Multi-channel band-pass filter design method, preparation method, test method and device

Abstract

The invention provides a multichannel band-pass filter design method, preparation method, test method and device, and the method comprises the steps: designing an 8-12 [mu] m long-wave infrared multi-spectrum band-pass filter with an initial film system structure of Sub (HL) s2H (LH) sAir; a matching layer structure is introduced into the initial film system structure, the film system structure after introduction of the matching layer is SubaLbH cL (HL) s 2H (LH) s dLAir, aLbH cL and dL are matching layers, and a, b, c and d are matching layer coefficients; selecting a proper central wavelength according to a spectral band range, performing simulation for multiple times by utilizing film system design software, and optimizing the film system structure without the dummy layer to determine a matching layer coefficient, wherein the film system structure without the dummy layer is SubaLbH cL dLAir; and on the basis of the determined matching layer coefficient, determining that the optimized film system structure is Sub1.8 LHL (HL) 12H (LH) 11.8 LAir. According to the technical scheme, the technical problems that in the prior art, infrared imaging detection sensitivity and accuracy are poor, and only the infrared band of single gas can be responded are solved.

Description

Technical Field

[0001] The present invention relates to the field of infrared spectrum imaging technology, and in particular to a multi-channel bandpass filter design method, a preparation method, a test method and a device. Background Art

[0002] The petrochemical industry is one of the key and critical industries for promoting high-quality economic development in my country. Once flammable and explosive gases such as petroleum gas leak, it is very likely to cause fires, explosions and other accidents, which will not only pollute the environment and affect the normal production of enterprises, but also seriously threaten the safety of life and property of the society and the people. Because petroleum gas is colorless and odorless, it is not easy for staff to detect when a trace leak occurs, thus creating a safety hazard. In recent years, petrochemical companies have an increasing demand for detection and positioning of petroleum gas leaks, and at the same time have put forward detection requirements with high reliability, high sensitivity and high stability. Chemical companies at home and abroad are committed to applying gas leak detection equipment with higher performance, and the development of related detection technologies and instruments and equipment has become a research focus that needs to be urgently addressed at home and abroad.

[0003] In the detection of dangerous gas leaks in petroleum, it is important to monitor the leakage of flammable gases (such as methane, ethane, etc.), hydrogen sulfide, carbon monoxide, ammonia, sulfur dioxide, nitrogen oxides, volatile organic compounds (VOCs), and the concentration of oxygen-deficient gases. By real-time monitoring of the concentration of these gases, leakage accidents can be discovered in a timely manner, and corresponding safety measures can be taken to ensure safety and environmental protection during oil and gas operations. The characteristic peaks of dangerous gases are concentrated in the 8-12μm long-wave infrared band.

[0004] Spectral imaging technology is a technology that uses the principle of spectral analysis to image objects. By obtaining the spectral data of the target at multiple wavelengths, the spatial image can be captured and the spectral features can be identified at the same time. Compared with traditional imaging technology, spectral imaging technology enriches spectral information and can better distinguish the properties of objects. With the continuous development of technology, the application scope of spectral imaging technology continues to expand and deepen. It has developed rapidly driven by electronic science and technology, new materials and process technologies, and has been widely used in smart agriculture, geological surveys, environmental monitoring, military anti-camouflage, food and medicine and other fields. In the past three decades of development, spectral imaging technology has become one of the indispensable and important tools in various fields.

[0005] The earliest method of oil and gas leak detection was manual inspection. Later, corresponding equipment such as portable geophones, leakage noise correlators, and noise recorders were developed. However, this method requires on-site sampling, has poor real-time performance, and cannot provide effective early warning of gas leaks. With the continuous advancement of science and technology, oil and gas leak detection technology is also constantly developing. At present, commonly used oil and gas leak detection technologies include negative pressure wave detection technology, sonar sensor technology, fiber optic sensing technology, and infrared spectral imaging technology. Among them, infrared spectral imaging technology has received widespread attention in the field of oil and gas leak detection technology due to its advantages such as large range, long distance, rapid positioning of leak sources, and dynamic and intuitive.

