A middle wave refrigeration infrared lens and an imaging device

Abstract

The application discloses a middle-wave refrigeration infrared lens, which comprises a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the transmission direction of the optical axis; the first lens and the third lens are both meniscus positive lenses with the convex surface facing the object side; the second lens is a meniscus negative lens with the convex surface facing the object side; the fourth lens is a meniscus negative lens with the convex surface 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 comprises a reflecting mirror arranged between the second lens and the third lens to change the direction of the optical axis; the lens provided by the application has the advantages of small lens length size, simple structure, large target surface, clear imaging, and the ability to match a 320*256 resolution and a 30 mu m refrigeration type detector; and the application further discloses an imaging device.

Description

Technical Field

[0001] This application belongs to the field of infrared optical equipment technology, specifically relating to a mid-wave cooled infrared lens and imaging device. Background Technology

[0002] Cooled infrared systems offer unparalleled advantages over uncooled infrared systems, primarily in terms of operating range and imaging quality. A wider field of view allows for the observation of more objects and reduces blind spots. Therefore, wide-field-of-view cooled infrared lenses are widely used in demanding applications such as military and aerospace. However, existing wide-field-of-view cooled infrared lenses are relatively long and large in size. Summary of the Invention

[0003] Based on this, this application provides a mid-wave cooled infrared lens and imaging device that is shorter in length and smaller in size.

[0004] The technical solution proposed in this application is as follows:

[0005] A mid-wave cooled infrared lens includes a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis transmission direction; the first lens and the third lens are both meniscus positive lenses with their convex surfaces facing the object side, the second lens is a meniscus negative lens with its convex surfaces facing the object side, and the fourth lens is a meniscus negative lens with its 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;

[0006] The lens also includes a reflector, which is disposed between the second lens and the third lens to change the direction of the optical axis.

[0007] Furthermore, the first lens has a center thickness of 8 mm, an object-side radius of curvature of 26.67 mm, and an image-side radius of curvature of 35.06 mm; the second lens has a center thickness of 5.3 mm, an object-side radius of curvature of 14.974 mm, and an image-side radius of curvature of 10.083 mm; the third lens has a center thickness of 8.5 mm, an object-side radius of curvature of 46.53 mm, and an image-side radius of curvature of -251.78 mm; and the fourth lens has a center thickness of 3 mm, an object-side radius of curvature of -45.802 mm, and an image-side radius of curvature of -54.971 mm.

[0008] Furthermore, the first lens and the lens satisfy the following condition: f1 / f > 1, where f1 is the effective focal length of the first lens and f is the effective focal length of the lens.

[0009] Furthermore, the fourth lens and the lens satisfy the following condition: 4.5 < f4 / f < 5.5, where f4 is the effective focal length of the fourth lens and f is the effective focal length of the lens.

[0010] Furthermore, the applicable spectral range of the lens is 3.2~3.5μm, the focal length of the lens is 23mm, and the F number is 1.5.

[0011] Furthermore, the lens employs a secondary imaging design.

[0012] Furthermore, the image-side surfaces of the first lens, the second lens, and the third lens, as well as the object-side surface of the fourth lens, are all aspherical surfaces, and the aspherical surfaces satisfy the following expression:

[0013]

[0014] Where 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, sixth, eighth, tenth and twelfth order surface coefficients, respectively.

[0015] 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.

[0016] An imaging device includes a mid-wave cooled infrared lens as described above and a detector that receives the image from the lens.

[0017] Furthermore, the detector has 320×256 pixels and a pixel size of 30μm.

[0018] The lens provided in this application has a small length, simple structure, large target surface, clear imaging, and can be used with a cooled detector with a resolution of 320×256 and 30μm. Attached Figure Description

[0019] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof.

[0020] Figure 1 This is a schematic diagram of the structure of an imaging device provided in an embodiment of this application;

[0021] Figure 2 MTF diagram of a mid-wave cooled infrared lens provided in an embodiment of this application;

[0022] Figure 3 A dot plot of a mid-wave cooled infrared lens provided in an embodiment of this application.

[0023] Label Explanation:

[0024] 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 Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] One embodiment of this application provides an imaging device, which includes a mid-wave cooled infrared lens and a detector for receiving the image captured by the lens. The lens has a focal length of 23mm, an applicable spectral range of 3.2~3.5μm, and an F-number of 1.5. The detector is a cooled detector with 320×256 pixels and a pixel size of 30μm.

[0027] Please see Figure 1 The lens includes a first lens 11, a second lens 12, a third lens 13, and a fourth lens 14 arranged sequentially along the optical axis transmission direction. The first lens 11 and the third lens 13 are both meniscus positive lenses with their convex surfaces facing the object side, the second lens 12 is a meniscus negative lens with its convex surface facing the object side, and the fourth lens 14 is a meniscus negative lens with its convex surface facing the image side. Furthermore, the lens also includes a reflecting mirror 15, which is disposed 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 segments that are perpendicular to each other, 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.

[0028] In one embodiment, the detector includes a protective window 21, a filter 22, and a detector focal plane array 23 arranged sequentially to... Figure 1 For example, 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, and then forms an image on the detector focal plane array 23 through the protective window 21 and the filter 22.

