8 research outputs found
PhasePack: A Phase Retrieval Library
Phase retrieval deals with the estimation of complex-valued signals solely
from the magnitudes of linear measurements. While there has been a recent
explosion in the development of phase retrieval algorithms, the lack of a
common interface has made it difficult to compare new methods against the
state-of-the-art. The purpose of PhasePack is to create a common software
interface for a wide range of phase retrieval algorithms and to provide a
common testbed using both synthetic data and empirical imaging datasets.
PhasePack is able to benchmark a large number of recent phase retrieval methods
against one another to generate comparisons using a range of different
performance metrics. The software package handles single method testing as well
as multiple method comparisons.
The algorithm implementations in PhasePack differ slightly from their
original descriptions in the literature in order to achieve faster speed and
improved robustness. In particular, PhasePack uses adaptive stepsizes,
line-search methods, and fast eigensolvers to speed up and automate
convergence
Untrained neural network embedded Fourier phase retrieval from few measurements
Fourier phase retrieval (FPR) is a challenging task widely used in various
applications. It involves recovering an unknown signal from its Fourier
phaseless measurements. FPR with few measurements is important for reducing
time and hardware costs, but it suffers from serious ill-posedness. Recently,
untrained neural networks have offered new approaches by introducing learned
priors to alleviate the ill-posedness without requiring any external data.
However, they may not be ideal for reconstructing fine details in images and
can be computationally expensive. This paper proposes an untrained neural
network (NN) embedded algorithm based on the alternating direction method of
multipliers (ADMM) framework to solve FPR with few measurements. Specifically,
we use a generative network to represent the image to be recovered, which
confines the image to the space defined by the network structure. To improve
the ability to represent high-frequency information, total variation (TV)
regularization is imposed to facilitate the recovery of local structures in the
image. Furthermore, to reduce the computational cost mainly caused by the
parameter updates of the untrained NN, we develop an accelerated algorithm that
adaptively trades off between explicit and implicit regularization.
Experimental results indicate that the proposed algorithm outperforms existing
untrained NN-based algorithms with fewer computational resources and even
performs competitively against trained NN-based algorithms
PhaseMax: Convex Phase Retrieval via Basis Pursuit
We consider the recovery of a (real- or complex-valued) signal from
magnitude-only measurements, known as phase retrieval. We formulate phase
retrieval as a convex optimization problem, which we call PhaseMax. Unlike
other convex methods that use semidefinite relaxation and lift the phase
retrieval problem to a higher dimension, PhaseMax is a "non-lifting" relaxation
that operates in the original signal dimension. We show that the dual problem
to PhaseMax is Basis Pursuit, which implies that phase retrieval can be
performed using algorithms initially designed for sparse signal recovery. We
develop sharp lower bounds on the success probability of PhaseMax for a broad
range of random measurement ensembles, and we analyze the impact of measurement
noise on the solution accuracy. We use numerical results to demonstrate the
accuracy of our recovery guarantees, and we showcase the efficacy and limits of
PhaseMax in practice