Ultrasonic Fingerprint Sensor Power Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional fingerprint sensors in mobile devices consume significant power, leading to rapid battery drainage due to their high power consumption, which is a challenge for maintaining an always-on state without excessive power usage.
Innovation Solution
The implementation of a fingerprint sensing system using a two-dimensional array of ultrasonic transducers, specifically piezoelectric micromachined ultrasonic transducers (PMUTs), which operate in an always-on mode with a low-power detection stage followed by a full-power analysis stage, allowing for continuous touch sensing while minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional fingerprint sensors are operated continuously to enable always-on functionality, then touch sensing capability is improved, but power consumption increases significantly
Solution Approach 1:
The sensor array is divided into multiple independently controllable groups or blocks. Instead of activating the entire sensor array, only specific segments are activated based on detected touch events or required monitoring zones, reducing overall power consumption while maintaining always-on functionality for touch detection.
Solution Approach 2:
The fingerprint sensor operates in periodic cycles, alternating between low-power sleep mode and active sensing mode. During sleep mode, minimal power is consumed while maintaining basic touch detection capability. When a touch event is detected, the sensor activates for brief analysis periods, then returns to sleep mode, enabling always-on functionality with significantly reduced average power consumption.
2Measurement precision
If conventional fingerprint sensors are activated frequently for fingerprint analysis, then authentication accuracy is improved, but battery life deteriorates
Solution Approach 1:
The system performs preliminary touch detection using low-power sensors or simplified detection mechanisms before activating the full fingerprint analysis function. This preliminary action filters out non-fingerprint touches and only triggers full fingerprint analysis when actually needed, maintaining authentication accuracy while reducing unnecessary power consumption and extending battery life.
Solution Approach 2:
Instead of performing complete fingerprint analysis on every touch event, the system applies partial analysis only when necessary. Basic touch presence is detected continuously with minimal power, and full fingerprint imaging and analysis are performed only when a valid fingerprint touch is detected, optimizing the balance between authentication accuracy and battery life.
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
This approach enables continuous or nearly continuous sensing of human touch without battery drainage, simplifies user-device interaction, and reduces manufacturing costs by eliminating the need for physical actuation devices, while maintaining accurate fingerprint detection and analysis.
Implementation Method 1
piezoelectric micromachined ultrasonic transducers (PMUTs)
Implementation Method 2
two-dimensional array of ultrasonic transducers
Data Source
AI summary
In a method for operating a fingerprint sensor comprising a plurality of ultrasonic transducers, a first subset of ultrasonic transducers of the fingerprint sensor are activated, the first subset of ultrasonic transducers for detecting interaction between an object and the fingerprint sensor. Subsequent to detecting interaction between an object and the fingerprint sensor, a second subset of ultrasonic transducers of the fingerprint sensor are activated, the second subset of ultrasonic transducers for determining whether the object is a human finger, wherein the second subset of ultrasonic transducers comprises a greater number of ultrasonic transducers than the first subset of ultrasonic transducers.