Efficient method for the compensation of dispersion mismatch in the frequency-scanning interferometry

Absolute distance measurements could be achieved by the technique of frequency scanning interferometry (FSI), which could provide a micron-level accuracy over several tens of meters. However, as the scanning range and distance increasing, the measurement accuracy and resolution would be seriously influenced by the dispersion mismatch effect, which is mainly caused by the dispersion difference between optical fiber and air. A dispersion compensation method was proposed in this paper, and the mismatch effect would be suppressed effectively without complicated calculations for each single measurement. The chirp in resampling clock would be corrected with a pre-calibration procedure, and the compensation factor is demonstrated for different distances. A calibration method of dispersion compensation factor is also proposed, and the linear regression residual is employed as the criterion. Then, the compensation method is evaluated by experiments with different spatial distances and scanning ranges. Finally, a 60-m experiment is carried out for accuracy comparison, and the measurement accuracy is better than 15 µm by comparing with commercial interferometers.