Differential Sensing for Touch Panel Noise Reduction
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Solution Overview
Problem
Touch panels experience adverse effects such as false touch readings and saturation of detection circuitry due to noise injected when touched, which conventional systems fail to adequately address.
Innovation Solution
The touch panel performs sensing operations in both stimulated and non-stimulated states to establish a baseline signal, allowing for the subtraction of noise levels from detection signals, thereby reducing the impact of injected noise and improving touch detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional touch panels sense touch only when stimulus is applied, then the detection process is simple, but noise injected by touch causes false readings and saturation
Solution Approach 1:
The patent applies preliminary action by performing a sensing operation in a non-stimulated state before the stimulated state sensing. This establishes a baseline measurement that captures the noise level present before the stimulus is applied, allowing this baseline to be subtracted from the stimulated state measurement to eliminate noise-induced false readings.
Solution Approach 2:
The patent implements feedback by using the baseline signal obtained from the non-stimulated state sensing to adjust and correct the signal from the stimulated state sensing. The baseline measurement provides feedback about the noise level, which is then used to subtract the noise component from the final touch detection signal.
2Reliability
If sensing is performed only in stimulated state, then the process is fast, but noise from touch injection causes saturation of detection circuitry
Solution Approach 1:
The patent performs preliminary sensing in the non-stimulated state to establish a baseline that captures the noise floor. This preliminary measurement allows the system to compensate for noise in the subsequent stimulated state sensing, preventing circuitry saturation while maintaining efficient operation.
Solution Approach 2:
The patent extracts the noise component by separating the sensing into two distinct phases: non-stimulated state sensing that captures only noise, and stimulated state sensing that captures both signal and noise. By extracting and removing the noise portion through subtraction, the system prevents saturation while maintaining speed.
3Measurement precision
If baseline signal is established through non-stimulated state sensing, then noise can be subtracted, but additional sensing operation is required
Solution Approach 1:
The patent establishes a baseline signal through preliminary non-stimulated state sensing, which enables accurate noise quantification. This additional sensing operation is performed efficiently by integrating it into the existing sensing framework, allowing noise subtraction to improve measurement precision without significantly impacting overall productivity.
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 effectively reduces false readings and saturation issues, enhancing the reliability of touch panel operations by quantifying and subtracting noise levels, leading to improved touch event detection.
Implementation Method 1
Mutual capacitance refers to the ability of two conducting drive and sense surfaces, arranged closely together but not directly coupled, to store a charge when a voltage is applied across them
Implementation Method 2
a touch by a user's finger or other object at that particular sensor location can form a capacitance pathway between the driving element and earth ground through the user's body
Data Source
AI summary
A touch panel can configured to reduce adverse effects associated with noise that can be injected into the panel when touched by performing a sensing operation at each sensor in both a panel-stimulated and non panel-stimulated state. The touch panel can detect a touch event by sensing touch in a non-stimulated state to quantify a noise level injected into the touch panel by the touch, and subtracting that noise level from a detection signal sensed in the stimulated state. In one embodiment, a sensing operation can be performed for a particular sensor at two successive time periods—one for each state—within a single scan cycle. In another embodiment, a sensing electrode configuration can be provided that enables a sensing operation to be performed for a particular sensor in both a panel-stimulated and non panel-stimulated state concurrently.