Medium-wave continuous zooming infrared lens and lens module

Abstract

The invention belongs to the technical field of infrared optics, and discloses a medium-wave continuous zooming infrared lens and a lens module. The lens comprises a front fixing group, a zooming group, a rear fixing group and a temperature compensation group which are sequentially arranged on the same optical axis from an object side to an image side. The front fixed group is a first lens; the zoom group comprises a second lens and a third lens which are arranged in sequence; the second lens and the third lens can move along the optical axis so as to realize continuous zooming; the rear fixed group comprises a fourth lens and a fifth lens; and the temperature compensation group is a sixth lens. The lens is arranged to be of a six-piece type lens structure, and the structure is simple; through a mode of moving zooming of the second lens and the third lens and temperature compensation of the sixth lens, a continuous zooming function is realized, and a good imaging effect is ensured at the same time; and continuous zooming with a large zoom ratio can be realized.

Description

Technical Field

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

[0002] In recent years, infrared detection technologies such as infrared thermal imaging have been widely used in military, industrial and civilian fields. For detectors, medium-wave cooled detectors have a more obvious price advantage than similar long-wave detectors due to their high sensitivity. For lenses, compared with fixed-focus lenses and step-by-step lenses, continuous zoom lenses can not only capture targets in a large field of view, but also adjust to a small field of view to aim and track targets after discovering the target; and in the process of focal length and field of view conversion, the continuity of the image of the observed target on the detector target surface can be maintained, which is conducive to the search and tracking of high-speed moving targets, and solves the defect of step-by-step zoom lenses that high-speed targets are easily lost when the field of view is switched. Therefore, medium-wave continuous zoom infrared lenses have a good prospect for use.

[0003] Existing medium-wave continuous zoom infrared lenses have the following disadvantages: (1) They generally use a large number of lenses, usually more than seven, which makes processing difficult and increases the cost and weight of the infrared lens; (2) There are many moving components, such as the use of three-component moving zoom, which leads to a complex structure and inconvenient focusing. Summary of the invention

[0004] In order to solve the above problems, one of the purposes of this application is to provide a medium-wave continuous zoom infrared lens. The specific technical solution is as follows: A medium-wave continuous zoom infrared lens comprises a front fixed group, a zoom group, a rear fixed group, and a temperature compensation group which are arranged in sequence on the same optical axis from the object side to the image side; The front fixed group is a first lens, which is a meniscus lens with a convex surface facing the object and has positive focal power; The zoom group includes a second lens and a third lens arranged in sequence; the second lens is a biconcave lens, and the third lens is a biconvex lens; the second lens and the third lens can move along the optical axis to achieve continuous zoom; The rear fixed group includes a fourth lens and a fifth lens; the fourth lens is a meniscus lens with a convex surface facing the image side and having a negative optical power; the fifth lens is a meniscus lens with a convex surface facing the object side and having a positive optical power; The temperature compensation group is a sixth lens, and the sixth lens is a biconvex lens.

[0005] Furthermore, during the zooming process, the second lens and the third lens move toward each other or away from each other along the optical axis.

[0006] Furthermore, the first lens, the third lens, the fifth lens and the sixth lens are made of silicon, and the second lens and the fourth lens are made of germanium.

[0007] Further, the image side surface of the first lens, the object side surface of the second lens, the object side surface of the third lens, the image side surface of the third lens, the object side surface of the fourth lens, the image side surface of the fifth lens, the object side surface of the sixth lens, and the image side surface of the sixth 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.

[0008] Furthermore, the object side surface of the fourth lens and the object side surface of the sixth lens are two-dimensional surfaces, satisfying the aspheric surface formula and satisfying the expression equation of the two-dimensional surface in Zemax: M(B 1 ρ 2 +B 2 ρ 4 ), where M is the diffraction order, B 1 , B 2 is the binary surface phase coefficient, and ρ is the normalized radius.

[0009] Furthermore, the working band of the infrared lens is 3.7 μm~4.8 μm, and the focal length is 20~200 mm.

[0010] Furthermore, the air gap between the first lens and the second lens is 12.4~24.271mm; the air gap between the second lens and the third lens is 22.788~2.7mm; the air gap between the third lens and the fourth lens is 2.6~10.817mm; the air gap between the fourth lens and the fifth lens is 0.2mm; and the air gap between the fifth lens and the sixth lens is 13.812mm.

