A long-wave infrared refrigeration reflective lens

Abstract

The utility model relates to optical technique field especially relates to a long wave infrared refrigeration reflection type lens, and the main reflector, secondary reflector and rear fixed group and last detector group are set up from object side to image side along the optical axis, and the rear fixed group includes first lens, second lens, third lens and fourth lens, long wave refrigeration detector includes: protection window, cold screen, cold diaphragm and imaging surface, the utility model uses reflection type optical structure, and the total length of optical system is effectively reduced, uses the metal reflector to replace the lens in traditional design, reduces the processing difficulty, and good imaging quality is obtained, has good application effect.

Description

Technical Field

[0001] This utility model relates to the field of optical technology, and in particular to a long-wave infrared cooled reflective lens. Background Technology

[0002] In recent years, long-wave infrared imaging technology has been widely used in military reconnaissance, security monitoring, industrial inspection, and medical diagnosis. Because the long-wave infrared band can penetrate obstacles such as smoke and dust and achieve clear imaging at night or in harsh environments, the demand for high-performance long-wave infrared optical systems is increasing.

[0003] Traditional long-wave infrared lenses mostly employ a transmissive design, relying on infrared optical materials such as germanium. However, transmissive lenses have the following problems: 1. High material cost: Infrared materials such as germanium are expensive and difficult to process, resulting in a high overall cost for the lens; 2. Large size and weight: To correct aberrations, transmissive lenses typically require multiple lens elements, making the system bulky and unsuitable for lightweight applications; 3. Poor thermal stability: The refractive index of infrared materials changes significantly with temperature, easily causing thermal defocusing and affecting image quality.

[0004] However, by using aspherical mirrors instead of transmission elements, reflective lenses can effectively avoid material limitations, reduce system weight, and improve thermal stability. However, existing reflective designs (such as Cassegrain structures) still have problems such as small field of view and insufficient aberration correction in the long-wave infrared band, making it difficult to meet the needs of high-resolution and large field of view applications. Utility Model Content

[0005] To overcome the problems of small field of view and insufficient aberration correction in the long-wave infrared band of existing reflective designs (such as Cassegrain structures), which make it difficult to meet the needs of high-resolution and large field of view applications.

[0006] The technical solution of this utility model is as follows: a long-wave infrared cooled reflective lens, which consists of a primary reflector, a secondary reflector, a rear fixing group, and a final detector arranged along the optical axis from the object side to the image side; the rear fixing group includes a first lens, a second lens, a third lens, and a fourth lens; the long-wave cooled detector includes a protective window, a cold screen, a cold aperture, and an imaging surface.

[0007] Preferably, the optical system of the long-wavelength cooled detector with a resolution of 640x512 and a pixel size of 15 micrometers has a total length of 148.88mm and a maximum aperture of 140mm. It has good imaging quality, compact structure, reasonable tolerance, simple assembly and adjustment, and is easy to mass-produce. In particular, it uses a reflective optical structure, which reduces the weight of the large-aperture lens and reduces the total length of the optical system.

[0008] As a preferred option, the following parameters are met: EFL = 275mm, F / # = 2.0, total length of optical system (including cooled detector) = 148.88mm, adapter detector 640x512, pixel size 15μm, and operating wavelength 7.7~9.6μm.

[0009] Preferably, the primary reflector is made of aluminum alloy with a parabolic surface, and the secondary reflector is made of aluminum alloy with a parabolic surface.

[0010] As a preferred embodiment, the protective window material is germanium single crystal, the cold screen material is germanium single crystal, the imaging surface resolution is 640x512, and the pixel size is 15μmx15μm.

[0011] Preferably, the first lens is a germanium negative lens with its concave surface facing the object side; the second lens is a biconvex germanium positive lens; the third lens is a zinc selenide negative lens with its concave surface facing the object side, and has an aspherical surface thereon; the fourth lens is a germanium positive lens with its concave surface facing the object side, and has an aspherical surface thereon.

[0012] Preferably, the horizontal field of view of the lens is 2ω = 2°.

[0013] Preferably, the aspherical surfaces in the lens element satisfy the following expression.

[0014]

[0015] Where z is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis, c represents the vertex curvature of the surface, k is the conic coefficient, and α2, α3, α4, α5, and α6 are higher-order aspherical coefficients.

[0016] The beneficial effects of this utility model are:

[0017] This long-wave infrared cooled reflective lens, with a total length of 148.88mm and a maximum aperture of 140mm, is adapted to a long-wave cooled detector optical system with a resolution of 640x512 and a pixel size of 15 micrometers. It has good imaging quality, a compact structure, reasonable tolerances, simple assembly and adjustment, and is easy to mass-produce. In particular, it uses a reflective optical structure, which reduces the weight of the large-aperture lens and the overall length of the optical system. Attached Figure Description

[0018] Figure 1 The diagram shown is of the optical system of this utility model;

[0019] Figure 2 The diagram shown is an optical transfer function diagram of this utility model;

[0020] Figure 3 The diagram shown is a dotted representation of this utility model.

[0021] Figure 4The image shown is an astigmatic distortion diagram of this utility model.

