FINE-TO-COARSE SCALE DISAMBIGUATION IN STEREOPSIS

Spatial frequency selectivity has been incorporated into various theor ies of stereo matching, along with spatial scale interactions operatin g from coarse-to-fine spatial scales. We concentrate here on the role of fine scale information in the stereo matching process and show that fine scale information is capable of disambiguating matches made at c oarser scales. An ambiguous coarse scale stimulus was created by prese nting a low frequency (2 c/deg) sine wave in anti-phase to the two eye s, whose endpoints betrayed no information about which way the sine wa ves should be matched. It could be seen with crossed or uncrossed disp arity equally validly and at chance from trial to trial. To this was a dded a fine scale (8 c/deg) filtered random dot stimulus specifying un ambiguously a certain disparity. Observers judged the apparent depth o f the two stimuli as the disparity of the fine scale stimulus was vari ed. The sine wave was usually perceived to have the same sign disparit y as the fine scale stimulus. Depth matching with the two superimposed stimuli confirmed that the coarse scale stimulus was actually disambi guated, and seen with disparities equal to half its spatial period. Th e results suggest the operation of a cross-spatial scale matching disa mbiguation process, which can operate in a fine-to-coarse fashion.