All-aluminum free-form surface off-axis low-temperature infrared optical lens and its assembly and adjustment method

Abstract

The present invention relates to an infrared optical lens and an installation method thereof, and specifically to an all-aluminum free-form surface off-axis low-temperature infrared optical lens and an installation method thereof, which are used to solve the shortcomings of existing low-temperature infrared optical lenses, such as small imaging field of view, large shielding ratio, and low engineering feasibility. The all-aluminum free-form surface off-axis low-temperature infrared optical lens effectively utilizes space to reduce mutual shielding between optical elements, so that light can propagate and form images within a larger field of view, significantly increasing the imaging field of view of the system; and a free-form surface mirror is used, and each reflector is eccentric and tilted with respect to the optical axis. Compared with a coaxial four-reflection optical system, cold reflection self-imaging of the detector will not occur, and there is no center shielding.

Description

Technical Field

[0001] The invention relates to an infrared optical lens and an installation and adjustment method thereof, and in particular to an all-aluminum free-form surface off-axis low-temperature infrared optical lens and an installation and adjustment method thereof. Background Art

[0002] Infrared detection systems perform well in complex environments and are particularly suitable for fields such as remote sensing and navigation. They have the advantages of high detection accuracy, low false alarm rate, and all-day / all-weather detection. In order to improve the sensitivity of infrared detection systems, especially the detection of weak targets at long distances, cryogenic optical technology is usually used to reduce the thermal radiation noise of the system itself. However, cryogenic optical technology faces major technical challenges in practical applications, namely, the environmental differences between the processing and assembly of optical systems at room temperature and pressure and when used in a cryogenic vacuum environment may lead to a decline in imaging quality.

[0003] There are two main technical means to solve the problem:

[0004] (1) Select appropriate optical and supporting structure materials to ensure that the components of the detection system can expand and contract in the same proportion at different temperatures to avoid defocusing. This method is applicable to all-reflective optical systems, such as the IRAS, Spitzer, Herschel, and GAIA telescopes. These systems usually use beryllium or silicon carbide as materials. However, this method has extremely high requirements in terms of material selection, processing, and assembly, and the cost and cycle time are also relatively high.

[0005] (2) A focusing mechanism is used to compensate for image plane defocus caused by temperature and pressure changes. This method is applicable to both catadioptric and transmissive optical systems, but it fails to solve the problem of decreased detection performance caused by changes in lens surface shape in a low-temperature vacuum environment. At the same time, the reliability of the focusing mechanism also faces challenges due to the extreme working environment.

[0006] Chinese patent CN113804311A and Chinese patent CN102004297A respectively adopt focusing mechanism and optical flat plate adjustment method to compensate for the defocus of low-temperature optics, but these methods do not consider the problem of decreased detection performance caused by changes in lens surface shape in a complex low-temperature vacuum environment; Chinese patent CN102902063A discloses a low-temperature optics room-temperature adjustment method and device using phase plate compensation, but this method requires the design and processing of phase plates (diffraction plates), and is only applicable to optical systems with a sufficiently large back focus, and has poor applicability; Chinese patent CN102338922A proposes an all-aluminum fully-reflective optical lens, which solves the problem of decreased detection performance caused by inconsistent material linear expansion coefficients of light and machine parts in a low-temperature vacuum environment, but the optical system has problems such as small imaging field of view and large occlusion ratio. Summary of the invention

[0007] The purpose of the present invention is to solve the shortcomings of existing low-temperature infrared optical lenses, such as small imaging field of view, large shielding ratio and low engineering feasibility, and to provide an all-aluminum free-form surface off-axis low-temperature infrared optical lens and an assembly method thereof.

[0008] In order to solve the deficiencies in the prior art, the present invention provides the following technical solutions:

[0009] An all-aluminum free-form surface off-axis low-temperature infrared optical lens, comprising an optical system and a supporting frame; the special features thereof are:

[0010] The optical system comprises a mirror surfaces which are arranged in sequence along the optical path and are all free-form surface off-axis reflectors, where a is an integer greater than or equal to 3;

[0011] The support frame is a hollow shell of a straight multi-prism structure, and the number of side edges b of the support frame is greater than or equal to 4; the support frame includes b side surfaces connected in sequence, and the a mirror surfaces are respectively arranged on the side surfaces of the support frame through corresponding mirror bodies, and at least two mirror bodies are provided with cylindrical bosses on the reverse sides, and the outer end surfaces of the cylindrical bosses are parallel to the side surfaces where they are located, and the side walls of the cylindrical bosses are provided with planes for ensuring the phase of the corresponding mirror surfaces, thereby facilitating quantitative adjustment;

[0012] Light path holes are provided on the c side surfaces for light to enter and output, 2≤c<b; frame mounting lugs are provided at the lower ends of the d side surfaces, 3≤d≤b, and a frame mounting hole is provided on each frame mounting lug along a direction perpendicular to the bottom surface of the supporting frame;

[0013] The support frame, all mirror surfaces and corresponding mirror bodies, cylindrical bosses, and frame mounting lugs are all made of aluminum alloy.

