Germanium-sulfur mixed 25-75 mm long wave infrared continuous zoom lens

Abstract

The invention discloses a germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens, and relates to the technical field of infrared continuous zoom lenses, the germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens comprises an optical system, the optical system is composed of five lenses, protective glass and a sensor, the five lenses comprise a first lens, a second lens, a third lens, a fourth lens and a fifth lens, and the germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens is characterized in that the protective glass comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens. The first lens and the fourth lens are made of chalcogenide glass materials, the first lens is a meniscus positive lens, the second lens is a biconcave negative lens, and the third lens is a biconvex positive lens. The germanium-sulfur mixed 25-75 mm long wave infrared continuous zoom lens provided by the invention has the technical effects of reducing the lens cost and improving the imaging quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of infrared continuous zoom lens, and particularly relates to a germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens. BACKGROUND

[0002] At present, the infrared continuous zoom lens has been widely applied to various fields such as security monitoring, auxiliary driving of vehicles such as automobiles, marine night vision navigation, law enforcement, private investigation, search and rescue, border and sea defense patrol, investigation and the like, and the requirements for the size, sensitivity, light amount and cost of the infrared continuous zoom lens are higher and higher, especially the cost. At present, the price of germanium rises, and the price of the full-germanium continuous zoom lens rises sharply, which cannot meet the cost demand of customers.

[0003] However, the traditional infrared continuous zoom lens is mostly made of germanium, the full-germanium long-wave infrared continuous zoom lens is expensive, the design of the small zoom ratio uses the full-germanium design with low cost performance, in addition, the temperature refractive index variation coefficient of germanium is large, and the imaging quality of the full-germanium long-wave infrared zoom lens is poor under the conditions of high temperature 80 degrees and low temperature-40 degrees. SUMMARY

[0004] The present application discloses a germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens, which aims to solve the technical problems of high cost and poor imaging quality of the traditional infrared continuous zoom lens.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0006] A germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens comprises an optical system, the optical system is composed of five lenses, a protective glass and a sensor, the five lenses comprise a first lens, a second lens, a third lens, a fourth lens and a fifth lens, characterized in that the first lens and the fourth lens are made of chalcogenide glass material.

[0007] In the present application, the optical system of the chalcogenide glass material mixed with germanium material reduces the cost of the lens to a certain extent, and compared with the large temperature refractive index variation coefficient of germanium material, the temperature refractive index variation coefficient of chalcogenide material is small, and the imaging quality under the conditions of high temperature 80 degrees and low temperature-40 degrees is higher than that of the full-germanium design.

[0008] In a preferred scheme, the first lens is a meniscus positive lens, the second lens is a double-concave negative lens, the third lens is a double-convex positive lens, the fourth lens is a meniscus negative lens, the fifth lens is a meniscus positive lens, and the outer diameter size of the first lens in the optical system is the largest.

[0009] The first lens with such a large size is made of chalcogenide material instead of germanium material, which significantly reduces the manufacturing cost.

[0010] In a preferred embodiment, the total optical length of the optical system is 137mm.

[0011] Compared with the optical system of most lenses on the market, the total optical length of 137mm has great advantages, such as lighter weight and more compact structure.

[0012] In a preferred embodiment, the surface type of the first lens is even aspheric surface, the curvature radius is 160mm, the thickness is 6.88mm, and the refractive index Nd is 2.77; the surface type of the second lens is even aspheric surface, the curvature radius is 700mm, and the thickness is 39mm; the surface type of the third lens is even aspheric surface, the curvature radius is-230mm, the thickness is 1.5mm, and the refractive index Nd is 4.04; the surface type of the fourth lens is even aspheric surface, the curvature radius is 200mm, and the thickness is 2.15mm; and the surface type of the fifth lens is even aspheric surface, the curvature radius is 140mm, the thickness is 4mm, and the refractive index Nd is 4.04.

[0013] As can be seen from the above, the germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens comprises an optical system, the optical system is composed of five lenses, a protective glass and a sensor, the five lenses comprise a first lens, a second lens, a third lens, a fourth lens and a fifth lens, and the first lens and the fourth lens are made of chalcogenide glass material. The germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens has the technical effects of reducing the cost of the lens and improving the imaging quality. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The figure is a schematic diagram of the optical system of the germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens.

[0015] Figure 2 The figure is a short-focus distortion performance diagram of the germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens.

[0016] Figure 3 The figure is a long-focus distortion performance diagram of the germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens.

[0017] Figure 4 The figure is a 25mm MTF performance diagram of the germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens.

[0018] Figure 5 The figure is a 35mm MTF performance diagram of the germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens.

