Suppression of speckle noise in laser Doppler vibrometry by signal diversity and dynamic ellipse fitting

The speckle effect caused by coherent light scattering from rough surfaces modulates the intensity and phase of the interference signal, which results in signal dropouts and phase noise for Laser-Doppler vibrometers (LDV), limiting the accuracy and resolution of LDV. Signal diversity has been demonstrated to significantly suppress the speckle noise in single-point LDV vibration measurements since two or more statistically independent reception channels significantly decrease the probability of speckle noise occurring. In this paper, an orthogonal interferometer based on polarization diversity is presented. We discuss the potential of suppressing the speckle noise with dynamic ellipse fitting and dual-channel data fusion. The displacement measurement of LDV is obtained by phase synchronization and a simple weighted sum method. The conclusion of this article is that signal diversity combined with a dynamic ellipse fitting algorithm is feasible to suppress speckle noise resulting from the periodic movement of the target.