Long-focal-length large-aperture medium-wave refrigeration infrared lens and imaging device

Abstract

The invention discloses a long-focal-length large-aperture medium-wave refrigeration infrared lens. The long-focal-length large-aperture medium-wave refrigeration infrared lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth 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, the fourth lens and the fifth lens are meniscus negative lenses with convex surfaces facing the object side, the sixth lens and the eighth lens are biconvex lenses, and the seventh lens is a meniscus negative lens with a convex surface facing the image side. The lens provided by the invention is simple in structure, large in target surface and clear in imaging, and can be matched with a 15 [mu] m refrigeration type detector with the resolution of 640 * 512. 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 long focal length, large aperture, medium wave cooled infrared lens and an imaging device. Background Art

[0002] The medium-wave refrigerated infrared thermal imaging movement is an advanced device that works on the principle of infrared radiation. It is the core component of the refrigerated infrared thermal imager. The movement uses refrigeration technology, which can significantly reduce the thermal noise of the detector and improve the detection sensitivity and image quality. The medium-wave refrigerated infrared thermal imaging movement has high sensitivity, long-distance detection, clear image details, modular design, and intelligent image processing. It is widely used in military and defense, industrial monitoring, medical diagnosis and other fields. In order to improve the accuracy of long-distance detection, a long focal length lens is required. Summary of the invention

[0003] Based on this, the present application provides a long focal length, large aperture, medium wave cooled infrared lens and an imaging device.

[0004] The technical solution proposed in this application is: A long focal length, large aperture, medium wave cooling infrared lens, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence 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, the fourth lens and the fifth lens are both negative meniscus lenses with convex surfaces facing the object side, the sixth lens and the eighth lens are both double convex lenses, and the seventh 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 55.917 mm, the air gap between the second lens and the third lens is 8.491 mm, the air gap between the third lens and the fourth lens is 143.845 mm, the air gap between the fourth lens and the fifth lens is 43.299 mm, the air gap between the fifth lens and the sixth lens is 89.976 mm, the air gap between the sixth lens and the seventh lens is 10.514 mm, and the air gap between the seventh lens and the eighth lens is 3.327 mm.

[0005] Furthermore, the center thickness of the first lens is 22mm, the radius of curvature of the object side is 255.26mm, and the radius of curvature of the image side is 495.716mm; the center thickness of the second lens is 8.5mm, the radius of curvature of the object side is 866.535mm, and the radius of curvature of the image side is 315.04mm; the center thickness of the third lens is 11.5mm, the radius of curvature of the object side is 322.545mm, and the radius of curvature of the image side is 626.092mm; the center thickness of the fourth lens is 4mm, the radius of curvature of the object side is 68.319mm, and the radius of curvature of the image side is 47.546mm m; the center thickness of the fifth lens is 5mm, the object side curvature radius is 17.496mm, and the image side curvature radius is 14.102mm; the center thickness of the sixth lens is 7.5mm, the object side curvature radius is 185.744mm, and the image side curvature radius is -450.442mm; the center thickness of the seventh lens is 4mm, the object side curvature radius is -67.692mm, and the image side curvature radius is -437.05mm; the center thickness of the eighth lens is 12.5mm, the object side curvature radius is 352.081mm, and the image side curvature radius is -67.924mm.

[0006] Furthermore, the first lens and the lens meet the following condition: 0<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 fifth lens and the lens satisfy the following condition: 0<f5 / f<1, wherein f5 is the effective focal length of the fifth lens, and f is the effective focal length of the lens.

[0008] Furthermore, the applicable spectral range of the lens is 3.7-4.8 μm, the focal length of the lens is 460 mm, and the F number is 2.

[0009] Furthermore, the lens adopts a long back focus design.

[0010] An imaging device comprises the long focal length, large aperture, medium wave cooling infrared lens as described above and a detector for receiving the image formed by the lens.

[0011] Furthermore, the number of pixels of the detector is 640×512, and the pixel size is 15 μm.

[0012] Furthermore, the detector includes a first window, a second window, a filter and a detector focal plane array which are arranged in sequence.

[0013] Furthermore, the detector further comprises an aperture, and the aperture is arranged between the filter and the detector focal plane array.

