A fixed focus infrared lens

Abstract

The application belongs to the technical field of infrared lens manufacturing, and discloses a fixed-focus infrared lens, which is sequentially provided with a first lens, a second lens, a third lens and a silicon window along the optical axis direction, the first lens is a concave-convex lens, the convex surface faces the object side, the second lens is a concave-convex lens, the convex surface faces the object side, the third lens is a double-convex lens, the silicon window is provided with a plane on each side, the focal length of the lens is 25 mm, and the lens is suitable for outdoor wide-temperature-range scenes.

Description

Technical Field

[0001] This invention relates to the field of infrared lens manufacturing technology, specifically a fixed-focus infrared lens. Background Technology

[0002] Long-wave infrared lenses operate at wavelengths of 8-12μm. Since the operating temperature of fixed-focus infrared lenses is typically 40-60℃, the lenses inside the lens will experience thermal expansion and contraction as the temperature changes. Therefore, designing heat-free fixed-focus infrared lenses is particularly important. Summary of the Invention

[0003] The purpose of this invention is to provide a fixed-focus infrared lens that, when used at a temperature of 40-60°C, does not cause image plane drift and provides stable and reliable imaging, thereby solving the problems mentioned in the background art.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a fixed-focus infrared lens, comprising a first lens, a second lens, a third lens, and a silicon window arranged sequentially along the optical axis. The first lens is a concave-convex lens with the convex surface facing the object side; the second lens is a concave-convex lens with the convex surface facing the object side; and the third lens is a biconvex lens with both sides of the silicon window being flat.

[0005] The first lens has an object-side radius of curvature of 15.996 mm, an image-side radius of curvature of 22.954 mm, a center thickness of 5.3 mm, and an outer diameter of 26.5 mm. It is made of chalcogenide glass. The second lens has an object-side radius of curvature of 15.073 mm, an image-side radius of curvature of 8.63 mm, a center thickness of 1.5 mm, and an outer diameter of 18 mm. It is made of germanium. The third lens has an object-side radius of curvature of 154.004 mm, an image-side radius of curvature of -39.26 mm, a center thickness of 3 mm, and an outer diameter of 18 mm. It is made of chalcogenide glass, with a silicon window thickness of 0.7 mm and an outer diameter of 13 mm.

[0006] As a preferred technical solution, the distance between the first lens and the second lens along the optical axis is 4.248 mm, the distance between the second lens and the third lens is 6.752 mm, and the distance between the third lens and the silicon window is 7.5 mm.

[0007] As a preferred technical solution, the side of the first lens is coated with an AR film.

[0008] Compared with the prior art, the beneficial effects achieved by the present invention are: The infrared lens of this application has a focal length of 25mm, an F number of 1.0, an effective imaging surface diameter of 10mm, and an HFOV / VFOV of 17.5°X14.0° (640X512 12um). Attached Figure Description

[0009] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the optical system of the present invention; Figure 2 This is the MTF of the present invention at 20°C; Figure 3 This is the MTF of the present invention at 40°C; Figure 4 This is the MTF of the present invention at 60°C. Detailed Implementation

[0010] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] As attached Figure 1-4 As shown, a fixed-focus infrared lens comprises, sequentially along the optical axis, a first lens 1, a second lens 2, a third lens 3, and a silicon window 4. The first lens 1 is a concave-convex lens with the convex surface facing the object side; the second lens 2 is a concave-convex lens with the convex surface facing the object side; the third lens 3 is a biconvex lens; and both sides of the silicon window 4 are flat.

[0012] The first lens 1 has an object-side radius of curvature of 15.996 mm, an image-side radius of curvature of 22.954 mm, a center thickness of 5.3 mm, and an outer diameter of 26.5 mm. It is made of chalcogenide glass. The second lens 2 has an object-side radius of curvature of 15.073 mm, an image-side radius of curvature of 8.63 mm, a center thickness of 1.5 mm, and an outer diameter of 18 mm. It is made of germanium. The third lens 3 has an object-side radius of curvature of 154.004 mm, an image-side radius of curvature of -39.26 mm, a center thickness of 3 mm, and an outer diameter of 18 mm. It is made of chalcogenide glass. The silicon window 4 has a thickness of 0.7 mm and an outer diameter of 13 mm.

[0013] The distance between the first lens 1 and the second lens 2 along the optical axis is 4.248 mm, the distance between the second lens 2 and the third lens 3 is 6.752 mm, the distance between the third lens 3 and the silicon window 4 is 7.5 mm, and the object side of the first lens 1 is coated with an AR film.

[0014] The infrared lens of this application has a focal length of 25mm, an F number of 1.0, an effective imaging surface diameter of 10mm, and an HFOV / VFOV of 17.5°X14.0° (640X512 12um).

[0015] Figures 2-4 The MTF charts are shown at 20℃, 40℃, and 60℃ respectively. Within the wide temperature range of 20℃-60℃, the MTF curves highly overlap, with no obvious thermal defocusing, stable image quality, and significant no thermal effect, meeting the requirements for outdoor wide temperature range working scenarios.

[0016] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and not restrictive.

Claims

1. A fixed-focus infrared lens, characterized in that: A first lens (1), a second lens (2), a third lens (3), and a silicon window (4) are arranged sequentially along the optical axis. The first lens (1) is a concave-convex lens with the convex surface facing the object side; the second lens (2) is a concave-convex lens with the convex surface facing the object side; the third lens (3) is a biconvex lens; both sides of the silicon window (4) are flat; the infrared lens has only the above three lenses with optical power. The first lens (1) has an object-side radius of curvature of 15.996 mm, an image-side radius of curvature of 22.954 mm, a center thickness of 5.3 mm, and an outer diameter of 26.5 mm. It is made of chalcogenide glass. The second lens (2) has an object-side radius of curvature of 15.073 mm, an image-side radius of curvature of 8.63 mm, a center thickness of 1.5 mm, and an outer diameter of 18 mm. It is made of germanium. The third lens (3) has an object-side radius of curvature of 154.004 mm, an image-side radius of curvature of -39.26 mm, a center thickness of 3 mm, and an outer diameter of 18 mm. It is made of chalcogenide glass. The silicon window (4) has a thickness of 0.7 mm and an outer diameter of 13 mm.

2. A fixed-focus infrared lens according to claim 1, characterized in that: The distance between the first lens (1) and the second lens (2) along the optical axis is 4.248 mm, the distance between the second lens (2) and the third lens (3) is 6.752 mm, and the distance between the third lens (3) and the silicon window (4) is 7.5 mm.

3. A fixed-focus infrared lens according to claim 1, characterized in that: The first lens (1) has an AR film coated on its surface.

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