Temporal acoustic point holography

Holographic acoustic levitation using phased arrays of transducers has facilitated innovative mid-air particle displays. However, current time-invariant methods for computing acoustic holograms often induce high phase changes and thus transducer amplitude fluctuations, severely limiting possible dynamic displays. In this work, we develop a wide range of temporal phase retrieval algorithms that suppress phase change and trade off computational time and solution optimality. We base our hardware implementation on Gerchberg-Saxton (GS), which we identify as gradient descent for maximizing focal amplitudes and thus acoustic trap quality. Following this, we adapt GS to additionally constrain transducers’ (and points’) phase changes from the previous time frame, and enable multiparticle animations without prior knowledge of particles’ paths and interactions. We experimentally showcase a series of levitated character animations depicting human motion and believe our work paves the way for natural dynamic multi-particle displays and unencumbered 3D delivery of other modalities such as haptics and audio.