Fast Surface Profiling by White-Light Interferometry Using a Sampling Theorem for Band-Pass Signals

Abstract

We devise a new method of increasing the data acquisition and processing speed in a scanning white-light interferometer for surface topography measurement. We introduce the concept of a characteristic function which is smoother than interference fringe (IF) and has a maximum at the same point as IF. We also show that IFs are band-pass signals, instead of low-pass signals. By using the sampling theorem for band-pass singals, an interpolation formula for the characteristic function is derived, which leads us to a fast surface profiling method. The number of sample points are reduced to 1/24 of that for the conventional method. Experimental results on a 9.947μm step height standard show that our method achieves the same level of accuracy as the conventional one.