| 摘要 |
<p>An illumination system comprises a polarization selective holographic element (18) comprising at least one optically anisotropic material arranged to separate light of a first polarization type from light of a second polarization type, and means (12, 20, 22, 26) for converting light of at least one of the first and second polarization types to light of a common polarization type. Where the polarization selective holographic element (18) separates two orthogonal components of plane polarized light from one another, the converting means may comprise a polarization rotator, for example a half wave plate (20), or alternatively a quarter wave plate (22) and a reflector (12, 26) arranged to reflect light back through the quarter wave plate (22). Where the polarization selective holographic element separates opposite handed components of circularly polarized light, the converting means may comprise a reflector (12, 26). <IMAGE></p> |
