Quantitative phase imaging with broadband fields

Recently, Wolf has shown that the phase measurement associated with fields that are not monochromatic, which is relevant for all x-ray structure investigations, must be properly defined via a cross-spectral density function under full spatial coherence conditions; otherwise, the problem is meaningless and has no solution [E. Wolf, Phys. Rev. Lett. 103, 075501 (2009)]. We propose an experimental realization for retrieving the phase across the entire field of an image. The demonstration is performed using broadband optical fields, but can be extended to other electromagnetic radiation, including x-rays.