A short-wave infrared and medium-wave infrared composite imaging lens

Abstract

The present invention belongs to the technical field of imaging lenses, and relates to a short-wave infrared and medium-wave infrared composite imaging lens, which is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a diaphragm arranged in sequence along an optical axis; wherein the first lens, the second lens, the third lens and the fourth lens are combined into a first lens group, and the fifth lens is a second lens group; the first lens and the second lens are positive meniscus lenses, and the third lens, the fourth lens and the fifth lens are negative meniscus lenses; and the object side surfaces of all lenses are convex. The present invention can obtain infrared images in the waveband from 1 micron to 5 microns.

Description

Technical Field

[0001] The invention belongs to the technical field of imaging lenses, and relates to a wide-band imaging lens operating in a short-wave infrared to medium-wave infrared band. Background Art

[0002] Short-wave infrared and medium-wave infrared are two different parts of the infrared spectrum, and they differ in wavelength range, imaging principle, and penetration ability. The wavelength range of short-wave infrared is roughly 1 micron to 2.5 microns, and its imaging is usually based on the reflection or transmission of environmental radiation by an object, similar to visible light imaging, which is more in line with the observation characteristics of the human eye than medium-wave infrared. The wavelength range of medium-wave infrared is generally 3 microns to 5 microns, and its imaging mainly depends on the thermal radiation of the object itself. The image reflects the temperature distribution characteristics of the object. Medium-wave infrared has a stronger ability to penetrate smoke, but short-wave infrared can obtain more image details and can penetrate glass for imaging. Combining the two will bring more image information and be suitable for more application scenarios.

[0003] Indium antimonide detectors have a high detection rate in the short-wave infrared to medium-wave infrared bands, and are the only choice for short-wave and medium-wave imaging. However, in terms of optical lenses, there are few optical materials that can work in both short-wave and medium-wave bands, making it difficult to achieve wide-band chromatic aberration correction and ensure high image quality in the entire band. The lenses currently seen are limited to imaging in a single band of short-wave or medium-wave infrared. Summary of the invention:

[0005] The technical problem to be solved by the present invention is to provide a short-wave infrared and medium-wave infrared composite imaging lens, which can overcome the problem that the existing infrared lens can only work in one band, and help to achieve wide-band infrared information acquisition and fusion of the shooting target.

[0006] In order to solve the above technical problems, the short-wave infrared and medium-wave infrared composite imaging lens of the present invention is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an aperture arranged in sequence along the optical axis; wherein the first lens, the second lens, the third lens and the fourth lens are combined into a first lens group, and the fifth lens is a second lens group; the first lens and the second lens are positive meniscus lenses, and the third lens, the fourth lens and the fifth lens are negative meniscus lenses; and the object side surfaces of all lenses are convex.

[0007] The front and rear surface curvature radii of the first lens are 103.716mm~104.051mm and 310.448 mm~305.803 respectively; the front and rear surface curvature radii of the second lens are 107.384mm~108.894mm and 253.893mm~256.967mm respectively; the front and rear surface curvature radii of the third lens are 332.18mm~336.547mm and 127.98mm~130.407mm; the front and rear surface curvature radii of the fourth lens are 351.394mm~359.507mm and 68.894mm~70.31mm; the front and rear surface curvature radii of the fifth lens are 27.5mm~27.956mm and 19.65mm~20.077mm.

[0008] The thicknesses of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are 15.78 mm to 15.95 mm, 11.17 mm to 11.24 mm, 4.95 mm to 5 mm, 4.95 mm to 5 mm, and 9.95 mm to 10 mm, respectively.

[0009] The air gap between the first lens and the second lens is 0.1mm~0.2mm, the air gap between the second lens and the third lens is 2.78mm~2.98mm, the air gap between the third lens and the fourth lens is 6.23mm~6.3mm, and the air gap between the fourth lens and the fifth lens is 67.32mm~70.29mm.

[0010] The first lens and the second lens are made of multi-spectral zinc sulfide material, and the third lens and the fifth lens are made of As 40 Se 60 Material: the fourth lens is made of calcium fluoride.

[0011] The air gap between the fifth lens and the aperture is 8.8 mm to 9.75 mm.

