Accelerated surface measurement using wavelength scanning interferometer with compensation of environmental noise

The optical interferometry has been widely explored for surface measurement due to the advantages of non-contact and high accuracy interrogation. Eventually, some interferometers are used to measure both rough and smooth surfaces such as white light interferometer and wavelength scanning interferometer (WSI). The WSI can measure large discontinuous surface profiles without the phase ambiguity problems. However, the WSI usually needs to capture hundreds of interferograms at different wavelength in order to evaluate the surface finish for a sample. Moreover, the measurement process might be affected by environmental disturbances if the surface inspection takes place in a production environment (e.g. in- process inspection). This paper introduces a wavelength scanning interferometer (WSI) for fast areal surface measurement of micro and nano-scale surfaces which is immune to environmental noise. The WSI system and operation principles are introduced in this paper. Mathematical description of data analysis is presented. This paper also describes an active servo control system that serves as a phase compensating mechanism to eliminate the effects of environmental noise. Finally, a parallel programming model is presented as a solution to accelerate the computing analysis in the WSI. This parallel programming is based on CUDATM C program structure that developed by NVIDIA. The presented system can be used for on-line or inprocess measurement on the shop floor.