Absolute measurement of small-amplitude vibrations by time-averaged   heterodyne holography with a dual local oscillator
  We report a demonstration of the measurement of the ratio between an optical modulation side band component and the non-shifted light component by time-averaged heterodyne holography in off-axis and frequency-shifting configuration, through coherent frequency-division multiplexing with a dual optical local oscillator. Experimental results of sinusoidal vibration sensing are reported. This technique enables absolute measurements of sub-nanometric out-of-plane vibration amplitudes. 
Nicolas Verrier, Michael Atlan
physics.optics