An infrared imaging system

Abstract

The application discloses an infrared imaging system, comprising: a lens L1, a lens L2, a lens L3 and a lens L4 arranged in sequence along the light propagation direction; wherein the lens L1 is a negative meniscus lens, the lens L2 is a positive meniscus lens or a double convex lens, the lens L3 is a double concave lens, and the lens L4 is a double convex lens; the thickness of the lens L1 is 2mm-5mm, the thickness of the lens L2 is 4mm-8mm, the thickness of the lens L3 is 2mm-5mm, and the thickness of the lens L4 is 5mm-9mm; the front surface of the lens L1 is a spherical surface, and the rear surface is an aspherical surface; the lens L2 is an aspherical lens; the front surface of the lens L3 is an aspherical surface, and the rear surface is a spherical surface; the front surface of the lens L4 is a spherical surface, and the rear surface is an aspherical surface; the air interval between the lens L1 and the lens L2 is 22mm-37mm, the air interval between the lens L2 and the lens L3 is 8mm-16mm, and the air interval between the lens L3 and the lens L4 is 0.2mm-2.0mm; thus, the infrared imaging system can realize a large field of view.

Description

Technical Field

[0001] This application relates to the field of infrared imaging technology, and more particularly to an infrared imaging system. Background Technology

[0002] With the development of infrared optics, various fields have placed higher demands on infrared imaging systems. Currently, the field of view of infrared imaging systems is relatively small, which cannot meet the requirements for a large field of view. Moreover, infrared imaging systems often need to operate over a wide temperature range. How to ensure that infrared imaging systems can maintain good imaging quality over a large temperature range is also an urgent problem to be solved. Summary of the Invention

[0003] In view of this, the present application provides an infrared imaging system to at least solve the above-mentioned technical problems existing in the prior art.

[0004] According to a first aspect of this application, embodiments of this application provide an infrared imaging system, including:

[0005] Lenses L1, L2, L3, and L4 are arranged sequentially along the direction of light propagation;

[0006] Among them, lens L1 is a negative meniscus lens, lens L2 is a positive meniscus lens or a biconvex lens, lens L3 is a biconcave lens, and lens L4 is a biconvex lens; the thickness of lens L1 is 2mm to 5mm, the thickness of lens L2 is 4mm to 8mm, the thickness of lens L3 is 2mm to 5mm, and the thickness of lens L4 is 5mm to 9mm; the front surface of lens L1 is spherical, and the rear surface is aspherical; lens L2 is an aspherical lens; the front surface of lens L3 is aspherical, and the rear surface is spherical; the front surface of lens L4 is spherical, and the rear surface is aspherical; the air gap between lens L1 and lens L2 is 22mm to 37mm, the air gap between lens L2 and lens L3 is 8mm to 16mm, and the air gap between lens L3 and lens L4 is 0.2mm to 2.0mm.

[0007] Optionally, if lens L2 is a positive meniscus lens, the front surface of lens L2 is aspherical and the rear surface is spherical;

[0008] The materials of lenses L1, L2, L3, and L4 are germanium, IRG203, zinc sulfide, and IRG207, respectively.

[0009] Optionally, the air gap between lens L1 and lens L2 is 31mm to 37mm, the air gap between lens L2 and lens L3 is 10mm to 16mm, and the air gap between lens L3 and lens L4 is 0.3mm to 2.0mm.

[0010] Optionally, the radii of curvature of the front and rear surfaces of lens L1 are 29mm-35mm and 16mm-22mm, respectively; the radii of curvature of the front and rear surfaces of lens L2 are 33mm-38mm and 110mm-200mm, respectively; the radii of curvature of the front and rear surfaces of lens L3 are -46mm--54mm and 66mm-76mm, respectively; and the radii of curvature of the front and rear surfaces of lens L4 are 48mm-56mm and -48mm--57mm, respectively.

[0011] Optionally, the fourth, sixth, and eighth term coefficients of lens L1 are 3.0e-7 to 7.0e-7, 1.0e-9 to 6.0e-9, and 6.0e-11 to 1.0e-10, respectively.