[0012] The air gap between the aperture and the detector image plane is 19.9 mm to 20.2 mm.

[0013] When the present invention is working, the lens can obtain infrared images from the 1 micron to 5 micron band, and can be used in conjunction with a shortwave camera, a medium wave camera or a short-medium wave wide band camera to obtain image information of the shortwave band, the medium wave band or the short-medium wave wide band. It can also be used as an objective lens for shortwave and medium wave spectral imaging.

[0014] Beneficial effects: The present invention utilizes appropriate material combinations to achieve wide-band imaging of 1 micron to 5 microns, and can obtain infrared images in the short-wave to medium-wave bands in conjunction with an indium antimonide wide-band detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0016] Figure 1 It is a schematic diagram of the structure of embodiment 1 of the present invention.

[0017] Figure 2 It is the modulation transfer function curve of embodiment 1 of the present invention.

[0018] Figure 3 This is the imaging point diagram of Example 1 of the present invention.

[0019] Figure 4 It is the modulation transfer function curve of embodiment 2 of the present invention.

[0020] Figure 5 This is the imaging point diagram of Example 2 of the present invention.

[0021] Figure 6 It is the modulation transfer function curve of embodiment 3 of the present invention.

[0022] Figure 7 This is the imaging point diagram of Example 3 of the present invention.

[0023] In the figure: 1. first lens, 2. second lens, 3. third lens, 4. fourth lens, 5. fifth lens, 6. aperture, 7. detector image plane. DETAILED DESCRIPTION

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] like Figure 1 As shown, the short-wave infrared and medium-wave infrared composite imaging lens of the present invention is composed of a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, and an aperture 6 arranged in sequence along the optical axis; wherein the first lens 1, the second lens 2, the third lens 3 and the fourth lens 4 are combined into a first lens group, and the fifth lens 5 is a second lens group. The first lens 1 and the second lens 2 are positive meniscus lenses, the third lens 3 and the fourth lens 4 are negative meniscus lenses, and the fifth lens 5 is a negative meniscus lens; all lenses have a convex side surface and a concave side surface; and the surface of each lens is a spherical surface. The target is imaged on the detector image plane 7 through the first lens group, the second lens group and the aperture 6.

[0026] The first lens 1 and the second lens 2 are made of multi-spectral zinc sulfide material, and the third lens 3 and the fifth lens 5 are made of As 40Se 60 Material: the fourth lens 4 is made of calcium fluoride.

[0027] The waveband selected by the lens design of the present invention is 1 μm-5 μm; the photosensitive surface size of the applicable detector is 9.6 mm×7.68 mm; and the focal length of the lens is 160 mm.

[0028] Example 1: The specific parameters of each lens are shown in Table 1. i represents the radius of curvature of the i-th optical surface, i=1,2,…,10; t j represents the thickness of the jth lens, j = 1, 2, ..., 5; d n represents the air gap from the rear surface of the nth lens to the front surface of the next lens, n=1,2,…,4, D5 represents the distance from the rear surface of the fifth lens to the center of the aperture 6, and D6 represents the distance from the center of the aperture 6 to the detector image plane 7:

[0029] Table 1

[0030]

[0031] The modulation transfer function curves of the present invention at the central field of view, 0.55°, 1.1°, 1.65° and 2.2° field of view are as follows: Figure 2 As shown in the figure, the modulation transfer function values ​​of each field of view at 20lp / mm are all higher than 0.4, indicating that the lens has good imaging quality in the entire field of view within the working band.

[0032] The imaging point diagram of the present invention is as follows Figure 3 As shown in the figure, it can be seen that the root mean square diameter of the geometric imaging spot of the lens in each field of view is less than 30 microns, and the imaging quality is good.

[0033] Example 2: The specific parameters of each lens are shown in Table 2. i represents the radius of curvature of the i-th optical surface, i=1,2,…,10; t j represents the thickness of the jth lens, j = 1, 2, ..., 5; d n represents the air gap from the rear surface of the nth lens to the front surface of the next lens, n=1,2,…,4, D5 represents the distance from the rear surface of the fifth lens to the center of the aperture 6, and D6 represents the distance from the center of the aperture 6 to the detector image plane 7:

[0034] Table 2

[0035]

[0036] The modulation transfer function curves of the present invention at the central field of view, 0.55°, 1.1°, 1.65° and 2.2° field of view are as follows: Figure 4As shown in the figure, the modulation transfer function values ​​of each field of view at 20lp / mm are all higher than 0.4, indicating that the lens has good imaging quality in the entire field of view within the working band.