[0011] Further, the center thickness of the first lens is 5.8mm, the radius of curvature of the object side is 49.55mm, and the radius of curvature of the image side is 96.105mm; the center thickness of the second lens is 1.6mm, the radius of curvature of the object side is -43.573mm, and the radius of curvature of the image side is 34.713mm; the center thickness of the third lens is 4mm, the radius of curvature of the object side is 56.762mm, and the radius of curvature of the image side is -41.466mm; the center thickness of the fourth lens is 1.5mm, the radius of curvature of the object side is -59.488mm, and the radius of curvature of the image side is -220mm; the center thickness of the fifth lens is 3.8mm, the radius of curvature of the object side is 7.457mm, and the radius of curvature of the image side is 5.079mm; the center thickness of the sixth lens is 2.8mm, the radius of curvature of the object side is 29.883mm, and the radius of curvature of the image side is -29.125mm.

[0012] Another object of the present application is to provide a lens module, comprising the above-mentioned continuous zoom infrared lens and a detector, wherein the number of pixels of the detector is 640×512 and the pixel size is 15 μm.

[0013] Furthermore, the detector is a medium-wave cooled infrared detector, and the detector includes a protective window, a chopping window, and a cold screen which are sequentially arranged between the sixth lens and the detector image plane; an aperture is provided on the side of the chopping window close to the cold screen.

[0014] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: (1) During the zooming process, the second lens and the third lens are adjusted to move coaxially. The overall structure has only six lenses with optical power, and the structure is relatively simple; (2) It can achieve continuous zoom with a large zoom ratio, such as a 10x zoom ratio and a focal length of 20~200mm; (3) Good image quality, such as a resolution of 640×512, 15μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0016] Figure 1 This is the optical path diagram of the medium-wave continuous zoom infrared lens in Example 1.

[0017] Figure 2This is a lens composition diagram of the medium-wave continuous zoom infrared lens in Example 1.

[0018] Figure 3 This is a point diagram of the medium-wave continuous zoom infrared lens with a focal length of 200 mm in Example 1.

[0019] Figure 4 This is the MTF diagram of the medium-wave continuous zoom infrared lens with a focal length of 200 mm in Example 1.

[0020] Figure 5 This is a point diagram of the medium-wave continuous zoom infrared lens with a focal length of 20 mm in Example 1.

[0021] Figure 6 This is the MTF diagram of the medium-wave continuous zoom infrared lens with a focal length of 20 mm in Example 1.

[0022] Figure numerals: 1, first lens; 2, second lens; 3, third lens; 4, fourth lens; 5, fifth lens; 6, sixth lens; 7, protection window; 8, chopping window; 9, cold screen; 10, detector image plane. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. It should be noted that the terms "first" and "second" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features.

[0024] For ease of understanding, the relevant terms involved are explained below.

[0025] The object side is the side of the lens along the direction of light propagation where the light is incident, that is, the surface of the lens close to the object side; the image side is the side of the lens along the direction of light propagation where the light is emitted, that is, the surface of the lens close to the image side; the meniscus lens, also known as a crescent lens, has one concave side and the other convex side near the optical axis.

[0026] like Figure 1 , Figure 2As shown, the medium-wave continuous zoom infrared lens of the present application includes a front fixed group, a zoom group, a rear fixed group, and a temperature compensation group, which are arranged on the same optical axis from the object side to the image side in sequence; wherein the front fixed group is a first lens 1, which is a meniscus lens with a convex surface facing the object side and has a positive optical focal length; the zoom group includes a second lens 2 and a third lens 3 which are arranged in sequence; the second lens 2 is a biconcave lens, and the third lens 3 is a biconvex lens; the rear fixed group includes a fourth lens 4 and a fifth lens 5; the fourth lens 4 is a meniscus lens with a convex surface facing the image side and has a negative optical focal length; the fifth lens 5 is a meniscus lens with a convex surface facing the object side and has a positive optical focal length; the temperature compensation group is a sixth lens 6, which is a biconvex lens; wherein the second lens 2 and the third lens 3 can move along the optical axis to achieve continuous zooming.

[0027] In the present invention, the relative positions of the lenses in the front fixed group and the rear fixed group are fixed, the temperature compensation group is used to compensate for the offset of the image plane position under different temperatures, and the zoom group is used to achieve continuous change of focal length. Specifically, during the zooming process, the second lens 2 and the third lens 3 move toward or away from each other along the optical axis to achieve switching between long focus, medium focus and short focus.

