Thermal shrinkage shaft joint and off-axis reflection type high-thermal-stability inter-satellite laser communication telescope

Abstract

The invention discloses a thermal shrinkage shaft joint and an off-axis reflection type inter-satellite laser communication telescope with high thermal stability. The axial fixing seat comprises a circular upper plate, a circular lower plate, a plurality of flexible supporting legs and supporting leg joints; the circular upper plate is connected with the reflector supporting structure, and the circular lower plate is connected with the telescope barrel; the flexible supporting legs are connected between the circular upper plate and the circular lower plate; a supporting leg joint is arranged in the middle of the flexible supporting leg, and the flexible supporting leg can be bent at the supporting leg joint; the thermal expansion coefficient of the radial driving ring is larger than that of the axial fixing base, and the inner circle face of the radial driving ring is fixed to the outer side of the supporting leg joint. In the laser communication telescope, a reflecting mirror is arranged on a telescope barrel through a reflecting mirror supporting structure and a thermal shrinkage shaft joint, and the thermal shrinkage shaft joint is connected between the reflecting mirror supporting structure and the telescope barrel. The axial thermal displacement of the thermal shrinkage shaft joint is changed by adjusting the thermal expansion coefficient and size of the radial driving ring and the included angle of the supporting legs of the axial fixing seat, so that the position stability of each mounting point is ensured.

Description

Technical Field

[0001] The present application relates to the technical field of optical-mechanical structures of space optical remote sensors, and in particular to a heat shrinkable shaft joint and an off-axis reflective high thermal stability intersatellite laser communication telescope. Background Art

[0002] In recent years, with the rapid development of intersatellite laser communication technology and the construction of large-scale constellations, the demand for intersatellite laser communication terminals has exploded. The telescope is a key component of the intersatellite laser communication terminal. The design requires good optical imaging quality, light weight, small envelope size, and good adaptability to the space thermal environment. The telescope adopts an off-axis four-mirror optical system. The primary mirror and the secondary mirror form the objective lens, the third mirror and the fourth mirror form the eyepiece, and the four reflector assemblies are centrally installed on the same support structure, which effectively reduces the envelope size and weight. The primary, secondary and fourth mirrors are quadratic surfaces, and the third mirror is a high-order aspheric surface. The surface accuracy and position accuracy stability of the reflector are key factors affecting the performance of the optical system. In order to achieve the requirement that the system wavefront is 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). Since the laser terminal telescope is installed outside the satellite cabin, it is affected by the surrounding heat source and solar radiation, and temperature fluctuations and uneven temperature distribution occur during the operation of the laser terminal telescope. The temperature change causes thermal deformation of the optical-mechanical structure, which ultimately leads to instability in the system transmission and beam divergence, affecting the efficiency of intersatellite communication. The laser terminal telescope can only work normally within a very narrow temperature range, so a complex thermal control design is made to ensure this, which increases the power consumption of the satellite and the risk of optical payload contamination. Summary of the invention

[0003] The present application provides a heat shrinkable shaft joint and an off-axis reflective high thermal stability intersatellite laser communication telescope, the purpose of which is to solve the problem of thermal stability support of the laser communication terminal telescope.

[0004] In a first aspect, a heat shrinkable shaft joint is provided, comprising:

[0005] The axial fixing seat comprises a circular upper plate, a circular lower plate, a plurality of flexible legs, and a leg joint; 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 legs, and the flexible legs can be bent at the leg joint;

[0006] A radial drive ring, the thermal expansion coefficient of the radial drive ring is greater than the thermal expansion coefficient of the axial fixing seat, and the inner circular surface of the radial drive ring is fixed on the outer side of the leg joint of the axial fixing seat.

[0007] In combination with the first aspect, in certain implementations of the first aspect, during the thermal deformation process, the radial drive ring radially extends ΔD, pulling the flexible legs to rotate around the leg joints, and the height of the flexible legs decreases by ΔH2, ΔH2 matches the normal thermal deformation 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 thermal expansion coefficient of the material of the radial driving ring, D is the inner diameter of the radial driving 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 driving ring is located.

