Holographic terrain surface display system

• US 4,317,610 A
• Filed: 07/20/1979
• Issued: 03/02/1982
• Est. Priority Date: 07/20/1979
• Status: Expired due to Term

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Breglia, Denis R., Rodemann, Alfred H.
• Primary Examiner(s): Pinkham, Richard C.
• Assistant Examiner(s): Brown, Scott L.
• Application Number:
  US06/059,921
• Time in Patent Office: 956 Days
• Field of Search: 35/12 N, 35/12 W, 35/12 R, 350/3.79, 350/3.75, 350/3.77, 350/3.78, 350/3.85, 350/3.86, 434/38, 434/40, 434/44, 434/47, 434/43
• US Class Current: 359/24
• CPC Class Codes: G03H 1/00 Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
• CPC Class Codes: G09B 9/305 by viewing with a camera a small-scale model of the terrain

Abstract

A holographic terrain surface display system for simulating the visual scs available to a trainee pilot with respect to a terrain surface. The holographic terrain surface display system according to the present invention comprises a holographic film, having a plurality of holograms, illuminated by a laser light beam. The laser light beam is focused on one of the plurality of holograms to generate a real image of the terrain surface. The real image of the terrain surface is then projected onto a spherical front projection screen to be observed by the trainee pilot, at a remote location, through a closed circuit television system.

Claims

1. An apparatus for the visual display of a terrain surface, comprising in combination:

means for generating a collimated monochromatic laser light beam;

means spatially disposed downstream from said laser light beam generating means for expanding said laser light beam to a predetermined cross-sectional area;

mirror means spatially disposed directly downstream from said means for expanding said laser light beam, and having a signal input;

a halographic film positioned adjacent to said mirror means and having thereon a plurality of Fraunhofer holograms, each of said plurality of Fraunhofer holograms having therein a plurality of Fraunhofer diffraction patterns;

said mirror means being adapted for reflecting said laser light beam onto said holographic film such that said laser light beam is incident upon only one of said plurality of Fraunhofer holograms during any time period;

said mirror means being adapted for varying the angle at which said expanded laser light beam is reflected thereby so as to vary the angle at which said expanded laser light beam is incident upon each of said Fraunhofer holograms;

each of said Fraunhofer diffraction patterns being correlated to a predetermined angle of incidence of said laser light beam upon said halogram, such that the respective Fraunhofer diffraction pattern is reconstructed at a predetermined image plane when said hologram is illuminated by said laser light beam at said predetermined angle of incidence; and

means spatially disposed downstream from said holographic film adapted for forming a real image upon receiving the Fraunhofer diffraction pattern for rotating said real image formed thereby so as to modify said real image in an azimuthal direction to allow for the viewing of said real image, and for projecting said modified real image.

2. An apparatus according to claim 1, wherein said means for expanding said laser light beam comprises an inverted telescope.

3. An apparatus according to claim 1, wherein said predetermined cross-sectional area comprises a circle having a diameter of five millimeters.

4. An apparatus according to claim 1, wherein said mirror means comprises:

an elongated base having an upwardly protruding member at one end of said base, said upwardly protruding member having a centrally located circular perforation;

a reversible control motor rigidly attached to the other end of said elongated base, said reversible control motor having a rotatable shaft and an input;

a coupling effectively attached to the shaft of said reversible control motor;

a rotatable threaded rod having one end thereof effectively connected to said coupling, and having the opposite end thereof passing through the centrally located circular perforation of said upwardly protruding member, said threaded rod to rotate in either a clockwise or counterclockwise direction when said reversible control motor is activated;

a galvanometer motor having an input, and a rotatable shaft;

a motor base having a threaded circular perforation through which said threaded rod passes and having said galvanometer motor mounted thereon, said motor base slidably mounted on said elongated base for movement when said control motor is activated;

a rotatable mirror effectively connected to the shaft of said galvanometer motor, said mirror to rotate when said galvanometer motor is activated; and

a computer having an output effectively connected to the input of said reversible control motor and the input of said galvanometer motor, said computer to provide a control signal so as to effect the activation of said galvanometer motor and said reversible control motor, thereby causing said mirror means to vary the angle at which said laser light beam is reflected thereby.