[0019] Figure 6 A 45mm MTF performance chart of a germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens is provided for the present application.

[0020] Figure 7 A 55mm MTF performance chart of a germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens is provided for the present application.

[0021] Figure 8 A 65mm MTF performance chart of a germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens is provided for the present application.

[0022] Figure 9 A 75mm MTF performance chart of a germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens is provided for the present application.

[0023] In the figure: 1, first lens; 2, second lens; 3, third lens; 4, fourth lens; 5, fifth lens; 6, protective glass; 7, sensor. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all.

[0025] The germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens disclosed in the present application is mainly applied to the scene where the traditional infrared continuous zoom lens has high cost and poor imaging quality.

[0026] REFERENCE Figure 1 A germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens, comprising an optical system, the optical system is composed of five lenses, a protective glass 6 and a sensor 7, the five lenses include a first lens 1, a second lens 2, a third lens 3, a fourth lens 4 and a fifth lens 5, the first lens 1 and the fourth lens 4 are made of chalcogenide glass material.

[0027] In actual use, the optical system using chalcogenide glass material mixed with germanium material reduces the cost of the lens to a certain extent, and compared with the large temperature refractive index change coefficient of germanium material, the temperature refractive index change coefficient of chalcogenide material is smaller, so the imaging quality at high temperature 80 degrees and low temperature-40 degrees is higher than that of full germanium design.

[0028] REFERENCE Figure 1 In a preferred embodiment, the first lens 1 is a meniscus positive lens, the second lens 2 is a double-concave negative lens, the third lens 3 is a double-convex positive lens, the fourth lens 4 is a meniscus negative lens, and the fifth lens 5 is a meniscus positive lens.

[0029] In the optical system, the first lens 1 has the largest outer diameter, and the first lens 1 with such a large size is made of a chalcogenide material instead of a germanium material, thereby significantly reducing the manufacturing cost.

[0030] In the optical system, the total optical length is 137 mm, which has a great advantage compared to the total optical length of most lenses on the market, and the optical system has a light weight and a compact structure. The focal length of the optical system is 25 mm to 75 mm, and the F value is 1.0 to 1.2.

[0031] In addition, the protective glass 6 is a binary surface protective glass, and the sensor 7 has a planar structure and is used to receive light rays imaged by the optical system.

[0032] It should be noted that the working wavelength of the optical system covers 8 μm to 12 μm, and the adaptive probe size is 1280×1024 pixels or 1920×1080 pixels.

[0033] Reference Figure 1 In a preferred embodiment, the first lens 1 has an even aspheric surface with a curvature radius of 160 mm, a thickness of 6.88 mm, and a refractive index Nd=2.77; the second lens 2 has an even aspheric surface with a curvature radius of 700 mm and a thickness of 39 mm; the third lens 3 has an even aspheric surface with a curvature radius of -230 mm, a thickness of 1.5 mm, and a refractive index Nd=4.04; the fourth lens 4 has an even aspheric surface with a curvature radius of 200 mm and a thickness of 2.15 mm; and the fifth lens 5 has an even aspheric surface with a curvature radius of 140 mm, a thickness of 4 mm, and a refractive index Nd=4.04.

[0034] It should be noted that the optical system in the present scheme satisfies the following conditions:

[0035] Let the focal length of the optical system be f, and the focal lengths from the first lens 1 to the sensor be f1, f2, f3, f4, f5, and f6, respectively. Then, f and f1, f2, f3, f4, f5, f6, and f7 have the following relationships: 0<|f / f1|<1; 1<|f / f2|<2; 2<|f / f3|<3; 1<|f / f4|<2; and 1<|f / f5|<2.

[0036] In the optical system, each aspheric surface satisfies the following formula:

[0037]

[0038] In the formula, f is the sag of the aspheric surface at a height h along the optical axis, R is the curvature of the aspheric surface, k is the conic coefficient, and A, B, C, D, E, and F are high-order coefficients.

[0039] Referring to Figure 2 , shows the measured data of distortion control within ±5% at 25mm focal length.

[0040] Referring to Figure 3 , shows the measured results of distortion ≤±3% at 75mm focal length.

[0041] Referring to Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 and Figure 9 , respectively show the MTF curves at 25mm, 35mm, 45mm, 55mm, 65mm, 75mm focal length, verifying the imaging quality at spatial frequency 42lp / mm.

[0042] Among them, the MTF curve is a quantitative index for measuring the signal transmission ability of the lens optical system at different spatial frequencies, which reflects the resolution and contrast characteristics of the lens by comparing the contrast attenuation degree of the original test board and the imaged one.

