Frequency Modulation Nonlinear Correction and Ranging in FMCW LiDAR
Yuchen Jiang, Miao Hu, Mengmeng Xu, Haozhen Li, Xuefang Zhou, Meihua Bi, Sunqiang Pan, Chong Liu
Abstract
The linearity of the laser frequency modulation is a crucial factor that affects the performance of the frequency-modulated continuous wave (FMCW) LiDAR ranging. Nonlinearity can influence ranging resolution and introduce errors. This paper proposes a method for correcting frequency modulation nonlinearity based on waveform preprocessing for the modulation signal of the laser. After correction, the residual nonlinearity (1-r2) of the laser is reduced to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.85\times 10^{-4}$ </tex-math></inline-formula> for the up-sweeping and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8.47\times 10^{-4}$ </tex-math></inline-formula> for the down-sweeping using the modulation signal with the repetition frequency of 50 kHz. The full-width at half of the maximum (FWHM) of the spectrum decreases by 86% compared to pre-correction, resulting in the ranging error of 0.37% at the distance of 38 cm. With distances of 0.90 m, 1.80 m, 2.89 m, and 4.13 m, respectively, the ranging error stabilizes at 0.2%, and the minimum deflection of distance can reach <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8~\mathrm {\mu m}$ </tex-math></inline-formula>.