A medium wave continuous zoom infrared lens and a lens module

Abstract

The application belongs to the field of infrared optical technology and discloses a middle-wave continuous zooming infrared lens and a lens module. The lens comprises a front fixed group, a zooming group, a rear fixed group and a temperature compensation group which are arranged along an optical axis in sequence from an object side to an image side. The front fixed group comprises a first lens, a second lens and a third lens. The zooming group comprises a fourth lens and a fifth lens. The fourth lens and the fifth lens can move along the optical axis between the third lens and a sixth lens to realize continuous zooming. The rear fixed group comprises the sixth lens and a seventh lens. The temperature compensation group comprises an eighth lens. The application has a high zooming ratio, an ultra-long focal length, a large imaging surface and a large field of view, and can easily capture details of a long-distance scene target. The application can match a detector with 640*512 pixels and a 15-micron pixel size.

Description

TECHNICAL FIELD

[0001] The present technology belongs to the field of infrared optical technology, and particularly relates to a middle-wave continuous zoom infrared lens and a lens module. BACKGROUND

[0002] With the increasing application demand of high zoom ratio, long distance detection and large range monitoring continuous zoom optical system in the fields of military, police and civilian such as photoelectric observation, search and monitoring, higher requirements are put forward for the matching continuous zoom lens.

[0003] Since the long focal length continuous zoom infrared optical system has long focal length and large aperture, the aberration is not easy to correct, and thus it is difficult to realize continuous zoom in a large focal length range. The existing continuous zoom infrared lens usually has a short variable focal length, and the longest focal length is also small, such as 100-500mm, 150-600mm, etc., and the longest focal length is generally less than 800mm. Thus, the existing continuous zoom infrared lens has insufficient shooting capability for long distance targets, and in addition, there is also a situation of insufficient resolution, which cannot meet the market demand. SUMMARY

[0004] In order to solve the above problems, one of the purposes of the present application is to provide a middle-wave continuous zoom infrared lens. The specific technical solutions are as follows:

[0005] A middle-wave continuous zoom infrared lens comprises, from the object side to the image side, a front fixed group, a zoom group, a rear fixed group and a temperature compensation group arranged in sequence along the optical axis;

[0006] The front fixed group comprises a first lens, a second lens and a third lens; the first lens is a meniscus lens with a convex surface facing the object side, and has positive refractive power; the second lens is a meniscus lens with a convex surface facing the object side, and has negative refractive power; the third lens is a meniscus lens with a convex surface facing the object side, and has positive refractive power;

[0007] The zoom group comprises a fourth lens and a fifth lens; the fourth lens is a double-concave lens, and the fifth lens is a double-convex lens; the fourth lens and the fifth lens are movable along the optical axis to realize continuous zoom;

[0008] The rear fixed group comprises a sixth lens and a seventh lens; the sixth lens is a meniscus lens with a convex surface facing the object side, and has negative refractive power; the seventh lens is a meniscus lens with a convex surface facing the object side, and has positive refractive power;

[0009] The temperature compensation group comprises an eighth lens, and the eighth lens is a double-convex lens.

[0010] Further, in the zooming process, the fourth lens and the fifth lens move in opposite directions or in the same direction along the optical axis.

[0011] 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.

[0012] 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:

[0013]

[0014] Among them, Z is the distance vector height from the aspheric surface vertex when the aspheric surface is at a height r along the optical axis; c=1 / R; R is the paraxial curvature fitting radius of the mirror surface; k is the cone coefficient; A, B, C, D, and E are high-order aspheric coefficients.

[0015] 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.

[0016] Furthermore, the operating band of the lens is 3.7 μm to 4.8 μm, and the focal length is 36 to 1150 mm.

[0017] 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.

