PHYSIOLOGICAL COMPUTATION OF BINOCULAR DISPARITY

We previously proposed a physiologically realistic model for stereo vi sion based on the quantitative binocular receptive field profiles mapp ed by Freeman and coworkers, Here we present several new results about the model that shed light on the physiological processes involved in disparity computation, First, we show that our model can be extended t o a much more general class of receptive field profiles than the commo nly used Gabor functions, Second, we demonstrate that there is, howeve r, an advantage of using the Gabor filters: similar to our perception, the stereo algorithm with the Gabor filters has a small bias towards zero disparity, Third, we prove that the complex cells as described by Freeman et al, compute disparity by effectively summing up two relate d cross products between the band-pass filtered left and right retinal image patches, This operation is related to cross-correlation but it overcomes some major problems with the standard correlator. Fourth, we demonstrate that as few as two complex cells at each spatial location are sufficient for a reasonable estimation of binocular disparity, Fi fth, we find that our model can be significantly improved by consideri ng the fact that complex cell receptive fields are, on average, larger than those of simple cells, This fact is incorporated into the model by averaging over several quadrature pairs of simple cells with nearby and overlapping receptive fields to construct a model complex cell, T he disparity tuning curve of the resulting complex cell is much more r eliable than that constructed from a single quadrature pair of simple cells used previously, and the computed disparity maps for random dot stereograms with the new algorithm are very similar to human perceptio n, with sharp transitions at disparity boundaries, Finally, we show th at under most circumstances our algorithm works equally well with eith er of the two well-known receptive field models in the literature. (C) 1997 Elsevier Science Ltd.