Localization of virtual objects in the near visual field

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. Mo nocular, biocular, and stereoscopic presentation of the virtual objects, ac commodation (required focus), participants' age, and the position of physic al surfaces were examined. Nearby physical surfaces were found to introduce localization errors that differ depending on the other experimental factor s. These errors apparently arise from the occlusion of the physical backgro und by the optically superimposed virtual objects, but they are modified by participants' accommodative competence and specific viewing conditions. Th e apparent physical size and transparency of the virtual objects and physic al surfaces, respectively, are influenced by their relative position when s uperimposed. The design implications of the findings are discussed in a con cluding section. Head-mounted displays of virtual objects are currently bei ng evaluated as aids for mechanical assembly and equipment maintenance. Oth er applications include telesurgery, surgical planning, telerobotics, and v isualization aids for robotic programming.