Thermal shrinkable hub and off-axis reflective high-thermal-stability inter-satellite laser communication telescope

Abstract

The application discloses a heat-shrinking axle joint and an off-axis reflective high-heat-stability inter-satellite laser communication telescope. The heat-shrinking axle joint comprises an axial fixing seat, a circular upper plate, a circular lower plate, a plurality of flexible legs, and a leg joint. The circular upper plate is connected with a mirror support structure, and the circular lower plate is connected with a telescope lens barrel. The flexible legs are connected between the circular upper plate and the circular lower plate. The middle part of the flexible leg is provided with the leg joint, and the flexible leg can be bent at the leg joint. The thermal expansion coefficient of a radial driving ring is greater than that of the axial fixing seat, and the inner circular surface of the radial driving ring is fixed outside the leg joint. In the laser communication telescope, the mirror is arranged on the telescope lens barrel through the mirror support structure and the heat-shrinking axle joint, and the heat-shrinking axle joint is connected between the mirror support structure and the telescope lens barrel. The axial thermal displacement of the heat-shrinking axle joint is changed by adjusting the thermal expansion coefficient and the size of the radial driving ring and the leg clamping angle of the axial fixing seat, so that the position stability of each mounting point is ensured.

Description

Technical Field

[0001] This application relates to the technical field of optomechanical structures of space optical remote sensors, and in particular to a thermally shrinkable joint and off-axis reflective high thermal stability inter-satellite laser communication telescope. Background Technology

[0002] In recent years, with the rapid development of inter-satellite laser communication technology and the construction of large-scale constellations, the demand for inter-satellite laser communication terminals has exploded. Telescopes are key components of inter-satellite laser communication terminals, requiring high optical imaging quality, light weight, small envelope size, and good adaptability to the space thermal environment. The telescope employs an off-axis four-mirror optical system. The primary and secondary mirrors form the objective lens, while the third and fourth mirrors form the eyepiece. All four mirror assemblies are mounted on the same support structure, effectively reducing the envelope size and weight. The primary, secondary, and fourth mirrors are quadric surfaces, while the third mirror is a high-order aspherical surface. The surface accuracy and positional stability of the mirrors are key factors affecting the performance of the optical system. To achieve a wavefront accuracy better than 1 / 30λ (rms), the surface shapes of the primary, secondary, third, and fourth mirrors are all required to be better than 1 / 100λ (rms). Because the laser terminal telescope is installed outside the satellite cabin, it is affected by ambient heat sources and solar radiation. During operation, the telescope experiences temperature fluctuations and uneven temperature distribution. These temperature changes cause thermal deformation of the optomechanical structure, ultimately leading to instability in the system's propagation and beam divergence angles, thus affecting inter-satellite communication efficiency. The laser terminal telescope can only operate normally within a very narrow temperature range, necessitating a complex thermal control design to ensure its proper functioning. This increases the satellite's power consumption and the risk of optical payload contamination. Summary of the Invention

[0003] This application provides a thermally shrinkable joint and off-axis reflective high thermal stability inter-satellite laser communication telescope, with the aim of solving the problem of thermal stability support for laser communication terminal telescopes.

[0004] Firstly, a heat-shrinkable joint is provided, comprising:

[0005] An axially fixed base includes a circular upper plate, a circular lower plate, several flexible legs, and leg joints; the circular upper plate is used to connect with the reflector support structure, and the circular lower plate is used to connect with the telescope tube; the flexible legs are connected between the circular upper plate and the circular lower plate; a leg joint is provided in the middle of the flexible leg, and the flexible leg can be bent at the leg joint;

[0006] The radial drive ring has a thermal expansion coefficient greater than that of the axial fixed seat, and its inner circular surface is fixed to the outer side of the outrigger joint of the axial fixed seat.

