Dual field of view infrared lens with large focal length range and imaging system

Abstract

The application provides an imaging system, comprising a dual field of view infrared lens, the lens comprising a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the transmission direction of the optical axis, the second lens can reciprocate along the direction of the optical axis, the air gap between the first lens and the second lens is 73.36-36.9mm, the air gap between the second lens and the third lens is 20.25-56.71mm, and the air gap between the third lens and the fourth lens is 38.44mm. The focal length range of the lens is large, and the imaging is clear and far.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of infrared optics, and particularly relates to a dual-view field infrared lens and an imaging system. BACKGROUND

[0002] CN114236793A discloses an F22.5-45MM dual-view field infrared focusing lens, an optical system of the lens is composed of a front fixed group, a field switching mirror and a rear fixed group arranged in sequence along the optical axis transmission direction from front to back; the front fixed group comprises a convex moon positive lens A facing the object side; the field switching mirror comprises a double-concave lens B; the rear fixed group comprises a double-convex lens C and a convex moon positive lens D facing the image side arranged in sequence along the optical axis transmission direction; the double-concave lens B can move back and forth along the optical axis transmission direction; the lens can work at a working temperature of-40℃ to 60℃, and has good imaging effect; the field switching is convenient, stable and fast.

[0003] However, the focal length range of the above-mentioned dual-view field infrared lens is small, and long-distance imaging cannot be achieved. SUMMARY

[0004] In view of the above technical problems, it is necessary to provide a dual-view field infrared lens with a large focal length range and an imaging system.

[0005] The technical scheme provided in the application is as follows:

[0006] A dual-view field infrared lens comprises a first lens, a second lens, a third lens and a fourth lens arranged in sequence along the optical axis transmission direction, the second lens can reciprocate along the optical axis direction, the air gap between the first lens and the second lens is 73.36-36.9mm, the air gap between the second lens and the third lens is 20.25-56.71mm, and the air gap between the third lens and the fourth lens is 38.44mm.

[0007] Further, the center thickness of the first lens is 8.5mm, the object side curvature radius is 125.050mm, and the image side curvature radius is 174.381mm; the center thickness of the second lens is 3mm, the object side curvature radius is-192.595mm, and the image side curvature radius is 190.370mm; the center thickness of the third lens is 7mm, the object side curvature radius is 364.486mm, and the image side curvature radius is-348mm; and the center thickness of the fourth lens is 6.3mm, the object side curvature radius is 1136.199mm, and the image side curvature radius is-258mm.

[0008] Further, the focal length is 40-120mm.

[0009] When the focal length is 40mm, the air gap between the first lens and the second lens is 36.9mm, and the air gap between the second lens and the third lens is 56.71mm;

[0010] When the focal length is 120mm, the air gap between the first lens and the second lens is 73.36mm, and the air gap between the second lens and the third lens is 20.25mm.

[0011] Further, the material of the first lens, the second lens, the third lens and the fourth lens is germanium single crystal.

[0012] Further, the first lens is a convex-to-object-side meniscus positive lens, the second lens is a double-concave negative lens, the third lens is a double-convex positive lens, and the fourth lens is a double-convex positive lens.

[0013] Further, 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 aspherical surfaces, and satisfy the aspherical surface formula:

[0014]

[0015] wherein Z is the distance from the vertex of the aspherical surface to the height r of the aspherical surface 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 and E are high-order aspherical surface coefficients.

[0016] Further, the object side surface of the third lens is a binary surface, satisfies the aspherical surface formula, and satisfies the expression equation of the binary surface in Zemax: M(B1ρ 2 +B2ρ 4 + B3ρ 6 ); wherein M is the diffraction order, B1, B2 and B3 are the phase coefficients of the binary surface, and ρ is the normalized radius. M is 1, B 1= -26.687, B 2= 2.9811, B 3= -0.0493, and ρ=35.

[0017] Further, the working waveband of the lens is 8~12μm, and the F number is 1.

[0018] An imaging system, comprising the dual-view infrared lens as described above and a detector for receiving the image formed by the dual-view infrared lens.

[0019] Further, the detector is a non-cooled detector, and the resolution of the detector is 1280×1024, and the pixel size is 12μm.

