Alignment system for multiple color pen cartridges

摘要

A multiple printhead cartridge color thermal ink jet printer having apparatus for measuring the offsets between the multiple printhead cartridges (C1, C2, C3, C4) each of which includes a nozzle array of one or more columns of nozzles, each column being parallel to the media axis of the printer. The cartridges are individually operated, stationarily and while scanning, to fire drops at an aperture plate (125) interposed between an optical drop detector (200) and the nozzle arrays of the printhead cartridges. The detection of drops passing through the aperture plate and the non-detection of drops blocked by the aperture plate provide information which is utilized in conjunction with the nature of the operation of the cartridges that produced the detected drops to determine the positions of the nozzle arrays of the cartridges relative to each other. The optical drop detector includes optical light benders (119) that advantageously positions the optical detection zones (134) of the optical detector closer to the aperture plate, which allows higher drop fire rates to be utilized for offset determination.