A machine vision measurement of slab camber in hot strip rolling

A machine vision approach to on-line slab camber measurement in the hot strip steel mill at Port Talbot is described. A digital image of the hot slab is transformed to obtain a plan view and its position is located using greyscale thresholding and binary morphology. The slab centre-line is extracted as an approximate medial axis from its Euclidean distance map and camber is calculated from the curvature of this centre-line. Additional processing stages are included to make the process robust to industrial conditions. The technique is validated through comparison with manual camber measurements made off-line and in this way the curvature accuracy of the final technique is shown to be ±0.9 × 10−3 m−1 at the 95% confidence level.