FMCW LiDAR Waveguide Layout for Longer-Range Beat Detection
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Solution Overview
Problem
Existing LiDAR technologies using FMCW technology face challenges in expanding the measurable distance range due to noise interference and overlapping beat frequencies, which limit the accuracy and range of distance and velocity measurements.
Innovation Solution
The proposed measurement apparatus employs a configuration that includes a light source, splitter, waveguides, and a photodetector, satisfying the condition fPD>2D1×Δf/cΔt, with specific optical path lengths to minimize noise interference and expand the measurable distance range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the optical path length of the first waveguide is increased to expand measurable distance range, then the measurable distance range is expanded, but noise interference increases and measurement precision deteriorates
Solution Approach 1:
The optical path is divided into multiple waveguides (first waveguide, second waveguide, third waveguide) with different optical path lengths. The first waveguide handles reflected light from distant objects, the second waveguide handles reflected light from nearby objects, and the third waveguide handles reference light. This segmentation allows each waveguide to be optimized for its specific function, reducing noise interference while expanding the overall measurable distance range.
Solution Approach 2:
The patent introduces a new dimension by adding multiple waveguides with different optical path lengths to the traditional single-waveguide FMCW LiDAR system. This dimensional expansion in the optical path length space enables the system to simultaneously measure both near and far objects with high precision, resolving the trade-off between measurable range and measurement accuracy.
2Measurement precision
If the frequency change rate is increased to improve distance resolution, then distance resolution is improved, but beat frequency increases beyond photodetector detection capability
Solution Approach 1:
The frequency modulation is segmented across different waveguides. Each waveguide processes a specific frequency range corresponding to its optical path length. This segmentation allows the system to achieve high distance resolution through frequency modulation while keeping the beat frequency within the photodetector's detection capability by distributing the frequency range across multiple channels.
3Reliability
If the optical path length difference between waveguides is increased to reduce noise interference, then noise interference is reduced, but device complexity increases
Solution Approach 1:
The optical system is segmented into multiple waveguides with specifically designed optical path length differences. The first waveguide has a longer optical path length for distant object detection, the second waveguide has a shorter optical path length for nearby object detection, and the third waveguide carries reference light. This segmentation reduces noise interference by separating different optical paths while maintaining manageable device complexity through systematic design.
Solution Approach 2:
The patent adds the dimension of multiple waveguides with different optical path lengths to the traditional single-waveguide FMCW LiDAR system. This dimensional expansion enables the system to simultaneously achieve high measurement precision for both near and far objects while managing device complexity through structured optical path design.
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 allows for a wider measurable distance range and improved accuracy in distance and velocity measurements by reducing noise interference, enabling flexible adjustment of light emission position and angle, and accommodating complex object shapes.
Implementation Method 1
a light source that emits light whose frequency varies with time
Implementation Method 2
a photodetector that detects interfering light generated by interference between the reflected light branched from the first waveguide and the reference light
Implementation Method 3
a photodetector that detects interfering light generated by interference between the reflected light branched from the first waveguide and the reference light
Implementation Method 4
a photodetector that detects interfering light generated by interference
Implementation Method 5
a first waveguide through which the irradiating light from the splitter and reflected light reflected from the physical object pass together
Data Source
AI summary
A measurement apparatus includes a light source that emits light whose frequency varies with time, a splitter that divides the light from the light source into irradiating light that is shone on a physical object and reference light, a first waveguide through which the irradiating light from the splitter and reflected light reflected from the physical object pass together, and a photodetector that detects interfering light generated by interference between the reflected light branched from the first waveguide and the reference light. The measurement apparatus satisfies fPD>2D1×Δf/(cΔt), where Δf is a change in the frequency during time Δt, c is the speed of light, D1 is an optical path length of the first waveguide, and fPD is a maximum value of a frequency that is able to be detected by the photodetector.