A long-wave continuous zoom infrared lens and lens module

Abstract

The application belongs to the field of infrared optical technology and discloses a long-wave continuous zooming infrared lens and a lens module. The lens comprises a first lens, a moving lens group and a fifth lens which are arranged along an optical axis from an object side to an image side. The first lens is a meniscus lens with a convex surface facing the object side, and the fifth lens is a meniscus lens with a convex surface facing the object side. The first lens and the fifth lens are fixed in position. The moving lens group comprises a second lens, a third lens and a fourth lens which are arranged in sequence. The second lens is a double-concave lens, the third lens is a double-convex lens, and the fourth lens is a meniscus lens with a convex surface facing the image side. The second lens, the third lens and the fourth lens can move along the optical axis to realize continuous zooming. The system has a short length, a small number of lenses, a high light transmittance, a good imaging quality and can match a detector with 1280*1024 image elements and 12 μm image element size.

Description

TECHNICAL FIELD

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

[0002] Compared with a fixed focus system, a zoom system has the advantages that a target can be identified and tracked when a small field of view is used, and a target can be searched in a large range when a large field of view is used, and has been more and more widely applied in the fields of search, navigation, detection and tracking.

[0003] With the increasingly wide application of an infrared continuous zoom system, higher requirements are put forward for the lens matched with the infrared continuous zoom system. For example, the long-wave infrared lenses on the market are mainly suitable for 320*256 or 640*512 pixel area arrays, and have the disadvantages of a small field of view and low imaging resolution. A new type of long-wave infrared area array detector has 1280*1024 pixels, smaller pixels and higher resolution, and needs to be matched with a continuous zoom lens with higher imaging quality. Although there are continuous zoom lenses with high resolution in the prior art, they often have the disadvantages of a small focal length range, low light transmittance, complex structure and too long total length of the system. SUMMARY

[0004] To solve the above problems, one purpose of the present application is to provide a long-wave continuous zoom infrared lens. The specific technical solutions are as follows.

[0005] A long-wave continuous zoom infrared lens, the lens comprising, from the object side to the image side, a first lens, a moving lens group and a fifth lens arranged in sequence along the optical axis;

[0006] The first lens is a meniscus lens with a convex surface facing the object side, and has positive refractive power; the fifth lens is a meniscus lens with a convex surface facing the object side, and has positive refractive power; the first lens and the fifth lens have fixed relative positions;

[0007] The moving lens group comprises, in sequence, a second lens, a third lens and a fourth lens; the second lens is a double-concave lens; the third lens is a double-convex lens; the fourth lens is a meniscus lens with a convex surface facing the image side, and has negative refractive power; the second lens, the third lens and the fourth lens are movable along the optical axis to realize continuous zooming.

[0008] Further, during the change of the lens from long focal length to short focal length, the second lens moves towards the object side; during the change of the lens from short focal length to long focal length, the second lens moves towards the image side;

[0009] when the lens is in the longest focal length state, the variable interval between the first lens and the second lens is in the maximum state, the variable interval between the second lens and the third lens is in the minimum state, the variable interval between the third lens and the fourth lens is in the maximum state, and the variable interval between the fourth lens and the fifth lens is in the minimum state.

[0010] when the lens is in the longest focal length state, the variable interval between the first lens and the second lens is in the maximum state, the variable interval between the second lens and the third lens is in the minimum state, the variable interval between the third lens and the fourth lens is in the maximum state, and the variable interval between the fourth lens and the fifth lens is in the minimum state.

[0011] Further, the materials of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are germanium.

[0012] Further, the object side surface of the second lens, the image side surface of the second lens, the object side surface of the third lens, the image side surface of the third lens, the image side surface of the fourth lens and the image side surface of the fifth lens are aspherical surfaces, and satisfy the aspherical surface formula:

[0013]

[0014] 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 coefficients.

[0015] Further, the object side surface of the third lens is a binary surface, satisfies the aspherical surface formula, and satisfies the expression equation of the binary surface in Zemax: M(B1ρ 2 +B2ρ 4 +B3ρ 6 ); wherein M is the diffraction order, B1, B2 and B3 are binary phase coefficients, and p is the normalized radius.

[0016] Further, a diaphragm is arranged on the object side surface of the third lens.

