Long-wave infrared zoom lens

Abstract

The long-wave infrared zoom lens sequentially comprises a front fixed group, a zoom group, a compensation group, a rear fixed group and a protection window from an object space to an image space along an optical axis, the front fixed group comprises a first lens, the zoom group comprises a second lens, the compensation group comprises a third lens, the rear fixed group comprises a fourth lens and a fifth lens, and the second lens and the third lens can reciprocate along an optical axis; the focal length of the long-wave infrared zoom lens ranges from 20 mm to 100 mm. According to the long-wave infrared zoom lens provided by the invention, the whole lens is composed of five lenses, and has the advantages of light weight and light volume; single lenses are respectively used for zooming and compensation, so that the stability of the optical axis in the zooming process can be well ensured, and the adjustment mode is simple; the requirement on the lens structure is low, production and assembly are simple, the precision of the lens is easy to guarantee, tolerance analysis is easy, and mass production is easier to realize.

Description

Technical Field

[0001] The present invention relates to the field of infrared optical technology, and in particular to a long-wave infrared zoom lens. Background Art

[0002] Compared with traditional optics, infrared systems have obvious advantages. For example, infrared systems can search, identify and track targets in adverse weather conditions, so they are widely used in aerospace and military air defense. Currently, most infrared zoom lenses on the market use 6 infrared lenses. Such lenses are generally large in size, heavy in weight and high in cost, which causes many inconveniences in actual use. Summary of the invention

[0003] On this basis, the present invention proposes a long-wave infrared zoom lens, and the specific technical solution is as follows.

[0004] A long-wave infrared zoom lens comprises a front fixed group, a magnification group, a compensation group and a rear fixed group in sequence from the object side to the image side along the optical axis; the front fixed group comprises a first lens, the magnification group comprises a second lens, the compensation group comprises a third lens, the rear fixed group comprises a fourth lens and a fifth lens, the second lens and the third lens are both capable of reciprocating along the optical axis; the focal length range of the long-wave infrared zoom lens is 20mm-100mm.

[0005] Preferably, the first lens is a positive meniscus lens with its convex surface facing the object side, the second lens is a double concave lens, the third lens is a double convex lens, the fourth lens is a negative meniscus lens with its convex surface facing the image side, and the fifth lens is a positive meniscus lens with its convex surface facing the object side.

[0006] Preferably, the focal length of the first lens is 148.41155 mm, the focal length of the second lens is -41.685426 mm, the focal length of the third lens is 44.806719 mm, the focal length of the fourth lens is -80.402764 mm, and the focal length of the fifth lens is 36.681550 mm.

[0007] Preferably, the center thickness of the first lens is 9.08 mm, the radius of curvature of the object side is 224.992 mm, and the radius of curvature of the image side is 440.408 mm; The center thickness of the second lens is 4.19 mm, the radius of curvature of the object side is -284.241 mm, and the radius of curvature of the image side is 226.360 mm; The central thickness of the third lens is 4.16 mm, the radius of curvature of the object side is 226.042 mm, and the radius of curvature of the image side is -328.232 mm; The center thickness of the fourth lens is 4 mm, the object side curvature radius is -36.512 mm, and the image side curvature radius is -46.549 mm; The central thickness of the fifth lens is 5.07 mm, the radius of curvature of the object side surface is 55.832 mm, and the radius of curvature of the image side surface is 105.452 mm.

[0008] Preferably, during the zooming process, the maximum displacement of the second lens is 52.7 mm, and the maximum displacement of the third lens is 24 mm.

[0009] Preferably, during the zooming process, the interval between the first lens and the second lens is in the range of 7.05622mm-59.72631mm, the interval between the second lens and the third lens is in the range of 5.98278mm-82.87384mm, the interval between the third lens and the fourth lens is in the range of 14.12166mm-38.34177mm, and the interval between the fourth lens and the fifth lens is 35.42mm.

