Multi-beam interference suppression method for detecting tunable diode laser absorption spectroscopy (TDLAS) gas in glass container

Abstract

The invention discloses a multi-beam interference suppression method for detecting tunable diode laser absorption spectroscopy (TDLAS) gas in a glass container. Multi-beam interference is formed by multiple reflections and transmissions, caused by the two walls of the glass container, of incident light, so that signal waveforms and detection accuracy are seriously affected. By slanting the glass container to be detected in the laser light path direction at a certain angle, the distances between all the transmission lights can be increased due to the enlargement of an incident angle, so that the multi-beam interference is effectively inhibited. The energy obtained after laser transmission is mainly focused on the direct transmission light and the reflected first transmission light, an incident angle expression, which enables the superimposed part of two coherent beams to be positioned outside a receiving detection range, is standardized, and the minimum value of the incident angle is worked out. On this basis, the maximum signal to noise ratio of a second harmonic signal characteristic value is taken as an optimizing index, and the optimal incident angle in a real system is obtained. The method provided by the invention can efficiently extract the second harmonic signal characteristic value for analyzing the gas in the glass container under the premise of not adding a complex optical device and not performing additional information anti-interference processing.

Description

technical field [0001] The invention relates to the technical field of gas detection, in particular to a system for detecting gas in a glass container based on TDLAS technology with an open single optical path and short optical path. Background technique [0002] Gas detection in glass containers is widely used. For example, glass medicine bottles used in the pharmaceutical industry generally use vacuuming or nitrogen filling to isolate the medicine from oxygen, thereby ensuring the stability and sterility of the medicine. However, due to unstable stoppering and capping processes, damage to the packaging material itself, and human factors, it is impossible to guarantee the absolute vacuum in the glass bottle, so that the oxygen concentration is too high, resulting in faster deterioration of the drug, affecting the efficacy of the drug, and even endangering the safety of drug users. . At present, the oxygen detection method in glass medicine bottles is mainly destructive sam...

AI Technical Summary

Problems solved by technology

Persson and Andersson proposed a balanced gas detection method using detector nonlinear compensation to suppress the influence of optical interference fringes, but it requires dual optical path detection, and complex instruments such as optical attenuation filters are required, which does not meet the requirements of real-time detection systems

Hanson et al. proposed to suppress the interference fringes by using a wedge-shaped window with a small inclination angle or an off-axis parabolic mirror, but they did not elaborate on the suppression principle, and this method is only applicable to the case where the gas sample is in the optical cell, and additional The optical components are not suitable for the open single optical path and short optical path in free space, which is called atmospheric space in the optical field, to detect the gas in the airtight glass container

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