White light interference (WLI) optical profiler had been used widely for structured surface measurement. To achieve high measuring accuracy, piezoelectric ceramic (PZT) was usually used as the vertical scanning unit, which was normally less than 100um and only for small range structured surface measurement. With the development of advanced manufacturing technology, precision structured surfaces with large step height were appearing. To satisfy the measurement requirements of this kind of precision structured surfaces, WLI optical profiler with large range had to be developed. In this paper, an optical profiler was proposed, in which a coarse-fine vertical scanning system was adopted to expand its measurement range to 10mm while its resolution still at nanometer level.
Piezoelectric ceramics with a flexible hinge guide was used for fine positioning at nanometer level, while a stepping motor was used for coarse positioning with a resolution at micrometer level, and their combination helped fulfillment of vertical scanning positioning with large range and nanometer resolution. A grating sensor was used for the real-time measurement of scanning displacement for close-loop positioning control. The properties of the flexible hinge guide was analyzed using ANSYS. Experimental results indicated the performance of the system was good. The system had a good application prospect in an optical profiler for surface measurement.