Multi-Segment Fingerprint Sensor Architecture for Faster Large-Area Scanning
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Solution Overview
Problem
Existing fingerprint sensors face limitations in accuracy, immunity to environmental variables, and inefficiencies in scanning large areas and moving objects, particularly in meeting high-resolution and high-bandwidth requirements for fingerprint acquisition profiles like FAP60.
Innovation Solution
A multi-segment pixel matrix architecture with independently driven pixel arrays and application-specific integrated circuits (ASICs) for thermal and capacitive sensing, combined with a microcontroller unit (MCU) for intelligent scanning and image processing, allowing for selective thermal and capacitive scans to enhance scanning speed, bandwidth, and power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single large pixel array is used to cover large sensing area, then the sensing area is sufficient, but the scan time becomes too long and power consumption increases
Solution Approach 1:
The pixel matrix is divided into multiple independently scannable pixel arrays (segments). Each pixel array can be scanned independently by dedicated ASICs, allowing parallel processing. This segmentation enables the large sensing area to be covered without requiring sequential scanning of all pixels, thus reducing total scan time while maintaining full sensing area coverage.
2Measurement precision
If thermal sensing is used to achieve high resolution, then measurement precision is improved, but power consumption increases
Solution Approach 1:
Instead of continuously scanning the entire pixel matrix with thermal sensing, the system performs partial scans only on regions where fingerprint patterns are detected. The pixel arrays are activated and scanned only when needed, reducing overall power consumption while maintaining high-resolution measurement capability when required.
Solution Approach 2:
The thermal sensing operation is performed periodically rather than continuously. The system uses capacitive sensing for initial detection and then activates thermal sensing only at specific intervals for high-resolution scanning, reducing power consumption while maintaining measurement precision when needed.
3Productivity
If multiple pixel arrays are added to increase scanning bandwidth, then productivity is improved, but device complexity increases
Solution Approach 1:
The pixel matrix is divided into multiple pixel arrays that can be scanned in parallel by dedicated ASICs. This segmentation increases scanning bandwidth by enabling simultaneous processing of multiple regions, while each segment remains relatively simple in structure.
Solution Approach 2:
Dedicated ASICs serve as intermediary components between the pixel arrays and the main processor. Each ASIC handles the scanning and initial processing of its assigned pixel array, reducing the burden on the main processor and simplifying the overall system architecture despite having multiple pixel arrays.
4Measurement precision
If continuous scanning is performed to capture moving objects, then measurement precision is maintained, but power consumption and scan time increase
Solution Approach 1:
The system performs scanning periodically rather than continuously. Capacitive sensing is used for continuous monitoring at low power, and thermal sensing is activated periodically for high-resolution image capture. This periodic action maintains image quality for moving objects while significantly reducing power consumption compared to continuous high-resolution scanning.
Solution Approach 2:
The system performs partial scans only on regions where motion or fingerprint patterns are detected, rather than scanning the entire sensing area continuously. This approach maintains measurement precision for relevant areas while reducing power consumption by avoiding unnecessary scans in empty regions.
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
The solution enables faster scan times, lower power consumption, and improved image quality, enabling fingerprint sensors to meet FAP60 standards by efficiently capturing high-resolution images from large areas and moving objects, including multiple fingers simultaneously.
Implementation Method 1
Each pixel array comprises thermal sensing pixels, which are configured to operate based on the active thermal sensing principle, in which a power heat pulse is applied to each pixel array and a response corresponding to a biometric pattern is measured
Implementation Method 2
Each pixel array further comprises a capacitive sensing grid comprising capacitive sensing nodes distributed in each pixel array
Data Source
AI summary
A multi-segment pixel matrix, a sensor or device, a system, and a method, for biometric sensing, are provided. Such a device or system includes a sensor comprising a pixel matrix having two or more pixel arrays as separate segments logically divided in the pixel matrix. The pixel matrix may include both thermal sensing pixels and capacitive sensing nodes. The device or system may include a plurality of application-specific intergrade circuits (ASICs) coupled to the sensor. Each ASIC is configured to capture image data of a biometric pattern measured by at least one pixel array. Each pixel array is independently driven and scanned by one or more of the plurality of the ASICs. The device or system further includes a microcontroller unit coupled to the plurality of ASICs and are used to process the image data and/or control operation of the system. Such a sensor can be a fingerprint sensor.