Medium and short wave infrared spectral imaging system

Abstract

The present invention belongs to spectroscopy technology and specifically relates to a medium- and short-wave infrared spectral imaging system, comprising an objective lens assembly and a detector; a focusing lens assembly, a relay lens assembly, and an imaging lens assembly, sequentially arranged in the optical path between the objective lens assembly and the detector; the focusing lens assembly comprising a first negative power lens with a convex surface facing the relay lens assembly and a drive unit thereof; the relay lens assembly comprising a first positive power lens with a convex surface facing away from the focusing lens assembly, a second biconcave negative power lens, and a second positive power lens with a convex surface facing the focusing lens assembly, sequentially arranged; and the imaging lens assembly comprising a third biconcave negative power lens and a third biconvex positive power lens, sequentially arranged. The present invention has the advantages of clear imaging and achromatic aberration without the need for diffractive components, and is therefore suitable for spectral imaging.

Description

Technical Field

[0001] The present invention relates to spectral technology, in particular to a medium- and short-wave infrared spectral imaging system. Background Art

[0002] Multispectral imaging combines the advantages of traditional spectrometers and photoelectric detection technologies to detect target scene information and analyze and extract spectral features, simultaneously providing two-dimensional image and spectral information, with the near-real-time characteristics of next-generation spectral telemetry. Wideband multispectral imaging technology is a new detection method that can both image the same target in multiple spectral bands and measure spectral features. It provides targeted enhancement based on the target's inherent radiation characteristics, thereby suppressing background clutter and improving target discrimination. This technology has been widely used in the remote sensing field, including early warning of thermal disasters, subway safety monitoring (detection of highly toxic and hazardous gases), coal mine monitoring (methane detection), high-voltage power transmission and distribution testing (detection of sulfur hexafluoride), and chemical plant leaks (detection of flammable and explosive gases).

[0003] To capture the target's radiation characteristics, a multispectral imaging system consists of a filter wheel system equipped with multiple filters and a wide-spectrum infrared optical system. Commonly used multispectral spectrometers are primarily used for remote sensing of targets beyond 1000 meters. For close-range detection in laboratory gas cells, limitations of the optical system prevent the detection of both long-range and close-range targets (within 2 meters).

[0004] Since the refractive index and dispersion characteristics of optical materials vary greatly in different bands, it is very difficult to correct chromatic aberration in optical systems over the entire wide wavelength range (1.5μm to 5.4μm). At the same time, the limited number of optical materials available within the wide wavelength range (1.5μm to 5.4μm) also increases the difficulty of designing wide-band optical systems. Summary of the Invention

[0005] In order to solve the deficiencies in the above-mentioned prior art solutions, the present invention provides a medium- and short-wave infrared spectral imaging system.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A medium- and short-wave infrared spectral imaging system includes an objective lens group and a detector; the imaging system also includes:

[0008] A focusing lens group, a relay lens group and an imaging lens group are sequentially arranged on the optical path between the objective lens group and the detector; the focusing lens group includes a first negative optical power lens with a convex surface facing the relay lens group and a driving unit thereof; the relay lens group includes a first positive optical power lens with a convex surface facing away from the focusing lens group, a biconcave second negative optical power lens and a second positive optical power lens with a convex surface facing the focusing lens group, which are sequentially arranged; the imaging lens group includes a biconcave third negative optical power lens and a biconvex third positive optical power lens, which are sequentially arranged.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] 1. Simple structure and low cost;

[0011] Without the need to use diffractive optical elements for achromatic design, high-quality imaging in a wide wavelength range of 1.5μm to 5.4μm (shortwave and mediumwave) is achieved simply by matching different lens materials, optimizing the surface parameters of each surface, and appropriately using aspheric surfaces. This greatly reduces system aberrations and corrects chromatic aberration across a wide spectral range.

[0012] 2. Clear imaging;

[0013] This application uses two reflectors to achieve a U-shaped secondary imaging configuration, and a single lens focusing lens group to achieve clear imaging from -40°C to 70°C for the entire optical system. The drive unit is a mature existing technology that is simple and easy to control.

[0014] 3. Large focusing range;

[0015] The focusing range from 2m to infinity is achieved through the focusing lens group, which can be used for short-range calibration in the laboratory to long-range detection in the field. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. Those skilled in the art will readily appreciate that these drawings are merely used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0017] Figure 1 It is a structural schematic diagram of the short-wave infrared spectrum imaging system of the present invention;

[0018] Figure 2 is the optical transfer function (MTF) of the present invention;

[0019] Figure 3 Schematic diagram of the diffuse spots of the optical system of the present invention;

[0020] Figure 4 is a schematic diagram of field curvature and distortion of the present invention;

[0021] Figure 5 is the MTF of the optical system after focusing at a close object distance of 2 m according to the present invention;

[0022] Figure 6 This is the diffuse spot of the optical system after focusing at a close object distance of 2m according to the present invention.

