Inkjet Dot Pattern Shifting for Indexing Error Robustness
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Solution Overview
Problem
Ink jet printing systems are sensitive to errors such as indexing errors and printhead carrier vibrations, which affect the placement of ink drops on the print medium, leading to suboptimal image quality due to the close dot size and spacing ratio.
Innovation Solution
A method is introduced to create a non-ideal vertically shifted pattern of dot locations by selectively shifting groups of dots in each raster, using a controller to adjust the index offset for each pass of the printhead, thereby increasing the robustness of the printing system to errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dot size and spacing are kept close to maintain high print resolution, then manufacturing precision is improved, but the system becomes more sensitive to indexing errors and vibrations
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-compensating for indexing errors through lookup tables that store correction values. The system determines the actual sheet position before printing and selects appropriate dot patterns from lookup tables that compensate for anticipated positioning errors, thereby maintaining print quality despite indexing inaccuracies.
Solution Approach 2:
The patent changes parameters by dynamically selecting different dot patterns based on detected indexing errors. When positioning errors are detected, the system modifies dot placement parameters by retrieving alternative patterns from lookup tables that adjust dot positions to compensate for the errors, thus maintaining image quality across varying printing conditions.
2Manufacturing precision
If the print medium is advanced by precise indexed moves between passes, then manufacturing precision is improved, but the system becomes more sensitive to small indexing errors
Solution Approach 1:
The system performs preliminary detection of sheet position using sensors before each printing pass. Based on the detected position, the controller pre-determines the actual index move required and selects appropriate compensatory dot patterns from lookup tables, thereby compensating for indexing errors before they affect print quality.
Solution Approach 2:
The patent implements feedback by continuously monitoring the actual sheet position during printing using sensors. The detected position information is fed back to the controller, which then adjusts subsequent dot placement by selecting appropriate patterns from lookup tables to compensate for accumulated indexing errors, ensuring consistent print quality.
3Manufacturing precision
If dot spacing is reduced to increase print resolution, then manufacturing precision is improved, but the system becomes more sensitive to printhead carrier vibrations
Solution Approach 1:
The system pre-determines vibration compensation parameters by detecting printhead position and velocity before each pass. Based on this preliminary information, the controller selects dot patterns from lookup tables that are designed to compensate for anticipated vibration effects, thereby maintaining dot placement accuracy despite vibrations.
Solution Approach 2:
The patent changes dot placement parameters dynamically by retrieving alternative patterns from lookup tables when vibrations are detected. The system modifies horizontal and vertical dot positions based on vibration magnitude and direction, selecting patterns that compensate for the distortion caused by printhead vibrations during printing.
Data Source
AI summary
A method for decreasing sensitivity to errors in an imaging apparatus includes, defining an ideal pattern of dot locations as a rectilinear grid formed by an intersection of a plurality of rasters and a plurality of vertical columns; for each raster of the plurality of rasters defining a plurality of groups of dot locations; and for each raster of the plurality of rasters, vertically shifting some groups of the plurality of groups of dot locations while not vertically shifting a remainder of groups of the plurality of groups of dot locations so as to define a non-ideal vertically shifted pattern of dot locations.