Inkjet Printer Registration via Optical Sensor Feedback
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Solution Overview
Problem
Inkjet printers face image quality degradation due to ink drop merging and pooling on coated media, which affects the absorption and drying of ink, leading to graininess in printed images.
Innovation Solution
A color inkjet printer is configured to print ink images in stages separated by ink drying, using optical sensors to analyze and register image features, allowing for partial printing on one side of the media sheet, followed by a second pass to complete the image without inverting the sheet, ensuring accurate registration and reducing merging or pooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If inkjet printers eject liquid ink onto coated media to form images, then images can be produced on image receiving surfaces, but ink drops merge or pool together due to coating attenuation, degrading image quality
Solution Approach 1:
The printing process is divided into multiple passes, with each pass printing only a portion of the color separations. This segmentation prevents excessive ink accumulation on coated media, reducing merge and pool effects while maintaining image quality.
Solution Approach 2:
The system performs preliminary printing of some color separations, dries the ink, and then returns the media for subsequent printing passes. This preliminary action allows the coating to absorb ink gradually without overwhelming saturation, preventing harmful pooling.
2Manufacturing precision
If the media sheet is returned to the media transport without inverting, then the first side can be printed a second time with accurate registration, but the system complexity increases due to additional optical sensors and registration analysis
Solution Approach 1:
The system uses optical sensors to create digital copies (images) of the printed features on the media sheet. These optical copies are used for registration analysis, allowing the system to track and correct positioning without physical measurement tools, reducing mechanical complexity.
Solution Approach 2:
The system implements feedback loops where optical sensors detect printed features, the controller analyzes their positions, and adjusts subsequent printing operations accordingly. This closed-loop feedback ensures accurate registration while automating the process.
3Manufacturing precision
If ink images are printed in stages separated by drying, then ink drops are fixed to the surface without merging or pooling, but the printing time increases due to multiple passes
Solution Approach 1:
The printing process uses periodic action by alternating between printing phases and drying phases. During printing, color separations are applied; during drying, ink is fixed to the surface. This periodic cycle prevents continuous ink accumulation that causes pooling, while the automated return path minimizes idle time.
Solution Approach 2:
The system maintains continuity by immediately returning the dried media through the return path to the media transport for the next printing pass. The automated actuator and optical registration ensure seamless transitions between passes, minimizing non-productive time and keeping the process continuously useful.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively fixes ink drops to the surface of coated sheets, improving image quality by minimizing merging and pooling, resulting in reduced overlay graininess and enhanced print quality.
Implementation Method 1
a dryer that follows the at least one printhead in the process direction and that precedes the second optical sensor in the process direction, the dryer being configured to expose the media sheet to heat
Data Source
AI summary
An inkjet printer prints on a first side of a media sheet less than all of the color separations in an image, generates a first set of image data of the printed color separations to identify image features, returns the partially printed media sheet to a position that precedes the print zone in the printer, generates a second set of image data of the partially printed media sheet before it reenters the print zone to identify the image features, compares the positions of the image features in the first set of image data to the positions of the image features in the second set of image data to register one or more color separations remaining to be printed with the color separations printed on the first side of the media sheet, and prints the remaining registered color separations on the first side of the partially printed media sheet.