A dual-color off-axis reflective laser beam expander for space use

Abstract

The application provides a spatial dual-color off-axis reflective laser beam expander lens, which comprises a transition plate module, a main mirror chamber, a main mirror barrel, a main mirror module, a first folding mirror module, a second folding mirror module and a secondary mirror module. The first folding mirror module and the second folding mirror module make the light emitted by the dual-color laser to be folded twice by 90 degrees, and then match the outgoing light axis with the geometric mechanical axis of the main mirror module and the secondary mirror module, thereby completing off-axis emission of the laser. The main mirror in the main mirror module and the secondary mirror in the secondary mirror module are both parabolic reflecting surfaces and are both coated with a polarization maintaining dielectric film. The output light of the second folding mirror module is expanded and emitted after being reflected by the secondary mirror and the main mirror in turn, and the emitted light is quasi-parallel light. The application uses an off-axis cassette type dual-reflection mirror, does not need to correct chromatic aberration, has no obstruction on the light path, ensures the system efficiency and has no return laser entering the laser interior, thereby ensuring the system life. Through thermodynamic structure simulation, the whole machine structure design is guided, the system environmental adaptability and service life are improved, and the system thermal control cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, in particular to a space dual-color off-axis reflective laser beam expander. BACKGROUND

[0002] The spaceborne atmospheric sounding laser radar obtains global large-scale, high-precision, high spatial resolution fine particulate matter, aerosol, cloud layer, and atmospheric molecule optical parameter information, including 532nm total attenuation backscattering, 1064nm total attenuation backscattering, color ratio (reflecting the size of particulate matter particles), and depolarization ratio (reflecting the shape of particulate matter particles), by receiving and processing backscattering echoes of emitted laser by particulate matter, aerosol, cloud layer, and atmospheric molecules in the atmosphere.

[0003] The laser emission system is an important component of the laser radar. For dual-color emitted laser, the existing laser beam expander cannot meet the high requirements of dual-color achromatism and environmental pollution sensitivity, while also avoiding the problems of reducing system emission efficiency and laser life caused by central obstruction.

[0004] Therefore, a dual-color space laser beam expander is needed, which can output dual-color laser coaxially and ensure system emission efficiency and long-term high stability in orbit. SUMMARY

[0005] The present application is to solve the chromatic aberration and long-term stability problem of the space dual-color laser beam expander, and provides a space dual-color off-axis reflective laser beam expander. The off-axis cassette double reflection mirror is used, without the need for chromatic aberration correction and no obstruction on the light path, ensuring system efficiency and no return laser entering the laser inside, ensuring system life. Through thermodynamic structure simulation, the whole machine structure design is guided, the system environmental adaptability and service life are improved, and the system thermal control cost is reduced.

[0006] The present application provides a space dual-color off-axis reflective laser beam expander, which comprises a transition plate module, a main mirror chamber, and a main mirror barrel connected in sequence from back to front, a main mirror module connected to the main mirror chamber and located inside the main mirror barrel, a first folding mirror module connected to the back of the center of the main mirror chamber, a second folding mirror module connected to the outside of the transition plate module and located on the output light path of the first folding mirror module, and a secondary mirror module connected to the outside of the main mirror barrel and located on the output light path of the second folding mirror module.

[0007] The middle of the transition plate module is provided with an opening on the light path of the double-color laser, the first folding mirror module is located on the output light path of the double-color laser, the first folding mirror module and the second folding mirror module each include a 45° folding mirror to make the light emitted by the double-color laser be folded twice by 90°, so that the light axis is matched with the geometric mechanical axis of the primary mirror module and the secondary mirror module, and the off-axis laser emission is completed, the primary mirror in the primary mirror module and the secondary mirror in the secondary mirror module are both parabolic reflecting surfaces and are both coated with a polarization maintaining dielectric film, the primary mirror is centrally glued and supported at the back, and the secondary mirror is annularly glued and supported, the output light of the second folding mirror module is expanded and emitted after being reflected by the secondary mirror and the primary mirror in turn, and the emitted light is quasi-parallel light;

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

[0009] The optical element deformation amount is obtained by performing gravity and temperature working condition tests on the double-color off-axis reflective laser beam expander lens, the beam expansion ratio under the action of gravity and heat is obtained through simulation according to the optical element deformation amount, and the beam expansion ratio under the action of gravity and heat still meets the design requirements.

