Double-view-field athermalization long-wave infrared lens and imaging device

Abstract

The invention discloses an imaging device. The imaging device comprises a double-view-field athermalization long-wave infrared lens and a detector for receiving an image formed by the infrared lens. The infrared lens can be switched between the focal length of 65 mm and the focal length of 130 mm. The infrared lens is composed of a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged in the optical axis direction. The first lens, the second lens, the fourth lens and the fifth lens are all meniscus positive lenses of which the convex surfaces face the object side; the third lens is a meniscus negative lens of which the convex surface faces the object side; the second lens and the third lens can move synchronously in the optical axis direction. According to the infrared lens, only one focusing group, namely the second lens and the third lens which move synchronously, is used, the stability of the imaging quality at the extreme temperature is realized through optical passive athermalization, mechanical compensation is not needed, and the structure is simple.

Description

Technical Field

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

[0002] With the development of science and technology, long-wave infrared imaging technology is increasingly being used in industry, national defense, and medical and health fields. Long-wave infrared generally refers to wavelengths of 8-14 micrometers. Light in this band has a strong ability to penetrate clouds and fog and identify camouflage. Furthermore, long-wave infrared detection is, in principle, a passive detection method, relying on the heat emitted by the target for imaging and identification, effectively avoiding interference from strong light and flashes. Long-wave infrared focusing lenses can change the focal length by altering the lens position to meet different observation needs; passive optical pyrolysis maintains relatively stable optical performance of the lens under extreme temperatures through the appropriate combination of lens materials, and has wide applications.

[0003] In optical lens design, to achieve different observation field of view requirements, continuous zoom systems or dual-field-of-view systems are often employed. Continuous zoom optical systems achieve focal length changes by precisely controlling the movement of the zoom group and compensation group while maintaining image sharpness. However, the system structure is relatively complex, difficult to manufacture and assemble, and places higher demands on the backend chip computing power and image processing capabilities. In contrast, dual-field-of-view optical systems have a simpler structure and higher reliability, enabling target searching at short focal lengths and precise target tracking and measurement at long focal lengths. However, dual-field-of-view lens designs typically require moving the focusing group to switch focal lengths and additional adjustment lenses to compensate for temperature changes. This means that, like continuous zoom lenses, dual-field-of-view lenses require two motors to adjust the imaging effect of the optical system, increasing structural complexity. Summary of the Invention

[0004] Therefore, it is necessary to provide a dual-field-of-view pyrometric long-wave infrared lens and imaging device with a relatively simple structure.

[0005] The technical solution proposed in this application is as follows: A dual-field-of-view pyrometric long-wave infrared lens is available, capable of switching between a 65mm focal length and a 130mm focal length. The infrared lens comprises a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis. The first, second, fourth, and fifth lenses are all positive meniscus lenses with their convex surfaces facing the object side, while the third lens is a negative meniscus lens with its convex surface facing the object side. The second and third lenses are capable of synchronous movement along the optical axis. The air gap between the second and third lenses is 16.107 mm, and the air gap between the fourth and fifth lenses is 36.920 mm. Furthermore, when the focal length of the infrared lens is 65 mm, the air gap between the first and second lenses is 9.346 mm, and the air gap between the third and fourth lenses is 57.868 mm. When the focal length of the infrared lens is 130 mm, the air gap between the first and second lenses is 57.978 mm, and the air gap between the third and fourth lenses is 9.236 mm.

[0006] Further, the first lens has a center thickness of 10.0 mm, an object-side radius of curvature of 108.589 mm, and an image-side radius of curvature of 118.860 mm; the second lens has a center thickness of 10.0 mm, an object-side radius of curvature of 66.314 mm, and an image-side radius of curvature of 82.798 mm; the third lens has a center thickness of 4.2 mm, an object-side radius of curvature of 154.590 mm, and an image-side radius of curvature of 61.033 mm; the fourth lens has a center thickness of 8.7 mm, an object-side radius of curvature of 119.267 mm, and an image-side radius of curvature of 5462.214 mm; and the fifth lens has a center thickness of 7.0 mm, an object-side radius of curvature of 47.024 mm, and an image-side radius of curvature of 50.392 mm.

[0007] Furthermore, the first lens, the third lens, and the fifth lens are all made of germanium single crystal, while the second lens and the fourth lens are both made of chalcogenide glass.

[0008] Furthermore, the infrared lens has a relative aperture of 1.0, an operating temperature of -40℃ to +60℃, and an operating wavelength of 8 to 12 μm.

[0009] Furthermore, the image-side surfaces of the second lens, the third lens, and the fourth lens are all aspherical and satisfy the aspherical formula:

[0010] 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.

[0011] Furthermore, the image-side surfaces of the third lens and the fourth lens are both binary surfaces, which include an aspherical surface and a diffraction surface.

[0012] An imaging device includes the aforementioned dual-field-of-view thermally ablation long-wave infrared lens and a detector that receives the image captured by the infrared lens.

[0013] Furthermore, the detector is an uncooled long-wave infrared detector with 640*512 pixels and a pixel size of 12μm.

