A secondary mirror adjusting mechanism applied to an off-axis telescope

Abstract

The application provides a secondary mirror adjusting mechanism applied to an off-axis telescope, comprising two symmetrical mounting plates, four axis-symmetrical flexible rods and a secondary mirror mounting seat; the secondary mirror mounting seat is a cylindrical ring structure with a closed end face, and stress relief grooves and glue injection holes are arranged on the side wall of the secondary mirror mounting seat; the secondary mirror mounting seat is connected with the mounting plates through the flexible rods, and the secondary mirror is mounted in the secondary mirror mounting seat. The application guarantees the stable optical performance of the telescope, realizes the self-adaptation of the off-axis telescope under a complex space temperature environment, and is especially suitable for a large temperature variation, long distance and high-speed laser communication scene.

Description

Technical Field

[0001] This invention belongs to the field of laser communication technology and relates to a secondary mirror adjustment mechanism. Background Technology

[0002] Optical telescopes, as key components in satellite laser communication systems for signal transmission and reception, directly impact the overall performance of the system. Off-axis reflecting telescopes, due to their high transmission and reception efficiency and wide field-of-view aiming and acquisition capabilities, are widely used in laser communication systems. However, the asymmetry and numerous degrees of adjustment inherent in off-axis telescope optical systems place higher demands on the positional accuracy of each reflector. During the transmission and on-orbit operation phases, the laser terminal is subject to complex external environmental factors, including transmission vibrations, gravitational release, and temperature variations. These factors alter the relative positions of the telescope's reflectors, leading to decreased image quality, optical axis shifts, and ultimately affecting the laser terminal's tracking and communication quality.

[0003] Currently, off-axis reflecting telescopes used in laser terminals mostly employ off-axis two-mirror or off-axis four-mirror optical systems. Compared to imaging remote sensing telescopes, they are smaller and more compact. Optical simulation analysis shows that the positional accuracy of the primary and secondary mirrors in an off-axis telescope has the most sensitive impact on its optical performance, typically at the micrometer level. Because the telescope tube, as the main load-bearing structure, usually has a high coefficient of thermal expansion, and the primary and secondary mirrors are located at opposite ends of the tube, with the secondary mirror far from the telescope's optical axis, changes in the positions of the primary and secondary mirrors under complex spatial temperature environments will deviate from their designed theoretical positions. This leads to a decrease in the telescope's optical performance and reduces the transceiver performance of the laser terminal. Therefore, ensuring the relative positions of the primary and secondary mirrors is a key challenge in the development of off-axis telescopes. Summary of the Invention

[0004] The technical problem this invention aims to solve is the degradation of optical performance in off-axis telescopes under complex temperature variations. This invention proposes a secondary mirror adjustment mechanism for off-axis telescopes. Utilizing the isosceles trapezoidal commutation principle and parasitic motion theory, it uses the thermal deformation of the mounting surface of the off-axis telescope's barrel adjustment mechanism as the driving displacement. This controls the secondary mirror to compensate for changes in the positions of the primary and secondary mirrors caused by environmental temperature variations, ensuring stable optical performance of the telescope. This achieves self-adaptation of the off-axis telescope in complex spatial temperature environments, making it particularly suitable for scenarios involving large temperature variations, long distances, and high-speed laser communication.

[0005] The technical solution adopted in this invention is: a secondary mirror adjustment mechanism for off-axis telescopes, comprising two symmetrical mounting plates, four axially symmetrically distributed flexible rods, and a secondary mirror mounting base; the secondary mirror mounting base is a cylindrical annular structure with one end face closed, and stress relief grooves and glue injection holes are provided on its side wall; the secondary mirror mounting base is connected to the mounting plates through the flexible rods, and the secondary mirror is installed in the secondary mirror mounting base.

[0006] Furthermore, the stress-relieving groove is a long groove, symmetrically distributed relative to the glue injection hole, with stress-relieving concentration holes at both ends, and the stress-relieving grooves are parallel to each other and parallel to the axis of the secondary mirror mounting base.

