Scanning FMCW LiDAR Doppler Spread Compensation
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Solution Overview
Problem
High mirror angular speed in scanning FMCW LIDAR systems causes mirror-induced Doppler effects, leading to broadened signal bandwidth, reduced signal intensity, and increased measurement errors, lowering signal intensity, and increased measurement errors, lowering signal intensity, and measurement errors, lowering detection probability, and reducing accuracy in range, velocity, and reflectivity measurements.
Innovation Solution
A LIDAR system with an optical scanner, optical processing system, and signal processing system that determines and applies a spread function to correct for mirror Doppler spread by calibrating scanning parameters, performing deconvolution, and using a matched filter or machine learning model to compensate for Doppler shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the scanning mirror angular speed is increased to achieve wide field of view and high frame rates, then the productivity and field of view are improved, but the mirror-induced Doppler spread broadens the signal bandwidth and reduces signal intensity
Solution Approach 1:
The system pre-calculates and stores spread functions for various scanning parameters before operation. During scanning, the appropriate pre-computed spread function is selected and applied to compensate for Doppler effects, preventing the degradation of detection probability before it occurs
Solution Approach 2:
The system uses measured scanning parameters (angular velocity, position) as feedback to dynamically select and apply the appropriate spread function from stored functions, continuously compensating for Doppler spread effects during operation
2Area of stationary object
If the scanning mirror angular speed is increased to achieve wide field of view, then the area covered is improved, but the measurement precision deteriorates due to increased Doppler spread
Solution Approach 1:
The system changes the parameter of the spread function based on the instantaneous scanning parameters (angular velocity, mirror position). By dynamically adjusting the compensation function parameters to match current operating conditions, the system maintains measurement precision across the entire field of view
3Reliability
If signal processing is performed to compensate for mirror Doppler spread, then the detection probability is improved, but the device complexity increases
Solution Approach 1:
The spread functions are pre-computed and stored in memory before the LIDAR system operates. This preliminary action eliminates the need for real-time complex calculations during scanning, reducing processing complexity while maintaining detection probability
Solution Approach 2:
Instead of computing unique spread functions for each scanning condition, the system creates a library of representative spread functions that can be selected and applied to multiple similar conditions, simplifying the processing requirement
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
Enhances detection probability and accuracy in range, velocity, and reflectivity measurements by correcting for mirror Doppler spread, resulting in improved signal quality and reduced measurement errors.
Implementation Method 1
an optical scanner to transmit an optical beam towards, and receive a return signal from, a target
Implementation Method 2
The high mirror angular speed may cause several impairments. For example, the mirror-induced Doppler shift at different parts of the laser beam on the mirror may broaden the received signal bandwidth
Data Source
AI summary
A method of a LIDAR system to compensate for mirror Doppler spread includes transmitting an optical beam towards a target, receiving a return signal from the target, and generating an electrical signal comprising a set of frequencies in a first frequency spectrum. The method further includes determining a value for each of a set of scanning parameters associated with the target, determining a spread function for the frequency spectrum based on the values for each of the scanning parameters, and performing a correction of the frequency spectrum based on the spread function.