FMCW LiDAR Optical Path Layout for Longer-Range Noise-Resilient Sensing
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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 from optical elements and fiber noise, which limits the accuracy and range of distance and velocity measurements.
Innovation Solution
The measurement apparatus employs a configuration with specific optical path lengths d1, d2, d4, and d5 to minimize noise interference by adjusting the optical paths, using a coaxial optical system with a splitter and waveguides to separate and combine light beams, and incorporates a processing circuit to compute distance and velocity based on beat frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FMCW technology is used to achieve wide dynamic range and high resolution, then measurement precision is improved, but noise interference from optical elements and fiber noise increases, limiting the measurable distance range
Solution Approach 1:
The optical path is divided into multiple segments using first and second waveguides with different optical path lengths. The first waveguide has optical path length L1 and the second waveguide has optical path length L2, where L1 ≠ L2. This segmentation allows the system to distinguish between signals from different distance ranges by exploiting the different phase delays introduced by the different path lengths, thereby reducing noise interference while maintaining measurement precision.
Solution Approach 2:
The patent introduces a new dimension of optical path length differentiation to separate noise from signal. By creating multiple optical paths with different lengths, the system adds a temporal dimension to the signal separation process, allowing the processing circuit to identify and eliminate noise based on the known path length differences, thus expanding the measurable distance range while preserving precision.
2Length of moving object
If optical path lengths are adjusted to minimize noise interference, then measurable distance range is expanded, but device complexity increases due to multiple waveguides and splitters
Solution Approach 1:
The patent combines multiple optical paths with different lengths into a single integrated optical system using waveguides and splitters. The first and second waveguides are coupled through a first coupler and second coupler, merging the functionality of multiple separate optical paths into one compact structure. This integration achieves extended measurable distance range while controlling device complexity through shared optical components.
Solution Approach 2:
The optical system is designed to perform multiple functions: the waveguides serve both as signal transmission media and as path length differentiation elements; the splitters and couplers simultaneously divide and combine optical paths. This multi-functionality reduces the need for separate components, thereby expanding the measurable distance range without proportionally increasing device complexity.
3Reliability
If multiple waveguides with different optical path lengths are used to separate noise and signal, then noise interference is reduced, but the number of optical components increases
Solution Approach 1:
The patent introduces couplers as intermediary components that mediate between the first and second waveguides. The first coupler and second coupler provide controlled optical coupling between the waveguides, enabling noise reduction through path length differentiation while using standardized intermediary components. This approach improves measurement reliability by systematically separating noise from signal without requiring complex custom optical structures.
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 reduces noise interference, expanding the measurable distance range and improving the accuracy of distance and velocity measurements, even in complex environments with varying optical path lengths and noise sources.
Implementation Method 1
The light source is controlled to emit light whose frequency changes with passage of time
Implementation Method 2
The photodetector detects interfering light generated by interference between the reflected light from the physical object and reference light from the light source
Implementation Method 3
Using the FMCW technology makes it possible to achieve both a wide dynamic range and high resolution for distance, makes it hard to be affected by disturbances, and makes it possible to detect not only the distance to but also the velocity of a moving physical object
Data Source
AI summary
A measurement apparatus includes a light source, a first splitter that divides light from the light source into irradiating light and reference light, a second splitter that divides the irradiating light into first irradiating light and second irradiating light, a first waveguide through which the first irradiating light and first reflected light reflected from a scene pass together, a second waveguide through which the second irradiating light and second reflected light reflected from the scene pass together, a third waveguide that branches off from the first waveguide and through which the first reflected light having passed through the first waveguide passes, a fourth waveguide that branches off from the second waveguide and through which the second reflected light having passed through the second waveguide passes, and a photodetector that detects the first reflected light, the second reflected light, and the reference light.