Midair Click of Dual-Layer Haptic Button

In this study, we propose a method to create a quasi-click sensation in midair based on two types of tactile stimulation methods that create different sensations both in the intensity and quality. We consider two-layers of regions in the space that forms a virtual button. A user's hand is tracked by a sensor and stimulated by the two methods according to the hand position. When the user's hand is in the upper or lower layer, the hand skin is stimulated weakly or strongly by the two methods, respectively. These two states indicate a neutral position and action completion. This midair click was enabled by a recent finding where an ultrasound focus motion on the skin produced a stronger perception than amplitude modulation given at a constant position. We conducted experiments to confirm whether two haptic layers can be perceived. In addition, we investigated whether a blind operation of button selection can be performed.