Adaptive confocal system for 3-D profiling

Abstract

Optical profilometers for micrometer resolutions are getting increasingly popular for non-contact measurement of surface profiles. Confocal profilometer is one such optical technique which can pick up sub-micron height variations of the object surface. Though the system is a single point measurement scanning in the X-Y directions enables one to plot the 3-D profile of the surface. However, the Z-scanning range is limited to ±1mm. In this work we report a system which can adapt itself to widen the scanning range in the Z-direction. For increasing the scan range we have added another translation stage in the Z axis which adapts itself when the system profiles a surface with step heights more than its original range. The X-Y-Z translation stage is connected to the computer and is controlled using a LabVIEW program. The 3-D plot is obtained by plotting the Z-values from the confocal system to the corresponding X-Y position of the translation stage. When ever the system goes out of range the Z translation stage is increased or decreased thus adapting itself to plot a 3D profile of the specimen.