New Coaxial Interference Method for Consumer Holographic Memory

We have developed a new coaxial interference method for the next-generation storage system. A signal beam and a reference beam are coaxially arranged and focused into a holographic medium using a bifocal lens. We can easily downsize the system because the optics is very simple. The reference beam is focused on the mirror surface of the medium, and the signal beam is defocused on this surface. A semicircular reference pattern is used to select normal playback or phase conjugate playback in a reproducing process. We have recorded a single hologram and a multiplexed hologram in a photopolymer medium with this method. These holograms are reconstructed successfully. We have found that our interference method has a 4 µm shift selectivity and excellent characteristics for the next-generation high-capacity optical memory.