PPG Liveness Detection via Light Sensing Unit
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Solution Overview
Problem
Conventional liveness detection methods using camera-based image capturing systems can be cheated by fake images, as they rely on heart rate calculations from periodic variations of lights and shadows, which can mimic living conditions, leading to incorrect verification.
Innovation Solution
A device and method for liveness detection that employs a light sensing unit and a signal processing module to extract physiological features from photoplethysmography (PPG) signals, determining whether a subject is living without using camera units or imaging photoplethysmography technology, thereby ensuring a simple structure and low cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If camera-based image capturing systems are used for liveness detection, then the system can capture visual information for verification, but the system can be cheated by fake images that mimic living conditions
Solution Approach 1:
The patent replaces the optical imaging system (camera) with an electrical signal detection system. Instead of capturing images and analyzing visual patterns, the system uses a light sensing unit to detect physiological signals such as heart rate, respiratory rate, and blood flow variations through photoplethysmography (PPG). This substitution fundamentally changes the detection modality from visual analysis to physiological signal analysis, making fake images ineffective since they cannot replicate actual physiological processes.
Solution Approach 2:
The patent introduces a light sensing unit as an intermediary between the subject and the detection system. This intermediary captures physiological information indirectly through light absorption and reflection changes in living tissue, rather than directly imaging the subject. The light sensing unit converts physiological movements and blood flow variations into detectable electrical signals, creating a mediation layer that fake images cannot bypass or replicate.
2Measurement precision
If imaging photoplethysmography technology is used, then physiological signals can be extracted from images, but the system remains vulnerable to periodic light and shadow variations on fake images
Solution Approach 1:
The patent replaces imaging photoplethysmography (which uses camera images to extract PPG signals) with direct electrical signal detection using a light sensing unit. This eliminates the intermediate step of converting images to PPG signals, which is vulnerable to lighting conditions. The light sensing unit directly detects physiological signals through optical absorption changes in tissue, providing more reliable and interference-resistant measurements.
3Measurement precision
If multiple image frames are collected for heart rate calculation, then more accurate physiological data can be obtained, but the detection process takes longer to complete
Solution Approach 1:
The patent implements continuous physiological signal monitoring through the light sensing unit, which can detect and process signals in real-time without requiring the accumulation of multiple discrete image frames. The system continuously captures physiological information as the subject performs verification actions, immediately converting light absorption changes into electrical signals for analysis. This continuous detection approach eliminates the time delay associated with collecting and processing multiple frames while maintaining measurement accuracy.
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
Effectively prevents cheating by fake images, as the system relies on actual physiological signals from a subject, providing immediate and accurate liveness detection without the need for image capturing, enhancing security in identification systems.
Implementation Method 1
a light sensing unit, being used for facing a sensing portion of a subject, so as to collect a diffuse light from the sensing portion
Data Source
AI summary
A device for liveness detection is disclosed. The liveness detecting device has a simplest structure that principally comprises a light sensing unit and a signal processing module. Particularly, the signal processing module is configured for having a physiological feature extracting unit and a liveness detecting unit therein. The physiological feature extracting unit is adopted for extracting a first physiological feature from a PPG signal, or extracting a second physiological feature from the PPG signal that has been applied with a signal process. As such, through the first and second physiological features, the liveness detecting unit is able to determine whether a subject is a living body or not. The liveness detecting device does not use any camera unit and iPPG technology, such that the liveness detecting device has advantages of simple structure, low cost and immediately completing liveness detection.