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Greedy solution of ill-posed problems: error bounds and exact inversion

L Denis1,2, D A Lorenz3 and D Trede4,5

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The orthogonal matching pursuit (OMP) is a greedy algorithm to solve sparse approximation problems. Sufficient conditions for exact recovery are known with and without noise. In this paper we investigate the applicability of the OMP for the solution of ill-posed inverse problems in general, and in particular for two deconvolution examples from mass spectrometry and digital holography, respectively. In sparse approximation problems one often has to deal with the problem of redundancy of a dictionary, i.e. the atoms are not linearly independent. However, one expects them to be approximatively orthogonal and this is quantified by the so-called incoherence. This idea cannot be transferred to ill-posed inverse problems since here the atoms are typically far from orthogonal. The ill-posedness of the operator probably causes the correlation of two distinct atoms to become huge, i.e. that two atoms look much alike. Therefore, one needs conditions which take the structure of the problem into account and work without the concept of coherence. In this paper we develop results for the exact recovery of the support of noisy signals. In the two examples, mass spectrometry and digital holography, we show that our results lead to practically relevant estimates such that one may check a priori if the experimental setup guarantees exact deconvolution with OMP. Especially in the example from digital holography, our analysis may be regarded as a first step to calculate the resolution power of droplet holography.


PACS

42.40.-i Holography

02.30.Zz Inverse problems

02.60.-x Numerical approximation and analysis

MSC

47A52 Ill-posed problems, regularization

65L09 Inverse problems

49N45 Inverse problems

65F22 Ill-posedness, regularization

Subjects

Mathematical physics

Computational physics

Optics, quantum optics and lasers

Dates

Issue 11 (November 2009)

Received 1 April 2009, in final form 16 July 2009

Published 5 November 2009



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