Inkjet Printhead Stitch Alignment Using Offset Test Patterns
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Solution Overview
Problem
Existing methods for aligning image data in multi-printhead printers fail to adequately account for density-dependent stitching characteristics, leading to visible artifacts and misalignment errors.
Innovation Solution
A method involving the application of a test image with specific patterns to determine an aim offset value by analyzing stitch scores at varying in-track offsets, using a curve-fitting process to correct for alignment errors between overlapping jetting modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing alignment methods are used in multi-printhead printers, then the printing process can be completed, but visible artifacts and misalignment errors occur due to failure to account for density-dependent stitching characteristics
Solution Approach 1:
The patent applies parameter changes by measuring stitch scores at multiple different in-track offsets and using curve-fitting to determine the optimal alignment. This involves changing the measurement parameters across multiple offset values to accurately capture density-dependent stitching characteristics, rather than using a single fixed alignment method.
Solution Approach 2:
The patent implements feedback by analyzing stitch scores from printed test patterns and using this information to determine correction values. The measured stitch scores provide feedback about actual alignment performance, which is then used to adjust and optimize the alignment parameters for production printing.
2Device complexity
If a single fixed alignment method is used, then the process is simple, but it cannot account for density-dependent stitching characteristics leading to visible boundaries
Solution Approach 1:
The patent applies preliminary action by printing test patterns with known geometric features before actual production printing. These test patterns are used to measure stitch scores at various offsets and determine optimal alignment parameters in advance, so that the alignment corrections can be applied during production without adding complexity to the main printing process.
3Measurement precision
If multiple test patterns with varying in-track offsets are printed and analyzed, then accurate alignment determination is achieved, but the calibration process becomes more time-consuming
Solution Approach 1:
The patent applies partial action by printing test patterns at multiple discrete in-track offset values rather than continuously varying offsets. This selective sampling at key offset points provides sufficient measurement data for accurate alignment determination while reducing the total calibration time compared to a continuous measurement approach.
Data Source
AI summary
Cross-track stitch errors in an inkjet printer are reduced by printing test patterns for a plurality of in-track offsets. A first test pattern portion to be printed with a first jetting modules includes a uniform density region having a slot with a slot width. A second test pattern portion to be printed with a second jetting modules includes a bar having a bar width, wherein the uniform density region of the first test pattern portion and the bar of the second test pattern portion overlap in the cross-track direction and are printed with jets in an overlap region between the jetting modules. The printed test patterns are analyzed to determine a stitch score that represents a degree of alignment between the slot in the first test pattern portion and the bar in the second test pattern portion. An aim offset value is determined where the slot and the bar are aligned.