SPAD Recharge Control Circuit for ToF Distance Measurement
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Solution Overview
Problem
Distance measurement using Time of Flight (ToF) techniques with Single Photon Avalanche Diodes (SPADs) faces challenges in high illuminance environments where SPAD recharge becomes impossible or takes time, leading to extended dead times and reduced accuracy.
Innovation Solution
A light receiving apparatus with a control circuit that switches between passive and active recharge methods for SPADs based on signal output, including error detection and correction, to optimize recharge strategies and minimize dead time across varying illuminance conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If passive recharge method is used for SPAD, then power consumption is reduced, but dead time increases in high illuminance environments
Solution Approach 1:
The patent implements dynamic switching between passive and active recharge methods based on real-time detection of photon reaction signals. The control circuit monitors the output signals from light receiving circuits and automatically selects the appropriate recharge method, transitioning from static to dynamic operation to optimize performance under varying illuminance conditions.
Solution Approach 2:
The control circuit receives feedback signals from light receiving circuits that have detected photons and uses this information to determine the appropriate recharge method. This feedback mechanism enables the system to adjust its operation based on actual photon detection activity, switching between recharge methods to minimize dead time while managing power consumption.
2Loss of time
If active recharge method is used for SPAD, then dead time is reduced, but power consumption increases
Solution Approach 1:
The system dynamically selects between active and passive recharge methods based on real-time conditions. When photon detection activity indicates high illuminance environments, the system switches to active recharge to minimize dead time. When activity is low, it transitions to passive recharge to reduce power consumption, making the system adaptive to changing conditions.
Solution Approach 2:
The patent changes the recharge parameter (method selection) based on operational conditions. The control circuit modifies the recharge strategy by switching between active and passive methods, effectively changing the system parameter to optimize performance. This parameter change allows the system to balance between reducing dead time and consuming power based on actual needs.
3Device complexity
If fixed recharge method is used for SPAD, then device complexity is reduced, but adaptability to varying illuminance conditions deteriorates
Solution Approach 1:
The control circuit implements dynamic decision-making by receiving signals from light receiving circuits and automatically selecting the appropriate recharge method. This dynamic approach provides adaptability to varying illuminance conditions without requiring complex manual intervention, as the system self-adjusts based on detected photon activity.
Solution Approach 2:
The system performs self-service by automatically determining which recharge method to use based on signals from its own light receiving circuits. The control circuit monitors the output of light receiving circuits and independently selects the appropriate recharge strategy, eliminating the need for external control and providing adaptive operation without adding significant complexity.
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 enables high-accuracy photon detection and distance measurement irrespective of illuminance levels by dynamically controlling the recharge method, reducing dead time and maintaining accuracy in both low and high illuminance environments.
Implementation Method 1
An avalanche photodiode (APD) is known as a light receiving element. In a Geiger-mode APD, a voltage greater than or equal to a breakdown voltage is applied across terminals, and an avalanche phenomenon occurs with an incidence of a single photon.
Implementation Method 2
it is then possible to detect a photon again
Data Source
AI summary
[Problem]To provide a light receiving apparatus, a light receiving circuit, and a distance measurement apparatus which can detect a photon with high accuracy, irrespective of illuminance in the environment.[Solution]A light receiving apparatus according to the present disclosure includes a first light receiving circuit configured such that it is possible to switch a recharge method for a light receiving element, and a control circuit configured to control the recharge method for the first light receiving circuit on the basis of a signal outputted by the first light receiving circuit in a reaction with a photon.