An axial support and positioning system for optical mirrors

Abstract

The application discloses an axial support and positioning system for an optical mirror, wherein a plurality of groups of seesaw self-balancing axial support mechanisms are arranged between the optical mirror and a base frame, the main body of the seesaw self-balancing axial support mechanism is a polygonal seesaw, one side of each corner point position of the seesaw is connected with the optical mirror through a first hinge, the other side of each corner point position of the seesaw is connected with a force actuator integrated with a force sensor through a second hinge, each force actuator can independently output a correction force, and the middle part of the seesaw is connected with the base frame through a third hinge. The application fully utilizes the advantages of the seesaw self-balancing axial support system, completely unloads the mirror weight and rigidly positions the mirror, so that the output force of the force actuator can be entirely used for correction of the mirror surface shape or generation of a required surface shape, and real-time active correction can be performed on the mirror surface shape and even the performance of the whole optical system.

Description

Technical Field

[0001] This invention relates to a support and positioning device for axial support and positioning of precision optical mirrors, particularly suitable for situations in ground-based or space-based astronomical telescopes where the curvature or surface shape of the supported mirror needs to be maintained or corrected under passive support conditions. Background Technology

[0002] Precision optical mirrors require precise and stable support and positioning. For example, during astronomical telescope tracking of celestial objects, the mirrors often need to rotate from pointing towards the ground plane to pointing towards the zenith, requiring an elevation angle ranging from 0 to 90 degrees. Furthermore, the mirrors must maintain the required surface shape and positioning accuracy throughout the tracking process. This necessitates proper support and positioning for all mirrors of the astronomical telescope. To address this issue, the traditional method involves using passive support structures for each mirror, often implementing axial and lateral support separately, such as using a lever-and-balance-weight mechanism (see...). Figure 1 Includes mirror 11, fulcrum 12 or hinge, lever 13, counterweight 14), and seesaw self-balancing mechanism (see...). Figure 2 The system includes a mirror 11, a fulcrum 12 or hinge, a lever 13, a floating frame 15, and a mirror chamber 16) to achieve precise support for the optical mirror. In particular, the seesaw self-balancing mechanism is widely used due to its outstanding self-balancing characteristics and ability to simultaneously provide rigid body positioning for the mirror. Its principle is simple and clear, and its structure is compact.

[0003] On the other hand, the surface shape of precision optical mirrors may have manufacturing defects or the aforementioned support system may not provide ideal support. Therefore, the surface shape of the mirror needs to be corrected during observation. Among the surface shape errors that are particularly easy to generate or require correction are curvature and low-order aberrations, such as astigmatism and coma.

[0004] With the development of automatic control technology, modern precision optical mirrors also widely adopt active support technology. This involves setting multiple force actuators, torque actuators, micro-displacement actuators, and sensors at the bottom of the mirror body. Under computer control, the position and shape of the mirror are corrected and controlled in real time, thereby ensuring that the mirror maintains the required surface shape accuracy and positioning accuracy during operation, such as when an astronomical telescope is tracking and observing.

[0005] The disadvantages of the above-mentioned mirror support methods are as follows: Traditional seesaw-based self-balancing passive support systems are complex in structure, require high dimensional accuracy, and have stringent assembly and adjustment requirements, making it difficult for the supported mirror to achieve an ideal surface shape. Furthermore, the supported mirror often has manufacturing errors, especially for thinner mirrors, where surface shape errors frequently occur during processing and operation. Astigmatism is the most typical and easily generated surface shape error, which the passive support self-balancing seesaw mechanism cannot address or correct. On the other hand, current active support methods for optical mirrors require real-time detection and closed-loop control, resulting in complex systems with high costs. The weight of the mirror itself consumes a large portion of the dynamic range of the active support mechanism's active correction force, and the system design does not utilize the aforementioned advantages of the self-balancing seesaw. Summary of the Invention

