CN118330838A - All-aluminum free-form surface off-axis low-temperature infrared optical lens and adjusting method thereof - Google Patents

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-mirror optical system, cold reflection self-imaging of the detector will not occur, and there is no center shielding.

Description

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

Technical Field

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 technique

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.

There are two main technical means to solve the problem:

(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.

(2) A focusing mechanism is used to compensate for image plane defocus caused by changes in temperature and pressure. 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.

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

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.

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

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:

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;

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;

The c sides are provided with light path holes for light entry and output, 2≤c＜b; the lower ends of the d sides are provided with frame mounting lugs, 3≤d≤b, and each frame mounting lug is provided with a frame mounting hole along a direction perpendicular to the bottom surface of the supporting frame;

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

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;

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.

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

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:

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;

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;

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;

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

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;

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 side surface of the supporting frame, and the first mirror body is connected to the third mirror body;

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;

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.

Further, the number b of the side edges of the support frame is equal to 5, the support frame comprises a first side surface, a second side surface, a third side surface, a fourth side surface and a fifth side surface which are sequentially connected, 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;

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

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

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

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.

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.

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 comprises the following steps:

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;

Step 2: Arrange each mirror surface on the side of the support frame through the corresponding mirror body;

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 along the optical path. The surface coincides with the bottom surface of the supporting frame;

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;

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 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.

Then the plane is measured by the articulated arm measuring instrument 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: 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.

Furthermore, the step 1 is specifically as follows:

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;

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;

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.

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

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

(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.

(2) The present invention adopts all-aluminum alloy material 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℃.

(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.

(4) The present invention takes into account the mechanical structure, optical performance and environmental adaptability as a whole in its design, ensuring 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.

(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

FIG1 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;

FIG2 is a schematic diagram of an optical path according to an embodiment of the present invention;

FIG3 is an axonometric view of a support frame according to an embodiment of the present invention;

FIG4 is a cross-sectional view of a support frame in an embodiment of the present invention;

FIG5 is an axonometric view 1 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;

6 is a second isometric 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;

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;

FIG8 is a schematic diagram of the principle of step 1.1 in an embodiment of the method for assembling and adjusting an all-aluminum free-form surface off-axis low-temperature infrared optical lens of the present invention;

FIG. 9 is a schematic diagram showing the principle of step 1.2 in an 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.

The following are the descriptions of the reference numerals:

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 ways

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

The present invention discloses an all-aluminum free-form surface off-axis low-temperature infrared optical lens, as shown in FIG1 , comprising an optical system, a supporting frame 1 , and an upper cover plate 2 .

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.

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.

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.

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.

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.

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.

1 , 3 and 4 , the present invention discloses another all-aluminum free-form surface off-axis low-temperature infrared optical lens, comprising an optical system, a support frame 1 and an upper cover plate 2 .

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 both 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.

1 to 3 , the optical system includes a first mirror 301, a second mirror 302 and a third mirror 303 sequentially arranged 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.

2 , the incident light is reflected by the first mirror 301 , the second mirror 302 and the third mirror 303 in sequence and then output 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 .

1 , 3 and 4 , the first side 101 and the third side 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 103, the fourth side 104 and the fifth side 105 are all provided with an optical path hole 123 for light to enter and output the optical system.

2, 5 to 7, the third mirror body 313 is provided with a third mirror surface 303 on the front side, and a cylindrical boss 321 is provided on the back side. The outer end face of the cylindrical boss 321 is parallel to the first side surface 101, and the side wall is provided with a plane 322, which is used 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 is provided with a first mirror surface 301 on the front side, and four weight-reducing grooves evenly distributed around the circumference are provided on the 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. The side wall is provided with a plane 322 for ensuring the phase of the second mirror surface 302, thereby facilitating 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.

1, 5 to 7, each reflector mounting lug 331 is provided with a reflector mounting hole, which 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 thereof, as shown in FIG1. 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, which is used to prevent the surface shape accuracy of the corresponding mirror surface from being reduced after the fastening screw 401 is installed.

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.

