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 comprises a first lens, a second lens and a third lens; the zoom group comprises a fourth lens and a fifth lens; the fourth lens and the fifth lens can respectively move between the third lens and the sixth lens along the optical axis to realize continuous zooming; the rear fixed group comprises a sixth lens and a seventh lens; and the temperature compensation group comprises an eighth lens. According to the invention, the zoom ratio is high, the focal length is super long, the imaging surface is large, the shooting visual field range is large, and the details of a long-distance scenery target are easy to shoot; and the detector with the pixel number of 640 * 512 and the pixel size of 15 microns can be matched.

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] As the application demand for continuous zoom optical systems with high zoom ratio, long-distance detection and large-scale monitoring in military, police and civilian fields such as optoelectronic observation, search and monitoring becomes more and more extensive, higher requirements are also placed on the continuous zoom lenses that match them.

[0003] Since the long focal length and large aperture of the long focal length continuous zoom infrared optical system make it difficult to correct aberrations, it is difficult to achieve continuous zoom within a large focal length range. The existing continuous zoom infrared lenses usually have a short variable focal length and a short maximum focal length, such as 100-500mm, 150-600mm, etc. The maximum focal length is generally less than 800mm. Therefore, the existing continuous zoom infrared lenses are not capable of shooting long-distance targets, and the resolution is insufficient, which cannot meet the market demand. 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 includes a first lens, a second lens, and a third lens; the first lens is a meniscus lens with a convex surface facing the object and having a positive focal power; the second lens is a meniscus lens with a convex surface facing the object and having a negative focal power; the third lens is a meniscus lens with a convex surface facing the object and having a positive focal power; The zoom group includes a fourth lens and a fifth lens; the fourth lens is a biconcave lens, and the fifth lens is a biconvex lens; the fourth lens and the fifth lens can move along the optical axis to achieve continuous zoom; The rear fixed group includes a sixth lens and a seventh lens; the sixth lens is a meniscus lens with a convex surface facing the object and having a negative optical power; the seventh lens is a meniscus lens with a convex surface facing the object and having a positive optical power; The temperature compensation group includes an eighth lens, and the eighth lens is a biconvex lens.

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

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

[0007] Furthermore, the image side surface of the second lens, the object side surface of the fourth lens, the image side surface of the fifth lens, the image side surface of the sixth lens, the image side surface of the seventh lens, and the image side surface of the eighth 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 eighth 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, the operating band of the lens is 3.7 μm to 4.8 μm, and the focal length is 36 to 1150 mm.

[0010] Furthermore, the air gap between the first lens and the second lens is 92.149 mm; the air gap between the second lens and the third lens is 8 mm; the air gap between the third lens and the fourth lens is 96.242~10 mm; the air gap between the fourth lens and the fifth lens is 8.999~125.592 mm; the air gap between the fifth lens and the sixth lens is 42.351~12 mm; the air gap between the sixth lens and the seventh lens is 30.071; and the air gap between the seventh lens and the eighth lens is 29.304 mm.

[0011] Further, the center thickness of the first lens is 17mm, the object side curvature radius is 247.173mm, and the image side curvature radius is 395.422mm; the center thickness of the second lens is 9mm, the object side curvature radius is 285mm, and the image side curvature radius is 175.688mm; the center thickness of the third lens is 11mm, the object side curvature radius is 190.991mm, and the image side curvature radius is 362.582mm; the center thickness of the fourth lens is 3.8mm, the object side curvature radius is -172.300mm, and the image side curvature radius is 96.221 mm; the center thickness of the fifth lens is 7 mm, the object side curvature radius is 143.383 mm, and the image side curvature radius is -156.002 mm; the center thickness of the sixth lens is 2.5 mm, the object side curvature radius is 490.384 mm, and the image side curvature radius is 110.839 mm; the center thickness of the seventh lens is 4 mm, the object side curvature radius is 11.399 mm, and the image side curvature radius is 8.843 mm; the center thickness of the eighth lens is 4 mm, the object side curvature radius is 75.843 mm, and the image side curvature radius is -65.498 mm.

[0012] Another object of the present application is to provide a lens module, comprising the above-mentioned medium-wave 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 protection window, a chopping window, and a cold screen which are sequentially arranged between the eighth lens and the detector image plane, and an aperture is provided on 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: The continuous zoom lens of the present invention has a high zoom ratio, an ultra-long focal length, a large imaging surface, a large field of view that can be photographed, and is easier to photograph details of distant objects; it can match a detector with a pixel number of 640×512 and a pixel size of 15 μm. 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 a lens composition diagram of the medium-wave continuous zoom infrared lens in Example 1.