[0010] As a preferred mode, the primary mirror module includes a primary mirror, a primary mirror cone sleeve and a primary mirror connecting piece connected in sequence, the back center of the primary mirror is provided with a tapered hole, the primary mirror cone sleeve is glued in the tapered hole, the front end of the primary mirror connecting piece is a convex structure, the rear end is a flat structure, the convex structure is embedded in the rear part of the tapered hole, and the flat structure is connected to the primary mirror chamber to support the primary mirror and the primary mirror cone sleeve.

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

[0012] The material of the primary mirror cone sleeve is 4J32 nickel steel, and the thermal expansion coefficient is matched with that of the primary mirror.

[0013] As a preferred mode, the secondary mirror module includes a secondary mirror frame, an adjusting gasket, a support leg and a secondary mirror connected in the secondary mirror frame.

[0014] The support leg is connected to the outside of the primary mirror barrel, the inner ring surface of the secondary mirror frame includes a glue injection ring and an outer glue injection hole, the secondary mirror is glued in the glue injection ring through the glue injection hole, and the secondary mirror frame is fixed in a glued manner.

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

[0016] The space dual-color off-axis reflective laser beam expander lens comprises a first mirror module, a second mirror module, a transition plate module, a main mirror and a secondary mirror.

[0017] The first mirror frame is connected to the back of the main mirror chamber and is made of invar steel, the first mirror is a quartz plane mirror coated with 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 .

[0018] The space dual-color off-axis reflective laser beam expander lens comprises a first mirror module, a second mirror module, a transition plate module, a main mirror and a secondary mirror.

[0019] The second mirror frame is connected to the outside of the transition plate module, the mirror polishing pad can adjust the incident optical axis pointing angle of the beam expander, the second mirror is a quartz plane mirror coated with 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 .

[0020] The space dual-color off-axis reflective laser beam expander lens comprises a first mirror module, a second mirror module, a transition plate module, a main mirror and a secondary mirror.

[0021] The connecting plate is installed at the light outlet of the dual-color laser and is provided with an opening in the middle, and the polishing leg is used to adjust the angle relationship between the beam expander and the dual-color laser.

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

[0023] The space dual-color off-axis reflective laser beam expander lens comprises a first mirror module, a second mirror module, a transition plate module, a main mirror and a secondary mirror.

[0024] The space dual-color off-axis reflective laser beam expander lens comprises a first mirror module, a second mirror module, a transition plate module, a main mirror and a secondary mirror.

[0025] The space dual-color off-axis reflective laser beam expander lens comprises a first mirror module, a second mirror module, a transition plate module, a main mirror and a secondary mirror.

[0026] The transition plate module, the primary mirror chamber, the primary mirror barrel, the primary mirror module, the first folding mirror module, the second folding mirror module and the secondary mirror module are positioned by using taper positioning pins and are subjected to lightweight design.

[0027] The gravity and temperature test method of the dual-color off-axis reflective laser beam expander lens for space use is preferably as follows: after the dual-color off-axis reflective laser beam expander lens is assembled, a heating sheet and a thermistor are pasted outside the primary mirror barrel, the interval of the primary mirror and the secondary mirror in use is ensured by controlling the temperature of the primary mirror barrel, the deformation cloud atlas in the X, Y and Z directions is obtained by analyzing the gravity in the X, Y and Z directions, and the primary and secondary mirror deformation parameters in the X, Y and Z directions are obtained, the primary and secondary mirror deformation parameters include: primary mirror surface change amount RMS, secondary mirror surface change amount RMS, primary and secondary mirror inclination angle change and primary and secondary mirror spacing change amount.

[0028] The deformation parameters of the lens under temperature conditions are obtained by applying 20 DEG C+ / -4 DEG C, and the deformation parameters of the lens under temperature conditions include: primary mirror surface change amount RMS, secondary mirror surface change amount RMS, first folding mirror surface change amount RMS, second folding mirror surface change amount RMS, primary and secondary mirror inclination angle change and primary and secondary mirror spacing change amount.

[0029] The simulation is performed according to the primary and secondary mirror deformation parameters in the X, Y and Z directions and the deformation parameters of the lens under temperature conditions.

