Feasibility of Detection and Location of Buried Metallic and Non-Metallic Objects using Laser-Based Thermal Wave Echo Imaging

In this research we propose evaluating the feasibility of adapting thermal wave echo imaging to the detection of buried metallic and non-metallic objects. The technique relies on monitoring the surface temperature distribution of the soil resulting from the propagation of a thermal energy pulse. In this research, the thermal pulse will be generated using a modulated C02 laser (l=10.6mm), as opposed to using conventional flash lamp sources. As the thermal pulse propagates into the soil it is reflected from buried objects and modifies the surface temperature distribution of the soil. It is the temperature differential between the region in close proximity to the buried object and the surrounding region that can be used to identify buried objects. Images of the time-varying surface temperature distribution will be acquired using a gated infrared camera, sensitive over a wavelength range of 8 - 12 mm. Post processing of the thermal images will be performed off-line using the Khoros progamming environment. The post processing will quantify the ability of the system to distinguish buried objects through analysis of the image contrast. The fundamental objective of the research is to quantitatively evaluate system detection capability as a function of laser characteristics, buried object size and material, burial depth, and soil type. The most immediate application of this technology will be for use in the detection and location of buried landmines, which is a growing worldwide problem. Beyond the huge potential for military use of this sensor, there is also a large market for similar instruments that can be used in civilian areas. One example would be for the non-destructive detection of detenioration in bridge structures.