Optically athermalized long-wave infrared imaging system and infrared camera

Abstract

The application provides an optical athermal long-wave infrared imaging system and an infrared camera. The optical athermal long-wave infrared imaging system comprises a first lens, a second lens and a third lens arranged in sequence along the same optical axis by a preset distance from an object plane to an image plane; the first lens is a meniscus lens, has opposite first concave and convex surfaces, the first concave surface is located on the side of the first lens away from the second lens, and the first convex surface is located on the side of the first lens close to the second lens; the second lens is a double-convex lens, has opposite second and third convex surfaces, the second convex surface is located on the side of the second lens close to the first lens, and the third convex surface is located on the side of the second lens close to the third lens; and the third lens is a meniscus lens, has opposite fourth convex and second concave surfaces, the fourth convex surface is located on the side of the third lens close to the second lens, and the second concave surface is located on the side of the third lens away from the second lens.

Description

Technical Field

[0001] This application relates to the field of photoelectric imaging and detection technology, and in particular to an optically athermalized long-wave infrared imaging system and an infrared camera. Background Technology

[0002] With the rapid development of infrared detection technology and the continuous expansion of its application scope, the requirements for the performance and application environment of infrared lenses are becoming increasingly stringent. Changes in ambient temperature can cause changes in the lens's shape, thickness, refractive index, spacing, and barrel, leading to defocusing of the infrared lens. Therefore, a thermal design is necessary for the lens. Currently, thermal design is mainly achieved through three methods: mechanical passive, electronic active, and optical passive.

[0003] Mechanical passive optical compensation compensates for the image plane by designing inverse changes in mechanical and optical materials; electronic active optical compensation compensates by moving the lens with a motor. Both methods have been tested in recent years. Mechanical passive compensation is limited by its structure, resulting in excessive size and weight, making it difficult to meet the miniaturization and compactness requirements of optical systems. Electronic active optical compensation is limited by electronic components or motors, leading to decreased reliability during temperature changes and restricting its application scenarios. Optical passive compensation utilizes the differences in the thermal properties of optical materials, employing different materials for optical compensation to ensure the stability of the imaging position. Compared to the other two compensation methods, optical passive compensation is characterized by its simple structure, small size, light weight, no power supply required, and high system reliability. With the increasing prevalence of diamond single-point lathes, the processing technology problems of aspherical and binary surfaces have been gradually solved. Furthermore, the performance and supply of domestic infrared optical materials have gradually stabilized, making calorimetric optical passive compensation the most mainstream technological approach.

[0004] Currently available infrared cameras use athermalized lenses with relatively small imaging apertures, making it difficult to achieve high-definition imaging of distant objects. Furthermore, they suffer from low spectral response sensitivity over a wide temperature range. Therefore, designing a athermalized lens with a large relative imaging aperture and adaptability to a temperature range of ±100℃ is a pressing technical challenge. Summary of the Invention

[0005] The purpose of this application is to provide an optically athermalized long-wave infrared imaging system and an infrared camera to achieve high-definition imaging of distant objects within a wide temperature range of ±100℃.

[0006] To address the aforementioned technical problems, the embodiments of this application provide the following technical solutions:

[0007] This application provides an optical athermalized long-wave infrared imaging system, comprising: a first lens, a second lens, and a third lens arranged sequentially along the same optical axis from the object plane to the image plane at a predetermined distance; the first lens is a meniscus lens, having a first concave surface and a first convex surface, the first concave surface being located on the side of the first lens away from the second lens, and the first convex surface being located on the side of the first lens closer to the second lens; the second lens is a biconvex lens, having a second convex surface and a third convex surface, the second convex surface being located on the side of the second lens closer to the first lens, and the third convex surface being located on the side of the second lens closer to the third lens, the radius of curvature of the second convex surface being smaller than the absolute value of the radius of curvature of the third convex surface; the third lens is a meniscus lens, having a fourth convex surface and a second concave surface, the fourth convex surface being located on the side of the third lens closer to the second lens, and the second concave surface being located on the side of the third lens away from the second lens; wherein, the focal length of the optical athermalized long-wave infrared imaging system is f, and the focal lengths of the first lens, the second lens, and the third lens are f1, f2, and f3 respectively, and satisfy: -30 <f1 / f<-3,1.2<f2 / f<2,1.3<f3 / f<3。

[0008] In some modified embodiments of the first aspect of this application, the center thickness of the first lens is 5.99 mm to 6.01 mm, the center thickness of the second lens is 5.37 mm to 5.38 mm, and the center thickness of the third lens is 5.99 mm to 6.01 mm; wherein the center distance between the first lens and the second lens is 4.79 mm to 4.81 mm, the center distance between the second lens and the third lens is 25.13 mm to 25.15 mm, and the center distance between the third lens and the focal plane is 10.65 mm to 10.67 mm.

