Exceeding the surface settling limit in acoustic ink printing

A method of ejecting ink droplets from an acoustic ink ejector assembly having a supply of liquid ink with a free ink surface, an acoustic ink droplet ejector, acoustically linked to the supply of liquid ink, a rf power source coupled to the acoustic droplet ejector, and a controller in operational connection with the rf power source, the method comprising the steps of:

• providing image data to the controller;
• choosing a threshold density of drops;
• processing the image data to determine the firing pattern, such that an ejector is not fired on subsequent time cycles until the density exceeds threshold;
• generating, by the controller, control signals in accordance with the firing pattern;
• supplying the control signals to the rf power source;
• exciting the droplet ejector to radiate the free ink surface with substantially focussed acoustic power pulses, in accordance with the control signals supplied to the rf power source;
• and
• ejecting individual droplets of ink from the free ink surface in accordance with the filler pattern, wherein the filler pattern includes data representing a desired sequence of the ink droplet ejection.

An acoustic ink printer including a printhead having a supply of liquid ink with a free surface;

• an acoustic ink cavity containing the ink, with one end of the cavity being defined by the free ink surface;
• a droplet ejector acoustically coupled to the ink;
• and a rf power source coupled to the droplet ejector for exciting the droplet ejector to radiate the free ink surface with substantially focused acoustic power pulses, whereby individual droplets of ink are ejected from the free ink surface on command at a controlled ejection velocity, the acoustic ink printer comprising:
• a controller in operational connection with the rf power source, the controller generating and issuing control signals to the rf power source to cause the rf signal source to excite the acoustic ink droplet ejector such that individual droplets are selectively ejected;
• and
• a filler pattern used by the controller to determine when the control signals are to be issued to the rf power source, the control signals determining an order in which droplets are to be ejected from the ejector.