Medium-wave refrigeration double-view-field infrared lens and imaging device

Abstract

The invention discloses a medium-wave refrigeration double-view-field infrared lens. The medium-wave refrigeration double-view-field infrared lens comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged in the optical axis transmission direction. The first lens is a meniscus positive lens with the convex surface facing the object side, the second lens is a biconcave lens, the third lens and the fifth lens are biconvex lenses, and the fourth lens is a meniscus positive lens with the convex surface facing the image side; the first lens can reciprocate along the optical axis direction, the second lens can reciprocate along the optical axis direction, the air interval between the first lens and the second lens is 15-27.9 mm, the air interval between the second lens and the third lens is 5-17.9 mm, the air interval between the third lens and the fourth lens is 25 mm, and the air interval between the fourth lens and the fifth lens is 24.92 mm. The lens provided by the invention is simple in structure, large in target surface and clear in imaging, and can be matched with a refrigeration type detector with the resolution ratio 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 field of infrared optical equipment technology, and specifically relates to a medium-wave cooled dual-field-of-view infrared lens and an imaging device. Background Art

[0002] As the name implies, dual-field lenses have two focal lengths and two fields of view. When the focal length is small, the field of view is relatively large, making it easier to find the target; when the focal length is large, the field of view is relatively small, and the target can be seen farther and tracked more easily. Dual-field infrared lenses can be used with medium-wave refrigeration gas detection instruments to detect gases, such as flammable gases or toxic gases. However, traditional dual-field infrared lenses have a large number of lenses. Summary of the invention

[0003] Based on this, the present application provides a medium-wave cooled dual-field-of-view infrared lens and an imaging device with a simple structure.

[0004] The technical solution proposed in this application is: A medium-wave cooled dual-field infrared lens, comprising a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the transmission direction of an optical axis; the first lens is a positive meniscus lens with a convex surface facing the object side, the second lens is a biconcave lens, the third lens and the fifth lens are both biconvex lenses, and the fourth lens is a positive meniscus lens with a convex surface facing the image side; Among them, the second lens can move back and forth along the optical axis, and the air gap between the first lens and the second lens is 15~27.93mm, the air gap between the second lens and the third lens is 5~17.93mm, the air gap between the third lens and the fourth lens is 25mm, and the air gap between the fourth lens and the fifth lens is 24.92mm.

[0005] Further, the center thickness of the first lens is 6 mm, the object side curvature radius is 56.99 mm, and the image side curvature radius is 101.086 mm; the center thickness of the second lens is 1.8 mm, the object side curvature radius is -62.699 mm, and the image side curvature radius is 72.82; the center thickness of the third lens is 5.5 mm, the object side curvature radius is 74.949 mm, and the image side curvature radius is -45.264 mm; the center thickness of the fourth lens is 4.6 mm, the object side curvature radius is -10.937 mm, and the image side curvature radius is -13.12 mm; the center thickness of the fifth lens is 5.5 mm, the object side curvature radius is 586.299 mm, and the image side curvature radius is -52.319 mm.

[0006] Furthermore, the first lens and the lens meet the following condition: f1 / f<3, 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: 0.3<f5 / f<1.3, 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: 3.2~3.5μm, the focal length of the lens is 18mm and 54mm, and the F number is 1.5; Among them, when the focal length of the lens is 18 mm, the air gap between the first lens and the second lens is 15 mm, and the air gap between the second lens and the third lens is 17.93 mm; when the focal length of the lens is 54 mm, the air gap between the first lens and the second lens is 27.93 mm, and the air gap between the second lens and the third lens is 5 mm.

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

[0010] Furthermore, the object-side surface of the fifth lens is a diffraction surface, and the diffraction surface satisfies the following expression: ; ; in, is the phase of the diffraction surface, r n is the planned radius of the diffraction surface, r is the height relative to the vertical direction of the optical axis, and A1 and A2 are the phase coefficients of the diffraction surface.

[0011] An imaging device comprises the above-mentioned medium-wave cooled dual-field infrared lens and a detector for receiving images formed by the lens.

[0012] Furthermore, the number of pixels of the detector is 320×256, and the pixel size is 30 μm.

[0013] 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 320×256 and 30μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to provide further understanding of the present application and constitute a part of the specification. They are used together with the embodiments of the present application to explain the present application and do not constitute a limitation of the present application.

