Mid-air ultrasonic pressure control on skin by adaptive focusing

Abstract

Mid-air ultrasound can remotely invoke tactile sensation to bare hand. However, it is difficult to control it precisely because the hand itself scatters ultrasound. In this paper, a scattering model, which can be solved in real-time, is proposed and, this model can create a stronger focal point as compared to the conventional model. The proposed algorithm is based on the boundary element method and is a natural extension of the previously proposed phased array synthesis algorithms. Numerical analysis shows the relationship between the error of the surface model, computation time, and focusing performance. Psychophysical experiment shows that the internal tactile intensity of the focused ultrasound is significantly improved using the proposed adaptive focusing method. The proposed method can be used for mid-air ultrasound as a test bench of precise weak force haptic interaction.