[0030] The performance requirement of the spaceborne atmospheric detection laser radar transmitting system is greatly improved, and the transmitting laser divergence angle can be compressed into the receiving field of view and has sufficient adjustment margin.

[0031] The application realizes the functions of expanding and compressing the divergence angle of the high-energy laser output by the dual-color laser for space use, solves the problem of central obstruction of the traditional coaxial reflective beam expander lens, improves the laser transmitting efficiency, solves the problems of the coaxial return light of the coaxial reflective beam expander lens damaging the internal devices of the laser, and the like, optimizes and guides the system structure through force and thermal simulation work, and improves the space on-orbit temperature stability of the system.

[0032] The application provides a dual-color off-axis reflective laser beam expander lens for space use, which comprises a primary mirror module, a secondary mirror module, a first folding mirror module, a second folding mirror module, a support primary mirror barrel and a transition plate module.

[0033] The application has the following advantages:

[0034] The application is a off-axis cassette double mirror design, without chromatic aberration correction; off-axis mode also makes no system center obstruction, ensuring system efficiency and no return laser into the laser inside, ensuring system life; design structure fully considers lightweight, light weight; by selecting structural materials with on-orbit experience for design, and through thermodynamic structure simulation, guiding the whole machine structure design, improving system environmental adaptability and service life, reducing system thermal control cost. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a structure perspective view of a space dual-color off-axis reflective laser beam expander lens;

[0036] Figure 2 It is a three-dimensional explosion view of a space dual-color off-axis reflective laser beam expander lens;

[0037] Figure 3 It is a light path design diagram of a space dual-color off-axis reflective laser beam expander lens;

[0038] Figure 4 It is an explosion view of a main mirror module in a space dual-color off-axis reflective laser beam expander lens;

[0039] Figure 5 It is a secondary mirror module structure diagram in a space dual-color off-axis reflective laser beam expander lens;

[0040] Figure 6 It is a second folding mirror module structure diagram in a space dual-color off-axis reflective laser beam expander lens;

[0041] Figure 7 It is a first folding mirror module structure diagram in a space dual-color off-axis reflective laser beam expander lens;

[0042] Figure 8 It is a transition plate module structure diagram of a space dual-color off-axis reflective laser beam expander lens;

[0043] Figure 9 It is a system wave phase difference measurement result diagram of a space dual-color off-axis reflective laser beam expander lens;

[0044] Figure 10a It is a deformation cloud picture of a space dual-color off-axis reflective laser beam expander lens in X direction affected by gravity;

[0045] Figure 10b It is a deformation cloud picture of a space dual-color off-axis reflective laser beam expander lens in Y direction affected by gravity;

[0046] Figure 10cIt is a deformation cloud chart of a space dual-color off-axis reflective laser beam expander lens Z three directions affected by gravity

[0047] Figure 11 It is a deformation cloud chart of a space dual-color off-axis reflective laser beam expander lens under temperature working condition

[0048] Figure 12a It is a space dual-color off-axis reflective laser beam expander lens polarization simulation Figure 1 ;

[0049] Figure 12b It is a space dual-color off-axis reflective laser beam expander lens polarization simulation Figure 2 ;

[0050] Figure 13a It is a space dual-color off-axis reflective laser beam expander lens divergence angle test result after thermodynamic test Figure 1 ;

[0051] Figure 13b It is a space dual-color off-axis reflective laser beam expander lens divergence angle test result after thermodynamic test Figure 2 .

[0052] Reference signs:

[0053] 1, transition plate module; 11, connecting plate; 12, dressing leg; 2, main mirror chamber; 3, main mirror barrel; 4, main mirror module; 41, main mirror; 42, main mirror cone sleeve; 43, main mirror connecting piece; 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 dressing pad; 63, second folding mirror; 7, secondary mirror module; 71, secondary mirror frame; 72, adjusting gasket; 73, support leg; 74, secondary mirror. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all.