[0014] Furthermore, the mirror body having a cylindrical boss on the reverse side has a plurality of reflector mounting lugs and a first stress unloading groove on its outer periphery;

[0015] Flexible grooves are provided at the connection between the front and back surfaces of each reflector mounting lug and the mirror body, and an adjustment gasket is provided between each reflector mounting lug and the side surface, and the adjustment gasket is used to adjust the angle and position of the corresponding mirror surface.

[0016] Furthermore, mounting holes for mounting the mirror body are provided on at least two side surfaces of the support frame.

[0017] At the same time, the present invention also provides an all-aluminum free-form surface off-axis low-temperature infrared optical lens, including an optical system and a supporting frame; the special features of the lens are:

[0018] The optical system comprises three mirror surfaces which are arranged in sequence along the optical path and are all free-form surface off-axis reflectors;

[0019] The support frame is a hollow shell of a straight multi-prism structure, and the number of side edges of the support frame is 4 or 5; the support frame includes 4 or 5 side surfaces connected in sequence, and the three mirror surfaces are respectively arranged on the side surfaces of the support frame through corresponding mirror bodies, and at least two mirror bodies are provided with cylindrical bosses on the reverse sides, and the outer end surfaces of the cylindrical bosses are parallel to the side surfaces where they are located, and the side walls of the cylindrical bosses are provided with planes for ensuring the phase of the corresponding mirror surfaces, thereby facilitating quantitative adjustment;

[0020] At least two side surfaces are provided with light path holes for light entry and output; at least three side surfaces are provided with frame mounting lugs at the lower ends, and each frame mounting lug is provided with a frame mounting hole in a direction perpendicular to the bottom surface of the supporting frame;

[0021] The support frame, all mirror surfaces and corresponding mirror bodies, cylindrical bosses, and frame mounting lugs are all made of aluminum alloy.

[0022] Furthermore, the three mirrors are respectively a first mirror, a second mirror and a third mirror arranged in sequence along the optical path; the first mirror, the second mirror and the third mirror are respectively arranged on the side of the supporting frame through a first mirror body, a second mirror body and a third mirror body;

[0023] The third mirror surface is arranged on the front side of the third mirror body, the cylindrical boss is arranged on the back side, and a plurality of reflector mounting lugs are arranged on the periphery; the first mirror surface is arranged on the front side of the first mirror body, the third mirror body is arranged on one of the side surfaces of the supporting frame, and the first mirror body is connected to the third mirror body;

[0024] The second mirror surface is arranged on the front side of the second mirror body, the cylindrical boss is arranged on the back side, and a plurality of reflector mounting lugs and a first stress unloading groove are arranged on the outer periphery;

[0025] An adjustment gasket is arranged between each reflector mounting lug and the side surface where it is located, and the adjustment gasket is used to adjust the angle and position of the corresponding mirror surface.

[0026] Further, the number b of the side edges of the support frame is equal to 5, the support frame includes a first side surface, a second side surface, a third side surface, a fourth side surface and a fifth side surface connected in sequence, the second side surface and the fifth side surface are parallel to each other and perpendicular to the first side surface, and the first side surface and the third side surface are respectively provided with a third mirror body mounting hole and a second mirror body mounting hole adapted to the third mirror body and the second mirror body;

[0027] The light path holes are arranged on the third side surface, the fourth side surface and the fifth side surface;

[0028] A second stress unloading groove is provided at the connection between the first mirror body and the third mirror body;

[0029] The outer peripheries of the second mirror body and the third mirror body are both provided with first stress unloading grooves;

[0030] A flexible groove is provided at the connection between the front and back surfaces of each reflector mounting lug and the third mirror body or the second mirror body.

[0031] Further, the frame mounting lug is provided at the connection between the lower end of the second side surface and the first side surface, the frame mounting lug is provided at the connection between the lower end of the second side surface and the third side surface, the frame mounting lug is provided at the connection between the lower end of the fourth side surface and the third side surface, and the frame mounting lug is provided at the connection between the lower end of the fifth side surface and the first side surface.

