CN110632026A - A device for optical detection of gas - Google Patents

Abstract

The invention discloses a gas sensor device based on the principle of optical interference. The entire device is integrated on the same silicon-based substrate 1, and a micromirror 3 is set in the microresonator 2. By adjusting the inclination angle of the micromirror, the incident light 7 forms an interference with gas absorption characteristics at the detection point 8. Spectrum, the composition and concentration of the measured gas are obtained through feature extraction. This method has the advantages of fast response, high sensitivity and strong anti-interference ability.

Description

A device for optical detection of gas

technical field

The invention belongs to the field of spectrum sensing, in particular to a photon sensor technology.

Background technique

In recent years, air quality has been increasingly valued by the government and the public, and efficient, timely and accurate automatic monitoring of pollutants in the ambient air has become a future development trend. At present, the mainstream air composition monitoring mainly relies on electrochemical sensors. Due to the limitation of the principle of electrochemical gas sensors, the actual application life is short, the maintenance cost is high, and it cannot be widely applied; some gas monitoring environments are relatively harsh and there is high humidity. , high temperature, corrosion and other environments greatly limit the application of electrochemical gas sensors; at the same time, electrochemical gas sensors can only identify specific types of gases, and the composition of the air is complex, which is often easily disturbed, resulting in inaccurate measurements.

All molecules in the ambient air have their own unique spectral characteristics. The method of using the spectral characteristics of molecules to identify ambient air components can theoretically identify all gas components in the air. It has a wide range of applications and a high degree of molecular recognition. It has the advantages of high sensitivity and wide monitoring range. However, the traditional method requires the use of large spectrometers for the collection and analysis of molecular spectra, which cannot be applied in real time and on a large scale.

Micro-electromechanical (mems) sensors have the advantages of small size and high reliability, and have been widely used in important fields such as mobile phones, automobiles, and transportation. The micro-optical sensing system designed with micro-electro-mechanical systems will integrate the advantages of traditional spectrometers and mems sensors. It can not only obtain molecular spectra in a cheap and efficient manner, but also facilitate integration and wide-ranging applications due to its small size.

CN107340317A mentions a micro-gas sensing device, which uses a micro-nano electric resonator. The principle is that it uses a gas adsorption voltage corresponding to a characteristic gas, and has the advantages of small size and fast response. CN110095508A mentions a micro gas sensor, the principle of which is to use a pulse voltage to heat the gas to obtain the maximum calculation time of the gas and the sequence of the gas sensitivity response value, and compare it with the sequence library to identify the gas. "Dual interband cascade laser based trace-gas sensor for environmental monitoring. Applied Optics, 2007, 46(23), 8202" mentions an optical reflection system to enhance the spectral absorption of characteristic gases. The system adopts a dual optical path design, The sensitivity is high, and unlike the present invention, the reflection system of the system is a fixed curved surface.

Contents of the invention

In order to solve the above-mentioned technical problems, the present invention proposes a method and device for identifying gas components based on an integrated micromirror based on optical principles. In a silicon-based resonant chamber, a micromirror is set; There is a gap between them. The incident light is incident on the micromirror at a certain angle from one end of the smooth mirror surface, and the micromirror is adjusted so that the light is reflected multiple times in the slit, and finally the characteristic absorption spectrum of the gas is emitted from the other end and detected by the detector.

A method of optically detecting a gas comprising.

In the silicon-based resonant chamber 2, an adjustable micromirror 3 is arranged, and the inclination angle of the micromirror can be adjusted by a micromotor.

There is a slit 6 between the smooth mirror surface 5 outside the resonant cavity and the resonant cavity. The size of the slit can satisfy the gas flowing through the slit 6, and the distance between the upper and lower interfaces of the slit can be adjusted according to the frequency of the incident laser light.

The incident light enters the slit 6 from the port, and is reflected multiple times in the upper and lower mirrors. By adjusting the micromirror 3 to control the number of light reflections in the gas path, the spectral absorption of the characteristic gas is enhanced.

