LiDAR Late-Lock Geiger Detection for Low-False-Alarm TOF
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Solution Overview
Problem
Existing LiDAR systems face challenges in accurately determining the time-of-flight of laser pulses due to unpredictable arrival times of reflected signals and high computational overhead in data processing, leading to false alarms and excessive data bandwidth requirements.
Innovation Solution
Employing a late-lock Geiger mode detection system with asynchronous avalanche photodiodes and a holdoff time between pulses that is equal to but slightly less than the laser pulse period, reducing synchronization delay to less than 10 nanoseconds, allowing for real-time data processing and minimizing noise integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional synchronous Geiger mode detection is used, then detection sensitivity is improved, but false alarms increase and data processing overhead becomes excessive
Solution Approach 1:
The patent implements dynamic holdoff time adjustment where the holdoff period is set to be slightly less than the laser pulse period, allowing the system to adaptively optimize between detection sensitivity and false alarm reduction. This dynamic timing parameter enables the photodetector to remain sensitive to valid returns while rejecting noise and spurious signals.
Solution Approach 2:
The system changes the temporal parameter of the holdoff time to resolve the contradiction. By setting holdoff time to be substantially equal to but slightly less than the laser pulse period, the system achieves optimal balance between maintaining detection sensitivity for valid laser returns and reducing false alarms from noise, thereby improving reliability without sacrificing measurement precision.
2Loss of information
If traditional LiDAR data processing is used, then complete data capture is achieved, but computational overhead and bandwidth requirements become excessive
Solution Approach 1:
The patent extracts and processes only the most critical timing information (time-of-flight measurements) while discarding redundant data. By focusing computation on essential parameters rather than processing all raw detector signals, the system maintains complete data capture for ranging purposes while dramatically reducing computational overhead and bandwidth requirements.
Solution Approach 2:
The system performs partial processing by selectively handling only the necessary data elements required for accurate ranging. Rather than processing complete data sets, the patent implements partial action on timing-critical information, achieving sufficient data capture completeness for LiDAR functionality while minimizing computational complexity.
3Productivity
If shorter holdoff time is used, then data bandwidth efficiency is improved, but noise integration increases
Solution Approach 1:
The patent optimizes the holdoff time parameter to be substantially equal to but slightly less than the laser pulse period. This precise parameter setting allows the system to achieve high data bandwidth efficiency by enabling rapid photodetector rearming while simultaneously minimizing noise integration, as the holdoff duration is carefully tuned to exclude noise periods while capturing valid returns.
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 approach enhances LiDAR performance by reducing false alarms, minimizing data processing requirements, and achieving a 10X improvement in data bandwidth efficiency, enabling real-time data processing with reduced computational overhead.
Implementation Method 1
a brief laser light pulse is emitted and a reflected light pulse is detected
Implementation Method 2
reflected light pulse is detected while the time between the emitted light pulse and the reflected light pulse is measured
Implementation Method 3
asynchronous avalanche photodiodes with a holdoff time between photodiode arm pulses
Data Source
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AI summary
A LiDAR system is proposed, which comprises: a pulsed laser for providing and transmitting towards an object an optical signal (LA_XMIT) which is reflected from the object thereby producing a reflected signal (LA_RCV), an avalanche photodiode (APD) photodetector for detecting the reflected signal (LA_RCV), a processing system for determining a time difference (TOF) between when the optical signal (LA_XMIT) is transmitted and when the reflected signal (LA_RCV) is detected, a synchronization delay between APD quench and APD arm, the synchronization delay defined by the following relationship: Synchronization Delay=(DurationLPP-DurationHO), wherein DurationLPP is the duration of the laser pulse period and DurationHO is the duration of a holdoff time; and wherein laser pulse period is the time period between transmission of optical signal pulses, holdoff time is a time period before the end of a detection frame during which GmAPD photodetector elements are disarmed and trapped charges in the GmAPDs can detrap and recombine.