[0018] Further, the first lens has a center thickness of 17 mm, an object side surface radius of curvature of 247.173 mm, and an image side surface radius of curvature of 395.422 mm; the second lens has a center thickness of 9 mm, an object side surface radius of curvature of 285 mm, and an image side surface radius of curvature of 175.688 mm; the third lens has a center thickness of 11 mm, an object side surface radius of curvature of 190.991 mm, and an image side surface radius of curvature of 362.582 mm; the fourth lens has a center thickness of 3.8 mm, an object side surface radius of curvature of -172.300 mm, and an image side surface radius of curvature of 96.221 mm; the fifth lens has a center thickness of 7 mm, an object side surface radius of curvature of 143.383 mm, and an image side surface radius of curvature of -156.002 mm; the sixth lens has a center thickness of 2.5 mm, an object side surface radius of curvature of 490.384 mm, and an image side surface radius of curvature of 110.839 mm; the seventh lens has a center thickness of 4 mm, an object side surface radius of curvature of 11.399 mm, and an image side surface radius of curvature of 8.843 mm; and the eighth lens has a center thickness of 4 mm, an object side surface radius of curvature of 75.843 mm, and an image side surface radius of curvature of -65.498 mm.

[0019] Another object of the present application is to provide a lens module, comprising the above-mentioned mid-wave continuous zoom infrared lens and a detector, wherein the detector has 640*512 pixels and each pixel has a size of 15 microns.

[0020] Further, the detector is a mid-wave refrigeration infrared detector, and the detector comprises, in sequence from the eighth lens to the detector image plane, a protective window, a chopping window, and a cold shield, wherein the cold shield is provided with a diaphragm.

[0021] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0022] The continuous zoom lens has a high zoom ratio, an ultra-long focal length, a large imaging surface, and a large field of view, and can easily capture details of a remote object. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the following embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0024] Figure 1 The lens composition diagram of the mid-wave continuous zoom infrared lens in Example 1.

[0025] Figure 2 Optical path diagram of the wave continuous zoom infrared lens in Example 1.

[0026] Figure 3 Point diagram of the wave continuous zoom infrared lens in Example 1 at a focal length of 1150mm.

[0027] Figure 4 MTF diagram of the wave continuous zoom infrared lens in Example 1 at a focal length of 1150mm.

[0028] Figure 5 Point diagram of the wave continuous zoom infrared lens in Example 1 at a focal length of 36mm.

[0029] Figure 6 MTF diagram of the wave continuous zoom infrared lens in Example 1 at a focal length of 36mm.

[0030] The reference signs: 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, protective window; 10, chopper window; 11, cold shield; 12, detector image plane. DETAILED DESCRIPTION

[0031] 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 a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application. It should be noted that the terms “first” and “second” are only used for the purpose of convenience, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features.

[0032] For the convenience of understanding, the related terms involved are explained as follows.

[0033] Object side, the side of the lens on which light is incident in the direction of propagation of the optical path, i.e. the surface of the lens close to the object side; image side, the side of the lens on which light is emitted in the direction of propagation of the optical path, i.e. the surface of the lens close to the image side; meniscus lens, also known as crescent-shaped lens, one of the sides close to the optical axis is concave, and the other side is convex.

[0034] As shown in FIG. 1, the wave continuous zoom infrared lens comprises, from the object side to the image side, a front fixed group, a zoom group, a rear fixed group and a temperature compensation group arranged in sequence along the optical axis. Figure 1 , Figure 2 As shown in FIG. 1, the wave continuous zoom infrared lens comprises, from the object side to the image side, a front fixed group, a zoom group, a rear fixed group and a temperature compensation group arranged in sequence along the optical axis.

[0035] The front fixed group comprises the first lens 1, the second lens 2 and the third lens 3; the first lens 1 is a meniscus lens with a convex surface facing the object side and has a positive focal power; the second lens 2 is a meniscus lens with a convex surface facing the object side and has a negative focal power; and the third lens 3 is a meniscus lens with a convex surface facing the object side and has a positive focal power.

[0036] The zoom group comprises the fourth lens 4 and the fifth lens 5; the fourth lens 4 is a double-concave lens; and the fifth lens 5 is a double-convex lens.

[0037] The rear fixed group comprises the sixth lens 6 and the seventh lens 7; the sixth lens 6 is a meniscus lens with a convex surface facing the object side and has a negative focal power; and the seventh lens 7 is a meniscus lens with a convex surface facing the object side and has a positive focal power.

