052] like Fig.11 and Fig.12 As shown, the mirror surface support device of this embodiment adopts an axial Whiffletree support 14, and other structures are the same as those of the first embodiment. The mirror surface support device can also adopt a pneumatic floating support or a hydraulic floating support.

[0053] Embodiment 4

[0054] like Fig.13 and Fig.14 As shown, the sub-mirrors of this embodiment are in the shape of a fan ring (11, 12), and the common support point 3' between adjacent sub-mirrors is located at the midpoint or both ends of the arc edge. The other structures are the same as those of the first embodiment.

[0055] The present invention adjusts the height difference of the sub-mirrors by setting a sub-mirror adjustment mechanism, and sets the displacement actuator at a common support point to achieve common adjustment of adjacent sub-mirrors, reduce the number of displacement actuators, and make the adjustment of adjacent sub-mirrors completely synchronized. The wavefront sensor measures the attitude error (Tip / Tilt error) of the spliced ​​sub-mirrors with high precision, and feeds back to the displacement actuator in real time for closed-loop correction, so that the splicing system can achieve the final confocal and common phase. The present invention can simplify the large-scale complex splicing mirror surface into the active optical confocal splicing of the splicing sub-mirror edge continuity, avoid the large-scale, expensive, high-precision nano-level electrical or optical edge displacement sensor that is susceptible to environmental influences, and avoid 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) in conventional splicing optical telescopes and upgraded complex versions of physical optics Shack-Hartmann wavefront sensors (for common phase calibration), the present invention no longer introduces edge sensors, crosses the bottlenecks of edge sensor concepts, technologies and prices, and has extremely low prices, stable performance, extremely low failure rates, extremely high precision, is not affected by environmental factors, and is extremely convenient to install, assemble and debug. The present invention is suitable for the engineering realization of splicing mirrors of various large-aperture astronomical telescopes and large-aperture optical systems.

Claims

1. An active optical splicing system for mirror edge continuity, characterized in that: The invention comprises a plurality of sub-mirrors, a sub-mirror supporting mechanism and a sub-mirror adjusting mechanism. The sub-mirror supporting mechanism is installed at the bottom of the sub-mirror to support the sub-mirror. The sub-mirror adjusting mechanism comprises a displacement actuator (8), a common supporting plate (3) installed on the displacement actuator (8), and a flexible adjusting device (9) installed on the common supporting plate (3). The displacement actuator (8) and the common supporting plate (3) are arranged on a common supporting point of adjacent sub-mirrors. The flexible adjusting device (9) comprises an adjusting driving device (91) and a flexible supporting rod (92). The adjusting driving device (91) is connected to one or more flexible supporting rods (92). Each flexible supporting rod (92) is connected to one of the adjacent sub-mirrors. The height of the sub-mirror perpendicular to the mirror surface direction is adjusted by the sub-mirror adjusting mechanism.

2. The active optical splicing system according to claim 1, characterized in that: The adjustment drive device (91) is a motor, the output end of the motor is connected to a guide rail (93), and the flexible support rod (92) is installed on the guide rail (93).

3. The active optical splicing system according to claim 1, characterized in that: The sub-mirror adjustment mechanism also includes a force sensor (94), which is installed in series with the adjustment drive device (91) and the flexible support rod (92) and is used to measure the force in a direction perpendicular to the mirror surface.

4. The active optical splicing system according to claim 1, characterized in that: The flexible support rod (92) is made of low expansion material.

5. The active optical splicing system according to claim 1, characterized in that: It also comprises a height detection sensor (10), which is arranged above the mirror surface of the sub-mirror and is used to detect the height difference between adjacent sub-mirrors.

6. The active optical splicing system according to claim 1, wherein: The sub-mirror supporting mechanism comprises a central hole supporting device and a mirror surface supporting device. The central hole supporting device is installed at the center of the sub-mirror, and the mirror surface supporting device is evenly arranged at the bottom of the sub-mirror surface.

7. The active optical splicing system according to claim 6, characterized in that: The central hole support device comprises a central hole support bracket (6) and a support member installed on the central hole support bracket (6), wherein the support member is a central hole diaphragm (5) or a central hole linear bearing (13).

8. The active optical splicing system according to claim 6, characterized in that: The mirror support device is one of an axial lever counterweight floating support, an axial Whiffletree support, a pneumatic floating support or a hydraulic floating support.

9. The active optical splicing system according to claim 1, wherein: The sub-mirror is in the shape of a regular hexagon or a fan.

10. A working method of the active optical splicing system according to any one of claims 1 to 9, characterized in that: Providing a Hartmann-Shack wavefront sensor comprises the following steps: S1, installing the sub-mirror support mechanism; S2, installing the sub-mirror adjustment mechanism; S3, perform optical imaging and data processing through the Hartmann-Shack wavefront sensor; place the Hartmann-Shack wavefront sensor behind the sub-mirror, so that the light beam of the sub-mirror enters the Hartmann-Shack wavefront sensor to form a spot signal, and measure the stitching error of the stitching system according to the following formula: θx=(dx / f)*(D / d), θy=(dy / f)*(D / d) Where, (θx, θy) is the sub-mirror attitude error, (dx, dy) is the center of mass position difference of the light spot of the wavefront sensor, f is the focal length of the small lens array in the Hartmann-Shack wavefront sensor, D is the sub-aperture on the pupil plane, and d is the diameter of the small lens in the Hartmann-Shack wavefront sensor; S4. Feedback the stitching error to the displacement actuator and adjust the sub-mirrors to make the stitching system achieve confocality and common phase.

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