Inkjet Nozzle Defect Detection via Distortion Correction
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Solution Overview
Problem
Conventional inkjet printing systems face challenges in accurately detecting defective nozzle ejections due to image distortion during the reading process, leading to incorrect analysis and potential misalignment of droplet hitting positions, especially in high-density printing where precise pattern detection is crucial.
Innovation Solution
An inkjet printing apparatus equipped with a printing device for creating test patterns, a reading device for image acquisition, a correcting device to adjust for image distortion, and a detecting device to accurately determine nozzle ejection states by correcting the analysis region's position based on the distorted image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reading device is used to read out the printed test pattern for detecting defective nozzles, then the ejection state of each nozzle can be determined, but image distortion occurs during reading causing inaccurate detection and misalignment of analysis regions
Solution Approach 1:
The patent implements feedback by detecting the actual positions of printed patterns through the reading device, comparing them with expected positions, and using the detected position information to correct the analysis region positions. This closed-loop feedback mechanism compensates for image distortion effects and enables accurate defective nozzle detection despite reading-induced distortion
Solution Approach 2:
The patent changes the parameters of the analysis regions by adjusting their positions based on the detected pattern positions. Instead of using fixed predetermined positions, the analysis region parameters (positions) are dynamically modified to match the actual printed pattern locations, thereby compensating for distortion effects
2Area of stationary object
If the print head is elongated to cover a wider printing region in full line type printing, then the printing width capability is improved, but the number of nozzles increases leading to higher generation rate of defective ejections
Solution Approach 1:
The patent segments the printing system into multiple independently detectable nozzle groups, each with its test patterns. By dividing the elongated print head into manageable segments and detecting each segment's nozzle status individually, the system can identify and compensate for defective nozzles, maintaining overall reliability despite the large number of nozzles
Solution Approach 2:
The patent implements self-service by enabling the printing system to automatically detect and identify defective nozzles through self-testing with test patterns. The system performs self-diagnosis and can compensate for defective nozzles without external intervention, maintaining reliability in full-line printing applications
3Loss of time
If the print head is not used for a long period, then maintenance time is reduced, but ink vaporizes from ejection openings causing solidification and clogging
Solution Approach 1:
The patent applies preliminary action by performing nozzle status detection and test printing before actual production printing. This preliminary check identifies potential issues caused by ink solidification or clogging, allowing for preventive maintenance or compensation before defective nozzles affect production quality
Solution Approach 2:
The patent uses feedback by detecting the actual ejection status of each nozzle through test pattern reading and comparing it with expected performance. This feedback mechanism identifies nozzles affected by ink solidification or clogging, enabling corrective actions to restore reliability
Data Source
AI summary
Even if an image distortion is generated in an image acquired by reading out a test pattern by a reading device, an analysis region of a pattern for detecting an ejection state of a nozzle is accurately set to determine the ejection state of the nozzle. A control device is provided for controlling the reading device to read out the pattern, and a detecting device is provided to detect a defect of an ejection based upon a distribution state of a density in a pattern in the analysis region. The detecting device corrects a position of the analysis region on the readout image determined based upon an arrangement of each nozzle on a design, corresponding to the distribution state of the density in the pattern in the analysis region.