Patent ID: 9738089
Date: 2017-08-22
CPC Classifications: B41J

Claim:
1. A liquid ejection apparatus comprising: a conveying mechanism configured to convey a recording medium in a conveying direction; a liquid ejection head having an ejection surface on which a plurality of nozzle arrays is arranged in the conveying direction, each of the plurality of nozzle arrays having a plurality of nozzles arranged in a direction perpendicular to the conveying direction, each of the plurality of nozzles for ejecting a liquid droplet on the recording medium conveyed by the conveying mechanism, a conveyance section being defined between a position at which a leading end of the recording medium reaches an ejection region and a position at which a trailing end of the recording medium has passed through the ejection region, the ejection region being a region in which at least part of the recording medium faces at least one nozzle on the ejection surface, the conveyance section being divided into a first divisional section in which the recording medium is conveyed a first conveyance amount per unit time and a second divisional section in which the recording medium is conveyed a second conveyance amount per unit time; and a controller configured to: correct image data to generate corrected image data, the image data including a plurality of dot data rows, each of the plurality of dot data rows having a plurality of dot elements that is arranged in a data array direction, the plurality of dot elements corresponding to a plurality of dots to be formed and arranged in the conveying direction on the recording medium, the plurality of dot elements and the plurality of dots having a one-to-one correspondence, an order of each of the dot elements in the data array direction being the same as an order of a corresponding one dot of the plurality of dots to be formed on the recording medium in the conveying direction, a density value being set for each of the plurality of dot elements; and control the liquid ejection head to record dots on the recording medium on a basis of the corrected image data such that liquid droplets are ejected from nozzles of the liquid ejection head on an assumption that the recording medium is conveyed a predetermined conveyance amount per unit time during a period of time in which the recording medium is conveyed within a conveyance section, the predetermined conveyance amount being equal to the first conveyance amount, wherein the controller is configured to generate the corrected image data by: setting, as a to-be-corrected dot element, a dot element corresponding to a dot to be formed on the recording medium during a period of time in which the recording medium is conveyed in the second divisional section, from among the plurality of dot elements included in each of the plurality of dot data rows; acquiring a correction amount for the to-be-corrected dot element, the correction amount being based on an offset in the conveying direction between: a formation position at which a dot corresponding to the to-be-corrected dot element is to be formed on the recording medium during the period of time in which the recording medium is conveyed the second conveyance amount per unit time; and a formation position at which a dot corresponding to the to-be-corrected dot element is to be formed on the recording medium during the period of time in which the recording medium is conveyed a reference conveyance amount per unit time; and executing correction on the to-be-corrected dot element by setting the density value that is set for the to-be-corrected dot element as a density value for a corresponding one dot element in the corrected image data, an order in the data array direction of the corresponding one dot element of the corrected image data being shifted from an order in the data array direction of the to-be-corrected dot element of the image data by a number of dot elements corresponding to the correction amount.