Patent ID: 9280055
Filing Date: 2016-03-08
CPC Classification: G03F

Claim Text:
1. An illumination system having a pupil plane, the illumination system comprising: a light source configured to produce projection light during use of the illumination system; a diffractive optical element between the light source and the pupil plane so that, during use of the illumination system, an irradiance distribution of the projection light in the pupil plane depends on a position of a field that is illuminated by the projection light on the diffractive optical element; an optical imaging system between the light source and the diffractive optical element; and a multiple beam folding system between the light source and the optical imaging system, wherein the multiple beam folding system comprises an element configured to vary an optical path length within the multiple beam folding system by displacing one or more prism or planar mirror in the multiple beam folding system, and the illumination system is a microlithographic illumination system.