APD Reverse-Bias Control for Avalanche Crosstalk Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Photoelectric conversion devices with avalanche photodiodes suffer from avalanche luminescence, leading to erroneous counting and deterioration in image quality due to crosstalk between adjacent pixels, which is exacerbated by the reverse bias voltage and exposure time.
Innovation Solution
A photoelectric conversion device that includes a processor and memory to control the reverse bias voltage applied to avalanche photodiodes based on exposure time and temperature, reducing the absolute value of excess bias to minimize crosstalk and improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reverse bias voltage is increased to improve photoelectric conversion efficiency, then sensitivity is improved, but avalanche luminescence increases causing erroneous counting and image quality deterioration
Solution Approach 1:
The patent applies dynamics by making the reverse bias voltage adjustable and time-dependent rather than fixed. The control unit dynamically modifies the reverse bias voltage applied to the APD based on detected avalanche luminescence levels, allowing the system to optimize between sensitivity and crosstalk suppression in real-time during the exposure period.
Solution Approach 2:
The patent changes the electrical parameter (reverse bias voltage) of the APD to control avalanche luminescence. By adjusting this parameter based on detected crosstalk levels, the system can reduce excessive voltage that causes luminous crosstalk while maintaining sufficient voltage for photon detection sensitivity.
2Measurement precision
If exposure time is extended to improve signal accumulation, then detection capability is improved, but crosstalk between adjacent pixels increases due to prolonged avalanche luminescence
Solution Approach 1:
The patent maintains continuous monitoring of avalanche luminescence levels throughout the exposure period and continuously adjusts the reverse bias voltage accordingly. This continuous action ensures that signal accumulation proceeds effectively while crosstalk is suppressed throughout the entire exposure duration, not just at discrete intervals.
Solution Approach 2:
The system implements feedback by detecting the level of avalanche luminescence in real-time and using this information to adjust the reverse bias voltage. The control unit receives feedback about crosstalk conditions and modifies the voltage to maintain optimal operation, creating a closed-loop control system that adapts to changing conditions during exposure.
3Object-generated harmful factors
If reverse bias voltage is reduced to suppress avalanche luminescence, then crosstalk is reduced, but photoelectric conversion efficiency decreases
Solution Approach 1:
The system dynamically adjusts the reverse bias voltage rather than using a fixed reduced voltage. This allows the voltage to be high enough to maintain detection efficiency when needed while being reduced only when and where avalanche luminescence becomes problematic, optimizing both efficiency and crosstalk suppression throughout the exposure period.
Solution Approach 2:
The patent applies different reverse bias voltage levels to different spatial regions or time periods based on local crosstalk conditions. By detecting avalanche luminescence levels and applying voltage adjustments locally or temporally, the system maintains high efficiency in regions/periods where crosstalk is low while suppressing crosstalk where it becomes problematic.
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 solution effectively curbs deterioration in image quality by reducing the probability of erroneous counting and luminous crosstalk, maintaining image integrity across varying exposure times and temperatures.
Implementation Method 1
photoelectric conversion devices having an APD (avalanche photodiode) digitally counting the number of photons that arrive
Implementation Method 2
photoelectric conversion element having pixels constituted of avalanche photodiodes
Implementation Method 3
a phenomenon such as avalanche luminescence occurs in photoelectric conversion devices having an APD
Implementation Method 4
the number of counts of adjacent pixel values increases due to generated secondary electrons incident on adjacent pixels
Data Source
AI summary
A photoelectric conversion device includes a photoelectric conversion element having pixels constituted of avalanche photodiodes, at least one processor, and a memory coupled to the at least one processor, the memory storing instructions that, when executed by the at least one processor, cause the at least one processor to control a reverse bias voltage applied to the avalanche photodiodes, set an exposure time of the photoelectric conversion element, and control the reverse bias voltage in accordance with the set exposure time.