DESIGN AND PERFORMANCE ANALYSIS OF AN OPTICAL PROFILOMETER FOR STAND-OFF CONTROL

A prototype non-contact high-bandwidth optoelectronic probe for surface topology and laser materials processing stand-off control is presented. Radiation from a low-power laser beam is focused onto a workpiece surface; the spatial variation in the reflected irradiance is modelled. A Gaussian beam and radiometric system model are investigated and compared with experimental results. The experimental results lie between the Gaussian and radiometric simulations which appear to be limiting cases. The system facilitates a measuring range of +/- 6 mm. A predicted performance is reported for the device. A set of experiments are performed, results are analysed and compared with the mathematical models. The approximate range of instrument linearity is +/- 1 mm for the 75 mm focal length main lens and +/- 2 mm for the 120 mm lens; in this linear range the optimal accuracy resolution is 1 mum.