Intermediate-short wave infrared spectrum imaging system

Abstract

The invention belongs to the spectrum technology, and particularly relates to a medium-short wave infrared spectrum imaging system which comprises an objective lens group and a detector. The focusing lens group, the relay lens group and the imaging lens group are sequentially arranged on a light path between the objective lens group and the detector; the focusing lens group comprises a first negative focal power lens with a convex surface facing the relay lens group and a driving unit of the first negative focal power lens; the relay lens group comprises a first positive focal power lens with a convex surface back to the focusing lens group, a biconcave second negative focal power lens and a second positive focal power lens with a convex surface facing the focusing lens group, which are arranged in sequence; and the imaging lens group comprises a biconcave third negative focal power lens and a biconvex third positive focal power lens which are arranged in sequence. The method has the advantages of clear imaging, achromatism without a diffraction part and the like, and is used in spectral imaging.

Description

Technical Field

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

[0002] Multispectral imaging combines the characteristics of traditional spectrometers and photoelectric detection technology, detects target scene information and analyzes and extracts spectral features, and provides two-dimensional image information and spectral information at the same time, with the quasi-real-time characteristics of the new generation of spectral telemetry. Wide-band multispectral imaging technology is a new detection method that can image the same target in multiple spectral bands and measure spectral features. It is targeted according to the target's own radiation characteristics, thereby suppressing background clutter and improving target identification capabilities. This technology has been widely used in the field of remote sensing, including: early thermal disaster warning, subway safety monitoring (highly toxic and dangerous gas detection) and coal mine monitoring (methane detection), high-voltage power transmission and transformation detection (sulfur hexafluoride detection), chemical plant leaks (flammable and explosive dangerous gas detection) and other applications.

[0003] In order to obtain the radiation characteristics of the target, the multi-spectral imaging system consists of a filter wheel system with multiple filters and a wide-spectrum infrared optical system. Commonly used multi-spectral spectrometers are mainly used for remote sensing of long-distance targets beyond 1000m. For close-range detection of laboratory gas pools, due to the limitations of the optical system, it is impossible to take into account the detection of long-distance targets and close-range targets (within 2m).

[0004] Since the refractive index and dispersion characteristics of optical materials vary greatly in different bands, it is very difficult to correct the chromatic aberration of optical systems in the entire wide band range (1.5μm~5.4μm). At the same time, the limited optical materials available in the wide wave range (1.5μm~5.4μm) also increase 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 objective of the present invention is achieved through the following technical solutions: A medium- and short-wave infrared spectrum imaging system, comprising an objective lens group and a detector; the imaging system also includes: A focusing lens group, a relay lens group, and an imaging lens group that 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 its driving unit, the relay lens group includes a first positive-power lens with a convex surface facing away from the focusing lens group, a double-concave second negative-power lens, and a second positive-power lens with a convex surface facing the focusing lens group that are sequentially arranged; the imaging lens group includes a double-concave third negative-power lens and a double-convex third positive-power lens that are sequentially arranged.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Simple structure and low cost; There is no need to use diffractive optical elements for achromatic design. By only matching different materials of the lenses, optimizing the surface shape parameters of each surface, and appropriately using aspherical surfaces, high-quality imaging of the system in the wide wavelength range of 1.5 μm to 5.4 μm (short wave, medium wave) is achieved, greatly reducing the system aberration and correcting the chromatic aberration of the system in the wide spectral range; 2. Clear imaging; This application uses two mirrors to achieve a secondary imaging configuration of U-shaped folding, and realizes clear imaging of the entire optical system from -40 °C to 70 °C through the focusing lens group of a single lens. The driving unit belongs to the mature prior art and is simple and easy to control; 3. Large focusing range; A focusing range from 2 m to infinity is achieved through the focusing lens group, which can realize close-range calibration in the laboratory and long-distance detection in the field. Description of the Drawings

[0008] Referring to the accompanying drawings, the disclosure of the present invention will become easier to understand. It is easy for those skilled in the art to understand that these drawings are only used to illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention. In the figures: Figure 1 is a schematic structural diagram of the short-wave infrared spectral imaging system of the present invention; Figure 2 is the optical transfer function (MTF) of the present invention; Figure 3 is a schematic diagram of the optical system spot diagram of the present invention; Figure 4 is a schematic diagram of the field curvature and distortion of the present invention; Figure 5 is the MTF of the optical system after focusing on a close object distance of 2 m of the present invention; Figure 6 is the optical system spot diagram after focusing on a close object distance of 2 m of the present invention.

