Multi-pass Inkjet Dot Pattern Variation for Density Uniformity
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Solution Overview
Problem
Existing image processing methods for multi-pass printing in inkjet printing apparatuses face challenges in achieving uniform image density across all-tone regions due to printing position displacement, leading to graininess and density unevenness, particularly in low-density, intermediate, and high-density regions.
Innovation Solution
An image processing method that distributes multi-valued image data into multiple pieces, quantizes each piece, and binarizes them using distinct dot patterns for each scan, ensuring the dot patterns differ in at least one value to maintain consistent coverage area regardless of printing position displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If mask patterns having a completing relationship are used for multi-pass printing, then dot coverage is enhanced, but printing position displacement causes density unevenness and graininess
Solution Approach 1:
The patent divides the mask patterns into multiple sets with different dot arrangement patterns for each printing scan. Instead of using a single repeating mask pattern, it employs multiple segmented patterns (first mask pattern, second mask pattern, etc.) that are specifically designed to compensate for potential printing position displacements. Each scan uses a different segmented pattern, ensuring that even if displacement occurs, the overall dot coverage and density remain uniform.
Solution Approach 2:
The patent changes the parameters of the mask patterns by introducing different dot arrangement configurations for each printing scan. The mask patterns are modified in terms of dot positioning and arrangement parameters across different scans, transforming from a static repeating pattern to a dynamic set of varied patterns. This parameter variation ensures that printing position displacement does not result in systematic density variations.
2Ease of manufacture
If multi-valued image data is binarized independently for each scan, then processing is simplified, but dot patterns lack completing relationship causing coverage variation
Solution Approach 1:
The patent performs preliminary design of multiple mask patterns with different dot arrangements before the actual printing process. These pre-prepared mask patterns are specifically crafted to maintain a completing relationship across different scans. By having these patterns ready in advance, the system can independently binarize image data for each scan while still ensuring that the resulting dot patterns complement each other, maintaining consistent coverage without requiring complex real-time coordination.
Data Source
AI summary
There is provided an image processing apparatus in which in a case of tone-expressing one pixel corresponding to a plurality of areas (printing resolution) in a multi-pass print, it is possible to output a uniform image without graininess or density unevenness over all-tone regions from a low-density region to a high-density region. To this end, by referring to dot patterns in which a print or a non-print of dots onto each pixel (area) corresponding to a printing resolution are in advance defined, quantization data is converted into binary data having the higher printing resolution. At this time, the dot patterns are prepared to be different from each other for M times of scans in a multi-pass print of M passes. In consequence, it is possible to restrict a variation of a coverage ratio due to a printing position displacement in each printing scan.