Dual view infrared lens and optical system

Abstract

The application discloses an optical system, which comprises a dual-view field infrared lens and a detector for receiving an image formed by the infrared lens. The infrared lens can be switched between 35mm and 85mm focal lengths and is composed of a first lens, a second lens, a third lens and a fourth lens arranged in sequence along an optical axis. The first lens is a convex moon positive lens with a convex surface facing an object side, the second lens is a double-concave lens, the third lens is a convex plane lens with a convex surface facing the object side, and the fourth lens is a convex moon positive lens with a convex surface facing an image side. The second lens and the third lens can move reciprocally along the optical axis. When the focal length of the infrared lens is 35mm, the F number is 1.0, and the horizontal field of view is 16.63°. When the focal length of the infrared lens is 85mm, the F number is 1.2, and the horizontal field of view is 6.73°. The infrared lens adopts a manual zooming design, has a simple and compact structure, is low in cost, and can form good images under different temperature environments and has stable imaging quality.

Description

Technical Field

[0001] This application belongs to the field of optical lens technology, specifically relating to a dual-field infrared lens and optical system. Background Technology

[0002] 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 changes in lens focal length by precisely controlling the movement of the zoom group and compensation group, while maintaining image sharpness throughout the process. However, the system structure is relatively complex, difficult to manufacture and assemble, and places higher demands on the computing power and image processing capabilities of the backend chips. In contrast, dual-field-of-view optical systems have a simpler structure, higher reliability, and can search for targets at short focal lengths while achieving precise target tracking and measurement at long focal lengths.

[0003] However, in the existing dual-field optical system design, 5 to 7 lenses are usually set, which is a large number of lenses. 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 also required, which further complicates the structure of the dual-field optical system. Summary of the Invention

[0004] The technical problem to be solved by this application is that the existing dual-field optical system structure has a large number of lenses. In order to solve this technical problem, a dual-field infrared lens and optical system with fewer lenses is provided.

[0005] The technical solution proposed in this application is as follows: A dual-field infrared lens is available, capable of switching between a 35mm focal length and an 85mm focal length. 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 plano-convex lens with its convex surface facing the object side, and the fourth lens is a meniscus lens with its convex surface facing the image side. The second lens and the third lens are capable of reciprocating along the optical axis. Wherein, when the focal length of the infrared lens is 35mm, the F number is 1.0, the horizontal field of view is 16.63°, the air gap between the first lens and the second lens is 16.13mm, the air gap between the second lens and the third lens is 40.24mm, and the air gap between the third lens and the fourth lens is 17.72mm; When the focal length of the infrared lens is 85mm, the F-number is 1.2, the horizontal field of view is 6.73°, the air gap between the first lens and the second lens is 34.52mm, the air gap between the second lens and the third lens is 4mm, and the air gap between the third lens and the fourth lens is 35.57mm.

[0006] Furthermore, the first lens has a center thickness of 9.89 mm, an object-side radius of curvature of 55.81 mm, and an image-side radius of curvature of 65.01 mm; the second lens has a center thickness of 4.66 mm, an object-side radius of curvature of -164.75 mm, and an image-side radius of curvature of 100.09 mm; the third lens has a center thickness of 7.4 mm and an object-side radius of curvature of 72.29 mm; and the fourth lens has a center thickness of 6.3 mm, an object-side radius of curvature of -84.22 mm, and an image-side radius of curvature of -55.12 mm.

[0007] Furthermore, the first lens, the second lens, the third lens, and the fourth lens are all made of chalcogenide glass.

[0008] Furthermore, the image-side surface of the first lens, the object-side surface of the second lens, the object-side surface of the third lens, and the object-side surface of the fourth lens are all aspherical surfaces, and satisfy the aspherical surface 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, D, E, and F are higher-order aspherical coefficients.

[0009] Furthermore, the object-side surface of the third lens is a binary surface, which includes an aspherical surface and a diffraction surface.

[0010] An optical system includes the dual-field-of-view infrared lens and a detector that receives images from the infrared lens.

[0011] Furthermore, the detector has a resolution of 640×512 and a pixel size of 12μm.