[0023] In the accompanying drawings: 1-fourth positive power lens, 2-fourth negative power lens, 3-first negative power lens, 4-first positive power lens, 5-second negative power lens, 6-second positive power lens, 7-first reflecting mirror, 8-second reflecting mirror, 9-third negative power lens, 10-third positive power lens, 11-filter, 12-detector. DETAILED DESCRIPTION

[0024] Figures 1-6 The following description describes optional embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. In order to teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art will understand that variations or substitutions derived from these embodiments will be within the scope of the present invention. Those skilled in the art will understand that the following features can be combined in various ways to form multiple variations of the present invention. Thus, the present invention is not limited to the following optional embodiments, but is limited only by the claims and their equivalents.

[0025] Example 1.

[0026] A medium and short wave infrared spectral imaging system, such as Figure 1 As shown, the imaging system includes:

[0027] An objective lens group, a focusing lens group, a relay lens group, a reflecting lens group, an imaging lens group, a filter 11 and a detector 12 are arranged in sequence.

[0028] The focusing lens assembly includes a first negative power lens 3 with its convex surface facing the relay lens assembly and its drive unit. The relay lens assembly includes a first positive power lens 4 with its convex surface facing away from the focusing lens assembly, a biconcave second negative power lens 5, and a second positive power lens 6 with its convex surface facing the focusing lens assembly, which are arranged in sequence. The imaging lens assembly includes a biconcave third negative power lens 9 and a biconvex third positive power lens 10, which are arranged in sequence.

[0029] In order to achieve optical path folding, the imaging system further includes:

[0030] The light transmitted from the relay lens group is reflected by the first reflector 7 and the second reflector 8 in sequence and enters the imaging lens group; the angle between the first reflector 7 and the second reflector 8 is 90 degrees.

[0031] In order to improve the optical performance, further, the fourth negative power lens 2, the first negative power lens 3, the first positive power lens 4 and the second positive power lens 6 are meniscus lenses.

[0032] In order to achieve high-quality imaging (reduce aberrations and correct chromatic aberrations), the fourth positive power lens 1, the first positive power lens 4 and the third positive power lens 10 are made of zinc selenide material, and the second negative power lens 5 and the third negative power lens 9 are made of barium fluoride material.

[0033] In order to eliminate chromatic aberration, except for the second negative power lens 5 and the third negative power lens 9, single surfaces of other lenses are aspherical.

[0034] Example 2.

[0035] An application example of the medium- and short-wave infrared spectral imaging system in Example 1 of the present invention.

[0036] In this application example, if Figure 1 As shown, the optical path is sequentially arranged with an objective lens assembly, a focusing lens assembly, a relay lens assembly, a first reflector 7, a second reflector 8, an imaging lens assembly, a filter 11, and a detector 12. The angle between the first reflector 7 and the second reflector 8 is 90 degrees. The detector 12 is cooled, and the aperture is located on the cold aperture of the cooled detector 12, ensuring 100% cold aperture efficiency for the system.

[0037] The objective lens assembly includes a fourth positive power lens 1 with its convex surface facing the object, and a fourth negative power lens 2 with its convex surface facing the object. The focusing lens assembly includes a first negative power lens 3 with its convex surface facing the relay lens assembly, and its drive unit. The relay lens assembly includes a first positive power lens 4 with its convex surface facing away from the focusing lens assembly, a biconcave second negative power lens 5, and a second positive power lens 6 with its convex surface facing the focusing lens assembly, arranged in sequence. The imaging lens assembly includes a biconcave third negative power lens 9 and a biconvex third positive power lens 10, arranged in sequence.

[0038] The fourth negative power lens 2, the first negative power lens 3, the first positive power lens 4, and the second positive power lens 6 are meniscus lenses. The fourth positive power lens 1, the first positive power lens 4, and the third positive power lens 10 are made of zinc selenide, while the second negative power lens 5 and the third negative power lens 9 are made of barium fluoride.

[0039] Except for the second negative power lens 5 and the third negative power lens 9, the other lenses have single aspheric surfaces. The displacement Z of the aspheric surface in the optical axis direction with the vertex as the reference is:

[0040] ;

[0041] y is the height of the optical axis, a is the lens curvature, K is the quadratic surface coefficient, and A, B, C, and D are the aspheric coefficients respectively.