[0010] Preferably, the materials of the first to fifth lenses are all germanium materials.

[0011] Preferably, the image side surface of the second lens, the object side surface of the third lens, the object side surface of the fourth lens, and the image side surface of the fifth lens are aspherical surfaces and satisfy the aspherical surface formula: Among them, Z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height r along the optical axis; c=1 / R; R is the paraxial curvature fitting radius of the mirror; k is the cone coefficient; A, B, C, D, and E are high-order aspherical coefficients.

[0012] Preferably, the object side surface of the first lens is coated with a DLC film, and the image side surface of the first lens and the object side surfaces and image side surfaces of the second to fifth lenses are coated with an anti-reflection film.

[0013] Preferably, the F number of the long-wave infrared zoom lens is 1.2, the total length of the optical system is 193 mm, and the field of view angle ranges from 8° to 40°, which is suitable for a detector with a resolution of 640×512 and a pixel size of 17 μm.

[0014] The long-wave infrared zoom lens provided by the present invention has the following technical effects: (1) The entire lens is composed of five lenses, which is lighter in weight and volume than the infrared zoom lens that uses six lenses in the prior art; (2) Using single lenses for zooming and compensation respectively, specifically using the second lens 2 for zooming and the third lens 3 for compensation. Since a moving single lens is used for zooming, the optical axis stability during the zooming process can be well guaranteed, and the adjustment method is simple; (3) The fifth lens can be moved slightly forward and backward to achieve focusing. On the one hand, it can make the imaging distance range of the entire lens from 2m to infinity, solving the problem of lens imaging defocus. On the other hand, the slight movement of the fifth lens can compensate for the high and low temperatures of the lens operating environment, so that the operating temperature of the lens can cover -40℃-60℃, killing two birds with one stone.

[0015] (4) The long-wave infrared zoom lens of the present invention can achieve a zoom range of 20 mm to 100 mm. During the zooming process, the image is clear and of excellent quality. The average MTF of the entire field of view is greater than 0.3. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide further understanding of the present application and constitute a part of the specification. They are used to explain the present application together with the embodiments of the present application and do not constitute a limitation of the present application.

[0017] Figure 1 A schematic diagram of the structure of a long-wave infrared zoom lens provided in an embodiment of the present application; Figure 2 An optical transfer function diagram of the long-wave infrared zoom lens provided in an embodiment of the present application when the focal length is 30 mm; Figure 3 An optical transfer function diagram of the long-wave infrared zoom lens provided in an embodiment of the present application when the focal length is 60 mm; Figure 4 This is an optical transfer function diagram of the long-wave infrared zoom lens provided in an embodiment of the present application when the focal length is 100 mm.

[0018] Among them, 1. the first lens, 2. the second lens, 3. the third lens, 4. the fourth lens, 5. the fifth lens, 6. the protective window. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0021] This embodiment provides a long-wave infrared zoom lens with an operating band of 8μm-12μm, a focal length of 20mm-100mm, an F number of 1.2, a total optical system length of 193mm, a maximum aperture of 104mm, a field of view angle range of 8°-40°, and can be adapted to detectors with a resolution of 640×512 and a pixel size of 17μm.

[0022] The long-wave infrared zoom lens in this example, such as Figure 1 As shown, along the optical axis from the object side to the image side, it includes a front fixed group, a zoom group, a compensation group, a rear fixed group and a protection window in sequence; the front fixed group includes a first lens 1, the zoom group includes a second lens 2, the compensation group includes a third lens 3, and the rear fixed group includes a fourth lens 4 and a fifth lens 5. Both the second lens 2 and the third lens 3 can move back and forth along the optical axis.

[0023] Among them, the first lens 1 is a positive meniscus lens with its convex surface facing the object side, the second lens 2 is a double concave lens, the third lens 3 is a double convex lens, the fourth lens 4 is a negative meniscus lens with its convex surface facing the image side, and the fifth lens 5 is a positive meniscus lens with its convex surface facing the object side.

