Absolute Distance Measurement Based on Coherent Detection by Femtosecond Optical Frequency Comb

An absolute distance measurement method is proposed based on coherent detection by a femtosecond optical frequency comb. The absolute distance measurement is realized by the detection of coherence patterns between measurement signals and reference signals. The measurement model of the first-order coherence function is studied. The measurement system based on an unbalanced Michelson interferometer is constructed. The target distance is obtained by the envelope fitting of the first-order coherence function and by the high-precision extraction of peaks on the overlapped pulse positions. The 3 m absolute distance measurement experiment on a long range guide is designed and a real-time comparison with those by the commercial interferometers is conducted. In addition, the ambient factors and system errors arc analyzed based on a large number of experimental results. The errors arc eliminated and compensated. The results show that in the 500 min long term measurement process, the maximum measurement error is 5.85 m and the standard deviation is 2.20 m as for the proposed method with a measurement range of 3 m.