Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Inspection technique using laser irradiation thermography

A technique has been developed for the rapid inspection of engineering ceramic, metallic and organic coatings. The technique uses the beam from a small laser to create a surface thermal transient, which is recorded with a single infrared detection. The laser beam and the field of view of the detector are raster scanned across the surface at high speed, having the advantages of being fast, noncontacting and capable of inspecting components of complicated shape and geometry as well as large, plane areas. A pre-prototype has demonstrated successfully the detection of coating thickness variations, disbands and thermal properties variations in a wide range of coatings, and spray parameter variations in plasma sprayed coatings. The optical resolution can be down to 50 um. The choice of laser can be compatible with optical fibre transmission (such as the neodymium yttrium aluminium garnet (Nd:YAC) laser), ensuring minimal inspection head dimensions. The technique is particularly suitable to automated on line inspection of coated products at an early stage in the manufacturing process, and to inspection of components during maintenance or overhaul.

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