A test pattern is printed and thereafter scanned with a carriage-mounted optical sensor in order to automatically calibrate relative location and alignment between the separate printheads such as CYMK printheads in both the X-axis (media advance) and the Y-axis (carriage scan). To improve the precision...http://www.google.de/patents/US6390587?utm_source=gb-gplus-sharePatent US6390587 - Calibration system and method scanning repeated subsets of print test patterns having common color reference markings
