Fingerprint Sensor Calibration via Bright-Dark Reference Images
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Solution Overview
Problem
Existing calibration methods for optical fingerprint sensors in electronic devices are inadequate in addressing changes in brightness due to aging displays or varying backgrounds, leading to reduced signal noise ratio and grid formation from touch panel wires.
Innovation Solution
A calibration method that determines a numerical value based on images collected from both bright and dark surfaces of a calibration box, allowing for adaptive calibration of fingerprint images to account for changes in light source brightness, thereby improving image quality and reducing false rejection rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed background noise subtraction calibration is performed, then initial fingerprint image quality is acceptable, but signal noise ratio decreases and grid artifacts appear when brightness changes occur
Solution Approach 1:
The calibration method transitions from a static fixed background subtraction approach to a dynamic adaptive calibration process. It performs real-time brightness detection and dynamically adjusts calibration parameters based on current lighting conditions, allowing the system to adapt to changing brightness levels caused by display aging or different background interfaces.
Solution Approach 2:
The system changes the calibration parameters based on detected brightness levels. By measuring the actual brightness of the display screen and adjusting the calibration offset accordingly, the system maintains accurate fingerprint recognition across varying light conditions rather than using a fixed calibration value.
2Adaptability or versatility
If adaptive calibration based on brightness detection is implemented, then adaptability to brightness changes improves, but system complexity increases
Solution Approach 1:
The calibration system performs self-calibration by automatically detecting its own operating conditions (brightness levels) and adjusting its calibration parameters accordingly. The fingerprint sensor system itself generates the test signals and performs the calibration without requiring external intervention or complex additional hardware.
Solution Approach 2:
The calibration mechanism serves multiple functions: it detects brightness levels, determines calibration offsets, and adjusts fingerprint recognition parameters all through a single integrated process. This multi-functionality reduces the need for separate calibration hardware and simplifies the overall system architecture.
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 method effectively adapts to changes in light source brightness, enhancing fingerprint image quality and reducing false rejection rates by accurately calibrating fingerprint images using a combination of bright and dark calibration images.
Implementation Method 1
Optical fingerprints have relatively high requirements on ambient light and stability of optical path
Implementation Method 2
the calibration is performed by adopting a differential calibration scheme involving two fixed reflective surfaces (i.e., bright surface and dark surface) of a calibration box
Data Source
AI summary
A calibration method, an electronic device, and a non-transitory computer-readable storage medium are provided. The calibration method is applicable to an electronic device including a fingerprint sensor. The calibration method includes the following. Fingerprint collection is performed with the fingerprint sensor to obtain a first fingerprint image. A first numerical value is determined according to the first fingerprint image, a first calibration image, and a second calibration image, where the first numerical value is indicative of a change in brightness of a light source for the fingerprint collection, the first calibration image is an image obtained by performing image collection on a bright surface of a calibration box, and the second calibration image is an image obtained by performing image collection on a dark surface of the calibration box. The first fingerprint image is calibrated according to the first numerical value to obtain a second fingerprint image.