Refrigeration passive athermalization infrared optical system

Abstract

The utility model provides a refrigeration passive athermalization infrared optical system, relates to the technical field of infrared optics, and aims to solve the problems that when an optical instrument is used in a larger temperature range, the focal power of a lens changes due to thermal expansion and cold contraction of a lens barrel material and an optical material, the temperature refractive index coefficient of the optical material, the thickness of a lens, the curvature and the like, and a defocusing phenomenon is generated. In order to solve the technical problem that infrared optical materials applied to an existing infrared optical system particularly have high requirements for the environment, passive athermalization is carried out, mutual compensation is carried out by combining thermal performance of different infrared optical materials and structural materials, and the infrared optical system can achieve the infrared imaging effect within the long-wave infrared band of 5-8 micrometers. Passive athermalization at-30 DEG C to 30 DEG C is achieved, and good imaging quality is kept.

Description

Technical Field

[0001] The utility model relates to the technical field of infrared optics. Background Art

[0002] When optical instruments are used in a large temperature range, the thermal expansion and contraction of the lens barrel material and optical material, as well as the temperature refractive index coefficient of the optical material, lens thickness, curvature, etc., will cause the lens optical power to change, resulting in defocus and deteriorating imaging quality, especially in infrared optical systems.

[0003] In addition, the infrared optical materials used in existing infrared optical systems have particularly high requirements on the environment. For example, CaF2 easily forms a white film on the optical surface. The distance between each lens is large, which makes the length of the entire lens group relatively large, and has high requirements on the structure. The lens is too curved, the edge is too thin, and it contains aspheric optical elements, which are costly and difficult to process and assemble. Utility Model Content

[0004] In order to solve the deficiencies existing in the above-mentioned prior art, the utility model provides a "refrigerated passive athermal infrared optical system".

[0005] like Figure 1 As shown, the cooled passive athermal infrared optical system includes

[0006] A first meniscus lens 1, the object side surface of which is convex and the other surface of which is concave;

[0007] The second meniscus lens 2 has a convex surface on the light incident side and a concave surface on the other side;

[0008] The third meniscus lens 3 has a convex surface on the light incident side and a concave surface on the other side;

[0009] The fourth biconvex lens 4 has a convex surface on the light incident side and a convex surface on the other side;

[0010] The fifth meniscus lens 5 has a convex surface on the light incident side and a concave surface on the image side.

[0011] Technical effect:

[0012] This optical system performs passive athermalization, combines different infrared optical materials, and compensates for each other in thermal properties of structural materials. Materials with large refractive index are conducive to correcting aberrations, combinations of materials with large differences in Abbe numbers are conducive to achromatization, and materials with large differences in optical focal temperature coefficient T of lenses are conducive to athermalization. Materials with large Abbe numbers and small optical focal temperature coefficient T of lenses are combined with materials with small Abbe numbers and large optical focal temperature coefficient T of lenses to achieve good optical imaging quality at different temperatures without athermalization; it can also work normally without being irradiated by external light sources such as the sun, has strong penetration into smoke and dust, and can achieve high background suppression capabilities and high signal-to-noise ratios in low-temperature environments in conjunction with the refrigerated detectors used.

[0013] Compared with existing infrared optical systems, this improvement has the following advantages:

[0014] 1. Use common optical materials to reasonably distribute and combine to eliminate heat difference, with small thermal expansion coefficient and low requirements on the use environment.

[0015] 2. It can achieve passive heat elimination at -30℃~30℃ in the long-wave infrared band of 5μm~8μm and maintain good imaging quality.

[0016] 3. The structure is simple and compact, keeping the system focal length at 175-190mm, reducing the number of lenses in the optical system (five pieces), controlling the minimum edge and centering coefficient of the lens, making the lens easy to process, and using spherical lenses, which greatly reduces the processing cost.

[0017] 4. At different temperatures, the MTF of each field of view is better than 0.4, such as Figure 2-4 shown.

[0018] 5. System distortion is better than 0.3%, improving imaging quality, such as Figure 5 shown.

[0019] 6. With real exit pupil, it achieves 100% cold aperture efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of the utility model's passive athermal cooling infrared optical system.

[0021] Figure 2 This is the MTF curve diagram of the embodiment of the utility model at -30°C.

[0022] Figure 3 This is the MTF curve diagram of the embodiment of the utility model at 0°C.

[0023] Figure 4 This is the MTF curve diagram of the embodiment of the utility model at 30℃.

[0024] Figure 5 Schematic diagram of field curvature (left) and distortion (right) of an embodiment of the utility model. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the solution of the utility model, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is only a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0026] like Figure 1-5 As shown, the utility model cooling passive athermal infrared optical system comprises: a first meniscus lens 1 made of silicon material, a second meniscus lens 2 made of germanium material, a third meniscus lens 3 made of zinc sulfide material, a fourth double convex lens 4 made of zinc selenide material, and a fifth meniscus lens 5 made of germanium material.