[0009] In some modified embodiments of the first aspect of this application, the first concave surface is a spherical surface and the first convex surface is an aspherical surface; the second convex surface is a spherical surface and the third convex surface is an aspherical surface plus a binary optical surface; the fourth convex surface is an aspherical surface and the second concave surface is a spherical surface.

[0010] In some modified embodiments of the first aspect of this application, the radius of curvature of the first concave surface is -25.18 mm to -25.16 mm, the radius of curvature of the first convex surface is -33.72 mm to -33.70 mm, the radius of curvature of the second convex surface is 67.55 mm to 67.57 mm, the radius of curvature of the third convex surface is -334.87 mm to -334.85 mm, the radius of curvature of the fourth convex surface is 21.10 mm to 21.12 mm, and the radius of curvature of the second concave surface is 19.61 mm to 19.63 mm.

[0011] In some modified embodiments of the first aspect of this application, the outer diameter of the first lens is 17.5 mm to 17.7 mm, the outer diameter of the second lens is 20.4 mm to 20.5 mm, and the outer diameter of the third lens is 13.3 mm to 13.5 mm.

[0012] In some modified embodiments of the first aspect of this application, the aspherical surface satisfies the following expression: Where Z(Y) is the sag of the aspherical surface along the same optical axis, R is the radius of curvature at the vertex of the aspherical surface, Y is the half-aperture of the aspherical surface perpendicular to the same optical axis, K is the conic coefficient, and A, B, C, D and E are the aspherical coefficients.

[0013] In some modified embodiments of the first aspect of this application, the binary optical surface satisfies the following expression: Φ = MA1Y 2 +MA2Y 4 Where Φ is the phase of the binary optical surface, M is the diffraction order, Y is the normalized polar coordinate, and A1 and A2 are the phase coefficients of the binary optical surface, respectively.

[0014] In some modified embodiments of the first aspect of this application, the first lens and the third lens are made of germanium material; the second lens is made of chalcogenide glass material.

[0015] The second aspect of this application provides an infrared camera, which includes: any of the optical athermalized long-wave infrared imaging systems provided in the first aspect of this application.

[0016] In some modified embodiments of the second aspect of this application, the focal length of the optical athermalized long-wave infrared imaging system is 24mm, the reciprocal of the relative aperture (F-number) is 0.9, the matched array size is 640*512, and the pixel size is 12μm.

[0017] Compared with the prior art, the optical athermalized long-wave infrared imaging system provided by the present application includes: a first lens, a second lens, and a third lens arranged in sequence along the same optical axis at a preset distance from the object plane to the image plane. The first lens is a meniscus lens with a relative first concave surface and a first convex surface, and its focal length is f1; the second lens is a biconvex lens with a relative second convex surface and a third convex surface, and its focal length is f2; the third lens is a meniscus lens with a relative fourth convex surface and a second concave surface, and its focal length is f3; the focal length of the optical athermalized long-wave infrared imaging system is f, and the focal lengths of the first lens, the second lens, and the third lens satisfy: -30 < f1 / f < -3, 1.2 < f2 / f < 2, 1.3 < f3 / f < 3. The optical athermalized long-wave infrared imaging system provided by the present application adopts the principle of refractive-diffractive hybrid, so that the system will not produce defocus phenomenon within a wide temperature range of ±100°C, ensuring that the system can achieve high-definition imaging without a focusing mechanism in different temperature environments. By utilizing the unique thermal expansion coefficient and dispersion characteristics of the diffractive element, it is characterized that the system has good ability to eliminate thermal difference, chromatic aberration, and secondary spectrum; a relatively large relative imaging aperture is used to increase the light flux, which can meet the imaging requirements at a relatively long distance. The optical athermalized long-wave infrared imaging system provided by the present application effectively solves the problem of high-definition imaging of distant objects within a wide temperature range of ±100°C. Brief Description of the Drawings

