Patent ID: 8576378

Claim:
An illumination optical system which illuminates a target illumination region with light provided by a light source, comprising: a first polarization control unit which is located between the light source and a pupil of the illumination optical system, and is configured to control a polarization state of the light; and a second polarization control unit which is located between the first polarization control unit and the pupil, and is configured to control the polarization state of the light, wherein a region on the pupil includes a plurality of partial regions, and the plurality of partial regions are classified into a first group including a partial region having a largest area, and a second group including a partial region different from the partial region having the largest area, wherein the second polarization control unit changes a polarization state in the partial region which belongs to only the second group, wherein a first polarization state formed in the region on the pupil by the first and second polarization control units can be changed to a second polarization state having a polarization state and a position of the partial region of the first group, which are different from those of the first polarization state, wherein the first polarization control unit differentiates the polarization state in the partial region of the first group between the first polarization state and the second polarization state by changing a polarization state of light emitted from the first polarization control unit, and wherein the second polarization control unit differentiates the position of the partial region of the first group between the first polarization state and the second polarization state by changing a position of a portion of the second polarization control unit, through which light incident on the partial region of the first group passes.