The present invention relates to a device for the illumination of a passive display element.
Various constructions of the devices for the illumination of passive display elements of the type under consideration have been known in the art. German patent publication DE-OS No. 31 45 127 discloses the device in which the passive display element is illuminated by direct through light. Although the known device is efficient this device requires a sufficient room, particularly in the direction of the depth of the device due to the fact that glow lamps utilized in this known device require relatively large space. It is also disadvantageous in the known device that such structural components as control blocks, are arranged only at the small peripheral portion in the region of the display element. This means that a complex path of the wiring from the display device is required.
A further device for the illumination of the passive display element has been described in German patent publication DE-OS No. 3,117,783. The light guide system in this known device is, however, relatively voluminous. Although fairly flat display elements are realizable the photoconductors available on the market have still relatively large width. This is particularly disturbing when a number of display elements should be accommodated in a narrow space. Finally, U-shaped light guide systems have been proposed. In such systems light emanated by a glow lamp is coupled via both arms of the light guide system from both sides of the field of visibility. The disadvantage of this system is a large volume of the photoconductive system resulted from the U-shaped design and also a large depth of the construction.