Laser speckle contrast analysis (LASCA) for flow measurement

Laser light, when scattered from a moving object or fluid, fluctuates in intensity. These fluctuations can yield information about the velocity of the scatterers involved. Most techniques analyse the temporal fluctuations of a single speckle. For information on the spatial distribution of velocities, some form of scanning is necessary. Exceptions include speckle photography and particle image velocimetry, which are full-field, double-exposure methods for measuring lateral velocities and now. Another full-field technique, laser speckle contrast analysis (LASCA), has the additional advantages of being a relatively cheap, single-exposure technique operating in quasi-real time and sensitive to both lateral and line-of-sight motion. LASCA was originally developed to monitor blood flow, but these advantages should also be useful in industrial now measurement.