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Proceedings Paper

On-line detection of surface defects on steel billets using multiple grazing-incidence light sources
Author(s): Marc L. Dufour; Marc Samson
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Paper Abstract

An optical method for on-line hot steel surface quality inspection is proposed. The method is based on the four laser sources illuminating the surface at grazing incidence from different directions. A CCD line array camera, located perpendicularly over the surface, captures the scattered light generated by each source separately. Surface defects induce shadow and bright field patterns which are related to each source direction and angle of incidence. Such a multiple source configuration is required for the discrimination of real surface defects from normal reflectivity and surface geometry variations. The patterns are digitized for each source separately and then combined using a simple and fast algorithm. The method was tested in our laboratory on cold steel billet samples. Characteristic signatures were obtained for most surface defects such as blisters, scale embedments, large cracks and pinholes. A scanning rate of several thousand lines per second is planned for the industrial prototype by selecting a different wavelength for each laser source and by using a four wavelength CCD line array camera.

Paper Details

Date Published: 1 March 1992
PDF: 10 pages
Proc. SPIE 1614, Optics, Illumination, and Image Sensing for Machine Vision VI, (1 March 1992); doi: 10.1117/12.57992
Show Author Affiliations
Marc L. Dufour, National Research Council Canada (Canada)
Marc Samson, Leco Instruments Ltd. (Canada)

Published in SPIE Proceedings Vol. 1614:
Optics, Illumination, and Image Sensing for Machine Vision VI
Donald J. Svetkoff, Editor(s)

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