Figure 2
Analyses of various optical characteristics of holographic speckle patterns. (a) Typical images of raw, high-pass filtered, and low-pass filtered holographic speckle patterns according to their PM concentration. Comparisons of optical characteristics of holographic speckle patterns: (b) mean intensity gradient, (c) speckle size, (d) speckle width, and (e) spatial frequency. The dotted red line (y = 0.0286) denotes the signal separation criterion with the Gaussian filter size R of 20. Segment sizes of speckle images: (Raw, LPF) 35 × 35 μm2; (HPF) 17.5 × 17.5 μm2.
