Medium wave refrigeration infrared lens and imaging device

Abstract

The medium-wave refrigeration infrared lens comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged in the optical axis transmission direction. The first lens and the third lens are meniscus positive lenses with convex surfaces facing the object side, the second lens is a meniscus negative lens with a convex surface facing the object side, the fourth lens is a meniscus negative lens with a convex surface facing the image side, and the air space between the first lens and the second lens is 1mm. The air interval between the second lens and the third lens is 54mm, and the air interval between the third lens and the fourth lens is 5mm; the lens further comprises a reflecting mirror, and the reflecting mirror is arranged between the second lens and the third lens so as to change the direction of the optical axis. The lens provided by the invention is small in length size, simple in structure, large in target surface and clear in imaging, and can be matched with a refrigeration type detector with the resolution of 320 * 256 and 30 [mu] m for use. The invention further discloses an imaging device.

Description

Technical Field

[0001] The present application belongs to the technical field of infrared optical equipment, and specifically relates to a medium-wave cooled infrared lens and an imaging device. Background Art

[0002] The cooled infrared system has incomparable advantages over the uncooled infrared system, which are mainly reflected in the working distance and imaging effect. The large field of view can observe more scenes and reduce the existence of blind spots. Therefore, in the use scenarios with higher requirements, such as military and aerospace fields, the cooled infrared lens with a large field of view is widely used. However, the existing cooled infrared lens with a large field of view is long and large in size. Summary of the invention

[0003] Based on this, the present application provides a medium-wave cooled infrared lens and an imaging device with a shorter length and smaller size.

[0004] The technical solution proposed in this application is: A medium-wave cooling infrared lens, comprising a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the transmission direction of an optical axis; the first lens and the third lens are both positive meniscus lenses with convex surfaces facing the object side, the second lens is a negative meniscus lens with convex surfaces facing the object side, the fourth lens is a negative meniscus lens with convex surfaces facing the image side, the air gap between the first lens and the second lens is 1 mm, the air gap between the second lens and the third lens is 54 mm, and the air gap between the third lens and the fourth lens is 5 mm; Wherein, the lens further includes a reflector, and the reflector is arranged between the second lens and the third lens to change the direction of the optical axis.

[0005] Furthermore, the center thickness of the first lens is 8 mm, the object side curvature radius is 26.67 mm, and the image side curvature radius is 35.06 mm; the center thickness of the second lens is 5.3 mm, the object side curvature radius is 14.974 mm, and the image side curvature radius is 10.083 mm; the center thickness of the third lens is 8.5 mm, the object side curvature radius is 46.53 mm, and the image side curvature radius is -251.78 mm; the center thickness of the fourth lens is 3 mm, the object side curvature radius is -45.802 mm, and the image side curvature radius is -54.971 mm.

[0006] Furthermore, the first lens and the lens meet the following condition: f1 / f>1, wherein f1 is the effective focal length of the first lens, and f is the effective focal length of the lens.

[0007] Furthermore, the fourth lens and the lens satisfy the following condition: 4.5<f4 / f<5.5, wherein f4 is the effective focal length of the fourth lens, and f is the effective focal length of the lens.

[0008] Furthermore, the applicable spectral range of the lens is 3.2-3.5 μm, the focal length of the lens is 23 mm, and the F number is 1.5.

[0009] Furthermore, the lens adopts a secondary imaging design.

[0010] Further, the image side surfaces of the first lens, the second lens and the third lens and the object side surface of the fourth lens are all aspherical surfaces, and the aspherical surfaces satisfy the following expression: Among them, z represents the distance of the surface from the vertex in the direction of the optical axis, c represents the curvature of the vertex, K represents the quadratic surface coefficient, h represents the distance from the optical axis to the surface, and B, C, D, E and F represent the fourth-order, sixth-order, eighth-order, tenth-order and twelfth-order surface coefficients respectively.

[0011] Furthermore, the first lens and the third lens are both made of silicon single crystal, and the second lens and the fourth lens are both made of germanium single crystal.

[0012] An imaging device comprises the above-mentioned medium-wave cooled infrared lens and a detector for receiving the image formed by the lens.

[0013] Furthermore, the number of pixels of the detector is 320×256, and the pixel size is 30 μm.

[0014] The lens provided in the present application has a small length, a simple structure, a large target surface, and clear imaging, and can be used with a refrigerated detector with a resolution of 320×256 and 30μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to provide further understanding of the present application and constitute a part of the specification. They are used to explain the present application together with the embodiments of the present application and do not constitute a limitation of the present application.