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

[0012] There are 4 to 8 flexible legs evenly distributed in the circumferential direction of the axial fixing seat;

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

[0014] The circular upper plate and the circular lower plate are both provided with circular holes in the center, the two circular holes are coaxially arranged, and the apertures are equal, so that the mounting screws of the reflector support structure pass through the central circular holes of the circular upper plate and the central circular holes of the circular lower plate to be connected with the telescope tube;

[0015] The radial drive ring is fixedly installed with the leg joint of the axial fixing seat through a locking pin or a rubber spot.

[0016] In combination with the first aspect, in certain implementations of the first aspect, when the radial drive ring and the leg joint are installed through the locking pin, the inner circular surface of the radial drive ring matches the outer side of the leg joint of the axial fixing seat, and there is stress-free assembly between the axial fixing seat and the radial drive ring.

[0017] In combination with the first aspect, in certain implementations of the first aspect, when the radial drive ring and the leg joint are installed through the glue spot, a gap is left between the radial drive ring and the axial fixing seat, and structural glue is injected through the glue injection hole.

[0018] In a second aspect, an off-axis reflective high thermal stability intersatellite laser communication telescope is provided, comprising a reflector assembly, a telescope barrel and a heat shrink joint as described in any one of the implementations of the first aspect above, wherein the reflector assembly comprises a reflector and a reflector support structure, the reflector is arranged on the telescope barrel via the reflector support structure and the heat shrink joint, and the heat shrink joint is connected between the reflector support structure and the telescope barrel.

[0019] In combination with the second aspect, in some implementations of the second aspect, when the temperature of the telescope barrel increases, the mounting surface of the reflector on the telescope barrel undergoes thermal deformation along the normal direction, and the deformation amount is ΔH1; the radial drive ring of the heat shrinkable shaft generates a radial elongation ΔD, satisfying:

[0020] ΔH1-α*D*tanβ<ε

[0021] ΔD=α*D*ΔT

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

[0023] In combination with the second aspect, in certain implementations of the second aspect, the selection of the heat shrink joint is based on the inner diameter D of the radial drive ring as a constraint condition, and according to the compensation amount ΔH1 of the reflector mounting point, the radial drive ring thermal expansion coefficient α and the leg inclination angle β are customized for the reflector mounting point to achieve precise compensation for the thermal deformation displacement of the reflector assembly.

[0024] In combination with the second aspect, in certain implementations of the second aspect, the reflector material is Si, microcrystals or fused quartz; the reflector support structure is made of titanium alloy or high volume fraction aluminum-based silicon carbide; the reflector and the reflector support structure are bonded with a blended adhesive with matching thermal properties; and the telescope barrel is made of high volume fraction aluminum-based silicon carbide.

[0025] In combination with the second aspect, in certain implementations of the second aspect, the number of the reflector assemblies is 4, namely a primary mirror assembly, a secondary mirror assembly, a three-mirror assembly, and a four-mirror assembly; the incident parallel light beam is reflected by the off-axis quadratic surface of the primary mirror assembly to form a converging light beam, which is incident on the off-axis quadratic surface of the secondary mirror assembly. The secondary mirror output light beam is incident on the off-axis high-order aspheric surface of the three-mirror assembly and forms a light beam after reflection by the three mirrors. The light beam is reflected by the off-axis quadratic surface of the four-mirror assembly to form a zero-field-of-view ray, which is perpendicular to the incident parallel light and reaches the image plane after being emitted from the light outlet.

