US Patent 7110084 Illumination optical system and exposure apparatus

Attempting to provide an illumination optical system and an exposure apparatus using the same, which provide a more uniform angular distribution of light for illuminating a mask than the prior art, an illumination optical system for illuminating an object surface includes an optical unit that converts light from a light source section into approximately parallel light, and includes first and second mirrors, wherein the first mirror has an opening, through which light reflected by the second mirror passes.