The composition and concentration of the measured gas are determined by comparing the outgoing light containing the measured gas information with the characteristic absorption value of the responding gas and the established relationship between the gas interference spectrum and the species concentration.

preferred.

The above-mentioned micromirror 3 can adjust the inclination angles in the front, rear, left, and right directions by means of a micro-motor. Preferably, the micromirror 3 can adjust the inclination angles in the front and back directions, and the adjustment range is -60°~60°.

The width of the above-mentioned slits 6 can be adjusted to an integer multiple of the laser wavelength by adjusting the relative spacing of the mirror surfaces, and the preferred relative spacing is more than 10 times the incident wavelength.

After adjusting the micromirror 3, the incident light is reflected multiple times in the slit 6, and the number of reflections is 2-500 times, preferably 10-100 times.

The light beam containing the characteristic spectrum of the gas to be measured is detected at the detection end, and its characteristic spectrum can be extracted using steady-state feature extraction algorithm, EMA algorithm, LDA algorithm and other algorithms, and the steady-state feature extraction algorithm is preferred.

Description of drawings

Figure 1 Front view of gas sensor section.

Figure 2 Top view of the appearance of the gas sensor.

Fig. 3 The side view of the appearance of the gas sensor.

Specific implementation examples

The working principle of the gas sensor will be described below with examples.

Embodiment one.

As shown in FIG. 1 , this embodiment provides a gas identification method, the steps are:

1) Turn on the two broadband laser beams and the detector so that the device elements are in a stable state.

2) Open the gas path control device, and let methane gas flow into the slit 6. The methane gas enters the sensor from the Gas in end and exits from the Gas out end.

3) At the same time, adjust the micromirror 3 and adjust the optical path so that the characteristic frequency interferes just at the detector, forming a characteristic spectrum to be detected by the detector.

4) Algorithm conversion is performed between the obtained characteristic interference spectrum and the established standard library to identify methane gas molecules and their corresponding concentrations.

Embodiment two.

As shown in Figure 1, this example provides a gas identification method, the steps are:

1) Turn on four broadband laser beams and detectors so that the device elements are in a stable state.

2) Open the gas path control device, and let in the standard mixed gas of methane and ethylene. The mixed gas enters the sensor from the Gas in end and goes out from the Gas out end.

3) At the same time, adjust the micromirror 3 so that various characteristic spectra interfere on the detector in turn, forming multiple groups of characteristic spectra to be recognized by the detector.

4) Algorithm conversion is performed between the obtained characteristic interference spectrum and the established standard library to identify methane and ethylene gas molecules and their respective concentrations.

Claims (5)

1. A gas sensor based on the principle of optical interference, characterized in that the whole device is integrated on the same silicon-based substrate, wherein in a resonant cavity 2, a micromirror 3 is arranged; another smooth micromirror 5 is arranged outside the resonant cavity, and a certain slit 6 is arranged between the two; incident light is incident on the micro mirror 3 from one end 7 of the smooth mirror surface at a certain angle, the micro mirror is adjusted by a micro motor to enable the light to be reflected for multiple times in the slit 6, and finally, a gas-containing characteristic absorption spectrum is emitted from the other end to be detected by a detector 8.

2. A micromirror 3 as claimed in claim 1, characterized in that the micromirror 3 is suspended in the resonant cavity 2 and the tilt angle of the micromirror can be adjusted by a micro-motor.

3. The slit 6 of claim 1, wherein the slit is sized to allow gas to flow therethrough, and the distance between the upper and lower boundary surfaces of the slit is adjusted according to the frequency of the incident laser light.

4. The gas sensor of claim 1, wherein the light is reflected multiple times in the slit, and the spectral absorption of the characteristic gas can be enhanced by adjusting the number of reflections with the micro-mirrors 3.

5. The gas sensor of claim 1, wherein the species and concentration identification of the gas is established based on a number of established relationships of gas interference spectra to species concentration.

Images