Broadband cholesteric optical device having a broadband cholesteric layer, a positive C-plate and a negative C-plate

摘要

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