Hologram writing apparatus and method

• US 4,655,539 A
• Filed: 10/23/1984
• Issued: 04/07/1987
• Est. Priority Date: 04/18/1983
• Status: Expired due to Fees

• Current Assignee: Aerodyne Products Corp (Industrial Technologies, Inc.)
• Original Assignee: Aerodyne Products Corp (Industrial Technologies, Inc.)
• Inventors: Caulfield, H. John, Camac, Morton
• Primary Examiner(s): Arnold, Bruce Y.
• Application Number:
  US06/664,392
• Time in Patent Office: 896 Days
• Field of Search: 350/3.66, 350/3.6, 350/3.67, 350/320, 358/90, 358/2
• US Class Current: 359/9
• CPC Class Codes: G03H 1/08 Synthesising holograms, i.e. holograms synthesized from objects or objects from hologramsusing electric digital computers G06F; G06T
• CPC Class Codes: G03H 2210/46 for subsequent optical processing G03H1/268 takes precedence

Abstract

An improved hologram writer writes a halogram from a three dimensional data stream or signal such as a signal corresponding to a scene, a picture, drawing or the like. A reference beam and an object or information beam are directed to a holographic recording member, and the information beam is focused through a point near the holographic recording member. A diverger means such as a diffuser, a lens array, a holographic element or the like adapted to form an expanding beam from a point image or spot receives a focused modulated information beam and directs it to the holographic recording member as a divergent beam. The beam may be sent directly to the recording member or it may be optically or otherwise relayed to the member. The point source may be in front of, behind or within the holographic recording member.

Claims

1. Apparatus for hologram writing comprising

a source of a holographic signal,

a laser,

a modulator adapted to impart signal information from said source to a beam from said laser,

a beam splitter, positioned to receive said beam from said laser, said beam splitter being adapted to split said laser beam into an information beam and a reference beam,

scanning means adapted to scan said laser beam in two coordinates,

means to direct both said reference beam and said information beam to said scanning means,

a holographic medium adapted and positioned to receive a reference beam and an information beam and to form a hologram therefrom,

means to direct said reference beam to said holographic medium, said reference beam thereby scanning across said holographic medium in said two coordinates,

a diffuser element adapted to receive a beam and form therefrom a light beam expanding from the equivalent of a point on said element,

means to direct said information beam from said scanning means to said diffuser element effectively at a point which is scanned across said diffuser element in two coordinates,

means to direct said expanding beam from said diffuser element to said holographic medium, and

means to change the effective distance of separation of the diffuser point source of said expanding beam from said holographic medium, thereby effectively providing scanning of said point source in the third coordinate.

2. The apparatus of claim 1, wherein said diffuser element and said holographic medium are positioned parallel with one another and wherein said means to change the effective distance of separation comprpises means to move at least one of said diffuser element and said holographic medium with respect to one another.

3. The apparatus of claim 1, wherein said diffuser element is mounted in a position slanted at a substantial angle with respect to said holographic medium, whereby said diffuser element point source is moved closer to and further away from said holographic medium as the position of said information beam is moved on said diffuser element.

4. The apparatus of claim 1, said means to direct said expanding beam including an optical relay means positioned and adapted to receive said expanding information beam from said diffuser element and to form an equivalent point source of said information beam from said diffuser element, said formed point source being closely adjacent to said holographic medium.

5. The apparatus of claim 1, said means to direct said expanding beam including a lens positioned and adapted to receive said expanding information beam from said diffuser element and to focus said information beam at a point closely adjacent to said holographic medium.

6. In a hologram writer adapted to write a holographic record of an object beam and a reference beam from input signals corresponding to x, y, z coordinates, the improvement comprising

mounting means for a holographic recording member,

a source of a narrow beam of coherent radiation,

a diffuser element adapted to transform a point of light from said source to an expanding light beam,

an object beam scanner adapted and positioned to receive a light beam from said source and to scan said beam as essentially a moving point on said diffuser element to form an expanding object beam,

a reference beam scanner adapted and positioned to receive a beam of coherent radiation and scan said beam on said recording member,

relaying means positioned to receive said expanding object beam and to relay said beam to said holographic recording member,

and means to move said holographic recording member with respect to said diffuser element.

7. The apparatus of claim 6, wherein said object beam scanner and said reference beam scanner are mechanical scanners.

8. The apparatus of claim 6, wherein at least one of said scanners is an accousto-optical scanner.

9. The apparatus of claim 6, wherein at least one of said scanners includes a spatial light modulator.

10. The apparatus of claim 6, wherein said diffuser element is a lens array.

11. Apparatus according to claim 6, wherein said relaying means comprises at least two lenses positioned and arranged sequentially along the path of said expanding beam to direct said beam to said holographic recording member.

