Fingerprint Sensor Aperture Layout for Ambient Light Rejection
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Solution Overview
Problem
Ambient light and light generated by information products affect the accuracy of fingerprint recognition, necessitating improvements in signal to noise ratio for enhanced performance.
Innovation Solution
Incorporation of a light blocking layer with specific openings and arrangements to reduce light noise entering the sensor unit, enhancing the signal to noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light blocking layer is added to reduce ambient light interference, then the signal to noise ratio improves, but the device structure becomes more complex
Solution Approach 1:
The light blocking layer is integrated within the existing display structure by nesting it between the substrate and the sensor unit. This nested arrangement allows the light blocking function to be incorporated without adding external components, thereby improving fingerprint recognition accuracy while minimizing structural complexity increases.
Solution Approach 2:
The light blocking layer serves multiple functions: it blocks ambient light from reaching the sensor unit, provides structural support within the display assembly, and maintains the overall device thickness. This multi-functionality approach improves measurement precision while avoiding additional dedicated components that would increase device complexity.
2Measurement precision
If the first opening width is made smaller to block more light, then the signal to noise ratio increases, but less light reaches the sensor unit
Solution Approach 1:
The light blocking layer features a selectively patterned structure with different opening widths in different regions. The first opening has a narrower width to block oblique ambient light, while the second opening has a wider width to allow sufficient light from the light emitting unit to reach the sensor unit. This local differentiation resolves the contradiction by applying different opening widths to different functional requirements.
Solution Approach 2:
The solution addresses the light intensity contradiction by considering the angular dimension of light propagation. The first opening's narrower width specifically blocks light from certain angles (ambient light), while the second opening's wider width allows light from other angles (emitted light) to pass through. This angular selectivity increases signal to noise ratio without significantly reducing the total light intensity reaching the sensor.
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 effectively reduces ambient light interference, improving the accuracy and performance of fingerprint recognition by increasing the signal to noise ratio.
Implementation Method 1
the electronic device includes a light blocking layer, the light noise entering a sensor unit can be reduced, and the signal to noise ratio can be further increased
Data Source
AI summary
An electronic device includes a substrate, a layer overlapped with the substrate and having a first side and a second side opposite to the first side, a sensor unit disposed between the substrate and the layer, a first blocking layer disposed on the first side, and a second blocking layer disposed on the sensor unit. The layer includes flexible material. The second side is disposed between the sensor unit and the first side, and the first side is between the first blocking layer and the second side. The first blocking layer has a first opening, and the second blocking layer has a second opening. A width of the first opening is smaller than a width of the second opening.