[0007] In conjunction with the first aspect, in some implementations of the first aspect, during the thermal deformation process, the radial drive ring radially elongates by ΔD, pulling the flexible outrigger to rotate around the outrigger joint, reducing the height of the flexible outrigger by ΔH2. ΔH2 matches the normal thermal deformation amount of the reflector mounting surface, and the radial drive ring satisfies:

[0008] ΔH2=α*D*tanβ

[0009] ΔD=α*D*ΔT

[0010] α is the coefficient of thermal expansion of the radial drive ring material, D is the inner diameter of the radial drive ring, ΔT is the temperature change during the thermal deformation process, and β is the inclination angle of the flexible leg relative to the plane where the radial drive ring is located.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the heat-shrinkable joint satisfies:

[0012] The axial fixing seat has 4 to 8 flexible legs evenly distributed in the circumferential direction;

[0013] The axial fixing seat is made of indium steel;

[0014] Both the upper and lower circular plates have a central hole. The two holes are coaxial and have the same diameter. This allows the mounting screws of the mirror support structure to pass through the central holes of the upper and lower circular plates and connect to the telescope tube.

[0015] The radial drive ring is fixedly installed to the outrigger joint of the axial fixed seat by locking pins or rubber patches.

[0016] In conjunction with the first aspect, in some implementations of the first aspect, when the radial drive ring and the outrigger joint are installed by means of a locking pin, the inner circular surface of the radial drive ring mates with the outer side of the outrigger joint of the axial fixing seat, and the axial fixing seat and the radial drive ring are stress-free assembled.

[0017] In conjunction with the first aspect, in some implementations of the first aspect, when the radial drive ring and the outrigger joint are installed by means of adhesive spots, a gap is left between the radial drive ring and the axial fixing seat, and structural adhesive is injected through the injection hole.

[0018] In a second aspect, an off-axis reflective high thermal stability inter-satellite laser communication telescope is provided, including a mirror assembly, a telescope tube, and a heat-shrinkable joint as described in any of the implementations of the first aspect above. The mirror assembly includes a mirror and a mirror support structure. The mirror is mounted on the telescope tube through the mirror support structure and the heat-shrinkable joint, and the heat-shrinkable joint is connected between the mirror support structure and the telescope tube.

[0019] In conjunction with the second aspect, in some implementations of the second aspect, when the temperature of the telescope tube rises, the mounting surface of the reflecting mirror on the telescope tube undergoes thermal deformation along the normal direction, with a deformation amount of ΔH1; the radial drive ring of the heat-shrinkable joint generates radial elongation ΔD, satisfying:

[0020] ΔH1-α*D*tanβ<ε

[0021] ΔD=α*D*ΔT

[0022] α is the thermal expansion coefficient of the radial drive ring material, D is the inner diameter of the radial drive ring, ΔT is the temperature change during the thermal deformation process, β is the inclination angle of the flexible leg relative to the plane where the radial drive ring is located, and ε is the temperature compensation error threshold.

[0023] In conjunction with the second aspect, in some implementations of the second aspect, the selection of the heat-shrinkable shaft joint is constrained by the inner diameter D of the radial drive ring. Based on the compensation amount ΔH1 of the reflector mounting point, the thermal expansion coefficient α of the radial drive ring and the leg tilt angle β are customized for the reflector mounting point to achieve precise compensation for the thermal deformation displacement of the reflector assembly.

[0024] In conjunction with the second aspect, in some implementations of the second aspect, the mirror material is Si, microcrystalline, or fused silica; the mirror support structure is made of titanium alloy or high volumetric silicon carbide; the mirror and the mirror support structure are bonded together using a thermally matched adhesive; and the telescope tube is made of high volumetric silicon carbide.

[0025] In conjunction with the second aspect, in some implementations of the second aspect, the number of the reflector assemblies is four, namely a primary mirror assembly, a secondary mirror assembly, a third mirror assembly, and a fourth mirror assembly; the incident parallel beam is reflected by the off-axis quadric surface of the primary mirror assembly to form a converging beam, which is then incident on the off-axis quadric surface of the secondary mirror assembly. The beam emitted from the secondary mirror is incident on the off-axis higher-order aspherical surface of the third mirror assembly, and after being reflected by the third mirror, it forms a beam. The beam is then reflected by the off-axis quadric surface of the fourth mirror assembly to form a zero-field-of-view ray, which is perpendicular to the incident parallel beam and exits from the light outlet to reach the image plane.