[0018] By referring to the following detailed description with reference to the accompanying drawings, the above and other objects, features, and advantages of the exemplary embodiments of the present application will become easily understandable. In the drawings, several embodiments of the present application are shown in an exemplary rather than restrictive manner, and the same or corresponding reference numerals represent the same or corresponding parts, where:

[0019] Figure 1 Shows a schematic structural diagram of the optical athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention;

[0020] Figure 2 Is the transfer function diagram of the optical athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention under the environment of +20°C;

[0021] Figure 3 Is the transfer function diagram of the optical athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention under the environment of -100°C;

[0022] Figure 4 Is the transfer function diagram of the optical athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention under the environment of +100°C;

[0023] Figure 5 Is the spot diagram of the optical athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention under the environment of +20°C;

[0024] Figure 6 The image shows the diffusion pattern of the optically calorimetric long-wave infrared imaging system proposed in Embodiment 1 of the present invention at -100℃.

[0025] Figure 7 The image shows the diffusion pattern of the optically calorimetric long-wave infrared imaging system proposed in Embodiment 1 of the present invention at +100℃.

[0026] Figure 8 The distortion image of the optically athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention at +20℃.

[0027] Figure 9 The distortion image of the optically calorimetric long-wave infrared imaging system proposed in Embodiment 1 of the present invention at -100℃.

[0028] Figure 10 This is a distortion image of the optically anechoic long-wave infrared imaging system proposed in Embodiment 1 of the present invention under a +100℃ environment.

[0029] Explanation of icon numbers:

[0030] 1. First lens; 1a. First concave surface; 1b. First convex surface; 2. Second lens; 2a. Second convex surface; 2b. Third convex surface; 3. Third lens; 3a. Fourth convex surface; 3b. Second concave surface; 4. Detector window; 5. Imaging surface. Detailed Implementation

[0031] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0032] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application shall have the ordinary meaning as understood by one of ordinary skill in the art to which this application pertains.

[0033] Example 1

[0034] Reference Appendix Figure 1Embodiment 1 of the present invention proposes an optically athermalized long-wave infrared imaging system, which comprises: a first lens 1, a second lens 2, and a third lens 3 arranged sequentially along the same optical axis from the object plane to the image plane at a predetermined distance; the first lens 1 is a meniscus lens, having a first concave surface 1a and a first convex surface 1b, the first concave surface 1a being located on the side of the first lens 1 away from the second lens 2, and the first convex surface 1b being located on the side of the first lens 1 closer to the second lens 2; the second lens 2 is a biconvex lens, having a second convex surface 2a and a third convex surface 2b, the second convex surface 2a being located on the side of the first lens 1 closer to the second lens 2; the second lens 2 is a biconvex lens, having a second convex surface 2a and a third convex surface 2b, the second convex surface 2a being located on the side of the first lens 1 closer to the second lens 2. Lens 2 is located on the side of the first lens 1. The third convex surface 2b is located on the side of the second lens 2 closest to the third lens 3. The radius of curvature of the second convex surface 2a is smaller than the absolute value of the radius of curvature of the third convex surface 2b. The third lens 3 is a meniscus lens, having a fourth convex surface 3a and a second concave surface 3b. The fourth convex surface 3a is located on the side of the third lens 3 closest to the second lens 2, and the second concave surface 3b is located on the side of the third lens 3 away from the second lens 2. The focal length of the optically athermalized long-wave infrared imaging system is f, and the focal lengths of the first lens 1, second lens 2, and third lens 3 are f1, f2, and f3 respectively, satisfying: -30°. <f1 / f<-3,1.2<f2 / f<2,1.3<f3 / f<3。

[0035] Specifically, the focal length of this athermalized long-wave infrared imaging system is f, and it comprises a first lens 1, a second lens 2, and a third lens 3 arranged sequentially along the same optical axis from the object plane to the image plane at a predetermined distance. The first lens 1 is a meniscus lens with a focal length of f1; the second lens 2 is a biconvex lens with a focal length of f2; and the third lens 3 is a meniscus lens with a focal length of f3. The focal lengths of the first lens 1, the second lens 2, and the third lens 3 respectively satisfy: -30 <f1 / f<-3,1.2<f2 / f<2,1.3<f3 / f<3。

