Extraction of optical velocity by use of multi-input Reichardt detectors.

We study the possibility of a metrical readout of velocity from an ensemble of Reichardt correlators. We show that with a suitable choice of spatial and temporal prefiltering of the correlator input it is possible to devise reliable (nonaliasing) velocity-tuned Reichardt detectors. However, because of the well-known covariance of spatial and velocity tuning of velocity detectors in biological motion vision, an ensemble consisting of these detectors has problems in extracting a pattern-invariant velocity. We find that pattern invariance of the motion estimate can be closely approximated with Reichardt correlators that sample the luminance pattern at more than the minimum number of two locations.