A simple spatial domain algorithm to increase the residues of wrapped phase maps

In phase unwrapping, the locations and densities of the residues are indicative of the severity of the unwrapping problem. Gdeisat et al. proposed an algorithm to increase the number of residues in a wrapped phase map to improve the results of phase unwrapping. The method proposed, though, is extremely time-consuming involving the computation of a Fourier transform along with the selection and shift of its spectral components. Moreover, there is no theoretical analysis on the reasons why the frequency shift should be able to increase the number of residues. In an attempt to address these problems, we propose a simple algorithm to increase the number of residues in a wrapped phase map. The algorithm uses a simple multiply operation in spatial domain to realize the frequency shift exploiting the frequency shift property of Fourier transform. We also discuss the relationship between the number of residues and frequency shift. Experimental results have demonstrated that the proposed method can speed u...