[0055] Embodiment 1

[0056] As shown in the drawings, Figures 1 to 9 a space dual-color off-axis reflective laser beam expander lens is composed of transition plate module 1, main mirror chamber 2, main mirror barrel 3, main mirror module 4, first folding mirror module 5, second folding mirror module 6, secondary mirror module 7 and other independent modules, laser is reflected by first folding mirror 52 mirror surface, is incident to second folding mirror 63 reflecting surface by 90° folding, is incident into the beam expander by 90° folding, and is reflected by secondary mirror 74 reflecting surface and main mirror 41 reflecting surface in turn, and laser beam expansion is completed and is emitted;

[0057] The transition plate module 1 is composed of three polishing legs 12 and a connecting plate 11, the connecting plate 11 is installed at the light outlet of the laser, and the connecting plate 11 is used to complete the butt joint of the whole beam expander lens and the laser, and the polishing legs 12 are used to adjust the installation angle of the whole beam expander lens relative to the laser; the connecting plate 11 is made of high-rigidity material Al / SiC, which has low thermal deformation and low density; the three polishing legs 12 are mainly used to adjust the laser incidence angle of the whole beam expander lens;

[0058] The primary mirror module 4 includes a primary mirror 41, a primary mirror cone sleeve 42 and a primary mirror connecting piece 43; the primary mirror 41 adopts a circular ring light weight design, the primary mirror 41 is supported by a back center glue bonding connection mode, the primary mirror cone sleeve 42 is made of 4J32 invar steel material, has a very small thermal expansion coefficient, and is thermally matched with the primary mirror 41 material, so as to realize very small thermal deformation and thermal stress, and enhance the temperature adaptability of the module;

[0059] The first folding mirror module 5 and the second folding mirror module 6 are used to complete the folding function of the outgoing laser angle, compensate the off-axis amount of the outgoing optical axis and the beam expander lens optical axis, and adjust the angle of the incident light entering the beam expander lens;

[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 steel mirror frame, which is fixed with the first folding mirror 52 by gluing, and mainly functions to complete the folding of the outgoing laser;

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

[0062] The secondary mirror module 7 includes a secondary mirror frame 71, an adjusting gasket 72, a supporting 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, the secondary mirror 74 is injected with glue in the glue injection ring of the inner ring surface of the secondary mirror frame 71 through an external glue injection hole, and the secondary mirror 74 is fixed by gluing;

[0063] The embodiment adopts an off-axis cassette type two-mirror design, the primary mirror 41 is non-axially symmetrical, and the primary mirror 41 and the secondary mirror 74 are both parabolic reflecting surfaces; the primary mirror 41 and the secondary mirror 74 are made of anti-radiation quartz glass material, and are coated with 532nm and 1064nm double-color high-reflectivity, high-damage threshold and polarization-maintaining dielectric films, which can resist laser irradiation with a single pulse total energy of 250mJ or more without damaging the film layer;

[0064] The embodiment adopts two folding mirror modules to change the outgoing position of the laser, so that the outgoing optical axis is matched with the geometric mechanical axis of the beam expander lens, and coaxial output is realized, thereby solving the problem of off-axis of the optical axis and the mechanical axis;

[0065] The primary mirror 41 is supported by a back center adhesive support, and the secondary mirror 74 is supported by a ring adhesive support;

[0066] The primary mirror 41 is fixed by a back center adhesive support, and a steel material matching the thermal expansion coefficient of the primary mirror 41 is selected as the adhesive primary mirror cone sleeve 42, the primary mirror cone sleeve 42 and the back cone hole of the primary mirror 41 are ground, the adhesive contact area is increased, and the adhesive contact area is more than 75%;

[0067] The embodiment is overall non-axially symmetric, and the outgoing laser needs to be folded twice;

[0068] The first folding mirror 52 and the second folding mirror 63 are designed with a 45° incidence surface, and the off-axis laser is emitted through two 90° folding;

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

[0070] The off-axis beam expander of the embodiment does not have a central obstruction, and the efficiency of the dual-wavelength system is more than 98%; there is no vertical reflecting surface in the optical path, and there is no central reflection of light back to the optical cavity of the laser, thereby reducing the service life of the laser, and the beam expansion ratio is more than 10 times;

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

[0072] Through optical calibration and size angle measurement, each part of the structure is ground and the pad is ground, so that a high-precision and high-stability optical system can be realized, and the system wavefront aberration RMS is more than 63.28 nm;

[0073] The off-axis reflective beam expander lens of the embodiment adopts a conical positioning pin between the parts, realizes high-precision positioning between the parts, and meets the requirements of repeated disassembly and guarantee of optical precision;

