Mid-wave infrared lens and imaging device

Abstract

The application provides an imaging device, which comprises a middle wave infrared lens and a detector for receiving an image formed by the infrared lens. The infrared lens has a focal length of 120 mm and is composed of a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along an optical axis from an object side to an image side. The first lens and the third lens are both convex moon positive lenses with a convex surface facing the object side. The second lens is a convex moon negative lens with a convex surface facing the object side. The fourth lens is a convex moon positive lens with a convex surface facing the image side. The fifth lens is a convex moon positive lens with a convex surface facing the image side. The detector matched with the infrared lens is a refrigeration type infrared detector, and the number of image elements is 640*512, and the size of the image elements is 15 microns. The infrared lens is designed through secondary imaging, realizes 100% cold stop efficiency, effectively suppresses stray light, has high imaging quality and can realize clear imaging of a large target surface.

Description

Technical Field

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

[0002] With the continuous advancement of focal plane array technology, the pixel scale of the focal plane is constantly increasing while the pixel size is constantly decreasing. This means that optical systems can effectively increase the field of view while maintaining the same focal length. For example, compared to a 320×256 detector, a 640×512 pixel detector can not only obtain high-definition images but also double the field of view while keeping the focal length constant. Currently, high-definition lenses that can be used in conjunction with this technology are needed. Summary of the Invention

[0003] Therefore, it is necessary to provide a mid-wave infrared lens and imaging device that can be matched with a detector with a resolution of 640×512 pixels.

[0004] The technical solution proposed in this application is as follows: A mid-wave infrared lens with a focal length of 120mm is provided. The mid-wave infrared lens is composed of a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the object side to the image side. 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, the fourth lens is a meniscus positive lens with its convex surfaces facing the image side, and the fifth lens is a meniscus positive lens with its convex surfaces facing the image side. The air gap between the first lens and the second lens is 17 mm, the air gap between the second lens and the third lens is 3.5 mm, the air gap between the third lens and the fourth lens is 36.83 mm, and the air gap between the fourth lens and the fifth lens is 13.24 mm.

[0005] Further, the first lens has a center thickness of 7.4 mm, an object-side radius of curvature of 55.87 mm, and an image-side radius of curvature of 84.29 mm; the second lens has a center thickness of 3 mm, an object-side radius of curvature of 50.55 mm, and an image-side radius of curvature of 29.86 mm; the third lens has a center thickness of 5 mm, an object-side radius of curvature of 35.7 mm, and an image-side radius of curvature of 69.37 mm; the fourth lens has a center thickness of 7.5 mm, an object-side radius of curvature of -12.24 mm, and an image-side radius of curvature of -15.31 mm; and the fifth lens has a center thickness of 5 mm, an object-side radius of curvature of -170.71 mm, and an image-side radius of curvature of -36.56 mm.

[0006] Furthermore, the first lens, the third lens, and the fifth lens are all made of silicon, while the second lens and the fourth lens are both made of germanium.

[0007] Furthermore, the image-side surface of the second lens, the object-side surface of the fourth lens, and the object-side surface of the fifth lens are all aspherical surfaces, and satisfy the aspherical surface 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.

[0008] Furthermore, the operating wavelength of the mid-wave infrared lens is 3.7μm~4.8μm, and the F-number is 2.0.

[0009] An imaging device includes the aforementioned mid-wave infrared lens and a detector for receiving images from the mid-wave infrared lens.

[0010] Furthermore, the detector has 640×512 pixels and a pixel size of 15μm.

[0011] Furthermore, the detector includes a protective window, a filter, a [01.1] cold aperture, and an image plane arranged sequentially. 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 2.6 mm, the air gap between the filter and the cold aperture is 0.26 mm, and the air gap between the cold aperture and the image plane is 20.47 mm.

[0012] In summary, the infrared lens in the imaging device provided in this application has a focal length of 120mm, an operating wavelength of 3.7μm~4.8μm, and an F-number of 2.0. The detector adapted to this infrared lens is a cooled infrared detector with a pixel count of 640×512 and a pixel size of 15μm. Through a secondary imaging design, this infrared lens achieves 100% cold stop efficiency, effectively suppressing stray light, resulting in high image quality and enabling clear imaging of large target surfaces. 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 optical path structure of an imaging device provided in an embodiment of this application; Figure 2 A dot plot of a mid-wave infrared lens provided in an embodiment of this application; Figure 3 MTF diagram of a mid-wave infrared lens provided in an embodiment of this application.

[0015] Label Explanation: 11. First lens; 12. Second lens; 13. Third lens; 14. Fourth lens; 15. Fifth lens; 21. Protective window; 22. Filter; 23. Cold stop; 24. Image plane. Detailed Implementation

[0016] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0017] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0018] This application provides an imaging device, including a mid-wave infrared lens and a detector capable of receiving the image captured by the infrared lens. The infrared lens has a focal length of 120mm, an operating wavelength of 3.7μm to 4.8μm, and an F-number of 2.0. The detector has 640×512 pixels, a pixel size of 15μm, and is a cooled infrared detector.

[0019] like Figure 1 As shown, in one embodiment, the infrared lens comprises a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, and a fifth lens 15 arranged sequentially along the optical axis from the object side to the image side. 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; the fourth lens 14 is a meniscus positive lens with its convex surface facing the image side; and the fifth lens 15 is a meniscus positive lens with its convex surface facing the image side. The air gap between the first lens 11 and the second lens 12 is 17 mm, the air gap between the second lens 12 and the third lens 13 is 3.5 mm, the air gap between the third lens 13 and the fourth lens 14 is 36.83 mm, and the air gap between the fourth lens 14 and the fifth lens 15 is 13.24 mm.

