Fingerprint Sensor Stable Contact Detection via Image Segmentation
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Solution Overview
Problem
Fingerprint sensors often activate prematurely or unintentionally due to incomplete or unstable finger contact, leading to unnecessary power consumption and resource usage, as existing methods struggle to ensure stable contact over the entire sensor area.
Innovation Solution
A method involving a fingerprint sensing system that acquires a time-sequence of images and divides the image area into overlapping regions to determine stable contact by analyzing changes in image intensity, ensuring comprehensive detection of contact points and stability over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the fingerprint sensor activates immediately upon any contact, then the response speed is improved, but false activations occur due to incomplete or unstable contact
Solution Approach 1:
The system performs preliminary assessments by acquiring a time-sequence of images and analyzing contact stability before triggering authentication. This preliminary action distinguishes between accidental touches and intentional fingerprint placement, resolving the contradiction between fast response and accurate activation.
2Measurement precision
If the sensor monitors the entire sensor area comprehensively, then the detection accuracy is improved, but the processing complexity increases
Solution Approach 1:
The sensor area is divided into multiple sub-arrays or regions, allowing independent analysis of contact stability in each region. This segmentation enables comprehensive monitoring of the entire sensor area while simplifying processing through modular, region-based analysis rather than analyzing the entire area as a single unit.
Solution Approach 2:
The system analyzes more data than minimally required by acquiring a time-sequence of images and evaluating contact stability across multiple time points and regions. This excessive action ensures reliable detection of stable contact while the modular processing approach keeps complexity manageable.
3Reliability
If the system requires stable contact verification before authentication, then the security is improved, but the authentication time increases
Solution Approach 1:
The system uses periodic sampling of the sensor area over time, acquiring images at multiple time points to assess contact stability. This periodic action provides sufficient security verification while limiting the total authentication time through controlled sampling rather than continuous monitoring.
4Productivity
If the fingerprint sensor activates without stable contact verification, then the productivity is improved, but power is wasted on unnecessary authentication attempts
Solution Approach 1:
The system uses feedback from time-sequence image analysis to determine whether contact is stable before proceeding with authentication. This feedback mechanism prevents wasted power on unsuccessful authentication attempts while maintaining high productivity by quickly rejecting unstable contacts and proceeding with valid ones.
Data Source
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AI summary
The present disclosure relates to a method of determining that a finger is in stable contact with a surface covering a sensor area of a fingerprint sensor. The method comprises, by means of the fingerprint sensor, acquiring a time- sequence of images of the fingerprint of the received finger. The method also comprises, for each image of the time-sequence, dividing an image area (41) of the image, corresponding to the sensor area of the fingerprint sensor, into a plurality of image regions (r), said regions partly overlapping each other and covering the whole image area. The method also comprises, based on image analysis of each of the plurality of image regions of each image of the time-sequence, determining that the finger is in stable contact with the surface covering the sensor area.