In case of reading a black-and-white original, the LEDs of R (red), G (green) and B (blue) colors are maintained at turn-on duty ratios same as those at the color image reading, and are turned on simultaneously or in succession, with the turn-on period reduced to , whereby the forward current of each...http://www.google.es/patents/US6456748?utm_source=gb-gplus-sharePatente US6456748 - Image reading system
