Aperture-divided infrared multispectral optical lens for gas imaging

Abstract

The invention discloses a sub-aperture infrared multispectral optical lens for gas imaging, and belongs to the technical field of gas imaging. Comprising a sub-aperture optical filter, a sub-aperture optical system and an imaging detector, wherein the sub-aperture optical filter is composed of N infrared optical filters with different band-pass wavebands; the sub-aperture optical system is composed of N sets of sub-lens groups with the same structure, and the sub-lens groups are respectively located in N apertures; the N sub-aperture optical filters correspond to the N sub-aperture optical systems, and imaging of the N channels shares one imaging detector. According to the invention, a plurality of spectrums are divided in a 7-14 [mu] m long-wave infrared spectrum range by adopting a sub-aperture technology, and multispectral images of the same image can be obtained on one detector at the same time. According to the invention, the mixed gas in a complex environment can be detected, the same target can be simultaneously measured in a plurality of wavebands, the environmental background interference is reduced, and a solution is provided for improving the gas detection precision.

Description

Technical Field

[0001] The invention relates to the technical field of gas imaging, and more particularly to a split-aperture infrared multi-spectral optical lens for gas imaging. Background Art

[0002] Infrared gas imaging has fast response speed, long detection distance, large coverage, and can detect a wide variety of gases. It is suitable for rapid detection and real-time online analysis, and is an important research direction in the field of gas detection. Multispectral technology is a technology that can simultaneously obtain spectral information in multiple wavelength ranges, and can provide more information on the physical properties of the target. The infrared band has a significant response to the vibration and rotational energy levels of gas molecules, especially in the mid-infrared band and long-infrared band of the "atmospheric window". Many hazardous gases such as hydrogen sulfide, methane, carbon monoxide, sulfur dioxide, etc. have significant selective absorption characteristics in this band. Infrared multispectral technology can be used to distinguish different types of gases and achieve accurate measurements.

[0003] Currently, devices that can achieve infrared multispectral imaging usually use filter wheels or grating splitting methods, which are not only complicated to assemble and adjust, bulky, and expensive, but also difficult to obtain multispectral image data of the target area at the same time. In addition, multispectral infrared technology that can achieve multi-channel splitting usually uses microlens arrays or multiple optical systems and multiple detectors. The system is large in size and expensive, and inconsistent performance of the optical system and detectors will lead to imaging errors. Devices that use aperture separation technology to achieve multispectral imaging usually have phenomena such as stray light crosstalk between channels.

[0004] Therefore, how to provide a divided-aperture infrared multi-spectral optical lens for gas imaging is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a split-aperture infrared multi-spectral optical lens for gas imaging, which is small in size, low in cost, high in real-time performance, simple in assembly and adjustment, and convenient for image data processing. The split-aperture technology is used to divide multiple spectra within the 7-14μm long-wave infrared spectrum, and multi-spectral images of the same image can be obtained simultaneously on one detector. It can realize the detection of mixed gases in complex environments, and simultaneously measure the same target in multiple bands, reducing environmental background interference and improving the accuracy of gas detection.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A fractional-aperture infrared multi-spectral optical lens for gas imaging, comprising a fractional-aperture filter, a fractional-aperture optical system and an imaging detector; wherein the fractional-aperture filter is composed of N infrared filters with different bandpass bands; the fractional-aperture optical system is composed of N sets of sub-lens groups with the same structure, which are respectively located in N apertures; N fractional-aperture filters correspond to N fractional-aperture optical systems, and imaging of N channels shares one imaging detector.

[0008] The number N depends on the size of the detector.

[0009] For example, a detector with a relatively square detection surface can be arranged in 2*2, 3*3, etc. channels, and a relatively narrow and long detector can be arranged in 2*3, etc. channels.

[0010] Furthermore, the imaging detector is a non-cooled detector.

[0011] Furthermore, the imaging detector has a response band of 7 to 14 μm and has a germanium window.

