Detection of line defects in steel billets using undecimated wavelet transform

In this paper, we present a new detection algorithm for line defects of scale-covered steel billets. Because of the presence of scales on the billet surface, features of surface images such as brightness and textures are non-uniform. To minimize the influence of scales and to improve the accuracy of detection, a new detection method based on undecimated wavelet transform is proposed. The vertical projection profile of subimage with high-frequency information produced by undecimated wavelet transform is used to detect the line defects. Experimental results conducted on billets surface image from actual steel production line show that the proposed algorithm is capable of detecting line defects on billet surface.