Optical apparatus and method

1. An apparatus comprising:

a first display;

an exit pupil expanding light guide, said exit pupil expanding light guide having an in-coupling region and an out-coupling region, the in-coupling region being disposed at the first display to in-couple primary video content from the first display, and the out-coupling region being disposed to out-couple the primary video content towards an eye of a user;

a second display disposed at the out-coupling region of the exit pupil expanding light guide to transmit secondary video content, through the exit pupil expanding light guide at the out-coupling region, towards the eye of the user, said second display conveying the secondary video content to coincide in place with and augment the primary video content, said second display including a display panel aligned with the out-coupling region in a plane substantially parallel to the out-coupling region;

at least one processor; and

at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to:

convey the primary video content to the user from the first display, said primary video content having a movement component in a first direction; and

convey the secondary video content coinciding in place with and augmenting the primary video content to the user from the second display, the secondary video content having a movement component in a second direction substantially opposite to the first direction,

whereby motion sickness symptoms caused by the primary video content are alleviated.

2. The apparatus as claimed in claim 1 , wherein the second display and the exit pupil expanding light guide are configured such that the secondary video content is coincident with at least some of the primary video content when the primary video content and the secondary video content exit the exit pupil expanding light guide at the out-coupling region.

3. The apparatus as claimed in claim 1 , wherein the primary video content forms a virtual image for the user, and the secondary video content forms a real image for the user.

4. The apparatus as claimed in claim 3 , wherein the real image is at least partially coincident with the virtual image.

5. The apparatus as claimed in claim 1 , wherein out-coupling region is substantially optically transparent to light transmitted by the second display.

6. The apparatus as claimed in claim 1 , wherein the in-coupling region comprises at least one in-coupling diffraction grating and the out-coupling region comprises at least one out-coupling diffraction grating.

7. The apparatus as claimed in claim 6 , wherein the exit pupil expanding light guide comprises a further diffraction grating configured to expand the first light in a first dimension, and the out-coupling diffraction grating is configured to expand the first light in a second dimension, orthogonal to the first dimension.

8. The apparatus as claimed in claim 1 , further comprising:

a polarizer or a shutter, positioned at least partially between the second display and the out-coupling region, configured to block light reflected from second display and directed towards the out-coupling region.

9. The apparatus as claimed in claim 1 , wherein the apparatus is a head-mounted display apparatus.

10. A method comprising:

conveying primary video content to a user from a first display, the first display being coupled to an in-coupling region of an exit pupil expanding light guide and the user receiving the primary video content at an out-coupling region of the exit pupil expanding light guide, the primary video content having a movement component in a first direction; and

conveying secondary video content to coincide in place with and to augment the primary video content from a second display, said second display including a display panel aligned with the out-coupling region of the exit pupil expanding light guide in a plane substantially parallel to the out-coupling region, the secondary video content having a movement component in a second direction substantially opposite to the first direction,

whereby motion sickness symptoms caused by the primary video content are alleviated.

11. The method as claimed in claim 10 , wherein the secondary video content is coincident with at least a portion of the primary video content when the primary video content and secondary video content exit the out-coupling region.

12. The method as claimed in claim 10 , wherein the primary video content forms a virtual image for the user, and the secondary video content forms a real image for the user.

13. The method as claimed in claim 12 , wherein the real image is at least partially coincident with the virtual image.