[0020] The imaging system provided by the present application comprises a dual-view field infrared lens and a detector, the focal length of the lens is 40-120mm, the working wave band is 8-12um, and the F number is 1; the detector is a non-refrigeration type detector, and the resolution of the detector is 1280x1024, and the pixel size is 12um. Meanwhile, the focal length range of the lens is large, the imaging is clear, and the lens can be applied to the monitoring of objects at different distances. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application, and are used to explain the present application together with the embodiments of the present application, and do not constitute a limitation on the present application.

[0022] Figure 1 The lens composition diagram of the imaging system provided by the present application;

[0023] Figure 2 The point array diagram of the dual-view field infrared lens provided by the present application when the focal length is 120mm;

[0024] Figure 3 The point array diagram of the dual-view field infrared lens provided by the present application when the focal length is 120mm;

[0025] Figure 4 The MTF diagram of the dual-view field infrared lens provided by the present application when the focal length is 40mm;

[0026] Figure 5 The point array diagram of the dual-view field infrared lens provided by the present application when the focal length is 40mm;

[0027] Label explanation:

[0028] 11, first lens; 12, second lens; 13, third lens; 14, fourth lens; 21, protective window; 22, detector focal plane array. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0030] The present application provides an imaging system, which comprises a dual-view field infrared lens and a detector, the focal length of the lens is 40-120mm, the working wave band is 8-12um, and the F number is 1; the detector is a non-refrigeration type detector, and the resolution of the detector is 1280x1024, and the pixel size is 12um.

[0031] As Figure 1 shown, the lens includes first lens 11, second lens 12, third lens 13, fourth lens 14 arranged in sequence along the transmission direction of optical axis. The second lens 12 can reciprocate along the direction of optical axis, and the air gap between the first lens 11 and the second lens 12 is 73.36~36.9mm, the air gap between the second lens 12 and the third lens 13 is 20.25~56.71mm, and the air gap between the third lens 13 and the fourth lens 14 is 38.44mm.

[0032] Specifically, when the focal length is 40mm, the air gap between the first lens 11 and the second lens 12 is 36.9mm, and the air gap between the second lens 12 and the third lens 13 is 56.71mm.

[0033] When the focal length is 120mm, the air gap between the first lens 11 and the second lens 12 is 73.36mm, and the air gap between the second lens 12 and the third lens 13 is 20.25mm.

[0034] In an embodiment, the detector includes a protective window 21 and a detector focal plane array 22, as Figure 1 shown, the light beam passes through the first lens 11, the second lens 12, the third lens 13, and the fourth lens 14 in sequence from left to right, and then passes through the protective window 21 to form an image on the detector focal plane array 22. In practical application, the air gap between the fourth lens 14 and the protective window 21 is 37.83mm.

[0035] In an embodiment, the first lens 11 is a convex moon positive lens facing the object side, the second lens 12 is a double-concave negative lens, the third lens 13 is a double-convex positive lens, and the fourth lens 14 is a double-convex positive lens.

[0036] Further, the central thickness of the first lens 11 is 8.5mm, the curvature radius of the object side is 125.050mm, and the curvature radius of the image side is 174.381mm; the central thickness of the second lens 12 is 3mm, the curvature radius of the object side is -192.595mm, and the curvature radius of the image side is 190.370mm; the central thickness of the third lens 13 is 7mm, the curvature radius of the object side is 364.486mm, and the curvature radius of the image side is -348mm; the central thickness of the fourth lens 14 is 6.3mm, the curvature radius of the object side is 1136.199mm, and the curvature radius of the image side is -258mm.

[0037] It can be understood that the direction of light incidence is the object side, and the direction of light emission is the image side. With Figure 1For example, from left to right along the optical axis, the left side of the lens is the object side, and the right side is the image side. For example, the S1 surface of the first lens 11 is the object side surface, and the S2 surface is the image side surface. The same applies to the other lenses.

[0038] In one embodiment, the first lens 11, the second lens 12, the third lens 13, and the fourth lens 14 are all germanium single crystals. The parameters of each lens can be found in Table 1.

[0039] Table 1: Lens Parameters

[0040]

[0041] In one embodiment, 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

[0042]

[0043] where Z is the distance from the vertex of the aspherical surface when the aspherical 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 conic coefficient; A, B, C, D, and E are high-order aspherical coefficients.

