Ultrasonic Sensor Frequency-Differentiating Layer for Dual-Depth Imaging
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Solution Overview
Problem
Existing ultrasonic sensor systems struggle to effectively image both fingerprints and sub-epidermal features due to cross-talk between higher and lower frequency waves, making them susceptible to spoofing and authentication unreliable.
Innovation Solution
An ultrasonic sensor system with a frequency-differentiating layer that includes materials with different acoustic impedances to transmit and receive ultrasonic waves at two or more peak frequencies, allowing for simultaneous imaging of fingerprints and sub-epidermal features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single ultrasonic frequency is used for imaging, then the imaging depth is sufficient to reach sub-epidermal features, but the surface fingerprint detail resolution is inadequate
Solution Approach 1:
The imaging function is segmented into two distinct frequency channels: a first frequency (e.g., 20 MHz) optimized for surface fingerprint imaging and a second frequency (e.g., 10 MHz) optimized for sub-epidermal feature imaging. The sensor array is divided into first and second subsets that operate at these different frequencies, allowing each subset to specialize in one imaging depth range without interfering with the other.
Solution Approach 2:
Different regions of the sensor system are assigned different frequency characteristics. The first subset of sensor elements operates at a higher frequency for surface detail, while the second subset operates at a lower frequency for deeper penetration. This local differentiation of frequency quality allows simultaneous optimization of both surface and subsurface imaging capabilities.
2Adaptability or versatility
If both higher and lower frequency ultrasonic waves are transmitted simultaneously, then both fingerprints and sub-epidermal features can be imaged, but cross-talk between frequencies degrades authentication reliability
Solution Approach 1:
The sensor array is segmented into two independent subsets operating at different frequencies. This physical and functional segmentation isolates the frequency channels, preventing cross-talk between the higher frequency (fingerprint imaging) and lower frequency (sub-epidermal imaging) waves, thereby maintaining authentication reliability while achieving dual-frequency versatility.
Solution Approach 2:
The system uses frequency as an intermediary to separate the imaging functions. By assigning distinct frequency bands to different sensor subsets and processing channels, the system acts as an intermediary that prevents interference between the two imaging modes, allowing both to coexist without degrading authentication reliability.
3Measurement precision
If higher frequency ultrasonic waves are used, then surface fingerprint detail is improved, but penetration depth to sub-epidermal features is reduced
Solution Approach 1:
The imaging task is segmented into two frequency-based channels: higher frequency (e.g., 20 MHz) for surface fingerprint detail with limited penetration, and lower frequency (e.g., 10 MHz) for deeper sub-epidermal imaging. Each sensor subset is dedicated to one frequency range, allowing optimal performance in each depth range without compromise.
Solution Approach 2:
The system changes the frequency parameter of the ultrasonic waves to optimize for different imaging depths. By transmitting and receiving at multiple discrete frequency values, the system can switch between surface-oriented high-resolution imaging and depth-oriented penetration imaging, effectively resolving the trade-off between surface detail and penetration depth.
4Length of stationary object
If lower frequency ultrasonic waves are used, then penetration depth to sub-epidermal features is improved, but surface fingerprint detail resolution is reduced
Solution Approach 1:
The sensor array is segmented into two functional subsets: one optimized for lower frequency operation to achieve deep penetration for sub-epidermal imaging, and another optimized for higher frequency operation to capture surface fingerprint details. This segmentation allows each subset to specialize in one imaging modality without compromising the other.
Solution Approach 2:
Different local regions of the sensor system are assigned different frequency optimization characteristics. The first subset operates locally at higher frequencies for surface detail, while the second subset operates locally at lower frequencies for penetration depth, creating local quality differentiation that resolves the global trade-off between surface resolution and depth penetration.
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 system provides reliable authentication by capturing detailed fingerprint and sub-epidermal features, reducing the likelihood of spoofing and enhancing security.
Implementation Method 1
The frequency-differentiating layer includes a first frequency-differentiating layer area including a first material having a first acoustic impedance and a second frequency-differentiating layer area including a second material having a second acoustic impedance
Implementation Method 2
The ultrasonic transceiver layer includes a plurality of piezoelectric or capacitive micromachined ultrasonic transducer (PMUT or CMUT) elements
Data Source
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AI summary
An apparatus may include an ultrasonic sensor system having an ultrasonic transceiver layer, a thin-film transistor (TFT) layer and a frequency-differentiating layer. In some examples, the frequency-differentiating layer may include a first frequency-differentiating layer area corresponding to a lower-frequency area of the ultrasonic sensor system. The first frequency-differentiating layer area may include a first material having a first acoustic impedance. In some such examples, the frequency-differentiating layer may include a second frequency-differentiating layer area corresponding to a higher-frequency area of the ultrasonic sensor system. The second frequency-differentiating layer area may include a second material having a second acoustic impedance. The first acoustic impedance may, for example, be higher than the second acoustic impedance.