The influence of photovoltaic dc field on holographic correlation recognition

The optical correlation technique based on volume holographic storage has a more obvious advantage on rapid processing, for the input image to be compared is computed with all stored templates simultaneously. Thus it is promising in application for pattern recognition, content addressing and associative recall. As the continuing progress in volume holographic storage, the volume holographic optical correlation technique will draw more and more attention. The volume holographic correlators always use Fe:LiNbO 3 as their storage materials, in which a nonuniform photovoltaic field was created during hologram recording exposure. As we have discussed before, the field not only reduced the dynamic range of the crystal, but also degraded the volume holograms. Furthermore, the field debases the recognition rate. In this paper, we analyze the influence of the field on holographic correlation recognition according to theories and experiments. A sodium chloride solution is used to short-circuit the crystal and suppress the influence of the photovoltaic dc field. 1000 holograms, which have been stored in a common volume of the crystal placed in the sodium chloride solution, have been reorganized with the rate of more than 84%.