Abstract
Simulator sickness and eye strain symptoms affect many head-mounted display (HMD) users. In our experiment we investigated the HMD misalignment, which is one possible cause of the experienced eye strain. The displays of a binocular HMD are misaligned if they are not directly in front of the eyes. Maintaining the binocular fusion in such a situation strains the eyes and thus a method for display misalignment detection and compensation could be used to increase viewing comfort. Our hypothesis was that interocular apparent movement might be used to detect the binocular distortion caused by the misalignment.
We examined the subjects' ability to detect interocular differences in the vertical and horizontal sizes of the half-images. In the first experiment we conducted a temporal 2AFC experiment in which the subjects viewed stereoscopic images and decided which time interval contained three-dimensionally distorted image. The presentation time of the stimuli was not limited. The second experiment was a temporal 2AFC experiment in which the shapes were presented as an interocularly flashing sequence and the task of the subjects was to detect the display interval that contained more apparent movement. The results show that subjects detected the apparent movement more accurately than 3D distortion.
The misalignment of HMD displays is visible to the user as stereoscopic distortion of the visual field. However, the distortion usually occurs gradually in the whole visual field, so it might be difficult to detect. Consequently, a method based on 3D shape evaluation may not be the best alternative. Our results suggest that transformational apparent movement is more sensitive method for distortion detection.