Printer Gradation Correction via Color Patch Fluctuation
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Solution Overview
Problem
Existing printer gradation correction methods fail to effectively address tone jumps and discontinuities in gradation characteristics, leading to unstable color reproducibility and measurement errors, especially when pseudo multi-gradation processing is used.
Innovation Solution
A method that involves creating a color patch image with added gradation fluctuations, where the total fluctuation in a measurement region is controlled to a predetermined value, allowing for accurate measurement and correction of printer gradation characteristics by averaging the gradation distribution across a range, thereby minimizing the influence of tone jumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If color patches are produced for all combinations of gradation values, then measurement precision is improved, but device complexity and productivity deteriorate due to the huge number of combinations (4 billion for 8-bit full color)
Solution Approach 1:
The patent segments the continuous gradation range into discrete gradation representative values (e.g., 5-9 points per color component). Instead of measuring all 4 billion combinations, only combinations of these representative values are measured, and intermediate values are obtained through interpolation. This segmentation reduces the measurement burden while maintaining acceptable precision through the interpolation assumption that characteristics change continuously between measured points.
Solution Approach 2:
The patent creates a virtual model of the printer's gradation characteristic through interpolation based on limited measurements. Rather than physically measuring every possible gradation combination, the system copies the measured representative points and interpolates between them to generate a complete gradation correction characteristic curve, effectively creating a mathematical model that represents the physical system.
2Measurement precision
If gradation correction characteristics are defined for all gradation values, then measurement precision is improved, but data volume increases to an impractical level
Solution Approach 1:
The gradation correction data is segmented into discrete representative values rather than continuous values. For each color component, only specific gradation representative values (e.g., 5-9 points) are measured and stored in the LUT. Intermediate correction values are calculated through interpolation when needed, reducing the stored data volume from 4 billion entries to a manageable number of representative points while maintaining correction precision through the interpolation process.
3Manufacturing precision
If pseudo multi-gradation processing is used to achieve continuous gradation, then manufacturing precision is improved, but tone jumps and discontinuities occur causing measurement errors
Solution Approach 1:
The patent applies beforehand cushioning by adding fluctuation to the gradation values of color patches before measurement. This fluctuation acts as a buffer that prevents the measurement from being overly sensitive to tone jumps and discontinuities in the pseudo multi-gradation processing. By intentionally varying the gradation values within a range and measuring the average effect, the system cushions against the harmful impact of abrupt gradation changes, achieving more stable and reliable measurements despite the underlying discontinuities in the printer's gradation characteristic.
Data Source
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AI summary
A printer gradation correcting method, comprises the steps of: outputting a color patch image by a printer based on image data of a color patch image; measuring a gradation of the outputted color patch image by a color measuring device so as to obtain a gradation measurement value; and correcting a gradation characteristic of the printer based on the gradation measurement value. The color patch image includes a patch-shaped image having a uniform gradation of a predetermined gradation representative value and gradation fluctuation of a predetermined color component added in the patch-shaped image, and the added gradation fluctuation is structured such that a total of gradation fluctuation measured in a measurement region by the color measuring device becomes a predetermined value. The gradation characteristic of the printer is corrected based on the gradation representative value, the predetermined value of the total of gradation fluctuation, and the gradation measurement value.