Fingerprint Sensor Card Surface Layout for Wet-Finger Accuracy
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Solution Overview
Problem
Conventional cards with integrated fingerprint sensors suffer from reduced sensitivity when users' fingers are wet due to moisture retention on matte surfaces affecting the captured fingerprint image.
Innovation Solution
A card design featuring a protective layer with distinct surface roughness areas, where the area covering the fingerprint sensor has a lower roughness to minimize moisture retention, and optionally coated with a hydrophobic material to further reduce moisture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the card surface is designed as a matte surface with high roughness, then the card provides good grip and aesthetic appearance, but moisture is retained on the surface affecting fingerprint sensing accuracy
Solution Approach 1:
The protective layer is designed with different surface roughness for different functional areas: the first area (non-sensing region) has high roughness for grip and aesthetics, while the second area (sensing region) has low roughness to minimize moisture retention and improve fingerprint sensing accuracy. This local differentiation resolves the contradiction between grip and sensing precision.
2Measurement precision
If the entire protective layer surface is made smooth, then fingerprint sensing accuracy is improved, but the card loses grip and aesthetic qualities
Solution Approach 1:
Instead of making the entire surface smooth, the invention applies smooth finish only to the second area where the fingerprint sensor is located, while maintaining rough texture on the first area for grip. This localized approach preserves both sensing accuracy and grip quality.
3Ease of manufacture
If a single uniform surface treatment is applied to the protective layer, then manufacturing is simplified, but the card cannot simultaneously optimize grip and fingerprint sensing
Solution Approach 1:
The protective layer surface is segmented into two distinct areas with different roughness characteristics. The first area maintains high roughness for grip while the second area has low roughness for sensing. This segmentation allows the card to achieve multiple functional optimizations simultaneously.
Solution Approach 2:
Different surface treatments are applied to different regions of the protective layer based on their specific functional requirements. The first area receives treatment for grip enhancement while the second area receives treatment for sensing optimization, achieving versatile functional performance.
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 fingerprint sensing accuracy by reducing moisture impact on the sensor, especially when fingers are wet, thereby improving identity verification reliability.
Implementation Method 1
a surface roughness of the first area is greater than a surface roughness of the second area and the second area covers the sensing area of the fingerprint sensor
Implementation Method 2
optionally coated with a hydrophobic material to further reduce moisture
Data Source
AI summary
A card having a fingerprint sensor and a manufacturing method of the same are provided. The fingerprint sensor is disposed between a substrate and a protection layer. The protection layer has a first area and a second area thereon. The roughness of the second area is smaller than the roughness of the first area. The second area corresponds to the sensing area of the fingerprint sensor. When the user's finger is wet, the second area may effectively keep the water from remaining on it. Thus, the water does not affect the effect of fingerprint sensing.