[0012] In summary, this application discloses an optical system including a dual-field-of-view infrared lens and a detector for receiving images from the infrared lens. The dual-field-of-view infrared lens can switch between a 35mm focal length and an 85mm focal length. When the focal length of the infrared lens is 35mm, the F-number is 1.0 and the horizontal field of view is 16.63°; when the focal length of the infrared lens is 85mm, the F-number is 1.2 and the horizontal field of view is 6.73°. The detector is an uncooled detector with a resolution of 640×512 and a pixel size of 12μm. The infrared lens in this optical system consists of only four chalcogenide glass lenses and employs a manual zoom design. The total optical length is 133mm, resulting in a simple and compact structure, low cost, and good imaging performance and stable image quality under different temperature conditions. Attached Figure Description

[0013] 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.

[0014] Figure 1 A schematic diagram of the optical path structure of a dual-field infrared lens at a focal length of 35mm according to an embodiment of this application; Figure 2 A schematic diagram of the optical path structure of a dual-field infrared lens at a focal length of 85mm according to an embodiment of this application; Figure 3 for Figure 1 The MTF diagram of the dual-field infrared lens at 20°C is shown. Figure 4 for Figure 1 The MTF plot of the dual-field infrared lens at -40℃ is shown. Figure 5 for Figure 1 The MTF diagram of the dual-field infrared lens at 60°C is shown. Figure 6 for Figure 2 The MTF diagram of the dual-field infrared lens at 20°C is shown. Figure 7 for Figure 2 The MTF plot of the dual-field infrared lens at -40℃ is shown. Figure 8 for Figure 2 The MTF diagram of the dual-field infrared lens at 60°C is shown.

[0015] Label Explanation: 11. First lens; 12. Second lens; 13. Third lens; 14. Fourth lens; 21. Protective window; 22. Image plane. Detailed Implementation

[0016] 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.

[0017] 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.

[0018] This application discloses an optical system including a dual-field-of-view infrared lens and a detector for receiving images from the infrared lens. The dual-field-of-view infrared lens can switch between a 35mm focal length and an 85mm focal length. When the focal length of the infrared lens is 35mm, the F-number is 1.0 and the horizontal field of view is 16.63°; when the focal length of the infrared lens is 85mm, the F-number is 1.2 and the horizontal field of view is 6.73°. The detector is an uncooled detector with a resolution of 640×512 and a pixel size of 12μm.

[0019] like Figure 1 As shown, in one embodiment, the infrared lens comprises a first lens 11, a second lens 12, a third lens 13, and a fourth lens 14 arranged sequentially along the optical axis. The first lens 11 is a meniscus lens with its convex surface facing the object side, the second lens 12 is a biconcave lens, the third lens 13 is a plano-convex lens with its convex surface facing the object side, and the fourth lens 14 is a meniscus lens with its convex surface facing the image side. The second lens 12 and the third lens 13 can reciprocate along the optical axis to allow the infrared lens to switch between a focal length of 35mm and 85mm.

[0020] Please refer to Table 1. In one embodiment, when the focal length of the infrared lens is 35mm, the air gap between the first lens 11 and the second lens 12 is 16.13mm, the air gap between the second lens 12 and the third lens 13 is 40.24mm, and the air gap between the third lens 13 and the fourth lens 14 is 17.72mm; when the focal length of the infrared lens is 85mm, the air gap between the first lens 11 and the second lens 12 is 34.52mm, the air gap between the second lens 12 and the third lens 13 is 4mm, and the air gap between the third lens 13 and the fourth lens 14 is 35.57mm.

[0021] Furthermore, the center thickness of the first lens 11 is 9.89 mm, the radius of curvature of the object side is 55.81 mm, and the radius of curvature of the image side is 65.01 mm; the center thickness of the second lens 12 is 4.66 mm, the radius of curvature of the object side is -164.75 mm, and the radius of curvature of the image side is 100.09 mm; the center thickness of the third lens 13 is 7.4 mm, and the radius of curvature of the object side is 72.29 mm; the center thickness of the fourth lens 14 is 6.3 mm, the radius of curvature of the object side is -84.22 mm, and the radius of curvature of the image side is -55.12 mm.

[0022] In one embodiment, the first lens 11, the second lens 12, the third lens 13, and the fourth lens 14 are all made of chalcogenide glass to reduce manufacturing costs. Specific materials can be found in Table 1. Furthermore, each lens surface is coated with an anti-reflective film.

[0023] In one embodiment, the detector includes a protective window 21 and an image plane 22 arranged in sequence.