[0006] With the rapid development of my country's petrochemical industry, the demand for infrared imaging detection technology for oil and gas leaks is increasing. In the international field, foreign research institutions and enterprises have continuously innovated in infrared spectral imaging technology and developed a series of high-performance infrared spectral imaging systems, but their key technologies and products are expensive, and some technologies are subject to technical blockade. In China, the research on infrared spectral imaging technology started late. In recent years, some scientific research institutions and universities have achieved important results in theoretical research and application development, but how to achieve rapid response and automated detection, reduce system costs, and improve system detection sensitivity and accuracy are still urgent problems to be solved. Furthermore, most of the existing detection technologies are aimed at single gases, such as methane gas leak detection. At present, in the gas leak infrared imaging detection system, the detector can only respond to the infrared band of a single gas, so there are performance limitations. Summary of the invention

[0007] The present invention provides a multi-channel bandpass filter design method, preparation method, test method and device, which can solve the technical problems in the prior art that infrared imaging detection sensitivity and accuracy are poor and can only respond to the infrared band of a single gas.

[0008] According to one aspect of the present invention, a multi-channel bandpass filter design method is provided, the multi-channel bandpass filter design method comprising: designing an 8-12 μm long-wave infrared multi-spectral bandpass filter, the initial film system structure is Sub|(HL) s 2H(LH) s |Air, where H is a high refractive index material, L is a low refractive index material, and s is the number of cycles of the reflective film stack; a matching layer structure is introduced into the initial film system structure, and the film system structure after the introduction of the matching layer is Sub|aLbH cL(HL) s 2H(LH) sdL|Air, where aLbH cL and dL are matching layers, and a, b, c and d are matching layer coefficients; select a suitable central wavelength according to the spectral range, use the film design software to perform multiple simulations, and the film structure without the dummy layer is Sub|aLbH cL dL|Air. The film structure without the dummy layer is optimized to determine the matching layer coefficient; based on the determined matching layer coefficient, the optimized film structure is determined to be Sub|1.8LHL(HL) 1 2H(LH) 1 1.8L|Air.

[0009] Furthermore, the high refractive index material H is Ge, and the low refractive index material L is ZnS.

[0010] According to another aspect of the present invention, a multi-channel bandpass filter is provided. The multi-channel bandpass filter is designed using the multi-channel bandpass filter design method as described above.

[0011] Furthermore, the film structure of the multi-channel bandpass filter is 1.8LHL (HL) 1 2H(LH) 1 1.8L, where 1.8LHL is the first matching layer, 1.8L is the second matching layer, (HL) 1 2H(LH) 1 It is a virtual layer.

[0012] Furthermore, the total film thickness of the multi-channel bandpass filter is 10.41 μm, the number of film layers is 9, the central wavelength is 9.98 μm, the peak transmittance is 99.16%, and the passband half width is 0.41 μm.

[0013] According to another aspect of the present invention, a method for preparing a multi-channel bandpass filter is provided. The method for preparing a multi-channel bandpass filter is used to prepare the multi-channel bandpass filter as described above.

[0014] Furthermore, the preparation method of the multi-channel bandpass filter includes: cleaning the substrate; depositing a lower Bragg mirror and a spacer layer structure on the substrate; performing multiple photolithography-etching processes to etch a step structure in the spacer layer; and depositing an upper Bragg mirror.

[0015] According to another aspect of the present invention, a spectral imaging chip structure is provided, which includes a multi-channel bandpass filter and a vanadium oxide detector. The multi-channel bandpass filter is pasted on the vanadium oxide detector, and the multi-channel bandpass filter is the multi-channel bandpass filter as described above.

[0016] According to another aspect of the present invention, a multi-channel spectral imaging camera system is provided. The multi-channel spectral imaging camera system includes an electronic imaging system, a host computer software unit and a structural shell. The electronic imaging system includes the spectral imaging chip structure as described above. The electronic imaging system is used to complete the driving, data reception and data transmission interface design of the detector. The host computer software unit is used to receive image data that meets the USB3.0 interface protocol sent by the electronic imaging system, and provide control signals to control the electronic imaging system to configure the detector and interpret the engineering parameters of the current detector. The electronic imaging system and the host computer software unit are arranged in the structural shell.

[0017] According to another aspect of the present invention, a multi-channel spectral imaging camera system testing method is provided, and the multi-channel spectral imaging camera system testing method comprises: connecting an image sensor processing circuit board of the multi-channel spectral imaging camera system to a computer via a network cable port, and controlling, collecting and storing spectral image data via a computer host computer; using a single-light instrument to test the linear array image sensor, the single-light instrument scans the spectral range of 7.8 to 11.15 μm, and the scanning step interval is selected to be 50 nm; extracting the grayscale value within the characteristic range as the spectral response, measuring the spectral response characteristics within the spectral range of the chip, and obtaining the spectral range, number of spectral bands and resolution index parameters of the filter.

