This invention relates to circuitry for non-impact printers that use light emitting diodes (LED's) to produce an image on a photoconductor and for controlling the output of each LED of a light emitting diode array that is part of the printer. A binary weighted duty cycle control is used to obtain substantial...http://www.google.se/patents/US4455562?utm_source=gb-gplus-sharePatent US4455562 - Control of a light emitting diode array