[0017] Further, the working waveband of the lens is 8-12 μm, and the focal length is 25-225 mm.

[0018] Further, the variable interval between the first lens and the second lens is 122.913-51.228 mm, the variable interval between the second lens and the third lens is 8.934-126.355 mm, the variable interval between the third lens and the fourth lens is 74.649-10.967 mm, and the variable interval between the fourth lens and the fifth lens is 38.117-57.066 mm.

[0019] Further, the first lens has a center thickness of 13 mm, an object-side surface radius of curvature of 242.955 mm, and an image-side surface radius of curvature of 369.549 mm; the second lens has a center thickness of 4 mm, an object-side surface radius of curvature of -331.554 mm, and an image-side surface radius of curvature of 212.430 mm; the third lens has a center thickness of 8 mm, an object-side surface radius of curvature of 385.056 mm, and an image-side surface radius of curvature of -312.355 mm; the fourth lens has a center thickness of 4 mm, an object-side surface radius of curvature of -93.890 mm, and an image-side surface radius of curvature of -164.769 mm; and the fifth lens has a center thickness of 10 mm, an object-side surface radius of curvature of 117.015 mm, and an image-side surface radius of curvature of 495.086 mm.

[0020] Another object of the present application is to provide a lens module comprising the long-wave continuous zoom infrared lens and a detector, wherein the detector has 1280x1024 pixels and each pixel has a size of 12 μm.

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

[0022] (1) The system length of the present application is relatively short, for example, the total length can be controlled within 330 mm.

[0023] (2) The number of lenses is relatively small, the light transmittance is relatively high, the imaging quality is good, and the system can match a detector having 1280x1024 pixels and each pixel having a size of 12 μm. BRIEF DESCRIPTION OF DRAWINGS

[0024] 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 any creative effort.

[0025] Figure 1 The figure is a light path diagram of the long-wave continuous zoom infrared lens of Example 1.

[0026] Figure 2 The figure is a lens composition diagram of the long-wave continuous zoom infrared lens of Example 1.

[0027] Figure 3 The figure is a spot diagram of the long-wave continuous zoom infrared lens of Example 1 in a longest focal length state.

[0028] Figure 4 The figure is an MTF diagram of the long-wave continuous zoom infrared lens of Example 1 in a longest focal length state.

[0029] Figure 5 This is a dot diagram showing the shortest focal length state of the long-wave continuous zoom infrared lens in Example 1.

[0030] Figure 6 This is the MTF diagram of the shortest focal length state of the long-wave continuous zoom infrared lens in Example 1.

[0031] Reference numerals: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Protective window; 7. Image plane. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that the terms "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features.

[0033] To facilitate understanding, the relevant terms are explained below.

[0034] The object side, along the direction of light propagation, is the side of the lens where light rays enter, i.e., the surface of the lens closest to the object; the image side, along the direction of light propagation, is the side of the lens where light rays exit, i.e., the surface of the lens closest to the image; a meniscus lens, also known as a crescent-shaped lens, has one concave surface and the other convex surface on one side near the optical axis.

[0035] like Figure 1 As shown, a long-wavelength continuous zoom infrared lens includes a first lens 1, a movable lens group, and a fifth lens 5 arranged coaxially from the object side to the image side. The first lens 1 is a meniscus lens with its convex surface facing the object side and has positive optical power. The fifth lens 5 is also a meniscus lens with its convex surface facing the object side and has positive optical power. The relative positions of the first lens 1 and the fifth lens 5 are fixed. The movable lens group includes a second lens 2, a third lens 3, and a fourth lens 4 arranged coaxially. The second lens 2 is a biconcave lens, the third lens 3 is a biconvex lens, and the fourth lens 4 is a meniscus lens with its convex surface facing the image side and has negative optical power. The second lens 2, the third lens 3, and the fourth lens 4 can move along the optical axis to achieve continuous zoom.

