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Abstract:
Half-occluded points (visible only in one eye) are perceived at a certain depth
behind the occluding surface without binocular rivalry, even though no disparity
is defined at such points. Here we propose a stereo model that reconstructs 3D
structures not only from disparity information of interocularly paired points
but also from unpaired points. Starting with an array of depth detection cells,
we introduce cells that detect unpaired points visible only in the left eye or
the right eye (left and right unpaired point detection cells). They interact
cooperatively with each other based on optogeometrical constraints (such as
uniqueness, cohesiveness, occlusion) to recover the depth and the border of 3D
objects. Since it is contradictory for monocularly visible regions to be visible
in both eyes, we introduce mutual inhibition between left and right unpaired
point detection cells. When input images satisfy occlusion geometry, the model
outputs the depth of unpaired points properly. An interesting finding is that
when we input two unmatched images, the model shows an unstable output that
alternates between interpretations of monocularly visible regions for the left
and the right eyes, thereby reproducing binocular rivalry. The results suggest
that binocular rivalry arises from the erroneous output of a stereo mechanism
that estimates the depth of half-occluded unpaired points. In this sense, our
model integrates stereopsis and binocular rivalry, which are usually treated
separately, into a single framework of binocular vision. There are two general
theories for what the "rivals" are during binocular rivalry: the two eyes, or
representations of two stimulus patterns. We propose a new hypothesis that
bridges these two conflicting hypotheses: interocular inhibition between
representations of monocularly visible regions causes binocular rivalry. Unlike
the traditional eye theory, the level of the interocular inhibition introduced
here is after binocular convergence at the stage solving the correspondence
problem, and thus open to pattern-specific mechanisms.
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