[0018] By applying the technical solution of the present invention, a multi-channel bandpass filter design method is provided. The method applies spectral imaging technology to realize the simultaneous detection of multiple gases in the same detector, improve the detection accuracy and efficiency, design a multi-channel bandpass filter covering the long-wave infrared spectrum, and use the multi-channel bandpass filtering method to realize the splitting of different spectral dimensions in different spatial regions. By introducing a matching layer and optimizing the filter structure, the problem of low spectral transmittance of the system is solved, and the transmittance is increased from 61.23% to 99.16%; by using a multi-channel narrow-band filter, the discrimination and accuracy of spectral targets can be improved to meet the needs of more detailed analysis and interpretation of spectral information. The multi-channel bandpass filter can process optical signals in multiple frequency ranges and is suitable for applications that require simultaneous analysis of multiple signals or frequency bands. Therefore, the multi-channel bandpass filter design method provided by the present invention effectively solves the technical problems of poor sensitivity and accuracy of infrared imaging detection in the prior art and can only respond to the infrared band of a single gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 A schematic diagram showing the basic structure and working principle of a multi-channel bandpass filter provided according to a specific embodiment of the present invention is shown;

[0021] Figure 2 A schematic diagram of the spectral transmittance of an initial film system provided according to a specific embodiment of the present invention is shown;

[0022] Figure 3 A schematic diagram showing the spectral transmittance after adding a matching layer according to a specific embodiment of the present invention is shown;

[0023] Figure 4 A schematic diagram of a membrane structure provided according to a specific embodiment of the present invention is shown;

[0024] Figure 5 A schematic diagram of a theoretical spectral transmittance curve provided according to a specific embodiment of the present invention is shown;

[0025] Figure 6 A schematic diagram of a process flow for preparing a multi-channel bandpass filter according to a specific embodiment of the present invention is shown;

[0026] Figure 7 A schematic diagram of a multi-channel bandpass filter photolithography-etching process flow is shown according to a specific embodiment of the present invention;

[0027] Figure 8 A schematic diagram of the structure of a spectral imaging chip provided according to a specific embodiment of the present invention is shown;

[0028] Fig. 9 A schematic diagram of a multi-channel spectral imaging camera system provided according to a specific embodiment of the present invention is shown;

[0029] Fig.10 A schematic diagram of a spectral response test process of an image sensor provided in a specific embodiment of the present invention is shown;

[0030] Fig.11 A schematic diagram of a spectral response test result of an image sensor provided according to a specific embodiment of the present invention is shown;

[0031] Fig.12 A physical diagram of a multi-channel bandpass filter provided according to a specific embodiment of the present invention is shown. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in 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.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0035] like Figure 1 As shown, according to a specific embodiment of the present invention, a multi-channel bandpass filter design method is provided, the multi-channel bandpass filter design method comprising: designing a 8-12 μm long-wave infrared multi-spectral bandpass filter, the initial film system structure is Sub|(HL) s 2H(LH) s |Air, where H is a high refractive index material, L is a low refractive index material, and s is the number of cycles of the reflective film stack; a matching layer structure is introduced into the initial film system structure, and the film system structure after the introduction of the matching layer is Sub|aLbH cL(HL) s2H(LH) s dL|Air, where aLbH cL and dL are matching layers, and a, b, c and d are matching layer coefficients; select a suitable central wavelength according to the spectral range, use the film design software to perform multiple simulations, and the film structure without the dummy layer is Sub|aLbH cLdL|Air. The film structure without the dummy layer is optimized to determine the matching layer coefficient; based on the determined matching layer coefficient, the optimized film structure is determined to be Sub|1.8LHL(HL) 1 2H(LH) 1 1.8L|Air.

[0036] By using this configuration, a multi-channel bandpass filter design method is provided. The method uses spectral imaging technology to realize the simultaneous detection of multiple gases in the same detector, improve the detection accuracy and efficiency, and design a multi-channel bandpass filter covering the long-wave infrared spectrum. The multi-channel bandpass filtering method is used to realize the splitting of different spectral dimensions in different spatial regions. By introducing a matching layer and optimizing the filter structure, the problem of low spectral transmittance of the system is solved, and the transmittance is increased from 61.23% to 99.16%; by using a multi-channel narrow-band filter, the discrimination and accuracy of spectral targets can be improved to meet the needs of more detailed analysis and interpretation of spectral information. The multi-channel bandpass filter can process optical signals in multiple frequency ranges and is suitable for applications that require simultaneous analysis of multiple signals or frequency bands. Therefore, the multi-channel bandpass filter design method provided by the present invention effectively solves the technical problems of poor sensitivity and accuracy of infrared imaging detection in the prior art and can only respond to the infrared band of a single gas.

