Aerial Vibrotactile Display Based on Multiunit Ultrasound Phased Array

In this paper, we report on an airborne vibrotactile display with a multiunit ultrasound phased array synthetic aperture. The system generates an ultrasound field with a location-tunable focus in the air, which exerts time-variant acoustic radiation pressure on the users skin, resulting in perceivable localized vibrotactile stimuli. The paper contains three major new contributions from previous related works. The first is an experimental validation of large-aperture focusing with improved synchronization offering an enlarged workspace in which sufficient acoustic power concentration is guaranteed. From the experiments, it is expected that perceivable vibrotactile focus can be generated 1 m away from a four-unit array system. The second is an experimental evaluation of the presented pressure for producing a broad variety of tactile perception, which shows that the generated ultrasound focus can serve as an vibrotactile actuator that has flat frequency characteristics in the domain of perceptual stimuli. The third is a psychophysical result of the detection threshold curve for sinusoidal stimuli offered by the system. The obtained curve shows similarity with conventionally known results, which have minimum values at approximately 200 Hz.