One invention aspect forms a mask and matrix of corresponding backups for values in the mask, checks when a mask value is not working, and replaces only that value with only a matching matrix entry. A second matrix of further backups is best formed. Another aspect forms a mask as a matrix of stacks of matching entries for mask positions; selects an entry for each position from the matching matrix stack; and prints using the selected entry at each position. Another aspect forms a mask as a matrix of stacks of matching entries for mask positions, and rotates each stack to select an entry for each position. Another aspect forms a mask and a matrix of stacks of backups; finds nonworking mask values and replaces such values with backups from a matching stack. Another aspect forms a seminal mask, tiles it to make a larger one with related properties, and injects noise to disrupt tiling-caused regularity and form a less-regular mask.
RELATED PATENT DOCUMENTS
This application claims benefit of provisional appln. No. 60/219,315 filed Feb. 29, 2000.
A closely related document is another, coowned U.S. utility-patent application filed in the United States Patent and Trademark Office substantially contemporaneously with this document. It is in the name of Zapata, identified as Hewlett Packard Company and entitled "BANDING REDUCTION IN INCREMENTAL PRINTING, BY SPACING-APART OF SWATH EDGES AND BY RANDOMLY SELECTED PRINT-MEDIUM ADVANCE"--subsequently assigned utility-patent-application Ser. No. 09/516,816. That document, and other related documents cited or discussed in it, are hereby incorporated by reference in their entirety into this document.
Another related document also wholly incorporated by reference herein is another, coowned U.S. utility-patent application filed in the U.S. Patent and Trademark Office generally contemporaneously with this document in the name of Gil, and is pertinent for its introduction of printmode techniques that promote smoothness of printmasks and consequently of printed images. That document is identified as Hewlett Packard Company entitled "BANDING REDUCTION IN INCREMENTAL PRINTING, THROUGH USE OF COMPLEMENTARY WEIGHTS FOR COMPLEMENTARY PRINTHEAD REGIONS"--and subsequently given application Ser. No. 09/516,323.
A mask pattern is employed for multi-pass printing. The mask pattern is the sum of a first mask pattern, relative to a first location that includes areas wherein dots are to be printed when a density value is smaller than a predetermined value, and a second mask pattern, relative to a second location that includes areas wherein dots are to be printed only when the density value is equal to or greater than the predetermined value. Using multiple scans, up to one dot is printed in the first region, while two dots or more are printed in the second region. With this arrangement, since the first mask pattern, which greatly affects a low-duty image, and the second mask pattern, which greatly affects a high-duty image, can be independently designed, problems that occur with images prepared at individual duties can be coped with by the separate mask patterns.
A technique for assessing nozzle health of a printhead nozzle array in a printing system includes printing a swath portion of an image, optically scanning the printed swath portion to capture a scanned image, comparing an expected image of the swath portion of the image with the scanned image, and assessing whether any nozzles of the nozzle array have malfunctioned. A sensor can be mounted on a printhead carriage to accomplish the image capture.
The image recording apparatus comprises: a recording head including recording elements which record an image onto a recording medium; an abnormal recording element specification device which specifies an abnormal recording element from the recording elements of the recording head; a correction dot pattern setting device which sets a correction dot pattern for preventing an image abnormality due to the abnormal recording element; an image processing device which generates dot data by performing quantization processing on image data using the correction dot pattern set by the correction dot pattern setting device; and a drive device which drives the recording elements according to the dot data generated by the image processing device.
A printing system is linearized automatically using measurements made with a simple optical sensor, such as a line sensor, that is onboard the system. The printing system itself is for forming images on plural printing media. Because the optical sensor is not a calorimeter or even a true densitometer, the sensor requires calibration, preferably based upon measurements using real inks. In the past it has been considered a requirement that such calibration be performed separately using each of the print media that was to be used for printing images. Linearization according to the invention, however, refers to a single calibration of the sensor, that calibration being used in common for essentially all media--even though the single calibration is performed with respect to exclusively a single one of the plural media.
