Patent ID: 6392612
Filing Date: 2002-05-21
Classification: H04N

Abstract:
A projection display apparatus, comprising:a display device forming an image for projection to illuminate a display screen; a current source generating a current; a current sink adjacent said display screen and coupled to said current source for receiving said current; and, a detector coupled to said current source and said current sink for receiving said current and detecting a presence of said received current; wherein a first condition, absent illumination by said projected image on said current sink, said current from said source divides and is coupled to said detector in accordance with a first ratio, said detector assuming a first state indicative of said absence of illumination, and in a second condition in accordance with an intensity of illumination by said projected image on said current sink, said current from said current source is received by said current sink in accordance with a second ratio and said detector, absent said received current, assumes a second state indicative of illumination on said current sink.