Detection of buried land mines with laser vibrometry

We have demonstrated that buried land mines can be detected by measuring acoustically induced surface vibrations with a coherent laser radar. The detection methods works well for anti-tank (AT) mines. Two AT mines were used as test objects giving clear resonances around 100 Hz. The objects used to simulate anti-personnel (AP) mines did not show any clear resonances, unfortunately, no real AP mines were tested. No resonances were observed for a stone that was used as a decoy. An important advantage with this method is the ability to perform remote detection of buried mines, both metal and plastic. Furthermore, we have shown that it is possible to keep the sensitive and expensive parts of the laser radar system far apart from the measurement head. By passing the local oscillator arm in the same fibre cable as feeding the measurement head, the system became fairly insensitive to both movements of the fibre cable and high sound pressure levels on the cable. Suggested future work includes outdoor field trials to investigate the performance in various types of soil and varied water content. Also, the ability to detect AP mines should be investigated.