1 March 2013 Effective frequency sensitivity of laser speckle contrast measurements
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How does speckle contrast K, measured at camera exposures T around 10 ms, give us information about temporal autocorrelation of the speckle pattern with time constants τ < 1 ms, corresponding to Doppler shifts in the KHz range? We explore the implications of this question and show that for any particular assumed temporal speckle autocorrelation function, K measured at T >> τ accurately measures τ, but that K measurements at T < τ are required in order to determine the actual shape of the autocorrelation function. Determining the shape of the autocorrelation function is important if we wish to distinguish between different types of flow or movement in tissue, for example distinguishing Brownian motion or the randomly-oriented flows in capillary networks from more ordered flow in resolvable vessels.
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O. B. Thompson, O. B. Thompson, E. R. Hirst, E. R. Hirst, M. K. Andrews, M. K. Andrews, "Effective frequency sensitivity of laser speckle contrast measurements", Proc. SPIE 8580, Dynamics and Fluctuations in Biomedical Photonics X, 858008 (1 March 2013); doi: 10.1117/12.2005312; https://doi.org/10.1117/12.2005312

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