Facsimile and static presentation processing – Static presentation processing – Data corruption – power interruption – or print prevention
Reexamination Certificate
1999-07-01
2001-04-10
Popovici, Dov (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Data corruption, power interruption, or print prevention
C358S001400
Reexamination Certificate
active
06215557
ABSTRACT:
FIELD OF THE INVENTION
The present invention is generally directed to detecting malfunctioning nozzles in an ink jet printer. More particularly, the invention is directed to a system for printing and evaluating a test pattern to determine whether a nozzle has malfunctioned.
BACKGROUND OF THE INVENTION
Ink jet printers form images on paper by ejecting ink droplets from an array of nozzles on a print head. During the operational lifetime of an ink jet print head, the nozzles can become clogged, thus blocking the ejection of ink from the nozzles. Although most current ink jet printers include mechanisms for clearing clogged nozzles, these mechanisms are not always successful, and nozzles remained clogged.
Generally, when printer driver software generates print data to be sent to the print head, the software typically assumes that all of the nozzles of the print head are functioning properly. Thus, the print data may address nozzles that are malfunctioning. If this is the case, pixels that should be printed by the malfunctioning nozzles will remain blank on the paper. The typical result is an unwanted horizontal strip of white space in a printed image. As more and more nozzles malfunction during a print head's lifetime, this situation becomes more and more noticeable in printed output.
Therefore, a system is needed for identifying malfunctioning ink jet nozzles and providing this information to a printer driver so that the printer driver can compensate for the malfunctioning nozzles when generating print data.
SUMMARY OF THE INVENTION
The foregoing and other needs are met by a system that identifies faulty ink jet nozzles among a plurality of ink jet nozzles in an ink jet print head based on evaluation of a test pattern printed by the print head. The printed test pattern consists of test images, where each of the test images is printed by a corresponding one of the plurality of ink jet nozzles. The test images occupy locations within the test pattern indicated by location coordinates. The test pattern is visually inspected to identify empty locations within the test pattern, where an empty location is a location in the test pattern not occupied by a test image. The empty locations are designated according to the location coordinates of the empty locations. The location coordinates of the empty locations are then correlated to ink jet nozzles that, if functioning properly, would have printed test images at the empty locations. The ink jet nozzles that, if functioning properly, would have printed test images at the empty locations are designated as faulty.
Preferred embodiments of the invention generate a faulty nozzle record indicating which nozzles are designated as faulty among the plurality of nozzles. The faulty nozzle record is accessed to determine which of the plurality of nozzles are designated as faulty. Based on the nozzles that are designated as faulty, the system generates print data to be sent to the print head. Based on the print data, only those nozzles which are not designated as faulty are activated in printing a desired image.
Thus, the present invention maintains the quality of print produced by an ink jet print head, even when nozzles on the print head have become clogged or have otherwise malfunctioned. Image pixels that would have been left blank due to the faulty nozzles are instead printed by other functioning nozzles. In this way, the invention compensates for the failed nozzles and prolongs the useable lifetime of the print head. When implemented with a print head cartridge containing a fixed amount of ink, the invention allows continued use of the print head until all of the ink is exhausted. When implemented with a print head supplied by a replenishable ink module, the invention allows use of the print head with no loss of print quality for substantially longer than was previously practical.
In another aspect, the invention provides an apparatus for identifying faulty ink jet nozzles. The apparatus includes an ink jet print head having a plurality of ink jet nozzles disposed adjacent a print medium. The print head prints test images at test image locations on the print medium by ejecting ink droplets from each of the nozzles separately and sequentially in response to the print commands. Each one of the test images is printed by and corresponds to a different one of the plurality of nozzles. The apparatus also includes a user input device for designating an empty location within the test pattern, where the empty location is one of the test image locations in the test pattern which is void of a test image. The apparatus further includes correlation means for correlating the empty location within the test pattern with one of the ink jet nozzles that, if functioning properly, would have printed a test image at the empty location. The correlation means also generate faulty nozzle identification information based on the correlation of the empty location to the failed nozzle.
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Hewlett-Packard Co., “Data Sheet for HP DesignJet CP Series Printers,”(Jun. 23, 1999).
Garcia Gabriel I.
Lambert D. Brent
Lexmark International Inc.
Neely, Esq. Andrew S.
Popovici Dov
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