[0032] The present invention also provides a method for assembling and adjusting the above-mentioned all-aluminum free-form surface off-axis low-temperature infrared optical lens, which is special in that it includes the following steps:

[0033] Step 1: Build an assembly and adjustment system on the optical platform, the assembly and adjustment system including an articulated arm measuring instrument, a 4D interferometer, an aperture, the above-mentioned all-aluminum free-form surface off-axis low-temperature infrared optical lens, and a spherical mirror or a plane mirror;

[0034] Step 2, setting each mirror surface on the side of the support frame through the corresponding mirror body;

[0035] Step 3: Define the first coordinate system for the support frame ,origin For one of the frame mounting lugs, The surface coincides with the side of the third mirror arranged in sequence along the optical path. The surface coincides with the bottom surface of the supporting frame;

[0036] Define the second coordinate system for the mirror surface with a cylindrical boss on the reverse side of the mirror body ,origin Located at the intersection of the central axis and the outer end surface of the cylindrical boss, The surface coincides with the outer end surface. The surface is parallel to the bottom surface; and the coordinates of the geometric center point of each mirror surface are defined as , the coordinates of the intersection of the central axis of each mirror body and the outer wall of the side surface are , the coordinates of the intersection of the central axis of the cylindrical boss and the outer end surface are ; Subscript Indicates the first Mirror, Pick integer in range;

[0037] The second coordinate system Next , , Transform to the first coordinate system Next, we get the first coordinate system The corresponding , , Theoretical value;

[0038] Step 4: For the mirror surface with a cylindrical boss on the reverse side of the mirror body, use the articulated arm measuring instrument to measure the Next , , The actual value is adjusted to the preset coordinate tolerance with the theoretical value obtained in step 3, thereby ensuring the center spacing between the mirror surfaces.

[0039] Then the plane is measured by the articulated arm measuring instrument to make it correspond to the second coordinate system of axis, axis, The roll, pitch and azimuth angles between the axes are ≯1′;

[0040] Step 5: Use a 4D interferometer to detect the transmission wavefront of the optical system after adjustment to determine whether the transmission wavefront of the central field of view and the transmission wavefront of the full field of view meet the preset requirements. If so, the adjustment of the all-aluminum free-form surface off-axis low-temperature infrared optical lens is completed; otherwise, return to step 4.

[0041] Furthermore, the step 1 is specifically as follows:

[0042] The support frame is fixed on the optical platform through the frame mounting lugs, and then the 4D interferometer with the plane standard mirror is fixed on the object plane of the optical system of the above-mentioned all-aluminum free-form surface off-axis low-temperature infrared optical lens, and the spherical mirror is fixed on the focal plane of the optical system; then the diaphragm is fixed at the corresponding position of the detector cold diaphragm, and the articulated arm measuring instrument is fixed on the optical platform;

[0043] Alternatively, the support frame is fixed on the optical platform through the frame mounting lugs, and then the 4D interferometer equipped with the spherical standard mirror is fixed on the focal plane of the optical system of the above-mentioned all-aluminum free-form surface off-axis low-temperature infrared optical lens, and the plane mirror is fixed on the object plane of the optical system; then the aperture is fixed at the corresponding position of the detector cold aperture, and the articulated arm measuring instrument is fixed on the optical platform;

[0044] In step 4, the difference between the theoretical value obtained in step 3 is adjusted to within a preset coordinate tolerance to ensure the center spacing between the mirror surfaces. Specifically, the thickness of the gasket is adjusted by grinding to achieve the center spacing requirement between the mirror surfaces.

[0045] Furthermore, the method further comprises step 6: fixing the upper cover plate on the top surface of the supporting frame.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) The all-aluminum free-form surface off-axis low-temperature infrared optical lens of the present invention effectively utilizes space and reduces mutual occlusion between optical elements, so that light can propagate and form images within a larger field of view, significantly increasing the imaging field of view of the system; and the free-form surface mirror is adopted, and each reflector is eccentric and tilted with respect to the optical axis. Compared with the coaxial four-mirror optical system, cold reflection self-imaging of the detector will not occur, and there is no center occlusion.

[0048] (2) The present invention adopts all-aluminum alloy materials to manufacture the mirror body and support frame, which has the advantages of light weight, high strength, and easy processing, which is conducive to the manufacture and installation of the system; and it is easier to achieve athermal design, so that it can still maintain good imaging quality or detection performance in a wide dynamic temperature environment of -150℃~+80℃.

