Fingerprint Sensor Noise Reduction via Differential Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fingerprint sensing technologies face challenges in effectively reducing noise interference, with methods like common ground plates being costly and complex, and oversampling or averaging prolonging sensing time.
Innovation Solution
A method involving two adjacent sensing plates and their respective circuits, where the difference between their sensing data is calculated to eliminate noise, allowing for noise-free fingerprint data determination without the need for a common ground plate, thereby reducing noise interference and shortening sensing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a common ground plate is used to reduce noise interference, then noise reduction is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the common ground plate from the fingerprint sensing system. Instead of using a separate ground plate to reduce noise, the invention uses differential sensing between adjacent sensing plates to achieve noise cancellation, thereby removing the need for additional ground plate components and simplifying the manufacturing process.
Solution Approach 2:
The sensing plates serve dual functions: they detect fingerprint patterns while simultaneously acting as noise reference elements. By comparing adjacent sensing plates, the system uses the same sensing elements to both capture fingerprint data and reference environmental noise, eliminating the need for separate ground plates.
2Object-affected harmful factors
If more sensing plates are added to reduce noise, then noise reduction improves, but cost and manufacturing complexity increase
Solution Approach 1:
The patent merges the noise reduction function with the existing sensing plates by using adjacent plates in pairs. Instead of adding separate noise-reduction components or extra sensing plates beyond what's needed for fingerprint capture, the invention combines the fingerprint sensing function with noise reference function using the same adjacent plate pairs.
3Object-affected harmful factors
If averaging method is used to reduce noise, then noise reduction is achieved, but sensing time increases due to noise fluctuation
Solution Approach 1:
The patent converts the harmful noise effect into a beneficial reference signal. By using adjacent sensing plates that are simultaneously affected by the same noise, the system transforms noise from a disturbance that requires prolonged averaging into a useful reference that enables immediate differential cancellation, thus reducing sensing time.
4Object-affected harmful factors
If common ground plate is used for noise reduction, then noise interference decreases, but device volume increases
Solution Approach 1:
The patent removes the common ground plate component entirely from the sensor structure. By using differential sensing between adjacent sensing plates, the system achieves noise reduction without requiring the additional space that a separate ground plate would occupy in the sensor assembly.
Data Source
AI summary
In a fingerprint sensor, two adjacent sensing plates are detected at a same time to obtain first sensing data and second sensing data therefrom respectively, so that the first sensing data and the second sensing data include a same noise, then the first sensing data is subtracted from the second sensing data to generate a difference by which the noise is eliminated, and the difference is added to first fingerprint data corresponding to the sensing plate which provides the first sensing data, resulting in second fingerprint data corresponding to the other sensing plate. The fingerprint portions on the two adjacent sensing plates are determined according to the first and the second fingerprint data respectively.