Correlative velocity estimation: visual motion analysis, independent of object form, in arrays of velocity-tuned bilocal detectors.

The visual estimation of object velocity in systems of tuned bilocal detector units (simplified Hassenstein-Reichardt detectors) is investigated. The units contain delay filters of an arbitrary low-pass characteristic. Arrays of such detector units with identical delay filters are assumed to cover the plane of analysis. The global evaluation of the output signals of suitably arranged detector units is exemplified by the analysis of frontoparallel translations of rigid objects. The correlative method permits the estimation of the instantaneous object velocity, independently of object form. The time course of the resulting estimate is shown to be the convolution of the true velocity profile with a time-invariant kernel that depends solely on the impulse response of the delay filters and thus characterizes the analyzer system. The mathematical analysis of the processing principle is illustrated by considering idealized detector systems. The response of correlative motion analyzers to compound motion and to motion of nonrigid objects is discussed.