Optical Fingerprint Interference Cancellation via Dynamic Luminance
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Solution Overview
Problem
Optical fingerprint systems face instability and security issues due to interference from ambient light, chip dark current, and temperature, which existing methods only partially address, leading to inaccurate calibration in varying environments.
Innovation Solution
A method involving the acquisition of multiple fingerprint images under different luminance conditions, with interference cancellation using an interference image having the same exposure time as the primary image, to reduce ambient light, chip dark current, and temperature interference, thereby improving system stability and security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If calibration is performed according to the impact of external interference in a typical environment, then the anti-interference ability is improved in that environment, but inaccurate calibration occurs for scenarios that differ from the typical environment
Solution Approach 1:
The patent implements dynamic calibration by capturing multiple images at different luminance levels and using linear interpolation to calculate calibration parameters that adapt to current environmental conditions. Instead of using fixed calibration values from a typical environment, the system dynamically adjusts calibration parameters based on the actual ambient light conditions during fingerprint capture, thereby maintaining accuracy across varying environments.
Solution Approach 2:
The patent changes the luminance parameter of the display screen during the calibration process by capturing images at multiple luminance levels (first luminance, second luminance, and third luminance). This parameter variation allows the system to model the relationship between luminance and image quality, enabling accurate calibration parameter selection for any intermediate luminance condition through linear interpolation.
2Measurement precision
If multiple images at different luminance levels are captured and processed using linear interpolation, then calibration accuracy in varying environments is improved, but processing complexity increases
Solution Approach 1:
The patent captures more calibration images than the minimum single image by taking images at three different luminance levels. This excessive action provides redundant data that enables linear interpolation, improving calibration accuracy across varying luminance conditions. The additional processing complexity is justified by the significant improvement in measurement precision for fingerprint quality assessment.
Data Source
AI summary
Embodiments of the present application provide a method and an apparatus for acquiring a fingerprint, a chip and a terminal device, which may reduce interference caused by ambient light, temperature and a chip dark current and other factors. The method includes: acquiring a first fingerprint image and at least one second fingerprint image, where a screen luminance for acquiring the first fingerprint image is higher than a screen luminance for acquiring the at least one second fingerprint image; determining a third fingerprint image according to the first fingerprint image and the at least one second fingerprint image, where the third fingerprint image is an interference image having a same exposure time as the first fingerprint image; and performing interference cancellation on the first fingerprint image according to the third fingerprint image to obtain a fourth fingerprint image.