[0024] In the long-wave infrared zoom lens of this embodiment, parameters of the first lens 1 to the fifth lens 5 are shown in Table 1.

[0025] Table 1 Lens parameters Among them, the focal length of the first lens 1 is 148.41155 mm, the focal length of the second lens 2 is -41.685426 mm, the focal length of the third lens 3 is 44.806719 mm, the focal length of the fourth lens 4 is -80.402764 mm, and the focal length of the fifth lens 5 is 36.681550 mm.

[0026] The center thickness of the first lens 1 is 9.08 mm, the radius of curvature of the object side is 224.992 mm, and the radius of curvature of the image side is 440.408 mm; The center thickness of the second lens 2 is 4.19 mm, the object side curvature radius is -284.241 mm, and the image side curvature radius is 226.360 mm; The center thickness of the third lens 3 is 4.16 mm, the object side curvature radius is 226.042 mm, and the image side curvature radius is -328.232 mm; The center thickness of the fourth lens 4 is 4 mm, the radius of curvature of the object side surface is -36.512 mm, and the radius of curvature of the image side surface is -46.549 mm; The central thickness of the fifth lens 5 is 5.07 mm, the radius of curvature of the object side surface is 55.832 mm, and the radius of curvature of the image side surface is 105.452 mm.

[0027] In this embodiment, during the zooming process, the maximum displacement of the second lens 2 is 52.7 mm, which is used to change the focal length of the lens, and the maximum displacement of the third lens 3 is 24 mm, which is used for compensation of the zoom group.

[0028] During the zooming process, the interval range between the first lens 1 and the second lens 2 is 7.05622mm-59.72631mm, the interval range between the second lens 2 and the third lens 3 is 5.98278mm-82.87384mm, the interval range between the third lens 3 and the fourth lens 4 is 14.12166mm-38.34177mm, and the interval between the fourth lens 4 and the fifth lens 5 is 35.42mm.

[0029] Preferably, in this embodiment, the materials of the first lens 1 to the fifth lens 5 are all germanium materials.

[0030] In this embodiment, the image-side surface S4 of the second lens 2, the object-side surface S5 of the third lens 3, the object-side surface S7 of the fourth lens 4, and the image-side surface S10 of the fifth lens 5 are aspherical surfaces and satisfy the aspherical surface formula: Among them, Z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height r along the optical axis; c=1 / R; R is the paraxial curvature fitting radius of the mirror; k is the cone coefficient; A, B, C, D, and E are high-order aspherical coefficients.

[0031] Among them, the data of each aspherical surface are shown in Table 2.

[0032] Table 2 Aspheric surface data of lens Preferably, the object side surface S1 of the first lens 1 is coated with a DLC film, and the image side surface of the first lens 1 and the object side surfaces and image side surfaces S2 to S10 of the second to fifth lenses are coated with an antireflection film.

[0033] On this basis, the long-wave infrared zoom lens provided in this embodiment has the following technical effects: (1) The entire lens is composed of five lenses, which is lighter in weight and volume than the infrared zoom lens that uses six lenses in the prior art; (2) Using single lenses for zooming and compensation respectively, specifically using lens 2 for zooming and using third lens 3 for compensation. Since a moving single lens is used for zooming, the optical axis stability during the zooming process can be well guaranteed, and the adjustment method is simple; (3) The fifth lens 5 can be slightly moved forward and backward to achieve focusing. On the one hand, the imaging distance range of the entire lens can be from 2m to infinity, solving the problem of lens imaging defocus. On the other hand, the slight movement of the fifth lens 5 can compensate for the high and low temperatures of the lens operating environment, so that the operating temperature of the lens can cover -40℃-60℃, killing two birds with one stone.

[0034] (4) Figure 2-4 The optical transfer function diagrams of the infrared zoom lens of this embodiment at focal lengths of 30mm, 60mm, and 100mm respectively, the long-wave infrared zoom lens of this embodiment can not only achieve 20mm-100mm zooming, but also achieve clear imaging and excellent imaging quality during the zooming process, and the average MTF of the entire field of view is greater than 0.3.

