Touchscreen Fingerprint Sensor Electrode Segmentation
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Solution Overview
Problem
Capacitive touchscreen devices with integrated fingerprint sensors face challenges in size reduction, manufacturing cost, and sensitivity due to the complexity of integrating high-resolution sensor arrays and ICs, leading to increased mutual capacitance that affects touch sensitivity and recognition accuracy.
Innovation Solution
The touchscreen device incorporates a touch area and a fingerprint and touch area with distinct electrode configurations, where Tx electrodes are grouped for touch sensing and FTx/FRx electrodes are individually driven for fingerprint sensing, reducing mutual capacitance and parasitic capacitance through strategic electrode connections and shielding, ensuring uniform capacitance and improved sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-resolution sensor array and IC are integrated using a silicon wafer for capacitive fingerprint sensing, then fingerprint recognition accuracy is improved, but device complexity and bezel size increase
Solution Approach 1:
The patent merges the fingerprint sensor array and IC onto a single silicon wafer substrate, eliminating the need for separate assembly structures and push buttons. This integration maintains high-resolution fingerprint sensing while simplifying the overall device configuration and reducing bezel size.
Solution Approach 2:
The silicon wafer serves multiple functions simultaneously: it acts as both the substrate for the high-resolution sensor array and the integrated circuit board for signal processing. This multi-functionality eliminates the need for separate components and reduces device complexity.
2Length of stationary object
If a push button is used for both home key and fingerprint sensing, then device thickness is reduced, but fingerprint sensing area is limited by button size
Solution Approach 1:
The patent transitions from a three-dimensional push button structure to a two-dimensional flat sensor array on a silicon wafer. This dimensional change allows the fingerprint sensing area to extend across the entire screen surface without increasing device thickness, effectively utilizing the planar space available.
3Area of stationary object
If tiny channels are grouped as touch group channels in high-density sensor pattern, then touch sensing coverage is improved, but mutual capacitance increases and touch sensitivity decreases
Solution Approach 1:
The patent segments the sensor array into distinct fingerprint sensing regions and touch sensing regions. The tiny channels in the fingerprint sensing area are individually connected to maintain high resolution for fingerprint recognition, while touch sensing is handled by separate electrode groups in other areas, preventing mutual capacitance interference and maintaining touch sensitivity.
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 configuration reduces power consumption, enhances touch report rates, and achieves accurate fingerprint sensing by minimizing mutual capacitance and parasitic capacitance, thereby improving the overall performance and sensitivity of the touchscreen device.
Implementation Method 1
the capacitive sensor detects a conductive object according to a change in capacitance
Implementation Method 2
the human body may be used as a shield to reduce the mutual capacitance between the electrode groups
Data Source
AI summary
The present disclosure provides a touchscreen device with an integrated fingerprint sensor. The touchscreen device including a touchscreen having a touch area for touch sensing and a fingerprint and touch area for touch sensing and fingerprint sensing, the touch area having Tx electrodes arranged in a first direction and Rx electrodes arranged in a second direction, and the fingerprint and touch area having FTx electrodes arranged in the first direction and FRx electrodes arranged in the second direction, and a touch IC that performs touch sensing through the touch area and the fingerprint and touch area and performs fingerprint sensing through the fingerprint and touch area, wherein the Rx electrodes form a plurality of groups, and the groups are individually and separately connected to Rx lines in the boundary region between the touch area and the fingerprint and touch area.