MULTI-CAVITY SUPERIMPOSED NON-RESONANT PHOTOACOUSTIC CELL AND GAS DETECTION SYSTEM

Abstract

The present invention belongs to the field of trace gas detection technology and provides a multi-cavity superimposed non-resonant photoacoustic cell and gas detection system. The multi-cavity superimposed non-resonant photoacoustic cell includes a cylindrical metal shell, a plurality of non-resonant photoacoustic cavities, a sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor, an optical glass window, an air inlet and an air outlet. The circular sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor is fixed on one side of the cylindrical metal shell, and the other side of the cylindrical metal shell is sealed by an optical glass window. The gas to be measured enters through the inlet, diffuses into a plurality of non-resonant photoacoustic cavities, and exits through the outlet on the other side.

Claims

1. A multi-cavity superimposed non-resonant photoacoustic cell, wherein the multi-cavity superimposed non-resonant photoacoustic cell comprises a cylindrical metal shell, a plurality of non-resonant photoacoustic cavities, a sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor, an optical glass window, an air inlet and an air outlet; the cylindrical metal shell has an open structure at both ends, interior of the cylindrical metal shell contains multiple interconnected cylindrical through-holes, polished as the non-resonant photoacoustic cavities; one end of the cylindrical metal shell is fixed by laser welding or gluing the sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor, and the other end is sealed by the optical glass window; one end of the cylindrical metal shell has the air inlet and the other end has the air outlet, and the gas to be measured enters through the air inlet, diffuses into the multiple non-resonant photoacoustic cavities, and then discharges through the air outlet at the other end.

2. A gas detection system based on the multi-cavity superimposed non-resonant photoacoustic cell of claim 1, wherein the gas detection system includes an infrared thermal radiation light source, a chopper, a filter, a multi-cavity superimposed non-resonant photoacoustic cell, a fiber-optic Fabry-Perot acoustic sensor, a tunable semiconductor laser, a circulator, a photodetector, a data acquisition card, and an industrial control computer; the broad-spectrum light emitted from the infrared thermal radiation light source becomes narrow-band light applicable to the absorption of a single gas after the modulation of the chopper and the band-pass effect of the filter; for multi-component gas measurements, multiple filters are configured; the narrow-band light is incident through the optical glass window into the multi-cavity superimposed non-resonant photoacoustic cell; due to the photoacoustic effect, the photoacoustic signal is generated in the non-resonant photoacoustic cavity, and the sound pressure at each place in the non-resonant photoacoustic cavity is equal; the fiber-optic Fabry-Perot acoustic sensor is used as the acoustic wave detection unit.

Description

DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a schematic diagram of the structure of a multi-cavity superimposed non-resonant photoacoustic cell.

[0010] FIG. 2 is a schematic diagram of a gas detection system based on a multi-cavity superimposed non-resonant photoacoustic cell.

[0011] In the figure: 1 cylindrical metal shell; 2 non-resonant photoacoustic cavity; 3 sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor; 4 optical glass window; 5 air inlet; 6 air outlet; 7 infrared thermal radiation light source; 8 chopper; 9 filter; 10 multi-cavity superimposed non-resonant photoacoustic cell; 11 fiber-optic Fabry-Perot acoustic sensor; 12 tunable semiconductor laser; 13 circulator; 14 photodetector; 15 data acquisition card; and 16 industrial control computer.

DETAILED DESCRIPTION

[0012] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings and technical solutions.

[0013] The present invention provides a multi-cavity superimposed non-resonant photoacoustic cell as shown in FIG. 1, mainly consisting of a cylindrical metal sheet 1, several non-resonant photoacoustic cavities 2, a sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor 3, an optical glass window 4, an air inlet 5 and an air outlet 6. The sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor 3 is fixed at one end of the multi-cavity superimposed non-resonant photoacoustic cell, and the photoacoustic signals generated in the multiple non-resonant photoacoustic cavities 2 are superimposed at the position of the sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor 3, causing the periodic vibration of the sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor 3. The concentration information of the gas to be measured can be obtained by demodulating and analyzing the vibration of the sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor 3. At the other end of the multi-cavity superimposed non-resonant photoacoustic cell, there is an optical glass window 4, which allows the excitation light to pass smoothly, and the side walls near the two ends of the multi-cavity superimposed non-resonant photoacoustic cell are equipped with air inlet 5 and air outlet 6, respectively.

[0014] FIG. 2 represents a gas detection system based on the multi-cavity superimposed non-resonant photoacoustic cell. The broad-spectrum light emitted from the infrared thermal radiation light source 7 becomes periodically modulated light after passing through the chopper 8, and the periodically modulated light becomes narrow-band light that can be absorbed by the gas to be measured after passing through the band-pass filter 9. The modulated narrow-band light passes through the optical glass window 4 into the multiple non-resonant photoacoustic cavities 2 of the multi-cavity superimposed non-resonant photoacoustic cell 10. The gas to be measured absorbs the periodically modulated narrow-band light in the non-resonant photoacoustic cavity 2 to generate a photoacoustic signal, and the photoacoustic signals in the multiple non-resonant photoacoustic cavities 2 are superimposed at the position of the sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor 3, causing periodic vibration of sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor 3. As the detection light source of the fiber-optic Fabry-Perot acoustic sensor 11, the laser from the tunable semiconductor laser 12 is incident into the Fabry-Perot cavity of the fiber-optic Fabry-Perot acoustic sensor 11 through the circulator 13, and the reflected light from the fiber end face and the reflected light from the sensitive diaphragm of the fiber-optic Fabry-Perot acoustic sensor 3 interferes. The periodic vibration of the sensitive diaphragm of the fiber optic Fabry-Perot acoustic sensor 3 causes a periodic change in the length of the Fabry-Perot cavity, which causes a periodic change in the interferometric light signal. The reflected interference light is received by the photodetector 14 through the circulator 13, which converts the interference light signal into an electrical signal, and the amplified electrical signal is collected by the data acquisition card 15, and finally the signal is sent to the industrial control computer 16 for processing. The data acquisition card 15 controls the tunable semiconductor laser 12 through the driver, and uses the wavelength tuning function of the tunable semiconductor laser 12 to compensate for the drift of the working point and achieve the stability of the working point.

[0015] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, which is subject to various changes and variations for a person skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.