Fingerprint Sensor Array Noise Cancellation via Segmented Region Scanning
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Solution Overview
Problem
The image quality of fingerprint identification systems is deteriorated due to common mode interference from power supply noise, which affects the identification effect.
Innovation Solution
The system divides a sensing electrode array into regions, obtains detection signals region by region, and adjusts these signals using noise signals from adjacent electrodes, improving image quality by mitigating common mode interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a low-voltage DC power supply with charging circuit is used to supply power to the fingerprint sensor, then the portable device can provide communication and personal information functions, but common mode noises from charging management chips and charger devices are transferred to the fingerprint sensor, blurring acquired fingerprint images and influencing identification effect
Solution Approach 1:
The sensing electrode array is divided into multiple regions, and detection signals are obtained region by region. This segmentation allows the system to process signals from different areas separately, enabling noise cancellation to be applied more effectively to each region and improving overall fingerprint image quality despite power supply noise
Solution Approach 2:
A noise signal obtained from sensing electrodes adjacent to the detected region serves as an intermediary to represent the common mode noise. This noise signal is then used to adjust and cancel the common mode noise in the detection signals, effectively removing the harmful interference from the charging circuit while preserving the useful fingerprint information
2Device complexity
If one or more analog-to-digital converters ADC are reused in time-sharing mode for image acquisition due to limited processing capability of control chip, then device complexity is reduced, but common mode noises vary with time and are superposed on the final acquired fingerprint image, influencing identification effect
Solution Approach 1:
The detection process is divided into multiple scanning periods with each period containing multiple scanning sub-periods. Different regions are scanned during different sub-periods, allowing the system to acquire signals from various parts of the fingerprint sensor sequentially. This time-division approach works synergistically with the noise cancellation mechanism to handle the time-varying common mode noise
Solution Approach 2:
The system obtains noise signals from adjacent sensing electrodes and uses these signals to adjust and cancel the common mode noise in the detection signals. This feedback mechanism continuously compensates for the time-varying noise characteristics, ensuring high-quality fingerprint image acquisition even when using time-sharing ADC mode
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 the quality of acquired fingerprint images by effectively addressing the degradation caused by power supply noise, leading to improved identification performance.
Implementation Method 1
The fingerprint sensor operated in capacitive mode acquires the pattern of a fingerprint (fingerprint pattern) by detecting capacitive changes based on valley and ridge lines of the fingerprint
Implementation Method 2
obtaining a noise signal from at least one of the plurality of sensing electrodes adjacent to at least one of the plurality of regions; and adjusting at least one of the detection signals by using the noise signal
Data Source
AI summary
Disclosed a detection method used in a fingerprint identification system, the fingerprint identification system includes an array composed of a plurality of sensing electrodes configured to obtain a detection signal of a fingerprint, the detection method comprises: dividing the array into a plurality of regions; obtaining detection signals region by region; obtaining a noise signal from at least one of the plurality of sensing electrodes adjacent to at least one of the plurality of regions; and adjusting at least one of the detection signals by using the noise signal. The present disclosure also disclosed a detection device used in the fingerprint identification system. The disclosure can improve the quality of the image acquired by collecting the fingerprint and solve the problem that the image quality of the fingerprint identification system is deteriorated due to the common mode interference of the power supply.