Abstract

We have investigated disparity averaging using a novel stimulus which yields two spatially coextensive disparity signals carried by different spatial scales at each point in a random dot stereogram. This was accomplished by sinusoidally modulating the luminance of dots carrying various disparities with phase differences between the two eyes’ views that were equal to or different from the dot disparity. In a 2AFC task observers judged the relative depths of two panels in a random dot stereogram. A reference panel carried equal texture and sinusoid disparities; the second panel carried a different texture disparity and a sinusoid of variable phase. Near the horopter, transparency was the norm. However, with larger disparity offsets from the horopter, disparity averaging occurred, even when the texture and sinusoid disparities differed by over 10 min arc. Either two disparity estimates are extracted and then averaged at each point, or else the tradeoff between fine and coarse scales occurs at the input to the disparity sensing mechanism. We have considered two schemes of the latter kind. An explanation based on low-pass monocular filtering and windowed cross-correlation fails to model the results. A more successful scheme postulates a disparity code involving the ratio of excitation of coarsely tuned mechanisms away from the horopter.

© 1991 Optical Society of America