Multi-layer holographic data reading method

• US 7,428,205 B2
• Filed: 11/27/2002
• Issued: 09/23/2008
• Est. Priority Date: 11/27/2002
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Harding, Kevin George
• Primary Examiner(s): Feild; Joseph
• Assistant Examiner(s): LAMB, CHRISTOPHER RAY
• Application Number:
  US10/065,882
• Publication Number:
  US 20040103136A1
• Time in Patent Office: 2,127 Days
• Field of Search: None
• US Class Current: 369/103
• CPC Class Codes: G11B 7/0065 Recording, reproducing or erasing by using optical interference patterns, e.g. holograms

Abstract

A plurality of holographic recording media are positioned one above the other on an optical substrate and contain conventional stationary or moving imagery or data sets such as binary data representative of for example written text. A plurality of memory address access media are alternately interleaved between the plurality of holographic recording media. The memory access media causes a pair of optical beams to create an interference pattern at particular hologram recording media layers causing that layer to be read out. The specific memory access media layer is selected by means of scanning the interference pattern spatially within the interrogation beam, or by means of scanning the interrogation beam in wavelength.

Claims

1. A method of reading a set of data stored in a memory device, the method comprising:

causing a first optical beam to interfere with a second optical beam at a prescribed angle therebetween at a first selected hologram containing at least a segment of the set of data and having a discrete location and a corresponding address in the memory device, generating thereby an N^th diffraction order wavefront;

wherein the first and second optical beams are characterized by a wavelength, an optical path length and a state of polarization;

sensing the N^th diffraction order wavefront diffracted from the hologram;

correlating the N^th diffraction order wavefront with a correlation pattern which includes the set of data;

where N is an integer;

if a correlation peak occurs, deconvolving the N^th order wavefront and the correlation pattern;

reading the set of data corresponding to the selected hologram and contained in the deconvolved N^th diffraction order wavefront; and

,

reading the set of data in the N^th diffraction order wavefront for a second selected hologram by changing the wavelength of one optical beam with respect to the other.

2. A method of reading a set of data stored in a memory device, the method comprising:

causing a first optical beam to interfere with a second optical beam at a prescribed angle therebetween at a first selected hologram containing at least a segment of the set of data and having a discrete location and a corresponding address in the memory device, generating thereby an N^th diffraction order wavefront;

wherein the first and second optical beams are characterized by a wavelength, an optical path length and a state of polarization;

sensing the N^th diffraction order wavefront diffracted from the hologram;

correlating the N^th order wavefront with a correlation pattern which includes the set of data;

where N is an integer;

if a correlation peak occurs, deconvolving the N^th diffraction order wavefront and the correlation pattern;

reading the set of data corresponding to the selected hologram and contained in the deconvolved N^th diffraction order wavefront; and

,

reading the set of data in the N^th diffraction order wavefront for a second selected hologram by changing the state of polarization of one optical beam with respect to the other.

3. A method of reading a set of data stored in a memory device, the method comprising:

causing a first optical beam to interfere with a second optical beam at a prescribed angle therebetween at a hologram having a discrete location and corresponding address in the memory device generating thereby a interference pattern;

wherein the first and second optical beams are characterized by a wavelength, an optical path length and a state of polarization;

sensing an N^th diffraction order wavefront diffracted from the hologram;

where N is an integer;

wherein the N^th diffraction order wavefront includes a correlation peak signal and the holographically stored data;

correlating the holographically stored data and the correlation peak signal in the N^th diffraction order wavefront;

if a correlation peak occurs, deconvolving the holographically stored data and the correlation peak signal;

reading the set of data in the deconvolved N^th diffraction order wavefront; and

,

reading the set of data in the N^th diffraction order wavefront for a second selected hologram by changing the wavelength of one optical beam with respect to the other.

4. A method of reading a set of data stored in a memory device, the method comprising:

causing a first optical beam to interfere with a second optical beam at a prescribed angle therebetween at a hologram having a discrete location and corresponding address in the memory device generating thereby a interference pattern;

wherein the first and second optical beams are characterized by a wavelength, an optical path length and a state of polarization;

sensing an N^th diffraction order wavefront diffracted from the hologram;

where N is an integer;

wherein the N^th diffraction order wavefront includes a correlation peak signal and the holographically stored data;

correlating the holographically stored data and the correlation peak signal in the N^th diffraction order wavefront;

if a correlation peak occurs, deconvolving the holographically stored data and the correlation peak signal;

reading the set of data in the deconvolved N^th diffraction order wavefront; and

,

reading the set of data in the N^th diffraction order wavefront for a second selected hologram by changing the state of polarization of one optical beam with respect to the other.

5. A data storage memory device comprising:

a plurality of recording media containing a set of holographically recorded data at discrete memory locations therein wherein each memory location is identified by a corresponding memory address;

means for creating an interference pattern between two beams of light at a selected one of the discrete memory locations in the recording media, generating thereby an N^th diffraction order wavefront;

means for sensing the N^th diffraction order wavefront emanating from the selected discrete memory location;

means for reading the holographically stored data from the N^th diffraction order wavefront;

wherein the plurality of recording media comprise layered holograms and wherein the interference pattern exists over a dimension less than a thickness of the recording media along the direction of travel of the beams of light.

6. A data storage memory device comprising:

a plurality of recording media containing a set of holographically recorded data at discrete memory locations therein wherein each memory location is identified by a corresponding memory address;

means for creating an interference pattern between two beams of light at a selected one of the discrete memory locations in the recording media, generating thereby an N^th diffraction order wavefront;

wherein the means for creating an interference pattern between two beams of light comprises a coherent source of light; and

wherein the two beams of light are crossed polarized with respect to one another and the means for creating an interference pattern comprises rotating at least one of the beams of light;

means for sensing the N^th diffraction order wavefront emanating from the selected discrete memory location; and

means for reading the holographically stored data from the N^th diffraction order wavefront.

7. A data storage memory device comprising:

a plurality of recording media containing a set of holographically recorded data at discrete memory locations therein wherein each memory location is identified by a corresponding memory address;

means for creating an interference pattern between two beams of light at a selected one of the discrete memory locations in the recording media, generating thereby an N^th order wavefront;

wherein the means for creating an interference pattern between two beams of light comprises a coherent source of light; and

wherein the two beams of light are crossed polarized with respect to one another and the means for creating an interference pattern comprises rotating at least one of the beams of light;

means for sensing the N^th diffraction order wavefront emanating from the selected discrete memory location; and

means for reading the holographically stored data from the N^th diffraction order wavefront;

wherein the plurality of recording access media which cause a change in phase of the two beams of light with respect to one another generating thereby non-cross polarized beams of light.