Under-Display Optical Sensor Anti-Spoofing
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Solution Overview
Problem
Conventional fingerprint sensors on mobile devices are limited by their separate design from the display screen, leading to space constraints and conflicting requirements for compactness and high spatial image resolution, which affects their reliability and efficiency in fingerprint sensing.
Innovation Solution
The integration of an optical sensor module under the display screen, utilizing the display screen's light for illumination and employing an optical sensor array, pinhole layer, and lens unit to capture fingerprint patterns, combined with capacitive sensing for liveness detection, to authenticate users without a separate fingerprint sensor area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate fingerprint sensor is used, then fingerprint sensing function is achieved, but device space is consumed and compactness is reduced
Solution Approach 1:
The patent combines the fingerprint sensor with the display screen by integrating the optical sensor array beneath the display layers. The display screen structure itself becomes part of the fingerprint sensing system, with the optical sensor array detecting light reflected from the fingerprint pattern on the display surface. This merging eliminates the need for a separate physical fingerprint sensor component.
Solution Approach 2:
The display screen is designed to serve multiple functions: it acts as both the visual display interface and the fingerprint sensing interface. The same display area that shows information also captures fingerprint patterns through the integrated optical sensor array, allowing one component to fulfill multiple roles and reducing overall device complexity.
2Area of stationary object
If the fingerprint sensor is integrated under the display screen, then compactness is improved, but spatial image resolution may be affected
Solution Approach 1:
The patent introduces an optical coupling layer as an intermediary between the display screen and the optical sensor array. This layer includes optical elements such as microlenses or light-guiding structures that channel and focus reflected light from the fingerprint pattern onto the sensor array, maintaining high spatial resolution despite the integrated configuration.
Solution Approach 2:
The optical sensor array is configured with locally optimized sensing regions that correspond to the display pixel structure. Each sensor element is positioned to receive light from specific display areas, creating a one-to-one mapping that preserves the spatial resolution of the fingerprint image while maintaining compact integration.
3Area of stationary object
If optical sensing is used under the display screen, then compact integration is achieved, but susceptibility to spoofing attacks increases
Solution Approach 1:
The patent implements preliminary liveness detection by analyzing temporal variations in the reflected light signal. The optical sensor array captures not only the spatial fingerprint pattern but also temporal characteristics such as blood flow pulsations or skin surface movements, which serve as preliminary indicators of whether the contacted object is a live finger before authentication is completed.
Solution Approach 2:
The system monitors multiple optical parameters simultaneously, including light intensity, wavelength distribution, and temporal dynamics of the reflected signal. By analyzing changes in these parameters over time, the system can distinguish between genuine fingerprints and spoofing attempts, as fake fingerprints do not exhibit the same physiological optical variations as live fingers.
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 solution enables robust, reliable, and compact fingerprint sensing that enhances user authentication by integrating optical and capacitive sensing, improving security and user experience while maintaining the display screen's functionality without additional hardware, thus overcoming the limitations of traditional fingerprint sensors.
Implementation Method 1
an optical sensor array of optical detectors configured to receive the probe light transmitted through the display screen and converting the probe light to detector signals indicating the fingerprint pattern
Implementation Method 2
a pinhole layer located above the optical sensor array and comprising a pinhole that is structured to produce an increased optical field of view in collecting the probe light and to transmit the probe light towards the optical sensor array
Implementation Method 3
a lens unit located between the pinhole layer and the optical sensor array configured to receive the probe light transmitted from the pinhole and to focus the received light onto the optical sensor array
Data Source
Figure 1~2A
Figure 2B~3A
Figure 3B~4A
AI summary
Devices and optical sensor modules are provided for provide on-screen optical sensing of fingerprints by using a under-LCD or OLED screen optical sensor module that captures and detects returned light and anti-spoofing sensing for rejecting fake fingerprint models based on capacitive sensing or optical sensing.