An optical raster element for an illumination system of a microlithographic projection exposure apparatus includes an array of refractive optical elements extending on a planar or curved surface. At least two of the optical elements are arranged side by side along a reference direction with a pitch of less than 2 mm. They have a height perpendicular to the surface of less than 50 μm and a surface profile along the reference direction which includes a central section, two transition sections adjacent the central section and two end sections adjacent the transition sections. The curvatures in the two transition sections are greater than the curvatures in the central section and the end sections. The optical raster element is intended for being used as a first channel plate in an optical integrator (honeycomb condenser) and can reduce the maximum light intensities occurring in or behind the second channel plate.