Under-screen Fingerprint System Using Bragg Grating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing under-screen fingerprint identification systems face challenges in effectively utilizing external light sources to irradiate fingerprints, especially in full-screen and slim-border mobile devices, where the light source is not integrated with the display module.
Innovation Solution
The system incorporates a Bragg polarization grating and a translucent cover with a light source and band pass filter, directing the sensing beam at a large incidence angle to increase total reflection and ensure full irradiation of the fingerprint, using a dispersed polymer material film layer and a backlight module with through holes to enhance imaging quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an external light source is used to irradiate fingerprints in under-screen fingerprint identification systems, then the fingerprint can be properly illuminated for sensing, but the integration of the light source with other components becomes complex and difficult to manage
Solution Approach 1:
The patent combines the light source, band pass filter, and Bragg polarization grating into a single integrated optical assembly that is disposed within the display module. This merging of components simplifies the overall system structure while maintaining effective fingerprint irradiation, directly resolving the technical contradiction between illumination intensity and device complexity
Solution Approach 2:
The display module serves multiple functions: it acts as both the display element and the housing for the fingerprint sensing components. The light source is integrated within the display module structure, allowing the same module to perform both display and fingerprint identification functions, thereby reducing overall device complexity while maintaining illumination capability
2Device complexity
If the light source is integrated within the display module, then the device structure is simplified, but the light distribution uniformity and irradiation effectiveness may be compromised
Solution Approach 1:
The Bragg polarization grating acts as an intermediary optical element that redistributes the light from the integrated light source. It converts the light into a polarized sensing beam and controls its propagation direction, ensuring uniform light distribution across the fingerprint sensing area while maintaining the simplified integrated structure
Solution Approach 2:
The band pass filter element is configured with specific wavelength transmission characteristics to selectively transmit the sensing wavelength while blocking other wavelengths. This parameter optimization ensures that the integrated light source produces uniform illumination at the required sensing wavelength, resolving the contradiction between integration and illumination effectiveness
3Strength
If a translucent cover is used to protect the display element, then the display is protected, but the light source integration and optical path management become more difficult
Solution Approach 1:
The Bragg polarization grating is disposed on the lower surface of the translucent cover, utilizing the z-dimension (depth) of the cover structure. This dimensional placement allows the grating to interact with light passing through the cover without interfering with the protective function, effectively managing the optical path while maintaining protection and simplifying integration
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 allows for efficient and comprehensive fingerprint irradiation, improving imaging quality and user experience by optimizing the reflection and transmission of the sensing beam, ensuring accurate fingerprint identification.
Implementation Method 1
the Bragg polarization grating adjusts the incidence angle of the sensing beam to increase total reflection
Implementation Method 2
increase total reflection, ensuring the object is fully irradiated
Implementation Method 3
the band pass filter element is disposed on the light incident surface of the translucent cover, wherein the first portion of the sensing beam having the first wavelength range enters the translucent cover passing through the band pass filter element, and the second portion of the sensing beam having the second wavelength range is blocked by the band pass filter element
Implementation Method 4
obtain the shape and the features of the fingerprint according to the different intensities of reflective beams corresponding to ridges and valleys of the fingerprint
Data Source
AI summary
An under-screen fingerprint identification system includes an image sensing element, a display element, a translucent cover, and a Bragg polarization grating. The display element is disposed on the image sensing element. The translucent cover is disposed on the display element, and the display element is located between the translucent cover and the image sensing element. The translucent cover has a first surface and a second surface opposite to each other, and the first surface is farther away from the display element than the second surface. The Bragg polarization grating is disposed on the second surface of the translucent cover.