Patent ID: 9423694
Filing Date: 2016-08-23
CPC Classification: F21V,G02B,G03F

Claim Text:
1. An illumination optical apparatus which illuminates an object having a pattern with illumination light, the illumination optical apparatus comprising: an optical integrator arranged in an optical path of the illumination light; and a polarization modulating member made of an optical material with optical activity, the polarization modulating member having a thickness that varies with respect to azimuthal positions about an optical axis of the illumination optical apparatus, the polarization modulating member being arranged in the optical path on an incidence side of the optical integrator and being arranged around the optical axis so as to surround the optical axis, a direction of an optic axis of the optical material being substantially coincident with a direction of the optical axis of the illumination optical apparatus, wherein the polarization modulating member rotates a polarization direction of the illumination light so that the illumination light, being incident on the polarization modulating member in a linearly polarized state having the polarization direction along a single direction, is changed to a linearly polarized state having polarization directions being substantially coincident with an azimuthal direction about the optical axis at a pupil plane of the illumination optical apparatus, wherein the polarization modulating member has a region without optical activity in an area perpendicular to the optical axis, the region being on the optical axis, and wherein the polarization modulating member has substantially constant thicknesses in at least two radial directions that are not parallel to each other.