Abstract
Vertical binocular disparity is a source of distance information allowing the portrayal of the layout and 3D metrics of the visual space. The role of vertical disparity in the perception of depth, size, curvature, or slant of surfaces was revealed in several previous studies using cue conflict paradigms. In this study, we varied the configuration of stereo-cameras to investigate how changes in the horizontal and vertical disparity fields, conflicting with the vergence cue, affect perceived distance and depth. In four experiments, observers judged the distance of a cylinder displayed in front of a large fronto-parallel surface. Experiment 1 revealed that the presence of a background surface decreases the uncertainty in judgments of distance, suggesting that observers use the relative horizontal disparity between the target and the background as a cue to distance. Two other experiments showed that manipulating the pattern of vertical disparity affected both distance and depth perception. When vertical disparity specified a nearer distance than vergence (convergent cameras), perceived distance and depth were underestimated as compared with the condition where vertical disparity was congruent with vergence cues (parallel cameras). When vertical disparity specified a further distance than vergence, namely an infinite distance, distance and depth were overestimated. The removal of the vertical distortion lessened the effect on perceived distance. Overall, the results suggest that the vertical disparity introduced by the specific camera configuration is mainly responsible for the effect. These findings outline the role of vertical disparity in distance and depth perception and support the use of parallel cameras for designing stereograms.
Highlights
The vivid impression of depth in viewing stereograms is possible through the detection and scaling of binocular disparity
JNDs increased with the removal of the background surface (Plane vs. Total Luminance Adjustment (TLA), p < .02; Plane vs. No Plane, p < .01), but there was no effect of the luminance adjustment (p > .05)
Comparing the results of the convex-distortion and no-distortion conditions, we found that distortions in the pattern of horizontal disparity had no significant effect on distance perception
Summary
The vivid impression of depth in viewing stereograms is possible through the detection and scaling of binocular disparity. (e.g., Brenner et al, 2001; Rogers & Bradshaw, 1993, 1995), several effects can be expected It is unclear what viewers will perceive from the combination of distortions in the patterns of horizontal disparity and vertical disparity. (b) Retinal projection of stereograms of a fronto-parallel plane captured with convergent cameras, shown on both eyes (top), and the resulting horizontal or vertical disparity shown when both retinas are superimposed (bottom). Converging the cameras on the center of the surface will produce horizontal and vertical differences in the two captured images, as observed in natural vision (Figure 1(a)). To study how the vertical disparity pattern can affect perceived distance, we displayed a large fronto-parallel surface located behind the stimulus target. The stimulus displayed in front of this surface enables the study of depth perception (i.e., the shape of the stimulus) as well as the scaling of the depth difference between the target (i.e., a cylinder) and the background surface
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