DIGITAL FILTERING SYSTEM FOR DECODING IN-LINE HOLOGRAMS.

The authors present a system of digital filters that is applied directly to the in-line hologram and maps the hologram into an image of the boundaries (edges) of the objects encoded in it provided that the object distribution function is real. The first stage is an approximate inverse filter in the form of a truncated series expansion in the Fourier transform domain. The nonlinear postfiltering consists of a covariance filter that replaces each input pixel by the estimate of the local covariance. A thresholding may be added prior to the covariance filtering if the edges of the reconstructed objects are not sharp enough.