THE EFFECT OF GAUSSIAN FILTER LONG WAVELENGTH CUTOFF λc IN TOPOGRAPHY MEASUREMENTS AND COMPARISONS

1. QUANTIFYING SURFACE TOPOGRAPHY DIFFERENCES USING CCFmax AND Ds Topography measurements play an important role in surface and nano-metrology, production quality control, tribology, bio-technology and forensic science [1]. Dozens of surface parameters are specified in national and international standards [2, 3]. Although none of these are designed for topography comparisons, statistical methods of autoand cross-correlation function (ACF and CCF) may be adapted to this purpose. At the National Institute of Standards and Technology (NIST), we use the CCF maximum (CCFmax) and a new parameter we call the profile (or topography) difference, Ds, to quantify differences between 2D profiles or between 3D topographies [4, 5]. The CCFmax is the value of the cross-correlation function when the two correlated 2D profiles or 3D topographies, A and B, are located in their maximum correlation position (or “zero-shift” position) after registration. At this position, profile (or topography) difference, B – A, is calculated. The parameter of the profile (or topography) difference, Ds, is defined as [4, 5]: