Abstract: An improved image registration system for a multicolor inkjet printer/plotter. The inventive system comprises a carriage assembly for retaining multiple inkjet cartridges. Each cartridge has a plurality of nozzles adapted to eject ink in response to the application of an electrical signal thereto. A first mechanism is provided for moving said carriage assembly means in a first axis. A second mechanism is provided for moving print media in a second axis transverse to the first axis, said first axis being a scan axis and said second axis being a media axis. A first position encoder senses the position of the carriage assembly in the first axis and a second position encoder senses the carriage assembly in the second axis and providing position encoder signals in response thereto. A control circuit provides electrical signals which cause the nozzles in the inkjet cartridges to eject ink onto the media and create an image thereon in response to timing signals.

Abstract: A test pattern for use with an optical sensor for an inkjet printer. The inventive pattern comprises a first plurality of vertical bars horizontally spaced and a second plurality of horizontal bars vertically spaced. The spacing between the bars is approximately equal to the width of the bars. In a particular implementation, the pattern is adapted for use with an inkjet printer having a plurality of pens. The first plurality of bars includes a first set of bars printed by each of the pens. The first plurality of bars includes a second set of bars printed by one of the pens moving at at least two different horizontal speeds. The second plurality of bars includes one column of vertically spaced bars for each of the pens. Each column of vertically spaced bars includes a first plurality of vertically spaced bars printed by a first pen. A respective column of vertically spaced bars includes a second plurality of vertically spaced bars printed by a respective one of the pens.

Abstract: A system for correcting for a time of flight delay of a drop of ink from an inkjet printhead. The inventive system includes a first mechanism for scanning the printhead along a first axis at a first velocity. A control circuit, responsive to inkjet timing signals, causes the printhead to eject ink onto a media to create a test pattern thereon as the printhead is scanned along the first axis. A sensor optically sense the test pattern and provides a time of flight dependent phase signal in response thereto. This signal is processed to provide time of flight delay corrected inkjet timing signals for the first velocity in response to the phase signal. In a particular implementation, the processor is adapted to add an additional delay to the corrected timing signals to correct for curvature.

Abstract: A phase plate adapted for use with an optical sensor module for an inkjet printer/plotter equipped with a photodetector to sense a test pattern having a plurality of horizontally spaced bars or vertically spaced bars and a photodetector. The inventive phase plate is in optical alignment with the photodetector and is constructed of opaque material. The phase plate includes a plurality of apertures horizontally spaced therein. The spacing between the apertures is equal to the spacing between the horizontally spaced bars in said test pattern. In the alternative, the plate may include a plurality of apertures vertically spaced therein. In this case, the spacing between the apertures is equal to the spacing between the vertically spaced bars in the test pattern. In a particular implementation, the phase plate includes both horizontally spaced apertures and vertically spaced apertures.

Abstract: Apparatus and techniques are disclosed for aligning the operation of the ink jet printheads of a multiple printhead ink jet swath printer, and particularly for aligning the operation of the printheads along the carriage scan axis. The relative positions of vertical test line segments printed by the cartridges at a fixed swath position are determined with an optical sensor. The relative position information is utilized to calculate horizontal alignment corrections for the printhead cartridges which are utilized to adjust the horizontal offset shifts provided for the swath data and to adjust the timing of the firing of the ink jet nozzles of the printhead cartridges.

Abstract: Apparatus for determining inter-pen offsets in a multiple pen ink jet printer including a drop detector for measuring flight time of ink drops, an aperture plate disposed in the print media plane, and a carriage position sensor for determining carriage position when ink drop flight time exceeds a predetermined value, which indicates that an ink jet is at the edge of the aperture plate. The sensed carriage positions for the respective pens provides information indicative of inter-pen offset in the scan axis direction. In a further embodiment of the invention, the aperture plate can have a stair-shaped boundary to facilitate the calibration of a plurality of nozzles in one scan. For determination of inter-pen offset in the media scan direction, the aperture includes a comb-like boundary that is utilized to produce detect/no detect pattern for a nozzle array in each of the pens, whereby the pattern for each of the pens provides information indicative of the offset between pens.

Abstract: Apparatus for determining inter-pen offsets in a multiple pen ink jet printer including a drop detector for measuring flight time of ink drops, an aperture plate disposed in the print media plane, and a carriage position sensor for determining carriage position when ink drop flight time exceeds a predetermined value, which indicates that an ink jet is at the edge of the aperture plate. The sensed carriage positions for the respective pens provides information indicative of inter-pen offset in the scan axis direction. In a further embodiment of the invention, the aperture plate can have a stair-shaped boundary to facilitate the calibration of a plurality of nozzles in one scan. For determination of inter-pen offset in the media scan direction, the aperture includes a comb-like boundary that is utilized to produce the detect/no detect pattern for a nozzle array in each of the pens, whereby the pattern for each of the pens provides information indicative of the offset between pens.