Issue date: 22 March 2001
Bumpy irregular surfaces on ceramic tiles, scratches on marble slabs and dents in ceramic products cost manufacturers a fortune in quality control systems. In many cases highly trained quality control staff are employed to scrutinise defects in product surfaces. This can be expensive, tedious, time consuming and inaccurate. A researcher from the Faculty of Engineering at the University of the West of England has come up with an automised technique to check surface defects which could solve this problem.
Dr Melvyn Smith said, "It is often very difficult for the naked eye to spot irregularities on patterned surfaces. Patterns distract from the surface so that bumps and dents are hidden from view. Some products require a smooth surface to be properly functional and it is a constant challenge to manufacturers of such products to maintain quality and thus retain custom.
"The technique which has been devised shows up defects on patterned surfaces by separating the two-dimensional coloured pattern from the underlying three-dimensional surface topography, so that the surface is shown in relief. This way it is possible to see surface irregularities, known as a bump map, hidden by the superimposed coloured pattern. The technique uses a special kind of light arrangement and software. The isolated surface defects are then analysed in terms of their size, shape and position. This information may be used to control the manufacturing process in order to eliminate further defects."
The illustration on www.uwe.ac.uk/facults/eng/research/melsmith show how a concealed underlying flaw can easily be revealed by automatically removing any coincident surface chromatic pattern.
Images available from Dr Smith, who has recently published a book entitled Surface Inspection Techniques, presented a poster to MPs at the House of Commons on Thursday 19 March during Science, Engineering and Technology week (SET 2001).
Further research is needed to develop the technique to a commercial system. The research into surface inspection is being partly supported by The Engineering and Physical Sciences Research Council and an industrial collaborator over the next 2.5 years.
Dr Melvyn Smith has recently published a book entitled Surface Inspection Techniques, using the integration of innovative machine vision and graphical modelling techniques published by Professional Engineering Publishing as part of their Engineering Research
Series. Investigations are currently being made into a patent application.