An apparatus and method to determine a property of a substrate by measuring, in the pupil plane of a high numerical aperture lens, an angle-resolved spectrum as a result of radiation being reflected off the substrate. The property may be angle and wavelength dependent and may include the intensity of...http://www.google.com/patents/US20060066855?utm_source=gb-gplus-sharePatent US20060066855 - Method and apparatus for angular-resolved spectroscopic lithography characterization
