Patent ID: 7320538

Claim:
An optical device comprising: a light source and an optical film having a first surface disposed to receive light from the light source and a structured surface facing away from the light source, the structured surface comprising a plurality of concave pyramid-shaped structures, each structure having a base including at least two first sides and at least two second sides, wherein each of the plurality of concave pyramid-shaped structures comprises five substantially planar surfaces, four surfaces being attached to the base, each of the four surfaces positioned to angle in from the base toward the fifth surface, wherein the two first sides are disposed opposite to each other along a first general direction and the two second sides are disposed opposite to each other along a second general direction, wherein the optical film transmits a substantial portion of light incident thereon along the first general direction when an angle of incidence is within a first angle with respect to an axis disposed at an angle to the first surface and reflects a substantial portion of light when the angle of incidence is outside the first angle, and wherein the optical film transmits a substantial portion of light incident thereon along the second general direction when an angle of incidence is within a second angle with respect to the axis and reflects a substantial portion of light when the angle of incidence is outside the second angle.