Patent ID: 8872763

Claim:
A position detecting system comprising: a screen divided into an array of sectors; a light source that applies a light-pulse pattern on said screen, said light pulse pattern consisting of a start light-pulse simultaneously applied to all of said sectors followed by a timing light-pulse sequential applied to each sector, in turn, at known intervals; a pointing device having a photo-sensor and a signal-transmitter, said photo-sensor being pointable at said screen and being effective for detecting the application of light-pulses on said screen by said light source, said signal-transmitter being effective for transmitting a pulse-detection signal in response to said photo-sensor detecting the application of any light-pulse on said screen; a reception unit that receives the pulse-detection signals; and a control unit in communication with said reception unit and that determines a position on the screen based on a plurality of received pulse-detection signals, said control unit differentiating between a received pulse-detection signal that indicates the detection of an applied start light-pulse and a received pulse-detection signal that indicates the detection of an applied timing light-pulse, wherein the control unit determines a time span from detection of an applied start light-pulse to detection of an applied timing light-pulse, and determination of said position on the screen includes comparing said time span with said known intervals at which said timing light-pulses are applied in said light-pulse pattern.