System for holography

• US 8,634,119 B2
• Filed: 03/06/2011
• Issued: 01/21/2014
• Est. Priority Date: 07/09/2010
• Status: Active Grant

• Current Assignee: Tipd, LLC
• Original Assignee: Tipd, LLC
• Inventors: Bablumyan, Arkady, Blanche, Pierre-Alexandre Jean, Peyghambarian, Nasser N.
• Primary Examiner(s): Allen, Stephone B
• Assistant Examiner(s): MADONNA, JEFFREY E
• Application Number:
  US13/041,407
• Publication Number:
  US 20120008482A1
• Time in Patent Office: 1,052 Days
• Field of Search: 359 1- 35, 359237-325, 359/902, 430 1- 2
• US Class Current: 359/11
• CPC Class Codes: G03H 1/0011 for security or authentication holograms on information-bearing cards B42D25/328; testing papers with holograms G07D7/0032
• CPC Class Codes: G03H 1/02 Details of features involved during the holographic process; Replication of holograms without interference recording
• CPC Class Codes: G03H 1/04 Processes or apparatus for producing holograms G03H1/26 takes precedence
• CPC Class Codes: G03H 1/26 Processes or apparatus specially adapted to produce multiple sub- holograms or to obtain images from them, e.g. multicolour technique
• CPC Class Codes: G03H 2001/0264 Organic recording material
• CPC Class Codes: G03H 2001/0482 Interference based printer
• CPC Class Codes: G03H 2001/2271 RGB holobject
• CPC Class Codes: G03H 2001/303 Interleaved sub-holograms, e.g. three RGB sub-holograms having interleaved pixels for reconstructing coloured holobject
• CPC Class Codes: G03H 2210/22 2D SLM object wherein the object beam is formed of the light modulated by the SLM SLM per se G03H2001/0224
• CPC Class Codes: G03H 2223/19 Microoptic array, e.g. lens array
• CPC Class Codes: G03H 2223/23 Diffractive element
• CPC Class Codes: G03H 2260/35 Rewritable material allowing several record and erase cycles
• CPC Class Codes: G03H 2260/54 Photorefractive reactivity wherein light induces photo-generation, redistribution and trapping of charges then a modification of refractive index, e.g. photorefractive polymer
• CPC Class Codes: G11B 7/0065 Recording, reproducing or erasing by using optical interference patterns, e.g. holograms

Abstract

The present invention provides systems of recording holograms that reduce the writing time, increase the diffraction efficiency, improve the resolution, or restitute color. These systems are well suited for use with an updateable 3D holographic display using integral holography and photorefractive polymer.

Claims

1. A holographic recording system, comprising:

a holographic recording material comprising a photorefractive (PR) polymer;

an electrode structure for receiving a voltage to apply an external electric field to the PR polymer;

a laser that produces a coherent beam;

a beam splitter that splits the coherent beam into an object beam and a reference beam, the intensity of the object beam is spatially structured with data for writing a hologram to form a modulated object beam;

a beam steering mechanism that steers the modulated object beam and the reference beam relative to the holographic recording material to interfere at different places in the material to record one or more holograms, said modulated object beam and said reference beam producing a grating vector at an angle to the external electric field that controls a diffraction efficiency of the PR polymer;

a first lens array that focuses the object beam on the recording material at multiple positions, said object beam spatially structured so that each position on the recording material corresponds to correct hologram data;

a second lens array that splits the reference beam into multiple reference beams that are directed to the first lens array that collimates the multiple reference beams so that the multiple object and multiple reference beams interfere at the multiple positions on the material to write multiple holograms simultaneously; and

a first holographic optical element (HOE) that diffracts one of the object or reference beams to reduce the angle between the grating vector and the external electric field and increase the diffraction efficiency of the PR polymer.

2. The holographic recording system of claim 1, wherein the first HOE is configured to allow one of the object or reference beams to pass there through unaffected and to diffract the other one of the object or reference beams.

3. The holographic recording system of claim 1, wherein the second lens array is a second HOE comprising an angularly selective grating.

4. The holographic recording system of claim 1, further comprising:

a second holographic optical element (HOE) that focuses the object beam on the recording material at multiple positions, said object beam spatially structured so that each position corresponds to the correct hologram data;

wherein said first HOE splits by diffraction the reference beam into multiple reference beams that are directed to the second HOE that collimates the multiple reference beams so that the multiple object and multiple reference beams interfere at the multiple positions on the material to write multiple holograms simultaneously.