[0037] Furthermore, in the present invention, the high refractive index material H is Ge, and the low refractive index material L is ZnS.

[0038] According to another aspect of the present invention, a multi-channel bandpass filter is provided, wherein the multi-channel bandpass filter is designed using the multi-channel bandpass filter design method as described above. In the present invention, the membrane structure of the multi-channel bandpass filter is 1.8LHL (HL) 1 2H(LH) 1 1.8L, where 1.8LHL is the first matching layer, 1.8L is the second matching layer, (HL) 1 2H(LH) 1 It is a virtual layer.

[0039] As a specific embodiment of the present invention, when designing a multi-channel bandpass filter, for the infrared band, commonly used substrate materials include Ge, Si, ZnS and ZnSe. Among them, the transparent area of ​​Si is 1 to 9 μm, which cannot cover the 8 to 12 μm band. The hardness of ZnS and ZnSe materials is relatively low, so Ge ​​is finally selected as the substrate. Ge and ZnS are selected as the materials. An 8 to 12 μm long-wave infrared multi-band bandpass filter is designed. The initial film system structure is, where H is the high refractive index material Ge, L is the low refractive index material ZnS, and s is the number of cycles of the reflective film stack. During the design process, it was found that the spectral transmittance was low. When s is 1, the spectral transmittance is as follows: Figure 2 As shown, the central wavelength is 10μm, the peak transmittance is 61.23%, and the passband half width is 1.42μm. The reason is that the refractive index difference between the substrate and the air is large, so the matching layer structure is introduced. The film system is Sub|aLbH cL(HL) s 2H(LH) s dL|Air, where aLbH cL and dL are matching layers, and a, b, c and d are matching layer coefficients (values ​​range from 0 to 3). Select a suitable central wavelength based on the spectral range, use the film design software to simulate multiple times, and select the central wavelength as 10μm. When s is 1, the bandwidth at the central wavelength is 3.5μm. According to the design theory of the matching layer, the film structure without the dummy layer is Sub|aL bH cL dL|Air. After optimization, it is determined that a=1.8, b=1, c=1, d=1.8. The optimized film structure is: Sub|1.8LHL(HL) 1 2H(LH) 1 1.8L|Air. Figure 3 It can be seen that after adding the matching layer, the peak transmittance is significantly improved, the central wavelength is 9.98μm, the peak transmittance is 99.16%, and the passband half width is 0.41μm. The physical thickness of the film layer is as follows Figure 4 As shown in the figure, the number of film layers is 9, and the total thickness of the film layers is 10.41μm. The thickness of the spacer layer changes from 0.69μm to 1.35μm. By simulating the film structure of the FP cavity filter, the long-wave infrared spectrum filtering is tuned from 7.95μm to 10.75μm. The spectral curve is shown in Figure 5 As shown, numbers 1# to 10# represent 10 spectral segments, respectively, showing the bandpass filtering effect under different spacing layer changes.

[0040] According to another aspect of the present invention, a method for preparing a multi-channel bandpass filter is provided, and the method for preparing a multi-channel bandpass filter is used to prepare the multi-channel bandpass filter as described above. The method for preparing the multi-channel bandpass filter comprises: cleaning a substrate; depositing a lower Bragg mirror and a spacer layer structure on the substrate; performing multiple photolithography-etching processes to etch a step structure in the spacer layer; and depositing an upper Bragg mirror.

[0041] By using this configuration, a method for preparing a multi-channel bandpass filter is provided. The method first cleans the substrate, then deposits the lower Bragg mirror and the spacer layer structure; then performs multiple photolithography-etching processes to etch the spacer layer into a step structure; and finally deposits the upper Bragg mirror. The preparation process combines thin film deposition with photolithography-etching processes to change the cavity length, and has the advantages of high processing accuracy, high stability, and simple process flow.

[0042] According to another aspect of the present invention, a spectral imaging chip structure is provided, which includes a multi-channel bandpass filter and a vanadium oxide detector. The multi-channel bandpass filter is pasted on the vanadium oxide detector, and the multi-channel bandpass filter is the multi-channel bandpass filter as described above.

