Capacitive Touch Sensor Proximity Detection via Electric Field Shunting
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Solution Overview
Problem
Current touch sensors face challenges in accurately detecting the presence and location of objects, particularly in capacitive touch screens, where changes in capacitance can be complex and require improved electrode configurations to enhance sensitivity and precision, especially for proximity detection without physical contact.
Innovation Solution
The implementation of a capacitive touch sensor with an array of drive and sense electrodes on substrates, utilizing a mechanical stack with optically clear adhesive and dielectric layers, and specific electrode configurations that include ground electrodes to shunt electric fields, allowing for improved sensitivity and detection of objects in proximity, including those hovering above the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive touch sensor uses a simple electrode configuration, then the device complexity is reduced, but the measurement precision and sensitivity of proximity detection deteriorates
Solution Approach 1:
The electrode array is segmented into multiple electrode groups along the first direction, with each group containing multiple electrodes. This segmentation allows the system to detect proximity at different positions independently, improving measurement precision while maintaining a structured, manageable configuration that doesn't excessively increase complexity.
Solution Approach 2:
Different electrode groups are assigned different sensing directions (first direction for vertical proximity, second direction for horizontal proximity). This local differentiation of quality allows the system to optimize detection precision for specific directional proximity events without requiring a completely complex omnidirectional configuration everywhere.
2Measurement precision
If the electrode array density is increased to improve detection sensitivity, then the measurement precision improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The high-density electrode array is segmented into repeating groups with predictable patterns. This segmentation makes the fabrication process more manageable by allowing standardized manufacturing techniques to be applied to each group, reducing the overall manufacturing difficulty despite the high total density of electrodes.
Solution Approach 2:
The patent utilizes a two-dimensional electrode arrangement where electrodes are distributed across both first and second directions. This dimensional approach allows sensitivity to be improved in multiple detection directions simultaneously without requiring excessive density in a single direction, thereby easing manufacturing constraints.
3Measurement precision
If ground electrodes are added to shunt electric fields for improved sensitivity, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
Ground electrodes are merged with the functional electrode groups, where certain electrodes in the array serve dual purposes as both sensing electrodes and ground electrodes at different times. This merging reduces the total number of separate electrode structures needed, improving precision without proportionally increasing complexity.
Solution Approach 2:
The system dynamically switches the function of electrodes between sensing and grounding roles based on the detection phase. This dynamic reconfiguration allows the same physical electrode structure to provide both measurement precision through sensing and field control through grounding, without requiring separate static structures for each 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
This configuration enhances the sensitivity and accuracy of touch and proximity detection, enabling precise determination of object positions both in contact and in proximity, improving the overall performance of capacitive touch screens by tuning the electrode arrangement for optimal sensitivity ranges.
Implementation Method 1
a drive signal may be applied to a first electrode of a sensor to generate an electric field extending from the first electrode toward a second electrode of the sensor
Implementation Method 2
a portion of the electric field may be shunted away from the second electrode
Implementation Method 3
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
Data Source
AI summary
In one embodiment, a method includes applying a drive signal to a first electrode of a sensor to generate an electric field extending at least in part from the first electrode toward a second electrode of the sensor. The electric field includes a first portion and a second portion, and the first portion extends farther away from a plane of the first electrode than the second portion. The method also includes shunting the second portion of the electric field away from the second electrode and receiving a sense signal from the second electrode produced at least in part by the first portion of the electric field. The sense signal indicates whether an object has come within proximity of the sensor.