Threshold Matrix Generating Method for Bidirectional Printing
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Solution Overview
Problem
Existing threshold matrix generating methods for image printing are prone to graininess and density unevenness due to mechanical errors during printing operations, particularly in bidirectional multipass printing, where misalignment can affect dot distribution and quality.
Innovation Solution
A method for generating two threshold matrices, one for each grayscale value, allowing for continuous dot patterns between them, ensuring that dot patterns from both matrices are printed in an overlapping manner to maintain image quality despite mechanical errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single threshold matrix is used for quantization, then the processing load is reduced and high-speed image processing is achieved, but mechanical errors during printing cause graininess and density unevenness
Solution Approach 1:
The patent divides the threshold matrix into multiple matrices (first threshold matrix and second threshold matrix) corresponding to different grayscale ranges. Each matrix is optimized for its specific grayscale range, allowing the system to maintain high processing speed while reducing the impact of mechanical printing errors on dot distribution uniformity.
Solution Approach 2:
The patent applies different threshold matrices to different local regions of the image based on their grayscale values. Low grayscale values use the first threshold matrix while high grayscale values use the second threshold matrix, allowing each region to be processed with optimal parameters for its specific characteristics.
2Manufacturing precision
If bidirectional multipass printing is performed to improve print quality, then dot dispersiveness is enhanced, but misalignment between forward and backward scans causes graininess and density unevenness
Solution Approach 1:
The patent pre-calculates and stores multiple threshold matrices before the printing process. These pre-prepared matrices allow the printing system to quickly select and apply appropriate thresholds without real-time calculation, enabling bidirectional multipass printing to proceed at high speed while maintaining dot dispersiveness and minimizing misalignment effects.
Solution Approach 2:
The patent changes the threshold parameters dynamically based on the grayscale values of different image regions. By adjusting which threshold matrix is applied (first or second) based on the local grayscale characteristics, the system maintains optimal dot distribution even when mechanical misalignment occurs during bidirectional printing.
3Ease of manufacture
If thresholds are set using conventional methods, then the quantization process is simple, but dot patterns lack continuity between different grayscale values
Solution Approach 1:
The patent merges the characteristics of multiple threshold matrices into a unified quantization process. The first and second threshold matrices are designed to be complementary, with their combined use ensuring continuous and stable dot patterns across all grayscale values while maintaining process simplicity through automated matrix selection based on grayscale ranges.
Data Source
AI summary
A first dot pattern printed according to a result of quantization performed on a multi-valued grayscale value by using a first threshold matrix and a second dot pattern printed according to a result of quantization performed on multi-valued grayscale value by using a second threshold matrix are printed on a print medium in an overlapping manner. In order to generate the threshold matrices, a first initial pattern being a dot pattern corresponding to a first grayscale value and a second initial pattern being a dot pattern corresponding to a second grayscale value lower than the first grayscale value are generated for pixel regions of the first and second threshold matrices. Then, thresholds of the first and second threshold matrices are set such that dot patterns having continuity with the first and second initial patterns are obtained at grayscale values between the first and second grayscale values.