Rapid optical measurement of surfaces

Abstract It is now accepted that more reliable engineering decisions can be made from 3D measurements of surfaces than is possible with conventional single line traces. Significant effort has been expended in determining useful parameterisation of 3D surfaces. There remains however the fundamental difficulty of acquiring the large data sets that are required in a reasonable period of time. Whilst stylus instruments still have a significant role to play in surface metrology, and can be made faster if optimised, the limited measurement bandwidth of conventional instruments prevents them from being of practicable use for this type of application. Certain optical measurement techniques, such as dynamic focusing, offer much faster measurement rates with comparable accuracy and precision. This paper describes the dynamic focusing measurement principle and details surface measurement applications which cannot be achieved by conventional means. The paper concludes with a brief discussion of the limitations of the dynamic focusing technique.