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

[0027] The present invention relates to a small and medium-caliber off-axis quadruple-reflector intersatellite laser communication terminal telescope, and provides an off-axis telescope structure based on thermal deformation reverse compensation, which has high temperature environment adaptability. The off-axis reflector support structure based on thermal deformation reverse compensation proposed by the present invention realizes adaptive adjustment under the conditions of temperature fluctuation and uneven temperature distribution, has strong environmental adaptability and high stability, and ensures that the laser terminal telescope works stably in a wide temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0033] Figure 6 It is a schematic diagram of the heat shrinkable shaft joint coordinate system and parameter definition. DETAILED DESCRIPTION

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

[0035] Figure 1 and Figure 2 The present invention shows an off-axis reflective intersatellite laser communication telescope with high thermal stability. The intersatellite laser communication telescope is an off-axis four-reflector terminal telescope for laser communication terminals, comprising a primary mirror 1, a secondary mirror 2, a third mirror 3, and a fourth mirror 4. The incident parallel light beam 21 is reflected by the primary mirror 1 (off-axis quadratic surface) to form a convergent light beam 22, which is incident on the secondary mirror 2 (off-axis quadratic surface). The secondary mirror output light beam 23 is incident on the third mirror 3 (off-axis high-order aspheric surface). Light rays of different fields of view are reflected by the third mirror to form a light beam 24. The light beam is reflected by the fourth mirror 4 (off-axis quadratic surface) to form a zero-field light beam 25 perpendicular to the incident parallel light, which is emitted from the light outlet 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 triple mirror assembly 33 (corresponding to triple mirror 3), a quad mirror assembly 34 (corresponding to quad mirror 4) and a telescope barrel 35. Each reflector assembly includes a reflector and a reflector support structure, and the reflector is arranged on the telescope barrel 35 through the reflector support structure. The reflector material can be Si, microcrystalline or fused quartz. The reflector support structure can be made of titanium alloy or high volume fraction aluminum-based silicon carbide. The reflector and the reflector support structure can be bonded by a blending adhesive with matching thermal properties. The telescope barrel 35 can be made of high volume fraction aluminum-based silicon carbide.

[0037] The off-axis four-mirror optical system has extremely high requirements on the position accuracy of the mirror spacing and the surface accuracy. The thermal performance matching of the mirror and the supporting structure material can ensure the surface accuracy index of several microns. The position accuracy is ensured by installing a thermal compensation structure between the mirror assembly and the telescope barrel 35.

[0038] The telescope is fixed on the satellite scanning mechanism through the interface flange 6, and the four-mirror assembly 34 is close to the installation interface. The thermal deformation of the telescope barrel 35 mainly affects the 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. The position accuracy is ensured by installing a heat shrinkable shaft joint with a thermal deformation reverse compensation function between the primary mirror assembly 31, the secondary mirror assembly 32, the third mirror assembly 33 and the telescope barrel 35.

[0039] Figure 3 The 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 comprises an axial fixing seat 51 and a radial driving ring 52.

[0040] Figure 4 The schematic structural diagram of the axial fixing seat 51 of the heat shrinkable shaft joint. The axial fixing seat 51 can be made of indium steel with a low thermal expansion coefficient. The axial fixing seat 51 includes a circular upper plate 61 with a central hole, a circular lower plate 62 with a central hole, a flexible leg 63, and a leg joint 64. The circular upper plate 61 is used to connect with the reflector support structure of the reflector assembly, and the circular lower plate 62 is used to connect with the telescope barrel 35. The circular upper plate 61 and the circular lower plate 62 both have a circular hole in the center, the two circular holes are coaxially arranged, and the aperture d is equal. The mounting screws of the reflector support structure pass through the central circular hole of the circular upper plate 61 and the central circular hole of the circular lower plate 62, and are connected to the telescope barrel 35. The flexible leg 63 is connected between the circular upper plate 61 and the circular lower plate 62 by integrated processing or welding. A leg joint 64 is provided in the middle of the flexible leg 63, and the flexible leg 63 can be bent at the leg joint 64. According to the connection stiffness requirement, 4 to 8 flexible legs 63 may be evenly distributed in the circumferential direction of the axial fixing seat 51 .

[0041] Figure 5 The schematic structural diagram of two radial drive rings 52 of the heat shrinkable shaft joint. The radial drive ring 52 can be made of a material with a high thermal expansion coefficient α, and is installed with the axial fixing seat 51 through a locking pin 53 or a high-strength rubber spot 54. Figure 5 The left side of FIG. 5 shows a radial drive ring 52 for mounting via a locking pin 53 . Figure 5 The right side of FIG. 4 shows a radial drive ring 52 for mounting via a high strength adhesive bead 54 .

