Method and apparatus for recording and displaying edge-illuminated holograms

• US 4,643,515 A
• Filed: 04/01/1985
• Issued: 02/17/1987
• Est. Priority Date: 04/01/1985
• Status: Expired due to Term

• Current Assignee: Environmental Research Institute Incorporated
• Original Assignee: Environmental Research Institute of Michigan
• Inventors: Upatnieks, Juris
• Primary Examiner(s): ARNOLD, BRUCE
• Application Number:
  US06/718,502
• Time in Patent Office: 687 Days
• Field of Search: 350/3.83, 350/3.84, 350/3.81, 350/3.85, 350/320, 350/3.67
• US Class Current: 359/10
• CPC Class Codes: G03H 1/0408 Total internal reflection [TIR] holograms, e.g. edge lit or substrate mode holograms
• CPC Class Codes: G03H 2001/264 One hologram being a HOE
• CPC Class Codes: Y10S 359/90 Methods

Abstract

Methods and apparatus for recording and displaying edge-illuminated holograms. Disclosed is a method for producing holograms whereby the reference beam, when recording, and the illumination beam, when displaying the hologram, impinge on the edge of the cover plate placed over the hologram. Edge-illumination of holograms makes possible holographic displays which fit in a volume having very little depth.

Claims

1. A method for recording a hologram, comprising:

placing a recording medium sensitive to electromagnetic energy in proximity to a body refractive of electromagnetic energy, said body having a plurality of surfaces and being adapted to refract electromagnetic energy impinging on at least a first of said plurality of surfaces onto said recording medium, the index of refraction of the body being greater than the index of refraction of the space adjacent said first of said plurality of surfaces;

filling the space between said recording medium and said refractive body with a layer of material transparent to electromagnetic energy, said material having an index of refraction greater than or equal to the index of refraction of said refractive body;

forming a plurality of beams from a coherent source of electromagnetic energy;

creating an object wavefront by illuminating an object to be holographically recorded with a first of said plurality of beams;

directing a portion of said object wavefront to impinge on said first of said plurality of surfaces, said portion being refracted onto said recording medium;

creating a reference wavefront within said reflective body by directing a second of said plurality of beams onto a second of said plurality of surfaces;

exposing said recording medium to the portion of said reference wavefront impinging on said second of said plurality of surfaces and being refracted onto the recording medium, creating an electromagnetic interference pattern between said wavefronts within the recording medium; and

rendering said interference pattern permanent in said recording medium.

2. The method of claim 1, wherein said electromagnetic energy is light energy.

3. The method of claim 2, wherein said recording medium is a photographic plate.

4. The method of claim 1, wherein said refractive body has two parallel planar surfaces, one being said first of said plurality of surfaces.

5. The method of claim 4, wherein said second of said surfaces is not parallel to said first of said surfaces.

6. The method of claim 5, wherein said electromagnetic energy is light energy.

7. The method of claim 6, wherein said photosensitive medium is a photographic plate.

8. A method for recording an edge-illuminated hologram, comprising:

placing a photographic plate substantially parallel to a first planar surface of a transparent cover plate, said cover plate having a second planar surface parallel to the first and a third planar surface perpendicular to the first and second surfaces;

filling the space between said photographic plate and said cover plate with a layer of transparent material having an index of refraction greater than or equal to the index of refraction of the cover plate;

forming two beams from a laser source of light;

illuminating an object to be holographically recorded with a first of said beams, creating an object wavefront;

directing a portion of said object wavefront to impinge on said second surface of said cover plate;

illuminating said third of said planar surfaces with the second of said light beams;

exposing said photographic plate to an interference pattern between said wavefront in the photographic plate; and

fixing said interference pattern in said photographic plate.

9. A method for displaying a hologram, comprising:

placing a hologram in proximity to a body refractive of electromagnetic energy, said body having a plurality of surfaces and being adapted to refract electromagnetic energy impinging on at least a first of said plurality of surfaces onto said hologram, the index of refraction of the body being greater than the index of refraction of the space adjacent said first of said plurality of surfaces;

filling the space between said hologram and said refractive body with a layer of material transparent to electromagnetic energy, said material having an index of refraction greater than or equal to the index of refraction of said refractive body; and

illuminating a selected subset of said surfaces with a plurality of beams of coherent electromagnetic energy, a portion of each beam of said plurality being refractively transmitted to said hologram and creating a displayed image.

10. The method of claim 9, wherein said electromagnetic energy is light energy.

11. A method for displaying an edge-illuminated hologram, comprising:

placing a hologram in uniformly displaced proximity to a first parallel surface of a transparent cover plate, said cover plate having a second planar surface parallel to said first parallel surface and an edge surface perpendicular to said first and second planar surfaces, the space between said photographic plate and said cover plate being filled with transparent material having an index of refraction greater than or equal to that of the material of the cover plate; and

illuminating said edge surface with a laser light beam, a portion of said light beam being refractively transmitted to said hologram and creating a displayed image.

12. An apparatus for displaying an edge-illuminated hologram comprising:

a hologram;

means refractive of electromagnetic energy, having a plurality of surfaces, a first of said surfaces adapted to receive a hologram in proximity, for refracting electromagnetic energy from the first surface onto the hologram;

a layer of material transparent to electromagnetic energy filling the space between said hologram and said first of said surfaces, said material having an index of refraction greater than or equal to the index of refraction of said first of said surfaces;

means for providing electromagnetic energy; and

means adapted to illuminate a second of said surfaces with said electromagnetic energy for refractively illuminating the hologram.

13. The apparatus of claim 12, wherein said electromagnetic energy is light energy.

14. The apparatus of claim 13, wherein said first and second surfaces are planar and whose planar extensions intersect.

15. An apparatus for displaying an edge-illuminated hologram comprising:

a hologram;

transparent cover plate means having a planar surface adapted to receive a hologram in uniformly displaced proximity and an edge surface perpendicular to said planar surface;

a layer of material transparent to electromagnetic energy filling the space between said hologram and said cover plate, said material having an index of refraction greater than or equal to the index of refraction of said cover plate;

light source means; and

means adapted to illuminate said edge surface with light produced by said light source means for refractively illuminating the hologram.