[0017] Figure 2 This is the optical path 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 1150 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 1150mm in Example 1.

[0020] Figure 5 This is a point diagram of the medium-wave continuous zoom infrared lens with a focal length of 36 mm in Example 1.

[0021] Figure 6 This is the MTF diagram of the medium-wave continuous zoom infrared lens of Example 1 with a focal length of 36 mm.

[0022] Figure numerals: 1, first lens; 2, second lens; 3, third lens; 4, fourth lens; 5, fifth lens; 6, sixth lens; 7, seventh lens; 8, eighth lens; 9, protection window; 10, chopping window; 11, cold shield; 12, 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 2 As shown, the medium-wave continuous zoom infrared lens 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.

[0027] The front fixed group includes a first lens 1, a second lens 2, and a third lens 3; the first lens 1 is a meniscus lens with a convex surface facing the object, and has a positive focal power; the second lens 2 is a meniscus lens with a convex surface facing the object, and has a negative focal power; the third lens 3 is a meniscus lens with a convex surface facing the object, and has a positive focal power; The zoom group includes a fourth lens 4 and a fifth lens 5; the fourth lens 4 is a biconcave lens, and the fifth lens 5 is a biconvex lens; The rear fixed group includes a sixth lens 6 and a seventh lens 7; the sixth lens 6 is a meniscus lens with a convex surface facing the object and having a negative optical power; the seventh lens 7 is a meniscus lens with a convex surface facing the object and having a positive optical power; The temperature compensation group includes an eighth lens 8, and the eighth lens 8 is a biconvex lens; The fourth lens 4 and the fifth lens 5 can respectively move along the optical axis between the third lens 3 and the sixth lens 6 to achieve continuous zooming.

[0028] 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 fourth lens 4 and the fifth lens 5 move toward or away from each other along the optical axis to achieve switching between long focus, medium focus and short focus.

[0029] For example, when the lens changes from long focal length to short focal length, the fourth lens 4 moves toward the object side and the fifth lens 5 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 fourth lens 4 moves toward the image side and the fifth lens 5 moves toward the object side. When the lens is in the longest focal length state, the air interval between the third lens 3 and the fourth lens 4 is at the maximum state, the air interval between the fourth lens 4 and the fifth lens 5 is at the minimum state, and the air interval between the fifth lens 5 and the sixth lens 6 is at the maximum state; when the lens is in the shortest focal length state, the air interval between the third lens 3 and the fourth lens 4 is at the minimum state, the air interval between the fourth lens 4 and the fifth lens 5 is at the maximum state, and the air interval between the fifth lens 5 and the sixth lens 6 is at the minimum state.

[0030] As a specific implementation, the second lens 2 , the fourth lens 4 , the sixth lens 6 , and the eighth lens 8 are made of germanium, and the first lens 1 , the third lens 3 , the fifth lens 5 , and the seventh lens 7 are made of silicon.

[0031] This application adopts a combination of aspherical surfaces and binary surfaces to effectively correct chromatic aberration and improve the imaging quality of the lens.

[0032] As a specific implementation, the image side surface S4 of the second lens 2, the object side surface S7 of the fourth lens 4, the image side surface S10 of the fifth lens 5, the image side surface S12 of the sixth lens 6, the image side surface S14 of the seventh lens 7, and the image side surface S16 of the eighth lens 8 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.

[0033] The image side surface S16 of the eighth lens 8 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.

[0034] Example 1 The following is an example of a specific continuous zoom infrared lens. Specific parameters of the lens of this embodiment are shown in Table 1, Table 2, and Table 3.

[0035] 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. Specifically, the air interval between the third lens 3 and the fourth lens 4, the air interval between the fourth lens 4 and the fifth lens 5, and the air interval between the fifth lens 5 and the sixth lens 6 are all variable intervals. For example, when the air interval D6 between the third lens 3 and the fourth lens 4 is 96.242 mm, the air interval D8 between the fourth lens 4 and the fifth lens 5 is 8.999 mm, and the air interval D10 between the fifth lens 5 and the sixth lens 6 is 42.351 mm, the system focal length is in the longest focal length state, and the longest focal length of this embodiment is 1150 mm. When the air interval D6 between the third lens 3 and the fourth lens 4 is 10 mm, the air interval D8 between the fourth lens 4 and the fifth lens 5 is 125.592 mm, and the air interval D10 between the fifth lens 5 and the sixth lens 6 is 12 mm, the system focal length is in the shortest focal length state, and the shortest focal length of this embodiment is 36 mm.