[0036] Specifically, the first lens 1 has a first concave surface 1a and a first convex surface 1b, with the first concave surface 1a located on the side of the first lens 1 away from the second lens 2, and the first convex surface 1b located on the side of the first lens 1 closer to the second lens 2; the second lens 2 has a second convex surface 2a and a third convex surface 2b, with the second convex surface 2a located on the side of the second lens 2 closer to the first lens 1, and the third convex surface 2b located on the side of the second lens 2 closer to the third lens 3, and the radius of curvature of the second convex surface 2a being smaller than the absolute value of the radius of curvature of the third convex surface 2b; the third lens 3 has a fourth convex surface 3a and a second concave surface 3b, with the fourth convex surface 3a located on the side of the third lens 3 closer to the second lens 2, and the second concave surface 3b located on the side of the third lens 3 away from the second lens 2.

[0037] As described above, the athermalized optical long-wave infrared imaging system provided in this application employs the principle of refractive-diffraction hybridization, ensuring that the system does not experience defocusing within a wide temperature range of ±100℃. It utilizes optical compensation to eliminate thermal aberrations, meeting the requirement for clear imaging within this wide temperature range without dynamic adjustment. This guarantees high-definition imaging in various temperature environments without the need for a focusing mechanism. By leveraging the unique photothermal expansion coefficient and dispersion characteristics of diffractive elements, the system possesses excellent capabilities in eliminating chromatic aberration and second-order spectral distortion, and a relatively large imaging aperture, meeting the imaging needs at greater distances. The athermalized optical long-wave infrared imaging system provided in this application effectively solves the problem of high-definition imaging of distant objects within a wide temperature range of ±100℃.

[0038] Further, see attached document. Figure 1 In the optical athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention, the center thickness of the first lens 1 is 5.99 mm to 6.01 mm, the center thickness of the second lens 2 is 5.37 mm to 5.38 mm, and the center thickness of the third lens 3 is 5.99 mm to 6.01 mm; wherein, the center distance between the first lens 1 and the second lens 2 is 4.79 mm to 4.81 mm, the center distance between the second lens 2 and the third lens 3 is 25.13 mm to 25.15 mm, and the center distance between the third lens 3 and the focal plane is 10.65 mm to 10.67 mm.

[0039] Further, see attached document. Figure 1 In the optical athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention, the first concave surface 1a is a sphere, the first convex surface 1b is an aspherical surface; the second convex surface 2a is a sphere, the third convex surface 2b is an aspherical surface plus a binary optical surface; the fourth convex surface 3a is an aspherical surface, and the second concave surface 3b is a sphere.

[0040] Further, see attached document. Figure 1 In the optical athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention, the radius of curvature of the first concave surface 1a is -25.18 mm to -25.16 mm, the radius of curvature of the first convex surface 1b is -33.72 mm to -33.70 mm, the radius of curvature of the second convex surface 2a is 67.55 mm to 67.57 mm, the radius of curvature of the third convex surface 2b is -334.87 mm to -334.85 mm, the radius of curvature of the fourth convex surface 3a is 21.10 mm to 21.12 mm, and the radius of curvature of the second concave surface 3b is 19.61 mm to 19.63 mm.

[0041] Further, see attached document. Figure 1In the optical athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention, the outer diameter of the first lens 1 is 17.5 mm to 17.7 mm, the outer diameter of the second lens 2 is 20.4 mm to 20.5 mm, and the outer diameter of the third lens 3 is 13.3 mm to 13.5 mm.

[0042] Furthermore, in the optical athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention, the first lens 1 and the third lens 3 are respectively made of germanium material; the second lens 2 is made of chalcogenide glass material.

[0043] Specifically, in this system, both the first lens 1 and the third lens 3 are made of germanium material through single-point diamond turning or polishing. The first lens 1 and the third lens 3 have high refractive indices, which are beneficial for correcting aberrations. Compared to chalcogenide glass, germanium material has higher wear resistance, and when combined with a diamond-like carbon film, it exhibits even higher scratch and wear resistance, enhancing the lens's protective capabilities and improving environmental adaptability.

[0044] Specifically, the second lens 2 is made of chalcogenide glass. Chalcogenide glass has a small temperature coefficient, giving it strong temperature adaptability and helping to reduce thermal differences. HWS5 chalcogenide glass is preferred, and it is manufactured by single-point diamond turning, polishing, or precision molding.

