A middle wave refrigeration infrared lens and an imaging device

Abstract

This invention discloses a mid-wave cooled infrared lens with a focal length of 45mm. The lens includes a first lens, a second lens, and a third lens coaxially arranged along the optical axis transmission direction. The air gap between the first and second lenses is 13mm, and the air gap between the second and third lenses is 18mm. The 45mm focal length mid-wave cooled infrared lens provided by this invention has the advantages of a large target area and clear imaging.

Description

Technical Field

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

[0002] With the continuous advancement of focal plane technology, the pixel scale of the focal plane is constantly increasing while the pixel size is constantly decreasing. This means that the optical system can effectively increase the field of view while maintaining the same focal length.

[0003] The emergence of 640×512 pixel detectors, compared to the previous 320×256 detectors, not only allows for high-definition images in their optical systems, but also doubles the field of view while maintaining the same focal length. Therefore, the development of high-definition lenses suitable for 640×512 mid-wave detectors is urgently needed.

[0004] To achieve high-definition imaging performance, existing lenses typically have a large number of lenses. Summary of the Invention

[0005] To address the above problems, this invention proposes a mid-wave cooled infrared lens and imaging device capable of matching an array size of 640×512. The specific technical solution is as follows: The technical solution proposed in this application is as follows: A mid-wave cooled infrared lens with a focal length of 45mm includes a first lens, a second lens, and a third lens arranged coaxially along the optical axis transmission direction. The air gap between the first lens and the second lens is 13mm, and the air gap between the second lens and the third lens is 18mm.

[0006] Furthermore, the first lens has a center thickness of 5.5 mm, an object-side radius of curvature of 39.09 mm, and an image-side radius of curvature of 42.73 mm; the second lens has a center thickness of 2.5 mm, an object-side radius of curvature of 343.35 mm, and an image-side radius of curvature of 112.7 mm; and the third lens has a center thickness of 4 mm, an object-side radius of curvature of 123.06 mm, and an image-side radius of curvature of -207.88 mm.

[0007] Furthermore, the first and third lenses are both made of silicon single crystal, while the second lens is made of germanium single crystal.

[0008] Furthermore, the image-side surface of the second lens is aspherical, satisfying the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

[0009] Furthermore, the lens operates in the wavelength range of 3.2μm-3.5μm and has an F-number of 1.5.

[0010] An imaging apparatus includes a mid-wave cooled infrared lens as described above and a detector for receiving images from the infrared lens.

[0011] Furthermore, the detector includes a protective window, a chopping window, an aperture, and a detector focal plane array arranged sequentially. Furthermore, the detector has 640×512 pixels and a pixel size of 15μm; the detector is a cooled detector.

[0012] The mid-wave cooled infrared lens provided by this invention has the advantages of a large target area and clear imaging. Attached Figure Description

[0013] 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.

[0014] Figure 1 This is a schematic diagram of the structure of an imaging device provided in an embodiment of this application; Figure 2 for Figure 1 The optical path diagram of the imaging device is shown below; Figure 3 A dot plot of a mid-wave cooled infrared lens provided in another embodiment of this application; Figure 4 MTF diagram of a mid-wave cooled infrared lens provided in another embodiment of this application.

[0015] Label Explanation: 1. First lens; 2. Second lens; 3. Third lens; 4. Protective window; 5. Chopper window; 6. Aperture; 7. Detector focal plane array. Detailed Implementation

[0016] 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.

[0017] This invention provides an imaging device comprising a mid-wave cooled infrared lens and a detector for receiving the image captured by the lens. The lens has a focal length of 45mm and offers advantages such as a large target surface and clear imaging. The following example uses this lens applied to a cooled detector with a resolution of 640×512 and 15μm, operating in the 3.2μm-3.5μm wavelength range.

[0018] like Figure 1 As shown, the lens includes a first lens 1, a second lens 2, and a third lens 3 arranged sequentially along the optical axis transmission direction. The air gap between the first lens 1 and the second lens 2 is 13 mm, and the air gap between the second lens 2 and the third lens 3 is 18 mm.