[0036] Figure 3 , Figure 4 They are the spot diagram and MTF diagram when the lens focal length is 1150mm. Figure 5 , Figure 6 The spot diagram and MTF diagram are respectively when the focal length of the lens is 36mm. 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.

[0037] The mid-wave continuous zoom infrared lens in this embodiment has a focal length range of 36~1150mm; a resolution of 640×512, 15μm; a working band of 3.7μm-4.8μm; and an F number of 5.5.

[0038] 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. As a specific implementation, the detector is a medium-wave cooling detector, and the detector includes a protective window 9, a chopping window 10, and a cold screen 11, which are sequentially arranged between the eighth lens 8 and the detector image plane 12. The cold screen 11 is provided with an aperture. For specific parameters, see Table 1.

[0039] 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 includes a first lens, a second lens, and a third lens; the first lens is a meniscus lens with a convex surface facing the object and having a positive focal power; the second lens is a meniscus lens with a convex surface facing the object and having a negative focal power; the third lens is a meniscus lens with a convex surface facing the object and having a positive focal power; The zoom group includes a fourth lens and a fifth lens; the fourth lens is a biconcave lens, and the fifth lens is a biconvex lens; the fourth lens and the fifth lens can move along the optical axis to achieve continuous zoom; The rear fixed group includes a sixth lens and a seventh lens; the sixth lens is a meniscus lens with a convex surface facing the object and having a negative optical power; the seventh lens is a meniscus lens with a convex surface facing the object and having a positive optical power; The temperature compensation group includes an eighth lens, and the eighth 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 fourth lens and the fifth 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 second lens, the fourth lens, the sixth lens and the eighth lens are made of germanium, and the first lens, the third lens, the fifth lens and the seventh lens are made of silicon.

4. The medium-wave continuous zoom infrared lens according to claim 1, characterized in that: The image side surface of the second lens, the object side surface of the fourth lens, the image side surface of the fifth lens, the image side surface of the sixth lens, the image side surface of the seventh lens, and the image side surface of the eighth 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 image side surface of the eighth 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 medium-wave continuous zoom infrared lens according to any one of claims 1 to 5, characterized in that: The working band of the lens is 3.7 μm~4.8 μm, and the focal length is 36~1150 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 92.149mm; the air gap between the second lens and the third lens is 8mm; the air gap between the third lens and the fourth lens is 96.242~10mm; the air gap between the fourth lens and the fifth lens is 8.999~125.592mm; the air gap between the fifth lens and the sixth lens is 42.351~12mm; the air gap between the sixth lens and the seventh lens is 30.071; the air gap between the seventh lens and the eighth lens is 29.304mm.

8. The medium-wave continuous zoom infrared lens according to claim 6, characterized in that: The center thickness of the first lens is 17mm, the radius of curvature of the object side is 247.173mm, and the radius of curvature of the image side is 395.422mm; the center thickness of the second lens is 9mm, the radius of curvature of the object side is 285mm, and the radius of curvature of the image side is 175.688mm; the center thickness of the third lens is 11mm, the radius of curvature of the object side is 190.991mm, and the radius of curvature of the image side is 362.582mm; the center thickness of the fourth lens is 3.8mm, the radius of curvature of the object side is -172.300mm, and the radius of curvature of the image side is 96.221mm The center thickness of the fifth lens is 7mm, the radius of curvature of the object side is 143.383mm, and the radius of curvature of the image side is -156.002mm; the center thickness of the sixth lens is 2.5mm, the radius of curvature of the object side is 490.384mm, and the radius of curvature of the image side is 110.839mm; the center thickness of the seventh lens is 4mm, the radius of curvature of the object side is 11.399mm, and the radius of curvature of the image side is 8.843mm; the center thickness of the eighth lens is 4mm, the radius of curvature of the object side is 75.843mm, and the radius of curvature of the image side is -65.498mm.

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 an eighth lens and the image plane of the detector, and an aperture is arranged on the cold screen.

Images