Fingerprint Detection Light Guide Plate with Grating Parts
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Solution Overview
Problem
Fingerprint recognition in bezel-less smartphones is prone to errors due to insufficient light collection by the image sensor, as the emitted light from the screen has a Lambert light source characteristic, necessitating an additional imaging optical path that reduces light availability.
Innovation Solution
An electronic device with a stacked configuration of an image sensor, light source, and a light guide plate featuring multiple grating parts that diffract and reflect light efficiently, eliminating the need for additional optical paths and enhancing light utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an imaging optical path is added between the image sensor and the screen to implement bezel-less screen design, then the screen coverage area is improved, but the light collection efficiency deteriorates because light occupies only a very small part of the emitted light
Solution Approach 1:
A light guide plate is introduced as an intermediary component between the screen and image sensor. The light guide plate receives emitted light from the screen and guides it to the image sensor through total internal reflection and grating structures, enabling efficient light transfer without requiring additional imaging optical paths that would reduce light availability.
Solution Approach 2:
The patent changes the optical parameters by using a light guide plate with specific refractive index and grating structures. The grating parts diffract light at specific angles to achieve total internal reflection, transforming the light propagation path and improving light collection efficiency while maintaining full-screen coverage.
2Measurement precision
If a light guide plate with multiple grating parts is used to improve light utilization, then the fingerprint recognition precision is improved, but the device structure complexity increases
Solution Approach 1:
The light guide plate integrates multiple functions into a single component: it serves as both a light guiding structure and a diffraction element through the incorporation of grating parts. This merging of functions improves light utilization and fingerprint recognition precision while avoiding the need for separate complex optical systems.
Solution Approach 2:
The light guide plate is designed to perform multiple functions simultaneously: guiding light from the screen, diffracting light through grating structures to achieve total internal reflection, and directing light to the image sensor. This multi-functionality reduces the need for additional components and simplifies the overall device structure.
3Use of energy by moving object
If the light guide plate uses multiple grating parts for light diffraction and total internal reflection, then the light energy utilization is improved, but the manufacturing difficulty increases
Solution Approach 1:
The light guide plate is divided into multiple grating parts with different orientations and positions. Each grating part is responsible for specific light diffraction and reflection functions, allowing for modular manufacturing and assembly while achieving complex light control patterns that improve light energy utilization.
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
The solution ensures high precision fingerprint recognition by maximizing light energy utilization and maintaining a compact device size, allowing for full-screen detection without increasing thickness.
Implementation Method 1
The first grating part is configured to: receive the emitted light through a light incident surface of the first grating part, diffract the emitted light to form first light
Implementation Method 2
The second grating part is configured to: form, based on the first light, second light propagated in the second grating part, and form, based on the second light, third light entering the third grating part
Implementation Method 3
The third grating part is configured to: form, based on the third light, fourth light propagated in the third grating part, form emergent light based on the fourth light
Implementation Method 4
the reflected light is light formed by totally reflecting the emergent light by a top surface, away from the light guide plate, of the cover plate
Implementation Method 5
the reflected light is light formed by reflecting the emergent light by the to-be-detected pattern
Data Source
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AI summary
This application discloses an electronic device having a fingerprint detection function. The electronic device includes: a light source, a light guide plate, and an image sensor. The light source is configured to emit emitted light. The light guide plate includes three grating parts. A first grating part is configured to: receive the emitted light through a light incident surface of the first grating part, diffract the emitted light to form first light, and enable the first light to enter a second grating part. A second grating part is configured to: form, based on the first light, second light propagated in the second grating part; and form, based on the second light, third light entering a third grating part. The third grating part is configured to: form, based on the third light, fourth light propagated in the third grating part; form emergent light based on the fourth light; and enable the emergent light to be emitted through a light emergent surface of the third grating part and then enter the cover plate. The image sensor is configured to receive reflected light passing through the light guide plate, to form image data of a to-be-detected pattern. The reflected light is light formed by totally reflecting the emergent light by a top surface, away from the light guide plate, of the cover plate; or the reflected light is light formed by reflecting the emergent light by the to-be-detected pattern.