Holographic image projection with holographic correction
There is provided a method of projection using an optical element having spatially variant optical power. The method comprises combining Fourier domain data representative of a 2D image with Fourier domain data having a first lensing effect to produce first holographic data. Light is spatially modulated with the first holographic data to form a first spatially modulated light beam. The first spatially modulated light beam is redirected using the optical element by illuminating a first region of the optical element with the first spatially modulated beam. The first lensing effect compensates for the optical power of the optical element in the first region.
1. A method of projection comprising:
providing first holographic data comprising hologram domain data representative of a display image and a first lensing function; and
providing a first spatially modulated light beam to a first viewing location by a method comprising
spatially modulating light with the first holographic data to form the first spatially modulated light beam; and
redirecting the first spatially modulated light beam using an optical combiner having
a first region having a first local curvature and
a second region having a second local curvature, the second local curvature being different from the first local curvature,
the redirecting being performed by illuminating the first region of the optical combiner with the first spatially modulated beam, the optical combiner redirecting the first spatially modulated light beam to the first viewing location to provide a first image corresponding to the display image at the first viewing location,
wherein the first lensing function compensates at the first viewing location for the first local curvature of the first region of the optical combiner.
2. The method of claim 1 , wherein the display image is a 2D image.
3. The method of claim 1 wherein the first lensing function negates at the first viewing location the first local curvature of the first region of the optical combiner.
4. The method of claim 1 , wherein the spatial modulation is a phase-only modulation.
5. The method of claim 1 wherein the optical combiner is a vehicle windscreen.
6. The method of claim 1 , wherein the redirecting of the first spatially modulated light beam is a reflecting of the first spatially modulated light beam.
7. The method of claim 1 , wherein the projection provides a head-up display image visible at the first viewing location, the head-up display providing an observer at the first viewing location a view through the optical combiner overlapped with the first image corresponding to the display image.
8. The method of claim 1 , wherein
spatially modulating light with the first holographic data to form a first spatially modulated light beam comprises:
representing the first holographic data on at least one spatial light modulator; and
illuminating the at least one spatial light modulator with a light source to form the first spatially modulated light beam corresponding to the first holographic data; and
the projection provides a head-up display image visible at the first viewing location.
9. The method of claim 1 , further comprising:
providing second holographic data comprising hologram domain data representative of the display image and a second lensing function different from the first lensing function; and
providing a second spatially modulated light beam to a second viewing location different from the first viewing location, by a method comprising
spatially modulating light with the second holographic data to form a second spatially modulated light beam; and
redirecting the second spatially modulated light beam using the optical combiner by illuminating the second region of the optical combiner with the second spatially modulated beam, the optical combiner redirecting the second spatially modulated light beam to the second viewing location to provide a second image corresponding to the display image at the second viewing location,
wherein the second lensing function compensates at the second viewing location for the second local curvature of the second region of the optical combiner.
10. The method of claim 1 wherein spatially modulating light with the first holographic data to form the first spatially modulated light beam comprises:
representing the first holographic data on at least one spatial light modulator; and
illuminating the at least one spatial light modulator with a light source to form the first spatially modulated light beam corresponding to the first holographic data.
11. The method of claim 10 , wherein the illumination with the light source illuminates the at least one spatial light modulator with a plane wave.
12. A projector comprising:
a computer processor configured to combine hologram domain data representative of a display image with hologram domain data having a first lensing function to produce first holographic data;
at least one spatial light modulator arranged to receive the first holographic data from the computer processer and spatially modulate light with the first holographic data to provide a first spatially modulated light beam;
an optical combiner comprising
a first region having a first local curvature and
a second region having a second local curvature, the second local curvature being different from the first local curvature, the optical combiner being configured to be illuminated by the first spatially modulated light beam in the first region thereof and redirect the first spatially modulated light beam to a first viewing location to provide a first image corresponding to the display image at the first viewing location;
wherein the first lensing function is configured to compensate at the first viewing location for the first local curvature of the first region of the optical combiner.
13. The projector of claim 12 , further comprising a light source arranged to illuminate the at least one spatial light modulator.
14. The projector of claim 12 , wherein the at least one spatial light modulator is at least one phase-only spatial light modulator.
15. The projector of claim 12 , wherein the optical combiner is configured to reflect the first spatially modulated light beam.
16. The projector of claim 12 , wherein the projector is configured to provide an observer at the first region of the viewing plane a view through the optical combiner overlapped with the first image corresponding to the display image.
17. The projector of claim 12 further comprising a repository of holographic domain data representative of a plurality of display images, the repository being configured to provide the holographic domain data to the computer processor.
18. The projector of claim 12 , wherein
the computer processor is further configured to combine hologram domain data representative of the display image with hologram domain data having a second lensing function to produce second holographic data;
the at least one spatial light modulator is arranged to receive the second holographic data from the computer processer and to spatially modulate light with the second holographic data to provide a second spatially modulated light beam;
the optical combiner is configured to be illuminated by the second spatially modulated light beam in the second region thereof and redirect the second spatially modulated light beam to a second viewing location to provide a second image corresponding to the display image at the second viewing location;
wherein the second lensing function is configured to compensate at the second viewing location for the second local curvature of the second region of the optical combiner.
19. A vehicle comprising the projector of claim 12 , wherein the optical combiner is a windscreen of the vehicle.