Image Dither Matrix Generation for Even Inkjet Nozzle Usage
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Solution Overview
Problem
Existing inkjet printers with multiple nozzle arrays face uneven discharge frequencies, leading to shortened nozzle lifetimes and degraded image quality due to uneven dot distribution across nozzle arrays.
Innovation Solution
A dither matrix generation method that generates dot patterns with blue or green noise characteristics, suppressing power in low frequency bands and nozzle array-specific dot assignments to ensure even nozzle usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dither matrix is used for halftone processing in a single-pass drawing system, then printing speed is improved, but the number of discharge dots varies between nozzles leading to shortened nozzle lifetime
Solution Approach 1:
The patent changes the parameters of the dither matrix by applying frequency domain filtering to suppress power at specific frequencies corresponding to nozzle array cycles and their multiples. This modifies the dot distribution pattern to achieve more uniform discharge frequencies across all nozzles, thereby extending nozzle lifetime while maintaining high printing speed through single-pass processing
Solution Approach 2:
The patent employs feedback by calculating the power spectrum of the dot pattern and using this information to adjust the dither matrix. The power spectrum analysis provides feedback about the discharge frequency distribution, allowing the system to modify the threshold matrix to achieve more even nozzle usage and extend lifetime
2Productivity
If multiple nozzle arrays are arranged in the recording head, then productivity is improved, but dot distribution becomes uneven across nozzle arrays causing degraded image quality
Solution Approach 1:
The patent modifies the dither matrix parameters by suppressing power at frequencies corresponding to the nozzle array arrangement cycle and its multiples in the frequency domain. This parameter change ensures that dot patterns generated by the dither matrix have uniform distribution across multiple nozzle arrays, maintaining image quality while preserving high productivity through multi-array parallel processing
3Manufacturing precision
If dither matrix is repeatedly deployed on image data in a tile pattern, then tone representation is achieved, but power in low frequency band is not suppressed resulting in visible dot pattern artifacts
Solution Approach 1:
The patent uses feedback from power spectrum analysis to modify the dither matrix. By analyzing the frequency content of the dot pattern and suppressing power at low frequencies and at frequencies corresponding to nozzle array cycles, the system achieves tone representation without visible dot pattern artifacts, improving image quality while maintaining processing efficiency
Data Source
AI summary
An image processing apparatus converts, based on a threshold matrix in which thresholds are arrayed, input image data into a first dot pattern representing dots recorded by a recording head, and obtains a second dot pattern representing dots recorded by each of L number of the nozzle arrays by assigning the dots of the first dot pattern to each of the nozzle arrays so that each nozzle of the recording head is used in a cycle of L. A power spectrum in a frequency domain of the first dot pattern has a blue noise characteristic or a green noise characteristic in which power in a low frequency band is suppressed, and power is suppressed at a frequency corresponding to the cycle of L and at frequencies of multiplications of the frequency.