Large-view-field low-distortion long-wave infrared lens and imaging device

Abstract

The invention discloses an imaging device. The imaging device comprises a large-view-field low-distortion long-wave infrared lens and a detector for receiving images formed by the lens. The lens is composed of a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from the object side to the image side along the optical axis, the first lens, the second lens, the third lens and the fourth lens are all made of chalcogenide glass, the first lens is a meniscus negative lens with the convex face facing the object side, the second lens is a biconcave lens, the third lens is a biconvex lens, and the fourth lens is a biconvex lens. The fourth lens is a meniscus positive lens of which the convex surface faces the image side; the air gap between the first lens and the second lens is 10.299 mm, the air gap between the second lens and the third lens is 2.589 mm, and the air gap between the third lens and the fourth lens is 5.469 mm. The lens is small in number of lenses, simple in structure and large in view field, and through cooperation of optical materials and the lens arrangement structure, distortion is reduced, and the imaging quality is improved.

Description

Technical Field

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

[0002] Infrared imaging technology, with its non-contact temperature measurement, smoke penetration, and all-weather operation capabilities, is widely used in military reconnaissance, industrial inspection, security monitoring, and medical diagnosis. As application scenarios become more sophisticated, the market demands higher resolution from infrared optical imaging systems. Infrared imaging optical systems, especially large-field-of-view lenses, are prone to barrel / pincushion distortion due to factors such as material refractive index temperature drift. In applications such as machine vision and multispectral fusion, distortion directly leads to coordinate positioning errors, reducing measurement accuracy and image registration reliability. Summary of the Invention

[0003] The technical problem to be solved by this application is that existing large field-of-view lenses are prone to distortion due to temperature, which affects the image quality. In order to solve this technical problem, a large field-of-view low-distortion long-wave infrared lens and imaging device that can reduce distortion and improve image quality is provided.

[0004] The technical solution proposed in this application is as follows: A large field-of-view, low-distortion long-wave infrared lens comprises a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis from the object side to the image side. The first lens, the second lens, the third lens, and the fourth lens are all made of chalcogenide glass. The first lens is a meniscus negative lens with its convex surface facing the object side, the second lens is a biconcave lens, the third lens is a biconvex lens, and the fourth lens is a meniscus positive lens with its convex surface facing the image side. The air gap between the first lens and the second lens is 10.299 mm, the air gap between the second lens and the third lens is 2.589 mm, and the air gap between the third lens and the fourth lens is 5.469 mm.

[0005] Furthermore, the first lens has a center thickness of 2 mm, an object-side radius of curvature of 38.44 mm, and an image-side radius of curvature of 13.91 mm; the second lens has a center thickness of 2.2 mm, an object-side radius of curvature of -96.55 mm, and an image-side radius of curvature of 53.78 mm; the third lens has a center thickness of 3.3 mm, an object-side radius of curvature of 103.96 mm, and an image-side radius of curvature of -16.46 mm; and the fourth lens has a center thickness of 4.1 mm, an object-side radius of curvature of -23.87 mm, and an image-side radius of curvature of -11.08 mm.

[0006] Furthermore, the lens has a focal length of 3.8mm, a relative aperture of 1.0, a field of view of 89.2°×75.9°, and an optical distortion of -3%.

[0007] Furthermore, the lens operates at a temperature of -40℃ to +60℃ and has a working wavelength of 10 to 12μm.

[0008] Furthermore, all surfaces of all lenses are aspherical and satisfy the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height Y along the optical axis; R is the paraxial curvature fitting radius of the mirror; K is the conic coefficient; and A, B, C, and D are higher-order aspherical coefficients.

[0009] Furthermore, it also includes an aperture stop, which is disposed between the second lens and the third lens, and the air gap between the second lens and the aperture stop is 2.489.

[0010] An imaging device includes the aforementioned large field-of-view, low-distortion long-wave infrared lens and a detector for receiving images from the lens.

[0011] Furthermore, the detector has 640*512 pixels, a pixel size of 12μm, and is an uncooled infrared detector.

[0012] Furthermore, the total optical length of the imaging device is 37.957 mm, and the back clipping is 8 mm.

