Abstract
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.