[0012] Furthermore, the imaging detector includes a detector window.

[0013] Furthermore, the imaging field angle of each of the divided-aperture optical systems is the same.

[0014] Furthermore, each set of sub-lens groups includes two lenses with positive optical power, namely, the first lens L1 of the sub-aperture optical system sub-lens group and the second lens L2 of the sub-aperture optical system sub-lens group.

[0015] Furthermore, each of the sub-aperture filters is located at the front end of the first lens L1 of each of the sub-aperture optical system sub-lens groups.

[0016] Furthermore, the distance between the second lens L2 of each of the sub-aperture optical system sub-lens groups and the detection surface is 8mm-10mm.

[0017] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a divided-aperture infrared multi-spectral optical lens for gas imaging, which has the following beneficial effects:

[0018] 1. It realizes light splitting and imaging by means of aperture division, and uses an imaging detector to obtain spectral imaging. It has the advantages of small size, simple installation and adjustment, low cost and good stability.

[0019] 2. Multi-spectral images of the same image can be obtained on one detector at the same time. It can detect mixed gases in complex environments and measure the same target in multiple bands at the same time, reducing environmental background interference, improving the accuracy of gas detection, and facilitating subsequent image data processing.

[0020] 3. The type of pre-filter can be replaced according to the characteristic absorption peak of different gases, so as to realize the imaging of various gases without changing the equipment. It has the characteristics of simple operation and low cost.

[0021] 4. The back focus of the lens is greater than 8mm, which can be adapted to infrared detectors with windows, effectively reducing the interference of background signals.

[0022] 5. The lens has a small F number (0.8~1), a large relative aperture, and a large energy receiving capacity, which can effectively improve the image signal-to-noise ratio.

[0023] 6. This lens uses only two lenses to achieve a large imaging field of view and high imaging quality.

[0024] 7. The number of channels with different apertures can be changed according to the size of the detector element, which has good flexibility and scalability.

[0025] 8. The lens has a large field of view (diagonal full field of view 50°~60°), and can obtain a larger image field of view area at the same imaging distance.

[0026] 9. The overall mechanical structure of the lens adopts an integrated design, which not only separates the optical structures of the six channels, but also effectively suppresses the stray light crosstalk between channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0028] Figure 1 The optical path diagram of the split-aperture infrared multi-spectral optical lens provided in Example 1 of the present invention;

[0029] Figure 2 A sub-channel modulation transfer function curve diagram of the divided-aperture infrared multi-spectral optical lens provided in Example 1 of the present invention;

[0030] Figure 3 A sub-channel point diagram of the aperture-divided infrared multi-spectral optical lens provided in Example 1 of the present invention;

[0031] Figure 4 A ray tracing diagram of all channels of the aperture-divided infrared multi-spectral optical lens provided in Example 1 of the present invention;

[0032] Figure 5 An optical path diagram of a split-aperture infrared multi-spectral optical lens provided in Example 2 of the present invention;

[0033] Figure 6 A sub-channel modulation transfer function curve diagram of the aperture-divided infrared multi-spectral optical lens provided in Example 2 of the present invention;

[0034] Figure 7 A sub-channel point diagram of the aperture-divided infrared multi-spectral optical lens provided in Example 2 of the present invention;

[0035] Figure 8 A ray tracing diagram of all channels of the aperture-divided infrared multi-spectral optical lens provided in Example 2 of the present invention;

[0036] Among them, 1. a divided aperture filter; 2. a first lens of a divided aperture optical system sub-lens group; 3. a second lens of a divided aperture optical system sub-lens group; 4. a detector window; 5. an imaging detector. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The purpose of the present invention is to provide a split-aperture infrared multi-spectral optical lens for gas imaging, including a split-aperture filter, a split-aperture optical system and an imaging detector; wherein the split-aperture filter is composed of N infrared filters with different bandpass bands; the split-aperture optical system is composed of N sets of sub-lens groups with the same structure, which are respectively located in N apertures; N split-aperture filters correspond to N split-aperture optical systems, and the imaging of N channels shares one imaging detector. The present invention uses split-aperture technology to divide multiple spectra within the 7-14μm long-wave infrared spectrum range, and can simultaneously obtain multi-spectral images of the same image on one detector. It can realize the detection of mixed gases in complex environments, and simultaneously measure the same target in multiple bands, reducing environmental background interference and providing a solution to improve the accuracy of gas detection.

