ARPA Image Understanding Workshop 1996 A critical challenge in the creation of autonomous mobile robots is the reliable detection of moving and static obstacles. In this paper, we present a passive vision system that recovers coarse depth information reliably and efficiently. This system is based on the concept of depth from focus, and robustly locates static and moving obstacles as well as stairs and dropoffs with adequate accuracy for navigation. We describe an implementation of this vision system on a mobile robot as well as real-world experiments both indoors and outdoors. These experiments have involved several hours of continuous and fully autonomous operation in crowded, natural settings. 1 Introduction A mobile robot must be able to avoid both static and moving obstacles in its path. This essential task often relies on sonars to provide distance measurements in the immediate vicinity of the robot. Sonars are inexpensive, relatively reliable, and require little computation t..