[0006] To overcome the shortcomings of traditional support systems for precision optical mirrors, while considering both cost and manufacturing performance, this invention fully combines the advantages of self-balancing seesaw structures and active support technology to provide an innovative support concept and system structure scheme. This scheme enables precise axial support and rigid positioning of optical mirrors, as well as precise control and correction of the mirror surface shape.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] An axial support and positioning system for an optical mirror includes several sets of seesaw self-balancing axial support mechanisms arranged between the optical mirror and a base frame. The main body of each seesaw self-balancing axial support mechanism is a polygonal seesaw. One side of each corner of the seesaw is connected to the optical mirror via a first hinge, and the other side of each corner of the seesaw is connected to a force actuator with an integrated force sensor via a second hinge. Each force actuator can independently output a correction force. The middle of the seesaw is connected to the base frame via a third hinge.

[0009] Furthermore, the first hinge, the second hinge, and the third hinge are slender elastic rod mechanisms or flexible hinge mechanisms.

[0010] Furthermore, the system's operating mode includes a closed-loop control mode, in which the surface shape detection system detects the surface shape of the optical mirror, provides the surface shape error that needs to be corrected, obtains the correction force that needs to be applied, and sends it to the force actuator for execution. The force sensor detects the output force of the force actuator and compares it with the target correction force value that needs to be applied until the control error requirement is met.

[0011] Furthermore, the system's operating mode includes an open-loop control mode, in which a corresponding correction force is set for repeatable surface shape errors caused by predictable environmental factors, and a pre-calculated or measured correction force is directly applied to the optical mirror surface.

[0012] Furthermore, the force actuator need not be located directly below the first hinge of the seesaw.

[0013] Furthermore, a seesaw with corner offset is used to offset the force actuator.

[0014] Furthermore, the seesaw self-balancing axial support mechanism is used to maintain or correct the curvature or surface shape of the supported optical mirror.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] This invention provides an axial support and positioning system for optical mirrors, enabling axial support and positioning of the mirror body while simultaneously correcting surface shape errors or generating the desired surface shape. This invention fully leverages the advantages of a seesaw self-balancing mechanism axial support system, completely unloading the mirror weight and achieving rigid body positioning. This allows the output force of the actuators to be entirely used for correcting the reflective mirror shape or generating the required surface shape, and enables each actuator to independently output correction force. After the mirror support system is completed and implemented, it facilitates the correction of the mirror surface shape based on the axial support conditions, including lateral support conditions, thereby reducing the design and manufacturing requirements of the mirror support system and simplifying engineering implementation. Furthermore, it allows for real-time active correction of the mirror surface shape and even the performance of the entire optical system based on the actual environmental influence on the mirror surface shape. This invention demonstrates advantages such as clear structural principles, structural symmetry, good feasibility, and strong adaptability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a mirror support system based on a lever-balanced counterweight mechanism;

[0018] Figure 2 This is a schematic diagram of a mirror axial support system based on a seesaw self-balancing mechanism;

[0019] Figure 3 This is a schematic diagram of the principle of the mirror axial active support system;

[0020] Figure 4 This is a schematic diagram of the principle of the mirror axial active support system without showing the base frame;

[0021] Figure 5 This is a schematic diagram of the mirror axial active support system of the offset mounting force actuator;

[0022] Figure 6This is a side view of the mirror axial active support system and positioning system;

[0023] Figure 7 This is a 3D diagram of the mirror axial active support and positioning system without showing the base frame;

[0024] Figure 8 This is a 3D diagram of the mirror axial active support and positioning system.

[0025] The diagram is labeled as follows: 1-Reflector, 2-Mirror connection hinge, 21-First elastic rod, 3-Triangular seesaw, 4-Force actuator hinge, 41-Second elastic rod, 5-Force actuator, 6-Seesaw fulcrum hinge, 61-Fulcrum flexible hinge, 7-Base frame, 8-Force sensor, 9-Surface shape detection system, 10-Computer, 11-Mirror, 12-Fulcrum, 13-Lever, 14-Weighted weight, 15-Floating frame, 16-Mirror chamber. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings.

