Fingerprint Sensor Combining Optical and Capacitive Sensing
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Solution Overview
Problem
Conventional fingerprint sensors primarily rely on capacitive methods and lack the capability to sense fingerprints using multiple recognition techniques, limiting their adaptability to various fingerprint recognition conditions.
Innovation Solution
A fingerprint recognition sensor that combines both optical and capacitive methods, utilizing a capacitive fingerprint sensing unit with a transistor-based structure and an optical fingerprint sensing unit with a photodiode, to detect fingerprints based on changes in capacitance and light/shade differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only capacitive method is used for fingerprint sensing, then the sensor structure can be simplified, but the adaptability to various fingerprint recognition conditions deteriorates
Solution Approach 1:
The patent combines capacitive sensing elements (sensing electrodes detecting capacitance changes from fingerprint contact) and optical sensing elements (photodiodes detecting light reflection differences from fingerprint ridges and valleys) into a single integrated sensor structure, enabling multi-method fingerprint recognition while maintaining structural compactness
Solution Approach 2:
The sensor is designed with dual functionality to perform both capacitive fingerprint sensing and optical fingerprint sensing through shared structural components and signal processing circuits, allowing the same device to adapt to different fingerprint recognition conditions and requirements
2Adaptability or versatility
If multiple sensing methods are integrated into one sensor, then fingerprint recognition adaptability is improved, but the device complexity increases
Solution Approach 1:
The sensor is divided into distinct functional modules: capacitive sensing units with sensing electrodes, optical sensing units with photodiodes, and shared signal processing circuits. Each module performs a specific sensing function, and the modular design facilitates easier manufacturing and maintenance while achieving multi-method recognition
Solution Approach 2:
The patent introduces a shared signal processing circuit that acts as an intermediary to process signals from both capacitive and optical sensing elements. This intermediary structure consolidates complex processing functions into a common platform, reducing overall system complexity while maintaining multi-sensing capabilities
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
Enables various fingerprint recognition environments by effectively utilizing both optical and capacitive methods, enhancing the adaptability and accuracy of fingerprint detection.
Implementation Method 1
an optical fingerprint sensing unit which changes the current flowing into the transistor T2 due to a difference in reverse current of a photodiode generated by light and shade depending on existence or non-existence of the fingerprint
Implementation Method 2
a capacitive fingerprint sensing unit that includes a transistor T2 in which a flowing current is changed depending on an output voltage of a fingerprint sensing electrode detecting a humans fingerprint
Data Source
AI summary
Provided is a fingerprint recognition sensor capable of sensing a fingerprint using optical and capacitive methods, the sensor including: a capacitive fingerprint sensing unit that includes a transistor (T2) in which a flowing current is changed depending on an output voltage of a fingerprint sensing electrode capable of sensing the humans fingerprint; and an optical fingerprint sensing unit which changes the flowing current in the transistor (T2) due to a difference in reverse current of a photodiode generated by light and shade depending on existence or non-existence of the fingerprint.