Multispectral LiDAR Transceiver With Polarization-Based Background Rejection
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Solution Overview
Problem
Multispectral LiDAR systems face challenges in mitigating interference from background light, which can lead to eye safety concerns and complexity in synchronization, especially when dealing with broad spectral widths or rapidly tuning wavelengths.
Innovation Solution
A simplified multispectral LiDAR transceiver that uses a pulsed broadband laser beam with polarization conversion and a wavelength selection unit to filter and steer the beam within a predefined solid angle, allowing for orthogonal polarization detection and synchronization without spectral requirements, thereby improving background rejection and eye safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a narrow band filter is placed in the receiver path to reduce background light influence, then background rejection is improved, but the system becomes complex to synchronize when using rapidly tuning wavelengths
Solution Approach 1:
The patent changes the spectral parameter from narrow band to broadband by using a supercontinuum laser source. This allows the receiver to detect all wavelengths simultaneously without requiring complex synchronization mechanisms, as the broadband source emits all wavelengths continuously rather than requiring rapid tuning
Solution Approach 2:
The patent segments the broadband spectrum into multiple wavelength channels using a tunable narrow band filter that can be sequentially tuned to different wavelengths. This segmentation allows the system to process multiple spectral channels while maintaining simple synchronization by only tuning the filter rather than the entire laser source
2Adaptability or versatility
If a broadband laser source is used to achieve multispectral capability, then spectral coverage is improved, but a significant amount of power is blocked by the tunable receiver raising eye safety concerns
Solution Approach 1:
The patent performs preliminary wavelength selection at the transmitter side using a tunable narrow band filter before the light enters the optical path. By pre-selecting the wavelength, the system ensures that only the desired narrow band of wavelengths is transmitted with high power, eliminating the need for the receiver to block power and resolving eye safety concerns
Solution Approach 2:
The tunable narrow band filter acts as an intermediary component between the broadband laser source and the optical path. It selectively transmits only the desired wavelength range while blocking other wavelengths, thereby controlling the spectral content before transmission and ensuring eye safety without compromising multispectral capability
3Object-affected harmful factors
If a tunable receiver is used to mitigate background light, then background rejection is improved, but power is lost when the transmitter has broad spectral width
Solution Approach 1:
The patent inverts the traditional approach by placing the narrow band filter at the transmitter side rather than at the receiver side. This inversion allows the system to transmit only the desired wavelength range with full power, eliminating power loss at the receiver while still achieving background light rejection through the pre-selected narrow band transmission
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 enhances background rejection, reduces crosstalk, and improves eye safety, enabling real-time colored imaging for applications like autonomous vehicles with higher scanning rates and more precise spectral response.
Implementation Method 1
a separating unit configured for transmitting the laser beam along a scanning optical path while changing the polarization into a circular one
Implementation Method 2
filtering the laser beam in order to get a filtered laser beam having a current wavelength that can be selected among a plurality of selectable wavelengths
Implementation Method 3
deflecting the filtered laser beam on a scanning unit along the scanning optical path, the scanning unit being configured to steer the deflected filtered laser beam along a plurality of current local directions inside a predefined solid angle
Implementation Method 4
the separating unit is further configured for deviating the reflections on a broadband detector while changing the orthogonal circular polarization into an orthogonal linear polarization compared to the linear polarization of the laser beam
Implementation Method 5
the broadband detector being configured to receive the deviated reflections, and to detect a time-of-flight and an optical power of the light reflection
Data Source
AI summary
A scanning device for laser detection and ranging (LiDAR), the scanning device includes, arranged in optical free space:an optical input for receiving a pulsed broadband laser beam having a linear polarization;a separating unit configured for transmitting the laser beam along a scanning optical path while changing the polarization into a circular one;a wavelength selection unit; anda scanning unit.The separating unit is configured for deviating the reflections (4) on a broadband detector while changing the orthogonal circular polarization into an orthogonal linear polarization compared to the linear polarization of the laser beam. The broadband detector is configured to receive the deviated reflections, and to detect a time-of-flight and an optical power of the light reflection.