Ink jet printing randomizing droplet placement apparatus

DETAILED DESCRIPTION The present invention resides in an ink jet printing apparatus for controlling the flight path of an ink drop ejected from an ink jet printing head.
The printing head is operated in response to control means to selectively apply or not apply dots to a number of dot positions located sequentially along a line scanned by the printing head.
In accordance with the present invention, the flight paths of ink drops ejected from a printing head are vertically randomized to print dots at positions randomly deviated vertically with respect to a line scanned by the printing head.
In one embodiment of the invention, means electrostatically charge an ink drop ejected from a printing head and the drop is deflected as it passes through an electric field which is created between deflection plates.
A variable amplitude control means is coupled to a deflection voltage source means to produce a randomly varying intensity bipolar electric field in a vertical direction perpendicular to the line of flight to randomly deflect the ink drop flight path in a first and opposite direction respectively with respect to a line scanned by the printing head.