Ultrasonic Fingerprint Sensor Under Display Panel With EMI Shield
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Solution Overview
Problem
Conventional display devices with fingerprint recognition capabilities face challenges such as reduced display area ratio due to the placement of fingerprint sensors, sensitivity issues with ultrasonic signals, electromagnetic interference, and image quality degradation, including shadow-mura and heat radiation problems.
Innovation Solution
An electroluminescence display panel with an ultrasonic fingerprint sensor positioned under the rear surface, incorporating an electromagnetic interference shield, a cushion member, and a heat dissipation member to minimize interference and enhance image quality while maintaining fingerprint recognition sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the fingerprint sensor is disposed on the rear surface of the electroluminescence display panel, then the display area ratio is maximized and the bezel width is minimized, but electromagnetic interference degrades the image quality and ultrasonic signal sensitivity
Solution Approach 1:
An electromagnetic interference shield is introduced as an intermediary component between the electroluminescence display panel and the fingerprint sensor. This shield blocks electromagnetic interference from reaching the fingerprint sensor, preventing degradation of image quality and ultrasonic signal sensitivity, while allowing the fingerprint sensor to be positioned on the rear surface to maximize display area ratio.
2Area of stationary object
If the fingerprint sensor is disposed on the rear surface of the electroluminescence display panel, then the display area ratio is maximized, but the flatness of the substrate is deteriorated causing visible pressed marks
Solution Approach 1:
A cushion member is positioned between the fingerprint sensor and the electroluminescence display panel substrate to provide beforehand cushioning. This cushion member absorbs and distributes the pressure from the fingerprint sensor, preventing direct contact that would cause pressed marks on the substrate, while still allowing the sensor to function on the rear surface to maximize display area.
3Area of stationary object
If the fingerprint sensor is disposed on the rear surface of the electroluminescence display panel, then the display area ratio is maximized, but light-shielding variations cause shadow-mura defects
Solution Approach 1:
A light-shielding member is selectively positioned in the non-display area on the rear surface of the electroluminescence display panel, directly beneath the fingerprint sensor. This local light-shielding measure prevents variations in light transmission that would cause shadow-mura defects in the displayed image, while allowing the fingerprint sensor to be disposed on the rear surface to maximize the overall display area ratio.
4Area of stationary object
If the fingerprint sensor is disposed on the rear surface of the electroluminescence display panel, then the display area ratio is maximized, but heat radiation variations cause image retention
Solution Approach 1:
A heat-radiating member is selectively positioned in the non-display area on the rear surface of the electroluminescence display panel, directly beneath the fingerprint sensor. This local heat radiation enhancement prevents temperature variations that would cause image retention, while allowing the fingerprint sensor to be disposed on the rear surface to maximize the overall display area ratio.
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 configuration maximizes the display area ratio, improves ultrasonic signal sensitivity, reduces electromagnetic interference, and minimizes image quality issues like shadow-mura and heat-related defects, resulting in enhanced fingerprint recognition speed and image quality.
Implementation Method 1
an electromagnetic interference EMI shield member between the support substrate and the fingerprint sensor, the EMI shield member shielding the fingerprint sensor from EMI
Implementation Method 2
an ultrasonic fingerprint sensor disposed under the rear surface of an electroluminescence display panel... capable of recognizing a fingerprint using an ultrasonic technique
Data Source
AI summary
Disclosed is a display device. The display device comprising a substrate, a display area including a fingerprint recognition area on the substrate, a support substrate configured to support the substrate, a fingerprint sensor positioned under a rear side of the support substrate and configured to output ultrasonic to the fingerprint recognition area, and an EMI (electromagnetic interference) shield member positioned between the support substrate and the fingerprint sensor.