Illumination system of a microlithographic projection exposure apparatus

An illumination system configured to illuminate an object moving along a scan direction, the illumination system comprising:

• an optical integrator configured so that, during use of the illumination system, the optical integrator produces a plurality of secondary light sources in a pupil plane of the illumination system, the optical integrator comprising a plurality of light entrance facets, each light entrance facet associated with a secondary light source, and the optical integrator configured so that, during use of the illumination system, images of the light entrance facets at least substantially superimpose in the object plane;
• a spatial light modulator having a light exit surface, the spatial light modulator configured so that, during use of the illumination system, the spatial light modulator transmits or reflects impinging projection light in a spatially resolved manner;
• a pupil forming unit configured so that, during use of the illumination system, the pupil forming unit directs projection light onto the spatial light modulator;
• an objective configured so that, during use of the illumination system, the objective images the light exit surface of the spatial light modulator onto the light entrance facets of the optical integrator so that an image of an object area on the light exit surface completely coincides with one of the light entrance facets;
• and
• a control unit configured so that, during use of the illumination system, the control unit controls the spatial light modulator so that along the scan direction a length of an image, which is formed on the object from a light pattern in the object area, gradually increases at a beginning of a scan cycle and gradually decreases at the end of the scan cycle,
• wherein the illumination system is a microlithographic illumination system.