AN ANALYSIS OF A THERMAL IMAGING METHOD FOR LANDMINE DETECTION USING MICROWAVE HEATING

Abstract

A land mine detection method based on measuring the differing thermal response rates of the sand above and beside a buried dummy mine has been investigated in laboratory experiments. Differing response rates are created when the sand is heated by a microwave generator, and then cooled by forced convection. In the experimental investigation, a surrogate mine11Throughout the paper the surrogate mine is referred to as a mine. is buried in sands which have a water content of 5% and 10% and in sand that is oven-dried. The results show that evaporative cooling at the surface of the sand is the main mechanism controlling the surface temperature. When a substitute mine is buried in sand, the temperature response rate of the surface above the mine changes during the heating part of the process. This change is due to a reduction in the rate of evaporative cooling in this region. In moist sand, the surface temperature differences of 1.5 °C between the sand above the mine and the sand beside the mine have been measured and a resultant infrared photographic image of the mine can be readily observed.The tests involving dry sand show that there is some heating of the sand surface by vapour condensation. The effect of this condensation is difficult to interpret since the migration of moisture into the sand cannot be evaluated. When the condensation effect is ignored, the analysis can be used to demonstrate the change in the values of surface temperature difference during cooling. Infrared photographs taken during the dry-sand tests show that the location of the mine can be observed where the mine is buried at 2 cm, but not at 3 cm.