Printhead Alignment for Interlaced Inkjet Banding
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Solution Overview
Problem
Inkjet printers face challenges in aligning printheads accurately due to media shrinkage and printhead deviations, leading to banding artifacts and registration issues in images, especially when different types of imaging surfaces are used or printheads are replaced, and intermittent jet performance.
Innovation Solution
A method involving identifying stitch errors at each color station to adjust the overlap between printheads, using actuators to move printheads in the cross-process direction, and compensating for media shrinkage by introducing intentional stitch errors to mitigate image quality defects, thereby reducing banding artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If printheads are positioned to overlap to compensate for media shrinkage, then color registration between different color stations is improved, but banding artifacts occur in the overlap regions
Solution Approach 1:
The patent applies different positioning strategies to different regions of the printhead array. Central printheads are positioned with overlap to compensate for media shrinkage, while outer printheads are positioned without overlap to avoid banding artifacts. This local differentiation resolves the contradiction by optimizing each region's positioning based on its specific requirements.
Solution Approach 2:
The printhead array is segmented into central printheads and outer printheads, each handled differently in the positioning process. The system identifies and treats central printheads (which benefit from overlap for shrinkage compensation) separately from outer printheads (which cause banding if overlapped), allowing optimized positioning for each segment.
2Manufacturing precision
If media shrinkage is compensated by adjusting printhead positions, then image registration accuracy is improved, but device complexity increases
Solution Approach 1:
The system uses the printheads themselves to perform alignment by ejecting test patterns and using optical sensors to detect their actual positions. This self-alignment approach eliminates the need for external alignment equipment and complex manual adjustment procedures, reducing device complexity while maintaining high registration accuracy.
Solution Approach 2:
The system implements a feedback loop where test patterns are printed, detected by optical sensors, and used to calculate actual printhead positions. This feedback information is then used to determine the optimal overlap positioning for each printhead, enabling automatic compensation for media shrinkage without complex manual intervention.
3Manufacturing precision
If all printheads are positioned with overlap to compensate for shrinkage, then color registration is improved, but intermittent jet failures become more noticeable
Solution Approach 1:
The patent applies overlap positioning only to central printheads where it provides benefit for shrinkage compensation, while outer printheads are positioned without overlap. This local differentiation reduces the visibility of banding artifacts caused by intermittent jet failures in overlap regions, while maintaining color registration accuracy where it matters most.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces or eliminates banding artifacts and improves image registration by accurately aligning printheads, compensating for media shrinkage and printhead deviations, resulting in enhanced image quality and reliability.
Implementation Method 1
compensating for media shrinkage by introducing intentional stitch errors
Data Source
AI summary
A method for aligning printheads, some of which are arranged in an overlapped configuration, in a printer has been developed. The method includes identifying a stitch error for each color station in a plurality of color stations in the printer. The stitch error is identified with reference to shrinkage of a print medium as the print medium passes the plurality of color stations. A portion of the stitch error is used to move at least one printhead in the color station corresponding to the stitch error to compensate for a banding issue caused by the overlapped printhead configuration. All or part of the stitch error may also be applied to other printheads in the color station to compensate for possible color to color registration issues.