<title>Shadowgraphic holography analysis for debris characterization</title>

Abstract

Shadowgraphic holography offers significant advantages when characterizing the particulates from debris-producing events. Holography can provide the spatial resolution to span the particle size range over a large depth of field. Also, particulate velocities can be determined by generating a double-pulsed hologram. A technique that provided such holograms of the debris over a 180- degree field of view at ordnance velocities is extended here to hypervelocities. The higher debris velocities necessitate a shorter duration laser pulse. An analysis has been performed to determine the laser pulse requirements versus particle size and velocity, and the optical conjugates of the holographic component layout. The approach includes a rigorous diffraction theory analysis for the recording of the hologram to prove the equivalence of the smearing of the reconstructed image from a hologram of a moving object to that from an object with a spatial transmission gradient. It is shown that the recorded interference pattern, while degraded because of particle motion, remains stationary over the exposure duration.