Printer Stitching Zone Decorrelated Masks
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Solution Overview
Problem
Page wide array printers face challenges in maintaining image quality due to mechanical variability between print heads, leading to gaps and defects in the stitching zone, while scanning printers struggle to hide defects in single-pass or low-pass modes, resulting in issues like grain, line banding, and tone shift banding.
Innovation Solution
The implementation of decorrelated weaving masks for overlapping nozzle arrays in the stitching zone, which are independent of the actual image data, ensures consistent optical density across the stitching and non-stitching zones, using halftone algorithms and contone ramps to generate patterns that compensate for print head alignment errors and variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overlapping nozzle arrays are used in page wide array printers to compensate for mechanical variability, then reliability of printing is improved, but image quality deteriorates due to defects in the stitching zone
Solution Approach 1:
The patent divides the overlapping stitching zone into multiple sub-zones and applies different ink distribution patterns to each sub-zone. This segmentation allows the system to maintain the redundancy benefits of overlapping nozzles while distributing defects across multiple smaller regions, preventing any single defect from degrading overall image quality.
Solution Approach 2:
The patent applies different ink distribution strategies to different regions within the stitching zone based on local characteristics. By analyzing the specific offset patterns and defect locations in each sub-zone, the system tailors the ink distribution locally to compensate for specific defects while maintaining overall image quality consistency.
2Productivity
If scanning printers operate in single-pass or low-pass mode to improve productivity, then printing speed is improved, but image quality deteriorates due to visible defects like grain, line banding, and tone shift banding
Solution Approach 1:
The patent performs preliminary analysis of the stitching zone characteristics and pre-calculates the optimal ink distribution patterns before printing. By preparing the compensation strategies in advance based on measured offset patterns, the system can execute single-pass printing at high speed while maintaining image quality through pre-planned defect compensation.
Solution Approach 2:
The patent dynamically adjusts ink distribution parameters within the stitching zone based on measured offset patterns and defect characteristics. By changing the ink distribution parameters locally in response to detected variations, the system compensates for defects while maintaining high-speed single-pass operation.
Data Source
AI summary
A printer for printing on a print medium as said print medium advances through a print zone, the printer including a number of print heads extending over the print zone, each print head including at least one nozzle array wherein at least two adjacent nozzle arrays overlap forming at least one stitching zone in the overlap region; and a printer controller for generating a sequence of nozzle firing commands for each nozzle array to selectively deposit droplets of print fluid on said print medium from said nozzle arrays in accordance with an image to be printed, wherein the printer controller further applies masks having decorrelated patterns to said sequence of firing commands for at least those overlapping nozzles of the nozzle arrays coinciding with the at least one stitching zone to obtain a predetermined optical parameter of the printed image in the stitching zone, irrespective of an offset between two adjacent nozzle arrays.