Fingerprint Sensor Collimator Layer Noise Light Blocking
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Solution Overview
Problem
Conventional fingerprint sensors in display devices face challenges in minimizing thickness while effectively blocking noise light, which can affect the accuracy of fingerprint recognition.
Innovation Solution
A fingerprint sensor design incorporating a light sensing layer with a collimator layer that includes a light-transmitting unit and a first and second light-blocking unit, where the refractive indices of the light-blocking units are lower than the light-transmitting unit, and the light guide unit is shaped to guide light efficiently to the sensing element, reducing noise light incidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a collimator with height is added to the fingerprint sensor, then noise light blocking capability is improved, but the overall thickness of the sensor increases
Solution Approach 1:
The patent changes the refractive index parameter of the light-transmitting unit to have a lower refractive index than the light-blocking unit. This parameter change enables effective noise light blocking through refractive index differences while reducing the required collimator height, thus maintaining thin profile without sacrificing noise blocking capability
Solution Approach 2:
Instead of increasing the vertical height of the collimator to block noise light, the patent uses the horizontal arrangement of light-transmitting and light-blocking units with different refractive indices. This dimensional approach allows noise blocking through lateral refractive index differentiation rather than vertical thickness accumulation
2Length of stationary object
If the collimator layer thickness is reduced to maintain a thin profile, then the overall device thickness is minimized, but noise light blocking effectiveness deteriorates
Solution Approach 1:
The patent employs refractive index as a key parameter differentiation between the light-transmitting unit and light-blocking unit. By creating a refractive index contrast without increasing physical thickness, the system achieves effective noise light blocking through optical property manipulation rather than geometric thickening
Solution Approach 2:
The collimator layer is constructed as a composite structure combining light-transmitting units with lower refractive index and light-blocking units with higher refractive index. This composite material approach enables simultaneous light transmission for fingerprint sensing and noise light blocking within a thin overall structure
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 design enhances the accuracy of fingerprint recognition by minimizing noise light interference while maintaining a thin profile, thus improving the overall performance of the fingerprint sensor.
Implementation Method 1
a light-transmitting unit configured to provide light to the light sensing element and a first light-blocking unit disposed on an inner surface of the light-transmitting unit
Implementation Method 2
a refractive index of the first light-blocking unit is smaller than a refractive index of the light-transmitting unit
Data Source
AI summary
A fingerprint sensor includes: a light sensing layer including a light sensing element, wherein a sensing current flows in the light sensing element according to incident light; and a collimator layer disposed on the light sensing layer and including a light guide unit guiding light to the light sensing element. The light guide unit includes: a light-transmitting unit configured to provide light to the light sensing element; and a first light-blocking unit disposed on an inner surface of the light-transmitting unit.