Random Wave Mask for Print Head Stitching
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Solution Overview
Problem
Conventional printing devices with staggered printheads and overlapping droplet ejection elements suffer from image quality defects due to sharp linear or regular sinusoidal masks, which are easily detectable and visible as vertical lines or patterns, especially with crossweb alignment errors.
Innovation Solution
The implementation of a random wave mask generation system that distributes data points based on a probability density function, particularly an inverted normal distribution, to create a wave curve with oscillating waveforms, which is used to generate a random wave mask that reduces the visibility of image quality defects by modifying the assignment of droplet ejection elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a sharp linear mask or regular sinusoidal mask is used to control overlapping droplet ejection elements, then the mask provides a clear pattern for droplet assignment, but image quality defects become visible as vertical lines or patterns especially with crossweb alignment errors
Solution Approach 1:
The patent applies asymmetry by transitioning from symmetric regular sinusoidal patterns to asymmetric random wave patterns. The random wave mask uses non-repeating, irregular waveforms that eliminate the periodicity causing visible stitching artifacts while maintaining effective droplet assignment between overlapping printheads.
Solution Approach 2:
The patent changes the parameters of the mask pattern from fixed regular sinusoidal waves with constant amplitude and frequency to random waves with varying amplitude, frequency, and phase. This parameter variation creates a more natural, less detectable transition zone between overlapping printhead regions.
2Productivity
If staggered printheads with overlapping droplet ejection elements are used to increase printing coverage, then productivity is improved, but image quality defects occur due to visible stitching artifacts
Solution Approach 1:
The patent converts the harmful visible stitching artifacts into a benefit by using the overlap region to create a random wave transition zone. The random wave pattern disguises the artificial boundary between printheads, making the stitching artifacts imperceptible while maintaining the productivity benefits of staggered printhead configuration.
3Stability of the object's composition
If a regular sinusoidal mask pattern is used for droplet ejection assignment, then the mask provides consistent coverage, but the regularity of the pattern makes image quality defects easily detectable
Solution Approach 1:
The patent applies dynamics by introducing variability and randomness into the mask pattern. Instead of a static regular sinusoidal pattern, the random wave mask dynamically varies its characteristics across the print width, creating an adaptive pattern that responds to local conditions and eliminates detectable regularity.
Data Source
AI summary
Example implementations relate to random wave mask generation. Some examples may distribute data points in a mask area based on a probability density function. The probability density function may have a maximum probability density located at a first edge and a second edge of the mask area. Some examples may also identify a wave curve that fits the data points. The wave curve may include oscillating waveforms of varying amplitudes. Some examples may also generate a random wave mask based on the wave curve.