A mask for use in a speckle-based x-ray or neutron phase contrast imaging system and methods of making the mask are disclosed. The mask may either absorb or change the phase of the incident x-ray or neutron beam. The mask in various embodiments has consistent statistics across the mask, is locally unique (thereby avoiding ambiguous correlations), has a speckle size on the order of the imaging system's resolution, has a speckle pattern that is visible through the sample being imaged, and/or is matched to the energy level of the imaging system and the sample density. These mask attributes are controlled by the method and materials used in the fabrication of the mask. Various embodiments use a pseudo-random binary array for generating the required speckle pattern.