[0012] The fourth, sixth, and eighth term coefficients of lens L2 are 4.0e-7 to 8.0e-7, -3.0e-009 to -1.0e-9, and -2.0e-10 to -6.0e-11, respectively.

[0013] The fourth, sixth, and eighth term coefficients of lens L3 are -6.0e-6 to -1.0e-6, 6.0e-8 to 1.6e-7, and -6.0e-10 to -1.0e-10, respectively.

[0014] The fourth, sixth, and eighth degree coefficients of lens L4 are -1.5e-5 to -5.0e-6, 2.0e-8 to 7.0e-8, and 1.0e-10 to 4.0e-10, respectively.

[0015] Optionally, if lens L2 is a biconvex lens, the front surface of lens L2 is spherical and the rear surface is aspherical;

[0016] The materials of lenses L1, L2, L3 and L4 are germanium, zinc sulfide, IRG203 and IRG203, respectively.

[0017] Optionally, the air gap between lens L1 and lens L2 is 22mm to 25mm, the air gap between lens L2 and lens L3 is 8mm to 15mm, and the air gap between lens L3 and lens L4 is 0.2mm to 2.0mm.

[0018] Optionally, the radii of curvature of the front and rear surfaces of lens L1 are 43mm to 53mm and 18mm to 23mm, respectively; the radii of curvature of the front and rear surfaces of lens L2 are 42mm to 49mm and -300mm to -190mm, respectively; the radii of curvature of the front and rear surfaces of lens L3 are -39mm to -45mm and 70mm to 80mm, respectively; and the radii of curvature of the front and rear surfaces of lens L4 are 45mm to 53mm and -43mm to -51mm, respectively.

[0019] Optionally, the fourth, sixth, and eighth term coefficients of lens L1 are 4.0e-8 to 9.0e-8, 4.0e-10 to 8.0e-10, and -4.0e-12 to -6.0e-13, respectively.

[0020] The fourth, sixth, and eighth term coefficients of lens L2 are -9.0e-6 to -5.0e-6, -9.0e-8 to -3.0e-8, and 1.0e-10 to 5.0e-10, respectively.

[0021] The fourth, sixth, and eighth term coefficients of lens L3 are -5.0e-6 to -1.0e-6, 4.0e-8 to 9.0e-8, and 1.0e-10 to 4.0e-10, respectively.

[0022] The fourth, sixth, and eighth degree coefficients of lens L4 are -8.0e-6 to -1.0e-6, -4.0e-8 to -6.0e-9, and -3.0e-10 to -7.0e-11, respectively.

[0023] Optionally, the infrared imaging system also includes:

[0024] The long-wavelength uncooled detector has a resolution of 1920×1080 and a pixel size of 8µm.

[0025] The infrared imaging system provided in this application embodiment comprises lenses L1, L2, L3, and L4 arranged sequentially along the direction of light propagation. Lens L1 is a negative meniscus lens, lens L2 is a positive meniscus lens or a biconvex lens, lens L3 is a biconcave lens, and lens L4 is a biconvex lens. The thickness of lens L1 is 2mm–5mm, the thickness of lens L2 is 4mm–8mm, the thickness of lens L3 is 2mm–5mm, and the thickness of lens L4 is 5mm–9mm. The front surface of lens L1 is spherical, and the rear surface is aspherical. Lens L2 is an aspherical lens. The system uses aspherical lenses; the front surface of lens L3 is aspherical, and the rear surface is spherical; the front surface of lens L4 is spherical, and the rear surface is aspherical; the air gap between lens L1 and lens L2 is 22mm to 37mm, the air gap between lens L2 and lens L3 is 8mm to 16mm, and the air gap between lens L3 and lens L4 is 0.2mm to 2.0mm; thus, the infrared imaging system can achieve a large field of view, with a simple structure, excellent imaging quality, and can be adapted to high-resolution long-wavelength uncooled detectors, and can operate over a wide temperature range.