[0035] Although the embodiments of the present application have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A long-wave infrared zoom lens, characterized in that: The optical axis includes a front fixed group, a zoom group, a compensation group and a rear fixed group from the object side to the image side; the front fixed group includes a first lens, the zoom group includes a second lens, the compensation group includes a third lens, the rear fixed group includes a fourth lens and a fifth lens, and the second lens and the third lens can both move back and forth along the optical axis; the focal length range of the long-wave infrared zoom lens is 20mm-100mm.

2. A long-wave infrared zoom lens as claimed in claim 1, characterized in that: The first lens is a positive meniscus lens with its convex surface facing the object side, the second lens is a double concave lens, the third lens is a double convex lens, the fourth lens is a negative meniscus lens with its convex surface facing the image side, and the fifth lens is a positive meniscus lens with its convex surface facing the object side.

3. A long-wave infrared zoom lens as claimed in claim 2, characterized in that: The focal length of the first lens is 148.41155 mm, the focal length of the second lens is -41.685426 mm, the focal length of the third lens is 44.806719 mm, the focal length of the fourth lens is -80.402764 mm, and the focal length of the fifth lens is 36.681550 mm.

4. The long-wave infrared zoom lens according to claim 3, characterized in that: The center thickness of the first lens is 9.08 mm, the radius of curvature of the object side is 224.992 mm, and the radius of curvature of the image side is 440.408 mm; The center thickness of the second lens is 4.19 mm, the radius of curvature of the object side is -284.241 mm, and the radius of curvature of the image side is 226.360 mm; The central thickness of the third lens is 4.16 mm, the radius of curvature of the object side is 226.042 mm, and the radius of curvature of the image side is -328.232 mm; The center thickness of the fourth lens is 4 mm, the object side curvature radius is -36.512 mm, and the image side curvature radius is -46.549 mm; The central thickness of the fifth lens is 5.07 mm, the radius of curvature of the object side surface is 55.832 mm, and the radius of curvature of the image side surface is 105.452 mm.

5. The long-wave infrared zoom lens according to claim 1, characterized in that: During the zooming process, the maximum displacement of the second lens is 52.7 mm, and the maximum displacement of the third lens is 24 mm.

6. The long-wave infrared zoom lens according to claim 5, characterized in that: During the zooming process, the interval between the first lens and the second lens ranges from 7.05622mm to 59.72631mm, the interval between the second lens and the third lens ranges from 5.98278mm to 82.87384mm, the interval between the third lens and the fourth lens ranges from 14.12166mm to 38.34177mm, and the interval between the fourth lens and the fifth lens is 35.42mm.

7. The long-wave infrared zoom lens according to claim 1, characterized in that: The materials of the first lens to the fifth lens are all germanium materials.

8. The long-wave infrared zoom lens according to claim 1, characterized in that: The image side surface of the second lens, the object side surface of the third lens, the object side surface of the fourth lens, and the image side surface of the fifth lens are aspherical surfaces and satisfy the aspherical surface formula: Among them, Z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height r along the optical axis; c=1 / R; R is the paraxial curvature fitting radius of the mirror; k is the cone coefficient; A, B, C, D, and E are high-order aspherical coefficients.

9. The long-wave infrared zoom lens according to claim 1, characterized in that: The object side surface of the first lens is coated with a DLC film, and the image side surface of the first lens and the object side surfaces and image side surfaces of the second lens to the fifth lens are coated with an anti-reflection film.

10. The long-wave infrared zoom lens according to claim 1, characterized in that: The F number of the long-wave infrared zoom lens is 1.2, the total length of the optical system is 193 mm, and the field of view angle range is 8°-40°, which is suitable for detectors with a resolution of 640×512 and a pixel size of 17 μm.

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