Apparatus and method for displaying a video image
A method of displaying a video image comprises receiving sequential image frames at a processor. Each image frame is processed to obtain a kinoform. A programmable diffractive element such as an SLM represents the sequence of kinoforms allowing reproduction of the image using a suitable illumination beam.
1. A method of projecting a 2-D video image onto a screen, the projected 2-D video image being made up of sequential image frames at a video frame rate, the method comprising:
receiving an input video image made up of video frames at a processor;
in the processor, processing each input in real-time to obtain quantized data representative of one or more respective phase-only kinoforms;
writing the quantized data representative of one or more respective phase-only kinoforms to a reflective phase-only spatial light modulator to sequentially represent each said kinoform;
illuminating the reflective phase-only spatial light modulator with visible light from an illumination source to provide a phase modulated output beam;
processing the phase modulated output beam from the reflective phase-only spatial light modulator by optics to reconstruct the sequential image frames across the screen at a replay field in real-time for viewing the 2-D video image; and
controlling the intensity to achieve a desired image brightness from frame to frame.
2. A method as claimed in claim 1 in which the video image is one of a time varying or still image.
3. A method as claimed in claim 1 , further comprising parallel processing respective sub-sets of an initial kinoform to obtain optimized sub-sets and recombining the optimized sub-sets.
4. A method as claimed in claim 3 , in which the initial kinoform sub-sets comprise initial kinoform segments.
5. A method as claimed in claim 3 , in which the initial kinoform is randomly generated or pre-determined or the result of an initial FFT, or a recycled phase distribution.
6. A method as claimed in claim 1 , in which image frames are processed to obtain a respective kinoform using any one of a bi-directional iterative optimization algorithm, a uni-directional iterative optimization algorithm or a bi-directional iterative quantization procedure, or a uni-directional non-iterative procedure.
7. A method as claimed in claim 6 , in which the optimization algorithm is based on the Gerchberg Saxton algorithm.
8. A method as claimed in claim 1 , further comprising controlling a parameter of operation to provide at least one of grey scale and color.
9. A method as claimed in claim 8 , in which the spatial light modulator is directly modulated to provide color and/or grey scale.
10. A method as claimed in claim 9 , in which the spatial light modulator provides a binary quantization scheme and is multiplexed frame sequentially to provide color and/or grey scale.
11. A method as claimed in claim 9 , in which the spatial light modulator provides a multi-level quantization scheme to provide color and/or grey scale.
12. A method as claimed in claim 9 , in which the illumination source is modulated in the color domain to provide color and/or grey scale.
13. A method as claimed in claim 8 , in which the illumination source is modulated in the time domain to provide color and/or grey scale.
14. A method as claimed in claim 1 , in which the kinoform obtained comprises one of a plurality of kinoforms which each reconstruct a spatial, color or intensity decomposition of the image frame.
15. A method as claimed in claim 14 , in which the plurality of kinoforms sum to give the real image.
16. A method as claimed in claim 1 , further comprising a noise reduction step, in which noise reduction is provided by programming the spatial light modulator to represent the kinoform according to a multi-level quantization scheme.
17. As method as claimed in claim 16 , in which additional noise reduction is provided by noise averaging over a plurality of image frames.
18. A method as claimed in claim 16 , in which the image frame and kinoform are pixellated, and wherein the kinoform contains excess pixels in relation to the image frame.
19. A method as claimed in claim 16 , in which additional noise reduction is provided by spatial multiplexing of each phase hologram.
20. A method as claimed in claim 19 , in which the phase holograms are spatially multiplexed on the spatial light modulator.
21. A method as claimed in claim 20 , in which each image frame comprises a plurality of sequential image sub-frames and the spatial multiplexing step comprises juxtaposing sequential sub-frames.
22. A method as claimed in claim 19 , in which the phase holograms are spatially multiplexed on an optically addressable spatial light modulator.
23. A method as claimed in claim 16 , in which additional noise reduction is provided by shaping an illumination source wave front to mitigate systematic noise.
24. A method as claimed in claim 1 , further comprising spatially multiplexing the kinoform on one of the spatial light modulator or an optically addressable spatial light modulator.
25. A method as claimed in claim 1 further comprising a noise reduction step in which noise reduction is provided by noise averaging over a plurality of sub-frames of each image frame.
26. A method as claimed in claim 25 in which each sub-frame is generated in an optimization algorithm.
27. A method as claimed in claim 1 wherein controlling the intensity is dependent on image content.
28. A projector for projecting a 2-D video image onto a screen, the projected 2-D video image being made up of sequential image frames at a video frame rate, the projector comprising:
a processor, a reflective phase-only spatial light modulator and an illumination source for illuminating the reflective phase-only spatial light modulator with visible light, the processor having an input for receiving an input video image made up of video frames and an output for writing data to the reflective phase-only spatial light modulator, the processor being arranged to:
process each input in real-time to obtain quantized data representative of one or more respective phase-only kinoforms; and
write the quantized data representative of one or more respective phase-only kinoforms to the reflective phase-only spatial light modulator to sequentially represent each said kinoform;
the illumination source arranged to illuminate the reflective phase-only spatial light modulator with visible light to provide a phase-modulated output beam, the projector further comprising optics to reconstruct the sequential image frames across the screen in real-time for viewing the 2-D video image; and
a controller arranged to control the intensity to achieve a desired image brightness from frame to frame.
29. A projector as claimed in claim 28 in which the video image comprises at least one of a time varying and still image.
30. A projector as claimed in claim 28 in which the spatial light modulator provides binary quantization.
31. A projector as claimed in claim 28 in which the spatial light modulator provides multi-level quantization.
32. A projector as claimed in claim 28 in which the spatial light modulator includes, as a programmable component, any one of nematic liquid crystal on silicon (LCOS), electroclinic LCOS, deformed helix LCOS and V-shaped switching LCOS.
33. A projector as claimed in claim 28 wherein the optics further comprise projection optics associated with the spatial light modulator.
34. A projector as claimed in claim 28 in which projection optics are programmed into the kinoform.
35. A projector as claimed in claim 28 wherein the controller is arranged to control the intensity dependent on image content.
36. A projector as claimed in claim 28 , in which the processor includes at least one of an FFT processor, a field programmable gate array processor or a digital signal processor.
37. A projector as claimed in claim 28 , in which the illumination source is a partially coherent illumination source.
38. A projector as claimed in claim 37 , in which the illumination source is arranged to be modulated to provide color and/or grey scale.
39. A projector as claimed in claim 37 , further comprising illumination source wave-front shaping optics arranged to shape an illumination beam to mitigate systematic noise in the display.
40. A projector as claimed in claim 37 , further including an optically addressable spatial light modulator (OASLM).
41. A projector as claimed in claim 40 , further comprising spatial multiplexing optics arranged to spatially multiplex the kinoform onto the OASLM.
42. A projector as claimed in claim 41 , in which the spatial multiplexing optics are further arranged to spatially multiplex temporally varying kinoform.
43. A projector as claimed in claim 37 , further comprising a display screen.
44. A projector as claimed in claim 43 , in which the display screen is located optically off-axis.
45. A projector as claimed in claim 28 , in which the controller is arranged to control the intensity of the illumination source.