Holographic memory system for recording digital information

Claim 1

A Fourier transform holographic memory apparatus comprising: a source of coherent light; first means for receiving the coherent light produced by said source and for controllably deflecting said coherent light; second means, receiving the light controllably deflected by said first means, for splitting said light into a reference beam and an object beam, respectively, along different optical paths; a random phase illumination hologram disposed in the path of said object beam for producing, from said object beam, an array of beams travelling along a plurality of discrete and separate paths from each respective location on said hologram, the phase of each beam being substantially constant across the beam and being randomly shifted with respect to the phases of the other beams, so as to function both as an illumination hologram and as a random phase shifter; a Fourier transform lens disposed in the path of said arrays of beams through which said beams pass; third means, disposed in the path of the arrays of beams passing through said lens, for modulating said beams in accordance with information supplied thereto; and fourth means, disposed in the path of said reference beam and said object beam, for recording the image formed by the impingement of said reference beam and said modulated arrays of beams thereon.