Abstract
Single optic night vision goggles (SONVGs) provide important visual function in dark, vision-less conditions. However, the visual function they do provide is greatly constrained. For instance, the field of view available through the optics is restricted and binocular stereopsis is lost. Even though monocular depth cues, including motion parallax, are still available, SONVG users often complain of perceptual problems involving depth and spatial relationships (Wiley, 1989). Here we investigate the hypothesis that motion parallax is affected with SONVGs due to interference with the pursuit signal (necessary for the unambiguous perception of depth from motion parallax; Nawrot & Joyce, 2006) in order to maintain ocular alignment with the SONVG optics. The study used a free-viewing task with a modified Howard-Dolman apparatus in which the participant used a string to align two identical black rods in the frontal-parallel plane. Unaided binocular (UB), unaided monocular motion parallax (UM) and night vision goggle monocular motion parallax (NV) viewing conditions were compared to psychophysically assess the accuracy of depth perception in each. Each participant completed all three conditions. In both monocular motion parallax conditions the horizontal movements of the right eye were measured using a Skalar IRIS IR eye-tracker as the participant performed the task. The largest mean offset and standard deviation was observed in the NV condition (4 orders of magnitude larger than the UB condition), followed by the UM condition (2 orders of magnitude larger than the UB condition) and UB condition. Eye movement recordings were analyzed for the magnitude of smooth pursuit eye movements. Smaller magnitude pursuit eye movements were observed in the NV condition as compared to the UM condition. These findings suggest that disambiguation of depth using motion parallax information is hindered due to smaller or absent eye movements in the NV condition relative to the UM condition.
Meeting abstract presented at VSS 2012