Synchronous measurement of velocity and distance with high resolution based on comb reference common-path interferometric FMCW lidar

Frequency modulated continuous wave (FMCW) laser measurement technology is widely used in industrial equipment calibration because it can realize high precision distance and speed synchronous measurement. However, the high-speed motion of the target will produce the phenomenon of frequency spectrum information velocity and distance coupling, which will lead to spectrum broadening and signal center frequency ambiguity. This seriously restricts the application scenarios of FMCW lidar. We propose a common-path interferometric FMCW lidar system that can be referenced to the optical frequency comb (OFC) and demonstrate its application in coherent laser velocity and distance simultaneous measurement. We take the interference peak generated by the OFC and the FMCW laser as the reference and reshape the whole measurement process to form multiple submeasurement intervals to suppress the spectrum broadening caused by the coupling of speed and distance. Compared with the existing FMCW lidar system, this method can effectively reduce the error caused by frequency modulation (FM) commutation and significantly improve the measurement resolution. The common-path interferometric structure we designed simplifies the complexity of the optical path system and improves the measurement efficiency. The experiment results show that the proposed FMCW lidar system has an error of less than 286 mu m/s and a standard deviation of less than 60 mu m/s for the 200 mm/s target, which has accurate and efficient measurement capability and broad application prospect in the industrial field.