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Imaging beyond aliasing

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Author: Volker, A.W.F. · Neer, P.L.M.J. van
Type:article
Date:2016
Publisher: American Institute of Physics AIP
Source:Bond, L.J.Chimenti, D.E., 42nd Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE 2015, incorporating the 6th European-American Workshop on Reliability of NDE, 26-31 July 2015, Minneapolis, MN, USA, 1706
series:
AIP Conference Proceedings
Identifier: 572402
ISBN: 9780735413535
Article number: 020009
Keywords: Observation, Weapon & Protection Systems · AS - Acoustics & Sonar · TS - Technical Sciences

Abstract

A sufficiently high spatial sampling is critical for high quality imaging. If the sampling criterion is not met, artifacts appear in the image generally referred to as grating lobes. Probes with a large aperture provide a large field of view, which allows for more efficient inspection. On the other hand this leads to an increase in the number of element to obey the sampling criterion. We have developed a method that reconstructs sparsely sampled data without assuming anything about the medium. The reconstruction method involves an iterative scheme using wave field extrapolation. After the reconstruction an aliasing free dataset is obtained which can be imaged properly. Aliased and non-aliased datasets were modeled based on point diffractors and reflectors with an increasing width. The datasets were imaged using a mapping in the wavenumber-frequency domain. Up to a factor four of under-sampling can be tolerated, providing the same image quality as a properly sampled dataset.