Superresolution using synthetic shaped acoustic vortex waves in water

Abstract

Acoustic vortex waves have previously been shown to be able to overcome the diffraction limit, through the use of subdiffraction-limited pressure nulls that propagate well into the farfield. Acoustic vortex waves, therefore, present a novel means to achieve farfield superresolution imaging. However, generating acoustic vortex waves in an experimental setting typically requires a complicated phased array consisting of multiple active elements in a fixed geometrical configuration. In this work, we describe how an acoustic vortex wave can be generated using a synthetized vortex wave array applied during post-processing to in-water 2D plane measurements obtained with a single moving acoustic source and a fixed receiver. The geometric versatility of the synthetic vortex array enables different shaped acoustic vortex patterns to be achieved using the same in-water measurements. Experimental and theoretical results of the magnitude and phase of the nearfield and farfield pressure fields will be presented for a variety of geometric configurations and vortex integer wave modes of the synthesized vortex wave array. The data show excellent agreement with expected results and demonstrates shaped acoustic vortices with superresolved features in both the nearfield and farfield. [Work supported by the Office of Naval Research.]