Patent ID: 7703931

Claim:
A linear retroreflector that retroreflects electromagnetic energy, comprising: a body of material, the body having a first surface and a second surface; a plurality of first linear prism structures on the first surface of the body, the first linear prism structures each having two facets that extend along planes that are substantially orthogonal to each other; and a plurality of second linear prism structures on the second surface of the body, the second linear prism structures each having two facets that lie along planes that are substantially orthogonal to each other; the body being constructed and arranged to be transparent to incident electromagnetic energy at a range of wavelengths and to have a thickness so that an incident electromagnetic energy ray that is incident at one of the first and second surfaces enters the body, and is redirected by both the first surface and the second surface so that both the first surface and the second surface contribute to retroreflection of the incident electromagnetic energy ray, and exits from the one of the first and second surfaces at which the incident electromagnetic energy ray was incident to emit a retroreflected electromagnetic energy ray of the incident electromagnetic energy ray, wherein the body is further constructed and arranged so that an incident electromagnetic energy ray that is incident at one of the first and second surfaces enters the body by refraction, exits the other of the first and second surfaces by refraction, reenters the other of the first and second surfaces by refraction, and exits from the one of the first and second surfaces at which the incident electromagnetic energy ray was incident to emit a retroreflected electromagnetic energy ray of the incident electromagnetic energy ray.