Ink Control Using Device-Independent Color Space
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Solution Overview
Problem
Existing methods for controlling ink layer thickness in printing presses, particularly in offset printing, face challenges in accurately regulating ink application to achieve desired color values, especially when using device-dependent color systems and overprinted colors, leading to inefficiencies in maintaining predefined image quality.
Innovation Solution
A method that predefines setpoint color values in a device-independent color space, activates an ink metering element based on calculated changes in ink layer thickness, and adjusts the ink application value to match actual color values, using partial derivatives and ICC profiles to determine necessary changes, ensuring precise ink layer thickness adjustments across multiple colors and zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If device-dependent color systems are used for ink application control, then the control process is simpler, but measurement precision and reliability deteriorate because density values are not meaningful for overprinted colors
Solution Approach 1:
The patent introduces an intermediary conversion process that transforms device-dependent color measurements into device-independent color space values. A color measuring device captures actual color values, which are then converted through a color profile to device-independent color space, allowing accurate comparison with setpoint values while maintaining compatibility with existing printing press equipment
Solution Approach 2:
The patent changes the parameter space from device-dependent density values to device-independent color values (such as L*a*b*). This parameter transformation enables meaningful measurement of overprinted colors by using colorimetric values that are independent of specific printing conditions and devices, thereby improving measurement precision without requiring fundamental changes to the printing press
2Difficulty of detecting and measuring
If density values are measured in color measuring strips for ink application control, then the measurement process is simpler, but manufacturing precision deteriorates because density values are insufficient for overprinted colors
Solution Approach 1:
The patent transforms the measurement parameter from density values to device-independent color values. This change enables accurate measurement of overprinted colors by using colorimetric parameters (L*a*b*) that remain meaningful regardless of the number of ink layers, thereby improving manufacturing precision while keeping the measurement process accessible through standard color measuring devices
Solution Approach 2:
The patent replaces the mechanical/direct measurement approach (density measurement in color strips) with a colorimetric measurement system that uses optical measurement and mathematical conversion. This substitution enables accurate measurement of complex overprinted colors by measuring actual color appearance and converting to device-independent values, rather than relying on direct density measurements that fail for multi-layer prints
3Manufacturing precision
If actual value control is implemented using device-independent color space, then manufacturing precision improves, but device complexity increases due to additional calculation requirements
Solution Approach 1:
The patent implements a feedback control loop where actual color values are measured, compared with setpoint values in device-independent color space, and the deviations are used to calculate corrective ink application changes. This closed-loop feedback system maintains high manufacturing precision by continuously adjusting ink application based on actual measurements, while the automation of calculations reduces the perceived complexity for the operator
Solution Approach 2:
The patent uses digital copies and mathematical models (color profiles, sensitivities, partial derivatives) to represent the complex relationships between ink application and color appearance. These digital models enable the control system to perform calculations efficiently without requiring complex physical measurement and adjustment mechanisms, thereby managing device complexity through virtual representation
Data Source
AI summary
A method and computer program product for controlling application of ink in a printing press include predefining a setpoint color value in a device-independent color space. An ink metering element is activated with an ink application value, producing an ink layer thickness, on printing material, associated with the setpoint color value. An actual color value from the ink layer thickness on the printing material is determined, measured or colorimetrically measured in the device-independent color space. Activation with a changed ink application value based on deviation of the actual color value from the setpoint color value, produces an ink layer thickness differing from the produced ink layer thickness. A necessary ink layer thickness change is calculated based on changes in the color values in the device-independent color space upon a change in the ink layer thickness at the point of the actual color value, to determine the changed ink application value.