Importance

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Abstract

An optical retro-reflective apparatus for application to reconfigurable displays for highway signs and other applications is disclosed. In a first preferred embodiment, the apparatus includes a retro-reflector such as a corner cube prism, three orthogonally arranged planer reflectors, or a plurality of either arranged as an array, or an array of micro-spheres or micro-prisms arranged as a corner-cube. In one embodiment, a holographic diffraction element is placed between a source of radiation such as visible light and one or more of the retro-reflectors. The diffraction element is made up of one or more stacked holographic devices in which pre-determined holographs are stored, operative to diffract a particular wavelength band of radiation (e.g. red, blue and green visible light). The hologram devices can be stacked and selectively deactivated so that the desired wavelength band (or color) to be diffracted is selected. In this way, the retro-reflective apparatus can be made to reflect or re-transmit light of a certain color. In a second embodiment, the retro-reflectors are arranged orthogonally and include the diffraction elements. The diffraction elements for each retro-reflector are programmed to diffract (and therefore reflect) a different wavelength band of light. Thus, only the retro-reflector that is in an active state will reflect (by diffraction) a portion of the incident radiation, and that portion is preferably red, green or blue visible light.

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First Claim