Abstract

This paper concerns the first functional level of visual processing in which basic image properties are measured and made available for later interpretation. We constrain this level to be a blind process, that is, an image-independent process which involves no previous or concurrent interpretation. Interpretation is postponed until a rich description of the image, including at least orientation and velocity information, is available. The simultaneous use of such different types of visual information will facilitate most subsequent tasks. For example, in the human visual system, primitive motion and depth information contribute significantly to early form interpretation. The velocity selective mechanisms we propose correspond to short-range motion processing in the human system and require no previous spatial interpretation. By contrast, current approaches to the determination of optic flow in machine vision rely on some degree of spatial interpretation (such as contour estimation, peak finding, or more elaborate spatial analysis). Here, we show the extraction of orientation and 2-D normal velocity based on layers of explicit (bottom-up) and implicit (lateral interactions) spatiotemporal processing. The hierarchy allows a very simple and efficient construction of mechanisms that are well localized in space–time and tuned to narrow ranges of orientation and speed. The degree of specificity can be altered by varying the number of layers in the cascade and the form of processing in each layer.

© 1985 Optical Society of America