Inkjet Print Mode Switching for Gray Scale Banding
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Solution Overview
Problem
One-pass bidirectional print modes in inkjet printers often produce image quality defects such as gray scale shift banding, especially when printing dark gray area fills, due to the different sequence of ink drops when the carriage moves left-to-right versus right-to-left, resulting in inadequate mixing of colorants.
Innovation Solution
The printing system automatically switches from a one-pass bidirectional print mode to a multi-pass bidirectional print mode for area fills that will be printed with a combination of different black inks, to ensure proper ink deposition and prevent visible image defects, by identifying area fills with high black ink density and adjusting the number of passes accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If one-pass bidirectional print mode is used, then printing speed is improved, but image quality deteriorates due to gray scale shift banding
Solution Approach 1:
The system dynamically switches between one-pass bidirectional mode and multi-pass bidirectional mode based on the detected print content characteristics. When area fills with combination black inks are detected, the system transitions to multi-pass mode to eliminate gray scale shift banding, otherwise it uses one-pass mode for high speed printing.
Solution Approach 2:
The invention applies different printing modes to different regions of the print content. Area fills printed with combination black inks receive multi-pass treatment to ensure uniform colorant mixing, while other regions use one-pass mode for speed, thus applying quality enhancement locally where needed.
2Productivity
If one-pass bidirectional print mode is used, then printing speed is improved, but colorant mixing deteriorates due to different ink drop sequences
Solution Approach 1:
The system dynamically adjusts the number of passes based on the print content. For area fills using combination black inks, it switches to multi-pass mode which deposits ink in a consistent sequence across passes, ensuring proper colorant mixing. For other content, it maintains one-pass mode for speed.
Solution Approach 2:
The system performs preliminary analysis of the print content to identify area fills that will be printed with combination black inks. This allows it to proactively switch to multi-pass mode before printing these problematic areas, ensuring proper colorant mixing is achieved in advance.
3Manufacturing precision
If multi-pass bidirectional print mode is used for area fills, then image quality is improved, but printing speed deteriorates
Solution Approach 1:
The invention applies multi-pass printing mode selectively only to area fills that use combination black inks and are likely to produce visible defects, while maintaining one-pass mode for all other regions. This localized application of multi-pass mode minimizes the impact on overall printing speed while still improving image quality where needed.
Solution Approach 2:
Instead of applying multi-pass mode to all print content, the system applies it partially only to the specific problematic areas (area fills with combination black inks). This partial application achieves the necessary quality improvement without the full speed penalty that would result from using multi-pass mode universally.
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 effectively reduces or eliminates gray scale shift banding in dark gray area fills by ensuring ink drops fall in a more similar sequence, improving image quality by using a multi-pass mode for high-density black ink areas and switching back to one-pass mode to minimize printing speed loss.
Implementation Method 1
Within each of the ink ejection chambers is an ink ejection element, such as a resistive heater or a piezoelectric element
Implementation Method 2
Within each of the ink ejection chambers is an ink ejection element, such as a resistive heater or a piezoelectric element
Implementation Method 3
Water in ink drops is immediately absorbed by the media and, therefore, the colorant is laid on the surface instantaneously
Data Source
AI summary
A method of printing a document using a fluid-ejection printing device includes receiving gray scale image data for the document, and identifying at least one area fill feature of the image data. It is determined whether the at least one area fill feature will be printed with a combination of different black inks and is likely to produce a visible image defect if printed in an N-pass bidirectional print mode, where N is an integer. Non-fill regions of the image data are printed using the N-pass bidirectional print mode. The method further includes automatically switching to an M-pass bidirectional print mode for printing the at least one area fill feature when it is determined that the at least one area fill feature will be printed with a combination of different black inks and is likely to produce a visible image defect, where M is an integer greater than N.