Coherent LiDAR Doppler Disambiguation via Variable Frequency Slopes
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Solution Overview
Problem
Current LiDAR systems face challenges in disambiguating Doppler frequency shift from range measurement, leading to increased computational complexity and processing time, especially when determining the velocity and range of targets.
Innovation Solution
The proposed solution involves an optical transmitter that scans a series of points with varying frequency slopes in each frame, allowing for the combination of partial data from different frames to disambiguate Doppler frequency shift, reducing the need for multiple frequency chirps at each point and leveraging data from nearby points to enhance signal processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple frequency chirps are performed at each point to disambiguate Doppler frequency shift, then measurement precision is improved, but processing time increases
Solution Approach 1:
The patent applies preliminary action by performing frequency sweeps with different slopes at different points in the scan before completing all measurements. This allows the system to establish initial Doppler frequency estimates from early measurements, which then serve as reference information for disambiguating later measurements without requiring multiple complete frequency chirp cycles at each point.
Solution Approach 2:
The patent merges measurements from multiple points and multiple frequency sweeps into a unified processing approach. By combining partial data from different frames and different points, the system creates a composite data set that enables Doppler disambiguation across the entire scan, rather than processing each point independently with multiple chirps.
2Measurement precision
If multiple frequency chirps are performed at each point to disambiguate Doppler frequency shift, then measurement precision is improved, but computational complexity increases
Solution Approach 1:
The system performs preliminary frequency sweeps with different slopes to establish initial Doppler estimates before final processing. This preliminary action reduces the computational burden of the final disambiguation step by providing pre-established reference information that constrains the solution space.
Solution Approach 2:
The patent uses partial data from frequency sweeps at different points to achieve Doppler disambiguation without requiring complete data sets from all points. By using available partial measurements strategically, the system avoids the computational burden of processing all possible combinations while still achieving accurate disambiguation.
3Reliability
If multiple frequency sweeps are performed at each point, then reliability of velocity measurement is improved, but productivity decreases
Solution Approach 1:
The system performs preliminary frequency sweeps with different slopes during the scanning process itself, rather than requiring separate measurement passes. This allows velocity measurement reliability to be improved while maintaining scanning productivity, as the preliminary sweeps are integrated into the normal scanning operation.
Solution Approach 2:
The patent maintains continuous scanning operation while simultaneously performing multiple frequency sweeps at different points. The useful action of scanning continues uninterrupted, while Doppler disambiguation is achieved through continuous data collection and processing across multiple sweeps, rather than pausing for separate measurement cycles.
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 reduces computational complexity and processing time by disambiguating Doppler frequency shift from range measurement, allowing for accurate determination of target velocity and range without the need for multiple frequency chirps at each point, thereby improving LiDAR system performance.
Implementation Method 1
An optical wave is transmitted from an optical source to target object(s) at a given distance and the light backscattered from the target object(s) is collected
Implementation Method 2
In a coherent LiDAR system the collected light is combined with a local oscillator (LO) that is coherent with the transmitted optical wave
Implementation Method 3
Some LiDAR systems optimize various aspects of the LiDAR configuration based on different criteria... determining the velocity and range of targets
Data Source
AI summary
Modulation of a frequency of a transmitted optical wave includes: at least a first and second slopes for respective frequency sweeps associated with respective points in at least one of a first or second frame. A computed range and a computed velocity are determined based on combining first partial data derived from at least one measurement associated with a first backscattered portion of the transmitted optical wave with second partial data derived from at least one measurement associated with a second backscattered portion of the transmitted optical wave. The first backscattered portion is received during a frequency sweep at the first slope associated with a first point in the first frame. The second backscattered portion is received during a frequency sweep at the second slope associated with a second point in the first frame different from the first point or associated with at least one point in the second frame.