Method of high-precision free-space distance measurement for noncooperative targets

Aimed at high-precision distance measurement for noncooperative targets in free space, a spatial distance measurement method is proposed. Based on the concept of optical carrier-based microwave interferometry, this method extracts distance information from the radiofrequency domain. The interference model of broadband light beams is established, and the optical interference can be eliminated by using a broadband light source. A spatial optical system with a Cassegrain telescope as the main body is designed to effectively receive the backscattered signal without cooperative targets. A free-space distance measurement system is built to verify the feasibility of the proposed method, and the results agree well with the set distances. Long-distance measurements with a resolution of 0.033 µm can be achieved, and the errors of the ranging experiments are within 0.1 µm. The proposed method has the advantages of fast processing speed, high measurement accuracy, and high immunity to disturbances as well as the potential for measurement of other physical quantities.