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Proceedings Paper

Laws of laser speckle movement and their application in flow visualization
Author(s): Yaozu Song; Wei-Bao Zhang
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Paper Abstract

In this paper a mathematical model for a laws of laser speckle movement in space when light beam pass through a phase object is proposed by using the Fresnel-Kirchhoff diffraction integral. By means of the theoretical analysis for this mathematical model, the following three conclusions can be got. First, when a light beam passes through a phase object, for example a transparent flow fluid, the movement state of speckles in space depends not only on the characteristic function on surface of speckle sources, but also on infinitely small variation of propagation direction of incident beam. If the characteristic function can be kept same during a double exposure, then the movement states of speckle in space and their corresponding speckle displacements depend only on the variation of propagation direction of incident beam. Second, to make the characteristic function same during a double exposure the considered light beams which produce a pair of correlation speckles must come from the same space zone on the surface of speckle source. Third, when a light beam passes through a diffusion surface, the variation of propagation direction of the beam can not be determined by the principle of geometrical optics because of scatting function of light beams on diffusion surface. But the principle of geometrical optics still can be used in discussion of the movement states of speckle in space and in determination of speckle displacements according to the mathematical model proposed in this paper. Above these analysis provides a theoretical basis for designing experimental arrangements of laser speckle photography in flow visualization. According to the laws of laser speckle movement in space six different experimental arrangements which can be used in flow visualization are presented. The formulas of processing the experimental data for measurement density field and temperature field in flow fluid are given. These results are very favorable for development of laser speckle photography technology in flow visualization.

Paper Details

Date Published: 13 October 1999
PDF: 12 pages
Proc. SPIE 3783, Optical Diagnostics for Fluids/Heat/Combustion and Photomechanics for Solids, (13 October 1999); doi: 10.1117/12.365729
Show Author Affiliations
Yaozu Song, Tsinghua Univ. (China)
Wei-Bao Zhang, Tsinghua Univ. (China)


Published in SPIE Proceedings Vol. 3783:
Optical Diagnostics for Fluids/Heat/Combustion and Photomechanics for Solids
Soyoung Stephen Cha; Peter John Bryanston-Cross; Carolyn R. Mercer, Editor(s)

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