A gas component analysis and concentration detection system based on multi-band infrared filter switching

Abstract

The application relates to a gas component analysis and concentration detection system based on multi-waveband infrared filter switching, which comprises a gas chamber, wherein an infrared light source, a solid-state switching unit, a filter array module and an infrared detector are arranged in the gas chamber; the filter array module comprises a plurality of filters fixed on a module substrate; the solid-state switching unit changes the optical parameters of materials by means of an electric field / sonic field under the electronic control of a control and signal processing module to realize wavelength selection; and the light beams from the filters at different spatial positions are sequentially guided to the infrared detector according to a preset time sequence. The gas component analysis and concentration detection system provided by the application adopts a single light source, a single detector and a filter array, realizes multi-gas detection through solid-state switching, avoids a plurality of NDIR sensors or a heavy filter wheel, is compact in structure, and is significantly reduced in cost.

Description

Technical Field

[0001] This invention belongs to the technical field of gas composition and concentration analyzers, and in particular relates to a gas composition analysis and concentration detection system based on multi-band infrared filter switching. Background Technology

[0002] A gas composition and concentration analyzer is a precision instrument used to quantitatively detect the type and volume / mass concentration of each gas component in a gas mixture. Infrared spectroscopy is a commonly used technique for gas detection. Different gas molecules have unique absorption fingerprints in the infrared band. For example, CO2 has a strong absorption peak near 4.25 μm, CO near 4.6 μm, CH4 near 3.3 μm, while water vapor has broad absorption bands at 2.7 μm and 6.3 μm.

[0003] Existing multi-gas detectors often employ the following solutions: 1. Fourier transform infrared spectrometer: High precision, capable of detecting a variety of gases, but the equipment is expensive, bulky, requires precise optical components and complex algorithms, and is not suitable for rapid on-site deployment and low-cost applications; 2. Non-dispersive infrared sensors: They are low in cost and simple in structure, but a single sensor can usually only detect one absorption band of a specific gas. To detect multiple gases, multiple independent NDIR sensor modules need to be integrated, which leads to increased device size, power consumption, and cost. 3. Filter wheel type multi-gas detector: This type uses an infrared light source and a detector, and switches between different wavelength filters through a mechanical filter wheel. However, this mechanical structure suffers from wear, limited lifespan, slow switching speed (usually on the order of seconds), and susceptibility to vibration, making it difficult to achieve high-speed, high-reliability real-time monitoring. Therefore, there is an urgent need in this field for a technical solution that can achieve simultaneous / rapid detection of multiple gases, and also has high reliability, long life, low cost and compact structure. Summary of the Invention

[0004] The purpose of this invention is to provide a gas composition analysis and concentration detection system based on multi-band infrared filter switching, which solves the technical problems mentioned in the background art.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: A gas composition analysis and concentration detection system based on multi-band infrared filter switching is provided, including a gas chamber. The gas chamber is equipped with an infrared light source, a filter array module, and an infrared detector. The gas chamber has a gas inlet and a gas outlet at its two ends. An infrared light source is installed at the gas inlet, with its optical path facing the gas outlet. Along the optical path, a filter array module, a solid-state switching unit, an infrared detector, and a control and signal processing module are arranged sequentially. The filter array module includes several filters fixed on a module substrate. The solid-state switching unit, under the electronic control of the control and signal processing module, changes the material's optical properties using an electric field / acoustic field. The wavelength selection is achieved by learning parameters, guiding light beams from filters at different spatial locations to the infrared detector in a preset timing sequence. The control and signal processing module includes a circuit board electrically connected to the infrared light source, the solid-state switching unit, and the infrared detector. The control and signal processing module is configured to perform the following steps: a. Controlling the solid-state switching unit to guide the transmitted light corresponding to different filters in the filter array module to the infrared detector in a preset sequence within one detection cycle; b. Synchronously acquiring and recording the output signal intensity of the infrared detector under each filter channel; c. Calculating the concentration of each target gas based on a preset differential absorption algorithm using the signal intensities of at least two different filter channels.

[0006] Preferably, the infrared light source is a broadband infrared source.

