Inkjet Nozzle Row Edge Density Control
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Solution Overview
Problem
Inkjet printers with closely spaced nozzle rows face image quality degradation due to positional deviations, leading to uneven density in image areas between heads, especially at the edges where lower dot generation rates result in lighter edges.
Innovation Solution
A fluid ejection device with multiple nozzle rows and a control system that uses a dither mask with varying threshold values to adjust dot generation rates, ensuring edge portions overlap to maintain consistent image quality by disabling specific nozzles and adjusting dot distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a dither mask with lower dot generation rate in edge areas is used for forming band images at edges, then overlapping between band images is improved, but edge portions of the image become lighter and image quality degrades
Solution Approach 1:
The patent applies local quality by differentiating the dot generation rate between edge areas and center areas of the dither mask. Specifically, the dither mask is designed with a first dot generation rate for edge areas and a second dot generation rate for center areas, where the second rate is higher than the first. This local differentiation ensures that edge portions maintain appropriate density while still achieving proper overlapping between band images.
2Productivity
If nozzle rows are arranged with extremely small spacing, then printing efficiency is improved, but positional deviation causes uneven density in image areas
Solution Approach 1:
The patent changes the parameter of dot generation rate in the dither mask to compensate for density unevenness caused by small nozzle spacing. By adjusting the dot generation rate differently in edge areas versus center areas, the system maintains density uniformity across the image even when nozzle rows are closely spaced, thereby preserving both printing efficiency and image quality.
Data Source
AI summary
A fluid ejection device includes first, second and third nozzle rows for forming first, second and third band images, respectively. The fluid ejection device forms an image in which an edge portion at one side in a prescribed direction in the first band image overlaps an edge portion at the other side in the second band image, and an edge portion at one side in the second band image overlaps an edge portion at the other side in the third band image. The fluid ejection device carries out a halftoning process whereby a center area of a dither mask equal in size to the input data for forming a band image but having a smaller dot generation rate in the edge areas than in the center area is associated with the input data for forming the edge portion to the other side of the first band image.