[0007] Furthermore, the flexible rod is a rectangular plate with flexible links at both ends, and the flexible rod is connected to the mounting plate and the secondary mirror mounting base through the flexible links.

[0008] Furthermore, each pair of flexible rods forms a group, and the two flexible rods are arranged symmetrically in parallel at an acute angle; the two groups of flexible rods are symmetrically distributed relative to the secondary mirror mounting base, and the surfaces formed by the two groups of flexible rods form an obtuse angle.

[0009] Furthermore, the mounting plate is a plate-shaped component, and each mounting plate is provided with several screw mounting through holes, which are connected to the telescope barrel.

[0010] Furthermore, the axis of the secondary mirror mounting base forms an acute angle with the mounting plate.

[0011] Furthermore, the secondary mirror adjustment mechanism is made of Invar metal.

[0012] Furthermore, the secondary mirror is connected to the secondary mirror mounting base via optical bonding adhesive, which is injected into the gap between the side wall of the secondary mirror and the secondary mirror mounting base through the injection hole.

[0013] When the temperature of the environment where the off-axis telescope is located changes by ΔT, the secondary mirror adjustment mechanism converts the Y-axis thermal deformation of the telescope tube into the Z-axis translation of the secondary mirror, controls the position of the secondary mirror to change with temperature, and realizes the position compensation of the primary and secondary mirrors.

[0014] The advantages of this invention compared to the prior art are:

[0015] (1) The present invention uses the thermal deformation of the telescope barrel as the driving displacement, which can ensure that the telescope has high optical performance in a wide temperature range, improve the temperature adaptability of the telescope, reduce the power consumption and weight of the telescope thermal control, reduce the laser terminal emission cost, and improve the on-orbit working life.

[0016] (2) This invention uses the thermal deformation of the lens barrel as the driving displacement to drive the secondary lens adjustment mechanism to adjust the position of the secondary lens, which has passive adaptive characteristics; it has a simple structure, light weight, high overall rigidity, and compact structure, and has a wide temperature application range.

[0017] (3) The secondary mirror adjustment mechanism of the present invention is a flexible adjustment mechanism with the characteristics of no hysteresis and no friction. It uses the elastic deformation of the structure to transmit motion. It adopts a symmetrical parallel flexible joint form to avoid the introduction of parasitic rotation and ensure the submicron level adjustment accuracy of the secondary mirror position. While realizing the adjustment of the secondary mirror position, no extraneous objects are generated, ensuring the cleanliness of the inside of the telescope.

[0018] (4) This invention utilizes the isosceles trapezoidal commutation principle to achieve a displacement magnification of more than 8 times, ensuring the adjustment amount of the secondary mirror; this invention uses Invar steel metal material with a low thermal expansion coefficient to avoid thermal deformation of the adjustment mechanism due to temperature changes, which would affect the adjustment accuracy of the secondary mirror; the material has good toughness and can avoid metal fatigue caused by cyclic temperature changes. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention;

[0020] Figure 2 This is a schematic diagram illustrating the application of the present invention in an off-axis telescope;

[0021] Figure 3 This is a schematic diagram of the secondary mirror mount of the present invention;

[0022] Figure 4 This is a schematic diagram of the flexible rod of the present invention;

[0023] Figure 5 This is a schematic diagram of the operation of the present invention. Figure 1 ;

[0024] Figure 6 This is a schematic diagram of the operation of the present invention. Figure 2 ;

[0025] Figure 7 This is a schematic diagram illustrating the working principle of the present invention;

[0026] Figure 8 This is a displacement cloud diagram of the present invention driven by the thermal deformation of the mirror barrel;

[0027] Figure 9 The diagram shows the wavefront aberration and dot plot of the off-axis telescope optical system before and after compensation, as used in this invention.

[0028] Figure 10(a) shows the optical performance of the telescope before temperature change;

[0029] Figure 10(b) shows the optical performance of the telescope after temperature change without compensation using the secondary mirror adjustment mechanism;

[0030] Figure 10(c) shows the optical performance of the telescope after temperature change compensation using the secondary mirror adjustment mechanism. Detailed Implementation

[0031] The present invention will be described in conjunction with the accompanying drawings.

