Integrated Capacitive Fingerprint Sensor With Floating Electrodes
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Solution Overview
Problem
Existing touch sensitive display devices face challenges in integrating fingerprint sensors without disrupting touch performance and maintaining optical quality, particularly when the fingerprint sensor is placed within the active display area, as it can degrade touch sensitivity and visibility.
Innovation Solution
The integration of a fingerprint sensor array with a higher pixel density over a touch sensor array in the display, where the fingerprint sensor electrodes are electrically floated during touch sensing periods to prevent interference and optimized routing and electrode configurations to minimize optical artifacts and maintain high sensing frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a fingerprint sensor is integrated within the active display area, then the bezel width is reduced and display area is increased, but touch sensing performance degrades and optical quality deteriorates
Solution Approach 1:
The fingerprint sensor electrodes are dynamically switched between two states: during touch sensing periods, they are electrically floated (disconnected) to prevent interference with touch detection; during fingerprint sensing periods, they are connected to sensing circuitry for fingerprint detection. This dynamic switching resolves the contradiction by making the fingerprint sensor inactive during touch sensing, thereby maintaining touch performance while enabling fingerprint functionality when needed.
Solution Approach 2:
The system operates in periodic cycles, alternating between touch sensing periods and fingerprint sensing periods. During touch sensing periods, the fingerprint electrodes are floated; during fingerprint sensing periods, they are activated. This periodic switching allows both functions to operate at optimal performance levels at different times, resolving the contradiction between integrating the fingerprint sensor and maintaining touch performance.
2Measurement precision
If a fingerprint sensor array with higher pixel density is integrated over the touch sensor array, then fingerprint sensing precision is improved, but manufacturing complexity and electrode routing difficulty increase
Solution Approach 1:
The patent combines the fingerprint sensor array and touch sensor array into a single integrated structure with shared electrodes and common sensing areas. The fingerprint sensor electrodes are formed over the touch sensor electrodes, creating a multi-functional sensor array that reduces overall device complexity despite the high pixel density requirement for fingerprint sensing.
Solution Approach 2:
The sensor array serves multiple functions: during fingerprint sensing periods, it performs high-precision fingerprint detection; during touch sensing periods, the same physical structure enables touch detection. This multi-functionality reduces the need for separate dedicated structures, thereby managing complexity while achieving high fingerprint sensing precision.
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
This approach allows for effective fingerprint sensing while preserving touch accuracy and optical quality, enabling a seamless user experience with a narrower bezel and improved display uniformity.
Implementation Method 1
capacitive fingerprint sensor
Implementation Method 2
electrically float a sensor electrode in the second plurality of sensor electrodes during a sensing period of the first sensor array
Data Source
AI summary
An input device includes a first sensor array having a first plurality of sensor electrodes disposed in a sensing area, wherein the first sensor array has a first pixel density, and a second sensor array having a second plurality of sensor electrodes disposed in the sensing area, wherein the second sensor array has a second pixel density different from the first pixel density. The input device also includes a processing system coupled to the second plurality of sensor electrodes and configured to electrically float a sensor electrode in the second plurality of sensor electrodes during a sensing period of the first sensor array.