Anti-spoofing Optical Fingerprint Sensor with Angular Detection
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Solution Overview
Problem
Fingerprint sensors struggle to distinguish between real and spoof fingerprints, particularly high-resolution spoof fingerprints, leading to unauthorized access issues due to their reliance on image-based authentication methods.
Innovation Solution
The implementation of a collimator-based optical fingerprint sensor design that utilizes apertured baffle-layers and color filters to detect the angular distribution of electromagnetic energy, allowing for enhanced spoof detection by differentiating between real and spoof fingerprints based on material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If image-based authentication is used, then authentication convenience is improved, but spoof detection capability deteriorates
Solution Approach 1:
The patent transitions from two-dimensional image-based authentication to three-dimensional angular distribution measurement. By detecting light scattering at multiple angles using an image sensor, the system captures depth and material property information that distinguishes real fingerprints from spoof attempts, adding a new dimensional layer to the authentication process.
Solution Approach 2:
The patent changes the measurement parameter from simple image intensity to angular distribution of scattered light. By analyzing how light scatters at different angles from the fingerprint sample, the system obtains material-specific signatures that enable reliable spoof detection while maintaining the convenience of optical sensing.
2Manufacturing precision
If high-resolution spoof fingerprints are created, then spoof fidelity is improved, but distinction from real fingerprints deteriorates
Solution Approach 1:
The patent utilizes spectral analysis by capturing light scattering across different wavelengths. Real fingerprints and spoof materials exhibit different spectral signatures in how they scatter light, allowing the system to distinguish between them even when visual appearance and resolution are identical.
Solution Approach 2:
The patent changes the measurement parameter from simple image intensity to angular distribution of scattered light. By analyzing how light scatters at different angles from the fingerprint sample, the system obtains material-specific signatures that enable reliable spoof detection while maintaining the convenience of optical sensing.
3Device complexity
If only image data is collected, then data processing simplicity is improved, but information completeness for spoof detection deteriorates
Solution Approach 1:
The patent transitions from two-dimensional image-based authentication to three-dimensional angular distribution measurement. By detecting light scattering at multiple angles using an image sensor, the system captures depth and material property information that distinguishes real fingerprints from spoof attempts, adding a new dimensional layer to the authentication process.
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 improves the accuracy of spoof detection by incorporating the angular distribution of electromagnetic energy, providing additional information that can be used with machine learning algorithms to effectively differentiate between genuine and fake fingerprints.
Implementation Method 1
The collimator helps map light from a specific region of the fingerprint sample to be detected by a corresponding region of the image sensor by forming channels the light must propagate through to reach the image sensor
Implementation Method 2
Each apertured baffle-layer has apertures aligned above each pixel of the image sensor, with the width of each aperture configured to transmit only a narrow cone of acceptable angles of incoming electromagnetic energy
Implementation Method 3
Within the glass of the fingerprint sensor, electromagnetic energy is scattered from the sample with a range of outgoing angles. This distribution of scattered electromagnetic energy depends on the material being sampled
Implementation Method 4
color filters may be incorporated in the collimator such that large-angle light passes through the color filters but small angle light does not
Data Source
AI summary
An optical fingerprint sensor with spoof detection includes a plurality of lenses; a pixel array including a plurality of first photodiodes, a line between a center of each first photodiode and an optical center of each lens forms an optical axis; at least one apertured baffle-layer positioned between the image sensor and the plurality of lenses, each having a respective plurality of aperture stops, each aperture stop being center-aligned with the optical axis; and a plurality of second photodiodes intercalated with the plurality of first photodiodes; and a color filter layer between the pixel array and the plurality of lenses, said color filter layer includes a plurality of color filters positioned such that each second photodiode is configured to detect electromagnetic energy having passed through lens, a color filter, and at least one aperture stop not aligned along the optical axis.