1. A security system for detecting the presence of one or more persons in a location to be monitored, said system comprising: (i) one or more light sources directed in the direction of said location; (ii) one or more light detectors for detecting reflections of said one or more light sources from said one or more persons to form an image representing eyes of said one or more persons; (iii) a scanning module to direct said one or more light sources and said one or more light detectors at narrow portions of said location at a time; (iv) a scanning controller for driving said scanning module; and (v) a processing unit for analyzing the images received on said one or more light detectors to form an image representing eyes in said location and to identify and count the number of eyes on said image.