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

A prototype non-contact high-bandwidth optoelectronic probe for surfac e topology and laser materials processing stand-off control is present ed. 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 co mpared 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 predict ed performance is reported for the device. A set of experiments are pe rformed, results are analysed and compared with the mathematical model s. The approximate range of instrument linearity is +/- 1 mm for the 7 5 mm focal length main lens and +/- 2 mm for the 120 mm lens; in this linear range the optimal accuracy resolution is 1 mum.