[0049] (3) The one-piece design of the support frame in the present invention improves the mechanical stability of the system and reduces the complexity of installation and maintenance.

[0050] (4) The present invention takes into account the mechanical structure, optical performance and environmental adaptability as a whole in its design to ensure the integrity and reliability of the system; and the modular design and high-precision adjustment mechanism make system maintenance more convenient, reducing the maintenance requirements caused by environmental changes or errors in use.

[0051] (5) The assembly and adjustment method of the all-aluminum free-form surface off-axis low-temperature infrared optical lens of the present invention adopts an articulated arm measuring instrument to assist in assembly. Compared with traditional assembly, it can realize intelligent auxiliary assembly and greatly shorten the assembly and adjustment cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a schematic structural diagram of an embodiment of an all-aluminum free-form surface off-axis low-temperature infrared optical lens of the present invention;

[0053] Figure 2 is a schematic diagram of an optical path of an embodiment of the present invention;

[0054] Figure 3 An axonometric view of a support frame in an embodiment of the present invention;

[0055] Figure 4 is a cross-sectional view of a support frame in an embodiment of the present invention;

[0056] Figure 5 The axonometric diagram of the first mirror surface, the first mirror body, the third mirror surface and the third mirror body in the embodiment of the present invention is shown in FIG. Figure 1 ;

[0057] Figure 6 The axonometric diagram of the first mirror surface, the first mirror body, the third mirror surface and the third mirror body in the embodiment of the present invention is shown in FIG. Figure 2 ;

[0058] Figure 7 is a cross-sectional view of the first mirror surface, the first mirror body, the third mirror surface and the third mirror body in an embodiment of the present invention;

[0059] Figure 8 It is a schematic diagram of the principle of step 1.1 in the embodiment of the method for assembling and adjusting the all-aluminum free-form surface off-axis low-temperature infrared optical lens of the present invention;

[0060] Fig. 9 It is a schematic diagram of the principle of step 1.2 in the embodiment of the method for assembling and adjusting the all-aluminum free-form surface off-axis low-temperature infrared optical lens of the present invention.

[0061] The following are the descriptions of the reference numerals:

[0062] 1-support frame, 101-first side, 102-second side, 103-third side, 104-fourth side, 105-fifth side, 110-frame mounting lug, 111-frame mounting hole, 121-third mirror body mounting hole, 122-second mirror body mounting hole, 123-optical path hole; 2-upper cover; 301-first mirror surface, 302-second mirror surface, 303-third mirror surface, 311-first mirror body, 312-second mirror body, 313-third mirror Body, 321-cylindrical boss, 322-plane, 331-reflector mounting lug, 332-first stress unloading groove, 333-second stress unloading groove, 334-flexible groove; 401-fastening screw, 402-adjusting gasket; 5-detector light window; 6-detector cold stop; 7-focal plane; 8-object plane; 9-4D interferometer, 91-plane standard mirror, 92-spherical standard mirror; 10-spherical mirror; 11-plane mirror; 12-articular arm measuring instrument; 13-aperture. DETAILED DESCRIPTION

[0063] The present invention will be further described below in conjunction with the accompanying drawings and exemplary embodiments.

[0064] The present invention discloses an all-aluminum free-form surface off-axis low-temperature infrared optical lens, such as Figure 1 As shown, it includes an optical system, a supporting frame 1, and an upper cover plate 2.

[0065] The optical system comprises a mirror surfaces which are arranged in sequence along the optical path and are all free-form surface off-axis reflectors, where a is an integer greater than or equal to 3.

[0066] The support frame 1 is an integrally formed frame. The support frame 1 is a hollow shell of a straight multi-prism structure. The number of side edges b of the support frame 1 is greater than or equal to 4. The support frame 1 includes a top surface and a bottom surface, and b side surfaces connected in sequence. The bottom surface is set to be closed or semi-closed to avoid external interference structures. The upper cover plate 2 is set on the top surface of the support frame 1. The a mirror surfaces are respectively set on the side surfaces of the support frame 1 through corresponding mirror bodies. At least two mirror bodies are provided with cylindrical bosses 321 on the reverse side. The outer end surface of the cylindrical boss 321 is parallel to the side surface where it is located. The side wall of the cylindrical boss 321 is provided with a plane 322 to ensure the phase of the corresponding mirror surface, so as to facilitate quantitative adjustment. A plurality of weight-reducing grooves are also provided on the cylindrical boss 321.

