Double-color off-axis reflection type laser beam expanding lens for space

Abstract

The invention provides a two-color off-axis reflection type laser beam expanding lens for space, which comprises a transition plate module, a primary lens chamber, a primary lens barrel, a primary lens module, a first folding lens module, a second folding lens module and a secondary lens module, the first folding mirror module and the second folding mirror module enable light emitted by the two-color laser to be subjected to 90-degree folding twice, then an emergent optical axis is matched with geometric mechanical axes of the primary mirror module and the secondary mirror module, off-axis laser emission is completed, and a primary mirror in the primary mirror module and a secondary mirror in the secondary mirror module are parabolic reflecting surfaces and are plated with polarization-maintaining dielectric films. The output light of the second refraction mirror module is reflected by the secondary mirror and the primary mirror in sequence and then is emitted in a beam expanding mode, and the emergent light is quasi-parallel light. The off-axis clamping type double reflectors are used, chromatic aberration correction is not needed, a light path is not shielded, the system efficiency is guaranteed, no returned laser enters the laser, and the service life of the system is guaranteed; through thermodynamic structure simulation, the whole machine structure design is guided, the system environment adaptability is improved, the service life is prolonged, and the system thermal control cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a two-color off-axis reflective laser beam expanding lens for space use. Background Art

[0002] The spaceborne atmospheric sounding lidar receives and processes the backscattered echoes of the emitted laser from targets such as particles, aerosols, clouds, and atmospheric molecules in the atmosphere, and obtains large-scale, high-precision, and high-spatial-resolution optical parameter information of fine particles, aerosols, clouds, and atmospheric molecules on a global scale, including 532nm total attenuated backscatter, 1064nm total attenuated backscatter, color ratio (reflecting the particle size of the particles), and depolarization ratio (reflecting the particle shape of the particles).

[0003] The laser emission system is an important component of the lidar. For dual-color laser emission, the existing laser beam expansion lens cannot meet the high requirements of dual-color achromatism and sensitivity to environmental pollution, while also avoiding the problems of reduced system emission efficiency caused by central obstruction and reduced laser life caused by on-axis return light.

[0004] Therefore, a dual-color space laser beam expander lens is needed that can not only output dual-color lasers coaxially but also ensure the system emission efficiency and long-term high stability in orbit. Summary of the Invention

[0005] The present invention aims to solve the chromatic aberration and long-term stability problems of a two-color laser beam expander lens for space use. It provides a two-color off-axis reflective laser beam expander lens for space use. The lens uses an off-axis card-type double reflector, does not require chromatic aberration correction, and has no obstructions on the light path, ensuring system efficiency and preventing return laser from entering the laser, thereby ensuring system life. Through thermodynamic structure simulation, it guides the overall structural design, improves the system's environmental adaptability and service life, and reduces the system's thermal control cost.

[0006] The present invention provides a two-color off-axis reflective laser beam expander lens for space use, comprising a transition plate module, a primary mirror chamber, a primary mirror barrel, which are sequentially connected from back to front; a primary mirror module connected to the primary mirror chamber and located inside the primary mirror barrel; a first fold mirror module connected to the back center of the primary mirror chamber; a second fold mirror module connected to the outside of the transition plate module and located on the output light path of the first fold mirror module; and a secondary mirror module connected to the outside of the primary mirror barrel and located on the output light path of the second fold mirror module.

[0007] An opening is set in the middle of the transition plate module on the output optical path of the dual-color laser. The first folding mirror module is located on the output optical path of the dual-color laser. The first folding mirror module and the second folding mirror module both include 45° folding mirrors, so that the output light of the dual-color laser is folded twice by 90°, and the output optical axis is matched with the geometric mechanical axis of the primary mirror module and the secondary mirror module to complete the off-axis emission of the laser. The primary mirror in the primary mirror module and the secondary mirror in the secondary mirror module are both parabolic reflection surfaces and are both coated with polarization-maintaining dielectric films. The primary mirror is supported by a back center adhesive, and the secondary mirror is supported by a circumferential adhesive. The output light of the second folding mirror module is reflected by the secondary mirror and the primary mirror in sequence and then expanded and emitted, and the output light is quasi-parallel light.

[0008] The dual-color off-axis reflective laser beam expander lens has no vertical reflective surface in the optical path, with a beam expansion ratio greater than 10 times and a wavefront aberration RMS better than 63.28nm;

[0009] The two-color off-axis reflective laser beam expander lens was tested under gravity and temperature conditions to obtain the deformation of the optical element. Based on the deformation of the optical element, simulation was performed to obtain the beam expansion ratio under gravity and thermal effects. The beam expansion ratio under gravity and thermal effects still met the design requirements.

