Vertical disparity experiments were carried out with deservers being asked to match the perceived amplitude of sinusocidally modulated cylinderical surfaces presented in a modified wheatstore stereoscope. Results were plotted in terms of matched peak to trough depth as a function of viewing distance. The function was horizontal indicating that the human visual system does not use gradients of vertical disparity to scale horizontal disparities.
In order to study optic flow and eye movements further, a dedicated system has been developed for the generation of moving spatial noise patterns that allows flexible generation of stimuli for a variety of psychophysical and electrophysiological experiments.
A dedicated computer (Atari) based image generator has also been developed to allow presentation of multiple moving noise fields in order to investigate how finely humans can discriminate orientation of contours defined by difference in motion.
The aim of the collaboration would be on several different levels. The first of these is the need to understand the nature of the underlying problem or task. Within the framework suggested by David Marr, this would be the adequate specification of the computational theory. For a biological system, this is not an easy task and there are already many examples in the field of computational vision where an inappropriate computational theory has been assumed. (The stress on the correspondence problem in stereopsis at the expense of the "interpretation" problem may be one example).
The second aim would be to define a program of empirical work which could address the problems of optic flow analysis at a theoretical level, a psychophysical level and a physiological level and which could exploit the results and evidence gained by using the different experimental techniques in the analysis of optic flow may suggest the presence of particular underlying mechanisms which can be tested using both psychophyical and physiological procedures. Koenderink's suggestion that an approximation by considering the outputs of local detectors signalling changes of orientation, could be tested by looking at : i) the results of psychophysical experiments which use optic flow patterns containing such local transformations and ii) the responses of single cells and their characteristics when presented with the appropriate local motion transformations. This work has already started as a result of our previous collaboration.
Funding SchemeCSC - Cost-sharing contracts
3000 Louvain / Leuven