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Embodiment 1:

[0041] The embodiment of the present invention discloses a split-aperture infrared multi-spectral optical lens for gas imaging, which includes a split-aperture filter, a split-aperture optical system group and an imaging detector. The split-aperture optical system includes 6 sets of sub-lens groups with the same structure, and each channel includes a front filter and a sub-lens group. Its working band is 7-14μm, the lens focal length is 7.5mm, F / #=1, and the full field of view is 40°×32°.

[0042] See attached Figure 1 The optical lens uses two kinds of glass materials, and the six sub-aperture channels are evenly distributed in a 3×2 format, including a sub-aperture filter group of 6 pieces and a sub-aperture lens group of 2×6 pieces. According to the incident direction of light, they are filter element 1, the first lens 2 of the sub-lens group, the second lens 3 of the sub-lens group, the detector window 4, and the imaging detector 5. The imaging detector 5 is placed at the common image plane position of the six sub-aperture channels.

[0043] In a specific implementation manner, the lens surface type of the sub-lens group of the split-aperture optical system can be selected as a standard spherical surface or an aspherical surface.

[0044] In a specific implementation manner, the off-axis eccentricity of the optical sub-channels is set to 4.8 mm, and vignetting is provided for each of the six sub-channels, which can better prevent the light of each channel from overlapping with each other.

[0045] In a specific implementation manner, the pixels of the detector 5 are set to 1920×1080, and the pixel size is 15 μm×15 μm, so that different spectral images of the same target can be obtained simultaneously.

[0046] The specific data of each lens of the divided-aperture infrared multi-spectral optical lens for gas imaging provided in this embodiment 1 and the materials used are shown in Table 1.

[0047] Table 1

[0048]

[0049] Specifically, each filter assembly in this embodiment can be selected according to the characteristic absorption peak of the detected target gas, and the wavelength range is within 7-14 μm. The detector can obtain six corresponding spectral images of the target object.

[0050] For details, see the attached Figure 2 , which is the modulation transfer function (MTF) curve of the system. At the Nyquist characteristic frequency of 33lp / mm, the MTF value of the system is greater than 0.3, which is close to the diffraction limit.

[0051] For details, see the attached Figure 3It is the spot diagram of the ray tracing image plane. The circle in the figure is the diffraction-limited Airy disk. The RMS radius of the spot diagram of each field of view is less than 10μm, which is much smaller than the size of a pixel of the detector. The imaging quality of the system is close to the diffraction limit.

[0052] For details, see the attached Figure 4 , which is the ray tracing diagram of all sub-aperture channels. The images formed by the 6 sub-aperture channels are distributed at different positions on the detection surface and do not interfere with each other. The system can effectively suppress stray light interference.

[0053] Embodiment 2:

[0054] This embodiment provides another structure of a split-aperture infrared multi-spectral optical lens for gas imaging, which includes a split-aperture filter, a split-aperture optical system group and an imaging detector. The split-aperture optical system includes 6 sets of sub-lens groups with the same structure, and each channel includes a front filter and a sub-lens group. Its working band is 7-14μm, the lens focal length is 6mm, F / #=0.8, and the full field of view is 46°×40°.

