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Martin S. Banks, Sergei Gepshtein, Heather Rose; Do we perceive stereoscopic surfaces from patches of constant disparity?. Journal of Vision 2004;4(8):173. doi: https://doi.org/10.1167/4.8.173.
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Recently, we found that stereoresolution (finest detectable disparity modulation) appears to be limited by a binocular-matching process that estimates the disparity of image patches and assumes that disparity is constant across the patch. Said another way, this process yields disparity estimates associated with piecewise frontal image patches. This hypothesis is consistent with the behavior of disparity-selective neurons in primate V1. If disparity estimation is based on constant patches, the form of the disparity-modulation waveform should have a significant effect on estimation. A square-wave provides constant-disparity patches while a sawtooth-wave does not. To test the constant-patch hypothesis, we compared detection of square- and sawtooth-wave corrugations using random-dot stereograms. Observers indicated on each trial the orientation of the waveform (+/− 10 deg from horizontal). In Experiment 1, the highest discriminable spatial frequency was determined for a range of dot densities. The highest frequency was somewhat higher for square- than for sawtooth-waves at high dot densities, where stereoresolution is high. In Experiment 2, we varied the mixture of signal and noise dots. Noise dots were assigned random disparities and signal dots specified a square- or sawtooth-wave. Coherence threshold (proportion of signal dots divided by total dots) was lower in most cases for the square-waves than for sawtooth-waves. Results from both experiments suggest that the ability to detect patterns composed of constant-disparity patches (square-waves) is generally greater than the ability to detect patterns containing no constant-disparity patches (sawtooth-waves). Our results support the idea that the matching process is based on estimating the disparity of constant-disparity patches. Thus, perceived depth maps may be constructed from piecewise frontal estimates.
NIH and AFOSR Research Grants
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