[0029] Furthermore, the detector also includes an aperture, which is disposed between the filter 22 and the detector focal plane array 23.

[0030] In one embodiment, the lens employs a secondary imaging design.

[0031] 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 air gaps are the air gaps along the optical axis.

[0032] In one embodiment, the first lens 11 has a center thickness of 8 mm, an object-side radius of curvature of 26.67 mm, and an image-side radius of curvature of 35.06 mm; the second lens 12 has a center thickness of 5.3 mm, an object-side radius of curvature of 14.974 mm, and an image-side radius of curvature of 10.083 mm; the third lens 13 has a center thickness of 8.5 mm, an object-side radius of curvature of 46.53 mm, and an image-side radius of curvature of -251.78 mm; and the fourth lens 14 has a center thickness of 3 mm, an object-side radius of curvature of -45.802 mm, and an image-side radius of curvature of -54.971 mm.

[0033] Understandably, 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; the upper side of the third lens 13 and the lower side of the fourth lens 14 is the object side, and the lower side is the image side. Furthermore, 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 are obtained sequentially, and will not be described in detail here.

[0034] In one embodiment, the first lens 11, the fourth lens 14, and the lens satisfy the following conditions:

[0035] f1 / f > 1, 4.5 < f4 / f < 5.5; where 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.

[0036] Table 1 Component Parameters

[0037]

[0038] It should be noted, in conjunction with Table 1, that all the lenses mentioned above are made of domestically produced optical materials.

[0039] As shown in Table 1, the image-side surfaces of the first lens 11, the second lens 12, and the third lens 13, as well as the object-side surface of the fourth lens 14, are all aspherical surfaces, and all aspherical surfaces satisfy the aspherical formula:

[0040]

[0041] Where z represents the distance of the surface from the vertex of the surface along 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, sixth, eighth, tenth, and twelfth order surface coefficients, respectively. Meanwhile, the aspherical data for each lens are shown in Table 2.

[0042] Table 2 Aspherical Data

[0043]

[0044] Figure 2 and Figure 3 The images show the MTF (Medium-Frequency Form) and dot plot of the mid-wave cooled infrared lens. In the MTF chart, the horizontal axis represents different spatial frequencies, and the vertical axis represents modulation depth. As can be seen from the drawings, this lens corrects various aberrations across different wavelengths, ensuring sufficient resolution in both the center and peripheral fields of view.

[0045] In summary, the mid-wave cooled infrared lens provided in this application operates in the 3.2~3.5μm band; has a focal length of f=23mm; and an F-number of 1.5. The lens provided in this application features a simple structure, a large target surface, clear imaging, and can be used with a 320×256 resolution, 30μm cooled detector.

[0046] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A mid-wave cooled infrared lens, characterized in that, It consists of a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis transmission direction; the first lens and the third lens are both meniscus positive lenses with their convex surfaces facing the object side, the second lens is a meniscus negative lens with its convex surfaces facing the object side, and the fourth lens is a meniscus negative lens with its 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. The lens further includes a reflector, which is disposed between the second lens and the third lens to change the direction of the optical axis; The first lens has a center thickness of 8 mm, an object-side radius of curvature of 26.67 mm, and an image-side radius of curvature of 35.06 mm; the second lens has a center thickness of 5.3 mm, an object-side radius of curvature of 14.974 mm, and an image-side radius of curvature of 10.083 mm; the third lens has a center thickness of 8.5 mm, an object-side radius of curvature of 46.53 mm, and an image-side radius of curvature of -251.78 mm; and the fourth lens has a center thickness of 3 mm, an object-side radius of curvature of -45.802 mm, and an image-side radius of curvature of -54.971 mm.

2. The mid-wave cooled infrared lens according to claim 1, characterized in that, The first lens and the lens satisfy the following condition: f1 / f > 1, where f1 is the effective focal length of the first lens and f is the effective focal length of the lens.

3. The mid-wave cooled infrared lens according to claim 1, characterized in that, The fourth lens and the lens satisfy the following condition: 4.5 < f4 / f < 5.5, where f4 is the effective focal length of the fourth lens and f is the effective focal length of the lens.

4. The mid-wave cooled 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 23mm, and the F number is 1.

5.

5. The mid-wave cooled infrared lens according to claim 1, characterized in that, The lens employs a secondary imaging design.

6. The mid-wave cooled infrared lens according to claim 1, characterized in that, The image-side surfaces of the first lens, the second lens, and the third lens, as well as the object-side surface of the fourth lens, are all aspherical surfaces, and the aspherical surfaces satisfy the following expression: Where 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, sixth, eighth, tenth and twelfth order surface coefficients, respectively.

7. The mid-wave cooled infrared lens according to claim 1, characterized in that, The first lens and the third lens are both made of silicon single crystal, while the second lens and the fourth lens are both made of germanium single crystal.

8. An imaging device, characterized in that, It includes the mid-wave cooled infrared lens as described in any one of claims 1-7 and the detector that receives the image from the lens.

9. The imaging apparatus according to claim 8, characterized in that, The detector has 320×256 pixels and a pixel size of 30μm.

Images