[0026] Compared with the prior art, the solution provided in this application has at least the following beneficial technical effects:

[0027] This invention relates to a small-to-medium aperture off-axis four-mirror inter-satellite laser communication terminal telescope, providing an off-axis telescope structure based on thermal deformation inverse compensation, which has high temperature environment adaptability. The off-axis mirror support structure based on thermal deformation inverse compensation proposed in this invention achieves adaptive adjustment under temperature fluctuations and uneven temperature distribution, exhibiting strong environmental adaptability and high stability, ensuring stable operation of the laser terminal telescope over a wide temperature range. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the telescope structure of the laser communication terminal of the present invention.

[0029] Figure 2 This is a schematic diagram of the telescope structure of the laser communication terminal of the present invention.

[0030] Figure 3 This is a schematic diagram of a heat-shrinkable joint structure for reverse compensation of thermal deformation of a reflector.

[0031] Figure 4 This is a schematic diagram of the axial fixing seat structure for a heat shrinkable joint.

[0032] Figure 5 This is a schematic diagram of the radial drive ring structure of a heat shrinkable shaft joint.

[0033] Figure 6 This is a schematic diagram of the coordinate system and parameter definition for a heat shrinkable shaft. Detailed Implementation

[0034] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0035] Figure 1 and Figure 2 This invention illustrates an off-axis reflective high thermal stability inter-satellite laser communication telescope. This inter-satellite laser communication telescope is an off-axis four-reflector terminal telescope for laser communication, comprising a primary mirror 1, a secondary mirror 2, a third mirror 3, and a fourth mirror 4. An incident parallel beam 21 is reflected by the primary mirror 1 (off-axis quadric surface) to form a converging beam 22, which is then incident on the secondary mirror 2 (off-axis quadric surface). The beam 23 emitted from the secondary mirror is incident on the third mirror 3 (off-axis higher-order aspherical surface). Light rays from different fields of view are reflected by the third mirror to form a beam 24. This beam is then reflected by the fourth mirror 4 (off-axis quadric surface) to form a zero-field-of-view beam 25 perpendicular to the incident parallel beam, which exits from the exit port 7 and reaches the image plane.

[0036] Figure 1 and Figure 2 The laser terminal telescope structure shown includes a primary mirror assembly 31 (corresponding to primary mirror 1), a secondary mirror assembly 32 (corresponding to secondary mirror 2), a three-mirror assembly 33 (corresponding to three-mirror 3), a four-mirror assembly 34 (corresponding to four-mirror 4), and a telescope tube 35. Each mirror assembly includes a mirror and a mirror support structure, with the mirror mounted on the telescope tube 35 via the mirror support structure. The mirror material can be Si, microcrystalline silicon, or fused silica. The mirror support structure can be made of titanium alloy or high-volume aluminum-based silicon carbide. The mirror and mirror support structure can be bonded together using a thermally compatible adhesive. The telescope tube 35 can be made of high-volume aluminum-based silicon carbide.

[0037] Off-axis four-mirror optical systems have extremely high requirements for the positional accuracy of the mirror spacing and the surface accuracy. Matching the thermal properties of the mirror and the supporting structure materials can ensure a surface accuracy of a few micrometers. Positional accuracy is ensured by installing a thermal compensation structure between the mirror assembly and the telescope tube 35.

[0038] The telescope is fixed to the satellite scanning mechanism via the interface flange 6. The four-mirror assembly 34 is close to the mounting interface. The thermal deformation of the telescope tube 35 mainly affects the inter-mirror spacing between the primary mirror 1 and the secondary mirror 2, the secondary mirror 2 and the third mirror 3, and the third mirror 3 and the fourth mirror 4. Positional accuracy is ensured by installing a heat shrinkable joint with reverse thermal deformation compensation function between the primary mirror assembly 31, the secondary mirror assembly 32, the third mirror assembly 33 and the telescope tube 35.