[0015] Figure 1A schematic diagram of the structure of an imaging device provided in an embodiment of the present application when the focal length of the lens is 18 mm; Figure 2 A schematic diagram of the structure of an imaging device provided in an embodiment of the present application when the focal length of the lens is 54 mm; Figure 3 This is an MTF diagram of a medium-wave cooled dual-field infrared lens provided in an embodiment of the present application when the focal length is 18 mm; Figure 4 A spot diagram of a medium-wave cooled dual-field infrared lens provided in an embodiment of the present application when the focal length is 18 mm; Figure 5 This is an MTF diagram of a medium-wave cooled dual-field infrared lens provided in an embodiment of the present application when the focal length is 54 mm; Figure 6 This is a point diagram of a medium-wave cooled dual-field infrared lens provided in an embodiment of the present application when the focal length is 54 mm.

[0016] Description of labels: 11. First lens; 12. Second lens; 13. Third lens; 14. Fourth lens; 15. Fifth lens; 21. Protective window; 22. Filter; 23. Aperture; 24. Detector focal plane array. DETAILED DESCRIPTION

[0017] 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.

[0018] An embodiment of the present application provides an imaging device, which includes a medium-wave cooled dual-field infrared lens and a detector for receiving the image formed by the lens. The focal length of the lens is 18 mm and 54 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.

[0019] See also Figure 1 The lens includes a first lens, a second lens, a third lens, a fourth lens and a fifth 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 biconcave lens, the third lens and the fifth lens are both biconvex lenses, and the fourth lens is a positive meniscus lens with a convex surface facing the image side. Furthermore, the detector includes a protective window, a filter and a detector focal plane array arranged in sequence, Figure 1For example, after the light beam passes through the first lens, the second lens, the third lens, the fourth lens and the fifth lens from left to right, it is imaged on the focal plane array of the detector through the protective window and the filter.

[0020] In one embodiment, the detector further comprises an aperture, which is arranged between the filter and the focal plane array of the detector.

[0021] In one embodiment, the lens adopts a secondary imaging design.

[0022] As shown in Table 1, as an example, the air gap between the first lens and the second lens is 15-27.93 mm, the air gap between the second lens and the third lens is 5-17.93 mm, the air gap between the third lens and the fourth lens is 25 mm, and the air gap between the fourth lens and the fifth lens is 24.92 mm; the air gap between the fifth lens and the protective window is 10 mm, the air gap between the protective window and the filter is 2.4 mm, the air gap between the filter and the aperture is 0.25 mm, and the air gap between the aperture and the detector focal plane array is 19.8 mm.

[0023] It can be seen that the second lens can move back and forth along the optical axis, thereby realizing the switching between a large field of view and a small field of view. Specifically, when the lens is in a large field of view, the focal length of the lens is 18mm, the air gap between the first lens and the second lens is 15mm, and the air gap between the second lens and the third lens is 17.93mm; when the lens is in a small field of view, the focal length of the lens is 54mm, the air gap between the first lens and the second lens is 27.93mm, and the air gap between the second lens and the third lens is 5mm. It can be understood that the above-mentioned air gap is the air gap on the optical axis.

[0024] In one embodiment, the center thickness of the first lens is 6 mm, the radius of curvature of the object side is 56.99 mm, and the radius of curvature of the image side is 101.086 mm; the center thickness of the second lens is 1.8 mm, the radius of curvature of the object side is -62.699 mm, and the radius of curvature of the image side is 72.82; the center thickness of the third lens is 5.5 mm, the radius of curvature of the object side is 74.949 mm, and the radius of curvature of the image side is -45.264 mm; the center thickness of the fourth lens is 4.6 mm, the radius of curvature of the object side is -10.937 mm, and the radius of curvature of the image side is -13.12 mm; the center thickness of the fifth lens is 5.5 mm, the radius of curvature of the object side is 586.299 mm, and the radius of curvature of the image side is -52.319 mm.

[0025] It is understandable that in Figure 1In 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 is the object side surface, and the S2 surface is the image side surface. Other lenses are not described in detail.

[0026] In one embodiment, the first lens, the fifth lens and the lens meet the following conditions: f1 / f<3, 0.3<f5 / f<1.3; wherein f is the effective focal length of the lens, f1 is the effective focal length of the first lens, and f5 is the effective focal length of the fifth lens.

[0027] Table 1 Component parameters In conjunction with Table 1, it should be noted that the above lenses are all made of domestic optical materials.

