Presenting sharp surface shapes using overlapped vibrotactile stimuli

Previous surface shape presenting methods had difficulties in generating high-density tactile information owing to blurriness in tactile images caused by lateral skin deformations. In this study, a new surface shape presenting method is proposed, and it employs overlapping small-amplitude vibrations instead of a single vibration. This method represents the mechanism of stationary boundary contacts (SBCs), a vibrotactile sensitivity enhancement method proposed in a previous research. A series of psychophysical experiments showed that the vibrations overlapping method can significantly enhance the human vibrotactile sensitivity and lead to the production of sharp tactile images. Moreover, the stimuli intensity can be controlled not only by changing the vibration amplitudes but also by changing the phase deviations between vibrations; this enables the presentation of various surface shape patterns that cannot be presented by using the previous SBC method alone.