Inkjet Nozzle Failure Detection via Column Profile Analysis
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Solution Overview
Problem
Inkjet printing machines face challenges in detecting and compensating for failed printing nozzles due to low camera resolution, geometric deviations, and overlapping colors, leading to reduced contrast and difficulty in identifying missing nozzles, which results in defects and unnecessary corrections.
Innovation Solution
A method using a computer to detect failed nozzles by printing a current image, recording it with an image sensor, digitizing, and creating a column profile, subtracting a defect-free reference profile, setting a threshold for nozzle detection, and compensating for marked nozzles in subsequent printing operations, while applying a median filter to reduce noise and focus on actual nozzle failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inline digital cameras are used to record printed images for nozzle detection, then real-time detection capability is improved, but measurement precision deteriorates due to reduced resolution and geometric deviations
Solution Approach 1:
The patent divides the printed image into multiple vertical columns and processes each column independently to create column profiles. This segmentation allows the system to detect nozzle failures by analyzing local variations in ink deposition across columns, thereby maintaining high measurement precision while using standard camera resolution for real-time detection.
Solution Approach 2:
The patent transforms the 2D printed image into 1D column profiles by summing pixel values across rows for each column. This dimensional reduction concentrates the detection task into analyzing vertical ink distribution patterns, which enhances the ability to detect nozzle failures without requiring high-resolution imaging of the entire print surface.
2Adaptability or versatility
If multiple colors are printed on top of one another to create the final image, then printing versatility is improved, but detection difficulty increases due to overlapping colors reducing contrast
Solution Approach 1:
The patent separates the detection task by color channel, creating individual column profiles for each color (C, M, Y, K). This allows the system to detect nozzle failures in each color independently, maintaining high contrast and detection accuracy even when multiple colors are overlaid in the final printed image.
3Measurement precision
If strict tolerance evaluation is applied to detect small nozzle positioning deviations, then measurement precision is improved, but false positive signals increase causing unnecessary corrections
Solution Approach 1:
The patent applies different evaluation criteria to different regions of the printed image based on their content. By analyzing column profiles and identifying patterns specific to nozzle failures (such as missing ink in specific columns) rather than applying uniform tolerance thresholds, the system achieves high measurement precision while minimizing false positives from normal printing variations.
Data Source
AI summary
A method for detecting and compensating for failed printing nozzles in an inkjet printing machine by using a computer, includes printing a current print image, recording the printed print image by using an image sensor and digitizing the recorded print image by using the computer, adding digitized color values of the recorded print image of every column over the entire print image height and dividing the added-up color values by the number of pixels to obtain a column profile, subtracting an optimized column profile without failed printing nozzles from the original column profile to obtain a differential column profile, setting a maximum value threshold defining a failed printing nozzle when exceeded, applying that maximum value threshold to the differential column profile to obtain a resultant column profile every maximum of which marks a failed printing nozzle. The marked printing nozzles are compensated in a subsequent printing operation.