The sensations of touch and force have come to be recognized as essential factors in virtual reality, and many efforts have been made to develop display devices that reproduce these sensations. Such devices are divided into two categories: wearing and nonwearing. In this paper, a method is proposed for representing virtual objects of arbitrary shapes using a nonwearing device. Based on this method, a device was fabricated to describe our approach. Our prototype device was designed to approximately represent part of the surface of a virtual object as a tangential surface (i.e., partial surface) to the user's fingertip. The device was implemented as a mechanism with five degrees of freedom that are commonly used to measure the fingertip position and to present the partial surface to the fingertip. The mechanism was controlled through two calculation loops: a model loop that gives a tangential surface from the fingertip position and the shape of objects, and a servo loop that manages the mechanism to represent the given tangential surface by the partial surface. Also, a stereoscopic, head-tracking visual system was implemented to realize the combined presentation of visual information and the partial surface.
As an example of the applications of the environment, a task of writing characters was simulated. From the observation of the performance of the task, the presentation of the partial surface was proved to have an effect on decreasing blur and dragging in written characters.