Multi-mode Capacitive Sensor Electrode Reuse for Presence Detection
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Solution Overview
Problem
Existing fingerprint sensor systems require additional dedicated presence detection elements, which are inaccurate and consume valuable device space, especially in portable applications, and often fail to accurately detect finger presence over the sensing array.
Innovation Solution
The system reuses selected sensor electrodes from the sensor array for presence detection, allowing for accurate finger presence indication without the need for additional dedicated elements, thereby enabling a more compact design and improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional dedicated presence detection sensing elements are used, then finger presence detection capability is provided, but device real estate is consumed and accuracy is reduced
Solution Approach 1:
The patent applies multi-functionality by enabling sensor electrodes to serve dual purposes: imaging mode for capturing fingerprint details and presence detection mode for detecting finger presence. The processing system configures the same sensor electrodes to operate in different modes, eliminating the need for separate dedicated presence detection elements while maintaining accurate detection capability across the entire sensor array area.
2Reliability
If additional dedicated presence detection sensing elements are used, then finger presence detection capability is provided, but device real estate is consumed
Solution Approach 1:
The patent eliminates device complexity by using the same sensor electrodes for both imaging and presence detection functions. The processing system dynamically configures the sensor electrodes between imaging mode and presence detection mode, removing the need for additional hardware components and simplifying the overall sensor structure.
Solution Approach 2:
The patent merges the presence detection function with the imaging function by using the same sensor electrodes for both purposes. This consolidation combines what were previously separate functions into a unified system, reducing the number of components and simplifying the sensor design.
3Area of stationary object
If the sensor array is made smaller, then device compactness is improved, but presence detection accuracy is reduced
Solution Approach 1:
The patent maintains presence detection accuracy in a compact sensor design by using the same sensor electrodes for both imaging and presence detection. This approach ensures that the entire sensor array area contributes to presence detection, rather than relying on smaller dedicated presence detection elements, thereby maintaining detection accuracy while enabling compact sensor design.
4Reliability
If the sensor operates in imaging mode continuously, then fingerprint imaging capability is maintained, but power consumption increases
Solution Approach 1:
The patent implements periodic action by using presence detection mode during intervals when imaging is not required. The processing system switches between presence detection mode (low power) and imaging mode (high power) based on operational needs, thereby reducing overall power consumption while maintaining fingerprint imaging capability when required.
Solution Approach 2:
The patent applies dynamics by dynamically switching the operational mode of the sensor electrodes between presence detection and imaging based on real-time requirements. This dynamic configuration allows the system to optimize power consumption by using the lower-power presence detection mode during idle periods while maintaining the ability to perform imaging when needed.
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 reduces power consumption and increases accuracy in detecting finger presence, allowing for smaller sensor designs while maintaining effective imaging capabilities.
Implementation Method 1
a sensing element that senses changes in capacitance in response to proximity of a finger to the sensor
Data Source
AI summary
A method and device for providing a multi-modal capacitive sensor, including a plurality of sensor electrodes, in an electronic device is provided. In a first mode, the capacitive sensor is configured to capture an image of a biometric object. In a second mode, the capacitive sensor is configured to provide presence detection functionality. In the second mode, the capacitive sensor includes at least one first electrode and at least one second electrode selected from a plurality of sensor electrodes. When operating in the second mode, the at least one first electrode is configured to receive a transmit signal, and the at least one second electrode is configured to receive a resulting signal capacitively coupled from the at least one first electrode. Based on the resulting signal, a processing system of the electronic device determines whether a biometric object to be imaged is present in the sensing area.