[0007] Preferably, the filter array module integrates at least three infrared bandpass filters with different center wavelengths. The operating bands of the infrared bandpass filters correspond to: the center wavelength of the characteristic absorption peak of at least one target gas, the absorption valley wavelength of the target gas or an interference-free reference wavelength, and a compensation wavelength for compensating for the influence of interfering gases or dust.

[0008] Preferably, the four infrared bandpass filters are as follows: Filter 1: center wavelength 4.25μm, half width at half maximum (WWHM) 0.1μm, corresponding to the strong absorption peak of CO2; Filter 2: center wavelength 3.95μm, WWHM 0.1μm, located in the CO2 absorption valley; Filter 3: center wavelength 4.6μm, WWHM 0.1μm, corresponding to the CO absorption peak; Filter 4: center wavelength 3.4μm, WWHM 0.1μm, corresponding to the CH4 absorption peak.

[0009] Preferably, the solid-state switching unit is one of a liquid crystal tunable filter, a MEMS micromirror array, or an acousto-optic tunable filter.

[0010] Compared with existing technologies, the beneficial effects are: 1. High integration and low cost: It adopts a single light source, a single detector and a filter array, and realizes multi-gas detection through solid-state switching, avoiding multiple NDIR sensors or bulky filter wheels. The system structure is compact and the cost is significantly reduced. 2. High reliability and long lifespan: The entire system has no moving mechanical parts, which fundamentally solves the wear and jamming problems of the filter wheel solution. It is suitable for harsh vibration environments such as industrial sites and vehicles, and its service life is greatly extended. 3. High-speed real-time detection: Solid-state switching speed can reach milliseconds or even microseconds, which is much faster than mechanical filter wheels (seconds), enabling rapid response and real-time monitoring of gas concentration; 4. High precision and strong anti-interference capability: By introducing a dedicated reference filter channel and compensation filter channel, and combining it with a differential absorption algorithm, the interference of light source fluctuation, optical window contamination, dust scattering, temperature and humidity changes and cross gas absorption is effectively overcome, and the measurement results are more accurate and reliable. 5. Modularity and scalability: By replacing or adding filters in the filter array, the system can be easily adapted to detect different gas combinations, resulting in strong product derivative capabilities.

[0011] The gas composition analysis and concentration detection system provided in this application is suitable for one or more application scenarios in environmental monitoring, industrial process control, automobile exhaust analysis, coal mine gas early warning, agricultural fermentation monitoring, or smart home air quality detection, and has broad market prospects. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a gas composition analysis and concentration detection system based on multi-band infrared filter switching.

[0013] Figure 2 for Figure 1 A schematic diagram of the layout of the filter array module.

[0014] Figure 3 for Figure 1 The engineering flowchart of the control and signal processing module.

[0015] Figure 4 for Figure 1 The simulated signal output diagram of the gas composition analysis and concentration detection system for CO2 and CO within one detection cycle.

[0016] Among them, 1-infrared light source; 2-gas chamber; 201-gas inlet; 202-gas outlet; 3-filter array module; 301-filter one; 302-filter two; 303-filter three; 304-filter four; 305-module substrate; 4-solid-state switching unit; 5-infrared detector; 6-control and signal processing module.

[0017] The same markings in each diagram represent the same component. Detailed Implementation

[0018] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0019] like Figure 1 As shown, this invention provides a gas composition analysis and concentration detection system based on multi-band infrared filter switching, including a gas chamber 2 through which the gas to be tested flows and infrared light passes. The gas chamber 2 is equipped with an infrared light source 1, a filter array module 3, and an infrared detector 5. The gas chamber 2 has a gas inlet 201 and a gas outlet 202 at its two ends. The infrared light source 1 is located at the gas inlet 201, and its optical path faces the gas outlet 202. Along the optical path, the filter array module 3, a solid-state switching unit 4, the infrared detector 5, and a control and signal processing module 6 are arranged sequentially.

[0020] The infrared light source 1 is a broadband infrared source used to emit infrared light covering the absorption band of the target gas.

