Patent ID: 7170686
Filing Date: 2007-01-30
Classification: G03F

Abstract:
1. An illumination optical system for illuminating a reticle, said illumination optical system comprising: plural-light-source forming means for forming a plurality of light source images by use of light from a light source; a relay optical system for directing light from the plurality of light source images to a mask; an imaging optical system for imaging the mask upon a surface of the reticle, by use of light from the mask, said imaging optical system including, in an order from a light entrance side thereof, a first lens group having a positive power, a second lens group having a negative power, and a third lens group having a positive power, wherein said second lens group includes a concave lens at a light exit side thereof and wherein said third lens group includes a convex lens at a light entrance side thereof; wherein a position of intersection between an optical axis of said imaging optical system and a principal ray of abaxial light is defined between said second lens group and said third lens group.