Review of nonlinearity correction of frequency modulated continuous wave LiDAR measurement technology

Li Chaolin; Liu Junchen; Zhang Fumin; Qu Xinghua

doi:10.12086/oee.2022.210438

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Li C L, Liu J C, Zhang F M, et al. Review of nonlinearity correction of frequency modulated continuous wave LiDAR measurement technology[J]. Opto-Electron Eng, 2022, 49(7): 210438. doi: 10.12086/oee.2022.210438

Citation:

Li C L, Liu J C, Zhang F M, et al. Review of nonlinearity correction of frequency modulated continuous wave LiDAR measurement technology[J]. Opto-Electron Eng, 2022, 49(7): 210438. doi: 10.12086/oee.2022.210438

Review of nonlinearity correction of frequency modulated continuous wave LiDAR measurement technology

1.
School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China
2.
State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China

Fund Project: National Key Research and Development Program of China (2018YFB2003501)

More Information

^*Corresponding author: zhangfumin@tju.edu.cn

Received Date 17 January 2022

Revised Date 08 April 2022

Published Date 25 July 2022

Abstract

Abstract

In modern measurement technology, frequency modulation continuous wave LiDAR combines the advantages of traditional radar and laser interferometry and plays an important role in the fields of the large-size space precision measurement, micro-distance measurement, and three-dimensional imaging with its characteristics such as non-contact, large measurement range, high resolution, and strong anti-jamming capability. However, in practical application, the frequency modulation of the laser light source can’t be completely linear, which greatly reduces the measurement accuracy of the frequency modulation continuous wave LiDAR technology. Therefore, how to suppress the effects of the laser frequency modulation nonlinearity has become a hot research topic in the field of frequency modulation continuous wave LiDAR measurement. This paper introduces the basic principle of the frequency modulation continuous wave LiDAR, and introduces four widely used nonlinear correction methods and some special nonlinear correction methods according to the different nonlinear correction schemes of the frequency modulation, and makes summaries and prospects.
- frequency modulation continuous wave /
- LiDAR /
- interferometry /
- nonlinear correction

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References

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Overview

Overview

In the 1980s, Skolnik from Switzerland proposed a theoretical model of frequency modulation continuous wave (FMCW), and single-mode semiconductor lasers were also gradually used by researchers, which led to the formation of the frequency modulated continuous wave (FMCW) LiDAR. Frequency modulation continuous wave LiDAR is a kind of laser detection and ranging, which belongs to coherent detection. FMCW LiDAR combines the advantages of traditional radar and laser interferometry and has the advantages of large measurement range, high precision, high sensitivity, fast speed, high resolution, no distance blind zone, low transmission power, strong anti-interference ability, and no need to cooperate with targets. It is widely used in various fields such as large-scale and precision equipment manufacturing, atmospheric exploration, aerospace, and the 3D imaging because of these advantages.

In principle, the FMCW LiDAR ranging system uses the interference of the frequency linearly modulated laser emission signal and echo signal to form a stable beat signal, then calculate the target’s distance based on the frequency or phase of the beat signal. Therefore, the FMCW LiDAR ranging system has very strict requirements on the linearity of frequency modulation. However, the frequency modulation of laser light source can’t be completely linear in practical application, seriously affecting the ranging accuracy, and resolution. This makes the nonlinearity correction of the FM become the research focus of the FMCW LiDAR ranging systems. According to the different correction schemes, we can summarize the methods of frequency modulation nonlinear correction into frequency sweep active linearization based on the phase-locked loop feedback, equal optical frequency interval resampling, optical frequency comb correction method, phase ratio method, and some other special correction methods, such as on-chip modulator-based approaches. These nonlinear correction methods have their advantages and disadvantages. And this paper introduces and analyzes the principles and research progress of these methods.

Although the FMCW LiDAR measurement technology has gradually matured, further exploration and research is still needed. At present, most of the nonlinear correction methods focus on the optical system and signal processing, but we hope to solve the problem from the design of the laser itself, and make further improvements in its mechanical structure, circuit design, and temperature control to avoid subsequent complicated work. In order to achieve true intelligence, on the one hand, we need to improve the efficiency of measurement (especially three-dimensional imaging). On the other hand, we must strive to miniaturize and integrate the FMCW LiDAR measurement system to bring more convenience and wider application scenarios.