A method of reducing the relative error of the laser Doppler vibrometer for measuring mechanical vibrations of small amplitudes at a considerable distance in a high noise level is proposed. The method is based on the principle of three-wave interference. It is shown that if the additional referent wave propagates together with the probe beam, so the output vibrometer signal may rise under certain conditions between their amplitudes and phases between the intervening laser waves. At the same time, and the rms measurement error remains practically at the initial level. Reducing the relative error estimated with the mathematical model and demonstrated experimentally.
laser Doppler vibrometer, vibrometry, vibration measurements