Landmine antenna

The device fires a tightly-focused beam of very loud sound at the ground, causing it to vibrate. This vibration is then measured using a reflected laser beam, and the signal reveals the telltale disturbances caused by any subsurface mines.The sound frequency employed must be low in order to shake the ground and normally this would mean focusing a beam using large parabolic reflectors. MIT researchers cunningly use a higher frequency signal, which can be focused more easily, to carry a lower frequency tone. As the focused beam hits the ground, the frequencies separate to create powerful, low frequency vibration.The patent application reveals that MIT has already tested the system on anti-personnel mines using a sound source and a laser on a tripod positioned 30 metres away. The resulting vibrations were analysed on a laptop, which quickly produces a map of the area, highlighting hidden mines.