Patent ID: 8891172

Claim:
A projection objective configured to image a reticle onto a wafer along a path of optical radiation, the projection objective comprising: a plane parallel plate including electrical conductor tracks at a region of the plane parallel plate; and a voltage supply electrically coupled to at least some of the electrical conductor tracks, wherein: the region of the plane parallel plate has a portion that is transmissive to the optical radiation and that comprises at least one portion of the electrical conductor tracks; during use of the projection objective, the plane parallel plate is in the path of the optical radiation so that the optical radiation is incident on the region of the plane parallel plate; during use of the projection objective, at least some of the electrical conductor tracks diffract the optical radiation; at least some regions of the electrical conductor tracks have a diameter of at most 50 micrometers in a direction lateral to a direction of incidence of the optical radiation on the plane parallel plate; and the projection objective is a microlithography projection objective.