Printer Calibration Using 3D CIELAB Allocation Tables
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Solution Overview
Problem
Existing printer calibration methods do not adequately account for the changing overprint behavior of primary colors, leading to visible differences despite calibration, and lack a consistent description of the printable color gamut, resulting in inaccurate color reproduction.
Innovation Solution
A method that creates a 3-dimensional or higher-dimensional allocation table incorporating CIELAB values for overprint colors, optimally limits primary color values, linearizes them, and interpolates intermediate values to achieve a visually even color space with neutral gray balance, ensuring accurate color reproduction by recalculating tonal values based on cumulative color differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional density-based linearization calibration is used, then the primary colors reach target density state, but the overprint behavior changes and visible differences remain
Solution Approach 1:
The patent transitions from traditional 1-dimensional density-based calibration tables to 3-dimensional or higher-dimensional allocation tables that incorporate CIELAB color values and overprint characteristics. This dimensional expansion allows the calibration system to account for interactions between multiple primary colors simultaneously, resolving the overprint consistency issue while maintaining density accuracy.
Solution Approach 2:
The patent changes the calibration parameters from simple density values to comprehensive CIELAB color values (L*, a*, b*) that capture the full color perception characteristics. This parameter transformation enables the calibration to account for human visual perception and overprint behavior, eliminating visible differences that pure density calibration cannot address.
2Measurement precision
If measured setpoints are used for calibration, then calibration data is obtained, but measurement fluctuations and inaccuracies affect results
Solution Approach 1:
The patent performs preliminary optimization of the calibration table by calculating optimal setpoints that account for measurement fluctuations. Instead of directly using raw measured values, the system pre-calculates compensated setpoints that anticipate and correct for typical measurement variations, ensuring more reliable and consistent calibration results.
Solution Approach 2:
The patent incorporates feedback mechanisms where the calibration system continuously refines the allocation tables based on measured deviations from target CIELAB values. This iterative feedback process adjusts the calibration data to compensate for measurement inaccuracies and fluctuations, improving both precision and reliability over time.
3Reliability
If 3-dimensional allocation table with overprint target values is created, then overprint behavior is accounted for, but calibration complexity increases
Solution Approach 1:
The patent segments the complex 3-dimensional calibration problem into manageable components: primary color characterization, overprint behavior analysis, and CIELAB space transformation. By dividing the calibration process into these distinct segments, the system can handle each aspect separately and combine them systematically, reducing the perceived complexity while maintaining accuracy.
Solution Approach 2:
The patent introduces CIELAB color space as an intermediary framework that bridges the gap between physical ink densities and perceived colors. This intermediary color model provides a standardized, perceptually uniform space that simplifies the relationship between primary colors and overprint results, making the complex calibration process more manageable and interpretable.
4Productivity
If linear interpolation of intermediate calibration values is used, then calibration table is completed, but color space uniformity and visual evenness may be compromised
Solution Approach 1:
The patent transforms the calibration approach by changing from simple linear interpolation in density space to optimization-based calculation in CIELAB color space. This parameter transformation ensures that intermediate values are distributed uniformly according to human visual perception, maintaining color space uniformity and visual evenness while still enabling efficient calibration table generation.
Data Source
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AI summary
In order to optimize the calibration tables of a printer, and to improve the calibration for combined printing with respect to one-dimensional calibration, a method for optimized printer calibration is proposed, comprising the following method steps: a) for each primary color, the maximal value is colorimetrically limited; b) each primary color is colorimetrically linearized; c) the maximal value of the combined printing of all primary colors is determined colorimetrically; d) a definition of the resulting color range is made; e) the outer layer of the color range is determined at equal spaces; and f) the intermediate values of the resulting calibration tables are interpolated.