Long-wave athermalization lens and imaging device
The long-wave athermalized lens with passive athermalization design uses chalcogenide glass lenses and specific aspheric formulas to solve the defocus problem of infrared lenses when the temperature changes, and achieves high-quality imaging and miniaturization of the lens in a wide temperature range.
Patent Information
- Application Number
- CN202511069601.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-31
- Publication Date
- 2025-09-16
AI Technical Summary
Infrared lenses experience severe defocusing when the ambient temperature changes. Existing active athermalization methods increase the size of the lens, necessitating an athermal solution with passive athermalization.
The long-wave athermalized lens is designed using a passive athermalization approach. Two chalcogenide glass lenses are used, and the lens surfaces are coated with an anti-reflection coating. The lenses meet a specific aspheric formula. The lens designs are meniscus positive lenses and biconvex lenses, which combine binary surfaces and diffraction surfaces to achieve athermalization.
The lens has stable imaging quality in a wide temperature range, simple structure, low cost, and is conducive to miniaturization design.
Smart Images
Figure CN120652661A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the field of infrared optical equipment technology, and specifically relates to a long-wave athermal lens and imaging device. Background Art
[0002] Typical infrared lenses require an operating temperature range of -40°C to 60°C. However, due to the large thermal expansion coefficient and temperature variation coefficient of the infrared lens material, changes in ambient temperature can significantly alter the refractive index, surface curvature, thickness, and spacing between adjacent lenses. This can cause significant defocusing in the infrared lens. Active athermalization increases the size of the infrared lens. Therefore, there is an urgent need for an infrared lens that uses passive athermalization to achieve athermalization. Summary of the Invention
[0003] Based on this, the present application provides a long-wave athermalized lens and imaging device that achieve athermalization through passive athermalization.
[0004] The technical solutions proposed in this application are: A long-wave athermal lens has an effective focal length of 9.7 mm, an F-number of 1.0, a maximum aperture of 14 mm, an operating band of 8 to 12 μm, and a horizontal field of view angle range of 2w = 26.8°. The long-wave athermal lens includes a first lens and a second lens arranged in sequence along the transmission direction of the optical axis, wherein the first lens is a positive meniscus lens with the convex surface facing the object side, and the second lens is a biconvex lens. The air gap between the first lens and the second lens is 6.85 mm.
[0005] The lens adopts passive athermalization to achieve athermalization of the lens and uses only two lenses. It has a simple structure, low cost and is conducive to miniaturization design.
[0006] Furthermore, the center thickness of the first lens is 2 mm, the curvature radius of the object side is 7.52 mm, and the curvature radius of the image side is 5.78 mm; the center thickness of the second lens is 4.21 mm, the curvature radius of the object side is 40.9 mm, and the curvature radius of the image side is -20.65 mm.
[0007] Furthermore, the first lens and the second lens are both made of chalcogenide glass.
[0008] Furthermore, surfaces of the first lens and the second lens are both coated with anti-reflection films.
[0009] Furthermore, the object-side surface and the image-side surface of the first lens, and the image-side surface of the second 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, D, and E are high-order aspheric coefficients.
[0010] 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.
[0011] An imaging device comprises the long-wave athermalized lens and a detector for receiving images formed by the long-wave athermalized lens.
[0012] Furthermore, the total optical length of the imaging device is 22.56 mm.
[0013] Furthermore, the detector is a non-cooled detector, and the number of pixels is 384*288, and the pixel size is 12μm. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] 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.
[0015] Figure 1 A schematic structural diagram of a long-wavelength athermalized lens provided in one embodiment of the present application; Figure 2 for Figure 1 The MTF graph of the long-wavelength athermalized lens at 20°C is shown; Figure 3 for Figure 1 The MTF graph of the long-wavelength athermalized lens at -40°C is shown; Figure 4 for Figure 1 The MTF graph of the long-wavelength athermalized lens at 60°C is shown; Figure 5 for Figure 1 The spot diagram of the long-wave athermalized lens shown at 20°C; Figure 6 for Figure 1 The spot diagram of the long-wave athermalized lens shown at -40°C; Figure 7 for Figure 1 The spot diagram of the longwave athermalized lens shown at 60°C.
[0016] Description of labels: 11. First lens; 12. Second lens; 21. Protective window; 22. Image plane. DETAILED DESCRIPTION
[0017] 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.
[0018] 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.
[0019] One embodiment of the present application provides an imaging device comprising a long-wavelength athermalized lens (hereinafter referred to as the lens) and a detector capable of receiving images generated by the lens. The lens has an effective focal length of 9.7 mm, an F-number of 1.0, a maximum aperture of 14 mm, an operating wavelength range of 8 to 12 μm, and a horizontal field of view of 2w = 26.8°. The detector is an uncooled detector with 384 x 288 pixels and a pixel size of 12 μm.
[0020] like Figure 1 As shown, the lens includes a first lens 11 and a second lens 12, arranged sequentially along the optical axis. First lens 11 is a positive meniscus lens with its convex surface facing the object side, while second lens 12 is a biconvex lens. Furthermore, the air gap between first lens 11 and second lens 12 is 6.85 mm, and the air gap between second lens 12 and the detector is 8.21 mm.