[0074] The space dual-color off-axis reflective laser beam expander lens of the embodiment adopts an off-axis reflective design, avoids the problem of dual-wavelength chromatic aberration, does not have a central obstruction of the beam expander, and ensures low loss of outgoing laser energy without an obstruction in the transmission path of the laser;

[0075] Compared with the on-axis reflective beam expander lens, the on-axis beam does not have a return laser, and part of the laser is not reflected back to the optical cavity of the laser and amplified, thereby causing damage to the internal devices of the laser;

[0076] The spatial dual-color off-axis reflective laser beam expander lens of the embodiment adopts an afocal optical system design, i.e., the focal length of the system is infinite, the incident laser is quasi-parallel light, and the outgoing light is also quasi-parallel light, only the aperture is enlarged, and the divergence angle is compressed;

[0077] The spatial dual-color off-axis reflective laser beam expander lens of the embodiment is designed by using CODE V optical design software according to input Gaussian laser parameters, the theoretical divergence angle of the incident laser is 1.5 mrad, and the divergence angle of the laser after beam expansion needs to be compressed to within 110 μrad, so the geometric magnification of the designed system should be greater than 13.6 times, and 15 times is taken, and due to the existence of errors in actual machining of the optical lens, the geometric magnification of the actual object will decrease;

[0078] The spatial dual-color off-axis reflective laser beam expander lens has an incident Gaussian laser beam aperture of 7.5 mm, according to the truncation effect of the aperture stop on the Gaussian beam, it is determined that the lens aperture should be not less than 1.45 times the diameter of the spot (corresponding to a truncation ratio of 2.2 and a transmittance of 98.8%), so the aperture of the secondary mirror 74 is determined to be 11.25, and the aperture of the primary mirror 41 is determined to be 168.75, considering the engineering implementation and the size limitation of the project, the aperture of the primary mirror 41 is determined to be 166 mm, and the effective aperture of the secondary mirror 74 is determined to be 11.06 mm (the off-axis amount is 6.67 mm), the actual laser truncation ratio is 2.17, and the transmittance is not less than 98%;

[0079] The spatial dual-color off-axis reflective laser beam expander lens has a distance d between the primary mirror 41 and the secondary mirror 74 of 196 mm, d is equal to the difference between the focal length of the primary mirror 41 and the focal length of the secondary mirror 74, and 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, the focal length of the secondary mirror 74 is 14 mm, the focal length of the primary mirror 41 is 210 mm, the curvature radius of the primary mirror 41 and the secondary mirror 74 is 2 times the focal length, so the curvature radius of the primary mirror 41 and the secondary mirror 74 is 420 mm and 28 mm respectively, the parabolic asphericity coefficient is -1, and finally the optical design software is used for optimization design;

[0080] The spatial dual-color off-axis reflective laser beam expander lens can realize high-precision and high-stability optical system through optical calibration and size and angle measurement, and realize system wavefront aberration RMS better than 63.28 nm;

[0081] The space dual-color off-axis reflective laser beam expander lens of the embodiment solves the problem of system athermalization through precise force-thermal simulation calculation, reasonable material selection and structural design form, makes the system have a very wide temperature adaptation range, ensures the stability of the system in orbit and reduces the cost of thermal control. According to the off-axis optical design form, the structure layout of the beam expander mirror adopts the traditional main mirror barrel support mode to strengthen the structural symmetry and stability; the four optical mirror elements are made of microcrystalline glass material, and the structural elements are made of titanium alloy, nickel steel, aluminum-based silicon carbide and other commonly used space optical machine structural materials, which meet the requirements of stiffness, strength and stability of the optical machine system for space use.

[0082] The structural design form is shown in Figure 1 and Figure 3 The four mirrors are uniformly installed 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 heating sheet and thermistor are pasted on the outside of the main mirror barrel 3 to ensure the interval of the main mirror 41 and the secondary mirror 74 in use. As shown in Figures 10a to 10c The X, Y and Z direction gravity analysis deformation cloud chart of the beam expander lens is shown in the following table.

[0083]

[0084]

[0085] The beam expander lens is subjected to a temperature condition of 20℃±4℃, and the deformation cloud chart is shown in Figure 11 The following table shows the deformation parameters of each lens under the temperature condition.

