i-DEQ: A stable inertial deep equilibrium model for image restoration
Abstract
Deep Equilibrium Models (DEQs) are an established framework for image restoration that learn a problem-adapted regularization by solving a fixed-point (i.e. equilibrium) problem. While flexible and expressive, DEQs are often hindered by high computational cost and training instability. We propose an inertial DEQ (i-DEQ) that learns an explicit nonconvex regularization within the DEQ formulation. By using momentum within the fixed-point iterations, i-DEQ has convergence guarantees and accelerated rates. Moreover, we observe that i-DEQ is significantly more stable during the training and robust to rough initialization than DEQs. Numerical experiments on various linear and nonlinear inverse problems demonstrate that i-DEQ achieves reconstruction quality comparable to state-of-the-art methods, while reducing DEQ's inference time by a factor of two.
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BibTeX
@misc{clerc2026ideq,
title = {{i-DEQ: A stable inertial deep equilibrium model for image restoration}},
author = {Antonin Clerc and Marien Renaud and Baudouin Denis De Senneville and Nicolas Papadakis},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2605.19705},
eprint = {2605.19705},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.19705},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - i-DEQ: A stable inertial deep equilibrium model for image restoration
AU - Antonin Clerc
AU - Marien Renaud
AU - Baudouin Denis De Senneville
AU - Nicolas Papadakis
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2605.19705
UR - https://arxiv.org/abs/2605.19705
AB - Deep Equilibrium Models (DEQs) are an established framework for image restoration that learn a problem-adapted regularization by solving a fixed-point (i.e. equilibrium) problem. While flexible and expressive, DEQs are often hindered by high computational cost and training instability. We propose an inertial DEQ (i-DEQ) that learns an explicit nonconvex regularization within the DEQ formulation. By using momentum within the fixed-point iterations, i-DEQ has convergence guarantees and accelerated rates. Moreover, we observe that i-DEQ is significantly more stable during the training and robust to rough initialization than DEQs. Numerical experiments on various linear and nonlinear inverse problems demonstrate that i-DEQ achieves reconstruction quality comparable to state-of-the-art methods, while reducing DEQ's inference time by a factor of two.
ER -