LiDAR Multi-Mode Waveguide Light Collection Efficiency
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Solution Overview
Problem
LiDAR systems face reduced light collection efficiency due to the inability to effectively handle spatially incoherent reflected light, even when the emitted light is spatially coherent, particularly when the outgoing light is not focused into a near-diffraction-limited spot in the far field.
Innovation Solution
A LiDAR system incorporating a single-mode optical waveguide, a multi-mode optical waveguide, and an optical switching network, along with an array of optical emitters, allows for the emission of light in a single mode and reception of light in different modes, enabling efficient collection of reflected light by routing light through a single-mode-multi-mode optical junction and using MEMS switches to control the routing of light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-mode waveguide is used to collect light, then the system maintains spatial coherence and mode purity, but light collection efficiency is reduced because only a subset of returning photons can be conveyed back into the waveguide
Solution Approach 1:
The patent segments the waveguide system into two distinct components: a single-mode waveguide for transmitting the outgoing coherent light and a multi-mode waveguide for collecting the returning reflected light. This segmentation allows each waveguide to be optimized for its specific function, resolving the contradiction between maintaining mode purity and improving light collection efficiency.
Solution Approach 2:
The patent introduces a mode scrambler as an intermediary component between the single-mode and multi-mode waveguides. The mode scrambler converts the spatially coherent single-mode light into spatially incoherent multi-mode light, enabling efficient coupling into the multi-mode waveguide while maintaining the benefits of single-mode transmission for the outgoing beam.
2Reliability
If the outgoing light is focused into a near-diffraction-limited spot in the far field, then spatial coherence is maintained, but light collection efficiency is severely reduced
Solution Approach 1:
The mode scrambler acts as an intermediary that decouples the relationship between spatial coherence and collectability. It transforms the focused, spatially coherent light into spatially incoherent light that can be efficiently collected by the multi-mode waveguide, while the single-mode waveguide ensures the outgoing light remains coherent.
3Loss of energy
If a multi-mode waveguide is used to collect reflected light, then light collection efficiency is improved, but the system cannot effectively handle spatially incoherent reflected light
Solution Approach 1:
The patent segments the functional requirements: the single-mode waveguide handles the outgoing coherent light transmission, while the multi-mode waveguide handles the incoming reflected light collection. This segmentation allows the multi-mode waveguide to efficiently collect spatially incoherent reflected light without compromising the coherence of the outgoing beam.
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 configuration enhances light collection efficiency by enabling the reception of reflected light in various modes, improving the system's ability to detect objects and reduce noise from stray light, while maintaining effective spatial resolution.
Implementation Method 1
a single-mode optical waveguide, a multi-mode optical waveguide
Implementation Method 2
The multi-mode optical waveguide and the array of optical emitters are configured to receive from the free space, by each optical emitter of the array of optical emitters, light of a mode different from the single mode
Implementation Method 3
only a subset of returning photons that pass through an aperture of the LiDAR system is successively conveyed back into the waveguide. The reduction is particularly severe if the outgoing light is not focused into a near-diffraction-limited spot in the far field
Implementation Method 4
using MEMS switches to control the routing of light
Implementation Method 5
A LiDAR system emits light into a scene (field of view) to scan the scene and receive light reflected from objects in the scene
Data Source
AI summary
A LiDAR system emits single mode light from a photonic integrated circuit (PIC) and is capable of receiving a different mode light, or multiple modes of light, into the PIC. Objects in the LiDAR's field of view may reflect light with a mode different from the mode of the light that illuminated the objects. Thus, in some embodiments, a single-mode optical waveguide, a single-mode-multi-mode optical junction, a multi-mode optical waveguide and an array of optical emitters on the PIC are configured to emit into free space light of a single mode from each optical emitter of the array of optical emitters. The multi-mode optical waveguide and the array of optical emitters are configured to receive from the free space light of a mode different from the single mode, or multiple modes, and to couple the light of the different mode or multiple modes into the multi-mode optical waveguide.