Playing back vibrotactile signals through actuators is commonly used to simulate tactile feelings of virtual textured surfaces. However, there is often a small mismatch between the simulated tactile feelings and intended tactile feelings by tactile designers. Thus, a method of modulating the vibrotactile perception is required. We focus on fine roughness perception and we propose a method using a pseudo-haptic effect to modulate fine roughness perception of vibrotactile texture. Specifically, we visually modify the pointer's position on the screen slightly, which indicates the touch position on textured surfaces. We hypothesized that if users receive vibrational feedback watching the pointer visually oscillating back forth and left right, users would believe the vibrotactile surfaces more uneven. We also hypothesized that as the size of visual oscillation is getting larger, the amount of modification of roughness perception of vibrotactile surfaces would be larger. We conducted user studies to test the hypotheses. Results of first user study suggested that users felt vibrotactile texture with our method rougher than they did without our method at a high probability. Results of second user study suggested that users felt different roughness for vibrational texture in response to the size of visual oscillation. These results confirmed our hypotheses and they suggested that our method was effective. Also, the same effect could potentially be applied to the visual movement of virtual hands or fingertips when users are interacting with virtual surfaces using their hands.
In this study, we developed vibrotactile display methods that can assist designers in product design. In order to achieve realistic sensations required for such designing purposes, we used real materials such as cloth, paper, wood, and leather and applied vibrotactile stimuli to modify the roughness sensations of these materials. This approach allowed us to present textures of various virtual materials with a strong sense of reality. We verified that our proposed methods could selectively modify the fine and macro-roughness sensations of real materials. The methods are expected to aid product designers in deciding tactile sensations suitable for their products. According to the duplex theory of tactile texture perception, detection of cutaneous vibrations produced when the exploring finger moves across a surface contributes importantly to the perception of fine textures. If this is true, a vibrating surface should feel different from a stationary one. To test this prediction, experiments were conducted in which subjects examined two identical surfaces, one of which was surreptitiously made to vibrate, and judged which of the two was smoother. In experiment 1, the vibrating surface was less and less often judged smoother as the amplitude of (150 Hz) vibration increased. The effect was comparable in subjects who realized the surface was vibrating and those who did not. Experiment 2 showed that different frequencies (150–400 Hz) were equally effective in eliciting the effect when equated in sensation level (dB SL). The results suggest that vibrotaction contributes to texture perception, and that, at least within the Pacinian channel, it does so by means of an inten...