Specklegram treatment involves mapping the displacement of a speckle pattern between exposures or during prolonged exposure. For photographic recording, this treatment can be performed by using point-by-point specklegram analysis or by optical processing of the whole specklegram. Using electronic speckle pattern recording, direct digital auto- or cross-correlation analysis of the recorded speckle patterns provides the sought displacements of speckles without traditional specklegram treatment. The same approach is used when a processed specklegram is digitized by electronic scanning or by using incoherent analysis of a microscopic portion of the specklegram. Some algorithms of such treatment will be described below as well as Young’s fringes analysis in Section 6.1, whereas the optical processing of the whole specklegram and spatial filtering technique will be discussed in Sections 6.2 and 6.3 respectively.
KeywordsAutocorrelation Convolution Crest Photography Velocimetry
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