Phase retrieval in electronic speckle pattern interferometry using the continuous wavelet transform

Several papers have recently been published in the field of speckle interferometry to evaluate the phase distribution contained in the correlation fringes using the continuous wavelet transform. Even though this approach has the advantage of avoiding the complex fringe analysis step of phase unwrapping, no studies were carried out to determine the accuracy of the retrieved phase map and the influence of the most common error sources. This paper presents an evaluation of the continuous wavelet transform method when it is used to determine the phase information contained in Electronic Speckle Pattern Interferometry fringes. It is shown that only fringe patterns that verify the stationary phase approximation and its asymptotic limit can be analysed with the wavelet method. The evaluation is performed using computer-simulated fringes, approach which allows knowing precisely the phase distribution encoded by them. It is shown that the use of continuous wavelet transform strongly depends on the filtering process used to smooth the fringes and also on the process utilized to extend the fringe pattern edges.