[0042] When installing through the locking pin 53, the inner circumference of the radial drive ring 52 cooperates with the outer side of the leg joint 64 of the axial fixing seat 51 to ensure that there is approximately no stress between the axial fixing seat 51 and the radial drive ring 52. When installing with the 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 adhesive injection hole.

[0043] Figure 6 The coordinate system of the heat shrink joint is shown. When the temperature of the telescope barrel 35 rises, the mounting surface of the reflector on the telescope barrel 35 undergoes thermal deformation along the normal direction (corresponding to the +Y direction of the heat shrink joint coordinate system), and the deformation amount is ΔH1, which drives the reflector to deviate in the +Y direction. At the same time, the radial drive ring 52 of the heat shrink joint produces a radial extension ΔD,

[0044] ΔD=α*D*ΔT

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

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

[0047] The radial drive ring 52 drives the leg joint 64 to stretch outward by ΔD, and the flexible leg 63 rotates around the leg joint 64, and the height H of the flexible leg 63 decreases by ΔH2, thereby compensating for the translation 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 leg joint 64), the thermal expansion coefficient α of the radial drive ring 52 material, and the inclination angle β of the flexible leg 63 relative to the plane where the radial drive ring 52 is located can be approximately expressed as the following formula:

[0048] ΔH1≈α*D*tanβ

[0049] The leg inclination angle β and the thermal expansion coefficient α of the radial drive ring 52 are variables. With 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 inclination angle β of the flexible leg 63 can be customized for each reflector mounting point according to the compensation amount ΔH1 of each reflector mounting point, so as to achieve precise compensation for the thermal deformation displacement of the reflector assembly. This ensures that the laser terminal telescope can work stably in a wide temperature range.

[0050] In summary, the laser communication terminal telescope optical system provided by the present invention includes a primary mirror assembly, a secondary mirror assembly, a three-mirror assembly, a four-mirror assembly and a telescope barrel. The primary, secondary, three-mirror and four-mirror assemblies are centrally installed on the telescope barrel, which highly compresses the envelope size of the telescope and achieves the design goal of small volume and light weight. The telescope barrel is used as the main support structure of the main body. The aluminum-based silicon carbide material with ultra-high thermal conductivity is used. In order to meet the requirements of laser communication for high isolation, the primary mirror, the secondary mirror, the three-mirror and the four-mirror are selected from silicon, microcrystalline and fused quartz with good surface finish. The reflector support structure adopts titanium alloy or aluminum-based silicon carbide that matches the thermal properties of the barrel material to avoid the extrusion stress caused by thermal deformation of different materials from affecting the reflector surface shape. A heat shrink shaft joint with a reverse compensation function for thermal deformation is installed between the primary mirror assembly, the secondary mirror assembly, the three-mirror assembly, the four-mirror assembly and the telescope barrel. The heat shrink shaft joint is composed of an axial fixing seat and a radial driving ring, and the axial fixing seat and the radial driving ring are fixed by screws or structural adhesive. The axial fixing seat is directly connected to the telescope tube. The structural form is to design 4 to 8 legs with adjustable angles and uniform distribution around the circumference between the upper and lower plates. Flexible joints are set on the legs to release the rotational freedom of the legs around the center of the telescopic ring section. The axial fixing seat adopts indium steel with low thermal expansion coefficient to reduce the thermal deformation of the axial fixing seat. The radial drive ring adopts a material with a high expansion coefficient. When the temperature rises, the telescope tube is extended, and the reflector mounting surface is thermally deformed along the normal direction, causing the reflector to translate along the optical axis + Z direction. The radial drive ring in the heat shrink shaft joint is extended radially, driving the axial fixing seat to shorten axially, which is opposite to the thermal deformation direction of the mounting surface, compensating for the position offset of the reflector caused by thermal deformation. The thermal deformation of each installation point is different. The axial thermal displacement of the heat shrink shaft joint can be changed by adjusting the thermal expansion coefficient and size of the radial drive ring and the angle of the axial fixing leg to ensure the position stability of each installation point.

