Acoustic hologram of the metasurface with phased arrays via optimality criteria

Abstract

Holography is a technique to generate arbitrarily complex acoustic fields, fundamental to applications such as acoustic imaging, particle manipulation, and energy deposition. In this paper, we develop a new approach for designing acoustic holograms with high-resolution sound images against background noise interference. The metasurface-based holograms are composed of phased arrays, such as helical units, to adjust the propagating sound phase from 0 to 2π flexibly. The problem aims to seek the optimal phase distribution at the output of the metasurface, so that sounds focus a prescribed image at the projection plane. The projection plane is divided into the target and background pixels according to the desired resolution of images. The optimization problem is established to maximize the sound intensity of the target pixels and minimize that of the background pixels simultaneously. The optimality criterion is adopted to iteratively update the phase distribution in arrays based on the derived sensitivity. Finally, the effectiveness of the proposed approach is validated numerically and experimentally.