[0036] In the present scheme, the continuous zooming of the optical system is achieved by moving the second lens 2, the third lens 3, the fourth lens 4 along the same optical axis. For example, when it is needed to change the lens of the present application from long focal length to short focal length, the second lens 2 moves towards the object side to compensate for the image plane movement caused by the movement of the lens; during the change of the lens from short focal length to long focal length, the second lens 2 moves towards the image side; when the lens is in the state of the longest focal length, the variable interval between the first lens 1 and the second lens 2 is in the maximum state, the interval between the second lens 2 and the third lens 3 is in the minimum state, the variable interval between the third lens 3 and the fourth lens 4 is in the maximum state, and the variable interval between the fourth lens 4 and the fifth lens 5 is in the minimum state; when the lens is in the state of the shortest focal length, the variable interval between the first lens 1 and the second lens 2 is in the minimum state, the variable interval between the second lens 2 and the third lens 3 is in the maximum state, and the variable interval between the third lens 3 and the fourth lens 4 is in the minimum state.

[0037] As a specific embodiment, the material of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4 and the fifth lens 5 is germanium.

[0038] As a specific embodiment, the object side S3 of the second lens 2, the image side S4 of the second lens 2, the object side S5 of the third lens 3, the image side S6 of the third lens 3, the image side S8 of the fourth lens 4 and the image side S10 of the fifth lens 5 are aspherical surfaces, and satisfy the aspherical surface formula:

[0039]

[0040] 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, the height r is the distance from the vertex of the aspherical surface, c = 1 / R; R is the paraxial curvature fitting radius of the mirror surface; k is the conic coefficient; A, B, C, D, E are high-order aspherical surface coefficients.

[0041] The object side S5 of the third lens 3 is a binary surface, which satisfies the above aspherical surface formula and the expression equation of the binary surface in Zemax: M(B1ρ 2 +B2ρ 4 +B3ρ 6 ); wherein M is the diffraction order, the diffraction order is 1, B1, B2, B3 are binary surface phase coefficients, and p is the normalized radius.

[0042] As a specific embodiment, a diaphragm is arranged on the object side S5 of the third lens 3.

[0043] Embodiment 1

[0044] The following is described by taking a specific continuous zooming infrared lens as an example. The specific parameters of the continuous zooming infrared lens of the present embodiment are shown in Table 1, Table 2 and Table 3.

[0045] Table 1 Parameters of each component

[0046]

[0047] Table 2 Aspheric surface data of the lens

[0048]

[0049] Table 3 Binary surface data of the lens

[0050]

[0051] When focusing, the first lens 1 and the fifth lens 5 are relatively fixed, and the second lens 2, the third lens 3 and the fourth lens 4 move between the first lens 1 and the fifth lens 5. The air gap between the first lens 1 and the second lens 2, the air gap between the second lens 2 and the third lens 3, the air gap between the third lens 3 and the fourth lens 4, and the air gap between the fourth lens 4 and the fifth lens 5 are all variable gaps. When the air gap between the first lens 1 and the second lens 2 is 122.913 mm, the air gap between the third lens 3 and the second lens 2 is 8.934 mm, the air gap between the third lens 3 and the fourth lens 4 is 74.649 mm, and the air gap between the fourth lens 4 and the fifth lens 5 is 38.117 mm, the system focal length is in the longest focal state, and the longest focal length of the embodiment is 225 mm. When the air gap between the first lens 1 and the second lens 2 is 51.228 mm, the air gap between the third lens 3 and the second lens 2 is 126.355 mm, the air gap between the third lens 3 and the fourth lens 4 is 10.967 mm, and the air gap between the fourth lens 4 and the fifth lens 5 is 56.064 mm, the system focal length is in the shortest focal state, and the shortest focal length of the embodiment is 25 mm.

[0052] Figure 3 Figure 4 respectively, the point spread diagram and the MTF diagram of the lens in the longest focal state (225 mm), Figure 5 Figure 6 respectively, the point spread diagram and the MTF diagram of the lens in the shortest focal state (25 mm). In the MTF diagram, the horizontal axis represents different spatial frequencies, and the vertical axis represents the modulation degree. All the field 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 Airy spot diameter, and the image quality is good.

[0053] The long-wave continuous zoom infrared lens of the embodiment has a working waveband of 8 μm~12 μm; a resolution of 1280×1024, 12 μm; an F number of 1.4; and a focal length range of 25~225 mm.

[0054] ​​Based on the same inventive concept, the embodiment provides a lens module, comprising the long-wave continuous zoom infrared lens and a detector, wherein the detector has 1280*1024 pixels, and each pixel has a size of 12 μm.

