Efficient 3-D characterization of surface defects in smooth specular coatings

Many smooth, highly specular coatings, such as automotive paints and appliance coatings, are subjected to considerable performance demands and manufacturers spend significant sums each year to monitor and repair coating surface quality. Additionally, changing product specifications and environmental regulations will continue to affect the processing parameters that influence surface appearance and quality. Therefore, it is vital to develop robust methods to monitor surface quality on-line and continuously examine the processes that significantly affect surface appearance in real time. As a critical step, this paper presents a cost-effective machine vision system design that utilizes surface reflectance models as a rational basis. Experimental and numerical investigations of diffuse angle images of specular coated surfaces confirm that these images yield a three dimensional characterization of surface defects, efficiently, from a single image. Images can be captured and processed on-board the sensor in milliseconds, facilitating an on-line system which can monitor surface quality in real time.