Method and apparatus for displaying video data

1. A method for displaying image frames by a projection device, comprising:

receiving an image frame, with associated depth information;

determining based on the depth information at least a first group of pixels and a second group of pixels, and for each group of pixels determining a different corresponding focal distance;

controlling a focusing element, configured to provide a variable focal distance, to sweep periodically, wherein in each time period the focusing element is controlled to sweep throughout a range of provided focal distances; and

displaying within each time period each of the groups of pixels in different time intervals, each of the groups is displayed at a time interval when the provided focal distance is the corresponding focal distance of that group.

2. The method of claim 1 , wherein the projection device is a head mounted display.

3. The method of claim 1 , wherein the projection device is an optical head mounted display, allowing to simultaneously perceive the projected video and an environment of the projection device.

4. The method of claim 3 , wherein the depth information is computed from the environment underlying the projected image.

5. The method of claim 1 , further comprising repeating said receiving, said determining, said controlling and said displaying for a multiplicity of images of a video stream, wherein the video stream is displayed at a frame rate of at about least 10 frames per second.

6. The method of claim 5 , wherein

the video is a stereo video, comprising a left eye channel and a right eye channel, and having stereo disparity between the left eye channel and the right eye channel, wherein

a first sequence comprising images to be displayed to a left eye of a viewer and a second sequence rising images to be displayed to a right eye of the viewer, are retrieved from the video, wherein

the depth information is determined from stereo disparity between the images to be displayed to the left eye, and the images to be displayed to the right eye, and wherein

said displaying comprises projecting the first sequence to the left eye of the viewer, projecting the second sequence is projected to the right eye of the viewer.

7. A projecting system, comprising:

an active matrix for forming an image to be projected;

an optical system for projecting the image onto a screen having a focusing element configured to provide a variable focal distance; and

a hardware processor configured to:

receive an image frame with associated depth information;

determine based on the depth information at least a first group of pixels and a second group of pixels, and for each group of pixels determine a different corresponding focal distance;

control the focusing element to sweep periodically, wherein in each time period the focusing element is controlled to sweep throughout a range of provided focal distances; and

display within each time period each of the groups of pixels in different time intervals, each of the groups is displayed at a time interval when the provided focal distance is the corresponding focal distance of that group.

8. The projecting system of claim 7 , wherein pixels in a first group of pixels in the image are turned on when the optical system assumes a first focus position, and are off at other focus positions, and pixels in a second group of pixels in the image are turned on when the optical system assumes a second focus position and are off at other focus positions.

9. The projecting system of claim 7 , wherein a first group of pixels in the image is displayed when the optical system assumes a first focus position and a second group of pixels in the image is displayed when the optical system assumes a second focus position.