Retroreflecting polarizer

Claim 1

A retroreflecting polarizer, comprising: (a) a first flexible material about 0.33 mm thick having a structured surface consisting of a linear array of isosceles prisms about 0.18 mm in height arranged side by side and having sides which make an angle in the range of 40° to 50° with respect to the tangent to a smooth surface opposite the structured surface, wherein the isosceles prisms are present at a frequency of about 28 per cm; (b) a second flexible material essentially like the first flexible material; (c) on the structured surface of at least one flexible material, at least one optical stack of alternating layers of high and low refractive index materials of selected optical thicknesses; the first and second flexible materials all optically cemented to form a single unit in which the refractive index of the first and second flexible materials, and the refractive indices and optical thickness of the layers of the optical stack, are all chosen to produce selective reflection of polarized light, and wherein the optical stack is configured to: (d) separate an incident light beam of mixed polarization having all wavelengths between about 400 and 700 nm into an s-polarized component and a p-polarized component; (e) reflect the s-polarized component onto another portion of the optical stack and there parallel to the incident beam but proceeding in an opposite direction; and (f) transmit the p-polarized component parallel to the incident beam.