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

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:

8 , the support frame 1 is fixed on the optical platform through the frame mounting lugs 110, and then the 4D interferometer 9 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, and the spherical mirror 10 is fixed on the focal plane 7 of the optical system; then the diaphragm 13 is fixed to the corresponding position of the detector cold diaphragm 6, and the articulated arm measuring instrument 12 is fixed on the optical platform for convenient measurement of each mirror surface;

Alternatively, referring to FIG9 , the support frame 1 is fixed to the optical platform by the frame mounting lug 110, and then the 4D interferometer 9 with the spherical standard mirror 92 is fixed to the focal plane 7 of the optical system of the all-aluminum free-form surface off-axis low-temperature infrared optical lens, and the plane mirror 11 is fixed to the object plane 8 of the optical system; then the aperture 13 is fixed to the corresponding position of the detector cold aperture 6, and the articulated arm measuring instrument 12 is fixed to the optical platform for convenient measurement of each mirror surface;

Step 2: Arrange each mirror surface on the side of the support frame 1 through the corresponding mirror body, specifically:

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;

Use the fastening screws 401 to fix the three reflector mounting lugs 331 on the outer periphery of the second mirror body 312 to the third side surface 103, and set an adjustment gasket 402 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, and the second mirror surface 302 is fixed;

Step 3: Referring to FIG. 4 , define a first coordinate system for the 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;

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 ;

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

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;

The coordinate values are shown in Table 1:

Table 1

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′;

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;

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;

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 (10)

1. An all-aluminum free-form surface off-axis low-temperature infrared optical lens comprises an optical system and a supporting frame (1);

The method is characterized in that:

the optical system comprises a mirror surfaces a which are sequentially arranged along the optical path and are free-form surface off-axis reflectors, wherein a is an integer greater than or equal to 3;

The supporting frame (1) is a hollow shell with a straight polygon prism structure, and the number b of the side edges of the supporting frame (1) is more than or equal to 4; the support frame (1) comprises b side surfaces which are sequentially connected, the a mirror surfaces are arranged on the side surfaces of the support frame (1) through corresponding mirror bodies respectively, cylindrical bosses (321) are arranged on the back surfaces of at least two mirror bodies, the outer end surfaces of the cylindrical bosses (321) are parallel to the side surfaces of the cylindrical bosses, and planes (322) are arranged on the side walls of the cylindrical bosses (321) and used for guaranteeing the phases of the corresponding mirror surfaces;

The c side surfaces are provided with light path holes (123) for light to enter and output, and c is more than or equal to 2 and less than b; d side lower ends are provided with frame mounting lugs (110), d is more than or equal to 3 and less than or equal to b, and each frame mounting lug (110) is provided with a frame mounting hole (111) along the direction of the bottom surface of the vertical supporting frame (1);

The supporting frame (1), all the mirror surfaces, the corresponding mirror bodies, the cylindrical bosses (321) and the frame mounting lugs (110) are all made of aluminum alloy.

2. The all-aluminum freeform off-axis low-temperature infrared optical lens according to claim 1, wherein:

The mirror body is provided with a cylindrical boss (321) on the back surface, and a plurality of mirror mounting lugs (331) and a first stress unloading groove (332) are arranged on the periphery of the mirror body;

each reflector mounting lug (331) is provided with a flexible groove (334) at the joint of the front surface, the back surface and the reflector body, an adjusting gasket (402) is arranged between each reflector mounting lug (331) and the side surface, and the adjusting gasket (402) is used for adjusting the angle and the position of the corresponding reflector.

3. The all-aluminum freeform off-axis low-temperature infrared optical lens according to claim 1 or 2, wherein: at least two side surfaces of the supporting frame (1) are provided with mounting holes for mounting the mirror body.

