Patent ID: 7942542

Claim:
A back-lit display structure comprising: a reflective surface, a light guide plate which receives light at an edge and guides it laterally through said light guide plate, said light guide plate having a multiplicity of light directing surface irregularities causing light to be directed transversely to said light guide plate, said surface irregularities being dimensioned and spaced apart in a manner to minimize non-uniformity in light intensity from different areas of said light guide plate, a plurality of light emitting diodes arranged to transmit light into at least one edge of said light guide plate, a transparent flat window on the front of said structure, the back of said window providing a fixed location for an image sheet, the window being placed at a space from said surface irregularities greater than the maximal distance between adjacent ones of said surface irregularities, paths through said space being transparent, a frame element holding the components of said structure in place, and removable fasteners for said window facilitating separation thereof to access said image sheet.