Quantization Method Using Basic Pattern for Inkjet Color Reproduction
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Solution Overview
Problem
Existing quantization methods for converting continuous-tone images into binary or multi-level dot images face challenges in expanding the color reproduction region while minimizing artifacts, particularly with checkered patterns that exhibit irregular boundaries, high periodicity, and interference issues in inkjet recording apparatuses.
Innovation Solution
A quantization method using a basic pattern with spatial frequency characteristics that suppress components near basic tone frequencies and enhance components at their outer periphery, allowing for a pattern with high frequent occurrence and uniform distribution of basic tone patterns, thereby expanding the color reproduction region and reducing artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a checkered pattern is used for quantization to expand the color reproduction region, then the color reproduction region is expanded, but artifacts occur due to irregular boundaries and high periodicity
Solution Approach 1:
The patent modifies the spatial frequency characteristics of the checkered pattern by suppressing components near basic tone frequencies and enhancing components at their outer periphery. This parameter change in the frequency domain allows the pattern to maintain high frequent occurrence for color reproduction while reducing the periodicity that causes artifacts
Solution Approach 2:
The patent introduces asymmetric modifications to the traditionally symmetric checkered pattern by selectively suppressing and enhancing specific frequency components. This creates an asymmetric frequency distribution that breaks the regular periodicity while preserving the overall checkered structure needed for color reproduction
2Adaptability or versatility
If a checkered pattern with high periodicity is used, then the color reproduction region is expanded, but interference between printing operation and pattern increases ink discharge at identical timing
Solution Approach 1:
The patent changes the frequency domain parameters of the checkered pattern by suppressing components near basic tone frequencies. This reduces the periodicity that causes synchronous ink discharge interference while maintaining the pattern's effectiveness for color reproduction expansion
3Object-generated harmful factors
If a blue noise pattern is used to reduce artifacts, then artifacts are suppressed, but the spectrum on high frequency side is suppressed reducing frequent occurrence of checkered patterns
Solution Approach 1:
The patent applies local quality modification in the frequency domain by selectively suppressing only the components near basic tone frequencies while preserving other frequency components. This localized approach reduces artifacts without suppressing the high frequency components needed for checkered pattern occurrence and color reproduction
Solution Approach 2:
The patent makes targeted parameter changes in the frequency spectrum by enhancing components at the outer periphery of basic tone frequencies while suppressing components near them. This selective parameter modification achieves artifact reduction while maintaining the spectral characteristics needed for color reproduction
Data Source
AI summary
A quantization method according to an aspect of the present invention includes the steps of quantizing a first image data by the use of a basic pattern and converting the first image data into a second image data that represents a binary or multi-level quantized pattern having a gray level smaller than that of the first image data. The basic pattern according to this aspect of the present invention presents high frequent occurrence of the basic tone patterns and a mostly uniform-distributed pattern of the clusters of different kinds of the basic tone patterns in the image with the long-distance autocorrelation (periodicity) of the basic tone patterns suppressed. Quantization by the use of this basic pattern provides a quantized pattern that reflects pattern characteristics of the basic pattern.