[0010] The present invention discloses a two-color off-axis reflective laser beam expander lens for space use. As a preferred embodiment, the primary mirror module includes a primary mirror, a primary mirror cone sleeve, and a primary mirror connector connected in sequence. A cone hole is provided at the back center of the primary mirror. The primary mirror cone sleeve is glued into the cone hole. The primary mirror connector has a convex structure at the front end and a flat structure at the rear end. The convex structure is embedded in the rear part of the cone hole. The flat structure is connected to the primary mirror chamber to support the primary mirror and the primary mirror cone sleeve.

[0011] The primary mirror is made of radiation-resistant quartz glass and coated with a 532nm and 1064nm polarization-maintaining dielectric film. The film has a reflection efficiency better than 99% and a damage threshold greater than or equal to 20J / cm 2 ;

[0012] The material of the primary mirror cone sleeve is 4J32 Invar, and its thermal expansion coefficient matches that of the primary mirror.

[0013] The present invention provides a two-color off-axis reflective laser beam expander lens for space use. As a preferred embodiment, the secondary mirror module includes a secondary mirror frame, an adjustment spacer, a support leg, and a secondary mirror connected to the secondary mirror frame.

[0014] The supporting legs are connected to the outside of the main mirror tube. The inner ring surface of the secondary mirror frame includes a glue injection ring and a glue injection hole arranged on the outside. Glue is injected into the secondary mirror and the glue injection ring through the glue injection hole to fix the secondary mirror frame by gluing.

[0015] The secondary mirror is coated with a 532nm and 1064nm polarization-maintaining dielectric film, with a reflection efficiency better than 99% and a damage threshold greater than or equal to 20J / cm 2 .

[0016] In the space-use two-color off-axis reflective laser beam expander lens of the present invention, as a preferred embodiment, the first folding mirror module includes a first folding mirror frame and a first folding mirror glued to the first folding mirror frame at a 45° incidence angle;

[0017] The first folding mirror frame is connected to the back of the main mirror chamber and is made of Invar. The first folding mirror is a quartz plane mirror coated with a 532nm and 1064nm polarization-maintaining dielectric film. The film has a reflection efficiency better than 99% and a damage threshold greater than or equal to 20J / cm. 2 .

[0018] The present invention provides a two-color off-axis reflective laser beam expander lens for space use. As a preferred embodiment, the second fold mirror module includes a second fold mirror frame, a fold mirror repair pad connected to the edge of the second fold mirror frame, and a second fold mirror glued to the second fold mirror frame at a 45° incidence.

[0019] The second folding mirror frame is connected to the outside of the transition plate module. The folding mirror training pad can adjust the incident light axis pointing angle of the beam expander. The second folding mirror is a quartz plane mirror coated with 532nm and 1064nm polarization-maintaining dielectric film. The film reflection efficiency is better than 99%, and the damage threshold is greater than or equal to 20J / cm 2 .

[0020] The present invention provides a two-color off-axis reflective laser beam expander lens for space use. As a preferred embodiment, the transition plate module includes a connecting plate and a grinding leg connected to the edge of the connecting plate;

[0021] The connecting plate is installed at the light outlet of the dual-color laser and an opening is set in the middle. Adjust the grinding legs to adjust the angle of the beam expander lens relative to the dual-color laser.

[0022] The material of the connecting plate is Al / SiC.

[0023] The present invention provides a two-color off-axis reflective laser beam expander lens for space use. As an optimal embodiment, both the primary mirror and the secondary mirror can withstand laser irradiation with a single pulse total energy of more than 250mJ.

[0024] The present invention provides a two-color off-axis reflective laser beam expander lens for space use. As an optimal embodiment, the primary mirror has an aperture of 166 mm, a focal length of 210 mm, and a curvature radius of 420 mm; the secondary mirror has an aperture of 11.06 mm, a focal length of 14 mm, and a curvature radius of 28 mm.

[0025] In the space-use two-color off-axis reflective laser beam expander lens of the present invention, as a preferred embodiment, the first fold mirror module, the second fold mirror module, and the secondary mirror module are all externally connected to a light shield;

[0026] The transition plate module, primary mirror chamber, primary mirror barrel, primary mirror module, first folding mirror module, second folding mirror module and secondary mirror module are all positioned using conical positioning pins and are all designed to be lightweight.

