Capacitive Fingerprint Sensor Humidity Adaptation
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Solution Overview
Problem
Capacitive fingerprint sensors face challenges with humidity levels, as high humidity can saturate images, making verification difficult or impossible, while low humidity can cause coupling issues, leading to poor fingerprint imaging.
Innovation Solution
A method for authenticating fingers with capacitive fingerprint sensors that involves determining the humidity level of a finger through image analysis and adjusting acquisition settings, such as gain and shift in the analogue to digital converter, to adapt the authentication process, selecting appropriate authentication models based on humidity levels, and providing user instructions to improve verification success.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitive fingerprint sensing is used, then small form factor and high performance are achieved, but humidity level variations cause image saturation or coupling issues
Solution Approach 1:
The patent applies dynamics by making the authentication process adaptive to changing humidity conditions. The system dynamically adjusts acquisition settings (gain, offset) and selects different authentication models based on detected humidity levels, transforming a static sensing system into one that adapts its parameters in real-time to maintain reliable verification across varying environmental conditions.
Solution Approach 2:
The patent implements parameter changes by modifying acquisition parameters (gain, offset) and authentication model parameters based on detected humidity levels. The system changes electrical parameters of the sensing system and algorithmic parameters of authentication models to compensate for humidity-induced variations in fingerprint image quality, thereby maintaining verification reliability.
2Measurement precision
If high humidity is present, then fingerprint imaging may be saturated, but verification becomes difficult or impossible
Solution Approach 1:
The patent applies preliminary action by detecting humidity levels and adjusting acquisition settings before the actual fingerprint authentication occurs. The system performs preliminary calibration and parameter adjustment based on environmental conditions, ensuring that the subsequent verification process operates under optimized settings that prevent saturation artifacts from compromising accuracy.
Solution Approach 2:
The patent implements feedback by using humidity detection results to dynamically adjust acquisition parameters and authentication model selection. The system continuously monitors environmental conditions and feeds this information back to modify sensing and processing parameters, creating a closed-loop system that maintains image quality and verification accuracy despite varying humidity levels.
3Reliability
If low humidity is present, then coupling issues occur, but fingerprint imaging quality deteriorates
Solution Approach 1:
The patent applies parameter changes by adjusting acquisition parameters (increasing gain) when low humidity is detected. The system modifies electrical sensing parameters to compensate for reduced capacitive coupling effects caused by dry skin conditions, thereby maintaining sufficient signal strength and image quality for reliable fingerprint extraction and verification.
4Measurement precision
If humidity level adaptation is implemented, then authentication accuracy improves, but process complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the authentication process into distinct stages: humidity detection, parameter adjustment, and model selection. The system segments the authentication workflow into manageable steps, each handling a specific aspect of humidity compensation, thereby organizing complexity into structured, modular components that can be implemented and maintained systematically.
Solution Approach 2:
The patent implements universality by creating a multi-functional authentication system that handles both humidity detection and authentication in a unified framework. The system uses a single adaptive authentication module that can select from multiple authentication models based on conditions, providing universal functionality across varying environmental scenarios without requiring separate dedicated systems for each condition.
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 approach enhances fingerprint authentication by maintaining contrast and dynamic range across varying humidity levels, improving feature extraction and matching accuracy, and providing effective user guidance to achieve successful verification.
Implementation Method 1
capacitive sensing is most commonly used... All capacitive fingerprint sensors provide an indicative measure of the capacitance between several sensing elements and a finger placed on the surface of the fingerprint sensor
Data Source
AI summary
The present invention generally relates to a method for authenticating a finger of a user of an electronic device comprising a fingerprint sensor for sensing a fingerprint pattern, the method comprising the steps of: acquiring a candidate fingerprint image; determining, based on the candidate fingerprint image, a humidity level indication indicative of the humidity level of the finger; performing an authentication pre-process based on the humidity level indication; performing a fingerprint authentication process based on the pre-process to authenticate the user.