Inkjet Printhead Nozzle Failure Compensation via Adaptive Density Control
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Solution Overview
Problem
Inkjet printing systems face non-uniformity issues due to failing nozzles, leading to linear imperfections in printed images, especially in one-pass systems, where compensation methods often result in either undercompensation or overcompensation, affecting optical density.
Innovation Solution
A method that selects failing nozzles and determines environment density to choose between two compensation mechanisms, adjusting the amount of colorant based on a predetermined threshold to better approximate the required optical density, incorporating mechanisms like signal transfer to neighboring nozzles and adding ink dots of another colorant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed compensation mechanism is used to provide additional ink near a missing dot, then the optical density is improved, but linear imperfections (undercompensation or overcompensation) occur due to inability to adapt to varying environmental conditions
Solution Approach 1:
The patent implements dynamic compensation by continuously monitoring the actual optical density around missing dots and adjusting the compensation amount in real-time. The system transitions from fixed compensation to adaptive compensation where the compensation quantity is dynamically modified based on measured environmental conditions, thereby eliminating linear imperfections while maintaining optical density uniformity.
Solution Approach 2:
The patent employs feedback mechanisms where the actual optical density is measured around missing dots and this information is fed back to the control system. Based on this feedback, the system calculates the actual compensation quantity needed and adjusts the ink application accordingly, ensuring precise compensation without undercompensation or overcompensation.
2Manufacturing precision
If additional ink is applied in the neighborhood of a missing dot to compensate for the failing nozzle, then the optical density is improved, but non-uniformity in the printed image occurs due to fixed compensation amounts
Solution Approach 1:
The system dynamically adjusts the compensation quantity based on real-time measurement of the actual optical density environment. Instead of applying a fixed amount of additional ink, the system modifies the compensation quantity according to the specific conditions at each missing dot location, ensuring uniform image composition without artificial patterns.
Solution Approach 2:
The patent changes the compensation parameter (amount of additional ink) based on the measured optical density environment. The system calculates the actual compensation quantity as a function of the environmental conditions, thereby adapting the ink application parameter to maintain image uniformity while compensating for the failing nozzle.
3Reliability
If a second printhead is placed behind the first printhead to provide a spare nozzle for each print position, then the reliability is improved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent enables the single printhead system to compensate for its own failures using its remaining functional nozzles. The system self-adjusts by redistributing ink application to neighboring nozzles based on measured optical density, eliminating the need for separate backup printheads while maintaining reliability.
Solution Approach 2:
The functional nozzles in the printhead are made multi-functional by enabling them to compensate for failing nozzles not only in their own color channel but also by coordinating with other color channels. This universal compensation capability replaces the need for dedicated backup printheads, reducing device complexity while maintaining reliability.
Data Source
AI summary
A method is provided for compensating a failing nozzle in a printhead comprising a series of print elements with nozzles for operation in an inkjet printing process in which a colorant is applied for locally changing an optical density, thereby printing an image. The method comprises at least two compensation mechanisms, each providing a different amount of additional optical density in the environment of a missing dot in the printed image. A nozzle is recorded as a failing nozzle if the associated print element does not apply an ink dot within predetermined specifications. An environment density is determined in an environment of a missing dot associated with said failing nozzle. The environment density is compared with a predetermined threshold, and an appropriate compensation mechanism is selected from the at least two compensation mechanisms. The method is applied in an inkjet printing system for balancing under- and overcompensated optical density.