[0022] Explanation of reference numerals in the attached drawings: 210, object space; 110, primary reflector; 120, secondary reflector; 130, rear fixed assembly; 132, first lens; 134, second lens; 136, third lens; 138, fourth lens; 310, cooled detector; 312, detector protection window; 314, cold screen; 316, cold aperture; 318, focal plane. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Please see Figures 1-4 This utility model provides an embodiment: a long-wave infrared cooled reflective lens, which consists of a primary reflector 110, a secondary reflector 120, a rear fixing group 130, and a final detector 310 arranged along the optical axis from the object side to the image side; the rear fixing group 130 includes a first lens 132, a second lens 134, a third lens 136, and a fourth lens 138; the long-wave cooled detector 310 includes a protective window 312, a cold screen 314, a cold aperture 316, and an imaging surface 318, satisfying the following parameters: EFL = 275mm, F / # = 2.0, total optical system length (including the cooled detector part) = 148.88mm, compatible detector 640x512, large pixel size. The image size is 15μm, the working wavelength is 7.7~9.6μm, the primary reflector 110 is made of aluminum alloy with a parabolic surface, the secondary reflector 120 is made of aluminum alloy with a parabolic surface, the rear fixing group 130 consists of four lenses: the first lens 132 is a germanium negative lens with its concave surface facing the object side; the second lens 134 is a biconvex germanium positive lens; the third lens 136 is a zinc selenide negative lens with its concave surface facing the object side and an aspherical surface on it; the fourth lens 138 is a germanium positive lens with its concave surface facing the object side and an aspherical surface on it; the protective window 312 is made of germanium single crystal, the cold screen 314 is made of germanium single crystal, the imaging surface 318 has a resolution of 640x512, and the pixel size is 15μmx15μm;

[0025] Of all the mirrors and lenses mentioned above, S2 to S10 are the various surfaces of the lenses. The surface of the primary mirror S1 and the secondary mirror S2 are coated with a metallic reflective film, while the remaining surfaces S3 to S10 are coated with an anti-reflective film.

[0026] Table 1 shows the optical structure parameters of the present invention:

[0027] Table 1

[0028]

[0029] The aspherical surfaces mentioned above are all even-order aspherical surfaces, and their expressions are as follows:

[0030]

[0031] Where z is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis, c represents the vertex curvature of the surface, k is the conic coefficient, and α2, α3, α4, α5, and α6 are higher-order aspherical coefficients.

[0032] Table 2 shows the aspherical coefficients of surfaces S1, S2, S7, and S10:

[0033] Table 2

[0034]

[0035] The effects of the present invention will be described in further detail below with reference to the aberration analysis diagram.

[0036] Figures 2-4 yes Figure 1 Aberration analysis diagram of a specific embodiment of the long-wave infrared cooled reflective lens. Figure 2 It is an MTF chart. Figure 3 It is a dot-matrix diagram. Figure 4 It is a field distortion diagram;

[0037] As can be seen from the figure, various aberrations have been well corrected, the blur spots have been corrected to near the size of the Allibben, the MTF is close to the diffraction limit, and the distortion is less than 1%. This shows that the long-wave infrared cooled reflective lens of this invention has good imaging quality. The optical system of the long-wave infrared cooled detector with a resolution of 640x512 and a pixel size of 15 micrometers has a total length of 148.88mm and a maximum aperture of 140mm. It has good imaging quality, a compact structure, reasonable tolerances, simple assembly and adjustment, and is easy to mass-produce. In particular, the use of a reflective optical structure reduces the weight of the large-aperture lens and the overall length of the optical system.

[0038] By optimizing the reflector surface shape and optical path structure through the above steps, the goal of large field of view and high imaging quality can be achieved while reducing cost and weight. This is suitable for high-performance scenarios of cooled infrared detectors, and solves the problems of small field of view and insufficient aberration correction in the long-wave infrared band of existing reflective designs (such as Cassegrain structures), which are difficult to meet the needs of high-resolution and large field of view applications.

Claims

1. A long-wave infrared cooled reflective lens, characterized in that: The optical axis is arranged from the object side to the image side, consisting of a primary reflector (110), a secondary reflector (120), a rear fixing group (130), and a final detector (310); The rear fixed assembly (130) includes a first lens (132), a second lens (134), a third lens (136) and a fourth lens (138). The long-wavelength cooled detector (310) includes a protective window (312), a cold screen (314), a cold aperture (316), and an imaging surface (318).

2. The long-wave infrared cooled reflective lens according to claim 1, characterized in that: It meets the following parameters: EFL=275mm, F / #=2.0, total length of optical system=148.88mm, compatible detector 640x512, pixel size 15μm, and working wavelength range of 7.7~9.6μm.

3. The long-wave infrared cooled reflective lens according to claim 1, characterized in that: The primary reflector (110) is made of aluminum alloy with a parabolic surface, and the secondary reflector (120) is also made of aluminum alloy with a parabolic surface.

4. A long-wave infrared cooled reflective lens according to claim 1, characterized in that: The protective window (312) is made of germanium single crystal, the cold screen (314) is made of germanium single crystal, the imaging surface (318) has a resolution of 640x512 and a pixel size of 15μmx15μm.

5. A long-wave infrared cooled reflective lens according to claim 1, characterized in that: The first lens (132) is a germanium negative lens with its concave surface facing the object side; the second lens (134) is a biconvex germanium positive lens; the third lens (136) is a zinc selenide negative lens with its concave surface facing the object side, and has an aspherical surface on it; the fourth lens (138) is a germanium positive lens with its concave surface facing the object side, and has an aspherical surface on it.

6. A long-wave infrared cooled reflective lens according to claim 1, characterized in that: The horizontal field of view of the lens is: .

7. A long-wave infrared cooled reflective lens according to claim 1, characterized in that: The aspherical surfaces in the lens elements satisfy the following expression ； in For an aspherical surface along the optical axis at a height of When the position is such that the distance from the vertex of the non-spherical surface is the sag, Represents the curvature at the vertices of the surface. The conic coefficient, , , , , It represents the higher-order aspheric coefficient.

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