[0055] See attached Figure 5 The optical lens uses only one kind of glass material, and the six sub-aperture channels are evenly distributed in a 3×2 format, including a sub-aperture filter group of 6 pieces and a sub-aperture lens group of 2×6 pieces. According to the incident direction of light, they are respectively a sub-aperture filter, a first lens 2 of the sub-aperture optical system sub-lens group, a second lens 3 of the sub-aperture optical system sub-lens group, a detector window piece 4, and an imaging detector 5. The imaging detector 5 is placed at a common image plane position of the six sub-aperture channels.

[0056] In a specific implementation manner, the lens surface type of the sub-lens group of the split-aperture optical system can be selected as a standard spherical surface or an aspherical surface.

[0057] In a specific implementation manner, the off-axis eccentricity of the optical sub-channels is set to 4.8 mm, and vignetting is provided for each of the six sub-channels, which can better prevent the light of each channel from overlapping with each other.

[0058] In a specific implementation, the pixels of the detector 10 are set to 1920×1080, and the pixel size is 15 μm×15 μm, so different spectral images of the same target can be obtained simultaneously.

[0059] Specifically, the specific data of each lens of the aperture-divided infrared multi-spectral optical lens for gas imaging provided in this embodiment and the materials used are shown in Table 2.

[0060] Table 2

[0061]

[0062]

[0063] Specifically, each filter assembly in this embodiment can be selected according to the characteristic absorption peak of the detected target gas, and the wavelength range is within 7-14 μm. The detector can obtain six corresponding spectral images of the target object.

[0064] For details, see the attached Figure 6 , which is the modulation transfer function (MTF) curve of the system. At the Nyquist characteristic frequency of 33lp / mm, the MTF value of the system is greater than 0.35, which is close to the diffraction limit.

[0065] For details, see the attached Figure 7 It is the spot diagram of the ray tracing image plane. The circle in the figure is the diffraction-limited Airy disk. The RMS radius of the spot diagram of each field of view is less than 10μm, which is much smaller than the size of a pixel of the detector. The imaging quality of the system is close to the diffraction limit.

[0066] For details, see the attached Figure 8 It is the ray tracing diagram of all sub-apertures and channels. The images formed by the 6 sub-aperture channels are distributed at different positions on the detection surface and do not interfere with each other. The system can effectively suppress stray light interference.

[0067] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0068] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A split-aperture infrared multi-spectral optical lens for gas imaging, characterized in that: It comprises a graded aperture filter, a graded aperture optical system and an imaging detector; wherein the graded aperture filter is composed of N infrared filters with different bandpass bands; the graded aperture optical system is composed of N sets of sub-lens groups with the same structure, which are respectively located in N apertures; the N graded aperture filters correspond to the N graded aperture optical systems, and the imaging of the N channels shares one imaging detector.

2. The aperture-divided infrared multi-spectral optical lens for gas imaging according to claim 1, characterized in that: The imaging detector is a non-cooling detector.

3. The aperture-divided infrared multi-spectral optical lens for gas imaging according to claim 1, characterized in that: The imaging detector has a response band of 7 to 14 μm and is provided with a germanium window.

4. The aperture-divided infrared multi-spectral optical lens for gas imaging according to claim 1, characterized in that: The imaging detector includes a detector window.

5. The aperture-divided infrared multi-spectral optical lens for gas imaging according to claim 1, characterized in that: The imaging field angle of each of the divided-aperture optical systems is the same.

6. The aperture-divided infrared multi-spectral optical lens for gas imaging according to claim 1, characterized in that: Each sub-lens group includes two lenses with positive optical power, namely the first lens L1 of the sub-aperture optical system sub-lens group and the second lens L2 of the sub-aperture optical system sub-lens group.

7. The aperture-divided infrared multi-spectral optical lens for gas imaging according to claim 6, characterized in that: Each of the sub-aperture filters is located at the front end of the first lens L1 of each of the sub-aperture optical system sub-lens groups.

8. The aperture-divided infrared multi-spectral optical lens for gas imaging according to claim 6, characterized in that: The distance between the second lens L2 of each sub-lens group of the aperture optical system and the detection surface is 8mm-10mm.

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