[0016] Figure 1 A schematic diagram of the structure of an imaging device provided in one embodiment of the present application; Figure 2 The MTF diagram of the medium-wave cooled infrared lens provided in one embodiment of the present application; Figure 3 This is a spot diagram of a medium-wave cooled infrared lens provided in one embodiment of the present application.

[0017] Description of labels: 11. First lens; 12. Second lens; 13. Third lens; 14. Fourth lens; 15. Reflector; 21. Protective window; 22. Filter; 23. Detector focal plane array. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] An embodiment of the present application provides an imaging device, which includes a medium-wave cooled infrared lens and a detector for receiving the image formed by the lens. The focal length of the lens is 23 mm, the applicable spectral range is: 3.2~3.5 μm, and the F number is 1.5. The detector is a cooled detector, and the number of pixels of the detector is 320×256, and the pixel size is 30 μm.

[0020] See also Figure 1 , the lens comprises a first lens 11, a second lens 12, a third lens 13 and a fourth lens 14 arranged in sequence along the transmission direction of the optical axis. The first lens 11 and the third lens 13 are both positive meniscus lenses with convex surfaces facing the object side, the second lens 12 is a negative meniscus lens with convex surfaces facing the object side, and the fourth lens 14 is a negative meniscus lens with convex surfaces facing the image side. Furthermore, the lens comprises a reflector 15, which is arranged between the second lens 12 and the third lens 13 to change the direction of the optical axis. For example Figure 1 As shown, by setting the reflector 15, the optical axis is divided into two perpendicular sections, that is, the arrangement direction of the first lens 11 and the second lens 12 is perpendicular to the arrangement direction of the third lens 13 and the fourth lens 14. In this way, the length of the lens can be effectively shortened, thereby reducing the size of the lens.

[0021] In one embodiment, the detector includes a protection window 21, a filter 22 and a detector focal plane array 23 arranged in sequence. Figure 1 For example, after the light beam passes through the first lens 11 , the second lens 12 , the third lens 13 and the fourth lens 14 from left to right, it is imaged on the detector focal plane array 23 through the protection window 21 and the filter 22 .

[0022] Furthermore, the detector further comprises an aperture, which is arranged between the filter 22 and the detector focal plane array 23 .

[0023] In one embodiment, the lens adopts a secondary imaging design.

[0024] As shown in Table 1, as an example, the air gap between the first lens 11 and the second lens 12 is 1 mm, the air gap between the second lens 12 and the third lens 13 is 54 mm, the air gap between the third lens 13 and the fourth lens 14 is 5 mm; the air gap between the fourth lens 14 and the protective window 21 is 12 mm, the air gap between the protective window 21 and the filter 22 is 1.6 mm, the air gap between the filter 22 and the aperture is 0.1 mm, and the air gap between the aperture and the detector focal plane array 23 is 12.3 mm. It can be understood that the above-mentioned air gaps are air gaps on the optical axis.

[0025] In one embodiment, the center thickness of the first lens 11 is 8 mm, the radius of curvature of the object side is 26.67 mm, and the radius of curvature of the image side is 35.06 mm; the center thickness of the second lens 12 is 5.3 mm, the radius of curvature of the object side is 14.974 mm, and the radius of curvature of the image side is 10.083 mm; the center thickness of the third lens 13 is 8.5 mm, the radius of curvature of the object side is 46.53 mm, and the radius of curvature of the image side is -251.78 mm; the center thickness of the fourth lens 14 is 3 mm, the radius of curvature of the object side is -45.802 mm, and the radius of curvature of the image side is -54.971 mm.

[0026] It is understandable that in Figure 1 In the illustrated embodiment, the optical axis transmission direction is from left to right, and from top to bottom after passing through the reflector 15; the left side of the first lens 11 and the second lens 12 is the object side, and the right side is the image side, and the upper side of the third lens 13 and the fourth lens 14 is the object side, and the lower side is the image side. In addition, the S1 surface of the first lens 11 is the object side surface, and the S2 surface is the image side surface. The other lenses can be obtained in sequence, and will not be described in detail here.

[0027] In one embodiment, the first lens 11, the fourth lens 14 and the lens meet the following conditions: f1 / f>1,4.5<f4 / f<5.5; wherein f is the effective focal length of the lens, f1 is the effective focal length of the first lens 11, and f4 is the effective focal length of the fourth lens.

[0028] Table 1 Component parameters In conjunction with Table 1, it should be noted that the above lenses are all made of domestic optical materials.

