Fig. 2: KCl powder results with sizes (i) ~106–180 μm and (ii) ~425–500 μm. | Nature Communications

Fig. 2: KCl powder results with sizes (i) ~106–180 μm and (ii) ~425–500 μm.

From: Extracting particle size distribution from laser speckle with a physics-enhanced autocorrelation-based estimator (PEACE)

Fig. 2: KCl powder results with sizes (i) ~106–180 μm and (ii) ~425–500 μm.

a Microscope and b commercial camera photos for two samples. c Raw speckle images collected by the CCD camera. d These four spatially integrated autocorrelation images are collected on the same sample with different particle positions. e The upper half image shows the averaged 1000 autocorrelation frames from the measurement. Since the particle position is ergodic, the temporal average equals the ensemble average of the autocorrelation image. The lower half image shows the calculation result from the forward operator. f The ground truth particle size distribution (PSD) and the corresponding estimator prediction are plotted together. g Cross-section plots of the averaged autocorrelations in e for different samples with ascending PSDs. The positions of the high-order lobes are marked. We raise the autocorrelation to the power of one-eighth to enhance the sidelobes’ visibility.

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