Display Pane Capacitive Touch Sensing for Light Contact Detection
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Solution Overview
Problem
Existing touch detection systems for screens and display elements are not sufficiently sensitive to detect light touches, especially in the presence of interference signals from electronic devices, which hinders accurate activation of functions like cursor control.
Innovation Solution
A capacitive touch detection system using strip-shaped electrodes on a glass pane connected by conductor tracks, combined with a resilient support and a modified gyrator circuit for high-quality factor inductance, allowing for precise measurement of capacitance changes to detect light touches while rejecting interference signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitive sensor is used to detect touch, then the system can detect touch input, but the sensitivity is insufficient to detect light touches in the presence of interference signals
Solution Approach 1:
The patent applies mechanical vibration by resonating the glass pane at its natural frequency (typically 20-100 Hz) using a piezoelectric actuator. This vibration creates a dynamic capacitive signal that is significantly stronger than static touch signals, enabling detection of light touches even in the presence of electronic interference. The resonant vibration amplifies the mechanical displacement caused by finger pressure, making the capacitive change detectable above noise floors.
Solution Approach 2:
The system uses periodic action by continuously driving the glass pane at its resonant frequency and sampling the capacitive signal synchronously with the vibration cycle. This periodic excitation creates a consistent signal pattern that can be easily distinguished from random electronic interference through synchronous detection techniques, significantly improving signal-to-noise ratio for light touch detection.
2Measurement precision
If the glass pane is made rigid for structural stability, then the display structure is stable, but the pane does not deflect sufficiently to detect light touches
Solution Approach 1:
Rather than making the glass more flexible, the patent maintains structural rigidity and instead uses resonant vibration to temporarily induce dynamic deflection. The glass pane is driven at its natural frequency where even small forces produce maximum amplitude vibrations, creating sufficient capacitive signal change for light touch detection while maintaining overall structural stability and strength.
3Measurement precision
If a coil with high inductance is used in the phase method sensor circuit, then the quality factor Q is high for better sensitivity, but significant space is consumed
Solution Approach 1:
The patent replaces the physical coil inductor with an electronic gyrator circuit that synthesizes high inductance values using operational amplifiers and resistors. This electronic substitution achieves the same electrical function (providing high Q factor for phase method sensitivity) without the physical space requirements of a large coil, reducing the sensor electronics footprint significantly.
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 reliable detection of light finger pressure with high sensitivity and accuracy, enabling efficient activation of functions like wake-up modes in devices like mobile phones and gaming computers, while minimizing space and construction changes.
Implementation Method 1
The support B can be designed in different ways, e.g. with metal or plastic springs, rubber profiles of various shapes or also strips of foam material. It is of particular advantage if the material works in the elastic (Hook's) range, which can be defined by a spring constant k
Implementation Method 2
The electrodes form a capacitance C in relation to the metal frame R located under the glass pane, which is given both by the entire area A of the electrodes and by the distance a according to C=εA/a. If, as shown in FIG. 1b, the glass pane including the applied electrode strips is supported by a support B resting resiliently on the metal frame R, contact with a force F results in a change in distance Δa and thus from Eq.1.1 a relative change in capacitance Δ C/C=−Δa/a
Data Source
Figure 1a~1b
Figure 2a~2b
AI summary
The present invention relates to a system by means of which light contact of a finger or stylus with a screen, display or other panel element can be recognized in order to thereby activate other functions, such as an initialization for a cursor control. The invention aims to solve the problem of enabling the detection of contact with said structures in an improved manner compared to previous solutions. The invention solves the problem by a display assembly having a pane body, an electrode device, a mounting structure for mounting the pane body such that said body undergoes sufficient displacement as a result of a pressure force exerted upon contact with the pane body, wherein the electrode device is coupled to the pane body and forms part of a capacitive system, the capacitance thereof changing when a load is applied to the mounting structure.