HOLOGRAPHIC IMAGE PROJECTION SYSTEMS

• US 20100142016A1
• Filed: 12/15/2008
• Published: 06/10/2010
• Est. Priority Date: 12/08/2008
• Status: Active Grant

• Current Assignee: Promethean Limited (Best Assistant Education Group Co.)
• Original Assignee: Light Blue Optics Ltd (Lifesize Communications Incorporated)
• Inventors: Routley, Paul, Lawrence, Nic, Cable, Adrian James
• Granted Patent: US 8,154,780 B2
• Time in Patent Office: Days
• US Class Current: 359/9
• 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 1/2205 using downstream optical component
• CPC Class Codes: G03H 1/2249 Holobject properties
• CPC Class Codes: G03H 2001/2215 Plane screen
• CPC Class Codes: G03H 2001/2218 being perpendicular to optical axis
• CPC Class Codes: G03H 2210/20 2D object

Abstract

We describe a holographic image projection system for projecting an image at an acute angle onto a surface, the system including: a spatial light modulator (SLM) to display a hologram; an illumination system to illuminate said displayed hologram; projection optics to project light from said illuminated displayed hologram onto said surface at an acute angle form said image; and a processor having an input to receive input image data for display and an output to provide hologram data for said SLM, wherein said processor is configured to: input image data and convert this to target image data; generate from said target image data hologram data for display as a hologram on the SLM to reproduce a target image; and wherein said target image is distorted to compensate for said projection of said hologram at an acute angle to form said image.

Claims

1. A holographic image projection system for projecting an image at an acute angle onto a surface, the system comprising:

a spatial light modulator (SLM) to display a hologram;

an illumination system to illuminate said displayed hologram;

projection optics to project light from said illuminated displayed hologram onto said surface at an acute angle form said image; and

a processor having an input to receive input image data for display and an output to provide hologram data for said spatial light modulator, and wherein said processor is configured to;

input image data;

convert said input image data to target image data;

generate from said target image data hologram data for display as a hologram on said spatial light modulator to reproduce a target image corresponding to said target image data; and

output said hologram data for said spatial light modulator; and

wherein said target image is distorted to compensate for said projection of said hologram at an acute angle to form said image.

2. A holographic image projection system as claimed in claim 1 wherein said conversion of said input image data to said target image data comprises mapping pixels of said target image data to pixels of said input image data and looking up values for said pixels of said target image data in said input image data.

3. A holographic image projection system as claimed in claim 1 wherein said conversion of said input image data to said target image data comprises mapping pixels of said input image data to pixels of said target image data such that a plurality of pixels of said target image data have values dependent on a single pixel of said input image data and additionally or alternatively such that a single pixel of said target image data has a value dependent on values of a plurality of pixels of said input image data.

4. A holographic image projection system as claimed in claim 1 wherein said conversion of said input image data to said target image data further comprises compensating for variations in per unit area brightness of said projected image due to said acute angle projection.

5. A holographic image projection system as claimed in claim 1 wherein said projected image comprises a multicolour image, wherein said illumination system comprises a multicolour illumination system and, wherein said conversion of said input image data to said target image data comprises compensating for different scaling of different colour components of said multicolour projected image due to said holographic projection.

6. A holographic image projection system as claimed in claim 5 wherein said compensating further comprises compensating for different aberrations of said different colour components by spatial mapping of said aberrations for a said colour component.

7. A holographic image projection system as claimed in claim 1 wherein said processor is configured to generate from said target image data hologram data for display by omitting to process portions of target image space in which said target image data is located from which data for said image is absent.

8. A holographic image projection system processor as recited in claim 1.

9. A holographic image projector including a holographic image projection system as claimed in claim 1 configured to stand on a surface and project downwards onto said surface, away from said projector, at said acute angle.

10. A holographic image projector as claimed in claim 9 wherein said surface is no more than 1 m, 0.5 m, 0.3 m, or 0.2 m away from an output of said projection optics.

11. A holographic image projection device having two configurations, a first configuration in which said device is able to project towards a vertical screen or surface and a second, table down projection configuration in which said device is configured to stand on a table surface and project downwards into said table surface, and wherein the device is further configured to apply distortion compensation to a holographically projected image when in said table down projection configuration, said distortion compensation compensating for distortion arising from projection of said image onto said table surface at an acute angle.

12. A holographic image projection device as claimed in claim 11 further comprising a sensor to automatically detect when said device is in said second configuration and to apply said distortion compensation in response to said automatic detection.

