Dynamic holographic interconnections for optical neural computers

A neural system comprised of p neurons with c interconnections per neuron requires cp degrees of freedom in its interconnections. If these interconnections are formed by interactions between narrow-band signals emitted by the p active elements, only p degrees of freedom are available at any given instant for modifying the interconnections. Thus a full and independent update of the interconnections requires that they be addressed c times. Constraints of this sort are natural to volume holography. While the number of interconnections which may be stored in a volume hologram scales as the volume of the system, N³, the number of optical beams which may be used to record holograms scales as the area enclosing the system, N². This means that in holographic systems cp ≤ N³ and p ≤ N². High density storage of holographic interconnections is therefore by necessity a dynamic process. The authors have developed dynamic recording processes which use photorefractive holography to record cp independent interconnections using p inputs. In implementing an optical neural architecture they use their control over the signals emitted by the p active elements to force the system to an interconnection pattern consistent with the needs of the neural system.