Interleaved Ultrasonic Pixels for High-Resolution Fingerprint Capture
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Solution Overview
Problem
Ultrasonic fingerprint sensors require a high density of sensor pixels to achieve the same resolution as capacitive-based systems, which is problematic for devices with large fingerprint-sensing areas due to increased cost, complexity, and power consumption.
Innovation Solution
Implementing an ultrasonic fingerprint sensor with interleaved sensor pixels that are acoustically coupled to a surface, where each pixel is divided into multiple ultrasonically-sensitive subregions surrounded by regions from other pixels, allowing for lower pixel density while maintaining high resolution through binning and touch location estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic fingerprint sensors use high pixel density to achieve high resolution, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
Each ultrasonic sensor pixel is divided into multiple ultrasonically-sensitive subregions (e.g., nine subregions per pixel), allowing the sensor to capture fingerprint details at a coarser pixel density while maintaining high effective resolution through subregion-level acoustic sensitivity
Solution Approach 2:
The patent introduces a hierarchical structure where each pixel contains multiple subregions, effectively adding a spatial dimension within each pixel. This allows the system to achieve high measurement precision without proportionally increasing the overall pixel density, thereby reducing device complexity
2Measurement precision
If ultrasonic fingerprint sensors use high pixel density to achieve high resolution, then measurement precision is improved, but power consumption increases
Solution Approach 1:
By segmenting each pixel into multiple ultrasonically-sensitive subregions, the system achieves high fingerprint resolution with fewer overall pixels, directly reducing the number of active sensing elements and their associated power consumption
Solution Approach 2:
Multiple ultrasonically-sensitive subregions within each pixel are electrically coupled to a common node, allowing them to share readout circuitry and processing resources, thereby reducing overall power consumption while maintaining high resolution capability
3Measurement precision
If ultrasonic fingerprint sensors use high pixel density to achieve high resolution, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The segmentation of pixels into multiple subregions allows the use of larger pixel pitch (lower density) while maintaining high effective resolution, reducing the total number of pixels required and thereby lowering manufacturing costs for large fingerprint-sensing areas
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 high-resolution fingerprint capture with reduced pixel density, resulting in decreased power consumption, faster read-out times, and lower costs for devices with large fingerprint-sensing areas.
Implementation Method 1
controlling the ultrasonic fingerprint sensor system for transmission of first ultrasonic waves towards a target object in contact with a surface... receiving first ultrasonic receiver signals from the ultrasonic fingerprint sensor, the first ultrasonic receiver signals including signals corresponding to reflections of the first ultrasonic waves from the target object
Implementation Method 2
each of a plurality of the ultrasonic receiving pixels is divided into and associated with a plurality of ultrasonically-sensitive subregions... receiving second ultrasonic receiver signals from the ultrasonic fingerprint sensor, the second ultrasonic receiver signals including signals corresponding to reflections of the second ultrasonic waves from the target object
Data Source
AI summary
An ultrasonic fingerprint sensor may include sensor pixels with interleaved ultrasonically-sensitive regions. Each of a plurality of sensor pixels in the ultrasonic fingerprint sensor may include nine distinct ultrasonically-sensitive regions electrically coupled to a common readout circuit, where there is an ultrasonically-sensitive region of another sensor pixel disposed between each of the nine distinct ultrasonically-sensitive regions. The ultrasonic fingerprint sensor may further include circuitry for binning together groups of sensor pixels during certain lower-resolution operations such as touch sensor operations. The ultrasonic fingerprint sensor may be used in capturing fingerprint images that are then used in an authentication process.