Hewlett-packard Company

Stephen King Glass

Mark S Hickman

Majid Azmoon

Donald G Harris

Nicholas Nicoloff, Jr

A printer including apparatus for reducing systematic print quality defects includes, in one embodiment, a printhead with variably spaced nozzles and, in another embodiment, a controller which varies the location along the carriage scan axis that ink is ejected from the nozzles.

Ink jet printer having apparatus for reducing systematic print quality defects

At least two different printmasks are used for different printing devices--such as inkjet pens--that operate concurrently, or different printing steps that proceed concurrently, to produce respective image swaths in a single, pixel-based printing machine. In one form of the invention, the different printing devices produce different respective pixel-row pitches (related to resolution) on a printing medium, and the different printmasks help to minimize adverse patterning effects that result from interaction of the different pitches with dot-placement errors. The different pitches on the print medium may be provided through different pitches of marking devices (for example, the number of inkjet nozzles per unit distance along a pen) or in other ways. In another form of the invention the different printing devices are provided with different respective liquid-base colorants, to mark in different colors on a printing medium, and the different masks facilitate physical separation of the different colorants to promote drying. Earlier-applied colorants have more time to dry and penetrate before later adjacent or superposed application of other colorants improving print attributes such as bleed, offset, cockle, curl, overall drying time and throughput.

Resolution-dependent and color-dependent print masking

At least two different printmasks are used for different printing devices--such as inkjet pens--that operate concurrently, or different printing steps that proceed concurrently, to produce respective image swaths in a single, pixel-based printing machine. In one form of the invention, the different printing devices produce different respective pixel-row pitches (related to resolution) on a printing medium, and the different printmasks help to minimize adverse patterning effects that result from interaction of the different pitches with dot-placement errors. The different pitches on the print medium may be provided through different pitches of marking devices (for example, the number of inkjet nozzles per unit distance along a pen) or in other ways. In another form of the invention the different printing devices are provided with different respective liquid-base colorants, to mark in different colors on a printing medium, and the different masks facilitate physical separation of the different colorants to promote drying. Earlier-applied colorants have more time to dry and penetrate before later adjacent or superposed application of other colorants.

The present invention improves the quality of halftone graphics patterns which convey shades of gray using dots. In the preferred embodiment, an initial low resolution graphics pattern is translated into a higher resolution graphics pattern by printing a variable number of high resolution dots for each dot in the low resolution graphics pattern. The number of high resolution dots printed for each initial low resolution dot is dependent upon the density of dots in the low resolution pattern. In another embodiment, the size of each dot printed, rather than the number of dots, is varied depending upon the density of dots in the low resolution pattern. When the dot density increases to where the low resolution pattern appears to be part of a text pattern, a different set of enhancement rules are then applied to correct the text pattern. Using the above method, an enhanced high resolution graphics pattern may be produced from a lower resolution graphics pattern without objectionable clumping of dots, thus producing a more homogenous and pleasing graphics pattern.

Growing community of inventors

San Diego, CA, United States of America

Stephen King Glass