[0027] First, let's explain the names involved in this invention: The term "mirror surface shape" refers to the curved shape of the reflective surface of a mirror. For a mirror with given geometric dimensions, its surface shape can be expressed using its surface normal coordinates or axial coordinates; the term "surface shape error" is expressed using the normal or axial deformation of the reflective surface, i.e., displacement; the term "rigid body positioning" refers to the mirror body being restricted in its corresponding degrees of freedom. For example, using a self-balancing seesaw-type axial support system, it can and should only restrict one translational degree of freedom of the mirror body in the axial or normal direction, without restricting the free deformation of the mirror body.

[0028] This invention proposes a precision reflective mirror axial support and rigid body positioning scheme based on a force actuator and a self-balancing seesaw structure. Based on the surface shape accuracy requirements of the mirror's reflective surface optical design, optimally numbered support points with their optimal distribution and position are set on the back of the mirror; then, a seesaw self-balancing structure is configured, such as... Figure 3 and Figure 4The diagram shows the principle of the axial active support system for the mirror surface of the present invention. A mirror connecting hinge 2 is installed on the upper side of the three corner points of each triangular seesaw 3 (or triangular lever), connecting it to the back of the reflector 1 to achieve axial support and positioning of the reflector 1. A force actuator 5 integrating a force sensor 8 is installed on the lower side of each of the three corner points of each triangular seesaw 3, and connected to the force actuator 5 by a force actuator hinge 4. A seesaw fulcrum hinge 6 is installed at the center of the triangular seesaw 3, connecting it to the base frame 7 of the entire system. All hinges can be slender elastic rod mechanisms or flexible hinge mechanisms. In this embodiment, a total of 9 axial support points are provided for the reflector, divided into 3 groups, each supported by one triangular seesaw, forming three groups of seesaw self-balancing axial support systems. Each group is equipped with 3 corresponding force actuator mechanisms to apply axial correction force for active correction and control of the reflector surface shape. This constitutes the axial active support and positioning system for the reflector surface. It should be noted that this embodiment only uses a triangular seesaw as an example for detailed description, but the seesaw in this invention is not limited to a triangular seesaw. The working principle of other polygonal seesaws is similar to that of the triangular seesaw, and they can all achieve the purpose of this invention.

[0029] It should be further noted that when implementing this support scheme in specific projects, under circumstances with size and space limitations or special requirements, Figure 4 The force actuator 5 does not need to be located directly below the mirror-connected hinge 2 on the triangular seesaw 3. The size and profile of the triangular seesaw 3 can be adjusted according to actual conditions and requirements. (See [reference]). Figure 5 A triangular lever / seesaw with its vertex offset can be used to offset the force actuator 5. This setup offers structural convenience, and because the vertex of the triangular seesaw is offset outwards, it effectively lengthens the lever arm of the force actuator, thus reducing the force amplitude of the force actuator when correcting the same surface shape.

[0030] exist Figure 6-8 In a preferred embodiment, the back of the reflector 1 is divided into three rotationally symmetrical regions by a plurality of elongated first elastic rods 21 at required positions. Each first elastic rod 21 within a region is fixed to a triangular seesaw 3. A force sensor 8 is connected to each first elastic rod 21 on the underside of the triangular seesaw 3. The force sensor 8 is then connected to the force output end of a force actuator 5 via an elongated second elastic rod 41. The force actuator 5 is fixed to the base frame 7. The triangular seesaw 3 is fixed to the base frame 7 via a fulcrum flexible hinge 61.

