Stacked Photodiode Optical Sensor Circuit for Sensitivity Stability
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Solution Overview
Problem
Existing optical sensors used for detecting fingerprint patterns and vascular patterns experience a change in sensitivity characteristics over time due to the application of a reverse bias voltage during detection.
Innovation Solution
A detection device comprising a plurality of optical sensors arranged on a substrate, where each optical sensor includes a first photodiode and a second photodiode coupled in series and in opposite directions, is used to reduce the change in sensitivity characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reverse bias voltage is supplied to the optical sensor during detection, then the detection capability is improved, but the sensitivity characteristics change over time
Solution Approach 1:
The optical sensor is segmented into two photodiodes with opposite polarity connections. Each photodiode has its anode and cathode connected to different potential lines (first and second potentials), creating two independent detection paths that can be differentially processed to cancel out time-dependent sensitivity drift caused by reverse bias voltage.
Solution Approach 2:
The invention changes the electrical parameter configuration by applying opposite polarity connections to the two photodiodes. By reversing the connection polarity of the second photodiode relative to the first, the system creates complementary detection signals that, when processed together, eliminate the sensitivity drift effect while maintaining detection capability under reverse bias conditions.
2Speed
If a reverse bias voltage is supplied to the optical sensor during detection, then the detection speed is improved, but the sensitivity characteristics change over time
Solution Approach 1:
The optical sensor is segmented into two photodiodes with opposite polarity connections. Each photodiode has its anode and cathode connected to different potential lines (first and second potentials), creating two independent detection paths that can be differentially processed to cancel out time-dependent sensitivity drift caused by reverse bias voltage.
Solution Approach 2:
The invention changes the electrical parameter configuration by applying opposite polarity connections to the two photodiodes. By reversing the connection polarity of the second photodiode relative to the first, the system creates complementary detection signals that, when processed together, eliminate the sensitivity drift effect while maintaining detection capability under reverse bias conditions.
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 described configuration helps to stabilize the sensitivity characteristics of the optical sensors over time, improving the accuracy and reliability of fingerprint and vascular pattern detection.
Implementation Method 1
Each of the optical sensors includes a first photodiode and a second photodiode
Data Source
AI summary
According to an aspect, a detection device includes a plurality of optical sensors arranged on a substrate. Each of the optical sensors includes a first photodiode and a second photodiode that is coupled in series and in an opposite direction to the first photodiode.