Patent ID: 8632195

Claim:
A projection objective configured to image radiation along a path from an object plane of the projection objective to an image plane of the projection objective, the projection objective comprising: a first partial objective comprising a first mirror without an opening to pass the radiation along the path; and a second partial objective comprising a primary mirror and a secondary mirror, the primary mirror having an opening to pass the radiation along the path, and the secondary mirror having an opening to pass the radiation along the path, wherein: the first mirror is downstream of the object plane along the path; the primary mirror is downstream of the first mirror along the path; the secondary mirror is downstream of the primary mirror along the path; the secondary mirror is upstream of the image plane along the path; the primary mirror is geometrically closest to the image plane; the path intersects a reflective surface of the primary mirror; and a shortest distance between the reflective surface of the primary mirror and the image plane is more than 12 millimeters.