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Cylindrical surface inspection

28 May 2014

A new industrial vision system, trevista Cylinder, from Stemmer Imaging allows automated inspection of milled, polished and galvanised cylindrical components for defects such as scratches, dents, discoloration and stress marks.

Using a patented inspection process, trevista Cylinder goes beyond the limits of conventional vision systems to provide reliable inspection of a range of surfaces from glossy components to diffusely scattering surfaces and even black plastic.

Supplied as a complete system with structured diffuse illumination, lens, camera, software and PC, trevista Cylinder, is based on a patented "shape from shading" technology. Information on the three-dimensional shape of an object can be deduced from the shading of its surfaces.

The cylindrical objects are rotated along their longitudinal axis under the special dome-shaped diffuser. During the rotation the line scan camera surveys the object with a scanning speed up to 4x. The profile data obtained are planar images of the uncoiled material surface. These synthetic images contain topographic information and a special calculation algorithm allows inspection for characteristics such as scratches, dents, discoloration and stress marks according to their inclination, curvature and texture.

The topographic images allow the display of three-dimensional surface shape, revealing defects down to just a few micrometres depth. These defects can be located quickly, reliably and free of interference, and can be readily distinguished from irrelevant stains caused by lubricants for example.