Vision-based gauge for online weld profile metrology

The development and application of an automated vision-based system for post weld inspection is discussed. The parameters of the weld bead profile have previously been measured manually using a variety of mechanical gauges. Such methods are slow, of dubious accuracy, and unsuited to online use. Here, structured light illumination, combined with fast, transputer based, image processing algorithms, provide weld profile metrology. A novel algorithm for analysing the laser stripe and finding the centre line of one pixel width is given. Speed is sufficient to provide online operation while accuracy is improved by a factor of ten. Results for butt and fillet welds are illustrated and an example of online operation provided