[0027] The present invention discloses a two-color off-axis reflective laser beam expander lens for space use. As a preferred embodiment, a gravity and temperature testing method for the two-color off-axis reflective laser beam expander lens is as follows: after assembling the two-color off-axis reflective laser beam expander lens, a heating plate and a thermistor are attached to the outside of the main lens barrel; the temperature of the main lens barrel is controlled to ensure the spacing between the primary mirror and the secondary mirror when in use; deformation cloud maps are analyzed by gravity in the X, Y, and Z directions to obtain deformation parameters of the primary and secondary mirrors in the X, Y, and Z directions, wherein the deformation parameters of the primary and secondary mirrors include: the RMS change in the primary mirror surface shape, the RMS change in the secondary mirror surface shape, the change in the inclination angle of the primary and secondary mirrors, and the change in the distance between the primary and secondary mirrors;

[0028] Apply 20℃±4℃ to obtain the deformation parameters of the lens under the temperature condition. The deformation parameters of the lens under the temperature condition include the RMS change of the primary mirror surface shape, the RMS change of the secondary mirror surface shape, the RMS change of the first fold mirror surface shape, the RMS change of the second fold mirror surface shape, the change of the primary and secondary mirror inclination angles, and the change of the primary and secondary mirror spacing;

[0029] Simulation is performed based on the deformation parameters of the primary and secondary mirrors in the X, Y and Z directions and the deformation parameters of the lenses under temperature conditions.

[0030] The present invention greatly improves the performance requirements of the satellite-borne atmospheric sounding lidar transmitting system, and can compress the emitted laser divergence angle into the receiving field of view angle while leaving sufficient adjustment margin.

[0031] The present invention realizes the function of expanding the high-energy laser output by a two-color laser for space use and compressing the divergence angle, solves the problem of the traditional coaxial reflective beam expander center blocking the laser energy, improves the laser emission efficiency, and simultaneously solves the problem of the coaxial return light of the coaxial reflective beam expander lens itself being amplified by the energy of the laser optical cavity and damaging the components inside the laser. Through mechanical and thermal simulation, the system structure is optimized and guided, and the system's on-orbit temperature stability in space is improved.

[0032] The present invention provides a two-color off-axis reflective laser beam expander lens for space use, comprising a primary mirror module, a secondary mirror module, a first folding mirror module, a second folding mirror module, a supporting primary mirror barrel, and a transition plate module. The lens adopts an off-axis card-type two-mirror design, wherein the primary and secondary mirror reflective surfaces are both parabolic, and the reflective mirror surfaces are coated with 532nm and 1064nm high damage threshold and high reflectivity dielectric films. The lens is used for expanding the beam of two-color high-energy emission lasers, and the beam expansion ratio is better than 10 times. The lens is designed by selecting structures and optical materials with on-orbit verification experience, and mechanical and thermal simulation is used to guide structural design and material selection, thereby improving the system's adaptability to on-orbit environments.

[0033] The present invention has the following advantages:

[0034] The present invention adopts an off-axis card-type double-reflector design, which does not require chromatic aberration correction. The off-axis method also eliminates the system center obstruction, ensuring system efficiency and no return laser entering the laser interior, thereby ensuring system life. The design structure fully considers lightweight and is light in weight. By selecting structural materials with on-orbit experience for design and using thermodynamic structure simulation to guide the overall structural design, the system's environmental adaptability and service life are improved, and the system's thermal control cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a structural stereogram of a two-color off-axis reflective laser beam expander lens for space use;

[0036] Figure 2 This is a three-dimensional exploded view of a two-color off-axis reflective laser beam expander lens for space use;

[0037] Figure 3 This is a design diagram of the optical path of a two-color off-axis reflective laser beam expander lens for space use;

[0038] Figure 4 An exploded view of the primary mirror module in a two-color off-axis reflective laser beam expander lens for space use;

[0039] Figure 5 This is a structural diagram of the secondary mirror module in a two-color off-axis reflective laser beam expander lens for space use;

[0040] Figure 6 This is a structural diagram of the second fold mirror module in a two-color off-axis reflective laser beam expander lens for space use;

[0041] Figure 7 This is a structural diagram of the first fold mirror module in a two-color off-axis reflective laser beam expander lens for space use;

[0042] Figure 8 This is a structural diagram of a transition plate module for a two-color off-axis reflective laser beam expansion lens for space use;

[0043] Figure 9 This is a diagram showing the wave phase difference measurement results of a two-color off-axis reflective laser beam expander lens system for space use;

[0044] Figure 10a This is a deformation cloud diagram of a two-color off-axis reflective laser beam expander lens for space use under the influence of gravity in the X direction.

