Shape from heating: A two-dimensional approach for shape extraction in infrared images

Pulse-transient IR thermography enables detection and quantification of subsurface defects. However, defect detection can be perturbed by the geometry of the part, if not planar. A method is presented that, from a single IR image recorded at the end of the thermal pulse, enables one to evaluate the shape of a nonplanar part and then apply a correction on subsequent thermograms in the time sequence to increase the reliability of defect detection. The method uses some of the concepts of the ''shape from shading'' theory from the machine vision field. (C) 1997 Society of Photo-Optical Instrumentation Engineers.