Optimization of a projection system is performed to obtain a starting configuration that is at a local minimum of the merit function or simply a previously known minimum system is used as the starting configuration. A zero-thickness meniscus lens is inserted at a surface in the local minimum starting...http://www.google.fr/patents/US7714307?utm_source=gb-gplus-shareBrevet US7714307 - Method of designing a projection system, lithographic apparatus and device manufacturing method
Method of designing a projection system, lithographic apparatus and device ...
