Branch cutting algorithm for unwrapping photoelastic phase map with isotropic point

A branch cutting algorithm is proposed to solve the wrapped isoclinic causing isochromatic discontinuity and thus to decouple the isoclinic–isochromatic interaction of photoelastic phase maps. Rather than pixel by pixel, the branch-cutting isoclinic wrapped map is then restored by a modified regional approach and is proved to be more time-effective and less effort needed than the author's earlier algorithm. The decoupled isochromatic data can be handled easily afterward. Two type of simulated samples (i.e., specimens with and without isotropic points) are used to detail why and how isoclinic and isochromatic are interactive with each other and the decoupling method of the present study. Experimental works prove the effectiveness, robustness and simplicity of the newly developed algorithm.

► We plan a modified regional unwrap algorithm for isoclinic phase retrieval of photoelastic phase map with isotropic point. ► Same polarities residues are paired only under special pairing condition. ► Upward and downward retrieval are done simultaneously in one single partition only if same polarity residues have been paired. ► The modified algorithm is excellent in noise resisting ability. ► Time effective rule makes in-situ measurement possible.