Long-wave continuous zooming infrared lens and lens module

Abstract

The invention belongs to the technical field of infrared optics, and discloses a long-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 meniscus lens of which the convex surface faces the object side and is used as a first lens; the zoom group comprises a biconcave lens and a biconvex lens which are arranged in sequence and are respectively used as a second lens and a third lens; the rear fixed group is a meniscus lens of which the convex surface faces the image side and is used as a fourth lens; and the temperature compensation group is a meniscus lens of which the convex surface faces the image side and is used as a fifth lens. According to the invention, the structure is relatively simple, the total length of the optical system is relatively short, the maximum movement amount of the lens is small, and the zoom ratio is greater than 4 times; the image quality is excellent, and the resolution ratio is 640 * 512, 12 [mu] m.

Description

Technical Field

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

[0002] 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 them; 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. With the widespread use of continuous zoom lenses in search, navigation, detection, tracking and other fields, higher requirements have been put forward for them.

[0003] In order to meet the requirements of wide band and multiple fields of view, and to correct aberrations, the continuous zoom infrared system often causes problems such as complexity, large size or poor image quality. Therefore, it is necessary to develop a continuous zoom infrared lens with a simple structure, good image quality and a certain zoom ratio. Summary of the invention

[0004] In order to solve the above problems, one object of the present invention is to provide a long-wave continuous zoom infrared lens. The specific technical solution is as follows: A long-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 meniscus lens with a convex surface facing the object side and having positive optical power, serving as the first lens; The zoom group includes a biconcave lens and a biconvex lens arranged in sequence, which serve as a second lens and a third lens respectively; the second lens and the third lens can move along the optical axis, the second lens is used to change the focal length of the lens, and the third lens is used to compensate for the movement of the image plane of the lens during the zooming process; The rear fixed group is a meniscus lens with a convex surface facing the image side and having negative optical power, serving as the fourth lens; The temperature compensation group is a meniscus lens with a convex surface facing the image side and having positive focal power. It serves as the fifth lens and is used to compensate for the displacement of the image plane position caused by temperature changes.

[0005] Furthermore, during the zooming process of the lens, 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 second lens, and the fourth lens are made of germanium, and the third lens and the fifth lens are made of chalcogenide glass.

[0007] Further, 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 object side surface of the fifth 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.

[0008] Furthermore, the image side surface of the third lens is a binary surface, which satisfies the aspheric surface formula and satisfies the expression equation of the binary 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.

[0009] Furthermore, a stop is provided on the object side of the third lens.

[0010] Furthermore, the lens has an operating band of 8 μm to 12 μm and a focal length of 30 to 137 mm.

[0011] Furthermore, the air gap between the first lens and the second lens is 52.338~32.955mm; the air gap between the second lens and the third lens is 4.798~43.478mm; the air gap between the third lens and the fourth lens is 25.797~6.5mm; and the air gap between the fourth lens and the fifth lens is 24.343mm.

[0012] Further, the center thickness of the first lens is 7.7mm, the object side curvature radius is 105.966mm, and the image side curvature radius is 162.315mm; the center thickness of the second lens is 2.2mm, the object side curvature radius is -172.518mm, and the image side curvature radius is 93.602mm; the center thickness of the third lens is 7.8mm, the object side curvature radius is 112.528mm, and the image side curvature radius is -105.031mm; the center thickness of the fourth lens is 2.2mm, the object side curvature radius is -40.020mm, and the image side curvature radius is -46.572mm; the center thickness of the fifth lens is 4.5mm, the object side curvature radius is -472.656mm, and the image side curvature radius is -72.778mm.

[0013] Another object of the present application is to provide a lens module, comprising the above-mentioned long-wave continuous zoom infrared lens and a detector, wherein the number of pixels of the detector is 640×512 and the pixel size is 12 μm.

[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) There are only two moving lenses in the zoom group, which can better ensure the stability of the optical axis during the zoom process; there are only five lenses with optical power in the overall structure, and the structure is relatively simple; (2) The total length of the optical system is short (e.g. 156 mm), the maximum movement of the lens is small (no more than 20 mm), and the zoom ratio is greater than 4 times (30 to 137 mm); (3) Excellent image quality, with a resolution of up to 640×512, 12μm. 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 long-wave continuous zoom infrared lens of Example 1.

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

[0018] Figure 3 This is a point diagram of the long-wave continuous zoom infrared lens of Example 1 with a focal length of 137 mm.

[0019] Figure 4 This is the MTF diagram of the long-wave continuous zoom infrared lens of Example 1 with a focal length of 137 mm.

[0020] Figure 5 This is a point diagram of the long-wave continuous zoom infrared lens of Example 1 with a focal length of 30 mm.

[0021] Figure 6 This is the MTF diagram of the long-wave continuous zoom infrared lens of Example 1 with a focal length of 30 mm.

[0022] Reference numerals: 1, first lens; 2, second lens; 3, third lens; 4, fourth lens; 5, fifth lens; 6, protective window; 7, 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 2 As shown, the long-wave continuous zoom infrared lens of the present application comprises a front fixed group, a zoom group, a rear fixed group, and a temperature compensation group which are arranged on the same optical axis in sequence from the object side to the image side; The front fixed group is a meniscus lens with a convex surface facing the object side and having positive focal power, serving as the first lens 1; The zoom group includes a biconcave lens and a biconvex lens arranged in sequence, which serve as a second lens 2 and a third lens 3 respectively; the second lens 2 and the third lens 3 can move along the optical axis, and the second lens 2 is used to change the focal length of the lens; the third lens 3 is used to compensate for the movement of the image plane of the lens during the zooming process; The rear fixed group is a meniscus lens with a convex surface facing the image side and having negative optical power, serving as the fourth lens 4; The temperature compensation group is a meniscus lens with a convex surface facing the image side and having positive optical power, and serves as the fifth lens 5 to compensate for the displacement of the image plane position caused by temperature change.

