Long-wave athermalization infrared lens and imaging device

Abstract

The invention discloses an imaging device which comprises a long-wave athermalization infrared lens and a detector for receiving an image formed by the infrared lens, the focal length of the infrared lens is 85 mm, and the infrared lens comprises a first lens, a second lens and a third lens which are sequentially arranged in the optical axis transmission direction; the first lens is a meniscus positive lens of which the convex surface faces the object side, the second lens is a meniscus negative lens of which the convex surface faces the object side, and the third lens is a biconvex lens; the air gap between the first lens and the second lens is 42.564 mm, and the air gap between the second lens and the third lens is 16.428 mm. The number of pixels of the detector is 1280 * 1024, the size of the pixels is 12 [mu] m, and the detector is an uncooled infrared detector. Large-target-surface clear imaging can be achieved only through the three lenses, the structure is simple, and cost is low.

Description

Technical Field

[0001] The present application belongs to the field of infrared optical lens technology, and specifically relates to a long-wave athermal infrared lens and an imaging device. Background Art

[0002] Infrared lenses are currently widely used in various surveillance applications, such as forest fire prevention, road monitoring, and airport security. Long-wave infrared lenses, a type of infrared lens, are now widely used. However, long-wave infrared lenses designed for large-area infrared systems typically have a large number of lenses, such as five or more, resulting in high costs. Summary of the Invention

[0003] The technical problem to be solved by the present application is that the existing long-wave infrared lens of a large-target infrared system has a large number of lenses. In order to solve this technical problem, a long-wave athermal infrared lens and an imaging device with a small number of lenses are provided.

[0004] The technical solutions proposed in this application are: A long-wave athermal infrared lens with a focal length of 85 mm, comprising a first lens, a second lens, and a third lens arranged in sequence along the optical axis transmission direction; the first lens is a positive meniscus lens with its convex surface facing the object side, the second lens is a negative meniscus lens with its convex surface facing the object side, and the third lens is a biconvex lens; The air gap between the first lens and the second lens is 42.564 mm, and the air gap between the second lens and the third lens is 16.428 mm.

[0005] Furthermore, the center thickness of the first lens is 9.07 mm, the radius of curvature of the object side surface is 60.754 mm, and the radius of curvature of the image side surface is 103.898 mm; the center thickness of the second lens is 2.382 mm, the radius of curvature of the object side surface is 21.11 mm, and the radius of curvature of the image side surface is 17.004 mm; the center thickness of the third lens is 2.679 mm, the radius of curvature of the object side surface is 214.449 mm, and the radius of curvature of the image side surface is -534.195 mm.

[0006] Furthermore, the first lens is made of chalcogenide glass, and the second lens and the third lens are both made of germanium.

[0007] Furthermore, the relative aperture of the long-wave athermal infrared lens is 1.1, the field of view angle is 10.1°×8.1°, and the operating band is -40°C to +65°C.

[0008] Furthermore, the object-side surface and the image-side surface of the first lens, and the image-side surfaces of the second lens and the third lens are all aspherical surfaces, and satisfy the aspherical surface formula: Among them, Z is the distance vector height from the aspheric surface vertex when the aspheric surface is at a height r along the optical axis; c=1 / R; R is the paraxial curvature fitting radius of the mirror surface; k is the cone coefficient; A, B, C, and D are high-order aspheric coefficients.

[0009] Furthermore, the image-side surface of the second lens is a binary surface, and the binary surface includes an aspherical surface and a diffractive surface.

[0010] Furthermore, the total weight of the first lens, the second lens, and the third lens is 160 g.

[0011] An imaging device comprises the long-wave athermal infrared lens and a detector for receiving images formed by the long-wave athermal infrared lens.

[0012] Furthermore, the total optical length of the imaging device is 83.293 mm, and the back focus is 10.17 mm.

[0013] Furthermore, the number of pixels of the detector is 1280×1024, the pixel size is 12 μm, and the detector is a non-cooled infrared detector.

[0014] In summary, the infrared lens provided in this application has a focal length of 85mm, a relative aperture of 1.1, a field of view of 10.1°×8.1°, an operating band of 10μm~12μm, and an operating temperature of -40℃~+65℃. The corresponding detector pixel number is 1280×1024, the pixel size is 12μm, and it is a non-cooled infrared detector. Only three lenses are used to achieve clear imaging of a large target surface, with a simple structure and low cost. At the same time, the total optical length of the imaging device is only 83.293mm, and the total weight of the three lenses is only 160g. The structure is compact and conducive to miniaturization design. In addition, the above-mentioned infrared lens can meet the optical focal length and heat elimination requirements of the imaging device without the aid of a focusing mechanism, that is, to achieve an optically passive athermal design. 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. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application.

