Optical Dynamic Frequency-Swept Interferometry: Theory and Applications

Frequency-swept interferometry (FSI) is an absolute distance measurement technique with a large unambiguous range, simple structure, and high flexibility. However, conventional FSI suffers from two major drawbacks: a slow measurement rate, as it provides only one measured value per sweep cycle; and high sensitivity to target motion, which necessitates that the target remain stationary or move at a constant velocity. To overcome these two limitations, dynamic FSI (DFSI) has been proposed, offering two key advantages: an ultra-high measurement rate, as it provides a distance value at each sampling point within a sweep cycle; and immunity to arbitrary motion-induced Doppler error, thereby removing motion restrictions. In addition, in certain applications, DFSI must also suppress errors caused by laser source nonlinearity, which interacts with the Doppler effect and further degrades measurement accuracy. Consequently, DFSI demonstrates strong potential for high-rate and high-accuracy distance measurement, though it is technically challenging. This chapter first introduces DFSI and presents the DFSI model along with associated signal preprocessing methods. It then discusses various DFSI approaches for eliminating Doppler errors and enhancing robustness against laser source nonlinearity. Subsequently, the applications of DFSI are presented, followed by concluding remarks.