Laser speckle photography and particle image velocimetry: photographic film noise

Abstract

Laser speckle photography (LSP) applied in fluid mechanics is more appropriately named particle image velocimetry (PIV). Traditional use of holographic films requires the use of high powered pulsed lasers to arrest the flow and record the seeding particle images. If resolution limits are satisfied, the use of more sensitive films can remove this restriction. This paper examines the noise contributed by films used in PIV and LSP and shows that, although sensitive films exhibit high noise levels due to phase distortions, signal-to-noise ratios can be preserved with the use of an index matching liquid gate during analysis of the negative.