STEREOSCOPIC SEGREGATION OF TRANSPARENT SURFACES AND THE EFFECT OF MOTION CONTRAST

Stereoscopic segregation in depth was studied using two superimposed f rontoparallel surfaces displayed in dynamic random dot stereograms, Th e two patterns were positioned symmetrically in front of and behind a binocular fixation point, They were either stationary, or they could m ove relative to each other. Sensitivity for segregation was establishe d by adding gaussian distributed disparity noise to the disparities sp ecifying the two planes, and finding the noise amplitude that gave thr eshold segregation performance, Observers easily segregate the two sur faces for disparity differences between similar to 6 and 30-40 arcmin. Motion contrast, which by itself provides no cue to perform the task, greatly improves sensitivity for segregation, Noise tolerance rises b y a factor of two or more when the patterns move at different speeds, or in different (frontoparallel) directions, The effect increases with directional difference, but the optimal directional difference deviat es from 180 deg, The optimal speed varies: with disparity difference. Thus, motion and disparity must interact in order to resolve the two t ransparent planes. (C) 1998 Elsevier Science Ltd, All rights reserved.