A multi-color image forming apparatus forming an image of a plurality of colors in one processing by using a plurality of laser beams and a plurality of developing devices, in the case where any of the laser beams becomes unusable during forming a mono-color image, makes the image data to have been outputted...http://www.google.es/patents/US5179392?utm_source=gb-gplus-sharePatente US5179392 - Multi-color image forming apparatus
