Display-Integrated PMUT Array for Gesture and Fingerprint Sensing
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Solution Overview
Problem
Current display touchscreens, such as LCD and OLED, have insufficient resolution and detection range for fingerprint imaging and gesture detection due to limitations in capacitive touch systems.
Innovation Solution
Implementing a piezoelectric micromechanical ultrasonic transducer (PMUT) array beneath or beside the display, capable of operating in multiple frequency modes for gesture detection, fingerprint imaging, and touch sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive touch screens are used for detection, then the display can detect touch input, but the resolution is insufficient for fingerprint imaging and stylus detection
Solution Approach 1:
The patent replaces the capacitive touch detection system with a piezoelectric ultrasonic transducer system. The piezoelectric materials convert electrical signals to mechanical ultrasonic vibrations and back, enabling high-resolution fingerprint imaging and stylus detection through acoustic wave interactions with the contact surface.
Solution Approach 2:
The patent divides the detection system into multiple sensor elements arranged in arrays. Each sensor element can independently detect ultrasonic signals, and by segmenting the sensing area into multiple elements, the system achieves high spatial resolution for fingerprint imaging while maintaining manageable complexity through systematic arrangement.
2Length of stationary object
If capacitive touch detection is used, then touch input can be detected, but the detection range is limited to a few millimeters from the touchscreen surface
Solution Approach 1:
The patent employs dynamic ultrasonic wave propagation and reflection principles. By emitting ultrasonic waves that can penetrate and reflect from objects at varying distances, the system dynamically adjusts detection range while maintaining precision through time-of-flight measurements and signal intensity analysis, overcoming the static limitation of capacitive systems.
3Adaptability or versatility
If separate touch sensors are implemented, then touch detection capability is provided, but the device structure becomes more complex
Solution Approach 1:
The patent integrates multiple detection functions into a single piezoelectric ultrasonic transducer system. The same sensor array that detects fingerprint patterns can also detect stylus input, touch gestures, and other contact-based interactions, providing universal multi-function capability without requiring separate specialized sensors for each function.
Solution Approach 2:
The patent merges fingerprint sensing, touch detection, and gesture recognition capabilities into a unified piezoelectric ultrasonic sensor system. By combining these functions into a single integrated array, the patent reduces overall device complexity compared to implementing separate sensor systems for each function.
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 PMUT array enhances gesture detection and fingerprint imaging capabilities, reducing the need for separate touch sensors and improving detection range and resolution.
Implementation Method 1
A piezoelectric element is formed on the bottom electrode
Implementation Method 2
detect whether a wave is reflected from the object
Data Source
Figure 1A
Figure 1B~1C
Figure 2
AI summary
An apparatus may include a one- or two-dimensional array of micromechanical ultrasonic transducer (PMUT) elements positioned below, beside, with, on, or above a backplane of a visual display. The backplane may be a thin-film transistor (TFT) backplane. The array of PMUT elements may be a piezoelectric micromechanical ultrasonic transducer (PMUT) array or a capacitive micromechanical ultrasonic transducer (CMUT) array. The PMUT array may be configurable to operate in modes corresponding to multiple frequency ranges. When operating in the low-frequency mode, the apparatus may be capable of gesture detection. A high-frequency mode may include a fingerprint sensor mode or a stylus detection mode.