[0013] In summary, the large field-of-view, low-distortion long-wave infrared lens provided in this application has a focal length of 3.8mm, a relative aperture of 1.0, a field of view of 89.2°×75.9°, an optical distortion of -3%, an operating temperature range of -40℃ to +60℃, and an operating wavelength range of 10~12μm. It is suitable for uncooled infrared detectors with a pixel count of 640*512 and a pixel size of 12μm. This lens has a small number of lenses, a simple structure, a large field of view, low distortion, and clear imaging. Furthermore, the imaging device has a total optical length of 37.957mm and a backstop of 8mm, making it compact, lightweight, and less affected by temperature. Through the coordination of optical materials and lens arrangement, temperature compensation can be achieved, ensuring the stability of the optical axis during temperature changes, thus achieving a thermal-free design and reducing distortion. Attached Figure Description

[0014] 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.

[0015] 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 MTF plot of a large field-of-view, low-distortion long-wave infrared lens at 20℃; Figure 3 MTF plot of a large field-of-view, low-distortion long-wave infrared lens at 60℃; Figure 4 MTF plot of a large field-of-view, low-distortion long-wave infrared lens at -40℃; Figure 5 A dot plot of a large field-of-view, low-distortion long-wave infrared lens at 20℃; Figure 6 A dot plot of a large field-of-view, low-distortion long-wave infrared lens at 60℃; Figure 7 A dot plot of a large field-of-view, low-distortion long-wave infrared lens at -40℃; Figure 8 This is a field curvature distortion diagram of a large field-of-view, low-distortion long-wave infrared lens.

[0016] Label Explanation: 11. First lens; 12. Second lens; 13. Third lens; 14. Fourth lens; 15. Aperture stop; 21. Protective window; 22. Image plane. Detailed Implementation

[0017] 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.

[0018] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[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 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.

[0020] This application provides an imaging device, including a large field-of-view, low-distortion long-wave infrared lens (hereinafter referred to as the lens) and a detector for receiving the image captured by the lens. The lens has a focal length of 3.8 mm, a relative aperture of 1.0, a field of view of 89.2° × 75.9°, an optical distortion of -3%, an operating temperature of -40℃ to +60℃, and an operating wavelength of 10 to 12 μm. The detector has 640*512 pixels, a pixel size of 12 μm, and is an uncooled infrared detector.

[0021] like Figure 1 As shown, in one embodiment, the lens comprises a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis from the object side to the image side. The first lens is a meniscus negative lens with its convex surface facing the object side, the second lens is a biconcave lens, the third lens is a biconvex lens, and the fourth lens is a meniscus positive lens with its convex surface facing the image side. All four lenses are made of chalcogenide glass.

[0022] Please also refer to Table 1. In one embodiment, the air gap between the first lens and the second lens is 10.299 mm, the air gap between the second lens and the third lens is 2.589 mm, and the air gap between the third lens and the fourth lens is 5.469 mm.

[0023] Furthermore, the first lens has a center thickness of 2 mm, an object-side radius of curvature of 38.44 mm, and an image-side radius of curvature of 13.91 mm; the second lens has a center thickness of 2.2 mm, an object-side radius of curvature of -96.55 mm, and an image-side radius of curvature of 53.78 mm; the third lens has a center thickness of 3.3 mm, an object-side radius of curvature of 103.96 mm, and an image-side radius of curvature of -16.46 mm; and the fourth lens has a center thickness of 4.1 mm, an object-side radius of curvature of -23.87 mm, and an image-side radius of curvature of -11.08 mm.

[0024] In one embodiment, the detector includes a protective window and an image plane arranged sequentially. The light beam passes through a first lens, a second lens, and a third lens sequentially from left to right, and then forms an image on the image plane through the protective window.

[0025] In one embodiment, the total optical length of the imaging system (distance from the object-side surface of the first lens to the image plane) is 37.957 mm, and the back clipping (distance from the image-side surface of the fourth lens to the image plane) is 8 mm. It can be determined that this imaging device has a short total optical length, a compact structure, and a small size, which is beneficial for achieving miniaturized design.

[0026] Understandably, with Figure 1 For example, the optical axis transmission 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 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.

[0027] Table 1 Parameters of each lens In one embodiment, all lens surfaces are aspherical and satisfy the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at height Y along the optical axis; R is the paraxial curvature fitting radius of the mirror; K is the conic coefficient; and A, B, C, D, and E are the higher-order aspherical coefficients. Furthermore, the data for each aspherical surface are shown in Table 2.

[0028] Table 2 Aspherical Data Based on the above embodiments, it can be determined that the large field of view, low distortion, long-wave infrared lens has a small number of lenses, a simple and compact structure, and all lenses are made of chalcogenide glass. All lens surfaces are aspherical, achieving passive adiabaticization, reducing distortion, and improving imaging quality.

