Multi-beam fibre-optic laser scanning system for surface defect recognition

Multi-beam scanning systems are being used in automated industrial manufacturing environments to determine surface defects. Recent methods of surface defect detection involve the use of fibre-optic light emitting and detection assemblies. This paper deals with the design and development of a new high-speed photo-electronic system. A line of five emitting diodes and five receiving photodiodes were used as light sources and detectors, respectively. These arrays of emitting diodes and photo-detectors were positioned opposite each other. Data capture was controlled and analysed by PC using LabView software. A newly developed technique of using an angled array of fibres allows an adjustable resolution to be obtained with the system, with a maximum system resolution of approximately 100 μm (the diameter of the collecting fibre core). This system was successfully used to measure various materials surface profile, surface roughness, thickness, and reflectivity. The advantages of this new system may be seen as lower cost, less bulky, greater resolution and flexibility.