Landmine Detection

Buried landmines produce distinct seismic surface vibrations when excited by acoustic or pressure energy. Many approaches to this problem are being investigated. To date the biggest problem is the slow demining rate due to dwell time requirements. The platform speed is governed by the necessary dwell time (100 ms for 10 Hz resolution) and the number of simultaneous measurements. To support a 1 m/s platform velocity with a 3 m wide swath and 2 cm resolution, a total of 5x150 beams (pixels) is required. Faster platform velocities are conceivable through a larger array. In principle a 25x150 array would support a 5 m/s platform velocity. CTI proposes to develop a novel scannerless acoustic landmine detection system using a coherent detection receiver to detect these minute surface vibrations on a moving platform. At present CTI is carrying two conceptual designs to be down-selected in Phase I. The first concept is a multi-channel conventional bistatic CW laser vibrometer. This multi-channel/beam lidar increases the demining rate through parallel beams. The second and more novel concept is a baseband imaging interferometer, which utilizes a low-noise high-speed CCD camera to image an interfereogram, thereby significantly reducing hardware complexity. Speckle mitigation is achieved through the a series of diversity techniques, which include some combination of the following : dual polarization receiver, multiple receive apertures for each transmit beam, multiple wavelengths, and temporal averaging. The sensor also employs platform motion sensors and advanced signal processing algorithms to optimally process the speckle diversity and mitigate platform motion induced noise. A post processor filters the data using knowledge of the mine-signatures to produce the mine detection signal.