Transparent Flat-Panel Holographic Display

• US 20160223988A1
• Filed: 12/31/2015
• Published: 08/04/2016
• Est. Priority Date: 08/11/2007
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Jolly, Sundeep, Bove, V. Michael Jr., Smalley, Daniel E.
• Granted Patent: US 10,452,026 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 6/10 of the optical waveguide type G02B6/02, G02B6/24 take precedence; devices or arrangements for the control of light by electric, magnetic, electro-magnetic or acoustic means G02F1/00; transferring the modulation of modulated light G02F2/00; optical logic elements G02F3/00; optical analogue/digital converters G02F7/00
• CPC Class Codes: G02F 1/125 in an optical waveguide structure
• CPC Class Codes: G03H 1/02 Details of features involved during the holographic process; Replication of holograms without interference recording
• CPC Class Codes: G03H 1/2294 Addressing the hologram to an active spatial light modulator
• CPC Class Codes: G03H 2001/0224 Active addressable light modulator, i.e. Spatial Light Modulator [SLM] corresponding details, see subgroups of G03H2225/00
• CPC Class Codes: G03H 2001/2292 Using scanning means
• CPC Class Codes: G03H 2223/17 Element having optical power
• CPC Class Codes: G03H 2225/21 Acousto-optic SLM [AO-SLM]

Abstract

A flat-panel holographic video display includes a control layer and waveguide elements. Each waveguide element has a light-guiding substrate and an array of transducers configured to produce a diffraction grating comprising surface acoustic waves. The grating causes the waveguide to outcouple light, focusing it to, or producing wavefront curvatures consistent with it having emanated from, one or more points, in order to form a holographic image. The transducer array may include a large number of densely packed, vertically-adjacent transducers for each hogel for full parallax or may include a small number of vertically-adjacent transducers and a cylindrical optical element for each hogel. A spatial filter may be used to block noise. The display may be edge-illuminated by a collinear multicolor source. The substrate exit face may have nanopatterned areas alternated with flat areas in order to create regions of optimal internal reflection next to regions of low reflection.

Claims

1. A flat-panel holographic video display, comprising:

a control layer, the control layer comprising electrical inputs and configured for controlling drive electronics and light sources; and

at least one waveguide element coupled to the control layer, each waveguide element comprising;

a light-guiding substrate physically coupled to the control layer and having optical inputs; and

an array of surface acoustic wave transducers arranged along an outer surface of the light-guiding substrate, the array being electrically connected to the control layer and configured to produce a diffraction grating comprising surface acoustic waves, wherein the surface acoustic wave diffraction grating causes the waveguide element to outcouple light bouncing within the substrate and focuses the outcoupled light to one or more points, or produces wavefront curvatures in the light consistent with its having emanated from one or more point sources, in order to form a holographic image.

2. The holographic video display of claim 1, wherein the transducers produce surface acoustic waves having at least one frequency component that is a standing wave.

3. The holographic video display of claim 1, wherein the transducers are arranged in a regularly spaced array and light bouncing within the substrate which is not diffracted and outcoupled at a first surface acoustic wave diffraction grating moves through the substrate to a next surface acoustic wave diffraction grating.

4. The holographic video display of claim 1, wherein the transducer array comprises a large number of densely packed, vertically-adjacent transducers for each hogel.

5. The holographic video display of claim 1, wherein the transducer array comprises a small number of vertically-adjacent transducers for each hogel and further comprising a cylindrical optical element placed in front of each hogel.

6. The holographic video display of claim 1, further comprising a spatial filter that allows the display light to pass but blocks internal noise from scatter at the backplane.

7. The holographic video display of claim 1, wherein the display is edge-illuminated by a collinear multicolor source.

8. The holographic video display of claim 1, wherein the exit face of the substrate has nanopatterned areas alternated with pristine flat surface areas in order to create regions of optimal internal reflection next to regions of low Fresnel reflection, thereby providing for lossless propagation of confined light and efficient exit of unconfined light.

