Inkjet Nozzle Compensation for Continuous Missing Raster Lines
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Solution Overview
Problem
Ink-jet printers face issues with defective nozzles causing missing dots due to clogging, which conventional neighborhood complementation methods fail to adequately address when multiple defective raster lines occur, leading to print quality deterioration.
Innovation Solution
A printing device and method that includes a control unit to manage defective nozzles by adjusting the position and size of ink dots using adjacent normal nozzles, specifically replacing the position of dots discharged by defective nozzles with those from normal nozzles and increasing the size of adjacent dots in the scanning directions to maintain print quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If neighborhood complementation is used to compensate for missing dots from defective nozzles, then print quality is improved for single defective nozzles, but print quality deteriorates when multiple defective raster lines occur continuously
Solution Approach 1:
The patent applies dynamics by making the complementation strategy adaptive rather than static. The control unit dynamically adjusts the complementation approach based on the detected pattern of defective nozzles. When multiple defective raster lines are detected in the sub-scanning direction, the system switches from simple neighborhood complementation to a more sophisticated approach that includes position replacement and selective dot expansion, thereby maintaining print quality stability under varying defect conditions.
Solution Approach 2:
The patent changes parameters of the ink dot formation process to compensate for defective nozzles. Specifically, it modifies the position parameter by replacing dot positions assigned to defective nozzles with positions from adjacent normal nozzles, and modifies the size parameter by expanding the size of adjacent dots. These parameter changes are applied conditionally based on the defect pattern, improving print quality while avoiding the deterioration that occurs with continuous application of fixed complementation methods.
2Manufacturing precision
If dot positions are replaced and sizes are increased to compensate for defective nozzles, then missing dots become less conspicuous, but dot placement precision may be compromised
Solution Approach 1:
The patent applies local quality by making the position replacement and dot expansion operations localized rather than global. Only specific dots adjacent to defective nozzles are expanded, and only dot positions corresponding to defective nozzles are replaced. The control unit identifies the exact locations of defective nozzles and applies compensation measures only in those local areas, thereby maintaining dot placement precision in regions unaffected by defects while improving dot formation quality at defective locations.
Solution Approach 2:
The patent performs preliminary action by detecting defective nozzles before the actual printing process and preparing a compensation strategy in advance. The control unit identifies defective nozzles and determines which dots will require position replacement or size expansion before printing begins. This preliminary detection and planning allows the system to maintain precise dot placement by pre-calculating the exact positions and sizes needed for compensated dots, rather than making adjustments during the printing process that could compromise precision.
Data Source
AI summary
A dot to be discharged by a first defective nozzle and a dot to be discharged by a second defective nozzle are determined to be adjacent to each other in a sub-scanning direction, the printing device replaces the position of the dot to be discharged by the first defective nozzle in a main scanning direction with the position of the dot to be discharged by the first normal nozzle in the main scanning direction and then converts the size of a dot adjacent in the sub-scanning direction to the dot to be discharged by the first defective nozzle or the dot to be discharged by the second defective nozzle into a larger size.