[0009] In the attached drawings: 1 - the fourth positive focal length lens, 2 - the fourth negative focal length lens, 3 - the first negative focal length lens, 4 - the first positive focal length lens, 5 - the second negative focal length lens, 6 - the second positive focal length lens, 7 - the first mirror, 8 - the second mirror, 9 - the third negative focal length lens, 10 - the third positive focal length lens, 11 - the filter, 12 - the detector. Detailed implementation manners

[0010] Figures 1-6 The following description and illustration depict alternative specific implementation manners of the present invention to teach those skilled in the art how to implement and reproduce the present invention. Some conventional aspects have been simplified or omitted for the purpose of teaching the technical solution of the present invention. Those skilled in the art should understand that variations or substitutions derived from these specific implementation manners will fall within the scope of the present invention. Those skilled in the art should 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 alternative specific implementation manners, but is only defined by the claims and their equivalents.

[0011] Embodiment 1.

[0012] A medium and short wave infrared spectral imaging system, as Figure 1 shown, the imaging system includes:

[0013] An objective lens group, a focusing lens group, a relay lens group, a mirror group, an imaging lens group, a filter 11 and a detector 12 are arranged in sequence.

[0014] The focusing lens group includes the first negative focal length lens 3 with its convex surface facing the relay lens group and its driving unit. The relay lens group includes the first positive focal length lens 4 with its convex surface facing away from the focusing lens group, the double concave second negative focal length lens 5 and the second positive focal length lens 6 with its convex surface facing the focusing lens group arranged in sequence. The imaging lens group includes the double concave third negative focal length lens 9 and the double convex third positive focal length lens 10 arranged in sequence.

[0015] In order to achieve optical path folding, further, the imaging system further includes: The light transmitted from the relay lens group is reflected by the first mirror 7 and the second mirror 8 in sequence and enters the imaging lens group; the included angle between the first mirror 7 and the second mirror 8 is 90 degrees.

[0016] In order to improve the optical performance, further, the fourth negative focal length lens 2, the first negative focal length lens 3, the first positive focal length lens 4 and the second positive focal length lens 6 are meniscus lenses.

[0017] In order to achieve high-quality imaging (reduce aberrations and correct chromatic aberrations), further, the fourth positive focal length lens 1, the first positive focal length lens 4, and the third positive focal length lens 10 are made of zinc selenide material, and the second negative focal length lens 5 and the third negative focal length lens 9 are made of barium fluoride material.

[0018] In order to correct chromatic aberration, further, except for the second negative focal length lens 5 and the third negative focal length lens 9, the single surfaces of other lenses are aspherical surfaces.

[0019] Embodiment 2.

[0020] According to the application example of the mid-wave and short-wave infrared spectral imaging system in Embodiment 1 of the present invention.

[0021] In this application example, as Figure 1 shown, on the optical path, an objective lens group, a focusing lens group, a relay lens group, a first mirror 7, a second mirror 8, an imaging lens group, a filter 11, and a detector 12 are sequentially arranged. The included angle between the first mirror 7 and the second mirror 8 is 90 degrees. The detector 12 is cooled, and the aperture stop is located on the cold aperture stop of the cooled detector 12, meeting the 100% cold aperture efficiency of the system.

[0022] The objective lens group includes a fourth positive focal length lens 1 with a convex surface facing the object side and a fourth negative focal length lens 2 with a convex surface facing the object side. The focusing lens group includes a first negative focal length lens 3 with a convex surface facing the relay lens group and its driving unit. The relay lens group includes a first positive focal length lens 4 with a convex surface facing away from the focusing lens group, a biconcave second negative focal length lens 5, and a second positive focal length lens 6 with a convex surface facing the focusing lens group arranged in sequence. The imaging lens group includes a biconcave third negative focal length lens 9 and a biconvex third positive focal length lens 10 arranged in sequence.

[0023] The fourth negative focal length lens 2, the first negative focal length lens 3, the first positive focal length lens 4, and the second positive focal length lens 6 are meniscus lenses. The fourth positive focal length lens 1, the first positive focal length lens 4, and the third positive focal length lens 10 are made of zinc selenide material, and the second negative focal length lens 5 and the third negative focal length lens 9 are made of barium fluoride material.

