Increasing an area from which reconstruction from a computer generated hologram may be viewed
A method of enlarging an observation window from which the reconstruction from a Computer Generated Hologram (CGH) may be viewed, including reproducing a CGH, and shifting a location of an exit pupil or observation window of an optical system reproducing the CGH. A method of increasing a viewing angle from which the reconstruction from a Computer Generated Hologram (CGH) may be seen, including producing a plurality of instances of a CGH, projecting each one of the instances in a different direction so that a first exit pupil of a first instance is close to a second exit pupil of a second instance. An optical system including a plurality of exit pupils associated with a plurality of optical components, further including a light deflector for jittering a location of a first exit pupil so as to increase an overlap of the first exit pupil with a second exit pupil. Related apparatus and methods are also described.
1. A method of enlarging an observation window of a projection system for displaying a Computer Generated Holographic (CGH) image, comprising:
producing a CGH image;
projecting the CGH image using an optical system, thereby producing an observation window from which the CGH image may be viewed by an observer;
using an image deflector optically coupled to the optical system to jitter a location of the observation window of the CGH image relative to a direction of an observer pupil location, thereby enlarging the observation window; and
controlling the jittering of the image deflector to keep the observation window at least partially overlapping the observer pupil during the jittering.
2. The method of claim 1 , in which an area of the observation window is enlarged laterally by jittering a direction of projection of the observation window relative to a direction of the observer pupil location.
3. The method of claim 2 , in which an area of the observation window is enlarged along a viewing direction by jittering the observation window along the direction of projection of the CGH image.
4. The method of claim 3 , and further comprising:
tracking a distance of an observer from the optical system used to project the CGH image;
shifting the observation window to correspond to the distance of the observer from the optical system; and
jittering the observation window along a direction to the observer.
5. The method of claim 2 , in which the area of the observation window, at the observer distance, is doubled.
6. The method of claim 2 , in which the jittering comprises jittering the direction in two dimensions.
7. The method of claim 6 , in which the image deflector comprises one of a group consisting of:
a mirror;
a prism; and
a tilted optical window.
8. The method of claim 2 , in which the jittering is performed by jittering a deflection direction of the image deflector, and wherein the image deflector is located at a location of a real CGH image.
9. The method of claim 1 , in which the producing a CGH image comprises projecting coherent light from a plurality of coherent light sources having a plurality of different colors onto one or more SLMs, thereby producing a plurality of different colored CGH images, and jittering locations of observation windows of the different colored CGH images relative to the observer location to substantially overlap the different colored CGH image observation windows.
10. The method of claim 1 , in which if the jittering comprises jittering a direction of the observation window relative to the observer location by an angle smaller than a threshold angle, a computer generated hologram for producing the CGH image is not changed to compensate for the change in direction.
11. The method of claim 1 wherein the observer pupil is kept at least partially inside the observation window over several cycles of jittering back and forth.
12. The method of claim 1 wherein the observer pupil is kept entirely inside the observation window during jittering.
13. The method of claim 1 wherein the direction of the observer's location is a direction of the observer pupil.
14. The method of claim 1 wherein controlling the jittering of the image deflector comprises controlling the jittering so that a first instance of the observation window of the CGH image overlaps a second instance of the observation window during the jittering.
15. The method of claim 1 and further comprising tracking a viewer's eye, and wherein jittering the location of the observation window of the CGH image relative to the direction of the observer pupil location comprises jittering an exit pupil of the optical system relative to the tracked direction of the viewer's eye pupil.
16. The method of claim 1 wherein the jittering is performed at a rate which is higher than a rate of refresh producing the CGH image.
17. Apparatus for projecting a Computer Generated Holographic (CGH) image, comprising:
a coherent light source;
a computer controlled Spatial Light Modulator (SLM) arranged to modulate the coherent light arranged to diffractively produce a CGH image;
an optical system arranged to project the CGH image, thereby producing an observation window from which the CGH image may be viewed by an observer; and
an optical element optically coupled to the optical system and arranged to cause a jitter of a location of the observation window of the CGH image relative to a direction of the observer pupil location and to keep the observation window at least partially overlapping the observer pupil during the jittering.
18. The apparatus of claim 17 , in which the optical element is configured to jitter a direction of projection of the observation window laterally relative to a direction of the observer pupil location, to laterally enlarge an area of the observation window.
19. The apparatus of claim 18 , in which the optical element is adapted to jitter light in two dimensions.
20. The apparatus of claim 17 , in which the optical element is configured to jitter the location of the observation window of the CGH image along a direction of a central ray of the projection of the CGH image.