[0067] At least two mounting holes are provided on the side of the support frame 1, and the mirror bodies of a mirror are respectively provided on the side of the support frame 1 through the corresponding mounting holes; a mirror body with a cylindrical boss 321 is provided on the back side, and a plurality of reflector mounting lugs 331 and a first stress unloading groove 332 are provided on the outer periphery of the mirror body; a flexible groove 334 is provided at the connection between the front and back sides of each reflector mounting lug 331 and the mirror body, and an adjustment gasket 402 is provided between each reflector mounting lug 331 and the side surface, and the adjustment gasket 402 is used to adjust the angle and position of the corresponding mirror.

[0068] Each reflector mounting lug 331 is provided with a flexible groove 334 at the connection between the front and back sides and the mirror body, and an adjustment gasket 402 is provided between each reflector mounting lug 331 and the side surface thereof, and the adjustment gasket 402 is used to adjust the angle and position of the corresponding mirror surface.

[0069] Light path holes 123 are provided on the c sides for light to enter and output the optical system, 2≤c<b; frame mounting lugs 110 are provided at the lower ends of the d sides, 3≤d≤b, and a frame mounting hole 111 is provided on each frame mounting lug 110 along a direction perpendicular to the bottom surface.

[0070] The support frame 1, all mirror surfaces and corresponding mirror bodies, cylindrical bosses 321, and frame mounting lugs 110 are all made of aluminum alloy.

[0071] Reference Figure 1 , Figure 3 , Figure 4 The present invention discloses another all-aluminum free-form surface off-axis low-temperature infrared optical lens, comprising an optical system, a supporting frame 1, and an upper cover plate 2.

[0072] The support frame 1 is an integrally formed frame. The support frame 1 is a hollow shell of a straight multi-prism structure, including a top surface and a bottom surface, and a first side surface 101, a second side surface 102, a third side surface 103, a fourth side surface 104 and a fifth side surface 105 connected in sequence. The top surface is provided with an upper cover plate 2, and the bottom surface is provided with a closed or semi-closed structure to avoid external interference. The second side surface 102 and the fifth side surface 105 are parallel to each other and are perpendicular to the first side surface 101. The angle between the first side surface 101 and the third side surface 103 is , the processing tolerance needs to be strictly controlled, generally about 1 / 3 of the optical system tolerance. Frame mounting lugs 110 are provided at the connection between the lower end of the second side surface 102 and the first side surface 101, the connection between the lower end of the second side surface 102 and the third side surface 103, the connection between the lower end of the fourth side surface 104 and the third side surface 103, and the connection between the lower end of the fifth side surface 105 and the first side surface 101. A frame mounting hole 111 is provided on each frame mounting lug 110 along a direction perpendicular to the bottom surface. The frame mounting hole 111 is used to be fixed to the outside through a fastening screw 401.

[0073] Reference Figures 1 to 3 The optical system includes a first mirror 301, a second mirror 302 and a third mirror 303 arranged in sequence along the optical path; the first mirror 301, the second mirror 302 and the third mirror 303 are respectively arranged on the side of the supporting frame 1 through a first mirror body 311, a second mirror body 312 and a third mirror body 313, and are all free-form off-axis reflectors.

[0074] Reference Figure 2 The incident light is reflected by the first mirror 301, the second mirror 302 and the third mirror 303 in sequence and then outputs from the optical system, and then passes through the detector light window 5 and the detector cold stop 6 in sequence, and finally forms an image on the focal plane 7.

[0075] Reference Figure 1 , Figure 3 , Figure 4 The first side surface 101 and the third side surface 103 are respectively provided with a third mirror body mounting hole 121 and a second mirror body mounting hole 122 adapted to the third mirror body 313 and the second mirror body 312, and the third side surface 103, the fourth side surface 104 and the fifth side surface 105 are all provided with an optical path hole 123 for light to enter and output the optical system.

[0076] Reference Figure 2 , Figures 5 to 7The third mirror body 313 has a third mirror surface 303 on its front side and a cylindrical boss 321 on its back side. The outer end face of the cylindrical boss 321 is parallel to the first side face 101, and the side wall is provided with a plane 322 to ensure the phase of the third mirror surface 303, so as to facilitate quantitative adjustment. The outer periphery of the third mirror body 313 is provided with three reflector mounting lugs 331 and a first stress unloading groove 332. The first mirror body 311 has a first mirror surface 301 on its front side and four weight-reducing grooves evenly distributed around the circumference on its back side. The first mirror body 311 is connected to the third mirror body 313, and a second stress unloading groove 333 is provided at the connection. The second mirror body 312 has a second mirror surface 302 on its front side and a cylindrical boss 321 on its back side. The outer end surface of the cylindrical boss 321 is parallel to the third side surface 103, and the side wall is provided with a plane 322 for ensuring the phase of the second mirror surface 302, so as to facilitate quantitative adjustment. The outer periphery of the second mirror body 312 is provided with three reflector mounting lugs 331 and a first stress unloading groove 332. The cylindrical boss 321 is also provided with a plurality of weight-reducing grooves evenly distributed around the circumference.

