Patent ID: 6049374
Filing Date: 2000-04-11
Classification: G03F

Abstract:
An illumination apparatus, comprisinga light source system for providing a light beam along a preselected path;an optical integrator, placed in said path of said light beam to form a plurality of light sources therefrom;a condenser optical system, placed in the path of light beams that have passed through said plurality of light sources, said condenser optical system guiding light from said optical integrator to an illuminated surface; anda filter, placed in a location that is in an optically conjugate relationship to said illuminated surface, said filter having at least a first area corresponding to a first portion of said plurality of light sources, and a second area corresponding to a second portion of said plurality of light sources other than said first portion; wherein,said filter has at least one first filter element having a first transmissivity distribution provided over the entirety of said first area of said filter; and hasat least one second filter element having a second transmissivity distribution that is the inverse of said first transmissivity distribution provided over the entirety of said second area of said filter.