Overlapping Dot Lattice Patterns for Print Misalignment
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Solution Overview
Problem
Existing image printing technologies fail to effectively mitigate graininess and density unevenness caused by print misalignment between scans, particularly in the sub-scanning direction, despite methods to address misalignment in the scanning direction.
Innovation Solution
The use of a robust pattern where two dot patterns are printed in an overlapping manner, ensuring translational symmetry and specific conditions are met to maintain consistent dot coverage and granularity despite misalignment, achieved through lattice patterns with different basis vectors and controlled dot arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multipass printing is performed with relative movement between print head and print medium, then printing area and productivity are improved, but print misalignment occurs causing graininess and density unevenness
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-positioning dots in a first print scan such that they are intentionally separated from dots in subsequent print scans. This preventive measure ensures that even if misalignment occurs during multipass printing, the separated dot positions prevent visual detection of graininess and density unevenness, thereby maintaining print quality while enabling productive multipass operation
2Quantity of substance
If dots are arranged to overlap in different print scans, then dot coverage is improved, but misalignment causes noticeable graininess and density variation
Solution Approach 1:
The patent applies local quality by creating non-uniform dot separation patterns where dots in different local regions are separated by different distances and in different directions. This localized variation in dot arrangement ensures that no two adjacent dots from different print scans align perfectly, thereby preventing periodic graininess while maintaining overall dot coverage
Solution Approach 2:
The patent applies asymmetry by using different separation distances and separation directions for dots in different regions. Instead of uniform symmetric overlap, the asymmetric arrangement ensures that dot patterns from different print scans do not align, thereby eliminating graininess while maintaining adequate coverage through varied dot distribution
3Ease of manufacture
If conventional dot arrangement methods are used, then printing process is simple, but graininess and density unevenness remain noticeable
Solution Approach 1:
The patent maintains printing process simplicity by implementing the dot separation logic within the existing image processing pipeline before printing. The preliminary calculation of separated dot positions is integrated into the standard multipass printing workflow, requiring no additional hardware or complex process changes while effectively eliminating graininess and density unevenness
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An object is to print a high quality image with resistance to print misalignment. To this end, the image processing apparatus (1) generates quantized data for printing a first dot pattern (101) and a second dot pattern (102) in an overlapping manner. The first dot pattern (101) and the second dot pattern (102) are lattice patterns varying in a combination of two basis vectors (al, a2, b1, b2). In a combined dot pattern (100) obtained by combining the first and second dot patterns (101, 102), there is a neighboring dot (105) in which a dot in the first dot pattern (101) and a dot in the second dot pattern (102) are arranged at an interval smaller than a lattice spacing. The neighboring dot (105) includes multiple neighboring dots varying in an approach direction.