4. An all-aluminum free-form surface off-axis low-temperature infrared optical lens comprises an optical system and a supporting frame (1); the method is characterized in that:

The optical system comprises three mirror surfaces which are sequentially arranged along the optical path and are all free-form surface off-axis reflectors;

The supporting frame (1) is a hollow shell with a straight polygon prism structure, and the number of side edges of the supporting frame (1) is 4 or 5; the support frame (1) comprises 4 or 5 side surfaces which are sequentially connected, the three mirror surfaces are respectively arranged on the side surfaces of the support frame (1) through corresponding mirror bodies, the back surfaces of at least two mirror bodies are provided with cylindrical bosses (321), the outer end surfaces of the cylindrical bosses (321) are parallel to the side surfaces of the cylindrical bosses, and the side walls of the cylindrical bosses (321) are provided with planes (322) for ensuring the phases of the corresponding mirror surfaces;

At least two sides are provided with light path holes (123) for light to enter and output; the lower ends of the at least three side surfaces are provided with frame mounting lugs (110), and each frame mounting lug (110) is provided with a frame mounting hole (111) along the direction of the bottom surface of the vertical supporting frame (1);

The supporting frame (1), all the mirror surfaces, the corresponding mirror bodies, the cylindrical bosses (321) and the frame mounting lugs (110) are all made of aluminum alloy.

5. The all-aluminum freeform off-axis low-temperature infrared optical lens according to claim 4, wherein:

the three mirrors are a first mirror (301), a second mirror (302) and a third mirror (303) which are sequentially arranged along the light path; 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 supporting frame (1) through a first mirror body (311), a second mirror body (312) and a third mirror body (313);

The front surface of the third mirror body (313) is provided with the third mirror surface (303), the back surface of the third mirror body is provided with the cylindrical boss (321), the periphery of the third mirror body is provided with a plurality of reflector mounting lugs (331), and the third mirror body (313) is arranged on one side surface of the supporting frame (1); the front surface of the first mirror body (311) is provided with the first mirror surface (301), and the first mirror body (311) is connected with the third mirror body (313);

the front surface of the second mirror body (312) is provided with the second mirror surface (302), the back surface is provided with the cylindrical boss (321), and the periphery is provided with a plurality of reflector mounting lugs (331);

an adjusting gasket (402) is arranged between each reflector mounting lug (331) and the side face of the reflector mounting lug, and the adjusting gasket (402) is used for adjusting the angle and the position of the corresponding reflector.

6. The all-aluminum freeform off-axis low-temperature infrared optical lens according to claim 5, wherein:

The side edges b of the support frame (1) are equal to 5, the support frame (1) comprises a first side face (101), a second side face (102), a third side face (103), a fourth side face (104) and a fifth side face (105) which are sequentially connected, the second side face (102) and the fifth side face (105) are parallel to each other and are perpendicular to the first side face (101), and a third mirror body mounting hole (121) and a second mirror body mounting hole (122) which are adapted to a third mirror body (313) and a second mirror body (312) are respectively arranged on the first side face (101) and the third side face (103);

The third side surface (103), the fourth side surface (104) and the fifth side surface (105) are provided with the light path holes (123);

A second stress unloading groove (333) is arranged at the joint of the first mirror body (311) and the third mirror body (313);

The peripheries of the second mirror body (312) and the third mirror body (313) are respectively provided with a first stress unloading groove (332);

And flexible grooves (334) are formed at the connection positions of the front surface and the back surface of each reflector mounting lug (331) and the third reflector body (313) or the second reflector body (312).

7. The all-aluminum freeform off-axis low-temperature infrared optical lens according to claim 6, wherein:

The frame mounting lug (110) is arranged at the joint of the lower end of the second side face (102) and the first side face (101), the frame mounting lug (110) is arranged at the joint of the lower end of the second side face (102) and the third side face (103), the frame mounting lug (110) is arranged at the joint of the lower end of the fourth side face (104) and the third side face (103), and the frame mounting lug (110) is arranged at the joint of the lower end of the fifth side face (105) and the first side face (101).