[0055] Obviously, the above-mentioned embodiment is only an example for clearly illustrating the technical solutions of the present application, and is not intended to limit the implementation manners of the present application. Based on the above-mentioned description, any modification, equivalent replacement and improvement made by those skilled in the art within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A long wave continuous zoom infrared lens characterized by, The lens comprises, sequentially from the object side to the image side, a first lens, a moving lens group and a fifth lens arranged along the optical axis; the first lens is a meniscus lens with a convex object side and has positive refractive power; the fifth lens is a meniscus lens with a convex object side and has positive refractive power; the first lens and the fifth lens have fixed relative positions; the moving lens group comprises, sequentially, a second lens, a third lens and a fourth lens; the second lens is a double-concave lens; the third lens is a double-convex lens; the fourth lens is a meniscus lens with a convex image side and has negative refractive power; the second lens, the third lens and the fourth lens are movable along the optical axis to realize continuous zooming; During the process of changing the lens from the long focal length to the short focal length, the second lens moves towards the object side; during the process of changing the lens from the short focal length to the long focal length, the second lens moves towards the image side; when the lens is in the longest focal length state, the variable interval between the first lens and the second lens is in the maximum state, the variable interval between the second lens and the third lens is in the minimum state, the variable interval between the third lens and the fourth lens is in the maximum state, and the variable interval between the fourth lens and the fifth lens is in the minimum state; when the lens is in the shortest focal length state, the variable interval between the first lens and the second lens is in the minimum state, the variable interval between the second lens and the third lens is in the maximum state, the variable interval between the third lens and the fourth lens is in the minimum state; The lens has five lenses with refractive power; and the focal length of the lens is 25-225 mm.

2. The long wave continuous zoom infrared lens of claim 1, wherein, The materials of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are germanium.

3. The long wave continuous zoom infrared lens of claim 1, wherein, The object side surface of the second lens, the image side surface of the second lens, the object side surface of the third lens, the image side surface of the third lens, the image side surface of the fourth lens, and the image side surface of the fifth lens are aspherical surfaces, and satisfy an aspherical surface formula: Wherein, Z is the distance from the vertex of the aspherical surface when the aspherical surface is at a position along the optical axis direction at a height r; 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.

4. The long wave continuous zoom infrared lens of claim 3, wherein, The object side surface of the third lens is a binary surface, satisfies an aspherical surface formula, and satisfies a binary surface expression equation in Zemax: M(B1ρ 2 +B2ρ 4 +B3ρ 6 ); wherein M is a diffraction order, B1, B2, and B3 are binary surface phase coefficients, and ρ is a normalized radius.

5. The long wave continuous zoom infrared lens of claim 1, wherein, The object side surface of the third lens is provided with a diaphragm.

6. The long wave continuous zoom infrared lens according to any one of claims 1 to 5, characterized in that, The working waveband of the lens is 8-12 μm.

7. The long wave continuous zoom infrared lens of claim 6, wherein, The variable interval between the first lens and the second lens is 122.913-51.228 mm, the variable interval between the second lens and the third lens is 8.934-126.355 mm, the variable interval between the third lens and the fourth lens is 74.649-10.967 mm, and the variable interval between the fourth lens and the fifth lens is 38.117-57.066 mm.

8. The long wave continuous zoom infrared lens of claim 6, wherein, The central thickness of the first lens is 13 mm, the object side surface curvature radius is 242.955 mm, and the image side surface curvature radius is 369.549 mm; the central thickness of the second lens is 4 mm, the object side surface curvature radius is -331.554 mm, and the image side surface curvature radius is 212.430 mm; the central thickness of the third lens is 8 mm, the object side surface curvature radius is 385.056 mm, and the image side surface curvature radius is -312.355 mm; the central thickness of the fourth lens is 4 mm, the object side surface curvature radius is -93.890 mm, and the image side surface curvature radius is -164.769 mm; and the central thickness of the fifth lens is 10 mm, the object side surface curvature radius is 117.015 mm, and the image side surface curvature radius is 495.086 mm.

9. A lens module, characterized by, The long-wave continuous zoom infrared lens and the detector with 1280*1024 pixels and 12μm pixel size according to any one of claims 1 to 8 are included.

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