Model of a laser-frequency measuring device

The authors propose a triple frequency phase range finder in this paper. By utilising three close frequencies, the instrument is able to determine ranges with absolute high precision. At the transmitter, the three frequencies are modulated with a laser beam and the resultant signal propagated. This composite signal (three frequencies modulating a laser beam) is ultimately reflected at the target. On reception, phase measuring circuits determine the phase changes/differences suffered by the individual frequencies and eventually the range is calculated. Because the oscillators may suffer frequency instabilities at times, several readings of the same range are taken before the average is taken to ensure high accuracy. The main advantage of the instrument is that the distance is calculated almost instantaneously without any extra calculations.