158 4 Haptics as a Substitute for Vision

the visually impaired was not as clear as expected. The reason is probably that the haptic display, in spite of the increased 3D information it provided, did not solve the general problem of haptic perception without vision, namely that of obtaining an overview of an object or scene. In order to be maximally useful for users without vision some help with the overview is needed, for instance, verbal introductory explanation and/or guidance for exploration of the object or scene. A suggestion to help the visually impaired to be oriented in a complex virtual context is to provide an external memory aid (Wall and Brewster 2004).

In another EU project, known as GRAB (GRAB, undated), a new haptic and audio virtual environment was developed. In the GRAB haptic display, the user puts two fingers in thimbles attached to two arms providing 3D force feedback. For the GRAB system three applications were developed and evaluated: a game, a chart data explorer and a city-map explorer. The evaluations indicated its usefulness for visually impaired people concerning these applications, as well as they gave suggestions for improvements. An example is the evaluation of the maps application (GRAB 2004).

A general problem concerning technically complicated devices such as these is that they may have shown their potential in laboratory contexts, but the usefulness in real situations may be more problematic. The intended users may find them difficult to use, possibly because they are not sufficiently adapted to the functioning of haptics (Hatwell 2006). To make good psychophysical studies is difficult because of the need to choose good methods, find exact definitions of proximal stimuli, and handle new hardware. Therefore close cooperation between several sciences, including psychology and engineering, is important (Tan 2006). Guidelines for the tactile and haptic interaction between computer users and relevant devices is under development by ISO (International Standards Organization) (van Erp et al. 2006).

4.8 Chapter Summary

Historically the sense of touch has been used extensively to generate information for the visually impaired person. This chapter surveyed the underlying fundamental principles and the perceptual capabilities of haptics achievable with the human hand.

After the presentation and explanation of these haptic fundamentals, the chapter proceeds to investigate how haptics can be used and enhanced through training or with the aid of specialist tools. A central section of the chapter concentrated on low-tech haptic applications; some, like the long cane and the guide dog, were for mobility whilst others, like Braille and embossed pictures, were for information from text, as well as embossed graphics. An important feature of this section was to identify lessons from the use of low-tech haptic assistive technology.

Subsequent sections in the chapter examined the more technologically advanced applications of haptic science. Of particular importance were the technologies for haptic computer interfaces and for haptic displays. A project to provide haptic access to museum statues and artefacts for visually impaired people was one demonstrable outcome of this advanced work.