Capacitive Fingerprint Sensing with Pre-Detection to Cut Scan Power
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Solution Overview
Problem
Current capacitive fingerprint detection systems consume high power due to constant full-array scanning, even when a finger is not present, leading to inefficient energy usage.
Innovation Solution
A method and apparatus that initiate full-array scanning only after reliable identification of a finger touch, using a capacitance detection module, detection electrode, and controller to perform fingerprint pre-detection and scanning, reducing power consumption by activating detection units sequentially and intermittently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fingerprint detection array constantly performs full-array scanning to ensure reliable fingerprint detection, then the detection reliability is improved, but the power consumption increases
Solution Approach 1:
The patent applies preliminary action by performing capacitance detection before full-array fingerprint scanning. The capacitance detection module first detects whether a finger is present on the detection electrode, and only when a finger is detected does the system initiate the full-array fingerprint scanning. This preliminary detection step avoids unnecessary full-array scanning when no finger is present, thereby reducing power consumption while maintaining reliable fingerprint detection when needed.
2Speed
If the fingerprint detection array performs continuous full-array scanning to capture fingerprint data, then the detection speed is improved, but the power consumption increases
Solution Approach 1:
The patent implements periodic action by alternating between low-power capacitance detection mode and high-speed full-array scanning mode. The system periodically performs capacitance detection to check for finger presence, and only activates the power-intensive full-array scanning when a finger is detected. This periodic switching between detection modes maintains fast fingerprint capture capability while significantly reducing average power consumption during periods when no finger is present.
3Measurement precision
If the fingerprint detection array activates all detection units for full-array scanning, then the measurement precision is improved, but the power consumption increases
Solution Approach 1:
The patent uses preliminary capacitance detection to determine whether full-array scanning with all detection units activated is necessary. Only when a finger is detected through capacitance measurement does the system activate all detection units for high-precision fingerprint imaging. This ensures that the power-intensive high-precision scanning mode is only activated when needed, maintaining fingerprint image quality while reducing overall power consumption.
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 significantly reduces power consumption by limiting full-array scanning to confirmed finger touches, improving both reliability and accuracy while minimizing continuous scanning.
Implementation Method 1
a first parasitic capacitance is formed between the detection electrode and a system ground; detecting, by the capacitance detection module, a capacitance on the detection electrode when a finger of a user touches the detection electrode
Implementation Method 2
the C 0 is a parasitic capacitance between the detection electrode and a system ground, and the C 1 is a parasitic capacitance between the finger and the system ground
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention provides a detection method and apparatus for fingerprint detection. The method comprises: S1. detecting a capacitance on a detection electrode which a fingerprint detection apparatus comprises; S2: when the capacitance exceeds a predetermined capacitance threshold, enabling a part of detection units of a fingerprint detection array to perform fingerprint pre-detection, and acquiring data information of the fingerprint pre-detection; and S3: when the data information exceeds a first predetermined threshold, enabling all the detection units of the fingerprint detection array to perform fingerprint scanning. With the method for fingerprint detection according to the embodiments of the present invention, the fingerprint detection array is initiated for full-array scanning upon reliable and effective identification that a finger touches a fingerprint detection apparatus, which greatly reduces the power consumption of the fingerprint detection.