Integrated Imaging System for Print Media Stretch Detection
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Solution Overview
Problem
Commercial inkjet printing systems face challenges in detecting and compensating for unanticipated stretch or shrink in print media, leading to color correlation loss and registration issues, particularly due to the absorption of aqueous ink and heat application, which affects the quality of printed content.
Innovation Solution
Incorporating multiple test patterns with varying marks on the print media, scanned while moving, to detect size variations through an integrated imaging system, analyzing signals to determine compensation values for adjusting the printing system's operation and settings to maintain print quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visible patterns such as dots, lines and polygons are printed on the print media for detection, then the ability to detect stretch or shrink is improved, but the cost of the system increases due to dedicated high speed cameras and the complexity increases due to multiple cameras and pattern trimming requirements
Solution Approach 1:
The imaging system is designed to perform multiple functions: it detects test patterns for stretch/shrink measurement, monitors printed content quality, and can track registration marks. This eliminates the need for separate dedicated cameras for each function, reducing system complexity and cost while maintaining high measurement precision through the same imaging hardware
Solution Approach 2:
The patent extracts the detection function from dedicated specialized cameras and integrates it into a general-purpose imaging system that captures images of the print media during normal operation. The test patterns are embedded within the printed content area rather than requiring separate pattern regions, allowing detection without additional hardware
2Measurement precision
If multiple test patterns are printed on the print media to detect size variations, then the measurement precision is improved, but the productivity decreases due to the need to print additional test patterns and trim them away before final product assembly
Solution Approach 1:
The test patterns are merged with the printed content by placing them within the content area rather than in separate margin regions. This allows the test patterns to be printed simultaneously with the actual content in a single printing pass, eliminating the need for separate pattern printing and trimming operations, thereby maintaining high productivity while achieving accurate size variation detection
Solution Approach 2:
Instead of trimming away test patterns after printing, the system recovers the value of the test patterns by using them for real-time detection during the printing process. The test patterns serve their detection purpose and then become part of the final printed product, eliminating waste and maintaining productivity
3Productivity
If the print media is heated to dry the ink, then the drying speed is improved, but the print media shrinks causing color correlation loss and registration issues
Solution Approach 1:
The imaging system provides real-time feedback on the actual position and size of printed features after drying. This feedback is used to calculate compensation values that adjust the printing parameters for subsequent lines or passes, compensating for the shrinkage caused by heat drying. This allows high-speed drying to continue while maintaining registration accuracy through active compensation
Solution Approach 2:
The system dynamically changes printing parameters such as droplet placement position, spacing, and timing based on detected shrinkage from previous passes. By adjusting these parameters in response to measured shrinkage, the system compensates for the effects of heat drying and maintains accurate color correlation and registration
4Productivity
If the print media travels at high speed through the printing system, then the productivity is improved, but the measurement precision decreases due to difficulty in detecting stretch or shrink at high speeds
Solution Approach 1:
The test patterns are printed and captured in advance during normal high-speed printing operation. The imaging system captures images of the test patterns immediately after they are printed but before the media undergoes significant drying shrinkage. This preliminary measurement allows calculation of compensation values that are applied to subsequent printing, maintaining accuracy despite high printing speeds
Solution Approach 2:
The patent replaces mechanical measurement methods (such as physical calipers or slow-speed mechanical sensors) with an optical imaging system that can accurately measure test patterns at high printing speeds. The imaging system captures images during high-speed media transport and uses image processing to detect dimensional changes, enabling precise measurement without reducing printing speed
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 detects and adjusts for size variations in real-time, ensuring accurate color correlation and registration across the print media, thereby improving the quality and consistency of printed content by compensating for stretch or shrink.
Implementation Method 1
scanning the test patterns as the print media is moving in a transport direction to produce test pattern signals
Implementation Method 2
a high speed and high magnification camera can record the pattern to determine if there are deviations from a reference value
Implementation Method 3
heat is typically applied at one or more locations in a printing system to dry the ink that has been applied to the print media. Drying of the print media can cause the print media to shrink
Implementation Method 4
Drying of the print media can cause the print media to shrink
Implementation Method 5
The print media can receive a large amount of ink during printing, especially with water-based ink or in high ink laydown regions of the printed content. The aqueous component of the ink is absorbed into the print media and can cause the print media to swell and stretch
Data Source
AI summary
A printing system includes a print media and one or more non-objectionable test patterns formed or printed on the print media. An integrated imaging system captures images of the one or more non-objectionable test patterns. The integrated imaging system includes a housing, an opening in the housing for receiving light reflected from a moving print media, a folded optical assembly in the housing that receives the reflected light and transmits the light a predetermined distance, and an image sensor within the housing that receives the light and captures one or more images of the one or more non-objectionable test patterns. A processing device can process the one or more images to determine if one or more size variations have occurred in the print media.