[0026] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of an infrared imaging system according to an embodiment of this application;

[0028] Figure 2 This is an optical dot plot of an infrared imaging system at +20°C in an embodiment of this application;

[0029] Figure 3 This is an optical transfer function diagram of an infrared imaging system at +20°C in an embodiment of this application;

[0030] Figure 4 This is an optical dot plot of the infrared imaging system at -80℃ in an embodiment of this application;

[0031] Figure 5 This is an optical transfer function diagram of the infrared imaging system at -80°C in an embodiment of this application;

[0032] Figure 6 This is an optical dot plot of the infrared imaging system at +80°C in an embodiment of this application;

[0033] Figure 7 This is an optical transfer function diagram of the infrared imaging system at +80°C in an embodiment of this application;

[0034] Figure 8 This is an optical dot plot of another infrared imaging system at +20°C in an embodiment of this application;

[0035] Figure 9 This is an optical transfer function diagram of another infrared imaging system at +20°C in an embodiment of this application. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] This application provides an infrared imaging system, such as... Figure 1 As shown, it includes:

[0038] Lenses L1, L2, L3, and L4 are arranged sequentially along the direction of light propagation.

[0039] Among them, lens L1 is a negative meniscus lens, lens L2 is a positive meniscus lens or a biconvex lens, lens L3 is a biconcave lens, and lens L4 is a biconvex lens; the thickness of lens L1 is 2mm to 5mm, the thickness of lens L2 is 4mm to 8mm, the thickness of lens L3 is 2mm to 5mm, and the thickness of lens L4 is 5mm to 9mm; the front surface of lens L1 is spherical, and the rear surface is aspherical; lens L2 is an aspherical lens; the front surface of lens L3 is aspherical, and the rear surface is spherical; the front surface of lens L4 is spherical, and the rear surface is aspherical; the air gap between lens L1 and lens L2 is 22mm to 37mm, the air gap between lens L2 and lens L3 is 8mm to 16mm, and the air gap between lens L3 and lens L4 is 0.2mm to 2.0mm.

[0040] In this embodiment, lenses L1, L2, L3, and L4 are all aspherical lenses. The front surfaces of lenses L1, L2, L3, and L4 are the surfaces where light enters along the direction of light propagation. The rear surfaces of lenses L1, L2, L3, and L4 are the surfaces where light exits along the direction of light propagation.

[0041] In specific implementation, such as Figure 1 As shown, the infrared imaging system also includes a target surface, which is planar. Light passing through lens L4 is transmitted onto the target surface. If lens L2 is a positive meniscus lens, the thickness of lens L1 is 2mm–5mm, the thickness of lens L2 is 4mm–8mm, the thickness of lens L3 is 2mm–4mm, and the thickness of lens L4 is 5mm–8mm. The air gap between lens 4 and the target surface is 13mm–25mm. If lens L2 is a biconvex lens, the thickness of lens L1 is 2mm–5mm, the thickness of lens L2 is 4mm–8mm, the thickness of lens L3 is 2mm–5mm, and the thickness of lens L4 is 5mm–9mm. The air gap between lens 4 and the target surface is 14mm–21mm.

[0042] In some embodiments, the infrared imaging system may further include a long-wavelength uncooled detector with a resolution of 1920×1080 and a pixel size of 8µm.

[0043] The infrared imaging system provided in this application embodiment comprises lenses L1, L2, L3, and L4 arranged sequentially along the direction of light propagation. Lens L1 is a negative meniscus lens, lens L2 is a positive meniscus lens or a biconvex lens, lens L3 is a biconcave lens, and lens L4 is a biconvex lens. The thickness of lens L1 is 2mm–5mm, the thickness of lens L2 is 4mm–8mm, the thickness of lens L3 is 2mm–5mm, and the thickness of lens L4 is 5mm–9mm. The front surface of lens L1 is spherical, and the rear surface is aspherical. Lens L2 is an aspherical lens. The front surface of lens L3 is aspherical, and the rear surface is spherical; the front surface of lens L4 is spherical, and the rear surface is aspherical; the air gap between lens L1 and lens L2 is 22mm to 37mm, the air gap between lens L2 and lens L3 is 8mm to 16mm, and the air gap between lens L3 and lens L4 is 0.2mm to 2.0mm; thus, the infrared imaging system can achieve a large field of view, reaching ±42.1°, and has a simple structure, excellent imaging quality, can be adapted to high-resolution long-wavelength uncooled detectors, and can operate over a wide temperature range.

