Coherent LiDAR Ranging with Shared Light Source and FFT Beat Detection
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Solution Overview
Problem
Existing LiDAR systems face high costs due to multiple light sources and complex frequency control configurations, which affect accuracy and increase costs, especially in coherent LiDAR systems.
Innovation Solution
A distance measuring device with a shared light source for both transmission and local oscillation beams, individually controlled for light emission and extinction, and optical deflection based on frequencies to generate and detect interference beams, reducing the need for multiple light sources and simplifying frequency control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple light sources are used for transmission beams and reference beams in LiDAR, then distance measurement accuracy is improved, but device cost increases
Solution Approach 1:
The patent merges the light source function by using a single light source to generate both transmission beams and reference beams through frequency division. The light source is divided into multiple frequency channels, where some channels serve as transmission beams and others serve as reference beams, eliminating the need for separate light sources for each function.
Solution Approach 2:
The single light source is designed to perform multiple functions by generating different frequency components that serve dual purposes. The same light source generates both the modulation light for distance measurement and the reference light for interference detection, making the light source a universal component that reduces system complexity and cost.
2Measurement precision
If frequency difference control is increased to maintain measurement accuracy, then distance measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the frequency parameter by introducing frequency division into the light source output. Instead of controlling frequency differences between separate light sources, the system divides one light source into multiple frequency channels, where the frequency difference between transmission and reference beams is determined by the channel assignment rather than complex control mechanisms.
3Measurement precision
If light receiving unit configuration is increased to achieve high accuracy, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent combines the reception of transmission beams and reference beams into a single light receiving unit. Instead of requiring separate reception paths for different beam types, the system uses one photodetector to receive all frequency components, which are then separated and processed through frequency-domain filtering and correlation analysis.
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 high-accuracy distance and relative speed measurement at a lower cost by optimizing light source usage and frequency control, enhancing measurement efficiency and reducing overall device costs.
Implementation Method 1
an optical deflection unit that deflects the transmission beams at angles depending on the frequencies
Implementation Method 2
a detection unit that detects an interference beam generated by interference with a reception beam received by reflection of the transmission beams by a measurement target
Data Source
AI summary
Provided is a distance measuring device and a distance measuring method capable of achieving LiDAR with high accuracy at low cost. In a plurality of division times obtained by dividing a modulation cycle for chirp-modulating frequencies of transmission beams of a plurality of channels, light emission and extinction of a plurality of light sources are controlled in a unique pattern for each light source, an interference beam between a reception beam and a transmission beam is detected, digitized into a reception signal sequence, and subjected to FFT to obtain a frequency spectrum, a beat frequency is specified from comparison of magnitude of peaks, and a distance to a measurement target and a relative speed are measured. The present disclosure can be applied to LiDAR.