LiDAR Optical Lens Alignment via LO Signal Fitting
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Solution Overview
Problem
FMCW LiDAR systems face challenges in precisely aligning optical lenses to maximize the signal-to-noise ratio due to the difficulty in aligning the optical lens with respect to the local oscillator and target return signals, especially at high scan speeds which lead to spatial misalignment and reduced performance.
Innovation Solution
The method involves placing the optical lens at a test position, moving it laterally across the detector to determine the characteristic line shape using fitting functions like Gaussian or Sigmoid, and adjusting its position to find the minimum beam width, then applying an offset to achieve precise alignment along all three axes, thereby improving the signal-to-noise ratio and system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical lens is manually aligned with respect to the LO signal and target return signal, then the alignment precision can be improved, but the alignment time and system complexity increase significantly
Solution Approach 1:
The system performs self-alignment by automatically measuring the LO signal distribution at multiple positions and using fitting functions to determine the optimal lens position. The processor autonomously calculates the beam center coordinates and adjusts the lens position without manual intervention, making the system self-sufficient in the alignment process.
Solution Approach 2:
The patent replaces manual mechanical alignment with an automated optical measurement and computational system. Instead of physically adjusting the lens by hand, the system uses a detector to measure signal distribution, processes the data through fitting functions, and automatically determines the optimal position, substituting mechanical adjustment with optical-electrical-computational methods.
2Reliability
If the optical lens is precisely aligned to maximize signal-to-noise ratio, then the LiDAR system performance is improved, but the difficulty of alignment and system complexity increase
Solution Approach 1:
The patent introduces a detector as an intermediary element between the LO signal and the processing system. The detector measures the signal distribution and provides data to the processor, which then uses fitting functions to determine the optimal lens position. This intermediary measurement system simplifies the alignment process while maintaining high precision.
Solution Approach 2:
The system implements a feedback mechanism where the detector continuously measures the LO signal distribution at different lens positions, and the processor uses this feedback information to calculate the optimal position through fitting functions. This closed-loop approach ensures high signal-to-noise ratio while automating the alignment process.
3Productivity
If the optical lens is aligned at high scan speeds, then the productivity of the LiDAR system is improved, but spatial misalignment occurs reducing measurement precision
Solution Approach 1:
The patent performs preliminary alignment by measuring the LO signal distribution and determining the optimal lens position before the actual LiDAR scanning operation begins. This pre-alignment ensures that the lens is correctly positioned to handle high-speed scanning without spatial misalignment, maintaining measurement precision even at high productivity levels.
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 accurate and fast alignment of the optical lens, enhancing the signal-to-noise ratio and overall performance of the LiDAR system by compensating for descan effects and maintaining efficient signal mixing.
Implementation Method 1
An optical lens is used to focus the target return signal and local signal onto the detector (e.g., photodetector)
Implementation Method 2
A FMCW LiDAR system mixes a local oscillator (LO) signal (e.g., LO beam) with a target return signal (e.g., target beam), which is the reflected light from a target
Data Source
AI summary
A method of aligning an optical lens in a LiDAR system includes emitting an optical beam by an optical source. The method includes placing the optical lens in front of a photodetector at a first predetermined position. The method further includes moving the optical lens to a plurality of Z-positions along a direction of an optical axis, the plurality of Z-positions corresponding to a plurality of parameter values of the LO signal. The method further includes generating a fitting function based on a set of values of the LO signal; and determining a parameter value of the LO signal for each Z-position. The method includes determining an initial Z-axis position of the optical lens by selecting a Z-position from the plurality of Z-positions based on a plurality of parameter values. The method includes determining a final Z-position of the optical lens by adding an offset to the initial Z-axis position.