A laser displacement measurement system including a radiation source for transmitting radiation to a target, an R.F. transmitter oscillator for modulating the amplitude of the radiation at a first frequency, a detector for sensing the radiation reflected from the target, an R.F. local oscillator for providing an R.F. signal at a second frequency, a first mixer circuit, responsive to the oscillators for providing a local I.F. signal which is the difference between the first and second frequencies, a second mixer circuit, responsive to the detector and the R.F. local oscillator, for providing a reflected I.F. signal which is the difference between the second frequency and the modulation frequency of the reflected radiation, and a phase detector, responsive to the local and reflected I.F. signals, for detecting a first phase difference between the signals representative of the distance of the target.