An optical integrator has characteristics to suppress influence of relative positioning error of a pair of optical members on an illuminance distribution and on a shape of an illumination field. The optical integrator is a wavefront splitting type optical integrator having a first optical member and...http://www.google.com/patents/US7706072?utm_source=gb-gplus-sharePatent US7706072 - Optical integrator, illumination optical device, photolithograph, photolithography, and method for fabricating device
