Inkjet Nozzle Defect Detection via Multi-Row Test Charts
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for detecting defective printing nozzles in inkjet printing machines are inefficient and inaccurate, as they rely on image comparison or test charts, which fail to reliably identify individual nozzles causing print defects and require extensive resources for analysis.
Innovation Solution
A method involving the printing of multi-row test charts and area coverage elements, where defects are detected in the area coverage element and then correlated with specific nozzles using pixel-to-printing nozzle allocation points and shading correction, allowing for precise identification and compensation of defective nozzles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image comparison methods are used to detect defective printing nozzles, then print quality monitoring is enabled, but the ability to identify individual defective nozzles is limited and false positives increase
Solution Approach 1:
The patent divides the detection process into two distinct phases: (1) printing test patterns where each nozzle group prints on a separate line, and (2) analyzing the recorded image to identify which specific line contains the defect, thereby locating the defective nozzle group. This segmentation enables precise identification of individual nozzles while maintaining detection accuracy.
2Measurement precision
If test charts are printed for every nozzle to identify defective ones, then individual nozzle detection is possible, but the complexity and time required for detection increases significantly
Solution Approach 1:
Instead of requiring every single nozzle to be tested individually, the patent uses a reduced set of test patterns where only representative nozzles from each nozzle group print test lines. This partial testing approach significantly reduces detection time while still enabling identification of defective nozzles through the systematic analysis of which test lines show defects.
3Measurement precision
If high-resolution image sensors are used to allocate defects to specific nozzles, then accurate nozzle identification is achieved, but the cost and complexity of the detection system increases
Solution Approach 1:
The patent introduces test patterns as an intermediary element that mediates between the printing nozzles and the image sensor. By having nozzles print distinctive test patterns (such as lines or geometric shapes) that are easily distinguishable in the recorded image, the system can accurately allocate defects to specific nozzles using a standard-resolution sensor, avoiding the need for complex high-resolution imaging systems.
4Reliability
If printing nozzle test charts are analyzed to detect defective nozzles, then nozzle functionality can be assessed, but the method cannot detect nozzles that are not currently needed for the print job
Solution Approach 1:
The patent performs preliminary testing of all printing nozzles by printing test patterns before the actual print job begins. This preliminary action ensures that even nozzles that will not be used during the current print job are still tested and identified as defective if necessary, allowing for proactive maintenance and compensation settings to be configured in advance.
Data Source
AI summary
A method for detecting defective printing nozzles in an inkjet printing machine includes printing a multi-row printing nozzle test chart formed of horizontal rows of equidistant vertical lines periodically underneath one another, with only printing nozzles in a print head contributing to every row of the test chart corresponding to the horizontal rows. An area coverage element geometrically associated with the test chart is printed, both elements are recorded by an image sensor and analyzed by the computer. The computer analyzes the recorded area coverage element to detect print defects and allocates defects to a region of geometrically close printing nozzles. An analysis of the test chart in the region identifies nozzles causing the defect. Defective printing nozzles are detected based on thresholds, the detected printing nozzles are then compensated, and in the analysis of the recorded area coverage element, influences of the sensor are eliminated by shading correction.