I. Introduction
A major portion of the research efforts of the computer vision community has been directed toward the study of the three-dimensional (3-D) structure of objects using machine analysis of images [1]. According to [2], we can view the problem of stereo analysis as consisting of the following steps: image acquisition, camera modeling, feature acquisition, image matching, depth determination, and interpolation. The key step is that of image matching, that is, the process of identifying the corresponding points in two images that are cast by the same physical point in 3-D space. This paper is devoted solely to this problem.