An illuminating optical system for illuminating an object comprises a light source emitting a radiation beam, means for dividing the radiation beam into a plurality of beams, a device for rotating at least one of the plurality of divided beams about an optic axis parallel to the direction of travel of...http://www.google.es/patents/US5048926?utm_source=gb-gplus-sharePatente US5048926 - Illuminating optical system in an exposure apparatus
Illuminating optical system in an exposure apparatus
