Color Patch Allocation for Printer Calibration
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Solution Overview
Problem
Color printers face challenges in color reproducibility due to color unevenness across the print surface, which is exacerbated by variations in ink transport and discharge, requiring an adjustment in the number of patches for effective calibration.
Innovation Solution
A method to determine the number of patches for each color in a test chart based on the degree of colorimetric variation, using standard deviation calculations and considering the CIE L*a*b* color space, to optimize patch allocation for accurate calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of patches of a color having a large degree of color unevenness is increased, then the accuracy of correction by calibration is improved, but the time required for colorimetry is increased
Solution Approach 1:
The patent applies local quality by determining the number of patches for each ink color individually based on its specific degree of color unevenness. Instead of using a uniform number of patches for all colors, the system calculates and allocates patches locally optimized for each color's characteristics, thereby improving calibration accuracy for colors with high unevenness while avoiding unnecessary patches for colors with low unevenness, thus reducing overall colorimetry time.
Solution Approach 2:
The patent changes the parameter of patch quantity from a fixed value to a dynamically determined value based on the degree of color unevenness. By calculating the standard deviation of colorimetric values for each ink color and using this parameter to determine the optimal number of patches, the system adapts the patch allocation to the actual printing conditions and color characteristics, resolving the contradiction between accuracy and time efficiency.
2Measurement precision
If the number of patches is increased, then the accuracy of correction by calibration is improved, but the time required for colorimetry is increased
Solution Approach 1:
The system implements local quality by tailoring the number of patches to each ink color's specific needs. Colors with high variability receive more patches for accurate calibration, while colors with low variability receive fewer patches, optimizing the overall calibration process efficiency without compromising accuracy where needed.
Solution Approach 2:
The patent applies partial action by allocating patches selectively based on necessity. Instead of uniformly increasing patches for all colors, the system applies the increased patch count only to colors that require it (those with high standard deviation), achieving the necessary calibration accuracy with minimal time investment.
3Measurement precision
If the number of patches of each color is uniformly increased, then the calibration accuracy for all colors is improved, but the time required for colorimetry is significantly increased
Solution Approach 1:
The patent rejects uniform patch allocation in favor of local quality optimization. Each ink color's patch count is independently determined based on its own degree of color unevenness, ensuring that calibration accuracy is improved only where necessary rather than uniformly across all colors, thus avoiding unnecessary time consumption.
Solution Approach 2:
The system changes the patch allocation parameter from a uniform value to a color-specific value determined by the standard deviation of each ink's colorimetric measurements. This parameter transformation enables differentiated patch allocation that optimizes the balance between calibration accuracy and time efficiency.
Data Source
AI summary
A test chart used for color calibration includes: the number of patches of a first color; and the number of patches of a second color. The number of patches of the first color is determined on the basis of the degree of variation in the colorimetric value of the first color in a color space on a medium, and the number of patches of the second color is determined on the basis of the degree of variation in the colorimetric value of the second color in the color space on the medium.