Stereo Optical Sensors for Multi-Touch Ghost Point Resolution
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Solution Overview
Problem
Conventional optical touch detection systems face challenges in accurately resolving multiple touch points due to the generation of ghost points, which increases computational complexity as the number of optical sensors increases, and are prone to errors from dust and ambient light exposure.
Innovation Solution
Implementing at least two pairs of optical sensors positioned along the edges of a touch area, each pair calculating its own set of potential points, and comparing these to identify true touch points by selecting potential point pairs with the shortest distances, thereby reducing the number of potential point pairs to evaluate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If more optical sensors are added to improve touch detection accuracy, then measurement precision is improved, but device complexity and computational complexity increase
Solution Approach 1:
The system segments the touch detection problem into two independent stereo pairs instead of using a single complex multi-sensor array. Each stereo pair independently processes a subset of shadows, dividing the computational workload and reducing overall system complexity while maintaining detection accuracy through coordinated processing of results from both pairs.
2Measurement precision
If more optical sensors are used to resolve multiple touch points, then measurement precision is improved, but the number of potential point pairs to evaluate increases
Solution Approach 1:
The computational task is segmented by assigning different stereo pairs to process different subsets of shadows. This segmentation reduces the number of potential point pairs each processor must evaluate compared to a centralized approach where all sensors process all shadows, thereby improving computational efficiency while maintaining the ability to resolve multiple simultaneous touch points.
Solution Approach 2:
Each stereo pair processes only a partial set of shadows rather than all shadows. This partial action approach reduces computational burden for each processing unit while the combination of results from multiple stereo pairs provides sufficient information to accurately resolve all touch points, achieving the desired precision with reduced computational effort.
3Measurement precision
If optical sensors are positioned to maximize field of view, then measurement precision is improved, but reliability decreases due to exposure to dust and ambient light
Solution Approach 1:
The system uses multiple stereo pairs positioned at different locations around the touch area, segmenting the detection coverage. This allows each sensor pair to be positioned in relatively protected locations while collectively providing comprehensive shadow detection coverage, balancing measurement precision with reduced exposure to environmental contaminants and ambient light interference.
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 significantly reduces the computational analysis needed to distinguish between ghost points and true touch points, improving accuracy and reducing the impact of sensor exposure to dust and ambient light, resulting in a more efficient multitouch scenario resolution.
Implementation Method 1
optical sensors 102A and 102B, which may be line scan sensors or area image sensors, are oriented to track the movement of any object within the touch area 104 by detecting interruptions of light within their fields of view
Implementation Method 2
retroreflective material 107 may be positioned along or mounted to certain segments of the bezel 106. Exemplary ray trace 108 in FIG. 1 indicates that light may thus be retroreflected from the bezel 106 back towards the optical sensor 102B
Data Source
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AI summary
An optical touch detection system including at least two stereo pairs of optical sensors, which are each used to identify a set of potential points, and methods for determining which of the potential points are true touch points. The first pair of optical sensors is used to identify a first set of potential points and the second set of optical sensors is used to identify a second set of potential points. Potential point pairs are then compared as between the first and second sets of potential points, i.e., each potential point pair includes a potential point from the first set and a potential point from the second set. Each potential point pair is evaluated to determine the distance between its constituent potential points. The true touch points are identified by selecting the potential point pairs having the shortest distances between their constituent potential points. Using at least two pairs of optical sensors reduces the total number of potential point pairs that must be evaluated to determine the true touch points, thus reducing necessary computational analysis.