[0016] Figure 1 A schematic diagram of the optical path structure of an imaging device provided in one embodiment of the present application; Figure 2 This is an MTF diagram of the infrared lens provided in one embodiment of the present application at 20°C; Figure 3This is an MTF diagram of the infrared lens provided in one embodiment of the present application at 65°C; Figure 4 This is an MTF diagram of the infrared lens provided in one embodiment of the present application at -40°C; Figure 5 This is a spot diagram of the infrared lens provided in one embodiment of the present application at 20°C; Figure 6 This is a spot diagram of the infrared lens provided in one embodiment of the present application at 65°C; Figure 7 This is a spot diagram of the infrared lens provided in one embodiment of the present application at -40°C.

[0017] Description of labels: 11. First lens; 12. Second lens; 13. Third lens; 21. Protective window; 22. Image plane. DETAILED DESCRIPTION

[0018] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0019] 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0020] This application provides an imaging device comprising a long-wavelength athermal infrared lens (hereinafter referred to as the infrared lens) and a detector that receives images from the infrared lens. The infrared lens has a focal length of 85 mm, a relative aperture of 1.1, a field of view of 10.1° × 8.1°, an operating wavelength range of 10 μm to 12 μm, and an operating temperature range of -40°C to +65°C. The detector has 1280 × 1024 pixels, a pixel size of 12 μm, and is an uncooled infrared detector.

[0021] like Figure 1As shown, in one embodiment, the infrared lens includes a first lens 11, a second lens 12, and a third lens 13, arranged in sequence along the optical axis. The first lens 11 is a positive meniscus lens with its convex surface facing the object side, the second lens 12 is a negative meniscus lens with its convex surface facing the object side, and the third lens 13 is a biconvex lens. Furthermore, the air gap between the first lens 11 and the second lens 12 is 42.564 mm, and the air gap between the second lens 12 and the third lens 13 is 16.428 mm.

[0022] In one embodiment, the center thickness of the first lens 11 is 9.07 mm, the radius of curvature of the object side surface is 60.754 mm, and the radius of curvature of the image side surface is 103.898 mm; the center thickness of the second lens 12 is 2.382 mm, the radius of curvature of the object side surface is 21.11 mm, and the radius of curvature of the image side surface is 17.004 mm; and the center thickness of the third lens 13 is 2.679 mm, the radius of curvature of the object side surface is 214.449 mm, and the radius of curvature of the image side surface is -534.195 mm.

[0023] Furthermore, the focal length of the first lens 11 is 72.525 mm, and the optical power is 0.014; the focal length of the second lens 12 is -51.517 mm, and the optical power is -0.019; the focal length of the third lens 13 is 51.07, and the optical power is 0.02.

[0024] In one embodiment, the detector includes a protective window 21 and an image plane 22 disposed sequentially. The air gap between the third lens 13 and the protective window 21 is 8.677 mm. In practical applications, the total optical length of the imaging device is 83.293 mm, and the back focus is 10.17 mm.

[0025] It is understandable that in Figure 1 In the embodiment shown, the optical axis is transmitted from left to right, that is, the light beam passes through the first lens 11, the second lens 12 and the third lens 13 in sequence, then passes through the protective window 21 and forms an image on the image plane 22. Figure 1 In the embodiment, taking the first lens 11 as an example, the left side S1 of the first lens 11 is the object side surface, and the right side S2 is the image side surface. The same is true for other lenses, which will not be described in detail here.

[0026] In one embodiment, the first lens 11 is made of chalcogenide glass, and the second lens 12 and the third lens 13 are both made of germanium. Furthermore, the total weight of the first lens 11, the second lens 12, and the third lens 13 is 160g. Specific lens parameters can be found in Table 1.

[0027] Table 1 Lens parameters In one embodiment, the object side and image side of the first lens 11 and the image side of the third lens 13 are all aspherical surfaces; the image side of the second lens 12 is a binary surface, and the binary surface includes an aspherical surface and a diffraction surface. Among them, all aspherical surfaces satisfy the aspherical surface formula Where Z is the distance from the aspheric surface vertex to the aspheric surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror surface; k is the conic coefficient; A, B, C, and D are the higher-order aspheric coefficients. In addition, the above aspheric surface data is shown in Table 2.

