An acoustic compound eye for omnidirectional broadband signal enhancement

Abstract

We propose an acoustic compound eye based on a three-dimensional meta-sphere, which can achieve omnidirectional broadband acoustic signal enhancement. Imitating the insect compound eye system, a meta-spherical array of subwavelength planar metasurfaces with multiple gradient refractive indices is formed in space. The meta-spherical compound eye has multi-direction focusing and free-field anti-interference capabilities, which can focus and "inhale" the acoustic signals from different incident directions into the space surrounded by the lens array. The compound eye array size can control the frequency band of interference reduction. At the same time, the parameters of each "sub-eye lens" are consistent, and there is no obvious phase difference between the signals in each direction. In this way, the incoming and focused signals from different "sub-eye lenses" can be further converged and enhanced over a broadband frequency. The bionic structure of the compound eye extends the previous metalens design from two-dimensional unidirectional planar-lens focusing to three-dimensional omnidirectional meta-sphere focusing. While maintaining the subwavelength thickness of the metasurface, the structure can get rid of the dependence of the metasurface on the space and incident direction, which has a wide range of engineering applications.