Article

# Stereopsis from contrast envelopes

Department of Psychology, Institute of Cognitive Neuroscience, University College London, London, WCIE 6BT, UK; Department of Computing and Information Science, Queens University, Kingston, K7L 3N6, Canada

Vision Research (Impact Factor: 2.14). 08/1999; DOI: 10.1016/S0042-6989(98)00271-5 Source: PubMed

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**ABSTRACT:**We recorded the initial vertical vergence eye movements elicited in monkeys at short latency ( approximately 70 ms) when the two eyes see one-dimensional (1D) horizontal grating patterns that are identical except for a phase difference (disparity) of one-quarter wavelength. With gratings composed of single sine waves, responses were always compensatory, showing Gaussian dependence on log spatial frequency (on average: peak = 0.75 cycles/deg; SD = 0.74; r(2) = 0.980) and monotonic dependence on log contrast with a gradual saturation well described by the Naka-Rushton equation (on average: n = 0.89; C(50) = 4.1%; r(2) = 0.978). With gratings composed of two sine waves whose spatial frequencies were in the ratio 3:5 and whose disparities were of opposite sign (the 3f5f stimulus), responses were determined by the disparities and contrasts of the two sine-wave components rather than the disparity of the features, consistent with early spatial filtering of the monocular inputs before their binocular combination and mediation by detectors sensitive to disparity energy. In addition, responses to the 3f5f stimulus showed a nonlinear dependence on the relative contrasts of the two sine waves. Thus on average, when the contrast of one sine wave was 2.3 times greater than that of the other, the one with the lower contrast was largely ineffective as though suppressed, and responses were determined almost entirely by the sine wave of higher contrast: Winner-Take-All. These findings are very similar to those published previously on the vertical vergence responses of humans, indicating that the monkey provides a good animal model for studying these disparity vergence responses.Journal of Neurophysiology 10/2008; 100(5):2907-18. · 3.30 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**There is a long history of research into depth percepts from very large disparities, beyond the fusion limit. Such diplopic stimuli have repeatedly been shown to provide reliable depth percepts. A number of researchers have pointed to differences between the processing of small and large disparities, arguing that they are subserved by distinct neural mechanisms. Other studies have pointed to a dichotomy between the processing of 1st- and 2nd-order stimuli. Here we review literature on the full range of disparity processing to determine how well different proposed dichotomies map onto one another, and to identify unresolved issues.Vision research 01/2009; · 2.29 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**In this work we propose a first principles dynamic optimization model for an intensive energetically integrated process, a natural gas processing plant, within a simultaneous dynamic optimization framework. We have developed rigorous models, including thermodynamics with a cubic equation of state, for separation tanks, distillation columns, turboexpanders and cryogenic countercurrent heat exchangers with partial condensation. The resulting partial differential algebraic equation system is transformed into an ordinary differential algebraic equation one (DAE) by applying the method of Lines for the spatial coordinate. The high integration between process units as well as path constraints have been efficiently handled by a simultaneous dynamic optimization approach in which the DAE is transformed into a large nonlinear programming problem through orthogonal collocation over finite elements in time and solved with an interior point algorithm. In the case study, we maximize ethane recovery under a ramp change in natural gas feed flowrate. The model provides temporal and spatial profiles of controlled and manipulated variables that are in good agreement with plant data.01/2010;

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