Abstract
Catadioptric omnidirectional sensors, consisting of a cam- era and a mirror, can track ob jects even when their bearings change suddenly, usually due to the observer making a significant turn. There has been much debate concerning the relative merits of several possible shapes of mirrors to be used by such sensors. This paper suggests that the conical mirror has some advantages over other shapes of mirrors. In particular, the pro jection beam from the cen- tral region of the image is refiected and distributed towards the horizon rather than back at the camera. Therefore a significant portion of the image resolution is not wasted.