Removal of local phase errors in conventional speckle phase retrieval using random phase patch perturbation method

Slow or non- convergence is a common problem in iterative phase retrieval. This may be due to the use of few intensity patterns and the lack of intensity variation which, in turn, is highly object-dependent. In cases of partial convergence, another type of problem may occur where local phase errors appear which may arise from overfitting in the algorithmic calculations. In this study, conditions that may lead to overfitting and the appearance of local phase errors in the conventional speckle phase retrieval are investigated. It was observed that using few speckle patterns (5 images) despite sufficient number of iterations (1000 iterations) resulted in the appearance of local phase errors for the test object wave used. A phase perturbation method that uses random phase patch (with 2π depth of randomization) to remove local phase errors was demonstrated experimentally. The local phase error-removal method may be used in conjunction with other phase retrieval techniques.