There is growing interest in the use of active control of image formation to simplify and accelerate scene understanding. AI research on machine vision emphasizes the use of declarative knowledge and explicit representation of goals to control the perceptual process. This book describes the first implemented vision system anywhere to integrate robotic camera control, ocular reflexes, reactive fixation, real-time image processing, image tracking, perceptual grouping, active 3D modeling, and object recognition. The book presents the results of the ESPRIT project BG 3038/7108 "Vision as Process" initiated in 1989. The presentation is organized as five parts which reflect the components developed for the resulting experimental test-bed system.