The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 16, 2010
Filed:
Apr. 03, 2006
Wilfried Clauss, Tuebingen, DE;
Wilfried Clauss, Tuebingen, DE;
Carl Zeiss SMT AG, Oberkochen, DE;
Abstract
A projection objective of a microlithographic projection exposure apparatus has a first lens, which is the penul-timate curved optical element on the image side. The first lens has a concave surface on the image side and contains a first intrinsically birefringent crystal, which has a first orientation of the crystal axes. The projection objective furthermore has a second lens, which is the last curved optical element on the image side and has a convex surface on the object side. The second lens contains a second intrinsically birefringent crystal, which has a second orientation of the crystal axes. The latter can be described by rotating the first orientation of the crystal axes about a symmetry axis of the first lens. The first and second orientations of the crystal axes are selected so that an intrinsic birefringence due to the first crystal, together with an intrinsic bire-fringence due to the second crystal, leads in total to at least approximately axisymmetric distribution of the overall birefringence.