Method of displaying a hologram on a display device comprising pixels

1. A method of displaying holograms using one or more spatial light modulators, each comprising light-modulating pixels, the method comprising:

receiving, at a spatial light modulator, a first hologram comprising a first plurality of hologram pixels each having a respective hologram pixel value;

displaying the first hologram on a plurality of light-modulating pixels of said spatial light modulator by displaying each hologram pixel value on a contiguous group of light-modulating pixels of the plurality of light-modulating pixels such that there is a one-to-many pixel correlation between each hologram pixel and the number of light-modulating pixels within the contiguous group, which display its pixel value, wherein each hologram pixel value within the first hologram is displayed on the same number of light-modulating pixels as each of the respective others

receiving, at a spatial light modulator, a second hologram comprising a second plurality of hologram pixels, each having a respective hologram pixel value; and

displaying the second hologram on a plurality of the light-modulating pixels of said spatial modulator by displaying each hologram pixel value on a contiguous group of light-modulating pixels of the plurality of light-modulating pixels such that there is a one-to-many or a one-to-one pixel correlation between each hologram pixel and the number of light-modulating pixels within the contiguous group displaying its pixel value, wherein each hologram pixel value within the second hologram is displayed on the same number of light-modulating pixels as each of the respective others; and

wherein a first number of light-modulating pixels are used to display each hologram pixel value of the first hologram and a second, different number of light-modulating pixels are used to display each hologram pixel value of the second hologram.

2. A method of displaying holograms as claimed in claim 1 wherein the first hologram and second hologram are displayed on the same spatial light modulator.

3. A method of displaying holograms as claimed in claim 1 wherein at least one light-modulating pixel is used to display a hologram pixel value of the first hologram at a first time and a hologram pixel value of the second hologram at a second time different to the first time.

4. A method of displaying holograms as claimed in claim 1 wherein the first hologram is displayed on a first spatial light modulator and the second hologram is displayed on a second spatial light modulator.

5. A method of displaying holograms as claimed in claim 1 further comprising illuminating the displayed hologram with light having a wavelength to project a holographic replay field having an area and illuminating the second displayed hologram with light having a second wavelength to project a second holographic replay field having a second area.

6. A method of displaying holograms as claimed in claim 5 wherein the different number of light-modulating pixels used to display the hologram and the second hologram is such that the area and second area are substantially the same size.

7. A method of displaying holograms as claimed in claim 6 further comprising overlapping the area and second area to form a composite colour replay field.

8. A holographic projector comprising:

a hologram engine arranged to provide a first hologram comprising a plurality of hologram pixels each having a respective hologram pixel value and a second hologram comprising a second plurality of hologram pixels each having a respective hologram pixel value;

one or more spatial light modulators; and

a controller arranged to

selectively-drive a plurality of light-modulating pixels of one of the spatial light modulators so as to display the first hologram by displaying each hologram pixel value on a contiguous group of light-modulating pixels of the plurality of light-modulating pixels such that there is a one-to-many pixel correlation between each hologram pixel and the number of light-modulating pixels displaying its pixel value, such that each hologram pixel value within the first hologram is displayed on the same number of light-modulating pixels as each of the respective others, and

to selectively-drive a plurality of light-modulating pixels of one of the spatial light modulators so as to display the second hologram by displaying each hologram pixel value on a contiguous group of light-modulating pixels of the plurality of light-modulating pixels such that there is a one-to-many or a one-to-one pixel correlation between each hologram pixel and the number of light-modulating pixels displaying its pixel value, such that each hologram pixel value within the second hologram is displayed on the same number of light-modulating pixels as each of the respective others,

such that a first number of light-modulating pixels are used to display each hologram pixel value of the first hologram and a second, different number of light-modulating pixels are used to display each hologram pixel value of the second hologram.

9. A holographic projector as claimed in claim 8 further comprising:

a light system arranged to illuminate the first displayed hologram with light having a wavelength so as to project a first holographic replay field having a first area; and

a second light system arranged to illuminate the second displayed hologram with light having a second wavelength so as to project a second holographic replay field having a second area.

10. A holographic projector as claimed in claim 9 wherein the different number of light-modulating pixels used to display the first hologram and the second hologram is such that the area and second area are substantially the same size.

11. A holographic projector as claimed in claim 10 further comprising a spatial light modulator arranged to display the hologram and second hologram or further comprising a spatial light modulator arranged to display the hologram and a second spatial light modulator arranged to display the second hologram.