Semester of Graduation

Spring 2024


Master of Science (MS)


Department of Physics and Astronomy

Document Type



Grating interferometry exploits wave interference to simultaneously image multiple physical properties of an object and can be performed using X-rays or neutrons. The modulated phase grating interferometer (MPGI) is a recently developed interferometry system that allows for the simultaneous acquisition of attenuation, differential-phase contrast, and dark-field images, which highlight X-ray or neutron absorption, refraction, and small angle scatter, respectively. This interferometry system uses a single grating, with a relatively high period envelope function, to produce interference fringes that can be directly resolved by standard high resolution detectors. The grating is sampled at a relatively low pitch, to meet coherence requirements typical of other grating interferometers. We present the theory of the MPGI by deriving the field at the detector produced by a monochromatic point-source using Fourier optics. We derive the conditions of maximum fringe visibility and demonstrate how to account for the effects of a finite focal spot size, detector point spread function, and polychromatic source. We then compare the presented theory with simulations performed using the Sommerfeld-Rayleigh Diffraction Integral (SRDI) simulator, with several orders of magnitude decreased simulation time. The presented theory will allow researchers to rapidly iterate when designing future MPGI systems, allowing them the ability to predict the fringe visibility prior to construction, without applying the SRDI simulator.



Committee Chair

Dey, Joyoni