An athermal long-wave fixed-focus lens and an imaging device
By designing an athermalized long-wavelength fixed-focus lens made of chalcogenide glass, the number of lenses is small and the structure is compact, which solves the problem of high cost of existing passive athermalized optical systems and achieves high-quality imaging over a wide temperature range.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHENGDU JINGPIN NIGHT VISION OPTOELECTRONICS TECHNOLOGY CO LTD
- Filing Date
- 2025-06-20
- Publication Date
- 2026-06-09
Smart Images
Figure CN120491283B_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of infrared lens technology, specifically relating to a non-thermalized long-wavelength fixed-focus lens and imaging device. Background Technology
[0002] Long-wave infrared uncooled optical systems have been widely used in both military and civilian fields because infrared lenses offer advantages such as good anti-interference performance, long operating range at night, strong penetration of smoke and haze, all-weather and all-time operation, multi-target panoramic observation, tracking, and target identification capabilities, and good anti-stealth capabilities. Therefore, increasingly higher demands are being placed on the imaging quality of these optical systems. Passive athermalization of optics compensates for image plane shifts caused by environmental temperature changes by using a reasonable combination of materials based on the differences in thermal analysis parameters of optical materials within the system, thereby fixing the optimal image plane and achieving a athermalized design for the system. However, existing passive athermalization optical systems often use germanium lenses, which are relatively expensive. Summary of the Invention
[0003] The technical problem to be solved by this application is that existing passive athermal optical systems use germanium lenses, which are costly. To solve this technical problem, this application provides a low-cost athermal long-wavelength fixed-focus lens and imaging device.
[0004] The technical solution proposed in this application is as follows:
[0005] A non-thermalized long-wavelength fixed-focus lens has an effective focal length of 4.5mm and an F-number of 1.0. The non-thermalized long-wavelength fixed-focus lens includes a first lens, a second lens, and a third lens arranged sequentially along the optical axis transmission direction. The first lens is a meniscus negative lens with its convex surface facing the object side, the second lens is a meniscus positive lens with its convex surface facing the image side, and the third lens is a biconvex lens. The first lens, the second lens, and the third lens are all made of chalcogenide glass.
[0006] Specifically, when the temperature of the anechoic long-wave fixed-focus lens is 20°C, the air gap between the first lens and the second lens is 6.45 mm, and the air gap between the second lens and the third lens is 8.6 mm.
[0007] The aforementioned athermalized long-wavelength fixed-focus lenses have fewer lenses, a simple and compact structure, and all lenses are made of chalcogenide glass, which reduces costs while achieving passive athermalization.
[0008] Furthermore, when the temperature of the anechoic long-wavelength fixed-focus lens is 20°C:
[0009] The first lens has a center thickness of 1 mm, an object-side radius of curvature of 9.16 mm, an aperture of 11 mm, an image-side radius of curvature of 5.8 mm, and an aperture of 9 mm; the second lens has a center thickness of 1.1 mm, an object-side radius of curvature of -109.7 mm, an aperture of 9.6 mm, an image-side radius of curvature of -38.66 mm, and an aperture of 10 mm; the third lens has a center thickness of 2.29 mm, an object-side radius of curvature of 43.91 mm, an aperture of 12.4 mm, an image-side radius of curvature of -20.73 mm, and an aperture of 12.4 mm.
[0010] Furthermore, the object-side surfaces of the first lens, the second lens, and the third lens are all aspherical, satisfying the aspherical formula:
[0011]
[0012] 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.
[0013] Furthermore, the image-side surface of the third lens is both a diffraction surface and an aperture stop, satisfying the diffraction surface expression:
[0014]
[0015] Where M is the diffraction order, N is the index of the polynomial coefficients in the series, and A i It is the coefficient of the 2ith power of ρ, where ρ is the normalized radius.
[0016] Furthermore, the object side of the first lens is coated with an HD film, and the image side of the first lens, as well as the surfaces of the second and third lenses, are coated with an AR film.
[0017] Furthermore, the horizontal field of view of the athermalized long-wave fixed-focus lens is 2ω = 42°.
[0018] An imaging device includes the aforementioned athermalized long-wavelength fixed-focus lens and a detector for receiving images from the athermalized long-wavelength fixed-focus lens.
[0019] Furthermore, the detector has 384×288 pixels, a pixel size of 12μm, and is an uncooled detector.
[0020] Furthermore, the total optical length of the imaging device is 29.94 mm, and the back clipping is 10.5 mm. Attached Figure Description
[0021] 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.
