Method and apparatus for illuminating a computer generated hologram

1. A holographic display system for displaying holographic images, said images having parallax substantially only in a single direction, said display comprising:

a spatial light modulator, SLM, having an active area for displaying a computer generated hologram, CGH,

a diffuse line light source, each portion of said light source illuminating the active area of said SLM, and

optics for guiding light modulated by the SLM to a display region.

2. A display according to claim 1 , wherein said single parallax direction is horizontal.

3. A display according to claim 2 , wherein the line light source is vertically oriented.

4. A display according to claim 1 , wherein said single parallax direction is vertical.

5. A display according to claim 4 , wherein the line light source is horizontally oriented.

6. A display according to claim 1 , wherein the SLM of the holographic display is an optically addressed spatial light modulator, OASLM.

7. A display according to claim 6 and comprising replicating optics for replicating fringes representative of a holographic image displayed on an electrically addressed spatial light modulator, EASLM on a rear surface of the OASLM, with said means for illuminating the SLM being arranged to direct light onto a front surface of the OASLM.

8. A display according to claim 1 , wherein the SLM is an EASLM.

9. A display according to claim 1 , wherein the means for illuminating the SLM comprises collimating optics arranged between the line light source and the SLM.

10. A display according to claim 1 , wherein the line light source comprises a linear array of discrete light sources, with each of the sources being substantially a point source.

11. A display according to claim 1 , wherein the line light source comprises a light source and a scanning mirror arranged to scan the output of the light source along a linear path.

12. A display according to claim 1 , wherein the line light source comprises a line LED, a flattened optical fibre bundle, or an edge emitting optical fibre.

13. A display according to claim 1 , wherein the line light source comprises a source of collimated light and a cylindrical lens arranged in front of the light source.

14. A display according to claim 1 , wherein said line light source is arranged so that the generated light originates from or appears to originate from said display region.

15. A display according to claim 14 , wherein said light originates from or appears to originate from a DC line area of the display region.

16. A method of displaying a hologram having parallax substantially in a single direction only, the method comprising the steps of:

displaying fringes representative of a holographic image on an active area of a spatial light modulator, SLM,

illuminating the SLM with a diffuse line light source, each portion of said light source illuminate the active area of said SLM, and guiding light modulated by the SLM to a display region.

17. A method according to claim 16 , wherein the line light source is vertically or horizontally aligned.