Numerical simulation and characterization of speckle noise for laser Doppler vibrometer on moving platforms (LDVom)

Laser Doppler Vibrometer (LDV) is extensively applied in remote and precise vibration measurements for structural monitoring. Speckle noise is a severe signal issue restricting LDV applications, mainly when an LDV scans from moving platforms. Realistic simulations and thorough characterizations of speckle noise can support the despeckle procedure. A novel approach to numerically simulate speckle noise is proposed based on the statistical properties of speckle patterns. Surface roughness and other affecting factors are thoroughly studied. The simulated distributions agree well with the literature when investigating speckle properties. Single-point and continuously scanning speckle noise are both numerically generated and experimentally acquired. Their corresponding time-series and fast Fourier spectra present good agreement. In addition, similar amplitude distributions, approximating a Gaussian distribution, are achieved. Speckle noise is different from Gaussian white noise because of the varying frequency distribution. The speckle noise grows with increasing surface roughness to a critical value. When simulating and acquiring the scanning speckle noise, the noise energy increases with the scanning speed, but the signal drop-outs decrease in intensity and density. These promising results demonstrate the simulation accuracy and can further support despeckle procedures.