5. An apparatus according to claim 1, wherein said means for forming a real image comprises:

a first lens spatially disposed downstream from said holographic film, for forming said real image upon receiving each Fraunhofer diffraction pattern of each of said plurality of Fraunhofer holograms;

a rotatable prism positioned directly downstream from said first lens for rotating said real image formed by said first lens so as to modify said real image to allow for the viewing of said real image in an azimuthal direction;

a motor having an input and a rotatable shaft connected to said rotatable prism, said motor to rotate said prism when said motor is activated;

a second lens spatially disposed directly downstream from said prism for projecting said modified real image onto a spherical front projection screen; and

a computer having an output effectively connected to the input of said motor, said computer to provide an azimuthal direction control signal so as to effect the activation of said motor, thereby causing said prism to rotate so as to allow for the viewing of said real image in said azimuthal direction.

6. An apparatus according to claim 1, wherein said real image is a terrain surface.

7. A holographic terrain surface display system comprising, in combination:

a laser light source for producing a collimated monochromatic laser light source;

a laser light beam expander spatially disposed downstream from said laser light source for expanding said laser light beam to a predetermined cross-sectional area;

a rotatable mirror assembly spatially disposed directly downstream from said laser light beam expander, and having a signal input;

a holographic film positioned adjacent to said rotatable mirror assembly and having thereon a plurality of Fraunhofer holograms, with each Fraunhofer hologram scaled equivalent to said expanded laser light beam;

said rotatable mirror assembly being adapted for reflecting said expanded laser light beam onto said holographic film such that said laser light beam is incident upon only one of said plurality of Fraunhofer holograms during any time period;

said rotatable mirror assembly being adapted for varying the angle at which said expanded laser light beam is reflected thereby so as to vary the angle at which said expanded laser light beam is incident upon each of said Fraunhofer holograms;

each of said plurality of Fraunhofer holograms having therein a plurality of Fraunhofer diffraction patterns;

each of said Fraunhofer diffraction patterns being correlated to a predetermined angle of incidence of said laser light beam upon said hologram, and each of said Fraunhofer diffraction patterns being reconstructed at a predetermined image plane when said hologram is illuminated by said laser light beam at said predetermined angle of incidence;

a first lens, spatially disposed downstream from said holographic film, said first lens being adapted for forming a real image upon receiving each Fraunhofer diffraction pattern of said Fraunhofer holograms;

a rotatable prism positioned directly downstream from said first lens for rotating said real image formed by said first lens so as to modify said real image in an azimuthal direction to allow for the viewing of said real image;

a motor having an input and a rotatable shaft connected to said prism, said motor to rotate said prism when activated;

a second lens spatially disposed directly downstream from said prism, for projecting said modified real image onto a spherical front projection screen; and

a computer having a first signal output, and a second signal output, with the first signal output thereof connected to the signal input of said rotating mirror assembly, and the second signal output thereof connected to the input of said motor, said computer to provide a first control signal so as to effect the activation of said rotatable mirror assembly such that said rotatable mirror assembly varies the angle at which said laser light beam is reflected thereby, and a second control signal to effect the activation of said motor, thereby causing said prism to rotate so as to allow for the viewing of said real image in an azimuthal direction.

8. A holographic terrain surface display system according to claim 7, wherein said laser beam expander comprises an inverted telescope.

9. A holographic terrain surface display system according to claim 7, wherein said rotatable mirror assembly comprises:

an elongated base having an upwardly protruding member positioned at one end thereof, said upwardly protruding member having a centrally located circular perforation;

a reversible control motor rigidly attached to the opposite end of said elongated base, said reversible motor having a rotatable shaft and an input connected to the first signal output of said computer;

a coupling effectively attached to the shaft of said reversible control motor;

a rotatable threaded rod having one end thereof effectively connected to said coupling and having the opposite end thereof passing through the centrally located circular perforation of said upwardly protruding member, said threaded rod to rotate in either a clockwise or counterclockwise direction when said reversible control motor is activated by the first control signal provided by said computer;

a galvanometer motor having an input connected to the second signal output of said computer, and a rotatable shaft;

a motor base having threaded circular perforation through which said threaded rod passes, and having said galvanometer motor mounted thereon, said motor base to slide along said elongated base when said control motor is activated, thereby moving said galvanometer motor upon said elongated base;

a rotatable mirror effectively connected to the shaft of said galvanometer motor, said mirror to rotate in either a clockwise or counterclockwise direction when said galvanometer motor is activated by the first control signal provided by said computer; and

said rotatable mirror to vary the angle at which said laser light beam is incident upon said holographic recording material.

10. A holographic terrain surface display system according to claim 7, wherein said real image comprises a terrain surface.