Under-Display Fingerprint Sensor Using Light Selection Structure
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Solution Overview
Problem
Conventional optical fingerprint sensors are bulky, making it difficult to integrate them into electronic devices like mobile phones and tablets, and capacitive fingerprint sensors struggle to be placed under display panels due to protective coverings and design constraints.
Innovation Solution
A display-integrated fingerprint detection system that uses a light selection structure, including a prism sheet and microlenses, to select and refract near-infrared light from ridges of a fingerprint, allowing an image sensor to generate a clear fingerprint image without the need for additional bulk components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional optical fingerprint sensor is used, then fingerprint detection function is achieved, but the device volume increases and integration into thin electronic devices becomes difficult
Solution Approach 1:
The patent merges the fingerprint sensor with the display panel by integrating the image sensor layer directly beneath the display panel. The display panel serves dual purposes: displaying information and providing the optical system for fingerprint detection. This eliminates the need for separate optical components (prism, mirror, lens) and integrates the light source function into the display panel itself, significantly reducing overall sensor volume while maintaining fingerprint detection capability.
Solution Approach 2:
The display panel is designed to perform multiple functions simultaneously: it acts as both the display interface and the optical system for fingerprint sensing. The image sensor layer beneath the display panel detects light reflected from fingerprints, while the display panel above provides both the light source and the protective glass cover contact surface, eliminating the need for dedicated separate components.
2Volume of moving object
If a capacitive fingerprint sensor is used, then the sensor can be placed under the display panel, but the protective glass cover and design constraints prevent proper sensor exposure and functionality
Solution Approach 1:
The patent introduces an optical intermediary system where light from the display panel passes through the protective glass cover to interact with the fingerprint. The glass cover, which would normally block capacitive sensing, becomes transparent to the optical detection method. The image sensor layer detects light reflected from the fingerprint ridges and valleys through the glass cover and display panel, allowing the sensor to function properly beneath the protective covering.
3Volume of stationary object
If the display panel is used as the light source, then additional bulk components are eliminated, but precise control of light incidence angles is required for clear fingerprint imaging
Solution Approach 1:
The patent applies local quality by using a light selection structure with microlenses positioned at specific locations beneath the display panel. Each microlens is configured to receive light at specific incidence angles from the display panel and direct it to the corresponding pixel in the image sensor layer. This localized angular control enables clear fingerprint imaging while using the display panel as the light source, without requiring additional bulk optical components.
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
Enables the integration of fingerprint sensors into thin electronic devices by using the display panel to emit and refract light, enhancing image clarity and contrast between ridges and valleys, thus overcoming size and placement limitations.
Implementation Method 1
a prism sheet that refracts the ray of light having a detection-target incidence angle from the rays of light having a plurality of incidence angles at a first angle
Implementation Method 2
microlens that is disposed below the prism sheet and refracts the ray of light refracted at the first angle at a second angle
Implementation Method 3
the image sensor may include a light receiving portion that generates a pixel current corresponding to the ray of light refracted at the second angle
Data Source
AI summary
A fingerprint sensor is disclosed. An embodiment according to an aspect of the present invention provides a display having a fingerprint recognition function. The display having a fingerprint recognition function may comprise: a display panel, which is disposed under a cover glass and allows rays to pass therethrough, the rays having various incident angles indicating ridges and troughs of a fingerprint that is in contact with the cover glass; and an image sensor layer, which is disposed under the display panel and detects a ray to be detected in the rays having the various incident angles to generate a fingerprint image.