Dither Matrix Switching for Ink Bleeding on Coated Paper
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Solution Overview
Problem
Concentration type dither matrices used in ink jet recording apparatuses face challenges in achieving optimal ink distribution and image quality due to ink bleeding and uneven fixation, especially on coated glossy paper, where ink does not spread smoothly, leading to irregular white spots and hue distortion.
Innovation Solution
A dither matrix system that switches between concentration and dispersion type dot arrangement orders based on halftone levels, using concentration type for lower levels and dispersion type for higher levels to prevent dot concentration issues, thereby improving ink distribution and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If concentration type dither matrix is used, then dot patterns are highly visible and unevenness in image density is hidden, but ink bleeding and uneven fixation occur especially on coated glossy paper
Solution Approach 1:
The patent applies different dither matrix types to different halftone level ranges: concentration type dither matrices are used for lower halftone levels (0-2) where dot visibility is important, while dispersion type dither matrices are used for higher halftone levels (3-7) where ink distribution uniformity is critical. This local differentiation resolves the contradiction by matching the dither matrix characteristics to the specific requirements of each tonal region.
Solution Approach 2:
The patent changes the parameter of dot arrangement pattern from concentrated to dispersed based on the halftone level parameter. By switching between different dither matrix types according to the input halftone level, the system optimizes both dot visibility in shadow regions and ink distribution uniformity in highlight regions, preventing ink bleeding while maintaining image quality.
2Reliability
If concentration type dither matrix is used, then patterns are highly visible, but irregular white spots and hue distortion occur on papers with low ink absorption rates
Solution Approach 1:
The patent differentiates the treatment of different halftone levels by applying concentration type dither matrices only to lower levels (0-2) where pattern visibility is essential for defining edges and details, while using dispersion type dither matrices for higher levels (3-7) where uniform ink coverage is needed to avoid white spots and hue distortion on low-absorption papers.
Solution Approach 2:
The system dynamically changes the dither matrix type parameter based on the halftone level input. This parameter switching ensures that the harmful effects of irregular white spots and hue distortion are prevented in highlight regions while maintaining the beneficial pattern visibility in shadow regions.
3Quantity of substance
If dispersion type dither matrix is used, then ink distribution is uniform, but dot patterns are less visible and unevenness in image density is not effectively hidden
Solution Approach 1:
The patent assigns dispersion type dither matrices to higher halftone levels (3-7) where uniform ink distribution is the primary requirement, while reserving concentration type dither matrices for lower halftone levels (0-2) where hiding unevenness and providing visible dot patterns are more critical. This spatial and functional differentiation resolves the contradiction.
4Device complexity
If a single dither matrix type is used for all halftone levels, then device complexity is reduced, but image quality deteriorates due to inability to address different requirements of highlight and shadow regions
Solution Approach 1:
The patent implements a multi-type dither matrix system where different matrix types are selectively applied to different halftone level ranges. This approach accepts increased system complexity as necessary to achieve superior image quality across all tonal regions, particularly addressing the different requirements of highlight and shadow areas.
Solution Approach 2:
The system dynamically selects the appropriate dither matrix type based on the input halftone level. This dynamic adaptation allows the system to optimize image quality for each specific tonal region, transitioning from concentration type for low levels to dispersion type for high levels, thereby resolving the contradiction between simplicity and performance.
Data Source
AI summary
A disclosed dither matrix is used in halftone processing for converting input image data having M input halftone levels into output image data having N (M>N>2) output halftone levels. In the halftone processing, a concentration type dither matrix is used as the dither matrix when an input halftone level is within a range of input halftone levels corresponding to an output halftone level that is lower than a predetermined threshold level T (N>T>1), and a dispersion type dither matrix is used as the dither matrix when the input halftone level is within a range of input halftone levels corresponding to an output halftone level that is equal to or higher than the predetermined threshold level T.