Image projector

1. A head-up display for a vehicle arranged to display a picture, the head-up display comprising:

a first optical sub-system arranged to output a spatially-modulated light field, wherein the first optical sub-system comprises:

a light source arranged to emit light; and

a spatial light modulator arranged to receive the light from the light source and spatially-modulate the light in accordance with a computer-generated hologram displayed on the spatial light modulator; and

a second optical sub-system arranged to receive the spatially-modulated light field from the first optical sub-system and to project the spatially-modulated light field onto a windscreen of the vehicle to form a virtual image on the windscreen,

wherein the first optical sub-system is arranged to be disposed proximate an upper region of the windscreen and the second optical sub-system is arranged to be disposed underneath the dashboard of the vehicle proximate a lower region of the windscreen.

2. A head-up display for a vehicle arranged to display a picture, the head-up display comprising:

a first optical sub-system arranged to output a spatially-modulated light field, wherein the first optical sub-system comprises:

a light source arranged to emit light; and

a spatial light modulator arranged to receive the light from the light source and spatially-modulate the light in accordance with a computer-generated hologram displayed on the spatial light modulator; and

a second optical sub-system arranged to receive the spatially-modulated light field from the first optical sub-system and to project the spatially-modulated light field onto a windscreen of the vehicle to form a virtual image on the windscreen,

wherein the first optical sub-system is arranged to be disposed proximate an upper region of the windscreen and the second optical sub-system is arranged to be disposed underneath the dashboard of the vehicle proximate a lower region of the windscreen; and

wherein the second optical sub-system is arranged to perform an optical Fourier transform of the spatially-modulated light field.

3. A head-up display as claimed in claim 1 , the head-up display being arranged for display of the picture to a viewer, arranged such that a lens of an eye of the viewer can perform an optical Fourier transform of the spatially-modulated light field.

4. A head-up display as claimed in claim 2 wherein the virtual image is a virtual image of the picture.

5. A head-up display as claimed in claim 1 wherein the first optical sub-system is disposed: on the vehicle roof; within the internal roof liner; on the rear-view mirror housing; on a roofline electronics panel; or on a sun visor.

6. A head-up display as claimed in claim 1 wherein the second optical sub-system comprises at least one reflective element.

7. A head-up display as claimed in claim 6 wherein the at least one reflective element of the second optical sub-system has optical power.

8. A head-up display as claimed in claim 6 wherein the at least one reflective element of the second optical sub-system comprises a freeform optic or comprises a freeform optical surface arranged to at least partially compensate for the shape of the windscreen in the area of the windscreen which receives light of the picture.

9. A head-up display as claimed in claim 1 wherein the at least one reflective element comprises a laser-line selective filter arranged to allow propagation of light of the picture through the head-up display and suppress the propagation of light of having a different wavelength through the head-up display.

10. A head-up display as claimed in claim 1 wherein the first optical sub-system is substantially planar and comprises a substantially planar waveguide arranged to guide light from the light source to the spatial light modulator and guide spatially-modulated light from the spatial light modulator to an output of the waveguide along a continuous optical path.

11. A head-up display as claimed in claim 1 wherein the first optical sub-system comprises at least one reflective element.

12. A head-up display as claimed in claim 11 wherein the at least one reflective element of the first optical sub-system has optical power.

13. A head-up display as claimed in claim 11 wherein the at least one reflective element of the first optical sub-system comprises a freeform optic or comprises a freeform optical surface arranged to at least partially compensate for the shape of the windscreen in the area of the windscreen which receives light of the picture.

14. A head-up display as claimed in claim 11 wherein the at least one reflective element comprises a laser-line selective filter arranged to allow propagation of light of the picture through the head-up display and suppress the propagation of light of having a different wavelength through the head-up display.

15. A method for displaying a picture using a head up display of a vehicle comprising a windscreen, the method comprising,

in a first optical sub-system disposed proximate an upper region of the windscreen, emitting light from a light source; and

receiving the light at a spatial light modulator and spatially-modulating the light in accordance with a computer-generated hologram displayed on the spatial light modulator;

receiving a spatially-modulated light field from the first optical sub-system at a second optical sub-system disposed underneath the dashboard of the vehicle proximate a lower region of the windscreen; and

in the second optical sub-system, projecting the spatially-modulated light field onto the windscreen of the vehicle to form a virtual image on the windscreen.

16. A method as claimed in claim 15 , wherein the method is for displaying the picture to a viewer, and wherein the projection of the spatially-modulated light field onto the windscreen is performed such that a lens of an eye of the viewer can perform an optical Fourier transform of the spatially-modulated light field.

17. A vehicle comprising a head-up display as claimed in claim 1 , wherein the first optical subsystem is disposed proximate an upper region of the windscreen and the second optical sub-system is disposed underneath the dashboard of the vehicle proximate a lower region of the windscreen.

18. A vehicle comprising a head-up display as claimed in claim 2 , wherein the first optical subsystem is disposed proximate an upper region of the windscreen and the second optical sub-system is disposed underneath the dashboard of the vehicle proximate a lower region of the windscreen.