LiDAR Aperiodic Pulse Train Spectral Delay Unit
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Solution Overview
Problem
LiDAR devices face challenges in discriminating between pulses with different signatures in noisy environments, leading to ambiguity in identifying which pulse is returned, especially when signal-to-noise ratios are low, and filtering reduces information per pulse.
Innovation Solution
A LiDAR device that emits an aperiodic pulse train with non-uniform time intervals, allowing for the determination of pulse rank and time-of-flight even in low signal-to-noise situations, using a spectral delay unit like a superstructured Fiber Bragg Grating to transform a broadband laser pulse into a pulse train with each pulse at a different wavelength, enabling spectral discrimination with a single detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If filtering is used to discriminate pulses based on information channels, then a single detector can be used achieving best sensitivity, but information per pulse is reduced by the number of channels
Solution Approach 1:
The pulse train is segmented into multiple pulses with different time intervals, where each pulse carries information for a specific depth range. This segmentation allows the single detector to process multiple channels simultaneously without filtering, preserving information while maintaining sensitivity.
Solution Approach 2:
The patent transitions from spectral dimension discrimination to temporal dimension discrimination. Instead of using filters in the spectral domain, the system encodes channel information in the time domain through non-uniform pulse intervals, allowing a single detector to resolve multiple channels based on arrival time differences.
2Device complexity
If monochromatic wavelength is used for LiDAR operation, then the system is simpler, but spectral reflectance diversity cannot be recorded
Solution Approach 1:
The patent changes the wavelength parameter by using broadband light sources instead of monochromatic lasers. This enables the system to capture spectral reflectance information across multiple wavelengths simultaneously, increasing versatility while maintaining relatively simple system architecture through the use of a single detector with temporal resolution.
3Device complexity
If uniform time intervals are used between pulses, then the pulse train is simpler to generate, but pulse rank identification becomes ambiguous when pulses are missing
Solution Approach 1:
The patent introduces asymmetric, non-uniform time intervals between pulses in the pulse train. This asymmetry creates a unique temporal signature for each pulse position, enabling unambiguous identification of pulse rank even when pulses are missing or detected out of sequence, thereby improving reliability without significantly increasing generation 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
This approach allows for accurate distance measurement and spectral characterization of objects in noisy conditions without losing information, improving the signal-to-noise ratio and reducing ambiguity, enabling 100% higher measurement distance with the same pulse energy.
Implementation Method 1
determine a delay of reception of a detected pulse, which is the addition of a time-of-flight and a function of the time-interval associated to the determined rank of the detected pulse
Implementation Method 2
using a spectral delay unit like a superstructured Fiber Bragg Grating to transform a broadband laser pulse into a pulse train with each pulse at a different wavelength
Data Source
AI summary
Disclosed is a laser detection and ranging, or LiDAR, device, adapted to: detect pulses from an aperiodic pulse-train of successive pulses, wherein each pulse has a rank in the pulse-train, and wherein a pulse having a defined rank is separated from the pulse of next rank above by a predefined time interval, wherein the predefined time interval is associated with the defined rank, such that the pulse-train form a series of predefined time intervals, wherein the predefined time interval is a predefined delay function of the rank.