Portable low-cost setup for outdoor implementation of dynamic speckle technique

Abstract

Dynamic speckle technique (DST) is based on speckle formation on the surface of objects illuminated with coherent light. Temporal speckle intensity fluctuations depend on the speed of micro-changes ongoing within the controlled objects. The DST visualizes as a set of 2D activity maps the temporal change of spatial speed distributions. In general, the DST set-up comprises components as a laser source with the required optics, vibration-isolated table, high-resolution camera and computer for data storage and image processing. Such setups are stationary, massive and relatively expensive, which decreases the number of possible DST biological or industrial applications. In this paper we propose a miniature portable device, based on a low-cost laser attached to a smartphone, and checked its efficiency under the field conditions. A strong argument for using a portable set-up is the fact that the absolute values of the speckle intensity are not needed to construct a reliable activity map. We proved this conclusion by numerical simulation of DST in noisy environment. We studied speckle patterns captured with a smartphone's camera. A personal computer (PC) was used for postprocessing o f speckle images. We conducted four sets of experiments. The raw data were recorded on the PC while the smartphone was connected as i) IP-camera and ii) USB-camera. In the third experiment, speckle images were captured and stored in the smartphone's memory. Data were transferred to the PC after the end of recording. To obtain ground truth activity maps, we repeated the experiment with the same object under laboratory conditions.

Spatially Multiplexed Speckle on 1D Sensors for High-Speed 2D Sensing Applications

“…Statistical analysis of speckle patterns has the potential to identify spatial areas where changes or activity occur at a slower or faster rate within the object. Various applications of this approach have been documented across fields such as medicine, biology, industry, and food quality assessment [ 4 , 5 , 6 , 7 , 8 , 9 ]. Sometimes, speckle imaging is also associated with ghost imaging [ 10 ].…”