GENERIC DETRENDING OF SURFACE PROFILES

A commonly used estimator for the microtopography of an optical surfac e is its rms-roughness. Raw surface profile data may contain trending components. Therefore they should be subjected to a detrending procedu re before estimating the rms value. This procedure is limited in most cases to the removal of piston, slope, and curvature. Consequently, un desired artifacts may arise, which negatively influence the precision of rms-roughness estimation. In scanning surface metrology, the eigenv alues and eigenvectors of the covariance matrix of the surface can be used for a robust and precise multivariate estimation of rms-roughness .