An illumination system comprises a radiation source and a broadband, cholesteric polarizer. Such a polarizer includes a layer of a polymeric material having a cholesteric ordering, the material being ordered such that the axis of the molecular helix is oriented transversely to the layer....http://www.google.se/patents/US5737044?utm_source=gb-gplus-sharePatent US5737044 - Illumination system using a broadband cholesteric polarizer having its surface of maximum helix pitch face the radiation source 
