An active optical stitching system and its working method for mirror edge continuity

Abstract

This invention discloses an active optical splicing system and its operating method for achieving continuous mirror edges. The system includes several sub-mirrors, a sub-mirror support mechanism, and a sub-mirror adjustment mechanism. The sub-mirror support mechanism is installed at the bottom of the sub-mirrors to support them. The sub-mirror adjustment mechanism includes a displacement actuator, a common support plate mounted on the displacement actuator, and a flexible adjustment device mounted on the common support plate. The displacement actuator and the common support plate are positioned at common support points of adjacent sub-mirrors. The flexible adjustment device includes an adjustment drive device and a flexible support rod. The adjustment drive device is connected to one or more flexible support rods, and each flexible support rod is connected to one of the adjacent sub-mirrors. The height of the sub-mirror perpendicular to the mirror surface is adjusted by the sub-mirror adjustment mechanism. This invention is applicable to the engineering implementation of spliced ​​mirrors in various large-aperture astronomical telescopes and large-aperture optical systems.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mosaic mirror optical system, in particular to a mirror edge continuous active optical mosaic system and working method. BACKGROUND

[0002] When building large aperture astronomical telescopes with more than 8 meters in diameter and future extremely large aperture astronomical telescopes, due to the limitations of mirror blank materials, processing and detection, mosaic mirror active optical technology is adopted without exception to realize the development of large aperture optical mirror or even secondary mirror. In order to realize the current mosaic mirror active optics, in order to obtain a large aperture mirror equivalent to a whole mirror, in addition to large-scale mosaic mirror blank, processing, detection, support, etc., high-precision nanometer displacement actuators, nanometer edge sensors and optical wavefront sensors and other core devices caused by the increasing aperture and the rapid expansion of the scale are also indispensable, which accordingly causes the mosaic mirror active optical technology and system to be more and more complex and expensive, and the failure rate is high. Especially in the high altitude, low pressure, wide temperature range of the field site suitable for astronomical telescopes, it brings great difficulties and pressure to the construction, operation and maintenance, and the current mosaic mirror will soon reach the technical development bottleneck of simply increasing the large scale and complexity as adaptive optics. In the selection of edge sensors, the United States 10-meter Keck telescope, 30-meter TMT telescope and Spain's GTC telescope all use capacitive sensors as edge sensors, and South Africa's SALT telescope and Europe's Extremely Large Telescope (ELT) use inductive sensors as edge sensors. These larger and larger electrical edge sensors are expensive and have a high failure rate, and domestic development is not yet fully mature, which is extremely incompatible with the rapid development of China's astronomical optical telescopes in the current and future period. A new type of mosaic mirror active optical technology and method is urgently needed to cross the electrical edge displacement sensor to realize the leap-forward development of China's astronomical optical technology.

[0003] There are also new methods to catch up with international electrical sensors in China, such as the invention patent with application number 201010120779.2, which proposes a high-precision capacitive displacement sensor for non-contact direct detection of mirror height difference. Although it can directly measure the mirror height difference with high precision, the capacitive sensor is greatly affected by the environment, expensive, and the domestic technology is not mature. Moreover, it can only measure the mirror height difference and cannot obtain the multiple degree of freedom errors (dihedral angle error and mirror height difference) of the mirror splicing error at the same time. The invention patent with application number 201911064429.6 proposes an edge sensor for spliced mirror based on interference principle and its working method. Through the equal-thickness interference principle, it can measure the mirror height error and tilt error with high precision. However, the system implementation needs to be realized through large-scale Newton ring detection, the hardware such as camera and cable is expensive, a visible light source which may cause stray light needs to be introduced, the obtained fringe is semicircular, the software algorithm and large-scale parallel processing are time-consuming and complex, and the installation process of the optical reflection surface seam across the mirror is complex, so the application scenarios are limited. SUMMARY

[0004] The purpose of the application is to provide a mirror edge continuous active optical splicing system and working method to solve the above problems.

[0005] Technical scheme: To solve the above problems, the application adopts a mirror edge continuous active optical splicing system, which includes 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 support plate installed on the displacement actuator, and a flexible adjusting device installed on the common support plate. The displacement actuator and the common support plate are arranged at the common support point of adjacent sub-mirrors. The flexible adjusting device includes an adjusting drive device and a flexible support rod. The adjusting drive device is connected with one or more flexible support rods. Each flexible support rod is connected with one of the adjacent sub-mirrors. The height of the sub-mirror perpendicular to the mirror surface is adjusted by the sub-mirror adjusting mechanism.

[0006] Further, the adjusting drive device is an electric motor, and the output end of the electric motor is connected with a guide rail, and the flexible support rod is installed on the guide rail.

