Detection of foreign matter in closed space based on acoustic excitation using laser

Abstract

This paper proposes a health monitoring system for detecting a foreign matter in a closed space based on acoustic excitation by the laser-induced plasma in the air, which is generated by a high power Nd:YAG pulse laser. Non-contact acoustic impulse excitation can be realized by laser-induced plasma. A microphone is used for measuring the acoustic pressure at a point in the closed space and its Fourier spectrum is analyzed. This study focuses on the detection of a foreign matter in the closed space. The Fourier spectrum is varied depending on the presence of the foreign matter and its damage is extracted to identify the foreign matter.