Capacitive Touch Sensor External Source Electrode Discrimination
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Solution Overview
Problem
Current touch sensors face challenges in accurately distinguishing between multiple touch objects and determining their positions within a touch-sensitive area, particularly in capacitive touch screens, where mutual capacitance measurements can be influenced by parasitic capacitance and signal-to-noise ratios.
Innovation Solution
The implementation of a capacitive touch sensor system with an array of drive and sense electrodes, where mutual-capacitance and self-capacitance modes are used to detect touch positions and identify objects by measuring changes in capacitance, and by employing external source electrodes embedded in user-proximate devices to enhance signal transfer and differentiate touch objects based on mutual capacitance thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If mutual capacitance measurements are used to detect touch positions, then touch position detection capability is improved, but measurement precision deteriorates due to parasitic capacitance interference
Solution Approach 1:
The patent introduces external source electrodes as intermediary elements that are coupled to the touch objects. These source electrodes act as mediators between the touch objects and the measuring electrodes, enabling indirect measurement of touch characteristics while avoiding direct parasitic capacitance interference. The source electrodes transfer signals through the touch objects to the measuring electrodes, allowing differentiation of multiple touch objects based on their unique signal paths.
2Adaptability or versatility
If multiple touch objects are detected simultaneously, then touch sensor functionality is improved, but object differentiation capability deteriorates due to signal interference
Solution Approach 1:
The patent segments the touch detection system into multiple independent measurement channels, each associated with a specific external source electrode. Each source electrode is coupled to a specific touch object, creating separate signal paths that can be independently measured. This segmentation allows the system to distinguish between multiple touch objects by analyzing signals from different source electrodes, even when they are in close proximity or simultaneously touching the sensor.
Solution Approach 2:
External source electrodes serve as intermediary elements that enable individual identification of each touch object. Each source electrode is uniquely coupled to a specific touch object, acting as a mediator that carries identification information through the touch object to the measuring electrodes. This intermediary approach allows the system to differentiate between multiple touch objects based on their unique source electrode connections.
3Measurement precision
If external source electrodes are added to enhance signal transfer, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
The external source electrodes are designed to serve multiple functions: they act as signal sources for capacitive coupling, serve as identification markers for different touch objects, and function as signal transfer mediators. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving improved signal-to-noise ratio and object differentiation capability.
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 precise detection and identification of multiple touch objects, improving the accuracy of touch position determination and object differentiation, even in complex environments with varying capacitance conditions, thereby enhancing user interaction and system responsiveness.
Implementation Method 1
A capacitive touch screen may include an insulator coated with a substantially transparent conductor in a particular pattern. When an object touches or comes within proximity of the surface of the capacitive touch screen, a change in capacitance may occur within the touch screen at the location of the touch or proximity.
Implementation Method 2
mutual-capacitance and self-capacitance modes are used to detect touch positions and identify objects by measuring changes in capacitance
Data Source
AI summary
In one embodiment, a method includes conducting a first signal to a first source electrode external to a touch sensor. The first source electrode is capacitively coupled to the touch sensor through a touch object. The method further includes measuring a mutual capacitance between the first source electrode and the first measuring electrode. The method further includes identifying, based at least in part on the measured mutual capacitance and using a controller of the touch sensor, the touch object touching the touch sensor at a detected touch position.