A small-f-number long-waveband infrared imaging optical system

Abstract

The application belongs to the technical field of optical imaging, and particularly relates to a small-F-number long-waveband infrared imaging optical system, which comprises an aperture plane, a first lens, a second lens, a third lens and an image plane; the first lens is a positive lens made of IRG206 material, and the second surface thereof is an aspheric surface; the second lens is a negative lens made of ZNS_IR material; and the third lens is a positive lens made of IRG204 material; the application adopts a 3-lens structure, has low material cost, high system transmittance, long detection distance, small relative aperture and F number=1; and expensive germanium material is replaced by low-cost materials such as zinc sulfide (ZNS_IR) and chalcogenide glass (IRG206), so that the application has the advantages of cost and mass production.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging technology, specifically a small F-number long-wavelength infrared imaging optical system. Background Technology

[0002] With the continuous development of detection technology, infrared detectors are being used more and more widely in both military and civilian fields, and their performance is constantly improving. Furthermore, infrared detectors are developing towards larger arrays, smaller pixels, and higher resolutions.

[0003] Currently, MTF (Mean Transfer Function) is commonly used to characterize detector performance. When testing the MTF of a detector, the transfer function of the standard imaging lens is required to be higher than that of the detector. Therefore, the MTF test for infrared high-resolution small-pixel detectors requires that their standard imaging lens, in addition to having good image quality with no central obstruction and diffraction limit, has a larger relative aperture, i.e., a smaller F-number, compared to traditional standard lenses. However, for optical systems, a smaller F-number makes optical design more difficult.

[0004] Therefore, this invention proposes a small F-number long-wavelength infrared imaging optical system. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0006] The technical solution adopted by this invention to solve its technical problem is: a small F-number long-wavelength infrared imaging optical system of this invention, comprising, from the object side to the image side, the following:

[0007] Aperture plane, first lens, second lens, third lens, and image plane;

[0008] The first lens is a positive lens made of IRG206 material, and its second surface is an aspherical surface;

[0009] The second lens is a negative lens made of ZNS_IR material;

[0010] The third lens is a positive lens made of IRG204 material;

[0011] The system satisfies the following relationship:

[0012]

[0013] Where z is the surface sag. Let y be the curvature of the surface vertex, y be the perpendicular coordinate to the surface vertex, k be the conic coefficient, and A, B, C, and D be the higher-order aspheric coefficients.

[0014] The system has a relative aperture ratio of 1:1, a focal length of 50 mm, an entrance pupil size of 53.6 mm, a field of view of 11.2°, and a total system length of 74 mm.

[0015] Furthermore, the second surface of the first lens is an even-order aspherical surface.

[0016] Furthermore, the materials of the first lens, the second lens, and the third lens are IRG206, ZNS_IR, and IRG204, respectively.

[0017] Furthermore, the system also includes a spatial gap between the object and the first lens.

[0018] Furthermore, the system also includes spatial intervals between the lenses.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. It adopts a 3-lens structure, which has low material cost, high system transmittance, and long detection distance;

[0021] 2. Relatively small aperture, F number = 1;

[0022] 3. Using low-cost materials such as zinc sulfide (ZNS_IR) and chalcogenide glass (IRG206) to replace expensive germanium materials has advantages in cost and mass production. Attached Figure Description

[0023] The invention will now be further described with reference to the accompanying drawings.

[0024] Figure 1 This is a schematic diagram of the lens arrangement structure;

[0025] Figure 2 It is the transfer function diagram of the lens;

[0026] Figure 3 It is a dot diagram of the lens;

[0027] In the diagram: 1. First lens; 2. Second lens; 3. Third lens. Detailed Implementation

[0028] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0029] like Figures 1 to 2As shown in the embodiment of the present invention, a low F-number long-wavelength infrared imaging optical system includes, from the object side to the image side, an aperture plane, a first lens, a second lens, a third lens, and an image plane. The first lens is made of IRG206 material, the second lens is made of ZNS_IR material, and the third lens is made of IRG204 material. The second surface of the first lens is aspherical, used to further eliminate aberrations and optimize image quality.

[0030] The specific parameters of the system are shown in Table 1:

[0031] Table 1

[0032] lens radius thickness Glass Remark surface unlimited 10 Spatial interval First lens 41.272 7 IRG206 Aperture (Ascetic surface) 64.784 3.522 Spatial interval Second lens 29.290 7 ZNS_IR 20.026 29.485 Spatial interval Third lens 34.980 6.030 IRG204 55.47 10.902 Spatial interval Image unlimited -

[0033] The aspherical coefficients of the second surface of the first lens are shown in Table 2 (unit: mm):

[0034] Table 2

[0035] coefficient value R 64.78382 K A 4.9160411e-007 B 5.8903074e-011 C 6.0229547e-014 D -1.7794171e-017

[0036] When the system is in operation, the light beam from the object side passes sequentially through the first lens, the second lens, and the third lens, ultimately forming a clear image on the image plane. The system's image quality is close to the diffraction limit, with good stray light suppression, and is suitable for 640×512 uncooled long-wave infrared detectors with a pixel size of 12μm.

[0037] exist In 1 / R, R is the radius of curvature at the vertex of the surface, specifically the radius of curvature at the vertex of the aspherical surface, measured in millimeters. It determines the degree of curvature of the lens surface at the vertex. The surface vertex curvature is the reciprocal of the radius of curvature, i.e. =1 / R.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low F-number long-wavelength infrared imaging optical system, characterized in that: From the object side to the image side, the system comprises: an aperture plane, a first lens, a second lens, a third lens, and an image plane; the infrared imaging optical system has three lenses with optical power. The first lens is a positive lens made of IRG206 material, and its second surface is an aspherical surface; The second lens is a negative lens made of ZNS_IR material; The third lens is a positive lens made of IRG204 material; As shown in the table below: The equation of the aspherical surface of the second surface is: The origin of the coordinate system is at the vertex, and ρ = 1 / R; Where z is the surface elevation, ρ is the curvature of the surface vertex, R represents the radius of the surface vertex, y is the perpendicular coordinate to the surface vertex, k is the conic coefficient, and A, B, C, and D are higher-order aspherical coefficients.

2. The low F-number long-wavelength infrared imaging optical system according to claim 1, characterized in that: The system has a relative aperture ratio of 1:1, a focal length of 50 mm, an entrance pupil size of 53.6 mm, a field of view of 11.2°, and a total system length of 74 mm.

3. The low F-number long-wavelength infrared imaging optical system according to claim 1, characterized in that: The system is suitable for a 640×512 uncooled long-wave infrared detector with a pixel size of 12μm.

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