Unambiguous range extension of a phase-shift based lidar by using two laser diodes with different modulation frequencies

In the phase-shift based lidar system, a distance between the lidar and an object can be determined via the phase difference between the reference signal and measured signal. The maximum unambiguous range for the phase-shift based lidar is inversely proportional to the modulation frequency of the signal. When the modulation frequency is increased for high distance resolution, the unambiguous range is decreased. In this paper, we described a method to extend the unambiguous range of the lidar, which is a considerable disadvantage of the phase-shift measurement method. In addition, we propose a method for implementing dual frequencies modulation technique with two laser diodes.