Infrared large field of view wide spectral range multispectral imaging spectrometer optical system

Abstract

The application discloses an infrared large-view-field wide-spectrum multi-spectrum imaging spectrometer optical system, which is coaxially arranged in sequence from an object plane to a focal plane as a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a filter wheel; the first lens and the fourth lens are meniscus positive lenses, the second lens, the third lens and the fifth lens are meniscus negative lenses, and the sixth lens is a double-convex positive lens. The application adopts common chalcogenide and zinc selenide crystal infrared materials, corrects aberration and chromatic aberration by optimizing surface shape parameters of each surface and adopting aspheric surfaces, realizes high-quality imaging in a wide waveband range of 2.5-15 mu m, has the characteristics of large view field, small distortion, athermalization and super-long back intercept, is easy to produce and adjust, has strong versatility, and can be applied to the fields of monitoring of chemical harmful gases, environmental protection, agriculture and food safety, medical treatment and health and judicial identification.

Description

Technical Field

[0001] This invention belongs to the field of infrared spectral detection technology and relates to an optical system for an infrared wide-field-of-view broadband multispectral imaging spectrometer, particularly an optical system for an infrared wide-field-of-view broadband multispectral imaging spectrometer with passive thermal differential correction function, which has a 2.5μm to 15μm infrared wide-field-of-view broadband multispectral imaging spectrometer. Background Technology

[0002] With the rapid development of chemical industry technology, multispectral imaging spectrometers with integrated imaging and spectral capabilities and real-time monitoring have become a key research area. Since traditional single-band infrared detection systems can only identify limited target information, the development of broadband multispectral infrared imaging spectrometers can improve target monitoring and identification.

[0003] Broadband multispectral imaging spectrometers have good platform versatility and, in addition to monitoring harmful chemical gases, have wide application value in fields such as environmental protection, agriculture and food safety, medical and health care, and forensic identification.

[0004] Due to the limitation of the spectral range, only a few infrared optical materials, such as zinc selenide, zinc sulfide, gallium arsenide, and chalcogenide glass, can cover a wide spectral band from 2.5 μm to 15 μm. The use of low-refractive-index materials presents problems such as difficulty in correcting system aberrations and chromatic aberrations.

[0005] Currently, there are almost no domestic or international patent documents related to wide-field-of-view, broad-spectrum, multispectral infrared optical systems. Existing patent documents suffer from problems such as narrow and discontinuous spectral bands and small field of view. For example:

[0006] Patent CN110398828A discloses a broadband, large relative aperture mid-to-long-wave infrared imaging optical system. The optical system operates in the 3μm–14μm wavelength range, has a focal length of 25mm, a field of view of 30°, a relative aperture of 1 / 1, and features active focusing at high and low temperatures to reduce thermal difference. However, because this optical system combines two independent optical systems (mid-wave 3μm–6μm and long-wave 6μm–14μm), miniaturization is difficult, and it is not a thermally absorbent system.

[0007] Patent CN112882210A discloses a mid-to-long wavelength wide-band confocal infrared optical system. The optical system operates in the 3μm–14μm wavelength range, has a focal length of 50mm, a field of view of 15.7°, and an F-number of 1.1. The optical system has a relatively small field of view and a narrow spectral band.

[0008] US Patent 2007183024A1 discloses an uncooled mid-to-long-range dual-band infrared optical system. The optical system operates in the 3μm–5μm and 8μm–12μm wavelength ranges, has a focal length of 1.72 inches, an f-number of 1.25, and a field of view of 45°. However, the optical system exhibits discontinuous and narrow spectral bands and cannot achieve passive calorimetric ablation. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by designing an optical system for a 2.5μm to 15μm infrared wide-field-of-view broadband multispectral imaging spectrometer. This system can be matched with a 640×512@17μm broadband uncooled area array infrared detector, satisfying the requirement of passive calorimetry to eliminate thermal differences at temperatures ranging from -50℃ to +80℃. The system achieves low distortion and high-quality imaging while ensuring a wide field of view.

[0010] The technical solution adopted by this invention to solve its technical problem is:

[0011] An optical system for a 2.5μm to 15μm infrared wide field-of-view broadband multispectral imaging spectrometer, wherein the system comprises, in sequence along the direction of light propagation: first objective lens, second objective lens, third objective lens, fourth objective lens, fifth objective lens, sixth objective lens, and filter wheel.

