Implications of the Method of Construction of UK Number Plates for Infrared Reflectance and Camera Settings on ANPR System

This paper considers the implications of two aspects of number plates firstly the varied manufacturing process in the physical construction of vehicle number plates that might affect the reflectance characteristics and secondly the ANPR camera settings that affect the night time capture performance. These parameters have an effect on the overall performance of an Automatic Number Plate Recognition system. A set of controlled experiments on number plates is carried out to establish variation in the retroreflective response to illumination as well as field analysis on real world number plates.