Double-view-field infrared lens and imaging device
By designing a combination of germanium single-crystal lenses with variable focal length, the problems of complex structure and high cost of dual-field infrared lenses were solved, achieving clear imaging over a wide temperature range, simplifying the lens structure and reducing costs.
Patent Information
- Application Number
- CN202511373004.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-24
- Publication Date
- 2025-12-05
AI Technical Summary
Existing dual-field infrared lenses have complex structures, high costs, and require additional temperature and distance compensation adjustment lenses, which affects the simplicity of the system.
Design an infrared lens consisting of a first lens, a second lens, a third lens, and a fourth lens. The lens material is germanium single crystal, and the lens surface is aspherical or binary. The focal length can be switched between 25mm and 75mm. Temperature compensation is achieved through optical passive thermal ablation, omitting the mechanical compensation structure.
It achieves clear imaging with variable focal length and dual field of view, with a temperature range of -40℃ to +60℃, requires no mechanical compensation, has a simple structure, and low cost.
Smart Images
Figure CN121069608A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of infrared equipment technology, specifically relating to a dual-field infrared lens and imaging device. Background Technology
[0002] With the development of science and technology, infrared imaging technology has been widely used in national defense, industry, medicine and other fields. Infrared detection has a certain ability to penetrate smoke, fog, haze and snow, as well as the ability to identify camouflage. It is not blinded by strong light or flashes, and can achieve long-distance, all-weather observation. It is especially suitable for target detection at night and under adverse weather conditions.
[0003] Dual-field-of-view infrared lenses enable wide-field-of-view search and precise identification in narrow-field-of-view applications. In modern military applications, dual-field-of-view infrared lenses are widely used in guidance, surveillance, forward-looking infrared systems, target detection, and tracking. In civilian applications, they can be used in photography and space remote sensing.
[0004] In the design of dual-field optical systems, there are usually many lenses, large volume, and high cost. In order to further compensate for the effects of temperature and distance, in addition to setting adjustment lenses for field switching, additional adjustment lenses for temperature and distance compensation are required, which further complicates the structure of dual-field optical systems. Summary of the Invention
[0005] Therefore, it is necessary to provide a dual-field infrared lens and imaging device with a relatively simple structure.
[0006] The technical solution proposed in this application is as follows: A dual-field infrared lens capable of switching between a 25mm focal length and a 75mm focal length, the infrared lens comprising a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis; the first lens is a meniscus 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 lens with its convex surface facing the image side; the second lens is movable along the optical axis. The air gap between the third lens and the fourth lens is 30.33 mm; and when the focal length of the infrared lens is 25 mm, the air gap between the first lens and the second lens is 12.59 mm, and the air gap between the second lens and the third lens is 31.43 mm; when the focal length of the infrared lens is 75 mm, the air gap between the first lens and the second lens is 40.32 mm, and the air gap between the second lens and the third lens is 3.7 mm.
[0007] Furthermore, the first lens has a center thickness of 9.7 mm, an object-side radius of curvature of 110.7 mm, and an image-side radius of curvature of 183.93 mm; the second lens has a center thickness of 3.55 mm, an object-side radius of curvature of -130.2 mm, and an image-side radius of curvature of 165.2 mm; the third lens has a center thickness of 5.55 mm, an object-side radius of curvature of 169.22 mm, and an image-side radius of curvature of -332.6 mm; and the fourth lens has a center thickness of 4.5 mm, an object-side radius of curvature of -731.7 mm, and an image-side radius of curvature of -101.85 mm.
[0008] Furthermore, the first lens, the second lens, the third lens, and the fourth lens are all made of germanium single crystal.
[0009] 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 14μm.
[0010] Furthermore, the image-side surfaces of the first lens and the second lens, as well as the object-side surfaces of the second lens, the third lens, and the fourth lens, 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.
[0011] Furthermore, the object-side surface of the third lens is a binary surface, which includes an aspherical surface and a diffraction surface.
[0012] An imaging device includes the aforementioned dual-field-of-view infrared lens and a detector that receives images from 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] In summary, the infrared lens provided in this application has a focal length that can switch between 25mm and 75mm, a zoom ratio of 3x, 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 14μm. 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 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 This is a schematic diagram of the optical path structure of a dual-field infrared lens with a focal length of 25mm, 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 This is a schematic diagram of the optical path structure of a dual-field infrared lens with a focal length of 75mm, 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; 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] like Figure 1 and Figure 8 As shown, this application provides an imaging device, including a dual-field-of-view 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, a zoom ratio of 3, and a focal length that can be switched between 25mm and 75mm. The relative aperture of the infrared lens is 1.0, the operating temperature is -40℃ to +60℃, and the operating wavelength is 8 to 14μm. 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, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis; the first lens is a meniscus 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 lens with its convex surface facing the image side; the second lens is movable along the optical axis.
[0022] Furthermore, the air gap between the third and fourth lenses is 30.33 mm. When the focal length of the infrared lens is 25 mm, the air gap between the first and second lenses is 12.59 mm, and the air gap between the second and third lenses is 31.43 mm; when the focal length of the infrared lens is 75 mm, the air gap between the first and second lenses is 40.32 mm, and the air gap between the second and third lenses is 3.7 mm.
