Experimental Investigation on the Ranging Resolution of a FMCW Lidar

Zhenzhen Xiao,Dianzuo Yue,Zaifu Jiang,Guangqiong Xia,Zhengmao Wu

doi:10.3390/photonics9010011

Zhenzhen Xiao, Dianzuo Yue + Show 3 more

Open Access

https://doi.org/10.3390/photonics9010011

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Journal: Photonics	Publication Date: Dec 28, 2021
Citations: 5	License type: CC BY 4.0

Affiliation: Southwest University, Jingchu University of Technology

Abstract

In some previous reports about frequency-modulated continuous-wave (FMCW) Lidar, observing the longer waveform of a de-chirped signal is considered an effective scheme for further improving the ranging resolution. In this work, the ranging resolution of a FMCW Lidar is experimentally investigated, and the feasibility of such a scheme is tested. During the experiment, a FMCW signal is generated via a Mach–Zehnder modulator in the transmitted port. In the received port, the de-chirped signal is extracted based on a homodyne detection scheme and is analyzed by an electrical spectrum analyzer. Two different methods are adopted to determine the ranging resolution. One is based on a single target, for which the ranging resolution is obtained through inspecting the shift of spectral peak position as the target moves. The other is based on two targets, for which the ranging resolution is acquired through inspecting the variation of spectrum distribution as the spacing of two targets changes. The experimental results demonstrate that extending the observed duration of the de-chirped signal cannot improve the ranging resolution, and the corresponding physical mechanism is revealed.

Highlights

Compared with short-pulsed Lidar based on cross-correlated time-of-flight (ToF) detection, frequency-modulated continuous-wave (FMCW), Lidar utilizing coherence detection mechanism could provide a larger dynamic range at low average power and more outstanding resolution [1]
We focus on the dependence of the ranging resolution of this Lidar on the observed duration of the de-chirped signal via two different methods
The other is based on two targets, and the ranging resolution is acquired through inspecting the variation of spectrum distribution as the spacing of two targets changes

Summary

Introduction

Compared with short-pulsed Lidar based on cross-correlated time-of-flight (ToF) detection, frequency-modulated continuous-wave (FMCW), Lidar utilizing coherence detection mechanism could provide a larger dynamic range at low average power and more outstanding resolution [1]. FMCW Lidar can be utilized to simultaneously measure the distance and the velocity of a target without increasing the cost and systematic complexity. In order to achieve high-accuracy measurement, a FMCW signal with excellent linearity is required as the emitted source of the Lidar. Based on the variation of the lasing frequency of a semiconductor laser (SL) with its current, a FWCM signal can be generated by a SL under current-modulation with a swept signal [8]. Such a generated technique is relatively simple, the linearity of the generated FMCW signal is relatively poor due to the nonlinear response of SL. In order to compensate for the nonlinearity, some schemes are proposed through introducing pre-distortion or adopting dual-path systems [9,10]

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