JPS54123034A - Ink jet printer - Google Patents

Abstract

PURPOSE:To make it possible to extend the range of density gradation by providing a plurality of printing heads having different printing density characteristics such that they are selectively biased in accordance with the density gradation. CONSTITUTION:If the level of image signals is lower than a preset value of a level detecting circuit 5, a selecting circuit 6 is operated in response to the output of the circuit 5 to select a drive circuit 22. Then, the image signals pulsating are fed to the circuit 22 and are converted into high voltage pulses, which are fed to an ink jet head 12. The aforementioned head 12 responds even to a relatively low level, because it has a small injection diameter, to inject ink droplets of a small diameter. When the level of the image signals exceed the preset value, a drive circuit 21 is selected by the circuits 5 and 6 so that the high voltage pulses are fed to an ink head 11 of a larger injection diameter. As a result, it is possible to obtain a densitity gradation of wide range. In the case of the same color of the same density, on the other hand, the same effects can be obtained for multiple colors.