Patent ID: 8891062

Claim:
An illumination optical system which illuminates an illumination surface with light from a light source, the system comprising: a divider which divides light from the light source to generate a plurality of light beams; a first reflective integrator including a plurality of reflective integrators respectively corresponding to the plurality of light beams generated by the divider, wherein the plurality of reflective integrators are configured to respectively uniformize the light intensity distributions of the plurality of light beams; a condenser which condenses the light beams from the first reflective integrator; a second reflective integrator which receives the light beams from the condenser and illuminates the illumination surface; and an aperture stop arranged between the second reflective integrator and the illumination surface, wherein the divider generates the plurality of light beams so that light beams each having a cross-sectional shape different from a cross-sectional shape of the light provided from the light source to the divider enter a plane on which the aperture stop is arranged.