Spectral Data Conversion for Printing Process Control
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Solution Overview
Problem
Existing methods for color management in printing processes struggle to accurately convert spectral characterization data into specified color or tone values, leading to deviations from desired process standards, especially when adjusting for different printing conditions, which results in loss of spectral data and inability to precisely adapt to new density standards.
Innovation Solution
A method that involves proof printing of test elements, spectral measurement, and targeted modification of spectral values in groups to minimize color difference (dE) between actual and target color values, using coefficients to optimize spectral curves and values, while retaining spectral data for process calibration and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional colorimetric adjustment methods are used to adapt characterization data to process standards, then color values can be adjusted, but spectral data is lost and cannot be retained for further use
Solution Approach 1:
The patent changes the approach from colorimetric parameter adjustment to spectral parameter adjustment. By modifying spectral curves directly through multiplication with correction factors derived from the difference between actual and target color values, the method adjusts colorimetric properties while preserving spectral information. This allows spectral data to be retained after adjustment rather than lost.
Solution Approach 2:
The patent replaces the conventional colorimetric adjustment mechanism with a spectral-based adjustment mechanism. Instead of working directly with colorimetric values (L*a*b*), the system works with spectral curves and uses spectral multiplication to achieve colorimetric adjustment, thereby substituting a more information-preserving mechanism.
2Manufacturing precision
If spectral values are modified to adapt to new density standards, then adaptation precision improves, but individual spectral value modification is complex and inefficient
Solution Approach 1:
The patent segments the spectral modification task by dividing it into two distinct phases: first calculating correction factors based on colorimetric differences, then applying these factors to spectral curves. This segmentation simplifies the overall complexity by breaking down the modification process into manageable, systematic steps rather than requiring complex individual value adjustments.
Solution Approach 2:
The patent changes the modification approach from adjusting individual spectral values to multiplying entire spectral curves by correction factors. This parameter change transforms a complex point-by-point adjustment task into a simpler scalar multiplication operation that achieves the same adaptation precision with reduced complexity.
3Ease of manufacture
If colorimetric data is used for process calibration, then calibration can be performed, but spectral data must be discarded and is no longer valid
Solution Approach 1:
The patent changes the calibration approach from colorimetric-based to spectral-based calibration. By performing calibration operations on spectral curves and retaining the modified spectral data, the system maintains spectral validity after calibration whereas conventional colorimetric calibration discards spectral information.
Data Source
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AI summary
The invention relates to a method for controlling color reproduction in the printing process of a printing press using a computer, comprising the following process steps: - Printing a test element with a selected number of color measurement patches and measuring the printed color measurement patches of the test element with a spectral colorimeter, - Calculating the actual colorimetric values from the measured color measurement values of the color measurement patches of the test element and displaying selected actual color values on a display device, - Inputting target color ranges and calculating adjusted spectral color values from the target color values, - Calculating densitometric, colorimetric, or spectral actual tonal values or actual tonal value increases from the calculated colorimetric actual color values of a subset of the color patches of the test element measured with the spectral colorimeter and displaying them on a display device, - Inputting densitometric,colorimetric or spectral target tonal values or target tonal value increases and calculation of adjusted spectral color values by comparison with the calculated colorimetric actual color values and storage of the adjusted spectral color values for the calculation of color profiles, process calibrations and process control values and "control" of the printing press based on the color profiles, process calibrations and process control values.