Dynamic photometric stereo for on line quality control of ceramic tiles

The rapid and automated detection of manufacturing flaws is becoming increasingly important in order to maintain competitive advantage in many production environments. In the case of natural and ornamental materials, the presence of both surface colouration and surface topography is often such that manual inspection, along with many conventional imaging techniques, fails to isolate physical or structural defects in the presence of complex and random patterns. In this paper the concepts of photometric stereo are adapted and extended for application in manufacturing environments. A case study on the high speed inspection of ceramic tiles is presented for the analysis of surfaces at production line rates of up to 30 m/min. This new technique, for the first time, demonstrates a genuine and commercially attractive potential for the practical automated quality control of complex surfaces. A commercial system, based on this research, is currently being developed. # 2005 Published by Elsevier B.V.