[0042] The parameters of this embodiment are shown in Table 1 below.

[0043] For a medium-wave infrared cooled wide-band focal plane detector 12 with an array size of 640×512 and a pixel size of 15μm, a medium- and short-wave infrared dual-color multispectral imaging optical system with a focal length of 100mm and an F number of 2 is designed.

[0044] Table 1 shows the parameters of each optical device.

[0045] .

[0046] In Table 1 above, the radius of curvature refers to the radius of curvature of each surface, and the pitch refers to the distance between adjacent lens surfaces. For example, the pitch of surface S1 is the distance between surface S1 and surface S2. The glass material is the material used in the manufacturing and processing of the lens.

[0047] Table 2 below lists the aspheric coefficients of S1 of the fourth positive power lens 1, S3 of the fourth negative power lens 2, S6 of the first negative power lens 3, S8 of the first positive power lens 4, S11 of the second positive power lens 6 and S17 of the third positive power lens 10.

[0048] Table 2 shows the parameters of the lens surface.

[0049] .

[0050] The displacement of the optical axis direction of an aspheric surface based on the vertex is defined as follows:

[0051] .

[0052] Among them, the meanings of each parameter are: Z—displacement in the direction of the optical axis, y—height of the optical axis, a—lens curvature, K—quadratic surface coefficient, A, B, C, D—aspheric surface coefficients.

[0053] The working band of the present invention is 1.5 μm to 5.4 μm; the aperture is located on the cold aperture of the refrigeration detector 12, meeting 100% cold aperture efficiency of the system.

[0054] The present invention adopts a secondary imaging design, in which the system entrance pupil is located on the first surface of the fourth positive optical power lens 1, the primary imaging surface is located between the first reflector 7 and the second reflector 8, and the secondary imaging surface is located on the focal plane of the detector 12.

[0055] like Figure 2-Figure 6As shown, the transfer function, field curvature, distortion and RMS diameter of the optical system of the present invention are all within the standard range. This shows that the present invention has good imaging quality.

Claims

1. A medium- and short-wave infrared spectral imaging system, comprising an objective lens assembly and a detector; characterized in that: The imaging system further comprises: A focusing lens group, a relay lens group, and an imaging lens group are sequentially arranged on the optical path between the objective lens group and the detector; the focusing lens group includes a first negative power lens with a convex surface facing the relay lens group and a driving unit thereof; the relay lens group includes a first positive power lens with a convex surface facing away from the focusing lens group, a biconcave second negative power lens, and a second positive power lens with a convex surface facing the focusing lens group, which are sequentially arranged; the imaging lens group includes a biconcave third negative power lens and a biconvex third positive power lens, which are sequentially arranged; The objective lens group includes a fourth positive power lens with a convex surface facing the object and a fourth negative power lens with a convex surface facing the object; The fourth positive power lens, the first positive power lens and the third positive power lens are made of zinc selenide, the second negative power lens and the third negative power lens are made of barium fluoride, and the first negative power lens and the second positive power lens are made of single crystal silicon. Except for the second negative power lens and the third negative power lens, single surfaces of other lenses are aspherical surfaces, the surfaces facing the object of the fourth positive power lens, the fourth negative power lens and the second positive power lens are aspherical surfaces, the surfaces facing away from the object of the first negative power lens and the first positive power lens are aspherical surfaces, and the surface facing away from the detector of the third positive power lens is aspherical surface.

2. The medium- and short-wave infrared spectral imaging system according to claim 1, characterized in that: The imaging system further comprises: The first reflector and the second reflector are used for reflecting the light transmitted from the relay lens group in sequence through the first reflector and the second reflector and then entering the imaging lens group; the angle between the first reflector and the second reflector is 90 degrees.

3. The medium- and short-wave infrared spectral imaging system according to claim 1, characterized in that: The fourth negative power lens, the first negative power lens, the first positive power lens, and the second positive power lens are meniscus lenses.

4. The medium- and short-wave infrared spectral imaging system according to claim 1, characterized in that: The displacement Z of the aspheric surface in the direction of the optical axis based on the vertex of the surface is: ； y is the height of the optical axis, a is the lens curvature, K is the quadratic surface coefficient, and A, B, C, and D are the aspheric coefficients respectively.

5. The medium- and short-wave infrared spectral imaging system according to claim 1, characterized in that: The imaging system further comprises: A filter is provided on the optical path between the imaging lens assembly and the detector.

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