[0045] Specifically, the first lens 1, made of germanium material combined with a diamond-like carbon film, can effectively improve the protective capability of the system, making it suitable for extreme environments such as sandstorms, water vapor, or salt spray. The second lens 2, made of chalcogenide glass, has its third convex surface 2b, an aspherical surface plus a binary optical surface, which can be processed by molding. This process helps to reduce production costs and meet the needs of mass production.

[0046] Specifically, the system also includes a detector window 4 and an imaging surface 5. In this system, the first lens 1, the second lens 2, the third lens 3, the detector window 4, and the imaging surface 5 are arranged sequentially along the same optical axis.

[0047] Specifically, the preferred parameters for each lens in this optical system are shown in the table below:

[0048]

[0049]

[0050] Furthermore, in the optically athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention, the aspherical surface satisfies the following expression: Where Z(Y) is the sag of the aspherical surface along the same optical axis, R is the radius of curvature at the vertex of the aspherical surface, Y is the half-aperture of the aspherical surface perpendicular to the same optical axis, K is the conic coefficient, and A, B, C, D and E are the aspherical coefficients.

[0051] Specifically, the preferred aspherical coefficients of each lens in this optical system are shown in the table below:

[0052] aspherical K A B C D E 1b 0 1.50E-6 1.16E-9 2.13E-12 8.08E-15 -1.02E-17 2b 0 -1.97E-6 7.29E-9 -1.09E-11 9.78E-15 -3.95E-18 3a 0 -2.21E-6 -4.09E-9 9.84E-12 -1.34E-13 2.77E-16

[0053] Furthermore, in the optically athermalized long-wave infrared imaging system proposed in Embodiment 1 of the present invention, the binary optical surface satisfies the following expression: Φ=MA1Y 2 +MA2Y 4 Where Φ is the phase of the binary optical surface, M is the diffraction order, Y is the normalized polar coordinate, and A1 and A2 are the phase coefficients of the binary optical surface, respectively.

[0054] Specifically, the preferred binary optical surface coefficients in this optical system are shown in the table below:

[0055] Binary optical surface M <![CDATA[A1]]> <![CDATA[A2]]> 2b 1 -44.04 0.94

[0056] Specifically, optical experiments were conducted on the optically athermalized long-wave infrared imaging system proposed in the embodiments of the present invention, which includes the above-mentioned preferred parameters, and optical transfer function curves were output under operating environments of +20℃, +100℃, and -100℃, respectively. According to the appendix... Figure 2 To be continued Figure 4 As shown, the cutoff frequency is 42 LP / mm. At the cutoff frequency, the modulation transfer function (MTF) value of the system is close to the diffraction limit.

[0057] Specifically, optical experiments were conducted on the optically athermalized long-wave infrared imaging system proposed in the embodiments of the present invention, including the above-mentioned preferred parameters, and dot plots were output under operating environments of +20℃, +100℃, and -100℃ to compare the dispersion at different temperatures. According to the appendix... Figure 5 To be continued Figure 7 As shown, the focused spot size of the system is comparable to that of the Airy disk in operating environments of +20℃, +100℃ and -100℃.

[0058] Specifically, based on the optical experiments conducted in working environments of +20℃, +100℃, and -100℃, it can be seen that the system can effectively guarantee imaging quality over a wide temperature range of ±100℃.

[0059] Specifically, optical experiments were conducted on the optically athermalized long-wave infrared imaging system proposed in the embodiments of the present invention, which includes the above-mentioned preferred parameters, and distortion curves were output under operating environments of +20℃, +100℃, and -100℃, respectively. According to the appendix... Figure 8 To be continued Figure 10 As shown, the distortion range of this system in working environments of +20℃, +100℃ and -100℃ does not exceed 1%, which is basically imperceptible to the naked eye. Therefore, this system can guarantee the correction of aberrations.

[0060] Example 2

[0061] Embodiment 2 of the present invention provides an infrared camera, which includes: the optical athermalized long-wave infrared imaging system proposed in any of the embodiments of the present application.

[0062] Furthermore, in the specific implementation of the infrared camera proposed in Embodiment 2 of the present invention, the focal length of the optical athermal long-wave infrared imaging system is 24mm, the reciprocal of the relative aperture (i.e., the F-number) is 0.9, the matching array size is 640*512, and the pixel size is 12μm.