[0007] Further, the sub-mirror adjusting mechanism further includes a force sensor, which is installed in series with the adjusting drive device and the flexible support rod, for measuring the force perpendicular to the mirror surface.

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

[0009] Further, it further includes a height detection sensor, which is arranged above the mirror surface of the sub-mirror, for detecting the height difference between the adjacent sub-mirrors.

[0010] Further, 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 uniformly arranged at the bottom of the mirror surface of the sub-mirror.

[0011] Further, the central hole supporting device comprises a central hole supporting bracket and a supporting piece installed on the central hole supporting bracket, and the supporting piece is a central hole diaphragm or a central hole linear bearing.

[0012] Further, the mirror surface supporting device is one of an axial lever counterweight floating support, an axial Whiffletree support, a gas pressure floating support or a hydraulic pressure floating support.

[0013] Further, the shape of the sub-mirror is a regular hexagon or a sector.

[0014] The application further provides a working method of the active optical mosaic system, and provides a Hartmann-Shack wavefront sensor, and specifically comprises the following steps:

[0015] S1, installing a sub-mirror supporting mechanism;

[0016] S2, installing a sub-mirror adjusting mechanism;

[0017] S3, optical imaging and data processing are performed through the Hartmann-Shack wavefront sensor; the Hartmann-Shack wavefront sensor is placed behind the sub-mirror, the light beam of the sub-mirror enters the Hartmann-Shack wavefront sensor, a light spot signal is formed, and the mosaic error of the mosaic system is measured according to the following formula:

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

[0019] Wherein, (θx, θy) is the attitude error of the sub-mirror, (dx, dy) is the light spot centroid position difference of the wavefront sensor, f is the focal length of the lenslet array in the Hartmann-Shack wavefront sensor, D is the sub-aperture on the pupil plane, and d is the diameter of the lenslet in the Hartmann-Shack wavefront sensor.

[0020] S4, the mosaic error is fed back to the displacement actuator, the sub-mirror is adjusted, and the mosaic system reaches the common focus and the common phase.

[0021] Beneficial effects: relative to the prior art, the present application has the following advantages: (1) by setting the height difference of the sub-mirror adjusting mechanism to adjust the sub-mirror, the displacement actuator is set at the common support point, the common adjustment of adjacent sub-mirrors is realized, the number of displacement actuators is reduced, and the adjustment of adjacent sub-mirrors is completely synchronized; (2) the wavefront sensor measures the high-precision attitude error (Tip / Tilt error) of the spliced sub-mirror, 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 cophasal. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Figure 1 is a schematic diagram of a sub-mirror splicing structure of an embodiment;

[0023] Figure 2 Figure 2 is a schematic diagram of a common support point of a sub-mirror of an embodiment;

[0024] Figure 3 Figure 3 is a schematic diagram of a sub-mirror support mechanism of an embodiment;

[0025] Figure 4 Figure 4 is a schematic diagram of a sub-mirror support mechanism and a sub-mirror adjusting mechanism of an embodiment;

[0026] Figure 5 Figure 5 is a schematic diagram of a flexible adjusting device structure of an embodiment;

[0027] Figure 6 Figure 6 is a schematic diagram of the installation of a height detection sensor of an embodiment;

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

[0029] Figure 8 Figure 8 is a schematic diagram of the correspondence between the pupil surface and the imaging surface of a Hartmann-Shack wavefront sensor;

[0030] Figure 9 Figure 9 is a schematic diagram of a sub-mirror support mechanism of an embodiment;

[0031] Figure 10 Figure 10 is a schematic diagram of a sub-mirror support mechanism and a sub-mirror adjusting mechanism of an embodiment;

[0032] Figure 11 Figure 11 is a schematic diagram of a sub-mirror support mechanism of an embodiment;

[0033] Figure 12 Figure 12 is a schematic diagram of a sub-mirror support mechanism and a sub-mirror adjusting mechanism of an embodiment;

[0034] Figure 13 Figure 13 is a schematic diagram of a sub-mirror splicing structure of an embodiment;

[0035] Figure 14 Figure 14 is a schematic diagram of a common support point of a sub-mirror of an embodiment. Detailed Implementation

