TWO-DIMENSIONAL HOLOGRAPHIC IMAGE PROJECTION SYSTEMS

• US 3,632,181 A
• Filed: 03/12/1970
• Issued: 01/04/1972
• Est. Priority Date: 03/12/1970
• Status: Expired due to Term

• Current Assignee: Mellon Bank National Association A National Banking Association
• Original Assignee: Jerald D. Lee
• Inventors: Lee, Jerald D.
• Primary Examiner(s): Schonberg, David
• Assistant Examiner(s): Stern, Ronald J.
• Application Number:
  US05/019,024
• Time in Patent Office: 663 Days
• Field of Search: 350/3.5,9 352/85 343/6,17 35/12N
• US Class Current: 359/26
• CPC Class Codes: G03H 1/22 Processes or apparatus for obtaining an optical image from holograms G03H1/26 - G03H1/34 take precedence
• CPC Class Codes: G03H 1/265 Angle multiplexing; Multichannel holograms G03H1/268 takes precedence
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A system for projecting an image onto a two-dimensional screen from a Fresnel-type off-axis hologram constructed of a threedimensional object. The hologram is illuminated with at least one narrow beam of reconstructing light having an area significantly smaller than that of the hologram. As the beam of reconstructing light is moved relative to the hologram, the two-dimensional image presents a changing view of the three-dimensional object. If two narrow parallel reconstructing beams illuminate the hologram, two images of the three-dimensional object are formed in a stereoscopic effect, the two images being separated from each other by distinct polarization of the two hologram reconstructing beams or by a provision of separate exit pupils. A plurality of holograms may be so reconstructed in succession to form an apparently continuously changing view of the object and has application to simulated motion relative to the object, such as that of an aircraft approaching a runway as an object.

Claims

1. In the art of holography wherein a Fresnel hologram is constructed by interfering at a finite angle object-modified and reference radiation beams, a method of projecting at least one image of the object onto a diffusion screen for viewing by an observer, comprising the steps of:

providing relative motion between the hologram and at least one narrow beam of reconstructing radiation having a crosssectional area significantly less than the area of said hologram and maintaining a uniform angular relationship therewith, whereby a portion of the intensity of said at least one radiation beam is diffracted by the hologram into at least one object-image-carrying beam, positioning the diffusion screen in said at least one diffracted object-image-carrying beam, projecting said at least one diffracted object-image-carrying beam to form at least one object image in real space coincident with the diffusion screen, and directing said object-image-carrying beam into an exit pupil of limited extent slightly larger in cross section than the observer'"'"''"'"'s eyes, thereby to conserve reconstructing radiation power.

2. The method according to claim 1 wherein the step of providing relative motion between the hologram and at least one narrow beam of reconstructing radiation includes providing relative motion betWeen the hologram and exactly two parallel narrow beams of reconstructing radiation, the two narrow beams of reconstructing radiation being individually polarized in directions displaced 90* from each other, whereby a portion of the intensity of the two reconstructing radiation beams is diffracted by the hologram into two object-image-carrying beams.

3. The method according to claim 1 wherein the step of providing relative motion between the hologram and at least one narrow beam of reconstructing radiation includes providing relative motion between the hologram and exactly two parallel narrow beams of reconstructing radiation, whereby a portion of the intensity of the two reconstructing radiation beams is diffracted by the hologram into two object-image-carrying beams, each of the two diffracted object-image-carrying beams being directed into spatially separate exit pupils by an imaging lens position near the diffusion screen.

4. A method of simulating controlled motion relative to a surroundings for viewing by an observer, comprising the steps of:

constructing a plurality of holograms of said surroundings along a predetermined path therethrough, illuminating each hologram in predetermined sequence by at least one narrow reconstructing radiation beam having a cross-sectional area significantly less than the area of the hologram, said illumination additionally being accomplished in a manner that images are successively reconstructed therefrom in substantially the same real space, positioning a diffusion screen in said reconstructed image real space to provide two dimensional images thereon, positioning a light-collecting lens relative to the diffusion screen to provide an exit pupil of limited extent slightly larger in cross section than the observer'"'"''"'"'s eyes, controlling the rate at which the successive holograms are reconstructed, thereby to control the simulated speed of motion through said surroundings, and controlling the location of each successive hologram that is illuminated by said at least one narrow reconstructing radiation beam, thereby to simulate a controlled lateral position within the surroundings relative to said predetermined path.

5. The method according to claim 4 wherein said plurality of holograms are formed on a film strip which is drawn during reconstruction through a reconstructing beam path, and wherein the reconstructing beam is pulsed once for each hologram that is positioned in said beam path.

6. The method according to claim 4 wherein the construction of each of said plurality of holograms includes recording thereon an image modification of said surroundings that may be reconstructed independently of said surroundings alone, and wherein the step of illuminating each hologram includes illumination thereof with a second narrow reconstructing radiation beam in a manner to reconstruct an image of said modification of said surroundings.

7. In a holography system wherein a Fresnel hologram is constructed by interfering at a finite angle object-modified and reference radiation beams, apparatus for projecting at least one image of an object onto a diffusion screen for viewing by an observer comprising, means for providing relative motion between the hologram and at least one narrow beam of reconstructing radiation having a cross-sectional area significantly less than the area of said hologram and for maintaining a uniform angular relationship therewith, whereby a portion of the intensity of said at least one radiation beam is diffracted by the hologram into at least one object-image-carrying beam, a diffusion screen positioned in said at least one diffracted object-image-carrying beam, means for projecting said at least one diffracted object-image-carrying beam to form at least one object image in real space coincident with said diffusion screen, and means for directing said image beam into an exit pupil of limited extent slightly larger in cross section than the Observer'"'"''"'"'s eyes thereby to conserve reconstructing radiation power.

8. Apparatus according to claim 7 wherein said diffusion screen has the characteristic of scattering light over only a narrow range of angles corresponding to said limited extent of said exit pupil.

9. Apparatus according to claim 7 wherein said directing means comprises a light-collecting lens which limits the extent of said exit pupil.