Nozzle-Specific Color Correction for Multi-Ink Printers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Color unevenness occurs in images printed using multiple inks due to variations in ejection characteristics among ink nozzles, leading to color shifts and inaccuracies in colorimetry, especially when superimposing inks, and existing head shading techniques are insufficient in addressing these issues.
Innovation Solution
An image processing apparatus and method that perform color correction processing by using a conversion table with table parameters specific to each nozzle, generating and selecting correction candidate values to adjust ink ejection amounts, and printing test color images to accurately correct color unevenness in a common region of the printing medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If head shading technique is used to correct density variation, then density unevenness of single color image is corrected, but color shift occurs in images expressed by superimposing two or more inks
Solution Approach 1:
The invention divides the correction approach by separating single-color density correction from multi-color colorimetric correction. It uses nozzle-specific conversion tables with parameters tailored for each nozzle's ejection characteristics, allowing independent optimization for each color channel while maintaining overall color accuracy through superimposition correction.
Solution Approach 2:
The invention changes the correction parameters from generic head shading parameters to nozzle-specific conversion table parameters. By storing and applying unique parameters for each nozzle based on its ejection characteristics, the system achieves both density uniformity and color accuracy simultaneously, resolving the contradiction between the two correction goals.
2Measurement precision
If spectrophotometric colorimeter reads reflected light within a certain spot diameter, then colorimetry is performed, but color unevenness in regions smaller than spot diameter cannot be accurately measured
Solution Approach 1:
The invention performs preliminary correction by generating and applying nozzle-specific conversion tables before actual printing. By pre-characterizing each nozzle's ejection characteristics and creating correction parameters in advance, the system compensates for nozzle variations proactively, enabling accurate color reproduction even when measurement devices have limited spatial resolution.
3Adaptability or versatility
If multiple inks are superimposed to perform color reproduction, then color image is formed, but color shift occurs due to different ejection amounts from nozzles
Solution Approach 1:
The invention implements a feedback mechanism by using measured ejection characteristics of each nozzle to generate specific conversion table parameters. The system measures actual nozzle performance, creates tailored correction parameters based on these measurements, and applies them during printing to compensate for variations, ensuring accurate color reproduction through superimposed inks.
Data Source
AI summary
Provided is an image processing apparatus that can accurately and efficiently reduce color unevenness that occurs in a color image, which is formed by color mixture of a plurality of different types of inks, due to a variation in ejection characteristic among nozzles. The inks are respectively ejected from the nozzle arrays to print patches; regions where color correction for test color images should be performed are specified; a different types of color correction processing for color signals corresponding to the color correction regions are performed to print color correction patches; a color correction patch to be used is selected; on the basis of selected color correction processing, a table parameter corresponding to a nozzle is formed; when the plurality of color correction patches are formed, only correction candidate values having larger color differences than a predetermined threshold value in a uniform color space are generated for color signals.