JPS5474435A - Dot shift compensating device for ink jet printing - Google Patents

Abstract

PURPOSE:To prevent the undesired dot shift by adjusting the injection biasing timing of an ink jet head in accordance with the printing signal level so that the printing may be always accomplished at a reference point. CONSTITUTION:Numerals 31 to 33 indicate ink jet heads of ink-on-demand type. The output printing signals C, M and Y of an image processing unit 2 are analog signals, which have their levels varied in accordance with density or gradation, and have their signal levels converted into digital codes by analog-digital converters 51 to 53 so that they are fed to delay circuits 61 to 63 such as shift resistors. These delay circuits 61 to 63 are used to compensate the dot shift due to the positional differences of the ink jet heads 31 to 33. In case, more specifically, the heads are arranged in the scanning direction AR of the heads, the printing operations are accomplished at the points, where the respective color inks of cyan C, Magenta M and yellow Y are separated, if the heads 31 to 33 are simultaneously biased for printing, so that the color expression of mixing cannot be expected. The respective color inks can be printed at the same point if the printing timings of the heads 32 and 33 are delayed by td and 2td, respectively.