9. The holographic video display of claim 1, further comprising a second array of surface acoustic wave transducers oriented at 90 degrees to the transducer array, configured so that the display'"'"'s optical characteristics are uniform regardless of viewing direction.

10. The holographic video display of claim 1, further comprising at least one internal or external filter to render the display opaque or semi-opaque.

11. A holographic video image produced using the video display of claim 1.

12. A waveguide element for a flat-panel holographic video display, the waveguide element comprising:

a light-guiding substrate physically coupled to the control layer and having optical inputs; and

an array of surface acoustic wave transducers arranged along an outer surface of the light-guiding substrate, the array being electrically connected to the control layer and configured to produce a diffraction grating comprising surface acoustic waves, wherein the surface acoustic wave diffraction grating causes the waveguide element to outcouple light bouncing within the substrate and focuses the outcoupled light to one or more points, or produces wavefront curvatures in the light consistent with its having emanated from one or more point sources, in order to form a holographic image.

13. The waveguide element of claim 12, wherein the transducers produce surface acoustic waves having at least one frequency component that is a standing wave.

14. The waveguide element of claim 12, wherein the transducers are arranged in a regularly spaced array and light bouncing within the substrate which is not diffracted and outcoupled at a first surface acoustic wave diffraction grating moves through the substrate to a next surface acoustic wave diffraction grating.

15. The waveguide element of claim 12, wherein the transducer array comprises a large number of densely packed, vertically-adjacent transducers for each hogel.

16. The waveguide element of claim 12, wherein the transducer array comprises a small number of vertically-adjacent transducers for each hogel and further comprising a cylindrical optical element placed in front of each hogel.

17. The waveguide element of claim 12, wherein the exit face of the substrate has nanopatterned areas alternated with pristine flat surface areas in order to create regions of optimal internal reflection next to regions of low Fresnel reflection, thereby providing for lossless propagation of confined light and efficient exit of unconfined light.

18. A holographic video display comprising an array of waveguide elements according to claim 12.

19. A holographic video image produced using the video display of claim 13.

20. A method for creating a holographic image, comprising:

providing one or more wavelengths of light to a holographic video display, the display comprising at least one waveguide element, each waveguide element comprising;

a light-guiding substrate physically coupled to the control layer and having optical inputs; and

an array of surface acoustic wave transducers arranged along an outer surface of the light-guiding substrate, the array being electrically connected to the control layer and configured to produce a diffraction grating comprising surface acoustic waves, wherein the surface acoustic wave diffraction grating causes the waveguide element to outcouple light bouncing within the substrate and focuses the outcoupled light to one or more points, or produces wavefront curvatures in the light consistent with its having emanated from one or more point sources, in order to form a holographic image;

providing holographic information to the video display;

coupling the light received at the holographic video display into the waveguide elements for diffraction according to the holographic information; and

scanning the diffracted light to form the holographic image.

21. The method for creating a holographic image of claim 20, wherein the transducers produce surface acoustic waves having at least one frequency component that is a standing wave.

22. The method for creating a holographic image of claim 20, wherein the transducer array comprises a large number of densely packed, vertically-adjacent transducers for each hogel.

23. The method for creating a holographic image of claim 20, wherein the transducer array comprises a small number of vertically-adjacent transducers for each hogel and further comprising a cylindrical optical element placed in front of each hogel.

24. The method for creating a holographic image of claim 20, further comprising edge-illuminating the display.

25. The method for creating a holographic image of claim 20, wherein the exit face of the substrate has nanopatterned areas alternated with pristine flat surface areas in order to create regions of optimal internal reflection next to regions of low Fresnel reflection, thereby providing for lossless propagation of confined light and efficient exit of unconfined light.

26. A holographic video display that performs the method of claim 20.

27. A holographic image produced using the method of claim 20.