[0038] The temperature compensation group comprises the eighth lens 8, which is a double-convex lens.

[0039] The fourth lens 4 and the fifth lens 5 can move along the optical axis between the third lens 3 and the sixth lens 6 to realize continuous zooming.

[0040] In the present application, 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 shift of the image plane position at different temperatures, and the zoom group is used to realize continuous change of the focal length.

[0041] For example, during the process of changing the lens from long focal length to short focal length, the fourth lens 4 moves towards the object side, and the fifth lens 5 moves towards the image side, so as to reduce the focal length of the optical system and compensate for the image plane shift caused by the movement of the lens; during the process of changing the lens from short focal length to long focal length, the fourth lens 4 moves towards the image side, and the fifth lens 5 moves towards the object side. When the lens is in the longest focal length state, the air gap between the third lens 3 and the fourth lens 4 is in the maximum state, the air gap between the fourth lens 4 and the fifth lens 5 is in the minimum state, and the air gap between the fifth lens 5 and the sixth lens 6 is in the maximum state; when the lens is in the shortest focal length state, the air gap between the third lens 3 and the fourth lens 4 is in the minimum state, the air gap between the fourth lens 4 and the fifth lens 5 is in the maximum state, and the air gap between the fifth lens 5 and the sixth lens 6 is in the minimum state.

[0042] As a specific embodiment, the materials of the second lens 2, the fourth lens 4, the sixth lens 6 and the eighth lens 8 are germanium, and the materials of the first lens 1, the third lens 3, the fifth lens 5 and the seventh lens 7 are silicon.

[0043] The present application uses the combination of aspheric surfaces and binary surfaces, effectively corrects chromatic aberration and improves the imaging quality of the lens.

[0044] As a specific embodiment, 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:

[0045]

[0046] wherein Z is the distance 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 surface; k is the conic coefficient; A, B, C, D, and E are high-order aspherical surface coefficients.

[0047] The image side surface S16 of the eighth lens 8 is a binary surface, satisfies the above aspherical surface formula, and satisfies the expression equation of the binary surface in Zemax: M(B1p 2 +B2p 4 ); wherein M is the diffraction order, B1and B2are the phase coefficients of the binary surface, and p is the normalized radius.

[0048] Embodiment 1

[0049] The following is described by taking a specific continuous zoom infrared lens as an example. The specific parameters of the lens of the embodiment are shown in Table 1, Table 2, and Table 3.

[0050] Table 1: Parameters of each component

[0051]

[0052] Table 2: Aspherical surface data of the lens

[0053]

[0054] Table 3: Binary surface data of the lens

[0055]

[0056] When focusing, the lens positions of the front fixed group and the rear fixed group are relatively fixed, and 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 gaps between the third lens 3 and the fourth lens 4, between the fourth lens 4 and the fifth lens 5, and between the fifth lens 5 and the sixth lens 6 are all variable. When the air gap D6 between the third lens 3 and the fourth lens 4 is 96.242 mm, the air gap D8 between the fourth lens 4 and the fifth lens 5 is 8.999 mm, and the air gap 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 the embodiment is 1150 mm. When the air gap D6 between the third lens 3 and the fourth lens 4 is 10 mm, the air gap D8 between the fourth lens 4 and the fifth lens 5 is 125.592 mm, and the air gap 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 the embodiment is 36 mm.

[0057] Figure 3 、 Figure 4 respectively are point spread function (PSF) diagram and modulation transfer function (MTF) diagram when the focal length of the lens is 1150 mm, Figure 5 、 Figure 6 respectively are point spread function (PSF) diagram and modulation transfer function (MTF) diagram when the focal length of the lens is 36 mm. In the MTF diagram, the horizontal axis represents different spatial frequencies, and the vertical axis represents modulation. All field of view represents the MTF curve of the meridional plane. It can be seen that the MTF is close to the diffraction limit, the root mean square diameter of the diffraction spot is smaller than the diameter of the Airy disk, and the image quality is good.

[0058] In the embodiment, the focal length range of the mid-wave continuous zoom infrared lens is 36-1150 mm; the resolution is 640x512, 15 μm; the working waveband is 3.7 μm-4.8 μm; and the F number is 5.5.

