Patent ID: 7854488
Filing Date: 2010-12-21
Classification: B41J

Abstract:
1. A dot measurement method of measuring at least one of a diameter of dots and an ejection volume of droplets of liquid ejected through nozzles arranged in a liquid ejection head, the ejected droplets being deposited on an ejection receiving medium to form the dots on the ejection receiving medium, the method comprising: a line pattern forming step of forming line patterns on the ejection receiving medium by ejecting and depositing the droplets on the ejection receiving medium through the nozzles while the liquid ejection head and the ejection receiving medium are being moved relatively to each other, each of the line patterns being parallel with a line direction and constituted of a row of the dots corresponding to one of the nozzles; a pattern reading step of capturing an image of the line patterns by means of an imaging apparatus including photoreceptors to acquire electronic image data representing the image of the line patterns, the photoreceptors of the imaging apparatus being aligned in a row that obliquely intersects with the line direction of the line patterns at a prescribed angle, the electronic image data being constituted of a plurality of pixels arranged in a two-dimensional lattice of which a lattice direction obliquely intersects with the line direction of the line patterns; a profile graph acquiring step of acquiring a plurality of profile graphs for each of the line patterns from the electronic image data, each of the profile graphs representing variations in an image signal value on a one-dimensional pixel row including pixels of the plurality of pixels aligned in a one-dimensional row, the one-dimensional pixel row being parallel with the lattice direction that obliquely intersects with the line direction of the line patterns; a characteristic position calculating step of calculating extreme value positions, first edge positions and second edge positions for each of the line patterns in accordance with the plurality of profile graphs acquired for said each of the line patterns, the extreme value positions indicating density centers of said each of the line patterns, the first edge positions indicating left-hand edges of said each of the line patterns, the second edge positions indicating right-hand edges of said each of the line patterns; an approximation line calculating step of calculating a line-center approximation line, a first edge approximation line and a second edge approximation line for each of the line patterns by applying a least-square method on the extreme value positions, the first edge positions and the second edge positions calculated for each of the line patterns in the characteristic position calculating step, the line-center approximation line corresponding to the extreme value positions, the first edge approximation line corresponding to the first edge positions, the second edge approximation line corresponding to the second edge positions; a deposition position calculating step of calculating positions of the dots deposited on the ejection receiving medium in accordance with a perpendicular distance between two of the line-center approximation lines corresponding to adjacent two of the line patterns; a line width calculating step of calculating a line width of each of the line patterns by calculating a perpendicular distance between the first edge approximation line and the second edge approximation line corresponding to said each of the line patterns; a correlation information acquiring step of beforehand acquiring at least one of a first relationship between the line width of the line pattern and the diameter of the dots on the ejection receiving medium, and a second relationship between the line width of the line pattern and the ejection volume of the droplets, the at least one of the first and second relationships being acquired beforehand for a combination of the liquid and the ejection receiving medium; and a measurement value calculating step of calculating at least one of the diameter of the dots and the ejection volume of the droplets of the liquid in accordance with the line width of each of the line patterns acquired in the line width calculation step and the at least one of the first and second relationships acquired in the correlation information acquiring step.