[0036] Example 1

[0037] like Figure 1 As shown, this embodiment of an active optical splicing system for continuous mirror edges includes seven sub-mirrors, a sub-mirror support mechanism, and a sub-mirror adjustment mechanism. All sub-mirrors are regular hexagons, with one sub-mirror located at the center and the remaining six sub-mirrors arranged around the six sides of this central sub-mirror. Figure 2 As shown, adjacent sub-mirrors (1, 2) have corresponding shared support points 3' at their joints. One end of the sub-mirror support mechanism is installed on the mirror chamber truss 7, and the other end is installed 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 support device. The central hole support device is installed at the center of the sub-mirror, and the mirror support devices are evenly distributed at the bottom of the sub-mirror surface to provide lateral support for 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 move freely within a certain range in the direction perpendicular to the mirror surface (axial direction). The mirror support device is an axial lever balance floating support 4. During the mirror surface pitching process, the axial component of gravity, together with the lever balance mechanism, can always maintain the axial unloaded floating motion balance of the sub-mirror, thereby achieving axial lever balance floating support and excellent surface shape maintenance.

[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 mounted on the common support plate 3, and a force sensor. The common support plate 3 is located on a 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 can be configured in two ways: One adjustment drive device is set up, connected to multiple flexible support rods, and each flexible support rod is connected to a sub-mirror, in which case all flexible support rods are driven together by one adjustment drive device; or multiple adjustment drive devices are set up, each connected to a flexible support rod, and each flexible support rod is connected to a sub-mirror, in which case each flexible support rod is driven independently by its own adjustment drive device. Both configurations can achieve adjustment of the height of the sub-mirror perpendicular to the mirror surface.

[0040] The adjusting driving device 91 is a precision motor, the output end of the precision motor is connected with a precision guide rail 93, and the 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 height of the mirror surface is adjusted, the flexible support rod only generates axial displacement perpendicular to the mirror surface, and does not generate lateral bending moment or stress deformation. The force sensor 94 is installed in series with the adjusting driving device 91 and the flexible support rod 92, and is used for measuring the force perpendicular to the mirror surface. The sub-mirror adjusting mechanism executes displacement adjustment commands through the displacement actuator 8, supports the common support point of the sub-mirror together with the flexible adjusting device 9, and realizes the adjustment of the height of the sub-mirror. The sub-mirror adjusting mechanism needs to release the lateral freedom (lateral translation error, Tip / Tilt error and sub-mirror spin error), so as to ensure that the flexible adjusting device and the displacement actuator are not locked and constrained during the adjustment process.

[0041] As shown in Figure 6 , the height detection sensor 10 is further arranged above the mirror surface of the sub-mirror, and is used for detecting the height difference between adjacent sub-mirrors. The height detection sensor 10 and the sub-mirror adjusting mechanism are used together to adjust the height difference between adjacent sub-mirrors, so that the mirror surface reaches the leveling state.

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

[0043] S1, install the sub-mirror support mechanism.

[0044] S2, install the sub-mirror adjusting mechanism.

[0045] S3, optical imaging and data processing are performed through the Hartmann-Shack wavefront sensor. As shown in Figure 7 , the light beam of the sub-mirror passes through the collimating mirror 16 for collimation, and then passes through the lenslet array 17 for convergence, and finally forms the light spot signal 19 on the imaging surface 18. As shown in Figure 8 , 15 is the sub-aperture corresponding to the wavefront sensor in the sub-mirror, and 19 is the imaging light spot after the wavefront sensor. The digital image signal measurement of the light spot centroid position is performed, data processing is performed by means of the Hartmann-Shack wavefront sensing principle, and the splicing error of the splicing system is measured according to the following formula:

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

[0047] Wherein, (θx, θy) is the attitude error of the sub-mirror, (dx, dy) is the light spot centroid position difference of the wavefront sensor, f is the focal length of the lenslet array in the Hartmann-Shack wavefront sensor, D is the sub-aperture on the pupil surface, and d is the diameter of the lenslet in the Hartmann-Shack wavefront sensor.

[0048] S4, the splicing error is fed back to the displacement actuator, and the sub-mirror is adjusted, so that the splicing system reaches the confocal and co-phase.

[0049] Embodiment two

[0050] As shown in Figure 9 and Figure 10 , the middle hole support device of the present embodiment adopts a middle hole support bracket 6 and a middle hole linear bearing 13 mounted on the middle hole support bracket 6, and other structures are the same as those of Embodiment one.

[0051] Embodiment three

[0052] As shown in Figure 11 and Figure 12 , the mirror surface support device of the present embodiment adopts an axial Whiffletree support 14, and other structures are the same as those of Embodiment one. The mirror surface support device can also adopt a gas pressure floating support or a hydraulic pressure floating support.

[0053] Embodiment four

[0054] As shown in Figure 13 and Figure 14 , the sub-mirror of the present embodiment is in the shape of a fan ring (11, 12), and the shared support points 3' between adjacent sub-mirrors are located at the midpoints or both ends of the arc edges. Other structures are the same as those of Embodiment one.