[0043] Working principle: when in use, the scheme uses the design of germanium-sulfur mixed 25-75mm long-wave infrared continuous zoom lens, the first lens 1 serves as the starting end of the light path, corrects the spherical aberration and provides positive refractive power, and preliminarily converges the incident light beam; the second lens 2 generates negative refractive power, balances the system focal length and optimizes the spherical aberration and coma; the third lens 3 further converges the light rays by using the high refractive index characteristic, and compresses the total optical length to 137mm; the fourth lens 4 corrects the chromatic aberration and optimizes the imaging quality of the edge field of view; the fifth lens 5, as the end of the light path, compensates for the remaining aberration of the system, and ensures the long-focus end imaging clarity.

[0044] It should be noted that its specific unique design is as follows:

[0045] Firstly, the application of chalcogenide material: the first lens 1 and the fourth lens 4 adopt chalcogenide glass (such as Ge-Sb-Se), and the temperature refractive index change coefficient (dn / dT≈1×10 -5 / ℃) thereof is significantly lower than that of germanium (dn / dT≈4×10 -5 / ℃), which maintains the imaging stability in the range of-40℃ to 80℃ (see Figures 2-3 Short / long focal length distortion comparison).

[0046] Secondly, the selection of germanium material: the third lens 3 and the fifth lens 5 retain germanium material, because the high refractive index (Nd=4.04) thereof can reduce the number of lenses and realize compact design (total length 137mm).

[0047] In addition, the thermal stability of the chalcogenide material: the first lens 1, the fourth lens 4 has small refractive index fluctuation when the temperature changes, avoids focal length drift, and ensures clear imaging at high temperature 80℃ and low temperature-40℃ (see Figures 4-9 MTF curves at different temperatures).

[0048] Finally, combined with the auxiliary compensation of germanium material: the germanium material of the third lens 3 and the fifth lens 5 forms a complementary temperature characteristic with the chalcogenide material, further inhibiting the thermal defocus phenomenon.

[0049] The above only describes the preferred specific embodiments of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent replacements or changes within the technical range disclosed by the present application according to the technical solution and the inventive concept of the present application, which should be covered within the protection scope of the present application.

Claims

1. A germanium-sulfur hybrid 25-75mm long-wave infrared continuous zoom lens, comprising an optical system, said optical system consisting of five lenses, a protective glass (6) and a sensor (7), said five lenses comprising a first lens (1), a second lens (2), a third lens (3), a fourth lens (4) and a fifth lens (5), characterized in that, The first lens (1) and the fourth lens (4) are made of chalcogenide glass.

2. The germanium-sulfur hybrid 25-75mm long-wave infrared continuous zoom lens according to claim 1, characterized in that, The first lens (1) is a meniscus positive lens, the second lens (2) is a biconcave negative lens, the third lens (3) is a biconvex positive lens, the fourth lens (4) is a meniscus negative lens, and the fifth lens (5) is a meniscus positive lens.

3. The germanium-sulfur hybrid 25-75mm long-wave infrared continuous zoom lens according to claim 1, characterized in that, The first lens (1) in the optical system has the largest outer diameter.

4. The germanium-sulfur hybrid 25-75mm long-wave infrared continuous zoom lens according to claim 1, characterized in that, The total optical length of the optical system is 137 mm.

5. A germanium-sulfur hybrid 25-75mm long-wave infrared continuous zoom lens according to claim 1, characterized in that, The protective glass (6) is a binary protective glass (6), and the sensor (7) is a planar structure used to receive light imaged by the optical system.

6. A germanium-sulfur hybrid 25-75mm long-wave infrared continuous zoom lens according to claim 1, characterized in that, The optical system has a focal length range of 25mm to 75mm and an F-value of 1.0 to 1.

2.

7. A germanium-sulfur hybrid 25-75mm long-wave infrared continuous zoom lens according to claim 1, characterized in that, The optical system operates at wavelengths from 8μm to 12μm and is compatible with detectors of 1280×1024 pixels or 1920×1080 pixels.

8. A germanium-sulfur hybrid 25-75mm long-wave infrared continuous zoom lens according to claim 1, characterized in that, The first lens (1) has an even-order aspherical surface with a radius of curvature of 160 mm, a thickness of 6.88 mm, and a refractive index of Nd = 2.77; the second lens (2) has an even-order aspherical surface with a radius of curvature of 700 mm and a thickness of 39 mm; the third lens (3) has an even-order aspherical surface with a radius of curvature of -230 mm, a thickness of 1.5 mm, and a refractive index of Nd = 4.04; the fourth lens (4) has an even-order aspherical surface with a radius of curvature of 200 mm and a thickness of 2.15 mm; and the fifth lens (5) has an even-order aspherical surface with a radius of curvature of 140 mm, a thickness of 4 mm, and a refractive index of Nd = 4.04.

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