[0020] Furthermore, the center thickness of the first lens 11 is 7.4 mm, the radius of curvature of the object-side surface is 55.87 mm, and the radius of curvature of the image-side surface is 84.29 mm; the center thickness of the second lens 12 is 3 mm, the radius of curvature of the object-side surface is 50.55 mm, and the radius of curvature of the image-side surface is 29.86 mm; the center thickness of the third lens 13 is 5 mm, the radius of curvature of the object-side surface is 35.7 mm, and the radius of curvature of the image-side surface is 69.37 mm; the center thickness of the fourth lens 14 is 7.5 mm, the radius of curvature of the object-side surface is -12.24 mm, and the radius of curvature of the image-side surface is -15.31 mm; and the center thickness of the fifth lens 15 is 5 mm, the radius of curvature of the object-side surface is -170.71 mm, and the radius of curvature of the image-side surface is -36.56 mm.

[0021] In one embodiment, the detector includes a protective window 21, a filter 22, a cold stop 23, and an image plane 24 arranged sequentially. The air gap between the fifth lens 15 and the protective window 21 is 10 mm, the air gap between the protective window 21 and the filter 22 is 2.6 mm, the air gap between the filter 22 and the cold stop 23 is 0.26 mm, and the air gap between the cold stop 23 and the image plane 24 is 20.47 mm. Specific parameters can be found in Table 1.

[0022] In one embodiment, the first lens 11, the third lens 13, and the fifth lens 15 are all made of silicon, while the second lens 12 and the fourth lens 14 are both made of germanium.

[0023] Table 1 Parameters of each lens Understandably, with Figure 1 For example, the optical axis direction is from left to right, with the left side being the object side and the right side being the image side. For instance, the S1 surface of the first lens 1111 is the object side surface and the S2 surface is the image side surface. The same applies to other lenses, which will not be elaborated here. Please refer to Table 1 for details.

[0024] In one embodiment, the image-side surface of the second lens 12, the object-side surface of the fourth lens 14, and the object-side surface of the fifth lens 15 are all aspherical surfaces and satisfy 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 coefficient data are shown in Table 2.

[0025] Table 2 Aspherical Data In one embodiment, the object-side surface of the fifth lens 15 is a diffraction surface and satisfies the equation for a binary surface in Zemax: M(B1ρ) 2 +B2ρ 4 Where M is the diffraction order, B1 and B2 are the phase coefficients of the binary surface, and ρ is the normalized radius. The binary surface data are shown in Table 3. Please see Figures 2 to 3 , Figure 2 and Figure 3 The figures show the dot plot and MTF (Mean Transformation Factor) of the infrared lens at room temperature. As can be seen from the figures, the infrared lens of this application exhibits an MTF close to the diffraction limit at room temperature, indicating good image quality.

[0026] In summary, the infrared lens in the imaging device provided in this application has a focal length of 120mm, an operating wavelength of 3.7μm~4.8μm, and an F-number of 2.0. The detector adapted to this infrared lens is a cooled infrared detector with a pixel count of 640×512 and a pixel size of 15μm. Through a secondary imaging design, this infrared lens achieves 100% cold stop efficiency, effectively suppressing stray light and resulting in high image quality, enabling clear imaging of large target surfaces.

[0027] 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 infrared lens, characterized in that, With a focal length of 120mm, the mid-wave infrared lens is composed of a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the object side to the image side. 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, the fourth lens is a meniscus positive lens with its convex surfaces facing the image side, and the fifth lens is a meniscus positive lens with its convex surfaces facing the image side. The air gap between the first lens and the second lens is 17 mm, the air gap between the second lens and the third lens is 3.5 mm, the air gap between the third lens and the fourth lens is 36.83 mm, and the air gap between the fourth lens and the fifth lens is 13.24 mm.

2. The mid-wave infrared lens according to claim 1, characterized in that, The first lens has a center thickness of 7.4 mm, an object-side radius of curvature of 55.87 mm, and an image-side radius of curvature of 84.29 mm; the second lens has a center thickness of 3 mm, an object-side radius of curvature of 50.55 mm, and an image-side radius of curvature of 29.86 mm; the third lens has a center thickness of 5 mm, an object-side radius of curvature of 35.7 mm, and an image-side radius of curvature of 69.37 mm; the fourth lens has a center thickness of 7.5 mm, an object-side radius of curvature of -12.24 mm, and an image-side radius of curvature of -15.31 mm; and the fifth lens has a center thickness of 5 mm, an object-side radius of curvature of -170.71 mm, and an image-side radius of curvature of -36.56 mm.

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

4. The mid-wave infrared lens according to claim 1, characterized in that, The image-side surface of the second lens, the object-side surface of the fourth lens, and the object-side surface of the fifth lens are all aspherical and satisfy 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.

5. The mid-wave infrared lens according to claim 1, characterized in that, The operating wavelength of the mid-wave infrared lens is 3.7μm~4.8μm, and the F number is 2.

0.

6. An imaging device, characterized in that, It includes the mid-wave infrared lens as described in any one of claims 1-5 and the detector that receives the image from the mid-wave infrared lens.

7. The imaging apparatus according to claim 6, characterized in that, The detector has 640×512 pixels and a pixel size of 15μm.

8. The imaging apparatus according to claim 6, characterized in that, The detector includes a protective window, a filter, a cold aperture, and an image plane arranged sequentially. 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 2.6 mm, the air gap between the filter and the cold aperture is 0.26 mm, and the air gap between the cold aperture and the image plane is 20.47 mm.

Images