Differentiated absolute phase contrast algorithm for the analysis of pulsed thermographic sequences

A depth inversion technique by pulsed phase thermography has been recently proposed based on the determination of the blind frequency fb, through phase contrast calculations. The differentiated absolute phase contrast algorithm (DAPhC) is proposed here as an efficient alternative to obtain fb, without the need of a sound area definition. DAPhC is based on the Hough transform to retrieve the phase profiles slopes reducing in the process the human intervention to a minimum. The final result is an image showing the fb values for each pixel. A straightforward relation between the depth and fb can be applied to extract the depth information.