Capacitance Touch Input System With Resonant Stylus And Antenna Loop
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Solution Overview
Problem
Capacitance-type touch screens face challenges in accurately detecting stylus pen touches due to small contact areas and mutual capacitance variations, leading to coordinate distortion and sensitivity issues, and struggle with palm rejection, requiring additional components and processes.
Innovation Solution
An input system utilizing a capacitance-type touch detection with a resonance circuit in the stylus pen and an antenna loop outside the sensor panel, enabling touch detection without auxiliary panels or electrode patterns, allowing for separate detection of finger and stylus pen touches and improved sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance-type touch detection is used with traditional electrode patterns, then finger touch detection is achieved, but stylus pen touch detection accuracy deteriorates due to small contact areas and mutual capacitance variations
Solution Approach 1:
The patent divides the touch detection function into two separate detection paths: one for finger touch using mutual capacitance between Tx and Rx electrodes, and another for stylus pen touch using self-capacitance detection at Tx electrodes. This segmentation allows each detection path to be optimized for its specific input device type, resolving the contradiction between accurate finger touch detection and stylus pen touch detection accuracy.
Solution Approach 2:
The patent changes the detection parameter from mutual capacitance (ΔCm) to self-capacitance (Csx) when detecting stylus pen touches. By switching to self-capacitance detection that measures the capacitance between the stylus and the Tx electrode directly, the system overcomes the limitation of small contact areas and mutual capacitance variations, thereby improving stylus pen touch detection accuracy while maintaining finger touch detection capability.
2Adaptability or versatility
If additional auxiliary panels or electrode patterns are added to enable stylus pen detection, then detection versatility is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent makes the existing Tx electrodes serve multiple functions: they act as both mutual capacitance electrodes for finger touch detection and self-capacitance electrodes for stylus pen touch detection. By enabling the same hardware components to perform multiple detection functions through different detection algorithms, the system achieves versatility in detecting both finger and stylus pen touches without adding auxiliary panels or extra electrode patterns, thereby reducing device complexity.
Solution Approach 2:
The Tx electrodes themselves serve as the sensing element for stylus pen detection through self-capacitance measurement, without requiring separate auxiliary sensing structures. The system uses the existing electrode infrastructure to detect stylus touches by measuring the self-capacitance change at each Tx electrode, eliminating the need for additional components and simplifying the overall device structure.
3Ease of manufacture
If traditional capacitance detection is used, then manufacturing is simplified, but palm rejection capability is lost
Solution Approach 1:
The patent introduces self-capacitance (Csx) as an intermediary measurement parameter that indirectly detects stylus pen touches without being directly affected by palm interference. By measuring the capacitance between the stylus and Tx electrode rather than relying on mutual capacitance between crossing electrodes, the system can distinguish stylus touches from palm touches, enabling palm rejection while maintaining manufacturing simplicity.
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 solution reduces production costs, simplifies manufacturing, enhances touch accuracy, and enables palm rejection, maintaining sensitivity uniformly across regions without the need for batteries in the stylus pen.
Implementation Method 1
an electromagnetic resonance generated in a resonance circuit provided in the stylus pen may be induced to the antenna loop by a second mutual inductance between a second coil provided in the resonance circuit and the antenna loop
Implementation Method 2
a signal from the first coil may be transmitted to the antenna loop by a first mutual inductance between the first coil and the antenna loop
Data Source
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AI summary
An input system and a method for detecting touch using the same are provided. An input system includes: a sensor panel including first and second channels crossing each other, a stylus pen including: a first coil and a second coil divided from each other, a resonance capacitor and a switch serially connected to the second coil, and a conductive tip connected to the first coil, a stylus ground connected to the stylus pen, an antenna loop formed in an outer region of the sensor panel, and a touch controller connected to the first and second channels and the antenna loop.