The present invention is in the context of the measurement of velocity fields of fluid flows containing many small scattering sites, which exist either in the form of particles or optically activated, discrete fluid volumes. The invention is directed to a method and apparatus for resolving ambiguity with respect to the direction of displacement of particle images recorded by multiple exposures on film or videographic media. The invention enables the elimination of directional ambiguity by means of shifting the image field between exposures by an amount that is greater than any negative displacement occurring in the image field. In this way, all recorded displacements are positive, and negative displacements are obtained from the measurements by mathematically subtracting the artificial shift after the measurements.
|Original language||English (US)|
|U.S. patent number||4866639|
|State||Published - Sep 12 1989|