Inline Color Matching Correction for Print Tone Value Drift
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Solution Overview
Problem
Existing color matching methods in image forming apparatuses impose a significant burden on users due to the need for frequent color measurement using external colorimeters, especially when dealing with changes in color over time, and the conversion from device-dependent RGB values to device-independent Lab values is inaccurate and prone to overcorrection or downtime.
Innovation Solution
An image processing apparatus and method that includes acquiring device-dependent color values from inline sensors, predicting color changes using a neighboring-color change prediction model, and correcting tone values based on a threshold to ensure accurate color matching without external colorimeters, using a correction unit to adjust tone values when the color difference exceeds a predetermined threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If color measurement is performed using an external colorimeter to ensure accurate color matching, then color matching accuracy is improved, but user burden and operation complexity increase
Solution Approach 1:
The image forming apparatus performs self-colorimetry using an inline sensor to automatically acquire colorimetric values of printed patches. This eliminates the need for external colorimeters and manual user operations, allowing the system to autonomously determine color matching directions and perform corrections
Solution Approach 2:
The patent replaces external mechanical color measurement devices with an inline sensor integrated into the image forming apparatus. This substitution enables automatic color value acquisition during the printing process itself, removing the need for separate measurement operations
2Measurement precision
If neighboring colors in a wide color gamut are output to ensure accurate color matching prediction, then prediction accuracy is improved, but the number of patches to be measured increases
Solution Approach 1:
The patent extracts only the essential target color patch from the comprehensive color chart for measurement, while utilizing pre-stored conversion tables to predict the directions of neighboring colors. This selective measurement approach maintains prediction accuracy while significantly reducing the number of patches requiring actual measurement
Solution Approach 2:
The system pre-stores conversion tables that map tone values to colorimetric values for various colors. These pre-computed tables allow the system to predict color matching directions without measuring all neighboring patches, as the conversion relationships are already established
3Device complexity
If conversion from device-dependent RGB values to device-independent Lab values is performed using a conversion table, then color matching process is simplified, but conversion accuracy deteriorates
Solution Approach 1:
The patent changes the parameter representation by storing and utilizing tone values (C, M, Y components) directly instead of converting through RGB to Lab values. This approach maintains device-independent color matching capability while avoiding the accuracy losses associated with multiple value conversions
Solution Approach 2:
The system uses tone values as an intermediary representation between device-dependent measurements and device-independent color matching. By working directly with CMY tone values and their corresponding colorimetric values from conversion tables, the system bypasses the inaccurate RGB-Lab conversion path
4Stability of the object's composition
If density correction is performed based on RGB value differences to maintain print density, then density consistency is improved, but determination of correction necessity becomes difficult
Solution Approach 1:
The patent substitutes RGB value-based correction determination with colorimetric value-based determination using the inline sensor. By measuring actual colorimetric values (L*, a*, b*) of printed patches and comparing them against target values, the system achieves objective and accurate determination of whether correction is necessary
Solution Approach 2:
The system implements feedback by continuously measuring colorimetric values of printed patches using the inline sensor and comparing them against target colorimetric values. Based on this feedback, the system automatically determines whether tone value correction is needed and performs appropriate adjustments to maintain density consistency
Data Source
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AI summary
An image processing apparatus for performing color matching of tone values for a same target color in a first state and a second state, includes: a first acquisition unit that acquires, from a first chart based on a first tone value of a target mixed color in the first state, a first color value of a patch corresponding to the first tone value; a second acquisition unit that acquires, from a second chart based on the first tone value in the second state, a second color value of a patch corresponding to the first tone value; and a correction unit that corrects the first tone value such that a mixed color based on the first tone value in the second state becomes the target mixed color, when a color difference between the second color value and the first color value is greater than or equal to a threshold.