Fig. 1.

Measurement of scattering dynamics with interferometric speckle visibility spectroscopy (iSVS). (a) Coherent light illuminates a dynamic scattering media, generating a time-varying speckle field. The speckle field is combined with a tilted reference beam to form a hologram on the sensor. (b) The movement of scatterers (e.g., red blood cells) within the sample create captured holograms with normalized intensities proportional to the speed of the scatterer movement. (c) A depiction of how the recorded holograms are formed. If the medium is dynamic, the speckle pattern changes during the camera exposure time, leading to a reduced overall speckle contrast and maximum intensity in the recorded hologram. In contrast, if the scattering medium is static, the captured speckle pattern integrated over the exposure time is static, leading to a higher contrast captured hologram. (Figure modified from Xu et al.⁹⁰)