Fingerprint Signal Calibration Circuit for Faster ADC Offset Correction
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Solution Overview
Problem
Conventional fingerprint recognition technologies slow down fingerprint data pickup speed due to software algorithm-based calibration methods.
Innovation Solution
A fingerprint signal processing system and method that calibrate offsets using calibration parameters stored in a register circuit, calculating average pixel values from peaks and troughs to update ADC offsets without relying on software algorithms, thereby increasing data pickup speed and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If software algorithm-based calibration methods are used to calibrate ADC offsets, then calibration accuracy can be achieved, but fingerprint data pickup speed is slowed down
Solution Approach 1:
The patent replaces software algorithm-based calibration with a hardware circuit-based calibration system. The offset calibration circuit performs calibration operations in hardware, substituting the software processing path with a dedicated hardware circuit that can execute calibration functions parallel to the main fingerprint data acquisition pipeline, thereby eliminating the speed bottleneck while maintaining calibration accuracy.
Solution Approach 2:
The patent implements background calibration that occurs in advance or in parallel with fingerprint data acquisition. The offset calibration circuit calculates calibration parameters and updates ADC offsets before or during the fingerprint scanning process, so that when actual fingerprint data is processed, the calibration is already complete or concurrently happening, eliminating sequential waiting time.
2Device complexity
If conventional averaging methods are used to calculate pixel values, then processing is simpler, but the results are more affected by fingerprint pressure variations
Solution Approach 1:
The patent applies different processing strategies to different parts of the pixel data based on their characteristics. For pixels identified as peaks or troughs (local extrema), a different averaging approach is used compared to regular pixels. This local differentiation allows the system to weight or select specific pixels that are less affected by pressure variations, improving overall calibration accuracy while maintaining reasonable processing complexity.
Solution Approach 2:
The patent creates multiple copies or representations of pixel data at different processing stages. By maintaining both the original pixel values and calculated peak/trough values, the system can compare and select the most reliable data for calibration, effectively creating a redundant data path that improves accuracy without significantly increasing processing complexity.
Data Source
AI summary
A fingerprint signal processing system for a fingerprint sensor includes a calibration control circuit, a register circuit, a decode circuit and a normalization circuit. The calibration control circuit is configured to receive a background calibration control signal and an image signal from the fingerprint sensor, and convert the image signal into a plurality of digital signals according to a plurality of offsets. When the background calibration control signal is at a high level, the calibration control circuit is configured to read a plurality of calibration parameters from the register circuit.