Tonejet Limited

Robin Timothy Bacon

Andrew John Clippingdale

John Lawton Sharp

Ammar Lecheheb

Ewan Hendrik Conradie

Peter James Brown

Jesse David Woolaston

Ian Butler Philip Ingham

Andrew Clippingdale

The invention relates to a method of printing a two-dimensional bit-mapped image having a number of pixels per row, the printhead having a row of ejection channels and each ejection channel having associated ejection electrodes to which voltages are applied in use. During printing, in order to cause volumes of fluid to be ejected from selected ejection channels of the printhead for printing, voltage pulses having values of predetermined amplitude and duration as determined by respective image pixel bit values generated by a raster image processor are applied, at a given pulse period, to the electrodes of the selected ejection channels. The part of the raster image corresponding to an ejection channel is scanned to determine the number of adjacent non-printing pixel periods prior to a pixel to be printed and, immediately prior to the printing of said pixel, a voltage pulse, having a value predetermined in accordance with the time, measured in units of the given pixel period, between the last pixel to be printed and said pixel to be printed, is applied to the ejection electrode.

Printhead calibration and printing

A method of printing a two-dimensional bit-mapped image having a number of pixels per row for printing using a plurality of overlapping printheads or a printhead or printheads indexed through overlapping positions, the or each printhead having a row of ejection channels, each ejection channel having associated ejection electrodes, the method comprising: applying a voltage to the ejection channels sufficient to cause concentration of particles in the printing fluid at the ejection channels, applying voltage pulses of respective predetermined amplitude and/or duration, as determined by respective image pixel bit values, to the electrodes of the selected ejection channels in order to cause volumes of printing fluid to be ejected from selected ejection channels of the overlapping printheads, thereby forming a pixel of a predetermined optical density, adjusting, for each row of the image, the values of the voltage pulses to be applied to the overlapping printheads to form pixels printed by overlapped ejection channels in dependence on the position of the pixel within an overlapped region of the printheads and in dependence on the predetermined optical density of the pixel, wherein, for at least one pixel in the overlapped region, the total volume of ink ejected by the overlapped channels is greater than that required if that pixel were formed by a single ejection channel.

Printhead control

A method of calibrating a printhead, for printing two-dimensional bit-mapped images having a number of pixels per row, is disclosed for printheads () having a row of printing channels (). During printing, in order to cause volumes of charged particulate concentrations of one of a number of predetermined volume sizes to be ejected from selected ejection channels of the printhead to form printed pixels, control pulse values of respective predetermined amplitude and duration, as determined by respective image pixel bit values, are applied to the selected printing channels. The calibration method comprises providing an image () that causes each channel of the printhead to be driven with the same pulse value, and printing one or more test prints of the image. The pulse value for all channels is then varied () in a set of defined steps within the test print or between the test prints and the optical density of the test print or test prints measured () at positions arranged on a grid () to obtain data of print density and pulse value at positions across the printhead. A desired tone reproduction curve () is pre-selected for the print process represented by optical density versus image grey level. Then pulse values are calculated () from the measured test print or test prints that are estimated to produce the desired values of print density corresponding to selected values of image grey level and which may include non-printing pulse values, and the pulse value for each of said positions across the printhead for each of said image grey levels is recorded in memory ().

A method of printing a two-dimensional bit-mapped image having a number of pixels per row for printing is disclosed. The method and apparatus use either a plurality of overlapping printheads () or a printhead or plurality of printheads indexed through overlapping positions. The or each printhead has a row of ejection channels (), each of which has associated ejection electrodes to which a voltage is applied to cause particulate concentrations to be formed from within a body of printing fluid. In order to cause volumes of charged particulate concentrations of one of a number of predetermined volume sizes to be ejected as printed droplets from selected ejection channels of the overlapping printheads, voltage pulses (V) of respective predetermined amplitude and duration, as determined by respective image pixel bit values, are applied to the electrodes of the selected ejection channels. For each row of the image, the values of the voltage pulses to be applied to the overlapping printheads to form pixels printed by overlapped ejection channels are adjusted in dependence on the position of the pixel within an overlapped region of the printheads and in dependence on the predetermined volume size of the pixel.

An ink manifold for an inkjet printhead is provided, comprising a number of substantially parallel transverse channelsconnected by one or more connecting passages. The resistance to flow provided by the connecting passages is substantially greater than the resistance to flow along the length of a transverse channel. The ink manifold provided by the present invention ensures that the ink pressure and flow rate presented to the ejectors of the printhead is uniform along the entire length of the ejector array and, moreover, does so in a shallower manifold design than has previously been known.

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Royston, United Kingdom

Robin Timothy Bacon