Inkjet Nozzle Ejection Deviation Detection via Shifted Test Patterns
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Solution Overview
Problem
Existing inkjet image forming apparatuses struggle to detect nozzles with ejection deviation, as they can only effectively identify non-ejection nozzles but not those with ink droplet position deviations, and often rely on density defects in band-shaped test patterns which fail to accurately determine individual nozzle malfunctions.
Innovation Solution
An image forming apparatus with a recording head, control unit, and ejection malfunction nozzle detecting unit that prints test patterns with shifted nozzle positions and analyzes density changes in scanned images to identify both non-ejection and ejection deviation nozzles, using a control unit to correct the image forming process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vertical line test pattern is printed to detect non-ejection nozzles, then non-ejection nozzles can be detected, but ejection deviation nozzles cannot be detected
Solution Approach 1:
The test pattern is segmented into multiple line-shaped or band-shaped images with different target nozzles set as non-ejection nozzles. By analyzing density defects in each segmented pattern, the system can identify both non-ejection nozzles and ejection deviation nozzles individually, rather than treating all nozzles uniformly.
Solution Approach 2:
The invention transitions from simple presence/absence detection (1D) to density quantification analysis (adding a density dimension). By measuring density decreasing amounts in scanned images of test patterns, the system can detect ejection deviation magnitude and distinguish it from complete non-ejection failures.
2Reliability
If a band-shaped test pattern with single density is printed to detect ejection malfunction, then density defects can be identified, but individual nozzle malfunction cannot be determined
Solution Approach 1:
The test pattern consists of multiple separate line-shaped or band-shaped images, each corresponding to a specific target nozzle. This segmentation allows the system to analyze density defects in each pattern individually, thereby identifying which specific nozzle is malfunctioning rather than just detecting that a malfunction exists.
Solution Approach 2:
The test pattern acts as an intermediary between the nozzle and the detection system. By printing test patterns with specific nozzles set as non-ejection nozzles and analyzing the resulting density defects, the system can trace density variations back to specific individual nozzles, enabling precise identification of malfunctioning nozzles.
3Reliability
If traditional detection methods are used, then non-ejection nozzles can be identified, but detection ratio of all malfunctioning nozzles remains low
Solution Approach 1:
The system performs periodic detection by printing multiple test patterns sequentially, each with different target nozzles set as non-ejection nozzles. This periodic testing approach ensures that all nozzles are systematically evaluated, increasing the overall detection ratio compared to single-pattern methods.
Solution Approach 2:
The system uses feedback from density defect analysis in scanned test pattern images to identify malfunctioning nozzles. The detection results feed back into the printing process, allowing for correction of ejection deviation by adjusting ink ejection amounts, thereby continuously improving detection and correction accuracy.
Data Source
AI summary
A control unit causes a recording head to eject ink from nozzles corresponding to an image to be printed. An ejection malfunction nozzle detecting unit prints a test pattern using the recording head, and detects an ejection malfunction nozzle on the basis of a scanned image of the test pattern. The test pattern includes plural test pattern images such that in each of the plural test pattern images a dot is not formed at a dot position of a target nozzle set as a non ejection nozzle, and the target nozzles of the plural test pattern images are sequentially shifted by one nozzle in a primary scanning direction. Further, the ejection malfunction nozzle detecting unit determines an ejection malfunction nozzle on which ejection deviation occurs, on the basis of density decreasing amounts of respective density decrease parts in the plural test pattern images in the scanned image.