[0031] The workflow of this embodiment is as follows: Computer 10 acquires the mirror surface shape detected by surface shape detection system 9, calculates the surface shape error, and calculates the required correction force, which is then sent to force actuator 5 to execute the force output. Force sensor 8 detects the output force of force actuator 5. Computer 10 acquires the force value of force sensor 8 and compares it with the calculated correction force. If the requirement is not met, the correction force value is adjusted and sent to force actuator 5 to continue closed-loop detection of the force value until the error requirement of the output force of force actuator 5 is met. Then, surface shape detection system 9 re-detects the mirror surface shape and sends it to computer 10, which calculates the correction force and continues closed-loop control of the output force of force actuator 5 until the surface shape error meets the requirement.

[0032] The working principle of this invention is as follows: a series of seesaw self-balancing mechanisms with optimal distribution and position of support points provide axial support and positioning for the reflective surface, enabling it to achieve the required surface shape under ideal conditions. When the mirror is affected by various factors during operation, or when there is a deviation between the theoretical design and engineering reality of the seesaw self-balancing support mechanism or other support systems, resulting in low-order spatial frequency errors in the reflective surface shape; or when a specific low-spatial frequency surface shape is required, the provided force actuator can be used to apply a given active correction force to deform the mirror, thereby correcting the mirror error or obtaining the required surface shape.

[0033] The working modes of this invention are as follows: There are two modes: closed-loop active control and open-loop active control. Closed-loop control mode: The surface shape detection system detects the reflector's surface shape in real time, identifies the surface shape error to be corrected, obtains the required correction force, and sends it to the force actuator for execution. The force sensor integrated into the force actuator collects the actuator's output force in real time and compares it with the target correction force value until the control error requirement is met; this is the closed-loop correction mode. Open-loop control mode: For repeatable surface shape errors caused by predictable environmental factors, a corresponding correction force is set, such as the reflector surface shape error caused by changes in gravity and ambient temperature. During the operation of the reflector, the corresponding gravity field or ambient temperature field causes repeatable and linearly superimposed surface shape errors, thus the corresponding correction force is also repeatable and linearly superimposed. Therefore, for known gravity and ambient temperature conditions, a pre-calculated or measured correction force can be directly applied to the reflector; this is the open-loop correction mode.

[0034] It should be further explained that in actual engineering, due to various factors affecting surface shape errors, multiple closed-loop corrections can be performed to reduce the surface shape error to within the required range.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An axial support and positioning system for an optical mirror, characterized in that, Several sets of seesaw self-balancing axial support mechanisms are arranged between the optical mirror and the base frame. The main body of each seesaw self-balancing axial support mechanism is a polygonal seesaw. One side of each corner of the seesaw is connected to the optical mirror via a first hinge, and the other side of each corner of the seesaw is connected to a force actuator with an integrated force sensor via a second hinge. The force actuator is fixed to the base frame, and each force actuator can independently output a correction force. The middle of the seesaw is connected to the base frame via a third hinge. The system's operating mode includes a closed-loop control mode, in which the surface shape detection system detects... The surface shape of the optical mirror is measured, the surface shape error to be corrected is given, the required correction force is obtained, and the force is sent to the force actuator for execution. The force sensor detects the output force of the force actuator and compares it with the target correction force value to be applied until the control error requirement is met. The system's working mode includes an open-loop control mode. In the open-loop control mode, for repeatable surface shape errors caused by predictable environmental factors, a corresponding correction force is set, and a pre-calculated or measured correction force is directly applied to the optical mirror. The force actuator does not need to be located directly below the first hinge of the seesaw; instead, the force actuator is installed at the corner position of the seesaw with the corner point offset outwards.

2. The axial support and positioning system for an optical mirror according to claim 1, characterized in that, The first hinge, the second hinge, or the third hinge is a slender elastic rod mechanism or a flexible hinge mechanism.

3. The axial support and positioning system for an optical mirror according to claim 1, characterized in that, The seesaw self-balancing axial support mechanism is used to maintain or correct the curvature or surface shape of the supported optical mirror.

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