A study of some parameters affecting performance of a laser vibrometer

For a laser vibrometer scanning a diffuse surface, the observed signal is dependent partly upon the visibility of the reflected speckle pattern. This study will show that the visibility of the speckle interference fringes is independent of the incident light intensity and dependent on the number of speckle spots. Theoretical aspects of the problem are discussed, and an experimental verification is presented. The results show how signal quality can be improved by using apertures and higher laser powers.