Fingerprint Recognition Circuit Threshold Voltage Compensation
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Solution Overview
Problem
The low temperature poly-silicon (LTPS) process for fingerprint recognition on glass substrates faces challenges due to non-uniform threshold voltages of thin film transistors, leading to inaccurate determination of concave and convex portions in fingerprints, which complicates fingerprint recognition.
Innovation Solution
A fingerprint recognition unit circuit is designed with a threshold compensation unit, amplification unit, and reset unit, utilizing transistors to generate and transmit current signals, and compensate for threshold voltages, ensuring accurate recognition by resetting the detection electrode between successive recognitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LTPS process is used for fingerprint recognition on glass substrate, then cost advantage is achieved, but threshold voltage uniformity deteriorates
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage compensation before fingerprint recognition. The circuit pre-charges the detection electrode to a reference voltage and compensates for threshold voltage variations in advance, ensuring accurate recognition despite LTPS process variations. This preliminary compensation step eliminates the adverse effect of non-uniform threshold voltages on recognition accuracy.
2Measurement precision
If threshold voltage compensation is implemented, then recognition accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated circuit. The threshold compensation unit, detection electrode, charge transfer unit, and reset unit are combined into one unified fingerprint recognition circuit. This integration achieves threshold voltage compensation and accurate fingerprint recognition while avoiding the complexity of separate independent circuits for each function.
Solution Approach 2:
The detection electrode serves multiple functions: it detects induction capacitance changes, stores charge during compensation, and transfers charge during recognition. The circuit components are designed to perform multiple operations sequentially, reducing the need for separate dedicated components and thereby limiting the increase in device complexity.
3Speed
If detection electrode is continuously monitored, then recognition speed is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic action through sequential circuit operations: reset phase, compensation phase, and recognition phase. The detection electrode is monitored and charged only during specific time intervals rather than continuously. This periodic operation achieves fast recognition through rapid sequential phases while significantly reducing energy consumption compared to continuous monitoring.
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 solution improves the accuracy and efficiency of fingerprint recognition on glass substrates by compensating for non-uniform threshold voltages, enhancing the stability and reliability of the recognition process while reducing costs.
Implementation Method 1
The detection electrode is configured to contact a surface of a finger to generate an induction capacitance
Data Source
AI summary
A fingerprint recognition unit circuit is provided, including a read line, a signal scanning terminal, a first power supply terminal, a second power supply terminal, a third power supply terminal, a first signal terminal, a second signal terminal, an exploring electrode, an output unit, a threshold compensation unit and a resetting unit. A method for controlling a fingerprint recognition unit circuit is applied to the fingerprint recognition unit circuit. A fingerprint recognition apparatus includes a glass substrate and the fingerprint recognition unit circuit.