[0077] Reference Figure 1 , Figures 5 to 7 Each reflector mounting lug 331 is provided with a reflector mounting hole, and the reflector mounting hole is used to be fixed to the support frame 1 by a fastening screw 401, and an adjustment gasket 402 is provided between each reflector mounting lug 331 and the side surface thereof, such as Figure 1 A flexible groove 334 is provided at the connection between the front and back surfaces of each reflector mounting lug 331 and the third mirror body 313 or the second mirror body 312 to prevent the surface accuracy of the corresponding mirror surface from being reduced after the fastening screw 401 is installed.

[0078] The first mirror surface 301, the second mirror surface 302, the third mirror surface 303, the first mirror body 311, the second mirror body 312, the third mirror body 313, all cylindrical bosses 321, all reflector mounting lugs 331, the support frame 1, the upper cover plate 2, and all fastening screws 401 are made of aluminum alloy.

[0079] A method for assembling and adjusting an all-aluminum free-form surface off-axis low-temperature infrared optical lens comprises the following steps:

[0080] Step 1: Build an adjustment system on the optical platform. The adjustment system includes an articulated arm measuring instrument 12, a 4D interferometer 9, an aperture 13, an all-aluminum free-form surface off-axis low-temperature infrared optical lens, and a spherical mirror 10 or a plane mirror 11. Specifically:

[0081] Reference Figure 8, fix the support frame 1 on the optical platform through the frame mounting lug 110, then fix the 4D interferometer 9 with the plane standard mirror 91 on the object plane 8 of the optical system of the all-aluminum free-form surface off-axis low-temperature infrared optical lens, and fix the spherical mirror 10 on the focal plane 7 of the optical system; then fix the diaphragm 13 to the corresponding position of the detector cold diaphragm 6, and fix the articulated arm measuring instrument 12 on the optical platform for convenient measurement of each mirror surface;

[0082] Or, refer to Fig. 9 , fix the support frame 1 on the optical platform through the frame mounting lug 110, then fix the 4D interferometer 9 with the spherical standard mirror 92 on the focal plane 7 of the optical system of the all-aluminum free-form surface off-axis low-temperature infrared optical lens, and fix the plane mirror 11 on the object plane 8 of the optical system; then fix the aperture 13 to the corresponding position of the detector cold aperture 6, and fix the articulated arm measuring instrument 12 on the optical platform for convenient measurement of each mirror surface;

[0083] Step 2: Set each mirror surface on the side of the support frame 1 through the corresponding mirror body, specifically:

[0084] The three reflector mounting lugs 331 on the outer periphery of the third mirror body 313 are fixed to the first side surface 101 using the fastening screws 401, and an adjustment gasket 402 is arranged between each reflector mounting lug 331 and the side surface where it is located, so that the third mirror body 313 is located in the third mirror body mounting hole 121, thereby completing the fixing of the first mirror surface 301 and the third mirror surface 303;

[0085] The three reflector mounting lugs 331 on the outer periphery of the second mirror body 312 are fixed to the third side surface 103 using the fastening screws 401, and an adjustment gasket 402 is arranged between each reflector mounting lug 331 and the side surface where it is located, so that the second mirror body 312 is located in the third mirror body mounting hole 121, thereby completing the fixing of the second mirror surface 302;

[0086] Step 3: Reference Figure 4 , define the first coordinate system for support frame 1 ,origin A right angle vertex of one of the frame mounting lugs 110 is provided, The surface coincides with the side surface (first side surface 101) where the third mirror surface 303 is located. The surface coincides with the bottom surface of the supporting frame 1;

[0087] The second coordinate system is defined for the mirror surface (the second mirror surface 302 and the third mirror surface 303) on the reverse side of the mirror body with the cylindrical boss 321 ,origin Located at the intersection of the central axis and the outer end surface of the cylindrical boss 321, The surface coincides with the outer end surface. The surface is parallel to the bottom surface of the support frame 1; and the coordinates of the geometric center point of each mirror surface are defined as , the coordinates of the intersection of the central axis of each mirror body and the outer wall of the side surface are , the coordinates of the intersection of the central axis of the cylindrical boss 321 and the outer end surface are ;

