Fingerprint Sensing System With Preliminary Finger Detection
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Solution Overview
Problem
Existing fingerprint sensing systems face challenges in achieving low energy consumption and reducing false attempts to sense a fingerprint pattern, as they often require the sensing elements to be in an active mode for finger detection, leading to high power consumption and potential false activations.
Innovation Solution
The method involves controlling a group of sensing elements to change their potential and monitoring capacitive coupling with finger detecting structures, providing a finger detection signal when the response signal exceeds a predefined threshold, allowing the sensing elements to operate in a low-power mode and reducing false activations by ensuring the finger is correctly placed before sensing the pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensing elements are kept in active mode for finger detection, then detection reliability is improved, but power consumption increases
Solution Approach 1:
The system performs preliminary finger detection using a separate finger detecting structure before activating the main sensing elements. This preliminary action ensures that the sensing elements are only activated when a finger is actually present, avoiding unnecessary power consumption while maintaining reliable detection capability.
Solution Approach 2:
The detection system is divided into two functional segments: a finger detecting structure for initial presence detection, and sensing elements for detailed fingerprint pattern sensing. This segmentation allows the system to use the low-power detection structure for continuous monitoring while keeping the high-power sensing elements dormant until needed.
2Measurement precision
If sensing elements are activated for finger detection, then detection accuracy is improved, but false attempts increase
Solution Approach 1:
The finger detecting structure performs preliminary verification of finger presence and correct placement before the sensing elements are activated. This preliminary check ensures that the sensing elements only operate when a finger is properly positioned, reducing false attempts while maintaining accurate detection.
Solution Approach 2:
The finger detecting structure acts as an intermediary between the user's finger and the main sensing elements. It verifies finger presence and correctness first, then gates the activation of the sensing elements, thereby preventing false attempts from reaching the main sensing system.
3Speed
If sensing elements operate continuously, then response time is improved, but energy efficiency deteriorates
Solution Approach 1:
The system uses periodic sampling with the finger detecting structure to monitor for finger presence, rather than keeping sensing elements continuously active. This periodic monitoring approach maintains readiness to detect fingers quickly while dramatically reducing energy consumption compared to continuous operation.
Solution Approach 2:
The finger detecting structure performs preliminary periodic checks to determine when activation of the sensing elements is warranted. This allows the system to maintain fast response capability by having the detection structure ready, while avoiding continuous operation of the power-intensive sensing elements.
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 minimizes false attempts to sense a fingerprint pattern by ensuring the finger is present and correctly positioned before activating the sensing elements, enhancing the energy efficiency and accuracy of the fingerprint sensing device.
Implementation Method 1
controlling a group of sensing elements to change a potential of a group of sensing structures comprised in the group of sensing elements; acquiring, in response to the variation in potential, a response signal from the finger detecting circuitry indicative of the capacitive coupling between the group of sensing structures and the finger detecting structure
Data Source
Figure 1~2
Figure 3
Figure 4a
AI summary
The present invention relates to amethod of sensing a fingerprint pattern of a finger (11) using a fingerprint sensing device(2). The method comprising: controlling (S802) agroup of sensing elements (8) to change a potential of a group of sensing structures (17) comprised in said group of sensing elements; acquiring(S804), in response to said variationin potential, a response signal from afinger detecting circuitry (9) indicative ofthe capacitive coupling between the group of sensing structures and the finger detecting structure; comparing (S806) a variation in theresponse signal with a predefined threshold value; and providing (S810) a signal indicating that a finger is present when the variation in response signal is greater than the threshold value.The invention also relates to a corresponding fingerprint sensing device. Publication Fig. 2