An algorithm to increase the residues of wrapped-phase in spatial domain
  In phase unwrapping, the locations and densities of residues are indicative of the severity of the unwrapping problem. The residues are used to detect and evade inconsistent phase areas. Gdeisat et al. proposed an algorithm to increase the number of residues in a wrapped-phase map to improve the results of phase unwrapping. But this method will take much time to make the Fourier transform, inverse Fourier transform, select and shift the spectral components, and there is no theoretical analysis on why the frequency shift can increase the number of residues. In view of the above problems, we proposed an algorithm to increase the number of residues in a wrapped-phase map, which only uses a simple multiply operation in spatial domain to realize frequency shift by taking advantage of the frequency shift property of Fourier transform. Besides that, we discuss the relationship between the number of residues and frequency shift. Finally, the experimental evaluation is conducted to prove the validity of the proposed method. Experimental results demonstrated that the proposed method can speed up more than 50%. 
Guangliang Du, Minmin Wang, Canlin Zhou, Shuchun Si, Hui Li, Zhenkun   Lei, Yanjie Li
physics.ins-det physics.optics