Infrared lens and imaging device

Abstract

The invention provides an imaging device. The imaging device comprises an infrared lens and a detector used for receiving an image formed by the infrared lens. The effective focal length of the infrared lens is 35 mm, the infrared lens comprises a first lens and a second lens which are sequentially arranged in the optical axis transmission direction, the first lens and the second lens are both meniscus positive lenses, and the convex faces of the first lens and the second lens face the object side. The second lens can move in the direction of the optical axis, and the air gap between the first lens and the second lens is 26.79-27.09 mm. By adopting the infrared lens, imaging at different distances can be realized by adjusting the position of the second lens along the direction of the optical axis, and only two lenses are arranged, so that the infrared lens is simple in structure and lower in cost. In addition, the moving stroke of the second lens is 0.3 mm, the moving stroke is moderate, and adjustment can be conveniently carried out in a knob mode.

Description

Technical Field

[0001] The invention belongs to the field of optical technology, and in particular relates to an infrared lens and an imaging device. Background Art

[0002] Infrared imaging technology identifies the target and obtains the target's image information by detecting the temperature difference between the target and the background. Due to the advantages of infrared systems such as strong camouflage identification ability, uninterrupted day and night, passive imaging, and not easily susceptible to interference, they are widely used in military anti-camouflage and concealment, space remote sensing, medical diagnosis, and security systems.

[0003] In order to achieve the goal of using one lens to see both near and far scenes, existing imaging devices usually use a variable-magnification lens. However, a variable-magnification lens requires a large number of lenses, and the cost is relatively high. Summary of the invention

[0004] The technical problem to be solved by the present invention is that it is very costly to use a variable-magnification lens to see distant and near scenes clearly. In order to solve the above technical problem, a low-cost infrared lens and imaging device capable of seeing distant and near scenes clearly are provided.

[0005] The technical solution proposed by the present invention is: An infrared lens with an effective focal length of 35 mm, comprising a first lens and a second lens arranged in sequence along an optical axis transmission direction, wherein the first lens and the second lens are both positive meniscus lenses, and the convex surfaces of the first lens and the second lens are both facing the object side; The second lens is movable along the optical axis, and an air gap between the first lens and the second lens is 26.79-27.09 mm.

[0006] Furthermore, the center thickness of the first lens is 4 mm, the object side curvature radius is 34.2 mm, and the image side curvature radius is 40.63 mm; the center thickness of the second lens is 3 mm, the object side curvature radius is 62 mm, and the image side curvature radius is 106.05 mm.

[0007] Furthermore, the object-side surface and the image-side surface of the first lens and the object-side surface of the second lens are all 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, E are high-order aspherical coefficients.

[0008] Furthermore, the working band of the infrared lens is 8 μm to 12 μm, and the F number is 1.0.

[0009] Furthermore, the horizontal field of view angle range of the infrared lens is 12.52°.

[0010] Furthermore, surfaces of the first lens and the second lens are both coated with a diamond-like carbon film.

[0011] An imaging device comprises the infrared lens as described above and a detector for receiving images formed by the infrared lens.

[0012] Furthermore, the detector includes a protective window and a detector focal plane array which are arranged in sequence, the air gap between the second lens and the protective window is 9.11-9.41 mm, and the air gap between the protective window and the detector focal plane array is 10.21 mm.

[0013] Furthermore, the detector is an uncooled infrared detector with a resolution of 640×512 and a pixel size of 12 μm.

[0014] Furthermore, the total length of the optical system of the imaging device is 45.5 mm, and the maximum aperture is 40 mm.

[0015] By using the above infrared lens, the position of the second lens can be adjusted along the optical axis to achieve imaging at different distances, and only two lenses are provided, which has a simple structure and lower cost. In addition, the moving stroke of the second lens is 0.3 mm, which is moderate and convenient for adjustment by knob. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0017] Figure 1 A schematic structural diagram of an imaging device provided by an embodiment of the present invention; Figure 2 for Figure 1 The optical path diagram of the imaging device shown; Figure 3 MTF diagram of the infrared lens provided for this application at 20°C; Figure 4 MTF diagram of the infrared lens provided for this application at -40°C; Figure 5 This is the MTF diagram of the infrared lens provided in this application at 60°C.

[0018] Description of labels: 110, first lens; 120, second lens; 210, protection window; 220, detector focal plane array. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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.

[0020] The present invention provides an imaging device, comprising an infrared lens and a detector for receiving images formed by the infrared lens. The total length of the optical system of the imaging device is 45.5 mm; the effective focal length of the infrared lens is 35 mm, and the horizontal field angle range is 12.52°; the detector is a non-cooled infrared detector, and the resolution is 640×512, and the pixel size is 12 μm.

[0021] See also Figure 1 The infrared lens includes a first lens 110 and a second lens 120 arranged in sequence along the optical axis transmission direction. The first lens 110 and the second lens 120 are both positive meniscus lenses, and the convex surfaces are both facing the object side. The second lens 120 can move along the optical axis direction, and the air gap between the first lens 110 and the second lens 120 is 26.79~27.09mm.

