Reduction of speckles in digital holography

The development of CCDs in the last years makes it possible to reconsider the applications of digital holography. The most important property is the distance between the pixels, which limits the maximum detectable spatial frequency in the hologram. The size of objective speckles under coherent illumination depends on the dimension of the object and its distance to the holographic layer (CCD-Camera). If these speckles are in the range of the pixel size of the CCD or larger they dramatically decrease the quality of the numeric reconstructed holograms. We show that an n-fold recording of the object with phase encoding of the illumination wave at the same time makes it possible to overlap the reconstructed holograms incoherently. One gets a drastically improvement of the reconstructed hologram without loosing the lateral resolution. Moreover the possibility is shown to increase the maximum recordable object size by using an adapted reference wave.