Inkjet Nozzle Detection Using Block Reference Positions
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Solution Overview
Problem
Conventional methods for detecting defective nozzles in inkjet printing apparatuses are inaccurate, especially when nozzles at the end portions of a block fail, leading to incorrect determination of ideal positions and insufficient detection accuracy.
Innovation Solution
A method involving printing a test chart divided into blocks with constant intervals, calculating errors and average errors for each linear pattern, setting a reference position based on minimum average errors, and determining nozzle defects by comparing actual and ideal positions, ensuring accurate detection even for end nozzles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to detect defective nozzles by comparing ideal positions with actual positions, then the detection process is simple, but the detection accuracy deteriorates when nozzles at end portions fail
Solution Approach 1:
The test chart is divided into multiple blocks, each containing multiple linear patterns. The detection process is segmented into: (1) calculating theoretical intervals between linear patterns within each block, (2) calculating actual intervals from captured images, (3) comparing theoretical and actual intervals to identify defective nozzles, (4) determining reference positions based on minimum average errors, and (5) calculating ideal positions based on reference positions. This segmentation allows accurate detection even when end nozzles are defective by using internal reference points within each block.
Solution Approach 2:
The patent introduces an intermediary reference position determination mechanism. Instead of directly comparing ideal positions with actual positions, the method first determines a reference position within each block by finding the linear pattern with minimum average error between theoretical and actual intervals. This reference position serves as an intermediary to calculate ideal positions for all linear patterns in the block, thereby eliminating the impact of end nozzle failures on the overall detection accuracy.
2Measurement precision
If the test chart is divided into blocks with multiple linear patterns, then the detection accuracy for end nozzles improves, but the complexity of calculating errors and reference positions increases
Solution Approach 1:
The method performs preliminary calculations of theoretical intervals and actual intervals for all linear patterns within each block before determining reference positions. By pre-calculating these interval values and storing them, the system avoids repeated complex calculations during the final defect determination stage, thereby reducing overall processing time while maintaining high accuracy for detecting end nozzle defects.
Data Source
AI summary
A theoretical value and an actual value of an interval between two linear patterns included in a test chart are calculated. For each linear pattern, a first error between an interval with a left adjacent linear pattern and the theoretical value, a second error between an interval with a right adjacent linear pattern and the theoretical value, and an average error between the first error and the second error are calculated. An actual position of the linear pattern where the minimum average error is obtained is set as a reference position. An ideal position of each linear pattern is calculated based on the reference position. A difference between the ideal position and a position in a captured image is calculated for each linear pattern, and whether or not a nozzle corresponding to each linear pattern is a defective nozzle is determined based on the difference.