Methods and related apparatus (SP) to correct phase shift image data for phase wrapping artifacts. The data is detected at a detector (D) of an imaging system (IM) including interferometric equipment (G0, G1, G2). In a phase unwrapping method that involves optimizing an objective function with regularization, a two-sage approach is proposed. The measured data is processed in one stage with regularization and in the other stage without regularization. This allows improving the accuracy of the corrected (phase unwrapped) phase shift data because an undesirable bias caused by the regularization can be avoided.
