Multi-Pass Printer Nozzle Gradient Control for Banding Suppression
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Solution Overview
Problem
Conventional printers face issues with banding in printed images due to irregularities in sheet conveyance, which are not adequately addressed by existing techniques that modify dot recording rates based on nozzle positions, leading to irregular printing densities during transitions between edge and middle region printing.
Innovation Solution
A printer with a multi-pass printing mechanism that controls the dot recording rates of active nozzles through a controller, employing an upstream and downstream gradient approach to ensure consistent printing density across the sheet, using a combination of pass processes with varying numbers of active nozzles to manage the conveyance and scanning mechanisms effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fewer nozzles are used for printing edge regions compared to middle regions, then banding caused by conveyance irregularities is suppressed, but irregularities in printing density occur during transitions between edge and middle region printing
Solution Approach 1:
The patent applies local quality by differentiating nozzle usage between edge regions and middle regions of the sheet. Specifically, fewer nozzles are activated when printing edge regions compared to middle regions, creating a spatially varying printing strategy that adapts to local requirements. This resolves the contradiction by suppressing banding at edges through reduced nozzle activity while maintaining adequate coverage in middle regions.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the number of active nozzles based on the printing region. The system transitions between different nozzle configurations: using fewer nozzles for edge regions and more nozzles for middle regions. This dynamic adaptation allows the system to optimize for banding suppression at edges while maintaining printing density uniformity in middle regions, resolving the contradiction between these two requirements.
2Productivity
If more nozzles are used for printing middle regions of the sheet, then printing coverage and efficiency are improved, but banding occurs due to irregularities in sheet conveyance
Solution Approach 1:
The patent applies segmentation by dividing the printing process into distinct phases: edge region printing and middle region printing. During edge region printing, fewer nozzles are activated to reduce sensitivity to conveyance irregularities. During middle region printing, more nozzles are activated to improve printing efficiency and coverage. This segmentation allows the system to optimize for reliability during edge printing and for productivity during middle region printing, resolving the contradiction between these two objectives.
Data Source
AI summary
A printer performs a multi-pass printing including a (a)-print process, a (b)-print process, and a (c)-print process between the (a)-print process and the (b)-print process. The (c)-print process includes a (c1)-pass process, a (c2)-pass process, and a process for conveying a sheet feed amount greater than feed amount used in the (a)-print process after the (c1)-pass process and before the (c2)-pass process. An upstream gradient of dot recording rates of active nozzles used for the (c1)-pass process is greater than that for the (a)-print process. A downstream gradient of the dot recording rates for the (c1)-pass process is greater than or equal to that for the (a)-print process. A downstream gradient of the dot recording rates of for the (c2)-pass process is the same as the upstream gradient for the (c1)-pass process.