Capacitive Touch Coordinate Accuracy via Noise Filtering
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Solution Overview
Problem
Capacitive multi-touch systems face inaccuracies in touch coordinate calculation due to noise from human bodies, environments, and panels, leading to unstable calculated coordinates and reduced signal-to-noise ratios, especially when multiple touch points are detected concurrently.
Innovation Solution
A method involving a capacitive touch panel, a driving and sensing device, an analog-to-digital converter (ADC), and a controller that initializes the system, generates raw data, performs de-noising and up-linearity operations, integrates data to reduce noise, cancels accumulated errors, and calculates accurate touch coordinates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mutual capacitance sensing is used to detect multiple touch points, then the ability to determine real touch coordinates is improved, but the signal-to-noise ratio is reduced and coordinate stability deteriorates due to noise from human body, environment, and panel
Solution Approach 1:
The patent applies preliminary action by performing de-noising and up-linearity operations on raw sensing data before integrating it for coordinate calculation. The controller pre-processes the signal by filtering noise and correcting non-linearities in advance, which prevents noise accumulation during integration and stabilizes the final coordinate output.
Solution Approach 2:
The patent introduces an intermediary processing stage between raw sensing and final coordinate output. The controller acts as an intermediary that performs de-noising, up-linearity, and integration operations on the raw data from driving and sensing devices, transforming noisy raw signals into stable coordinate information before presenting the final result.
2Reliability
If integration operation is performed on raw sensing data to reduce noise, then the signal-to-noise ratio is improved, but accumulated errors are introduced that degrade measurement precision
Solution Approach 1:
The patent converts the harmful effect of accumulated errors into a beneficial process by explicitly identifying and canceling them. The controller performs integration to reduce noise, then separately identifies and cancels the accumulated errors that resulted from this integration, transforming what was originally a harmful side effect into a controlled and corrected process.
Solution Approach 2:
The patent implements feedback by having the controller continuously monitor and adjust for accumulated errors in the integrated data. The error cancellation step uses feedback from the integration process itself, where the controller detects patterns of accumulated error and applies corrective adjustments to maintain measurement precision.
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
The method enhances the accuracy of touch coordinate calculation and signal-to-noise ratio by filtering noise and stabilizing data, effectively reducing errors and improving the reliability of multi-touch applications.
Implementation Method 1
A typical capacitive touch panel is driven by sensing the grounded capacitance on each conductor line. Thus, a change of the grounded capacitance is used to determine whether an object approaches the capacitive touch panel
Implementation Method 2
it senses the magnitude change of mutual capacitance Cm to thereby determine whether the object approaches the touch panel. Likewise, the mutual capacitance Cm is not a physical capacitor but a mutual capacitance between the conductor lines in the first direction and in the second direction
Data Source
AI summary
In a method for increasing accuracy of touch coordinate calculation in a capacitive multi-touch system, it performs operations on obtained data for de-noising of the obtained data and increasing its linearity so as to generate data with excellent stability and linearity. An integral accumulation operation is performed to generate data for each sensing channel, cancel the accumulation error in data, and calculate coordinates for touch points on a capacitive touch panel.