Illumination optic for projection lithography

An illumination optical unit configured to illuminate an object field with illumination light from a light source along an illumination beam path, the illumination optical unit comprising:

• a field facet mirror comprising a plurality of field facets;
• and
• a pupil facet mirror comprising a plurality of pupil facets,
• wherein:
• the field facets and the pupil facets are configured so that in each case a partial beam of the illumination light is guided over exactly one field facet and exactly one pupil facet along an illumination channel from the light source to the object field;
• the field facet mirror is a component of a field facet transfer optical unit configured to image a light source image along in each case one illumination channel onto one of the pupil facets;
• the pupil facet mirror is a component of a pupil facet transfer optical unit configured to superimposedly image the field facets into the object field;
• and
• the illumination optical unit is configured to set a spatial resolution of an illumination light illumination of an entrance pupil of a projection optical unit arranged downstream of the object field in the illumination light beam path to image the object field into an image field.