FMCW laser ranging system based on equal-frequency resampling with direct injection current modulaton

This paper describes a laser ranging system based on modulation signal resampling to address the nonlinearity of Frequency-modulated in frequency-modulated continuous wave (FMCW) lidar. Using a 1550 nm DFB laser as a frequency-modulated light source, the modulation scheme adopts direct modulation of the injected current into the semiconductor laser. Based on the equal-frequency resampling method, the clock signal used for resampling undergoes data acquisition, data analysis, and data processing steps to identify and eliminate erroneous sampling points caused by laser frequency noise, mode hopping in frequency-modulated lasers, and sweep reversal points in the injection current. It solves the nonlinear error caused by the relaxation-oscillation effect of the prior art. Additionally, compared with the manual division of sampling points, the algorithm dividing the sampling area can retain as many correct sampling points as possible to improve the distance resolution and repeatability accuracy of the FMCW ranging system. Under the condition of approximately 20 GHz laser modulation bandwidth, the resolution of 10 m in free-space optical ranging is about 6.8 mm and the standard deviation (STD) of 1 m in free-space optical ranging is 0.19 mm.