Printhead Color Density Correction via Integrated Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Commercial inkjet printing systems face challenges in fabricating uniform nozzles and components, 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
1Productivity
If multiple nozzle plates are used to increase printing capacity, then the number of nozzles increases to 12,000-30,000, but manufacturing precision deteriorates due to challenges in fabricating small nozzles uniformly
Solution Approach 1:
The system performs preliminary measurement by printing test patterns and capturing images before actual production printing. This allows density variations to be detected and corrected in advance, preventing waste of print media. The correction values are calculated and stored before the main printing job begins.
Solution Approach 2:
The system implements feedback control by measuring the actual ink density using image sensors, comparing it with target values, and adjusting the printing parameters accordingly. The measured density values feed back into the control system to generate correction values that are applied to subsequent printing operations.
2Ease of manufacture
If fabrication tolerances are relaxed to ease manufacturing, then production becomes easier, but ink laydown uniformity deteriorates leading to unpredictable density variations
Solution Approach 1:
The printing system performs self-diagnosis and self-correction by automatically measuring its own output density and adjusting its printing parameters without external intervention. The system prints test patterns, measures the results, calculates corrections, and applies them automatically, making the system self-regulating despite manufacturing variations.
Solution Approach 2:
The system dynamically changes printing parameters such as ink droplet volume, frequency, or timing based on measured density values. By adjusting these parameters in response to actual performance data, the system compensates for manufacturing tolerances and maintains uniform ink laydown.
3Device complexity
If corrections are delayed until after printing, then manufacturing process remains simple, but waste increases due to unusable printed content requiring correction
Solution Approach 1:
The system performs preliminary measurement by printing test patterns and capturing images before actual production printing. This allows density variations to be detected and corrected in advance, preventing waste of print media. The correction values are calculated and stored before the main printing job begins.
Solution Approach 2:
The system implements feedback control by measuring the actual ink density using image sensors, comparing it with target values, and adjusting the printing parameters accordingly. The measured density values feed back into the control system to generate correction values that are applied to subsequent printing operations.
4Manufacturing precision
If real-time density measurement is implemented, then ink laydown uniformity improves, but device complexity increases due to integrated imaging system
Solution Approach 1:
The imaging system serves multiple functions: it captures images of test patterns for density measurement, provides feedback for correction calculations, and can potentially monitor print quality throughout production. This multi-functionality justifies the added complexity by providing comprehensive quality control capabilities.
Solution Approach 2:
The system replaces complex mechanical adjustment mechanisms with optical measurement and electronic control. Instead of physically adjusting each nozzle, the system uses image sensors to measure density and electronically adjusts printing parameters, simplifying the control architecture despite adding imaging components.
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 system effectively corrects for density variations in real-time, 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
a folded optical assembly in the housing that receives the reflected light and transmits the light a predetermined distance
Implementation Method 2
The image sensor or sensors each include a color filter array having a known capture response. The color filter array or arrays can be complementary to the ink colors.
Implementation Method 3
one or more image sensors within the housing that each receive the light and capture one or more images
Data Source
AI summary
A method for color density correction in a printing system that includes a linehead, with one or more printheads, that jets ink onto a moving print media and an integrated imaging system that captures images of content printed on the moving print media is provided. One or more pixel data values and a measured density value trace for a printed test block are produced by scanning the test block and averaging pixel data in a print media transport direction. A color and a density of the ink in the printed test block are determined using the pixel data values. The measured density value trace is compared with a respective reference density value. It is determined whether there is a difference between the measured density value trace and a reference density value is determined. If there is a difference, ink laydown for the printhead is adjusted based on the difference.