[0044] In an optional embodiment, lens L1 is a negative meniscus lens, lens L2 is a positive meniscus lens, lens L3 is a biconcave lens, and lens L4 is a biconvex lens. The front surface of lens L1 is spherical, and the rear surface is aspherical; the front surface of lens L2 is aspherical, and the rear surface is spherical; the front surface of lens L3 is aspherical, and the rear surface is spherical; and the front surface of lens L4 is spherical, and the rear surface is aspherical. As shown in Table 1, the thickness of lens L1 is 2mm–5mm, the thickness of lens L2 is 4mm–8mm, the thickness of lens L3 is 2mm–4mm, and the thickness of lens L4 is 5mm–8mm.

[0045] The materials of lenses L1, L2, L3 and L4 are germanium (GE), IRG203, zinc sulfide (ZNS) and IRG207, respectively.

[0046] The air gap between lens L1 and lens L2 is 31mm to 37mm, the air gap between lens L2 and lens L3 is 10mm to 16mm, and the air gap between lens L3 and lens L4 is 0.3mm to 2.0mm. The air gap between lens 4 and the target surface is 13mm to 25mm.

[0047] The radii of curvature of the front and rear surfaces of lens L1 are 29mm~35mm and 16mm~22mm, respectively; the radii of curvature of the front and rear surfaces of lens L2 are 33mm~38mm and 110mm~200mm, respectively; the radii of curvature of the front and rear surfaces of lens L3 are -46mm~-54mm and 66mm~76mm, respectively; and the radii of curvature of the front and rear surfaces of lens L4 are 48mm~56mm and -48mm~-57mm, respectively.

[0048] The fourth, sixth, and eighth order coefficients of lens L1 are 3.0e-7 to 7.0e-7, 1.0e-9 to 6.0e-9, and 6.0e-11 to 1.0e-10, respectively; the fourth, sixth, and eighth order coefficients of lens L2 are 4.0e-7 to 8.0e-7, -3.0e-009 to -1.0e-9, and -2.0e-10 to -6.0e-11, respectively. The fourth, sixth, and eighth order coefficients of lens L3 are -6.0e-6 to -1.0e-6, 6.0e-8 to 1.6e-7, and -6.0e-10 to -1.0e-10, respectively; the fourth, sixth, and eighth order coefficients of lens L4 are -1.5e-5 to -5.0e-6, 2.0e-8 to 7.0e-8, and 1.0e-10 to 4.0e-10, respectively.

[0049] Table 1

[0050]

[0051]

[0052] Note: The units for radius of curvature, thickness, diameter, and air gap are mm; α2, α3, and α4 are the fourth, sixth, and eighth degree coefficients of the radial coordinate, respectively, and their detailed calculation formulas are as follows:

[0053]

[0054] Where z represents the sag height; c represents the vertex curvature of the lens; r represents the aperture radius of the lens; and k is the conic coefficient.

[0055] In a more specific implementation, the parameters of each lens in the infrared imaging system (such as radius of curvature, thickness, material, fourth-order coefficients, etc.) are shown in Table 2.

[0056] Table 2

[0057]

[0058] Note: The units for radius of curvature, thickness, diameter, and air gap are mm; α2, α3, and α4 are the fourth, sixth, and eighth degree coefficients of the radial coordinate, respectively.

[0059] In this embodiment, by setting the materials of lens L1, lens L2, lens L3 and lens L4 to germanium (GE), IRG203, zinc sulfide (ZNS) and IRG207 respectively, and by setting the air gap between each lens as shown in Table 1 or Table 2, the transfer function of the lens optical system reaches the system diffraction limit, ensuring excellent imaging quality of the lens.

[0060] In this embodiment, by using an aluminum alloy lens barrel and setting the aspherical coefficients of each lens, including α2, α3, and α4, as shown in Table 1 or Table 2 above, the entire infrared imaging system can meet the operating temperature range of -80℃ to +80℃, and the imaging quality can meet the usage requirements.