13. A holographic image projection device as claimed in claim 11 wherein said device includes a stand to support said device at a said acute angle to said table surface in said second, table down projection configuration.

21. A method as claimed in claim 12 wherein said acute angle is less than 65°

, 60°

, 55°

, 50°

, or 45°

.

22. A method as claimed in claim 12 wherein said light projecting to reproduce said image comprises projecting over a first distance to a nearest edge of said displayed image from optics performing said projecting and projecting over a second distance to a farthest edge of said displayed image from optics performing said projecting, and wherein said second distance is at least 50%, 100%, 150%, 200% or 250% greater than said first distance.

23. A method as claimed in claim 12 wherein said surface is no more than 1 m, 0.5 m, 0.3 m, or 0.2 m away from an output of optics projecting said light onto said surface.

14. A method of projecting an image onto a surface at an acute angle, the method comprising:

inputting display image data defining an image for display;

processing said display image data to generate target image data defining a target image for projection, wherein said target image comprises a version of said image for display distorted to compensate for projection onto said surface at said acute angle;

performing a holographic transform on said target image defined by said target image data to generate hologram data for a hologram of said target image;

displaying said hologram data on a spatial light modulator illuminated by at least one laser; and

projecting light from said at least one laser modulated by said hologram data displayed on said spatial light modulator onto said surface at said acute angle, to reproduce a substantially undistorted version of said image on said surface.

15. A method as claimed in claim 14 wherein said generating of said target image data comprises:

assigning values to pixels of said target image by identifying, for a pixel of said target image, a corresponding pixel in said image for display and assigning a value to said pixel of said target image dependent on said value of said corresponding pixel in said input image for display.

16. A method as claimed in claim 15 wherein said identifying of said corresponding pixel in said image for display comprises:

mapping a location of said target image to a location of said corresponding pixel in said image for display by mapping to a space of said input image for display a target image space comprising a version of a space of said projected image distorted to compensate for said acute angle projection, said target image space including said target image.

17. A method as claimed in claim 15 wherein said assigning of a value to said pixel of said target image dependent on said value of said corresponding pixel in said input image comprises scaling a brightness of target image pixel to compensate for a brightness for unit area distortion of said acute angle projection.

18. A method as claimed in claim 14 wherein said generating of said target image data comprises mapping pixels of said input image for display to pixels of said target image, filling in holes in pixel values of said target image data using said display image data.

19. A method as claimed in claim 14 wherein said input image for display comprises a multicolour image, wherein said display image data and said target image data comprise data for a plurality of colour planes of said input image, and wherein said light comprises light of a corresponding plurality of different wavelengths, the method further comprising scaling said colour planes of said target image to compensate for differing diffraction angles of said different wavelengths of light by said spatial light modulator.

20. A method as claimed in claim 19 further comprising applying different said distortions to different colour planes of said target image data to compensate for chromatic aberrations in said projecting of said multicolour image.

24. A carrier carrying processor control code to implement a method of projecting an image onto a surface at an acute angle, the method comprising:

inputting display image data defining an image for display;

processing said display image data to generate target image data defining a target image for projection, wherein said target image comprises a version of said image for display distorted to compensate for projection onto said surface at said acute angle;

performing a holographic transform on said target image defined by said target image data to generate hologram data for a hologram of said target image; and

outputting said hologram data for display of said hologram on a spatial light modulator (SLM) for reproducing said image for display on said surface.

25. A carrier as claimed in claim 24 further comprising code for assigning values to pixels of said target image by identifying, for a pixel of said target image, a corresponding pixel in said input image for display and assigning a value to said pixel of said target image dependent on said value of said corresponding pixel in said input image for display.

26. A method of sharing an image between a group of people, the method comprising:

providing a holographic image projection device having a table-down projection configuration in which said device is configured to stand on a table surface and project downwards onto said table surface; and

projecting an image holographically onto said table surface to share said image.

27. A method as claimed in claim 26 wherein said device is configurable between two image projection configurations, a first configuration in which said device is able to project towards a vertical screen or surface and said table-down projection configuration, the method further comprising selecting one of said first configuration and said table down projection configuration.

28. A method as claimed in claim 27 further comprising said holographic image projection device automatically detecting a selected configuration and applying distortion composition to said projected image on detection of said table down projection configuration to compensate for distortion arising from projection of said image onto said table surface at an acute angle.

29. A method as claimed in claim 27 further comprising generating a plurality of temporal holographic subframes for display in rapid succession said that corresponding temporal subframe images average in an observer'"'"'s eye to give the impression of a reduced—

noise displayed image.