Transparent Electromagnetic Shielding Layer for Under-Display Fingerprint Sensors
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Solution Overview
Problem
The integration of a fingerprint sensor under a display screen is hindered by electromagnetic noise from the screen's electronic circuits, which interferes with the image sensor's signal capture, particularly in OLED devices where keeping the screen on is necessary for fingerprint scanning.
Innovation Solution
A thin, transparent electromagnetic shielding layer, made of materials like gold, indium tin oxide, or PEDOT:PSS, is interposed between the active portions of the screen and the image sensor, coupled to the ground to reduce electromagnetic interference while allowing light transmission, thereby minimizing noise and maintaining the screen's functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the screen is kept on for fingerprint scanning in OLED devices, then the screen functionality is maintained, but electromagnetic noise from the screen's electronic circuits interferes with the image sensor's signal capture
Solution Approach 1:
A transparent electromagnetic shielding layer is introduced as an intermediary component between the display screen and the image sensor. This layer selectively blocks electromagnetic noise while allowing light to pass through, enabling the screen to remain on during fingerprint scanning without interfering with the sensor's signal capture.
Solution Approach 2:
The electromagnetic shielding layer is positioned specifically in the region where electromagnetic interference occurs (between the screen and sensor), providing localized protection. The layer is made transparent to allow light transmission in the optical path while maintaining electromagnetic shielding properties in the radio frequency range.
2Object-affected harmful factors
If a traditional electromagnetic shielding layer is used, then electromagnetic noise is blocked, but the layer blocks light transmission to the image sensor
Solution Approach 1:
The shielding layer is designed with location-dependent properties: it provides electromagnetic shielding in the radio frequency range while maintaining optical transparency in the visible spectrum. This is achieved by selecting materials and thicknesses that are selective to different wavelength ranges.
Solution Approach 2:
The electromagnetic shielding layer is constructed from composite materials or multi-layer structures that combine electromagnetic shielding properties with optical transparency. Examples include transparent conducting oxides (ITO, IZO), metal nanowire networks, or thin metal films that allow visible light to pass while blocking radio frequency electromagnetic waves.
3Object-affected harmful factors
If the electromagnetic shielding layer is made thicker to improve noise reduction, then electromagnetic noise blocking is enhanced, but the device thickness increases
Solution Approach 1:
The shielding layer thickness is optimized to a specific range (typically nanometers to micrometers) that provides sufficient electromagnetic noise reduction while maintaining optical transparency. By changing the thickness parameter within this optimized range, effective noise blocking is achieved without significantly increasing device thickness.
Solution Approach 2:
Highly efficient electromagnetic shielding materials with exceptional shielding performance per unit thickness are employed. These include transparent conducting oxides, metal nanowire networks, or ultra-thin metal films that achieve effective noise blocking with thicknesses in the nanometer to micrometer range, minimizing the impact on overall device thickness.
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 effectively decreases electromagnetic noise by approximately 17% and improves the signal-to-noise ratio by more than one dB, enhancing the performance of fingerprint sensors integrated under OLED screens without increasing the device's thickness.
Implementation Method 1
a first electromagnetic shielding layer permeable to light is arranged between active portions of the screen and active portions of the image sensor
Data Source
AI summary
A device includes a display screen and an image sensor. A first electromagnetic shielding layer permeable to light is arranged between active portions of the display screen and active portions of the image sensor.