[0028] For example, when the lens changes from long focal length to short focal length, the second lens 2 moves toward the object side and the third lens 3 moves toward the image side, so as to reduce the focal length of the optical system and compensate for the image plane movement caused by the lens movement; and when the lens changes from short focal length to long focal length, the second lens 2 moves toward the image side and the third lens 3 moves toward the object side. When the lens is in the longest focal length state, the air gap between the first lens 1 and the second lens 2 is in the maximum state, the air gap between the second lens 2 and the third lens 3 is in the minimum state, and the air gap between the third lens 3 and the fourth lens 4 is in the maximum state; when the lens is in the shortest focal length state, the air gap between the first lens 1 and the second lens 2 is in the minimum state, the air gap between the second lens 2 and the third lens 3 is in the maximum state, and the air gap between the third lens 3 and the fourth lens 4 is in the minimum state.

[0029] As a specific implementation, the material of the first lens 1 , the third lens 3 , the fifth lens 5 , and the sixth lens 6 is silicon, and the material of the second lens 2 and the fourth lens 4 is germanium.

[0030] As a specific implementation, the image side surface S2 of the first lens, the object side surface S3 of the second lens, the object side surface S5 and the image side surface S6 of the third lens, the object side surface S7 of the fourth lens, the image side surface S10 of the fifth lens, and the object side surface S11 and the image side surface S12 of the sixth 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.

[0031] The object side surface S7 of the fourth lens and the object side surface S11 of the sixth lens are two-dimensional surfaces, satisfying the above aspheric surface formula and the expression equation of the two-dimensional surface in Zemax: M(B 1 ρ 2 +B 2 ρ 4 ), where M is the diffraction order, B 1 , B 2 is the binary surface phase coefficient, and ρ is the normalized radius.

[0032] Example 1 The following is an example of a specific continuous zoom lens. Specific parameters of the continuous zoom lens of this embodiment are shown in Table 1, Table 2, and Table 3.

[0033] Table 1 Parameters of each component Table 2 Aspheric surface data of lens Table 3. Binary surface data of lens When focusing, the lens positions of the front fixed group and the rear fixed group are relatively fixed, while the two lenses of the zoom group move along the optical axis between the front fixed group and the rear fixed group. The air interval D2 between the first lens 1 and the second lens 2, the air interval D4 between the second lens 2 and the third lens 3, and the air interval D6 between the third lens 3 and the fourth lens 4 are all variable intervals. If the air interval D2 between the first lens 1 and the second lens 2 is 12.4mm, the air interval D4 between the second lens 2 and the third lens 3 is 22.788mm, and the air interval D6 between the third lens 3 and the fourth lens 4 is 2.6mm, the system focal length is in the shortest focal length state, and the shortest focal length of this embodiment is 20mm. When the air interval D2 between the first lens 1 and the second lens 2 is 24.271mm, the air interval D4 between the second lens 2 and the third lens 3 is 2.7mm, and the air interval D6 between the third lens 3 and the fourth lens 4 is 10.817mm, the system focal length is in the longest focal length state, and the longest focal length of this embodiment is 200mm.

[0034] Figure 3 , Figure 4 They are the point diagram and MTF diagram of the lens at 200mm telephoto. Figure 5 , Figure 6The spot diagram and MTF diagram of the lens at short focal length of 20mm are shown respectively. In the MTF diagram, the horizontal axis represents different spatial frequencies and the vertical axis represents the modulation degree. All fields of view represent the MTF curve of the meridian plane. It can be seen that the MTF is close to the diffraction limit, the root mean square diameter of the diffuse spot is smaller than the diameter of the Airy disk, and the image quality is good.

[0035] The mid-wave continuous zoom infrared lens in this embodiment achieves the following optical indicators: working band is 3.7μm-4.8μm; focal length f′ is 20~200mm; resolution is 640×512, 15μm; F number is 4.0.

[0036] Based on the same inventive concept, this embodiment provides a lens module. The lens module includes the above-mentioned medium-wave continuous zoom infrared lens and a detector, the number of detector pixels is 640×512, and the pixel size is 15μm. The detector includes a protection window 7, a chopping window 8, and a cold screen 9, which are sequentially arranged between the sixth lens 6 and the detector image plane 10. The chopping window 8 is provided with an aperture on the side close to the cold screen 9. The specific parameters can be seen in Table 1.

