Inkjet Head Voltage Correction via Luminance Analysis
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Solution Overview
Problem
Conventional head voltage correcting methods for inkjet printing apparatuses face challenges in accurately distinguishing between main and satellite droplets using low-resolution scanners, leading to inadequate voltage correction and potential print quality issues.
Innovation Solution
The method involves printing testing charts with varying drive voltages, analyzing luminance distributions to determine the presence and distance of satellite droplets, and adjusting the reference voltage based on both distance and size thresholds to ensure accurate ink droplet density, using characteristic points extracted from the luminance distribution to improve correction accuracy even with low-resolution scanners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a low-resolution scanner is used to read testing charts, then the cost and complexity of the apparatus is reduced, but the ability to accurately distinguish between main droplets and satellite droplets deteriorates
Solution Approach 1:
The patent transitions from two-dimensional image analysis to one-dimensional luminance distribution analysis by projecting droplet information onto a luminance axis. This dimensional transformation allows satellite droplets to be distinguished from main droplets based on their luminance characteristics rather than spatial resolution, enabling accurate measurement even with low-resolution scanners.
Solution Approach 2:
The patent replaces the mechanical/optical measurement system (scanner resolution) with an electrical/signal processing system (luminance distribution analysis). By converting spatial information into luminance distribution data and analyzing characteristic points in the luminance domain, the system achieves accurate droplet measurement without relying on high scanner resolution.
2Reliability
If the reference voltage is corrected to eliminate satellite droplets, then the print quality is improved, but the ink droplet density may become too low to satisfy specifications
Solution Approach 1:
The patent introduces a new parameter (luminance distribution characteristic points) to evaluate droplet quality instead of simply eliminating satellite droplets. By identifying characteristic points in the luminance distribution that correspond to both main and satellite droplets, the system can adjust the reference voltage to optimize both droplet spacing and overall density simultaneously.
Solution Approach 2:
The patent establishes a feedback mechanism where the luminance distribution of testing chart images is analyzed to determine characteristic points, which then feed back into the reference voltage correction process. This feedback loop enables continuous optimization of the reference voltage to achieve both proper droplet spacing and sufficient ink density.
Data Source
AI summary
A head voltage correcting method for inkjet printing apparatus which perform printing by dispensing ink droplets from a head to a printing medium. The method includes the following steps:a step of printing testing charts; a step of acquiring images of the testing charts; a step of determining presence or absence of satellite droplets for each drive voltage; a step of obtaining distances between the main droplets and the satellite droplets for each drive voltage; a step of obtaining a distance reference drive voltage from a relationship of the distances for each drive voltage and a distance threshold; a step of obtaining ink droplet sizes for each drive voltage; a step of obtaining a size reference drive voltage; and a step of comparing the distance reference drive voltage and the size reference drive voltage, and making correction by adopting a larger one as the reference voltage.