3D display

• US 20040042161A1
• Filed: 05/07/2003
• Published: 03/04/2004
• Est. Priority Date: 11/07/2000
• Status: Active Grant

• Current Assignee: Mind Fusion, LLC (Ascend Innovation Management, LLC)
• Original Assignee: F Poszat Hu LLC (Intellectual Ventures LLC)
• Inventors: Cameron, Colin D, Slinger, Christopher W
• Granted Patent: US 7,230,746 B2
• Time in Patent Office: Days
• US Class Current: 361/681
• CPC Class Codes: G03H 1/0808 Methods of numerical synthesis, e.g. coherent ray tracing [CRT], diffraction specific
• 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 1/2249 Holobject properties
• CPC Class Codes: G03H 1/2294 Addressing the hologram to an active spatial light modulator
• CPC Class Codes: G03H 2001/0072 for wavefront conjugation wherein the hologram generates a wavefront conjugating a predetermined object, e.g. null testing, positioning, comparative holography
• CPC Class Codes: G03H 2210/30 3D object

Abstract

A method of generating a Computer Generated Hologram (CGH) using the diffraction specific algorithm allows a curved wavefront to be produced from a single hogel, rather than the planar waves of the prior art. This allows a wavefront from a singel hogel to generate a point in the image volume. An imaginary wavefron is transmitted from each point in the image volume and sampled at a plurality of points over the hogel. These samples are used to produce a set of complex Fourier coefficients that can be used to approximate the original waveform.

Claims

1. A computer generated holographic display comprising at least a light diffracting panel notionally divided into a plurality of hogels, and image calculation means, wherein image data is created by the steps of

for each point in the image volume, a wavefront is mathematically projected from the point to each hogel;

the wavefront at each hogel is sampled at a plurality of points across the hogel;

the wavefront is approximated into a set of frequency coefficients, which are stored;

the coefficients are used to produce a diffraction pattern across the hogel such that light diffracted by the hogel produces a curved wavefront, this wavefront going on to produce at least one point in the image volume.

2. A computer generated holographic display as claimed in claim 1 wherein the number of samples taken across a hogel is changed according to the position of the hogel in the display panel.

3. A computer generated holographic display as claimed in claim 1 wherein the number of samples taken across a hogel is changed according to an estimated number required.

4. A computer generated holographic display as claimed in any of the above claims wherein a fast Fourier transform algorithm is used to approximate the frequency components of the wavefront.

5. A computer generated holographic display as claimed in claims 1 to 3 wherein a numerical integration algorithm is used to approximate the frequency components of the wavefront.

6. A computer generated holographic display as claimed in any of the above claims wherein the curved wavefront emanating from a given hogel is focussed to a point after passing through Fourier optics.

7. A computer generated holographic display as claimed in claims 1 to 5 wherein the curved wavefront emanating from a given hogel is focussed to a point without passing through Fourier optics.

8. A computer generated hologram display system as claimed-in any of the above claims wherein the image calculation means is arranged to calculate a plurality of image points that together make up an image having full parallax.

9. A computer generated hologram display system as claimed in any of the claims 1 to 7 wherein the image calculation means is arranged to calculate a plurality of image points that together make up an image having horizontal parallax only.

10. A computer generated hologram display system as claimed in claim 1 wherein the display system comprises:

a light source,

a first spatial light modulator means having an associated updating frame rate, that modulates light from the light source,

relay optics means in the path of the light from the first spatial light modulator means for guiding the modulated light therefrom,

a second spatial light modulator having an associated read-out frame rate in the path of the guided light from the relay optics means and arranged to produce a real image therefrom for display,

wherein the updating rate of the first spatial light modulator means is greater than the read-out frame rate of the second spatial light modulator means.

13. A computer program product capable of producing a computer generated hologram on a display according to claim 1.

14. A carrier including a computer program according to claim 13.

11. A method of producing a computer generated hologram on a display comprising at least a light diffracting panel notionally divided into a plurality of hogels, and image calculation means, where the method comprises the steps of:

for each point in the image volume, mathematically projecting a wavefront from the point to each hogel;

sampling the wavefront at each hogel at a plurality of points across the hogel;

approximating the wavefront into a set of frequency coefficients, which are stored;

producing a diffraction pattern across the hogel using the coefficients such that light diffracted by the hogel produces a curved wavefront, this wavefront going on to produce at least one point in the image volume.

15. A computer program product capable of producing a computer generated hologram according to the method of claim 11.

16. A carrier including a computer program according to claim 15.

12. A method of correcting for known aberrations present in the optical system of a computer generated hologram display system comprising an image volume and a light diffraction panel notionally divided up into a plurality of hogels, wherein:

a first wavefront is mathematically projected from a point in the image volume through the optical system to a hogel, the wavefront being distorted by any aberrations in the optical system;

the calculated distortions in the first wavefront are used to generate a real, pre-distorted second wavefront emanating from the hogel, such that as the second wavefront passes through the distorting optics the pre-distortions on the second wavefront are removed.

17. A computer generated holographic display substantially as described herein with reference to FIGS. 5, 6b, 9, 10 and 11.

18. A method of correcting for known aberrations present in the optical system of a computer generated hologram display system substantially as described herein with reference to FIG. 11.