FMCW LiDAR Distance Measurement Correction for Non-Linearity
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Solution Overview
Problem
FMCW LiDAR systems face performance degradation due to non-linearity in frequency change between up-chirp and down-chirp durations, affecting accuracy in distance and velocity measurements.
Innovation Solution
A measurement apparatus that includes a light source with frequency modulation during both up-chirp and down-chirp durations, a photodetector for generating detection signals, and a processing circuit that uses separate correction data for each duration to correct the signals, improving measurement accuracy by accounting for non-linear frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency modulation is applied to light source for FMCW LiDAR measurement, then distance and velocity measurement capability is achieved, but non-linearity in frequency change between up-chirp and down-chirp durations degrades measurement accuracy
Solution Approach 1:
The patent divides the frequency modulation process into two distinct segments: up-chirp duration and down-chirp duration. Separate correction data are stored and applied for each segment, allowing independent optimization and correction of non-linearity characteristics for each direction of frequency change, thereby resolving the measurement accuracy degradation caused by non-linear frequency modulation.
2Measurement precision
If separate correction data for up-chirp and down-chirp durations is stored and applied, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary correction by pre-storing correction data for both up-chirp and down-chirp durations in the storage apparatus. This preliminary preparation allows the processing circuit to simply retrieve and apply the appropriate correction data during measurement, avoiding complex real-time calculations and reducing processing complexity while maintaining high measurement accuracy.
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
The solution enhances the accuracy of distance and velocity measurements by correcting detection signals based on specific correction data for each chirp duration, reducing the impact of non-linearity and improving overall measurement performance.
Implementation Method 1
a light source (110) emitting light whose frequency is modulated in a period including an up-chirp duration in which the frequency increases and a down-chirp duration in which the frequency decreases
Implementation Method 2
an interference optical system (120) splitting the light emitted from the light source into reference light and output light and generating interfering light by causing reflected light resulting from reflection of the output light on an object to interfere with the reference light
Implementation Method 3
a photodetector (130) receiving the interfering light and outputting a detection signal indicating strength of the interfering light
Implementation Method 4
a processing circuit (140) that corrects, based on correction data stored in a storage apparatus (150), the detection signal outputted from the photodetector
Data Source
AI summary
A measurement apparatus includes a light source, an interference optical system, a photodetector, a processing circuit, and a storage apparatus. The interference optical system splits light emitted from the light source into reference light and output light and generates interfering light between reflected light resulting from reflection of the output light on an object and the reference light. The photodetector outputs a detection signal corresponding to strength of the interfering light. The processing circuit modulates the frequency of the light outputted from the light source with a period including an up-chirp duration in which the frequency increases and a down-chirp duration in which the frequency decreases. The storage apparatus stores first correction data for the up-chirp duration and second correction data for the down-chirp duration. The processing circuit determines distance or velocity based on a signal obtained by correcting the detection signal based on the first or second correction data.