On-line detection of surface defects on steel billets using multiple grazing-incidence light sources

Marc L. Dufour; Marc Samson

doi:10.1117/12.57992

1 March 1992 On-line detection of surface defects on steel billets using multiple grazing-incidence light sources

Marc L. Dufour, Marc Samson

Proceedings Volume 1614, Optics, Illumination, and Image Sensing for Machine Vision VI; (1992) https://doi.org/10.1117/12.57992
Event: Robotics '91, 1991, Boston, MA, United States

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.

Citation Download Citation

Marc L. Dufour and Marc Samson "On-line detection of surface defects on steel billets using multiple grazing-incidence light sources", Proc. SPIE 1614, Optics, Illumination, and Image Sensing for Machine Vision VI, (1 March 1992); https://doi.org/10.1117/12.57992

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