Patent ID: 7589818
Filing Date: 2009-09-15
Classification: B41C,G03F

Abstract:
1. A method of converting a projection lens system of a lithographic projection apparatus, the method comprising (i) exchanging a compensating optical element in the optical path of the projection lens system for another compensating optical element, or (ii) adding a further compensating optical element in the optical path of the projection lens system, or (iii) removing a further compensating optical element in the optical path of the projection lens system, or any combination selected from (i)-(iii), wherein the compensating optical element is exchanged from, added to, or removed from a position prior to a final element in the projection lens system along the optical path, such that with a liquid between the projection lens system and the point of focus of the projection lens system, the distance of the point of focus of the projection lens system from a non parallel optical element will remain the same as without the liquid between the projection lens system and the point of focus of the projection lens system.