At the reception site of a laser transmission system the received laser light beam is converted into a focusing cone of light. The cone of light is directed to partially illuminate the inner area of the quad photo detector array which is used to provide a highly accurate positional measurement...http://www.google.fr/patents/US5790291?utm_source=gb-gplus-shareBrevet US5790291 - Beam steering and tracking of laser communication links by dual-quadrant tracker and photodiode assembly
Beam steering and tracking of laser communication links by dual-quadrant ...