[0037] The imaging point diagram of the present invention is as follows Figure 5 As shown in the figure, it can be seen that the root mean square diameter of the geometric imaging spot of the lens in each field of view is less than 30 microns, and the imaging quality is good.

[0038] Example 3: The specific parameters of each lens are shown in Table 3. i represents the radius of curvature of the i-th optical surface, i=1,2,…,10; t j represents the thickness of the jth lens, j = 1, 2, ..., 5; d n represents the air gap from the rear surface of the nth lens to the front surface of the next lens, n=1,2,…,4, D5 represents the distance from the rear surface of the fifth lens to the center of the aperture 6, and D6 represents the distance from the center of the aperture 6 to the detector image plane 7:

[0039] Table 3

[0040] .

[0041] The modulation transfer function curves of the present invention at the central field of view, 0.55°, 1.1°, 1.65° and 2.2° field of view are as follows: Figure 6 As shown in the figure, the modulation transfer function values ​​of each field of view at 20lp / mm are all higher than 0.4, indicating that the lens has good imaging quality in the entire field of view within the working band.

[0042] The imaging point diagram of the present invention is as follows Figure 7 As shown in the figure, it can be seen that the root mean square diameter of the geometric imaging spot of the lens in each field of view is less than 30 microns, and the imaging quality is good.

Claims

1. A short-wave infrared and medium-wave infrared composite imaging lens, characterized in that The invention is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an aperture which are arranged in sequence along the optical axis; wherein the first lens, the second lens, the third lens and the fourth lens are combined into a first lens group, and the fifth lens is a second lens group; the first lens and the second lens are positive meniscus lenses, and the third lens, the fourth lens and the fifth lens are negative meniscus lenses; the object side surfaces of all lenses are convex; the front and rear surface curvature radii of the first lens are 103.716 mm to 104.051 mm and 310.448 mm to 305.803 respectively; the front and rear surface curvature radii of the second lens are 107.384 mm to 108.894 mm and 253.893 mm to 256.967 mm respectively; the front and rear surface curvature radii of the third lens are 332.18 mm to 336.547 mm and 127.98 mm to 130.407 mm; the front and rear surface curvature radius of the fourth lens is 351.394 mm ~359.507mm, 68.894mm~70.31mm; the curvature radii of the front and rear surfaces of the fifth lens are 27.5mm~27.956mm, 19.65mm ~20.077mm.

2. The short-wave infrared and medium-wave infrared composite imaging lens according to claim 1, characterized in that The thicknesses of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are 15.78 mm to 15.95 mm, 11.17 mm to 11.24 mm, 4.95 mm to 5 mm, 4.95 mm to 5 mm, and 9.95 mm to 10 mm, respectively.

3. The short-wave infrared and medium-wave infrared composite imaging lens according to claim 1, characterized in that The air gap between the first lens and the second lens is 0.1mm~0.2mm, the air gap between the second lens and the third lens is 2.78mm~2.98mm, the air gap between the third lens and the fourth lens is 6.23mm~6.3mm, and the air gap between the fourth lens and the fifth lens is 67.32mm~70.29mm.

4. The short-wave infrared and medium-wave infrared composite imaging lens according to claim 1, characterized in that The first lens and the second lens are made of multi-spectral zinc sulfide material, and the third lens and the fifth lens are made of As 40 Se 60 Material: the fourth lens is made of calcium fluoride.

5. The short-wave infrared and medium-wave infrared composite imaging lens according to claim 1, characterized in that The air gap between the fifth lens and the aperture is 8.8 mm to 9.75 mm.

6. The short-wave infrared and medium-wave infrared composite imaging lens according to claim 1, characterized in that The air gap between the aperture and the detector image plane is 19.9 mm to 20.2 mm.

Images