[0043] Furthermore, according to another aspect of the present invention, a multi-channel spectral imaging camera system is provided, which includes an electronic imaging system, a host computer software unit and a structural shell. The electronic imaging system includes the spectral imaging chip structure as described above. The electronic imaging system is used to complete the driving, data reception and data transmission interface design of the detector. The host computer software unit is used to receive image data that meets the USB3.0 interface protocol sent by the electronic imaging system, and provide control signals to control the electronic imaging system to configure the detector and interpret the engineering parameters of the current detector. The electronic imaging system and the host computer software unit are arranged in the structural shell.

[0044] Furthermore, according to another aspect of the present invention, a multi-channel spectral imaging camera system testing method is provided, and the multi-channel spectral imaging camera system testing method includes: connecting the image sensor processing circuit board of the multi-channel spectral imaging camera system to a computer through a network cable port, and controlling and collecting and storing spectral image data through a computer host computer; using a single light instrument to test the linear array image sensor, the single light instrument scans the spectral range of 7.8 to 11.15 μm, and the scanning step interval is selected to be 50 nm; extracting the grayscale value within the characteristic range as the spectral response, measuring the spectral response characteristics within the spectral range of the chip, and obtaining the spectral range, number of spectral bands and resolution index parameters of the filter.

[0045] By using this configuration, a multi-channel spectral imaging camera system test method is provided. For the spectral response test of the image sensor integrated with a multi-channel bandpass filter, a single-light instrument is used to test the spectral performance of the linear image sensor. The test method is as follows: Fig.10 As shown. The single-light instrument has adjustable steps, with a minimum of 20nm, and the grating spectral range is 5.5-14.5μm. The image sensor processing circuit board is connected to the computer through the network cable port, and the spectral image data is controlled and collected and stored by the computer host. The linear image sensor is tested with a single-light instrument. The single-light instrument scans the spectral range of 7.8-11.15μm, and the scanning step interval is selected to be 50nm. The scanning range covers a wide wavelength region. The 50nm sampling interval can meet the test requirements, ensure continuity and accuracy, and reduce the complexity of the test. The grayscale value within the characteristic range is extracted as the spectral response, and the spectral response characteristics within the spectral range of the chip are measured to obtain the spectral range, number of spectral bands and resolution index parameters of the filter.

[0046] In order to further understand the present invention, the following Figures 1 to 12 The multi-channel bandpass filter design method, preparation method, test method and related devices provided by the present invention are described in detail.

[0047] like Figures 1 to 12 As shown, the present invention introduces an oil and gas leak detection chip structure based on infrared spectral imaging technology. The chip combines the advantages of infrared spectral imaging technology to meet the simultaneous detection of multiple hazardous gases.

[0048] Spectral imaging technology is an advanced technology that uses the principle of spectral analysis to image objects. It combines the advantages of spectral analysis technology and imaging technology to provide richer information for detection. This technology can obtain the spectral characteristics of objects at different wavelengths, and combine this spectral information with the spatial position information of the object to generate a three-dimensional data cube containing spectral information and spatial position information, thereby identifying and quantifying the chemical composition, physical properties and spatial distribution of the object.

[0049] Infrared spectral imaging gas detection technology aims to accurately identify gas types and precisely measure gas concentrations. It identifies gas types through detailed comparison and processing of spectral data cubes with known spectral data in the gas spectral database, and uses pre-calibrated concentration parameters to determine the concentration of the detected gas.

[0050] 1. Multi-channel bandpass filter

[0051] 1.1 Theoretical Study of Multi-channel Bandpass Filters

[0052] The spectral imaging system realizes the simultaneous detection of multiple channels by relying on multi-channel bandpass filters. The use of narrowband filters can separate light signals of different wavelengths for spectral analysis. Multi-channel bandpass filters can be used to identify and distinguish light signals of different wavelengths, thereby detecting spectral features and processing spectral images. The basic structure and working principle of multi-channel narrowband filters are as follows: Figure 1 shown.

[0053] The transmittance of the central wavelength of the bandpass filter is:

[0054]

[0055] Where T1 and T2 are the transmittance of the upper and lower Bragg mirrors, R1 and R2 are the reflectivity of the upper and lower Bragg mirrors, and λ is the center wavelength. is the reflection phase shift, ndcosθ is the optical path, and the position of the central wavelength can be tuned by changing the optical path. If you want to change the optical path, you can adjust it by changing the refractive index n, cavity length d and incident angle θ to achieve the purpose of tunability. The multi-channel narrowband filter is on the same substrate, and different areas transmit light of different wavelengths. In this process, changing the material refractive index n and the incident angle θ is relatively complicated, so it is usually chosen to change the cavity length d (that is, the distance between the upper and lower reflectors) to change the cavity length of the FP cavity, thereby achieving a change in the center wavelength of the filter.

