Fingerprint Sensor Light Guide Layer for Under-Display Integration
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Solution Overview
Problem
Fingerprint sensors integrated into display devices face challenges with light blocking structures that reduce light incidence on the sensing area, leading to decreased accuracy due to increased noise light and reduced light transmittance, especially when positioned under the display panel.
Innovation Solution
A fingerprint sensor design featuring a light sensing layer with a light guide layer comprising first and second light-transmitting films, a light-blocking film, and a transparent adhesive member, where the refractive index of the second light-transmitting film is either equal to or different from the first, optimizing light transmittance and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the area of the light-blocking part of the collimator is reduced to increase light incidence on the light sensing part, then the amount of light incident on the light sensing part increases, but noise light incident on the light sensing part also increases, lowering fingerprint recognition accuracy
Solution Approach 1:
The light guide layer is divided into multiple functional regions: light-transmitting films for guiding signal light, light-blocking films for blocking noise light, and second light-transmitting films for providing optical pathways. This segmentation allows different areas to perform specialized functions, enabling the system to increase overall light transmission while maintaining noise blocking capabilities in specific zones.
Solution Approach 2:
Different regions of the light guide layer are assigned different optical properties: some areas have high light transmission (second light-transmitting films) to increase signal light incidence, while other areas maintain light blocking (light-blocking films) to prevent noise light. This local differentiation of optical quality allows simultaneous optimization of both light incidence and noise rejection.
2Measurement precision
If a light-blocking film is used to block noise light, then noise light is reduced, but light transmittance to the sensing area is reduced, decreasing recognition accuracy
Solution Approach 1:
The second light-transmitting film acts as an intermediary optical pathway between the light-blocking film and the light sensing part. It provides a dedicated channel for signal light to reach the sensor while the light-blocking film blocks noise light from other directions. This intermediary structure enables the coexistence of light blocking and light transmission functions.
Solution Approach 2:
The patent introduces a vertical layering dimension with multiple film layers (first light-transmitting films, second light-transmitting films, and light-blocking films) stacked at different heights. This dimensional arrangement allows light-blocking films to block noise light from certain angles while second light-transmitting films transmit signal light from other angles, resolving the contradiction through spatial differentiation.
3Adaptability or versatility
If the fingerprint sensor is disposed under the display panel to integrate display and sensing functions, then an integrated solution is provided, but light-blocking structures in the display area reduce light incidence on the sensor
Solution Approach 1:
The light guide layer serves multiple functions simultaneously: it guides light from the display panel to the fingerprint sensor, blocks noise light from external sources, and provides structural integration between the display and sensing layers. This multi-functionality enables the integrated design to overcome the light blocking issue while maintaining display-sensing integration.
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
Enhances light transmittance to the fingerprint sensor, improving recognition accuracy by minimizing noise light and compensating for reduced light-blocking film widths during etching, while maintaining effective light guidance.
Implementation Method 1
a light guide layer disposed on the light sensing layer. The light guide layer includes first light-transmitting films spaced apart from one another
Implementation Method 2
a light-blocking film disposed between the first light-transmitting films
Implementation Method 3
where the refractive index of the second light-transmitting film is either equal to or different from the first, optimizing light transmittance
Implementation Method 4
a light sensing layer having a light sensing element in which a sensing current flows according to incident light
Data Source
AI summary
A fingerprint sensor includes a light sensing layer having a light sensing element in which a sensing current flows in response to incident light and a light guide layer disposed on the light sensing layer. The light guide layer includes first light-transmitting films spaced apart from one another, a light-blocking film disposed between the first light-transmitting films, and a second light-transmitting film disposed between each of the first light-transmitting films and the light-blocking film.