Jul/090
Of Holograms
Not long ago we could see the impresive presentation from D'strict for Samsumg. Combining a set of motion sensors, projectors, semi transparent screens and a dark enough atmosphere the system was able to understand up to 17 gestures to make the floating images on the stage rotate, translate and change size. It is quite complicated to explain, is much better seeing it.
Holography is nothing new, in 1947 Denis Gabor got a Nobel price in Physics on his work on this subjet. Holography is usually compared with 3D photography, but even when the results are similar, the way it is produce is closer to how we actually record stereo audio, and the way we manage to reproduce that audio in the same conditions and spacial distribution than when it was recorded. Comparing with photography, a image sensor is able to capture the amplitude of a wave and its wave length - when capturing colour photography, while in an hologram we not only capture those two properties, but also the phase of the wave. The most common holograms are usually produced for an specific wave length, that is the reason they look green-ish or red-ish, but it is also possible to produce colour holograms.
To be able to store all this information, a beam of light is splitted into two beams, the illumination and the reference beam. The illumination one is directed to the real object while the reference is made to create an interference with the reflection of the illumination bean coming from the object. The result of the interference is capture by a image sensor. The result is a matrix of dots, which does not resemble the original object at all.
To produce the hologram, the result of the above process is iluminated by a similar beam than the one used to capture the data. The bean is difracted and, as a result, a wave with a amplitude, wave lenght and phase same as the original one is produce. The viewer can now clearly see the object. Usually a laser bean is used to generate holograms. This is due to the fact that it is much easier to create an intereference between the reference and the object beams if a laser source is used. In the eraly stages of this process mercury based lamps where used.
You can see much more here.