[0086]

[0087] The deformation amount of the system optical element caused by the above working conditions is brought into the optical design software for simulation operation. Under the combined action of gravity and temperature condition, the final system magnification changes from the initial design value of 15 times to 13.78 times, which still meets the design index. The local thermal control temperature range of the whole satellite is 20℃±2℃, which leaves enough deformation allowance for the whole machine structure design, and can ensure its high in-orbit force-thermal stability.

[0088] The space dual-color off-axis reflective laser beam expander lens of the embodiment adopts quartz material for the main mirror 41, the secondary mirror 74, the first folding mirror 52 and the second folding mirror 63, which has strong radiation resistance, high film reflectivity and high damage threshold, and can meet the requirements of continuous high-energy laser irradiation without affecting the reflection efficiency.

[0089] The space dual-color off-axis reflective laser beam expander lens of the embodiment has good polarization maintaining effect of the optical element film layer, which can realize a polarization extinction ratio better than 1%, as shown inFigures 12a to 12b The simulation diagram of the polarization state of the laser emitted by the beam expander is shown in the figure, and it can be seen that the polarization state of the emitted laser is basically consistent with the polarization state of the incident laser, and the polarization state of the emitted laser can be restored to the maximum extent.

[0090] The spatial dual-color off-axis reflective laser beam expander of the embodiment adopts an open design, and light shields are designed outside the first folding mirror module 5, the second folding mirror module 6 and the secondary mirror module 7 to prevent scattered laser from entering the human eye and improve the operation and use safety.

[0091] The spatial dual-color off-axis reflective laser beam expander of the embodiment is provided with a conical positioning pin between each connecting piece of the beam expander, so as to meet the optical precision of repeated disassembly and assembly of the system.

[0092] The spatial dual-color off-axis reflective laser beam expander of the embodiment has a beam expansion ratio of more than 10 times, and after the whole machine is subjected to a thermodynamic test, a spot analyzer is used to measure the divergence angle of the emitted light of the dual-wavelength laser and the dual-wavelength laser after the beam expander, respectively, the average value of the divergence angle measured by the former is 0.483 mrad, and the average value of the divergence angle measured by the latter is 0.038 mrad, as shown in Figure 13a 、 13b The geometric beam expansion ratio of the beam expander is calculated to be 12.7 times.

[0093] The spatial dual-color off-axis reflective laser beam expander of the embodiment is lightweight designed, and the system strength and rigidity requirements are ensured while the maximum lightweight effect is achieved.

[0094] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A two-color off-axis catadioptric laser beam expander for space applications, characterized in that: The double-color off-axis reflective laser beam expander lens comprises, from back to front, a transition plate module (1), a main mirror chamber (2), a main mirror barrel (3), 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 of the 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 transition plate module (1) is provided with an opening located on the light output path of the double-color laser, the first folding mirror module (5) is located on the output light path of the double-color laser, the first folding mirror module (5) and the second folding mirror module (6) each comprise a 45° folding mirror, so that the light output by the double-color laser is folded twice by 90°, and the exiting light axis is matched with the geometric mechanical axis of the main mirror module (4) and the secondary mirror module (7), so that the off-axis laser is exited, the main mirror in the main mirror module (4) and the secondary mirror in the secondary mirror module (7) are both parabolic reflecting surfaces and are both coated with a polarization maintaining dielectric film, the main mirror is supported by glue at the back center, and the secondary mirror is supported by glue in a ring shape, the output light of the second folding mirror module (6) is reflected by the secondary mirror and the main mirror in sequence and then expanded and exited, and the exited light is quasi-parallel light; The double-color off-axis reflective laser beam expander lens has no vertical reflecting surface in the optical path, the beam expansion ratio is greater than 10 times, and the wavefront aberration RMS is better than 63.28 nm; The optical element deformation amount is obtained by performing gravity and temperature working condition tests on the double-color off-axis reflective laser beam expander lens, the beam expansion ratio under the action of gravity and heat is obtained through simulation according to the optical element deformation amount, and the beam expansion ratio under the action of gravity and heat still meets the design requirements; The main mirror module (4) comprises a main mirror (41), a main mirror cone sleeve (42) and a main mirror connecting piece (43) connected in sequence, the back center of the main mirror (41) is provided with a tapered hole, the main mirror cone sleeve (42) is glued in the tapered hole, the front end of the main mirror connecting piece (43) is a protruding structure, the rear end is a flat structure, the protruding structure is embedded in the rear part of the tapered hole, and the flat structure is connected to the main mirror chamber (2) and supports the main mirror (41) and the main mirror cone sleeve (42); The material of the main mirror (41) is anti-radiation quartz glass and is coated with 532 nm and 1064 nm polarization maintaining dielectric films, the film layer reflection efficiency is better than 99%, and the damage threshold is greater than or equal to 20 J / cm 2 ; The material of the main mirror cone sleeve (42) is 4J32 nickel steel, and the thermal expansion coefficient is matched with that of the main mirror (41).

