This edge follower could easily find the outlines of white cubes on a black table, but was prone to error in less carefully controlled environments. Our studies of its inadequacies have stimulated the development of a more powerful edge follower, which overcomes most of the limitations of the old one. This program is currently the initial stage of visual processing in the Stanford hand-eye system (2). It has demonstrated an ability to track weak edges under adverse lighting conditions 2. HARDWARE The edge follower uses a standard vidicon television camera, modified to provide computer control of orientation (a pan-tilt head), focal length (a lens turret), color filter, focus, and target voltage. The lens iris is set manually. The pan-tilt head, lens turret, and focus motor *This research was supported by the Advanced research Projects Agency of the Department of Defense under Contract No. SD-183. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the Advanced Research Projects Agency of the U.S. Government.