High capacity holographic storage system

• US 5,519,651 A
• Filed: 10/07/1993
• Issued: 05/21/1996
• Est. Priority Date: 10/07/1993
• Status: Expired due to Term

• Current Assignee: ForceTEC Co., Ltd. (Duk-Soo Kang)
• Original Assignee: Tamarack Storage Devices
• Inventors: Redfield, Stephen R.
• Primary Examiner(s): Yoo, Do Hyun
• Application Number:
  US08/133,504
• Time in Patent Office: 957 Days
• Field of Search: 365/216, 365/125, 365/112, 365/215, 365/234, 365/64, 369/103, 369/112, 359/22, 359/24, 359/25, 359/29, 359/30
• US Class Current: 365/125
• CPC Class Codes: G03H 1/02 Details of features involved during the holographic process; Replication of holograms without interference recording
• CPC Class Codes: G03H 2001/0216 Optical components G03H2001/0224, G03H1/0256 take precedence; corresponding details, see subgroups of G03H2223/00
• CPC Class Codes: G03H 2001/0232 Mechanical components or mechanical aspects not otherwise provided for
• CPC Class Codes: G03H 2001/2675 Phase code multiplexing, wherein the sub-holograms are multiplexed according to spatial modulation of the reference beam
• CPC Class Codes: G03H 2223/24 Reflector; Mirror
• CPC Class Codes: G11B 7/0065 Recording, reproducing or erasing by using optical interference patterns, e.g. holograms
• CPC Class Codes: G11C 13/042 using information stored in the form of interference pattern

Abstract

A holographic storage assembly is provided which utilizes a large holographic storage media (36) disposed between two reflecting surfaces (40) and (42). An optics system (44) is disposed between the two reflecting surfaces (40) and (42) is operable to generate both a reference beam (58) and a data beam (50). The data beam (50) and reference beam (58) are generated on a virtual spot plane (100), which is then imaged from the surface of the reflecting surface (42) onto the much larger surface of the media (36). This is operable to record an interference grating at a storage location (56). During a playback operation, a reconstructed data beam (64) is generated and reflected from the surface of the mirror (40) onto a detector (68) in the deflector system (44).

Claims

1. A holographic storage system for storing information, comprising:

a holographic storage media having two substantially parallel surfaces, and a plurality of storage regions, each for storing a plurality of separately addressable pages of holographic stored data images;

a first reflective surface for being disposed on one side of said holographic storage media and having a predetermined curvature;

a second reflective surface for being disposed on the opposite side of said holographic storage media from said first reflective surface and having a predetermined curvature;

a first optics system disposed on the same side of said first reflective surface as said storage media, said first optics system having;

a first laser for generating a first coherent laser beam,

a first reference beam deflection system for directing said first laser beam as a first reference beam to reflect from said first reflective surface to a select one of said plurality of storage regions in said storage media,

a first addressing device for imparting addressing information to said first reference beam associated with a select one of said stored data images in said select storage region to allow for reconstruction thereof as a first reconstructed data beam; and

a first detection system for receiving said first reconstructed data beam and detecting a data therein; and

a second optics system disposed on the same side of said second reflective surface as said storage media, said second optics system having;

a second laser for generating a second coherent laser beam,

a second reference beam deflection system for directing said second laser beam as a second reference beam to reflect from said second reflective surface to a select one of said plurality of storage regions in said storage media,

a second addressing device for imparting addressing information to said second reference beam associated with a select one of said stored data images in said select storage region to allow for reconstruction thereof as a second reconstructed data beam; and

a second detection system for receiving said second reconstructed data beam and detecting a data therein.

2. The holographic storage system of claim 1, wherein said first and second detection systems each comprise:

a photodetector having a detection surface and disposed on the opposite side of said holographic storage media from said respective first and second optics systems and in a location wherein said respective first and second reconstructed data beams from any of said storage locations will fail on said respective detection surfaces after being directed thereto by said respective second and first reflective surfaces.

3. The holographic storage system of claim 1, and further comprising:

a first beam splitter for splitting off a portion of said first laser beam as a first data beam;

a first spatial light modulator for superimposing a first data image onto said first data beam;

a first data beam deflector for directing said first data beam toward said first reflective surface for reflection therefrom to said select region to interfere with said reference beam, said first data beam deflector and said first reflective surface performing a Fourier transform on the first data image superimposed on said first data beam;

a second beam splitter for splitting off a portion of said second laser beam as a second data beam;

a second spatial light modulator for superimposing a second data image onto said second data beam; and

a second data beam deflector for directing said second data beam toward said second reflective surface for reflection therefrom to said select region to interfere with said second reference beam, said second data beam deflector and said second reflective surface performing a Fourier transform on the second data image superimposed on said second data beam.

4. The holographic storage system of claim 3, wherein said first data beam deflector comprises:

a first focusing lens for receiving said first data beam after the first data image is superimposed thereon;

a first focal spot plane;

a first directing system for directing an output of said first focusing lens through select locations on said first focal spot plane such that a focal point of said first focusing lens is substantially coplanar with said first focal spot plane for all positions of said first directing system; and

said first focal spot plane disposed relative to said first reflective surface such that the first data beam will be imaged onto said storage media with each of said select locations on said first focal spot plane corresponding to one of said storage regions on said holographic storage media.

5. The holographic storage system of claim 4, wherein said second data beam deflector comprises:

a second focusing lens for receiving said second data beam after the second data image is superimposed thereon;

a second focal spot plane;

a second directing system for directing an output of said second focusing lens through select location on said second focal spot plane such that a focal point of said second focusing lens is substantially coplanar with said second focal spot plane for all positions of said second directing system; and

said second focal spot plane disposed relative to said second reflective surface such that the second data beam will be imaged onto said storage media with each of said select locations on said second focal spot plane corresponding to one of said storage regions on said holographic storage media.

6. The holographic storage system of claim 1, wherein each of the stored data images in a given storage region is phase encoded such that a reference beam encoded with phase information corresponding to one of the stored data images and illuminating said given storage region at a predetermined angle, will generate a reconstructed data beam corresponding to the one of the stored data images, said first and second addressing devices comprising:

respective first and second beam expanders for expanding said respective first and second laser beams to provide respective first and second expanded laser beams;

respective first and second phase corrugators for imparting relative phase information to select portions of said respective first and second expanded laser beams to provide respective first and second phase encoded laser beams; and

respective first and second deflecting systems for directing said respective first and second phase encoded laser beams as said respective first and second reference beams to reflect from said respective first and second reflective surfaces such that all portions of said respective first and second phase encoded laser beams intersect in respective first and second common points on the respective surface of said holographic storage media within said respective select storage region.

7. The holographic storage system of claim 6, wherein said respective first and second deflecting systems comprise:

respective first and second focusing lenses for receiving said respective first and second phase encoded laser beams;

respective first and second focal spot planes;

respective first and second directing systems for directing an output of said respective first and second focusing lenses through a select location on said respective first and second focal spot planes such that a focal point of said respective first and second focusing lenses is substantially coplanar with said respective first and second focal spot planes for all positions of said respective first and second directing systems; and

said respective first and second focal spot planes disposed relative to said respective first and second reflective surfaces such that said respective first and second focal spot planes will be imaged onto said storage media, and said select location on said respective first and second focal spot planes corresponds to one of said plurality of storage regions.