Hewlett-packard Development Company, L.p.

Hewlett-packard Company

Francesc Subirada

Carles Flotats

David Claramunt

Jose M Rio Doval

Rodrigo Ruiz

Xavier Soler

David Gaston

Marc Jansa

Francisco Guerrero

Joan Manuel Garcia

Francisco Javier Rodriguez

Fernando Juan

David Herbert Donovan

Miquel Boleda

Johan Maurice Lammens

Gonzalo Gaston

Jose Julio Doval

James A Mott

Oscar Martinez

Jose Luis Valero

Jorge Menendez

Jorge Castano

Pau Soler

Albert Serra

Santiago Reyero

Joaquim Veciana

Javier Lagares

Oscar Ciordia

Roger Vinas

Santiago Garcia Reyero

Marcelo Ymbern

Chris T Armijo

Joan Villoldo

Joan-Manel Garcia

Antoni Gil

Santiago Garcia Reyerp

A printer device comprising a mechanism adapted to generate an image on an image surface, the device comprising a sensor adapted to image a predetermined optical object located substantially on the image surface, the device being adapted to determine at least one dimension of the object's image and thereby determine the distance separating the mechanism and the image surface.

Media-position sensor system

CDE is measured for each nozzle array, to enable modification of a mapping between input image data and intended printing marks to compensate for the CDE. Printing proceeds using the modified mapping, which is either an optical-density transformation of data to printing marks or a spatial-resolution relation between image data and intended pixel grid. The density transformation preferably includes a dither mask (but can be error-diffusion thresholding instead); the resolution relation includes scaling of image data to pixel grid. For some invention forms, CDE includes printing-density defects, measured and used to derive a correction pattern&#x2014;in turn used to modify halftone thresholding. For other forms CDE includes swath-height error, but still this is measured and used to derive a correction pattern etc. For still other forms, however, CDE includes swath-height error and correction takes the form of scaling. When the halftoning forms are applied to plural-pass printing, a printmask is used to map the dither mask etc. to the nozzle array, enabling application of the correction to the mask. Halftone forms ideally uses a gamma function, though threshold or linear corrections are possible instead. Halftone correction is effective in single-pass printing. The swath-height correction can modify heights of all nozzle arrays. Computations are done at most only once for a full image.

Apparatus and method for mitigating colorant-deposition errors in incremental printing

A diagnostic technique allows an easy visual detection of poor media advance calibration. The diagnostic technique employs a print mode that prints different areas of the plot at different passes with a controlled amount of advances between them. The dot positioning error in the different areas has a non-systematic nozzle contribution, that tends to cancel out, and a systematic contribution due to the accumulative media advance error. Different patterns can be used to make the dot positioning error due to the accumulative media advance error show up. By increasing the number of media advances between the printing of sets of pixels, e.g. pixels in a horizontal line, the effect of accumulated errors and the apparent visual effect is increased.

Diagnostic for visual detection of media advance errors

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.

Method and apparatus for assessing nozzle health

A multicolor-printer has at least a first and a second print station, first and second optical sensors and a surface recordings comparator. The first and second print stations are arranged to print images on a surface of a moving recording medium. The first and second optical sensors view, at the first and second print stations, an area of the recording medium surface to obtain at least one first surface recording, in a manner related to the first print station's image printing, and second surface recordings, respectively. A storage is arranged to store the first surface recording. The surface recordings comparator is arranged to test, during the recording medium movement, for correspondence of second surface recordings with the stored first surface recording. The printer is arranged to repeatedly, within one image, register raster lines of the image of the second print station to corresponding raster lines of the image of the first print station in response to correspondences found between the first and second surface recordings.

Multicolor-printer and method of printing images

When condition of a printing element (e.g. inkjet nozzle) changes, essentially full mask rows invoking the element are redone from scratch, best so as to fully satisfy pixel-grid neighbor conditions. This is faster than redoing a whole mask as in prior popup or precook /reheat methods, and yields better printouts than prior row-by-row mask revision (e.g. directly replacing a weak nozzle by a good one across whole rows). This method is best independent of prior mask versions, and uses no prebuilt matrix of backup/alternate entries. The number of rows redone is typically 7% to 14% below a nominal/baseline value.

Progressive and fast printmask revision based on incremental changes to printing element condition

A method for image recognition. In the method, a section of an element is imaged while the element is at a first speed to obtain a first image pattern. The section of the element is also imaged while the element is at a second speed to obtain a second image pattern. The first speed differs from the second speed. In addition, the apparent speeds of the element in the first image pattern and the second image pattern are made to appear approximately the same.

