Focusing lens and imaging device

Abstract

The invention provides an imaging device. The imaging device comprises a focusing lens and a detector used for receiving an image formed by the focusing lens. The effective focal length of the focusing lens is 19 mm, the focusing lens comprises a first lens and a second lens which are sequentially arranged in the optical axis transmission direction, the first lens is a meniscus positive lens, the convex face of the first lens faces the object side, the second lens is a meniscus negative lens, the convex face of the second lens faces the image side, the air gap between the first lens and the second lens is 13.98 mm, and the air gap between the first lens and the second lens is 13.98 mm. The first lens and the second lens can move synchronously in the optical axis direction. According to the focusing lens, the positions of the first lens and the second lens can be adjusted in the optical axis direction, imaging at different distances can be achieved, only two lenses are arranged, the structure is simple, and cost is lower. Meanwhile, the first lens and the second lens integrally and synchronously move, so that the stability of the optical axis can be improved.

Description

Technical Field

[0001] The invention belongs to the field of optical technology, and in particular relates to a focusing 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-power lens to see distant and near scenes clearly. To solve the above technical problem, a low-cost focusing lens and imaging device capable of seeing distant and near scenes clearly are provided.

[0005] The technical solution proposed by the present invention is: A focusing lens with an effective focal length of 19 mm comprises a first lens and a second lens which are sequentially arranged along an optical axis transmission direction, wherein the first lens is a positive meniscus lens with a convex surface facing the object side, and the second lens is a negative meniscus lens with a convex surface facing the image side, an air gap between the first lens and the second lens is 13.98 mm, and the first lens and the second lens can move synchronously along the optical axis direction.

[0006] Furthermore, the center thickness of the first lens is 2.02 mm, the object side curvature radius is 24.14 mm, and the image side curvature radius is 39.79 mm; the center thickness of the second lens is 2 mm, the object side curvature radius is -27.27 mm, and the image side curvature radius is -18.58 mm.

[0007] Furthermore, the image side surface of the first lens and the object side surface of the second lens are both 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 focusing lens is 8 μm to 12 μm, and the F number is 1.0.

[0009] Furthermore, the horizontal field angle range of the focusing lens is 13.83°.

[0010] Furthermore, surfaces of the first lens and the second lens are coated with anti-reflection films.

[0011] An imaging device comprises the focusing lens as described above and a detector for receiving images formed by the focusing 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 7.18-7.58 mm, and the air gap between the protective window and the detector focal plane array is 0.29 mm.

[0013] Furthermore, the detector is an uncooled infrared detector with a resolution of 384×288 and a pixel size of 12 μm.

[0014] Furthermore, the total length of the optical system of the imaging device is 26.5 mm, and the maximum aperture is 21 mm.

[0015] By adopting the above-mentioned focusing lens, the positions of the first lens and the second lens can be adjusted along the optical axis to achieve imaging at different distances, and only two lenses are provided, so the structure is simple and the cost is lower. At the same time, since the first lens and the second lens move synchronously as a whole, the stability of the optical axis can be improved. 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 diagram of the structure 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 focusing lens provided in this application at 20°C; Figure 4 MTF diagram of the focusing lens provided for this application at -40°C; Figure 5 This is the MTF diagram of the focusing lens provided in this application under 60°C environment.

[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 a focusing lens and a detector for receiving the image formed by the focusing lens. The total length of the optical system of the imaging device is 26.5 mm; the effective focal length of the focusing lens is 19 mm, and the horizontal field angle range is 13.83°; the detector is a non-cooling infrared detector, and the resolution is 384×288, and the pixel size is 12 μm.

[0021] See also Figure 1 The focusing lens includes a first lens 110 and a second lens 120 which are sequentially arranged along the transmission direction of the optical axis. The first lens 110 is a positive meniscus lens with a convex surface facing the object side, and the second lens 120 is a negative meniscus lens with a convex surface facing the image side. The air gap between the first lens 110 and the second lens 120 is 13.98 mm, and the first lens 110 and the second lens 120 can move synchronously along the optical axis direction.

[0022] By using the above-mentioned focusing lens, the positions of the first lens 110 and 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. At the same time, since the first lens 110 and the second lens 120 move synchronously as a whole, the stability of the optical axis can be improved.

[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 protective window 210. The air gap between the second lens 120 and the protective window 210 is 7.18-7.58 mm, that is, the moving stroke of the first lens 110 and the second lens 120 is 0.4 mm, which is moderate and convenient for adjustment by knob; the thickness of the protective window 210 is 1 mm, and the air gap between the protective window 210 and the detector focal plane array 220 is 0.29 mm.

[0024] As shown in Table 1, as an example, the center thickness of the first lens 110 is 2.02mm, the object side curvature radius is 24.14mm, and the image side curvature radius is 39.79mm; the center thickness of the second lens 120 is 2mm, the object side curvature radius is -27.27mm, and the image side curvature radius is -18.58mm. 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 image side surface of the first lens 110 and the object side surface of the second lens 120 are both 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 21 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 anti-reflection films to increase light transmittance.

[0028] Figures 3 to 5 The MTF diagrams of the focusing lens at 20℃, -40℃ and 60℃ are shown respectively. In the MTF diagram, 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 focusing 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 384×288, and the pixel size is 12μm. The focusing 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, low cost, high optical axis stability, etc. In addition, through the overall moving focusing method of two lenses, the imaging distance is greater than or equal to 0.5m, 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. A focusing lens, characterized in that: The effective focal length is 19mm. The focusing lens includes a first lens and a second lens arranged in sequence along the transmission direction of the optical axis. The first lens is a positive meniscus lens with a convex surface facing the object side. The second lens is a negative meniscus lens with a convex surface facing the image side. The air gap between the first lens and the second lens is 13.98mm, and the first lens and the second lens can move synchronously along the optical axis.

2. The focusing lens according to claim 1, characterized in that: The center thickness of the first lens is 2.02 mm, the object side curvature radius is 24.14 mm, and the image side curvature radius is 39.79 mm. The center thickness of the second lens is 2 mm, the object side curvature radius is -27.27 mm, and the image side curvature radius is -18.58 mm.

3. The focusing lens according to claim 1, characterized in that: The image side surface of the first lens and the object side surface of the second lens are both 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 focusing lens according to claim 1, characterized in that: The working band of the focusing lens is 8 μm to 12 μm, and the F number is 1.

0.

5. The focusing lens according to claim 1, characterized in that: The horizontal field angle range of the focusing lens is 13.83°.

6. The focusing lens according to claim 1, characterized in that: The surfaces of the first lens and the second lens are both coated with anti-reflection films.

7. An imaging device, characterized in that: It comprises the focusing lens according to any one of claims 1 to 6 and a detector for receiving images formed by the focusing 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 7.18-7.58 mm, and the air gap between the protection window and the detector focal plane array is 0.29 mm.

9. The imaging device according to claim 7, characterized in that: The detector is an uncooled infrared detector with a resolution of 384×288 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 26.5 mm, and the maximum aperture is 21 mm.

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