Print Bar Nozzle Uniformity Calibration via Optical Feedback
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Solution Overview
Problem
Digital printing systems face challenges in achieving uniformity of ink images due to variations in nozzle behavior and environmental factors, leading to non-uniformities even when printing a uniform tone or luminance.
Innovation Solution
A multi-nozzle and multi-head print bar system that performs calibration by printing a digital input-calibration-image, optically imaging the output, and computing tone-reproduction functions to derive an image-correction-function, which is applied to the printing signal to correct for non-uniformities across the print bar, ensuring consistent ink deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-nozzle and multi-head print bar is used to increase printing coverage and speed, then productivity is improved, but image non-uniformity increases due to variations in nozzle behavior and environmental factors
Solution Approach 1:
The patent divides the print bar into multiple independent nozzle groups or heads, each capable of being individually calibrated and corrected. This segmentation allows the system to maintain high productivity through parallel operation while addressing uniformity issues by treating each segment separately with specific correction functions.
Solution Approach 2:
The patent implements dynamic adjustment of printing parameters (such as ink deposition amount, nozzle activation patterns, or timing) based on real-time feedback from sensors and pre-characterized correction data. This allows the system to compensate for nozzle variations and environmental factors while maintaining high-speed operation.
2Manufacturing precision
If calibration and correction processes are implemented to improve image uniformity, then manufacturing precision is improved, but device complexity increases due to additional scanning and computing requirements
Solution Approach 1:
The patent performs comprehensive calibration and characterization of each nozzle and nozzle group during the manufacturing or setup phase, storing correction data in advance. This preliminary action eliminates the need for complex real-time correction mechanisms during printing, reducing operational complexity while maintaining precision.
Solution Approach 2:
The patent uses optical scanning to create a digital representation of the printed test pattern, which is then processed to generate correction data. This copying approach allows for non-contact, automated characterization of print quality without requiring physical measurement devices at the print head.
3Manufacturing precision
If real-time correction is applied to reduce image non-uniformity, then manufacturing precision is improved, but loss of time increases due to additional processing during print runs
Solution Approach 1:
The patent performs all extensive calibration, characterization, and correction function generation during setup or offline phases, storing the results for rapid application during production. This shifts the time investment away from operational printing, making the correction process virtually instantaneous during print runs.
Solution Approach 2:
The patent implements correction at strategic points in the printing process rather than continuously throughout. For example, correction may be applied only to specific problem areas identified during calibration, or only at the beginning of print runs, reducing overall processing time while maintaining sufficient uniformity.
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
The solution effectively reduces image non-uniformities by compensating for nozzle variations and environmental factors, resulting in improved tone reproduction and uniformity of ink images across the print surface.
Implementation Method 1
a multi-nozzle and multi-head print bar for depositing ink droplets on a target surface in dependence upon a received electrical printing signal to form ink images on the target surface
Implementation Method 2
optically imaging the ink calibration image to obtain a digital output calibration image
Data Source
AI summary
Some embodiments relate to a digital printing system and method for depositing ink droplets onto a target surface in dependence upon a received electrical printing signal containing data indicating the desired image to be printed while improving the uniformity of intended tone reproduction of the printed image.