Detection of antipersonnel land mines based on waterjet-induced thermal images

Abstract

The shape and thermal properties of buried objects can result in a variation in the temperature profile on the surface of the ground. IR imaging has been used to exploit this variation to detect the presence of buried objects. The thermal signature in such cases is normally induced by natural means such as diurnal cycles. This method requires observation at specific times of day and has not in general allowed reliable detection and discrimination, especially for small antipersonnel mines. We have developed a process that uses an array of heated waterjets to rapidly induce a thermal signature of buried objects in the region of interest. The high-pressure, small diameter waterjets penetrate the soil but are deflected by a formed buried objects. A temperature profile on the ground surface is formed due to the radiation and conduction of heat from the water blocked and reflected by the surface of the buried object and the heating of the object itself due to heat transferred from the object to a blurred 2D IR image of the surface. Deblurring and other physics-based image processing techniques are used to correct for the heat diffusion and an estimate can be made of the 3D shape of the part of the buried object which is covered by the waterjet. A time history of the thermal profile is also available when several IR images are acquired after the waterjets are applied. This allows further analysis of the nature of the properties of the buried objects. Known properties of land mines can be used to discriminate them from other buried objects. Shape feature properties based on Fourier descriptors have been developed to allow discrimination of objects.