High spatial resolution midair tactile display using 70 kHz ultrasound

Abstract

We fabricated a midair tactile display using a 70 kHz airborne ultrasound. The spatial resolution of the display was improved 1.75 times compared with the conventional 40 kHz ultrasound tactile display. Since the focal spot diameter was smaller than a finger pad, the user could perceive a localized spot on the finger pad. In the experiment determining the physical properties, we found that the ultrasound attenuation at 70 kHz was comparable to that at 40 kHz. The small focal spot was successfully created as expected using the theory. The psychophysical experimental results showed that the minimum perceivable radiation force for the focal spot of 70 kHz was smaller than that for the 40 kHz case in average under 40 or 100 Hz modulations, and the smaller focal spot was easier to perceive. We also conducted a comparison test of the perceived force area with real contacts.