Printhead Color Density Correction via Integrated Imaging
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Solution Overview
Problem
Commercial inkjet printing systems face challenges in fabricating uniform nozzles, leading to non-uniform ink laydown and resulting in unpredictable variations in dark and light density regions, causing waste and increased costs due to the need for extensive corrections across large print media lengths.
Innovation Solution
A printing system with integrated imaging that captures images of test blocks printed on moving media, using image sensors with color filter arrays to determine ink color and density, and adjusts ink laydown based on comparisons with reference values to correct for density variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple nozzle plates are used to increase printing capability, then the number of nozzles increases (12,000 to 30,000), but manufacturing uniformity deteriorates making it challenging to fabricate small nozzles consistently
Solution Approach 1:
The system performs preliminary measurement of ink laydown characteristics during the printing process itself. Test blocks are printed and immediately measured by the integrated imaging system to characterize each nozzle plate's performance before it affects production printing, allowing for proactive adjustment rather than reactive correction.
Solution Approach 2:
The system implements continuous feedback by measuring actual ink density with the integrated imaging system and using this information to adjust printing parameters. The measured ink laydown characteristics are fed back to control the printhead operation, creating a closed-loop system that compensates for manufacturing variations in real-time.
2Manufacturing precision
If nozzle diameter is reduced to five to twenty micrometers to improve printing resolution, then printing precision improves, but manufacturing difficulty increases leading to non-uniform ink laydown
Solution Approach 1:
The system replaces mechanical adjustment methods with optical measurement and digital control. Instead of physically adjusting nozzle components to compensate for variations, the system uses an integrated imaging system to measure ink density and employs digital signal processing to adjust the ejection pattern, substituting mechanical precision requirements with optical and electronic control.
Solution Approach 2:
The system dynamically changes printing parameters such as drop size, ejection frequency, and ink concentration based on measured ink laydown characteristics. By adjusting these parameters in real-time based on actual measurement data, the system compensates for nozzle variations without requiring perfect manufacturing uniformity.
3Manufacturing precision
If ink laydown is adjusted to correct density variations, then printing quality improves, but corrections must be made hundreds or thousands of feet along the print media, increasing time and cost
Solution Approach 1:
The system performs preliminary characterization of each nozzle plate by printing test blocks and measuring them immediately. This preliminary measurement allows the system to establish baseline ink laydown characteristics for each nozzle plate before production printing begins, enabling proactive adjustment rather than reactive correction during the printing process.
Solution Approach 2:
The system maintains continuous measurement and adjustment throughout the printing process. The integrated imaging system continuously monitors ink density and the control system continuously adjusts printing parameters, ensuring consistent quality without interruption. This continuous action eliminates the need for separate correction passes and reduces overall printing time.
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 solution enables precise color density correction, reducing waste and costs by ensuring consistent ink deposition across the print media, improving the quality and efficiency of the printing process.
Implementation Method 1
an opening in the housing for receiving light reflected from the print media
Implementation Method 2
one or more image sensors within the housing that each receive the light and capture one or more images of the printed test block or blocks on the moving print media. The image sensor or sensors each include a color filter array having a known capture response
Data Source
AI summary
A printing system includes a linehead that jets ink onto a moving print media to print a test block and an integrated imaging system positioned downstream of the linehead with respect to a media transport direction. The integrated imaging system includes an opening in a housing for receiving light reflected from a moving print media. A folded optical assembly in the housing receives the reflected light and transmits the light a distance. One or more image sensors, having known color filter arrays, within the housing each receive the light and capture one or more images of the printed test block. An image processing device is connected to the integrated imaging system for receiving pixel data from the one or more image sensors and configured to determine a color of the ink and a density of the printed test block using the pixel data.