[0039] Figure 3 This is a schematic structural diagram of a heat-shrinkable joint for reverse compensation of thermal deformation of a reflector, provided by the present invention. The heat-shrinkable joint includes an axial fixing seat 51 and a radial driving ring 52.

[0040] Figure 4 This is a schematic structural diagram of the axial mounting base 51 of the heat-shrinkable joint. The axial mounting base 51 can be made of indium steel with a low coefficient of thermal expansion. The axial mounting base 51 includes a circular upper plate 61 with a central opening, a circular lower plate 62 with a central opening, a flexible support leg 63, and a support leg joint 64. The circular upper plate 61 is used to connect with the mirror support structure of the mirror assembly, and the circular lower plate 62 is used to connect with the telescope barrel 35. Both the circular upper plate 61 and the circular lower plate 62 have central openings, which are coaxially arranged and have the same diameter d. The mounting screws of the mirror support structure pass through the central openings of the circular upper plate 61 and the circular lower plate 62 and are connected to the telescope barrel 35. The flexible support leg 63 is connected between the circular upper plate 61 and the circular lower plate 62 by integral machining or welding. A support leg joint 64 is provided in the middle of the flexible support leg 63, and the flexible support leg 63 can be bent at the support leg joint 64. Depending on the required connection stiffness, 4 to 8 flexible legs 63 can be evenly distributed in the circumferential direction of the axial fixed seat 51.

[0041] Figure 5 This is a schematic structural diagram of two types of radial drive rings 52 for heat shrinkable joints. The radial drive ring 52 can be made of a material with a high coefficient of thermal expansion α and is installed with the axial fixing seat 51 via a locking pin 53 or a high-strength adhesive pad 54. Figure 5 The left side shows the radial drive ring 52 for installation via the locking pin 53. Figure 5 The right side shows a radial drive ring 52 for installation via a high-strength adhesive patch 54.

[0042] When installed using locking pin 53, the inner surface of the radial drive ring 52 mates with the outer side of the leg joint 64 of the axial fixing seat 51, ensuring an approximately stress-free assembly between the axial fixing seat 51 and the radial drive ring 52. When installed using high-strength adhesive patch 54, a gap is left between the radial drive ring 52 and the axial fixing seat 51, and high-strength structural adhesive is injected through the injection hole.

[0043] Figure 6 The coordinate system of the heat-shrinkable joint is shown. When the temperature of the telescope tube 35 rises, the mounting surface of the reflector on the telescope tube 35 undergoes thermal deformation along the normal direction (corresponding to the +Y direction in the coordinate system of the heat-shrinkable joint), with a deformation amount of ΔH1, causing the reflector to shift in the +Y direction. Simultaneously, the radial drive ring 52 of the heat-shrinkable joint undergoes radial elongation ΔD.

[0044] ΔD=α*D*ΔT

[0045] α — Coefficient of thermal expansion of the radial drive ring 52

[0046] D—Inner diameter of radial drive ring 52

[0047] The radial drive ring 52 causes the outrigger joint 64 to stretch outward by ΔD, and the flexible outrigger 63 rotates around the outrigger joint 64, reducing the height H of the flexible outrigger 63 by ΔH2, thus compensating for the translational error caused by the thermal deformation of the lens barrel. The relationship between the thermal deformation displacement ΔH1 of the lens barrel, the inner diameter D of the radial drive ring 52 (i.e., the outer diameter of the outrigger joint 64), the thermal expansion coefficient α of the radial drive ring 52 material, and the inclination angle β of the flexible outrigger 63 relative to the plane containing the radial drive ring 52 can be approximately expressed by the following formula:

[0048] ΔH1≈α*D*tanβ

[0049] The leg tilt angle β and the thermal expansion coefficient α of the radial drive ring 52 are variables. Using the inner diameter D of the radial drive ring 52 as a constraint, the thermal expansion coefficient α of the radial drive ring 52 and the leg tilt angle β of the flexible leg 63 can be customized for each mirror mounting point according to the compensation amount ΔH1, achieving precise compensation for the thermal deformation displacement of the mirror assembly. This ensures stable operation of the laser terminal telescope over a wide temperature range.

