Avalanche Photodiode Pulse Pile-Up Detection
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Solution Overview
Problem
Existing photoelectric conversion devices face errors in photon counting at high luminance due to interference between signals from multiple photons, leading to inaccurate output values and increased error rates.
Innovation Solution
Incorporating a detection unit within each pixel to determine if the pulse width from the light receiving portion exceeds a predetermined threshold, allowing the signal generation unit to adjust the output signal accordingly and reduce errors by distinguishing between single and multiple photon incidents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a photoelectric conversion device counts photons using a count circuit and integration circuit, then it can support a wide range of light amounts, but at high luminance multiple signals interfere with each other causing the output value to be much lower than the ideal value and increasing error
Solution Approach 1:
A detection unit is introduced as an intermediary component between the light receiving portion and the signal generation unit. This detection unit specifically detects pulse width information and provides it to the signal generation unit, which then uses this information to determine whether to output count values. The detection unit acts as a mediator that enables the system to distinguish between single photon events and pile-up events, thereby resolving the accuracy problem at high luminance while maintaining wide dynamic range capability.
Solution Approach 2:
The detection unit provides feedback information about pulse width to the signal generation unit. Based on this feedback, the signal generation unit adjusts its output behavior - outputting count values when pulse width indicates single photon events and suppressing output when pulse width indicates pile-up events. This feedback mechanism enables the system to adapt its operation based on the actual light conditions, maintaining accuracy across a wide range of luminance levels.
2Reliability
If multiple photons arrive simultaneously and their signals interfere, then the count circuit outputs incorrect values, but adding detection logic increases device complexity
Solution Approach 1:
The pixel structure is segmented into distinct functional units: a light receiving portion for detecting photons, a detection unit for analyzing pulse width characteristics, and a signal generation unit for producing output signals. This segmentation allows each unit to perform its specific function independently, with the detection unit specifically tasked with analyzing pulse width to distinguish single photon events from pile-up events. The modular segmentation improves reliability without excessively increasing overall complexity by assigning specific detection responsibilities to dedicated components.
Solution Approach 2:
The detection unit serves multiple functions: it detects pulse width information, determines whether pile-up events have occurred, and provides control signals to the signal generation unit. By making the detection unit multi-functional, the patent reduces the need for separate dedicated components for each function, thereby improving reliability through comprehensive detection while minimizing the increase in device complexity through functional integration.
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 enhances the accuracy of photon counting at high luminance by reducing errors and maintaining reliable output values, thereby improving the overall photoelectric conversion operation.
Implementation Method 1
a light receiving portion that outputs a pulse in response to incidence of a photon
Implementation Method 2
photoelectric conversion device comprising an array avalanche photodiodes
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A disclosed photoelectric conversion device includes a plurality of pixels each including a light receiving portion that outputs a pulse in response to incidence of a photon and a signal generation unit that outputs a signal based on output from the light receiving portion, and each of the plurality of pixels further includes a detection unit that detects whether or not a width of a pulse output from the light receiving portion exceeds a predetermined threshold value.