Linear Printhead In-Track Error Correction via Digital Resampling
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Solution Overview
Problem
Digital printing systems with linear printheads face significant in-track alignment errors between color channels, leading to objectionable alignment issues, which existing methods struggle to address without complex and costly fixtures.
Innovation Solution
A method involving the creation of a test target with alignment marks, capturing images, analyzing positions, determining correction functions, and resampling image data to correct for in-track position errors, allowing for non-linear corrections and reduced alignment errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If complex and costly fixtures are used to correct in-track position errors, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates a digital copy (correction function) of the in-track position errors by measuring alignment mark positions and generating a correction lookup table. This digital correction data replaces the need for complex physical fixtures, allowing software-based correction of printhead alignment errors without adding mechanical complexity
Solution Approach 2:
The patent substitutes mechanical correction fixtures with a software-based correction system. By using image capture to measure errors and applying digital resampling to correct image data, the system replaces complex mechanical alignment fixtures with computational methods, reducing device complexity while maintaining manufacturing precision
2Device complexity
If in-track position errors are not corrected, then device complexity remains low, but manufacturing precision deteriorates due to alignment errors between color channels
Solution Approach 1:
The patent performs preliminary measurement and correction function generation before actual printing operations. By capturing images of alignment marks, determining in-track position errors, and creating correction lookup tables in advance, the system prepares correction data that can be applied during normal printing without adding complexity to the printing process itself
Solution Approach 2:
The patent introduces an intermediary correction function (lookup table) that mediates between the printhead's inherent alignment errors and the final printed output. This correction data structure acts as a bridge, translating measured errors into compensatory adjustments that improve color channel alignment without requiring direct mechanical intervention
3Productivity
If linear printhead is used for digital printing, then productivity is improved, but manufacturing precision worsens due to in-track alignment errors between color channels
Solution Approach 1:
The patent implements a feedback mechanism by capturing images of printed alignment marks, measuring actual in-track positions, comparing them to reference positions, and using the measured errors to generate correction functions. This closed-loop feedback allows the system to maintain high productivity with linear printheads while compensating for alignment errors through software correction
Data Source
AI summary
A method for correcting in-track position errors in a digital printing system having a linear printhead includes printing a test target including a plurality of alignment marks. A data processing system is used to automatically analyze a captured image of the printed test target to determine a measured in-track position for each of the alignment marks. The measured in-track positions for the alignment marks are compared to reference positions to determine measured in-track position errors. An in-track position correction function is determined responsive to the measured in-track position errors, wherein the in-track position correction function specifies in-track position corrections to be applied as a function of cross-track position. A corrected digital image is determined by resampling an input digital image responsive to the in-track position correction function.