stereo paper available

[Ning Qian]

The following paper (and some related ones, see below) on stereo
vision can be downloaded from the web site:

http://brahms.cpmc.columbia.edu/


        Physiological Computation of Binocular Disparity
                   Ning Qian and Yudong Zhu
                (to appear in Vision Research)

We previously proposed a physiologically realistic model for
stereo vision based on the quantitative binocular receptive field
profiles mapped 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 to a much more general class of receptive field profiles
than the commonly used Gabor functions.  Second, we demonstrate that
there is, however, 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 related 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.  Fifth, we find that our model can
be significantly improved by considering 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 {\em
several} quadrature pairs of simple cells with nearby and overlapping
receptive fields to construct a model complex cell.  The disparity
tuning curve of the resulting complex cell is much more reliable than
that constructed from a {\em 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
perception, with sharp transitions at disparity boundaries.  Finally,
we show that under most circumstances our algorithm works equally well
with either of the two well-known receptive field models in the
literature.


Related papers on the same web site:

"A Physiological Model for Motion-stereo Integration and a Unified
Explanation of Pulfrich-like Phenomena", Ning Qian and Richard A.
Andersen, Vision Research, (in press).

"Binocular Receptive Field Profiles, Disparity Tuning and
Characteristic Disparity" Yudong Zhu and Ning Qian, Neural
Computation, 1996, 8:1647-1677.

"Computing Stereo Disparity and Motion with Known Binocular Cell
Properties", Ning Qian, Neural Computation, 1994, 6:390-404.