Abstract: An acoustic lens to steer an acoustic beam includes a first structure, a second structure spaced from the first structure, an array of projections disposed between the first and second structures, each projection of the array of projections extending from the first structure toward the second structure to define a respective gap between the projection and the second structure, and an actuator configured to move the first structure, the second structure, or the array of projections for collective adjustment of the respective gaps of the array of projections. Each projection is configured to define one or more respective unit cells, each unit cell having a sub-wavelength size relative to the acoustic beam to establish an effective refractive index profile for the acoustic beam between the first and second structures.

Abstract: An acoustic lens to steer an acoustic beam includes a first structure, a second structure spaced from the first structure, an array of projections disposed between the first and second structures, each projection of the array of projections extending from the first structure toward the second structure to define a respective gap between the projection and the second structure, and an actuator configured to move the first structure, the second structure, or the array of projections for collective adjustment of the respective gaps of the array of projections. Each projection is configured to define one or more respective unit cells, each unit cell having a sub-wavelength size relative to the acoustic beam to establish an effective refractive index profile for the acoustic beam between the first and second structures.