[0021] The solid-state switching unit 4, under the electronic control of the control and signal processing module, achieves wavelength selection by changing the optical parameters of the material through electric / acoustic fields, guiding light beams from filters at different spatial locations to the infrared detector 5 in a preset time sequence. The solid-state switching unit 4 is one of a liquid crystal tunable filter, a MEMS micromirror array, or an acousto-optic tunable filter. All optional components of the aforementioned solid-state switching unit 4 are free of rotating motors, wheels, and mechanically displaced lenses, belonging to solid-state electronically controlled beam splitting devices. In the liquid crystal tunable filter, the liquid crystal molecules are deflected by the electric field, with no macroscopic movement of physical components; in the MEMS micromirror array, the micron-sized mirrors oscillate slightly, without external transmission gears, guide rails, or turntables; in the acousto-optic tunable filter, ultrasonic waves propagate inside the crystal, while the crystal itself remains stationary.

[0022] The control and signal processing module 6 includes a circuit board electrically connected to the infrared light source 1, the solid-state switching unit 4, and the infrared detector 5.

[0023] In this embodiment, the control and signal processing module 6 is configured to perform the following steps: a. Control the solid-state switching unit 4 so that it guides the transmitted light corresponding to different filters to the infrared detector 5 in a preset order within one detection cycle; b. Synchronously acquire and record the output signal strength of the infrared detector 5 under each filter channel; c. Based on a preset differential absorption algorithm, the concentration of each target gas is calculated using the signal intensity of at least two different filter channels.

[0024] The infrared detector 5 is used to receive infrared light that passes through the filter array module 3 and convert it into an electrical signal.

[0025] The filter array module 3 integrates at least three infrared bandpass filters with different center wavelengths on the module substrate 305. The operating bands of the infrared bandpass filters correspond to: the center wavelength of the characteristic absorption peak of at least one target gas, the absorption valley wavelength of the target gas or an interference-free reference wavelength, and a compensation wavelength for compensating for the influence of interfering gases or dust.

[0026] like Figure 2 In one specific embodiment shown, four infrared bandpass filters are integrated on the module substrate 305, namely: Filter 1 301: center wavelength 4.25μm, half width at half maximum (WWHM) 0.1μm, corresponding to the strong absorption peak of CO2; Filter 2 302: center wavelength 3.95μm, WWHM 0.1μm, located in the CO2 absorption valley, serving as a reference filter channel; Filter 3 303: center wavelength 4.6μm, WWHM 0.1μm, corresponding to the CO absorption peak; Filter 4 304: center wavelength 3.4μm, WWHM 0.1μm, corresponding to the CH4 absorption peak, and can also be used as a compensation filter channel.

[0027] Taking the solid-state switching unit 4 as an example of a MEMS micromirror array, the light emitted from filters at different spatial positions is reflected to a shared infrared detector 5 by dynamically deflecting the micromirror angle. MEMS micromirror arrays are existing technology. Each micromirror in the array consists of a mirror surface, an elastic torsion arm, and a micro-driving electrode. The array is arranged in a matrix and uses the most common driving method, electrostatic driving: the control and signal processing module 6 controls the micro-driving electrodes to apply voltage, generating an electrostatic force that pulls the mirror surface to deflect. Its advantages include low power consumption and mature mass production capabilities.

[0028] The differential absorption algorithm executed by the control and signal processing module 6 is as follows: C gas =k*ln(V ref / V meas ) Among them, C gas Let V be the concentration of the gas to be measured, k be the system calibration coefficient, and V be the concentration of the gas to be measured. ref To reference the signal strength of the filter channel, V meas The signal intensity of the filter channel at the absorption peak.

[0029] During operation, the control and signal processing module 6 presses... Figure 3 The process is as follows: After the system is powered on and initialized, infrared light source 1 is turned on. Subsequently, the control and signal processing module 6 drives the MEMS micromirror array to sequentially reflect the emitted light from filter 1 301, filter 2 302, filter 3 303, and filter 4 304 onto the infrared detector 5, and simultaneously records the signal voltage value V of the four filter channels. A V B V C V D .

