[54] SPINNING DISC VOLUME HOLOGRAPHIC MEMORY
[75] Inventor: Harold M. Stoll, Rancho Palos Verdes, Calif.
[73] Assignee: Northrop Grumman Corporation, Los
Angeles, Calif.
[21] Appl. No.: 09/226,069 [22] Filed: Jan. 6, 1998
Related U.S. Application Data
[62] Division of application No. 08/819,793, Mar. 18, 1997.
[51] Int. CI. G11B 7/00
[52] U.S. CI 369/103; 369/112
[58] Field of Search 369/103, 100,
369/109, 110, 112, 102, 44.12, 44.11, 44.14,
59, 47, 58
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Primary Examiner—Muhammad Edun
Attorney, Agent, or Firm—Terry J. Anderson; Karl J. Hoch,
Jr.
[57] ABSTRACT
A volume holographic memory has a spinning disk comprised of photorefractive medium, object beam optics configured to direct an object beam through the outer edge of the disk, and reference beam optics configured to simultaneously direct a reference beam through the outer edge of the disk. An angle multiplexer manipulates the reference beam to facilitate the formation of angle multiplexed volume holograms. The object beam and the reference beam cooperate within the photorefractive medium to sequentially form a plurality of sets of angle multiplexed volume holograms therein while the disk is spinning. A phase conjugator directs a conjugate reference beam back through the disk after the reference beam has previously passed therethrough, so as to form a conjugate object beam to facilitate read-out. Amplitude monitoring is provided to facilitate use of an exposure schedule. Path length monitoring assures consistent phase relationship between the object and reference beams for write and erase operations. Calibration of the angle multiplexer is provided.
12 Claims, 4 Drawing Sheets
