Analysis of a thermal imaging method for landmine detection, using infrared heating of the sand surface

Abstract The detection of a buried surrogate land mine is investigated by use of a pulsed thermographic method driven by a high powered infrared heater. In this experimental and analytical investigation, the surface of the sand is initially heated by infrared lamps and is then cooled by natural convection, and during this second phase a dry layer of sand develops on the surface. The temperature distribution of the dry sand surface is influenced by the presence of the buried mine. The experimental investigation was performed in a laboratory where a surrogate mine was buried at depths between 1 cm and 4 cm in dry sand, and sand which had initial water contents of 2.5%, 5% and 10%. The results show that an observable ‘hot spot’ develops on the sand surface above the mine, during the cooling phase of most tests. The water content of the sand was found to have a strong influence on the development of the hot spot. The surface temperature variation for dry sand tends to be less than that found for sands that contain water and the only test where the hot spot was not detected was in dry sand where the mine was buried at 4 cm. A one-dimensional finite difference model was used to describe the heat and mass transfer mechanisms and interpret the experimental results.