Optical Sensor Edge Detection Using Dual Thresholds
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Solution Overview
Problem
In liquid ejecting apparatuses, such as inkjet printers, the progressive abrasion of paper support surfaces leads to increased reflectivity, causing optical sensors to erroneously detect protrusions as the medium edge due to reduced light intensity differences between the medium and protrusions, resulting in inaccurate edge detection.
Innovation Solution
A two-step detection process using different threshold values to differentiate between the medium and protrusions, where the first detection unit sets a threshold value that prevents protrusion detection and the second unit corrects the edge position using a comparison value and output value from the optical sensor, ensuring accurate medium edge detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single threshold value is used for edge detection, then the detection process is simple, but protrusions are erroneously detected as medium edges due to reduced light intensity differences
Solution Approach 1:
The detection process is segmented into two distinct stages: a first detection unit that identifies potential edge regions using a first threshold value, and a second detection unit that confirms actual medium edges using a second threshold value. This segmentation allows each unit to focus on specific detection criteria, preventing protrusion误检测 while maintaining accuracy.
Solution Approach 2:
Different threshold values are applied at different stages of detection. The first threshold value (higher) is used for initial screening to identify candidate regions, while the second threshold value (lower) is used for final confirmation. This local differentiation of detection sensitivity ensures that only true medium edges are confirmed, not protrusions.
2Device complexity
If the optical sensor detects protrusions as medium edges, then the detection process remains simple, but positional accuracy deteriorates due to increased reflectivity from abrasion
Solution Approach 1:
The first detection unit performs a preliminary detection using a higher threshold value to identify potential edge regions before the second detection unit performs final confirmation. This preliminary action filters out false positives (protrusions) early in the process, preventing them from affecting final position accuracy.
Solution Approach 2:
The second detection unit uses feedback from the optical sensor's light intensity measurements to confirm whether a detected region is indeed a medium edge. By comparing the light intensity against the second threshold value, the system provides feedback that validates or rejects initial detections, ensuring high position accuracy.
3Device complexity
If a constant correction amount is used for edge position, then the correction process is simple, but it cannot compensate for sensor fouling or aging changes
Solution Approach 1:
The system dynamically adapts the threshold values based on the optical sensor's current performance state. By using two different threshold values that can be adjusted according to detection conditions, the system can compensate for sensor fouling or aging changes, maintaining reliability without requiring complex dynamic correction calculations.
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
This approach reliably detects the medium edge while avoiding erroneous detection of protrusions, maintaining consistent positional deviation correction regardless of sensor fouling or sensitivity changes, simplifying the edge detection process.
Implementation Method 1
a light reflection optical sensor (an edge sensor) was provided to the carriage, and a widthwise edge position of the sheet of paper was detected by the optical sensor while the carriage was being moved in the movement direction
Data Source
AI summary
To provide a liquid ejecting apparatus and a method for detecting a medium edge position in a liquid ejecting apparatus, whereby the position of an edge of a medium can be detected while also avoiding an event where a protrusion present in a region targeted for detection by an optical sensor is erroneously detected as being the medium, a carriage is moved so as to traverse a sheet of paper in the width direction, and a determination is made as to whether or not an output voltage of a sheet width sensor provided to the carriage has crossed over a first threshold value.