Stimulation Conditions to Generate Velvet Hand Illusion through a Dot-matrix Display

To enhance the reality of touch feeling in VR, one effective presentation is the texture sensation of a virtual object. Although the texture sensation makes persons perceive a virtual object to be a real one, research on texture sensation has not always progressed due to the difficulty of developing a stimulus presentation device. To compensate for this hardware problem, we focus on the Velvet Hand Illusion (VHI), which is one of the tactile illusion phenomena, as a method of presenting texture sensation. In our previous study, VHI was generated by a tactile display using a refreshable braille display (dot-matrix display). Since the dot-matrix display can provide various dot patterns through combinations of stimulus-pin protrusions, it can be applied to clarify the essential stimulus conditions for VHI through a series of psychophysical experiments. We expect to obtain the essential conditions for VHI, which will then become the fundamentals of the VHI model. In the psychophysical experiments, two parallel lines formed by the dot-matrix display were reciprocated on the subject's palm. First, we investigated the relationship between the interval of pins forming lines and the VHI strength. Second, we investigated the relationship between the length of two parallel lines and the strength of VHI. As a result, VHI hardly occurred when the interval between pins forming lines was more than a two-point threshold. Consequently, it was clarified that the sensation of touching a line is an essential condition for VHI and that line length of 29 mm is the absolute threshold of VHI.