Fingerprint Signal Correction Using Reference Row Compensation
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Solution Overview
Problem
Fingerprint recognition systems face limitations due to noise and offset issues in fingerprint image signals, leading to suboptimal performance in fingerprint sensing devices, particularly in optical fingerprint recognition schemes.
Innovation Solution
A fingerprint sensing device and signal processing method that include a readout circuit, analog front-end (AFE) circuit, compensation circuit, and output circuit, which calculate and apply brightness correction, relative illumination correction, and gain values to enhance image signal quality by correcting offsets and adjusting ADC full scale range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical fingerprint recognition is used to capture fingerprint images, then fingerprint recognition capability is provided, but noise and offset issues reduce signal quality and recognition performance
Solution Approach 1:
The patent applies preliminary action by reading a reference row before the actual fingerprint image rows and calculating correction values (brightness correction, RI correction, and gain) in advance. These correction values are then applied to subsequent fingerprint image rows to eliminate noise and offset issues, thereby improving signal quality and recognition performance without affecting the actual fingerprint capture process
Solution Approach 2:
The patent implements feedback by using the reference row data to calculate correction values that are fed back to correct the fingerprint image signals. The correction circuit continuously adjusts the image signals based on the reference measurement, creating a closed-loop system that compensates for noise and offset variations, thus improving measurement precision while maintaining reliability
2Measurement precision
If correction values are calculated from a predetermined row and applied to correct image signals, then signal quality and recognition accuracy are improved, but additional processing steps increase device complexity
Solution Approach 1:
The patent merges the reference row reading and correction value calculation into the existing fingerprint image acquisition pipeline. The correction circuit integrates multiple correction functions (brightness correction, RI correction, and gain adjustment) into a single processing stage that operates concurrently with the image signal reading, thereby improving signal quality without proportionally increasing device complexity
Solution Approach 2:
The correction circuit is designed with multi-functionality, serving multiple purposes: it calculates brightness correction values, RI correction values, and gain values from a single reference row, and applies all three corrections to subsequent fingerprint image rows. This universal correction mechanism reduces the need for separate processing circuits, thereby limiting the increase in device complexity while achieving improved measurement precision
Data Source
AI summary
The fingerprint sensing device that includes a first analog front end (AFE) circuit, a compensation circuit, a correction circuit and an output circuit is introduced. The AFE circuit generates a first image signal according to the fingerprint data read from the plurality of rows of the fingerprint sensor. The correction circuit receives a first output digital code that is generated by reading a predetermined row among the plurality of rows of the fingerprint sensor, and calculates a brightness correction value and a relative illumination (RI) correction value according to the first output digital code. The compensation circuit modifies the first image signal according to the brightness correction value and the RI correction value to generate a second image signal. The output circuit is configured to generate a second output digital code according to the second image signal.