Particle distribution measurements using in-line Fraunhofer holography

In-line Fraunhofer holography has been developed and implemented at the Los Alamos National Laboratory to measure particle distributions of fast moving particles. Holography is a unique diagnostic that gives unambiguous information on the size and shapes of particle distribution over a 3D volume. Currently, the capability of measuring particles two microns in size which travel many mm/microsecond(s) ec has been demonstrated in hydrodynamic experiments at the Pegasus Pulsed Power Facility. Usually, for setting up an in-line holography experiment for measuring particles a few microns in size, the holographic film would be placed less than one centimeter from the particles. However, due to the high kinetic energy associated with the dynamic experiment, an optical relay system is used to relay the interference pattern 35 cm so that the glass hologram will survive. After the hologram has been recorded the data must be extracted. A spatially filtered laser is used to reconstruct a real image which is a projection of the particles over a 3D volume. Planes of data from this volume are digitized via a CCD camera by moving the hologram with a three axis actuator. After the data has been digitized it is then analyzed with intelligent image processing algorithms.