Two methods of reducing the dynamic range of a holographic filter
Résumé
Two methods of reducing the dynamic range of the transmittance of computer-generated interconnec-tion holograms are presented and compared. The holograms are used in an optical implementation of an associative memory to connect the input and the output planes but are representative of more general N 4 interconnection holograms. Because the holograms play a double correlation-reconstruction role, the standard spectrum-smoothing techniques 1e.g., random phase2 cannot be applied. We show, in computer simulations and optical experiments, that by using deterministic phase functions that can be realized in the optical system 1defocusing the hologram or controlling the phases of the diffraction spots of a Dammann grating used in the system input2 the hologram dynamic range can be lowered, reducing the errors during the hologram binarization and increasing the hologram's diffraction efficiency. r