2. The two-color off-axis reflective laser beam expander for space application according to claim 1, wherein: The secondary mirror module (7) comprises a secondary mirror frame (71), an adjusting gasket (72), a support leg (73) and a secondary mirror (74) connected in the secondary mirror frame (71) in sequence; The support leg (73) is connected to the outside of the main mirror barrel (3), the inner ring surface of the secondary mirror frame (71) comprises a glue injection ring and is provided with a glue injection hole outside, the secondary mirror (74) is injected with glue in the glue injection ring through the glue injection hole, and the secondary mirror frame (71) is fixed in a glued manner; The secondary mirror (74) is coated with 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 .

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

4. The two-color off-axis reflective laser beam expander for space application according to claim 1, wherein: The second folding mirror module (6) comprises a second folding mirror frame (61), a folding mirror polishing pad (62) connected to the edge of the second folding mirror frame (61), and a second folding mirror (63) cemented in the second folding mirror frame (61) at an incident angle of 45°; The second folding mirror frame (61) is connected outside the transition plate module (1), the folding mirror adjusting pad (62) can adjust the incident light axis pointing angle of the expander, and the second folding mirror (63) is a quartz plane mirror coated with 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 .

5. The two-color off-axis reflective laser beam expander for space application according to claim 1, wherein: The transition plate module (1) comprises a connecting plate (11) and a polishing 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 has an opening in the middle, and the polishing leg (12) is adjusted to adjust the angle relationship of the entire beam expander lens relative to the entire dual-color laser. The material of the connecting plate (11) is Al / SiC.

6. The two-color off-axis reflective laser beam expander for space application according to claim 1, wherein: The main mirror and the secondary mirror can resist laser irradiation with a total energy of 250mJ or more per pulse.

7. The two-color off-axis reflective laser beam expander for space application according to claim 1, wherein: The main mirror has an aperture of 166mm, a focal length of 210mm, and a curvature radius of 420mm, and the secondary mirror has an aperture of 11.06mm, a focal length of 14mm, and a curvature radius of 28mm.

8. The two-color off-axis reflective laser beam expander for space application according to claim 1, wherein: 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 main mirror chamber (2), the main mirror barrel (3), the main 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 designed to be lightweight.

9. The two-color off-axis reflective laser beam expander for space application according to claim 1, wherein: The gravity and temperature testing method of the dual-color off-axis reflective laser beam expander lens comprises the following steps: after the dual-color off-axis reflective laser beam expander lens is assembled, heating sheets and thermistors are pasted outside the main mirror barrel (3), the interval between the main mirror and the secondary mirror in the use state is ensured by controlling the temperature of the main mirror barrel (3), the X, Y, and Z direction deformation cloud maps are obtained by analyzing the gravity in the X, Y, and Z directions, and the X, Y, and Z direction deformation parameters of the main mirror and the secondary mirror are obtained, including the main mirror surface type change amount RMS, the secondary mirror surface type change amount RMS, the main and secondary mirror inclination angle change, and the main and secondary mirror spacing change amount; The deformation parameters of the lens under the temperature condition of 20℃±4℃ are obtained, including the main mirror surface type change amount RMS, the secondary mirror surface type change amount RMS, the first folding mirror surface type change amount RMS, the second folding mirror surface type change amount RMS, the main and secondary mirror inclination angle change, and the main and secondary mirror spacing change amount; The simulation is performed according to the X, Y, and Z direction deformation parameters of the main mirror and the secondary mirror and the deformation parameters of the lens under the temperature condition.

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