There is provided an inexpensive light emitting display device which has a simple wiring structure and produces a bright screen display. A photo-transistor is connected in series with a light emitting diode. The photo-transistor is arranged so that light emitted from the light emitting diode enters into...http://www.google.co.uk/patents/US5546496?utm_source=gb-gplus-sharePatent US5546496 - Light emitting display device having light receiving element for receiving light from light emitting element and self-holding and optical passage for guiding drive light to the light receiving element
