Fingerprint Sensing Circuit Temporal Weighting for Ridge Valley Identification
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Solution Overview
Problem
Fingerprint sensing circuits face challenges in identifying ridges and valleys due to thick insulation layers and hardware limitations, which affect the resolution and identification ability of fingerprint images.
Innovation Solution
A fingerprint sensing circuit with sensing units arranged in columns and rows, where the sensing circuit is electrically connected to multiple sensing units in different periods to obtain fingerprint grey levels, and weighting summation is performed on these levels to enhance identification ability without altering the area or thickness of the sensing electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the area of the sensing electrode is increased to improve identification ability, then the identification ability is improved, but the area of the circuit increases or the resolution of the fingerprint image decreases
Solution Approach 1:
The patent transitions from spatial expansion (increasing electrode area) to temporal expansion (multiple sensing periods). By sensing multiple sensing units sequentially across different time periods and combining the results through weighting summation, the system achieves enhanced identification ability without increasing the physical area of individual electrodes or the overall circuit footprint.
2Ease of manufacture
If the insulation layer is made very thick for safety or manufacturing reasons, then the manufacturing is easier, but it becomes hard to identify the ridges and valleys
Solution Approach 1:
The patent changes the parameter of measurement from single-point capacitance to combined capacitance from multiple sensing units. By performing weighting summation on capacitance values from multiple sensing units, the system amplifies the capacitance difference signal between ridges and valleys, thereby improving identification ability even when the insulation layer thickness reduces the individual sensing capability.
3Measurement precision
If multiple sensing units are sensed in different periods to enhance identification ability, then the identification ability is improved, but the time required for sensing increases
Solution Approach 1:
The patent employs periodic action by dividing the sensing process into multiple distinct time periods, where each period is dedicated to sensing specific sensing units. This systematic periodic approach allows for comprehensive data collection from multiple sensing units while maintaining an organized and efficient sensing sequence, balancing improved identification ability with manageable sensing time.
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
Improves the identification ability of fingerprint images by increasing the capacitance difference between ridges and valleys, enhancing the resolution without changing the hardware configuration.
Implementation Method 1
A fingerprint image is generated by the capacitance difference between the sensing electrodes and a human finger for identifying ridges and valleys on the human finger
Data Source
AI summary
The fingerprint sensing circuit includes sensing units and a sensing circuit. The sensing units are arranged as columns and rows. Each of the sensing units includes a sensing electrode. The sensing circuit is electrically connected to the sensing electrodes in at least two first sensing units of the sensing units in a first period to obtain a first fingerprint grey level.