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We propose a partially learned approach for the solution of ill posed inverse problems with not necessarily linear forward operators. The method builds on ideas from classical regularization theory and recent advances in deep learning to…

Optimization and Control · Mathematics 2017-11-27 Jonas Adler , Ozan Öktem

The goal of 2D tomographic reconstruction is to recover an image given its projections from various views. It is often presumed that projection angles associated with the projections are known in advance. Under certain situations, however,…

Image and Video Processing · Electrical Eng. & Systems 2021-11-16 Mona Zehni , Zhizhen Zhao

Recent work in machine learning shows that deep neural networks can be used to solve a wide variety of inverse problems arising in computational imaging. We explore the central prevailing themes of this emerging area and present a taxonomy…

Image and Video Processing · Electrical Eng. & Systems 2020-05-14 Gregory Ongie , Ajil Jalal , Christopher A. Metzler , Richard G. Baraniuk , Alexandros G. Dimakis , Rebecca Willett

Reversible image conversion (RIC) suffers from ill-posedness issues due to its forward conversion process being considered an underdetermined system. Despite employing invertible neural networks (INN), existing RIC methods intrinsically…

Image and Video Processing · Electrical Eng. & Systems 2025-08-05 Yuanfei Huang , Hua Huang

Many machine learning methods operate by inverting a neural network at inference time, which has become a popular technique for solving inverse problems in computer vision, robotics, and graphics. However, these methods often involve…

Computer Vision and Pattern Recognition · Computer Science 2022-06-22 Ruoshi Liu , Chengzhi Mao , Purva Tendulkar , Hao Wang , Carl Vondrick

Optimization algorithms for solving nonconvex inverse problem have attracted significant interests recently. However, existing methods require the nonconvex regularization to be smooth or simple to ensure convergence. In this paper, we…

Computer Vision and Pattern Recognition · Computer Science 2020-03-26 Qingchao Zhang , Xiaojing Ye , Hongcheng Liu , Yunmei Chen

The solution of inverse problems is of fundamental interest in medical and astronomical imaging, geophysics as well as engineering and life sciences. Recent advances were made by using methods from machine learning, in particular deep…

Computer Vision and Pattern Recognition · Computer Science 2023-12-29 Moritz Piening , Fabian Altekrüger , Johannes Hertrich , Paul Hagemann , Andrea Walther , Gabriele Steidl

The aim of this paper is to investigate the use of an entropic projection method for the iterative regularization of linear ill-posed problems. We derive a closed form solution for the iterates and analyze their convergence behaviour both…

Optimization and Control · Mathematics 2020-01-29 Martin Burger , Elena Resmerita , Martin Benning

Blind inverse problems arise in many experimental settings where both the signal of interest and the forward operator are (partially) unknown. In this context, methods developed for the non-blind case cannot be adapted in a straightforward…

Machine Learning · Computer Science 2026-04-21 Nathan Buskulic , Luca Calatroni , Lorenzo Rosasco , Silvia Villa

These lecture notes evolve around mathematical concepts arising in inverse problems. We start by introducing inverse problems through examples such as differentiation, deconvolution, computed tomography and phase retrieval. This then leads…

Numerical Analysis · Mathematics 2025-08-26 Danielle Bednarski , Tim Roith

Real-time magnetic resonance imaging (MRI) methods generally shorten the measuring time by acquiring less data than needed according to the sampling theorem. In order to obtain a proper image from such undersampled data, the reconstruction…

Numerical Analysis · Mathematics 2013-12-05 Housen Li , Markus Haltmeier , Shuo Zhang , Jens Frahm , Axel Munk

We consider solving ill-posed imaging inverse problems without access to an image prior or ground-truth examples. An overarching challenge in these inverse problems is that an infinite number of images, including many that are implausible,…

Image and Video Processing · Electrical Eng. & Systems 2023-11-02 Oscar Leong , Angela F. Gao , He Sun , Katherine L. Bouman

This paper provides an overview of current approaches for solving inverse problems in imaging using variational methods and machine learning. A special focus lies on point estimators and their robustness against adversarial perturbations.…

Image and Video Processing · Electrical Eng. & Systems 2024-07-10 Alexander Auras , Kanchana Vaishnavi Gandikota , Hannah Droege , Michael Moeller

We learn, in an unsupervised way, an embedding from sequences of radar images that is suitable for solving the place recognition problem with complex radar data. Our method is based on invariant instance feature learning but is tailored for…

Computer Vision and Pattern Recognition · Computer Science 2021-10-07 Matthew Gadd , Daniele De Martini , Paul Newman

Undersampling the k-space in MRI allows saving precious acquisition time, yet results in an ill-posed inversion problem. Recently, many deep learning techniques have been developed, addressing this issue of recovering the fully sampled MR…

Image and Video Processing · Electrical Eng. & Systems 2020-07-28 Mélanie Gaillochet , Kerem C. Tezcan , Ender Konukoglu

Undersampling the k-space during MR acquisitions saves time, however results in an ill-posed inversion problem, leading to an infinite set of images as possible solutions. Traditionally, this is tackled as a reconstruction problem by…

Image and Video Processing · Electrical Eng. & Systems 2022-02-10 Kerem C. Tezcan , Neerav Karani , Christian F. Baumgartner , Ender Konukoglu

Diverse inverse problems in imaging can be cast as variational problems composed of a task-specific data fidelity term and a regularization term. In this paper, we propose a novel learnable general-purpose regularizer exploiting recent…

Optimization and Control · Mathematics 2020-02-19 Erich Kobler , Alexander Effland , Karl Kunisch , Thomas Pock

We study the problem of regularization of inverse problems adopting a purely data driven approach, by using the similarity to the method of regularization by projection. We provide an application of a projection algorithm, utilized and…

Numerical Analysis · Mathematics 2021-03-11 Andrea Aspri , Leon Frischauf , Yury Korolev , Otmar Scherzer

A promising way to mitigate the expensive process of obtaining a high-dimensional signal is to acquire a limited number of low-dimensional measurements and solve an under-determined inverse problem by utilizing the structural prior about…

Machine Learning · Computer Science 2024-07-11 Gianluigi Silvestri , Fabio Valerio Massoli , Tribhuvanesh Orekondy , Afshin Abdi , Arash Behboodi

This paper investigates the shape reconstructions of sub-wavelength objects from near-field measurements in transverse electromagnetic scattering. This geometric inverse problem is notoriously ill-posed and challenging. We develop a novel…

Mathematical Physics · Physics 2023-05-03 M. H. Ding , H. Y. Liu , G. H. Zheng