Under-display fingerprint sensing with angle-focused narrow FOV filters
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Solution Overview
Problem
Existing under-display optical fingerprint sensors face challenges with consistency in performance due to unstable glass-air interfaces and are not cost-effective, and they struggle to separate reflection rays at various angles, leading to long image capture times.
Innovation Solution
The implementation of an under-display fingerprint sensing apparatus with angle-focused narrow field-of-view filtering, which includes a light-emitting layer, an optical layer, and a pixelated image sensor, utilizing misaligned apertures and microlenses to process reflected light and reduce occlusion effects, enhancing fingerprint spoof detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple illumination patterns are used to separate reflection rays at various angles, then the separation of reflection rays is improved, but the image capture time increases significantly
Solution Approach 1:
The patent divides the optical path into multiple spatial channels using a microlens array, where each microlens focuses light from a specific angle onto a corresponding pixel region. This segmentation allows simultaneous capture of multiple reflection angles in a single image, eliminating the need for sequential illumination patterns and reducing capture time while maintaining separation precision.
Solution Approach 2:
The patent introduces a spatial dimension by arranging microlenses and pixels in specific geometric patterns (e.g., hexagonal or square grids) that map angular information to spatial positions on the sensor. This dimensional transformation enables angle-encoded imaging, where different reflection angles are separated through their spatial distribution rather than temporal sequencing.
2Speed
If conventional optical sensors are integrated into the display, then authentication speed is improved, but performance consistency deteriorates due to unstable glass-air interfaces
Solution Approach 1:
The patent introduces an intermediary optical structure consisting of microlenses and aperture arrays positioned between the display glass and the image sensor. This intermediary system creates a controlled optical path that is insensitive to variations in the glass-air interface, maintaining consistent performance by mediating the light interaction and eliminating dependence on unstable external conditions.
Solution Approach 2:
The patent changes the optical parameters by using microlenses with specific focal lengths and aperture sizes optimized for the display integration geometry. By adjusting these parameters, the system achieves an optical configuration where the focal point and acceptance angles are designed to be insensitive to glass thickness variations and interface instability, thereby maintaining performance consistency.
3Area of stationary object
If large-area CMOS sensors are used for fingerprint sensing, then sensing area is improved, but cost-effectiveness deteriorates
Solution Approach 1:
The patent makes the image sensor serve multiple functions: it acts as both the fingerprint sensing element and the display integration interface. The same pixel array captures both the fingerprint pattern and the occlusion pattern from the display glass, eliminating the need for separate sensors and reducing overall system cost while maintaining adequate sensing area through efficient multi-functional design.
Solution Approach 2:
The patent implements a nested structure where the fingerprint sensing function is embedded within the display structure. The microlens array and aperture filters are positioned within the display assembly, and the image sensor is integrated behind the display, creating a compact nested configuration that achieves large-area sensing without requiring a separate dedicated sensor module, thereby improving cost-effectiveness.
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 solution improves the stability and speed of fingerprint image capture, reducing occlusion effects and enabling efficient separation of reflection types, resulting in a stronger and more stable image pattern with a significant gain in performance compared to existing systems.
Implementation Method 1
The optical layer includes a plurality of optical elements... utilizing misaligned apertures and microlenses to process reflected light and reduce occlusion effects
Implementation Method 2
scan a sample fingerprint of a person to form an image... allows transmission of reflected light from the surface to the optical layer
Implementation Method 3
Separation of different reflection rays at various angles is another challenge... angle-focused narrow field-of-view filters
Implementation Method 4
The pixelated image sensor can sense the spatially processed light
Data Source
AI summary
An apparatus for fingerprint sensing includes a light-emitting layer, an optical layer, a filter layer and a pixelated image sensor. The light-emitting layer is covered by a transparent layer, and can illuminate a surface touching the transparent layer and allows transmission of reflected light from the surface to the optical layer. The optical layer includes a plurality of optical elements. The filter layer includes a number of apertures and spatially processes the reflected light. The pixelated image sensor can sense the spatially processed light. At least one of the optical layer or the filter layer enables an angle-focused FOV filtering of the reflected light.