[0014] The lens provided in this application has a simple structure, a large target surface, clear imaging, and can be used with a refrigerated detector with a resolution of 640×512 and 15μm. 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 for Figure 1 A schematic diagram of the structure of a detector in the imaging device shown; Figure 3 The MTF diagram of the long focal length, large aperture, medium wave cooling infrared lens provided in one embodiment of the present application; Figure 4 This is a spot diagram of a long focal length, large aperture, 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. Fifth lens; 16. Sixth lens; 17. Seventh lens; 18. Eighth lens; 20. Detector; 21. First window; 22. Second window; 23. Filter; 24. Stop; 25. 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 long focal length, large aperture, medium wave cooled infrared lens and a detector for receiving the image formed by the lens. The focal length of the lens is 460 mm, the applicable spectral range is: 3.7~4.8 μm, and the F number is 2. The detector is a cooled detector, and the number of pixels of the detector is 640×512, and the pixel size is 15 μm.

[0020] See also Figure 1The lens comprises a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, a fifth lens 15, a sixth lens 16, a seventh lens 17 and an eighth lens 18 which are sequentially arranged along the transmission direction of the optical axis. The first lens 11 and the third lens 13 are positive meniscus lenses with convex surfaces facing the object side, the second lens 12, the fourth lens 14 and the fifth lens 15 are negative meniscus lenses with convex surfaces facing the object side, the sixth lens 16 and the eighth lens 18 are double convex lenses, and the seventh lens 17 is a negative meniscus lens with convex surfaces facing the image side.

[0021] like Figure 2 As shown, further, the detector 20 includes a first window 21, a second window 22, a filter 23 and a detector focal plane array 25 which are arranged in sequence. Figure 1 and Figure 2 For example, after the light beam passes through a plurality of lenses from left to right in sequence, it is imaged on the detector focal plane array 25 through the first window 21 , the second window 22 and the filter 23 .

[0022] In one embodiment, the detector 20 further includes an aperture 24 , which is disposed between the filter 23 and the detector focal plane array 25 .

[0023] In one embodiment, the lens adopts a long back focus design.

[0024] As shown in Table 1, as an example, the air spacing between the first lens 11 and the second lens 12 is 55.917 mm, the air spacing between the second lens 12 and the third lens 13 is 8.491 mm, the air spacing between the third lens 13 and the fourth lens 14 is 143.845 mm, the air spacing between the fourth lens 14 and the fifth lens 15 is 43.299 mm, the air spacing between the fifth lens 15 and the sixth lens 16 is 89.976 mm, the air spacing between the sixth lens 16 and the seventh lens 17 is 10.514 mm, and the air spacing between the seventh lens 17 and the eighth lens 18 is 3.327 mm; the air spacing between the eighth lens 18 and the first window 21 is 14 mm, the air spacing between the first window 21 and the second window 22 is 6 mm, the air spacing between the second window 22 and the filter 23 is 2.6 mm, the air spacing between the filter 23 and the diaphragm 24 is 0.26 mm, and the air spacing between the diaphragm 24 and the detector focal plane array 25 is 20.47 mm. It can be understood that the above-mentioned air gap is an air gap on the optical axis.

[0025] Further, the center thickness of the first lens 11 is 22mm, the radius of curvature of the object side is 255.26mm, and the radius of curvature of the image side is 495.716mm; the center thickness of the second lens 12 is 8.5mm, the radius of curvature of the object side is 866.535mm, and the radius of curvature of the image side is 315.04mm; the center thickness of the third lens 13 is 11.5mm, the radius of curvature of the object side is 322.545mm, and the radius of curvature of the image side is 626.092mm; the center thickness of the fourth lens 14 is 4mm, the radius of curvature of the object side is 68.319mm, and the radius of curvature of the image side is 47.546m m; the center thickness of the fifth lens 15 is 5 mm, the radius of curvature of the object side is 17.496 mm, and the radius of curvature of the image side is 14.102 mm; the center thickness of the sixth lens 16 is 7.5 mm, the radius of curvature of the object side is 185.744 mm, and the radius of curvature of the image side is -450.442 mm; the center thickness of the seventh lens 17 is 4 mm, the radius of curvature of the object side is -67.692 mm, and the radius of curvature of the image side is -437.05 mm; the center thickness of the eighth lens 18 is 12.5 mm, the radius of curvature of the object side is 352.081 mm, and the radius of curvature of the image side is -67.924 mm.

[0026] It is understandable that in Figure 1 In the embodiment shown, the optical axis transmission direction is from left to right, the left side of the lens is the object side, and the right side is the image side, such as the S1 surface of the first lens 11 is the object side surface, and the S2 surface is the image side surface. The other components are similar and will not be described here.

