Multiple-Exposure Laser Speckle Velocimetry for Fluid Flow Measurement

T. D. Dudderar; R. Meynart

doi:10.1117/12.939777

10 September 1987 Multiple-Exposure Laser Speckle Velocimetry for Fluid Flow Measurement

T. D. Dudderar, R. Meynart

Proceedings Volume 0746, Industrial Laser Interferometry; (1987) https://doi.org/10.1117/12.939777
Event: OE LASE'87 and EO Imaging Symposium, 1987, Los Angeles, CA, United States

Abstract

In laser speckle velocimetry or LSV a sheet of laser light is used to illuminate a plane of interest within a volume of moving fluid which has been properly seeded to assure efficient scattering. An accurately focussed photograph of the resulting side scattered intensity field provides a pattern of (depending on the effective seeding concentration) either particle images or coherent speckle which is directly related to the existing two-dimensional flow field in the plane of interest. If the illumination is appropriately interrupted while recording particle images, the resulting photograph or LSV specklegram will include many discrete recordings of each particle image. A positive transparency print of this multiple exposure LSV particle image specklegram may readily by analyzed optically by either a point-by-point "Young's fringe" technique or a full-field "Fourier filtering" technique to produce quantitative velocity field informa-tion with superior signal-to-noise characteristics. Computer aided image processing and data interpretation techniques are also used to provide further enhancement and conve-nience. In this paper the sources and consequences of signal decorrelation and noise are discussed in detail, and compared with those obtained using double exposure LSV (either coherent speckle or particle image).

Citation Download Citation

T. D. Dudderar and R. Meynart "Multiple-Exposure Laser Speckle Velocimetry for Fluid Flow Measurement", Proc. SPIE 0746, Industrial Laser Interferometry, (10 September 1987); https://doi.org/10.1117/12.939777

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