Photoacoustic spectrometry trace gas detection device suitable for broadband divergent beams

Abstract

The invention belongs to the field of trace gas detection, and particularly relates to a photoacoustic spectrometry trace gas detection device suitable for broadband divergent beams. The device comprises an optical module, a photoacoustic cavity module and a data processing module; wherein the photoacoustic cavity module comprises a gas absorption cell arranged on a light path of the optical module and an acoustic resonant cavity arranged perpendicular to the light path; the optical module comprises a broadband light source, an optical chopper, an optical filter, a first lens and a second lens; a light beam emitted by the broadband light source sequentially passes through the first lens, the optical chopper, the optical filter and the second lens from the broadband light source along a light path and enters the gas absorption cell; and the data processing module comprises a pre-amplifier electrically connected with the acoustic microphone, a lock-in amplifier electrically connected with the output end of the pre-amplifier, a data acquisition card electrically connected with the output end of the lock-in amplifier, and data terminal processing equipment. By means of the device, broadband light source which is poor in current light beam quality and low in cost can be applied to trace gas detection.

Description

technical field [0001] The invention belongs to the field of trace gas detection, and in particular relates to a photoacoustic spectrum trace gas detection device suitable for broadband diverging light beams. [0002] technical background [0003] The high-sensitivity detection of trace gases is of great significance for the governance of the current atmospheric environment, the improvement of human living environment, and the control and monitoring of industrial processes. Due to its high sensitivity, simple structure, low cost, and zero background, photoacoustic spectroscopy has been gradually used in the detection of trace gases in recent years. Photoacoustic spectroscopy is a laser spectroscopy technology developed based on the photoacoustic effect discovered by A.G. Bell in 1880. Its basic principle is that when a light source in the absorption band of trace gas molecules irradiates gas molecules, the gas molecules absorb light energy and transition to excited Molecules...

AI Technical Summary

Problems solved by technology

Although photoacoustic cavities with this structure are now widely used, they are basically combined with light sources with better beam quality. For broadband light sources with poor beam quality, such as infrared thermal radiation light sources, the use of this traditional resonant photoacoustic cavity is likely to cause the beam to irradiate in the On the wall of the resonant cavity, causing a large background interference

[0005] Patent CN202404020U proposes to use a broadband light source for the detection of trace gases, but because the light output by the broadband light source is not focused by the focusing lens, its optical path will be divergent, and because the photoacoustic cell it uses is a traditional resonant photoacoustic cavity, the resonant cavity The inner diameter is generally small, and the divergent beam is easy to hit the wall of the resonant cavity, resulting in unavoidable background noise, thereby reducing the detection limit of the system, and cannot meet the measurement of trace gas concentration in extreme environments

Patent EP1936355A1 uses a broadband blackbody light source to detect trace gases. However, due to the long photoacoustic cell length of 320mm and the long optical path of the entire system, the broadband light source with poor beam quality will inevitably hit the on the wall of the resonator, causing background interference

Patent CN108535184A removes the buffer body of the traditional resonant photoacoustic cavity, leaving only the acoustic resonant cavity. Its operating frequency is 10-100Hz, and it is relatively easy to be disturbed by environmental noise and 1 / f noise during the measurement of trace gases. Yes, the light source with poor beam quality will hit the wall of the resonant cavity and cause unavoidable background interference, which will reduce the detection limit of the system

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