Uniform Color Rendering via Inverse Spatial Maps
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Solution Overview
Problem
High-quality printing systems face challenges in rendering spatially uniform colors due to output device quality errors, particularly when images printed with CMYK primaries are not rendered consistently across the page or over time, leading to non-uniformity issues with memory colors like 'Xerox red' or 'IBM blue'.
Innovation Solution
A method involving an array of sensors to scan a test image, extract memory color objects, and generate an inverse spatial color map to adjust pixel colors based on position, ensuring uniformity across the page and between printers, using a processor to create a system with a scanner, printer, and image data source for consistent color generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If images are printed with CMYK primaries using conventional printing systems, then production efficiency is maintained, but spatial uniformity of color rendering deteriorates due to output device quality errors
Solution Approach 1:
The system performs preliminary characterization of the print engine by printing test images and scanning them to capture spatial non-uniformity errors before actual production printing. This advance measurement allows the creation of inverse spatial maps that pre-compensate for device-specific defects, enabling high-speed production printing without sacrificing color uniformity.
Solution Approach 2:
The invention applies location-specific correction factors through inverse spatial maps that vary across different regions of the printed page. Each spatial location has its own correction characteristics based on measured non-uniformity, allowing localized compensation for charging variations, development wire history effects, and photoreceptor variations without affecting overall printing efficiency.
2Manufacturing precision
If spatial non-uniformity correction is implemented across the entire printed page, then color uniformity improves, but system complexity increases due to additional sensing and processing requirements
Solution Approach 1:
The system introduces an intermediary inverse spatial map that mediates between the print engine's inherent non-uniformity and the desired uniform output. This computational intermediary layer processes color values based on spatial location and measured error characteristics, providing correction without requiring complex hardware modifications to the print engine itself.
Solution Approach 2:
The system implements feedback by scanning printed test images and using the measured spatial non-uniformity to refine the inverse spatial maps. This closed-loop approach allows the system to adapt to changes in print engine characteristics over time, maintaining color uniformity while using relatively simple sensing equipment.
3Measurement precision
If memory colors are rendered with consistent CMYK mixtures, then color accuracy to input is maintained, but spatial uniformity deteriorates due to print engine variations
Solution Approach 1:
The system applies location-specific adjustments to memory color rendering by using the inverse spatial map to modify CMYK values based on spatial position. This allows the same memory color to be rendered with slightly different CMYK mixtures at different locations on the page, compensating for local print engine variations while maintaining overall color accuracy and spatial uniformity.
Data Source
AI summary
The present disclosure is directed to a system and method to render spatially uniform memory colors when images printed with CMYK primaries are not rendered uniformly due to output device quality errors. The disclosed method uses an array of sensors to scan a test image. Colors of interest are printed at the desired location first and then adjusted (iterated) to achieve a desired output quality. Iterations are carried out on the image on desired memory colors at the spatial resolution available in the measurement system. Colors of pixels are modified based on position where the pixels will be rendered, thereby compensating for any position/process related differences. Also disclosed is a process for incorporating modified memory colors before rendering, and the extension of memory color concepts to adjust colors for the uniform blocks (not edges), with uniformity defined by user definable thresholds.