Patent ID: 8913316

Claim:
A catadioptric projection objective for imaging a pattern, which is arranged on an object plane of the projection objective, to an image plane of the projection objective when the pattern is illuminated with ultraviolet light, the projection objective comprising: a first objective part for imaging the pattern to a first intermediate image, a second objective part for imaging the first intermediate image to a second intermediate image, wherein the second objective part comprises only one concave mirror and at least one lens, a third objective part for imaging the second intermediate image to the image plane, and a first folding mirror for deflecting the ultraviolet light toward the concave mirror and a second folding mirror for deflecting the ultraviolet light from the concave mirror, and wherein the concave mirror is an active mirror comprising manipulators configured to vary a shape of a reflective surface of the concave mirror to compensate for imaging errors, the third objective part comprises a first lens group having a positive refractive power, a second lens group, which immediately follows the first lens group and has a negative refractive power, a third lens group which immediately follows the second lens group and has a positive refractive power, a fourth lens group which immediately follows the third lens group and has a positive refractive power, and an aperture stop which is arranged in a transitional region from the third lens group to the fourth lens group, the third lens group has an entry surface which is located in a vicinity of a point of inflection of a marginal ray height between the second lens group and the third lens group, with no negative lens being arranged between the entry surface and the aperture stop, and only positive lenses are arranged between the entry surface and the image plane.