[0012] The objective lens is described as follows: the first lens is a positive power meniscus lens with its concave surface facing the object side; the second lens is a negative power meniscus lens with its concave surface facing the object side; the third lens is a negative power meniscus lens with its concave surface facing the object side; the fourth lens is a positive power meniscus lens with its concave surface facing the object side; the fifth lens is a negative power meniscus lens with its concave surface facing the image side; and the sixth lens is a positive power biconvex lens.

[0013] The ranges of the focal lengths f1, f2, f3, f4, f5, and f6 of the first, second, third, fourth, fifth, and sixth objective lenses, divided by the total focal length f of the optical system, are as follows:

[0014] 3.1 < f1 / f < 5.2;

[0015] -3.5 < f² / f < -2.1;

[0016] -2.2 < f3 / f < -1.3;

[0017] 1.1 < f4 / f < 1.8;

[0018] -6.5 < f5 / f < -3.8;

[0019] 1.1 < f6 / f < 1.8.

[0020] The optical system of the 2.5μm~15μm infrared wide-field-of-view broadband multispectral imaging spectrometer utilizes a total of seven aspherical surfaces: the rear surface of the first objective lens, the front and rear surfaces of the second objective lens, the rear surface of the third objective lens, the front surface of the fourth objective lens, the front surface of the fifth objective lens, and the front surface of the sixth objective lens. The aspherical surface configuration used in the system is as follows:

[0021]

[0022] In the formula: Z represents the distance sag from the vertex of the aspherical surface at a height of r along the optical axis; c is the radius of curvature; k is the conic coefficient; and A, B, C, and D are higher-order aspherical coefficients.

[0023] The optical system of the 2.5μm~15μm infrared wide field of view broadband multispectral imaging spectrometer has the following components: the first objective lens, the second objective lens, the fifth objective lens, and the filter wheel can be made of zinc selenide, zinc sulfide, or gallium arsenide; the third objective lens, the fourth objective lens, and the sixth objective lens are made of chalcogenide glass.

[0024] The beneficial effects of this invention are:

[0025] 1) This invention uses common infrared materials (chalcogenide and zinc selenide). By optimizing the surface parameters of each surface and appropriately using aspherical surfaces, high-quality imaging of the system in a wide band of 2.5μm to 15μm is achieved, greatly reducing the system's chromatic aberration and correcting the aberrations of the system in a wide spectral range.

[0026] 2) This invention uses 6 lenses, which are small in size, compact in structure, and easy to assemble and adjust the optical mechanism, making it suitable for widespread application;

[0027] 3) This invention adopts an F-number of 1 to ensure that the energy reaching the detector is strong enough to clearly image targets at long distances with small temperature differences;

[0028] 4) This invention has an ultra-long back cutoff and functional expansion capabilities, allowing for the placement of a correction baffle and 1-2 sets of filter wheels;

[0029] 5) This invention also meets the requirement of small distortion while ensuring a large field of view (30.5°×24.6), ensuring that the spectral edge acquisition is not distorted;

[0030] 6) This invention uses a rotating infrared filter to divide the light reflected from the object entering the infrared objective into multiple spectral channels. The image information of the object in each spectral channel is acquired by the imaging detector, thereby calculating the spectrum of the target.

[0031] 7) This invention combines sulfide-based and zinc selenide glass, which have good thermal difference elimination effects, to achieve passive calorific thermal difference elimination in the entire temperature range of -50℃ to 80℃. This ensures the high imaging quality of the lens in this temperature range and can be applied to places with harsh environmental temperatures.

[0032] 8) The optical lens in this invention meets the technical requirements for machining on a conventional diamond lathe, thus reducing production costs.

[0033] 9) This invention has a wide range of applications, such as chemical industry gas monitoring, environmental protection, agriculture and food safety, medical and health care, and forensic identification. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the working principle of a wide field-of-view, broadband multispectral imaging spectrometer.

[0035] Figure 2 This is a schematic diagram of the filter wheel.

[0036] Figure 3 This is a schematic diagram of the optical system of the present invention.

[0037] Figure 4 This is the field curvature and distortion curve diagram of the present invention.