[0045] Figure 10b This is a deformation cloud diagram of a two-color off-axis reflective laser beam expander lens for space use under the influence of gravity in the Y direction.

[0046] Figure 10cThis is a deformation cloud diagram of a two-color off-axis reflective laser beam expander lens for space use under the influence of gravity in the three Z directions.

[0047] Figure 11 This is a deformation cloud diagram of a two-color off-axis reflective laser beam expander lens for space use under temperature conditions;

[0048] Figure 12a Polarization-maintaining simulation for a two-color off-axis reflective laser beam expander lens for space use Figure 1 ;

[0049] Figure 12b Polarization-maintaining simulation for a two-color off-axis reflective laser beam expander lens for space use Figure 2 ;

[0050] Figure 13a The divergence angle test results of a two-color off-axis reflective laser beam expander lens for space use after thermal testing Figure 1 ;

[0051] Figure 13b The divergence angle test results of a two-color off-axis reflective laser beam expander lens for space use after thermal testing Figure 2 .

[0052] Reference numerals:

[0053] 1. Transition plate module; 11. Connecting plate; 12. Repair leg; 2. Primary mirror chamber; 3. Primary mirror barrel; 4. Primary mirror module; 41. Primary mirror; 42. Primary mirror cone sleeve; 43. Primary mirror connector; 5. First folding mirror module; 51. First folding mirror frame; 52. First folding mirror; 6. Second folding mirror module; 61. Second folding mirror frame; 62. Folding mirror repair pad; 63. Second folding mirror; 7. Secondary mirror module; 71. Secondary mirror frame; 72. Adjustment gasket; 73. Support leg; 74. Secondary mirror. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0055] Example 1

[0056] like Figures 1 to 9 As shown, a two-color off-axis reflective laser beam expander lens for space use is composed of independent modules such as a transition plate module 1, a primary mirror chamber 2, a primary mirror barrel 3, a primary mirror module 4, a first fold mirror module 5, a second fold mirror module 6, and a secondary mirror module 7. The laser is reflected by the first fold mirror 52, deflected 90° and incident on the reflective surface of the second fold mirror 63, deflected 90° and incident on the beam expander, and is reflected by the reflective surface of the secondary mirror 74 and the reflective surface of the primary mirror 41 in sequence to complete the laser beam expansion and emission;

[0057] The transition plate module 1 consists of three repair legs 12 (repair pads) and a connecting plate 11. The connecting plate 11 is installed at the laser light outlet to complete the docking of the entire beam expander lens and the laser. The repair leg 12 completes the adjustment of the installation angle of the entire beam expander lens relative to the laser. The connecting plate 11 is made of high-rigidity material Al / SiC, which has a low density while ensuring low mechanical and thermal deformation. The three repair legs 12 are mainly used to adjust the overall angle of the beam expander relative to the laser incident angle.

[0058] The primary mirror module 4 includes a primary mirror 41, a primary mirror cone sleeve 42, and a primary mirror connector 43. The primary mirror 41 adopts a lightweight circular ring design. The primary mirror 41 support adopts a back-center adhesive connection method. The primary mirror cone sleeve 42 is made of 4J32 Invar steel, which has a very small thermal expansion coefficient and is thermally matched with the primary mirror 41 material, achieving extremely small thermal deformation and thermal stress, and enhancing the module's temperature adaptability.

[0059] The first folding mirror module 5 and the second folding mirror module 6 are used to fold the angle of the outgoing laser, compensate for the off-axis amount between the outgoing optical axis and the optical axis of the beam expander, and adjust the angle at which the incident light enters the beam expander;

[0060] The first folding mirror module 5 includes a first folding mirror frame 51, a 45° first folding mirror 52 and a pressing ring. The first folding mirror frame 51 is an Invar frame and is fixed to the first folding mirror 52 by gluing. Its main function is to complete the deflection of the emitted laser light.

[0061] The second folding mirror module 6 includes a second folding mirror frame 61, a folding mirror training pad 62, a 45° second folding mirror 63 and a pressure ring. The folding mirror training pad 62 is used to adjust the incident light axis pointing angle of the beam expander;

[0062] The secondary mirror module 7 includes a secondary mirror frame 71, an adjustment spacer 72, a support leg 73, and a secondary mirror 74. The secondary mirror module 7 is fixed by the secondary mirror frame 71. The inner ring surface of the secondary mirror frame 71 is designed with a glue injection ring. Glue is injected into the glue injection ring on the inner ring surface of the secondary mirror frame 71 through an external glue injection hole to fix the secondary mirror 74 by gluing.