8. The method for adjusting the off-axis low-temperature infrared optical lens with the full aluminum free-form surface as claimed in claim 4, which is characterized by comprising the following steps:

Step 1, setting up an adjusting system on an optical platform, wherein the adjusting system comprises an articulated arm measuring instrument (12), a 4D interferometer (9), a diaphragm (13), the all-aluminum free-form surface off-axis low-temperature infrared optical lens as claimed in claim 4, and a spherical mirror (10) or a plane mirror (11);

Step 2, arranging each mirror surface on the side surface of the supporting frame (1) through a corresponding mirror body respectively;

Step 3, defining a first coordinate system for the support frame (1) Origin of pointOne of the apexes of the lugs (110) is mounted for one of the frames,The surface coincides with the side surface of the third mirror surface which is arranged along the light path in turn,The surface is overlapped with the bottom surface of the supporting frame (1);

Defining a second coordinate system for the mirror surface with the cylindrical boss (321) arranged on the back surface of the mirror body Origin of pointIs positioned at the intersection point of the central axis of the cylindrical boss (321) and the outer end surface,The surface is overlapped with the outer end surface,The surface is parallel to the bottom surface; and defining the geometric center point coordinates of each mirror surface asThe intersection point coordinates of the central axis of each mirror body and the outer wall of the side face where the central axis is positioned are as followsThe intersection point coordinate of the central axis and the outer end surface of the cylindrical boss (321) is; Subscript ofRepresenting the first one arranged in sequence along the optical pathThe number of the mirror surfaces is equal to the number of the mirror surfaces,Taking outIntegers within the range;

Will be a second coordinate system Lower part (C)、、Conversion to a first coordinate systemNext, a first coordinate system is obtainedLower corresponding、、Theoretical values;

Step 4, measuring a mirror surface with a cylindrical boss (321) on the back surface of the mirror body in a first coordinate system by adopting an articulated arm measuring instrument (12) Lower part (C)、、The actual value is adjusted to be within the preset coordinate tolerance with the difference value of the theoretical value obtained in the step 3, so that the center interval between the mirror surfaces is ensured,

The plane (322) is then measured with the articulated arm surveying instrument (12) in correspondence with the second coordinate systemA kind of electronic deviceA shaft(s),The axis of the shaft is provided with a plurality of grooves,The roll, pitch and azimuth angles between the shafts are no more than 1';

Step 5, detecting the transmitted wavefront of the adjusted optical system by adopting a 4D interferometer (9), judging whether the transmitted wavefront of the central view field and the transmitted wavefront of the full view field meet preset requirements, and if so, finishing the adjustment of the off-axis low-temperature infrared optical lens of the full aluminum free-form surface; otherwise, returning to the step 4.

9. The method for adjusting the off-axis low-temperature infrared optical lens with the full aluminum free-form surface according to claim 8, wherein the method comprises the following steps:

the step 1 specifically comprises the following steps:

Fixing a supporting frame (1) on an optical platform through a frame mounting lug (110), fixing a 4D interferometer (9) provided with a plane standard mirror (91) on an object plane (8) of an optical system of the all-aluminum free-form surface off-axis low-temperature infrared optical lens according to claim 4, and fixing a spherical mirror (10) on a focal plane (7) of the optical system; then, fixing a diaphragm (13) at a position corresponding to the cold diaphragm (6) of the detector, and fixing an articulated arm measuring instrument (12) on an optical platform;

or fixing the supporting frame (1) on an optical platform through a frame mounting lug (110), fixing a 4D interferometer (9) provided with a spherical standard mirror (92) on a focal plane (7) of an optical system of the all-aluminum free-form surface off-axis low-temperature infrared optical lens according to claim 4, and fixing a plane mirror (11) on an object plane (8) of the optical system; then, fixing a diaphragm (13) at a position corresponding to the cold diaphragm (6) of the detector, and fixing an articulated arm measuring instrument (12) on an optical platform;

In step 4, the difference between the theoretical value obtained in step 3 and the theoretical value obtained in step 3 is adjusted to be within a preset coordinate tolerance, so as to ensure that the center interval between the mirror surfaces is specifically: the thickness of the spacer (402) is adjusted by grinding to achieve the center spacing requirement between the mirrors.

10. The method for adjusting an all-aluminum freeform off-axis low-temperature infrared optical lens according to claim 8 or 9, further comprising the step of 6: the upper cover plate (2) is fixed on the top surface of the supporting frame (1).