[0061] In this embodiment, the optical dot pattern of the infrared imaging system at +20°C is as follows: Figure 2 As shown. The optical transfer function diagram of the infrared imaging system at +20℃ is as follows. Figure 3 As shown. Optical dot plot of a long-wave infrared imaging system at -80℃. Figure 4 As shown. The optical transfer function diagram of the -80℃ long-wave infrared imaging system is as follows. Figure 5 As shown. The optical dot plot of the infrared imaging system at +80℃ is as follows. Figure 6 As shown. The optical transfer function diagram of the +80℃ long-wave infrared imaging system is as follows. Figure 7 As shown. From Figure 2-7 It can be seen that the infrared imaging system can operate in harsh environmental temperatures ranging from -80℃ to +80℃.

[0062] The infrared imaging system provided in this application embodiment can achieve the following performance indicators:

[0063] a) Focal length: 12.0mm;

[0064] b) F-number: 1;

[0065] c) Band: 8µm~12µm;

[0066] d) Field of view: ±41.8°;

[0067] e) Adapter detector: 1920×1080, 8um;

[0068] f) MTF: >0.15@63lp / mm;

[0069] g) Operating temperature: -80℃~+80℃.

[0070] The infrared imaging system provided in this application adopts a different structural form than before, achieving a large field of view of ±41.8° and excellent imaging quality while maintaining a simple structure. It is compatible with long-wavelength uncooled detectors with a resolution of 1920×1080 and a pixel size of 8µm. Using a long-wavelength uncooled detector with a resolution of 1920×1080 and a pixel size of 8µm can improve the overall resolution of the infrared imaging lens; it is also compatible with detectors with resolutions of 1280×1024, 1024×768, and 640×512. Through optimized design of the long-wavelength infrared imaging system, it achieves normal operation and excellent image quality in harsh environmental temperatures ranging from -80℃ to +80℃.

[0071] In an optional embodiment, lens L1 is a negative meniscus lens, lens L2 is a biconvex lens, lens L3 is a biconcave lens, and lens L4 is a biconvex lens. The front surface of lens L1 is spherical, and the rear surface is aspherical; the front surface of lens L2 is spherical, and the rear surface is aspherical; the front surface of lens L3 is aspherical, and the rear surface is spherical; the front surface of lens L4 is spherical, and the rear surface is aspherical. As shown in Table 3, the thickness of lens L1 is 2mm–5mm, the thickness of lens L2 is 4mm–8mm, the thickness of lens L3 is 2mm–5mm, and the thickness of lens L4 is 5mm–9mm. The air gap between lens 4 and the target surface is 14mm–21mm.

[0072] The materials of lenses L1, L2, L3 and L4 are germanium, zinc sulfide, IRG203 and IRG203, respectively.

[0073] The air gap between lens L1 and lens L2 is 22mm to 25mm, the air gap between lens L2 and lens L3 is 8mm to 15mm, and the air gap between lens L3 and lens L4 is 0.2mm to 2.0mm.

[0074] The radii of curvature of the front and rear surfaces of lens L1 are 43mm~53mm and 18mm~23mm, respectively; the radii of curvature of the front and rear surfaces of lens L2 are 42mm~49mm and -300mm~-190mm, respectively; the radii of curvature of the front and rear surfaces of lens L3 are -39mm~-45mm and 70mm~80mm, respectively; and the radii of curvature of the front and rear surfaces of lens L4 are 45mm~53mm and -43mm~-51mm, respectively.

[0075] The fourth, sixth, and eighth order coefficients of lens L1 are 4.0e-8 to 9.0e-8, 4.0e-10 to 8.0e-10, and -4.0e-12 to -6.0e-13, respectively; the fourth, sixth, and eighth order coefficients of lens L2 are -9.0e-6 to -5.0e-6, -9.0e-8 to -3.0e-8, and 1.0e-10 to 5.0e-10, respectively. The fourth, sixth, and eighth order coefficients of lens L3 are -5.0e-6 to -1.0e-6, 4.0e-8 to 9.0e-8, and 1.0e-10 to 4.0e-10, respectively; the fourth, sixth, and eighth order coefficients of lens L4 are -8.0e-6 to -1.0e-6, -4.0e-8 to -6.0e-9, and -3.0e-10 to -7.0e-11, respectively.