[0063] This embodiment adopts an off-axis card-type double-reflector design. The primary mirror 41 is non-axisymmetric. The primary mirror 41 and the secondary mirror 74 are both parabolic reflectors. Both the primary mirror 41 and the secondary mirror 74 are made of radiation-resistant quartz glass and are coated with a 532nm and 1064nm dual-color high-reflectivity, high-damage-threshold, polarization-maintaining dielectric film. The film can withstand single-pulse laser irradiation with a total energy of more than 250mJ without damage.

[0064] This embodiment uses two folding mirror modules to change the laser emission position, so that the emission optical axis matches the geometric mechanical axis of the beam expander, and the output is coaxial, which solves the problem of the optical axis and the mechanical axis being off-axis.

[0065] The primary mirror 41 is supported by adhesive bonding at the back center, and the secondary mirror 74 is supported by adhesive bonding in the annular direction;

[0066] The primary mirror 41 is fixed by adhesive support at the back center. Invar steel, which has a thermal expansion coefficient that matches that of the primary mirror 41, is used as the primary mirror cone sleeve 42 for bonding. By grinding the primary mirror cone sleeve 42 and the cone hole at the back of the primary mirror 41, the adhesive contact area is increased to better than 75%.

[0067] This embodiment is not axisymmetric as a whole, and the emitted laser needs to be folded twice;

[0068] The first fold mirror 52 and the second fold mirror 63 adopt a 45° incident surface design, and complete the off-axis emission of the laser through two 90° folds;

[0069] All lenses are coated with a high damage threshold polarization-maintaining film with a reflection efficiency better than 99% and a damage threshold of 20J / cm 2 @532&1064nm;

[0070] The off-axis beam expander in this embodiment has no central obstruction, and the efficiency of the dual-wavelength system is better than 98%. There is no vertical reflection surface in the optical path, and there is no problem of central reflection back into the laser optical cavity, thereby reducing the service life of the laser. The beam expansion ratio is better than 10 times.

[0071] This embodiment has a higher depolarization ratio and can well maintain the polarization state of the incident laser. The system depolarization ratio is better than 1%.

[0072] Through optical calibration and dimension angle measurement, and by refining the structure and pads of each part, a high-precision and high-stability optical system can be achieved, with the system wavefront aberration RMS better than 63.28nm.

[0073] The off-axis reflective beam expander lens of this embodiment uses tapered positioning pins between the parts to achieve high-precision positioning between the parts, meeting the requirements of repeated disassembly and assembly to ensure optical accuracy;

[0074] The dual-color off-axis reflective laser beam expander lens for space use in this embodiment adopts an off-axis reflective design to avoid the problem of dual-wavelength chromatic aberration. There is no central obstruction of the beam expander, so there is no obstruction on the laser transmission path, ensuring low loss of output laser energy.

[0075] Compared to on-axis reflective beam expanders, the dual-color off-axis reflective laser beam expander lens for space use in this embodiment has no return laser on the axis beam, and will not reflect part of the laser back into the laser optical cavity and amplify it, thereby causing damage to the internal components of the laser.

[0076] The spatial dual-color off-axis reflective laser beam expander lens of this embodiment adopts an afocal optical system design, that is, the focal length of the system is infinite, the incident laser is quasi-parallel light, and the output laser is also quasi-parallel light, but the aperture is larger and the divergence angle is compressed;

[0077] The spatial two-color off-axis reflective laser beam expander lens of this embodiment is optically designed using CODE V optical design software based on the input Gaussian laser parameters. The theoretical divergence angle of the incident laser is 1.5 mrad. The laser divergence angle after beam expansion needs to be compressed to within 110 μrad. Therefore, the geometric magnification of the designed system should be greater than 13.6 times, preferably 15 times. Due to the existence of errors in the actual processing of optical lenses, the geometric magnification of the actual object will be reduced.

[0078] The above space uses a two-color off-axis reflective laser beam expander lens. The incident Gaussian laser beam has an aperture of 7.5mm. According to the truncation effect of the aperture stop on the Gaussian beam, the lens aperture is determined to be no less than 1.45 times the spot diameter (corresponding to a truncation ratio of 2.2 and a transmittance of 98.8%). Therefore, the secondary mirror 74 has an aperture of 11.25 and the primary mirror 41 has an aperture of 168.75. Taking into account the engineering implementation and project size limitations, the primary mirror 41 has an aperture of 166mm and the secondary mirror 74 has an effective aperture of 11.06mm (off-axis amount of 6.67mm). The actual laser truncation ratio is 2.17 and the transmittance is no less than 98%.

