Variable Droplet Ejection for Banding Reduction in Inkjet Printing
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Solution Overview
Problem
Banding issues occur in ink jet printing due to variations in sub scans, leading to density unevenness and affecting image quality, particularly in serial-type printing apparatuses, where the use of multiple devices and complex control systems increase costs and complexity.
Innovation Solution
An image printing apparatus that determines the number and placement of dots of varying sizes based on pixel density levels, using a print head capable of ejecting multiple dot sizes, to ensure optimal dot alignment and minimize banding by preferentially using larger dots in low-tone areas and adjusting dot positions in the sub scan direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple inks with different densities are used to reduce granularity in highlight areas, then image quality is improved, but apparatus size and running costs increase
Solution Approach 1:
The invention changes the parameter of droplet size rather than introducing multiple ink types. By controlling the print head to eject droplets of different sizes (large and small droplets), the system achieves granularity reduction in highlight areas without adding complex ink delivery systems. This parameter change approach resolves the contradiction by maintaining a simple single-ink system while improving image quality through variable droplet ejection.
2Manufacturing precision
If higher resolution printing is achieved with smaller droplets, then image quality is improved, but processing time and load increase
Solution Approach 1:
The invention segments the printing process into two distinct modes: high-speed printing mode using large droplets and high-resolution printing mode using small droplets. This segmentation allows the system to process images at different quality levels with appropriate time investment, resolving the contradiction between resolution and processing time by not requiring all printing operations to achieve maximum resolution.
Solution Approach 2:
The print head dynamically switches between large and small droplet ejection modes based on the specific printing requirements of different image regions. This dynamic adaptation allows the system to optimize processing time for each local area, achieving high resolution where needed while maintaining fast processing speeds overall, thus resolving the contradiction between resolution and time.
3Loss of time
If INDEX patterning processing is introduced to reduce processing load, then processing time is reduced, but banding issues occur in serial-type printing
Solution Approach 1:
The invention applies different dot size strategies to different tonal regions of the image. Large droplets are used for low-tone areas (reducing banding effects) while small droplets are used for high-tone areas (maintaining resolution). This local quality differentiation resolves the contradiction by addressing the specific problem of banding in low-tone regions without sacrificing the resolution benefits of INDEX patterning processing in high-tone regions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces banding and temperature rise in the print head, maintaining high printing speed and quality while simplifying the printing process and reducing costs by minimizing the need for additional devices and complex control systems.
Implementation Method 1
a print head for ejecting ink as a droplet, and forms an image on a printing medium such as a paper sheet or a thin plastic plate, by printing dot patterns based on image information
Data Source
AI summary
In an image printing apparatus for printing an image by combining dots of a plurality of sizes, a banding problem attributable to variations in conveying operation, and a temperature rise of a print head with an increase of the number of ejections are solved with a relatively simple configuration. To this end, a combination of dots of a plurality of sizes is assigned to each of pixels expressed at a plurality level of density. In this assignment, a dot larger than a pitch of an image resolution is preferentially allocated to a pixel having a density level higher than that to which one dot smaller than the pitch of the image resolution is allocated.