Redundant APD Bias Timing for LiDAR Blinding Mitigation
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Solution Overview
Problem
Avalanche photodiodes (APDs) in LIDAR systems suffer from blinding spots due to saturation, making it difficult to detect multiple return light signals accurately, as they become insensitive to light during reverse bias recovery, limiting the system's ability to detect peaks in multi-return signals.
Innovation Solution
Implementing a redundant APD system with space and time diversity, where a secondary attenuated APD operates off the main optical plane and with a delayed bias signal to minimize saturation and detect hidden pulses, combining signals using MIMO processing to enhance detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single APD is used to detect light signals, then the device complexity is low, but the measurement precision deteriorates due to blinding spots caused by saturation
Solution Approach 1:
The system divides the detection function into multiple independent APDs (primary and secondary), where each APD handles specific detection tasks. The primary APD detects strong return signals while the secondary APD detects weaker signals that would otherwise be missed due to saturation, thereby segmenting the detection range to maintain precision across varying signal intensities
Solution Approach 2:
The patent employs variable attenuation applied to the secondary APD signal path, dynamically adjusting the attenuation level based on the detected signal strength. This parameter change allows the system to adapt to different lighting conditions and maintain optimal detection precision across varying signal intensities without being limited by fixed detection thresholds
2Measurement precision
If the APD operates at high sensitivity to detect weak signals, then the measurement precision improves, but the reliability deteriorates due to increased susceptibility to saturation and blinding spots
Solution Approach 1:
The patent introduces an intermediary attenuation mechanism in the secondary APD signal path that mediates between the need for high sensitivity to detect weak signals and the need to avoid saturation. By dynamically adjusting attenuation levels, the system allows the secondary APD to operate at high sensitivity without becoming vulnerable to saturation from stronger signals
Solution Approach 2:
The detection system combines multiple APDs with different characteristics (primary APD for strong signals, secondary APD for weak signals) into a composite detection architecture. This composite approach leverages the strengths of each APD type while compensating for their individual weaknesses, achieving both high precision and reliability across varying light conditions
3Productivity
If the APD recovery time is reduced to detect multiple returns quickly, then the productivity improves, but the measurement precision worsens due to insufficient recovery from saturation
Solution Approach 1:
The system performs preliminary detection using the primary APD for strong return signals, allowing the secondary APD to be pre-configured with appropriate attenuation settings before detecting subsequent weaker returns. This preliminary action enables the system to prepare for and accurately detect multiple returns in quick succession without sacrificing precision
Solution Approach 2:
The patent implements periodic switching between primary and secondary APDs based on the detection needs, with the secondary APD activated periodically to detect weaker return signals that occur after stronger ones. This periodic action pattern allows the system to maintain high detection rates while ensuring accurate detection of each return signal through appropriate APD selection
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 redundant APD system effectively mitigates blinding spots, allowing for accurate detection of multi-return light signals by decoding hidden pulses and improving the overall performance of LIDAR systems in environments with saturated APDs.
Implementation Method 1
Avalanche photodiodes (APDs) in LIDAR systems suffer from blinding spots due to saturation
Implementation Method 2
Since the photodiodes of the LIDAR systems may saturate and exhibit reverse bias avalanche recovery phenomena
Data Source
AI summary
Described herein are systems and methods that that mitigate avalanche photodiode (APD) blinding and allow for improved accuracy in the detection of a multi-return light signal. A blinding spot may occur due to saturation of a primary APD. The systems and methods include the incorporation of a redundant APD and the utilization of time diversity and space diversity. Detection by the APDs is activated by a bias signal. The redundant APD receives a time delayed bias signal compared to the primary APD. Additionally, the redundant APD is positioned off the main focal plane in order to attenuate an output of the redundant APD. With attenuation, the redundant APD may not saturate and may have a successful detection during the blinding spot of the primary APD. Embodiments may include multiple primary APDs and multiple secondary APDs.