[0037] The lens of the present application is set to a six-lens structure with a relatively simple structure. By moving the second lens and the third lens for zooming and the sixth lens for temperature compensation, a continuous zoom function is achieved while ensuring a good imaging effect. Continuous zoom with a large magnification ratio can be achieved.

[0038] Obviously, the above embodiments are merely examples for clearly explaining the technical solutions of the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the protection of the claims of the present invention.

Claims

1. A medium-wave continuous zoom infrared lens, characterized in that: It includes a front fixing group, a zoom group, a rear fixing group, and a temperature compensation group which are arranged in sequence on the same optical axis from the object side to the image side; The front fixed group is a first lens, which is a meniscus lens with a convex surface facing the object and has positive focal power; The zoom group includes a second lens and a third lens arranged in sequence; the second lens is a biconcave lens, and the third lens is a biconvex lens; the second lens and the third lens can move along the optical axis to achieve continuous zoom; The rear fixed group includes a fourth lens and a fifth lens; the fourth lens is a meniscus lens with a convex surface facing the image side and having a negative optical power; the fifth lens is a meniscus lens with a convex surface facing the object side and having a positive optical power; The temperature compensation group is a sixth lens, and the sixth lens is a biconvex lens.

2. The medium-wave continuous zoom infrared lens according to claim 1, characterized in that: During the zooming process, the second lens and the third lens move toward each other or away from each other along the optical axis.

3. The medium-wave continuous zoom infrared lens according to claim 1, characterized in that: The first lens, the third lens, the fifth lens and the sixth lens are made of silicon, and the second lens and the fourth lens are made of germanium.

4. The medium-wave continuous zoom infrared lens according to claim 1, characterized in that: The image side surface of the first lens, the object side surface of the second lens, the object side surface of the third lens, the image side surface of the third lens, the object side surface of the fourth lens, the image side surface of the fifth lens, the object side surface of the sixth lens, and the image side surface of the sixth 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.

5. The medium-wave continuous zoom infrared lens according to claim 4, characterized in that: The object side surface of the fourth lens and the object side surface of the sixth lens are two-dimensional surfaces, satisfying the aspheric surface formula and the expression equation of the two-dimensional surface in Zemax: M(B1ρ 2 +B2ρ 4 ), where M is the diffraction order, B1 and B2 are the binary surface phase coefficients, and ρ is the normalized radius.

6. The medium-wave continuous zoom infrared lens according to any one of claims 1 to 5, characterized in that: The working band of the infrared lens is 3.7 μm to 4.8 μm, and the focal length is 20 to 200 mm.

7. The medium-wave continuous zoom infrared lens according to claim 6, characterized in that: The air gap between the first lens and the second lens is 12.4~24.271mm; the air gap between the second lens and the third lens is 22.788~2.7mm; the air gap between the third lens and the fourth lens is 2.6~10.817mm; the air gap between the fourth lens and the fifth lens is 0.2mm; and the air gap between the fifth lens and the sixth lens is 13.812mm.

8. The medium-wave continuous zoom infrared lens according to claim 6, characterized in that: The center thickness of the first lens is 5.8mm, the radius of curvature of the object side is 49.55mm, and the radius of curvature of the image side is 96.105mm; the center thickness of the second lens is 1.6mm, the radius of curvature of the object side is -43.573mm, and the radius of curvature of the image side is 34.713mm; the center thickness of the third lens is 4mm, the radius of curvature of the object side is 56.762mm, and the radius of curvature of the image side is -41.466mm; the center thickness of the fourth lens is 1.5mm, the radius of curvature of the object side is -59.488mm, and the radius of curvature of the image side is -220mm; the center thickness of the fifth lens is 3.8mm, the radius of curvature of the object side is 7.457mm, and the radius of curvature of the image side is 5.079mm; the center thickness of the sixth lens is 2.8mm, the radius of curvature of the object side is 29.883mm, and the radius of curvature of the image side is -29.125mm.

9. A lens module, characterized in that: It comprises the medium-wave continuous zoom infrared lens and the detector as described in any one of claims 1 to 8, wherein the number of pixels of the detector is 640×512 and the pixel size is 15 μm.

10. The lens module according to claim 9, characterized in that: The detector is a medium-wave cooled infrared detector, and comprises a protection window, a chopping window, and a cold screen which are sequentially arranged between the sixth lens and the image plane of the detector; a stop is arranged on the side of the chopping window close to the cold screen.

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