Ceramic tile inspection for colour and structural defectsC. Boukouvalas, J. Kittler, R. Marik, M. Mirmehdi, M. Petrou, Ceramic tile inspection for colour and structural defects. Proceedings of AMPT95. ISBN 1 872327 01 X, pp. 390–399. August 1995. PDF, 358 Kbytes.
The ceramic tiles manufacturing process has now been completely automated with the exception of the final stage of production concerned with visual inspection. This paper is concerned with the problem of automatic inspection of ceramic tiles using computer vision. It must be noted that the detection of defects in textured surfaces is an important area of automatic industrial inspection that has been largely overlooked by the recent wave of research in machine vision applications. Initially, We outline the benefits to the tile manufacturing industry. This is followed by a categorisation of typical tile defects. Next, we review a number of techniques recently developed to detect various kinds of defects in plain and textured tiles. The techniques range from pin hole and crack detectors for plain tiles based on a set of separable line filters, through textured tile crack detector based on the Wigner distribution and a novel cojoint spatial-spatial frequency representation of texture, to a colour texture tile defect detection algorithm which looks for abnormalities both in chromatic and structural properties of textured tiles. The above automatic inspection procedures have been implemented and tested on a number of tiles using synthetic and real defects. The results suggest that the performance is adequate to provide a basis for a viable commercial visual inspection system.