[0076] Table 3

[0077]

[0078] Note: The units for radius of curvature, thickness, diameter, and air gap are mm; α2, α3, and α4 are the fourth, sixth, and eighth degree coefficients of the radial coordinate, respectively.

[0079] In a more specific implementation, the parameters of each lens in the infrared imaging system (such as radius of curvature, thickness, material, fourth-order coefficients, etc.) are shown in Table 4.

[0080] Table 4

[0081]

[0082] Note: The units for radius of curvature, thickness, diameter, and air gap are mm; α2, α3, and α4 are the fourth, sixth, and eighth degree coefficients of the radial coordinate, respectively.

[0083] In this embodiment, by setting the materials of lens L1, lens L2, lens L3 and lens L4 to germanium, zinc sulfide, IRG203 and IRG203 respectively, and by setting the air gap between each lens as shown in Table 3 or Table 4, the transfer function of the lens optical system reaches the system diffraction limit, ensuring excellent imaging quality of the lens.

[0084] In this embodiment, by using an aluminum alloy for the lens barrel and setting the aspherical coefficients of each lens, including α2, α3, and α4, as shown in Table 3 or Table 4 above, the entire infrared imaging system can meet the operating temperature range of -80℃ to +80℃, and the imaging quality can meet the usage requirements.

[0085] In this embodiment, the optical dot pattern of the infrared imaging system at +20°C is as follows: Figure 8As shown. The optical transfer function diagram of the infrared imaging system at +20℃ is as follows. Figure 9 As shown.

[0086] The infrared imaging system provided in this application embodiment can achieve the following performance indicators:

[0087] a) Focal length: 12.0mm;

[0088] b) F-number: 1;

[0089] c) Band: 8µm~12µm;

[0090] d) Field of view: ±42.1°;

[0091] e) Adapter detector: 1920×1080, 8um;

[0092] f) MTF: >0.15@63lp / mm;

[0093] g) Operating temperature: -80℃~+80℃.

[0094] The infrared imaging system provided in this application adopts a different structural form than before, achieving a large field of view of ±42.1° and excellent imaging quality while maintaining a simple structure. It is compatible with long-wavelength uncooled detectors with a resolution of 1920×1080 and a pixel size of 8µm. Using a long-wavelength uncooled detector with a resolution of 1920×1080 and a pixel size of 8µm can improve the overall resolution of the infrared imaging lens; it is also compatible with detectors with resolutions of 1280×1024, 1024×768, and 640×512. Through optimized design of the long-wavelength infrared imaging system, it achieves normal operation and excellent image quality in harsh environmental temperatures ranging from -80℃ to +80℃.

