Capacitive Touch Sensing With Deflection Signal Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Single-electrode layer capacitive touch input devices are susceptible to background interference due to stray capacitance and mechanical deflection, which increases manufacturing costs and reduces accuracy in determining touch location.
Innovation Solution
Compensating for undesired signals by measuring output signals from electrodes separated from the point of contact and estimating the amount of background capacitance due to mechanical deflection, allowing for more accurate determination of touch location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single electrode layer is used to reduce manufacturing cost, then manufacturing cost is reduced, but susceptibility to background interference from mechanical deflection increases
Solution Approach 1:
The patent divides the electrode layer into multiple segments or zones, allowing independent measurement and compensation of deflection effects in different regions. This segmentation enables the system to track and compensate for mechanical deflection locally, reducing background interference while maintaining the cost benefits of a single electrode layer structure.
Solution Approach 2:
The patent changes operational parameters by measuring capacitance values at multiple different time points during the touch detection process. By taking measurements at different times, the system can distinguish between static background interference (including mechanical deflection) and dynamic touch signals, thereby compensating for deflection effects without adding physical complexity.
2Measurement precision
If measurements are taken at multiple time points to compensate for mechanical deflection, then accuracy of touch location detection is improved, but measurement time and processing complexity increase
Solution Approach 1:
The patent implements periodic measurements at multiple time points within a defined measurement window. This periodic sampling approach allows the system to capture temporal variations in capacitance signals, enabling differentiation between touch events and mechanical deflection. The periodic nature of these measurements provides sufficient data for compensation while maintaining efficient processing timing.
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
Improves the accuracy of touch location detection in single-electrode layer capacitive touch devices by reducing the impact of background interference, thereby maintaining performance at lower manufacturing costs.
Implementation Method 1
The electrodes may be coupled to capacitance sensing circuitry including analog-to-digital converters that measure values associated with the electrodes, such as the capacitance, current, charge, impedance or voltage associated with the electrodes.
Implementation Method 2
Stray capacitance between the sensing electrodes and the palm of the hand or other body parts of the user is one source of background interference.
Implementation Method 3
Mechanical deflection of the touch device is another source of background interference. For example, touch induced pressure against the device may cause mechanical deflection between sensing electrodes and an underlying ground plane.
Data Source
AI summary
A location of contact with a touch sensitive device is determined. Output signals associated with a plurality of electrodes such as formed on a single layer of the touch sensitive device are measured to identify a first electrode positioned at an approximate location of contact with the touch sensor. An output signal associated with a different electrode that is separated from the first electrode is measured to determine an undesired signal amount, such as due to deflection. An undesired single amount associated with the first electrode may be estimated based on the undesired signal amount measured at the other electrode. The signal amount measured at the first electrode is then compensated by the estimated undesired signal amount. The location of contact with the touch sensor is then determined based on the compensated signal amount.