[0088] The second coordinate system Next , , Transform to the first coordinate system Next, we get the first coordinate system The corresponding , , Theoretical value;

[0089] Step 4: Use the articulated arm measuring instrument 12 to measure the second mirror surface 302 in the first coordinate system Next , , Actual value, the third mirror surface 303 in the first coordinate system Next , , The actual value is adjusted to be within the preset coordinate tolerance with the theoretical value obtained in step 3, so as to ensure the center spacing between the mirror surfaces; specifically, the thickness of the gasket 402 is adjusted by grinding to meet the center spacing requirement between the mirror surfaces;

[0090] The coordinate values ​​are shown in Table 1:

[0091] Table 1

[0092]

[0093] Then, the articulated arm measuring instrument 12 is used to measure the plane 322 so that it corresponds to the second coordinate system of axis, axis, The roll, pitch and azimuth angles between the axes are ≯1′;

[0094] By adjusting the coordinate position of each mirror and the angle of plane 322, it is ensured that the phase (phase change of light wave after reflection from the mirror), angle and center interval of each mirror meet the requirements of the optical system;

[0095] Step 5, using the 4D interferometer 9 to detect the transmission wavefront of the optical system after adjustment, to determine whether the transmission wavefront of the central field of view is ≤0.6λ and the transmission wavefront of the full field of view is ≤1λ, λ=632.8nm. If so, the optical system adjustment is completed and step 6 is executed; otherwise, return to step 4;

[0096] Step 6: Apply epoxy glue or thread anti-loosening glue to the fastening screws 401 in the reflector mounting hole to prevent the fastening screws 401 from loosening, improve the reliability of the optical system, maintain the accuracy of the optical system, prevent the influence of the external environment, and simplify maintenance work; then fix the upper cover plate 2 to the top surface of the support frame 1 by the fastening screws 401; complete the installation and adjustment of the all-aluminum free-form surface off-axis low-temperature infrared optical lens.

Claims

1. An all-aluminum free-form surface off-axis low-temperature infrared optical lens, comprising an optical system and a supporting frame (1); characterized in that: The optical system comprises a first mirror surface (301), a second mirror surface (302) and a third mirror surface (303) which are arranged in sequence along the optical path and are all free-form surface off-axis reflectors; The support frame (1) is a hollow shell of a straight multi-prism structure, and the number of side edges of the support frame (1) is 5; the support frame (1) comprises a first side surface (101), a second side surface (102), a third side surface (103), a fourth side surface (104), and a fifth side surface (105) which are connected in sequence, and the second side surface (102) and the fifth side surface (105) are parallel to each other and perpendicular to the first side surface (101); the first side surface (101) and the third side surface (103) are respectively provided with a third mirror body mounting hole (121) and a second mirror body mounting hole (122) adapted to the third mirror body (313) and the second mirror body (312); the third side surface (103), the fourth side surface (104), and the fifth side surface (105) are all provided with an optical path hole (123); The first mirror surface (301), the second mirror surface (302) and the third mirror surface (303) are respectively arranged on the side surface of the support frame (1) through the first mirror body (311), the second mirror body (312) and the third mirror body (313); the third mirror surface (303) is arranged on the front surface of the third mirror body (313), and a cylindrical boss (321) is arranged on the back surface, and a plurality of reflector mounting lugs (331) are arranged on the periphery; the first mirror surface (301) is arranged on the front surface of the first mirror body (311), the first mirror body (311) is connected to the third mirror body (313), and a second stress unloading groove (333) is arranged at the connection between the first mirror body (311) and the third mirror body (313); The second mirror surface (302) is arranged on the front side of the second mirror body (312), a cylindrical boss (321) is arranged on the back side, and a plurality of reflector mounting lugs (331) are arranged on the outer periphery; An adjustment gasket (402) is provided between each reflector mounting lug (331) and the side surface thereof, and the adjustment gasket (402) is used to adjust the angle and position of the corresponding mirror surface; a flexible groove (334) is provided at the connection between the front and back surfaces of each reflector mounting lug (331) and the third mirror body (313) or the second mirror body (312); The outer peripheries of the second mirror body (312) and the third mirror body (313) are both provided with first stress unloading grooves (332); The side wall of the cylindrical boss (321) is provided with a plane (322) for ensuring the phase of the corresponding mirror surface; A frame mounting lug (110) is provided at the connection between the lower end of the second side surface (102) and the first side surface (101), a frame mounting lug (110) is provided at the connection between the lower end of the second side surface (102) and the third side surface (103), a frame mounting lug (110) is provided at the connection between the lower end of the fourth side surface (104) and the third side surface (103), and a frame mounting lug (110) is provided at the connection between the lower end of the fifth side surface (105) and the first side surface (101), and a frame mounting hole (111) is provided on each frame mounting lug (110) along the bottom surface direction of the vertical support frame (1); The support frame (1), all mirror surfaces and corresponding mirror bodies, cylindrical bosses (321), and frame mounting lugs (110) are all made of aluminum alloy.

