Patent ID: 7297393

Claim:
A multilayered optical film, comprising: a plurality of alternating layers of a first and second material, the material layers having refractive indices nx, ny associated respectively with orthogonal in-plane x and y axes parallel to a surface of the film, the material layers also having refractive indices nz associated with a z-axis perpendicular to the film plane; wherein adjoining layers of the first and second material form an interface, the first material layer being birefringent and having an index of refraction associated with at least one of the in-plane axes that is higher than the associated in-plane index of the second material layer; and wherein the refractive index nz of the first material layer is selected to be less than the refractive index nz of the second material layer, such that reflectivity of the interface for p-polarized light monotonically increases with angle of incidence.