Astronomical Image Denoising Using Dictionary Learning

TL;DR

This paper introduces the Centered Dictionary Learning (CDL) method for denoising astronomical images, demonstrating its superior performance over traditional wavelet and dictionary learning techniques in reducing noise while preserving photometric accuracy.

Contribution

The paper proposes a novel Centered Dictionary Learning approach tailored for astronomical image denoising, improving noise reduction and photometry preservation compared to existing methods.

Findings

CDL outperforms wavelet-based denoising in astronomical images.

CDL provides better noise suppression while maintaining photometric integrity.

Comparison shows CDL's advantages over classic dictionary learning techniques.

Abstract

Astronomical images suffer a constant presence of multiple defects that are consequences of the intrinsic properties of the acquisition equipments, and atmospheric conditions. One of the most frequent defects in astronomical imaging is the presence of additive noise which makes a denoising step mandatory before processing data. During the last decade, a particular modeling scheme, based on sparse representations, has drawn the attention of an ever growing community of researchers. Sparse representations offer a promising framework to many image and signal processing tasks, especially denoising and restoration applications. At first, the harmonics, wavelets, and similar bases and overcomplete representations have been considered as candidate domains to seek the sparsest representation. A new generation of algorithms, based on data-driven dictionaries, evolved rapidly and compete now with the off-the-shelf fixed dictionaries. While designing a dictionary beforehand leans on a guess of the most appropriate representative elementary forms and functions, the dictionary learning framework offers to construct the dictionary upon the data themselves, which provides us with a more flexible setup to sparse modeling and allows to build more sophisticated dictionaries. In this paper, we introduce the Centered Dictionary Learning (CDL) method and we study its performances for astronomical image denoising. We show how CDL outperforms wavelet or classic dictionary learning denoising techniques on astronomical images, and we give a comparison of the effect of these different algorithms on the photometry of the denoised images.