2. A method for assembling and adjusting the all-aluminum free-form surface off-axis low-temperature infrared optical lens according to claim 1, characterized in that: The steps include: Step 1, constructing an assembly and adjustment system on an optical platform, the assembly and adjustment system comprising an articulated arm measuring instrument (12), a 4D interferometer (9), an aperture (13), the all-aluminum free-form surface off-axis low-temperature infrared optical lens according to claim 1, and a spherical mirror (10) or a plane mirror (11); Step 2, arranging each mirror surface on the side surface of the support frame (1) through the corresponding mirror body; Step 3: Define the first coordinate system for the support frame (1) ,origin For one vertex of one of the frame mounting lugs (110), The surface coincides with the side of the third mirror arranged in sequence along the optical path. The surface coincides with the bottom surface of the supporting frame (1); A second coordinate system is defined for the mirror surface having a cylindrical boss (321) on the reverse side of the mirror body. ,origin Located at the intersection of the central axis and the outer end surface of the cylindrical boss (321), The surface coincides with the outer end surface. The surface is parallel to the bottom surface; and the coordinates of the geometric center point of each mirror surface are defined as , the coordinates of the intersection of the central axis of each mirror body and the outer wall of the side surface are The coordinates of the intersection of the central axis of the cylindrical boss (321) and the outer end surface are ; Subscript Indicates the first Mirror, Pick integer in range; The second coordinate system Next , , Transform to the first coordinate system Next, we get the first coordinate system The corresponding , , Theoretical value; Step 4: For the mirror surface with a cylindrical boss (321) on the reverse side of the mirror body, use the articulated arm measuring instrument (12) to measure the Next , , The actual value is adjusted to the preset coordinate tolerance with the theoretical value obtained in step 3, thereby ensuring the center spacing between the mirror surfaces. Then, the plane (322) is measured by using the articulated arm measuring instrument (12) so that it corresponds to the second coordinate system of axis, axis, The roll, pitch and azimuth angles between the axes are ≯1′; Step 5, using a 4D interferometer (9) to detect the transmission wavefront of the optical system after adjustment, to determine whether the central field of view transmission wavefront and the full field of view transmission wavefront meet the preset requirements, if so, the adjustment of the all-aluminum free-form surface off-axis low-temperature infrared optical lens is completed; otherwise, return to step 4.

3. The method for assembling and adjusting the all-aluminum free-form surface off-axis low-temperature infrared optical lens according to claim 2, characterized in that: The step 1 is specifically as follows: The support frame (1) is fixed on the optical platform through the frame mounting lug (110), and then the 4D interferometer (9) equipped with the plane standard mirror (91) is fixed on the object plane (8) of the optical system of the all-aluminum free-form surface off-axis low-temperature infrared optical lens according to claim 1, and the spherical mirror (10) is fixed on the focal plane (7) of the optical system; then the diaphragm (13) is fixed at the corresponding position of the detector cold diaphragm (6), and the articulated arm measuring instrument (12) is fixed on the optical platform; Alternatively, the support frame (1) is fixed on the optical platform by means of the frame mounting lugs (110), and then the 4D interferometer (9) equipped with the spherical standard mirror (92) is fixed on the focal plane (7) of the optical system of the all-aluminum free-form surface off-axis low-temperature infrared optical lens according to claim 1, and the plane mirror (11) is fixed on the object plane (8) of the optical system; then the aperture (13) is fixed on the corresponding position of the detector cold aperture (6), and the articulated arm measuring instrument (12) is fixed on the optical platform; In step 4, the difference between the theoretical value obtained in step 3 is adjusted to within a preset coordinate tolerance to ensure the center spacing between the mirror surfaces. Specifically, the thickness of the gasket (402) is adjusted by grinding to achieve the center spacing requirement between the mirror surfaces.

4. The method for assembling and adjusting the all-aluminum free-form surface off-axis low-temperature infrared optical lens according to claim 2 or 3, characterized in that: The method also includes step 6: fixing the upper cover plate (2) on the top surface of the supporting frame (1).

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