  Hidden defects affecting the interface in a composite slab are evaluated from
thermal data collected on the upper side of the specimen. First we restrict the
problem to the upper component of the object. Then we investigate heat transfer
through the inaccessible interface by means of Thin Plate Approximation.
Finally, Fast Fourier Transform is used to filter data. In this way we obtain a
reliable reconstruction of simulated flaws in thermal contact conductance
corresponding to appreciable defects of the interface.