[0056] According to their spectroscopic methods, multi-channel narrowband filters can be divided into MEMS tunable filters, linear gradient filters, waveguide filters, and filter arrays. At present, most long-wave infrared spectroscopy technologies are driven by MEMS, but MEMS tunable filters are limited by their structure, the tuning range is usually small, and they cannot be imaged. Linear gradient filters are often used in visible and near-infrared bands, and have low spectral resolution and signal-to-noise ratio. The system design and preparation process of waveguide filters and mosaic filter arrays are relatively complex. Linear scanning filter arrays have a simple structure and flexibility, and can achieve more spectral bands. They are currently more used in visible and near-infrared bands, and have not yet been used in long-wave infrared bands. This paper proposes the use of line scanning filter arrays to prepare 8-12μm multi-channel bandpass filters.

[0057] 1.2 Multi-channel bandpass filter design

[0058] For the infrared band, commonly used substrate materials include Ge, Si, ZnS and ZnSe. Among them, the transparent area of ​​Si is 1-9μm, which cannot cover the 8-12μm band. The hardness of ZnS and ZnSe materials is relatively low, so Ge ​​is finally selected as the substrate. Ge and ZnS are selected as the materials.

[0059] Design of 8~12μm long-wave infrared multi-spectral bandpass filter, the initial film structure is Sub|(HL) s2H(LH) s |Air, where H is the high refractive index material Ge, L is the low refractive index material ZnS, and s is the number of cycles of the reflective film stack. During the design process, it was found that the spectral transmittance was low. When s was 1, the spectral transmittance was as follows: Figure 2 As shown, the central wavelength is 10 μm, the peak transmittance is 61.23%, and the passband half width is 1.42 μm.

[0060] The reason is that the refractive index difference between the substrate and the air is large, so a matching layer structure is introduced. The film system is Sub|aL bH cL(HL) s 2H(LH) s dL|Air, where aL bH cL and dL are matching layers, and a, b, c and d are matching layer coefficients (values ​​range from 0 to 3). Select a suitable central wavelength based on the spectral range, use the film design software to simulate multiple times, and select the central wavelength as 10μm. When s is 1, the bandwidth at the central wavelength is 3.5μm. According to the design theory of the matching layer, the film structure without the dummy layer is Sub|aL bH cL dL|Air. After optimization, it is determined that a=1.8, b=1, c=1, d=1.8. The optimized film structure is: Sub|1.8LHL(HL) 1 2H(LH) 1 1.8L|Air. Figure 3 It can be seen that after adding the matching layer, the peak transmittance is significantly improved, the central wavelength is 9.98μm, the peak transmittance is 99.16%, and the passband half width is 0.41μm.

[0061] The physical thickness of the film is Figure 4 As shown, the number of film layers is 9 and the total thickness of the film layers is 10.41 μm.

[0062] The thickness of the spacer layer changes from 0.69μm to 1.35μm. By simulating and designing the membrane structure of the FP cavity filter, the long-wave infrared spectrum filtering is tuned from 7.95μm to 10.75μm. The spectral curve is as follows Figure 5 As shown, numbers 1# to 10# represent 10 spectral segments, respectively, showing the bandpass filtering effect under different spacing layer changes.

[0063] 2. Spectral imaging chip preparation

[0064] The preparation process of multi-channel bandpass filter is as follows Figure 6 As shown, the substrate is first cleaned, and then the lower Bragg mirror and spacer layer structure are deposited; then multiple photolithography-etching processes are performed to etch the spacer layer into a step structure; finally, the upper Bragg mirror is deposited. This preparation process combines thin film deposition with photolithography-etching processes to change the cavity length, and has the advantages of high processing accuracy, high stability and simple process flow.

[0065] 2.1 Lithography-Etching Process Research

[0066] Figure 7 The process flow of photolithography-etching of multi-channel bandpass filter is demonstrated. The number of layers of long-wave infrared (8-12μm) multi-channel line scan filter structure starts from the 1st layer. When it grows to the 6th layer, the Ge growth thickness is 1.35μm (i.e. Hmax). Then exponential photolithography-etching is performed. The photoresist is applied to the whole body, and the photolithography process is performed according to the designed mask. Through the steps of exposure and development, the pattern of the first layer of FP cavity film is formed. Then, the developed photoresist is removed. Next, the Ge layer is etched to a certain thickness using reactive ion etching technology. The etching depth can be expressed by the following formula:

[0067]

[0068] Where is the nth etching depth, is the maximum thickness of the light-transmitting layer, is the minimum thickness of the light-transmitting layer, is the number of spectral bands, and the etching times are repeated. Then remove the excess photoresist on the surface and grow the 7th to 9th layers on the surface. The preparation of the long-wave infrared scanning multi-channel bandpass filter is completed.

