Research On Laser Self-mixing Interference Vibration Measuring Method For Acoustic Landmine Detection

In recent years,the severity jeopardize caused by landmine has become a global problem for us to solve urgently,for the detection of metal landmine we can make use of the metal detector based on electromagnetic induction to probe,but hard to detect non-metal landmine.Owing to the huge mechanical characteristic discrepancy between non-metal and soil,so according to mechanical characteristics and acoustic-to-seismic coupling mechanism,we can use acoustic waves to stimulate the soil to induce surface vibration and we can also recognize the type and location information of underground object by laser self-mixing interference principle.We were based on the theory of acoustic-to-seismic coupling mechanism and laser-mixing interference,the experimental study of its application in acoustic wave-laser landmine detection was carried out,the main contents are displayed as follows:1.The resonance model analysis of acoustic landmine detection and the diversification of resonance frequency system when different parameters have changed.Based on the research results at home and abroad,the acoustic-to-seismic coupling processes was analyzed and summarized,resonance analysis,anti-resonance analysis and multi-modal resonance analysis were performed on the landmine detection model and established equivalent circuit.2.The construct of laser self-mixing interference test system.We can utilize laser self-mixing interference principle to achieve the non-contact measurement of asthenic vibration signal and illustrate indoor vibration measuring system which include laser drive,signal preprocessing and acoustic wave launcher,meantime verify the effectiveness of the acoustic wave detection method which using laser self-mixing effect.The vibration measurement system includes an interference channel so that made the measuring device more compact,it will realize miniaturization of vibration sensor more easily.3.Under the existing conditions,a mine detection experiment system based on self-mixing interference laser vibrometer was set up.The system uses a high-powered loudspeaker to emit single-frequency adjustable sine sound waves to stimulate the ground,and the surface vibration signal is collected and transmitted by the laser vibrometer and use the computer for analysis and processing.The vibration of the surface caused by two types of mines is the strongest by analyzing the range of acoustic frequencies that are stimulated in the experiment,which provides a reference for future research.