Line Sensor Threshold Determination for Sheet Edge Detection
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Solution Overview
Problem
Existing position detection devices for recording sheets face inaccuracies in detecting lateral edge positions due to variations in sheet surface reflection characteristics and light sensitivity among light receiving elements, leading to incorrect threshold settings and misalignment corrections.
Innovation Solution
A position detection device that determines a threshold based on the light and dark levels of the specific light receiving element block actually detecting the lateral edge, using a line sensor with multiple pixel blocks to accurately binarize signals and determine the edge position, thereby improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the threshold is set to the middle level between light and dark levels, then the detection should be accurate, but the accuracy decreases when sheet surface deviates from focal point due to undulation
Solution Approach 1:
The threshold determination unit dynamically determines the threshold based on the actual output levels detected by each light receiving element, rather than using a fixed middle level. This allows the threshold to adapt to variations in light levels caused by sheet undulation, improving detection reliability while maintaining accuracy.
Solution Approach 2:
The system changes the threshold parameter for each light receiving element based on its actual output levels. By determining thresholds individually for each element rather than using a uniform threshold, the system compensates for element-specific variations and maintains accurate detection under varying sheet conditions.
2Device complexity
If a uniform threshold is used for all light receiving elements, then the device complexity is reduced, but the measurement precision decreases due to varying sensitivity among elements
Solution Approach 1:
The system segments the threshold determination process by individually determining thresholds for each light receiving element based on its specific output levels. This segmentation allows each element to have an optimized threshold, improving measurement precision while the automated process keeps complexity manageable.
Solution Approach 2:
Each light receiving element essentially determines its own threshold based on its output levels from the sheet and conveyance guide surfaces. This self-service approach eliminates the need for external calibration or complex manual threshold setting, achieving high precision without excessive complexity.
3Device complexity
If the threshold is determined based on light levels from a different light receiving element, then the device complexity is reduced, but the measurement precision decreases due to sensitivity variations
Solution Approach 1:
The system applies local quality by determining thresholds specifically for each light receiving element based on its own output characteristics. This ensures that each element uses an appropriate threshold suited to its sensitivity, rather than using a generic threshold that may not account for element-specific variations.
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 enhances the accuracy of lateral edge position detection by setting the threshold to the middle value between the highest and lowest output levels of the relevant element block, ensuring precise alignment corrections even with undulated surfaces and varying sheet types.
Implementation Method 1
detecting a change of the level of an output signal from a comparator from an output level caused by reflected light from a surface of a recording sheet to an output level caused by reflected light from the black surface of the conveyance guide
Implementation Method 2
a plurality of light receiving elements included in the line sensor... the plurality of light receiving elements do not necessarily output the same level of a signal in response to the same amount of incident light
Data Source
AI summary
A threshold for detecting a position of a lateral edge of a sheet is more accurately determined, whereby the accuracy of detection of the lateral edge position of the sheet is improved. A line sensor includes a plurality of element blocks. Each element block includes a plurality of pixels. The threshold for detecting the lateral edge position is determined based on a light level and a dark level of signals output from an element block that is actually used to detect the lateral edge position of the sheet.