Halftone Independent Color Drift Correction Using 2x2 Printer Model
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Solution Overview
Problem
Printers experience temporal and media color drift, leading to inconsistent color output over time and across different printing media, making existing color correction methods time-consuming and impractical, especially for xerographic printers with multiple halftone screens.
Innovation Solution
A method using the 2×2 printer model to predict and compensate for color drift by determining true and estimated tone response curves for each color channel, allowing for halftone-independent color correction without the need for full color calibration, by printing and measuring 2×2 test patches and applying a halftone correction factor to adjust tone response curves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full color characterization is performed to correct for temporal color drift or media color drift, then color accuracy is improved, but time consumption increases significantly
Solution Approach 1:
The patent segments the color correction process by separating halftone-dependent measurements from halftone-independent corrections. Instead of performing full color characterization for all halftone methods simultaneously, the system performs measurements for a single halftone method and uses the 2×2 printer model to predict corrections across all halftone methods, thereby reducing time consumption while maintaining color accuracy.
Solution Approach 2:
The patent creates a mathematical copy of the printer's color behavior using the 2×2 printer model. This model copies the essential color drift characteristics without requiring actual physical measurements for all possible halftone combinations, enabling prediction of color corrections without the time-consuming full characterization process.
2Ease of manufacture
If 1-D TRC calibration is used for each color channel, then ease of implementation is improved, but measurement intensity increases due to halftone dependency
Solution Approach 1:
The patent makes the calibration process universal by developing a halftone-independent correction method. The 2×2 printer model with Yule-Nielsen equation can correct color drift across different halftone methods (screen angles, dot shapes, overlapping patterns) using the same measurement process, eliminating the need for separate calibration for each halftone method and reducing overall measurement intensity.
Solution Approach 2:
The patent changes the fundamental parameter of the calibration approach from halftone-specific to halftone-independent. By using the 2×2 printer model that parameters color behavior in terms of ink coverage rather than specific halftone patterns, the system achieves color correction without being tied to any particular halftone method, thereby reducing measurement requirements.
3Measurement precision
If conventional 1-D TRC calibration is performed for each halftone method, then color correction accuracy is improved, but device complexity increases due to multiple test patches required
Solution Approach 1:
The patent merges all halftone method corrections into a single unified correction process. Instead of requiring separate test patch sets for each halftone method, the system uses one set of test patches measured with a single halftone method and combines the results with the 2×2 printer model to generate corrections for all halftone methods, thereby reducing device complexity while maintaining correction accuracy.
Data Source
AI summary
A method for compensating for color drift in a printer includes determining a first true tone response curve for a color channel when said printer is in a first state. A first estimated tone response curve for the color channel is also determined when said printer is in the first state. A second estimated tone response curve for the color channel is determined when the printer is in a second, color-drifted state relative to the first state. A second true tone response curve for the color channel is mathematically predicted using the first true tone response curve, the first estimated tone response curve, and the second estimated tone response curve. The first and second estimated tone response curves are estimated using a 2×2 printer model. A printing apparatus includes an image processing unit for implementing the color-drift correction process.