Phase-TOF: single shot interferometric pulse laser ranging with nanometer accuracy

Pulse ‘time of flight’ and interferometric measurement have long been two major approaches of laser ranging, with the former featuring simple and robust, suitable for long distance absolute ranging in a relatively poor accuracy and the latter behaving highly precise but complicated, suitable for follow-up measurement. Here we show these two approaches can be combined together to realize highly accurate and dynamic interferometric pulse laser ranging. By incorporating four frequency stabilized lasers to constitute a set of cascaded synthetic wavelengths, interferometric phase information of laser pulses can be effectively utilized to determine the ranging distance at up-to MHz pulse repetition rate with nano-meter accuracy. Pulse averaging was applied in the preliminary experiments while single shot ranging can be expected with improved apparatus. The approach can be used broadly to improve the performance of space-based telescope array, lithography and high precision three-dimensional survey Light Detection and Ranging (LiDAR).