Shock Front Observation Using High-Speed, Fourier-Plane Holography

For the past several years, research has been underway to study the detonation dynamics of dispersed particle explosives using high speed time resolved holography. The goal of the research has been to determine how a detonation wave is propagated through a volume containing a dispersion of microscopic explosive particles, in effect studying how individual particles interact. The recorded holograms contain information from both amplitude and phase objects: the individual particles of explosive and the propagating shock fronts, respectively. In addition, the particles themselves may be translucent, depending on their composition. Typical field of view for such experiments is on the order of millimeters; the individual particles range from 10 to 100m m in extent. A limiting factor in this research has been the poor quality of reconstructed images. The reconstructions tend to suffer from depth-of-field noise and speckle noise, which act together to make distinguishing individual particles and their associated shock fronts extremely difficult.

The work presented here has evolved in an effort to improve both particle and shock front visibility in the reconstructed holograms by applying various optical filtering techniques. The general theory behind the optical filtering/recording technique will be discussed. Experimental results using this technique to investigate dispersed explosive detonations will also be presented.