Quasi‐one‐dimensional volume‐type hologram memory

Abstract

When two different wavelengths are used for recording and reading in a volumetype hologram memory, construction of a space modulator and photodiode array becomes difficult because unwanted patches appear on a reconstructed image. This can be avoided in a one‐dimensional hologram; however, storage density is reduced. This paper proposes a quasi‐one‐dimensional volume‐type hologram which preserves thick film memory (high density memory) while configuration of a space modulator and a photodiode array is simplified and simultaneous reading at different wavelengths is possible. With a PMMA film with thickness 400 μm a storage density of (0.3 ∼ 1.0) × 105 bits/mm2 was realized, Conditions for simultaneous reading at a different wavelength have been clarified.