  We report on an experimental demonstration of surface acoustic waves
monitoring on a thin metal plate with heterodyne optical holography. Narrowband
imaging of local optical pathlength modulation is achieved with a
frequency-tunable time-averaged laser Doppler holographic imaging scheme on a
sensor array, at video-rate. This method enables robust and quantitative
mapping of out-of-plane vibrations of nanometric amplitudes at
radiofrequencies.