[0030] The data processing employs a differential algorithm. For example, for calculating CO2 concentration: C CO2 =k1*ln(V B / V A ) In addition, for the calculation of CO concentration, a double-difference method can be used to eliminate the weak absorption interference of CO2 near 4.6 μm: C CO =k2*[ln(V B / V C )-α*ln(V B / V A )], where α is the cross-interference compensation coefficient, which is obtained through prior calibration.

[0031] Figure 4 This demonstrates the rapid acquisition of signals from the four filter channels within a single detection cycle. It can be seen that when CO2 is present in gas chamber 2, V... A The signal is significantly lower than V B Signal.

Claims

1. A gas composition analysis and concentration detection system based on multi-band infrared filter switching, comprising a gas chamber, wherein the gas chamber is equipped with an infrared light source, a filter array module, and an infrared detector, characterized in that, The gas chamber has a gas inlet and a gas outlet at each of its two sections. An infrared light source is installed at the gas inlet, with its optical path facing the gas outlet. Along the optical path, a filter array module, a solid-state switching unit, an infrared detector, and a control and signal processing module are arranged sequentially. The filter array module includes several filters fixed on a module substrate. The solid-state switching unit, under the electronic control of the control and signal processing module, achieves wavelength selection by changing the material's optical parameters through electric / acoustic fields, guiding light beams from filters at different spatial locations to the infrared detector in a preset time sequence. The control and signal processing module includes a circuit board electrically connected to the infrared light source, the solid-state switching unit, and the infrared detector. The control and signal processing module is configured to perform the following steps: a. Control the solid-state switching unit to guide the transmitted light corresponding to different filters in the filter array module to the infrared detector in a preset order within one detection cycle; b. Synchronously acquire and record the output signal strength of the infrared detector under each filter channel; c. Based on a preset differential absorption algorithm, the concentration of each target gas is calculated using the signal intensity of at least two different filter channels.

2. The gas composition analysis and concentration detection system based on multi-band infrared filter switching according to claim 1, characterized in that, The infrared light source is a broadband infrared source.

3. The gas composition analysis and concentration detection system based on multi-band infrared filter switching according to claim 1, characterized in that, The filter array module integrates at least three infrared bandpass filters with different center wavelengths. The operating bands of the infrared bandpass filters correspond to: the center wavelength of the characteristic absorption peak of at least one target gas, the absorption valley wavelength of the target gas or an interference-free reference wavelength, and a compensation wavelength for compensating for the influence of interfering gases or dust.

4. The gas composition analysis and concentration detection system based on multi-band infrared filter switching according to claim 3, characterized in that, The four infrared bandpass filters are as follows: Filter 1: center wavelength 4.25μm, half width at half maximum (WWHM) 0.1μm, corresponding to the strong absorption peak of CO2; Filter 2: center wavelength 3.95μm, WWHM 0.1μm, located in the CO2 absorption valley; Filter 3: center wavelength 4.6μm, WWHM 0.1μm, corresponding to the CO absorption peak; Filter 4: center wavelength 3.4μm, WWHM 0.1μm, corresponding to the CH4 absorption peak.

5. The gas composition analysis and concentration detection system based on multi-band infrared filter switching according to claim 1, characterized in that, The solid-state switching unit is one of a liquid crystal tunable filter, a MEMS micromirror array, or an acousto-optic tunable filter.

6. The gas composition analysis and concentration detection system based on multi-band infrared filter switching according to claim 1, characterized in that, The differential absorption algorithm executed by the control and signal processing module is as follows: C gas =k*ln(V ref / V meas ), Among them, C gas Let V be the concentration of the gas to be measured, k be the system calibration coefficient, and V be the concentration of the gas to be measured. ref To reference the signal strength of the filter channel, V meas The signal intensity of the filter channel at the absorption peak.

7. The gas composition analysis and concentration detection system based on multi-band infrared filter switching according to claim 1, characterized in that, For CO concentration calculation, the double difference algorithm is used: C CO =k2*[ln(V B / V C )-α*ln(V B / V A )], Where α is the cross-interference compensation coefficient, which is obtained through prior calibration.

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