Fingerprint Sensor Reference Signal Adjustment
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Solution Overview
Problem
Fingerprint sensors face challenges in achieving high resolution due to the small difference in capacitance between fingerprint ridges and valleys, leading to small differences in analog signal magnitudes, which affects the accuracy of fingerprint pattern representation.
Innovation Solution
A fingerprint sensor design incorporating a pixel array, an analog-to-digital converter, and a reference signal generator that adjusts the reference signal's magnitude and rate based on digital signals to enhance the resolution of fingerprint patterns, allowing for more accurate digital data generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitance-based fingerprint sensor is used, then the sensor can detect fingerprint patterns, but the resolution is low because the capacitance difference between ridges and valleys is very small
Solution Approach 1:
The patent changes the reference voltage parameter dynamically during the analog-to-digital conversion process. The reference voltage is adjusted based on the detected signal characteristics to amplify the difference between ridge and valley capacitance values, thereby improving measurement precision without requiring a larger signal magnitude difference
Solution Approach 2:
The patent implements a dynamic reference voltage adjustment mechanism where the reference voltage is not fixed but varies during the conversion process. This dynamic adjustment allows the system to adapt to different fingerprint patterns and optimize the resolution for each specific measurement, transforming a static low-resolution system into a dynamic high-resolution system
2Measurement precision
If the reference signal magnitude is fixed, then the device complexity is reduced, but the measurement precision cannot be optimized for different fingerprint patterns
Solution Approach 1:
The patent incorporates a feedback mechanism where the analog-to-digital converter monitors the detected signal and feeds back information about the signal characteristics to the reference voltage generation circuit. This feedback loop enables the system to automatically adjust the reference voltage magnitude based on the actual fingerprint pattern detected, optimizing measurement precision while keeping the overall system relatively simple through automated adjustment
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 effectively increases the resolution of the fingerprint sensor, enabling more accurate representation and differentiation of fingerprint patterns by adjusting the reference signal's magnitude and rate, thereby improving the sensor's ability to capture detailed fingerprint data.
Implementation Method 1
a fingerprint sensor obtains a fingerprint image of a finger by detecting a capacitance between a sensing electrode and a finger
Implementation Method 2
The analog-to-digital converter performs an analog-to-digital conversion operation on the analog signal to generate a digital signal
Data Source
AI summary
A fingerprint sensor includes a pixel array, an analog-to-digital converter, and a reference signal generator. The pixel array includes a plurality of unit pixels arranged in rows and columns, and each of the plurality of unit pixels generates an analog signal by detecting a fingerprint of a user. The analog-to-digital converter performs an analog-to-digital conversion operation on the analog signal to generate a digital signal. The analog-to-digital converter is configured to perform the analog-to-digital conversion based on a reference signal. The reference signal generator generates the reference signal such that the reference signal decreases at a first rate from a start voltage, and adjusts a magnitude of the start voltage based on the digital signal.