[0022] Figure 1 This is a schematic diagram of the optical path of an imaging device provided in an embodiment of this application;
[0023] Figure 2 A dot plot of a non-thermalized long-wave fixed-focus lens provided in an embodiment of this application at -40°C;
[0024] Figure 3 MTF diagram of an anechoic long-wave fixed-focus lens provided in an embodiment of this application at -40°C;
[0025] Figure 4 Field curvature distortion diagram of an anechoic long-wave fixed-focus lens provided in an embodiment of this application at -40°C;
[0026] Figure 5 A dot plot of an anechoic long-wave fixed-focus lens provided in an embodiment of this application at 80°C;
[0027] Figure 6 MTF diagram of an anechoic long-wave fixed-focus lens provided in an embodiment of this application at 80°C;
[0028] Figure 7 Field curvature distortion diagram of an anechoic long-wave fixed-focus lens provided in an embodiment of this application at 80°C;
[0029] Figure 8 A dot plot of a non-thermalized long-wave fixed-focus lens provided in an embodiment of this application at 20°C;
[0030] Figure 9 MTF diagram of an anechoic long-wave fixed-focus lens provided in an embodiment of this application at 20°C;
[0031] Figure 10 The field curvature distortion diagram of a non-thermalized long-wave fixed-focus lens provided in an embodiment of this application at 20°C.
[0032] Label Explanation:
[0033] 11. First lens; 12. Second lens; 13. Third lens; 100. Protective window; 101. Image plane. Detailed Implementation
[0034] 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.
[0035] 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.
[0036] 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.
[0037] This application provides an imaging device, which includes an athermalized long-wavelength fixed-focus lens and a detector for receiving the image captured by the athermalized long-wavelength fixed-focus lens. The athermalized long-wavelength fixed-focus lens has an effective focal length of 4.5 mm, an F-number of 1.0, and a horizontal field of view of 2ω = 42°. The detector is an uncooled detector with 384 × 288 pixels and a pixel size of 12 μm.
[0038] like Figure 1 As shown, in one embodiment, the athermalized long-wavelength fixed-focus lens includes a first lens, a second lens, and a third lens arranged sequentially along the optical axis transmission direction. The first lens is a meniscus negative lens with its convex surface facing the object side, the second lens is a meniscus positive lens with its convex surface facing the image side, and the third lens is a biconvex lens. The first, second, and third lenses are all made of chalcogenide glass. When the temperature of the athermalized long-wavelength fixed-focus lens is 20°C, the air gap between the first and second lenses is 6.45 mm, and the air gap between the second and third lenses is 8.6 mm.
[0039] Furthermore, when the temperature of the anechoic long-wavelength fixed-focus lens is 20℃: the center thickness of the first lens is 1mm, the radius of curvature of the object side is 9.16mm, the aperture of the object side is 11mm, the radius of curvature of the image side is 5.8mm, and the aperture of the image side is 9mm; the center thickness of the second lens is 1.1mm, the radius of curvature of the object side is -109.7mm, the aperture of the object side is 9.6mm, the radius of curvature of the image side is -38.66mm, and the aperture of the image side is 10mm; the center thickness of the third lens is 2.29mm, the radius of curvature of the object side is 43.91mm, the aperture of the object side is 12.4mm, the radius of curvature of the image side is -20.73mm, and the aperture of the image side is 12.4mm.
[0040] In one embodiment, the detector includes a protective window and an image plane arranged sequentially along the optical axis transmission direction. The light beam passes through a first lens, a second lens, and a third lens sequentially from left to right, and then passes through the protective window sequentially to form an image on the image plane. In practical applications, the air gap between the third lens and the protective window is 7.65 mm, the thickness of the protective window is 0.7 mm, the material is germanium, and the air gap between the protective window and the image plane is 2.15 mm.
[0041] In one embodiment, the total optical length of the imaging device (the distance from the S1 surface of the first lens to the image plane) is 29.94 mm, and the back clipping (the distance from the S6 surface of the third lens to the image plane) is 10.5 mm. It can be determined that the imaging device has a short total optical length, a compact structure, and a small size, which is beneficial for achieving miniaturized design of the device.
[0042] 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.
[0043] Table 1 Parameters of each lens
[0044]
[0045] The aforementioned athermalized long-wavelength fixed-focus lenses have fewer lenses, a simple and compact structure, and all lenses are made of chalcogenide glass, which reduces costs while achieving passive athermalization.
[0046] In one embodiment, the object-side surfaces of the first lens, the second lens, and the third lens are all aspherical and satisfy the aspherical formula:
[0047]
[0048] 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.
[0049] Table 2 Aspherical Data
[0050]
[0051] In one embodiment, the image-side surface of the third lens is both a diffraction surface and an aperture stop, satisfying the diffraction surface expression:
[0052]
[0053] Where M is the diffraction order, N is the index of the polynomial coefficients in the series, and A i It is the coefficient of the 2ith power of ρ, where ρ is the normalized radius. Additionally, the diffraction coefficients are shown in Table 3.
[0054] Table 3 Diffraction coefficients
[0055]
[0056] In one embodiment, the object-side surface of the first lens is coated with an HD film to improve light transmittance and reduce glare and ghosting while providing some physical protection; the image-side surface of the first lens and the surfaces of the second and third lenses are coated with an AR film to reduce reflection and increase light transmittance while providing some physical protection, thereby improving image quality.
