Acoustic Biometric Touch Scanner Using Thin Film Piezoelectric Transducers
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Solution Overview
Problem
Existing fingerprint scanning technologies face challenges such as contamination issues with optical scanners and ease of forgery with capacitive scanners, while ultrasound-based systems encounter high insertion loss and complex fabrication with waveguides.
Innovation Solution
An acoustic biometric touch scanner using a thin film piezoelectric device transmitting ultrasound signals in the 50 MHz to 500 MHz range, with row-column addressing and beamforming, to achieve high resolution and low insertion loss, capable of scanning both skin layers and internal tissue, and detecting temperature and force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If waveguide-based ultrasound systems are used, then fingerprint scanning capability is achieved, but insertion loss increases and fabrication complexity increases
Solution Approach 1:
The patent removes the waveguide component from the ultrasound system, directly coupling the piezoelectric transducer array to the finger. This extraction eliminates the insertion loss and fabrication complexity associated with waveguides while maintaining fingerprint scanning capability through direct acoustic coupling.
Solution Approach 2:
The patent introduces a thin acoustic coupling layer (5-50 micrometers) as an intermediary between the transducer array and the finger. This thin layer provides necessary acoustic coupling while minimizing signal loss, replacing the thicker waveguide structure that caused high insertion loss.
2Reliability
If waveguide-based ultrasound systems are used, then fingerprint scanning capability is achieved, but device complexity increases
Solution Approach 1:
The patent removes the waveguide component entirely, simplifying the device structure to a direct array transducer configuration. This extraction eliminates the complex fabrication processes required for waveguide integration while maintaining ultrasound fingerprint scanning capability.
Solution Approach 2:
The patent employs a thin acoustic coupling film (5-50 micrometers) that provides necessary acoustic coupling without the bulk and fabrication complexity of waveguide structures. This thin film approach simplifies manufacturing while achieving the required acoustic performance.
3Productivity
If optical fingerprint scanners are used, then scanning speed is fast, but contamination resistance deteriorates
Solution Approach 1:
The patent replaces optical scanning with ultrasound-based scanning, using acoustic waves instead of light to image the fingerprint. This substitution maintains fast scanning speed while providing resistance to contamination, as ultrasound can penetrate through oils, moisture, and dirt that would interfere with optical methods.
Solution Approach 2:
The patent utilizes the different acoustic impedance properties of various materials (skin, oil, water, dirt) to distinguish fingerprint ridges from contaminants. By detecting acoustic reflections and transmissions, the system can differentiate between legitimate fingerprint features and contaminant layers, maintaining accuracy despite contamination.
4Device complexity
If capacitive fingerprint scanners are used, then device simplicity is maintained, but security against forgery deteriorates
Solution Approach 1:
The patent replaces capacitive sensing with ultrasound-based imaging, using acoustic wave propagation and reflection to capture fingerprint details. This substitution maintains relatively simple device structure while dramatically improving security, as ultrasound can detect subsurface fingerprint features and verify liveness through acoustic properties that are difficult to replicate with fake fingerprints.
Solution Approach 2:
The patent uses acoustic impedance variations and sound wave propagation characteristics to detect liveness and prevent forgery. Live tissue exhibits specific acoustic properties (such as sound speed and attenuation) that differ from artificial materials, enabling the system to distinguish real fingerprints from fake ones while maintaining device simplicity.
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 provides robust, cost-effective fingerprint scanning with high resolution and liveness detection, resistant to contamination and forgery, and capable of generating 3D images and estimating pulse rate.
Implementation Method 1
The device includes ultrasonic transducers configured to transmit an ultrasound signal, the ultrasonic transducers comprising a piezoelectric film
Implementation Method 2
The processor is configured to generate biometric information based on a reflection of the ultrasound signal
Data Source
AI summary
An acoustic biometric touch scanner device and method is disclosed. In one aspect, an acoustic fingerprint sensing device includes an array of ultrasonic transducers configured to transmit an ultrasound signal having a frequency in a range from 50 megahertz (MHz) to 500 MHz. The acoustic fingerprint ultrasonic transducers include a piezoelectric film. The acoustic fingerprint sensing device further includes a receiving surface configured to receive a finger. The acoustic fingerprint sensing device further includes a processor configured to generate an image of at least a portion of a fingerprint of the finger based on a reflection of the ultrasound signal from the finger.