There is provided a collector unit for illumination systems with a wavelength of .ltoreq.193 nm, preferably .ltoreq.126 nm, and especially preferably in the region of EUV wavelengths. Rays of a beam bundle impinge on the collector unit, and the beam bundle emerges from an object in an object plane. The collector unit includes at least one mirror shell that receives the rays of the beam bundle emerging from the object and shows an optical effect, and a periodic structure with at least one grating period applied to at least a part of the mirror shell. An illumination system and an EUV projection exposure system are also provided.