[0028] As shown in Table 1, the image side surfaces of the first lens and the third lens and the object side surfaces of the second lens, the fourth lens and the fifth lens 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.

[0029] Table 2 Aspheric surface data In one embodiment, the object-side surface of the fifth lens is a diffractive surface, and the diffractive surface satisfies the following expression: ; ; in, is the phase of the diffraction surface, r n is the planned radius of the diffraction surface, r is the height relative to the vertical direction of the optical axis, and A1 and A2 are the phase coefficients of the diffraction surface.

[0030] The parameters of the above diffraction surface are shown in Table 3.

[0031] Table 3 Diffraction surface parameters Figure 3 and Figure 4 They are the MTF diagram and spot diagram of the medium-wave cooled dual-field infrared lens at a focal length of 18mm; Figure 5 and Figure 6These are the MTF and point diagrams of the mid-wave cooled dual-field infrared lens at a focal length of 54mm. In the MTF diagram, the horizontal axis represents different spatial frequencies, and the vertical axis represents the modulation degree. Combined with the drawings, 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.

[0032] In summary, the medium-wave cooled dual-field infrared lens provided by the present application has an operating band of 3.2~3.5μm; focal length f=18mm and 54mm; F ​​number is 1.5. The lens provided by the present application has a simple structure, a large target surface, clear imaging, and can be used with a resolution of 320×256, 30μm cooled detector.

[0033] 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 cooled dual field of view infrared lens, characterized in that: It comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged 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 biconcave lens, the third lens and the fifth lens are both biconvex lenses, and the fourth lens is a positive meniscus lens with a convex surface facing the image side; Among them, the second lens can move back and forth along the optical axis, and the air gap between the first lens and the second lens is 15~27.93mm, the air gap between the second lens and the third lens is 5~17.93mm, the air gap between the third lens and the fourth lens is 25mm, and the air gap between the fourth lens and the fifth lens is 24.92mm.

2. The medium wave cooled dual field of view infrared lens according to claim 1, characterized in that: The center thickness of the first lens is 6 mm, the radius of curvature of the object side is 56.99 mm, and the radius of curvature of the image side is 101.086 mm; the center thickness of the second lens is 1.8 mm, the radius of curvature of the object side is -62.699 mm, and the radius of curvature of the image side is 72.82 mm; the center thickness of the third lens is 5.5 mm, the radius of curvature of the object side is 74.949 mm, and the radius of curvature of the image side is -45.264 mm; the center thickness of the fourth lens is 4.6 mm, the radius of curvature of the object side is -10.937 mm, and the radius of curvature of the image side is -13.12 mm; the center thickness of the fifth lens is 5.5 mm, the radius of curvature of the object side is 586.299 mm, and the radius of curvature of the image side is -52.319 mm.

3. The medium wave cooled dual field of view infrared lens according to claim 1, characterized in that: The first lens and the lens meet the following condition: f1 / f<3, 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 cooled dual field of view infrared lens according to claim 1, characterized in that: The fifth lens and the lens meet the following condition: 0.3<f5 / f<1.3, wherein f5 is the effective focal length of the fifth lens, and f is the effective focal length of the lens.

5. The medium wave cooled dual field of view infrared lens according to claim 1, characterized in that: The applicable spectral range of the lens is: 3.2~3.5μm, the focal length of the lens is 18mm and 54mm, and the F number is 1.5; Among them, when the focal length of the lens is 18 mm, the air gap between the first lens and the second lens is 15 mm, and the air gap between the second lens and the third lens is 17.93 mm; when the focal length of the lens is 54 mm, the air gap between the first lens and the second lens is 27.93 mm, and the air gap between the second lens and the third lens is 5 mm.

6. The medium wave cooled dual field of view infrared lens according to claim 1, characterized in that: The lens adopts a secondary imaging design.

7. The medium wave cooled dual field of view infrared lens according to claim 1, characterized in that: The object side surface of the fifth lens is a diffraction surface, and the diffraction surface satisfies the following expression: ； ； in, is the phase of the diffraction surface, r n is the planned radius of the diffraction surface, r is the height relative to the vertical direction of the optical axis, and A1 and A2 are the phase coefficients of the diffraction surface.

8. An imaging device, characterized in that: It comprises the medium-wave cooled dual-field-of-view infrared lens as described in any one of claims 1 to 7 and a detector for receiving images formed by the lens.

9. The imaging device according to claim 8, characterized in that: The number of pixels of the detector is 320×256, and the pixel size is 30 μm.

Images