Patent ID: 8711479

Claim:
A method of producing a polarization-modulating element that modulates a polarization state of incident light into a predetermined polarization state, the polarization-modulating element being used with an illumination optical apparatus, the method comprising: preparing an optical material having optical activity; and providing the optical material with a circumferentially varying thickness profile and a central region that is an aperture having no optical activity, wherein the thickness profile is set so that light in a linearly polarized state having a direction of polarization substantially along a single direction, is transformed into light in an azimuthal polarization state having a direction of polarization substantially along a circumferential direction or into light in a radially polarized state having a direction of polarization substantially along the radial direction, wherein the step of providing the circumferentially varying thickness profile provides a thickness profile such that thicknesses of two arbitrary regions adjacent to each other among a plurality of circumferentially separated regions are different from each other, two arbitrary regions opposite to each other among the plurality of regions have their respective angles of optical rotation substantially equal to each other, and said two arbitrary regions opposite to each other have their respective thicknesses substantially equal to each other.