Application of in-line digital holography to multiple plane velocimetry

We present the preliminary results of a digital holographic system that can determine the two-dimensional velocity vector fields in several slices of a sample volume. A CCD camera directly records the diffraction patterns of small particles illuminated by a double-pulse laser diode. In fact, the dif fraction can be interpreted as a convolution with a wavelet family of funct ions. The scale parameter a is related to the distance z between a particle and the CCD camera. Then, the intensity distributions in a plane located a t a distance z are reconstructed by computing the wavelet components for th e corresponding scale parameter a. Afterwards, a particle image velocimetry algorithm is applied to the numerically reconstructed pair of images. The feasibility of this technique is demonstrated for two simulated displacemen ts.