Photodiode Bias Control for Uniform Optical Detection Accuracy
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Solution Overview
Problem
Existing optical biometric detection devices using organic photodiodes face challenges in maintaining detection accuracy and imaging characteristics due to variations in the organic semiconductor layer, leading to degradation in performance.
Innovation Solution
A detection device is designed with a power supply control circuit that individually controls the reverse bias voltage of photodiodes, applying a first potential during a setting period and a second potential during the detection period based on signal output levels, to optimize the reverse bias voltage for each partial detection area, thereby reducing variations in the AFE signal output level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed reverse bias voltage is applied to all photodiodes, then the device structure is simple, but variations in the organic semiconductor layer cause degradation in detection accuracy and imaging characteristics
Solution Approach 1:
The detection area is divided into multiple partial detection areas, and each photodiode is independently controlled by separate power supply circuits. This segmentation allows individual adjustment of reverse bias voltage for each photodiode based on its specific characteristics, thereby improving detection accuracy while managing the complexity through modular control architecture
Solution Approach 2:
Different reverse bias voltages are applied to different photodiodes according to their local characteristics and signal output levels. The power supply control circuit adjusts the voltage locally for each photodiode, optimizing performance in regions with varying organic semiconductor layer quality rather than applying a uniform voltage across the entire detection area
2Measurement precision
If the reverse bias voltage is increased to improve signal output, then detection sensitivity improves, but variations in signal output level across partial detection areas increase
Solution Approach 1:
The power supply control circuit measures the signal output level from each photodiode during a setting period and uses this feedback information to adjust the reverse bias voltage applied to each photodiode during the detection period. This feedback mechanism ensures that photodiodes with lower signal output receive higher voltage compensation, while those with higher output receive lower voltage, thereby equalizing the overall signal output consistency across all partial detection areas
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 improves detection accuracy and imaging characteristics by reducing variations in the AFE signal output level across the detection area, enhancing the overall performance of the detection device.
Implementation Method 1
a plurality of photodiodes configured to detect information on an object to be detected in a detection area
Data Source
AI summary
According to an aspect, a detection device includes: photodiodes configured to perform detection in a detection period, a power supply control circuit, and power supply circuits configured to supply, to each photodiode, a first potential or a second potential based on a control signal from the power supply control circuit. The photodiodes are respectively provided for partial detection areas of a detection area. The power supply control circuit is configured to detect an output level of a signal output from each of the partial detection areas when the first potential is supplied to the photodiodes during a setting period different from the detection period, and control the power supply circuits so as to supply the second potential to the photodiode of the partial detection area in which the output level of the signal is equal to or higher than a predetermined threshold during the detection period.