Serial Printer Dot Density Adjustment for Seam Line Reduction
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Solution Overview
Problem
Existing image processing methods for serial type inkjet printers fail to effectively reduce seam lines caused by sudden conveyance errors, especially in high-density areas, leading to noticeable white and black stripes even with a small number of multi-passes.
Innovation Solution
The method adjusts the number of dots printed in boundary portions to be greater than in other areas, based on the density level of the image data, using specific dot arrangement patterns and mask patterns to ensure more dots are printed in high-density areas, thereby reducing the visibility of seam lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multi-pass printing is performed to reduce seam lines, then the visibility of seam lines is reduced, but the printing time increases
Solution Approach 1:
The patent applies local quality by differentiating the number of dots printed in boundary portions versus non-boundary portions. Specifically, boundary portions (where seam lines occur) receive a higher number of dots than non-boundary portions, creating localized compensation for conveyance errors only where needed most, rather than uniformly increasing dot density across the entire image.
Solution Approach 2:
The patent implements partial action by applying enhanced dot printing only to boundary portions rather than the entire image area. The adjustment is concentrated specifically at the boundaries where seam lines are most visible, using a controlled amount of excessive dot printing (more dots than the average area) precisely where the harmful effect occurs.
2Object-affected harmful factors
If the conveyance amount is adjusted to avoid black or white stripes, then seam lines are reduced, but the method cannot handle sudden conveyance errors
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-determining which portions of the image are boundary portions before actual printing occurs. The system identifies boundary portions in advance based on the image data and conveys this information to the printing control, allowing preemptive adjustment of dot numbers in those specific areas to compensate for potential conveyance errors.
Solution Approach 2:
The patent implements feedback by using the actual conveyance amount measured during printing to adjust the number of dots printed in boundary portions. The control unit receives feedback about the conveyance amount and modifies the dot printing accordingly, creating a closed-loop system that adapts to actual conveyance conditions rather than relying solely on predetermined values.
3Object-affected harmful factors
If more dots are printed in boundary portions to compensate for conveyance errors, then seam lines are reduced, but the number of main scans increases
Solution Approach 1:
The patent applies parameter changes by modifying the dot arrangement pattern and dot density parameters specifically in boundary portions rather than changing the fundamental printing process parameters across the entire image. The system adjusts local parameters (number of dots, dot arrangement) while maintaining the overall multi-pass printing structure, thus reducing seam lines without significantly increasing the number of main scans required.
Data Source
AI summary
Provided is an image processing apparatus and image processing method that are capable of outputting an image wherein seam lines caused by sudden conveyance error are difficult to notice even for a small number of multi passes printing. In order to achieve this, the number of dots that are printed in pixels is adjusted according to the density level so that the number of dots that are printed in pixels corresponding to boundary portions is larger than in pixels corresponding to areas that are not boundary portions, and so that the number of dots that are printed in pixels corresponding to boundary portions increases the higher the density level of the pixels is. As a result, it is possible to avoid the occurrence of white stripes in high-density areas without emphasizing black stripes in low-density areas.