Under-Display Fingerprint Sensor with Wavelength Filtering
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Solution Overview
Problem
Current fingerprint authentication technologies in display devices, such as smartphones and tablets, face challenges in accurately distinguishing between genuine and fake fingerprints, particularly in fields requiring high security like e-commerce, where unauthorized purchases can occur.
Innovation Solution
A fingerprint authentication system that includes a sensor device with a first and second area, where the first optical filter blocks light of a specific wavelength range (e.g., 600 nm or more) in the first area but not in the second area, allowing the detection circuit to calculate a light ratio from sensing signals from both areas to determine if a fingerprint is fake based on whether the ratio falls within a reference range, which varies with external light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional fingerprint sensor is used without wavelength filtering, then the device structure remains simple and manufacturing cost is low, but the ability to distinguish fake fingerprints from real fingerprints is insufficient
Solution Approach 1:
The sensor device is divided into a first area and a second area with different optical filtering characteristics. The first area includes a first optical filter that blocks light of a first wavelength range, while the second area includes a second optical filter that transmits light of the first wavelength range. This segmentation allows the system to capture both filtered and unfiltered light signals, enabling differentiation between real and fake fingerprints based on light absorption characteristics without requiring a completely complex new sensor design.
Solution Approach 2:
Different regions of the sensor device are assigned different optical filtering properties. The first area is configured with specific wavelength blocking to detect certain light characteristics, while the second area maintains different filtering properties to detect complementary characteristics. This local differentiation of optical properties enables the system to extract multiple features from the same fingerprint sample, improving authentication accuracy while keeping the overall device structure manageable.
2Reliability
If multiple optical filters are added to distinguish fake fingerprints, then fingerprint detection accuracy improves, but manufacturing cost increases
Solution Approach 1:
The first and second optical filters are integrated within a single sensor device structure, sharing common components such as the sensor array and control circuitry. This merging approach allows the system to achieve enhanced fake fingerprint detection capability through multiple filtering paths while avoiding the need for completely separate detection systems, thereby controlling manufacturing complexity and cost.
Solution Approach 2:
The sensor device is designed to perform multiple functions: it can detect fingerprints under different optical filtering conditions using the same sensor array and processing circuitry. The first area with its wavelength-blocking filter and the second area with its transmitting filter work together to provide comprehensive fingerprint authentication and fake fingerprint detection, eliminating the need for separate dedicated systems for each function.
3Object-affected harmful factors
If the sensor device covers the entire fingerprint area with optical filters, then light blocking capability is maximized, but the ability to capture sufficient light for accurate sensing is reduced
Solution Approach 1:
The sensor device is divided into a first area and a second area with different optical filtering characteristics. The first area includes a first optical filter that blocks light of a first wavelength range, while the second area includes a second optical filter that transmits light of the first wavelength range. This segmentation allows the system to capture both filtered and unfiltered light signals, enabling differentiation between real and fake fingerprints based on light absorption characteristics without completely blocking light across the entire sensor area.
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 enhances the accuracy and reliability of fingerprint detection without increasing manufacturing costs or requiring complex configurations, effectively differentiating between actual and fake fingerprints.
Implementation Method 1
The first optical filter blocks the light of a first wavelength range
Implementation Method 2
The sensor device is for sensing light passing through the display panel
Data Source
AI summary
A display device includes a display panel and a fingerprint authentication device disposed under the display panel. The fingerprint authentication device includes a sensor device and an optical filter. The sensor device includes a first area and a second area in a plan view and sensing light passing through the display panel. The optical filter is disposed between the display panel and the sensor device, overlaps the first area and does not overlap the second area in the plan view, and blocks the light of a certain wavelength range.