Ultrasonic Fingerprint Sensor Electrode Segmentation for Leakage Reduction
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Solution Overview
Problem
In ultrasonic fingerprint identification devices, electric leakage occurs during the process of converting ultrasonic waves to electrical signals, leading to inaccurate fingerprint images and reduced identification accuracy.
Innovation Solution
A fingerprint identification device comprising a receiving electrode layer, a piezoelectric material layer, and a drive electrode layer, where the piezoelectric material layer is between the receiving and drive electrode layers, and a processor is used to apply varying voltages to the electrodes to emit and receive ultrasonic waves simultaneously, reducing electrical leakage and improving image accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the piezoelectric material layer converts ultrasonic waves to electrical signals using a single electrode configuration, then the conversion process is simple, but electric leakage occurs leading to inaccurate fingerprint images
Solution Approach 1:
The electrode layer is segmented into drive electrodes and receiving electrodes that are spatially separated. The drive electrodes apply voltage to generate ultrasonic waves, while the receiving electrodes detect the reflected waves. This segmentation prevents electric leakage by isolating the high-voltage drive region from the sensitive receiving region, thereby improving fingerprint image accuracy without significantly increasing device complexity.
Solution Approach 2:
Different regions of the electrode layer are assigned different functions: drive electrodes in certain regions generate ultrasonic waves, while receiving electrodes in other regions detect reflected waves. This local differentiation of electrode functions allows simultaneous emission and reception with reduced electrical interference, improving measurement precision while maintaining a relatively simple overall structure.
2Reliability
If ultrasonic waves are emitted and received sequentially, then electrical leakage is reduced, but real-time fingerprint identification is compromised
Solution Approach 1:
The drive electrode layer and receiving electrode layer are merged into a single integrated electrode structure with distinct functional regions. This allows ultrasonic waves to be emitted and received simultaneously in real-time, enabling continuous fingerprint identification without sequential switching, thereby maintaining both signal stability and identification speed.
Solution Approach 2:
The electrode system transitions from a single-layer sequential operation to a multi-layer simultaneous operation. By stacking drive and receiving electrodes in different layers with different functional regions, the system achieves spatial separation of functions while maintaining temporal simultaneity, enabling real-time fingerprint identification with reduced electrical leakage.
3Measurement precision
If the same electrode region is used for both emitting and receiving ultrasonic waves, then device structure is simplified, but electrical interference and signal accuracy deteriorate
Solution Approach 1:
The electrode layer is divided into distinct drive electrode regions and receiving electrode regions within the same electrode layer. This spatial segmentation allows separate functions for wave emission and reception, reducing electrical interference and improving signal detection accuracy while maintaining a relatively simple single-layer structure.
Solution Approach 2:
Different local regions of the electrode layer are assigned different functional qualities: drive regions for wave generation and receiving regions for wave detection. This local functional differentiation improves ultrasonic signal detection accuracy by preventing electrical interference, while the overall electrode layer structure remains simple and integrated.
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
The solution enables real-time emission and reception of ultrasonic waves, enhancing the accuracy and stability of fingerprint identification by suppressing electrical leakage and improving the performance of the identification device.
Implementation Method 1
the piezoelectric material layer is configured to emit ultrasonic waves under an excitation of at least a drive voltage
Implementation Method 2
the piezoelectric material layer is further configured to convert ultrasonic waves, which are emitted by the piezoelectric material layer and reflected by a fingerprint to be detected, into electrical signals
Data Source
AI summary
A fingerprint identification device, a driving method thereof, and a display device are disclosed. The fingerprint identification device includes: a receiving electrode layer, a piezoelectric material layer, and a drive electrode layer. The piezoelectric material layer is between the receiving electrode layer and the drive electrode layer, the piezoelectric material layer is configured to emit ultrasonic waves under an excitation of at least a drive voltage, and is further configured to convert ultrasonic waves, which are emitted by the piezoelectric material layer and reflected by a fingerprint to be detected, into electrical signals; the drive electrode layer is configured to receive the drive voltage and a first fixed voltage simultaneously, and the receiving electrode layer is configured to output the electrical signals while receiving a second fixed voltage; the electrical signals are used for obtaining a fingerprint image.