Image Processor Nozzle Ejection Correction
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Solution Overview
Problem
Existing image processing techniques, such as head shading, fail to effectively reduce color unevenness in composite colors printed by inkjet printers due to variations in nozzle ejection amounts, leading to color shifts when different inks are overlapped, especially in multi-value printers.
Innovation Solution
An image processor and method that utilize conversion tables to correct image data for each nozzle group, aligning ink colors across multiple nozzle arrays, thereby reducing color unevenness by dividing the printable area into unit areas and arraying nozzles in a direction perpendicular to their arrangement, ensuring accurate color representation across the print medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If head shading technique is used to correct density unevenness, then density uniformity is improved, but color accuracy deteriorates due to color shift in overlapped ink areas
Solution Approach 1:
The invention divides the printable area into multiple unit areas along the nozzle arrangement direction, and further segments each unit area into first and second sub-areas. This segmentation allows different correction methods to be applied to different regions: head shading correction for first sub-areas (where density uniformity is prioritized) and conversion table correction for second sub-areas (where color accuracy is prioritized), thereby resolving the contradiction between density uniformity and color accuracy.
Solution Approach 2:
The invention applies different correction characteristics to different local regions of the printable area. Specifically, head shading correction is applied to first sub-areas while conversion table correction is applied to second sub-areas. This local differentiation allows the system to optimize for density uniformity in some regions and color accuracy in other regions, simultaneously addressing both requirements without compromise.
2Measurement precision
If conversion table correction is applied to all areas, then color accuracy is improved, but processing time increases
Solution Approach 1:
The invention segments the printable area into multiple unit areas and further into first and second sub-areas, applying conversion table correction only to the second sub-areas where color accuracy is critical. By limiting the computationally intensive conversion table correction to only these specific regions rather than applying it universally, the system achieves improved color accuracy where needed while minimizing overall processing time.
Solution Approach 2:
Instead of applying conversion table correction to all areas (excessive action), the invention applies it partially only to the second sub-areas where color accuracy is most important. This partial application reduces the total processing load while still achieving the desired color accuracy improvement in the critical regions, effectively balancing quality and speed.
3Productivity
If nozzle ejection variation is not corrected, then processing speed is maintained, but color unevenness occurs in composite colors
Solution Approach 1:
The invention segments the correction process into two parts: head shading correction applied to first sub-areas and conversion table correction applied to second sub-areas. This segmentation allows the system to maintain processing speed through simpler head shading correction in regions where it is sufficient, while applying the more complex conversion table correction only in second sub-areas where color uniformity is critical, thus balancing speed and precision.
Solution Approach 2:
The invention applies different levels of correction to different local regions: simpler head shading correction to first sub-areas and more sophisticated conversion table correction to second sub-areas. This local differentiation maintains processing speed in regions where simple correction is adequate while ensuring color uniformity in regions where it is most important, achieving overall optimization of both speed and quality.
Data Source
AI summary
The present invention is intended to provide an image processor that can reduce color unevenness occurring in a composite color image formed by overlapping different types of inks due to a variation in printing characteristic among a plurality of nozzles while suppressing a reduction in processing speed in generation of printing data. The image processor converts a color signal indicating the image represented by a plurality of elements to a color signal corresponding to the plurality of inks with use of a conversion table determined on the basis of ejection characteristics of nozzle groups corresponding to the plurality of inks so as to suppress color unevenness occurring in a composite color image due to a variation in ejection characteristic among the plurality of nozzles.