Numerical simulation of speckle noise in laser vibrometry

This paper considers the fundamental mechanism by which speckle noise is generated in Laser Vibrometry before describing a new numerical simulation for prediction of speckle noise level in a real measurement. Factors within the simulation include rate of change of phase within individual speckle transitions, low pass filtering to match the frequency range of experimental data with which comparison is to be made, a track-and-hold facility for periods of low signal amplitude and wavefront curvature effects. The simulation data provides real insight into the phase and amplitude modulation of the Doppler signal and good agreement is found in the final comparison with experimental data from a measurement on a rotating target.