SPAD Recharge Current Mirroring for Stable Dead Time
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Solution Overview
Problem
The length of the dead time in single photon avalanche diode (SPAD) photon detection systems varies due to temperature and manufacturing variations in transistor characteristics, making it difficult to control the recharge current and thus the dead time effectively.
Innovation Solution
A light reception device with a generation unit that generates a reference current and a copying unit that copies this reference current to supply a consistent recharge current to the SPAD, allowing for controlled dead time and improved photon detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transistor is used to generate the recharge current for the SPAD, then the device complexity is reduced, but the recharge current becomes unstable due to temperature and manufacturing variations
Solution Approach 1:
The patent uses a current mirror circuit that copies a stable reference current to generate the recharge current for the SPAD. The current mirror consists of multiple transistors configured to replicate the reference current, ensuring that the recharge current remains stable despite temperature and manufacturing variations. This copying mechanism allows the system to maintain reliable photon detection without requiring complex additional control circuits.
2Productivity
If the recharge current is increased to shorten the dead time, then the photon detection efficiency is improved, but the sensitivity of the SPAD decreases due to excessive current
Solution Approach 1:
The patent employs a current mirror circuit with specifically designed transistor parameters to generate a recharge current with an optimal magnitude. By carefully selecting the transistor dimensions and configuration in the current mirror, the system achieves a balance where the recharge current is sufficient to maintain appropriate dead time without being so large as to reduce SPAD sensitivity. This parameter optimization allows the system to achieve both high photon detection efficiency and maintained sensitivity.
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 solution enables more efficient photon detection by stabilizing the dead time and enhancing the consistency of the recharge current, leading to improved sensitivity and accuracy in photon detection.
Implementation Method 1
Light receiving elements capable of converting received light into electrical signals by photoelectric conversion
Implementation Method 2
capable of obtaining a large current in response to incidence of one photon by avalanche multiplication
Data Source
AI summary
A light reception device according to an embodiment includes: a light receiving element (10001 to 1000n) in which a current flows according to an incident photon in a state where a predetermined voltage is applied and that returns to the state by a recharge current; a generation unit (1100a) that generates a reference current; and a copying unit (10011 to 1001n) that copies the reference current generated by the generation unit to generate a copy reference current. A recharge current based on the copy reference current is supplied to the light receiving element.