Fingerprint Sensor Vertical Line Voltage Compensation
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Solution Overview
Problem
Fingerprint sensors in display devices face challenges in enhancing fingerprint sensing sensitivity due to variations in threshold voltage between sensor pixels, leading to inconsistent performance and accuracy.
Innovation Solution
A fingerprint sensor system that adjusts reference voltages on a vertical line basis using a power supply unit and a controller, which detects threshold voltages of transistors in sensor pixels and generates compensation information to optimize voltage levels, thereby improving sensing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference voltages are applied uniformly to all sensor pixels, then the device structure remains simple, but fingerprint sensing sensitivity deteriorates due to threshold voltage variations between pixels
Solution Approach 1:
The voltage supply system is segmented into multiple independent power lines, each serving a specific vertical line of sensor pixels. The controller divides the sensor array into multiple groups and applies different reference voltages to each group through dedicated power lines, enabling localized compensation for threshold voltage variations without requiring individual voltage control for each pixel.
Solution Approach 2:
Different reference voltages are applied to different vertical line groups of sensor pixels based on their specific threshold voltage characteristics. The controller measures threshold voltages for each group and determines optimized reference voltages locally, allowing each region to operate at its optimal voltage level rather than using a uniform voltage across the entire sensor array.
2Measurement precision
If individual voltage compensation is applied to each sensor pixel, then sensing sensitivity is maximized, but device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
Instead of individual pixel compensation, the system segments pixels into manageable vertical line groups. Each group shares common power lines and control logic, reducing the number of independent voltage supply channels from the number of pixels to the number of vertical lines, thereby simplifying manufacturing while maintaining effective compensation.
Solution Approach 2:
The power lines serve multiple functions: they provide reference voltages to sensor pixels, carry sensing signals from multiple pixels simultaneously, and are controlled through a unified control logic in the controller. This multi-functionality reduces the overall component count and simplifies the manufacturing process.
3Measurement precision
If threshold voltage compensation is implemented, then sensing accuracy improves, but the operational complexity and control requirements increase
Solution Approach 1:
The controller performs threshold voltage measurement and reference voltage optimization in advance, before actual fingerprint sensing operations. During initialization, the system measures the threshold voltage of each vertical line group and determines the optimal reference voltage for each group. This preliminary compensation setup eliminates the need for complex real-time adjustments during fingerprint scanning, simplifying operational control.
Solution Approach 2:
The system implements a feedback mechanism where the controller measures the actual threshold voltages of sensor pixel groups and uses this information to adjust and optimize the reference voltages applied to each group. This closed-loop approach automatically compensates for manufacturing variations and environmental changes without requiring manual intervention or complex operational procedures.
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 enhances fingerprint sensing sensitivity by compensating for voltage differences, leading to improved accuracy and reliability in recognizing fingerprints and palm prints.
Implementation Method 1
when a touch of a hand of a user occurs on the fingerprint sensor, the sensor electrode may form a second capacitor with the hand of the user, and recognize a fingerprint or a palm print of the user based on a change in capacitance of the second capacitor corresponding to the touch
Data Source
AI summary
A fingerprint sensor includes: sensor pixels, each including a first transistor which controls a sensing signal to be outputted to a corresponding one of output lines; power lines disposed on a vertical line basis and each electrically connected to sensor pixels disposed on a corresponding vertical line; and a power supply unit which supplies reference voltages to the power lines. The power supply unit supplies the reference voltages, which is adjusted on the vertical line basis, to the power lines.