Prior to printing, ink drops are ejected from an ink ejection head or nozzle (28) and an amount of deflection is sweepingly varied until the ink drops hit a target (57), thereby providing a reference which compensates for variations in an amount of charge of the ink drops, a deflection voltage and an...http://www.google.com.au/patents/US4310846?utm_source=gb-gplus-sharePatent US4310846 - Deflection compensated ink ejection printing apparatus
