Liquid Ejection Head Positioning via Speckle Pattern Detection
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Solution Overview
Problem
Conventional inkjet image formation methods face challenges in achieving high accuracy for the impact position of ejected liquid on a print medium in the orthogonal direction, leading to suboptimal image quality due to difficulties in detecting and compensating for lateral position changes of the print medium.
Innovation Solution
A liquid ejection device equipped with sensors, such as CMOS image sensors and FPGA circuits, that detect speckle patterns on the print medium to compute the movement and position changes, allowing for precise adjustment of the liquid ejection heads to compensate for orthogonal direction shifts, thereby improving the accuracy of ink placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensors and methods are used to detect lateral position changes of the print medium, then the system structure remains simple, but the measurement precision of the impact position in the orthogonal direction is insufficient
Solution Approach 1:
The patent replaces conventional mechanical position detection methods with optical field-based detection. A sensor captures images of the print medium, and image processing algorithms calculate the impact position based on these optical images, achieving sub-pixel precision without mechanical contact or complex mechanical adjustment mechanisms.
Solution Approach 2:
The patent introduces an intermediary calculation process that uses the relationship between transport direction position and orthogonal direction impact position. By detecting position in the transport direction and calculating the corresponding orthogonal position through image processing, the system achieves high precision impact position measurement without direct orthogonal detection hardware.
2Manufacturing precision
If the print medium lateral position is not accurately detected and compensated, then the system operation remains simple, but the manufacturing precision of the printed image deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the sensor continuously detects the actual impact position on the print medium, and the control unit adjusts the ejection timing or head position based on this feedback to compensate for lateral position changes, ensuring consistent print quality without manual intervention.
Solution Approach 2:
The patent performs preliminary detection of the print medium position before the liquid ejection occurs. By capturing images and calculating the impact position in advance, the system can pre-adjust the ejection parameters to ensure accurate placement, preventing quality issues before they occur.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the accuracy of ink placement on the print medium in the orthogonal direction, reducing color shifts and improving overall image quality by enabling precise compensation for print medium position changes during continuous-form printing.
Implementation Method 1
A liquid ejection device equipped with sensors, such as CMOS image sensors and FPGA circuits, that detect speckle patterns on the print medium to compute the movement and position changes
Data Source
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Figure 3A~3B
AI summary
A liquid ejection device includes a plurality of liquid ejection head units to eject liquid to a print medium at different positions on a transport path respectively, a conveying roller to transport the print medium on the transport path, a detection unit, disposed at a distance of an integral multiple of a peripheral length of the conveying roller away from an impact position where the liquid ejected from each of the plurality of liquid ejection head units reaches the print medium, to output a detection result indicating a lateral position of the print medium in a direction orthogonal to a transport direction in which the print medium is transported, and a movement unit to move the corresponding one of the plurality of liquid ejection head units based on the detection result from the detection unit.