Method and system for correcting media shift during identification of printhead roll

A method of operating a printer comprising:

• generating with an optical sensor in the printer image data corresponding to an array of marks formed a plurality of inkjets in the printhead on an image receiving member that moves in a process direction, the array of marks including a plurality of series of marks arranged in a cross-process direction on the image receiving member, each series of marks being arranged in the process direction on the image receiving member and being formed by one inkjet in the plurality of inkjets that each form a first mark in the corresponding series of marks at a different time;
• identifying a relationship between relative cross-process locations of successive marks in each series of marks in the plurality of series of marks in the image data with reference to predetermined times at which each mark in each series of marks in the plurality of series of marks was formed;
• and
• generating an estimate of a cross-process direction movement of the image receiving member over time with reference to the identified relationships between the marks in each series of marks in the plurality of series of marks in the image data.

An inkjet printer comprising:

• a media transport configured to move a media web through a print zone in a process direction;
• a printhead positioned in the print zone and having a plurality of inkjets configured to eject ink drops onto the media web;
• a plurality of optical detectors configured in a cross-process direction across the image receiving member, each optical detector in the plurality of optical detectors being configured to detect light reflected from the image receiving member;
• and
• a controller operatively connected to the printhead and the plurality of optical detectors, the controller being configured to:
• operate the plurality of inkjets in the printhead to form an array of marks on the media web, each inkjet in the plurality of inkjets forming one series of marks in the array of marks extending in the process direction and the array of marks including a plurality of series of marks extending in the cross-process direction, each inkjet in the plurality of inkjets commencing formation of a corresponding series of marks in the plurality of series of marks at a time that is different from a time at which at least one other inkjet commences formation of another one of the plurality of series of marks;
• generate image data corresponding to the array of marks with the plurality of optical detectors;
• identify a cross-process direction location of each mark in the array of marks with reference to the image data;
• identify a relationship between relative cross-process locations of successive marks in each series of marks in the plurality of series of marks in the image data with reference to predetermined times at which each mark in each series of marks was formed;
• generate an estimate of a cross-process direction movement of the media web over time with reference to the relationship for each series of marks in the plurality of series of marks in the image data;
• generate a corrected cross-process direction location for each of the series of marks in the array of marks with reference to the identified cross-process location of each mark and an estimated cross-process direction offset of the media web at a time at which each mark was formed with reference to the estimate of cross-process direction movement of the media web;
• identify with reference to the corrected cross-process direction location of each mark in the array of marks a cross-process direction distance between a first series of marks and at least one other series of marks;
• and
• identify a difference between an angular orientation of the printhead and the cross-process direction with reference to the identified cross-process direction distance.