Human Systems Integration Division @ NASA Ames

We examined errors in the localization of nearby virtual objects presented via see-through helmet-mounted displays as a function of viewing conditions and scene content in four experiments using a total of 38 participants. Monocular, binocular, and stereoscopic presentation of the virtual objects, accomodation (required focus), participants age, and the position of the physical surfaces were examined. Nearby physical surfaces were found to introduce localization errors that differ depending on the other experimental factors. These errors apparently arise from the occlusion of the physical background by the optically superimposed virtual objects, but they are modified by the participants' accommodative competence and specific viewing conditions. The apparent physical size and transparency of the virtual objects and physical surfaces, respectively, are influenced by their relative position when superimposed. The design implications of the findings are discussed in a concluding section. Head-mounted displays of virtual objects are currently being evaluated as aids for mechanical assembly and equipment maintenance. Other applications include telesurgery, surgical planning, and virtualization aids for robotic programming.