Broadband cholesteric optical device, polariser, filter, Liquid crystal device and polarising beam-splitter

摘要

A broadband cholesteric optical device such as a polariser or spectral filter comprises a broadband cholesteric layer 1, for instance of the graded pitch type such that the cholesteric pitch increases monotonically from one surface 2 of the film 1 to the other 3. In order to improve the off-axis performance, a compensator is provided in the form of a positive birefringence film 8 whose optic axis is substantially perpendicular to the film. Another negative birefringence film 9 whose optic axis is also perpendicular to the film may also be provided. <IMAGE>