Touch Sensor With Loop Electrodes For Fingerprint Sensitivity
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Solution Overview
Problem
Conventional fingerprint readers on smartphones have low sensitivity and high resistance due to small, transparent electrodes, which obstruct image visibility and reduce driving speed.
Innovation Solution
A touch sensor design featuring a grid of first and second electrodes with loop patterns, configured as metal lines with small resistivity, allowing for increased mutual capacitance variation and improved sensitivity while maintaining image clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transparent electrodes are used in the fingerprint reader, then image visibility is maintained, but sensitivity decreases and resistance increases
Solution Approach 1:
The electrode structure is segmented into multiple components: transparent electrodes for visibility, metal lines for low resistance, and loop patterns for sensitivity enhancement. Each segment performs a specific function, resolving the contradiction between visibility and performance.
Solution Approach 2:
The patent employs a composite electrode structure combining transparent materials (for visibility) with metal materials (for low resistance and high sensitivity). This composite approach allows simultaneous achievement of image visibility and electrical performance requirements.
2Reliability
If transparent electrodes are made smaller to increase sensitivity, then sensitivity improves, but resistance increases
Solution Approach 1:
The electrode system is divided into transparent electrodes (for sensitivity) and separate metal line connections (for low resistance). This segmentation allows the transparent electrodes to be small for sensitivity while metal lines provide low-resistance pathways.
Solution Approach 2:
Metal lines act as intermediary conductors between the small transparent electrodes and the external circuitry. These intermediaries transfer signals from the sensitive transparent electrodes without significant resistance loss.
3Illumination intensity
If metal lines with small line width are used, then image visibility is maintained, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the line width parameter of metal lines to balance visibility and manufacturability. By carefully selecting and controlling the line width within specific ranges, both good image visibility and feasible manufacturing precision are achieved.
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
Enhances sensitivity and driving speed of touch and fingerprint pattern detection without obstructing image visibility, using electrodes with small resistivity and loop patterns to increase capacitance variation.
Implementation Method 1
a capacitance measurer configured to obtain mutual capacitances between the plurality of first electrodes and the plurality of second electrodes
Implementation Method 2
a driver configured to apply a driving voltage to the plurality of first electrodes
Data Source
AI summary
A touch sensor includes a plurality of first electrodes, a plurality of second electrodes, and a capacitance measurer configured to measure mutual capacitances between the plurality of first electrodes and the plurality of second electrodes. Each of the first electrodes includes a plurality of loop patterns.