We develop a heat transfer model to reconstruct pulsed thermographic data of layered objects. One of its salient features is its incorporation of normalized variables for a generalized approach to such problems. Additionally, we establish a methodology to determine the spatial and temporal limits of the data reconstruction process. Moreover, we describe an effective nondestructive technique for detecting and characterizing internal defects in multilayer objects. This inspection technique is verified on the construction of physical models and their examination. The depth, transverse dimensions, and front-surface shape of the detected defects are straightforwardly obtained from 3D depthgrams.

We develop a technique to analyze pulsed thermography videos in order to detect and reconstruct subsurface defects in homogeneous and layered objects. The technique is based on the analysis of the thermal response of an object to a heat pulse. This thermal response is compared to the predictions of a finite-difference model that is systematically and progressively adjusted to minimize a cost function. With this minimization process, we obtain a depth and a thickness function that allow us to determine the three-dimensional shape, size, depth, thickness, and location of internal defects. The detected defects are reliably reconstructed with graphics of easy interpretation.

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