[0019] like Figure 2 As shown, the light beam passes through the first lens 1, the second lens 2, and the third lens 3 from left to right, then through the protective window 4, the chopper window 5, and the aperture 6, and is imaged on the detector focal plane array 7.

[0020] As shown in Table 1, as an example, the center thickness of the first lens 1 is 5.5 mm, the object-side radius of curvature is 39.09 mm, and the image-side radius of curvature is 42.73 mm; the center thickness of the second lens 2 is 2.5 mm, the object-side radius of curvature is 343.35 mm, and the image-side radius of curvature is 112.7 mm; the center thickness of the third lens 3 is 4 mm, the object-side radius of curvature is 123.06 mm, and the image-side radius of curvature is -207.88 mm.

[0021] It can be determined that, along the optical axis from left to right, the left side is the object side and the right side is the image side. For example, the S1 surface of the first lens 1 is the object side surface and the S2 surface is the image side surface. Other lenses will not be described in detail here.

[0022] Furthermore, the air gap between the third lens 3 and the protective window 4 is 12 mm, the air gap between the protective window 4 and the chopper window 5 is 2.15 mm, the air gap between the chopper window 5 and the aperture 6 is 0.5 mm, and the air gap between the aperture 6 and the detector focal plane array 7 is 19.8 mm.

[0023] Table 1 Parameters of each lens In one embodiment, the image-side surface of the second lens 2 is aspherical and satisfies the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients. The aspherical data of the second lens 2 are shown in Table 2.

[0024] Table 2 Aspherical data of lenses Figure 3 and Figure 4 The images show the dot plot and MTF (Mean Transformation Factor) plot of the mid-wave cooled infrared lens, respectively. In the MTF plot, the horizontal axis represents different spatial frequencies, and the vertical axis represents the modulation index. It can be seen that the MTF is close to the diffraction limit, the root mean square diameter of the diffuse spot is smaller than the Airy disk diameter, and the image quality is good.

[0025] In summary, it should be noted that the operating wavelength of the mid-wave cooled infrared lens in this invention is 3.2μm-3.5μm, the F-number is 1.5, and the resolution of the detector used to receive the image from this lens is 640×512, with a pixel size of 15μm. The lens provided by this invention has advantages such as a large target surface and clear imaging.

[0026] 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 refrigerated infrared lens characterized in that, With a focal length of 45mm, the mid-wave cooled infrared lens is composed of a first lens, a second lens, and a third lens arranged coaxially along the optical axis transmission direction. The air gap between the first lens and the second lens is 13mm, and the air gap between the second lens and the third lens is 18mm. The first lens has a positive light angle, with its object side being convex and its image side being concave. The second lens has a negative light angle, with its object side being convex and its image side being concave. The third lens has a positive light angle, with its object side being convex and its image side being convex. The first lens has a center thickness of 5.5 mm, an object-side radius of curvature of 39.09 mm, and an image-side radius of curvature of 42.73 mm; the second lens has a center thickness of 2.5 mm, an object-side radius of curvature of 343.35 mm, and an image-side radius of curvature of 112.7 mm; the third lens has a center thickness of 4 mm, an object-side radius of curvature of 123.06 mm, and an image-side radius of curvature of -207.88 mm.

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

3. The mid-wave refrigerated infrared lens according to claim 1, wherein, The image-side surface of the second lens is aspherical, satisfying the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

4. The mid-wave refrigerated infrared lens according to any one of claims 1 to 3, characterized in that The lens operates in the 3.2μm-3.5μm wavelength range and has an F-number of 1.

5.

5. An imaging device, characterized by It includes the mid-wave cooled infrared lens as described in any one of claims 1 to 4 and a detector for receiving the image formed by the infrared lens.

6. The imaging apparatus according to claim 5, wherein The detector includes a protective window, a chopping window, an aperture, and a detector focal plane array arranged sequentially.

7. The imaging apparatus according to claim 5, wherein The detector has 640×512 pixels and a pixel size of 15μm; the detector is a cooled detector.

Images