[0024] Except for the second negative focal length lens 5 and the third negative focal length lens 9, the single surfaces of other lenses are aspherical surfaces. The displacement Z of the aspherical surface in the optical axis direction with respect to the vertex of the surface is: ; y is the height of the optical axis, a is the curvature of the lens, K is the conic coefficient, and A, B, C, and D are the aspherical coefficients respectively.

[0025] The parameters of this embodiment are shown in Table 1 below.

[0026] For a medium-wave infrared cooled wide-band focal plane detector 12 with an array size of 640×512 and a pixel size of 15 μm, a medium- and short-wave infrared dual-color multi-spectral imaging optical system with a focal length of 100 mm and an F number of 2 is designed.

[0027] Table 1 shows the parameters of each optical device.

[0028] .

[0029] In Table 1 above, the radius of curvature refers to the radius of curvature of each surface, and the spacing refers to the distance between two surfaces of adjacent lenses. For example, the spacing of surface S1 is the distance between surface S1 and surface S2. Glass material is the material used for manufacturing and processing of the lens.

[0030] 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.

[0031] Table 2 shows the parameters of the lens surface.

[0032] .

[0033] The displacement of the optical axis direction of an aspherical surface based on the vertex is defined as follows: .

[0034] Among them, the meanings of each parameter are: Z—position change 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.

[0035] The working band of the present invention is 1.5 μm to 5.4 μm; the diaphragm is located on the cold diaphragm of the refrigeration detector 12, satisfying the 100% cold diaphragm efficiency of the system.

[0036] The present invention adopts a secondary imaging design, wherein the system entrance pupil is located on the first surface of the fourth positive power lens 1 , the primary imaging plane is located between the first reflector 7 and the second reflector 8 , and the secondary imaging plane is located on the focal plane of the detector 12 .

[0037] like Figures 2-6 As shown, the optical system transfer function, field curvature, distortion and RMS diameter of the point dispersion spot of the present invention are all within the standard range. It can be seen that the present invention has good imaging quality.

Claims

1. A mid-wave and short-wave infrared spectral imaging system, comprising an objective lens group and a detector; characterized in that, The imaging system further includes: A focusing lens group, a relay lens group, and an imaging lens group that 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 its driving unit, the relay lens group includes a first positive-power lens with a convex surface facing away from the focusing lens group, a double-concave second negative-power lens, and a second positive-power lens with a convex surface facing the focusing lens group that are sequentially arranged; the imaging lens group includes a double-concave third negative-power lens and a double-convex third positive-power lens that are sequentially arranged.

2. The mid-wave and short-wave infrared spectral imaging system according to claim 1, wherein The imaging system further includes: A first reflector and a second reflector, the light transmitted from the relay lens group sequentially passes through the first reflector and the second reflector and is reflected into the imaging lens group; the included angle between the first reflector and the second reflector is 90 degrees.

3. The mid-wave and short-wave infrared spectral imaging system according to claim 1, wherein The objective lens group includes a fourth positive-power lens with a convex surface facing the object side and a fourth negative-power lens with a convex surface facing the object side.

4. The mid-wave and short-wave infrared spectral imaging system according to claim 3, 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.

5. The mid-wave and short-wave infrared spectral imaging system according to claim 3, wherein The fourth positive-power lens, the first positive-power lens, and the third positive-power lens are made of zinc selenide material.

6. The mid-wave and short-wave infrared spectral imaging system according to claim 3, wherein The second negative-power lens and the third negative-power lens are made of barium fluoride material.

7. The mid-wave and short-wave infrared spectral imaging system according to claim 3, wherein Except for the second negative-power lens and the third negative-power lens, the single surfaces of other lenses are aspherical surfaces.

8. The mid-wave and short-wave infrared spectral imaging system according to claim 7, characterized in that, The displacement Z of the aspherical surface in the optical axis direction with the vertex of the surface as the reference is: ； y is the height of the optical axis, a is the lens curvature, K is the conic coefficient, and A, B, C, and D are the aspherical coefficients respectively.

9. The mid-wave and short-wave infrared spectral imaging system according to claim 1, wherein The imaging system further includes: A filter, the filter is arranged on the optical path between the imaging lens group and the detector.

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