Abstract
The perceived depth from disparity in random-dot stereogram varied with luminance contrast and the spatial frequency (SF) of depth modulation (Chen et al., 2016). Here, we varied the number of cycles to investigate whether this effect may be due to local disparity gradient or global surface configuration. The test stimuli were rectangular random dot stereograms (1.27 × 3.44 degree) with three kinds of surface configuration: (a) a low SF (0.29cyc/deg) single-cycle cosine bulge, (b) a higher SF (0.87cyc/deg) 3-cycle corrugated surface, and (c) a higher SF (0.87cyc/deg) single-cycle cosine bulge. For each surface configuration, maximum test disparity ranged from −20 to 20 arcmin while luminance contrast ranged from 5% to 80%. The observers adjusted the length of a horizontal bar to match the perceived depth in the test stimuli. In all conditions, the perceived depth was a Gaussian derivative disparity matching function whose positive/negative magnitudes and disparities of the peak depths increased with luminance contrast. The magnitude for the 3-cycle corrugated surface was significantly smaller than that for both the low and high SF single-cycle bulge, which themselves differed in peak disparity but not in peak magnitude. Thus, the global configuration affects the depth magnitude but not peak disparity while local disparity gradient affects peak disparity but not peak magnitude.