Patent ID: 6333781
Filing Date: 2001-12-25
Classification: G02B,G03F

Abstract:
A dioptric projection optical system that forms an image of a pattern of an object onto a workpiece over an exposure field, said system comprising along an optical axis:a) a variable size aperture stop, disposed at a location along the optical axis, for determining an image-side numerical aperture NA;b) a front lens group comprising a plurality of lenses and positioned between the object and said aperture stop;c) a rear lens group comprising a plurality of lens elements and positioned between said aperture stop and the workpiece; andd) wherein said system satisfies the condition:0.005<d.sub.Q /{L.times.(1-NA)}<0.2 (1)wherein L is the distance along the optical axis from the object to the image, d.sub.Q is the distance along the optical axis from said aperture stop location to a position Q where a paraxial principal ray intersects the optical axis, wherein said paraxial principal ray corresponds to a ray from the workpiece side impinging upon said projection optical system parallel to the optical axis.