ESTIMATING THE OPTIMUM ANGULAR SCALE OF THE REFLECTION OF A RETROREFLECTIVE MARKER OF AN OBSERVABLE OBJECT

This paper discusses an active viewing system with the radiation sourc e and detector separated in space, modeling the illumination and obser vation conditions that characterize an automobile driver in the fog. A retroreflector is chosen as an object of observation. The calculation s are carried out for a Gaussian angular distribution of its radiance centered around a direction opposite the direction of incidence of the radiation on the object. Most of the attention is directed to a study of how the angular scale of the reflection affects the contrast of su ch a marker. It is shown that there are optimum reflection characteris tics that provide the maximum contrast and the best visibility of the object. Estimates are given of the angular scale in various practical cases. (C) 1998 The Optical Society of America.