[0079] In the spatial two-color off-axis reflective laser beam expander lens of this embodiment, the distance d between the primary mirror 41 and the secondary mirror 74 is 196 mm, where d is equal to the difference between the focal lengths of the primary mirror 41 and the secondary mirror 74. The geometric magnification is 15, so the focal length of the primary mirror 41 is 15 times the focal length of the secondary mirror 74, and the focal length of the secondary mirror 74 is 14 mm. The focal length of the primary mirror 41 is 210 mm, and the curvature radii of the primary mirror 41 and the secondary mirror 74 are twice the focal length. Therefore, the curvature radii of the primary mirror 41 and the secondary mirror 74 are 420 mm and 28 mm, respectively. The parabolic aspheric coefficient is -1. Finally, the lens is brought into the optical design software for optimization design.

[0080] The space-use dual-color off-axis reflective laser beam expander lens of this embodiment can realize a high-precision and high-stability optical system through optical calibration and dimension angle measurement, and through the repair and polishing of various structural parts and pads, and achieve a system wavefront aberration RMS better than 63.28nm.

[0081] This embodiment of the space-use dual-color off-axis reflective laser beam expander solves the problem of athermalization through precise mechanical and thermal simulation calculations, rational material selection, and structural design. This allows the system to adapt to a wide temperature range, ensuring on-orbit operational stability and reducing thermal control costs. Based on the off-axis optical design, the beam expander's structural layout utilizes a traditional main barrel support method to enhance structural symmetry and stability. The four optical reflector elements are made of glass-ceramic material, while the structural elements are constructed from commonly used space optomechanical materials such as titanium alloy, invar, and aluminum-based silicon carbide, meeting the rigidity, strength, and stability requirements of optomechanical systems for space use.

[0082] Structural design forms such as Figure 1 and Figure 3 As shown, the four reflectors are uniformly mounted and fixed on the main mirror barrel 3 and the main mirror chamber 2 structure, and then connected to the laser head mounting surface by the transition plate module 11. The outside of the main mirror barrel 3 is attached with a heating plate and a thermistor. By controlling the temperature of the main mirror barrel 3, the distance between the primary mirror 41 and the secondary mirror 74 when in use is guaranteed. Figures 10a to 10c The following table shows the deformation cloud diagrams of the beam expander lens in the X, Y and Z directions obtained by gravity analysis, and the deformation parameters of the primary mirror 41 and the secondary mirror 74 are shown.

[0083]

[0084]

[0085] Apply 20℃±4℃ temperature condition to the beam expander lens and get the following Figure 11 The deformation cloud diagram is shown, and the table below shows the deformation parameters of each lens under temperature conditions.

[0086]

[0087] The deformation of the system's optical components caused by the above working conditions was brought into the optical design software for simulation calculations. Under the combined effects of gravity and temperature conditions, the final system magnification increased from the initial design value of 15 times to 13.78 times, still meeting the design indicators. In addition, the local thermal control temperature range allocated to the entire satellite is 20℃±2℃, which leaves sufficient deformation margin for the overall structural design, ensuring its high on-orbit thermal stability.

[0088] In this embodiment of the space-use dual-color off-axis reflective laser beam expander lens, the primary mirror 41, the secondary mirror 74, the first folding mirror 52, and the second folding mirror 63 are all made of quartz material, which has strong radiation resistance, high film reflectivity, and high damage threshold, and can meet the needs of continuous high-energy laser irradiation without affecting its reflection efficiency.

[0089] The two-color off-axis reflective laser beam expander lens for space use in this embodiment has a good polarization-maintaining effect on the optical element film layer, which can achieve a depolarization ratio better than 1%. Figures 12a-12b The figure shows the simulated polarization state of the laser emitted by the beam expander. As can be seen from the figure, the outgoing polarization state is basically consistent with the incident polarization state, which can restore the polarization state of the outgoing laser to the greatest extent;

[0090] The space-use dual-color off-axis reflective laser beam expander lens of this embodiment adopts an open design. The first folding mirror module 5, the second folding mirror module 6 and the secondary mirror module 7 are all designed with light shielding covers to prevent scattered laser light from entering the human eye, thereby improving operation and use safety.