[0051] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may 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 shall be based on the scope defined by the claims of the present invention.

Claims

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

2. The heat shrinkable joint according to claim 1, characterized in that: During the thermal deformation process, the radial drive ring (52) radially extends by ΔD, pulling the flexible legs (63) to rotate around the leg joints (64), and the height of the flexible legs (63) decreases by ΔH2, ΔH2 matching the normal thermal deformation of the reflector mounting surface, and the radial drive ring (52) satisfies: ΔH2=α*D*tanβ ΔD=α*D*ΔT α is the thermal expansion coefficient of the material 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 where the radial drive ring (52) is located.

3. The heat shrinkable joint according to claim 1 or 2, characterized in that: The heat shrinkable joint meets at least one of the following requirements: The axial fixing seat (51) is evenly distributed with 4 to 8 flexible legs (63) in the circumferential direction; The axial fixing seat (51) is made of indium steel; The circular upper plate (61) and the circular lower plate (62) are both provided with circular holes at the center, the two circular holes are coaxially arranged and have equal apertures, and are used to allow the mounting screws of the reflector support structure to pass through the central circular holes of the circular upper plate (61) and the central circular holes of the circular lower plate (62) to be connected to the telescope tube; The radial drive ring (52) is fixedly mounted on the leg joint (64) of the axial fixing seat (51) via a locking pin (53) or a rubber spot (54).

4. The heat shrinkable joint according to claim 3, characterized in that: When the radial drive ring (52) and the leg joint (64) are installed through the locking pin (53), the inner circumferential surface of the radial drive ring (52) matches the outer side of the leg 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 the radial drive ring (52) and the leg joint (64) are installed through the adhesive 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 adhesive injection hole.

6. An off-axis reflective intersatellite laser communication telescope with high thermal stability, characterized in that: The invention comprises a reflector assembly, a telescope barrel (35) and a heat shrink joint as claimed in any one of claims 1 to 5, wherein the reflector assembly comprises a reflector and a reflector support structure, the reflector is arranged on the telescope barrel (35) via the reflector support structure and the heat shrink joint, and the heat shrink joint is connected between the reflector support structure and the telescope barrel (35).

7. The laser communication telescope according to claim 6, characterized in that: When the temperature of the telescope tube (35) rises, the reflector mounting surface on the telescope tube (35) undergoes thermal deformation along the normal direction, with a deformation amount of ΔH1; the heat shrinkable shaft radial drive ring (52) produces a radial elongation ΔD, satisfying: ΔH1-α*D*tanβ<ε ΔD=α*D*ΔT α is the thermal expansion coefficient of the material 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 where the radial drive ring (52) is located, 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 shaft joint is based on the inner diameter D of the radial drive ring (52) as a constraint condition. According to the compensation amount ΔH1 of the reflector mounting point, the thermal expansion coefficient α of the radial drive ring (52) and the leg inclination angle β are customized for the reflector mounting point, thereby realizing 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, microcrystal or fused quartz; the reflector support structure is made of titanium alloy or high volume fraction aluminum-based silicon carbide; the reflector and the reflector support structure are bonded by a blending adhesive with matching thermal properties; and the telescope tube (35) is made of high volume fraction 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 components is 4, which are respectively a primary mirror component (31), a secondary mirror component (32), a third mirror component (33), and a fourth mirror component (34); an incident parallel light beam is reflected by the off-axis quadratic surface of the primary mirror component (31) to form a convergent light beam, which is incident on the off-axis quadratic surface of the secondary mirror component; an output light beam from the secondary mirror is incident on the off-axis high-order aspheric surface of the third mirror component (33), which is reflected by the third mirror to form a light beam; and the light beam is reflected by the off-axis quadratic surface of the fourth mirror component (34) to form a zero-field-of-view ray, which is perpendicular to the incident parallel light and is emitted from a light outlet to reach an image plane.

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