Suppression of the Moiré effect in sub-picosecond digital in-line holography.

Digital in-line holography is widely used in flow studies where the 3D position, size and velocity of particles or fibers have to be known at a given time. When holograms are recorded by using a sub-picosecond laser the enlargement of the spectral distribution acts as a spatial low-pass filter over the intensity distribution of the diffraction pattern. This is not a disadvantage as regards to the spatial sampling. Indeed, the Moiré effect, due to the sub-sampling of the fringe pattern is naturally reduced. Experimental results are provided.