Patent ID: 8854605

Claim:
An illumination optical system for illuminating an illumination target surface with a light beam from a light source, the system comprising: a field stop configured to define an illumination region on the illumination target surface; and a plurality of adjustment units each having one of a reflectance distribution or a transmittance distribution to adjust an incident angle distribution of the light beam impinging on the illumination target surface, wherein the plurality of adjustment units includes: a first adjustment unit configured to adjust at least one of light amount differences, in a first direction, of incident angle distribution of light incident on the illumination target surface, or light amount differences, in a second direction different from the first direction, thereof; and a second adjustment unit configured to adjust differences between light amounts, in the first direction, of incident angle distribution of light incident on the illumination target surface, and light amounts, in the second direction, thereof, wherein the first adjustment unit is arranged between the light source and the field stop, and includes an adjustment coating having one of a reflectance distribution or a transmittance distribution in a first region through which a principal ray that enters the illumination region passes, the first region having a reflectance of 1.0% or more, and wherein the second adjustment unit is arranged between the illumination target surface and the field stop, and includes an adjustment coating having one of a reflectance distribution or a transmittance distribution in a region other than a second region through which a principal ray that enters the illumination region passes, the second region not having an adjustment coating and having a reflectance of less than 1.0%.