Analysis of bacterial chemotactic response using dynamic laser speckle.

Chemotaxis has a meaningful role in several fields, such as microbial physiology, medicine and biotechnology. We present a new application of dynamic laser speckle (or biospeckle) to detect different degrees of bacterial motility during chemotactic response experiments. Encouraging results showed different bacterial dynamic responses due to differences in the hardness of the support in the swarming plates.

Vortex analysis in dynamic speckle images.

Optical vortex analysis has become an important tool in optical metrology. It has been shown to be able to measure small displacements with up to nanometric precision. We analyze optical vortex behavior in dynamic speckle patterns with the boiling phenomenon.

Speckle activity images based on the spatial variance of the phase.

We propose the display of the local spatial variance of the temporal variations of the phase as an activity descriptor in dynamic speckle images. The spatial autocorrelation of the speckle intensity is calculated in sliding windows, and an estimation of the variance of the phase variations in each region of the sample is determined. The activity images obtained in this way depict some interesting features and in some cases they could be related to physical magnitudes in the samples.