Automated inspection of textured ceramic tiles

An innovative object-centred approach for the visual inspection of textured ceramic tiles has been developed for the acquisition of product quality co ntrol data. A demonstrator system has been constructed for the analysis of complex surfaces, surfaces which possess detailed three-dimensional topogra phic features, which are concealed by coincident regular or random chromati c patterns. The technique is able to isolate mixed topographic and chromati c surface features in order to allow for subsequent separate analysis. Surf ace topography is captured as an array of perturbed surface normals, known as a surface bump map, while the surface reflectance is isolated as a separ ate albedo image. Synthetically rendered images of the bump map description allow surface topography to be viewed off-line under user defined virtual illumination conditions, and in isolation from the surface albedo. Topograp hic features defined by the bump map description may be subject to analysis in terms of perturbation thresholding, or integrated to recover their thre e-dimensional relief. The technique has application for the quality inspect ion of a wide range of manufactured and processed surfaces, uses a low-cost fixed lighting configuration, requires no initial training, is largely pos e invariant, and has been tested on a representative range of real tile sam ples. Experimental results are presented in the paper. (C) 2000 Elsevier Sc ience B.V. All rights reserved.