Optical Processors for Holographic Velocimetry Data

摘要

The application of holographic velocimetry (HV) to two simple water flow problems has emphasized the need to investigate further the delta z accuracy problem. Attempts to improve upon the plus or minus 1 mm delta z accuracy using spherical wave recording and direct processing led to the theoretical development of the spherical intensity equation and the accuracy enhancement provided by using spherical waves in the recording phase. It appears conclusive that the millimeter barrier will be difficult to break using direct processing. Assuming the in-line Fraunhofer hologram is no better in focusing than a thin lens, it is shown that the same limitation in accuracy exists for holographic reconstruction processing schemes appropriate to HV. Optical data processing techniques, although not researched to the degree of direct and reconstruction schemes, appear to offer promise for better delta z resolution. Two important exploratory experiments on the selectivity characteristics of optical matched filters are reported. (Author)