Performance Evaluation of Phase Unwrapping Algorithms for Noisy Phase Measurements

Phase unwrapping still plays an important role in optical metrology field. The phase unwrapping process has direct influence on the accuracy of final results. This is why many algorithms have been proposed for phase unwrapping. In spite of this, there is no agreement between the current phase unwrapping algorithms for different applications. This is due to the existence of disturbance in the measured phase data. In the case that there is no disturbance in the phase data, the unwrapped phase can be obtained by integrating the phase gradients over the whole data set which is independent from the integration path. However, there are several sources of errors. Firstly, phase aliasing occurs when the true phase changes by more than one cycle (2

π

radian) between samples, which was caused by long baselines, objects discontinuities or high deformation. The second source is noise, which may be caused by speckle noise, electronic noise and/or fringe breaks. In the presence of these errors, it is hard to unwrap a phase map correctly.