Hewlett-packard Company

Hewlett-packard Development Company, L.p.

Javier Lagares

Gonzalo Gaston

Shailendra Kumar

Francesc Subirada

Josep Maria Serra

Francisco Guerrero

Joan Manuel Garcia

Juan Carles Vives

Chris T Armijo

Antoni Gil

A program creates a unitary mask for use over a whole image, with one pattern. The mask need not be full image size; it may be tiled. In the field a printer forms a mask and prints with it, best in the same session, before another image needing another mask, whether due to different image activity or type, or operating conditions. Constraints are controlled to ensure solution. Printout can start before a mask (even the part needed to finish a top swath) is done, going columnwise in each swath. In other invention facets, a program forms a mask of size significant relative to the program and prints with it. Other facets check print conditions and form adapted masks; or find nozzles that cannot back up a known-failed nozzle and to back it up form masks with all able nozzles; or assess image activity and inject mask randomness accordingly.

Masks on demand for use in incremental printing

A nozzle detection test pattern has been developed which can be sensed by an optical sensor located on an inkjet printer carriage. By having the same nozzle print ink drops on multiple pixels to form a single thickened test line during multiple passes of the printhead, it is possible to thereafter scan across such test line and automatically determine by the light contrast ratios which nozzles are not firing properly. A green light LED is used to illuminate the magenta, cyan and black test patterns as they are being sensed, and a blue light LED is used to illuminate the yellow test pattern as it is being sensed. A separate test pattern is used for each printhead ink color. The test pattern constitutes six rows with forty test lines on each row for a printhead having 240 active nozzles.

Detection of non-firing printhead nozzles by optical scanning of a test pattern

Described is a dynamic multi-pass print mode correction method which corrects for malfunctioning or inoperable ink ejection elements by substituting a fully functioning ink ejection element. The method comprises the steps of obtaining a printmask; identifying ink ejection elements which are malfunctioning; ascertaining potential replacement ink ejection elements from the printmask for the ejection elements which are malfunctioning; selecting replacement ink ejection elements from the potential replacement ink ejection elements; and modifying the printmask by removing the malfunctioning ink ejection elements from the printmask and replacing them with the selected replacement ink ejection elements.

Dynamic multi-pass print mode corrections to compensate for malfunctioning inkjet nozzles

Growing community of inventors

Castellv de la Marca, Spain

Javier Lagares