[0038] Figure 5 This is a transfer function curve of the present invention at 30mm / lp, with the horizontal axis representing the number of line pairs per millimeter and the vertical axis representing the contrast value.

[0039] Figure 6 This is the system dispersion pattern of the present invention.

[0040] The labels for each of the attached figures are as follows: 1-First objective lens, 2-Second objective lens, 3-Third objective lens, 4-Fourth objective lens, 5-Fifth objective lens, 6-Sixth objective lens, 7-Filter wheel. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings.

[0042] To provide a wide-band multispectral imaging system for a near real-time field-level multispectral infrared imaging spectrometer, referencing Figure 1 As shown, this invention discloses an optical system for a 2.5μm–15μm infrared wide-field-of-view broadband multispectral imaging spectrometer. Figure 3 .

[0043] As a basic implementation example, this system can be used with a 640×512@17μm broadband uncooled area array infrared detector, with an operating wavelength of 2.5μm to 15μm, a focal length of 21mm, a field of view of 30.5°×24.6°, an F-number (the ratio of the system focal length to the aperture) of 1, and distortion of less than 2%.

[0044] The optical system consists of, in sequence along the direction of light propagation: objective lens 1, objective lens 2, objective lens 3, objective lens 4, objective lens 5, objective lens 6, and filter wheel 7.

[0045] The objective lens 1 is a positive power meniscus lens with its concave surface facing the object; the objective lens 2 is a negative power meniscus lens with its concave surface facing the object; the objective lens 3 is a negative power meniscus lens with its concave surface facing the object; the objective lens 4 is a positive power meniscus lens with its concave surface facing the object; the objective lens 5 is a negative power meniscus lens; and the objective lens 6 is a positive power biconvex lens. The filter wheel 7 is placed perpendicular to the incident light beam and is divided into multiple spectral channels. The light reflected from the object entering the infrared objective lens reaches the filter and is cut off before a specific wavelength by the broadband pass filter. The image information of the object in each spectral channel is acquired by the imaging detector, thereby calculating the spectrum of the target.

[0046] The focal lengths of the first objective lens 1, the second objective lens 2, the third objective lens 3, the fourth objective lens 4, the fifth objective lens 5, and the sixth objective lens 6 are f1, f2, f3, f4, f5, and f6, respectively, and their relationships with the total focal length f of the optical system are as follows:

[0047] 3.1 < f1 / f < 5.2;

[0048] -3.5 < f² / f < -2.1;

[0049] -2.2 < f3 / f < -1.3;

[0050] 1.1 < f4 / f < 1.8;

[0051] -6.5 < f5 / f < -3.8;

[0052] 1.1 < f6 / f < 1.8.

[0053] Values ​​exceeding the upper limit or falling below the lower limit of the aforementioned range will make it difficult to correct wide-band chromatic aberration or aberrations in the optical system. Obviously, those skilled in the art can find reasonable values ​​within the aforementioned range and combine them appropriately to achieve the objectives of this invention.

[0054] Table 1 lists the technical parameters of the optical system of the 2.5μm~15μm infrared wide field-of-view broadband multispectral imaging spectrometer.

[0055] Table 1

[0056]

[0057] Table 2 lists the specific design data of the optical system.

[0058] Table 2

[0059]

[0060] Table 3 lists the positions and aspheric coefficients of the aspheric surfaces in the optical system. The aspheric surface form used in the system is as follows:

[0061]

[0062] In the formula: Z represents the distance sag from the vertex of the aspherical surface at a height of r along the optical axis; c is the radius of curvature; k is the conic coefficient; and A, B, C, and D are higher-order aspherical coefficients.

[0063] Table 3

[0064]

[0065] Preferably, the focal lengths of the first objective lens 1, the second objective lens 2, the third objective lens 3, the fourth objective lens 4, the fifth objective lens 5, and the sixth objective lens 6 are f1, f2, f3, f4, f5, and f6, respectively, and the relationships between these focal lengths and the total focal length f of the optical system are f1 / f, f2 / f, f3 / f, f4 / f, f5 / f, and f6 / f, respectively, which are 3.97, -2.66, -1.67, 1.4, -4.98, and 1.41.

