Storage Capacity of Holo-Interferograms

The practical storage capacity of a holographic medium can be found by finely comparing reconstructions from independent holograms of an information-dense object wave. With the help of two orthogonally polarized reference waves, a pair of volume holograms is recorded simultaneously at imprint densities as high as 4.1 x 1010 bits /cm3 . As a consequence of polarization, the holograms are not mutually coherent, and the twin encodings of the object wave can be reconstructed separately. These are brought into fine registration interferometrically and then scanned by a CCD camera. Experiments on glass-mounted Agfa 8E56, a fine-grained silver halide emulsion designed for holography, are reported. When the object wave was moderately dense in information, grain noise was the main cause of the reconstruction errors. Emulsional plasticity was the more significant factor both when the object wave was optically sparse and when it was extremely dense. Plasticity noise limited the information that could be retrieved to 2.7 x 1010 bits /cm3 , which is 2 orders of magnitude below the capacity suggested by the emulsionʹs bandwidth and grain-noise figures alone