[0069] 2.2 Chip Packaging and System Integration

[0070] The prepared long-wave infrared multi-channel bandpass filter is integrated into the vanadium oxide detector in the following manner: Figure 8 As shown. By using the packaging process of the vanadium oxide detector and the design of the electrical signal conversion circuit, the spectral image sensor integrated with the multi-channel bandpass filter is packaged and electrically connected to the IC circuit. Finally, the multi-channel spectral imaging camera is completed after packaging and integration.

[0071] The multi-channel spectral imaging camera system consists of an electronic imaging system, a host computer software and a structural shell. The camera system consists of Fig. 9 As shown. The electronic imaging system is mainly responsible for completing the detector drive and data reception, and the data transmission interface design. The host computer software is responsible for receiving the image data that meets the USB3.0 interface protocol sent by the camera electronic imaging system, and providing control signals to control the electronic imaging system to configure the detector and interpret the current engineering parameters of the detector. The structural shell has a standard C-port, which is convenient for imaging with a C-port lens.

[0072] 3. Test and analysis of multi-channel spectral imaging system

[0073] For the spectral response test of the image sensor integrated with multi-channel bandpass filter, a single light instrument is used to test the spectral performance of the linear image sensor. The test method is as follows: Fig.10As shown. The single-light instrument has adjustable steps, with a minimum of 20nm, and the grating spectral range is 5.5-14.5μm. The image sensor processing circuit board is connected to the computer through the network cable port, and the spectral image data is controlled and collected and stored by the computer host. The linear image sensor is tested with a single-light instrument. The single-light instrument scans the spectral range of 7.8-11.15μm, and the scanning step interval is selected to be 50nm. The scanning range covers a wide wavelength region. The 50nm sampling interval can meet the test requirements, ensure continuity and accuracy, and reduce the complexity of the test. The grayscale value within the characteristic range is extracted as the spectral response, and the spectral response characteristics within the spectral range of the chip are measured to obtain the spectral range, number of spectral bands and resolution index parameters of the filter.

[0074] Spectral responsivity is used to describe the response of a photodetector to light of different wavelengths and is defined as:

[0075]

[0076] dX e (λ) = X e (λ)dλ(4)

[0077] Where is the output change of the photodetector at the wavelength, which represents the energy change of the incident light in a small range near the wavelength.

[0078] The normalized test results are as follows Fig.11 As shown in the figure, 10 spectral bands are split, and the numbers 1# to 10# correspond to 10 spectral bands, and each channel is evenly distributed. It covers the 8-12μm spectral range, and the bandwidth is between 0.3 and 0.4μm, which is less than 0.5μm, meeting the system usage requirements.

[0079] The actual picture of multi-channel bandpass filter is as follows Fig.12 As shown in the figure, there are obvious boundaries between different channels of the filter, and the sample size is 16.95×13.95×0.32mm. The multi-channel bandpass filter is integrated into the spectral imaging camera, which realizes the simultaneous acquisition of multiple spectral bands and improves the efficiency of spectral data acquisition. It brings significant performance improvement to the gas leak infrared imaging detection system, which helps to achieve fast and accurate detection of different gas leaks.

[0080] Infrared spectral imaging detection technology has shown great potential in the field of oil and gas leak detection due to its high efficiency, accuracy and non-contact characteristics. The research on infrared spectral imaging detection components in China is imminent. This paper studies and designs a spectral imaging chip structure covering the long-wave infrared spectrum, and uses a multi-channel bandpass filtering method to achieve spectral separation in different spatial regions and different spectral dimensions.

[0081] Aiming at the problem of multi-information acquisition in long-wave infrared spectral imaging system, the method of applying line scanning filter array was proposed, and the preparation of multi-channel bandpass filter was completed by combining thin film deposition process and photolithography-etching process. The preparation of 8-12μm multi-step array was completed on Ge substrate, and the spectral resolution of 10 spectral bands was achieved, and the spectral resolution was better than 0.5μm. The filter was bonded to the imaging detector to obtain the infrared spectral imaging detection component.

[0082] By introducing a matching layer and optimizing the filter structure, the problem of low spectral transmittance of the system was solved, and the transmittance was increased from 61.23% to 99.16%.

