Fingerprint Sensing Module With Spacer Pattern and Light Collimation
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Solution Overview
Problem
Under-display fingerprint sensing modules face issues with stray light incidence at large angles due to microlens spacing, leading to blurry images and increased risk of microlens damage from external forces, particularly in curved displays, which affects reliability and process yield.
Innovation Solution
The fingerprint sensing module incorporates a spacer pattern with columnar and extension portions between microlens groups, and a light-shielding pattern layer with openings to improve light collimation and external force tolerance, along with a filter layer to enhance sensitivity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the spacing between microlenses is increased to reduce manufacturing complexity, then the manufacturing process becomes easier, but stray light incident at large angles increases causing blurry fingerprint images
Solution Approach 1:
A light-shielding pattern layer is introduced as an intermediary component between the microlenses and the external environment. This layer blocks stray light from reaching the microlenses at large angles, preventing image blur while allowing the microlenses to maintain larger spacing for easier manufacturing. The light-shielding pattern acts as a mediator that resolves the conflict between manufacturing ease and image quality.
2Measurement precision
If the microlenses are positioned closer to the display panel to improve sensing sensitivity, then the sensing sensitivity increases, but the risk of crushing the microlenses from external forces increases
Solution Approach 1:
A spacer pattern is positioned between the microlenses and the display panel to provide beforehand cushioning against external forces. When a user presses the display panel, the spacer pattern absorbs and distributes the mechanical stress, preventing direct transmission of crushing forces to the microlenses. This allows the microlenses to be positioned closer to the display panel for improved sensing sensitivity while maintaining reliability through prior protective cushioning.
3Measurement precision
If the spacing between microlenses is reduced to improve light collimation, then the light collimation improves, but the manufacturing precision requirements increase
Solution Approach 1:
The light-shielding pattern layer serves as a manufacturing template and positional reference for the microlenses. By first forming the light-shielding pattern with precise openings, then using these openings as guides for microlens placement, the system achieves high light collimation without requiring direct high-precision positioning of microlenses during manufacturing. The light-shielding pattern mediates the positioning process, reducing the direct precision requirements for microlens placement.
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 increases the module's tolerance to external forces, improves light energy utilization, and enhances sensing sensitivity, resulting in improved reliability and process yield by preventing microlens damage and optimizing light collimation.
Implementation Method 1
the electronic apparatus controls the display panel to emit light to illuminate the surface of the user's finger. This sensing light is then reflected (diffusely) by the user's finger and enters the fingerprint sensing module
Implementation Method 2
the reflected light is converged on a photosensitive element through multiple microlenses and collimation structures
Implementation Method 3
The light-shielding pattern layer has a plurality of openings, and the openings are respectively overlapped with a plurality of microlenses
Data Source
AI summary
A fingerprint sensing module includes a first substrate, an active device, a photosensitive element layer, a collimation structure layer, a second substrate, a plurality of micro lenses, and a spacer pattern. The active device is disposed on the first substrate. The photosensitive element layer is disposed on the first substrate and is electrically connected to the active device. The collimation structure layer is disposed on the photosensitive element layer. The second substrate is disposed on the collimation structure layer. The micro lenses are disposed on a surface of the collimation structure layer facing away from the photosensitive element layer, and overlap the photosensitive element layer. The micro lenses are divided into a plurality of microlens groups, and the microlens groups are respectively located in a plurality of sensing pixel areas of the fingerprint sensing module. The spacer pattern extends between the microlens groups.