Imaging optical unit for euv microlithography

An imaging optical unit, comprising:

• a plurality of mirrors configured to image an object field in an object plane into an image field in an image plane and, in so doing, to guide imaging light along an imaging light beam path,
• wherein:
• an imaging light beam section extends between the object field and a first mirror in the imaging light beam path at an angle with respect to a normal of the object plane of less than 3°;
• the first mirror in the imaging light beam path is in an object plane mirror half space with respect to the object plane;
• a last mirror in the imaging light beam path is in an image plane mirror half space with respect to the image plane;
• the object plane mirror half space opens into an object plane mirror half space direction specified by a direction of a normal of the object plane emanating from the object plane, which normal extends into the object plane mirror half space;
• the image plane mirror half space opens into an image plane mirror half space direction specified by a direction of a normal of the image plane emanating from the image plane, which normal extends into the image plane mirror half space;
• a half space direction angle between the object plane mirror half space direction and the image plane mirror half space direction is of less than 30°;
• and
• the imaging optical unit has an image-side numerical aperture greater than 0.6.