Inkjet Print Head Joint Placement for Seamless Wide-Format Printing
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Solution Overview
Problem
Inkjet printing on wide objects requires multiple heads that often result in visible stitching errors, such as light or dark lines, due to gaps or overlaps between print dots, which are particularly problematic in halftone images and challenging to correct at high production speeds without disrupting the image.
Innovation Solution
A method that adjusts the position of the joint between inkjet print heads based on image data analysis to place the joint in light or dark areas, using a two-dimensional Fourier transform to evaluate and correct for visible frequencies, and iteratively improves the positioning to make the joint invisible to the human eye.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple inkjet print heads are used to print on wide objects, then the printing width is increased, but visible stitching errors such as light or dark lines appear at the joints between print heads
Solution Approach 1:
The patent applies local quality by analyzing the image content at each joint location and adapting the joint placement strategy to the local image characteristics. Different regions of the printed image receive different joint placement treatments based on their visual sensitivity, with joints placed in light areas for dark image regions and in dark areas for light image regions, thereby making joints locally invisible throughout the entire printed width
Solution Approach 2:
The patent implements dynamics by making the joint location variable rather than fixed. The joint position is dynamically adjusted based on the local image content, placing joints in optically less sensitive areas. This dynamic adaptation allows the system to maintain seamless appearance across diverse image content while using multiple print heads
2Manufacturing precision
If the joint location is continuously varied to make it invisible, then stitching errors are reduced, but the printed image may be disrupted by undesired visual effects
Solution Approach 1:
The patent resolves this contradiction by applying local quality through content-dependent joint placement. Instead of uniform random variation, the joint location is selectively placed in light or dark areas based on the local image content analysis. This ensures joints are hidden in visually less sensitive regions while maintaining overall image consistency and avoiding undesired visual disruptions in critical image areas
3Manufacturing precision
If mechanical position correction for print heads is implemented, then stitching accuracy is improved, but the system complexity increases and may fail at high production speeds
Solution Approach 1:
The patent replaces the mechanical position correction system with a digital/image-processing-based solution. Instead of using complex mechanical feedback control to physically adjust print head positions, the invention analyzes image data and computationally determines optimal joint locations, then adjusts print data accordingly. This substitution of mechanical correction with digital processing reduces system complexity and enables operation at high production speeds
Data Source
AI summary
A method for creating a printed image with sections on an object using at least two inkjet print heads, includes forming the image of first and second image sections, in a y direction at a fixed angle different than 0° and 180° relative to an object conveying direction, printing print dots of the first and second sections using first and second heads having first and second inkjet nozzles with the sections partially overlapping in a region and potentially forming a light or dark line, defining first and second complementary nozzle fields of the first and second heads to be active for each column of dots in the y direction, and placing a joint between the fields in the overlap region in a light or dark area of the column for each column of dots, avoiding potentially disruptive light or dark lines at the joint and keeping the image without defect.