[0027] The optical system can achieve passive athermalization in the long-wave infrared band of 5 μm to 8 μm, at -30°C to 30°C, with a focal length of 175-190 mm, preferably 180 mm, a half field of view of 1.6°, and an F number of 2-3.

[0028] like Figure 2-4 As shown in the figure, by analyzing the system transfer function MTF graphs at -30℃, 0℃, and 30℃, the system transfer function MTF curves do not change much, and are all greater than 0.50 at the detector diffraction limit of 20lp / mm. Common infrared materials are used to reduce the air gap between lenses to reduce the total length of the optical system, keep the system focal length at 175-190mm, control the minimum edge and centering coefficient of the lens, and make the lens easy to process, such as Figure 5 As shown, the control system distortion is better than 0.3%.

[0029] The center thickness of the first meniscus lens 1 is 30.540-30.695 mm, the radius of curvature of the light incident surface is 133.537-134.547 mm, and the radius of curvature of the light emitting surface is -310.055--310.098 mm;

[0030] The center thickness of the second meniscus lens 2 is 10.003-10.016 mm, the radius of curvature of the light incident surface is 606.065-607.167 mm, and the radius of curvature of the light emitting surface is -176.878--176.908 mm;

[0031] The central thickness of the third meniscus lens 3 is 10.40-10.42 mm, the curvature radius of the light incident surface is 559.885-560.996 mm, and the curvature radius of the light emitting surface is -1811.234--1813.773 mm;

[0032] The fourth biconvex lens 4 has a central thickness of 78.19-78.25 mm, a light incident surface curvature radius of 419.974-420.083 mm, and a light exit surface curvature radius of 686.649-687.676 mm;

[0033] The central thickness of the fifth meniscus lens 5 is 1.502-1.509 mm, the curvature radius of the light incident surface is 119.547-120.568 mm, and the curvature radius of the light emitting surface is -108.284--109.302 mm.

[0034] Unless otherwise stated, any technical solution disclosed in the present invention disclosed above, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any technician in the field should understand that the preferred numerical range is only a numerical value with a more obvious technical effect or representative value among many implementable numerical values. Since there are too many numerical values ​​to be exhaustive, the present invention discloses some numerical values ​​to illustrate the technical solution of the present invention, and the numerical values ​​listed above should not constitute a limitation on the scope of protection of the present invention.

Claims

1. A cooled passive athermal infrared optical system, characterized in that: include: A first meniscus lens (1) having a convex object surface and a concave other surface; A second meniscus lens (2) having a convex surface on the light incident side and a concave surface on the other side; A third meniscus lens (3) having a convex surface on the light incident side and a concave surface on the other side; A fourth biconvex lens (4) having a convex surface on the light incident side and a convex surface on the other side; The fifth meniscus lens (5) has a convex surface on the light incident side and a concave surface on the image side.

2. The cooled passive athermal infrared optical system according to claim 1, characterized in that: The invention comprises a first meniscus lens (1) made of silicon material, a second meniscus lens (2) made of germanium material, a third meniscus lens (3) made of zinc sulfide material, a fourth double convex lens (4) made of zinc selenide material, and a fifth meniscus lens (5) made of germanium material.

3. The cooled passive athermal infrared optical system according to claim 2, characterized in that: The center thickness of the first meniscus lens (1) is 30.540-30.695 mm, the radius of curvature of the light incident surface is 133.537-134.547 mm, and the radius of curvature of the light exit surface is -310.055--310.098 mm; The central thickness of the second meniscus lens (2) is 10.003-10.016 mm, the radius of curvature of the light incident surface is 606.065-607.167 mm, and the radius of curvature of the light emitting surface is -176.878--176.908 mm; The third meniscus lens (3) has a central thickness of 10.40 to 10.42 mm, a light incident surface curvature radius of 559.885 to 560.996 mm, and a light exit surface curvature radius of -1811.234 to -1813.773 mm; The fourth biconvex lens (4) has a central thickness of 78.19-78.25 mm, a light incident surface curvature radius of 419.974-420.083 mm, and a light exit surface curvature radius of 686.649-687.676 mm; The central thickness of the fifth meniscus lens (5) is 1.502-1.509 mm, the radius of curvature of the light incident surface is 119.547-120.568 mm, and the radius of curvature of the light emitting surface is -108.284--109.302 mm.

4. The cooled passive athermal infrared optical system according to claim 1, characterized in that: The optical system can achieve passive athermalization in the long-wave infrared band of 5 μm to 8 μm and at -30°C to 30°C, with a focal length of 180 mm, a half field of view of 1.6°, and an F number of 2-3.

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