Linear lamp holographic trapped beam center high mounted stoplight

Claim 1

A holographic stoplight for a vehicle having a rear window, comprising: a hologram mounted adjacent said rear window for diffracting playback illumination to produce a holographic stoplight image visible from behind the vehicle; a light source for providing playback illumination, said source comprising a gas-filled lamp tube excited by electrical energy, wherein said playback illumination enters said light guiding means through an input aperture, and said light guiding means comprises an optical light guide and means for trapping said playback illumination through total internal reflection at air/light guilde interfaces, except light which is diffracted by said hologram into the ambient, wherein said optical light guide comprises a solid member of transparent material characterized by planar surfaces, and said hologram is affixed adjacent a first one of said surfaces; an optical concentrator for collecting and collimating light generated by said light source to within a predetermined angular range; light guiding means for guiding the collected and collimated light from said concerntrator to said hologram; and wherein the efficiency of said hologram is graded, so that the hologram has a lower efficiency adjacent the Unput aperture than the hologram efficiency at a distance remote from said input aperture and further wherein the light source and the concentrator provide a substantially uniform illumination over the surface area of said hologram;