gratinginterferometry

Grating interferometry is an optical and wave-based measurement technique that uses periodic structures called gratings to generate and analyze interference patterns. It is applicable to light, X-rays, and neutrons, enabling phase-contrast and small-angle scattering measurements in addition to conventional absorption imaging.

In a typical grating interferometer, three gratings are arranged along the beam path: a source grating (G0), a phase or amplitude grating (G1), and an analyzer grating (G2). G0 creates partial coherence from an extended or incoherent source. G1 imposes a known modulation on the wavefront, producing a fringe pattern by the Talbot effect at a downstream plane. G2 samples these fringes; by translating G2 or performing phase stepping, one collects a set of intensity measurements from which differential phase, absolute phase, and the visibility of the fringes (the dark-field signal) can be reconstructed.

The technique yields three contrast channels: conventional absorption, differential phase contrast (sensitive to refractive-index variations), and dark-field contrast (sensitive to sub-resolution scattering). This combination makes grating interferometry particularly useful when structures impart phase shifts or microstructure scattering without strong absorption.

Applications span X-ray imaging for medical diagnostics, materials science, and nondestructive testing, as well as neutron imaging in materials research. Variants such as the Talbot–Lau interferometer are common for partially coherent X-ray sources. Common challenges include precise alignment, mechanical stability for phase stepping, and design constraints on grating period and spectral range. Ongoing advances in grating fabrication and data reconstruction continue to enhance sensitivity and throughput.