Patent ID: 8002482

Claim:
A transparent screen, comprising: a Fresnel optical element in which a first plurality of Fresnel prisms each including a refractive surface for refracting a light ray applied thereto from a light emitting body and a reflecting surface for reflecting the light ray refracted by said refractive surface are arranged in a sawtooth shape along a surface of the Fresnel optical element; a second plurality of Fresnel prisms each of which is smaller than said first plurality of Fresnel prisms and has a shape approximately similar to each of said first plurality of Fresnel prisms arranged in a sawtooth shape on a non-light incidence portion of the surface of said Fresnel optical element, a light ray applied from said light emitting body being blocked from being applied to the second plurality by a Fresnel prism of the first plurality, wherein the second plurality of Fresnel prisms arranged on the non-light incidence surface portion of the Fresnel optical element receives control signal light applied thereto from remote operation equipment, and emits said control signal light toward a photo detector.