Acoustic biometric touch scanner
Inventors
Rasmussen, Morten Fischer • Touma, Gerard • Khuri-Yakub, Butrus T.
Assignees
Leland Stanford Junior University
Publication Number
US-12353935-B2
Publication Date
2025-07-08
Expiration Date
2037-05-25
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Abstract
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.
Core Innovation
The invention is an acoustic biometric touch scanner device configured to transmit ultrasound signals in a frequency range from 50 MHz to 500 MHz to generate high-resolution biometric images, particularly fingerprints. The device includes an array of ultrasound transducers comprising a piezoelectric film, orthogonal row and column metal lines for addressing the transducers, and a receiving surface configured to receive a finger. The processor analyzes reflections of the ultrasound from the finger to generate detailed two- or three-dimensional images of at least a portion of the fingerprint, achieving resolutions of at least 500 pixels per inch.
The background problem addresses challenges in existing fingerprint scanning technologies. Optical scanners struggle with contamination, capacitive scanners can be forged by molds, and previous ultrasound scanners have complex constructions involving waveguides or operate at ultra-high frequencies that do not penetrate tissue effectively. These deficiencies include high insertion loss, difficulty in fabrication, high voltage needs, and complexity in addressing large arrays of transducers required for high resolution.
The innovation solves these problems by employing a thin-film piezoelectric ultrasound transducer array without waveguides, operating at intermediate frequencies (50 MHz to 500 MHz) to achieve sufficient resolution and penetration for fingerprint and tissue imaging. The row-column electrode addressing reduces complexity and interconnects. The design also enables additional biometric sensing functions such as liveness detection via temperature and force measurement. The device can be integrated in various formats, including embedding within smart cards, improving robustness, reducing manufacturing complexity, and facilitating multi-factor authentication.
Claims Coverage
The patent contains multiple independent claims detailing ultrasonic biometric sensing devices and corresponding methods featuring specific configurations and functionalities.
High-frequency ultrasonic transducer array with row-column addressing
An array of ultrasonic transducers with piezoelectric layers and electrodes arranged as orthogonal row and column lines on opposing sides, configured to transmit ultrasound signals of frequencies up to 500 MHz to achieve 50 μm resolution or better, with a receiving surface to contact an object, and a processor to generate an image based on ultrasound reflections.
Liveness parameter generation from ultrasound reflections
The processor generates a liveness parameter associated with the object based on ultrasound reflections, which can include a force parameter related to the contact force or a temperature parameter derived from sound speed, and uses this to authenticate the object.
Ultrasonic biometric sensing device without waveguides
The ultrasound transducer array is implemented without waveguides between the array and the surface to simplify construction and improve robustness.
Transmit focusing via post-processing synthetic aperture focusing
The device performs transmit focusing on a selected portion of the surface using post-processing synthetic aperture focusing to improve image quality and resolution.
Method of biometric authentication using ultrasound
A method comprising transmitting an ultrasound signal using an array of ultrasonic transducers with piezoelectric layers and orthogonal electrodes, receiving reflections from an object on a surface, generating a high-resolution image of at least a portion of the object, detecting a liveness parameter from the reflection, and authenticating the object based on the image and liveness parameter.
The independent claims cover ultrasonic biometric devices with piezoelectric transducer arrays addressed by orthogonal electrodes enabling high-frequency ultrasound transmission for high-resolution imaging, processing for liveness detection including force and temperature parameters, without waveguides, and methods to transmit, receive, image, and authenticate based on these parameters.
Stated Advantages
Achieves high resolution fingerprint imaging (at least 500 pixels per inch) using ultrasound frequencies between 50 MHz and 500 MHz without requiring complex waveguides.
Enables robust imaging through intermediate media such as glass or plastic, facilitating integration into devices like smart cards and mobile phones.
Allows acquisition of three-dimensional ultrasound images of both epidermal and dermal fingerprint layers, enhancing security and liveness detection.
Implements row-column addressing to reduce the number of electrical interconnections, simplifying fabrication and device complexity.
Provides additional biometric sensing capabilities such as liveness detection via temperature and force sensing, and pulse rate estimation, increasing authentication reliability.
Manufacturing uses thin film piezoelectric materials deposited by sputtering, enabling cost-effective and precise transducer fabrication.
Can be embedded within smart cards and other portable form factors, enabling multi-factor authentication.
Documented Applications
Fingerprint recognition and biometric authentication systems.
Liveness detection to prevent forgery with molds or prosthetics via temperature, force, and pulse rate measurement.
Integration within smart cards for secure multi-factor authentication, such as credit cards, debit cards, identification cards, and insurance cards.
Use in consumer electronics including smartphones, tablets, doors, door handles, walls, steering wheels, and security or safety devices.
Medical or health-related biometric sensing, including pulse rate detection and tissue stiffness estimation.
Interested in licensing this patent?