[0029] As shown in Table 1, the image side surfaces of the first lens 11, the second lens 12, and the third lens 13 and the object side surface of the fourth lens 14 are all aspherical surfaces, and all aspherical surfaces satisfy the aspherical surface formula: Among them, z represents the distance of the surface from the vertex of the surface in the direction of the optical axis, c represents the curvature of the vertex of the surface, K represents the quadratic surface coefficient, h represents the distance from the optical axis to the surface, and B, C, D, E and F represent the fourth-order, sixth-order, eighth-order, tenth-order and twelfth-order surface coefficients respectively. At the same time, the aspherical data of each lens are shown in Table 2.

[0030] Table 2 Aspheric surface data Figure 2 and Figure 3 These are the MTF diagram and point diagram of the mid-wave cooled infrared lens. In the MTF diagram, the horizontal axis represents different spatial frequencies, and the vertical axis represents the modulation degree. Combined with the diagram, it can be seen that the lens corrects various aberrations in each band, so that both the center and the edge of the field of view have sufficient resolution.

[0031] In summary, the working band of the medium-wave cooled infrared lens provided by the present application is 3.2~3.5μm; the focal length f=23mm; the F number is 1.5. The lens provided by the present application has a simple structure, a large target surface, and clear imaging, and can be used with a 30μm cooled detector with a resolution of 320×256.

[0032] Although the embodiments of the present application 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 application, and that the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A medium wave cooling infrared lens, characterized in that: It comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged along the transmission direction of the optical axis; the first lens and the third lens are both positive meniscus lenses with convex surfaces facing the object side, the second lens is a negative meniscus lens with convex surfaces facing the object side, the fourth lens is a negative meniscus lens with convex surfaces facing the image side, the air gap between the first lens and the second lens is 1 mm, the air gap between the second lens and the third lens is 54 mm, and the air gap between the third lens and the fourth lens is 5 mm; Wherein, the lens further includes a reflector, and the reflector is arranged between the second lens and the third lens to change the direction of the optical axis.

2. The medium wave cooling infrared lens according to claim 1, characterized in that: The center thickness of the first lens is 8 mm, the radius of curvature of the object side is 26.67 mm, and the radius of curvature of the image side is 35.06 mm; the center thickness of the second lens is 5.3 mm, the radius of curvature of the object side is 14.974 mm, and the radius of curvature of the image side is 10.083 mm; the center thickness of the third lens is 8.5 mm, the radius of curvature of the object side is 46.53 mm, and the radius of curvature of the image side is -251.78 mm; the center thickness of the fourth lens is 3 mm, the radius of curvature of the object side is -45.802 mm, and the radius of curvature of the image side is -54.971 mm.

3. The medium wave cooling infrared lens according to claim 1, characterized in that: The first lens and the lens meet the following condition: f1 / f>1, wherein f1 is the effective focal length of the first lens, and f is the effective focal length of the lens.

4. The medium wave cooling infrared lens according to claim 1, characterized in that: The fourth lens and the lens meet the following condition: 4.5<f4 / f<5.5, wherein f4 is the effective focal length of the fourth lens, and f is the effective focal length of the lens.

5. The medium wave cooling infrared lens according to claim 1, characterized in that: The applicable spectral range of the lens is 3.2-3.5 μm, the focal length of the lens is 23 mm, and the F number is 1.

5.

6. The medium wave cooling infrared lens according to claim 1, characterized in that: The lens adopts a secondary imaging design.

7. The medium wave cooling infrared lens according to claim 1, characterized in that: The image side surfaces of the first lens, the second lens, and the third lens and the object side surface of the fourth lens are all aspherical surfaces, and the aspherical surfaces satisfy the following expression: Among them, z represents the distance of the surface from the vertex in the direction of the optical axis, c represents the curvature of the vertex, K represents the quadratic surface coefficient, h represents the distance from the optical axis to the surface, and B, C, D, E and F represent the fourth-order, sixth-order, eighth-order, tenth-order and twelfth-order surface coefficients respectively.

8. The medium wave cooling infrared lens according to claim 1, characterized in that: The first lens and the third lens are both made of silicon single crystal, and the second lens and the fourth lens are both made of germanium single crystal.

9. An imaging device, characterized in that: It comprises the medium-wave cooled infrared lens as described in any one of claims 1 to 8 and a detector for receiving the image formed by the lens.

10. The imaging device according to claim 9, characterized in that The number of pixels of the detector is 320×256, and the pixel size is 30 μm.

Images