The invention relates to a filter device for an illumination system, especially for the correction of the illumination of the illuminating pupil, including a light source, with the illumination system being passed through by a bundle of illuminating rays from the light source to an object plane, with...http://www.google.de/patents/US7798676?utm_source=gb-gplus-sharePatent US7798676 - Filter device for the compensation of an asymmetric pupil illumination
