OPTIMAL SAMPLING AND RANGE OF MEASUREMENT IN DISPLACEMENT-ONLY LASER-SPECKLE CORRELATION

A statistical analysis of the subjective laser-speckle pattern is performed with emphasis on its spectral distribution. An optimal sampling resolution of the laser-speckle pattern is obtained using the Shannon sampling theorem. Experiments show that the displacement-only correlation using laser speckles is a reliable measurement as long as the sampling requirement is satisfied. Upper limits of measurement such as accuracy, measurable area and measurable deformation are discussed. A method of changing the measurement capabilities by adjusting the speckle-recording arrangement is also given.