Capacitive Touch Positioning Underwater via Orthogonal Demodulation
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Solution Overview
Problem
Capacitive touch screens struggle to accurately determine touch positions underwater due to the significant difference in dielectric constants between air and water, leading to inaccurate impedance variations and touch detection.
Innovation Solution
The method involves orthogonally demodulating output signals from capacitor nodes to acquire orthogonal components Q, comparing these components to a reference, and determining the touch position based on decreased orthogonal components Q, which improves accuracy in underwater environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitive screen is operated underwater with water as the dielectric medium, then the impedance between capacitor nodes becomes smaller, but the touch position determination accuracy deteriorates due to the significantly different dielectric constant of water compared to air
Solution Approach 1:
The patent inverts the traditional touch detection logic by detecting capacitor nodes where the orthogonal component Q decreases rather than increases. This inversion resolves the contradiction because water's high dielectric constant causes capacitance increase that traditionally masks touch signals, but by looking for Q decreases instead, the patent successfully detects touches underwater while maintaining position accuracy.
2Adaptability or versatility
If the dielectric medium changes from air to water, then the capacitance variation of capacitor nodes changes, but the existing touch judgment method becomes inaccurate
Solution Approach 1:
The patent changes the detection parameter from traditional capacitance variation to orthogonal component Q variation. By using orthogonal demodulation to extract the Q component and detecting its decrease rather than capacitance increase, the system adapts to underwater environments while maintaining precise touch position determination despite the dielectric medium change from air to water.
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 enhances the accuracy of touch position determination on capacitive screens when used underwater by clearly differentiating touched and non-touched regions through inverse variations in orthogonal component Q, effectively addressing the challenge posed by water's high dielectric constant.
Implementation Method 1
a finger touch to the touch screen may cause the capacitances of the capacitor nodes of the touch screen to vary, and thus touch detection may be implemented according to this feature
Implementation Method 2
the dielectric medium of each capacitor node becomes the water, of which the dielectric constant is greatly different from the air
Data Source
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AI summary
Embodiments of the present application provide a method and apparatus for determining a touch position of a capacitive screen. The method includes: acquiring an output signal of each capacitor node, and orthogonally demodulating the output signal to obtain a corresponding orthogonal component Q; judging whether corresponding orthogonal components Q associated to some of the capacitor nodes have increased relative to a reference orthogonal component Q in an underwater mode, and corresponding orthogonal components Q associated to some other of capacitor nodes have decreased relative to the reference orthogonal component Q in the underwater mode; and determining that the capacitive screen has been touched, and determining the touch position based on coordinates of the capacitor nodes whose orthogonal component Q have decreased if a result of the judging is true.