Multigrid Optimization for Large-Scale Ptychographic Phase Retrieval

Abstract

Ptychography is a popular imaging technique that combines diffractive imaging with scanning microscopy. The technique consists of a coherent beam that is scanned across an object in a series of overlapping positions, leading to reliable and improved phase reconstruction. Computationally, ptychography is extremely expensive, as ptychographic microscopes allow for large fields to be imaged at high resolution. In this work, we propose a multigrid-based optimization framework to reduce the computational burdens of large-scale ptychographic phase retrieval. Our proposed method exploits the inherent hierarchical structures in ptychography through tailored restriction and prolongation operators for the object and data domains. Our numerical results show that our proposed scheme accelerates the convergence of its underlying solver and outperforms the state-of-the-art method in the optics community.