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Abstract

A printhead uses large and small drop ejectors to achieve efficient gray scale printing. The printhead is arranged with a close packed configuration of alternating large and small nozzles positioned to maximize coverage while minimizing the volume of ejected ink. The printhead may be operated in a single pass mode or dual pass mode. In the single pass mode, complete coverage is effected by rippling through the odd numbered jets first and then rippling through the even numbered jets. The position of the small spots from the even numbered jets can be adjusted to maximize coverage and counteract offset between nozzle centers. Printheads with different size nozzles can also be operated by a staggered firing method using dual passes to offset spots in the scan direction by shifting the printhead between passes or alternating between groups of large and small nozzles. Further improvements to image quality can be realized by shifting the spots in the direction perpendicular to the scanning direction by tilting the printhead or offsetting the nozzles with respect to the ink channels on the printhead.

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First Claim