The detection of intensity changes by computer and biological vision systems

Abstract

This article describes the implementation of a theory for the detection of intensity changes, proposed by Marr and Hildreth ( Proc. R. Soc. London, Ser. B 207, 1980, 187–217). According to this theory, the image is first processed independently through a set of different size operators, whose shape is the Laplacian of a Gaussian, ▿ 2 G( x, y). The loci, along which the convolution outputs cross zero mark the positions of intensity changes at different resolutions. These zero-crossings can be described by their position, slope of the convolution output across zero, and two-dimensional orientation. The set of descriptions from different operator sizes forms the input for later visual processes, such as stereopsis and motion analysis. There are close parallels between this theory and the early processing of information by the human visual system.