Transient thermal image inversion using seismic migration

A new reconstruction technique is described to obtain the interior temperature field of composites from the reflected surface transient time-varying temperature response, or reflection thermogram. It is shown that the temperature field at an imaging time (t=0) represents the cross-section of the composite, which may be used to determine the presence, or otherwise, of any manufacturing flaws in the material. The generation of simulated reflection thermograms (forward problem), using a finite difference implicit method, is presented first. This method is then verified experimentally by comparing simulations with recorded data. The reconstruction technique (inverse problem) is then developed using theoretical principles derived for seismic migration algorithms. It is shown that the reflection thermogram migration algorithm involves forward extrapolation of the thermogram followed by an imaging step