Optical Fingerprint Sensor Light-Shielding Layers and Microlenses
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical fingerprint sensors face low sensitivity and inadequate field of view due to blocked inclined light by light-shielding layers, limiting their ability to collect sufficient light and maintain image contrast.
Innovation Solution
The optical fingerprint sensor design includes a substrate with photoelectric conversion units, multiple light-shielding layers with strategically arranged apertures, and groups of microlenses, where each group consists of a central microlens and peripheral microlenses forming a polygon, optimizing light collection and maintaining a wide field of view by ensuring consistent light reception across microlenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light-shielding layer is used to block inclined light, then image contrast is improved, but sensitivity deteriorates due to insufficient light collection
Solution Approach 1:
The light-shielding layer is segmented into multiple layers (first light-shielding layer and second light-shielding layer) with different aperture patterns. Each layer selectively blocks or transmits light from specific angles, allowing the system to maintain image contrast while collecting more inclined light through the coordinated action of multiple segmented layers
Solution Approach 2:
The patent introduces a vertical dimension by stacking multiple light-shielding layers at different heights above the photodiode array. This multi-layer vertical structure enables light from different incident angles to reach the photodiodes through different layers, increasing overall light collection while maintaining contrast through selective blocking at each layer
2Reliability
If a microlens array is added to collect light from various angles, then sensitivity is improved, but field of view remains insufficient
Solution Approach 1:
The microlens array is segmented into multiple groups, with each group containing multiple microlenses (e.g., 5-9 microlenses per group) corresponding to one photoelectric conversion unit. This segmentation allows each microlens to capture light from different angles and directions, collectively providing a wider field of view while maintaining high sensitivity
Solution Approach 2:
Multiple microlenses are merged into groups that collectively serve a single photodiode. The combined light-collecting capability of multiple microlenses in each group increases the effective field of view and light gathering power, allowing the system to capture more inclined light from various directions
3Area of stationary object
If multiple microlenses are arranged in groups to widen field of view, then light collection is improved, but device complexity increases
Solution Approach 1:
Each group of microlenses serves multiple functions: it collects light from various angles, maintains a wide field of view, and provides consistent light reception across all microlenses in the group. This multi-functionality reduces the need for additional separate components, managing device complexity while achieving wide field of view and improved light collection
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 enhances sensitivity and field of view, improving image uniformity and resolution, while maintaining proper pitch sizes to prevent cross-talk and uneven images, achieving optimal performance between 254 dpi and 635 dpi.
Implementation Method 1
a plurality of groups of microlenses disposed on the second light-shielding layer. Each group of the microlenses includes a central microlens and a plurality of peripheral microlenses surrounding the central microlens
Implementation Method 2
a substrate having a plurality of photoelectric conversion units
Data Source
AI summary
An optical fingerprint sensor is provided. The optical fingerprint sensor includes a substrate, a plurality of light-shielding layers and a plurality of groups of microlenses. The substrate has a plurality of photoelectric conversion units disposed therein. The light-shielding layers are sequentially disposed on the substrate. Each light-shielding layer includes a plurality of apertures formed therein. Each group of microlenses is disposed above the apertures formed in an uppermost light-shielding layer and overlies one photoelectric conversion unit.