Phase Extraction in Dynamic Speckle Interferometry by Empirical Mode Decomposition
In many respects, speckle interferometry techniques are now considered as mature tools in the experimental mechanics circles. These techniques have enlarged considerably the field of optical metrology, featuring nanometric sensitivities in whole-field measurements of profile, shape, and deformation of mechanical rough surfaces. Nonetheless, the phase extraction of speckle interferometry patterns is still computationally intensive, preventing a more widespread use of this technique especially in dynamic experiments. A promising approach lies in the temporal analysis of the pixel signals of photodetector arrays. The basic idea is to extract the instantaneous frequency (IF) of these signals, in order to obtain, in fine, the phase, i.e. the quantity of interest. A pioneering work has been done in this direction in  by using the ridge tracking method of Delprat et al  applied to the Morlet wavelet transform (MT).