Yoji Yamada

There is increasing demand for tactile feedback functions for touch panels. We investigated whether virtual roughness texture quality can be improved through simultaneous use of vibrotactile and electrostatic-friction stimuli. This conjunctive use is expected to improve the perceptual quality of texture stimuli, because vibrotactile and electrostatic-friction stimuli have complementary characteristics. Our previous studies confirmed that these conjunct stimuli yield enhanced realism for simple grating roughness. In this study, we conducted experiments using simple and complex sinusoidal surface profiles consisting of one or two spatial wave components. Three different evaluation criteria were employed. The first criterion concerned the subjective realism, i.e., similarity with actual roughness textures, of virtual roughness textures. Participants compared the following three stimulus conditions: vibrotactile stimuli only, electrostatic-friction stimuli only, and their conjunct stimuli. The conjunct stimuli yielded the greatest realism. The second criterion concerned roughness texture identification under each of the three stimulus conditions for five different roughness textures. The highest identification accuracy rate was achieved under the conjunct stimulus condition; however, the performance difference was marginal. The third criterion concerned the discrimination threshold of the grating-scale spatial wavelength. There were no marked differences among the results for the three conditions. The findings of this study will improve virtual texture quality for touch-panel-type surface tactile displays.