A crossed light beam coordinate detection and encoding system having a plurality of emitter/detector pairs along each axis of the display space is disclosed. The emitters are modulated in amplitude and the detectors are biased with a low load resistance to provide a wide dynamic range. The wide dynamic...http://www.google.com.tw/patents/US4652741?utm_source=gb-gplus-share專利 US4652741 - Radiant beam coordinate detector
