Human capability of discriminating relief-like 2D figures in tactile displaying

Abstract

SUMMARYTo enhance tactile display capability, we performed a series of experiments based on psychophysics in which we adopted a circle and eight kinds of ovals as stimuli of the convex line (hereafter tactile image). The circle's diameter is 10 mm, the minor axes of the eight ovals are decreased in 3% steps from the circles, and each major axis is adjusted so that the area of each oval equals the circle area. Human subjects judged which stimuli (presented on the left or the right tactile images) equal the circle. The experiment was conducted on both the finger pads and the thenar parts to compare their experimental sensitivity ratios with the sensitivity ratio estimated on the basis of mechanoreceptor density. The discrimination sensitivity for the thenar part is inferior to that for the finger pad in terms of the low density of the mechanoreceptor in the thenar part. The tactile image was mainly recognized by a slowly adaptive type I unit, but the first adaptive type II unit was not affected by specimen cooling due to discrimination precision. Subsequently, discrimination sensitivity was not different between the free and restricted haptic motions. Since this result implies that the tactile image is modified by a motor signal for the haptic motion to prevent blurring of the tactile image, perhaps the motion movement in the tactile display is changed based on the design convenience.