Illumination optical unit

An illumination optical unit configured to transfer illumination radiation having a predefined intensity distribution in an intermediate focal plane from the intermediate focal plane to an object field along a beam path, the illumination optical unit comprising:

• a first faceted element;
• and
• a second faceted element downstream of the first faceted element along the beam path, the second faceted element comprising a multiplicity of displaceable micromirrors that are groupable to define facets in a variably flexible manner,
• wherein the displaceable micromirrors are grouped to define facets so that, during use of the illumination optical unit, an intensity distribution on at least one facet has a minimum (Imin) and a maximum (Imax), and Imin≧0.05 Imax.