Spatially and Temporally Resolved Diagnostics of Dense Sprays Using Gated, Femtosecond, Digital Holography

This is a proposal to develop a unique, gated, picosecond, digital holography system for characterizing dense particle fields in high pressure combustion environments; a critical requirement clearly defined in the NASA solicitation. Most imaging methods fail to provide this capability because noise from multiple scattering buries the signal needed to acquire a useful image. Solutions to this problem are expensive, difficult to implement, and not ideal candidates for field experiments. The proposed innovation combines digital holography and picosecond, optical gating to limit the amount of optical noise sufficiently to enable high resolution, 3D imaging, effectively generalizing existing pseudo-ballistic imaging systems that have been used for imaging through dense particle fields. Storing the complete wavefront in a hologram enables use of a wide range of optical diagnostics methods including image processing and interferometry to improve image and information quality. The result is a new sensor concept that will be extremely useful in the experimental study of dense sprays and other particles fields, providing a detailed, instantaneous look at the structure and position of all of the particles as well as density field information in a large three dimensional sample volume. Moreover, the system can record dynamic information at high frequency.