An experimental approach to establish a single channel holographic associative memory with bipolar neural states and bipolar interconnections is presented. The optical implementation of bipolar interconnections is fulfilled by biasing the interconnection weights and dynamically thresholding the output estimate. To give the optical neurons bipolar features, a proper distributed offset is added to the output. A holographic associative memory was established. To record the memory hologram, a pair of transparencies are prepared for each of the stored patterns. Each transparency bears an additional transparent part whose aperture size is determined by the difference of transparent and opaque parts of the corresponding stored pattern. Numerical simulations show that its performance is in perfect coincidence with an ideal bipolar memory. Preliminary experimental results are also shown.
"Holographic associative memory with bipolar features", Proc. SPIE 1558, Wave Propagation and Scattering in Varied Media II, (11 November 1991); doi: 10.1117/12.49658; https://doi.org/10.1117/12.49658