Patent ID: 8861084

Claim:
An optical element, comprising: a polarization-modulating optical element comprising an optically active crystal having an optical axis, the polarization-modulating optical element having a thickness profile that, as measured in the direction of the optical axis, is variable, wherein the polarization-modulating optical element has an element axis oriented substantially in the direction of the optical axis of the optically active crystal, and the thickness profile in relation to the element axis has a variation that depends only on an azimuth angle θ, where θ is measured from a reference axis that runs perpendicular to the element axis and intersects the element axis, wherein, for linearly polarized light that travels along the optical axis of the optically active crystal, a plane of oscillation of an electric field vector is rotated by an angle with a magnitude proportional to a distance traveled by the linearly polarized light inside the optically active crystal, and wherein the polarization-modulating optical element is configured to transform an entering light bundle with a first linear polarization distribution into an exiting light bundle with a second linear polarization distribution different from the first linear polarization distribution.