Forward-looking acoustic mine detection system

Abstract

A desirable characteristic for a landmine detection system is the ability of the detector to 'look' out in front of the vehicle a significant distance. The obvious reason for this is to reduce the risk to the vehicle and its operators and to allow a safe stopping distance for the vehicle. Several experiments were conducted at Fort A. P. Hill to investigated the feasibility of a forward-looking system based on acoustic-to-seismic coupling. The system, developed at the National Center for Physical Acoustics, insonifies the ground with high amplitude (120 dB), broadband (80-300 Hz) sound and measures the resulting ground vibration with a scanning Laser Doppler Vibrometer (LDV). Images produced by these scans show a distinct contrast in several frequency bands between ground vibrations over a buried mine and those not over a buried mine. In a forward-looking system, both the sound source and the LDV are moved farther from the scanned area. This configuration both reduces the sound pressure level at the scanned area and decreases the angle at which the LDV beam strikes the ground. These effects reduce the contrast between the over-mine and off-mine signals. In addition, the image is distorted at the shallower LDV-ground angles. However, the results from the experiments demonstrate that the acoustic-to-seismic forward-looking approach is feasible once these technical hurdles are overcome.