Patent ID: 8436983

Claim:
An optical system including an illumination optical system which illuminates a surface to be illuminated, the optical system comprising: a birefringent element, disposed in an optical path of the optical system and including an optically transparent member which is made of uniaxial crystal material and crystallographic axis of which is arranged substantially in parallel with an optical axis of the optical system, that achieves a substantially circumferential distribution or a substantially radial distribution as a fast axis distribution in a lens aperture, the birefringent element is located at or near a position optically conjugate with the surface to be illuminated, in an optical path of the illumination optical system; and an optical rotator disposed on an image side of the birefringent element and adapted to rotate a polarization state in the lens aperture, wherein a beam bundle in a substantially circular polarization state is incident to the optically transparent member.