Patent ID: 6353489
Filing Date: 2002-03-05
Classification: E01F,G02B

Abstract:
An optical retro-reflection apparatus comprising:a retro-reflector operative to receive radiation incident thereon and to reflect and/or re-emit the received radiation from said device in a direction parallel to its direction of incidence; one or more holographic diffraction elements, each having one or more holographic devices, each of the devices operative to diffract a predetermined wavelength band of radiation incident on said apparatus and switchable between an active, diffracting state and an inactive, non-diffracting state; a control circuit couple to each of the devices of each of said one or more diffraction elements, said control circuit operative to switch said holographic devices between their active and inactive states; and wherein the radiation reflected or re-emitted by said retro-reflector is the radiation diffracted by said diffraction device.