Electric-photosensitive printing is accomplished with an LD providing a laser scanning beam that is modulated to affect printing, and the power output of the LED is maintained constant through negative feedback by a holding voltage provided by a capacitor having its charge determined only during a non-printing...http://www.google.fr/patents/US4908634?utm_source=gb-gplus-shareBrevet US4908634 - Laser power control for cut-paper printer
