2. Speckle activity images using statistic cumulants

GRACIELA ROMERO; HECTOR RABAL; NELLY CAP; RICARDO ARIZAGA; MARCELO TRIVI

Sydney Australia

Congreso; International Commission for Optics ICO 21 - 2008 Congress; 2008

ICO

The development in statistic cumulants is a useful tool to describe certain functions in optics. In particular, the autocorrelation of the intensity as a function of time is frequently used in dynamic speckle applications. Cumulants of the autocorrelation were employed to quantitative describe bruising in fruits, drying of onion and post harvest orange characterization by dynamic speckle techniques. In this work we show its use in the generation of activity images on dynamic speckle. A stack of consecutive frames is registered of a dynamic scene. A cumulant generator function is then calculated as the logarithm of the autocorrelation of the time history of each pixel. For the first cumulant, a numerical approximation to the derivative is calculated near the origin of the lag. The second cumulant is calculated by fitting the cumulant generator function by a parabola.  The resulting cumulants are then shown as grey levels in a set of images. Applications on a qualitative display of the drying of paint, corn seeds and bruised apple are shown.