[0055] The present application adjusts the height difference of the sub-mirror by setting a sub-mirror adjusting mechanism, and sets a displacement actuator at the shared support point to realize the common adjustment of adjacent sub-mirrors, thereby reducing the number of displacement actuators and making the adjustment of adjacent sub-mirrors completely synchronized. The wavefront sensor measures the high-precision attitude error (Tip / Tilt error) of the spliced sub-mirror, and feeds back to the displacement actuator for closed-loop correction in real time, so that the splicing system can achieve the final confocal and co-phase. The present application can simplify the large-scale and complex splicing of the mirror into a simple active optical confocal splicing of the continuous edge of the splicing sub-mirror, avoid the large-scale, expensive, high-precision nanometer-level, and environmentally affected electrical or optical edge displacement sensors, and further avoid the high complexity and time-consuming algorithms in the current large-scale sub-mirror splicing error calibration based on complex multi-wavelength and physical optical splicing error calibration. Compared with the international leading solution of the edge displacement sensor (used for confocal maintenance and co-phase maintenance) and the upgraded complex version of the physical optical Shack-Hartmann wavefront sensor (used for co-phase calibration) in the conventional splicing optical telescope, the present application does not introduce the edge sensor, crosses the concept, technology and price bottleneck of the edge sensor, and has extremely low price, stable performance, extremely low failure rate, extremely high precision, no environmental factor influence, and extremely convenient installation, assembly and debugging. The present application is suitable for the engineering implementation of the splicing mirror of various large-aperture astronomical telescopes and large-aperture optical systems.

Claims

1. An active optical stitching system for mirror edge continuation, characterized by, The sub-mirror includes 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 (8), a common support plate (3) installed on the displacement actuator (8), and a flexible adjusting device (9) installed on the common support plate (3), the displacement actuator (8) and the common support plate (3) are arranged at the common support points of adjacent sub-mirrors, the flexible adjusting device (9) includes an adjusting driving device (91) and a flexible support rod (92), the adjusting driving device (91) is connected with one or more flexible support rods (92), each flexible support rod (92) is connected with one of the adjacent sub-mirrors, and the height of the sub-mirror perpendicular to the mirror surface is adjusted through the sub-mirror adjusting mechanism; The sub-mirror supporting mechanism includes 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 uniformly arranged at the bottom of the mirror surface of the sub-mirror; the central hole supporting device includes a central hole supporting bracket (6) and a supporting piece installed on the central hole supporting bracket (6), and the supporting piece is a central hole diaphragm (5) or a central hole linear bearing (13); the mirror surface supporting device is one of an axial lever counterweight floating support, an axial Whiffletree support, a gas pressure floating support or a hydraulic floating support.

2. The active optical splicing system of claim 1, wherein, The adjusting driving device (91) is a motor, the output end of the motor is connected with a guide rail (93), and the flexible support rod (92) is installed on the guide rail (93).

3. The active optical splicing system of claim 1, wherein, The sub-mirror adjusting mechanism further includes a force sensor (94), the force sensor (94) is installed in series with the adjusting driving device (91) and the flexible support rod (92), and is used for measuring the force perpendicular to the mirror surface.

4. The active optical splicing system of claim 1, wherein, The flexible support rod (92) is made of low-expansion material.

5. The active optical splicing system of claim 1, wherein, A height detection sensor (10) is further included, the height detection sensor (10) is arranged above the mirror surface of the sub-mirror, and is used for detecting the height difference between adjacent sub-mirrors.

6. The active optical splicing system of claim 1, wherein, The shape of the sub-mirror is a regular hexagon or a sector.

7. A method of operating an active optical splicing system as claimed in any one of the claims 1-6, characterized in that, A Hartmann-Shack wavefront sensor is provided, and specifically includes the following steps: S1, installing a sub-mirror supporting mechanism; S2, installing a sub-mirror adjusting mechanism; S3, optical imaging and data processing are performed through the Hartmann-Shack wavefront sensor; the Hartmann-Shack wavefront sensor is placed behind the sub-mirror, the light beam of the sub-mirror enters the Hartmann-Shack wavefront sensor, a light spot signal is formed, and the stitching error of the stitching system is measured according to the following formula: θx=(dx / f)*(D / d), θy=(dy / f)*(D / d) Wherein, (θx, θy) is the attitude error of the sub-mirror, (dx, dy) is the light spot centroid position difference of the wavefront sensor, f is the focal length of the 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, the stitching error is fed back to the displacement actuator, the sub-mirror is adjusted, and the stitching system reaches the common focus and the common phase.

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