Dynamic Speckle Holography:
Measuring Small Motion over a Large Field of View

Dynamic Speckle Holography uses lasers with two scattering angles to create an image of a speckle pattern which can be analyzed to measure small scale motion over a large field of view. Here the motion is a model system of flow in a channel.

Weitz developed a new light scattering technique which they call dynamic speckle holography (DSH). Developed by postdoctoral fellow Stefano Aime, DSH creates an image of a speckle pattern of light scattered by a sample. The speckles are then analyzed to determine the time scale of their temporal correlations, providing an image of time scales across the sample. This can be used to measure the motion of the sample. In the figure on the right, the sample is fluid flowing in a channel. However, DSH can also be used to measure the strain field in a sample undergoing fracture. The power of DSH is that it relies on interference effects to sense the motion, and these are much more sensitive than other methods which inevitably entail measuring the motion of a scattering object. This makes DSH much more sensitive to motion and breaks the usual relationship between sensitivity and resolution. Weitz and Spaepen are applying DSH to investigate fracture phenomena.

Aime, S., M. Sabato, L. Xiao, and D.A. Weitz, "Dynamic Speckle Holography," Physical Review Letters 127 088003 (2021) open url in new window open pdf in new window

Frans Spaepen (Material Science) and David A. Weitz (Physics & Applied Physics)
2020-2021 Harvard MRSEC (DMR-1420570)