[0022] By using the above infrared lens, the position of the second lens 120 can be adjusted along the optical axis to achieve imaging at different distances, and only two lenses are provided, which has a simple structure and lower cost. In addition, the moving stroke of the second lens 120 is 0.3 mm, which is moderate and convenient for adjustment by knob.

[0023] It should be noted that the detector includes a protection window 210 and a detector focal plane array 220 which are arranged in sequence, that is, Figure 2 As shown, the light beam passes through the first lens 110 and the second lens 120 from left to right, and then forms an image on the detector focal plane array 220 through the protection window 210. The air gap between the second lens 120 and the protection window 210 is 9.11-9.41 mm; the thickness of the protection window 210 is 0.7 mm, and the air gap between the protection window 210 and the detector focal plane array 220 is 2.16 mm.

[0024] As shown in Table 1, as an example, the center thickness of the first lens 110 is 4 mm, the object side curvature radius is 34.2 mm, and the image side curvature radius is 40.63 mm; the center thickness of the second lens 120 is 3 mm, the object side curvature radius is 62 mm, and the image side curvature radius is 106.05 mm. It can be determined that from left to right along the optical axis, the left side is the object side and the right side is the image side. For example, the S1 surface of the first lens 110 is the object side surface, and the S2 surface is the image side surface. Other lenses are not described here.

[0025] Table 1 In one embodiment, the object-side surface and the image-side surface of the first lens 110 and the object-side surface of the second lens 120 are all aspherical surfaces and satisfy the aspherical surface formula: Wherein, Z is the distance vector height from the vertex of the aspheric surface 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, E are high-order aspheric coefficients. The aspheric surface data of the first lens 1101 are shown in Table 2.

[0026] Table 2 In one embodiment, the maximum aperture of the imaging device is 40 mm, and the maximum aperture is located at the first lens 110 .

[0027] In one embodiment, the surfaces of the first lens 110 and the second lens 120 are coated with a diamond-like carbon film to enhance hardness and wear resistance while ensuring light transmittance.

[0028] Figures 3 to 5 These are the MTF graphs of the infrared lens at 20℃, -40℃ and 60℃ respectively. In the MTF graph, the horizontal axis represents different spatial frequencies and the vertical axis represents the modulation degree. 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.

[0029] In summary, it should be noted that the working band of the infrared lens in the present invention is 8μm~12μm, the F number is 1.0, the resolution of the detector used to receive the image formed by the lens is 640×512, and the pixel size is 12μm. The infrared lens provided by the present invention can see the distant and near scenes clearly, and has the advantages of a small number of lenses, light weight, and low cost. In addition, through the mobile focusing method of the second lens 120, the imaging distance is greater than or equal to 2m, and the defocus problem is solved, and the defocus problem caused by temperature changes can also be compensated.

[0030] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An infrared lens, characterized in that: The effective focal length is 35 mm. The infrared lens comprises a first lens and a second lens arranged in sequence along the transmission direction of the optical axis. Both the first lens and the second lens are positive meniscus lenses, and the convex surfaces are both facing the object side. The second lens is movable along the optical axis, and an air gap between the first lens and the second lens is 26.79-27.09 mm.

2. The infrared lens according to claim 1, characterized in that: The center thickness of the first lens is 4 mm, the object side curvature radius is 34.2 mm, and the image side curvature radius is 40.63 mm. The center thickness of the second lens is 3 mm, the object side curvature radius is 62 mm, and the image side curvature radius is 106.05 mm.

3. The infrared lens according to claim 1, characterized in that: The object-side surface and the image-side surface of the first lens and the object-side surface of the second lens are all 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, E are high-order aspherical coefficients.

4. The infrared lens according to claim 1, characterized in that: The infrared lens has an operating band of 8 μm to 12 μm and an F number of 1.

0.

5. The infrared lens according to claim 1, characterized in that: The horizontal field of view angle of the infrared lens is 12.52°.

6. The infrared lens according to claim 1, characterized in that: The surfaces of the first lens and the second lens are both coated with a diamond-like carbon film.

7. An imaging device, characterized in that: It comprises the infrared lens as claimed in any one of claims 1 to 6 and a detector for receiving images formed by the infrared lens.

8. The imaging device according to claim 7, characterized in that: The detector comprises a protection window and a detector focal plane array which are arranged in sequence, the air gap between the second lens and the protection window is 9.11-9.41 mm, and the air gap between the protection window and the detector focal plane array is 10.21 mm.

9. The imaging device according to claim 7, characterized in that: The detector is an uncooled infrared detector with a resolution of 640×512 and a pixel size of 12 μm.

10. The imaging device according to claim 9, characterized in that The total length of the optical system of the imaging device is 45.5 mm, and the maximum aperture is 40 mm.

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