Phase unwrapping in dual-wavelength digital holographic microscopy with total variation regularization.

A two-step dual-wavelength phase imaging method with total variation (TV) regularization in digital holographic microscopy (DHM) is presented. The rough height map is first denoised with TV regularization, and then it is used as a guiding map for accurate phase unwrapping. By combining the principle of dual-wavelength interferometry and TV regularization, the problem of phase unwrapping is converted into a minimization problem that can be efficiently solved with the Split Bregman algorithm. The proposed algorithm allows a synthetic wavelength that can be arbitrarily large in principle to a single wavelength, while the accuracy of the phase map can achieve the same level in single-wavelength DHM. Moreover, the unwrapping method is robust to the change of weighting parameters. Comparative topographic measurements of a sample with abrupt steps are illustrated, and the results verified the effectiveness of the method.