Illumination optical unit for projection lithography

An illumination optical unit for projection lithography serves for illuminating an object field (8), in which an object (12) to be imaged is arrangeable, along an illumination beam path. A first facet mirror (6) has first facets (21) for reflecting guidance of illumination light (3) and for arrangement in a used region of a far field of an EUV light source. A second facet mirror (7) serves for reflecting guidance of the illumination light (3) reflected by the first facet mirror (6) to the object field (8). The second facet mirror (7) has second facets (25) for guiding respectively one illumination light partial beam (26) into the object field (8). The first facet mirror (6) is arranged in a field plane (6a) of the illumination optical unit. The second facet mirror (7) is arranged at a distance from a field plane (6a) and from a pupil plane (12b) of the illumination optical unit. The two facet mirrors (6, 7) are arranged in relation to one another in such a way that at least some of the illumination light part