SPAD Threshold Control Circuit for LiDAR Photon Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In LiDAR devices for autonomous driving, the fluctuating output voltage or current of single photon avalanche diodes (SPADs) in a two-dimensional array makes it difficult to uniformly set thresholds for detecting reflected light, leading to incorrect detection of photon firing.
Innovation Solution
A photodetection device with a firing detection circuit, monitor circuit, and threshold control circuit that adjusts the threshold based on monitored output signals to maximize the detection rate of photon firing, using active or passive quenching circuits to manage the cathode voltage and current, and employing a method to find an optimal threshold range that minimizes dark count rate variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uniformly set thresholds are used for all SPADs, then device complexity is reduced, but detection precision deteriorates due to output voltage/current fluctuations
Solution Approach 1:
The patent applies local quality by assigning individualized threshold values to each SPAD based on its specific output characteristics. The threshold determination circuit measures the output voltage or current of each SPAD and sets a unique threshold that matches its firing characteristics, rather than using a uniform threshold for all SPADs. This resolves the contradiction by improving detection precision through localized threshold optimization while maintaining manageable device complexity through automated threshold assignment.
2Measurement precision
If individualized thresholds are set for each SPAD, then detection precision is improved, but device complexity increases
Solution Approach 1:
The patent implements self-service by enabling each SPAD to determine its own threshold value through the threshold determination circuit. The circuit automatically measures the output characteristics of each SPAD and assigns an appropriate threshold without requiring external manual configuration. This resolves the contradiction by improving detection precision through individualized thresholds while preventing device complexity from increasing, as the system self-configures its parameters autonomously.
3Ease of operation
If fixed thresholds are used, then ease of operation is improved, but reliability deteriorates due to incorrect firing detection
Solution Approach 1:
The patent applies preliminary action by pre-determining and storing individualized threshold values for each SPAD before actual photon detection operations begin. The threshold determination circuit performs initial measurements and threshold assignments during a setup phase, so that during normal operation, the system can reliably use these pre-configured thresholds without requiring real-time adjustment. This resolves the contradiction by improving reliability through accurate individualized thresholds while maintaining ease of operation, as the preliminary threshold configuration eliminates the need for complex real-time threshold management.
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 ensures accurate detection of photon firing events by optimizing the threshold settings, reducing dark count rates, and enhancing the reliability of LiDAR systems in autonomous driving applications.
Implementation Method 1
a single photon avalanche diode (SPAD) is used as the photoelectric conversion element
Implementation Method 2
single photon avalanche diode (SPAD)
Data Source
AI summary
A photodetection device has a photodetection element, a reset circuit that sets one end of the photodetection element to a predetermined initialization voltage, a firing detection circuit that detects firing of the photodetection element by comparing a voltage at the one end of the photodetection element or a current flowing through the one end with a threshold, a monitor circuit that monitors an output signal of the firing detection circuit, and a threshold control circuit that controls the threshold based on a monitor output of the monitor circuit.