Inkjet Halftone Processing for Color Uniformity
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Solution Overview
Problem
Ink jet printers face challenges with color unevenness due to variations in ink ejection characteristics among multiple heads or nozzle groups, requiring costly correction mechanisms and time-consuming adjustments to maintain printing quality.
Innovation Solution
An image processing method that performs multiple halftone processes for each region of the image data, generating separate halftone data for each nozzle group or head, and allocates this data to pass operations to ensure uniform ink ejection across the entire image region, eliminating the need for correction mechanisms and adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple heads are arranged to increase printing speed, then productivity is improved, but color unevenness occurs due to variation in ink ejection characteristics among individual heads
Solution Approach 1:
The patent segments the printing process by performing separate halftone processes for different nozzle groups (first nozzle group and second nozzle group). Each nozzle group processes different regions of the image data independently, allowing customization of halftone parameters for each group to compensate for their individual ejection characteristics variations.
Solution Approach 2:
The patent applies local quality by using different halftone processing parameters for different nozzle groups. The first halftone process and second halftone process can have different parameters optimized for their respective nozzle groups' characteristics, ensuring each group produces uniform output despite inherent variations.
2Manufacturing precision
If correction mechanisms are provided for each head to suppress color unevenness, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses software-based halftone processing as a virtual correction mechanism. Instead of physical correction hardware for each head, the system creates corrected output through computational halftone processes that generate dot patterns compensating for ejection variations.
Solution Approach 2:
The patent changes processing parameters (halftone parameters) for different nozzle groups to compensate for their ejection characteristics. By adjusting halftone processing parameters rather than physical head parameters, the system achieves correction without adding complex hardware.
3Manufacturing precision
If correction mechanisms are provided for each head to suppress color unevenness, then manufacturing precision is improved, but adjustment time increases
Solution Approach 1:
The patent performs preliminary halftone processing for each nozzle group before actual printing. The halftone parameters are pre-calculated and stored, allowing rapid switching between different nozzle groups without real-time adjustment during printing operations.
Data Source
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AI summary
An image processing method of generating print data to cause a printing system (printing apparatus) that prints a print image based on image data to execute printing, by repeating a pass operation in which nozzle arrays form dots on a printing medium by while moving relative to the printing medium in an X-axis direction (main scanning direction), and a feed operation in which the nozzle arrays and the printing medium are moved relative to each other in a subscanning direction that intersects with the X-axis direction (main scanning direction) includes: performing multiple halftone processes (first and second halftone processes) for a same region of image data, the halftone processes being to generate halftone data to determine a formation state of dots formed by each nozzle array that ejects a same color of ink; and allocating the generated halftone data to the pass operations.