[0024] Table 1 Data for each component It needs to be explained that, in Figure 1 In the embodiment shown, taking the first lens 11 as an example, the left S1 surface of the first lens 11 is the object side surface and the right S2 surface is the image side surface. The same applies to other lenses, which will not be described in detail here.

[0025] In one embodiment, as shown in Table 1, the image-side surface of the first lens 11, the object-side surface of the second lens 12, the object-side surface of the third lens 13, and the object-side surface of the fourth lens 14 are all aspherical surfaces and satisfy the aspherical surface formula: 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, E, and F are higher-order aspherical coefficients. The aspherical data are shown in Table 2.

[0026] Table 2 Aspherical Data In one embodiment, the object-side surface of the third lens 13 is a binary surface, comprising an aspherical surface and a diffractive surface. The object-side surface of the third lens 13 satisfies the Zemax equation for a binary surface: 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 3 to 8 , Figures 3-5 The images show the MTF (Mean Transformer Format) of the infrared lens at a 35mm focal length under conditions of 20℃, -40℃, and 60℃. Figures 6-8 The MTF (Mean Transformation Factor) of the infrared lens at an 85mm focal length is shown at 20℃, -40℃, and 60℃. The figures demonstrate that the MTF of this infrared lens approaches the diffraction limit under all temperature conditions, with an average MTF > 0.25@42lp / mm across the entire field of view, indicating stable image quality.

[0027] In summary, this application discloses an optical system including a dual-field-of-view infrared lens and a detector for receiving images from the infrared lens. The dual-field-of-view infrared lens can switch between a 35mm focal length and an 85mm focal length. When the focal length of the infrared lens is 35mm, the F-number is 1.0 and the horizontal field of view is 16.63°; when the focal length of the infrared lens is 85mm, the F-number is 1.2 and the horizontal field of view is 6.73°. The detector is an uncooled detector with a resolution of 640×512 and a pixel size of 12μm. The infrared lens in this optical system consists of only four chalcogenide glass lenses and employs a manual zoom design. The total optical length is 133mm, resulting in a simple and compact structure, low cost, and good imaging performance and stable image quality under different temperature conditions.

[0028] 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 infrared lens, characterized in that, Capable of switching between 35mm and 85mm focal lengths, 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 plano-convex lens with its convex surface facing the object side, and the fourth lens is a meniscus lens with its convex surface facing the image side; the second lens and the third lens are capable of reciprocating along the optical axis; Wherein, when the focal length of the infrared lens is 35mm, the F number is 1.0, the horizontal field of view is 16.63°, the air gap between the first lens and the second lens is 16.13mm, the air gap between the second lens and the third lens is 40.24mm, and the air gap between the third lens and the fourth lens is 17.72mm; When the focal length of the infrared lens is 85mm, the F-number is 1.2, the horizontal field of view is 6.73°, the air gap between the first lens and the second lens is 34.52mm, the air gap between the second lens and the third lens is 4mm, and the air gap between the third lens and the fourth lens is 35.57mm.

2. The dual-field infrared lens according to claim 1, characterized in that, The first lens has a center thickness of 9.89 mm, an object-side radius of curvature of 55.81 mm, and an image-side radius of curvature of 65.01 mm; the second lens has a center thickness of 4.66 mm, an object-side radius of curvature of -164.75 mm, and an image-side radius of curvature of 100.09 mm; the third lens has a center thickness of... The thickness of the fourth lens is 7.4 mm, and the radius of curvature of the object side is 72.29 mm. The center thickness of the fourth lens is 6.3 mm, the radius of curvature of the object side is -84.22 mm, and the radius of curvature of the image side is -55.12 mm.

3. The dual-field infrared lens according to claim 1, characterized in that, The first lens, the second lens, the third lens, and the fourth lens are all made of chalcogenide glass.

4. The dual-field infrared lens according to claim 1, characterized in that, The image-side surface of the first lens, the object-side surface of the second lens, the object-side surface of the third lens, and the object-side surface of the fourth lens are all aspherical surfaces and satisfy the aspherical surface 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, D, E, and F are higher-order aspherical coefficients.

5. The dual-field infrared lens according to claim 4, characterized in that, The object-side surface of the third lens is a binary surface, which includes an aspherical surface and a diffraction surface.

6. An optical system, characterized in that, It includes the dual-field infrared lens as described in any one of claims 1-5 and the detector that receives the image from the infrared lens.

7. The optical system according to claim 6, characterized in that, The detector has a resolution of 640×512 and a pixel size of 12μm.

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