[0014] The infrared lens provided in this application has a focal length that can switch between 65mm and 130mm, a zoom ratio of 2x, and achieves clear imaging in both fields of view. It has a relative aperture of 1.0, an operating temperature range of -40℃ to +60℃, and an operating wavelength range of 8 to 12μm. The corresponding detector has a pixel count of 640*512, a pixel size of 12μm, and is an uncooled long-wave infrared detector. It uses only one focusing group, namely a synchronously moving second and third lens, and achieves stable imaging quality under extreme temperatures through passive optical pyrolysis, requiring no mechanical compensation and featuring a simple structure. Attached Figure Description

[0015] 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.

[0016] Figure 1 A schematic diagram of the optical path structure of a dual-field-of-view thermally ablated long-wave infrared lens with a focal length of 65mm, provided in an embodiment of this application; Figure 2 for Figure 1 The diagram shows the dot pattern of the infrared lens at 20°C. Figure 3 for Figure 1 The diagram shows the dot pattern of the infrared lens at -40℃. Figure 4 for Figure 1 The diagram shows the dot pattern of the infrared lens at 60°C. Figure 5 for Figure 1 The MTF diagram of the infrared lens shown is displayed at 20°C. Figure 6 for Figure 1 The MTF plot of the infrared lens shown is displayed at -40℃. Figure 7 for Figure 1 The MTF diagram of the infrared lens at 60°C is shown. Figure 8 A schematic diagram of the optical path structure of a dual-field-of-view thermally ablated long-wave infrared lens with a focal length of 130mm, provided in an embodiment of this application. Figure 9 for Figure 8 The diagram shows the dot pattern of the infrared lens at 20°C. Figure 10 for Figure 8 The diagram shows the dot pattern of the infrared lens at -40℃. Figure 11 for Figure 8 The diagram shows the dot pattern of the infrared lens at 60°C. Figure 12 for Figure 8 The MTF diagram of the infrared lens shown is displayed at 20°C. Figure 13 for Figure 8 The MTF plot of the infrared lens shown is displayed at -40℃. Figure 14 for Figure 8 The MTF diagram of the infrared lens at 60°C is shown.

[0017] Label Explanation: 11. First lens; 12. Second lens; 13. Third lens; 14. Fourth lens; 15. Fifth lens; 21. Protective window; 22. Image plane. Detailed Implementation

[0018] 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.

[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] Please see Figure 1 and Figure 8 This application discloses an imaging device, including a dual-field-of-view thermal differential long-wave infrared lens (hereinafter referred to as the infrared lens) and a detector for receiving images from the infrared lens. The infrared lens has a dual field of view, can switch between a 65mm focal length and a 130mm focal length, and has a relative aperture of 1.0, an operating temperature of -40℃ to +60℃, and an operating wavelength of 8 to 12μm. The detector is an uncooled long-wave infrared detector with 640*512 pixels and a pixel size of 12μm.

[0021] 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. The first lens 11, second lens 12, fourth lens 14, and fifth lens 15 are all positive meniscus lenses with their convex surfaces facing the object side, and the third lens 13 is a negative meniscus lens with its convex surface facing the object side. The second lens 12 and the third lens 13 are capable of moving synchronously along the optical axis.

[0022] As shown in Table 1, the air gap between the second lens 12 and the third lens 13 is 16.107 mm, and the air gap between the fourth lens 14 and the fifth lens 15 is 36.920 mm. Furthermore, when the focal length of the infrared lens is 65 mm, the air gap between the first lens 11 and the second lens 12 is 9.346 mm, and the air gap between the third lens 13 and the fourth lens 14 is 57.868 mm; when the focal length of the infrared lens is 130 mm, the air gap between the first lens 11 and the second lens 12 is 57.978 mm, and the air gap between the third lens 13 and the fourth lens 14 is 9.236 mm.

[0023] Furthermore, the center thickness of the first lens 11 is 10.0 mm, the radius of curvature of the object-side surface is 108.589 mm, and the radius of curvature of the image-side surface is 118.860 mm; the center thickness of the second lens 12 is 10.0 mm, the radius of curvature of the object-side surface is 66.314 mm, and the radius of curvature of the image-side surface is 82.798 mm; the center thickness of the third lens 13 is 4.2 mm, the radius of curvature of the object-side surface is 154.590 mm, and the radius of curvature of the image-side surface is 61.033 mm; the center thickness of the fourth lens 14 is 8.7 mm, the radius of curvature of the object-side surface is 119.267 mm, and the radius of curvature of the image-side surface is 5462.214 mm; and the center thickness of the fifth lens 15 is 7.0 mm, the radius of curvature of the object-side surface is 47.024 mm, and the radius of curvature of the image-side surface is 50.392 mm.

[0024] In one embodiment, the detector includes a protective window 21 and an image plane 22 arranged sequentially. Light passes sequentially through a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, and a fifth lens 15, then through the protective window 21 and forms an image on the image plane 22. Further, the air gap between the fifth lens 15 and the protective window 21 is 32.031 mm, and the air gap between the protective window 21 and the image plane 22 is 2.155 mm.

