Using a high-efficiency grating interferometer for hard X rays (10-30 keV) and a phase-stepping
technique, separate radiographs of the phase and absorption profiles of bulk samples
can be obtained from a single set of measurements. Tomographic reconstruction yields
quantitative three-dimensional maps of the X-ray refractive index, with a spatial
resolution down to a few microns. The method is mechanically robust, requires little
spatial coherence and monochromaticity, and can be scaled up to large fields of view,
with a detector of correspondingly moderate spatial resolution. These are important
prerequisites for use with laboratory X-ray sources.