[0021] In one embodiment, the detector includes a protective window 21 and an image plane 22 arranged in sequence. Figure 1 In the figure, the light beam passes through the first lens 11 and the second lens 12 from left to right, and then passes through the protective window 21 to form an image on the image plane 22. The air gap between the second lens 12 and the protective window 21 is 8.21 mm, and the air gap between the protective window 21 and the image plane 22 is 0.29 mm.
[0022] Furthermore, in combination with the above data, it can be seen that the total optical length of the imaging device is 22.56 mm and the back focus is 9.5 mm.
[0023] In one embodiment, the center thickness of the first lens 11 is 2 mm, the radius of curvature of the object side surface is 7.52 mm, and the radius of curvature of the image side surface is 5.78 mm; the center thickness of the second lens 12 is 4.21 mm, the radius of curvature of the object side surface is 40.9 mm, and the radius of curvature of the image side surface is -20.65 mm.
[0024] In one embodiment, the first lens 11 and the second lens 12 are both made of chalcogenide glass, specifically IRG209 for the first lens 11 and IRG206 for the second lens 12. Furthermore, the surfaces of the first lens 11 and the second lens 12, namely, the object-side and image-side surfaces of the first lens 11 and the object-side and image-side surfaces of the second lens 12, are coated with an antireflection coating.
[0025] It should be noted that the specific parameters of the above lenses can be found in Table 1. Figure 1 In the figure, the light beam passes through the first lens 11 and the second lens 12 from left to right, and then passes through the protective window 21 to form an image on the image plane 22. The left surface of the first lens 11 is the object side surface, numbered S1, and the right surface is the image side surface, numbered S2. The left surface of the second lens 12 is the object side surface, numbered S3, and the right surface is the image side surface, numbered S4.
[0026] Table 1 Lens parameters In one embodiment, the object-side surface and the image-side surface of the first lens 11 and the image-side surface of the second lens 12 are all aspherical surfaces and 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, D, and E are the higher-order aspheric coefficients. The above aspheric surface data is shown in Table 2.
[0027] Table 2 Aspheric surface data In one embodiment, the image side surface of the second lens 12 is a binary surface, and the binary surface includes an aspheric surface and a diffractive surface. Specifically, 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.
[0028] Table 3 Two-dimensional surface data See also Figures 2 to 7 , Figure 2 This is the MTF diagram of the lens at 20°C. Figure 3 This is the MTF diagram of the lens at -40℃. Figure 4 This is the MTF diagram of the lens at 60°C; Figure 5 is the spot diagram of the lens at 20°C, Figure 6 This is the spot diagram of the lens at -40°C. Figure 7 The spot diagram of the lens at 60°C is shown in the figure. As can be seen from the attached figure, the average MTF of the lens over the entire field of view is greater than 0.25, indicating good imaging quality.
[0029] In summary, the imaging device provided herein has a lens with an effective focal length of 9.7 mm, an F-number of 1.0, a maximum aperture of 14 mm, an operating wavelength range of 8 to 12 μm, a horizontal field of view of 2w = 26.8°, and an uncooled detector with 384 x 288 pixels and a pixel size of 12 μm. This lens utilizes passive athermalization to achieve athermalization, and uses only two lenses, resulting in a simple structure, low cost, and favorable miniaturization.
[0030] 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 athermalized lens, characterized in that: The effective focal length is 9.7mm, the F number is 1.0, the maximum aperture is 14mm, the working band is 8~12μm, and the horizontal field of view angle range is 2w=26.8°; the long-wave athermal lens includes a first lens and a second lens arranged in sequence along the transmission direction of the optical axis, the first lens is a meniscus positive lens with the convex surface facing the object side, the second lens is a biconvex lens, and the air gap between the first lens and the second lens is 6.85mm.
2. The long-wavelength athermalized lens according to claim 1, wherein: The center thickness of the first lens is 2 mm, the radius of curvature of the object side is 7.52 mm, and the radius of curvature of the image side is 5.78 mm; the center thickness of the second lens is 4.21 mm, the radius of curvature of the object side is 40.9 mm, and the radius of curvature of the image side is -20.65 mm.
3. The long-wavelength athermalized lens according to claim 1, wherein: The first lens and the second lens are both made of chalcogenide glass.
4. The long-wavelength athermalized lens according to claim 1, wherein: Surfaces of the first lens and the second lens are both coated with antireflection films.
5. The long-wave athermalized lens according to claim 1, wherein: The object-side surface and the image-side surface of the first lens, and the image-side surface of the second 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, D, and E are high-order aspheric coefficients.
6. The long-wave athermalized 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. An imaging device, characterized in that: The invention comprises the long-wave athermalized lens according to any one of claims 1 to 6 and a detector for receiving images formed by the long-wave athermalized lens.
8. The imaging device according to claim 7, wherein The total optical length of the imaging device is 22.56 mm.
9. The imaging device according to claim 7, wherein The detector is a non-cooled detector, and the number of pixels is 384*288, and the pixel size is 12μm.