Spot Color Rendering via Feedback Optimization
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Solution Overview
Problem
Current methods for optimizing image quality in spot color rendition in commercial printing are computationally intensive and often result in noisy prints due to the lack of a feedback-based approach that can simultaneously minimize multiple image quality attributes, limiting the ability to optimize CMYK recipes for accurate and smooth color reproduction across all colors.
Innovation Solution
A feedback control loop system that adjusts set points for process actuators and color recipes to minimize a function of image quality attributes, using in-line spectrophotometer measurements or array sensors, allowing for simultaneous optimization of multiple image quality attributes for selected spot colors, thereby achieving stability and optimality in color rendition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If open-loop multi-objective optimization is used to optimize CMYK recipes for spot color rendition, then color accuracy can be improved, but the computational complexity increases significantly and the method cannot simultaneously optimize multiple image quality attributes
Solution Approach 1:
The patent implements a feedback-based optimization system where image quality attributes are measured after printing and fed back to adjust the optimization process. This allows the system to iteratively improve multiple image quality attributes simultaneously while reducing computational complexity compared to exhaustive open-loop methods. The feedback loop enables real-time adjustment of CMYK recipes based on actual print outcomes.
2Manufacturing precision
If exhaustive search of all CMYK recipes is performed to find optimal color reproduction, then color accuracy improves, but processing time and computational resources increase significantly
Solution Approach 1:
The system performs preliminary characterization of the printing device to establish the relationship between CMYK inputs and image quality attributes. This pre-computed model allows for rapid optimization of CMYK recipes without performing exhaustive searches during actual printing operations. The preliminary device characterization creates a lookup table or model that enables quick determination of optimal recipes.
3Manufacturing precision
If process actuators are optimized for a single color at a time, then optimization precision for that color improves, but the ability to optimize multiple colors simultaneously deteriorates
Solution Approach 1:
The patent merges the optimization of multiple colors into a unified feedback-based optimization framework. Instead of treating each color separately, the system combines image quality measurements from multiple colors and optimizes process actuators to minimize a composite objective function that accounts for all selected colors simultaneously. This approach maintains optimization precision while enabling multi-color capability.
Data Source
AI summary
What is disclosed is a feedback control based system and method for selecting spot color recipes for improved spot color rendition while simultaneously minimizing a function of image quality attributes formed with states defined as vectors such as L*, a*, b*, mottle, graininess, etc. Color is measured with an in-line spectrophotometer or with a full/partial width array. If the sensor is not available, then a model of the print device is used to optimize the function of image quality attributes. In one example embodiment, a spot color of interest is selected along with a set of image quality attributes to be improved for the spot colors of interest. Set points for process actuators and color recipes of the color marking device are adjusted such that a function of the image quality attributes is minimized when the spot color is rendered on the device. Various workflows are disclosed.