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Sparse Image Reconstruction on the Sphere: Analysis and Synthesis

Wallis, CGR; Wiaux, Y; McEwen, JD; (2017) Sparse Image Reconstruction on the Sphere: Analysis and Synthesis. IEEE Transactions on Image Processing , 26 (11) pp. 5176-5187. 10.1109/TIP.2017.2716824. Green open access

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Abstract

We develop techniques to solve ill-posed inverse problems on the sphere by sparse regularization, exploiting sparsity in both axisymmetric and directional scale-discretized wavelet space. Denoising, in painting, and deconvolution problems and combinations thereof, are considered as examples. Inverse problems are solved in both the analysis and synthesis settings, with a number of different sampling schemes. The most effective approach is that with the most restricted solution-space, which depends on the interplay between the adopted sampling scheme, the selection of the analysis/synthesis problem, and any weighting of the ℓ1 norm appearing in the regularization problem. More efficient sampling schemes on the sphere improve reconstruction fidelity by restricting the solution-space and also by improving sparsity in wavelet space. We apply the technique to denoise Planck 353-GHz observations, improving the ability to extract the structure of Galactic dust emission, which is important for studying Galactic magnetism.

Type: Article
Title: Sparse Image Reconstruction on the Sphere: Analysis and Synthesis
Open access status: An open access version is available from UCL Discovery
DOI: 10.1109/TIP.2017.2716824
Publisher version: http://dx.doi.org/10.1109/TIP.2017.2716824
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Harmonic analysis, Wavelet transforms, Manganese, Inverse problems, Image reconstruction, Dictionaries, sampling, spheres, rotation group, Wigner transform
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery-pp.ucl.ac.uk/id/eprint/1518566
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