Patent ID: 8842296
Filing Date: 2014-09-23
Classification: G01B,G03F

Abstract:
1. A method for determining a Goos-Hänchen correction (GHC) in an optical autofocus system that uses light reflected from a substrate to determine corresponding changes in a height of the substrate, the method comprising: using an optical height sensor, obtaining a first set of height data of at least a region of the substrate, the height data corresponding to respective loci on the substrate and comprising measurements involving at least one optical wavelength and/or at least one polarization state of light utilized by the optical height sensor; from the first set of height data, determining a first GHC function including respective coefficients; determining a first map of the substrate surface by applying the first GHC function to the first set of height data corresponding to at least the region; using a physical height sensor, obtaining a second set of height data of at least the region of the substrate; from the second set of height data, determining a second map of the substrate surface corresponding to at least the region; and in at least the region of substrate, correcting the first GHC function by comparing the first and second maps of the substrate.