Dither Mask Generation for Inkjet Printers
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Solution Overview
Problem
Conventional dither mask generation methods for inkjet printers result in poor dot dispersibility and graininess, especially at low recording duties, leading to banding and density irregularities due to restricted nozzle ejection rate control and dot distribution distortions.
Innovation Solution
A dither mask generation method that determines and reflects nozzle ejection rates for each nozzle, allowing for optimal threshold setting and dot arrangement to achieve target nozzle ejection rates, independent of recording duty, by incorporating nozzle ejection rate determination, corresponding nozzle specification, and threshold setting processes, along with gradation conversion and low-pass filtering to improve dot dispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dot suppression threshold is applied to specific pixels to control nozzle ejection rate, then banding is suppressed, but dot distribution becomes distorted and dispersibility deteriorates
Solution Approach 1:
The patent applies different threshold values to different pixel positions in the dither mask. Specifically, pixels corresponding to nozzles at both ends of the nozzle array are assigned higher thresholds (dot suppression) compared to intermediate pixels, creating local quality differences that control nozzle ejection rates while maintaining overall dot distribution quality
Solution Approach 2:
The patent performs preliminary determination of nozzle ejection rates and corresponding pixel identification before threshold setting. This preliminary action allows the system to pre-identify which pixels require threshold adjustment and calculate appropriate threshold values in advance, ensuring both banding suppression and dot distribution uniformity
2Reliability
If dot suppression is applied to specific pixels, then nozzle ejection rate is controlled, but dot density becomes concentrated around suppressed pixels causing graininess
Solution Approach 1:
The patent changes the threshold parameter values in the dither mask based on pixel position and corresponding nozzle characteristics. By adjusting threshold values (a key parameter) for different pixels, the system controls nozzle ejection rates while distributing dots uniformly, preventing concentration and graininess in the dot arrangement
3Ease of manufacture
If conventional dither mask threshold setting is used, then generation process is simple, but dot dispersibility is poor and graininess occurs especially at low recording duties
Solution Approach 1:
The patent performs preliminary determination of nozzle ejection rates and identification of corresponding pixels before threshold setting. This preliminary action enables the system to maintain a relatively simple generation process while achieving improved dot dispersibility through targeted threshold adjustment based on pre-calculated parameters
Solution Approach 2:
The patent modifies threshold parameters in the dither mask based on pixel-position-corresponding nozzle ejection rates. This parameter change approach maintains the basic dither mask generation framework while improving dot dispersibility and eliminating graininess, especially at low recording duties
Data Source
AI summary
The dither mask generation method includes: a nozzle ejection rate determination process of determining a nozzle ejection rate of each nozzle in a recording head; a corresponding nozzle specifying process of specifying the nozzle corresponding to individual pixels of a dither mask by making at least one nozzle in charge of recording at each pixel position correspond to the individual pixels of the dither mask; a nozzle ejection rate reflecting processing process of performing processing of reflecting the nozzle ejection rate on an evaluation index when individual thresholds of the dither mask are set; and a threshold setting process of setting the thresholds to the individual pixels of the dither mask on the basis of the evaluation index.