Digital Printing Color Correction with Position-Dependent Screening
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Solution Overview
Problem
Existing digital printing methods struggle with achieving consistent color accuracy across the print width due to variations in print dot size, nozzle errors, and substrate properties, leading to visible banding and artifacts, especially in solid-color images.
Innovation Solution
A method using a raster image processor and screening algorithm that accounts for print position-dependent correction values to create rasterized color separations, integrating print-position-dependent correction values and error distribution algorithms to enhance color correction efficiency and reduce artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If correction data is determined using test images and applied to digital printer, then color deviations can be corrected, but the homogeneity achieved in individual colors is not maintained when printing overlays, leading to visible banding
Solution Approach 1:
The patent applies local quality by determining correction values for individual print positions across the print width. Each position receives a specific correction value based on measured deviations, allowing localized adjustment of color properties. This ensures that each area of the print width is corrected according to its specific characteristics, maintaining homogeneity both in individual colors and across overlays.
Solution Approach 2:
The patent implements feedback by measuring actual color values of printed test images at multiple positions across the print width, comparing these measurements to target values, and using the differences to calculate correction values. This closed-loop feedback mechanism ensures that correction data is based on actual print performance, improving both color homogeneity and consistency across overlays.
2Productivity
If printhead voltage is adjusted to quickly correct color deviations, then correction speed is improved, but the optimal operating point of the printhead is changed, limiting correction effectiveness
Solution Approach 1:
The patent applies preliminary action by determining correction values in advance through test image printing and measurement, before actual production printing. The correction data is calculated and stored based on measured deviations, allowing rapid application during production without real-time adjustments to printhead voltage. This maintains optimal operating points while achieving fast correction through pre-computed position-dependent correction values.
3Manufacturing precision
If color management system is used to generate new print data with color correction, then color accuracy is improved, but the process takes a considerable amount of time
Solution Approach 1:
The patent performs color correction analysis in advance by printing test images, measuring color values at multiple positions, and calculating correction values before production printing. The position-dependent correction data is determined preliminarily and applied during production, avoiding time-consuming color management processing during actual printing while maintaining high color accuracy.
Solution Approach 2:
The patent changes the parameter of correction application by using position-dependent correction values that are directly applied to adjust color output at different print positions. This approach optimizes the correction process by targeting specific positions with tailored correction values, achieving accurate color correction more efficiently than general color management systems.
4Manufacturing precision
If correction signals are sent to print head controller to adjust number and size of print dots, then color correction is achieved, but special hardware is required and corrections cannot be applied equally in print feed direction and along print width
Solution Approach 1:
The patent replaces the mechanical approach of adjusting print dot number and size through hardware control with a digital image processing approach. Position-dependent correction values are applied to modify the digital print data itself, eliminating the need for special hardware controllers and enabling uniform correction application in both print feed direction and print width without complex mechanical systems.
Data Source
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AI summary
The present invention proposes a method for color correction in a digital printing process, wherein a rasterized color separation (104) is created from at least one color separation (101) of a predetermined digital image (102) using a raster image processor (100) with a screening algorithm (103), wherein the screening algorithm (103) reads in color values of the color separation sequentially along a screening path and creates points for the rasterized color separation on the basis of the read-in color values and at least one predetermined threshold value, wherein a printing position-dependent correction value is taken into account in each case in which the screening algorithm creates a point.