Phase-retrieval X-ray microscopy by Wigner-distribution deconvolution

Microdiffraction data collected in a scanning transmission X-ray microscope (STXM) are used to obtain phase and amplitude images of objects, to the same resolution as STXM incoherent bright-field images (in this case, 45 nm). The images are retrieved by deconvolving an estimate of the Wigner distribution of the objective lens from the data set. A full characterisation of the phase and amplitude of the microscope transfer function is made from data sets collected from a known test object. This has allowed very accurate phase and amplitude maps of specimens to be retrieved. The effects of the coherence of the beam incident on the objective lens are studied, and maps of the mutual coherence function are obtained. The theory of Wigner-deconvolution phase-retrieval is reviewed with reference to X-ray microscopes.