An electrophotographic digital copier capable of identifying a particular color existing in a document image. The copier copies both of a bicolor document and a monocolor document in the same period of time. Even when monocolor documents and bicolor documents are to be copied together, the copier executes...http://www.google.de/patents/US5280362?utm_source=gb-gplus-sharePatent US5280362 - Digital copier for copying a bicolored document at the same speed as a monocolored document
