BlindAid, a virtual environment system developed in part for orientation and mobility training of newly, adventitiously, and congenitally blind persons, allows interaction with different virtual structures and objects via auditory and haptic feedback. This research examined whether and how the system might help people who are blind develop orientation and mobility skills within a traditional rehabilitation program. Nine clients at The Carroll Center for the Blind (Newton, MA) explored VEs and performed virtual orientation tasks in addition to their traditional orientation and mobility training. The virtual training gave the participants additional time to learn systematic exploration and orientation strategies and their performance was evaluated using qualitative and quantitative methods. The findings supply strong evidence that practicing with the BlindAid system does enhance traditional orientation and mobility training in these areas.

A prototype near-field virtual environment system is described that incorporates a CrystalEyes stereoscopic display (viewed in a mirror), a PHANToM manipulandum, and a stereo auditory display. The apparatus, which was designed to achieve registration of three sensory modalities (visual, haptic, and auditory), has a wide range of applications and has been used for both psychophysics and training research. Calibration-verification experiments are described in which human subjects positioned a physical probe attached to the manipulandum so that it appeared to coincide with a visual target on the stereoscopic display. The readings from the manipulandum and the calculated positions of the targets corresponded roughly within ± 0.5 cm over a large volume, although differences greater than 1 cm were observed near the sides of the workspace. The calibration of the manipulandum was tested independently on the z axis (running through the center of the workspace), and the perceived depth of the targets (probe z coordinate) was found to agree with the calculated depth within the accuracy of the measurements (± 0.4 cm). Some subjects had poorer positioning resolution when the visual target was far from the plane of the display screen (although their mean response was unaffected), and we hypothesize that this may have been caused by the different levels of accommodation that were needed to view the physical probe and the displayed target.

This paper presents the foundation for a theory of presence that seeks to answer important questions about telepresence and virtual presence. The theory, which develops the definition of telepresence to include virtual presence as a special case, permits the precise definition of various types and degrees of telepresence. General categories of telepresence are defined, using different types of presence that are proposed in the paper. Three types of specifications are used to make the definitions more precise: (1) a set of tasks, (2) a transformation imposed on the human operator's control output and sensory input, and (3) a transformation of the region of presence. The proposed quantitative measure of telepresence involves both objective and subjective measures. The degree of (objective) telepresence is equal to the probability of successfully completing a specified task. The degree of subjective telepresence is equal to the probability that a human operator perceives that he or she is physically present in a given remote environment. The measure of subjective telepresence involves a psychophysical test and is analyzed using signal detection theory. Real-world complications are addressed and a practical example of a subjective telepresence test is described.