[0057] Please see Figures 2 to 10 , Figure 2 This is a dot plot of the athermalized long-wavelength fixed-focus lens at -40℃. Figure 3 This is the MTF chart of the athermalized long-wavelength fixed-focus lens at -40℃. Figure 4 The field curvature distortion of the anechoic long-wave fixed-focus lens at -40℃ is shown. Figure 5 This is a dot plot of the athermalized long-wavelength fixed-focus lens at 80°C. Figure 6 This is the MTF chart of the athermalized long-wavelength fixed-focus lens at 80℃. Figure 7 The field curvature distortion of the anechoic long-wave fixed-focus lens at 80℃ is shown. Figure 8 This is a dot plot of the athermalized long-wavelength fixed-focus lens at 20°C. Figure 9 This is the MTF chart of the athermalized long-wavelength fixed-focus lens at 20°C. Figure 10 This is the field curvature distortion (FCD) diagram of the athermalized long-wavelength fixed-focus lens at 20°C. In the MTF plot, the horizontal axis represents different spatial frequencies, and the vertical axis represents modulation density. (Combined with...) Figures 2 to 10It can be seen that the image quality of this athermalized long-wave fixed-focus lens is very good, and it can adapt to a temperature range of -40℃ to 80℃.
[0058] In summary, the anechoic long-wavelength fixed-focus lens provided in this application has an effective focal length of 4.5mm, an F-number of 1.0, and a horizontal field of view that meets the requirement of 2ω=42°. It is suitable for uncooled detectors with a pixel count of 384×288 and a pixel size of 12μm. It has a small number of lenses, a simple structure, and produces clear images. Furthermore, the imaging device has a total optical length of 29.94mm and a back focal length of 10.5mm, making it compact, lightweight, and less affected by temperature. By combining the different thermal properties of various optical materials and through the arrangement of different optical materials and lenses, temperature compensation can be achieved, ensuring the stability of the optical axis during temperature changes, thus realizing an anechoic design.
Claims
1. A non-heating long-wavelength fixed-focus lens, characterized in that, The effective focal length is 4.5mm and the F number is 1.
0. The anechoic long-wave fixed-focus lens is composed of a first lens, a second lens and a third lens arranged sequentially along the optical axis transmission direction. The first lens is a meniscus negative lens with its convex surface facing the object side, the second lens is a meniscus positive lens with its convex surface facing the image side, and the third lens is a biconvex lens. The first lens, the second lens and the third lens are all made of chalcogenide glass. Specifically, when the temperature of the anechoic long-wavelength fixed-focus lens is 20°C, the air gap between the first lens and the second lens is 6.45 mm, and the air gap between the second lens and the third lens is 8.6 mm. The first lens has a center thickness of 1 mm, an object-side radius of curvature of 9.16 mm, an aperture of 11 mm, an image-side radius of curvature of 5.8 mm, and an aperture of 9 mm. The second lens has a center thickness of 1.1 mm, an object-side radius of curvature of -109.7 mm, an aperture of 9.6 mm, an image-side radius of curvature of -38.66 mm, and an aperture of 10 mm. The third lens has a center thickness of 2.29 mm, an object-side radius of curvature of 43.91 mm, an aperture of 12.4 mm, an image-side radius of curvature of -20.73 mm, and an aperture of 12.4 mm.
2. The athermalized long-wavelength fixed-focus lens according to claim 1, characterized in that, The object-side surfaces of the first lens, the second lens, and the third lens are all aspherical, satisfying 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.
3. The athermalized long-wavelength fixed-focus lens according to claim 1, characterized in that, The image-side surface of the third lens is both a diffraction surface and an aperture stop surface, satisfying the diffraction surface expression: Where M is the diffraction order, N is the index of the polynomial coefficients in the series, and A i It is the coefficient of the 2ith power of ρ, where ρ is the normalized radius.
4. The athermalized long-wavelength fixed-focus lens according to claim 1, characterized in that, The object side of the first lens is coated with an HD film, and the image side of the first lens, as well as the surfaces of the second and third lenses, are coated with an AR film.
5. The athermalized long-wavelength fixed-focus lens according to claim 1, characterized in that, The horizontal field of view of the athermalized long-wave fixed-focus lens is 2ω = 42°.
6. An imaging device, characterized in that, It includes the athermalized long-wavelength fixed-focus lens as described in any one of claims 1-5 and the detector that receives the image from the athermalized long-wavelength fixed-focus lens.
7. The imaging apparatus according to claim 6, characterized in that, The detector has 384×288 pixels, a pixel size of 12μm, and is an uncooled detector.
8. The imaging apparatus according to claim 6, characterized in that, The imaging device has an optical length of 29.94 mm and a back focal length of 10.5 mm.