[0032] like Figure 1 As shown, a secondary mirror adjustment mechanism for an off-axis telescope includes a mounting plate 1, a flexible rod 2, and a secondary mirror mounting base 3. Each of the two symmetrically arranged mounting plates 1 has three screw mounting holes. The secondary mirror adjustment mechanism is connected to the telescope barrel via six screws. Figure 2 As shown.

[0033] like Figure 3 As shown, the secondary mirror mounting base 3 is a cylindrical annular structure with one end face closed. Its cylindrical sidewall is provided with an injection hole 4 and a stress relief groove 5. The secondary mirror adopts a mushroom-shaped structure and is connected to the secondary mirror mounting base 3 by optical bonding adhesive. The optical bonding adhesive is injected into the gap between the secondary mirror and the sidewall of the secondary mirror mounting base 3 through the injection hole 4. The stress relief groove 5 is symmetrically distributed relative to the injection hole 4. Stress relief concentration holes 6 are provided at both ends of the stress relief groove 5. The stress relief groove 5 is parallel to the axis of the secondary mirror mounting base 3, which can effectively isolate the cyclic deformation at the connection between the secondary mirror mounting base 3 and the flexible rod 2 during the adjustment process and ensure the bonding strength of the secondary mirror.

[0034] like Figure 4 As shown, the flexible rod 2 includes a connecting rod 7 and a flexible link 8. The connecting rod 7 is a cuboid with a relatively thick cross-section, possessing a certain rigidity; the flexible link 8 is a cuboid with a relatively thin cross-section, possessing a certain flexibility. The flexible rod 2 is connected to the mounting plate 1 and the secondary mirror mounting base 3 through the flexible link 8. Figure 5 As shown, the flexible rods 2 are symmetrically connected in pairs to form groups, with an included angle α, where α is an acute angle. The two groups of flexible rods 2 are symmetrically distributed relative to the secondary mirror mounting 1, forming an obtuse angle β.

[0035] like Figure 6 , 7 As shown, a Cartesian coordinate system O-XYZ is established, with the origin located at the intersection of the axes of the mounting plate 1 and the secondary mirror mounting base 3. The Z-axis lies within the plane of symmetry of the secondary mirror mounting base 3 and is perpendicular to the mounting plate 1; the Y-axis is perpendicular to the plane of symmetry of the secondary mirror mounting base 3. Through optomechanical integration analysis, when the temperature of the off-axis telescope's environment changes by ΔT, controlling the movement of the secondary mirror along the Z-axis can compensate for the positional changes between the primary and secondary mirrors.

[0036] like Figure 7 , 8As shown, this invention is simplified to an isosceles trapezoid A1B1B2A2. Based on the isosceles trapezoid reversal principle: while keeping the lengths of line segments A1B1, A2B2, and B1B2 constant, points A1 and A2 are moved horizontally relative to each other along the line containing line segment A1A2. When A1 moves Δu to A1', and A2 moves the same distance Δu to A2', line segment B1B2 will move along the symmetry line H1H2 of the isosceles trapezoid to B1'B2'. Using this principle, the Y-direction displacement Δu can be converted into the Z-direction displacement Δh, with the following relationship:

[0037]

[0038] When the temperature of the environment where the off-axis telescope is located changes by ΔT, the secondary mirror adjustment mechanism can convert the Y-axis thermal deformation of the telescope tube into the Z-axis translation of the secondary mirror, control the position of the secondary mirror to change with temperature, and realize the position compensation of the primary and secondary mirrors.

[0039] Through the analysis of the flexibility and degrees of freedom of this invention, when the two symmetrical mounting plates 1 are driven in the Y direction, the secondary mirror mounting base can be translated along the Z direction without any other parasitic rotation. To ensure the stability of the angular position of the primary and secondary mirrors when the secondary mirror moves along the Z direction to compensate, the axis of the secondary mirror mounting base 3 is arranged at an angle γ with the normal of the mounting plate 1. The angle γ is obtained based on optomechanical integration analysis.

