Hierarchical construction of orientation and velocity selective filters

As a step towards the early measurement of visual primitives, the authors outline design criteria for the extraction of orientation and velocity information, and present a variety of tools useful in the construction of simple linear filters. A hierarchical parallel-processing scheme is used in which nodes compute a weighted sum of inputs from within a small spatio-temporal neighborhood. The resulting scheme is easily analyzed and provides mechanisms sensitive to narrow ranges of both image velocity and orientation. The hierarchical approach in combination with separability in the first levels yields an efficient implementation