12. Apparatus according to claim 6, wherein said relaying means is a dielectric lens.

13. Apparatus according to claim 6, wherein said relaying means is at least one Fresnel lens.

14. Apparatus according to claim 6, wherein said relaying means is at least one holographic lens.

15. In the apparatus of claim 6, said object beam scanner and said reference beam scanner being positioned and adapted to direct said beams to opposite sides of said holographic recording means to produce a reflection hologram.

16. In the apparatus of claim 6, said object beam scanner and said reference beam scanner being positioned and adapted to direct said beams to the same side of said holographic recording member to produce a transmission hologram.

17. In the apparatus of claim 6, said holographic recording member and said diffuser element being positioned parallel with one another.

18. Apparatus according to claim 17 having means to move said holographic recording member and said diffuser element relative to one another, whereby motion between said member and said element varies the length of the light path therebetween.

19. In the apparatus of claim 6, said holographic recording member and said diffuser element being positioned to slant at a substantial angle with respect to one another, whereby different positions along said diffuser element represent different distances from said holographic recording member.

20. Apparatus according to claim 19, whereby motion between said holographic recording member and said diffuser element varies the length of the light path therebetween.

21. Apparatus according to claim 6 wherein the means to move said holographic recording member with respect to said diffuser element is adapted to vary the length of the light path between said diffuser element and said holographic member and wherein motion therebetween is adapted to be continuous motion.

22. Apparatus according to claim 6 wherein the means to move said holographic recording member with respect to said diffuser element is adapted to vary the length of the light path between said diffuser element and said holographic recording member and wherein motion therebetween is adapted to be stepped motion.

23. In a hologram writer adapted to write a holographic record of an object beam and a reference beam from input signals corresponding to x,y,z coordinates, the improvement comprising

mounting means for a holographic recording member,

a source of a narrow beam of coherent rediation,

a diffuser element adapted to transform a point of light from said source to an expanding light,

an object beam scanner adapted and positioned to receive a light beam from said source and to scan said beam as effectively a moving point on said diffuser element in positions corresponding to three coordinates,

means to direct said expanding object beam to said holographic recording member,

a reference beam scanner adapted and positioned to receive a beam from said source and to scan said beam on said holographic recording member,

means to vary the size of said reference beam in coordination with the size of said object beam at said holographic recording member,

and means to move one of said holographic recording member and said diffuser element with respect to one another to vary the beam distance therebetween.

24. A hologram writer according to claim 23, wherein the size and relative shape of said reference beam at said holographic recording member conforms with the size and relative shape of said object beam at said holographic recording member.

25. Apparatus according to claim 23 having a spatial light modulator adapted to modulate the size of said reference beam.

26. Apparatus according to claim 23 having modulating means adapted to simultaneously modulate the intensities of both the reference beam and the object beam, whereby said hologram writier is enabled to produce holograms having shades of gray.

27. A method of writing holograms from input signals of three dimensional graphic information comprising

forming from said input signals an object beam having a small diameter substantially equivalent to a point source and directing said object beam to a movable point on a diffuser element, thereby producing an expanding object beam emanating from a position on said diffuser element as an diffuser point source, and scanning said object beam on said diffuser element in two directions corresponding to x and y coordinates,

directing to a holographic recording member the emanating object beam from said diffuser element and scanning the distance between said equivalent point source and said holographic recording member to correspond to a scanning z coordinate,

simultaneously directing a coherent reference beam to said holographic recording member and synchronously scanning said reference beam in the x and y coordinate directions in unison with said object beam on said holographic member, and adjustably maintaining the diameter of said reference beam at said holographic recording member of a size substantially equal to the size of said expanding object beam on said holographic recording member.

28. The method of claim 27 wherein one of said holographic recording member and said diffuser element is moved with respect to the other of said member and element in the z coordinate direction.

29. The method of claim 27, wherein said equivalent point source on said diffuser element is relayed optically to a movable point close to said holographic recording member and said movable point is moved in the Z coordinate direction with respect to said holographic recording member.

30. The method of claim 27, wherein said small diameter substantially equivalent point source is scanned in said z coordinate direction to positions in front of said holographic recording member, behind said holographic member and within said holographic recording member.

31. In a method of hologram writing wherein an information-containing object beam and a reference beam are simultaneously scanned across a holographic recording member, the improvement comprising

scanning an object beam as substantially a point in two coordinate directions on a diffuser element to form a diverging object beam from a scanning equivalent point source on said diffuser element,

directing said beam to a holographic recording member from said point source, thereby scanning said expanding object beam on said member in two coordinate directions,

varying the distance between said point source and said holographic recording member to represent a varying third coordinate direction, and

simultaneously scanning said reference beam on said holographic recording member synchronously with said scanning object beam and controlling the area and shape of said reference beam synchronously with the area and shape of said expanding object beam as the size of said expanding object beam varies with the distance between said point source and said holographic recording member.