[0040] Through force and heat simulation analysis, the displacement cloud diagram of the secondary mirror adjustment mechanism driven by the Y-direction displacement is as follows: Figure 9 As shown. By setting the length of the flexible rod 2 and the included angle α, the secondary mirror adjustment mechanism can provide a displacement magnification of more than 8 times, which can convert the small deformation of the mounting surface of the mirror tube adjustment mechanism caused by temperature change into a large deformation to compensate for the optical system, ultimately ensuring that the telescope has excellent optical performance in temperature-changing environments.

[0041] The secondary mirror adjustment mechanism is designed with Invar steel in one piece, featuring a low coefficient of thermal expansion that matches the secondary mirror, ensuring good surface accuracy over a wide temperature range. Furthermore, Invar steel possesses good ductility and toughness, preventing metal fatigue under cyclic thermal deformation.

[0042] like Figures 10(a) to 10(c) As shown, through photomechanical and thermal simulation analysis, under a certain temperature change, the optical performance (wavefront aberration, dot plot, etc.) of the telescope after compensation using the secondary mirror adjustment mechanism is significantly better than the optical performance without it, and is basically close to the optical performance of the telescope before the temperature change.

[0043] The parts of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A secondary mirror adjustment mechanism for an off-axis telescope, characterized in that, It includes two symmetrical mounting plates (1), four axisymmetrically distributed flexible rods (2) and a secondary mirror mounting base (3); the secondary mirror mounting base (3) is a cylindrical ring structure with one end face closed, and stress relief grooves (5) and glue injection holes (4) are provided on its side wall; the secondary mirror mounting base (3) is connected to the mounting plate (1) through the flexible rods (2), and the secondary mirror is installed in the secondary mirror mounting base (3); When the temperature of the environment in which the off-axis telescope is located changes. At time T, the secondary mirror adjustment mechanism converts the Y-axis thermal deformation generated by the mirror barrel into the Z-axis translation of the secondary mirror, controls the position of the secondary mirror to change with temperature, and realizes the position compensation of the primary and secondary mirrors. The stress relief groove (5) is a long groove, which is symmetrically distributed relative to the glue injection hole (4). Stress relief concentration holes (6) are provided at both ends. The stress relief grooves (5) are parallel to each other and parallel to the axis of the secondary mirror mounting base (3). The flexible rod (2) is a rectangular plate with flexible links (8) at both ends. The flexible rod (2) is connected to the mounting plate (1) and the secondary mirror mounting base (3) through the flexible links (8).

2. The secondary mirror adjustment mechanism for an off-axis telescope according to claim 1, characterized in that, Two flexible rods (2) form a group, and the two flexible rods (2) are arranged symmetrically in parallel with acute angles; the two groups of flexible rods (2) are symmetrically distributed relative to the secondary mirror mounting base (3), and the surfaces formed by the two groups of flexible rods (2) are at an obtuse angle.

3. The secondary mirror adjustment mechanism for an off-axis telescope according to claim 1, characterized in that, The mounting plate (1) is a plate-shaped piece, and each mounting plate (1) is provided with several screw mounting through holes, which are connected to the telescope barrel through the screw mounting through holes.

4. The secondary mirror adjustment mechanism for an off-axis telescope according to claim 1, characterized in that, The axis of the secondary mirror mounting base (3) forms an acute angle with the mounting plate (1).

5. The secondary mirror adjustment mechanism for an off-axis telescope according to claim 1, characterized in that, The secondary mirror adjustment mechanism is made of Invar metal.

6. The secondary mirror adjustment mechanism for an off-axis telescope according to claim 1, characterized in that, The secondary mirror is connected to the secondary mirror mounting base (3) by optical bonding adhesive, which is injected into the gap between the secondary mirror and the side wall of the secondary mirror mounting base (3) through the injection hole (4).

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