Touch Sensor Layout for Stylus and Finger Detection at Display Edges
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Solution Overview
Problem
Existing touch screens, particularly capacitive touch screens, struggle to distinguish between a finger and a stylus pen, leading to operational errors and sensitivity degradation at the edge portions of the display screen, necessitating additional sensor films and separate software for differentiation.
Innovation Solution
An electronic device with a sensor unit comprising overlapping patterns, including edge patterns in the dead space, that allows simultaneous sensing of a stylus pen and a finger without requiring a separate digitizer, by using a controller to form current loops and magnetic fields for stylus pen detection and improve sensitivity at the edge areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a C-type capacitive touch screen is used to enable stylus pen input, then the touch screen can recognize stylus pen contact, but it generates operational errors caused by unintended contact of hand because it is difficult to physically distinguish between finger and stylus pen
Solution Approach 1:
The patent replaces the conventional capacitive sensing method with an electromagnetic resonance (EMR) method. Instead of detecting capacitance changes caused by conductive objects, the system uses a magnetic field generated by a coil to induce resonance in the stylus pen's coil, enabling distinction between stylus pen and finger through magnetic field interaction rather than electrical conductivity detection
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the touch screen and the stylus pen. A coil generates a magnetic field that penetrates the display panel, and the stylus pen's coil resonates with this magnetic field, creating an indirect detection mechanism that avoids direct electrical contact and enables stylus-specific detection
2Reliability
If electromagnetic resonance method is used to distinguish hand from stylus pen, then operational accuracy is improved, but additional sensor film and separate FPCB are required which increases device complexity
Solution Approach 1:
The patent merges the EMR sensing function with the existing display panel structure. The coil is integrated into the dead space area of the display panel rather than requiring a separate sensor film, and the controller utilizes existing touch sensing circuits to detect stylus pen resonance, thereby achieving EMR functionality without additional complex components
Solution Approach 2:
The patent makes the existing touch sensing circuits multi-functional by using them to detect both conventional touch input and EMR-based stylus pen input. The same sensing circuits that detect finger capacitance changes are also used to detect magnetic field-induced resonance signals from the stylus pen, eliminating the need for separate dedicated sensing hardware
3Ease of manufacture
If sensor patterns are confined to active area, then manufacturing is simplified, but sensitivity degradation occurs at edge portion of active area
Solution Approach 1:
The patent extends the sensor patterns from the traditional two-dimensional active area into the third spatial dimension by utilizing the dead space area surrounding the active display region. This dimensional expansion allows edge-sensitive areas to be covered by patterns positioned in the peripheral dead space, improving edge detection sensitivity without complicating the core active area manufacturing
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 accurate and sensitive detection of both stylus pens and fingers without additional sensors, enhancing operational reliability and reducing sensitivity degradation at the edge of the display screen.
Implementation Method 1
the EMR method has an advantage of being insensitive to a display and an external noise by using a magnetic field instead of an electric field as driving force when using a touch function with the stylus pen
Implementation Method 2
When a position of the stylus pen that generates a magnetic field is changed, a separate integrated circuit detects the change of the magnetic field generated by an interaction
Data Source
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AI summary
The present disclosure relates to an electronic device, and more particularly, to an electronic device capable of simultaneously sensing a stylus pen and an object such as a finger brought into proximity or contact with the electronic device from the outside and capable of improving sensitivity degradation at an edge portion of an active area of a display screen.