[0050] In summary, the laser communication terminal telescope optical system provided by this invention includes a primary mirror assembly, a secondary mirror assembly, a third mirror assembly, a fourth mirror assembly, and a telescope tube. The primary, secondary, third, and fourth mirror assemblies are centrally mounted on the telescope tube, significantly compressing the telescope's envelope size and achieving the design goals of small size and lightweight construction. The telescope tube, as the main support structure, uses aluminum-based silicon carbide material with ultra-high thermal conductivity. To meet the high isolation requirements of laser communication, the primary, secondary, third, and fourth mirrors are made of silicon, microcrystalline, or fused silica with good surface finish. The mirror support structure uses titanium alloy or aluminum-based silicon carbide with thermal properties matching the tube material, avoiding the impact of compressive stress caused by thermal deformation of different materials on the mirror surface shape. A heat-shrinkable joint with reverse thermal deformation compensation function is installed between the primary mirror assembly, secondary mirror assembly, third mirror assembly, fourth mirror assembly, and telescope tube. The heat-shrinkable joint consists of an axial fixing seat and a radial drive ring, which are fixed together by screws or structural adhesive. The axial mounting bracket is directly connected to the telescope tube. Its structure consists of 4-8 evenly distributed, adjustable legs with adjustable included angles between the upper and lower plates. Flexible joints are installed on the legs to release their rotational freedom around the center of the telescopic ring section. The axial mounting bracket is made of indium steel with a low coefficient of thermal expansion to reduce thermal deformation, while the radial drive ring is made of a material with a high coefficient of thermal expansion. When the temperature rises, the telescope tube elongates, and the mirror mounting surface undergoes thermal deformation along the normal direction, causing the mirror to translate along the optical axis +Z. Meanwhile, the radial drive ring in the thermal shrinking joint elongates radially, causing the axial mounting bracket to shorten axially, opposite to the direction of thermal deformation of the mounting surface. This compensates for the mirror's positional shift caused by thermal deformation. The amount of thermal deformation varies at each mounting point. The axial thermal displacement of the thermal shrinking joint can be changed by adjusting the coefficient of thermal expansion and size of the radial drive ring, as well as the included angle of the axial mounting bracket legs, to ensure the positional stability of each mounting point.

[0051] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A heat-shrinkable joint, characterized in that, include: The axial fixing seat (51) includes a circular upper plate (61), a circular lower plate (62), several flexible legs (63), and a leg joint (64); the circular upper plate (61) is used to connect with the reflector support structure, and the circular lower plate (62) is used to connect with the telescope tube; the flexible legs (63) are connected between the circular upper plate (61) and the circular lower plate (62); the flexible legs (63) are provided with a leg joint (64) in the middle, and the flexible legs (63) can be bent at the leg joint (64); The radial drive ring (52) has a thermal expansion coefficient greater than that of the axial fixed seat (51). The inner circular surface of the radial drive ring (52) is fixed to the outside of the leg joint (64) of the axial fixed seat (51).

2. The heat-shrinkable joint according to claim 1, characterized in that, During the thermal deformation process, the radial drive ring (52) extends radially by ΔD, pulling the flexible support leg (63) to rotate around the support leg joint (64). The height of the flexible support leg (63) decreases by ΔH2, and ΔH2 matches the normal thermal deformation of the reflector mounting surface. The radial drive ring (52) satisfies the following: ΔH2=α*D*tanβ ΔD=α*D*ΔT α is the thermal expansion coefficient of the radial drive ring (52), D is the inner diameter of the radial drive ring (52), ΔT is the temperature change during the thermal deformation process, and β is the inclination angle of the flexible leg (63) relative to the plane of the radial drive ring (52).