[0083] In summary, the present invention provides a multi-channel bandpass filter design method, preparation method, test method and device. The present invention applies a line-scan filter array in the long-wave infrared to develop a 10-band multi-channel bandpass filter with 8 to 12 μm in different spatial regions, thereby improving the ability to simultaneously acquire long-wave multi-spectral information. In the chip structure of the long-wave infrared, a matching layer is introduced to optimize the filter structure, thereby solving the problem of low spectral transmittance of the system, and the transmittance is increased from 61.23% to 99.16%.

[0084] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0085] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-channel bandpass filter design method, characterized in that: The multi-channel bandpass filter design method comprises: Design of 8~12μm long-wave infrared multi-spectral bandpass filter, the initial film structure is Sub|(HL) s 2H(LH) s |Air, where H is the high refractive index material, L is the low refractive index material, and s is the number of cycles of the reflective film stack; Introduce a matching layer structure into the initial film system structure. The film system structure after the introduction of the matching layer is Sub|aLbH cL(HL) s 2H(LH) s dL|Air, where aLbH cL and dL are matching layers, and a, b, c and d are matching layer coefficients; According to the spectral range, a suitable central wavelength is selected, and multiple simulations are performed using the film system design software. The film system structure without the dummy layer is Sub|aLbH cL dL|Air. The film system structure without the dummy layer is optimized to determine the matching layer coefficient. Based on the determined matching layer coefficient, the optimized film structure is determined to be Sub|1.8LHL(HL) 1 2H(LH) 1 1.8L|Air.

2. The multi-channel bandpass filter design method according to claim 1, characterized in that: The high refractive index material H is Ge, and the low refractive index material L is ZnS.

3. A multi-channel bandpass filter, characterized in that: The multi-channel bandpass filter is designed using the multi-channel bandpass filter design method as claimed in claim 1 or 2.

4. The multi-channel bandpass filter according to claim 3, characterized in that: The film structure of the multi-channel bandpass filter is 1.8LHL (HL) 1 2H(LH) 1 1.8L, where 1.8LHL is the first matching layer, 1.8L is the second matching layer, (HL) 1 2H(LH) 1 It is a virtual layer.

5. The multi-channel bandpass filter according to claim 4, characterized in that: The total film thickness of the multi-channel bandpass filter is 10.41 μm, the number of film layers is 9, the central wavelength is 9.98 μm, the peak transmittance is 99.16%, and the passband half width is 0.41 μm.

6. A method for preparing a multi-channel bandpass filter, characterized in that: The method for preparing the multi-channel bandpass filter is used to prepare the multi-channel bandpass filter as claimed in any one of claims 3 to 5.

7. The method for preparing a multi-channel bandpass filter according to claim 6, characterized in that: The preparation method of the multi-channel bandpass filter comprises: Performing substrate cleaning; On the substrate, depositing a lower Bragg mirror and a spacer layer structure; Perform multiple photolithography-etching processes to etch the spacer layer into a step structure; The upper Bragg mirror deposition is performed.

8. A spectral imaging chip structure, characterized in that: The spectral imaging chip structure comprises a multi-channel bandpass filter and a vanadium oxide detector. The multi-channel bandpass filter is pasted on the vanadium oxide detector. The multi-channel bandpass filter is the multi-channel bandpass filter according to any one of claims 3 to 5.

9. A multi-channel spectral imaging camera system, characterized in that: The multi-channel spectral imaging camera system includes an electronic imaging system, a host computer software unit and a structural shell. The electronic imaging system includes the spectral imaging chip structure as described in claim 8. The electronic imaging system is used to complete the driving, data reception and data transmission interface design of the detector. The host computer software unit is used to receive image data that meets the USB3.0 interface protocol sent by the electronic imaging system, and provide control signals to control the electronic imaging system to configure the detector and interpret the engineering parameters of the current detector. The electronic imaging system and the host computer software unit are arranged in the structural shell.

10. A multi-channel spectral imaging camera system testing method, characterized in that: The multi-channel spectral imaging camera system testing method comprises: The image sensor processing circuit board of the multi-channel spectral imaging camera system is connected to the computer through the network cable port, and the spectral image data is controlled, collected and stored by the computer host computer; The linear array image sensor was tested using a single-light instrument, which scanned the spectral range of 7.8 to 11.15 μm, with a scanning step interval of 50 nm. The grayscale value within the characteristic range is extracted as the spectral response, the spectral response characteristics within the spectral range of the chip are measured, and the spectral range, number of spectral bands and resolution index parameters of the filter are obtained.

Images