Light Detecting Device for Fingerprint Recognition with Fluctuation Compensation
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Solution Overview
Problem
Existing light detecting technologies face challenges in accurately identifying fingerprint ridges and valleys due to fluctuations in light source brightness, which can lead to noise and errors in fingerprint recognition.
Innovation Solution
A light detecting device with a light fluctuation detecting circuit that enables or disables the connection between the photoelectric node and the voltage follower circuit, allowing for the detection of brightness fluctuations and outputting a fluctuation indication signal to process the voltage and determine the actual brightness of the light, thereby reducing noise and improving fingerprint recognition accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light source is used to illuminate fingerprint lines for recognition, then fingerprint recognition can be performed, but brightness fluctuations of the light source generate noise and reduce recognition accuracy
Solution Approach 1:
The patent introduces a feedback mechanism where the detected light intensity is used to dynamically adjust the compensation value in the differential pulse mode. The system continuously monitors the light source brightness and adjusts the reference level accordingly, creating a closed-loop control that eliminates the impact of light fluctuations on fingerprint recognition accuracy.
Solution Approach 2:
The patent changes the operational parameters by using differential pulse illumination instead of continuous illumination. By controlling the light source to emit pulses with varying intensities and using different integration times for detection, the system can distinguish between actual fingerprint features and noise caused by brightness fluctuations, thereby improving recognition reliability.
2Measurement precision
If continuous illumination is used to ensure sufficient light for detection, then detection sensitivity is improved, but light fluctuation noise increases and affects valley and ridge identification
Solution Approach 1:
The patent employs periodic pulsed illumination instead of continuous lighting. The light source emits periodic pulses with controlled duration and intensity, and the detection system synchronizes its integration windows with these pulses. This periodic action allows the system to capture light signals at optimal moments while ignoring fluctuations that occur between pulses, thereby maintaining high detection sensitivity while reducing noise.
Solution Approach 2:
The patent performs preliminary measurements of the light source brightness before actual fingerprint detection. By characterizing the light source behavior in advance and pre-calculating compensation values or reference levels, the system prepares the detection algorithm to correctly interpret subsequent measurements, reducing the impact of brightness fluctuations on valley and ridge identification accuracy.
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
The device effectively reduces the impact of light source fluctuations, enhancing the accuracy of fingerprint recognition by filtering and weighting voltage differences to obtain reliable brightness values, thus improving the determination of fingerprint ridges and valleys.
Implementation Method 1
a photodiode PD in a reverse biased state... configured to convert a received optical signal into a corresponding electrical signal
Data Source
AI summary
The light detecting device provided by the present disclosure includes a reset circuit, a photoelectric conversion circuit, a voltage follower circuit, a selection circuit, and a light fluctuation detecting circuit. The light fluctuation detecting circuit is connected to each of a light fluctuation detection control terminal, a photoelectric node and an input terminal of the voltage follower circuit. The light fluctuation detecting circuit is configured to enable or disable a connection between the photoelectric node and the input terminal of the voltage follower circuit. When the light fluctuation detecting circuit is turned off, a drain current of the light fluctuation detecting circuit may change as the brightness of light received by the light fluctuation detecting circuit changes. The voltage at the output node is used to determining brightness of light received by the photoelectric conversion circuit and whether is a fluctuation in the in the brightness of the light.