Video hologram and device for reconstructing video holograms for large objects
A video holographic display device operates so that the size of a reconstructed three dimensional scene is a function of the size of the hologram-bearing medium; the reconstructed three dimensional scene can then be anywhere within a volume defined by the hologram-bearing medium and a virtual observer window through which the reconstructed three dimensional scene must be viewed. This contrasts with conventional holograms, in which the size of the reconstructed scene is localised to a far smaller volume and is not a function of the size of the hologram-bearing medium at all.
1. A display device for video holography, in which the device enables a holographic reconstruction of a three dimensional scene to be generated; the device including a light source and an optical system to illuminate a hologram-bearing medium encoded with a hologram, the optical system imaging the light source into an image plane of the light source;
wherein the device is adapted such that the reconstructed three dimensional scene is generatable anywhere within a volume defined by the physical boundary provided by the hologram-bearing medium and a virtual observer window through which the reconstructed three dimensional scene must be viewed wherein the virtual observer window is located approximately at the image plane of the light source and wherein the virtual observer window is the location where an observer places at least one eye to view the holographic reconstruction representing the three-dimensional scene.
2. The device of claim 1 in which the observer window is constrained to be substantially at an image plane of the light source.
3. The device of claim 1 operable to time sequentially encode a hologram on the spatial light modulator first for one eye of an observer and then for the other eye of the observer.
4. The device of claim 1 operable such that the holographic reconstruction is described by the Fresnel transform of the hologram and not the Fourier transform of the hologram.
5. The device of claim 1 which is operable such that a direct or inverse Fourier transform of the hologram is generated at an observer plane at which the observer's eyes must be placed.
6. The device of claim 1 in which the virtual observer window is smaller than the hologram bearing medium.
7. The device of claim 1 in which there are separate virtual observer windows, one for each eye of an observer.
8. The device of claim 7 in which each virtual observer window is approximately 1 cm×1 cm.
9. The device of claim 7 operable to track a location of an observer's eyes and to alter a position of the virtual observer windows so that the observer maintains a view through each virtual observer window even when moving his or her head.
10. The device of claim 1 in which the light source includes several light sources.
11. The device of claim 1 in which the hologram bearing medium is a TFT flat screen.
12. The device of claim 1 in which the device is a television.
13. The device of claim 1 in which the device is a multimedia device.
14. The device of claim 1 in which the device is a gaming device.
15. The device of claim 1 in which the device is a medical image display device.
16. The device of claim 1 in which the device is a military information display device.
17. A holographic reconstruction generated by the display device as defined in claim 1 .