5. The holographic recording system of claim 1, wherein the hologram is recorded using integral holography to form a display, further comprising:

a reading beam that is diffracted by the holographic recording material at an angle; and

a second holographic optical element (HOE) positioned after the recording material to redirect the diffracted beam approximately orthogonal to the recording material toward a viewer position.

6. The holographic system of claim 1, wherein said object and reference beams interfere at multiple positions that are spaced apart on an x-y grid, said beam steering mechanism translating the first and second lens arrays along a single axis at an oblique angle to the x-axis to write multiple holograms over the entire surface of the recording material as a series of parallel rows.

7. The holographic recording system of claim 1, in which a color hologram is recorded using integral holography in a transmission geometry, further comprising:

a spatial light modulator (SLM) having different zones loaded with hogel data for different colors to spatially structure the object beam and form the modulated object beam; and

a focusing lens that redirects the different zones of the modulated object beam at correct angles of incidence for each color towards the recording material such that transmission of a color reading beam through the recording material produces multiple object beams at different colors that superimpose at a common viewer position.

8. The holographic recording system of claim 1, in which the system uses integral holography in a full-parallax transmission geometry to record and display holograms, further comprising:

a mask/mirror positioned between the laser and the holographic recording material, said mask/mirror comprising an aperture that defines the extent of an individual hogel in the hologram and a mirror surface facing the recording material;

a translation stage that moves the mask/mirror to synchronize a position of the aperture with the location of the steered object and reference beams; and

a read source positioned on the opposite side of the recording material to direct a reading beam through the material where the reading beam reflects off the mirrored surface and is transmitted back through the hologram in the material where the reading beam is diffracted to produce a diffracted beam to display the hologram.

9. The holographic recording system of claim 1 for the display of holograms in a horizontal parallax only (HPO) geometry in which horizontal and vertical image planes need to be disassociated during the holographic recording, further comprising:

a spherical lens that shapes the object beam; and

a spherical mirror positioned at an angle to the object beam, astigmatism of the spherical mirror disassociating an image plane so a horizontal image plane is near a Fourier cylindrical lens and a vertical image plane is near the holographic recording material.

10. The holographic recording system of claim 1 for recording of a color holographic stereogram in a transmission geometry, further comprising:

a first optical system to separate the coherent beam into the reference and object beams having both first and second orthogonal polarization components; and

a second optical system to split the object beam into first, second and third object beams, said first and second object beams having said first polarization component and said third object beam having said second polarization component, said first and second object beams positioned to have a symmetrical angle of incidence so that the grating vector of a hologram formed by cross-talk is perpendicular to the external electric field in the photorefractive material so that the diffraction efficiency is near zero;

wherein angles of incidence for all three object beams satisfy a Bragg equation so that when each hologram is read with a different color it displays a full color hologram in a direction of an audience.

11. The holographic recording system of claim 1, wherein the object beam is used to simultaneously erase the structure of a previous hologram and write a current hologram, the laser power being sufficiently high to erase the previous hologram without leaving a ghost image and low enough to record the current hologram without causing a permanent set.

12. The holographic recording system of claim 11, wherein the object beam reduces the diffraction efficiency of the previous hologram to less than 20% when writing the current hologram.

13. The holographic recording system of claim 1, wherein the electrode structure comprises a pair of interleaved electrodes deposited on only one surface of the PR polymer.

14. A holographic recording system, for recording a hologram using integral holography for a display, comprising:

a holographic recording material comprising a photorefractive (PR) polymer;

an electrode structure for receiving a voltage to apply an external electric field to the PR polymer;

a laser that produces a coherent beam;

a beam splitter that splits the coherent beam into an object beam and a reference beam, the intensity of the object beam is spatially structured with data for writing a hologram to form a modulated object beam;

a beam steering mechanism that steers the modulated object beam and the reference beam relative to the holographic recording material to interfere at different places in the material to record one or more holograms, said modulated object beam and said reference beam producing a grating vector at an angle to the external electric field that controls a diffraction efficiency of the PR polymer;

a first holographic optical element (HOE) that diffracts one of the object or reference beams to reduce the angle between the grating vector and the external electric field and increase the diffraction efficiency of the PR polymer;

a second holographic optical element (HOE) that focuses the object beam on the recording material at multiple positions, said object beam spatially structured so that each position corresponds to the correct hologram data, wherein said first HOE splits by diffraction the reference beam into multiple reference beams that are directed to the second HOE that collimates the multiple reference beams so that the multiple object and multiple reference beams interfere at the multiple positions on the material to write multiple holograms simultaneously; and

a third holographic optical element (HOE) positioned after the recording material to redirect a reading beam transmitted through the recording beam approximately orthogonal to the recording material toward a viewer position.