US 7,321,540 B2
Waveguide multilayer holographic data storage
Emine Goulanian, Richmond (Canada); Nariman Ashurbekov, Richmond (Canada); and Faouzi Zerrouk, Vancouver (Canada)
Assigned to Southbourne Investments Limited, Jersey (United Kingdom)
Appl. No. 10/495,578
PCT Filed Nov. 18, 2002, PCT No. PCT/CA02/01849
§ 371(c)(1), (2), (4) Date Feb. 25, 2005,
PCT Pub. No. WO03/044574, PCT Pub. Date May 30, 2003.
Claims priority of application No. 2363279 (CA), filed on Nov. 16, 2001.
Prior Publication US 2005/0201247 A1, Sep. 15, 2005
Int. Cl. G11B 7/00 (2006.01)
U.S. Cl. 369—103 16 Claims
OG exemplary drawing
 
1. A multilayer holographic data storage system, comprising:
a) at least two groups of layers, each group containing:
i) a hologram layer (11i) having holograms (14ijk) for storing data, said holograms arranged in one or more hologram rows, wherein within each of said rows said holograms are non-overlapping and wherein said holograms within any one of said rows can be reconstructed simultaneously by one guided wave;
ii) a waveguide layer (13i) provided with a coupler (15i); and
iii) a cladding layer (12i) located on the outer surface of said waveguide layer between adjoining layer groups,
wherein each said hologram (14ijk) is capable of reconstructing radiation towards a planar output surface (02) and wherein said radiation from each said hologram is restricted in its spatial angle in order to provide for separation from radiation from adjacent ones of said holograms, and
wherein said holograms (14ijk) in said hologram layers are recorded such that radiation therefrom is focused at a common focusing plane (04),
b) a photodetector (50) for receiving radiation from said holograms (14ijk), said photodetector disposed at or near said common focusing plane (04);
c) a hologram access unit (40) located in a region between said output surface (02) and plane of intersection of said radiation (03), said hologram access unit operative to separate radiation from a selected one of said holograms from radiation from other ones of said holograms;
d) a layer and row access unit (30) for forming and directing a readout beam (20) to a selected layer and, through a respective coupler (15i), thereinto along one of said rows;
wherein a row of data pixel images from each said hologram at a receiving surface of the photodetector is parallel to rows of pixels of said photodetector, and wherein a pitch of said data pixel images in a direction parallel to said rows of data pixel images is equal to, or a whole number multiple of, a pitch of pixels of said photodetector in said direction;
wherein said pitch of data pixel images is equal to said pitch of said pixels of said photodector and a center of each data pixel image is disposed at a center of a corresponding one of said photodetector pixels;
wherein said photodetector (50) is disposed in an area of the intersection of radiation from said holograms; and
wherein a number of said photodetector pixels in said direction is sufficient to cover data pixel images from all said holograms without moving the photodetector in the focusing plane (04) and determined by an expression:
Q ≧[h(q−1)/p+M], where
h is the hologram pitch,
q is the number of holograms in the hologram row,
p is the photodetector pixel pitch,
M is the number of data pixel images in said direction.