The ability to view and image an environment panoramically is useful in a number of applications in machine vision and robotics. Conventional video cameras have limited fields of view, which make them restrictive for certain applications in computational vision. A catadioptric vision system uses a combination of lenses and mirrors placed in a carefully arranged configuration to capture a much wider field of view. In this paper, we discuss the existing catadioptric configurations, single viewpoint constraint of these systems and non-single viewpoint catadioptric systems.