[0095] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0096] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0097] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0098] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An infrared imaging system, characterized in that, It consists of lenses L1, L2, L3 and L4 arranged sequentially along the direction of light propagation; Among them, lens L1 is a negative meniscus lens, lens L2 is a positive meniscus lens or a biconvex lens, lens L3 is a biconcave lens, and lens L4 is a biconvex lens; the thickness of lens L1 is 2 mm to 5 mm, the thickness of lens L2 is 4 mm to 8 mm, the thickness of lens L3 is 2 mm to 5 mm, and the thickness of lens L4 is 5 mm to 9 mm; the front surface of lens L1 is spherical, and the rear surface is aspherical; lens L2 is an aspherical lens; the front surface of lens L3 is aspherical, and the rear surface is spherical; the front surface of lens L4 is spherical, and the rear surface is aspherical; the air gap between lens L1 and lens L2 is 22 mm to 37 mm, the air gap between lens L2 and lens L3 is 8 mm to 16 mm, and the air gap between lens L3 and lens L4 is 0.2 mm to 2.0 mm; If lens L2 is a positive meniscus lens, the front surface of lens L2 is aspherical and the rear surface is spherical; the materials of lens L1, lens L2, lens L3 and lens L4 are germanium, IRG203, zinc sulfide and IRG207 respectively; the radii of curvature of the front and rear surfaces of lens L1 are 29 mm to 35 mm and 16 mm to 22 mm respectively, the radii of curvature of the front and rear surfaces of lens L2 are 33 mm to 38 mm and 110 mm to 200 mm respectively, the radii of curvature of the front and rear surfaces of lens L3 are -46 mm to -54 mm and 66 mm to 76 mm respectively, and the radii of curvature of the front and rear surfaces of lens L4 are 48 mm to 56 mm and -48 mm to -57 mm respectively. If lens L2 is a biconvex lens, the front surface of lens L2 is spherical and the rear surface is aspherical; the materials of lens L1, lens L2, lens L3 and lens L4 are germanium, zinc sulfide, IRG203 and IRG203, respectively; the radii of curvature of the front and rear surfaces of lens L1 are 43 mm to 53 mm and 18 mm to 23 mm, respectively; the radii of curvature of the front and rear surfaces of lens L2 are 42 mm to 49 mm and -300 mm to -190 mm, respectively; the radii of curvature of the front and rear surfaces of lens L3 are -39 mm to -45 mm and 70 mm to 80 mm, respectively; and the radii of curvature of the front and rear surfaces of lens L4 are 45 mm to 53 mm and -43 mm to -51 mm, respectively.

2. The infrared imaging system according to claim 1, characterized in that, If the lens L2 is a positive meniscus lens The air gap between lens L1 and lens L2 is 31mm to 37mm, the air gap between lens L2 and lens L3 is 10mm to 16mm, and the air gap between lens L3 and lens L4 is 0.3mm to 2.0mm.

3. The infrared imaging system according to claim 1, characterized in that, If the lens L2 is a positive meniscus lens The fourth, sixth, and eighth term coefficients of lens L1 are 3.0e-7 to 7.0e-7, 1.0e-9 to 6.0e-9, and 6.0e-11 to 1.0e-10, respectively. The fourth, sixth, and eighth term coefficients of lens L2 are 4.0e-7 to 8.0e-7, -3.0e-009 to -1.0e-9, and -2.0e-10 to -6.0e-11, respectively. The fourth, sixth, and eighth term coefficients of lens L3 are -6.0e-6 to -1.0e-6, 6.0e-8 to 1.6e-7, and -6.0e-10 to -1.0e-10, respectively. The fourth, sixth, and eighth term coefficients of lens L4 are -1.5e-5 to -5.0e-6, 2.0e-8 to 7.0e-8, and 1.0e-10 to 4.0e-10, respectively.

4. The infrared imaging system according to claim 1, characterized in that, If the lens L2 is a biconvex lens The air gap between lens L1 and lens L2 is 22 mm to 25 mm, the air gap between lens L2 and lens L3 is 8 mm to 15 mm, and the air gap between lens L3 and lens L4 is 0.2 mm to 2.0 mm.

5. The infrared imaging system according to claim 1, characterized in that, If the lens L2 is a biconvex lens The fourth, sixth, and eighth term coefficients of lens L1 are 4.0e-8 to 9.0e-8, 4.0e-10 to 8.0e-10, and -4.0e-12 to -6.0e-13, respectively. The fourth, sixth, and eighth term coefficients of lens L2 are -9.0e-6 to -5.0e-6, -9.0e-8 to -3.0e-8, and 1.0e-10 to 5.0e-10, respectively. The fourth, sixth, and eighth term coefficients of lens L3 are -5.0e-6 to -1.0e-6, 4.0e-8 to 9.0e-8, and 1.0e-10 to 4.0e-10, respectively. The fourth, sixth, and eighth degree coefficients of lens L4 are -8.0e-6 to -1.0e-6, -4.0e-8 to -6.0e-9, and -3.0e-10 to -7.0e-11, respectively.

6. The infrared imaging system according to claim 1, characterized in that, Also includes: A long-wavelength uncooled detector with a resolution of 1920×1080 and a pixel size of 8µm.

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