[0063] Specifically, the infrared camera has an imaging focal length of 24mm, an F-number that is the reciprocal of the relative aperture (F-number) of 0.9, a matching array size of 640*512, a pixel size of 12μm, and is suitable for a wide temperature range of ±100℃.

[0064] It should be noted that in the description of this specification, the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, 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, and therefore should not be construed as a limitation of the present invention; the terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present invention can be understood according to the specific circumstances.

[0065] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0066] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An optically athermalized long-wave infrared imaging system, characterized in that, include: It consists of a first lens, a second lens, and a third lens arranged sequentially at a predetermined distance from the object plane to the image plane along the same optical axis. The first lens is a meniscus lens, which has a first concave surface and a first convex surface. The first concave surface is located on the side of the first lens away from the second lens, and the first convex surface is located on the side of the first lens closer to the second lens. The second lens is a biconvex lens, which has a second convex surface and a third convex surface opposite each other. The second convex surface is located on the side of the second lens closer to the first lens, and the third convex surface is located on the side of the second lens closer to the third lens. The radius of curvature of the second convex surface is smaller than the absolute value of the radius of curvature of the third convex surface. The third lens is a meniscus lens, which has a fourth convex surface and a second concave surface. The fourth convex surface is located on the side of the third lens closer to the second lens, and the second concave surface is located on the side of the third lens away from the second lens. Wherein, the focal length of the optical athermalized long-wave infrared imaging system is f, and the focal lengths of the first lens, the second lens, and the third lens are f1, f2, and f3 respectively, and satisfy: -30 <f1 / f<-3,1.2<f2 / f<2,1.3<f3 / f<3; The center thickness of the first lens is 5.99 mm to 6.01 mm, the center thickness of the second lens is 5.37 mm to 5.38 mm, and the center thickness of the third lens is 5.99 mm to 6.01 mm. The center distance between the first lens and the second lens is 4.79 to 4.81 mm, the center distance between the second lens and the third lens is 25.13 to 25.15 mm, and the center distance between the third lens and the focal plane is 10.65 to 10.67 mm. The first concave surface is a spherical surface, and the first convex surface is an aspherical surface; The second convex surface is a spherical surface, and the third convex surface is an aspherical surface plus a binary optical surface; The fourth convex surface is an aspherical surface, and the second concave surface is a spherical surface; The radius of curvature of the first concave surface is -25.18 mm to -25.16 mm, and the radius of curvature of the first convex surface is -33.72 mm to -33.70 mm. The radius of curvature of the second convex surface is 67.55 mm to 67.57 mm, and the radius of curvature of the third convex surface is -334.87 mm to -334.85 mm. The radius of curvature of the fourth convex surface is 21.10 mm to 21.12 mm, and the radius of curvature of the second concave surface is 19.61 mm to 19.63 mm.

2. The optically athermalized long-wave infrared imaging system according to claim 1, characterized in that, The outer diameter of the first lens is 17.5 mm to 17.7 mm, the outer diameter of the second lens is 20.4 mm to 20.5 mm, and the outer diameter of the third lens is 13.3 mm to 13.5 mm.

3. The athermalized long-wave infrared imaging system according to claim 1, characterized in that, The aspherical surface satisfies the following expression: Where Z(Y) is the sag of the aspherical surface along the same optical axis, R is the radius of curvature at the vertex of the aspherical surface, Y is the half-aperture of the aspherical surface perpendicular to the same optical axis, K is the conic coefficient, and A, B, C, D and E are the aspherical coefficients.

4. The optically athermalized long-wave infrared imaging system according to claim 1, characterized in that, The binary optical surface satisfies the following expression: Φ=MA1Y 2 +MA2Y 4 ; Where Φ is the phase of the binary optical surface, M is the diffraction order, Y is the normalized polar coordinate, and A1 and A2 are the phase coefficients of the binary optical surface, respectively.

5. The optically athermalized long-wave infrared imaging system according to any one of claims 1-4, characterized in that, The first lens and the third lens are both made of germanium. The second lens is made of chalcogenide glass.

6. An infrared camera, characterized in that, include: The optically athermalized long-wave infrared imaging system as described in any one of claims 1-5.

7. The infrared camera according to claim 6, characterized in that, The optical athermalized long-wave infrared imaging system has a focal length of 24mm, an F-number that is the reciprocal of the relative aperture (F-number) of 0.9, a matching array size of 640*512, and a pixel size of 12μm.

Images