[0027] In one embodiment, the first lens 11, the fifth lens 15 and the lens meet the following conditions: 0<f1 / f<1, 0<f5 / f<1; wherein f is the effective focal length of the lens, f1 is the effective focal length of the first lens 11, and f5 is the effective focal length of the fifth lens 15.

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

[0029] As shown in Table 1, the image side surfaces of the fourth lens 14, the fifth lens 15 and the eighth lens 18 and the object side surface of the seventh lens 17 are all aspherical surfaces, and the other surfaces are all spherical surfaces. 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 3 and Figure 4 These are the MTF diagram and point diagram of the long focal length, large aperture, medium 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 markets have sufficient resolution.

[0031] In summary, the long focal length, large aperture, medium wave cooled infrared lens provided by the present application has an operating band of 3.7-4.8 μm, a focal length of f=460 mm, and an F number of 2. The lens provided by the present application has a simple structure, a large target surface, and clear imaging, and can be used with a 15 μm cooled detector 20 with a resolution of 640×512.

[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 long focal length, large aperture, medium wave cooling infrared lens, characterized in that: It comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth 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, the fourth lens and the fifth lens are both negative meniscus lenses with convex surfaces facing the object side, the sixth lens and the eighth lens are both biconvex lenses, and the seventh 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 55.917 mm, the air gap between the second lens and the third lens is 8.491 mm, the air gap between the third lens and the fourth lens is 143.845 mm, the air gap between the fourth lens and the fifth lens is 43.299 mm, the air gap between the fifth lens and the sixth lens is 89.976 mm, the air gap between the sixth lens and the seventh lens is 10.514 mm, and the air gap between the seventh lens and the eighth lens is 3.327 mm.

2. The long focal length, large aperture, medium wave cooling infrared lens according to claim 1, characterized in that: The center thickness of the first lens is 22mm, the radius of curvature of the object side is 255.26mm, and the radius of curvature of the image side is 495.716mm; the center thickness of the second lens is 8.5mm, the radius of curvature of the object side is 866.535mm, and the radius of curvature of the image side is 315.04mm; the center thickness of the third lens is 11.5mm, the radius of curvature of the object side is 322.545mm, and the radius of curvature of the image side is 626.092mm; the center thickness of the fourth lens is 4mm, the radius of curvature of the object side is 68.319mm, and the radius of curvature of the image side is 47.546mm; The center thickness of the fifth lens is 5 mm, the radius of curvature of the object side is 17.496 mm, and the radius of curvature of the image side is 14.102 mm; the center thickness of the sixth lens is 7.5 mm, the radius of curvature of the object side is 185.744 mm, and the radius of curvature of the image side is -450.442 mm; the center thickness of the seventh lens is 4 mm, the radius of curvature of the object side is -67.692 mm, and the radius of curvature of the image side is -437.05 mm; the center thickness of the eighth lens is 12.5 mm, the radius of curvature of the object side is 352.081 mm, and the radius of curvature of the image side is -67.924 mm.

3. The long focal length, large aperture, medium wave cooling infrared lens according to claim 1, characterized in that: The first lens and the lens meet the following condition: 0<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 long focal length, large aperture, medium wave cooling infrared lens according to claim 1, characterized in that: The fifth lens and the lens meet the following condition: 0<f5 / f<1, wherein f5 is the effective focal length of the fifth lens, and f is the effective focal length of the lens.

5. The long focal length, large aperture, medium wave cooling infrared lens according to claim 1, characterized in that: The applicable spectral range of the lens is 3.7-4.8 μm, the focal length of the lens is 460 mm, and the F number is 2.

6. The long focal length, large aperture, medium wave cooling infrared lens according to claim 1, characterized in that: The lens adopts a long back focus design.

7. An imaging device, characterized in that: The invention comprises the long focal length large aperture medium wave cooling infrared lens as claimed in any one of claims 1 to 6 and a detector for receiving the image formed by the lens.

8. The imaging device according to claim 7, characterized in that: The number of pixels of the detector is 640×512, and the pixel size is 15 μm.

9. The imaging device according to claim 7, characterized in that: The detector comprises a first window, a second window, a filter and a detector focal plane array which are arranged in sequence.

10. The imaging device according to claim 9, characterized in that The detector further comprises an aperture, which is arranged between the filter and the detector focal plane array.

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