THERMAL TOMOGRAPHIC DETECTION OF INHOMOGENEITIES

Thermal tomography is a nondestructive method for detecting inhomogene ities in a material by localizing variations in its thermal conductivi ty. Based on a finite element discretization of the heat conduction eq uation, we obtain a set of equations that relate the conductivity of a medium to temperature measurements on the surface of the medium. We i nvestigate the use of both a linearization and regularization techniqu e and a randomized search procedure based on a genetic algorithm to in vert this set of equations. We found a tradeoff exists between the acc uracy of the conductivity mapping and the resolution of the conductivi ty mapping. To increase the resolution of the mapping, we propose a zo oming method in which the finite elements are grouped into blocks and a low-resolution mapping of the conductivity is obtained. Improved map pings are then obtained by increasing the number of blocks in regions where inhomogeneities appear to be present and repeating the inversion process.