[0091] In this embodiment of the space dual-color off-axis reflective laser beam expander lens, tapered positioning pins are designed between each connecting part of the beam expander to meet the optical precision of repeated disassembly and assembly of the system;

[0092] The space dual-color off-axis reflective laser beam expander lens of this embodiment has a beam expansion ratio of better than 10 times. After the whole machine was subjected to thermodynamic tests, the divergence angle of the output light of the dual-wavelength laser and the dual-wavelength laser with a beam expander was measured using a spot analyzer. The average divergence angle measured by the former was 0.483mrad, and the latter was 0.038mrad. Figure 13a 、 13b As shown, the geometric beam expansion ratio of the beam expander is calculated to be 12.7 times;

[0093] In the space-use dual-color off-axis reflective laser beam expander lens of this embodiment, all components and modules are designed to be lightweight, achieving the maximum lightweight effect while ensuring the strength and rigidity requirements of the system.

[0094] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A two-color off-axis reflective laser beam expander lens for space use, characterized by: The invention comprises a transition plate module (1), a main mirror chamber (2), and a main mirror barrel (3) connected in sequence from back to front; a main mirror module (4) connected to the main mirror chamber (2) and located inside the main mirror barrel (3); a first folding mirror module (5) connected to the back center of the main mirror chamber (2); a second folding mirror module (6) connected to the outside of the transition plate module (1) and located on the output light path of the first folding mirror module (5); and a secondary mirror module (7) connected to the outside of the main mirror barrel (3) and located on the output light path of the second folding mirror module (6); The middle of the transition plate module (1) is provided with an opening on the light path of the dual-color laser output; the first folding mirror module (5) is located on the light path of the dual-color laser output; the first folding mirror module (5) and the second folding mirror module (6) both include 45° folding mirrors, so that the light output from the dual-color laser is folded twice by 90°, and the output optical axis is matched with the geometric mechanical axis of the primary mirror module (4) and the secondary mirror module (7), so as to complete the off-axis emission of the laser; the primary mirror in the primary mirror module (4) and the secondary mirror in the secondary mirror module (7) are both parabolic reflection surfaces and are both coated with polarization-maintaining dielectric films; the primary mirror is supported by adhesive bonding at the back center, and the secondary mirror is supported by adhesive bonding in the annular direction; the output light of the second folding mirror module (6) is reflected by the secondary mirror and the primary mirror in sequence, and then expanded and emitted, and the emitted light is quasi-parallel light; The dual-color off-axis reflective laser beam expander lens has no vertical reflective surface in the optical path, with a beam expansion ratio greater than 10 times and a wavefront aberration RMS better than 63.28nm; The dual-color off-axis reflective laser beam expander lens is subjected to gravity and temperature working condition tests to obtain the deformation of the optical element. Based on the deformation of the optical element, simulation is performed to obtain the beam expansion ratio under gravity and thermal effects. The beam expansion ratio under gravity and thermal effects still meets the design requirements.

2. The two-color off-axis reflective laser beam expander lens for space use according to claim 1, characterized in that: The primary mirror module (4) comprises a primary mirror (41), a primary mirror cone sleeve (42), and a primary mirror connecting piece (43) connected in sequence, a cone hole is provided at the center of the back of the primary mirror (41), the primary mirror cone sleeve (42) is glued into the cone hole, the primary mirror connecting piece (43) has a convex structure at the front end and a flat structure at the rear end, the convex structure is embedded in the rear part of the cone hole, and the flat structure is connected to the primary mirror chamber (2) and supports the primary mirror (41) and the primary mirror cone sleeve (42); The material of the primary mirror (41) is radiation-resistant quartz glass and is coated with a 532nm and 1064nm polarization-maintaining dielectric film, the film layer has a reflection efficiency better than 99%, and a damage threshold greater than or equal to 20J / cm 2 ; The primary mirror cone sleeve (42) is made of 4J32 Invar steel and has a thermal expansion coefficient that matches that of the primary mirror (41).

3. The two-color off-axis reflective laser beam expander lens for space use according to claim 1, characterized in that: The secondary mirror module (7) comprises a secondary mirror frame (71), an adjustment gasket (72), a support leg (73), and a secondary mirror (74) connected to the secondary mirror frame (71). The supporting legs (73) are connected to the outside of the main lens barrel (3); the inner ring surface of the secondary lens frame (71) includes a glue injection ring and a glue injection hole is arranged on the outside; glue is injected into the secondary lens (74) and the glue injection ring through the glue injection hole, and the secondary lens frame (71) is fixed in an adhesive manner; The secondary mirror (74) is coated with a 532nm and 1064nm polarization-maintaining dielectric film, the film layer has a reflection efficiency better than 99%, and a damage threshold greater than or equal to 20J / cm 2 .

