In this paper the gray scale fidelity of images retrieved from photorefractive volume holographic memories is studied in detail. We propose, for the first time to our knowledge, to use the correlation coefficient between the original and the retrieved images as one of the measures for proper assessment of the gray-scale fidelity. The influence of recording object-reference beam ratio on the fidelity is investigated by using these quantities, and the dynamic evolution of the gray scale fidelity during hologram recording is calculated and experimentally measured.
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