[0059] Based on the same inventive concept, the embodiment provides a lens module. The lens module comprises the above-mentioned mid-wave continuous zoom infrared lens and a detector, and the number of pixels of the detector is 640x512, and the size of the pixel is 15 μm. As a specific embodiment, the detector is a mid-wave refrigeration detector, and the detector comprises a protective window 9, a chopping window 10, and a cold shield 11 arranged in sequence between the eighth lens 8 and a detector image surface 12, and the cold shield 11 is provided with a diaphragm. The specific parameters can be referred to Table 1.

[0060] Obviously, the above embodiments are only examples for clearly illustrating the technical solutions of the present application, and are not intended to limit the manner of the present application. Any modification, equivalent replacement and improvement made on the basis of the above description by those skilled in the art shall be included in the protection scope of the claims of the present application.

Claims

1. A medium wave continuous zoom infrared lens characterized by, The front fixed group, the zoom group, the rear fixed group and the temperature compensation group are arranged along the optical axis in sequence from the object side to the image side; The front fixed group comprises a first lens, a second lens and a third lens; the first lens is a meniscus lens with a convex surface facing the object side and has positive refractive power; the second lens is a meniscus lens with a convex surface facing the object side and has negative refractive power; and the third lens is a meniscus lens with a convex surface facing the object side and has positive refractive power; The zoom group comprises a fourth lens and a fifth lens; the fourth lens is a double-concave lens and the fifth lens is a double-convex lens; the fourth lens and the fifth lens are movable along the optical axis to realize continuous zooming; The rear fixed group comprises a sixth lens and a seventh lens; the sixth lens is a meniscus lens with a convex surface facing the object side and has negative refractive power; and the seventh lens is a meniscus lens with a convex surface facing the object side and has positive refractive power; The temperature compensation group comprises an eighth lens, which is a double-convex lens.

2. The mid-wave continuous zoom infrared lens of claim 1, wherein, During zooming, the fourth lens and the fifth lens move along the optical axis in opposite directions or in the same direction.

3. The mid-wave continuous zoom infrared lens of claim 1, wherein, 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 mid-wave continuous zoom infrared lens of claim 1, wherein, 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: wherein Z is the sag of the aspherical surface at a height r along the optical axis; c=1 / R; R is the paraxial curvature fitting radius of the mirror surface; k is the conic coefficient; and A, B, C, D and E are high-order aspherical coefficients.

5. The mid-wave continuous zoom infrared lens of claim 4, wherein, The image side surface of the eighth lens is a binary surface, satisfies an aspherical surface formula, and satisfies a binary surface expression equation in Zemax: M(B1ρ 2 +B2ρ 4 ); wherein M is a diffraction order, B1 and B2 are binary surface phase coefficients, and ρ is a normalized radius.

6. The mid-wave continuous zoom infrared lens according to any one of claims 1 to 5, characterized in that, The working waveband of the lens is 3.7-4.8 microns, and the focal length is 36-1150 mm.

7. The mid-wave continuous zoom infrared lens of claim 6, wherein, 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 mm; and the air gap between the seventh lens and the eighth lens is 29.304 mm.

8. The mid-wave continuous zoom infrared lens of claim 6, wherein, 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 96.221mm ; The center thickness of the fifth lens is 7mm, the object side curvature radius is 143.383mm, and the image side curvature radius is -156.002mm; the center thickness of the sixth lens is 2.5mm, the object side curvature radius is 490.384mm, and the image side curvature radius is 110.839mm; the center thickness of the seventh lens is 4mm, the object side curvature radius is 11.399mm, and the image side curvature radius is 8.843mm; the center thickness of the eighth lens is 4mm, the object side curvature radius is 75.843mm, and the image side curvature radius is -65.498mm.

9. A lens module, characterized by, It comprises the medium-wave continuous zoom infrared lens and the detector according to 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, wherein, The detector is a medium-wave cooled infrared detector, which includes a protection window, a chopping window, and a cold screen which are sequentially arranged between the eighth lens and the image plane of the detector, and an aperture is provided on the cold screen.

Images