[0028] Table 2 Aspheric surface data In one embodiment, the image side surface of the second lens 12 satisfies the expression equation of the binary surface in Zemax: M(B1ρ 2 +B2ρ 4 ), where M is the diffraction order, B1 and B2 are the binary surface phase coefficients, and ρ is the normalized radius. The binary surface data are shown in Table 3.

[0029] Table 3 Two-dimensional surface data See also Figure 2-Figure 7 , Figure 2-Figure 4 The MTF diagrams of infrared lenses at 20℃, 65℃ and -40℃ are respectively. Figure 5-Figure 7 The spot diagrams of the infrared lens at 20°C, 65°C, and -40°C are shown. As can be seen from the figures, the MTF of the infrared lens is close to the diffraction limit at each temperature, the RMS diameter of the diffuse spot is smaller than the Airy disk diameter, and the image quality is good.

[0030] In summary, the infrared lens provided in this application has a focal length of 85mm, a relative aperture of 1.1, a field of view of 10.1°×8.1°, and an operating band of -40°C~+65°C. The corresponding detector pixel number is 1280×1024, the pixel size is 12μm, and it is a non-cooled infrared detector. Clear imaging of a large target surface can be achieved by using only three lenses, with a simple structure and low cost. At the same time, the total optical length of the imaging device is only 83.293mm, and the total weight of the three lenses is only 160g. The structure is compact and conducive to miniaturization design. In addition, the above-mentioned infrared lens can meet the optical focal length and heat elimination requirements of the imaging device without the aid of a focusing mechanism, that is, to achieve an optically passive athermal design.

[0031] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A long-wave athermal infrared lens, characterized in that: The focal length is 85mm, and the lens includes a first lens, a second lens, and a third lens arranged in sequence along the optical axis transmission direction; the first lens is a positive meniscus lens with a convex surface facing the object side, the second lens is a negative meniscus lens with a convex surface facing the object side, and the third lens is a biconvex lens; The air gap between the first lens and the second lens is 42.564 mm, and the air gap between the second lens and the third lens is 16.428 mm.

2. The long-wave athermal infrared lens according to claim 1, characterized in that: The center thickness of the first lens is 9.07 mm, the radius of curvature of the object side is 60.754 mm, and the radius of curvature of the image side is 103.898 mm; the center thickness of the second lens is 2.382 mm, the radius of curvature of the object side is 21.11 mm, and the radius of curvature of the image side is 17.004 mm; the center thickness of the third lens is 2.679 mm, the radius of curvature of the object side is 214.449 mm, and the radius of curvature of the image side is -534.195 mm.

3. The long-wave athermal infrared lens according to claim 1, characterized in that: The first lens is made of chalcogenide glass, and the second lens and the third lens are both made of germanium.

4. The long-wave athermal infrared lens according to claim 1, characterized in that: The long-wave athermal infrared lens has a relative aperture of 1.1, a field of view of 10.1°×8.1°, an operating band of 10μm~12μm, and an operating temperature of -40°C~+65°C.

5. The long-wave athermal infrared lens according to claim 1, characterized in that: The object-side surface and the image-side surface of the first lens, and the image-side surfaces of the second lens and the third lens are all aspherical surfaces, and satisfy the aspherical surface formula: Among them, Z is the distance vector height from the aspheric surface vertex when the aspheric surface is at a height r along the optical axis; c=1 / R; R is the paraxial curvature fitting radius of the mirror surface; k is the cone coefficient; A, B, C, and D are high-order aspheric coefficients.

6. The long-wave athermal infrared lens according to claim 5, characterized in that: The image-side surface of the second lens is a binary surface, and the binary surface includes an aspherical surface and a diffractive surface.

7. The long-wave athermal infrared lens according to claim 1, characterized in that: The total weight of the first lens, the second lens, and the third lens is 160 g.

8. An imaging device, characterized in that: The invention comprises the long-wave athermal infrared lens according to any one of claims 1 to 7 and a detector for receiving images formed by the long-wave athermal infrared lens.

9. The imaging device according to claim 8, wherein The total optical length of the imaging device is 83.293 mm, and the back focus is 10.17 mm.

10. The imaging device according to claim 8, wherein The number of pixels of the detector is 1280×1024, the pixel size is 12 μm, and the detector is a non-cooling infrared detector.

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