Touch Sensor Array Multiple Position Estimation
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Solution Overview
Problem
Current touch sensor devices, particularly those using capacitance sensing, are unable to resolve the location of multiple simultaneous touches, often confusing actual touches with 'ghost' touches, limiting them to detecting a single touch at a time.
Innovation Solution
A method for estimating multiple touch positions on a touch sensor array by calculating centroids in the vicinity of local cell maxima, involving raw data filtering, baseline and signal calculation, and centroid computation, which allows for the identification and differentiation of actual touch locations among multiple simultaneous inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a touchpad uses an XY matrix sensor array to detect multiple touches, then the capability to detect multiple touches is improved, but the ability to resolve the location of simultaneous touches deteriorates
Solution Approach 1:
The patent divides the touch sensor array into multiple independent one-dimensional sensor strips (rows and columns) that can be processed separately. Each strip detects capacitance changes independently, and the system segments the analysis by identifying local maxima in each strip to determine potential touch locations, then resolves ambiguities by cross-referencing between strips.
Solution Approach 2:
The patent transforms the two-dimensional touch detection problem into a series of one-dimensional problems by analyzing row and column strips separately. It then reintroduces the second dimension by cross-referencing results between orthogonal strips to resolve ambiguous touch locations, effectively using dimensional decomposition and reconstruction.
2Quantity of substance
If a touchpad detects multiple simultaneous touches, then the quantity of touch inputs is improved, but the reliability of touch location detection deteriorates due to ghost touches
Solution Approach 1:
The patent implements a feedback mechanism where the system identifies potential touch locations by finding local maxima in sensor readings, then uses this information to adjust and refine touch location determination. The system continuously monitors capacitance changes and updates touch position estimates based on the identified maxima, allowing it to distinguish actual touches from ghost touches through iterative refinement.
Solution Approach 2:
The patent performs preliminary analysis by identifying local maxima in the sensor data before finalizing touch location determination. This preliminary step allows the system to pre-identify potential touch candidates and validate them against multiple sensor strips, filtering out false positives (ghost touches) before committing to final touch location results.
3Measurement precision
If a touchpad resolves only single touch locations, then the measurement precision for single touches is maintained, but the adaptability to handle multiple touches deteriorates
Solution Approach 1:
The patent creates a universal touch detection system that can handle both single and multiple touches using the same sensor array and processing methodology. The system maintains the ability to precisely locate single touches while simultaneously gaining the capability to detect and resolve multiple touches by analyzing patterns across multiple sensor strips and identifying multiple local maxima.
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
Enables the accurate detection and resolution of multiple touch positions on a touch sensor device, distinguishing actual touches from 'ghost' touches, thereby enhancing the capability to handle multiple simultaneous inputs.
Implementation Method 1
One type of touchpad operates by way of capacitance sensing utilizing capacitance sensors. The capacitance detected by a capacitance sensor changes as a function of the proximity of a conductive object to the sensor.
Data Source
AI summary
A method of estimating multiple touch positions on a touch sensor array, based on centroids calculated in the vicinity of a local maxima determined for the touch sensor array.