ILLUMINATION SYSTEM FOR A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS

摘要

An illumination system for a microlithographic projection exposure apparatus comprises a light source (14), a first optical unit (26; 26') having an exit pupil (32), an optical raster element (34) positioned in or in close proximity to the exit pupil (32) of the first optical unit (26; 26') and a field plane (26) that is conjugated to the exit pupil (32) of the first optical unit (26; 26') by Fourier transformation. The illumination system further comprises a second optical unit (42) imaging the field plane (36) into an image plane (44) and having at its object side a homocentric entrance pupil that at least substantially coincides with the exit pupil (32) of the first optical unit. This allows to dispense with a condenser lens that is usually required for conjugating the exit pupil (32) to the field plane (36).