2D Printhead Alignment Using Camera-Captured Dot Patterns
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Solution Overview
Problem
Existing methods for aligning printing heads in printing devices lack the required precision for high-quality printing, particularly in two-dimensional printing heads with nozzles arranged in columns and rows, as they do not provide specific details about the test patterns used for position adjustment.
Innovation Solution
A method involving simultaneous dispensing of ink drops at multiple nozzles to print a dot pattern, capturing it with a camera having a pixel size less than half the distance between adjacent nozzles, determining deviations, and adjusting the printing heads' position and orientation based on the captured image, allowing for precise alignment without mechanical adjustments in the advance direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing alignment methods are used, then the alignment process can be performed, but the required precision for high-quality printing is not achieved
Solution Approach 1:
The patent replaces mechanical alignment adjustment mechanisms with an optical measurement system (camera) that captures images of printed test patterns. The camera system with sub-pixel resolution capability allows precise measurement of nozzle positions without mechanical contact, achieving higher alignment precision than traditional mechanical methods.
Solution Approach 2:
The patent uses a camera to create an optical copy (image) of the printed test pattern on the substrate. This digital copy is then processed to determine actual nozzle positions and deviations from the geometric pattern, enabling precise measurement without physically touching or disturbing the printing head or substrate.
2Measurement precision
If a camera with sufficient resolution is used to capture the dot pattern, then accurate position determination is achieved, but data processing time and costs increase
Solution Approach 1:
The patent focuses the camera's measurement capability on specific critical regions - the test pattern areas where dots are printed at known nozzle positions. Rather than capturing and processing entire substrate images at maximum resolution, the system concentrates processing resources on localized pattern regions, reducing overall data volume while maintaining measurement precision.
Solution Approach 2:
The patent uses a camera with resolution capability exceeding the minimum theoretical requirement (pixel size less than half the nozzle spacing). This excessive resolution ensures that even with variations in printing conditions, the system can always accurately determine dot positions. The oversampling provides a margin of error that simplifies data processing by reducing the need for complex error correction algorithms.
3Measurement precision
If the pixel size of the camera is less than half the distance between adjacent nozzles, then accurate dot capture is achieved, but the camera cost and complexity increase
Solution Approach 1:
The patent specifies camera pixel size requirements in advance of the actual measurement process, ensuring the optical system is designed with sufficient resolution from the outset. By pre-defining that the pixel size must be less than half the nozzle spacing, the system avoids the need for complex real-time interpolation or error correction algorithms, simplifying the overall measurement system design.
Data Source
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AI summary
A method for aligning printing heads (12) of a printing device is provided, the printing heads (12) being two-dimensional printing heads (12) comprising a plurality of nozzles (30). In one method step, an ink drop is dispensed at a plurality of nozzles (30) of every printing head (12) simultaneously to print an image, preferably at all nozzles (30) of every printing head (12). In another step, the printed image is captured by a camera (20) whose resolution may be smaller than the print resolution. The position and/or orientation of each of the printing heads (12) is determined based on the image captured by the camera (20) and the deviation of the position and/or orientation of each printing head (12) from a target position and/or orientation is determined. The position and/or the orientation of the printing heads (12) is adjusted based on the determined deviation. Moreover, a printing device (10) is provided.