Patent ID: 7859748

Claim:
An objective including an object plane, an image plane, a pupil plane, and an optical axis, the objective being configured to direct radiation from the object plane to the image plane during operation, the objective comprising: a plurality of optical elements positioned along the optical axis between the object plane and an image plane, the plurality of optical elements comprising in sequence from the object plane to the image plane: a first mirror, the first minor being a concave mirror positioned near the pupil plane; one or more additional mirrors including at least one curved mirror; and a plurality of lenses forming a positive lens group, wherein: the objective is a microlithographic reduction projection catadioptric objective; the optical axis is a straight line extending between the object plane and the image plane; each of the mirrors in the objective comprise a surface that is at least a portion of a symmetric surface that is rotationally symmetric about the optical axis; and for each mirror surface that reflects the radiation, an entire area of the minor surface that reflects the radiation is a continuous area that does not surround an aperture in the minor surface.