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Masahiro Ishii, Minoru Fujii; Depth percept from motion parallax by backward/forward head movements. Journal of Vision 2013;13(9):1180. doi: https://doi.org/10.1167/13.9.1180.
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© ARVO (1962-2015); The Authors (2016-present)
Three experiments were conducted to examine depth percept from motion parallax by backward/forward head movements. Depth percept thresholds were measured for backward/forward and rightward/leftward head movements. For a given depth, the retinal motion is independent of the visual eccentricity for rightward/leftward movements. On the other hand it depends on the eccentricity for backward/forward movements; a larger eccentricity causes a larger retinal motion. The stimuli were vertically oriented cylindrical surfaces generated using the ray-tracing representation on a computer. The frontal plane of the cylinder was the image plane. They subtended about 77x62deg at 50cm viewing distance. In a darkroom, observers moved and viewed monocularly the stimuli. They were asked to report the apparent curvature: convex or concave. (1)Thresholds were measured using random-dot surfaces. No difference found between backward/forward and rightward/leftward head motion. (2)A change of viewpoint transforms the stimulus boundary on the screen, e.g., perspective, pincushion/barrel distortion. To eliminate the effect of boundary transformation, rectangular-cropped random-dot surfaces were presented. With rightward/leftward head movement, the thresholds of depth percept for cropped stimuli were equivalent to those for the uncropped stimuli. With backward/forward movement, depth percept from motion parallax was deficient even if the stimuli had a large curvature. This result suggests that the change in the stimulus shape on the retina has important role to evoke depth percept when the observer moves backward/forward. The visual system needs to extract depth information from expanding/contracting dot motion produced by backward/forward head movement. In addition, it needs to estimate depth from eccentricity depending information. It seems that the processing is complicated for the visual system. (3)To investigate the effect of boundary transformation, solid white-colored surfaces were presented. With backward/forward head movement, the subject could perceive depth even if the stimulus had a small curvature.
Meeting abstract presented at VSS 2013
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