27 March 2018 Far-field superresolution imaging using shaped acoustic vortices
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The limitations on resolution due to the effects of diffraction have presented a significant barrier to generating and observing small features with acoustic or electromagnetic waves. Previously proposed methods to overcome this limit, and therefore achieve superresolution, have largely been restricted to operating within the near-field region of the aperture. In this work, we will describe how acoustic helicoidal waves generated using a phased acoustic aperture (such as a traditional phased array or acoustic metasurface) can create acoustic vortices that are well below the resolution limit, and how this can enable far-field superresolution acoustic imaging. The acoustic vortices generated in this manner propagate from the near-field into the far-field through an arrangement of stable integer mode vortices, thereby enabling the generation of far-field superresolved features in the acoustic pressure field. Through the use of non-axisymmetric vortex beam distributions, splitting of the on-axis vortex occurs. This leads to arbitrary off-axis arrangements of vortices, enabling more complicated superresolved structures to be created such as squares, triangles and multi-point stars. In this paper, theoretical and numerical results will be presented for an acoustic aperture which is capable of generating superresolved far-field features in the radiated acoustic pressure, and results will be shown illustrating the superresolution capability of this novel technique.
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Matthew D. Guild, Matthew D. Guild, Jeffrey S. Rogers, Jeffrey S. Rogers, Charles A. Rohde, Charles A. Rohde, Theodore P. Martin, Theodore P. Martin, Gregory J. Orris, Gregory J. Orris, } "Far-field superresolution imaging using shaped acoustic vortices", Proc. SPIE 10600, Health Monitoring of Structural and Biological Systems XII, 1060015 (27 March 2018); doi: 10.1117/12.2296671; https://doi.org/10.1117/12.2296671

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