Avalanche Photodiode Counting Control Under High-Luminance Recharging
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Solution Overview
Problem
The existing photon-counting photoelectric conversion apparatus fails to accurately count periods of avalanche multiplication when high-luminance light is incident, leading to undercounting and reduced image luminance due to photon detection during recharging periods.
Innovation Solution
A photoelectric conversion apparatus with a photodiode, a generation circuit, and control circuits that generate and manage control signals to accurately detect and count periods of avalanche multiplication, using an AND circuit to determine photon incidence and a pulse generation circuit to manage the photodiode's recharging state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reset pulse is input to recharge the photodiode, then the photodiode returns to standby state, but photon detection during recharging causes undercounting and reduced image luminance
Solution Approach 1:
The patent introduces a control signal as an intermediary between the reset pulse and the counting operation. The control signal is generated by ANDing the reset pulse with its inverted form, creating a precise timing signal that enables the counting circuit only during valid avalanche multiplication periods and disables it during recharging periods, thereby preventing undercounting while maintaining accurate photon detection
Solution Approach 2:
The patent implements feedback by using the reset pulse itself (which indicates recharging state) to generate the control signal that gates the counting operation. By feeding back the reset pulse timing information to the counting enable logic, the system automatically adjusts counting activity based on the photodiode's operational state, preventing detection during recharging while maintaining detection during standby periods
2Quantity of substance
If the apparatus detects photons during recharging periods, then more photons are detected, but the counting accuracy decreases due to undercounting
Solution Approach 1:
The patent applies dynamics by making the counting operation conditional rather than continuous. The counting circuit dynamically enables and disables based on the control signal generated from the reset pulse timing. This dynamic gating ensures that counting occurs only during appropriate avalanche multiplication periods and is suppressed during recharging periods, maintaining both detection quantity and 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
Enables accurate detection of avalanche multiplication periods, even during high-luminance conditions, thereby improving image luminance and reliability of photon counting.
Implementation Method 1
a photodiode configured to perform avalanche multiplication
Data Source
AI summary
A photoelectric conversion apparatus includes a photodiode, a generation circuit, a first control circuit, and a second control circuit. The photodiode is configured to perform avalanche multiplication. The generation circuit is configured to generate a control signal. The first control circuit is configured to be controlled by the control signal to be in a standby state where the avalanche multiplication by the photodiode is possible and in a recharging state for returning the photodiode having performed the avalanche multiplication to the standby state. The second control circuit is configured to count a number of periods in which the avalanche multiplication has occurred among a plurality of periods of the standby state by using the control signal and a signal corresponding to an output of the photodiode.