Block Coordinate Plug-and-Play Methods for Blind Inverse Problems

Weijie Gan, Shirin Shoushtari, Yuyang Hu, Jiaming Liu, Hongyu An, Ulugbek Kamilov

Keywords: inverse problems, plug-and-play priors, computational imaging, nonconvex optimization

TL;DR: We present a block-coordinate PnP method with theoretical analysis for blind inverse problems by applying learned denoisers as priors on both the image and measurement operator.

Abstract: Plug-and-play (PnP) prior is a well-known class of methods for solving imaging inverse problems by computing fixed-points of operators combining physical measurement models and learned image denoisers. While PnP methods have been extensively used for image recovery with known measurement operators, there is little work on PnP for solving blind inverse problems. We address this gap by presenting a new block-coordinate PnP (BC-PnP) method that efficiently solves this joint estimation problem by introducing learned denoisers as priors on both the unknown image and the unknown measurement operator. We present a new convergence theory for BC-PnP compatible with blind inverse problems by considering nonconvex data-fidelity terms and expansive denoisers. Our theory analyzes the convergence of BC-PnP to a stationary point of an implicit function associated with an approximate minimum mean-squared error (MMSE) denoiser. We numerically validate our method on two blind inverse problems: automatic coil sensitivity estimation in magnetic resonance imaging (MRI) and blind image deblurring. Our results show that BC-PnP provides an efficient and principled framework for using denoisers as PnP priors for jointly estimating measurement operators and images.

Submission Number: 5241