Patent ID: 7136220
Filing Date: 2006-11-14
Classification: G02B,G03F

Abstract:
1. A catadioptric projection lens for imaging a pattern situated in an object plane onto an image plane, comprising: an optical axis; a first catadioptric lens section having a concave mirror and a physical beamsplitter having a beamsplitting surface; and a second lens section arranged following the beamsplitter; the first and second lens sections being arranged between the object plane and the image plane; wherein the object plane is arranged at a working distance from a first optical surface of the projection lens; positive refractive power is arranged in an optical near-field of the object plane where a marginal-ray height is less than about 30% of a marginal-ray height at the concave mirror; and the beamsplitter is arranged in a zone having low marginal ray height where a projection of marginal-ray heights onto a plane orthogonal to the optical axis at an intersection of the beam splitting surface with the optical axis is within a range from 10% to 70% of the marginal-ray height at the concave mirror.