[0027] In the present application, the relative positions of the lenses in the front fixed group and the rear fixed group are fixed, and the two lenses of the zoom group move along the optical axis between the front fixed group and the rear fixed group to achieve the purpose of continuous change of focal length and compensation of image plane movement caused by focal length change. 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 3 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 first lens 1 , the second lens 2 , and the fourth lens 4 are made of germanium; the third lens 3 and the fifth lens 5 are made of chalcogenide glass, such as IRG206.

[0030] As a specific implementation, the object-side surface S3 of the second lens 2, the object-side surface S5 and the image-side surface S6 of the third lens 3, the object-side surface S7 of the fourth lens 4, the object-side surface S9 of the fifth lens 5, 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] The image side surface S6 of the third lens 3 is a binary surface, which satisfies the above aspheric surface formula and satisfies the expression equation of the binary 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.

[0032] As a specific implementation, a stop is provided on the object-side surface S5 of the third lens 3 .

[0033] Example 1 The following is an example of a long-wave continuous zoom infrared lens. Specific parameters of the long-wave continuous zoom infrared lens of this embodiment are shown in Table 1, Table 2, and Table 3.

[0034] Table 1 Parameters of each component Table 2 Aspheric surface data of lens Table 3. Binary surface data of lens 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. For example, when the air interval D2 between the first lens 1 and the second lens 2 is 32.955 mm, the air interval D4 between the second lens 2 and the third lens 3 is 43.478 mm, and the air interval D6 between the third lens 3 and the fourth lens 4 is 6.5 mm, the focal length of the system is 30 mm.

[0035] Figure 3 , Figure 4 They are the point diagram and MTF diagram of the lens at a telephoto of 137mm. Figure 5 , Figure 6 The spot diagram and MTF diagram of the lens at short focal length of 30mm 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 RMS diameter of the diffuse spot is smaller than the Airy disk diameter, and the image quality is good.

[0036] The long-wave continuous zoom infrared lens of this embodiment achieves the following optical indicators: focal length range 30-137 mm; working band 8 μm-12 μm; resolution 640×512, 12 μm; F number 1.4.

[0037] Based on the same inventive concept, this embodiment provides a lens module, which includes the long-wave continuous zoom infrared lens and a detector, wherein the number of pixels of the detector is 640×512 and the pixel size is 12 μm.

[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 long-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 meniscus lens with a convex surface facing the object side and having positive optical power, serving as the first lens; The zoom group includes a biconcave lens and a biconvex lens arranged in sequence, which serve as a second lens and a third lens respectively; the second lens and the third lens can move along the optical axis, the second lens is used to change the focal length of the lens, and the third lens is used to compensate for the movement of the image plane of the lens during the zooming process; The rear fixed group is a meniscus lens with a convex surface facing the image side and having negative optical power, serving as the fourth lens; The temperature compensation group is a meniscus lens with a convex surface facing the image side and having positive focal power. It serves as the fifth lens and is used to compensate for the displacement of the image plane position caused by temperature changes.

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

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

4. The long-wave continuous zoom infrared lens according to claim 1, characterized in that: 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 object side surface of the fifth 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.

5. The long-wave continuous zoom infrared lens according to claim 4, characterized in that: The image side surface of the third lens is a binary surface, which satisfies the aspheric surface formula and satisfies the expression equation of the binary 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 long-wave continuous zoom infrared lens according to claim 1, characterized in that: An aperture is provided on the object side of the third lens.

7. The long-wave continuous zoom infrared lens according to any one of claims 1 to 6, characterized in that: The lens has an operating band of 8 μm to 12 μm and a focal length of 30 to 137 mm.

8. The long-wave continuous zoom infrared lens according to claim 7, characterized in that: The air gap between the first lens and the second lens is 52.338~32.955mm; the air gap between the second lens and the third lens is 4.798~43.478mm; the air gap between the third lens and the fourth lens is 25.797~6.5mm; the air gap between the fourth lens and the fifth lens is 24.343mm.

9. The long-wave continuous zoom infrared lens according to claim 7, characterized in that: The center thickness of the first lens is 7.7mm, the object side curvature radius is 105.966mm, and the image side curvature radius is 162.315mm; the center thickness of the second lens is 2.2mm, the object side curvature radius is -172.518mm, and the image side curvature radius is 93.602mm; the center thickness of the third lens is 7.8mm, the object side curvature radius is 112.528mm, and the image side curvature radius is -105.031mm; the center thickness of the fourth lens is 2.2mm, the object side curvature radius is -40.020mm, and the image side curvature radius is -46.572mm; the center thickness of the fifth lens is 4.5mm, the object side curvature radius is -472.656mm, and the image side curvature radius is -72.778mm.

10. A lens module, characterized in that: It comprises the long-wave continuous zoom infrared lens and the detector as claimed in any one of claims 1 to 9, wherein the number of pixels of the detector is 640×512 and the pixel size is 12 μm.

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