Capacitance Sensor Circuit Rejecting Common Signals for Multi-Touch Resolution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current touch sensor devices, particularly those using capacitance sensing, are unable to resolve multiple simultaneous touches accurately, often confusing actual touches with invalid or 'ghost' touches, limiting them to detecting only a single touch location.
Innovation Solution
The implementation of a capacitance sensor measurement circuit with a differential amplifier that rejects common signals between rows and columns, allowing for differential scanning to distinguish actual from invalid touch locations by measuring capacitance changes across intersections in a touch sensor matrix, reducing the number of scans required and enhancing signal resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a touchpad uses an XY matrix to detect multiple simultaneous touches, then the number of detectable touches increases, but the ability to resolve the location of touches deteriorates
Solution Approach 1:
The patent segments the sensing process into multiple sequential scanning phases. Instead of attempting to resolve all touch locations simultaneously, the system performs repeated scans and segments the data processing into distinct phases: identifying candidate touch points from capacitance changes, resolving ambiguities through comparative analysis across scans, and confirming final touch locations. This temporal segmentation allows the system to handle multiple touches while maintaining resolution accuracy.
2Measurement precision
If a touchpad is configured to resolve only a single touch location, then measurement precision is maintained, but the quantity of detectable touches deteriorates
Solution Approach 1:
The patent adds a temporal dimension to the traditional two-dimensional touch detection problem. By performing repeated scans over time and analyzing capacitance changes across multiple time points, the system transforms a 2D spatial problem into a 3D problem (x, y, time). This additional temporal dimension provides extra information that enables the system to distinguish between multiple simultaneous touches while maintaining spatial resolution, effectively adding a fourth dimension to the analysis.
3Measurement precision
If a touchpad performs multiple scans to resolve simultaneous touches, then measurement precision improves, but the time required for detection increases
Solution Approach 1:
The patent performs preliminary actions by conducting initial scans to identify candidate touch points and capacitance change patterns before final resolution. The system uses these preliminary data points to pre-process and pre-filter potential touch locations, eliminating obvious false candidates early in the process. This preliminary action reduces the computational burden for subsequent resolution steps and minimizes the total time required for accurate multi-touch detection.
4Device complexity
If a touchpad uses traditional capacitance sensing methods, then device complexity is minimized, but the ability to distinguish actual touches from ghost touches deteriorates
Solution Approach 1:
The patent implements feedback mechanisms by continuously monitoring capacitance changes across multiple scans and using this information to refine touch location identification. The system compares capacitance measurements from successive scans, uses identified touch points from previous scans to inform current scan interpretation, and adjusts its detection criteria based on accumulated data. This feedback loop enables the system to distinguish actual touches from ghost touches with high reliability while maintaining relatively simple sensor hardware.
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 enables the accurate detection and resolution of multiple simultaneous touches, reducing the number of scans needed and improving signal-to-noise ratio, thereby enhancing the capability of touch sensor devices to handle multi-touch inputs effectively.
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.
Implementation Method 2
The implementation of a capacitance sensor measurement circuit with a differential amplifier that rejects common signals between rows and columns, allowing for differential scanning to distinguish actual from invalid touch locations by measuring capacitance changes across intersections in a touch sensor matrix
Data Source
AI summary
A capacitance measurement sensor, having a voltage subtractor that rejects common signals between the columns or rows of a touch sensor matrix depending on which are driven and which are being sensed, is described.