Measurement of time-varying displacement fields by multiple-exposure speckle photography

It is shown how multiple-exposure speckle photography may be used to measure the time-varying in-plane displacement field of a specimen undergoing deformation. The technique is based on holographic speckle photography, which involves recording a shifted reference speckle pattern on the same photograph. An image processing system analyzes the photograph by calculating the autocorrelation function region by region. Results from a six-exposure photograph are presented. This new technique is compared with conventional double-exposure speckle photography in terms of accuracy, sensitivity, and spatial resolution.