Patent ID: 7253880

Claim:
A lithographic apparatus, comprising: an illumination system configured to provide a beam of radiation; a support configured to support a patterning device, the patterning device configured to impart a pattern to the beam of radiation; a substrate table configured to hold a substrate; a projection system configured to project the patterned beam onto a target portion of the substrate; wherein the illumination system, or the projection system, or both the illumination system and the projection system, includes a focusing element to reflect the beam of radiation, and the apparatus further comprises a disc positioner configured to place a stop disc adjacent the focusing element so that the beam of radiation passes through an aperture in the stop disc; and a disc changer configured to select the stop disc from a plurality of stop discs and supply the selected stop disc to the disc positioner, the disc changer being external to the focusing element, wherein the disc changer and the focusing element are, in use, enclosed within a vacuum.