4. The two-color off-axis reflective laser beam expander lens for space use according to claim 1, characterized in that: The first folding mirror module (5) comprises a first folding mirror frame (51) and a first folding mirror (52) glued to the first folding mirror frame (51) at a 45° incidence; The first folding mirror frame (51) is connected to the back of the main mirror chamber (2) and is made of invar. The first folding mirror (52) is a quartz plane mirror coated with a 532nm and 1064nm polarization-maintaining dielectric film. The film layer has a reflection efficiency better than 99% and a damage threshold greater than or equal to 20J / cm. 2 .

5. The two-color off-axis reflective laser beam expander lens for space use according to claim 1, characterized in that: The second folding mirror module (6) comprises a second folding mirror frame (61), a folding mirror training pad (62) connected to the edge of the second folding mirror frame (61), and a second folding mirror (63) glued to the second folding mirror frame (61) at a 45° incidence; The second folding mirror frame (61) is connected to the outside of the transition plate module (1); the folding mirror training pad (62) can adjust the incident light axis pointing angle of the beam expander; the second folding mirror (63) is a quartz plane mirror coated with a 532nm and 1064nm polarization-maintaining dielectric film; the film layer reflection efficiency is better than 99% and the damage threshold is greater than or equal to 20J / cm 2 .

6. The two-color off-axis reflective laser beam expander lens for space use according to claim 1, characterized in that: The transition plate module (1) comprises a connecting plate (11) and a grinding leg (12) connected to the edge of the connecting plate (11); The connecting plate (11) is installed at the light outlet of the dual-color laser and an opening is provided in the middle. The grinding legs (12) are adjusted to adjust the angle relationship of the beam expander lens unit relative to the dual-color laser unit. The connecting plate (11) is made of Al / SiC.

7. The two-color off-axis reflective laser beam expander lens for space use according to claim 1, characterized in that: Both the primary mirror and the secondary mirror can withstand laser irradiation with a single pulse total energy of more than 250 mJ.

8. The two-color off-axis reflective laser beam expander lens for space use according to claim 1, characterized in that: The primary mirror has an aperture of 166 mm, a focal length of 210 mm, and a radius of curvature of 420 mm. The secondary mirror has an aperture of 11.06 mm, a focal length of 14 mm, and a radius of curvature of 28 mm.

9. The two-color off-axis reflective laser beam expander lens for space use according to claim 1, characterized in that: The exteriors of the first folding mirror module (5), the second folding mirror module (6) and the secondary mirror module (7) are all connected to light shields; The transition plate module (1), the primary mirror chamber (2), the primary mirror barrel (3), the primary mirror module (4), the first folding mirror module (5), the second folding mirror module (6) and the secondary mirror module (7) are all positioned using conical positioning pins and are all lightweight in design.

10. The two-color off-axis reflective laser beam expander lens for space use according to claim 1, characterized in that: The gravity and temperature testing method of the dual-color off-axis reflective laser beam expander lens comprises the following steps: assembling the dual-color off-axis reflective laser beam expander lens, attaching a heating plate and a thermistor to the outside of the primary mirror barrel (3), controlling the temperature of the primary mirror barrel (3), ensuring the interval between the primary mirror and the secondary mirror when in use, analyzing the deformation cloud map in the X, Y and Z directions by gravity, and obtaining the deformation parameters of the primary and secondary mirrors in the X, Y and Z directions, wherein the deformation parameters of the primary and secondary mirrors include: the RMS of the primary mirror surface type change, the RMS of the secondary mirror surface type change, the inclination angle change of the primary and secondary mirrors, and the distance change of the primary and secondary mirrors; Applying 20°C ± 4°C to obtain deformation parameters of the lens under a temperature condition, wherein the deformation parameters of the lens under the temperature condition include the RMS change of the primary mirror surface shape, the RMS change of the secondary mirror surface shape, the RMS change of the first fold mirror surface shape, the RMS change of the second fold mirror surface shape, the change of the primary and secondary mirror inclination angles, and the change of the primary and secondary mirror spacing; The simulation is performed based on the deformation parameters of the primary and secondary mirrors in the X, Y and Z directions and the deformation parameters of the lenses under the temperature conditions.

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