Making the apparent speed of elements imaged at different speeds approximately the same for image recognition

A media-positioning sensor assembly in one embodiment of the invention is disclosed that includes a mechanism and a media-positioning sensor. The mechanism moves back and forth over media along a first axis. The media advances past the mechanism along a second axis perpendicular to the first axis. The media-positioning sensor is situated on the mechanism and is to detect positioning of the media relative to the mechanism along at least one of the first axis and the second axis.

Dual-axis media-positioning sensor

Techniques for calibrating a scanner mounted on a scanning carriage of an image forming device. In one embodiment, a method of calibrating an optical sensor of a color image forming device includes positioning a prefabricated optical sensor target at the service area of the image forming device, the target including a plurality of target patches of predetermined different colors, moving the carriage to the service area, acquiring one or more images of the plurality of target patches, and using the one or more images to perform a plurality of calibrations of the optical sensor. In another embodiment, a method of measuring a reference position of a carriage mounted sensor array for an image forming device includes moving the carriage to a service area, generating a light beam from a carriage-mounted light source at a position adjacent an end of a sensor array, the light beam at an acute angle relative to an array axis, reflecting the beam from a reference target mounted in the service area at a known position, acquiring an image of the reflected beam by the sensor array, and using the location of a high intensity area of the image to determine the reference position of the optical sensor.

Calibration and measurement techniques for printers

A method and apparatus is used to detect and compensate for printhead rotation in an inkjet printer. The detecting operation includes receiving an initial image of a pattern taken from a medium as the printhead passes over the medium, receiving a subsequent image of the pattern taken from the medium as the printhead continues to pass over the medium, comparing the initial image of the pattern and the subsequent image of the pattern taken from the medium and identifying a rotation of the printhead in the inkjet printer passing over the medium if the comparison indicates the initial image of the pattern is rotated relative to the subsequent image of the pattern. The compensation operation includes modifying the timing settings associated with the firing of the nozzles in the inkjet printhead to compensate for the rotation of the printhead.

Method and system for printhead rotation detection using photosensors

A sensor system for detecting skew in print media along the feed path of a hardcopy device is disclosed. In one embodiment of the invention the system is arranged to generate a first image of a portion of print media at a first position along the feed path and to generate a second image of the portion of print media at a second position along the feed path, the system is arranged to compare the first and second images and thereby detect a change in the angle of skew of the media between the first and second positions.

Media-position media sensor

To compensate for color-calibration sensor drift, a measurement of bare-print-medium tonal value is taken in immediate time juxtaposition to each color test pattern; measured bare-medium tone is then used to correct color-patch readings. A line sensor or the like, on the scanning printhead carriage, is used for the reading. Preferably two such readings are taken, one at each end of each test pattern; ideally separate scans of the bare medium are taken without any test-pattern patch to develop longterm and short-term drift profiles, for refining the corrections. To compensate for calibration error due to runout in the carriage track&#x2014;particularly for wide-bed printers&#x2014;sensor response to bare medium is used to represent variations in carriage-to-medium spacing along the track; these variations are corrected in later sensor use.

Compensating for drift and sensor proximity in a scanning sensor, in color calibrating incremental printers

A scan axis assembly for a printer comprises first and second tracks, the tracks being rigidly located relative to one another by one or more track support members, and each track being arranged to support a print carriage such that the print carriage may move along the track to traverse a print zone.

Scan axis assembly for a printer

By implementation of an optical scanner, the calibration of printheads of a printing mechanism may be performed in a relatively short period of time as compared to known techniques. In one respect, the time required to perform the calibration may be substantially reduced by virtue of the relatively wide field of view of the optical scanner. The relatively wide field of view generally enables for the scanning of test patterns to be performed with a relatively fewer number of scanning passes, thus reducing the time required to perform the scanning operations as well as the calibration operations. In addition, the scanning operations may yield relatively more accurate results as compared to known scanning operations. In one respect, optical scanners are capable of detecting smaller drops of ink on print media by virtue of their higher resolution capabilities. In another respect, all of the printed colors may be accurately detected through implementation of a red, green, blue (RGB) charge coupled device (CCD) contained in the optical scanners.

Method and system for calibrating ink ejection elements in an image forming device

A method of an embodiment of the invention is disclosed in which a linear imaging array captures a first one pixel-wide image of media, and the media is effectively advanced relative to the linear imaging array. The linear imaging array captures a second one pixel-wide image of the media, and the first and the second one pixel-wide images are compared to determine relative advancement of the media.

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Castellbisbal, Spain

Francesc Subirada