Design and development of a novel noncontact fibre optic laser scanning system

Examples of sheet materials for which optical inspection systems have been reported include paper webs, textile fabric, glass material, hot slabs and cold-rolled metal strip. These inspection systems are essential tools for the implementation of modem statistical process control procedures. Interferometric methods, despite their high accuracy, are mostly too sensitive to be practical for application in production. Laser triangulation is frequently the best solution for these types of applications because it combines the advantage of noncontact inspection with the ability to measure with sub-micrometer resolution. A fibre optic intensity-based sensor however requires a much simpler optical system, and therefore, can be made very small. These systems also are less costly and can be used to detect surface roughness. Such a laser scanner consists of two parts: an illumination part and an imaging part. The intensity of the detected light in the imagining part depends upon how far the reflecting surface is from the fibre optic end(s). Light scattering from a test surface may be a changed by different microstructures encountered. However, a sudden change in the light intensity would occur when the incident light beam encounters a defect.