[0044] Table 2: Aspherical Coefficients

[0045]

[0046] Further, the object side surface of the third lens is a binary surface, satisfying the aspherical surface formula and the expression equation in Zemax: M(B1ρ 2 +B2ρ 4 + B3ρ 6 ); where M is the diffraction order, B1, B2, and B3 are binary phase coefficients, and p is the normalized radius. M is 1, B1 is -26.687, B2 is 2.9811, B3 is -0.0493, and p is 35.

[0047] Figure 2 is the MTF graph when the focal length is 120 mm, Figure 3 is the point spread function when the focal length is 120 mm; Figure 4 is the MTF graph when the focal length is 40 mm, Figure 5 is the point spread function when the focal length is 40 mm. In the MTF graph, the horizontal axis represents different spatial frequencies, and the vertical axis represents the modulation degree. It can be seen that the MTF is close to the diffraction limit, the root mean square of the diffraction spot is smaller than the diameter of the Airy disk, and the image quality is good.

[0048] In summary, the imaging system provided by the application comprises a dual field of view infrared lens and a detector, the focal length of the lens is 40-150mm, the working waveband is 8-12um, and the F number is 1; the detector is a non-cooled detector, and the resolution of the detector is 1280*1024, and the pixel size is 12um. Meanwhile, the lens has clear imaging and a large focal length range.

[0049] Although the embodiments of the application have been shown and described, it is to be understood that the application is not limited to these embodiments. It will be obvious to those skilled in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the spirit and scope of the application, which should be limited only by the appended claims and their equivalents.

Claims

1. A dual-field-of-view infrared lens, characterized in that, It consists of a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis transmission direction. The second lens can reciprocate along the optical axis direction. The air gap between the first lens and the second lens is 73.36~36.9mm, the air gap between the second lens and the third lens is 20.25~56.71mm, and the air gap between the third lens and the fourth lens is 38.44mm. The first lens has a center thickness of 8.5 mm, an object-side radius of curvature of 125.050 mm, and an image-side radius of curvature of 174.381 mm; the second lens has a center thickness of 3 mm, an object-side radius of curvature of -192.595 mm, and an image-side radius of curvature of 190.370 mm; the third lens has a center thickness of 7 mm, an object-side radius of curvature of 364.486 mm, and an image-side radius of curvature of -348 mm; the fourth lens has a center thickness of 6.3 mm, an object-side radius of curvature of 1136.199 mm, and an image-side radius of curvature of -258 mm. The first lens, the second lens, the third lens, and the fourth lens are made of germanium single crystal. The first lens is a meniscus positive lens with its convex surface facing the object side, the second lens is a biconcave negative lens, the third lens is a biconvex positive lens, and the fourth lens is a biconvex positive lens.

2. The dual-field infrared lens as described in claim 1, characterized in that, Focal length is 40~120mm; When the focal length is 40mm, the air gap between the first lens and the second lens is 36.9mm, and the air gap between the second lens and the third lens is 56.71mm; When the focal length is 120mm, the air gap between the first lens and the second lens is 73.36mm, and the air gap between the second lens and the third lens is 20.25mm.

3. The dual-field infrared lens as described in 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 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.

4. The dual-field infrared lens as described in claim 3, characterized in that, The object-side surface of the third lens is a binary surface, satisfying the aspherical formula and the equation for the binary surface in Zemax: M(B1ρ) 2 +B2ρ 4 + B3ρ 6 ); where M is the diffraction order, B1, B2, B3 are the two-dimensional phase coefficients, and ρ is the normalized radius; M is 1, B 1= -26.687, B 2= 2.9811, B 3= -0.0493, ρ=35.

5. The dual-field infrared lens according to claim 1, characterized in that, The lens operates in the 8~12μm wavelength range and has an F-number of 1.

6. An imaging system, characterized in that, It includes the dual-field-of-view infrared lens as described in any one of claims 1-5 and a detector for receiving images from the dual-field-of-view infrared lens.

7. The imaging system according to claim 6, characterized in that, The detector is an uncooled detector with a resolution of 1280×1024 and a pixel size of 12μm.

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