[0066] The materials of the first objective lens 1, the second objective lens 2, the fifth objective lens 5, and the filter wheel 7 can be zinc selenide, zinc sulfide, or gallium arsenide; the third objective lens 3, the fourth objective lens 4, and the sixth objective lens 6 are chalcogenide.

[0067] Preferably, the materials of the first objective lens 1, the second objective lens 2, the fifth objective lens 5, and the filter wheel 7 are zinc selenide. The third objective lens 3, the fourth objective lens 4, and the sixth objective lens 6 are IRG206 lenses.

[0068] The sixth lens 6 of the invention has an ultra-long back cutoff of 28mm between it and the detector window, and the distance between the filter wheel 7 and the image plane is 10mm.

[0069] This invention combines sulfide and zinc selenide glass, which have good thermal differential properties, to achieve passive calorimetric thermal differential reduction in the entire temperature range of -50℃ to +80℃, ensuring high-quality imaging of the lens across the entire temperature range.

Claims

1. An optical system for an infrared wide-field-of-view broadband multispectral imaging spectrometer, comprising an infrared detector, characterized in that: The optical system includes, in sequence along the direction of light propagation, a first objective lens (1), a second objective lens (2), a third objective lens (3), a fourth objective lens (4), a fifth objective lens (5), a sixth objective lens (6), and a filter wheel (7). The objective lens first lens (1) is a positive power meniscus lens with its concave surface facing the object side, the objective lens second lens (2) is a negative power meniscus lens with its concave surface facing the object side, the objective lens third lens (3) is a negative power meniscus lens with its concave surface facing the object side, the objective lens fourth lens (4) is a positive power meniscus lens with its concave surface facing the object side, the objective lens fifth lens (5) is a negative power meniscus lens with its concave surface facing the image side, and the objective lens sixth lens (6) is a positive power biconvex lens. The rear surface of the first objective lens (1), the front and rear surfaces of the second objective lens (2), the rear surface of the third objective lens (3), the front surface of the fourth objective lens (4), the front surface of the fifth objective lens (5), and the front surface of the sixth objective lens (6) are aspherical; the front surface of the first objective lens (1), the front surface of the third objective lens (3), the rear surface of the fourth objective lens (4), the rear surface of the fifth objective lens (5), and the rear surface of the sixth objective lens (6) are spherical. The relationships between the focal lengths f1, f2, f3, f4, f5, and f6 of the first objective lens (1), the second objective lens (2), the third objective lens (3), the fourth objective lens (4), the fifth objective lens (5), and the sixth objective lens (6) and the total focal length f of the optical system are as follows: ； The optical system has a field of view of 30.5° × 24.6°, distortion of less than 2%, and an operating wavelength of 2.5μm to 15μm.

2. The optical system of the infrared large field-of-view broadband multispectral imaging spectrometer as described in claim 1, characterized in that: The distance between the sixth objective lens (6) and the detector window ranges from 5mm to 32mm.

3. The optical system of the infrared large field-of-view broadband multispectral imaging spectrometer as described in claim 1, characterized in that: The distance between the filter wheel (7) and the image plane is 10mm to 30mm.

4. The optical system of the infrared large field-of-view broadband multispectral imaging spectrometer as described in claim 1, characterized in that: The materials of the first objective lens (1), the second objective lens (2), the fifth objective lens (5) and the filter wheel (7) are zinc selenide, zinc sulfide or gallium arsenide; the materials of the third objective lens (3), the fourth objective lens (4) and the sixth objective lens (6) are chalcogenide glass.

5. The optical system of the infrared large field-of-view broadband multispectral imaging spectrometer as described in claim 1, characterized in that: The aspherical form is: ； In the formula: Z represents the distance sag from the vertex of the aspherical surface at a height of r along the optical axis; c is the radius of curvature; k is the conic coefficient; and A, B, C, and D are higher-order aspherical coefficients.

6. The optical system of the infrared large field-of-view broadband multispectral imaging spectrometer as described in any one of claims 1-5, characterized in that: The optical system passively and calorily eliminates heat difference at temperatures ranging from -50℃ to +80℃.

7. The optical system of the infrared large field-of-view broadband multispectral imaging spectrometer as described in any one of claims 1-5, characterized in that: The infrared detector is a broadband uncooled area array infrared detector with a resolution of 640×512@17μm, 640×512@12μm, 1024×768@12μm, or 1280×1024@12μm.

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