Compact Laser Ultrasound Scanner for Wide-Area Persistent Monitoring

Abstract

In this study we evaluate the feasibility of using a simple, unstabilized, homodyne interferometer configuration for local wavenumber estimation of guided waves, a process known as acoustic wavenumber spectroscopy [1]. Acoustic wavenumber spectroscopy identifies damage in a two-dimensional scan on a pixel by pixel basis, by estimating the wavenumber of a structure’s response to a steady-state, single frequency, ultrasonic excitation. By leveraging the requirement to measure only a single known frequency it may be possible to use a simplified laser doppler vibrometer (LDV). A simple and inexpensive laser ultrasound scanning device would provide convenient and rapid stand-off inspection for evaluating structural damage in a variety of settings. Due to the typical cost, complexity, and size of commercial LDV systems, they are often only used for one-off measurements in the laboratory. A simplified system could enable permanent deployment of LDV technology for persistent structural health monitoring applications.