Aerial Push-Button with Two-Stage Tactile Feedback using Reflected Airborne Ultrasound Focus.

We developed a new aerial push-button with tactile feedback using focused airborne ultrasound. This study has two significant novelties compared to past related studies: 1) ultrasound emitters are equipped behind the user's finger and reflected ultrasound emission that is focused just above the solid plane placed under the finger presents tactile feedback to a finger pad, and 2) tactile feedback is presented at two stages during pressing motion; at the time of pushing the button and withdrawing the finger from it. The former has a significant advantage in apparatus implementation in that the input surface of the device can be composed of a generic thin plane including touch panels, potentially capable of presenting input touch feedback only when the user touches objects on the screen. We experimentally found that the two-stage tactile presentation is much more effective in strengthening perceived tactile stimulation and believability of input completion when compared with a conventional single-stage method. This study proposes a composition of an aerial push-button in much more practical use than ever. The proposed system composition is expected to be one of the simplest frameworks in the airborne ultrasound tactile interface.