3. The heat-shrinkable joint according to claim 1 or 2, characterized in that, The heat shrinkable joint satisfies at least one of the following: The axial fixing seat (51) has 4 to 8 flexible legs (63) evenly distributed in the circumferential direction; The axial fixing seat (51) is made of indium steel; Both the upper circular plate (61) and the lower circular plate (62) have a central hole. The two holes are coaxial and have the same diameter. This allows the mounting screws of the mirror support structure to pass through the central holes of the upper circular plate (61) and the lower circular plate (62) and connect to the telescope tube. The radial drive ring (52) is fixedly mounted to the outrigger joint (64) of the axial fixing seat (51) by means of locking pin (53) or adhesive pad (54).

4. The heat-shrinkable joint according to claim 3, characterized in that, When the radial drive ring (52) and the outrigger joint (64) are installed by the locking pin (53), the inner circular surface of the radial drive ring (52) matches the outer side of the outrigger joint (64) of the axial fixing seat (51), and the axial fixing seat (51) and the radial drive ring (52) are assembled without stress.

5. The heat-shrinkable joint according to claim 3, characterized in that, When installing the radial drive ring (52) and the outrigger joint (64) through the glue spot (54), a gap is left between the radial drive ring (52) and the axial fixing seat (51), and structural adhesive is injected through the glue injection hole.

6. An off-axis reflective inter-satellite laser communication telescope with high thermal stability, characterized in that, The device includes a reflector assembly, a telescope tube (35), and a heat-shrinkable joint as described in any one of claims 1 to 5. The reflector assembly includes a reflector and a reflector support structure. The reflector is mounted on the telescope tube (35) via the reflector support structure and the heat-shrinkable joint. The heat-shrinkable joint is connected between the reflector support structure and the telescope tube (35).

7. The laser communication telescope according to claim 6, characterized in that, When the temperature of the telescope tube (35) rises, the mounting surface of the reflector on the telescope tube (35) undergoes thermal deformation along the normal direction, with a deformation amount of ΔH1; the radial drive ring (52) of the thermal shrink joint generates radial elongation ΔD, satisfying: ΔH1-α*D*tanβ<ε ΔD=α*D*ΔT α is the thermal expansion coefficient of the radial drive ring (52), D is the inner diameter of the radial drive ring (52), ΔT is the temperature change during the thermal deformation process, β is the inclination angle of the flexible leg (63) relative to the plane of the radial drive ring (52), and ε is the temperature compensation error threshold.

8. The laser communication telescope according to claim 7, characterized in that, The selection of the heat shrinkable joint is constrained by the inner diameter D of the radial drive ring (52). Based on the compensation amount ΔH1 of the reflector mounting point, the thermal expansion coefficient α of the radial drive ring (52) and the leg tilt angle β are customized for the reflector mounting point to achieve accurate compensation for the thermal deformation displacement of the reflector assembly.

9. The laser communication telescope according to any one of claims 6 to 8, characterized in that, The reflector material is Si, microcrystalline or fused silica; the reflector support structure is made of titanium alloy or high volumetric aluminum-based silicon carbide; the reflector and the reflector support structure are bonded together with a thermally matched adhesive; the telescope tube (35) is made of high volumetric aluminum-based silicon carbide.

10. The laser communication telescope according to any one of claims 6 to 8, characterized in that, The number of the reflector assemblies is 4, namely the primary mirror assembly (31), the secondary mirror assembly (32), the third mirror assembly (33), and the fourth mirror assembly (34). The incident parallel beam is reflected by the off-axis quadric surface of the primary mirror assembly (31) to form a converging beam, which is then incident on the off-axis quadric surface of the secondary mirror assembly. The beam emitted from the secondary mirror is incident on the off-axis high-order aspherical surface of the third mirror assembly (33), and is reflected by the third mirror to form a beam. The beam is reflected by the off-axis quadric surface of the fourth mirror assembly (34) to form a zero field of view ray, which is perpendicular to the incident parallel light and is emitted from the light outlet to reach the image plane.

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