US Patent 7556338 Jetting timing determining method and liquid-droplet jetting method

Combinations of delay times in jetting timings, for a predetermined number of nozzle groups selected from a plurality of nozzle groups, are set; and jetting speeds at each of the delay-time combinations are measured. Next, a variation in jetting speeds when the ink is jetted from the plurality of nozzle groups is estimated from the jetting speeds measured for each of the predetermined number of nozzle groups. Further, a combination of the delay times in the jetting timings is determined such that the estimated variation in the jetting speeds is smaller than a predetermined threshold value. Accordingly, it is possible to determine a combination of delay times in the jetting timings such that a variation in discharge characteristics when the ink is jetted concurrently from the plurality of nozzles is small, thereby improving the reproducibility of image.