Optical Touch Dynamic Threshold Detection
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Solution Overview
Problem
Conventional optical touch systems without reflective borders face challenges in accurately determining touch points due to varying distances between the light pen and the optical sensor, leading to incorrect threshold settings that can result in premature detection or missed signals.
Innovation Solution
The system employs two optical sensors and a processor to dynamically adjust the threshold value based on sensing signals, dividing the touch panel into zones and using lookup tables to determine the appropriate threshold values, ensuring accurate detection of touch points regardless of the light pen's distance from the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed threshold value is used to determine touch contact, then the system is simple to operate, but the measurement precision deteriorates because the detection accuracy varies with distance between light pen and sensor
Solution Approach 1:
The patent implements dynamic threshold adjustment by using a second optical sensor to detect the distance between the light pen and touch panel, then automatically selecting appropriate threshold values from a lookup table based on detected distance zones. This transforms the static threshold system into a dynamic one that adapts to varying distances, resolving the contradiction between operational simplicity and measurement precision.
Solution Approach 2:
The system changes the threshold parameter dynamically based on distance conditions. By dividing the detection range into multiple zones and assigning different threshold values to each zone, the system optimizes touch detection accuracy for different distances while maintaining simple operation through automated parameter selection.
2Device complexity
If a fixed threshold value is used, then the device complexity is low, but the reliability deteriorates because touch signals may be missed or falsely detected at different distances
Solution Approach 1:
The patent segments the detection range into multiple distance zones and assigns different threshold values to each zone. This segmentation allows the system to optimize detection reliability for each specific distance range, preventing both missed signals and false detections that occur with a single fixed threshold value.
Solution Approach 2:
The system uses feedback from the second optical sensor to continuously monitor light pen distance and automatically adjusts the threshold value accordingly. This closed-loop feedback mechanism ensures reliable touch signal detection across varying distances without requiring manual intervention, thereby improving reliability while keeping the system relatively simple.
3Measurement precision
If the threshold value is lowered to detect distant light pens, then the measurement precision for distant objects improves, but false detection increases when the light pen is near the sensor
Solution Approach 1:
The patent applies different threshold values to different spatial zones (distance ranges). By matching the threshold level to the specific distance zone where detection is occurring, the system achieves high precision for distant objects while preventing false detections when the light pen is nearby, as each zone has optimally tuned threshold characteristics.
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 touch point detection by adapting to different distances and light pen characteristics, reducing the likelihood of misjudging touch points and improving the reliability of the optical touch system.
Implementation Method 1
The light pen reflects light that is emitted from a light emitting diode (LED) of the optical sensor
Data Source
AI summary
An optical touch apparatus and an optical touch method are disclosed. The optical touch apparatus comprises a touch panel, a first optical sensor, a second optical sensor and a processor. The first optical sensor senses a light pen to output a first sensing signal. The second optical sensor senses the light pen to output a second sensing signal. The processor decides a threshold value according to the second sensing signal, and determines whether the first sensing signal is greater than the threshold value. The processor determines that the light pen touches the touch panel if the first sensing signal is greater than the threshold value.