NATURE OF COARSE-TO-FINE CONSTRAINTS ON BINOCULAR FUSION

Several stereo-matching algorithms posit that processing on coarse (lo w spatial frequency) scales constrains processing on fine (high spatia l frequency) scales by shifting the disparity range over which fine me chanisms operate. If this were the case, stereo increment thresholds f or high frequencies in the presence of low frequencies would be consta nt, regardless of base disparity. In contrast, we find that in the pre sence of low spatial frequencies, increment thresholds for high spatia l frequencies increase with base disparity, as do increment thresholds for high frequencies presented alone. As a further test of whether in formation on coarse scales enhances processing on fine scales, diplopi a thresholds were measured. In the presence of low frequencies, fusion ranges for high frequencies were severely reduced. These constraints were found to exhibit a power-law dependence on low frequency contrast and to operate over relatively localized areas of the visual field.