[0023] Furthermore, the center thickness of the first lens is 9.7 mm, the radius of curvature of the object side is 110.7 mm, and the radius of curvature of the image side is 183.93 mm; the center thickness of the second lens is 3.55 mm, the radius of curvature of the object side is -130.2 mm, and the radius of curvature of the image side is 165.2 mm; the center thickness of the third lens is 5.55 mm, the radius of curvature of the object side is 169.22 mm, and the radius of curvature of the image side is -332.6 mm; and the center thickness of the fourth lens is 4.5 mm, the radius of curvature of the object side is -731.7 mm, and the radius of curvature of the image side is -101.85 mm.
[0024] In one embodiment, the detector includes a protective window and an image plane arranged sequentially. Light passes sequentially through a first lens, a second lens, a third lens, and a fourth lens, then through the protective window and is imaged on the image plane. Further, the air gap between the fourth lens and the protective window is 20.78 mm, and the air gap between the protective window and the image plane is 0.67 mm.
[0025] It should be noted that, understandably, in Figure 1 and Figure 8 In the embodiment shown, light is transmitted from left to right. Taking the first lens as an example, the left side S1 of the first lens is the object side and the right side S2 is the image side. The same applies to other lenses, which will not be described in detail here.
[0026] In one embodiment, the first lens, second lens, third lens, and fourth lens are all made of germanium single crystal, and the object side of the first lens is coated with an anti-friction hard carbon film. 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 first lens and the second lens, as well as the object-side surfaces of the second lens, the third lens, and the fourth lens, 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 object-side surface of the third lens is a binary surface, and the binary surface includes an aspherical surface and a diffractive surface. Furthermore, the object-side surface of the third lens satisfies the equation for a binary surface in Zemax: M(B1ρ) 2 +B2ρ 4 +B3ρ 6 Where M is the diffraction order (1), B1, B2, and B3 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 25mm under conditions of 20℃, -40℃, and 60℃. Figures 5-7 MTF charts of the infrared lens at a focal length of 25mm at 20℃, -40℃, and 60℃. Figures 9-11 The image shows the dot plots of the infrared lens at a focal length of 75mm under conditions of 20℃, -40℃, and 60℃. Figures 12-14 The image shows the MTF (Mean Transformation Factor) of the infrared lens at a focal length of 75mm 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 25mm and 75mm, a zoom ratio of 3x, 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 14μm. 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 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 view infrared lens characterized in that, The infrared lens can be switched between 25mm focal length and 75mm focal length, and is composed of a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the optical axis; the first lens is a convex moon positive lens facing the object side, the second lens is a double-concave lens, the third lens is a double-convex lens, and the fourth lens is a convex moon positive lens facing the image side; the second lens can move along the optical axis; Wherein, the air gap between the third lens and the fourth lens is 30.33mm; and when the focal length of the infrared lens is 25mm, the air gap between the first lens and the second lens is 12.59mm, the air gap between the second lens and the third lens is 31.43mm, when the focal length of the infrared lens is 75mm, the air gap between the first lens and the second lens is 40.32mm, and the air gap between the second lens and the third lens is 3.7mm.
2. The dual view infrared lens of claim 1, wherein, The center thickness of the first lens is 9.7mm, the curvature radius of the object side is 110.7mm, and the curvature radius of the image side is 183.93mm; the center thickness of the second lens is 3.55mm, the curvature radius of the object side is-130.2mm, and the curvature radius of the image side is 165.2mm; the center thickness of the third lens is 5.55mm, the curvature radius of the object side is 169.22mm, and the curvature radius of the image side is-332.6mm; the center thickness of the fourth lens is 4.5mm, the curvature radius of the object side is-731.7mm, and the curvature radius of the image side is-101.85mm.
3. The dual view infrared lens of claim 1, wherein, The materials of the first lens, the second lens, the third lens and the fourth lens are all germanium single crystals.
4. The dual view infrared lens of claim 1, wherein, The relative aperture of the infrared lens is 1.0, the working temperature is-40℃~+60℃, and the working waveband is 8~14μm.
5. The dual view infrared lens of claim 1, wherein, The image side of the first lens, the second lens, and the object side of the second lens, the third lens and the fourth lens are all aspheric surfaces, and satisfy the aspheric surface formula: Wherein, Z is the distance vector height of the aspheric surface at the height r along the optical axis direction; c=1 / R; R is the paraxial curvature fitting radius of the mirror surface; k is the conic coefficient; A, B, C, D, E are high-order aspheric coefficients.
6. The dual view infrared lens of claim 5, wherein, The object side of the third lens is a binary surface, and the binary surface includes an aspheric surface and a diffractive surface.
7. An image forming apparatus characterized by comprising: The dual-view infrared lens of any one of claims 1-6 and a detector receiving the image formed by the infrared lens are included.
8. The imaging apparatus according to claim 7, wherein The detector is a non-cooled long-wave infrared detector with 640*512 pixels and a pixel size of 12μm.