Methods and apparatus for light field projection

Patent metadata

Field	Value
Publication number	US-9405124-B2
Application number	US-201414248539-A
Country	US
Kind code	B2
Filing date	Apr 9, 2014
Priority date	Apr 9, 2013
Publication date	Aug 2, 2016
Grant date	Aug 2, 2016

Abstract

In exemplary implementations of this invention, light from a light field projector is transmitted through an angle-expanding screen to create a glasses-free, 3D display. The display can be horizontal-only parallax or full parallax. In the former case, a vertical diffuser may positioned in the optical stack. The angle-expanding screen may comprise two planar arrays of optical elements (e.g., lenslets or lenticules) separated from each other by the sum of their focal distances. Alternatively, a light field projector may project light rays through a focusing lens onto a diffuse, transmissive screen. In this alternative approach, the light field projector may comprise two spatial light modulators (SLMs). A focused image of the first SLM, and a slightly blurred image of the second SLM, are optically combined on the diffuser, creating a combined image that has a higher spatial resolution and a higher dynamic range than either of two SLMs.

First claim

What is claimed is:

1. A method that comprises using a light field projector to project a set of light rays onto a screen, wherein:
(a) each respective light ray, out of the set of light rays, enters a first side of the screen at an entrance angle and exits a second, different side of the screen at an exit angle; and
(b) over an interval of the entrance angles, which interval does not include the angle zero, the magnitude of the exit angle of each respective light ray is greater than the magnitude of the entrance angle of the respective light ray;
angles in each case being defined relative to a direction that is perpendicular to the screen.

2. The method of claim 1 , wherein the light rays create an automultiscopic display.

3. The method of claim 2 , wherein the automultiscopic display exhibits parallax in only a first dimension.

4. The method of claim 3 , wherein a diffuser that is positioned before or after the screen diffuses light, such that a light ray impacting the diffuser is spread only in a plane that is perpendicular to the first dimension.

5. The method of claim 2 , wherein the display exhibits parallax in two different directions, the two different directions being perpendicular to each other.

6. The method of claim 1 , wherein:
(a) the screen comprises a first planar array of optical elements and a second planar array of optical elements;
(b) the optical elements in each case are lenslets or lenticules;
(c) a plane located between the first and second planar arrays is conjugate to optical elements of the first planar array and to optical elements of the second planar array.

7. The method of claim 1 , wherein the screen comprises a first planar array of lenticules and a second planar array of lenticules.

8. The method of claim 1 , wherein the screen comprises a first planar array of lenslets and a second planar array of lenslets.

9. The method of claim 1 , wherein, within the light field projector, light is transmitted through or reflected from two or more spatial light modulators that each display time-varying spatial light modulation patterns.

10. The method of claim 1 , wherein the light field projector includes a coded aperture.

11. The method of claim 1 , wherein, over the interval of entrance angles, the exit angles of the respective light rays map to the entrance angles of the respective light rays according to a linear function.

12. A system comprising, in combination
(a) a screen, and
(b) a light field projector for projecting light onto the screen,
wherein the screen is configured such that, over a range of entrance angles, for each light ray that enters a first side of the screen at a non-zero entrance angle and exits a second, different side of the screen at an exit angle:
(1) the entrance angle has a first magnitude;
(2) the exit angle has a second magnitude; and
(3) the second magnitude is larger than the first magnitude;
angles being defined relative to a direction that is perpendicular to the screen.

13. The system of claim 12 , wherein the light field projector is configured to project an automultiscopic display on or through the screen.

14. A method comprising using a light field projector to project light rays through a focusing lens onto a diffusive screen, which screen is either transmissive or reflective, wherein:
(a) the light field projector comprises a first spatial light modulator and a second light modulator;
(b) the first spatial light modulator displays a first spatial light attenuation pattern;
(c) the second spatial light modulator displays a second spatial light attenuation pattern;
(d) an image projected on the screen comprises a product of the first and second patterns; and
(e) the image has a higher spatial resolution than the first spatial light modulator and a higher spatial resolution than the second light modulator.

15. The method of claim 14 , wherein the image has a higher dynamic range than the first spatial light modulator and a higher dynamic range than the second light modulator.

16. A system comprising, in combination:
(a) a diffusive screen, which screen is either transmissive or reflective;
(b) a focusing lens; and
(c) a light field projector for projecting light through the focusing lens onto the screen:
wherein
(i) the light field projector includes a first spatial light modulator and a second spatial light modulator; and
(ii) the projector is configured such that, during the projecting
(A) the first spatial light modulator displays a first spatial light attenuation pattern;
(B) the second spatial light modulator displays a second spatial light attenuation pattern;
(C) an image projected on the screen comprises a product of the first and second patterns; and
(D) the image has a higher spatial resolution than the first spatial light modulator and a higher spatial resolution than the second light modulator.

17. The system of claim 16 , wherein the image has a higher dynamic range than the first spatial light modulator and a higher dynamic range than the second light modulator.

Assignees

• Hirsch Matthew
• Wetzstein Gordon
• Raskar Ramesh
• Lee Vincent
• Massachusetts Inst Technology

Inventors

• Hirsch Matthew
• Wetzstein Gordon
• Raskar Ramesh
• Lee Vincent

Classifications

• H04N13/363

  using image projection screens (volumetric display H04N13/388) · CPC title

• H04N13/305

  using lenticular lenses, e.g. arrangements of cylindrical lenses · CPC title

• G03B21/00

  Projectors or projection-type viewers; Accessories therefor (devices for changing pictures G03B23/00) · CPC title

• G02B30/27 Primary

  involving lenticular arrays · CPC title

• H04N5/7416

  involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal · CPC title