Capacitive Sensor Parasitic Capacitance Pattern for Biometric Accuracy
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Solution Overview
Problem
Capacitive sensors often incorrectly detect skin tissue or sweat as biometric data due to their conductivity, leading to erroneous readings.
Innovation Solution
A capacitive sensor design with electrodes having different parasitic capacitances arranged in a pattern distinct from biometric information, allowing for the differentiation between genuine biometric data and non-biometric conductors like skin tissue or sweat by analyzing the distribution of parasitic capacitances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor uses a uniform electrode arrangement to detect biometric information, then the sensor structure is simple and manufacturing is easy, but the sensor cannot distinguish between genuine biometric data and non-biometric conductors such as skin tissue or sweat
Solution Approach 1:
The patent applies local quality by assigning different parasitic capacitance values to different electrodes within the sensor array. Specifically, first electrodes have a first parasitic capacitance value while second electrodes have a second parasitic capacitance value different from the first. This local differentiation allows the sensor to distinguish between genuine biometric patterns and false readings from conductive residues, as the non-biometric conductors will interact uniformly with all electrodes whereas genuine biometric features will produce characteristic patterns against the differentiated electrode backdrop.
2Productivity
If the sensor surface is touched with a body part, then biometric information can be acquired, but skin tissue or sweat residue adhering to the sensor surface causes erroneous detection
Solution Approach 1:
The patent implements preliminary action by pre-configuring the electrode array with known different parasitic capacitance values before biometric acquisition occurs. This preliminary differentiation creates a reference pattern that enables the system to later identify and filter out false readings from conductive residues. The processing unit uses this pre-established electrode characteristic map to distinguish genuine biometric data from artifacts, thereby maintaining reliability without sacrificing acquisition efficiency.
3Measurement precision
If electrodes with different parasitic capacitances are arranged in a prescribed pattern, then non-biometric regions can be detected and discarded, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the electrode array into distinct groups with different parasitic capacitance characteristics. First electrodes are segmented from second electrodes based on their capacitance values, creating discrete segments with known properties. This segmentation simplifies the processing logic, as the system only needs to compare readings against two known capacitance patterns rather than handling continuous variations, thereby achieving improved measurement precision without excessive device complexity.
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
Effectively discards images with significant non-biometric regions, ensuring accurate biometric data acquisition and reducing false positives from residual conductive materials.
Implementation Method 1
a body part placed in contact with or in close proximity to a sensor surface acts as an electrode opposing an electrode provided within the sensor. That is, a charge stored between the sensor electrode and the body part causes a change in capacitance.
Implementation Method 2
If residue such as skin tissue or sweat adhere to the sensor surface when the sensor surface is touched with the body part, or if moisture condenses on the sensor surface, since such foreign matter is also an electrical conductor, the capacitance between this electrical conductor and the sensor electrode also changes.
Data Source
AI summary
A capacitive sensor includes a plurality of electrodes each of which outputs an electrical signal corresponding to a capacitance determined by a distance between a surface of the capacitive sensor and an electrical conductor. The plurality of electrodes include electrodes having a first parasitic capacitance and electrodes having a second parasitic capacitance different from the first parasitic capacitance, and are arranged in a prescribed pattern different than a pattern of biometric information of a body part to be read by the capacitive sensor.