Inspection Method and Apparatus, Lithographic Apparatus, Lithographic Processing Cell and Device Manufacturing Method

摘要

An inspection apparatus configured to measure a property of a substrate includes an illumination source, a beam splitter, a first polarizer positioned between the illumination source and the beam splitter, an objective lens and an optical device that alters a polarization state of radiation traveling through it positioned between the beam splitter and the substrate and a second polarizer positioned between the beam splitter and a detector. An axis of the second polarizer is rotated with respect to an axis of the first polarizer. Radiation polarized by the first polarizer that reflects off any optical elements between the beam splitter and the optical device is prevented from entering the detector by the second polarizer. Only radiation that passes twice through the optical device has its polarization direction rotated so that it passes through the second polarizer and enters the detector.