Illumination system

摘要

An optical attenuator device operates to remove a part of a beam of radiation having a higher than average intensity using at least one optical attenuator element (4). The device has application in a radiation system, and/or a lithographic apparatus, in particular a scanning lithographic apparatus, wherein the optical attenuator element(s) are provided in a central part of the beam, for example perpendicularly to a scanning direction.