Self-bending airborne ultrasound beam using a binary lens based on the Airy function

Abstract

Abstract Self-bending of a beam of sound was previously achieved by an acoustic metasurface that modified the amplitude and phase modulations. However, fabricating a fine-structured device for ultrasound is difficult because it has a short wavelength. In this paper, we propose a simple binary acoustic lens for a self-bending ultrasound beam in air at 40 kHz. The lens has transparent and opaque areas and was designed using the Airy function. The beam bending was evaluated by simulations and experiments. The simulations showed that the proposed lens achieved beam self-bending, although the concentration of energy in the main beam was inferior to that for phase-coded modulation. The experiments demonstrated that self-bending is feasible using a binary lens made of a polypropylene sheet, and the measured sound fields agreed well with the simulations. These results suggest that a self-bending beam of ultrasound is possible with a lens having a simple binary structure.