Bidirectional Printer Masking for Banding Reduction
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Solution Overview
Problem
Existing color printing technologies face challenges in minimizing banding artifacts, particularly in bidirectional printing modes where differences in ink laydown order and timing between passes lead to systematic variations in optical density and color hue, which are not effectively addressed by current masking strategies.
Innovation Solution
The proposed solution involves applying masks with mesa portions and side ramp portions to rows of fluid ejection nozzles, where the mesa portions have varying firing frequencies with peaks and valleys, ensuring that different color inks are deposited in a consistent order and sequence across passes, minimizing banding effects while maintaining a balanced nozzle usage profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If masks are applied to nozzles in multi-pass printing mode, then visible artifacts such as image banding are prevented or reduced, but systematic variations in optical density and color hue occur due to differences in ink laydown order and timing between passes
Solution Approach 1:
The patent applies different mask patterns to different nozzle groups within the same print head. Specifically, first mask patterns are applied to first groups of nozzles while second mask patterns are applied to second groups of nozzles. This local differentiation ensures that nozzles printing different colors follow consistent laydown sequences, eliminating banding artifacts while maintaining overall image quality.
Solution Approach 2:
The patent segments the nozzle array into multiple groups, where each group is assigned a specific mask pattern. This segmentation allows independent control of ink laydown sequences for different color groups, ensuring that cyan, magenta, yellow, and black inks are deposited in a consistent order regardless of printing direction, thereby preventing banding artifacts.
2Productivity
If bidirectional printing mode is used, then printing productivity is improved, but banding artifacts are generated due to inconsistent ink deposition order between passes
Solution Approach 1:
The patent implements direction-dependent mask patterns where the mask applied to each nozzle group varies based on the printing direction. When printing in the forward direction, first mask patterns are applied; when printing in the reverse direction, second mask patterns are applied. This ensures consistent ink laydown sequences bidirectionally, enabling high-speed printing without banding artifacts.
Solution Approach 2:
The patent dynamically adjusts mask patterns based on printing direction. The control system detects the current printing direction and automatically switches between different mask patterns for different nozzle groups. This dynamic adaptation maintains consistent ink deposition order whether printing forward or backward, enabling productive bidirectional printing without quality degradation.
3Device complexity
If conventional mask patterns are applied to all nozzles, then printing process is simplified, but banding artifacts persist due to inconsistent ink laydown sequence across different nozzle groups
Solution Approach 1:
The patent applies different mask patterns to different nozzle groups based on their specific color output requirements. First mask patterns are applied to first groups of nozzles while second mask patterns are applied to second groups of nozzles. This localized masking strategy, while more complex than uniform masking, ensures consistent ink laydown sequences and eliminates banding artifacts, justifying the increased complexity through superior image quality.
Data Source
AI summary
A method of controlling a printer is described, for printing a pattern from a first row of fluid ejection nozzles and a second row of fluid ejection nozzles in a multi-pass printing mode. The first and second rows of fluid ejection nozzles eject fluid of a first type and fluid of a second type, respectively. The method comprises: assigning respective parts of the pattern to be printed to the first and second rows of fluid ejection nozzles; applying a first mask to the first row of said ejection nozzles and a second mask to the second row of fluid ejection nozzles for printing with selected nozzles of each of the rows of fluid ejection nozzles during each pass; wherein the first mask comprises a mesa portion and the second mask comprises a mesa portion wherein the mesa portion of the first mask includes at least a first peak and the mesa portion of the second mask includes at least a second valley, the first peak overlapping with the second valley.