Illuminating optical system and exposure apparatus utilizing the same

A projection exposure apparatus for projecting a pattern of a reticle, uniformly illuminated by an illuminating optical system, onto a substrate through a projection optical system, wherein said illuminating optical system comprises:

• parallel beam generating means for supplying a parallel light beam;
• a first optical integrator for forming a first substantially planar light source by the light beam from said parallel beam generating means;
• a first condensing optical system for condensing the light beam from said first planar light source;
• a second optical integrator for forming a second substantially planar light source by the light beam condensed by said first condensing optical system;
• and
• a second condensing optical system for illuminating an illuminated plane in overlapping manner by condensing the second planar light source formed by said second optical integrator;
• wherein at least either one of said first optical integrator and said first condensing optical system has a variable focal length, and the size of said second planar light source is rendered variable by the change in said focal length, while the size of said illuminated area is maintained constant.

An illuminating optical system comprising:

• parallel beam generating means for supplying a parallel light beam;
• a first optical integrator for forming a first substantially planar light source by the light beam from said parallel beam generating means;
• a first condensing optical system for condensing the light beam from said first planar light source;
• a second optical integrator for forming a second substantially planar light source by the light beam condensed by said first condensing optical system;
• and
• a second condensing optical system for illuminating an illuminated plane in overlapping manner by condensing the light beam from the second planar light source formed by said second optical integrator;
• wherein said first optical integrator includes at least a first lens element group and a second lens element group;
• and
• the size of said second planar light source is rendered variable by the change in the mutual distance of said lens element groups while the size of said illuminated area is maintained constant.

An illuminating optical system comprising:

• parallel beam generating means for supplying a parallel light beam;
• a first optical integrator for forming a first substantially planar light source by the light beam from said parallel beam generating means;
• a first condensing optical system for condensing the light beam from said first planar light source;
• a second optical integrator for forming a second substantially planar light source by the light beam condensed by said first condensing optical system;
• and
• a second condensing optical system for illuminating an illuminated plane in overlapping manner by condensing the light beam from said second planar light source formed by said second optical integrator;
• wherein said first condensing optical system includes at least a first lens group and a second lens group;
• and
• the size of said second planar light source is rendered variable by the change in the mutual distance of said first and second lens groups, while the size of the illuminated area is maintained constant.