FSI Combined With Heterodyne Interferometer for Non-Cooperative Targets Distance Measurement

The frequency-scanning interferometer (FSI) is an advantageous distance measurement method. We propose an FSI-based non-cooperative target distance measurement system that is combined with a heterodyne interferometer. The heterodyne interferometer is parallel to the FSI and can measure the vibration of the target synchronously, and the measuring result is used to correct the Doppler effect in the FSI signal. To extract the vibration accurately, a circle fitting in the Lissajous curve is used to correct the influence of the multipath interference, which may damage the vibration measurement result, especially when the target is non-cooperative. Then, with a post-processing algorithm, the distance could be obtained. Finally, the distance to a non-cooperative target located at 15 m is experimentally measured using this method, and a standard deviation of 3.39 $\mu \text{m}$ is obtained.