[0025] It should be noted that, understandably, in Figure 1 and Figure 8In the embodiment shown, light is transmitted from left to right. Taking the first lens 11 as an example, the left side S1 surface of the first lens 11 is the object side surface, and the right side S2 surface is the image side surface. The same applies to other lenses, which will not be described in detail here.

[0026] In one embodiment, the first lens 11, the third lens 13, and the fifth lens 15 are all made of germanium single crystal, while the second lens 12 and the fourth lens 14 are made of chalcogenide glass. Specific parameters of the lenses can be found in Table 1.

[0027] Table 1 Parameters of each lens In one embodiment, the image-side surfaces of the second lens 12, the third lens 13, and the fourth lens 14 are all aspherical and satisfy the aspherical formula.

[0028] 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. Furthermore, the above aspherical data are shown in Table 2.

[0029] Table 2 Aspherical Data In one embodiment, the image-side surfaces of the third lens 13 and the fourth lens 14 are both binary surfaces, which include an aspherical surface and a diffractive surface. Furthermore, the image-side surfaces of the third lens 13 and the fourth lens 14 satisfy the equation for binary surfaces 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. Table 3 Binary Surface Data Please see Figures 2-7 as well as Figures 9 to 14 , Figures 2-4 The image shows the dot plots of the infrared lens at a focal length of 65mm under conditions of 20℃, -40℃, and 60℃. Figures 5-7 MTF charts of the infrared lens at a focal length of 65mm at 20℃, -40℃, and 60℃. Figures 9-11 The image shows the dot plots of the infrared lens at a focal length of 130mm under conditions of 20℃, -40℃, and 60℃. Figures 12-14The image shows the MTF (Mean Transformation Factor) of the infrared lens at a focal length of 130mm at temperatures of 20℃, -40℃, and 60℃. The images show that the MTF of this infrared lens is close to the diffraction limit at all temperatures, and the root mean square diameter of the diffuse spot is smaller than the Airy disk diameter, indicating good image quality.

[0030] In summary, the infrared lens provided in this application has a focal length that can switch between 65mm and 130mm, a zoom ratio of 2x, achieves clear imaging in both fields of view, has a relative aperture of 1.0, an operating temperature range of -40℃ to +60℃, and an operating wavelength range of 8 to 12μm. The corresponding detector has 640*512 pixels, a pixel size of 12μm, and is an uncooled long-wave infrared detector. It uses only one focusing group, namely the synchronously moving second lens 12 and third lens 13, and achieves stable imaging quality under extreme temperatures through passive optical pyrolysis, requiring no mechanical compensation and featuring a simple structure.

[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 dual-field-of-view thermally differential long-wave infrared lens, characterized in that, Capable of switching between a 65mm focal length and a 130mm focal length, the infrared lens consists of a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis; the first lens, the second lens, the fourth lens, and the fifth lens are all positive meniscus lenses with their convex surfaces facing the object side, and the third lens is a negative meniscus lens with its convex surfaces facing the object side; the second lens and the third lens can move synchronously along the optical axis. The air gap between the second and third lenses is 16.107 mm, and the air gap between the fourth and fifth lenses is 36.920 mm. Furthermore, when the focal length of the infrared lens is 65 mm, the air gap between the first and second lenses is 9.346 mm, and the air gap between the third and fourth lenses is 57.868 mm. When the focal length of the infrared lens is 130 mm, the air gap between the first and second lenses is 57.978 mm, and the air gap between the third and fourth lenses is 9.236 mm.

2. The dual-field-of-view thermally differential long-wave infrared lens according to claim 1, characterized in that, The first lens has a center thickness of 10.0 mm, an object-side radius of curvature of 108.589 mm, and an image-side radius of curvature of 118.860 mm; the second lens has a center thickness of 10.0 mm, an object-side radius of curvature of 66.314 mm, and an image-side radius of curvature of 82.798 mm; the third lens has a center thickness of 4.2 mm, an object-side radius of curvature of 154.590 mm, and an image-side radius of curvature of 61.033 mm; the fourth lens has a center thickness of 8.7 mm, an object-side radius of curvature of 119.267 mm, and an image-side radius of curvature of 5462.214 mm; and the fifth lens has a center thickness of 7.0 mm, an object-side radius of curvature of 47.024 mm, and an image-side radius of curvature of 50.392 mm.

3. The dual-field-of-view thermally differential long-wave infrared lens according to claim 1, characterized in that, The first lens, the third lens, and the fifth lens are all made of germanium single crystal, while the second lens and the fourth lens are both made of chalcogenide glass.

4. The dual-field-of-view thermally differential long-wave infrared lens according to claim 1, characterized in that, The infrared lens has a relative aperture of 1.0, an operating temperature of -40℃ to +60℃, and an operating wavelength of 8 to 12μm.

5. The dual-field-of-view thermally differential long-wave infrared lens according to claim 1, characterized in that, The image-side surfaces of the second lens, the third lens, and the fourth 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.

6. The dual-field-of-view thermally differential long-wave infrared lens according to claim 5, characterized in that, The image-side surfaces of the third lens and the fourth lens are both binary surfaces, which include an aspherical surface and a diffraction surface.

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

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

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