Optical Fingerprint Sensor Using Polarization for Fake Detection
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Solution Overview
Problem
Existing optical fingerprint identification systems are vulnerable to forged planar fake fingerprints, compromising security as they cannot effectively distinguish between real and fake fingerprints.
Innovation Solution
An optical fingerprint apparatus is designed with a light directing layer that directs light signals from a finger in multiple oblique directions, allowing an optical sensing array to capture and compare light signals, determining whether the finger is real or fake based on differences in signal polarization characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical fingerprint sensing is used, then fingerprint identification can be implemented, but the system cannot distinguish between real and fake fingerprints
Solution Approach 1:
The patent introduces a new dimension of measurement by capturing light signals from multiple oblique directions (at least two different angles) in addition to the conventional vertical direction. This multi-directional light signal acquisition enables the system to detect polarization characteristics that differ between real and fake fingerprints, thereby resolving the inability to distinguish authentic from forged fingerprints.
Solution Approach 2:
The patent changes the measurement parameters by detecting not only the intensity of light signals but also their polarization characteristics. By analyzing polarization differences in light signals captured from multiple oblique directions, the system can identify the three-dimensional structural properties of real fingerprints versus the planar structure of fake fingerprints, thus improving reliability.
2Reliability
If multiple oblique directions are used to capture light signals, then real vs fake fingerprint distinction is enabled, but device complexity increases
Solution Approach 1:
The optical sensing array is segmented into multiple sensing units, each configured to receive light signals from specific oblique directions. This segmentation allows the system to capture light signals from at least two different directions simultaneously, enabling polarization analysis without requiring complex mechanical movement or sequential scanning mechanisms.
Solution Approach 2:
The optical sensing units are designed with multi-functionality, serving both to capture light signals from oblique directions and to detect polarization characteristics. This universal design reduces device complexity by combining multiple functions into a single integrated sensing structure, avoiding the need for separate components for each function.
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 effectively differentiates between real and fake fingerprints by analyzing differences in light signal polarization, enhancing the security of fingerprint identification by accurately identifying 3D real fingers and 2D fake ones.
Implementation Method 1
capturing a light signal formed by reflection or transmittance of light by a finger
Implementation Method 2
direct a light signal returned from a finger above the display screen to an optical sensing array along at least two directions
Implementation Method 3
projections of the at least two directions on the display screen are at different angles with a polarization direction of the display screen
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3~4
AI summary
Provided are an optical fingerprint apparatus and an electronic device, which can identify real and fake fingerprints, thereby improving security of fingerprint identification. The optical fingerprint apparatus is configured to be disposed under a display screen of an electronic device and includes: a light directing layer configured to direct a light signal returned from a finger above the display screen to an optical sensing array along at least two directions, where the at least two directions are oblique with respect to the display screen, and projections of the at least two directions on the display screen are at different angles with a polarization direction of the display screen; and the optical sensing array including a plurality of sensing unit groups, each sensing unit group including at least two optical sensing units, and each optical sensing unit being configured to receive a light signal in one direction of the at least two directions, where light signals in the at least two directions are used to obtain a fingerprint image of the finger, and a difference between the light signals in the at least two directions received by the sensing unit group is used to determine whether the finger is a real finger.