[0029] Please see Figures 2 to 8 , Figure 2 This is the MTF chart of the lens at 20°C. Figure 3 This is the MTF chart of the lens at 60°C. Figure 4 This is the MTF chart of the lens at -40℃. Figure 5 Figure 6 shows the point plot of the lens at 20°C, and Figure 7 shows the point plot of the lens at 60°C. Figure 7 This is a dot plot of the lens at -40℃. Figure 8 This is a field curvature distortion diagram of the lens. As can be seen from the attached diagram, the image quality of the lens is good, and the aberrations in all temperature ranges are well corrected, with the blur spots corrected to near the size of the Airy disk.

[0030] In summary, the large field-of-view, low-distortion long-wave infrared lens provided in this application has a focal length of 3.8mm, a relative aperture of 1.0, a field of view of 89.2°×75.9°, an optical distortion of -3%, an operating temperature range of -40℃ to +60℃, and an operating wavelength range of 10~12μm. It is suitable for uncooled infrared detectors with a pixel count of 640*512 and a pixel size of 12μm. This lens has a small number of lenses, a simple structure, a large field of view, low distortion, and clear imaging. Furthermore, the imaging device has a total optical length of 37.957mm and a backstop of 8mm, making it compact, lightweight, and less affected by temperature. Through the coordination of optical materials and lens arrangement, temperature compensation can be achieved, ensuring the stability of the optical axis during temperature changes, thus achieving a thermal-free design and reducing distortion.

[0031] 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 long-wave infrared lens with a large field of view and low distortion, characterized in that, It is composed of a first lens, a second lens, a third lens and a fourth lens arranged sequentially from the object side to the image side along the optical axis. The first lens, the second lens, the third lens and the fourth lens are all made of chalcogenide glass. The first lens is a meniscus negative lens with its convex surface facing the object side, the second lens is a biconcave lens, the third lens is a biconvex lens and the fourth lens is a meniscus positive lens with its convex surface facing the image side. The air gap between the first lens and the second lens is 10.299 mm, the air gap between the second lens and the third lens is 2.589 mm, and the air gap between the third lens and the fourth lens is 5.469 mm.

2. The large field-of-view, low-distortion long-wave infrared lens according to claim 1, characterized in that, The first lens has a center thickness of 2 mm, an object-side radius of curvature of 38.44 mm, and an image-side radius of curvature of 13.91 mm; the second lens has a center thickness of 2.2 mm, an object-side radius of curvature of -96.55 mm, and an image-side radius of curvature of 53.78 mm; the third lens has a center thickness of 3.3 mm, an object-side radius of curvature of 103.96 mm, and an image-side radius of curvature of -16.46 mm; and the fourth lens has a center thickness of 4.1 mm, an object-side radius of curvature of -23.87 mm, and an image-side radius of curvature of -11.08 mm.

3. The large field-of-view, low-distortion long-wave infrared lens according to claim 1, characterized in that, The lens has a focal length of 3.8mm, a relative aperture of 1.0, a field of view of 89.2°×75.9°, and an optical distortion of -3%.

4. The large field-of-view, low-distortion long-wave infrared lens according to claim 1, characterized in that, The lens operates at a temperature of -40℃ to +60℃ and has a working wavelength of 10 to 12μm.

5. The large field-of-view, low-distortion long-wave infrared lens according to claim 1, characterized in that, All surfaces of all lenses are aspherical and satisfy the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height Y along the optical axis; R is the paraxial curvature fitting radius of the mirror; K is the conic coefficient; and A, B, C, and D are higher-order aspherical coefficients.

6. The large field-of-view, low-distortion long-wave infrared lens according to claim 1, characterized in that, It also includes an aperture stop, which is disposed between the second lens and the third lens, and the air gap between the second lens and the aperture stop is 2.

489.

7. An imaging device, characterized in that, It includes the large field-of-view, low-distortion long-wave infrared lens as described in any one of claims 1-6, and the detector that receives the image from the lens.

8. The imaging apparatus according to claim 7, characterized in that, The detector has 640*512 pixels, a pixel size of 12μm, and is an uncooled infrared detector.

9. The imaging apparatus according to claim 7, characterized in that, The imaging device has an optical length of 37.957 mm and a back clip of 8 mm.

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