Touch Detection Device with Air Gap Electrodes
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Solution Overview
Problem
Capacitive touch detection systems struggle to effectively detect touch locations of non-conductive objects and measure the magnitude of force applied by both conductive and non-conductive objects on a capacitive sense array.
Innovation Solution
A touch detection device with a one-layer electrode structure, including a touch sensing electrode layer and a conductive layer separated by an air gap, uses mutual capacitance scanning for force sensing and self-capacitance scanning for touch sensing, enabling detection of touch locations and force magnitude through a processing device that alternates between touch and force sensing states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional capacitive touch detection is used, then touch locations of conductive objects can be detected, but touch locations of non-conductive objects cannot be effectively detected and force magnitude cannot be measured
Solution Approach 1:
The patent combines self-capacitance sensing and mutual-capacitance sensing into a single touch detection device. The self-capacitance sense electrodes detect touches of any object type, while the mutual-capacitance force electrodes specifically detect force magnitude. This merging allows the system to handle both conductive and non-conductive objects effectively while providing force measurement capability.
Solution Approach 2:
The touch detection device is designed with multi-functionality to detect both touch location and force magnitude using the same electrode structure. The force electrodes can operate in both self-capacitance mode (for general touch detection) and mutual-capacitance mode (for force sensing), making the device universally applicable to different object types and detection needs.
2Device complexity
If a single electrode layer is used for both touch sensing and force sensing, then device complexity is reduced, but the ability to independently optimize touch and force detection performance is limited
Solution Approach 1:
The electrode system is segmented into two distinct functional groups: self-capacitance sense electrodes for touch location detection and mutual-capacitance force electrodes for force magnitude detection. This segmentation allows each electrode type to be optimized for its specific function while maintaining a relatively simple single-layer structure, balancing complexity and performance.
Solution Approach 2:
The air gap between the electrode layer and the substrate acts as an intermediary that enables force sensing. When force is applied, the air gap compresses, changing the capacitance between the force electrodes and the substrate. This intermediary mechanism allows force detection without adding complex mechanical sensing components.
3Ease of operation
If self-capacitance scanning is used for touch detection, then touch locations can be detected, but force magnitude cannot be measured
Solution Approach 1:
The system continuously performs both self-capacitance scanning and mutual-capacitance scanning operations. The self-capacitance sense electrodes continuously monitor touch location, while the mutual-capacitance force electrodes continuously measure force magnitude. This continuous dual operation ensures that both touch position and force information are available without interrupting either detection function.
Solution Approach 2:
The patent employs asymmetric electrode configurations where self-capacitance sense electrodes and mutual-capacitance force electrodes have different operational characteristics. The sense electrodes are optimized for detecting capacitance changes from any object, while the force electrodes are specifically optimized for measuring force-induced capacitance changes, allowing each to excel at its designated function.
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 accurate detection of touch locations and force magnitude for both conductive and non-conductive objects, improving the capability of capacitive touch detection systems beyond conventional limitations.
Implementation Method 1
measure self-capacitance of each electrode of a subset of the sense electrodes and detect one or more touch locations
Implementation Method 2
measure mutual capacitance at each electrode of a subset of the sense electrodes with respect to the at least one force electrode, and detect a touch force
Implementation Method 3
The conductive layer is disposed substantially in parallel with the touch sensing electrode layer and separated from the touch sensing electrode by at least an air gap
Data Source
AI summary
This application is directed to a touch detection device that has a plurality of sense electrodes, at least one force electrode, and a processing device electrically coupled to the sense electrodes and the force electrode. The sense electrodes are disposed substantially in parallel with the force electrode and separated therefrom by at least an air gap. While operating in a touch sensing state, the processing device leaves the force electrode electrically afloat, measures self-capacitance of each of a subset of sense electrodes, and detects a touch location of an object. While operating in a force sensing state, the processing device drives the force electrode by a transmit signal, measures mutual capacitance of each of a subset of sense electrodes with respect to the force electrode, and detects a touch force on a touch location when an object touches a top surface of the touch detection device.