High-resolution frequency-modulated continuous-wave laser ranging for precision distance metrology applications

Frequency-modulated continuous wave (FMCW) laser ranging is one of the most interesting techniques for precision distance metrology. In order to ensure the theoretical measurement range and precision, a narrow linewidth external cavity tunable laser with large tuning range is chosen. In practical situations, the tuning nonlinearity of the laser reduces the measurement precision, hence an auxiliary interferometer is used to measure the laser tuning rate and linearize the frequency ramp. Then, fast Fourier transform algorithm is applied to the resampled signal of the main interferometer, and the full-width at half maximum of the frequency spectrum is narrowed. In the end, the experiments are carried out using the FMCW laser ranging system and demonstrate 50-μm range resolution at 8.7 m.