Angled Filter Under-OLED Fingerprint Sensor
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Solution Overview
Problem
Under-OLED sensors suffer from poor signal-to-noise ratio (SNR), particularly when detecting fingerprints from dry fingers, leading to suboptimal sensing performance.
Innovation Solution
An optical sensor system with an angled collimator structure is implemented, allowing incident light within a non-zero acceptance angle to pass through, optimizing the ridge/valley contrast by adjusting the incident angle relative to the normal of the sensing surface, and utilizing an angled filter with light collimating apertures and blocking material to enhance signal conditioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional under-OLED sensor is used, then the device structure is simple, but the signal-to-noise ratio is poor
Solution Approach 1:
The sensor system is segmented into multiple functional layers: light emitters, transparent substrate, angled filter, and image sensor array. This segmentation allows each layer to perform its specific function optimally, with the angled filter specifically designed to segment light paths by angle to improve signal-to-noise ratio.
Solution Approach 2:
The angled filter introduces local quality differentiation by allowing light within a specific acceptance angle range to pass through while blocking other angles. This creates localized optical paths that enhance signal detection from specific directions (ridges) while suppressing noise from other directions (valleys).
2Measurement precision
If light is allowed to pass through at normal incidence, then the optical path is simple, but the ridge/valley contrast is insufficient
Solution Approach 1:
The angled filter introduces asymmetry into the optical system by defining a specific acceptance angle that is not centered at normal incidence. This asymmetric angular filtering creates different optical paths for light reflected from ridges versus valleys, enhancing the contrast between them.
Solution Approach 2:
The filter changes the angular parameter of light transmission by defining a specific acceptance angle range. This parameter change optimizes the incident angle of light on the fingerprint surface, thereby maximizing the reflection difference between ridges and valleys for improved contrast.
3Reliability
If an angled filter is introduced, then the signal-to-noise ratio improves, but the device complexity increases
Solution Approach 1:
The angled filter serves multiple functions simultaneously: it acts as an angular selective aperture, a light path definer, and a contrast enhancer. By combining these functions into a single component, the design improves sensing performance while limiting the increase in overall device complexity.
Solution Approach 2:
The angled filter acts as an intermediary element between the light emitters and the image sensor array. It mediates the light paths by selectively transmitting angles, thereby improving signal-to-noise ratio without requiring fundamental changes to the primary sensor architecture.
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 significantly improves the signal-to-noise ratio (SNR) and ridge/valley contrast, enhancing the performance of fingerprint sensing by optimizing the angle of incidence, thereby improving the differentiation between ridges and valleys.
Implementation Method 1
an angled filter disposed below the transparent substrate of the display, wherein the angled filter is configured to allow light within a tolerance angle of an acceptance angle to pass through the angled filter
Implementation Method 2
providing a bundle of optical fibers in which each of the optical fibers includes a core surrounded by a light absorbing material
Implementation Method 3
the angled filter comprising a plurality of light collimating apertures and light blocking material, wherein the angled filter is configured to allow light reflected from an input surface towards the image sensor array that is within a tolerance angle of an acceptance angle to pass through
Data Source
AI summary
Disclosed is a device for optical sensing, comprising: a display comprising a transparent substrate and a plurality of light emitters disposed above the transparent substrate; a transparent cover layer disposed above the display, wherein a top surface of the transparent cover layer provides an input surface for sensing an input object; and, an angled filter disposed below the transparent substrate of the display, wherein the angled filter is configured to allow light within a tolerance angle of an acceptance angle to pass through the angled filter, wherein the acceptance angle is centered around a non-zero angle relative to a normal of the input surface.