Single-Photon LiDAR Ranging With Geiger-Mode APD Correlation
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Solution Overview
Problem
Current pulse-based LiDAR systems using linear-mode avalanche photodiodes face inefficiencies due to low-power laser sources, which affect distance measurement precision, especially under low-light conditions and with low-reflectance targets, leading to increased noise and time-walk errors.
Innovation Solution
Implementing a LiDAR device with Geiger-mode avalanche photodiodes that utilize modulated light with a binary code sequence for single photon detection, allowing for improved signal-to-noise ratio and reduced noise susceptibility by determining time-of-flight based on cross-correlation of the received digital signal with the emitted binary code.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If linear-mode avalanche photodiodes are used with low-power laser sources, then human vision safety is maintained, but measurement precision deteriorates due to insufficient signal strength for distant or low-reflectance targets
Solution Approach 1:
The patent changes the operating mode of the avalanche photodiode from linear-mode to Geiger-mode, which fundamentally alters the detection mechanism. In Geiger-mode, the APD operates above breakdown voltage and detects single photons through avalanche multiplication, enabling detection of weak reflected signals from distant or low-reflectance targets while maintaining compatibility with low-power laser sources that are safe for human vision
Solution Approach 2:
The patent replaces the conventional linear-mode detection mechanism with a single-photon detection mechanism. By using Geiger-mode avalanche photodiodes, the system substitutes the analog signal detection approach with a digital single-photon counting approach, dramatically improving sensitivity and measurement precision without requiring higher laser power
2Object-affected harmful factors
If low-power laser sources are used, then safety requirements are met, but signal-to-noise ratio deteriorates leading to increased noise and miss-detection errors
Solution Approach 1:
The patent changes the detection parameter from analog signal amplitude measurement to single-photon counting. By operating the avalanche photodiode in Geiger-mode with threshold detection, the system can reliably distinguish true photon signals from noise, achieving high signal-to-noise ratio even with low-power laser sources that satisfy safety requirements
Solution Approach 2:
The patent implements a feedback mechanism where the detected photon signals are processed through correlation algorithms that compare received signals with expected transmission patterns. This feedback processing enhances the signal-to-noise ratio by distinguishing genuine reflected photons from noise or miss-detections, maintaining reliability while using safe low-power laser sources
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
Enhances the accuracy of time-of-flight measurements and distance determination in autonomous vehicles by reducing noise and miss-detection errors, even with low-power laser sources and in low-light situations.
Implementation Method 1
Geiger-mode avalanche photodiodes that utilize modulated light with a binary code sequence for single photon detection
Implementation Method 2
detect objects by measuring time-of-flight (ToF) information and then getting the distance from surrounding spots
Data Source
AI summary
In one embodiment, a computer-implemented method performed by an autonomous driving vehicle (ADV) that utilizes a light detection and range (LiDAR) device that includes a light emitter and an optical sensor, the method emits, using the light emitter, an optical signal onto an object. The method receives, using the optical sensor, at least a portion of the optical signal reflected by the object. The method produces a digital signal based on the received portion of the optical signal and determines a position of the object based on the digital signal and the optical signal.