Corrective Device for Disparity Control

1 - 20 . (canceled)

21 . A head-up display for a vehicle, comprising:

a picture generating unit arranged to project an image onto a screen;

a replicator arranged to receive the image from the screen and to output a plurality of replicas of the image from an output surface;

a corrective device located in an optical path of the plurality of replicas downstream from the replicator, the corrective device arranged to compensate for a complex curvature of an optical combiner downstream from the corrective device,

wherein the optical combiner is arranged to form a virtual image of the image that is visible from a plurality of viewing positions of a viewing window of the head-up display, the virtual image comprising a plurality of virtual image points; and

wherein the corrective device is further arranged such that a first depth cue provided in relation to a first part of the virtual image is different to a second depth cue provided in relation to a second part of the virtual image.

22 . The head-up display of claim 21 , wherein the first depth cue is provided by a first disparity offset introduced by the corrective device to at least some of the plurality of virtual image points, the first disparity offset of each virtual image point being substantially constant for the plurality of viewing positions of the viewing window.

23 . The head-up display of claim 22 , wherein the first disparity offset is a function of the position of the virtual image point in the virtual image.

24 . The head-up display of claim 22 , wherein the virtual image has a first side and a second side, and wherein the first disparity offset of the plurality of virtual image points increases in a first direction from the first side to the second side of the virtual image.

25 . The head-up display of claim 24 , wherein the first direction is orthogonal to the output surface of the replicator.

26 . The head-up display of claim 24 , wherein the increase in the first disparity offset is linear.

27 . The head-up display of claim 24 , wherein a top part of the virtual image appears at a deeper plane than a bottom part of the virtual image.

28 . The head-up display of claim 22 , wherein the corrective device is further arranged to introduce a second disparity offset to at least some of the plurality of virtual image points, the second disparity offset being substantially constant in a second direction across the virtual image, the second direction being orthogonal to the first direction.

29 . The head-up display of claim 28 , wherein the virtual image has an axis orthogonal to the first direction, and wherein the first disparity offset of the virtual image points on the axis is substantially zero.

30 . The head-up display of claim 21 , wherein the corrective device comprises a bulk optic having non-uniform power that compensates for non-uniform power of the optical combiner, wherein the non-uniform power of the bulk optic is refractive.

31 . The head-up display of claim 21 , wherein the corrective device comprises a Fresnel structure.

32 . The head-up display of claim 21 , wherein the corrective device has a non-complex surface or plurality of surfaces, each surface arranged at an angle relative to the output surface of the replicator.

33 . The head-up display of claim 21 , wherein the picture generating unit comprises a spatial light modulator arranged to display a hologram.

34 . The head-up display of claim 21 , wherein the screen is a diffuser.

35 . The head-up display of claim 21 , wherein the replicator is a waveguide.

36 . The head-up display of claim 21 , wherein the optical combiner is a windscreen of the vehicle.

37 . A method of head-up display in a vehicle, the method comprising:

projecting an image onto a screen using a picture generating unit;

receiving the image from the screen at a replicator and outputting a plurality of replicas of the image from an output surface of the replicator;

passing the plurality of replicas through a corrective device located in an optical path of the plurality of replicas downstream from the replicator, the corrective device compensating for a complex curvature of an optical combiner downstream from the corrective device;

forming a virtual image of the image using the optical combiner, the virtual image being visible from a plurality of viewing positions of a viewing window of the head-up display, the virtual image comprising a plurality of virtual image points; and

providing, using the corrective device, a first depth cue in relation to a first part of the virtual image that is different to a second depth cue provided in relation to a second part of the virtual image.

38 . The method of claim 37 , wherein the first depth cue is provided by introducing a first disparity offset to at least some of the plurality of virtual image points using the corrective device, the first disparity offset of each virtual image point being substantially constant for the plurality of viewing positions of the viewing window.

39 . The method of claim 38 , wherein the first disparity offset is a function of the position of the virtual image point in the virtual image.

40 . The method of claim 38 , wherein the virtual image has a first side and a second side, and wherein the first disparity offset of the plurality of virtual image points increases in a first direction from the first side to the second side of the virtual image.