Fingerprint Sensor Integrated Touch Screen Panel Design
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Solution Overview
Problem
Capacitive fingerprint sensors integrated with touch screens face issues such as increased bezel area, complexity in construction, and degraded touch sensitivity due to mutual capacitance, which leads to dead zones and impaired touch recognition.
Innovation Solution
A fingerprint sensor integrated touch screen panel design with touch and fingerprint electrodes arranged in the active area, using a time division method to apply distinct driving voltages for touch and fingerprint sensing, and employing a readout IC with integrators and A/D converters to enhance resolution and prevent parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a capacitive fingerprint sensor is integrated with a push button assembly, then fingerprint sensing capability is achieved, but device complexity and bezel area increase
Solution Approach 1:
The patent merges the fingerprint sensor and touch sensor into a single integrated structure where the fingerprint sensor electrodes are formed within the active area of the touch sensor. This combination eliminates the need for separate push button assemblies while maintaining both fingerprint sensing and touch sensing functionalities, thereby reducing device complexity and bezel area.
Solution Approach 2:
The integrated sensor structure serves multiple functions: it acts as both a fingerprint sensor for biometric authentication and a touch sensor for general touch interactions. The same electrode structure and active area are utilized for both fingerprint ridge/valley detection and touch position sensing, maximizing the utility of the integrated design.
2Adaptability or versatility
If a push button is used for fingerprint sensing, then fingerprint recognition is enabled, but the sensing area is limited by the push button size and thickness increases
Solution Approach 1:
The patent transitions from a three-dimensional push button structure to a planar two-dimensional integration within the active area. By forming fingerprint sensor electrodes in the same plane as the touch sensor electrodes, the design eliminates the thickness increase associated with push buttons while expanding the fingerprint sensing area to cover the entire active region.
3Adaptability or versatility
If the fingerprint sensor occupies a portion of the display area, then fingerprint sensing is achieved, but dead zones are created where touch sensing is impaired
Solution Approach 1:
The integrated electrode structure performs dual functions: detecting fingerprint ridges and valleys through capacitance variations and detecting touch positions through mutual capacitance changes. The same electrode regions that sense fingerprints also participate in touch sensing, ensuring no dead zones are created and maintaining uniform touch sensitivity across the entire active area.
Solution Approach 2:
The system employs time-division multiplexing to alternately perform fingerprint sensing and touch sensing operations. During fingerprint sensing mode, the system measures capacitance at fingerprint sensor electrodes; during touch sensing mode, it measures mutual capacitance for touch position detection. This periodic switching allows both functions to operate without interference, eliminating dead zones.
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 design prevents dead zones, maintains touch sensitivity, and allows for accurate touch and fingerprint recognition without overlapping modes, resulting in a narrower bezel area and improved user interface performance.
Implementation Method 1
The capacitive fingerprint sensor utilizes difference of electric charges charged between ridges and valley of the finger contacted thereto
Implementation Method 2
the mutual capacitances between the first channel electrodes 111 and the second channel electrodes 112 are significantly increased
Data Source
AI summary
A touch sensing device comprises touch electrodes having a first resolution for sensing touch in the active area. The touch sensing device also includes combination touch and fingerprint electrodes having a second resolution for sensing both touch and a fingerprint in the active area, the second higher than the first resolution. The touch sensing device also includes a touch and fingerprint controller that respectively applies a touch driving voltage for sensing touch to the plurality of touch electrodes and the plurality of combination touch and fingerprint electrodes during a touch driving mode of a touch period of the touch sensing device, and the touch and fingerprint controller applies a fingerprint driving voltage for sensing a fingerprint to the plurality of combination touch and fingerprint electrodes during a fingerprint mode of the touch period.