Hewlett-packard Company

Otto K Sievert

Gregory D Nelson

Robert D Blanton

Patrick J Brennan

Joseph P Milkovits

Nonoptical properties of inks can be brought to bear in locating ink that is invisible to an automatic sensor. Physical characteristics of inks as liquids can be exploited to reveal their locations with surprising precision. The system includes an optical sensor. Using ink that is visible to the sensor, a preferably fractional fill pattern is printed on a region of a printing medium. Using ink that is invisible to the sensor, calibration indicia or other patterns are printed on particular portions of the same region. Bleed (running together of the liquids of the two inks) tends to convert the fractional fill pattern into a solid fill, within the particular portions that were also printed with the 'invisible' ink. Resulting optoelectronic signals provide amply high contrast between (1) fractional fill in the particular portions where the 'invisible' ink is applied and (2) the original fractional fill elsewhere. The sensor responds to areas where bleed has converted the fractional fill pattern into a relatively more solid fill. Preferably, to enhance contrast, the visible-ink fractional pattern is printed as aggregations of multiple adjacent pixels, rather than individual, mutually separated pixels--but these aggregations are spaced apart. These two preferences together lead to a pattern that bleeds most effectively of any that were tested. Ideal fill density is roughly twenty-five percent.

Systems and method for determining presence of inks that are invisible

A full color copier having an inkjet printer includes a controller and algorithm for switching automatically intra page between one of two independent high speed carriage velocities and between one of two independent pen firing frequencies for maximize throughput relative to low ink density and high ink density graphic images to improve print quality images having densely inked areas by substantially reducing ink pen starvation, droplet trajectory errors, and fuzzy text edges.

Copier having full color high speed inkjet printer with two intra page

The invention is a system for determining positional deviation of at least one automatic marking implement from a nominal position, and an apparatus and method for establishing positional accuracy of such an implement. Calibration patterns including diagonal indicia are formed along only one dimension of a printing medium by the implement, or implements. Preferably a sensor automatically scans the diagonal pattern along one dimension, ideally the same dimension--without operating in a second, orthogonal direction. Nevertheless scanning of the diagonal indicia enables development of composite information about deviations in both directions. There is no necessity of either forming or sensing any pattern that is extended (by more than one marking-implement swath) in two different directions. The composite information is combined with information about deviations along the same scanning direction exclusively, to extract in isolated form the deviation information for the second, orthogonal direction. The invention is particularly useful in determining deviations from nominal offsets between plural marking implements, such as thermal-inkjet pens holding ink of different colors in a computer-controlled printer.

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Encinitas, CA, United States of America

Otto K Sievert